Purdue University
Purdue e-Pubs
International Compressor Engineering Conference
School of Mechanical Engineering
1996
Study of Accelerating Torque Requirements of a
Reciprocating Compressor
V. K. Rao
Siel Refrigeration Industries
P. S. Murty
Siel Refrigeration Industries
M. S. Reddy
Siel Refrigeration Industries
S. A. Sundaresan
Siel Refrigeration Industries
Follow this and additional works at: http://docs.lib.purdue.edu/icec
Rao, V. K.; Murty, P. S.; Reddy, M. S.; and Sundaresan, S. A., "Study of Accelerating Torque Requirements of a Reciprocating
Compressor" (1996). International Compressor Engineering Conference. Paper 1083.
http://docs.lib.purdue.edu/icec/1083
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STUDY OF ACCELERATING TORQUE REQ
UIREMENTS
OF A RECIPROCATING COMPRESSOR
AUTHORS
v Ko tesw ara Rao , P Sat yan ara yan a Mu
rty,
M
Sri niv asa Red dy, S A Sun dar esa n
Sie l Re frig era tio n Ind ust rie s
Hyd era bad - 500 037 , Ind ia
ABSTRACT
Du ring sta rta bil ity tes ts,
eit her 1) sta rt and run wit hou a rec ipr oca tin g com pre sso r can
all or 3) tur ns ove r but doe s t any pro ble m or 2) not sta rt at
not sta rt or 4) sta rts and cro sse
the cri tic al poi nt and the n
s
sta
acc ele rat ing tor que of the com lls . Of the abo ve phe nom ena ,
bu ilt up in the sys tem . In pre sso r dep end s on the pre ssu re
the pre sen t pap er,
the tor que
req uir em ent s are stu die d and the
per for ma nce of the the ore tic al
mo tor des ign is com par ed at
dif fer ent
dif fer ent
als o
sta rtin g phe nom ena are the n vol tag es. And
exp lain ed from
the
exp erim ent al res ult s.
INTRODUCTION
One of the imp ort ant par am
the des ign of a mo tor for a her ete rs tha t is con sid ere d dur ing
tor que req uir em ent . Usi ng thi me tic com pre sso r is the sta rtin g
the low est
vol tag e dow n to whi ch the com pres sta rtin g tor que ,
sso
r
can
sta
rt
can
be
est ima ted .
How eve r, the sta rtin g tor que alo
ne
is
not
suf
fic
ien
t
for
sta rtin g
and run nin g the com pre sso r.
The
inf
orm
atio
n
nee
ded
is the
acc ele rat ing tor que cha rac ter ist
ic of the pum p.
For sus tain ed run nin g, the
equ al or hig her tha n the acc ele mo tor pul l-u p tor que has to be
the pum p at all spe eds til l the rat ing tor que cha rac ter ist ic of
poi nt. Par am ete rs suc h as the bal com pre sso r cro sse s the cri tic al
anc ed pre ssu re at sta rtin g, the
rat es at whi ch the suc tio n and
dis
on the sys tem and ope rat ing con cha rge pre ssu res cha nge dep end
fix ed for a giv en com pre sso r dit ion s. The oth er par am ete rs are
fun ctio n of bot h the des ign and des ign . Fri cti on, how eve r, is a
the amo unt of ref rig era nt dis sol the ope rat ing con dit ion s suc h as
ved in the oil and the spe ed. For
a giv en mo tor des ign , onl y the
vol tag e aff ect the pul l-u p tor que win din g tem per atu re, and the
.
An exp erim ent al met hod
is des crib ed for eva lua tin g
acc ele rat ing tor que cha rac ter ist
the
the ore tic al mod el for est im atin ic of the com pre sso r and als o a
g thi s is pre sen ted .
At dif fer ent sup ply vol tag es the
mo tor tor que s are com par ed
wit h tor que req uir em ent s of com
pre
sso
r
and the dif fer ent sta rtin g
phe nom ena are exp lain ed.
55
EXPERIMENTAL SET UP
the foll owi ng item s:
The exp erim enta l set up con sist s of
- Tes t com pres sor with out hou sing s
com pres sor sha ft
- Tor que and Spe ed sen sor cou pled to
sha ft
- Dri ve mot or cou pled to Tor que sen sor s wit h air tigh t lid
item
ve
abo
lose
enc
- Spe cial hou sing to
l set up is in fig 1.0 .
The diag ram show ing the exp erim enta
the tes t com pres sor are
The suc tion and disc har ge tub es of
cha rged afte r eva cua tion to
con nec ted to a syst em. The syst em is mot or are con nec ted to the
e
norm al cha rge . The lead s of the driv
ed and torq ue sen sor are
spe
the
of
s
lead
and
pow er sup ply
icat ors out put con nec ted to a
con nec ted to the ind icat ors and ind mot or is ene rgis ed the spe ed
stor age osc illo sco pe. When the driv e
the osc illo sco pe for a giv en
and torq ue valu es are reco rded in
avio ur of the suc tion ·an d
tim e. Sim ilar ly the tran sien t beh usin g stor age osc illo sco pe.
disc har ge pre ssu res are also reco rded list ed in tab le l.O
The obs erv atio ns of the· exp erim ent are
not be reco rde d pro per ly
The beh avio ur at low er spe eds cou ld
on eno ugh to reco rd qui ck
as the sen sor use d is not pre cisi
cisi on inst rum ent atio n this
resp ons es. How ever by usin g the pre
can also be reco rded .
firs t prin cip les.
The Fri ctio nal Tor que is mea sure d from
Pre ssu re
Bac k
exp erim ent is rep eate d for a Low ing s are giv en
The
reco rded read
app lica tion com pres sor for whi ch.t he
in tab le2 .0.
THEORETICAL MODEL
A.. STARTING TORQUE
end s on the cran k ang le
The sta rtin g torq ue requ irem ent dep
er volu me at tha t cran k ang le,
pos itio n (Re fere nce [l]) ,the cyl ind e of star ting , pis ton are a,
syst em equ alis ed pre ssu re at the tim
to ope n the disc har ge valv e,
the dif fer ent ial pre ssu re req uire d ran t and the sta tic fric tion .
the pol ytro pic inde x for the refr ige as
The sta rtin g torq ue can be exp ress ed
Ts
= f(Pe ,V(¢ )
V(~)
= Vc+Ap
- (l)
,Pc, Ap, n,x) + Tf
Cr{1+Cos(~)+
Cl/C r [l-
~ 1-(Cr/Cl~
].
Tf is calc ula ted bas ed on Ref eren ce[2
56
-2
Sin (¢) ] }
- {2)
Ts
Ap
n
vc
Cl
Pe
Pc
~
Sta rti ng To rqu e
Tf
Fr ict ion al To rqu e
Pis ton Are a
v ({l)) Cy lin der Vo lme
Po lyt rop ic Ind ex
X
Pis ton lin ea r dis pla cem ent
cle are nce vol um e
Cr
Co nne cti ng rod rad ius
Co nne cti ng rod len gth
¢
Cra nk An gle
Eq ual ise d pre ssu re at the tim e of
Pre ssu re in the cy lin de r to ope n sta rti ng
the Di sch arg e Va lve
ACCELERATING TORQUE
The tra ns ien t beh avi ou r
of the suc tio n and
pre ssu res in the sys tem are
dis cha rge
cal cu lat ed usi ng Re fer enc es
Ind ica ted wo rk is cal cu lat ed
[3- 5] .Th e
fro m the po lyt roi c eq ua tio n
n-1 /n
Wi = (n/ n-1 ) Ps Vs ( (Pd /Ps )
- 1)
- (3)
Ps Su cti on pre ssu re
Pd Dis cha rge pre ssu re
Vs Vo lum e of Va pou r suc ked
The acc ele rat ing tor qu e is
cal cu lat ed as sho wn bel ow
Ta = Wi*C + Td f
- (4)
C
Co nve rsi on fac tor
Tdf
To rqu e req uir ed to ove rco me
Dy nam ic fri cti on
He re Td f is ass um ed to be 5%
of the cal cu lat ed To rqu e.
DESCRIPTION OF RESULTS
As sho wn in Fig 2 the mo tor
sel ect ed for the HBP com pre
beh ave s in the fol low ing ma
sso
nne
r
at
dif fer en t vo lta ge s. At 120 r
mo tor doe s no t sta rt{ No Sta
V
rt) at all . At 140 V mo tor
sta lls (T urn s on No St art ).
tur
ns
and
At
rea chi ng the fu ll spe ed. Ab 160 V mo tor sta rts and sta lls aft er
ove 160 V it sta rts and run
any pro ble m.
s wi tho ut
As
beh ave s
all . At
sta lls .
sho wn in Fig 3 the mo tor sel
in the fol low ing ma nne r. At ect ed for the LBP com pre sso r
140 V and 160 V the mo tor sta 120 V mo tor doe s no t sta rt at
Ab ove 160 V it sta rts and runrts and rea che s fu ll spe ed and
s wi tho ut any pro ble m.
CONCLUSIONS
The val ues cal cu lat ed fro
wi th the exp eri ma nta l val ues m the pro pos ed the ory are ma tch ing
sa tis fac tor ily . Fu rth er stu
thi s dir ec tio n may ext end
die s in
the
ap pli ca bil ity of thi s the ory
dif fer en t ap pli cat ion s to pre
to
dic t the To rqu e req uir em ent
com pre sso r and hen ce mo tor
s
of
the
can be des ign ed ap pro pri ate
the com pre sso r.
ly to su it
57
REFERENCES
1.
2.
3.
4.
5.
6.
er,
, Ted 0. Phil and Rona ld , R. Wisning
Gate cliff, G. w.
rocat
"Ana lytica l Pred ictio n of the Start abili ty of Recip
with
comp arison
inclu ding
comp resso rs
Refri gerat ion
ressor
Comp
of the 1976 Purdu e
Expe rimen t",Pro ceedi ngs
25.
221-2
,
pp.
,1974
rence
Techn ology Confe
a,
Venk atesw arlu, K. , Rao, N. J. , Venu gopal , E. V. , Akell
Comp ressor
S.,"A n Integ rated Appro ach to Recip rocat ing
Comp ressor
e
Purdu
1990
the
of
Desig n",Pr oceed ings
-291.
282
pp.
,
Engin eerin g Confe rence , 19-90
mic
G.T. Karts ounes and R.A. Erth, "Calc ulatio n of Therm odyna
tal
Digi
a
using
R502
&
22
prop ertie s of Refri geran ts R12,R
ressor
Comp
e
Purdu
1972
Proce eding s of the
Comp uter",
Techn ology Confe rance , 1972 , pp. 285
of the
Rajen dran, N. and Pata, M.B., "A Comp uter model gerat
ion
Refri
n
ressio
comp
start -up trans ients in a vapo r
of
tute
Insti
nal
natio
system n. Prep rints of the 1986 Inter
1986.
5-8,
st
Augu
40,
Refri gerat ion Meeti ng, Purdu e, pp. 129-1
nce
Niels Jorge n Josia ssen , ••sim ulatio n of Cond ition sequem",
syste
ion
gerat
durin g start -up of an Evap oratio n Refri
Techn ology
of the 1978 Purdu e Comp ressor
Proce eding s
Confe rence , 1978 , pp. 309-3 16.
tion
Vein ott, C . G. , "Theo ry and Desig n of Small Induc
1959
,NY,
York
Moto rs", McGr aw-H ill Book Comp any, Inc., New
EVAPORATOR
DISCHARGE MUFFLER
COMPRESS OR
FIG 1.
SCHEMATIC DIAGRAM OF TEST SETUP
58
COMPARISION OF THEORETIC
AL AND EXPERIMENTAL DA
TA OF HBP COMPRESSOR
SUCTION PRESSURE DI SC H.
PRESSURE
TORQUE
TIME
(P sia )
(P
sia
)
(O z-F t)
(Se c)
SPEED
THEORE- EX PE RI- THEORE(RPM)
EX PE RI- THEORE- EX PE RITICAL
MENTAL
TICAL
MENTAL
TICAL
MENTAL
0
13 4.7
13 4.7
13 4.7
13 4.7
9.1 6
14 5
I
0
3.4 55
3.6
10 0
16 8.4
15 .98 2
16 .6
0.5 0
13 4
13 4
~40
1.0 0
13 2
13 1.5
16 2
12 9
19 8
20 3
32 .45
33 .9
12 5
23 0
23 4.6
45 .04
46 .2
12 2.8
27 4
28 0
58 .31
60 .1
11 6
29 6
30 3
64 .19
66 .0
1.5 0
13 0
2.0 0
12 6
3.0 0
4.0 0
12 4
11 8
I
I
8.6
!
I
I
I
30 5 I
93 3
I 16 00
I
25 90
I
29 00
Ta ble 1.0
COMPARISION OF THEORETIC
AL AND EXPERIMENTAL DA
TA OF LBP COMPRESSOR
SUCTION PRESSURE DI SC H.
PRESSURE
TIME
TORQUE
(P sia )
(P
sia
)
{S ec}
(O z-F t)
SPEED
THEORE- EX PE RI- THEORE
(RP M)
- EX PE RI- THEORE- EX PE
TICAL
RIMENTAL
TIC AL
MENTAL
TICAL
ME NT AL
0
69 .7
0.3 7
68 .1
0.8 9
66 .67
1.3 9
65 .2
1.9 0
63 .7
2.3 0
63 .2
90 .00
25 .7
69 .7
69 .7
69 .7
9.1 6
8.8
0
69 .2
10 8.7
11 0.4
3.0 14 6
3.1
75
68 .1
11 4.7
11 9.2
3.4 27 5
3.6
23 9
67 .1
11 .9. 7
12 4.0
3.7 54
3.9
73 0
65 .73
12 9.7
13 3.1
4.2 95
4.5
20 20
64 .5
13 4.7
13 9.8
4.5 21 6
4.7
28 00
26 .8
16 5.7
17 1.5
4.2 98
4.5
29 00
Ta ble 2.0
59
l
I
MOTOR
SPEED VS TORQUE CURVES OF rlBP COMPRESSOR AND
-------------~
--,----~-------------
200"1~---------------
lliE----* COtv1PRESSOR TORQUE
J
150
\\
'\
100
w
..--,
;:;
::c
c
1000
SPEED IN RPM
3000
2000
FIG 2
AND MOTOR (CSIR)
SPEED VS TORQUE CURVES OF LBP COMPRESSOR
MOTOR
12
"<:f
--- ---
0
X
I--
LL
N
---
----- --- ---
0
1--
''
'
'
\.
' ' ....
8
...
.....
...
''
E -160V
..-- -~-----------~ ...
____R_CURV
____MOTO
z
a:
''
---
~, ...
0
w
~
a
--~-
CUR~~-~:~?Y~--------------~,
"'
MOTOR CURVE -i40V
--, ;.- --- --- --, ... __ -......:...
.......
~~--~
120;-4 r--.;:_·___ ___ ___ ___ _ MOTOR CURV~-
.
' .
'\
\
\
~\
"- ' \
--- --- --- -- '
--........
.
~-----------~~--------- C?_~B_ES_?_OR_J069U~- C\lf3Vf. _______ ;._-..=_-::-::~~~\
""'---
1;~-------""
!,;,..,
:
0
-----
----------
.
.
.
~.
--
\
'
-----M
-------------~--~--~--~-
L---------~-------------
0
1000
'
SPEED IN RPM
FIG 3
60
2000
3000