Performance study of the MSU Mach 3 wind tunnel
by Bradley Barney Rogers
A thesis submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE
in Mechanical Engineering
Montana State University
© Copyright by Bradley Barney Rogers (1981)
Abstract:
The aerodynamic parameters governing the operation of a supersonic wind tunnel are considered.
These parameters are determined from measurements of the supersonic flow stream. The Mach
Number is found to be near 3 while the Reynolds Number can be varied between 30,000 and 60,000
per centimeter. The capabilities of the facility as a research tool are presented in a form that will be
useful to future users of the facility. STATEMENT OF PERMISSION TO COPY
In p r e s e n t i n g t h i s t h e s i s in p a r t i a l f u l f i l l m e n t o f t h e r e q u i r e m e n t s
f o r an advanced d e g r e e a t Montana S t a t e U n i v e r s i t y , I a g r e e t h a t th e
L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r i n s p e c t i o n .
I f u r t h e r agree
t h a t p e r m i s s i o n f o r e x t e n s i v e co py in g o f t h i s t h e s i s f o r s c h o l a r l y p u r ­
po s e s may be g r a n t e d by my m a jo r p r o f e s s o r , o r , in h i s a b s e n c e , by t h e
D irector of L ib ra rie s.
I t i s u n d e r s t o o d t h a t any co py in g o r p u b l i c a t i o n
o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t be a l lo w ed w i t h o u t my w r i t ­
ten, permission.
Signature
■ PERFORMANCE STUDY OF THE MSU
i
■
MACH 3 WIND TUNNEL
.
.
by
BRADLEY BARNEY ROGERS .
A t h e s i s submitted in p a r t i a l f u l f i l l m e n t
o f the requirem ents f o r .the degree
of
MASTER OF SCIENCE
in
Mechanical E n g i n e e r i n g
Approved
C h a i r p e r s o n , G rad ua te Committee
Head, Major Department
MONTANA STATE UNIVERSITY
Bozeman, Montana
F e b r u a r y , 1981
ACKNOWLEDGMENTS
The a u t h o r w ish es t o t h a n k Dr. A. Deme triad es and Mr. D. H.. Drum­
mond f o r t h e i r h e l p and g u id a n c e i n t h e perf or ma nce o f t h i s s t u d y .
S i n c e r e t h a n k s a r e a l s o due t o S c o t t Woodhead f o r p h o t o g r a p h i n g t h e
wind t u n n e l com ponents, and t o my w i f e , Mary, and C h a r l e n e Townes f o r
t h e i r h e l p i n p r e p a r i n g t h e f i n a l copy o f t h i s t h e s i s .
TABLE OF CONTENTS
Page
V I T A ............................................................
Ii
ACKNOWLEDGMENTS....................... ' . . . . . .............................................................i i i
LIST OF TABLES . ....................... ...........................
....................................................... r
vi
LIST OF F I G U R E S .......................................................................... ..................................... vi i
NOMENCLATURE .. ............................................................ .................................................. ....
ix
ABSTRACT . . . . . . . . . . . . . . . .
xi
.......................
CHAPTER I .
INTRODUCTION....................... ....
CHAPTER 2.
DESCRIPTION OF COMPONENTS . ...............................................
2.1 HISTORY
.
2.2
........................• . ...............................
4
6
INLET SYSTEM........................................
2 . 3 THROTTLING.VALVE . . . . . . . . .
..........................................
9
........................................................................................
12
. 2 . 5 UPSTREAM TRANSITION SECTION
2.6
4
..................................................................................
2 . 4 STILLING TANK
I
. . .
16
NOZZLE .........................................................................................................
17
. 2 . 7 SUPERSONIC DIFFUSER
.
................................
................................................... ....
2 . 8 DOWNSTREAM TRANSITION
. . .
............................................................
19
20
2 . 9 SUBSONIC DIFFUSER
..................
20
2 . 1 0 VACUUM SYSTEM . . .
'......................................................
21
2.11 WIND TUNNEL X-Y-Z PROBE ACTUATORS .......................
2 .1 2 SCHLI EREN SYSTEM
. . . .
................................ .................................... ....
.2 .1 3 WIND TUNNEL PRESSURESTATION
.........................
CHAPTER 3. ' WIND TUNNEL PERFORMANCE.....................
3.1 INTRODUCTION...........................
25
.
25
27
33
33
V
Page
3.2
WIND TUNNEL PRESSURE RATIO...................... .....................................
34
. 3 . 3 . PRESSURE RATIO OBSERVATIONS ......................................................
47
3 . 4 STATIC PRESSURE MEASUREMENTS ...............................................
50
3 . 5 STATIC PRESSURE MEASUREMENT RESULTS
. .
. . . . . . . . .
51
3 . 6 STAGNATION PRESSURE MEASUREMENTS ...............................................
58
3 . 7 STAGNATION PRESSURE MEASUREMENT RESULTS
73
3 . 8 BOUNDARY LAYER PROFILES
........................ ....
. . . . . . . . .............................84
3 . 9 RESULTS OF BOUNDARY LAYER PROFILES . . . . . .
.
89
3 . 1 0 TEMPERATURE OBSERVATIONS........................................................
.
95
3.11 MEASUREMENT ERROR . . . ..................................................................
95
CHAPTER 4.
CONCLUSIONS
. .........................................................................................
97
APPENDIX . OPERATING PROCEDURES . ♦ ......................................................................
100
REFERENCES . . . ,■ . . . . . . ..................................................................; . .
107
vi
LIST OF TABLES
Tabl e
Page
2.1
Nozzle C o o r d i n a t e s ................... .............................................................................18
2.2
A c t u a t o r Speeds and L i m it s o f Tra v e l
3.1
S t a t i c P r e s s u r e Nozzle C a l i b r a t i o n ............................................................
3.2
Comparison o f R e s u l t s ........................................................................................... 82
3.3
Boundary Layer T h i c k n e s s e s ..................................................
.......................................................... 26
52
94
vi i
LIST OF FIGURES
Figure
Page
2.1
Wind Tunnel C i r c u i t ..................................................
5
2.2
I n l e t System
7
2.3
T h r o t t l i n g V a l v e ...........................................................
10
2.4
S t i l l i n g T a n k ..................................................................................
13
2.5
S u p e r s o n i c S e c t i o n s ..................................
15
2.6
SWT Pump
2.7
S c h l i e r e n System
28
2.8
Wind Tunnel P r e s s u r e S t a t i o n ...........................
29
2.9
S che m atic o f P r e s s u r e S t a t i o n ................................
30
. . . . . . . . .
............................................................................................................................22
2 . 1 0 Example T r a n s d u c e r C a l i b r a t i o n
3.1
C u r v e f i t o f Pump O p e r a t i n g Curve
3.2-3.5
.......................
. .........................................
31
.......................................... . . . . .
38
Flovy Breakdown P r e d i c t i o n s ..................................................................... 39
3.6
O p e r a t i n g L i m i t s According t o Temp era tu re .............................................. 43
3.7
Flow Breakdown O b s e r v a t i o n s ......................
48
3.8
Results of S t a t i c Pressure Tests
53
3.9
E f f e c t o f S t a g n a t i o n P r e s s u r e on Mach Number
.......................................................
..................................... 54
3 . 1 0 Change o f t h e D is pl ac e m en t T h i c k n e s s due t o P r e s s u r e
................... 56
3.11 C o o r d i n a t e S y s t e m .......................................................................................
59
3 . 1 2 S t a g n a t i o n Tube R a k e ..................................................................
61
3 . 1 3 S t a g n a t i o n P r e s s u r e Measuring System
..............................................
3 . 1 4 S t a g n a t i o n Probe Behind Shock ................................
3 . 1 5 S i n g l e S t a g n a t i o n Probe f o r X-Y P lan e T r a v e r s e
. . 62
. . . . . . . . .
................................
64
65
viii
Figure
3.16
Page
P o s i t i o n i n g o f Rake i n T e s t S e c t i o n ........................................................ 6 7
3.17-3.20
Y-Z P lan e P l o t s ......................................... ...................... ...................... - 6 8
3.21 P o s i t i o n i n g , o f Rake i n T e s t S e c t i o n .....................................
3.22-3.26
72
Y-Z P la n e P l o t s .............................................................................................. 74
3 .2 7 X-Y Pla ne P l o t ..................................... .... ............................................. ....
79
3 . 2 8 V a r i a t i o n o f Mach Number Along T e s t S e c t i o n .......................................... 85
3 .2 9 F l a t t e n e d P i t o t P r o b e ..................................... .................................................. . 8 6
3.30-3.31
Boundary Layer P l o t s
. . . . . .
................................................... 87
3 . 3 2 Boundary Layer P r o f i l e s ...............................................................
3 .3 3 P r oc ed ur e f o r C a l c u l a t i n g D is p la ce m en t T h ic kn es s
. . . . . . .
91
93
4.1
O p e r a t i n g Range o f SWT
. . ...............................................................................98
A.I
Cont ro l Console . ................................. .... ................................................................102
IX
NOMENCLATURE
Symbol
Description
A
Area
A*
Area o f n o z z l e t h r o a t
a .
Speed o f sound
a*
Speed o f sound a t n o z z l e t h r o a t
ao .
Speed o f sound a t s t a g n a t i o n c o n d i t i o n s
M
Mach Number
M1
m
Mach Number ahead o f shock
Mass f lo w r a t e
P
■
Pressure
pi
Pump i n l e t p r e s s u r e
V
Stagnation pressure
S t a g n a t i o n p r e s s u r e ahead o f shock
pOl
O
CM
CL
S t a g n a t i o n p r e s s u r e beh in d shock
R
U n iv e r s a l gas c o n s t a n t
Re ; ‘
Reynolds Number
T
Tem perature
Ti
'
Pump i n l e t t e m p e r a t u r e
T0
Stagnation temperature ,
V,
Volume flo w r a t e
Y
Ratio o f s p e c i f i c h eats (1.4 f o r a i r )
6.
Boundary l a y e r t h i c k n e s s
X
Symbol
D escription
6*
D is pl ac e m en t t h i c k n e s s
P
Density
P*
Density a t th e nozzle t h r o a t
pO
pT
■
■
; '
Stagnation d ensity
Pump i n l e t d e n s i t y
xi
ABSTRACT
•
The a e r o dy n a m ic p a r a m e t e r s g o v e r n i n g t h e o p e r a t i o n o f a
wind t u n n e l a r e c o n s i d e r e d .
These p a r a m e t e r s a r e d e t e r m i n e d
m e asu re me nt s o f t h e s u p e r s o n i c f lo w s t r e a m .
The Mach Number
t o be n e a r 3 w h i l e t h e Reynolds Number can be v a r i e d between
and 6 0 , 0 0 0 p e r c e n t i m e t e r .
The c a p a b i l i t i e s o f t h e f a c i l i t y
r e s e a r c h t o o l a r e p r e s e n t e d -in. a form t h a t w i l l be u s e f u l t o
users of the f a c i l i t y .
-supersonic
from v '
i s found
30,000 .
as a
future
CHAPTER I
INTRODUCTION' ■
In t h e summer o f 1979, the" Ford A er o sp ace and Communications Corp­
o r a t i o n , l o c a t e d i n Newport Beach, C a l i f o r n i a , d o n a t e d t h e s u p e r s o n i c
wind t u n n e l f a c i l i t y t h a t was l o c a t e d on company g r oun ds t o t h e Mechani­
c a l E n g i n e e r i n g Dep art me nt o f Montana S t a t e U n i v e r s i t y . . The f a c i l i t y
was d i s m a n t l e d i n C a l i f o r n i a and moved t o Bozeman, Montana i n June o f
1979.
The wind t u n n e l was r e a s s e m b l e d , with’ e x t e n s i v e m o d i f i c a t i o n , in
Room 5-D o f . t h e Ryon L a b o r a t o r y b u i l d i n g on t h e campus o f MSU.
The
f a c i l i t y was s u c c e s s f u l l y o p e r a t e d i n i t s new l o c a t i o n i n June o f 1980.
When t h e t u n n e l was f i r s t o p e r a t e d i n C a l i f o r n i a , i n 1965, a b r i e f
r e p o r t c o n c e r n i n g i t s o p e r a t i o n was p u b l i s h e d .
2
Th is r e p o r t had n o t
been based on mea sur em ent s e x t e n s i v e and a c c u r a t e enough t o p r o v i d e a
good u n d e r s t a n d i n g o f t h e c a p a b i l i t i e s o f t h e wind t u n n e l .
Also, sin c e
t h e f a c i l i t y u nd erw en t e x t e n s i v e m o d i f i c a t i o n when i t was r e a s s e m b l e d in
Montana, t h e
a p p l i c a b i l i t y o f t h e o r i g i n a l r e p o r t was q u e s t i o n a b l e .
The p u r p o s e o f t h i s t h e s i s i s t o p r o v i d e , by m e as u re m en t, t h e a e r o ­
dynamic c h a r a c t e r i s t i c s o f t h e S u p e r s o n i c Wind Tunnel (SWT), and t o
detail
i t s c a p a b i l i t i e s as a r e s e a r c h t o o l .
Q u e s t i o n s t o be answered
include the follow ing:
I)
What m o d i f i c a t i o n s have t h e components o f t h e SWT u n d e r g o n e ,
s i n c e b e i n g moved t o MSU?
performance o f th e tunnel?
How have t h e s e ch an g e s a f f e c t e d t h e
2
2)
Have t h e pump c h a r a c t e r i s t i c s changed beca use o f f a t i g u e o r
o t h e r me cha nic al d e t e r i o r a t i o n ?
I f s o , what i s t h e c h a r a c t e r ­
i s t i c now? . At what s t a g n a t i o n p r e s s u r e can flo w breakdown
( " c h o k i n g " ) be e x p e c t e d ?
3)
What i s t h e Mach Number a l o n g t h e n o z z l e ?
from t h e o r y ?
4)
How does i t d i f f e r
How i s i t a f f e c t e d by s t a g n a t i o n p r e s s u r e change s?
Are t h e r e any waves p r e s e n t i n t h e t e s t s e c t i o n ?
I s t h e flow
in t h e t e s t s e c t i o n uniform?
5)
How t h i c k a r e t h e boundary l a y e r s in t h e t e s t s e c t i o n ?
Are
they laminar or tu rb u le n t?
6)
What ran ge o f s t a g n a t i o n t e m p e r a t u r e s a r e a t t a i n a b l e in t h e
tunnel?
These and o t h e r q u e s t i o n s a r e a d d r e s s e d in t h i s document.
The second c h a p t e r o f t h i s t h e s i s . d e a l s with t h e components o f t h e
SWT.
A d e s c r i p t i o n o f each component and ma jor a c c e s s o r y i s p r o v i d e d .
A b r i e f d i s c u s s i o n o f t h e h i s t o r y and o r i g i n a l pu rp o se o f t h e SWT i s
a ls o provided.
The t h i r d c h a p t e r d e a l s w ith t h e aerodynamic p a r a m e t e r s gover ning
t h e o p e r a t i o n o f t h e wind t u n n e l .
Q u e s ti o n s 2 - 6 above a r e , f o r t h e
most p a r t , answered by t h e r e s u l t s and d i s c u s s i o n s which a r e p r e s e n t e d
in t h i s c h a p t e r .
The f o u r t h c h a p t e r i s a s h o r t s e c t i o n o u t l i n i n g t h e c o n c l u s i o n s
drawn from t h e r e s u l t s o f C h a p t e r 3.
A s h o r t ap pe nd ix g i v i n g a condensed s e t o f o p e r a t i n g i n s t r u c t i o n s
f o r t h e SWT i s a l s o i n c l u d e d .
CHAPTER 2
DESCRIPTION OF COMPONENTS
2.1
HISTORY
The s u p e r s o n i c wind t u n n e l a t MSU i s an open c i r c u i t , c o n t in u o u s
4
wind t u n n e l .
.
The t u n n e l was f i r s t o p e r a t e d i n Newport Beach, C a l i f o r ­
n i a in F e b r u a r y o f 1965.
I t was o r i g i n a l l y d e s ig n e d t o s t u d y s u p e r s o n i c
wakes; s p e c i f i c a l l y , t o g e n e r a t e i n f o r m a t i o n l e a d i n g t o an a d e q u a te
d e s c r i p t i o n o f t h e flo w f i e l d behi nd r e - e n t r y v e h i c l e s .
The o r i g i n a l
d e s i g n p a r a m e t e r s o f t h e SWT a r e c o n t a i n e d in r e f e r e n c e 2.
When t h e t u n n e l was r e a s s e m b l e d a t MSU some r e p a i r s and r o u t i n e
m a in te n a n c e were done on s e v e r a l o f t h e m a jo r components.
Some o f t h e
work t h a t was done i s l i s t e d below:
1)
The d r y e r was t a k e n a p a r t and c l e a n e d , and th e n r e f i l l e d with
desiccant.
2)
S e v e r a l components o f t h e a i r d r y i n g mechanism, were r e p a i r e d .
3)
The t h r o t t l i n g v a l v e was c l e a n e d and r e p a i r e d .
•4)
The p i p i n g was c l e a n e d o f r u s t and s c a l e .
5)
The i n t e r i o r s o f t h e pumps were c l e a n e d .
6 ) . The c o n t r o l s . a n d c o n t r o l c o n s o l e were m o d i f i e d .
O th er r e p a i r s were a l s o done on any p a r t t h a t was n o t o b v i o u s l y in good
condition.
There has been no change in t h e broad d e s i g n g o a l s o f t h e SWT s i n c e
i t has. been moved t o MSU.
S e v e r a l changes have been made t o t h e i n d i v i ­
dual p a r t s o f t h e t u n n e l , however, m o s t l y in t h e form o f new s a f e t y
5
6
KEY
D
*—8
1
2
3
4
5
6
7
8
^ll
9
10
11
12
13
14
15
16
17
A ir I n l e t
C hiller
Dryer
R e l i e f Valve
T h r o t t l i n g Valve
S t i l l i n g Tank
Upstream T r a n s i t i o n
Nozzle and T e s t S e c t i o n
Downstream T r a n s i t i o n
Subsonic D i f f u s e r
Bellows Expansion J o i n t
Pump Motor
Pump F i r s t S ta ge
Pump Second S ta g e
Bypass Valve
Silencer
Exhaust
D
I
F i g u r e 2-1
Wind Tunnel C i r c u i t
i n t e r l o c k systems.
The r e s t o f t h i s c h a p t e r d e s c r i b e s t h e components o f
t h e SWT a s t h e y e x i s t t o d a y .
'
2.2
INLET SYSTEM
. The MSU SWT draws i t s a i r s u p p l y from t h e a t m o s p h e r e .
Because o f
t h i s , an a i r d r y i n g s y st em i s n e c e s s a r y t o p r e v e n t c o n d e n s a t i o n o f m o i s ­
t u r e a t t h e low s t a t i c t e m p e r a t u r e s t h a t o c c u r i n t h e t e s t s e c t i o n .
The
s ys te m o n ; t h e MSU t u n n e l i s made by De somatic P r o d u c t s o f A l e x a n d r i a ,
V irginia.
The d r y e r i s d e s i g n e d t o p r o v i d e a de w p o in t o f -30°F
a t d r y e r i n l e t flo w s r a n g i n g as l a r g e a s 700 SCFM ( S t a n d a r d Cubic F e e t
per M inute).
The a m b ie n t a i r e n t e r s t h r o u g h a s c r e e n l o c a t e d on t h e s i d e o f t h e
dryer.
The a i r th e n p a s s e s , t h r o u g h a c h i l l e r u n i t t h a t lo w er s t h e a i r
t e m p e r a t u r e t o ar ou nd 40°F.
Some w a t e r i s condensed o f f a t t h i s p o i n t .
The a i r t h e n p a s s e s t h r o u g h a p p r o x i m a t e l y 550 pounds o f s i l i c a gel which
d r i e s t h e a i r f u r t h e r t o a d ew p o in t o f a r o u n d -SO0F.
Above t h e d e s i c c a n t bed ( s i l i c a gel bed) i s a t h r e e - p h a s e , 480 v o l t ,
30 KW h e a t e r which i s used t o c o n t r o l t h e s t a g n a t i o n t e m p e r a t u r e o f t h e
a i r d u r i n g an e x p e r i m e n t .
tro l panel.
Th is h e a t e r i s c o n t r o l l e d from t h e main co n ­
•
Above t h e h e a t e r i s a plenum f i l t e r s e c t i o n which removes any p a r ­
t i c l e s o f s i l i c a gel which may be c a r r i e d al o n g w i t h t h e s t r e a m .
F i g u r e 2-2
I n l e t System
3
The d r y e r i s d e s i g n e d t o p e r m i t up t o f o u r hours o f c o n t i n u o u s
o p e r a t i o n a t maximum flow .
The d r y e r can o p e r a t e l o n g e r a t lower, flow
r a t e s an d, s i n c e t h e t u n n e l i s n o t n o r m a l l y o p e r a t e d a t maximum flow f o r
such a long p e r i o d o f t i m e , an e x p e r i m e n t can be t a i l o r e d t o p r o v i d e a
fu ll day's operation.
A f t e r t h e d e s i c c a n t has become s a t u r a t e d i t i s n e c e s s a r y t o r e g e n ­
e r a t e t h e d e s i c c a n t bed.
Thi s i s acc om p li sh e d by f lo w in g a i r o v e r t h e
h e a t e r c o i l s and down t h r o u g h t h e s i l i c a g e l .
c a r r i e d o u t o f t h e d e s i c c a n t bed.
Absorbed w a t e r i s th en
The r e g e n e r a t i o n c y c l e l a s t s f o u r
hour s and i s n o r m a l ly done o v e r n i g h t .
The d e s i c c a n t bed can t a k e as
long as 72 ho ur s t o cool o f f a f t e r a r e g e n e r a t i o n c y c l e i f i t i s l e f t
alone.
3
Once t h e t u n n e l i s s t a r t e d , however, i t c o o l s o f f in l e s s th a n
20 m i n u t e s .
The o n l y m a jo r m o d i f i c a t i o n s on t h i s s e c t i o n a r e t h a t t h e o n - o f f
s w i t c h f o r t h e r e g e n e r a t i o n c y c l e has been removed and an o n - o f f s w i tc h
has been i n s t a l l e d f o r t h e c h i l l e r .
The r e a s o n f o r t h e removal o f t h e
o n - o f f s w i t c h f o r t h e r e g e n e r a t i o n c y c l e i s t h a t when t h e d e s i c c a n t ta n k
was i n s p e c t e d i t s bottom was found r u s t e d from i n s u f f i c i e n t r e g e n e r a t i o n
of the s i l i c a g e l .
To make s u r e t h a t t h e bed i s always f u l l y r e g e n e r a ­
t e d t h e o n - o f f s w i t c h f o r t h e r e g e n e r a t i o n c y c l e was removed so t h a t ,
once s t a r t e d , t h e c y c l e must run i t s f u l l c o u r s e .
The f o u r - h o u r r e g e n e r a t i o n time was a r r i v e d a t e x p e r i m e n t a l l y .
was fo u n d , by p l a c i n g a t e m p e r a t u r e probe i n t h e d e s i c c a n t bed and
It
9
s t a r t i n g t h e r e g e n e r a t i o n c y c l e , t h a t t h e bed t e m p e r a t u r e s t a b i l i z e d
a f t e r s l i g h t l y l e s s th a n f o u r hou rs a t a t e m p e r a t u r e o f 350°F, i n d i c a ­
t i n g t h e bed was d r y . *
In i t s p r e v i o u s i n s t a l l a t i o n , t h e c h i l l e r u n i t d i d n o t have an ono f f switch.
The o n l y way i t co u l d be t u r n e d o f f a f t e r t h e main power
was a c t i v a t e d was by u n d er g oi ng a s a f e t y shutdown, such as o v e r h e a t i n g .
The c h i l l e r a u t o m a t i c a l l y "came on" when t h e main power was t u r n e d on.
An o n - o f f s w i t c h has been i n s t a l l e d on t h e main c o n t r o l panel so t h e
o p e r a t o r can s h u t t h e c h i l l e r o f f and c o n t i n u e o p e r a t i n g t h e tu n n e l i f
t h e need s h o u ld a r i s e .
2.3
THROTTLING VALVE
A f t e r p a s s i n g t h r o u g h t h e plenum f i l t e r , t h e a i r moves on th ro ugh
f o u r f e e t o f 1 2 - in c h p i p e .
The flow channel th e n co n v e r g e s t o a 6- i n c h
f l a n g e , t o which i s c o n n e c te d a Mason-Neilan Model 37-3312 s o f t - s e a t
b u tte r f ly valve.
A f t e r p a s s i n g th r o u g h t h i s v a l v e , h e r e a f t e r r e f e r r e d
t o as t h e t h r o t t l i n g v a l v e , t h e flow d i v e r g e s back t o a 12- inc h d i a m e t e r
p i p e and c o n t i n u e s on t o t h e s t i l l i n g t a n k , which i s d e s c r i b e d in t h e
next s e c tio n .
(See F ig u r e 2 . 3 ) .
The t h r o t t l i n g v a l v e i s used t o r e g u l a t e t h e a i r flo w r a t e and, as
a consequence, the s ta g n a t io n p re s s u re .
Thi s v a l v e i s p n e u m a t i c a l l y
c o n t r o l l e d by t h e o p e r a t o r from t h e main c o n t r o l p a n e l .
*This measurement was performed by Mr. D. H. Drummond.
A Mason-Neilan
10
F i g u r e 2-3
T h r o t t l i n g Valve
11
7000 s e r i e s s p r i n g - d i a p h r a g m c o n t r o l v a l v e p o s i t i o n e r o p e r a t e s t h e v a l v e
and p o s i t i o n s t h e . b u t t e r f l y f o r a i r flo w c o n t r o l d u r i n g o p e r a t i o n .
A Mas on -Ne ilan Model 141-2 Manual Loading S t a t i o n i s l o c a t e d on t h e
main c o n t r o l p a n e l so t h e o p e r a t o r can p o s i t i o n t h e v a l v e i n o r d e r t o
obtain the d e sire d sta g n a tio n pressure.
ti o n f o r t h i s system.
There a r e two modes o f o p e r a ­
These a r e a manual mode and an a u t o m a t i c mode.
The manual mode i s n o r m a l l y used when s t a r t i n g and s t o p p i n g t h e t u n n e l ,
b u t w i l l n o t p r o v i d e s t a b l e o p e r a t i o n d u r i n g an e x p e r i m e n t .
In t h e ' :
manual mode, t h e p o s i t i o n o f t h e v a l v e i s f i x e d a n d , i f l e f t a l o n e , no .
c o r r e c t i o n w i l l be made f o r v a r y i n g i n l e t o r a t m o s p h e r i c c o n d i t i o n s ,
thereby causing the s ta g n a tio n pressure to f l u c t u a t e several m illim e te rs
o f Mercury.
For t h i s r e a s o n , d u r i n g a t u n n e l r u n , t h e a u t o m a t i c mode i s
n o r m a l l y us ed once t h e t u n n e l has been s t a r t e d and a l l o w e d t o come i n t o
equilibrium .
In t h i s mode t h e d e s i r e d s t a g n a t i o n p r e s s u r e i s s e t once
by t h e o p e r a t o r and t h e sy ste m a u t o m a t i c a l l y m a i n t a i n s t h a t c o n d i t i o n by
v a r y i n g t h e p o s i t i o n o f t h e b u t t e r f l y as i n l e t c o n d i t i o n s c h a n g e .
The t h r o t t l i n g v a l v e i s opened by i n c r e a s i n g t h e pneumatic" p r e s s u r e .
I f , f o r any r e a s o n , t h e c o n t r o l system l o s e s i t s a i r p r e s s u r e , t h e
t h r o t t l i n g valve w ill s h u t.
When t h i s happens t h e vacuum pump w i l l p u l l
a l a r g e vacuum t h r o u g h o u t t h e sy stem.
Th is w i l l c a u s e t h e s a f e t y r e l i e f
v a l v e (c he c k v a l v e ) t h a t i s l o c a t e d n e a r t h e pumps t o o p e n , a s i s d e s ­
c rib e d l a t e r in t h i s c h a p t e r .
This v a l v e does n o t o p e n , however, u n t i l
t h e r e i s a l r e a d y a l a r g e vacuum t h r o u g h o u t the- w i n d - t u n n e l c i r c u i t . -
12
Because o f t h i s vacuum, t h e pumps w i l l s t a r t f r e e w h e e l i n g backwards
a f t e r t h e mot or s h u t s o f f , b l o w i n g . w h a t e v e r might be i n t h e pumps, most­
l y r u s t and w a t e r , back th r o u g h t h e t e s t s e c t i o n .
Th is can be very
damaging t o t h e t e s t s e c t i o n a n d . w h a t e v e r m ig ht be in i t a t t h e t i m e .
For t h i s r e a s o n , ex tre me c a r e i s always ta k e n t o n e v e r a l l o w t h e t h r o t t ­
l i n g v a l v e c o n t r o l p r e s s u r e t o g e t t o o low.
As a n o t h e r s a f e g u a r d
a g a i n s t t h i s p o s s i b i l i t y , a s a f e t y i n t e r l o c k system has been i n s t a l l e d
t o p r e v e n t t h e vacuum pump motor from s t a r t i n g i f t h e t h r o t t l i n g v al v e
is closed.
A l o w - a i r - p r e s s u r e shutdown se quence has a l s o been i n s t a l l e d
t o s t o p t h e motor i f t h e b u i l d i n g a i r s u p p l y p r e s s u r e s h o u ld f a l l too
low t o o p e r a t e t h e pneum atic d e v i c e s on t h e wind t u n n e l , such as t h e
th r o t tli n g valve.
Thi s seq uen ce i s s e t t o s t a r t i f t h e s u p p l y p r e s s u r e
f a l l s below 70 p s i . 3
2.4
STILLING TANK
D i r e c t l y downstream from t h e t h r o t t l i n g v a l v e i s t h e s t i l l i n g t a n k .
The pur pos e o f t h i s t a n k i s t o a l l o w chanc e d i s t u r b a n c e s , such as l a r g e
s c a l e t u r b u l e n c e , t o damp o u t b e f o r e t h e a i r e n t e r s t h e t e s t s e c t i o n .
I t c o n s i s t s o f a 7 . 5 f e e t long by 3 . f e e t wide c y l i n d r i c a l v e s s e l
F ig u r e 2 . 4 ) .
(see
The h u m i d it y o f t h e wind t u n n e l a i r i s measured from an
a i r sample t a k e n from t h i s t a n k d u r i n g an e x p e r i m e n t .
A i r e n t e r s t h e s t i l l i n g t a n k from t h e 1 2 - i n c h l i n e t h r o u g h a pip e
f l a n g e t h a t i s welded t o t h e t o p o f t h e v e s s e l .
The a i r e x i t s t h e ta n k
Figure 2-4
S t i l l i n g Tank
14
t h r o u g h t h e end as i s shown in F ig u r e 2 . 4 .
At t h e downstream end o f t h e
s t i l l i n g ta n k , d i r e c t l y before the a i r e n t e r s the t e s t s e c ti o n , is a
honeycomb' f l o w s t r a i g h t e n e r .
Each p a s s a g e i n t h i s f lo w s t r a i g h t e n e r
measured o n e - h a l f , i n c h s q u a r e in c r o s s - s e c t i o n and i s t h r e e in c h e s l o n g .
The p us p os e o f t h e fl o w s t r a i g h t e n e r i s t o b r e a k up Targe e d d i e s t h a t
may be coming from t h e s t i l l i n g t a n k . . I t does l i t t l e t o damp o u t . s m a l l
.scale turbulence.
These small s c a l e f l u c t u a t i o n s a r e damped o u t t o some
d e g r e e by t u r b u l e n c e f i l t e r s c r e e n s t h a t a r e l o c a t e d a t ea ch end o f t h e
flow s t r a i g h t e n e r .
The u p s tr e a m s c r e e n i s 32 mesh, .006 in c h d i a m e t e r
w i r e s w h i l e t h e downstream s c r e e n i s 40 mesh, .006 in c h d i a m e t e r w i r e s
(see Figure 2.5)
Hot w i r e measurements o f t h e t u r b u l e n c e c o n t e n t o f t h e f r e e s t r e a m
were made when t h e f a c i l i t y was a t i t s p r e v i o u s l o c a t i o n .
The t u r b u ­
l e n c e l e v e l was measured a t both Tow (420 mm Hg) and h ig h (735 mm Hg)
stagnation pressures.
The e n e r g y s p e c tr u m o f t h e t u r b u l e n c e l e v e l was
taken a t th e se p re s s u re s p rim a rily to ensure t h a t the frequency le v el of
t h e e l e c t r o n i c s was a d e q u a t e and i n f e r t h e s c a l e o f t h e d i s t u r b a n c e s .
The mass f l o w f l u c t u a t i o n s were 1 .4 7 p e r c e n t f o r t h e low p r e s s u r e and
.82 p e r c e n t f o r t h e h ig h p r e s s u r e .
The a b s o l u t e t e m p e r a t u r e f l u c t u a t i o n s
were .42 p e r c e n t f o r t h e low p r e s s u r e and .23 p e r c e n t f o r t h e high
pressure.
The c o r r e l a t i o n c o e f f i c i e n t between t h e s e two f l u c t u a t i o n s
was found t o be + . 8 7 f o r t h e low p r e s s u r e and + . 5 0 f o r t h e h ig h ! p r e s s u r e .
T h e s e : f i g u r e s a r e a f a c t o r o f two o r t h r e e h i g h e r t h a n was o r i g i n a l l y
2
Subsonic
D iffuser
Downstream
T ransition
Extension
Block
• Supersonic
D iffuser
N o zz le
Bloc k
Upst rea m
T ransition
S traighte n e r and
turbulence
F ilters
S tilling
Tank
Figure 2-5
Supersonic S e ctio n s
16
d e s i r e d , b u t t h e y s t i l l r e p r e s e n t an a c c e p t a b l e s tr e a m t u r b u l e n c e l e v e l .
(
Th at i s , t h e y r e p r e s e n t a l e v e l c o n s i d e r a b l y lower th a n t h a t which i s
found in a t u r b u l e n t wake, which i s what t h i s t u n n e l was d e s i g n e d t o
study.
section.
The lev el, has a l s o been found t o be u nif or m t h r o u g h o u t t h e t e s t
Hot w i r e t e s t s have s u g g e s t e d t h a t t h e s e . m e a s u r e m e n t s have n o t
1
changed t o any g r e a t d e g r e e .
2.5
UPSTREAM TRANSITION SECTION
The g e o m e t r i c a l t r a n s i t i o n between t h e 6 - i n c h c i r c u l a r c r o s s - s e c t i o n
a t t h e e x i t o f t h e s t i l l i n g t a n k and t h e 3.1 x 6 inc h r e c t a n g u l a r s e c t i o n
t h a t forms t h e t e s t s e c t i o n i n l e t ch a n n e l i s hand le d by t h e u p s tr e a m
A 3 x 6 in c h c h a n n e l was f i r s t m i l l e d a l o n g t h e
tra n s itio n section.
a x i s o f t h i s s e c t i o n , f o l l o w e d by a 6 - i n c h bas e d i a m e t e r r i g h t a n g l e
v
*
cone be in g m i l l e d a l o n g t h e same a x i s .
The f l u i d e n t e r s t h r o u g h t h e
p l a n e o f t h e c o n e , c o n v e r g e s g e n t l y to w a r d i t s ap ex , th e n g r a d u a l l y
t r a n s i t s in to the re c ta n g u la r ch a n n e l.
The i n t e r s e c t i o n o f t h e cone and t h e t r i a n g l e forms a s h a r p edge
and i t was o r i g i n a l l y f e a r e d t h a t t h i s would g e n e r a t e v o r t i c e s .
t u n a t e l y , t h e edge i s n e a r l y p a r a l l e l
Fo r­
t o t h e flow and t h e flo w component
normal t o i t i s p r a c t i c a l l y n o n e x i s t e n t .
T o t a l t e m p e r a t u r e and t o t a l p r e s s u r e measurements o f t h e t u n n e l a i r
fl o w a r e p er fo rm e d by p r e s s u r e and t e m p e r a t u r e probe c o n n e c t i o n s i n t h i s
s e c t i o n . . A l s o , t h e s u p p o r t s t r u t f o r a x i s y m m e t r i c t e s t models i s
-
17
lo c a te d in t h i s s e c ti o n .
2.6
NOZZLE
The wind t u n n e l t e s t s e c t i o n c o n s i s t s o f a r e c t a n g u l a r p a r a l l e l
pi p e d made o f b r a s s and c o n t a i n s a tw o - d im en s io n al DeLaval. n o z z l e , a
s h o r t s t r a i g h t s e c t i o n , and a s u p e r s o n i c d i f f u s e r , a l l made o f aluminum.
The n o z z l e c o o r d i n a t e s were computed by a p p r o p r i a t e s c a l i n g from a
Mach 3 n o z z l e c a l c u l a t i o n s u p p l i e d by t h e J e t P r o p u l s i o n L a b o r a t o r y
(JPL).
The JPL d e s i g n was f o r a 20 x 20 in c h s q u a r e n o z z l e e x i t w it h a
t u r b u l e n t boundary l a y e r growing a l o n g t h e n o z z l e w a l l .
For r e a s o n s o f
e x p e d i e n c y , t h e JPL c o o r d i n a t e s were r e du ce d by a f a c t o r o f 3:20 t o
o b t a i n a 3 x 3 in c h u n if or m o r i n v i s c i d flo w c o r e .
The t u r b u l e n t boun-
d a r y l a y e r t h i c k n e s s was red uc e d by a f a c t o r o f ( 3 : 2 0 )
'
to account fo r
t h e usual s c a l i n g o f t h e t u r b u l e n t boundary l a y e r w it h l i n e a r d i s t a n c e .
No a c c o u n t o f t h e Reynolds Number was t a k e n i n t h i s s im p l e t r a n s f o r m a ­
tion of coordinates.
In t h i s manner, t h e a c t u a l d i s t a n c e from th e
f l o o r t o t h e c e i l i n g i n t h e t e s t s e c t i o n was found t o be 3 . 2 i n c h e s f o r
'
a un if or m flo w c o r e m e as ur i ng 3 in c h e s h i g h . The n o z z l e c o o r d i n a t e s a r e
give n i n Ta bl e 2 . 1 .
The d i s t a n c e between s i d e w a l l s , c o u l d be c a l c u l a t e d p r e c i s e l y o n ly
by a c c o u n t i n g f o r t h e boundary l a y e r growth alo ng t h e s e w a l l s which
remained p l a n e and p a r a l l e l , a v e r y d i f f i c u l t c a l c u l a t i o n .
Instead, a
s i d e w a l l - t o - s i d e w a l l d i s t a n c e o f 3.1 i n c h e s was chosen as an e m p i r i c a l
18
T ab l e 2-1
N ozzle C oordinates
plane o f symmetry).
x (inches)
0.0
0.1500
0.2999
0.4499
0:5999
. 0.7499
0.8999
1.0499
1.1998
1.3498
I .4998
1.6498
1.7998
1.9498
2.0997
2.2497
2.3997
• 2.5497
2.6996
2.8497
2.9996
3.1496
3.2996
3.4496
3.5996
3.7185
3.8224
3.9300
4.0414
4.1567
4.2761
4.3997
4.5277
4.6600
4.7970
4.9386
5.0851
5.2364
5.3932
5.5551
(X i s 0 a t th e t h r o a t , Y i s 0 a t th e
|
y (inches)
.3541
.3551
.3581
.3629
.3696
.3779
.3879
.3995
.4124
.4268
.4426
.4595
.4776
. .4969
.5170
.5382
.5600
.5820
.6060 .
.6296 .
.6545
.6793
.7046
.7301
.7558
.7762
.,.7942
.8127
.8318
.8515
;8720
.8930
.9144
.9366
.9592
.9824
1.0061
1.0300
1.0544
1.0792
!
y
x (inches)
5.7223
5.8951
6.0735
6.2577
6.4479
6.6440
' 6.8464
7.0551
7.1618
7.2703
7.4920
7.7204
7.9559
8.1987 .
8.4488
8.7066
8.9724
9.2434
9.5167
9.7922
10.0692
10.3475
10.6277
10.9074
11.1883
11.4693
11.7501
12.0304
12.3100
12.5888
12.8661
13.1419
13.4157
13.6882
13.9577
14.2257
14.4906
14.7605
15.0125
15.1411
■
inches)"
1.1043
.1296
.1551
.1807
.2064
.2320
.2575
.2827
.2952
.3077
.3322
.3563
.3799
.4030
.4254
.4472
.4682
.4882
.5071
.5247
.5402
.5564
.5706
1.5836
1.5956
1.6066
1.6167
1.6258
1.6341
1.6415
1.6483
1.6543
1.6598
1.6647
1.6691
1.6730
1.6766
I .6798
.1.6829
1.6844
19
compromise.
E q u a l l y e m p i r i c a l was t h e d e s i g n o f t h e s e c t i o n between t h e
t e s t s e c t i o n e n t r a n c e and t h e n o z z l e t h r o a t .
The c o n t o u r chosen al lo w s
t h e flow t o co nv erg e smooth ly toward t h e t h r o a t and i s t a n g e n t t o t h e
nozzle contour a t th e nozzle t h r o a t .
S i x t e e n .024 in c h s t a t i c p r e s s u r e p o r t s a r e d r i l l e d on t h e lower
n o z z l e b lo c k e x t e n d i n g a l o n g i t s c e n t e r l i n e b e g i n n in g a t t h e e x a c t l o c a ­
tio n of the t h r o a t .
throat.
The f i r s t p o r t i s 1 .1 4 i n c h e s downstream o f t h e
The p o r t s a r e spa ced one in c h a p a r t t h e r e a f t e r .
The d eg r ee o f
cho king can be e a s i l y d e t e r m i n e d by g l a n c i n g a t a Mercury manometer bank
t h a t i s l o c a t e d n e x t t o t h e s t i l l i n g t a n k and c o nn ec te d t o t h e s e p r e s ­
sure p o rts.
A 5 - i n c h long aluminum e x t e n s i o n in t h e form o f s e p a r a t e upper and
lowe r b l o c k s , i s l o c a t e d im m ed ia te ly downstream o f t h e n o z z l e .
These
b l o c k s form a s t r a i g h t s e c t i o n and e x t e n d t h e u s e f u l t e s t a r e a .
2.7
SUPERSONIC DIFFUSER
The f i x e d s u p e r s o n i c d i f f u s e r was d e s i g n e d by sim p ly c o n t r a c t i n g
t h e flow channel t o t h e minimum d i f f u s e r t h r o a t a r e a a l l o w i n g a normal
shock t o be swallowed d u r i n g t h e s t a r t i n g o p e r a t i o n .
The p r e s s u r e r a t i o
r e q u i r e d t o run t h e t u n n e l w i t h t h i s d i f f u s e r was deduced from d a t a
ac c um ul a te d from o t h e r wind t u n n e l s and found t o be a b o u t 5 . 2 ,
4
The p e r t i n e n t a r e a r a t i o , w i t h o u t boundary l a y e r c o r r e c t i o n s , i s
found t o be:
20
Nozzle T h r o a t Area _ 0 . 7 0 8 _ n
D i f f u s e r T h r o a t Area ” 1.35 0 "
D i f f u s e r boundary l a y e r c o r r e c t i o n s were n o t made.
Instead the
d i f f u s e r t h r o a t was e n l a r g e d by m i l l i n g t h e apex o f i t s t r i a n g u l a r p r o f i l e so t h a t t h e p r o f i l e became t r a p e z o i d a l .
Rough c o m p u t a t i o n s showed
t h a t by t h i s means t h e d i s p l a c e m e n t t h i c k n e s s o f t h e boundary l a y e r , as
well a s t h e model s u p p o r t s t r u t s p a s s i n g t h r o u g h t h e n o z z l e t h r o a t ,
c o u l d be a c c o u n t e d f o r .
2.8
DOWNSTREAM TRANSITION '
The t r a n s i t i o n from t h e downstream t e s t s e c t i o n end back t o a 6-
.
in c h d i a m e t e r p i p e i s ac c o m p li sh e d with, t h e same c o n f i g u r a t i o n as i s
d e s c r i b e d i n S e c t i o n 2 . 5 (Upstream T r a n s i t i o n ) .
The s e c t i o n i s simply
t u r n e d around t o a l l o w t r a n s i t i o n back t o t h e round p i p i n g c o n f i g u r a t i o n .
Three f o u r - i n c h p i p e s t u d s a r e a r r a n g e d in a "T" around t h e c e n t e r l i n e of the tunnel through t h i s t r a n s i t i o n .
These s t u d s a r e equi ppe d
w i t h f o u r - i n c h p ip e f l a n g e s and a l l o w a c c e s s t o t h e flo w channel f o r
instrum entation.
The X - a c t u a t o r mechanism i s l o c a t e d on t h e to p f l a n g e
of th is section.
2.9
SUBSONIC DIFFUSER '
Thi s s e c t i o n o f t h e t u n n e l i s l o c a t e d d i r e c t l y downstream o f t h e
downstream t r a n s i t i o n s e c t i o n .
I t i s a c o n i c a l l y - s h a p e d t u b e , 36 in c h e s
l o n g , d i v e r g i n g from a 6 - i n c h d i a m e t e r a t t h e downstream t r a n s i t i o n
21
c o n n e c t i o n t o a 12- i n c h d i a m e t e r a t t h e d i f f u s e r e x i t f o r c o n n e c t i o n t o
t h e s t a n d a r d 12- i n c h wind t u n n e l plumbing.
A 12 - in c h d i a m e t e r b e l l o w s ex p a n s io n j o i n t downstream o f t h i s s e c ­
t i o n a l l o w s enough i n - l i n e movement t o remove and r e p l a c e any wind t u n \
.
.
.
nel component from t h i s p o i n t t o t h e s t i l l i n g t a n k e x i t .
2 . 1 0 VACUUM SYSTEM
A R o o t s - C o n n e r s v i l i e No. 36-RGVS-2 vacuum pump g e n e r a t e s t h e flow
i n t h e wind t u n n e l .
The pump c o n s i s t s o f two Roots b lo w er s con n ec te d
on t h e same s h a f t w it h a 200 Horsepower Westinghouse 480 V o l t , t h r e e phase i n d u c t i o n m o t o r , t u r n i n g a t 890 r e v o l u t i o n s p e r m in ut e ( s e e F ig u r e
2 . 6) .
Near t h e f i r s t s t a g e i n l e t , a check v a l v e i s l o c a t e d t o p r o t e c t
a g a i n s t pump o v e r l o a d i n g s h o u ld an e x c e s s i v e vacuum o c c u r .
I f t h e pump
i n l e t p r e s s u r e goes below 48 mm Hg t h i s v a l v e w i l l open and a l l o w a i r
i n t o t h e i n l e t o f t h e b l o w e r , s i n c e d an ge r o u s o v e r h e a t i n g w i l l o c c u r i f
t h e pump o p e r a t e s below t h i s p r e s s u r e f o r any o t h e r th a n a v e r y s h o r t
period o f time.
The openi ng o f t h e check v a l v e s h o u ld n o t be co n fu se d
w it h t h e low a i r p r e s s u r e s a f e t y shutdown s e q ue n ce .
(The low a i r p r e s ­
s u r e shutdown o c c u r s when t h e b u i l d i n g s u p p l y p r e s s u r e i s t o o low t o
o p e r a t e t h e p n e u m a t i c a l l y c o n t r o l l e d d e v i c e s on t h e wind t u n n e l . )
check v a l v e does n o t s h u t t h e sy stem o f f when i t open s.
The
I t s o n ly f u n c ­
t i o n i s t o p r e v e n t o v e r h e a t i n g o f t h e pumps due t o e x c e s s i v e l y Tow i n l e t
F i g u r e 2-6
'I
SWT Pump
23
pressure.
J u s t u p s tr e a m from t h e i n l e t t o t h e f i r s t s t a g e o f t h e vacuum pumps
i s t h e t u n n e l bypass v a l v e .
Th is i s a p n e u m a t i c a l l y o p e r a t e d v a l v e t h a t
a l l o w s a t m o s p h e r i c a i r i n t o t h e f i r s t s t a g e o f t h e vacuum pumps.
valve i s closed except during the s ta r t u p o f the t u n n e l.
Th is
I t opens a s
t h e motor i s s t a r t e d t o a l l o w t h e b lo w e r s t o g e t up t o speed w i t h o u t
ha v i n g t o " p u l l " a vacuum t h r o u g h o u t t h e e n t i r e wind t u n n e l c i r c u i t .
Orice t h e b lo w er s have r e a c h e d o p e r a t i n g s p e e d , t h e b y p as s v a l v e i s s h u t and t h e t u n n e l i s in o p e r a t i o n .
The b lo w er s a r e w a t e r s e a l e d , .
t h e a i r d u c t on t h e i n l e t s i d e .
Each b lo w e r has a p i p e r u n n in g i n t o
Water i s d i r e c t e d , i n t h e form o f a
fan-shaped sp ray , over th e su rfa c e o f th e r o t o r to provide s e a lin g .
A Tow w a t e r p r e s s u r e s a f e t y shutdown s eq u en ce has been i n s t a l l e d
and i s a c t i v a t e d s h o u ld t h e w a t e r p r e s s u r e i n t h e l i n e s f e e d i n g t h e
b lo w er s f a l l
below 25 p s i .
At t i m e s , t h i s shutdown has been a c t i v a t e d
by sudden momentary d r o p s in t h e w a t e r p r e s s u r e .
To p r e v e n t t h i s , i t
has become n e c e s s a r y t o i n s t a l l a s u r g e t a n k t o m a i n t a i n t h e p r e s s u r e i n
t h e w a t e r l i n e s d u r i n g t h e s e momentary p r e s s u r e d r o p s .
Thus , t h e w a t e r
p r e s s u r e must f a l l below 25 p s i and s t a y t h e r e f o r a f i n i t e p e r i o d o f
ti m e (a few s e c o n d s ) b e f o r e t h e low w a t e r p r e s s u r e shutdown i s a c t i v a t e d
The o i l system on t h e b lo w er s a l s o has two s a f e t y i n t e r l o c k s i n ­
s t a l l e d in i t , one f o r low o i l p r e s s u r e and a n o t h e r f o r high o i l te m p e r a
ture.
The mot or w i l l a u t o m a t i c a l l y s h u t o f f i f e i t h e r one o f t h e s e
t
-
24
s eq ue n ce s i s a c t i v a t e d .
A w arning l i g h t w i l l a l s o be d i s p l a y e d on t h e
main c o n t r o l panel s h ou ld e i t h e r one o f t h e s e problems a r i s e .
When t h e b lo w er s a r r i v e d h e r e a t MSU t h e y were v e r y r u s t e d .
This
had o c c u r r e d b ec a u se i n t h e p a s t t h e y had been a l lo w ed t o remain i n a c ­
t i v e f o r long p e r i o d s o f time w i t h w a t e r i n them.
To p r e v e n t t h i s from
o c c u r r i n g a g a i n , a d r y shutdown seq uen ce has been i n s t a l l e d .
When t h e
d r y shutdown i s a c t i v a t e d t h e s e a l i n g w a t e r flow t o t h e blow ers i s s h u t
o f f and a i r i s blown t h r o u g h t h e w a t e r sy ste m around t h e blo we rs and
th r o u g h t h e s p r a y n o z z l e s t h e m s e l v e s .
Th is i s done t o p r o t e c t t h e
blow ers from t h e c o r r o s i o n problems t h a t a r i s e when s t a g n a n t w a t e r i s
l e f t i n them.
A f t e r t h r e e m i n ut es o f o p e r a t i o n in t h e d r y shutdown mode
t h e motor a u t o m a t i c a l l y s h u t s o f f .
The d r y shutdown i s n o r m a l ly used
o n l y when t h e t u n n e l i s n o t going t o be r e s t a r t e d a g a i n f o r t h e r e s t o f
t h e day.
I n s i d e t h e motor i s a t h e r m i s t o r imbedded i n t h e a r m a t u r e windings
t h a t w i l l s h u t t h e motor o f f i f i t g e t s t o o h o t .
I f t h i s s h o u ld o c c u r ,
t h e r e w i l l be no i n d i c a t i o n o f t h e c a u s e o f t h e shutdown.
I t has been o b s e r v e d t h a t t h e n o z z l e s d i r e c t i n g t h e f a n - s h a p e d
s p r a y o v e r t h e l o b e s o f t h e blowers o f t e n g e t plugged due t o p a r t i c l e s
t h a t have been c a r r i e d a l o n g th r o u g h t h e w a t e r system.
When t h i s o c c u r s
t h e n o z z l e s must be t a k e n o u t and c l e a n e d .
The f i r s t i n d i c a t i o n o f l o s s o f w a t e r i s a t e m p e r a t u r e r i s e a t t h e
blo w er o u t l e t s .
Because o f t h e damage t h a t c o u l d r e s u l t t o t h e blowers
25
i f t h i s went u n n o t i c e d , t h e s e t e m p e r a t u r e s must be watched c o n t i n u o u s l y
while the tunnel i s in o p e ra tio n .
A f t e r t h e a i r has p a s s e d t h r o u g h t h e blowers', t h e wet e x h a u s t i s
d i r e c t e d i n t o a l a r g e d i s c h a r g e l i n e s i l e n c e r which removes some c o l l e c '
t e d w a t e r t o a '1d r a i n and r e d u c e s t h e pump d i s c h a r g e n o i s e .
A fte r leaving
t h e s i l e n c e r , t h e a i r i s d i r e c t e d up th r o u g h t h e c e i l i n g and i s d i s ­
c h a r g e d o u t s i d e i n t o t h e at m o s p h er e.
2.11 WIND TUNNEL X-Y-Z PROBE ACTUATORS
A p r o b e . a c t u a t o r sy ste m c a p a b l e o f moving a probe i n t h r e e d i r e c ­
t i o n s a t v a r i a b l e sp ee d s and a t c l o s e l y c a l i b r a t e d d i s t a n c e s i s i n s t a l l e d
i n t h e wind t u n n e l t e s t s e c t i o n .
P o s i t i o n i n g t o 0.001 in c h i s accom­
p l i s h e d w i t h d i r e c t g e a r e d mech anic al o u t p u t w h i l e an e l e c t r i c p o s i t i o n
o u t p u t i s p r o v i d e d by a 1 0 - t u r n h e l i p o t on each a x i s .
The a c t u a t o r
d r i v e s t h e e l e c t r i c mot ors w it h a s s o c i a t e d r e v e r s i b l e v a r i a b l e speed
control.
The v e r t i c a l a c t u a t o r i s eq u i p p ed w it h an a d j u s t a b l e l i m i t
syst em.
A c t u a t o r spqeds ang l i m i t s o f t r a v e l a r e given i n Ta bl e 2 . 2 .
2 .1 2 SCHLIEREN SYSTEM
An 8- inc h p o r t a b l e S c h l i e r e n . system has been f a b r i c a t e d f o r o b s e r ­
ving t h e wind t u n n e l t e s t s e c t i o n f lo w .
The system c o n s i s t s o f two
wheeled t a b l e s s u p p o r t i n g a l l o p t i c s and e l e c t r o n i c s in a p r e - a l i g n e d '
position.
Two l i g h t s o u r c e s a r e used w i t h a s s o c i a t e d c o n d e n s e r s and
plane m irro rs providing e i t h e r continuous illu m in a tio n f o r o p tic a l
TABLE 2 . 2
A c t u a t o r Speeds and L i m i t s o f T r av e l
L i n e a r Speed
Axis
L i m it s o f Trav el
X
min
.
.003 i n / s e c
max
.0 70 i n / s e c
3
in
Y
.002 i n / s e c
.066 i n / s e c .
3
in
.016 i n / s e c
0 .4 0 in
Z
0.0
i n/sec
27
a l i g n m e n t and ti m ed p h o t o g r a p h y , o r a s p a r k s o u r c e f o r us e i n high speed
p h o to g r a p h y a t e x p o s u r e t i m e s o f 0 . 5 m i c r o s e c o n d s .
The 8 - in c h p a r a b o l i c
m i r r o r s c o v e r t h e wor king s e c t i o n a d e q u a t e l y w h i l e t h e i r 6 4 - i n c h f o c a l
l e n g t h a l l o w s a compact d e s i g n .
The camera i s o f f i x e d f o c a l l e n g t h
d e s i g n e q u i p p e d with, a s h u t t e r - d i a p h r a g m and P o l a r o i d back p ack .
Image
m a g n i f i c a t i o n a t t h e camera i s 0 . 7 3 , r e d u c i n g t h e e n t i r e S c h l i e r e n f i e l d
t o a 4 x 5 in c h P o l a r o i d pack f i l m s i z e .
O p t i c a l components employed i n
t h e s y st em a r e ground t o w i t h i n o n e - f o u r t h w av el e n g th o f Mercury l i g h t
p e r in c h w h i l e t h e t u n n e l t e s t s e c t i o n windows a r e o f s e l e c t e d s t r i a t i onf r e e p l a t e g l a s s p r o v i d i n g h ig h s y s t e m s e n s i t i v i t y and minimum d i s t o r ­
t i o n (see Figure 2 . 7 ) .
-
2 . 1 3 WIND TUNNEL PRESSURE STATION
v
The SWT i s e q u i p p e d w i t h a p r e s s u r e m e a s u r i n g s ys te m c a p a b l e o f
m o n i t o r i n g 12 s e p a r a t e i n p u t p r e s s u r e s .
The system i s e q u i p p e d w it h
r t h r e e Wal lac e and T i e r n a n a b s o l u t e p r e s s u r e gages and t h r e e impedence
type p re s s u re t r a n s d u c e r s .
P r e s s u r e gage A r e a d s from 0 t o 20 mm Hg, gage B r e a d s from 0 t o
100 mm Hg, and gage C r e a d s from 0 t o 400 mm Hg.
Pressure transducer
B r e a d s from 0 t o 50 mm Hg, t r a n s d u c e r c r e a d s from 0 t o 250 mm Hg, and
t r a n s d u c e r D r e a d s from 0 t o 750 nrn Hg.
The e l e c t r i c a l o u t p u t from
t h e s e t r a n s d u c e r s can be f e d i n t o v a r i o u s o t h e r p r e s s u r e - m o n i t o r i n g
e l e c t r o n i c co m pon ent s.
A p h o t o g r a p h o f t h e system i s shown i n ' .
X'-;.'-;
28
4
-—
3
^
KEY
1
2
3
4
5
L i g h t Source
S lit
M irrors
F i e l d o f View
Camera Box
6 Knife Edge
F i g u r e 2-7
S c h l i e r e n System
3
29
Figure 2-8
Wind Tunnel P r e s s u r e S t a t i o n
30
PRESSURE INPUTS
TOGGLE
VALVES
MANIFOLD
NEEDLE
VALVES'
0-100
TRANS­
DUCERS
VACUUM GAGES
RED
BLACK
GREEN
WHITE
TO ELECTRONICS
F i g u r e 2-9
Schematic o f P r e s s u r e S t a t i o n
( V o l t s do)
Voltage
Transducer C
10/2/80
E x i t a t i o n = 5 Vdc
Gain = 10
Pressure
F i g u r e 2-10
(mm Hg)
Example T r a n s d u c e r C a l i b r a t i o n
32
Figure 2-8.
A s c h e m a ti c o f t h e sy stem i s shown in F i g u r e 2 - 9 .
A typical
c a l i b r a t i o n c u r v e f o r t h e t r a n s d u c e r s i s shown in F i g u r e 2 - 1 0 .
I
CHAPTER 3
WIND TUNNEL PERFORMANCE
3.1
INTRODUCTION
B e f o r e any e x p e r i m e n t can be p e r f o r m e d i n a f a c i l i t y such a s t h e
MSU SWT, t h e v a r i o u s p a r a m e t e r s u n d e r which t h e e x p e r i m e n t i s t o be
c a r r i e d o u t must be o u t l i n e d .
For i n s t a n c e , one may wis h t o i n v e s t i g a t e
t h e b e h a v i o r o f a b o u nd ar y l a y e r o v e r a r a n g e o f s t a g n a t i o n t e m p e r a t u r e s
and p r e s s u r e s ( a r a n g e o f Reynolds Numbers)-.
t o d e t e r m i n e t h e r a n g e o f d a t a t h a t he n e e d s .
The e x p e r i m e n t e r w i l l have
He w i l l t h e n have t o
check t o s e e i f t h e f a c i l i t y t h a t he was p l a n n i n g on u s i n g i s c a p a b l e o f
s u p p l y i n g t h e n e c e s s a r y ran ge o f c o n d i t i o n s .
I f i t i s n o t , t h e n he must
e i t h e r modify h i s e x p e r i m e n t o r f i n d a n o t h e r f a c i l i t y .
sons,
For t h e s e r e a ­
i n f o r m a t i o n a b o u t t h e c o n d i t i o n s u n d e r which t h e SWT i s c a p a b l e o f
operating is v ita l ^
The pu rp os e o f t h i s c h a p t e r i s t o o u t l i n e t h e c o n ­
d i t i o n s u n d e r which t h e MSU SWT has been o b s e r v e d t o o p e r a t e .
T her e a r e s e v e r a l p a r a m e t e r s n o r m a l l y c o n s i d e r e d i n s u p e r s o n i c wind
tunnel t e s t i n g .
The p a r a m e t e r t h a t l i e s a t t h e r o o t o f a l l c o m p r e s s i b l e
flo w s i s t h e Mach Number.
Mach Number mea sur em ent s were t a k e n by two
means:
s t a t i c and s t a g n a t i o n p r e s s u r e m e as ur em ent s w i t h t o t a l p r e s s u r e
known.
S t a t i c p r e s s u r e measurements were t a k e n a l o n g t h e l e n g t h o f t h e
n o z z l e . i n o r d e r t o o b s e r v e t h e change o f t h e Mach Number a l o n g t h e
nozzle.
The s t a g n a t i o n p r e s s u r e mea sure men ts were t a k e n b o th t o measure
t h e Mach Number t h r o u g h o u t t h e t e s t s e c t i o n (and t h u s v e r i f y t h e s t a t i c
p r e s s u r e m e a s u r e m e n t s ) , and t o check t h e f l o w u n i f o r m i t y i n t h e t e s t
34
section.
A nother p a r a m e t e r a f f e c t i n g t h e t u n n e l flow i s t h e s t a g n a t i o n tem­
perature.
Since, t h e MSU SWT i s eq u ip ped w i t h an a i r h e a t e r a t t h e i n l e t
a r an g e o f t e m p e r a t u r e s i s p o s s i b l e .
The b e h a v i o r o f t h e boundary l a y e r s i n t h e n o z z l e and t e s t s e c t i o n
i s , o f c o u rse , very im portant.
Boundary l a y e r p r o f i l e s a t one p o i n t
al o n g t h e n o z z l e have been t a k e n and a r e i n c l u d e d in t h i s c h a p t e r .
The fu ndamental p a r a m e t e r l i m i t i n g t h e ran ge o f o p e r a t i o n o f t h e
w i n d - t u n n e l i s t h e minimum p r e s s u r e r a t i o r e q u i r e d t o m a i n t a i n s u p e r ­
s o n i c flow .
The s t a g n a t i o n p r e s s u r e a t which s u p e r s o n i c flo w i s l o s t in
t h e t e s t s e c t i o n i s , o b v i o u s l y , t h e lo w er l i m i t on s t a g n a t i o n p r e s s u r e
i n t h i s wind t u n n e l .
Because o f i t s i m p o r t a n c e , t h i s p a r a m e t e r i s d e a l t
with in d e t a i l in the next s e c tio n of t h i s c h ap ter.
3.2
WIND TUNNEL PRESSURE RATIO
One o f t h e most i m p o r t a n t p a r a m e t e r s g o v e r n in g t h e o p e r a t i o n o f t h e
wind t u n n e l i s t h e minimum a t t a i n a b l e s t a g n a t i o n p r e s s u r e .
Th is comes
a b o u t b ec a u se a minimum p r e s s u r e r a t i o a c r o s s t h e t u n n e l i s r e q u i r e d i n
o r d e r t o m a i n t a i n s u p e r s o n i c flow i n t h e t e s t s e c t i o n . ^
The minimum a t ­
t a i n a b l e s t a g n a t i o n p r e s s u r e governs t h e r ang e o f t e s t s t h a t can be p e r ­
formed i n t h e t u n n e l .
T h i s , in t u r n , t e l l s us t h e l i m i t a t i o n s o f t h e
t u n n e l and w h e th e r o f n o t a given problem can be a d e q u a t e l y i n v e s t i g a t e d
in t h i s f a c i l i t y .
35
From o n e - d i m e n s i o n a l gas d yn am ic s t h e o r y a r e l a t i o n s h i p between t h e
i n l e t s t a g n a t i o n p r e s s u r e , Pq , and t h e pump i n l e t p r e s s u r e , P . , can be
derived.
T h i s i s a c c o m p l i s h e d by f i r s t e q u a t i n g t h e mass fl o w r a t e s a t
two d i f f e r e n t p o i n t s in t h e t u n n e l c i r c u i t .
The mass fl o w r a t e a t t h e
pump i n l e t i s :
m = P 1V1
(3-1)
where p i s d e n s i t y ; V i s volume f l o w r a t e , and t h e s u b s c r i p t " i " d e n o t e s
pump i n l e t c o n d i t i o n s .
I t i s a l s o known t h a t t h e flow a t t h e n o z z l e
th r o a t is sonic: .
.
*
*
*
m -= p a A
- (3-2)
where a i s t h e l o c a l speed o f s o u n d, A i s t h e c r o s s - s e c t i o n a l a r e a , and
t h e * d e n o t e s c o n d i t i o n s a t t h e n o z z l e t h r o a t , where t h e Mach Number i s
unity.
Assuming s t e a d y f lo w :
* * *
P a A
P 1V1
(3-3)
*
(3-4)
P 1V1
P0 pP t
a° A*
The z e r o s u b s c r i p t d e n o t e s s t a g n a t i o n c o n d i t i o n s . .We can now u t i l i z e
t h e e q u a t i o n o f s t a t e f o r a p e r f e c t g a s , a s well as t h e r e l a t i o n s h i p f o r
t h e speed o f sound i n a p e r f e c t g a s :
(YRT)
1/2
to ob tain the fo llo w in g :
Pi Vi
po
RTl-
Po a o RV
(3-5)
YRTo , 1 / 2 A *
where I r e p r e s e n t s t e m p e r a t u r e , R i s t h e u n i v e r s a l gas c o n s t a n t , and y
is the r a t i o o f s p e c if ic heats.
f o r a i r we g e t :
(F o r a i r , y = 1 . 4 . )
'
*
2 - = .6339
po
a*
| - = .9129
aO
The t h r o a t a r e a o f thw SWT i s :
.
2
A = 2 . 19 54 i n /
S i m p l i f y i n g e q u a t i o n ( 3 - 5 ) we o b t a i n :
P1V1
1/?
P0 = 2.3111 4 - 1 (T0 ) , / Z .
(3-6)
where t h e t e m p e r a t u r e s a r e in d e g r e e s R a n k i n e , t h e volume flo w r a t e i s
i n c u b i c f e e t p e r s e c o n d , and t h e p r e s s u r e s a r e i n any c o n s i s t e n t s e t o f
units.
Equation (3-6) thus gives th e " d riv in g " p re s s u re r a t i o :
(T ) 1/2
2.3111
Ki.
i
0
(3.7)
37
In o r d e r t o d e t e r m i n e t h i s r a t i o , i . e . t o f i n d P. f o r any g i v e n Pq , we
need t o have V\ a s a f u n c t i o n o f P . :
V1 - f t p , )
The r e l a t i o n s h i p i s o b t a i n e d from t h e m a n u f a c t u r e r ' s o p e r a t i n g c u r v e o f
t h e SWT pumps.
Th is c u r v e has been f i t u s i n g a l e a s t s q u a r e s c u r v e f i t
I
method , y i e l d i n g t h e r e s u l t :
.
<J. = 1 6 . 1 1 9 0 9 5 1 n ( P . ) - 7.5317078
(3-8a)
Vi = 45.658371 + -2.692 35 041 n( P.)
(3-8b)
Eq uat ion ( 3 - 8 a ) i s v a l i d f o r t h e ran ge o f pump i n l e t p r e s s u r e s between
35 mm Hg and 60 mm Hg.
E q u a t io n ( 3 - 8 b ) i s v a l i d f o r pump i n l e t p r e s s u r e s
g r e a t e r t h a n 60 mm Hg.
The g r a p h i c a l r e p r e s e n t a t i o n s o f e q u a t i o n s ( 3 -
8a and b) a r e shown on F i g u r e 3.1 su perim posed on t h e m a n u f a c t u r e r ' s
s p e c i f i c a t i o n f o r t h e pump v o l u m e t r i c c h a r a c t e r i s t i c V^(Pi ) . ■
Combining e q u a t i o n s ( 3 - 7 ) and ( 3 - 8 a and b ) , i t i s now p o s s i b l e t o
f i n d t h e d r i v i n g p r e s s u r e r a t i o , PqZP^ as a f u n c t i o n o f any ch os en s t a g ­
n a t i o n p r e s s u r e , w i t h t h e t e m p e r a t u r e s Tq and T. as p a r a m e t e r s .
Th is
has been done on F i g u r e s 3 . 2 t h r o u g h 3 . 6 f o r a s e t o f f o u r t y p i c a l *
* Using e q u a t i o n s ( 3 - 7 ) and ( 3 - 8 a and b ) , a F o r t r a n pr ogram named HEETLOSS has been w r i t t e n and i s p e r m a n e n tl y on t h e wind t u n n e l a c c o u n t . To
run t h e pr ogram, s i m p l y i n p u t t h e a s s i g n e d s t a g n a t i o n t e m p e r a t u r e in °F,
f o l l o w e d , on t h e same l i n e , by t h e assumed pump i n l e t t e m p e r a t u r e i n °F.
The program w i l l t h e n e x e c u t e and o u t p u t t h e p r e s s u r e r a t i o s t h a t a r e t o
be e x p e c t e d .
Volume Flow Rate
(CFM)
4000
C urvefit
Pump C h a r a c t e r i s t i c
3000
2400
I
20
50
,
100
I n l e t P r e s s u r e , P^ (mm Hg)
F i g u r e 3-1
C u r v e f i t o f Pump O p e r a t i n g Curve
150
n °“ breakdown Pr e d f c t 1
40
48 mm Hg
Required P ressu re R atio
P
F igure 3 -3
(mm Hg)
Flow Breakdown P r e d i c t i o n s
41
P
o
48 mm Hg
Required P ressu re R atio
P
F igure 3-4
(mm Hg)
Flow Breakdown P r e d i c t i o n s
42
48 mm Hg
Required P ressu re R atio
P
F igure 3-5
(mm Hg)
Flow Breakdown P r e d i c t i o n s
(mm Hg)
F i g u r e 3-6
O p e r a t i n g L i m it s According t o Temperature
44
operating stag n atio n tem peratures, T .
o
The maximum v a l u e shown o f T =
o
125°F i s c o n s i d e r e d t o be c l o s e t o t h e maximum a v a i l a b l e u s i n g t h e
present heater.
D i f f e r e n t g r a p h s a r e shown f o r ea ch o f f o u r pump i n l e t t e m p e r a t u r e s .
The T V s a r e assumed t o be a t 50, 75 , 100, and 125°F.
The e x a c t v a l u e
o f t h e pump i n l e t t e m p e r a t u r e i s h ar d t o e s t i m a t e s i n c e i t depends on
Tq and complex h e a t l o s s e s a l o n g t h e t u n n e l - c o n d u i t .
Presumably, the
ran ge o f T^ between 50 and 125°F c o v e r s a l l e x p e c t e d c a s e s f o r t h e i n l e t temperature.
As w i t h Tq , t h e g ra p hs a l l o w i n t e r p o l a t i o n w i t h i n t h i s
range.
The c u r v e s on F i g u r e s 3 . 2 th r o u g h 3 . 6 a l l o w t h e c o m p u t a t i o n o f P..
( o r P0ZPi ) f o r e ac h ch os en Pq (and t h e accompanying p a i r o f t e m p e r a ­
t u r e s ) and r e p r e s e n t t h e a v a i l a b l e p r e s s u r e r a t i o f o r d r i v f n g t h e SWT'.
The r e q u i r e d p r e s s u r e r a t i o , on t h e o t h e r hand, which w i l l d e t e r m i n e
t h e r e a l i s t i c r a n g e o f Pq , i s c o n t r o l l e d by a) t h e wind t u n n e l d i f f u s e r |
and b) t h e minimum p o s s i b l e o p e r a t i n g pump i n l e t p r e s s u r e a s s p e c i f i e d ,
by t h e m a n u f a c t u r e r .
C o n s i d e r i n g t h e d i f f u s e r l i m i t f i r s t , a minimum p r e s s u r e r a t i o i s
r e q u ire d in a l l
s u p e r s o n i c wind t u n n e l s b e f o r e "unchoked" f l o w e x i s t s i n
the t e s t s e c tio n .
T h i s r a t i o i s e x t r e m e l y complex t o c a l c u l a t e , b u t f o r
t h i s t u n n e l has been found e m p i r i c a l l y t o be on t h e o r d e r o f 5 . 2 . ^
This
i s t h e v a l u e shown by a h o r i z o n t a l l i n e drawn a c r o s s F i g u r e s 3 . 2 t h r o u g h f
3.5.
The p o i n t where ea ch d r i v i n g p r e s s u r e c u r v e c r o s s e s t h e d i f f u s e r
I
45
l i m i t g i v e s t h e minimum P
prescribed tem peratures.
f o r which SWT o p e r a t i o n i s p o s s i b l e f o r t h e
The minimum o p e r a t i n g Pq i S a r e t h u s p l o t t e d
vs . Tq ( w i t h T^ a s a p a r a m e t e r ) on F i g u r e 3 . 6 .
Note t h a t t h e s i t u a t i o n
improves ( t h a t i s Pq min. d e c r e a s e s ) when t h e s u p p l y t e m p e r a t u r e Tq i s .
t h e h i g h e s t , and when t h e h e a t l o s s e s i n t h e wind t u n n e l c i r c u i t a r e a t
a maximum (T^ i s t h e s m a l l e s t ) .
The p h y s i c a l r e a s o n f o r t h i s i s t h a t
when Tq i s h i g h , t h e mass flow t h r o u g h t h e n o z z l e t h r o a t i s low.
Thi s
a r i s e s from t h e f a c t t h a t d e n s i t y i s i n v e r s e l y p r o p o r t i o n a l t o t e m p e r a ­
ture.
At t h e same ti m e a low pump i n l e t t e m p e r a t u r e means t h a t t h e
pumps a r e a d m i t t i n g a high mass flo w r a t e , f o r t h e same reason."
s e t t i n g , t h e r e f o r e , pumping i s e f f i c i e n t and l o a d i n g i s l i g h t .
At t h i s
At t h e
o p p o s i t e e x t r e m e , t h e pump i s r e q u i r e d t o a b s o r b a h ig h f l o w r a t e a t a
r e d uc e d e f f i c i e n c y and t h e t u n n e l c h o k e s .
I t follows t h a t the best
o p e r a t i o n i s a c h i e v e d a t t h e h i g h e s t p o s s i b l e Tq s e t t i n g , and by c o o l in g ,
as much as p o s s i b l e , t h e d u c t s between t h e t e s t s e c t i o n and t h e pump
entrance.
: F o r ex am pl e, t h e b e n e f i t shown by t h e c u r v e s on F i g u r e 3 . 6
■
'
*
.-
■■ -I
I .
. c a u s e s a n - i n c r e a s e i n - t h e o p e r a t i n g r a n g e o f Pq a s f o l l o w s : I
Poor O p e r a t i o n :
Tq = T^ = IOO0F; P
p° max = 2.76
r o min
min. = 228 mm Hg;
Good O p e r a t i o n :
Tq = 125°F; T^ = 50°F; Pq min = 153 nm Hg;
P
o max _ a I o
'
.'^cTiirb " 4 ’ 12
which i s s u b s t a n t i a l . • Pq m a x , - i s ta k e n a s 630 mm Hg f o r t h e s e c a l c u l a tions.
The se cond t y p e o f l i m i t i s t h e minimum a b s o l u t e pump i n l e t p r e s •
,
s u r e , P. m i n . , s u g g e s t e d by t h e m a n u f a c t u r e r .
At v e r y low pump i n l e t -
p r e s s u r e s t h e l a t t e r s t a t e s t h a t t h e pumps may o v e r h e a t i f o p e r a t e d
c o n t i n u o u s l y , and t h e r e f o r e , one s h o u l d n o t o p e r a t e below t h i s p r e s s u r e ' .
A ls o , t h e che ck v a l v e d e s c r i b e d in C h a p t e r 2 opens when t h e pump i n l e t
p r e s s u r e goes t o o low, t h u s c a u s i n g flow breakdown in t h e t e s t s e c t i o n ,
t h i s minimum o p e r a t i n g p r e s s u r e i s in t h e n ei gh bo rho od o f 48 mm Hg.
In
F i g u r e s 3 . 2 t h r o u g h 3 . 5 , - t h i s l i m i t a p p e a r s as a s t r a i g h t l i n e p a s s i n g
th r o u g h t h e o r i g i n . . To t h e l e f t o f t h i s l i n e , t h e pump i n l e t p r e s s u r e
i s below t h e minimum.
For i n s t a n c e , i n
'
each c a s e ,
i t i s s ee n t h a t t h e c u r v e s c r o s s t h e
pump l i m i t l i n e b e f o r e t h e y c r o s s t h e d i f f u s e r l i m i t .
T h u s , one would
e x p e c t t h e c a u s e o f f lo w breakdown in t h e s e c a s e s t o be t h e che ck v a l v e
o p e n i n g . . The e x a c t p r e s s u r e a t which t h e check v a l v e op ens i s n o t known
and i t i s s p e c u l a t e d t h a t i t coul d v a r y between 35 and 60 mm Hg.
3 .3
PRESSURE RATIO OBSERVATIONS
E x p e r i m e n t a l o b s e r v a t i o n s o f t h e wind t u n n e l p r e s s u r e r a t i o a r e
p l o t t e d on F i g u r e 3 . 7 f o r two s t a g n a t i o n t e m p e r a t u r e s .
The pump i n l e t
t e m p e r a t u r e has n o t been o b s e r v e d t o v a r y a g r e a t d ea l from t h e s t a g n a ­
tio n tem perature ( u s u a lly le s s t h a t 5 °F ).
T h e r e f o r e , t h e c u r v e s on
F i g u r e s 3 . 2 t h r o u g h 3 . 5 which i n d i c a t e no h e a t l o s s , t h a t i s , Tq = T . ,
a re expected to b e t t e r p r e d i c t th e performance o f th e t u n n e l .
T em pe r at u re i s o b s e r v e d t o p l a y a m a j o r r o l e in fl o w breakdown, a s
was p r e d i c t e d by t h e t h e o r y p r e s e n t e d i n S e c t i o n 3 . 2 .
As can be seen
from i n s p e c t i o n o f F i g u r e 3 . 7 , t h e flo w breakdown f o r a s t a g n a t i o n tem­
p e r a t u r e o f 75°F o c c u r s a t a d r i v i n g p r e s s u r e r a t i o o f a b o u t 4 . 8 8 .
It
o c c u r s when t h e c u r v e c r o s s e s t h e minimum pump i n l e t p r e s s u r e c u r v e ,
P. = 48 mm Hg.
i
T h e r e f o r e , in t h i s c a s e , fl o w breakdown i s a t t r i b u t e d t o
ope ning o f t h e ch ec k v a l v e and n o t t o r e a c h i n g t h e t u n n e l ' s minimum r e ­
q u i r e d d r i v i n g p r e s s u r e r a t i o , even though t h e p r e s s u r e r a t i o o f 4 . 8 8 i s
well below t h e p r e d i c t e d minimum o f 5 . 2 .
At t h e h i g h e r t e m p e r a t u r e , Tq = T^ = . IOO0F, flow breakdown o c c u r s
a t a p r e s s u r e r a t i o o f 5 . 4 , which i s s u b s t a n t i a l l y above t h e p r e d i c t e d
minimum.
In t h i s c a s e , however, fl o w breakdown c a n n o t be a t t r i b u t e d t o
op eni ng o f t h e che ck v a l v e s i n c e t h e pump i n l e t p r e s s u r e i s w el l above
48 mm Hg a t t h e p o i n t where ch ok in g o c c u r s .
T h i s was, i n f a c t , o b s e r v e d
The o n l y o t h e r p o s s i b l e r e a s o n f o r flo w breakdown i s t h e d r i v i n g p r e s s ­
u r e r a t i o i s l e s s th a n t h e minimum p r e s s u r e r a t i o r e q u i r e d f o r t h e s e
48
• - T
100 F
Theory ( T
48 mm Hg
Required P ressu re R atio E stim ate
XX- Flow Breakdown
Po (mm Hg)
F i g u r e 3-7
O b s e r v a t i o n s o f Flow Breakdown
49
conditions.
ratio
This le a d s .o n e to the co n c lu sio n t h a t th e d r iv in g p re s s u re ,
i s d e p e n d e n t on t h e t e m p e r a t u r e o f t h e a i r s t r e a m .
This hypo­
t h e s i s ha s b e e n s u p p o r t e d by o t h e r o b s e r v a t i o n s of. t h e t u n n e l
not p resen te d in t h i s
section.
(The se o b s e r v a t i o n s t o o k p l a c e when
p e r f o r m i n g o t h e r e x p e r i m e n t s , such a s t h e s t a t i c
measurements o f S e c tio n 3 . 5 ) .
th a t are
p r e s s u r e Mach Number
As t h e t e m p e r a t u r e i s
in c re a se d , the
f l o w b r e a k s down a t a h i g h e r p r e s s u r e r a t i o . - ' T h i s o b s e r v a t i o n ca n
be e x p l a i n e d t o some d e g r e e by t h e c o n c l u s i o n r e a c h e d i n S e c t i o n 3 . 2
t h a t a t t h e l o w e r pump i n l e t t e m p e r a t u r e s t h e pumping e f f i c i e n c y i s
somewhat e n h a n c e d .
The c o n c l u s i o n ^ o n e r e a c h e s from a l l
of th is
is
t h a t t h e minimum
p r e s s u r e r a t i o o f . 5 . 2 i s by no means an a b s o l u t e g u i d e l i n e .
w ill
Choking
occur in t h i s neighborhood but th e e x a c t p r e s s u r e r a t i o t h a t w ill
c a u s e f l o w bre ak d o w n i s c o m p l i c a t e d t o p r e d i c t , a n d w i l l
tem perature.
depend on t h e
The pump i n l e t p r e s s u r e o f .48 mm Hg i s a good p r e d i c t i o n
o f when t h e c h e c k v a l v e w i l l o p en .
Fo r a g r e a t many o f t h e
experi­
ments on t h i s t u n n e l i t w i l l be t h i s p a r a m e t e r t h a t c a u s e s t h e tu nn el
t o c h o ke , e s p e c i a l l y when t h e s t a g n a t i o n t e m p e r a t u r e i s . low.
F in ally ,
i t s h o u l d be n o t e d t h a t t h e s e r e s u l t s w e r e o b t a i n e d w i t h
t h e t e s t s e c t i o n em pty .
I t is doubtful
t h a t t h e minimum p r e s s u r e s t h a t
w e r e a t t a i n e d c o u l d h a v e been r e a c h e d i f l a r g e m o d e l s o r p r o b e s w e r e
p o s itio n e d in th e t e s t s e c tio n .
50
I
For t h e r e a s o n s o u t l i n e d ' a b o v e , t h e c o n c l u s i o n i s r e a c h e d t h a t one
s h o u ld n o t p l a n on b e i n g a b l e t o run t h e t u n n e l a t s t a g n a t i o n p r e s s u r e s
below 300 mm Hg.
P r e s s u r e s lo w e r t h a n t h i s can be o b t a i n e d u n d e r c e r ­
t a i n c o n d i t i o n s , b u t a t . o t h e r t i m e s may be u n a t t a i n a b l e .
3.4
STATIC PRESSURE MEASUREMENTS
Along t h e b o t t o m s u r f a c e o f t h e n o z z l e t h e r e a r e 1 6 . 0 2 4 in c h h o l e s
d r i l l e d i n t h e n o z z l e s u r f a c e and l o c a t e d h al fw ay between t h e s i d e w a l l s
which a r e u s e d f o r m e as ur e m en t o f s t a t i c p r e s s u r e a l o n g t h e n o z z l e .
These h o l e s s t a r t a t t h e n o z z l e t h r o a t , t h e f i r s t one downstream i s l o ­
c a t e d 1 . 1 4 i n c h e s , from t h e t h r o a t , and t h e y a r e s p a c e d one i n c h a p a r t
thereafter.
Thes e p o r t s a r e n o r m a l l y c o n n e c t e d t o a Mercury manometer
bank t h a t i s l o c a t e d n e a r t h e s t i l l i n g t a n k i n f u l l view o f t h e o p e r a t o r .
.
•
For t h e s t a t i c p r e s s u r e m e as ur e m en ts d e s c r i b e d i n t h i s s e c t i o n , t h e
p o r t s were c o n n e c t e d t o t h e wind t u n n e l p r e s s u r e s t a t i o n .
S t a t i c p r e s s u r e m e as ur e m en ts were t a k e n f o r se v en s t a g n a t i o n p r e s - ,
s u r e s , r a n g i n g from 600 down t o 300 mm Hg.
The Mach Number was d ed uce d
from t h e i s e n t r o p i c r e l a t i o n s h i o between s t a t i c and s t a g n a t i o n p r e s s u r e
(measured i n t h e u p s t r e a m t r a n s i t i o n s e c t i o n ) f o r an i d e a l
gas:
where Pq i s t h e s t a g n a t i o n p r e s s u r e , P i s t h e s t a t i c p r e s s u r e , and y i s
the r a ti o o f s p e c if i c h eats
(y = 1 . 4 f o r a i r ) .
The r e s u l t s a r e p l o t t e d
51
on F i g u r e 3 . 8 and t a b u l a t e d i n Ta bl e 3 . 1 .
3.5
STATIC PRESSURE MEASUREMENT RESULTS
The Mach Numbers o b t a i n e d , from t h e s e measurements a r e lo w er than
one would e x p e c t from i n v i s c i d flow t h e o r y , a s i s i l l u s t r a t e d in F ig u r e
3 .8 ..
Thi s was n o t u n e x p e c t e d , however, s i n c e t h e flow i s n o t t r u l y i n ­
v i s c i d and t h e r e i s a boundary l a y e r growing al o n g t h e n o z z l e w a l l .
The Mach Number i s o b s e r v e d t o i n c r e a s e s l i g h t l y a s t h e s t a g n a t i o n
p r e s s u r e d e c r e a s e s u n t i l a c e r t a i n p o i n t where t h e Mach Number r e a c h e s a
maximum and b e g i n s t o d e c r e a s e s l i g h t l y as t h e s t a g n a t i o n p r e s s u r e i s
d e c r e a s e d f u r t h e r ( s e e F ig u r e 3 . 9 ) .
For i n v i s c i d i d e a l g a s s e s , t h e o n ly
f a c t o r a f f e c t i n g t h e Mach Number i s t h e c r o s s - s e c t i o n a l a r e a o f t h e flow
chann el in r e l a t i o n t o t h e c r o s s - s e c t i o n a l a r e a where t h e Mach. Number i s .
equa l t o u n i t y .
The flo w a r e a i s n o t r e a l l y t h e e n t i r e a r e a o f th e
channel s i n c e n e a r t h e wall t h e flow i s n o t i n v i s c i d and a boundary
l a y e r w i l l be growing.
The a r e a o f the. channel must be m o d i f i e d t o a c ­
c o u n t f o r t h e d i s p l a c e m e n t e f f e c t o f t h e boundary l a y e r .
Th is i s accom­
p l i s h e d by t a k i n g i n t o a c c o u n t t h e d i s p l a c e m e n t t h i c k n e s s o f t h e boundary
l a y e r , which i s d e f i n e d a s t h e d i s t a n c e t h e wall must b e d i s p l a c e d in
o rd e r f o r th e i n v i s c i d s o lu ti o n to c o r r e c t l y p r e d i c t the c h a r a c t e r i s t i c s
o f t h e flow.
The m a th em a ti c al d e f i n i t i o n o f t h i s q u a n t i t y i s a s f o l l o w s :
•
5 *
=
K 0O
CO
d y
52
Ta bl e 3-1
S t a t i c P r e s s u r e Nozzle C a l i b r a t i o n
D i s t a n c e . Mach.
From
Number
Throat
(P =600
( i n c h e s ) mrrrHg)
Mach.
Number
(P =550
mm°Hg)
Mach
Number
(P-=500
mnrHgj)
Mach
Number
(P =450
mnr Hg)
Mach
Number
(Pn=400.
mm°Hg)
Mach
Number
(P =350
mm°Hg)
Mach
Number
(P =303
mnrHg)
15.14
2:965
2.991
3.00 0
3. 0 0 0
2.971
2.94 3
2.934
14.14
2.97 9
2.99 5
3.007
.3.009
2.982
2.9 5 8
2.94 8
13.14
2.951
2.97 3
2.980
2.986
2.959
2. 9 3 3
2.938
12.1 4
2.952
2.96 9
2.974
2.9 8 4
2.93 4
2.93 3
2.916
11.14
2.91 7
2.932
2.940
2.94 7
2.900
2. 9 1 4
2.866
10.14
2.869
2.886
2.889
2.89 8
2.855
2.871
2.850
9.14
2.821
2.827
2.83 0
2.84 5
2.798
2. 8 2 8
2.793
8.14
2.741
2.771 .
2.75 4
2.77 3
2.742
2.754
2.72 8
7 .1 4
2.70 2
2.729
2.721
2.73 3
2.71 3
2.711
2.696
6.14 .
2.615
2.64 3
2.636
2.6 6 0
2.633
2. 6 3 0
2.615
53
Design Mach Number
H»ch Number (M)
Ran^e o f Data
Mach Number From Area Change
10 • 12
D istan ce From Throat (in c h e s )
F i g u r e 3-8
R e s u l t s o f S t a t i c P r e s s u r e - Te s t s
MACH NUMBER (M)
54
STAGNATION PRESSURE
F i g u r e 3-9
(Pq )
E f f e c t o f S t a g n a t i o n P r e s s u r e on Mach
Number
(X = 14.14 i n c h e s )
55
where Uoo i s t h e f r e e s t r e a m v e l o c i t y , u i s t h e v e l o c i t y a t any given
p o i n t , pa, i s t h e f r e e s t r e a m d e n s i t y , p i s t h e d e n s i t y a t any given
p o i n t , and y i s measured p e r p e n d i c u l a r t o t h e w a l l .
For l a m i n a r boun­
d a r y l a y e r s t h e d i s p l a c e m e n t t h i c k n e s s i s known t o v a r y i n v e r s e l y w ith
3
the square r o o t o f the s ta g n a tio n p re s s u re :
6*
I
(3-10)
172
<Po>
For t u r b u l e n t boundary l a y e r s , t h e d i s p l a c e m e n t t h i c k n e s s does n o t der
pend, t o any s i g n i f i c a n t d e g r e e , on t h e s t a g n a t i o n p r e s s u r e .
However,
when t h e boundary l a y e r i s t u r b u l e n t , t h e d i s p l a c e m e n t t h i c k n e s s w i l l be
somewhat l a r g e r th a n i t i s f o r most l a m i n a r f l o w s , a s i s i l l u s t r a t e d in
Figure 3-10.^
When t h e d i s p l a c e m e n t t h i c k n e s s i s a t a minimum, t h e flo w a r e a w i l l
be a t a maximum and hence t h e Mach Number w i l l be a t a maximum.
I t is
a l s o known t h a t t h e p o i n t o f t r a n s i t i o n from l a m i n a r t o t u r b u l e n t flow
in t h e boundary l a y e r moves u p s tr ea m a s t h e s t a g n a t i o n p r e s s u r e i s
increased.
Using t h e p r i n c i p l e s o u t l i n e d i n t h e p r e v i o u s p a r a g r a p h , i t i s now
p o s s i b l e t o o f f e r an e x p l a n a t i o n o f t h e o b s e r v e d v a r i a t i o n o f Mach
Number w it h t h e s t a g n a t i o n p r e s s u r e t h a t has been o b s e r v e d in t h e s e
measu rem ent s.
At t h e f u r t h e s t downstream p o r t ( 1 5 .1 4 i n c h e s downstream
o f t h e t h r o a t ) t h e Mach Number i s o b s e r v e d t o i n c r e a s e as t h e s t a g n a t i o n
p r e s s u r e i s i n c r e a s e d from i t s minimum v a l u e o f 303 mm Hg.
Thi s i s
DISPLACEMENT THICKNESS
56
LAMINAR
REGION
TRANSITION
REGION
TURBULENT
REGION
STAGNATION PRESSURE
F i g u r e 3-10
Change o f t h e D is p la ce m en t T h i c k n e s s o f
a Boundary Lay er due t o P r e s s u r e
57
p r e d i c t e d by t h e r e l a t i o n s h i p g iv e n in E q u a t io n ( 3 - 1 0 ) .
T h i s phenomenon
c o n t i n u e s u n t i l a s t a g n a t i o n p r e s s u r e semewhere between 450 and 500 mm
Hg i s r e a c h e d .
At t h i s p o i n t t h e t r e n d r e v e r s e s and t h e Mach Number
d e c re ase s as th e s t a g n a t i o n p re s s u re i s in c re ased f u r t h e r .
Assuming t h a t t h e bo un da ry l a y e r i s l a m i n a r a t t h e minimum s t a g n a ­
t i o n p r e s s u r e * t h e i n c r e a s i n g t h i c k n e s s o f t h e boundary l a y e r i s c o r r e c t ­
l y p r e d i c t e d by E q u a t i o n ( 3 - 1 0 ) .
Assume a l s o t h a t t h e bo u nd ary l a y e r
t r a n s i s t s from l a m i n a r t o t u r b u l e n t a t a s t a g n a t i o n p r e s s u r e between
450 and 500 mm Hg .
As t h e s t a g n a t i o n p r e s s u r e i s i n c r e a s e d f u r t h e r ,
t h e p o i n t o f t r a n s i t i o n t o t u r b u l e n t flo w moves u p s t r e a m , g i v i n g t h e
boundary l a y e r more d i s t a n c e o v e r which t o grow b e f o r e r e a c h i n g t h e
downstream s t a t i c p o r t .
S i n c e t h e bou nd ary l a y e r has had more d i s t a n c e
t o grow, t h e d i s p l a c e m e n t t h i c k n e s s w i l l be l a r g e r and t h e Mach Number
w i l l be s m a l l e r .
As t h e s t a g n a t i o n p r e s s u r e i s f u r t h e r i n c r e a s e d , t h i s
phenomenon w i l l c o n t i n u e and t h e Mach Number w i l l d e c r e a s e f u r t h e r .
Alth oug h t h e above d i s c u s s i o n i s u s e f u l a s f a r a s p i n p o i n t i n g t h e
p o i n t o f t r a n s i t i o n , t h e o v e r a l l e f f e c t o f t h e bo undary l a y e r s on t h e
f r e e s t r e a m Mach Number i s v e r y s m a l l .
The v a r i a t i o n o f t h e Mach Number
from maximum t o minimum i s l e s s t h a n two p e r c e n t .
T h u s , t h e r e a r e no
problems f o r e s e e n i n t h i s t u n n e l due t o t h e v a r i a t i o n o f Mach Number due
. '
to the sta g n a tio n p re ssu re .
* See S e c t i o n 3 . 9 o f t h i s c h a p t e r .
58
3.6
STAGNATION PRESSURE MEASUREMENTS
The s t a t i c p r e s s u r e measurements d e s c r i b e d in t h e p r e v i o u s s e c t i o n
a r e i n f o r m a t i v e a b o u t t h e f r e e s t r e a m Mach Number al o n g t h e n o z z l e .
They do n o t , however, g i v e any i n f o r m a t i o n a b o u t t h e u n i f o r m i t y o f t h e
flow in t h e n o z z l e and t e s t s e c t i o n o r t h e p r e s e n c e o f waves in t h e
flow.
For t h i s r e a s o n , a l o n g w it h a d e s i r e t o co n f ir m t h e s t a t i c p r e s ­
s u r e r e s u l t s o f t h e p r e v i o u s s e c t i o n , i t was deemed n e c e s s a r y t o i n t r o ­
duce p i t o t p ro b es i n t o t h e t e s t s e c t i o n t o measure s t a g n a t i o n p r e s s u r e
(and hence t h e Mach Number) a t v a r i o u s p l a n e s al o n g t h e n o z z l e and t e s t
section.
A c a r t e s i a n c o o r d i n a t e system has been u t i l i z e d t o d e s c r i b e t h e
p o s i t i o n o f t h e p r o b e s in t h e t u n n e l .
The X-coo.rdinate i s a l o n g t h e .
d i r e c t i o n o f flo w and i s r e f e r e n c e d t o z e r o a t t h e n o z z l e t h r o a t , t h e
downstream d i r e c t i o n b e i n g t a k e n as p o s i t i v e .
The Y - c o o r d i n a t e i s t h e
v e r t i c a l a x i s and i s r e f e r e n c e d t o z e r o halfw ay between t h e t o p and b o t ­
tom s u r f a c e s o f t h e n o z z l e , t h e p o s i t i v e d i r e c t i o n b ei n g upward, th e
n e g a t i v e downward..
The Z - a x i s i s t h e h o r i z o n t a l c o o r d i n a t e , p e r p e n d i ­
c u l a r t o t h e flow .
The z e r o p o s i t i o n i s t h a t p o i n t h al fw ay between t h e
sidew alls.
For an o b s e r v e r f a c i n g t h e d i r e c t i o n o f f l o w , p o s i t i v e i s
measured t o t h e r i g h t , n e g a t i v e t o t h e l e f t .
North wall i s n e g a t i v e Z . )
(South wall, i s p o s i t i v e Z,
See F ig u r e 3 . 1 1 .
The Y-Z p l a n e flow measurements have been t a k e n a t 10 X - p o s i t i o n s
a l o n g t h e n o z z l e and t e s t s e c t i o n .
These measurements were t a k e n w it h
59
Nozzle Block
F i g u r e 3-11
C o o r d i n a t e System
60
t h e a i d o f a p i t o t ( s t a g n a t i o n ) t u b e r a k e t h a t i s i l l u s t r a t e d in F ig u r e
3.12.
The i n d i v i d u a l p r e s s u r e l i n e s from each t u b e run i n t o t h e body o f
t h e ra k e and o u t t h e back en d.
These l i n e s were th e n c o n n e c t e d t o t h e
wind t u n n e l p r e s s u r e s t a t i o n .
The body o f t h e r a k e was suspended from Y - a c t u a t o r p o s t s a t two
p o s i t i o n s a l o n g t h e body o f t h e r a k e so t h a t t h e Y - a c t u a t o r c o u l d be
used t o move t h e r a k e up and down a l o n g t h e Y - a x i s .
The r a k e was c a r e ­
f u l l y p o s i t i o n e d and l e v e l e d b e f o r e each run.
A f t e r t h e t u n n e l was s t a r t e d and a l lo w e d t o come t o e q u i l i b r i u m t h e
p o r t c l o s e s t t o t h e s o u t h wall was opened.
was th e n r e a d w i t h t h e a i d o f t r a n s d u c e r C.
The p r e s s u r e i n t h i s l i n e
The e l e c t r i c a l o u t p u t from
t h i s t r a n s d u c e r was t h e n f e d i n t o t h e X - a x is a c t u a t o r o f a H e w le tt Packard model 7004B X-Y r e c o r d e r .
The s i g n a l from t h e Y - a x is a c t u a t o r
on t h e wind t u n n e l was s i m i l a r l y f e d i n t o t h e Y- axi s a c t u a t o r o f t h e X-Y
recorder.
See F i g u r e 3 . 1 3 .
Thus, as t h e r a k e was moved down th ro ugh
t h e t e s t s e c t i o n , t h e v a r i a t i o n o f s t a g n a t i o n p r e s s u r e a l o n g t h e Y -axis
a t t h a t p a r t i c u l a r X and Z p o s i t i o n was t r a c e d on t h e X-Y r e c o r d e r .
When t h e r a k e r e a c h e d i t s low er l i m i t in t h e t e s t s e c t i o n , t h e p o r t
b e i n g measured was c l o s e d , t h e pen on t h e X-Y r e c o r d e r was r a i s e d , and
t h e r a k e was r a i s e d back t o i t s up p er l i m i t n e a r t h e t o p o f t h e t e s t
section.
The X = O p o s i t i o n on t h e X-Y r e c o r d e r was t h e n s h i f t e d t o t h e
r i g h t by one h a l f o f a d i v i s i o n ( . 2 5 v o l t s ) i n o r d e r t o p r e v e n t o v e r ­
lapping of the tr a c e s .
The n e x t p o r t was th e n opened ( i n t h i s example
A
F i g u r e 3-12
S t a g n a t i o n Tube Rake
62
P r e s s u r e S ig na l
Transducer
V olt­
m e te r
Y- axi s
actuator
X -a xi s
Y -ax is
X-Y Recor de r
F i g u r e 3-13
S t a g n a t i o n P r e s s u r e Measuring System
i t would be p o r t B o n . F i g u r e 3 . 1 2 ) , and t h e p r o c e d u r e was r e p e a t e d u n t i l
a l l o f t h e t r a c e s f o r t h a t p a r t i c u l a r X p o s i t i o n had been o b t a i n e d .
I t i s w ell known from t h e t h e o r y o f s u p e r s o n i c f l o w s t h a t t h e p r e s ­
sure in th e p i t o t tube i s not the t r u e s ta g n a t io n p r e s s u r e , but the
p r e s s u r e b e h i n d a normal shock as i s i l l u s t r a t e d i n F i g u r e 3 . 1 4 .
On t h e
s t a g n a t i o n s t r e a m l i n e , t h e . s h o c k J s _a normal sh ock and t h e t o t a l p r e s s u r e
r e l a t i o n s h i p f o r a normal shock a p p l i e s :
[I +
where Pq ^ i s t h e s t a g n a t i o n p r e s s u r e ahead o f t h e s h o c k ,
s t a g n a t i o n p r e s s u r e b eh i n d t h e sh oc k ,
i s t h e Mach Number b e f o r e t h e
sh o ck , and y i s t h e - r a t i o of. s p e c i f i c h e a t s .
I . 4 for a i r .
S i n c e t h e r a t i o Pc^ Z pOl
i s the
.
T h i s r a t i o i s known t o be
known, t h e o n l y unknown i s M^.
One X-Y p l a n e measurement al o n g Z = O has a l s o been t a k e n f o r t h e
p u r p o s e o f v e r i f y i n g e a r l i e r measurements and o b s e r v i n g , on one p l o t ,
t h e v a r i a t i o n o f Mach Number w ith d i s t a n c e from t h e t h r o a t i n t h e t e s t
region.
T h i s measurement was ta k e n w i t h t h e a i d o f a s i n g l e p i t o t
.probe t h a t was s u sp e n de d from t h e Y - ax is a c t u a t o r p o s t s a t two p o s i t i o n s
and d r i v e n f o r w a r d w i t h t h e a i d o f t h e X - a x i s a c t u a t o r mechanism ( s e e
Figure 3 .1 5 ) .
The p r o b e t r a v e r s e d from 18.38 in c h e s downstream o f t h e t h r o a t t o
I I . 68 i n c h e s downstream o f t h e t h r o a t .
T r a c e s were t a k e n f o r f i v e Y
64
M1 > I
Shock Wave
F i g u r e 3-14
S t a g n a t i o n Probe Behind Shock
/////////(////////////////////////////////////////Z y y y y y y y z ///
i
_L _]
F i g u r e 3-15
J
i
S i n g l e S t a g n a t i o n Probe For Use i n X-Y P la ne T r a v e r s e
66
positions.
T r a n s d u c e r C. was a g a i n u t i l i z e d f o r p r e s s u r e measurements.
On t h i s p l o t , , however, t h e s i g n a l from t h e t r a n s d u c e r was p u t i n t o t h e
i
Y - a x is a c t u a t o r o f t h e X-Y r e c o r d e r , w h i l e t h e o u t p u t from t h e X -axis
a c t u a t o r o f t h e wind t u n n e l was f e d i n t o t h e X -axis a c t u a t o r o f t h e X-Y
recorder.
The r e s u l t i s a p l o t where t h e pen moved h o r i z o n t a l l y i n s t e a d
of v e rtic a lly .
A f t e r one t r a c e was c o m p l e t e d , t h e p h y s i c a l p o s i t i o n i n g
o f t h e probe a l o n g t h e Y - a x is in t h e t e s t s e c t i o n was changed by use o f
t h e Y - a c t u a t o r mechanism o f t h e wind t u n n e l .
The Y=O p o s i t i o n o f t h e
pen was a l s o changed f o r each new t r a c e so t h a t o v e r l a p p i n g o f t h e t r a c e
was a v o i d e d .
The r e s u l t i s F ig u r e 3 . 2 7 .
The fl o w p r o f i l e s t h a t have j u s t been d e s c r i b e d a r e p r e s e n t e d on
the next sev eral pages.
The r e a d e r s h o u ld n o t e t h e l a b e l i n g o f t h e z e r o
p o s i t i o n o f t h e h o r i z o n t a l a x i s o f t h e p l o t s (and t h e v e r t i c a l , a x i s o f
F ig ur e 3 . 2 7 ) .
For t h e Y-Z p r o f i l e s a t r a c e was t a k e n o f p o r t A using;
t h e l e f t hand margin o f t h e graph p a p e r as t h e X=O p o s i t i o n ( s e e Fig ur e
3.16).
When t h i s was c o m p le te d , p o r t A was c l o s e d and p o r t B o p en ed .
zTlie X=O p o s i t i o n was th e n moved t o t h e r i g h t by .25 v o l t s and t h e p r o ­
f i l e f o r p o r t B was t a k e n .
Thi s was done f o r each p o r t , i n o r d e r , u n t i l
a co m pl ete p r o f i l e was o b t a i n e d .
The z e r o p o s i t i o n o f ea ch t r a c e i s
c l e a r l y l a b e l e d on t h e p l o t s .
F ig u r e 3 . 1 6 i s a dia gram o f t h e p o s i t i o n i n g o f t h e r a k e in t h e t u n ­
nel and r e f e r s t o measurements ta k e n u p s tr ea m o f X = 15.063 in c h e s
(Figures 3.17 through 3 .2 0 ).
F ig u r e 3.21 i s a s i m i l a r dia gram and
South Wall
0. 2 9 7
North Wall
F igure 3-16
P o s i t i o n i n g o f Rake in T e s t S e c t i o n
Z er o e s o f T r a c e s
A
B C D E F
G H I
G :H
CAUMATIO* Of TEST SECTIO*
10/ 10/80
|
DATE:
1
STAtoATIO* MlESStoE:
STViHATIto TEMAERATUJIE:
ACTUATOA SPEED SETTING:
T r«nl. C. 10/2/60
COHEIlTS:
,
Origin of tr a c e
3.2 3.1 3.0 2.9 2.8 2,7
Mach Number
F igure 3-17
Y-Z P l a n e P l o t
I ind J l t i k .
1
Z ero es o f T r a c e s
A B C D E F G H
G FT
CAUMATIO* Of TtST SECTION
10/10/80
STAtTAtION m c s s u it:
WO ■» Hf
STAhTATIOT TENAtAATVITts
100 6F
ACTlIATO* SAttO S tT T I* :
CAU STATION:
CTKTtNTS:
I
O rigin of t r a c e
3.2 3.1 3.0 2.9 2.8 2.7
Mach NumbeI.
F igure 3-1 8
Y-Z P l a n e P l o t
I . AAd J W ik.
T r im . C1 10/2/80
Z ero es o f T r a c e s
A B C D E F G H I
CAUMATIOI Of T£$T SECTION
STAGNATION MCSSUNE:
STAGNATION TWtAATUNt:
ACTUATOA S fttO SETTING:
TrAiiS. C. 10/2/80
I POSITION:
CONSENTS: I AnA U I t A k .
I
Origin of tra c e
5.2 3.1 3.0 2.9 2.8 2i7
Mach Number
F igu re 3-19
Y -Z P l a n e P l o t
12.14 Inchts
larnac
A
B
C
D
n f
E
i
F
G
I
—
' T
i
_
-
"
i
^
\
+ y t
I—
'
_
i'
-y +
.
i
"
I
I
I'::
i\
• I '
- J _
!
I
|
!
~
'
r ~
!
!
I
V
\
O n g m of tra c e
M ach
N u m b e r
" I
'
..-J :
— |—
: i
:: •
'
I
F igure 3-20
16/ 1/80
M O ™ Hg
S T A M A T I M TEMPERATURE:
TOO 6 F
ACTUATOR SPEEO SETT 1* 6:
CA U IAA TIM :
AS
T riM . C,
I PO S IT IO N :
W W l n c h A*
.... j . . . I
—
•
: '
. .
—
•:
I
I'
•
10/ 1/80
- _ L :
I .
'
I T
-
I
: 'I '
;
"
i i :'
■ .
i
I
’ ! •
: .
—
’
-
.
!_ _
:
I
:
;
T
•
i
Y-Z P l a n e P l o t
• •
I
;
:::••*•
:
.
I
!
;
I.
SATE:
S T A M A T I ON PRESSURE:
COKENTS: I i M J l t * l .
I
I;
I
r
C A U M A T I M O f TEST S E C T I M
i
-
.
'T -r— r — I
1
S.2 3.1 3.0 2.9 2.8 2,7
. m i
I .•
J j . :
I
'
:. j . .
•:
!'
I
I
■
- I -
....
T
i
I
:
.|T
i
;
.s
"I
I
....
i t
-
-
'
T
—
T
Il-'
I
4
i
... j
I;.:
I
:
' I
. . V
i
j
T
iii
... I
■
I
T
i
'
jZ T
I•
!
i
I
I
—
.-1
.I—
'
•;
.I
T i
-
' I
I
I
i
!
Ji
'
H
Ig
!
-
i
. i
!
1
F
•:|
i
..J
I
\
! E
:
I
" T
i
. 4
j
:|
I T
'T
'i
I
I
!
i
I
I
•1
•:
r
■ !
D
I
!—
...
I
;I
|C
I :
I
J : . .
!
I
i
|_ _ _ _
;
;
!
-
'
B
l
L
.—
I
i
I A
— —
.Llii
0
r
•
•
...
H
I
i
• ; }
•
T r a r o c
!
.
i . . i ..
i
. I
■■
•
South Wall
0.297
North Wall
F igure 3-21
P o s i t i o n o n g o f Rake in T e s t S e c t io n
73
r e f e r s t o measurements t a k e n a t 15.063 i n c h e s and f u r t h e r downstream
( F i g u r e s 3 . 2 2 th r o u g h 3 . 2 6 ) .
The p o s i t i o n o f t h e r ake was c a r e f u l l y
checked b e f o r e each new p l o t was t a k e n .
The t r a n s d u c e r was a l s o f r e ­
quently r e - c a l ib r a t e d .
3.7
STAGNATION PRESSURE MEASUREMENT RESULTS
The p l o t s o b t a i n e d w i t h t h e a i d o f t h e p i t o t tu b e r a k e show t h e
flow t o be u n i f o r m , a l t h o u g h t h e r e i s some e v i d e n c e o f some minor waves
in t h e p r o f i l e s t a k e n downstream o f X = 16.563 i n c h e s .
The c o n i c a l
shaped wave t h a t i s e v i d e n t in F ig u r e 3 . 2 4 has been t r a c e d t o a l e a k a t
t h e s t a t i c p o r t 10.1 4 i n c h e s downstream from t h e t h r o a t which has s i n c e
been c o r r e c t e d .
The m a jo r c o n t r i b u t i o n o f t h e s e p l o t s i s t o v e r i f y t h a t t h e flow i n
the t e s t sectio n i s ,
i n d e e d , u n if o r m .
The measurements e x t e n d from t h e
downstream end o f t h e e x t e n s i o n b l o c k , which i s 21.063 i n c h e s downstream
from t h e t h r o a t , t o d i r e c t l y above t h e s t a t i c p o r t l o c a t e d 8 . 1 4 in c h e s
downstream from t h e t h r o a t .
The waves t h a t a r e e v i d e n t i n t h e f u r t h e r
downstream measurements p r o b a b l y o r i g i n a t e a t th e u p s tr e a m end o f t h e
ex tension block.
These d i s t u r b a n c e s a r e r e l a t i v e l y small and do n o t
s i g n i f i c a n t l y a l t e r t h e f r e e s t r e a m Mach Number.
For i n s t a n c e , in F i g ­
u r e 3 . 2 5 , waves a p p e a r a p p r o x i m a t e l y 1 / 4 in c h above and below t h e Y=O
p o s i t i o n on t h e g r a p h s , b u t t h e ch ang es i n Mach Number due t o t h e s e
waves i s on t h e o r d e r o f 2 p e r c e n t .
The e f f e c t s o f t h e l e a k a t t h e
'
Z er o e s o f T r a c e s
A
B
C
D
E
F
G
H
I
J
CALIBKATIOX Of TEST SECTION
I DATE:
]
STAGNATION MESSUAE:
.
STAGNATION TCWElATUNE:
10/ 1/80
I ACTUATOR SKEO S tT T I* :
•
CAU MATlO*:
;
I POSITION:
COntNTS: J 1» I* IfluNdAry
j
O rigin of tr a c e
5.2 3.1 3.0 2.9 2.8 2:7
Mach Number
F igure 3-22
Y-Z P l a n e P l o t
T n i r t. C. 10/2/80
-
Z er o e s o f T r a c e s
A B C D E F G H
O tlM A T IC W O f U S T SECTION
STAGNATION PRESSURE:
600 ■
Hg
STAGNATION TEMPERATURE:
ACTUATOR SPEED SETTING:
Trews. C, 10/2/80
16.56 Inches
COWERTS:
i
Origin of tra c e
S.2 3.1 3.0 2.9 2.8 2,7
Mach Number
F igure 3-23
Y -Z P l a n e P l o t
J Is Iw boundsry l e / e r
Z er o e s o f T r a c e s
A
B
C
D
E
F
G
H
I
J
CAUMATH* Of TCST SECTION
10/6/80
I— y=<3
STAGNATION PNCSSUftC:
600 m H9
STAGNATION TCNPCRATUNE:
ACTUATOft SPEED SETTING:
Trent. C. 10/2/M
COKNCNTS: J I l I n bovndery I e y tr
,
O rigin of t r a c e
1 2 3.1 3.0 2.9 2.8 2,7
Mach Number.
|
F igure 3-2 4
Y-Z P l a n e P l o t
Z er o e s o f T r a c e s
A
B
C
D
E
F
G
H
I
J
CAUMATIO* Of TEST SECTION
10/3/60
STAGNATION PRESSURE:
STAGNATION TEMPERATURE:
ACTUATOR SPEED SETTING:
Trans. C. 10/2/60
COMMENTS: J Is In boundary la y er
t
O rigin of tr a c e
5.2 3.1 3.0 2.9 2.8 2,7
^ c h Number
F igure 3-25
Y -Z P l a n e P l o t
Z er o e s o f T r a c e s
A
B
C
D E
F
G H
I
J
CAL IMAT10* Of TEST SECTION
10/3/60
STAGNATION NAESSUtE:
STASWTIOt TEWCtATVtE:
ACTUATOt SMlO SETTING:
T rtn s. <
10/2/00
21.00 Inclsti
CONTENTS: J I t In bound*ry T ly tr.
k
Origin of tr a c e
S.2 3.1 3.0 2.9 2.8 2.7
Mach Number
F igure 3-26
Y-Z P l a n e P l o t
Co IfI ref ico o f
jgcf.cn , X-Y ,0 Iere j/crL Z i
W i l HO
! P-rrncvA f, ffg <«W 6 0
1
i f j g n a f o r . P r^ jjjrg
bOQmmrt^
LaIibraHch: Irens. L
5 f e ^ R o f o n ; T g n f ; r j t y r i - : 1f " F
X r llJ T /'
F igure 3-27
X-Y P l a n e P l o t
80
s t a t i c p o r t 10 .1 4 i n c h e s from t h e t h r o a t a r e th o u g h t t o be m i n i m a l , even
though t h i s l e a k was n o t d i s c o v e r e d u n t i l t h e ra k e had been moved f o r ­
ward t o 15 i n c h e s from t h e t h r o a t .
Furthermore, th e se s l i g h t d e fe c ts
can be (and were) c o r r e c t e d .
Boundary l a y e r e f f e c t s a r e c l e a r l y v i s i b l e in t h e measurements t h a t
were t a k e n f u r t h e r downstream.
The t u b e s o f t h e p i t o t r a k e t h a t were
n e a r e s t t h e wall, were found t o be c o m p l e t e l y . i n t h e boundary l a y e r below
14 in c h e s downstream o f t h e t h r o a t ( F i g u r e s 3 . 2 0 , 3.2 2 t h r o u g h 3 . 2 6 ) .
T h i s i m p l i e s a boundary l a y e r t h i c k n e s s o f a t l e a s t .2 i n c h e s a t t h e s e
points.
Upstream from t h e r e t h e boundary l a y e r t h i c k e n i n g n e a r th e c o r ­
n e r s i s o b s e r v e d , b u t t h e p o r t s n e a r t h e wall a r e o u t o f t h e boundary
l a y e r f o r t h e m a jo r p a r t o f t h e i r t r a v e r s e .
Downstream measurements were t a k e n f i r s t , and a f t e r t h e measurement
a t X = 15.063 i n c h e s was t a k e n t h e r a k e was removed from t h e t e s t s e c ­
t i o n and r e - i n s t a l l e d on s u p p o r t s t h a t were l o c a t e d f u r t h e r ups tream .
When t h e ra k e was r e - i n s t a l l e d i t was found t h a t p o r t s I and J were l e a k ­
ing r a t h e r b a d l y .
E f f o r t s t o c o r r e c t t h i s problem were u n s u c c e s s f u l so
t h e r e s t o f t h e measurements were t a k e n w i t h o u t t h e use o f . t h e s e p o r t s .
The p o r t s t h a t were l e a k i n g were t h o s e t h a t were l o c a t e d n e a r e s t t h e
.
n o r t h w a l l , and i t i s u n l i k e l y t h a t t h e r e i s a d i s t u r b a n c e i n t h i s r e g i o n
t h a t c o u l d s i g n i f i c a n t l y a f f e c t t h e r e s u l t s w i t h o u t showing e v i d e n c e o f
i t s e l f in t h e measurements t h a t were t a k e n f u r t h e r downstream.
81
The speed o f t r a v e r s e o f t h e r a k e was d et e r m in e d e x p e r i m e n t a l l y .
A ■
s e t t i n g o f 45 on t h e Y - a c t u a t o r speed c o n t r o l was s e t t l e d on a s bei ng
t h e f a s t e s t s p ee d a t which a l l
q u a t e l y d i s p l a y e d on t h e p l o t s .
s i g n i f i c a n t d i s t u r b a n c e s would be a d e ­
( = . 0 3 i n c h e s p e r second)
Al I o f t h e f lo w p r o f i l e s were t a k e n a t a s t a g n a t i o n p r e s s u r e o f
600 mm Hg.
I t was d e c i d e d a t t h e o u t s e t t h a t t h e r e was no. need t o t a k e
p l o t s f o r o t h e r p r e s s u r e s s i n c e most d i s t u r b a n c e s o f t h e f l o w a r e n o t
functions o f the s ta g n a tio n pressu re.
The Mach,Number i s o b s e r v e d t o s t a y i n t h e g e n e r a l v i c i n i t y o f M=3.
D e v i a t i o n s from t h i s v a l u e a r e small a n d , f o r t h e most p a r t , p r e d i c t a b l e .
The Mach Number c o n t i n u e s t o grow w i t h d i s t a n c e from t h e t h r e a t u n t i l
ar oun d 15 i n c h e s downstream from t h e t h r o a t .
slowly.
I t th en b e g i n s t o d e c l i n e
Th is i s t o be e x p e c t e d s i n c e t h e channel c e a s e s t o d i v e r g e a t .
t h i s p o i n t b u t t h e bo un da ry l a y e r s c o n t i n u e t o grow, p r o v i d i n g t h e e f ­
f e c t of a supersonic d if f u s e r .
T h i s bo u nd ary l a y e r growth i s o b s e r v e d
i n t h e t r a c e s t a k e n o f p o r t A i n t h e flo w p r o f i l e s .
The e f f e c t o f t h e
two d i m e n s i o n a l i t y o f t h e n o z z l e i s o b s e r v e d i n t h e t r a c e s t a k e n in t h e
d i v e r g i n g p o r t i o n o f t h e n o z z l e a s a 'bowing o u t 1 o f t h e t r a c e s .
The p r o f i l e s p r e s e n t e d i n F i g u r e s 3 . 1 7 th ro u g h 3 . 2 0 were p u r p o s e l y
t a k e n d i r e c t l y above s t a t i c p o r t s where t h e Mach Number had a l r e a d y
■
been me asured.
-
-
.
.
The co m pa ris on i s p r e s e n t e d in Tabl e 3 . 2 .
The r e s u l t s
from t h e two methods a r e n o t i n c o m p le te ag re e m en t b u t a r e w e l l w i t h i n
t h e bounds o f e r r o r which one would e x p e c t u s i n g t h e e q ui p m en t u s e d .
T ab l e 3 . 2
Comparison o f R e s u l t s (X.= 10 .1 4 i n )
Stagnation Pressure
. 600 mm Hg
500 mm Hg
Mach Number From
■Area Change
3.02 5
3.025
Mach Number From
S ta tic Pressure
Tests
2.88 9
2.86 9
Mach Number From
Stagnation
Pressure Tests
2.95
t e s t not
performed
Mach Number From
Area Change w i t h
Boundary Layer
Correction
2.902
2.898
83
The s t a t i c p r e s s u r e , m e a s u r e m e n t s i n v o l v e d m e a s u r i n g p r e s s u r e s an o r d e r
o f ma gn itu d e low er th a n t h e s t a g n a t i o n me asurements and t o t a l agree men t
was n o t e x p e c t e d i
A l s o , t h e tw o - d i m e n s i o n a l n a t u r e o f t h e n o z z l e i s
i m p o r t a n t s i n c e t h e s t a t i c measurements o n l y i n v o l v e d a p r e s s u r e meas­
u r e d a t t h e . w a l l and t h e Mach Number v a r i e d t o some d e g r e e a c r o s s t h e
nozzle.
See S e c t i o n 3.11 o f t h i s c h a p t e r f o r a more c o m p le te d i s c u s s i o n
of th i s question.
.
■
• •
• F i g u r e 3 . 2 7 . i s t h e r e s u l t o f t h e X-Y p l a n e . p r o f i l e t h a t w a s - t a k e n
with the s in g le s ta g n a tio n probe.
The s p ee d o f t r a n s l a t i o n o f t h i s
pr ob e w a s . a g a i n d e t e r m i n e d e x p e r i m e n t a l I y . j A s e t t i n g o f 60 ( = .0 4 i n / s e c )
on t h e X - a x i s a c t u a t o r c o n t r o l was d e t e r m i n e d t o be t h e b e s t s p e e d .
The r e s u l t s from t h i s p l o t c o n f i r m e a r l i e r o b s e r v a t i o n s o f t h e Y-Z
plane p l o t s .
When compared t o t h e Mach Number measurements o b t a i n e d in
t h e p i t o t r a k e me asurements t h e r e i s no n o t i c e a b l e d i f f e r e n c e ;
The p l o t
c o n f i r m s . e a r l i e r o b s e r v a t i o n s o f t h e v a r i a t i o n o f Mach Number w it h d i s ­
t a n c e from t h e t h r o a t .
ti o n of the nozzle u n til
The Mach Number g^rows a l o n g t h e d i v e r g e n t p o r ­
r e a c h i n g a maximum around 15 i n c h e s from t h e
t h r o a t and b e g i n s to. d e c l i n e as t h e pr o be i s moved f u r t h e r downstream.
There a r e some waves e v i d e n t in t h i s p l o t , b u t t h e y a r e a t t h e f a r
downstream end o f t h e e x t e n s i o n b l o c k .
The a r e a where t h e s e waves a r e
l o c a t e d , i s w ell o u t o f the. way o f any t e s t t h a t mi gh t be p er f o r m e d i n
the tunnel.
I t is thought t h a t th e upstream support o f th e Y -actu a to r
mechanism i s t h e o r i g i n o f t h e s e waves.
84
A p l o t o f t h e Mach Number al o n g t h e t e s t s e c t i o n i s p r e s e n t e d on
Fig ur e 3 . 2 8 .
3.8
Thi s p l o t was d e r i v e d from t h e t r a c e shown on F ig u r e 3 .2 7 .
BOUNDARY LAYER PROFILES
Boundary l a y e r p r o f i l e s have been ta k e n a t X = 10.14 i n c h e s a t t h e
to p s u r f a c e o f t h e n o z z l e , a l l a t Z=0, f o r t h r e e s t a g n a t i o n p r e s s u r e s .
A f l a t t e n e d p i t o t probe was u t i l i z e d f o r t h e s e measu rem ent s, and i s i l ­
l u s t r a t e d in F ig u r e 3 . 2 9 .
t h e probe a g a i n s t t h e w a l l .
An o p t i c a l m i cro sc op e was used t o p o s i t i o n
The speed o f t r a v e r s e o f t h e probe was
a g a i n d e t e r m in e d e x p e r i m e n t a l l y and a s e t t i n g o f 15 on t h e Y - a c t u a t o r
speed c o n t r o l knob was chosen as t h e b e s t sp eed.
I t was hoped t h a t t h e
r e s u l t s o f t h e s e measurements would f u r t h e r c o n f ir m o b s e r v a t i o n s made
a bo ut t h e flow.
The X-Y r e c o r d e r t h a t was used f o r t h e e a r l i e r s t a g n a t i o n probe
p r o f i l e s was u t i l i z e d f o r t h e boundary l a y e r p r o f i l e s .
The p r e s s u r e in
t h e p i t o t probe was re a d by t r a n s d u c e r C, whose o u t p u t was f e d i n t o t h e
X-axis a c t u a t o r o f t h e X-Y r e c o r d e r .
The wind tu n n e l Y -axis a c t u a t o r
o u t p u t was p u t i n t o t h e Y -a xi s i n p u t on t h e X-Y r e c o r d e r .
The p r o f i l e s
t h u s o b t a i n e d a r e p r e s e n t e d in F i g u r e s 3 .3 0 and 3 . 3 1 .
Boundary l a y e r p r o f i l e s were ta k e n f o r s t a g n a t i o n p r e s s u r e s o f 600,
500, and 400 mm Hg.
The p r o f i l e a t 400 mm Hg was st o p p e d as soon as th e
f r e e s tr e a m was r ea c h ed bec au se o f a flow breakdown.
Because o f th e
problem o f flow breakdowns no p r o f i l e s were a t t e m p t e d a t s t a g n a t i o n
Mach Number
3.1
2.9
:
OO
CJl
2.8
12
13
14
X -position
F igure 3-28
15
16
17
(inches]
V a r i a t i o n o f Mach N um b er A l o n g T e s t S e c t i o n
18
86
W a ll
F i g u r e 3-29
F l a t t e n e d P i t o t Probe
Boundary
Layer
P rofilti
X : 1 0 . 14 T n c h t s
F igure 3-30
down^^rfti/n O'T i Hg
jh ro o l
Boundary L ayer P lo ts
CClh’b r g h 'c n ', / O / l / S * fr o ^ i. C (P :/e f. 7 r \ / )
S L o y f r
rrj
inches
dovyiutnom
F ig u re 3-31
,'on:
Bound ary L a y e r P l o t
Iron/. C . 1 6 / 7 / 9 0 ( P * I M
89
p r e s s u r e below 400 mm Hg.
3.9
RESULTS OF BOUNDARY LAYER PROFILES
From i n s p e c t i o n o f t h e p r o f i l e s on F i g u r e s 3 . 3 0 and 3.31 i t i s s ee n
t h a t t h e p r o f i l e t a k e n a t a s t a g n a t i o n p r e s s u r e o f 600 mm Hg i s t u r b u ­
l e n t w h i l e t h o s e t a k e n a t t h e lo w er p r e s s u r e s a r e l a m i n a r .
d e m o n s t r a t e d by t h e s h ap e o f t h e c u r v e s . ;
This i s
These o b s e r v a t i o n s c o n f ir m
t h e e x p l a n a t i o n t h a t has been o f f e r e d f o r t h e v a r i a t i o n o f Mach Number
w i t h s t a g n a t i o n p r e s s u r e t h a t has been o f f e r e d in S e c t i o n 5 o f t h i s
chapter.
At t h e h i g h e r s t a g n a t i o n p r e s s u r e , t h e b o un dar y l a y e r i s t u r ­
b u l e n t , and t h u s t h i c k e r , c a u s i n g t h e e f f e c t i v e a r e a o f t h e n o z z l e t o
d e c r e a s e and f o r c i n g t h e Mach Number t o go down.
I t s h o u l d be note d a t
t h i s p o i n t t h a t i t i s n o t t h e t o t a l t h i c k n e s s o f t h e bou nd ary l a y e r t h a t
c a u s e s t h i s e f f e c t b u t , r a t h e r , t h e d i s p l a c e m e n t t h i c k n e s s o f t h e boun­
dary lay er.
I t i s shown l a t e r on i n t h i s s e c t i o n t h a t t h i s d i s p l a c e m e n t
t h i c k n e s s d o e s , i n d e e d , i n c r e a s e when t h e bou nd ary l a y e r t r a n s i s t s from
l a m i n a r t o t u r b u l e n t . - As t h e p r e s s u r e i s r e d u c e d , t h e boundary l a y e r
becomes l a m i n a r an d , a t l e a s t i n i t i a l l y , t h i n n e r .
a t a p o i n t s h r i n k s , t h e Mach Number w i l l
increase.
As t h e boundary l a y e r
As t h e p r e s s u r e i s
r e d u c e d f u r t h e r , t h e boundary l a y e r w i l l obey t h e r e l a t i o n s h i p o f e q u a ­
t i o n ( 3 - 1 0 ) and b e g i n t o grow a g a i n , c a u s i n g t h e Mach Number t o d e c r e a s e .
At t h i s p o i n t i t i s i n t e r e s t i n g t o o b s e r v e t h a t t h e l a m i n a r boun­
d a r y l a y e r s o f F i g u r e s 3 . 3 0 and 3.31 p r o v i d e t h e e x p e r i m e n t a l t e s t f o r
90
t h e r e l a t i o n s h i p o f e q u a t i o n ( 3 - 1 0 ) . - Th at i s :
V
6
. I
„
(3-12)
. «
(P. l ) 1 / 2 ^ ’ , 2 " (Po 2 , 1 / 2
The s u b s c r i p t s I and 2 d e n o t e 500 and 600 mm Hg r e s p e c t i v e l y .
Since th e
bou n da ry l a y e r p r o f i l e s a r e t a k e n a t t h e same p o i n t i t i s r e a s o n a b l e to-..
assume t h e p r o p o r t i o n a l i t y i s t h e same f o r each c a s e ' . " ' ' T h a t i s :
*1
'/(Pol)
52
l / ( P o 2 ) 1 /2
(Po2/Po1
1/2
(3-13)
Using t h e d a t a we h a v e , assume:
P jl = 500 mm Hg
Pp 2 = 400 mm Hg
I t can be seen from i n s p e c t i o n o f t h e p r o f i l e s t h a t :
5 1 = 1 . 0 7 in c h e s
52 = 1.21 in c h e s
4'
: ( V
.884
p01 >, / 2 = - 892
These two an s w er s d i f f e r by l e s s th a n one p e r c e n t .
.
Th is c o n f ir m s t h a t
our data follows the r e l a t i o n s h i p o f equation (3-10).
Data t a k e n o ff . F i g u r e 3 . 3 0 has been u t i l i z e d t o p l o t boundary l a y e r
p r o f i l e s i n t h e form o f v e l o c i t y r a t i o v e r s u s d i s t a n c e r a t i o .
p l o t s a r e p r e s e n t e d on F i g u r e 3 . 3 2 .
These
S i n c e t h e boundary l a y e r a t 400 mm Hg
F i g u r e 3-32
Boundary Layer P r o f i l e s
(X = 10 .1 4 i n c h e s )
92
i s known t o be l a m i n a r and o f a s i m i l a r p r o f i l e t o t h a t a t 500 mm Hg, i t
was n o t p l o t t e d .
From i n s p e c t i o n o f F ig u r e 3 . 3 2 , i t can be deduced t h a t t h e p r o f i l e
a t a s t a g n a t i o n p r e s s u r e o f 500 mm Hg i s l a m i n a r and t h e p r o f i l e a t 600
c
mm Hg i s t u r b u l e n t .
D is pl ac e m en t t h i c k n e s s e s o f t h e s e two boundary l a y e r s have been
c a l c u l a t e d by a n u me ric al p r o c e d u r e .
As has a l r e a d y been s t a t e d , t h e
d i s p l a c e m e n t t h i c k n e s s i s d e f i n e d as t h a t d i s t a n c e by which t h e wall
must be d i s p l a c e d i n o r d e r f o r t h e i n v i s c i d s o l u t i o n t o a p p l y .
I t is
d e f i n e d m a t h e m a t i c a l l y , f o r c o m p r e s s i b l e f l o w s , as t h e f o l l o w i n g :
6* = f
(I - / n - ) d y
0
where:
.
” °0
( 3- 14)
OO
p
= t h e d e n s i t y a t any p o i n t ;
Poo
= the f r e e stream v e l o c i t y ;
u
= t h e v e l o c i t y a t any p o i n t ; and
Uoo = t h e f r e e s t r e a m v e l o c i t y .
F ig u r e 3 . 3 3 i l l u s t r a t e s t h e p r o c e d u r e used t o d e t e r m i n e t h e d i s p l a c e ­
ment t h i c k n e s s .
The r e s u l t s a r e t a b u l a t e d i n Tabl e 3 . 3 .
Using t h e d i s p l a c e m e n t t h i c k n e s s t o a c c o u n t f o r boundary l a y e r
e f f e c t s , t h e Mach Number can now be c a l c u l a t e d w it h some d e g r e e o f con­
fidence.
In t h i s a n a l y s i s t h e boundary l a y e r a t t h e t h r o a t w i l l be
ig n o r e d s i n c e i t w i l l o b v i o u s l y be v e r y t h i n .
The r e s u l t s t h a t w i l l be
93
F i g u r e 3-33
P r o ce d u r e f o r C a l c u l a t i n g D isp lac em en t
T h ic k n es s
T ab l e 3-3
Boundary Lay er T h i c k n e s s e s
Stagnation Pressure
600 mm Hg
500 mm Hg
Boundary Layer
Thickness
0. 1 0 5 i n
0. 1 2 1 i n
D is p la c e m e n t
Thickness
0.038 in
C alculation
not
performed
95
t h u s o b t a i n e d do n o t t a k e i n t o a c c o u n t . t h e tw o -d im en s io n al n a t u r e o f t h e .
n o z z l e , and w i l l t h u s be d i f f i c u l t t o compare t o t h e s t a g n a t i o n p r e s s u r e
r e s u l t s w h ic h , a t t h e p o i n t where t h e boundary l a y e r p r o f i l e s were
t a k e n , show t h e e f f e c t o f t h e tw o - d i m e n s i o n a l n a t u r e o f t h e n o z z l e q u i t e
vividly.
When t h e c a l c u l a t i o n i s c a r r i e d o u t , i t i s found t h a t t h e Mach
Number a t t h i s p o i n t i s 2.90 2 f o r a s t a g n a t i o n p r e s s u r e o f 600 mm Hg,
and 2. 89 8 f o r a s t a g n a t i o n p r e s s u r e o f 500 nrn Hg.
These numbers a r e in
good agree men t w i t h t h o s e o b t a i n e d from t h e s t a t i c p r e s s u r e measurements.
3 . 1 0 TEMPERATURE OBSERVATIONS
I t has been o b s e r v e d t h a t t h e h e a t e r i s c a p a b l e o f r a i s i n g t h e
t e m p e r a t u r e o f t h e i n l e t a i r s t r e a m a p p r o x i m a t e l y 40°F a t t h e maximum
flow r a t e .
The h e a t e r i s c a p a b l e o f r a i s i n g t h e t e m p e r a t u r e somewhat
more th a n t h i s , b u t w i l l n o t p r o v i d e s t a b l e o p e r a t i o n i f t h i s i s done.
The r e a s o n t h a t t h e o p e r a t i o n w i l l n o t be s t a b l e i s t h a t i f t h e h e a t e r
i s used a t maximum o u t p u t i t w i l l be p u t t i n g o u t a c o n s t a n t amount o f .
e n e r g y w h i l e t h e am b ien t c o n d i t i o n s can be v a r y i n g c o n s i d e r a b l y .
S in ce
t h e maximum h e a t e r o u t p u t i s a c o n s t a n t , t h e t e m p e r a t u r e o f t h e wind
t u n n e l a i r w i l l v a r y w i t h t h e am b ien t c o n d i t i o n s , t h u s d e f e a t i n g much o f
t h e p u r po s e o f t h e h e a t e r .
3.11 MEASUREMENT ERROR
The q u e s t i o n t h a t always a r i s e s in a s t u d y such a s t h i s i s "How
good a r e t h e r e s u l t s ? " .
An e v a l u a t i o n o f t h e e r r o r s in t h e measurements
96.
o f t h i s c h a p t e r has been c a r r i e d o u t .
Th is was done by ad d i n g a l l po s­
s i b l e e r r o r s f o r each measurement and c a l l i n g t h i s sum t h e g r e a t e s t
possible e rro r.
For i n s t a n c e , f o r t h e s t a g n a t i o n p r e s s u r e measurements
t h e a n a l y s i s was c a r r i e d o u t a s f o l l o w s :
Error
Magnitude
l e a k s i n p r e s s u r e system
±10 mm Hg
transducer erro r
± 2 mm Hg
e r r o r in p o sitio n in g
graph on X-Y r e c o r d e r
± 4 mm Hg
e r r o r in r e a d i n g
a m bi en t p r e s s u r e
± 5 mm Hg
e r r o r in r e a d i n g graph
± 2 mm Hg
T o t a l ma gnitude o f e r r o r = 23 mm Hg
Assuming a Mach Number o f 3 ,
T ot al p e r c e n t e r r o r = ± 4 .3 p e r c e n t
An e r r o r . a n a l y s i s was a l s o c a r r i e d o u t f o r t h e s t a t i c p r e s s u r e mea sur e­
m e n ts , t h e boundary l a y e r me as u re m en ts, and t h e t e m p e r a t u r e measurements,
The r e s u l t s a r e as f o l l o w s :
S t a t i c p r e s s u r e mea sur em ent s:
Mg c t u a ^ = Mfixp
± .3%
Boundary l a y e r t h i c k n e s s :
Sa c t u a I = Sfixp
±8.0%
T em per at ure measu rem ent s:
Tg c t u a l = Tfixp
± 2°F
Th is e r r o r a n a l y s i s shows t h a t t h e measurements c o n t a i n e d i n t h i s cha p­
t e r a r e r e a s o n a b l y a c c u r a t e and t h u s a r e r e l i a b l e .
. CHAPTER 4
CONCLUSIONS
From t h e measurements and r e s u l t s in C h a p t e r 3 , one i s l e d t o con­
c l u d e t h a t t h e pe rf o rm a n ce o f t h e wind t u n n e l has n o t . b e e n d e t r i m e n t a l l y
a f f e c t e d s i n c e moving t o Montana.
expected t o .
The f a c i l i t y o p e r a t e s much a s i t was
The f o l l o w i n g a r e among t h e s p e c i f i c , c o n c l u s i o n s t h a t have
been r e a c h e d :
1)
The Mach Number i s found t o be i n t h e g e n e r a l v i c i n i t y o f 3 ,
and d e v i a t i o n s from t h e norm a r e p r e d i c t a b l e .
2)
There a r e no waves p r e s e n t i n t h e t e s t s e c t i o n o f s u f f i c i e n t
ma gni tud e which c a n n o t be s im p l y c o r r e c t e d o r which can s e r i o u s ­
l y a f f e c t t h e flow .
The fl o w i n t h e n o z z l e and t e s t s e c t i o n i s
unif or m.
3)
The boundary l a y e r s a r e t h i n and behave as t h e y were e x p e c te d
to.
4)
The t e m p e r a t u r e o f t h e a i r s t r e a m can be a d e q u a t e l y c o n t r o l l e d .
The t e m p e r a t u r e o f t h e s t r e a m can be r a i s e d 4 0 ° F S which means
i t i s u s e f u l f o r c o n t r o l p u r p o s e s o n ly .
5)
The minimum s t a g n a t i o n p r e s s u r e a t t a i n a b l e f o r unchoked flow i s
c o m p l i c a t e d t o c a l c u l a t e , b u t i s n o r m a l ly between 200 and 300
mm Hg.
F i n a l l y , i t s h o u ld be emphasized t h a t t h e d i m e n s i o n l e s s p a r a m e te r
t h a t v a r i a t i o n i n t h e flow c o n d i t i o n s a f f e c t i s t h e Reynolds Number.
F i g u r e 4.1 shows t h e o p e r a t i n g r an ge o f t h e wind t u n n e l , a l o n g w ith t h e
98
I n c r e a s i n g Re
-1----------------------->-
MO ■
130 •
Rwnge o f Operation
I PO ■
E-
110
'
100
■
90
'
80
1
Re=SOxlO
cm
Re=GOxlO
0
70
60
1
50
— .
200
....................
300
400
i
500
Pq (mm Hg)
F i g u r e 4-1
O p e r a t i n g Range o f SWT
600
cm
99
d i r e c t i o n o f i n c r e a s i n g Reynolds Number and t h e a p p r o x im a te magnitude o f
t h i s parameter.
APPENDIX
OPERATING PROCEDURES
START-UP
I..
Check t h e b a r o m e t r i c p r e s s u r e and a d j u s t gages a c c o r d i n g l y .
T.
F l i p c o n t r o l panel d i s c o n n e c t s w i t c h (10)
3.
Check pumps t o make s u r e t h e y a r e i n o p e r a t i n g c o n d i t i o n .
s
ic
t o "on" p o s i t i o n .
Make
sure the w ater li n e s are connected, e tc .
4.
Make s u r e t h a t t h e t e s t s e c t i o n and downstream p o r t s a r e c l o s e d up
t i g h t and t h a t any model o r o b j e c t in t h e t e s t s e c t i o n and i t s
a s s o c i a t e d m e a su r i n g eq u i p m en t i s r e a d y t o go.
5.
P r e s s c o n t r o l power "on" b u t t o n ( 1 5 ) .
6.
P r e s s t h r o t t l i n g v a l v e "on" b u t t o n ( 2 8 ) .
Make s u r e t h e bypass
valve c o n tro l i s in th e "auto" p o s i t i o n (19).
Make s u r e t h e w ar n ­
i n g beacon i s on ( 2 1 ) .
7.
Make s u r e t h r o t t l i n g v a l v e has opened.
8.
P r e s s . v a c u u m pump " s t a r t " b u t t o n ( 2 4 ) .
9.
Press c h i l l e r " s t a r t " button (37).
10.
P r e s s h e a t e r "on" b u t t o n ( 4 9 ) .
Adjust to d esired temperature.
NORMAL SHUT-DOWN
1.
Swi tch p r e s s u r e c o n t r o l t o manual ( 6 ) .
2.
Press c h i l l e r "stop" button (38).
3.
Press h e a te r "off" button (50).
* Numbers in p a r e n t h e s e s r e f e r t o F i g u r e A - I .
101
4.
P r e s s vacuum pump " s t o p " b u t t o n ( 2 5 ) .
5.
Press t h r o t t l i n g valve "off" button (29).
6.
P r e s s c o n t r o l power " o f f " b u t t o n ( 1 6 ) .
7.
Make s u r e t h e r e i s no w a t e r f lo w in g i n t o t h e pumps by c h ec k in g t h e
f lo w m et er above t h e pumps.
I f t h e r e i s any w a t e r go in g th ro u g h
t h e f l o w m e t e r , s h u t t h e w a t e r o f f IMMEDIATELY.
DRY SHUT-DOWN
For t h e d r y shut-down s t e p s 1-3 a r e t h e same as f o r t h e normal s h u t
down.
S te p 4 o f t h e normal s h u t down i s r e p l a c e d w it h t h e p r o ce d u r e
w r i t t e n below.
4.
P r e s s t h e d r y shut-down b u t t o n ( 3 1 ) .
run i t s 6 - m i n u te c y c l e .
Allow t h e d r y shut-down t o
I f t h e pumps do n o t s h u t o f f a f t e r 3
m i n u t e s , p r e s s t h e vacuum pump " o f f " b u t t o n (25) !
Allow t h e dry
shut-down t o f i n i s h r u n n in g i t s c y c l e (3 more m i n u t e s ) .
S t e p s 5-7 a r e t h e same a s f o r t h e normal shut-down.
102
rm
.
63
c m 44
I------
»84
*
>
17 18
68
34 35
8
F i g u r e A-I
%
4
Control Console
103
Key t o F i g u r e A-I
1.
H eise p r e s s u r e gauge
2.
Vacuum sy ste m c o n t r o l panel l a t c h
3.
Vacuum sy ste m a u t o m a t i c p r e s s u r e c o n t r o l p o i n t e r s
4.
Vacuum system s u p p l y p r e s s u r e gauge
5.
Automatic vacuum system o u t l e t p r e s s u r e gauge
6.
Vacuum sy ste m c o n t r o l knob
7.
Vacuum sy ste m p r e s s u r e gauge
8.
Vacuum system c o n t r o l p r e s s u r e knob
9.
Pump i n l e t p r e s s u r e gauge
10.
Co n tro l panel d i s c o n n e c t s w i tc h
11.
D igital stagnation pressure in d ic a to r
12.
T em per at ure r e c o r d e r panel l a t c h
13.
T em per at ure r e c o r d e r c h a r t
14.
Cont ro l power i n d i c a t o r l i g h t
15.
Cont ro l power "on" b u t t o n
16.
Cont ro l power " o f f " b u t t o n
17.
Bypass v a l v e "open" i n d i c a t o r l i g h t
18.
Bypass v a l v e " c l o s e d " i n d i c a t o r l i g h t
19.
Bypass v a l v e p o s i t i o n s e l e c t o r s w i t c h
20.
Warning beacon i n d i c a t o r l i g h t
21.
Warning beacon o n - o f f s w i tc h
22.
Vacuum pump " r ea d y" i n d i c a t o r l i g h t
. 104
23.
Vacuum pump "on" i n d i c a t o r l i g h t
24.
Vacuum pump " s t a r t " b u t t o n
25.
Vacuum pump " s t o p " b u t t o n
26.
T h r o t t l i n g v a l v e power i n d i c a t o r l i g h t
27.
T h r o t t l i n g v a l v e "open" i n d i c a t o r l i g h t
28.
T h r o t t l i n g v a l v e "on" b u t t o n
29.
T h r o t tli n g valve "off" button
30.
Dry shutdown i n d i c a t o r l i g h t
31.
Dry shutdown " s t a r t " b u t t o n
32.
High o i l t e m p e r a t u r e i n d i c a t o r l i g h t
33.
Low o i l p r e s s u r e i n d i c a t o r l i g h t
34.
Low w a t e r p r e s s u r e i n d i c a t o r l i g h t
35.
Low o i l p r e s s u r e i n d i c a t o r l i g h t
36.
C hiller indicator lig h t
37. . C h i l l e r " s t a r t " b u t t o n
38.
C h ille r "stop" button
39.
S u p e r s o n i c flow i n d i c a t o r " r ead y" l i g h t
40.
S u p e r s o n i c flow i n d i c a t o r ala rm
41.
S u p e r s o n i c flow i n d i c a t o r o n - o f f s w i t c h
42.
S u p e r s o n i c flow i n d i c a t o r r e s e t b u t t o n
43.
S t a g n a t i o n t e m p e r a t u r e gage
44.
D ig ita l sta g n a tio n tem perature i n d i c a t o r
45.
H e a t e r o v e r t e m p e r a t u r e c o n t r o l gauge
105
46.
H e a t e r o v e r t e m p e r a t u r e c o n t r o l a d j u s t m e n t knob
47.
H e a t e r t e m p e r a t u r e c o n t r o l a d j u s t m e n t knob
48.
H e a t e r t e m p e r a t u r e c o n t r o l , gauge
49.
H e a t e r power "on" b u t t o n
50.
H e a t e r power " o f f " b u t t o n
51.
H e a t e r power on i n d i c a t o r l i g h t
52.
Heater over tem perature i n d i c a t o r l i g h t
53.
H e a t e r on i n d i c a t o r l i g h t
54.
Heater fuse
55.
H e a t e r minimum o u t p u t a d j u s t m e n t
56.
H e a t e r p e r c e n t o f maximum o u t p u t a d j u s t m e n t
57.
H e a t e r p e r c e n t o f maximum o u t p u t gauge
58.
Regenerator i n d i c a t o r l i g h t
59.
Regenerator " s t a r t " button
60.
Panel l i g h t s dimmer knob
61.
Warning s i g n i n d i c a t o r l i g h t
62.
Warning s i g n " o n - o f f " s w i tc h
63.
Atmosp heri c r e f e r e n c e dew p o i n t i n d i c a t o r
64.
Tunnel dew p o i n t d i g i t a l i n d i c a t o r
65.
Dew p o i n t sample flo w i n d i c a t o r
66.
Dew p o i n t i n d i c a t o r w a t e r flow r a t e gauge
67.
Dew p o i n t i n d i c a t o r s c a l e m u l t i p l i e r s w i tc h
68.
Dew p o i n t i n d i c a t o r hou sin g
106
69.
Dew p o i n t i n d i c a t o r i n l e t p r e s s u r e gauge
70.
Dew p o i n t i n d i c a t o r mixing chamber v a l v e
71.
Dew p o i n t i n d i c a t o r t r i m v a l v e
REFERENCES
1.
Car nahan, B r i c e , H. A. L u t h e r , and James 0. W il k es , A pp lie d Numeri­
c a l Methods, New York: . John Wiley & Sons I n c . , 1969.
2.
D e m e t r i a d e s , A. and L. Von S e g g e r n 9 D es ig n , Performance and Opera­
t i o n o f t h e S u p e r s o n i c Wind T u n n e l , T ec h n ic al R e p o r t , 1965.
3.
Drummond, D. H ., P er s o na l C o n v e r s a t i o n s .
4.
Liepmann, H. W., and A. Roshko, Elements o f Gasdynamic s , New York:
John Wiley & Sons I n c . , 1957.
5.
S c h l i c h t i n g , H ., Boundary Layer T h e o r y , Seventh E d i t i o n , New York:
McGraw-Hill Book Company, 1975.
M ONTANA ST A T E U N IV E R SIT Y L IB R A R IE S
RL
stks N378.R631@Theses
3
1
A137?