DIESEL INJECTION OF COAL-WATER SLURRY
BY
TIMOTHY MARK CLOSE
B.S.,UNITED STATES COAST GUARD ACADEMY
(1982)
SUBMITTED TO THE DEPARTMENT OF
OCEAN ENGINEERING
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS
FOR THE DEGREES OF
MASTER OF SCIENCE IN NAVAL ARCHITECTURE AND MARINE ENGINEERING
AND
MASTER OF SCIENCE IN MECHANICAL ENGINEERING
at the
@
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
JUNE 1986
The author hereby grants to MIT and the U.S. Government
permission to reproduce and distribute copies of this thesis
document in whole or in part.
Signature of author: __________
Department
Certified by:
of Ocean Engineering
__
Wai K. Cheng, Thesis supervisor
Accepted by:
A. Douglas tarmichael, Thesls Reader and
ntal Graduate Committee
Chairman, Depar
gineering
Department
Accepted by:
____
Ain A. Sonin, Chairman
Departmental Graduate Committee
Department of Mechanical Engineering
MASSACHUSETTS INSTITUTE
OF TECHNOLOGY
AUG 06 1986
LIBRARIE
ARCHIVES
DIESEL INJECTION OF COAL-WATER SLURRY
by
TIMOTHY MARK CLOSE
Submitted to the Department of Ocean Engineering in
partial fulfillment of the requirements for the degree
of Master of Science in Naval Architecture and Marine
Engineering and Master of Science in Mechanical
Engineering.
ABSTRACT
The use of coal-water slurry as a diesel engine fuel
can lead to a reduction in fuel costs in large bore diesel
A single injection, high-pressure bomb was used to
engines.
study the spray characteristics of coal slurry injected from a
modified high-pressure pintle nozzle at injection pressures up
Each injection
to 4200 psi and bomb pressures up to 1400 psi.
was filmed using a high speed camera and the films were
Baseline
analyzed for spray velocities and spray patterns.
series of injections were conducted with water and No.2 diesel
These injections and films show that for the four
fuel.
different types of coal slurries tested, as well as for water
and No.2 diesel fuel, the injection velocity at the nozzle
exit is not sensitive to fuel types, and may be obtained by
using a flow coefficient which only depends on the internal
Still photographs were made to
geometry of the nozzle.
determine the drop sizes using a 500 nanosecond flash tube
which was able to "freeze" the droplets of coal slurry during
Atomization of the slurry was generally poor
the injection.
and the majority of the slurry remained as large globules.
Thesis Advisor:
Title:
Doctor Wai K. Cheng
Associate Professor of Mechanical
2
Engineering
ACKNOWLEDGEMENTS
The author wishes to express his gratitude to Professor
Wai
K.
Cheng for his guidance and assistance
His expertise, devotion, and
work.
throughout
this
insight were greatly
appreciated.
I also wish to acknowledge the Fannie and John Hertz
Foundation who sponsored me at M.I.T.
Their dedication to
current research
in Applied Physical Sciences and their
benevolence have
made me proud to be associated with such an
outstanding group of people.
Special
Arthur D.
thanks are
in order to Ms. Karen Benedek of
Inc.
for her assistance and direction
Little,
in
this project, especially in the later stages of the work.
Her efforts to keep me
shielded from sponsorial
screams for
results were also greatly appreciated.
For the answers to a myriad of questions mostly unrelated
to their own work,
I am most thankful
to my friends Eric
Balles, David Patterson, and Stefan Pischinger.
selflessness was unequalable.
And without the advice and
expert help of the laboratory staff
Howard Lunn, and Dave Rouse,
Their
including Don Fitzgerald,
this work would have been much
more difficult.
Finally, this thesis
is dedicated to my parents who
provided me with much support and encouragement, and to my
wife, Peggy, who
is my source of strength and a
with.
3
joy to be
This work was sponsored by Arthur D. Little,
Inc.,
Cambridge,
Massachusetts with funding from the U.S.
Department
of Energy.
4
TABLE OF CONTENTS
page
Page......... ..................
Title
...... 1
..........
Abstract..............................................2
.
.
.
.
.
.
.
.
.
.
.
.
.
.
........ 3
Table of Contents. .
.
.
.
.
.
.
.
.
.
.
.
.
.
.......- 5
Acknowledgements..
List of Tables........................................8
List of Figures..... ..
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.. 9
List of Plates.......................................10
I.
11
INTRODUCTION......
A.
Background.....
.
11
B.
Incentives.....
.
11
.
13
C. Initial Sizing of the Equipment.
II.
MATERIALS AND EQUIPMENT.
.15
A. SLURRIES.............
.15
B.
1. Properties....
.15
2. Energy........
.17
3. Stoichiometry.
.18
.19
INJE CTION / HIGH SP EE D MOVIE TESTS..
1.
The Bomb..... an
.21
2.
The Injector an d Nozzle.......
.22
3.
The Needle Lift S ensor..
.23
. . ..
..
..
..
..
...
4.
The
Pressure Transducer.
.23
5.
The Solenoid Valve......
.23
6.
The Accumulator.........
5
..
.
.24
.......
C.
III.
IV.
7.
The Piston Interface...... ..
.
.
..
.
.
25
8.
Valves and Tubing......... ..
.
.
..
.
.
26
9.
The Movie
..
.
.
..
.
. 27
10.
Lighting..........
..
.
.
..
.
.
11.
Controls..........
..
.
.
..
.
. 28
12.
Data Acquisition..
..
.
.
..
.
.
29
13.
The Air Compressor
..
.
.
..
.
.
29
14.
The Rolling Mixer.
..
.
.
..
.
.
30
STILL PHOTOGRAPHY TESTS.
..
.
.
..
.
.
30
1.
The Camera........
..
.
.
..
.
.
30
2.
The Light Source..
..
.
.
..
.
.
32
3.
The Controls......
..
.
.
..
.
.
32
Camera and Lens
28
SLURRY HANDLING..
34
A. SETTLING.......
34
B. CLOGGING.......
35
C. DRYING.........
37
D. WEAR...........
37
PROCEDURES..............
A. INJECTION / HIGH SPEED MOVIE
TESTS..
1. Test Matrix......
2. System Evolution.
3. Method...........
4.
Other
Instrumentation..
47
B. INJECTION / STILL PHOTOGRAPH Y TESTS. ..........
..
2. Method.................
V.
47
.....
1. Test Matrix............
.
..
.
48
RESULTS AND DISCUSSION.........
.51
A. HIGH SPEED MOVIES............
.51
1. Spray Penetration Analys
2.
Penetration Times.......
3. The Cone Angles.........
B. STILL PHOTOGRAPHS............
6
......
.51
.55
.59
.60
VI.
63
CONCLUSIONS .....................................
VII. FUTURE RESEARCH.................................64
REFERENCES...........................................66
Appendices
A.
Plates........................................68
B.
Droplet Size Distribution Graphs..............75
7
LIST OF TABLES
page
Table
1.
Coal Slurry Properties
Table
2.
Injection / High Speed Movie
Table
3.
Injection Still Photography Test Matrix
49
Table
4.
Droplet Size Averages
61
16
8
Test Matrix
41
LIST OF FIGURES
page
Figure
1.
Injection System Diagram
20
Figure
2.
Injection System Evolution
42
Figure
3.
Typical
Penetration Histories
52
Figure 4.
Injection Correlation
54
Figure 5.
Penetration Time Graphs
57
9
LIST OF PLATES
page
Plate
1.
Injection System
69
Plate
2.
High Speed Movie Comparison
70
Plate
3.
Droplet Still Photograph #1
71
#2
72
#3
73
#4
74
10
I.
INTRODUCTION
A.
BACKGROUND
The concept of using a coal-based fuel
engine dates back to the
1890's to Rudolph Diesel's early
experiments with powdered coal.
Pawlikowski,
met
His colleague,
success prior to World War I with his
RUPA engine which used compressed air to
into the engine.
coal-based fuels
the late
in a diesel
Research
inject coal dust
in the U.S. on the
use of
in diesel engines did not begin until
1940's and fuel
problems showed little
injection difficulties and wear
promise.
a slow-speed two-stroke diesel
Engine tests
in
1979 on
using a pulverized
coal-water slurry demonstrated finally that it was
feasible to use coal-based fuel
in a diesel cycle, and
relatively high fuel conversion efficiencies were
obtained. (Ref. 1)
B.
INCENTIVES
The motivation for the use of coal-water slurry is
to provide a long term readily available energy
resource.
The depletion of oil supplies and the
dependence on
imported oil has created
11
interest
in the
abundant domestic coal
supplies.
Handling problems with
powdered coals are avoided to a large
extent with coal
slurries, and of the various possible slurries that can
be
used, coal-water slurry seems to be
economical.(Ref. 2)
amounts to a small
the coal,
The presence of water
in the slurry
energy penalty, 3%-7% of the energy
depending on the coal concentration
slurry.(Ref.3)
in
in the
Despite this penalty, available
literature suggests that there
savings
the most
in fuel costs for large
may be a considerable
medium-speed and
slow-speed diesel engines such as
in stationary power
plants, marine propulsion systems, and railroad
locomotives.(Ref.4,5)
Indications from thermodynamic
analyses of the combustion of coal-water slurry show that
the possibility exists also to reduce
the peak combustion
temperature and thus reduce the NOx emissions
from the
diesel engine.(Ref.1)
Several engine tests have been conducted using
coal-oil slurries and coal-jet fuel slurries and
coal-water slurries with little
investigation of
injection properties of the slurry.(Ref.6,7)
The
completeness and duration of combustion of coal-water
slurry is greatly affected by the atomization (and
subsequently the penetration) of the
injection spray.
Tests done in simulated diesel environments showed
incomplete combustion due to
inadequate spray atomization
of coal-water slurry which they felt could also result
12
in
It is
spray impingement on the cylinder walls.(Ref.2)
believed that the droplet sizes in the spray may in fact
be
more significant than the
fuel-air mixing rate as the
limiting step in combustion of coal-water slurry because
the droplet size will eventually determine
time
the general
scale for evaporation of the water, and ignition of
the coal
The
particles.(Ref.4)
significant energy penalties associated with the
twin-fluid atomizers
use of
the use
of mechanical
for use
study
in
(air-blast atomizers)
injection systems worthy of
further
engines.
diesel
Some extensive work has been done on the
and atomization of coal,
diesel
make
injection
charcoal, and coke particles
fuel at various conditions (Ref.8), but less
known about the diesel
in
is
injection and atomization of coal
particles in water. It is hoped that this thesis will
shed some light on this subject.
C.
INITIAL SIZING OF THE EQUIPMENT
Since coal burns much slower than diesel
fuel,
the
use of coal slurry as a viable fuel for diesel engines
will be
restricted to
large,
slow or medium-speed engines
in which a longer allowable time for combustion exists.
A rough estimate of the smallest diesel engine
that could
conceivably use coal slurry is one with a bore of eight
13
inches.
Multi-hole centerline
fuel
injection common
in
this size engine was simulated in this work by using a
single hole
injector with a pintle nozzle and injecting
from the side of a four inch diameter chamber.
Consequently, the bomb used for the
designed with a
injection testing was
four inch bore which also corresponded
exactly to the bore of the Rapid Compression Machine
which will
be used for combustion research
future.
14
in the
II.
A.
MATERIALS AND EQUIPMENT
SLURRIES
Four different coal
slurries were
used
in the
injection tests, and each was composed of approximately
50% coal
and 50% water by mass.
Small
amounts of
chemical additives were used to keep the slurries from
agglomeration and settling, and to vary the transport
properties.
The most extensive testing and high speed
filming was
done on the slurry supplied by Resource
Engineering Incorporated (referred to as the REI
slurry).
The other three slurries were supplied by AMAX
Corporation and were basically similar except they were
each of different viscosities (referred to as AMAX
A,BC).
1. Properties
Table 1 lists some of the pertinent physical
properties of the
coal,
water,
four slurries.
The differences
and additive percentages
in
were necessary to
achieve the different viscosities in the three AMAX
slurries.
Differences in the ultimate analysis and the
15
TABLE 1
REI slurry
I COAL
7 WATER
7.ADDITIVES
Reagent
Stabilizer
Surfactant/Dispers.
Anti-foaa
50.3
49.7
C
H
0
N
S
C1
V
85.06
5.41
6.72
1.49
0.68
0.15
0.0003
ULTIMATE
ANALYSIS
OF COAL
AMAX C
AMAX B
AMAX A
51.4
47.7
51.1
47.62
51.8
47.68
0.90
0.0031
1.28
0.0046
0.52
0.0016
81.15
5.42
10.93
1.75
0.75
-
81.15
5.42
10.93
1.75
0.75
-
81.15
5.42
10.93
1.75
0.75
-
-
-
-
1.10
0.05
0.54
0.54
0.54
0.49
% ash
PROXIMATE
34.8
34.8
34.8
37.97
% vol
ANALYSIS
64.66
64.66
64.66
61.54
X carb
OF COAL
----------------------------------------------52.4 %
52.4 X
52.4 7
20.5 7
(5
PARTICLE
32.7 %
32.7 1
32.7 %
45.5 %
5-10
SIZE
11.9 %
11.9 7
11.9 %
33.5 %
11-20
DISTRIBUTION
3.0 %
3.0 1
3.0 /
0.5 X
>20
in microns
6.2
6.2
6.2
7.0
mean
----------------------------------------------1112
1120
1051
1088
DENSITY (kg/m3)
780
260
580
254
@12.6/sec @1000/sec @1000/sec p1000/sec
-----------------------------------------------
VISCOSITY (cps)
HEATING
VALUE (kJ/kg)
16,575
17,141
16
17,141
17,274
proximate analysis of the coal between the REI
and the
AMAX slurries are the result of different coals used by
the manufacturers, and although the mean particle size of
the REI slurry and the AMAX slurries are similar, the
size distributions are very different.
densities are all similar.
The
slurry
The viscosities were supplied
by the slurry manufacturers and here
it should be noted
that since slurry is a non-Newtonian fluid, the viscosity
is dependent on the shear rate.
The REI slurry has a
viscosity of 254 centipoise at a shear rate of
sec
while the viscosities of the
measured at a shear rate of
12.62
AMAX slurries were
1000 sec~I
therefore making
exact comparisons not possible.
2. Energies
The net energy per unit mass of the REI
calculated from the coal energy content
slurry was
(the value
was
provided by the manufacturer), the percentages of coal
and water
in the slurry, and the energy required to
vaporize the water.
The basic equation
HV slurry=(%coal)(HV coal)
-
is as follows:
(%water)(vap.energywater
where the heating values are
in kJ/kg and
the vaporization energy of water
17
is 2260 kJ/kg.
For the REI slurry, the heating value was determined to
be
16,575 kJ/kg which is approximately 2.5 times less
than that of diesel
fuel.
This means that the total
volume of slurry injected would have to be
2.5 times
larger than that of diesel
the same
fuel
to produce
amount of work.
The heating values of the
AMAX slurries were
provided by the manufacturer and are also summarized in
Table
1.
3. Stoichiometry
The stoichiometric ratio
air to the mass of
occur.
fuel
is the
ratio of the mass of
for complete combustion to
For example, approximately 15.04 grams of air are
needed to completely combust 1.0 grams of diesel fuel,
therefore the stoichiometric ratio
of fuel
is 15.04 for diesel
fuel.
of mass of air to mass
This
is determined by
first balancing a simplified chemical equation for
combustion to find the number of moles of air necessary
for complete combustion
(combustion in which there
neither unburned fuel or unused air remaining
is
in the
The comparison of the number of
combustion products).
moles of air (oxygen plus nitrogen) times the molecular
weight of air to the
number of moles of fuel
molecular weight of the
fuel
times the
is thus the air to fuel
18
ratio by mass for complete combustion,
i.e.,
the
stoichiometric ratio.
To determine the stoiciometric ratio for coal
slurry, several
assumptions/simplifications were made.
It was assumed that only the carbon and the hydrogen in
the coal actually reacted with the air, and
that the
remainder of the coal components had little effect on the
reaction.
The water in the
slurry was
also assumed to
have little effect, merely passing through the equation
to appear as water vapor
in the combustion products.
The
stoichiometric ratio for the REI slurry was calculated to
be 5.84:1
mass of air to the mass of slurry and for the
AMAX slurries, 5.66:1.
slurries is due
to the
The slight differences between
slightly different chemical
compositions of the coals used.
B.
INJECTION / HIGH SPEED MOVIE TESTS
The basic injection system
constant pressure
the
is shown in Figure
1.
is applied on a working fluid through
inlet on the accumulator (element #1),
three-way D.C. solenoid valve
(element #2).
up to a
When the
solenoid Is energized, the pressure travels through the
working fluid up to a
free-floating piston (element #3)
which separates the working fluid from the fuel
19
to be
A
FIGURE 1
DIAGRAM OF THE INJECTION SYSTEM
INL ET
©
RELIEF
20
injected.
is pressurized past a
Consequently, the fuel
into
pressure transducer (element #4)
(element #6)
injector needle
The high-pressure
has a clearance of
1.5
1.0
The
lift
sensor (element
stainless steel bomb (element #7)
inch and
is 4.0
inches
in
inch thick Pyrex windows allow
viewing and filming the
1.
The needle lift
to lift.
is measured by a Hall-Effect needle
diameter. Two
injector
mounted on the top of the high-pressure bomb
and causes the
#5).
the
for
injection spray.
Bomb
The bomb was made of 304 stainless
inch diameter bore and a one
steel with a four
inch clearance.
A pyrex
window was used on each side of the clearance volume
allow for viewing the
in diameter and
injection and each was 4.75
1.5 inches thick.
were designed for testing up to
pressure with an adequate
place
1500 psi
internal
The windows
inside and were held
from the outside with stainless steel
teflon gaskets.
The
inches
The bomb and windows
safety margin.
were sealed with o-rings on the
to
in
flanges and
injector was mounted on the top of
the bomb and nitrogen was used to pressurize
21
the bomb.
2.
The
Injector and Nozzle
The
injector used was a commercially available
standard Robert Bosch injector (part # 0-431-201-021)
with an opening pressure which was variable through the
use
of an adjustment screw.
American Bosch ADN-4S-1
was chosen because
it
The nozzle
(single hole)
used was an
pintle nozzle.
It
is both commonly used and
relatively inexpensive.
This
last feature
was deemed
desirable because significant permanent nozzle clogging
was
foreseen which would necessitate replacement
nozzles.
Nozzle clogging did occur frequently but the
nozzles were fairly easy to clean.
discussed
in more detail
in a
With a pintle nozzle,
This will be
later section.
the spray pattern
is dependent
on the shape, or flair, of the needle tip and the
internal profile
a
of the
straight passage
pattern.
orifice.
The present nozzle had
and therefore produced a narrow spray
This nozzle was acceptable for comparison of
atomization properties of the slurries and
it was never
intended to be the choice for optimal spray
characteristics.
Plans
for future research
design of a different nozzle
include
the
expressly for coal slurry
which will be optimized for atomization properties and
spray pattern for the particular engine geometry.
22
3.
The Needle Lift Sensor
A Hall-Effect
needle
lift of the
was mounted to the
"Microsensor" was used to record the
A samarian-cobalt magnet
injector.
lower spring seat
high temperature epoxy.
in the
injector with
This spring seat rode directly
on top of the needle and the resulting changes
in the
magnetic field with the needle movement were picked up by
the sensor.
The sensor itself was mounted through the
leak-off fitting on the top of
the
injector.
distances as converted from the needle
highly dependent on the
lift sensor were
initial distance
the sensor from the magnet.
lift was most useful and the
needle
lift occurred was clearly visible.
The
of the end of
However, the timing of the
needle
4.
Actual
point where
maximum
Pressure Transducer
A Data Instruments AB-5000 pressure transducer with
a
maximum rating of 5000 psi was used to measure rail
pressure
in the fuel
line
prior to the
injector for the
injection tests.
5.
The Solenoid Valve
A three-way 28 volt DC solenoid valve
23
was used to
control the
injection pulse.
It was commercially
available from Circle Seal Corporation and was rated for
6000 psi applications.
In a de-energized status, the
line was open to atmospheric pressure via
injection rail
the normally open port
When energized,
in the solenoid.
this port was
sealed off and
the pressurized port was
opened to the
injection rail
line.
solenoid lift
itself
The action of the
imposed a minimum on the
injection
duration partly because of the pressure equalization of
the three ports as the
not yet
seated.
solenoid needle
Attempts to reduce
the
was
lifting but
injection
duration further than a certain value would simply result
in a pressure rise at the
the
injector needle.
the solenoid valve
injector
insufficient to
The relatively small passages
The o-rings,
seats, and seals
6.
in a
in the
valve did not stand up to repeated use with coal
and had to be
in
led to clogging of the solenoid valve
by the slurry and will be discussed in more detail
later section.
lift
slurry
frequently replaced.
The Accumulator
The accumulator acted as a pressurized reservoir.
It was made
316 stainless
from 316 stainless steel
steel
stainless steel
80 end caps,
schedule
flanges.
schedule 80 pipe,
The
24
and
150 psi
316
flanges had an additional
four bolt holes drilled to make them eight hole
to prevent
flanges
leakage through deflection of the flanges.
The end caps and flanges were professionally vacuum
welded to two short pipe
sections
in such a way that the
accumulator could be taken apart at the middle.
stainless
steel stir shaft was
A 304
installed through the top
end cap and was sealed with a thrust bearing and two
o-rings.
This shaft was driven by a high-torque,
motor mounted to the
original
outside of the
accumulator.
low-rpm
The
intent of this stir shaft was to keep the slurry
agitated during periods between
accumulator was not pressurized.
injection tests when the
In practice,
this was
necessary very few times as the accumulator was kept
pressurized for the most part and later,
modified and slurry was replaced in
another working fluid.
the system was
the accumulator with
The shaft seal
though held very
well.
7.
The Piston Interface
This device was used to
the solenoid control
valve.
isolate the coal
It
is a
five
slurry from
inch long,
304
stainless steel cylinder flanged at each end enclosing a
free-floating aluminum piston inside.
diameter, one
in a groove
The two
inch
inch thick piston was sealed with an o-ring
cut
into the piston.
25
The device was
initially designed to be an
interface between high
pressure air and the fuel that was being Injected.
However, the
increasing volume on
the air side
of the
piston as the piston moved greatly effected the
the
fuel was actually pressurized, and
time
that
injection
durations shortened with each successive
injection until
the
to
fuel
was not pressurized long enough
injection needle.
as
the
The
lift the
solution involved using the piston
interface between two different fluids,
being tested and another liquid.
as this other liquid because of
properties which would prolong
Diesel
its
fuel
the
fuel
was chosen
lubricative
the solenoid valve
performance.
8.
Valves and Tubing
Concern over possible
valves
leaking and clogging of
led to the choice of ball
valves over other types
due to the sweeping motion of the ball
to clean the seats.
The valves used
which would tend
in the
system were two-way stainless steel ball
a maximum operating pressure
supplied with Kel-F ball
Teflon retainer seals.
valves did not
wear despite
the
of 6000 psi.
injection
valves rated to
They were
seats, Teflon stem packing and
Throughout
the testing, these
leak, clog, or exhibit signs of excessive
extensive
testing
with slurry.
26
The
tubing used was
tubing with a wall
stainless steel
thickness of
rated to a working pressure
9.
.035
1/4
inches.
inch (O.D.)
It was
of approximately 6300 psi.
The Movie Camera and Lens
The movie camera used was a Hycam II
16mm motion
picture camera operating on a rotating prism principle
and was used with a Kern
lens of 75mm f/1.9.
The camera
is equipped with an electronic speed control with an
operating range of 20 to
11,000 full
frames/sec.
Kodak 4-
X reversal
film type 7277 (black and white) was used for
all
injection tests.
of the
With
100 feet long rolls of
film, a frame rate of 6000 frames/sec was used as that
was the
fastest rate at which a essentially constant film
speed was obtainable.
A triggering signal was sent from
the camera to correspond with this constant frame rate
through the use of a built-in feature which converted
electronic speed control
tachometer pulses
film that had passed through the camera.
reached a value
to feet of
When the count
corresponding to the selected triggering
film footage determined from performance charts, the
triggering signal was sent to the control
injection event would be started.
27
system and the
10.
Lighting
Three
light
300 Watt lamps were used to provide
for the
filming.
light
The
lamps was bounced off of a 98%
that was
Direct frontal
goose-neck
reflective card positioned
filmed tests would be
behind the bomb so that the
back-lit.
from these
sufficient
lighting produced a picture
with back-lighting which
inferior to those
showed density variations
in the spray patterns very
clearly.
11.
Controls
Each
camera.
injection test was begun by starting the movie
Based on acceleration graphs for the camera, the
film length of 52 feet was used as
triggering signal
controller.
the point at which the
was sent from the camera to the
A manual
trigger the event for
fire button could also be used to
trial
injections.
The controller
was a DCI preset counter comparator with which the
duration of the energizing voltage
was set.
for the solenoid valve
The minimum duration for which the
could be energized and
approximately 70 to 80
injection would still
solenoid
occur was
milliseconds for the coal
slurries, water, and diesel
durations both resulted in
fuel.
These
minimum
injection durations of between
28
30 and 40 milliseconds.
When the
reached the controller, a signal
oscilloscope
the
12.
which triggered
triggering signal
was also sent to the
it to begin recording both
injector needle lift and the rail
line
fuel
pressure.
Data Acquisition
The rail
needle
lift
line
fuel pressure trace and the
trace were
injector
monitored and recorded on an
oscilloscope which received an external trigger from the
control system.
Recorded simultaneously, these
signals were extremely useful
in troubleshooting
system
the
in
the early stages
injection tests, the
of
testing.
two
In the actual
traces were a history of the
and a photograph was made of
the
the
event
oscilloscope screen to
permanently record the traces.
13.
The Air Compressor
A small,
used as
portable high pressure air compressor was
the source of the
convenient.
injection pressure and was very
It was capable
of producing 5000 psi
air at
a flow rate of 3.0 cubic feet per minute and was equipped
with self-relieving regulator.
29
14.
The Rolling Mixer
A problem that must be
slurry
is
that of settling of the
the REI coal
solid matter.
Because
slurry which was used extensively had in
relatively small
to settle
faced when dealing with a
amounts of chemical
out rather quickly.
returned to the
it
sludge on
it was ready to be
the bottom of
tested and had to be
manufacturer for remixing.
A rolling
mixer was then constructed which could spin three,
gallon jugs of the
slurry homogenous.
parallel
slurry at
tended
The ten gallon shipment
settled to an almost impenetrable
the barrel before
additives,
it
one
100 rpm thus keeping the
The mixer was an arrangement of two
shafts padded with short sections of rubber hose
on which the jugs rode.
One
of the shafts was driven by
a small electric motor and the second shaft was driven
off
C.
of the first with an o-ring belt.
INJECTION / STILL PHOTOGRAPHY TESTS
1.
The Camera
The camera used to take
the still photographs was
specially designed at Arthur D. Little,
Inc. to use three
separate lenses simultaneously to photograph different
30
bomb as the
areas of the
lens
One
injection occurred.
had no magnification but was used to record a relatively
large part of the spray for general
lenses of 5:1
Two other
overall spray.
the
magnification
image across the core
spray with one recording the
spray and the
other recording the
image
more at the edge
of
internal to the camera and thus provided three
baffles
images of the
separate and distinct
injection on the
the back of
A Graflock type holder was mounted at
film.
of the
The lenses were separated by a series
the spray.
the camera to hold a type 545 Land film holder.
which provided both an
to determine
immediate
film
picture of the
injection
injection was captured and a fine
if the
grain, high resolution negative
later
The
55/positive-negative
was Polaroid 4x5 Land Film type
were
the
focused on smaller, but overlapping parts of
were
of
observations about
from which enlargements
made.
The camera was mounted on a jack stand and abutted
frontpiece that
one window of the bomb with a
inside
place.
the flange
It was
fit snuggly
on the bomb that held the window
in
focused by moving the entire camera closer
to or further from the window while viewing through the
back of the camera.
very
A
feature of the camera that was
important was that the lenses could be moved as a
unit vertically, horizontally, or both with respect to
the
frontpiece so that photographs could be
taken at
(top, middle,
bottom).
various locations
in the bomb
31
The
travel of the
total
2.
lenses was approximately 2.5
inches.
The Light Source
Lighting for the photographs was provided by a 500
nanosecond Xenon
in place
It was held
flash tube.
opposite side of the bomb from the
camera about
inches away from the outside of the window.
diffuser with a diameter of approximately
held in front of the
A
1.5
on the
1.5
light
inches was
flash tube against the window to
provide a diffused back-lighting.
3.
The Controls
The film was exposed not by the action of a shutter,
but by the
otherwise
500 nanosecond flash of light
shrouded bomb.
This meant
into an
that a delay circuit
had to be employed to synchronize the flash with the
injection event.
This delay was designed at A.D. Little,
Inc. and received its
of the
start signal
injection system controls.
delay, a
from the
button
After the prescribed
15,000 volt pulse was sent to the
circuitry and the 500 nanosecond
"fire"
flash tube
flash occurred.
The
sensitivity of the adjustable delay control was such that
the
length of the
injection had to be
32
increased somewhat
to ensure that the event was actually captured on film.
33
III.
SLURRY HANDLING
Coal
slurry must be handled in a way different from
more conventional
slurry
liquid
fuels.
is a very fine dust that
Suspended
is
in water, the
subject to settling
and which also can clog or partially clog almost any
passage.
Whereas most liquid fuels are
basically
uneffected by small amounts of evaporation when exposed
to air, the water in coal
slurry will evaporate and leave
a slurry of a different composition or worse,
Another significant problem that coal slurry
sludge.
in the
creates
The
fuel
injection system is that of wear.
following sections will
solutions found
A.
coal
in the
discuss problems and
handling of coal
slurry.
SETTLING
The REI slurry was received just over one
before
the
month
injection system was completed and therefore
was stored and undisturbed for that time.
The
settling
that occured was so severe that manual mixing was
impossible and mechanical mixing was very difficult.
The
entire sample had to be returned to the manufacturer for
remixing which
involved mechanical
stirring with a large
propeller at a high speed for several
34
hours.
This
settling exhibited the need
for a device that could mix
The
the slurry on a daily basis.
rolling mixer was then
designed to meet this need by spinning one gallon jugs of
the
slurry at about
The
100 rpm.
jugs of slurry were
their sides so that any settling that did occur
stored on
would be remixed by the spinning action of the slurry
If done daily, fifteen minutes of spinning would
itself.
keep the slurry
in
its
original state, and approximately
thirty minutes of spinning would negate a weekend's
settling.
The AMAX slurry had larger amounts of
stabilizers added to them and did not exhibit settling as
quickly as
the REI slurry did.
A thorough mixing on the
rolling mixer once or twice a week was sufficient to keep
the samples homogenous.
B.
CLOGGING
In general, clogging occurred
which the
slurry had to
in small passages
lay for any period of time.
clogging mechanism appeared to be one
particles
in
The
in which the coal
in the slurry agglomerated along the walls and
eventually blocked the passage, a process distinctly
different from slurry drying.
Most of the clogs could be
dislodged with running water and a thin piece
of wire,
but could definitely not be dislodged by trying to
operate
the system with a higher pressure.
35
The most critical clogging occurred in the nozzle.
Initially,
needle
it was observed that clogs built up around the
tip of the pintle nozzle and caused the needle to
become seized
seized,
Once the needle was
in the nozzle body.
the clogs built up through the three
in the nozzle and sometimes
Clogging of this type was
increasing the
into
injector body.
the
eliminated for the most part by
diametric clearance
body and the needle by
fuel ports
.001
between the nozzle
Nozzle clogging
inches.
continued to occur after the modification but was not as
frequent, and then only after slurry sat
and nozzle
for a period of
in
the
With the REI
time.
this period of time was approximately 5-7
injector
slurry,
minutes whereas
with the AMAX slurries the period of time extended to
well
over one hour.
Clogging also occurred regularly in the solenoid
valve due
to the
small
passages
internal
to the valve
Again, clogging appeared to be the result of
mechanism.
the water being displaced by coal
particles.
problem was alleviated only by changing the
system so
that slurry would not have
to pass
This
injection
through the
solenoid valve.
This was accomplished by employing a
two-fluid system
in which diesel
of hydraulic fluid to relay the
slurry via a
fuel
injection pressure
free-floating piston
36
was used as a sort
interface.
to the
C.
DRYING
Drying only ever appeared to occur when the slurry
was actually exposed to open air
time
for a short period of
such as when the clogs were being removed from the
nozzle and the
tubing to which the
was exposed to the air.
injector was attached
With great care,
application of pressure could clear
a short
the plug of
dried/partly dried slurry from the end of the
.25
the tubing had only been exposed for a
inch
tubing
if
time.
If left exposed to the air for an extended time
(1/2 hour or more)
short
running water and manual extraction
was required.
D.
WEAR
The abrasiveness of the coal
created wear problems
valve.
particles
in both the nozzle
The noticeable wear
in the slurry
and the
in the nozzle occured
seat between the needle and the nozzle body.
solenoid
in the
Excessive
wear was deemed to have occurred when the pressurized
nitrogen
in the bomb forced
and displaced the
and
injector.
its way up
slurry from the
Close-up
inside
inside the
of the nozzle
inspection of the needle
showed pits and scoring, and although
seat
into the nozzle
nozzle was
impossible,
37
seat
inspection of the
it
is plausible
to
assume
that
it was equally worn.
Significant wear was also
observed in the
solenoid
valve when slurry was routinely passing through
wear manifested itself when the valve
allowed the slurry to
leak through the
large
pieces.
inside the
the soft,
Also the
valve were
valve.
likely caused
resulted
was
in
o-rings used as seals
These
to the coal
in the
they were slid past the
housing.
valve
frequently observed to be missing
caused by abrasion due
more
Inspection
rubber seats were missing
several
scallop shaped chunks.
large
The
seals and seats
showed that although the stainless steel
perfect condition,
it.
could have been
particles, but
installation of the
several ports
The frequent clogging of the
were
o-rings as
in the valve
solenoid valve
in frequent removal and reinstallation of these
o-rings which only increased the risk of damage
to them.
This problem was eliminated when the slurry was removed
from the solenoid valve
injection
in favor of the two-fluid
system.
38
IV.
A.
PROCEDURES
INJECTION / HIGH SPEED MOVIE TESTS
1. Test Matrix
Three
different injection pressures were
with three different bomb pressures
for the series
2000 psi,
pressures were
3000 psi,
and
injection
4200 psi and were
of pressures within the
chosen to cover a wide range
limits of the
The
high speed camera.
injection system.
The bomb pressures were
and
1400 psi
room temperature)
to cover
chosen to be atmospheric pressure, 600 psi,
(pressurized with nitrogen at
a
large range
kg/m3,
slurry at the
conditions and looked very promising.
spray pattern were noticeable and the
injection to penetrate
with the
The
107.9 kg/m3 respectively).
first series was done with the REI
the
(1.1
of chamber environment densities
47.8 kg/m3, and
of
These tests were
injection tests which were conducted.
filmed using the
used along
selected
Differences
time required for
to the opposite wall
varied
These results will
injection pressure.
in
be
discussed in a later section.
A baseline
series was done
conditions with No.2 diesel
fuel
39
for the same test
because much
is known
about
injection of diesel
fuel and a second baseline
series was done with water for a direct comparison with
the water-based coal
The three AMAX slurries
slurry.
two
with the various viscosities were only tested at
conditions for a simple comparison with REI
complete test matrix is
A
slurry.
2.
shown in Table
2. System Evolution
The
injection system underwent two
modifications as
major
injection tests were being done.
modifications had no effect on the actual
the slurries, water, or diesel
fuel,
The
injection of
but had significant
effect on the repeatability and reliability of the system
as a whole and are worthwhile discussing.
Figure 2a.
shows the original
was constantly pressurized to
system
in which slurry
injection pressure
in the
accumulator and tubing up to the normally closed port
the solenoid valve,
and additional
tubing up to the nozzle.
When the
slurry filled the
solenoid valve was
lifted and sealed off the relief port
the pressure traveled through the
in
(normally open),
tubing to the
nozzle
tip and built up until a pressure was reached high enough
to lift the needle and cause an injection.
When the
solenoid valve was dropped, the pressure was relieved
through the relief port (normally open) and the
40
injection
TABLE 2
1400 psi
bomb
600 psi
bomb
atmospheric
bomb
-------------------------------------------------------------REI
2000 psi
injection
slurry
water
Diesel fuel
REI
REI
slurry
water
Diesel fuel
slurry
----------------------------------------------
REI
3000 psi
injection
:
:
REI slurry
AMAX AB,C
:
slurry
water
Diesel fuel
AMAX A,B,C
:
:
slurry
water
Diesel fuel
:
REI
REI
----------------------------------------------
g
4200 psi
injection
slurry
water
Diesel fuel
REI
----------------------------------------------
41
:
slurry
water
Diesel fuel
FIGURE 2
INJECTION SYSTEM EVOLUTION
a.
VCuT~
pjr- i P -E-3s.
Ar)e-
AjatLgE Ljr--
b
A~
Y.3~
I4rTEkFACE
Hi4 H P/4
A u?
c.
46nL
LIFr1
sEcAsop.
HIGH pAc5
-i-WO
PLS5bAI
P19c-0AcI
42
was halted.
The problem with this system was clogging
and wear of the
solenoid valve.
The clogging was very
frequent and was very time consuming to remove.
The solution was to redesign the system so
slurry did not have
valve.
to be
in or pass
that
through the solenoid
This was done by using a two-fliud system with a
free-floating piston
fluids.
interface
to separate
The high pressure air source
directly to the
the two
was plumbed
normally closed port of the solenoid
where the pressurized slurry had previously been as
in Figure
2b.
When the
solenoid valve
pressure would build up on the air side
causing the piston to travel
until
the
was
lifted, the
of the piston
short distance necessary
the pressure was equalized on the opposite
which was filled with slurry.
increase
in the rail
fuel
shown
side
The resulting pressure
line would cause the needle to
lift and injection to occur.
The closing
valve would relieve the pressure
of the solenoid
on the air side
of the
piston which would again move and equalize the pressure
on the slurry side.
An initial normal
followed by successively shorter
injection would be
injections until
the
pressure pulse was not long enough to cause a pressure
rise at the
needle tip sufficient
to lift
the needle.
The problem was simply that with each injection, the
piston was translated a small but finite distance which
increased the volume of the cylinder that had to be
filled with air on the
following
43
injection attempt.
Since the solenoid valve
lift
time was kept constant,
the
increased time required to build up sufficient injection
pressure on the air side of the piston resulted
shorter time
of
A possible
injection.
have been to alter the
solenoid valve
injection, but this would have been
repeatable
injections
was
solenoid valve
2c.
lubricated.
fuel
The
Diesel
accumulator as
diesel
the
air
was chosen
system is
shown in Figure
large number of
fuel was pressurized
slurry had been
fuel also filled the
in the
system up to the piston
solenoid pressurized the diesel
the piston
in the
initial setup and
interface although at atmospheric pressure.
of the
side of
internal seals of the
that was used successfully for a
injection tests.
impossible.
to replace
it would also keep the
with each
imprecise and
the system with a fluid, and diesel
because
solution would
lift time
would have been
alternative
A better
in a
fuel
The
and
lifting
in turn
interface which increased the pressure on the
slurry up to the
nozzle and
injection occurred as usual.
Pressure was relieved on the diesel
relief port of the
solenoid valve
fuel
through the
the same as
it had been
when slurry and then air was used.
When the bomb was
first pressurized with nitrogen,
the windows fogged up completely.
corrected by drilling a second hole
This minor problem was
in the bomb which
could be capped and through which nitrogen was allowed to
pass
removing the moist air prior to actual
pressurization.
44
3. Method
The high speed movie camera was set up prior to
filling the
injection system.
The camera was
a very heavy, sturdy base to prevent
operation due
to the high torque
and once the gross
made,
of
the base was not
moved.
in the middle
film drive
focused on
of the clearance
a distance
of
four feet
The magnification was such that the whole
inch inside diameter) covered roughly the
field of
view.
motor
slight distance discrepancies were
and with a 75mm lens,
bomb (4
the
The camera was
between the bomb windows, but at
important.
movement during
location and height adjustments were
a plane approximately
not
mounted on
The focus was rechecked between
tests because the bomb was
frequently bumped as
injection.
being cleaned after an
The
full
injection
it was
film was loaded
into the camera next and the camera was ready.
It was easiest to
starting with
To use the
use
the
it completely empty of all
system, all of the air
slurry side which also sucked
its limit on that side.
the
valve to the
slurry was sucked
in the system had to
the free
With the
shifted to the diesel
floating piston to
vacuum sealed on that
slurry supply was opened and
into the system.
slurry supply still
working fluids.
The vacuum was first applied to the
first be evacuated.
side,
injection system when
fuel
The
vacuum was then
side and with the
open, the free
45
valve
to the
floating piston was
sucked to
its limit on the diesel
side pulling
fuel
additional slurry into the system and filling it.
vacuum sealed on that side,
the
valve was opened to the
accumulator which was filled with diesel
allowed to fill
fuel which was
its side of the piston.
At
filled with the
two
the vacuum on
this point, the system was completely
To check
working fluids with no pockets of air present.
the system,
several
With a
were
injections
always made
prior
to
every test shot ensuring that there were no clogs and
that the pressure rise
in the
fuel
rail
line was that
which was set at the air compressor regulator.
test
injections were made
If the
bomb.
These
into open air outside of
the
system was operating correctly, the
injector was then bolted
into the side
of the bomb and
the bomb was pressurized with nitrogen to the desired
density.
The delayed signal
from the camera triggered the
injection and the camera was started by switching the
remote
camera switch to the
After the
injection was completed and the camera had
stopped, the bomb was
and the
"on" position.
depressurized, a window was removed
slurry was cleaned from the
inside of
With the window replaced and a new roll
the
of film
bomb.
in the
camera, the system was again ready provided no clogs had
formed
in
the
meantime.
46
4. Other Instrumentation
The pressure
trace
in the rail
fuel line and the
injector needle lift were monitored and they were
useful
in determining where
system.
fuel rail
line could either have
pressure rise
been due
of air on one or both sides of the piston
interface,
to the piston having reached the
its travel.
A complete pressure rise
in the
or
limit of
fuel
line
lift or only a very short uneven needle
with no needle
that the
injector and/or nozzle
The duration of the needle lift
(the
closely observed because problem-free
were clogged.
injection time)
injections
was
injections were
very repeatable and thus different durations
successive
in the
to the presence
possibly due
lift meant
in the
the problems were
For example, an incomplete
very
for
signalled trouble.
B. INJECTION / STILL PHOTOGRAPHY TESTS
1. Test Matrix
The most extensive
testing with the still
photography apparatus was done with the AMAX A slurry
because more
information was known for the AMAX slurries
than the REI
slurry such as exact additive amounts and
47
also the relationships
for those slurries between shear
stress and shear rate over a wide range of shear rates.
Tests with the AMAX A slurry were
pressurized to 600 psi
pressures of 3000 and
conducted with the bomb
with nitrogen and
4200 psi
injection
to compare droplet size
differences due to different driving pressures.
location of the
three
lenses also was varied from top to
bottom within their travel
over one
inch
bomb window.
AMAX B slurry at an
from the
bomb pressure of 600 psi
of 3000 psi and a
test matrix
size
to compare droplet
differences between slurries essentially
A complete
center of the
tests were also conducted with the
injection pressure
for their viscosities
just
limits which amounted to
in either direction
Several
The
(AMAX A -
identical
580cp, AMAX B -
except
260cp).
is shown in Table 3.
2. Method
For the still
photography tests,
injection system was unchanged from
speed movie
injection,
and
the slurry
the earlier high
Prior to the
injection tests.
first
the still photography camera was positioned
focused on the center plane of the clearance
the bomb windows.
The distance
between
from the camera body to
the bomb flange was noted and for subsequent
injection
tests, the camera was returned to this distance and
48
TABLE 3
near top
of bomb
:
at middle
of bomb
AMAX A
3000 psi inj.
600 psi bomb
2 tests
3 tests
AMAX A
4200 psi inj.
600 psi bomb
1 test
1 test
AMAX B
3000 psi inj.
600 psi bomb
1 test
1 test
49
:
near bottom
of bomb
2 tests
1 test
refocusing for each shot was not needed.
For each test,
the film was loaded into the Land film holder and the
holder was then placed
film was exposed just prior to the
The
removing the
tube
the
film cover.
injection system "fire"
mentioned earlier,
the
manufacturer's
film was
button, and it was this
light for the capture of the
film. After the
replaced and the
new
As
injection by
flash
was triggered from a delay circuit operating off of
that provided the
on
in the camera's Graflock holder.
flash
injection
injection was over, the film cover was
film was developed according to the
instructions.
The bomb was then cleaned,
loaded, the vertical
position of the
lenses
was adjusted if desired, and the system was ready for
another
test
pending developed clogs.
50
V.
RESULTS AND DISCUSSION
A.
HIGH SPEED MOVIES
1. Spray Penetration Analysis
Tracings of the visible
every
few frames
injection until
the bomb.
time
fuel
for each movie
jet boundary were made
from the start of
the spray impacted the
From these
tracings, graphs were
Typical penetration histories are
Samples
from several
tangent
is
shown
movies are shown
in Plate
penetration trajectories to obtain an
This velocity
spray.
in Figure
fitted to the early part of the
2.
3.
A
tip
initial
is correlated to
of
made of the
penetration distance of the
history of the
the spray.
opposite wall
the
velocity of
injection
pressure and the bomb pressure.
injection velocity
The
be correlated in the
for liquid fuel
injection may
form of
U. .=KU
inj
o
U
where:
U
o
=
[ 2(P
.-P
inj
bomb
is the theoretical
)/p
initial
]
velocity
idealized flow with no head loss,
51
for an
FIGURE 3
TYPICAL PENETRATION HISTORIES
PENETRATION HISTORIES
3000 psi ilnjecion, '00 psi bomb
5
4
1V
3
LU
2
0
1
0
4
02
o
REI SLURRY
+
iME (ms'I
52
WATER
o
No.2 DF
P.
is
inj
injection pressure,
the
bomb,
in the
is the pressure
Pbomb
p
is the density of the
K
is a
fuel being
injected,
flow coefficient depending on nozzle
geometry
For a high enough jet Reynolds Number
the
jet velocity and orifice diameter),
approximately constant, and therefore
velocity
is not
The validity of
is
slurry
The
(Re
> 10 4,
the
injection
examined here.
velocities
initial
movies and the
from the
obtained from the
injection pressures, and bomb pressures.
injection velocities
fuel,
and the
for REI
AMAX slurries
inj
=
It can be seen
slurry, water, No.2
for the
flow coefficient
internal
and would be different for different nozzles.
significantly, however,
This
types,
of
same line,
is dependent on the nozzle
correlation.
4.
.25(2(P.inj.-P bomb )p
particular value
this case)
fuel
for the range
injection conditions fall along the
U.
injection
in Figure
The experimental values cover a wide range of
The
fuel.
this correlation as applied to coal
conditions were plotted against each other
diesel
is
value of K
sensitive to the viscosity of the
corresponding values for U 0
that the
based on
(0.25
in
geometry,
More
is the existence of such a
is because such a correlation would
53
FIGURE 4
INJECTION CORRELATION
100
0
HI:
80
60
-J
w
-J
20
HI:
20
0
0
50
100
150
THEORETICAL VELOCITY
13 REI Slurry
A Wate r
No. 2
X AMAX
AMAX
AMAX
200
( I/s]
Diesel Fuel
A Slurry
B Slurry
C Slurry
54
250
enable
the
slurry to be
injection velocity of coal
calculated if the corresponding velocity for diesel
is known for
injection
the latter
is known by the
flow of diesel
fuel
The amount of coal slurry
injected based on the U inj
injection duration
Much of
injector/nozzle manufacturers
who have extensive data bases on the
through their nozzles.
injector.
the particular
fuel
the
orifice size, and
the
is consistent with experiments
conducted in which the slurry from an
injection was
actually collected and weighed.
2.
Penetration Times
The
time
for the
spray
the
to penetrate
distance
across the bomb and impact the opposite wall
indication of how well the
Sprays that penetrate
spray
is being atomized.
more slowly can be
better atomized as smaller droplets have
momentum transfer with the ambient
effected more by the dense
data was analysed
to view
is a rough
said to be
much faster
fluid, and tend to be
environment
the effects
in the bomb.
of
The
injection
pressure and bomb pressure on the spray penetration and
comparisons were also made between the
With the bomb pressure constant,
injection pressure decreased the
time
penetration monotonically for the REI
55
fuels
tested.
increasing the
for complete
slurry.
The
increasing the
For No.2 diesel
in Figure 5.
results are shown
injection pressure had the opposite
effect, with the
time of penetration
injection pressure was raised.
explained in terms of the
fuels.
the
The
fuel,
increasing as the
These results may be
atomizing properties of the
time to penetrate a
fixed distance depends on
initial spray velocity and the rate of momentum
transfer of the
fuel droplets to the charge air.
diesel spray, the
with the
initial
injection velocity
pressure drop across
the nozzle,
but
For the
increases
the
resulting atomization yields much finer droplets.
much faster momentum loss of
charge air overpowers the
and the
together
fine droplets to the
increase
overall penetration
slurry spray, the
the
time
in initial
increases.
velocity,
For the coal
surface energy that holds the drop
is much larger than that of
of the same
The
size.
This
the diesel droplet
is because of the surface
difference between diesel
tension
fuel and water, and more
importantly, the significant presence of the extra
liquid-coal
particle
interface.
As a result,
the
droplets are rather large, and they do not exchange
momentum readily with the charge air.
time would, therefore,
velocity.
The penetration
be mainly dependent on the
initial
With an increasing nozzle pressure drop,
therefore, a shorter penetration time
interesting note
is obtained.
An
is that there appears, to be a certain
injection pressure
(" 2300psi)
56
below which diesel
fuel
FIGURE 5
PENETRATION TIME VS INJECTION PRESSURE
600 psi B0MB
8
7-
5
E
wi
a
3
a
2-
1 -
0
o
2
o
4
(Thousanda)
PRESSU
+
RE SLURRY
INJECTION
(PSI
190.2 DF
1400 psi BOMB
15
1413
1211
10+
0l
8-
F
7-
54
3
2
1
0
0
o
2
(Th oumandai
INJECOlN PRESSU E (PSi
RD SLURRY
+ No.2 DF
57
4
penetrates faster than the slurry and above which slurry
penetrates faster
psi
in both the
Increasing the
bomb.
600 psi
bomb and the
1400
injection pressure appeared to
is
on the penetration time of water which
have no effect
likely the result of slightly increased atomization
sufficient enough to slow the droplets and partially
overcome
larger initial
the
velocity thus resulting in
what appears to be a constant penetration
time
injection pressure.
independent of
For a constant injection pressure, the
to the
sprays to penetrate
opposite wall
times
increased as the
fuel and water
increased for each
pressure
in the bomb
tested.
These results were expected as a denser
environment would
for the
invariably slow the penetration of a
spray through it.
No trend
in the penetration time could be seen
between the
three AMAX slurries each with a different
viscosity.
The AMAX slurries were essentially comparable
to the REI
concerned.
slurry as far as the penetration
finely dispersed as
likely due
the two slurries.
-
a gel-network
the AMAX slurries did not appear as
the REI
to
the differences
The REI
This difference
slurry did.
in additives
the REI
in
slurry had no stabilizer added
forming additive
to retard settling -
consequently appeared to atomize better.
though,
is
However, based solely on observations of the
high speed movies,
was most
time
Unfortunately
slurry settled very quickly and was
58
and
therefore much more difficult to work with.
3. The
Cone Angles
The
full cone angle was measured for each injection
directly from the high speed movies at a point
injection after the
and while
the
Generally,
spray had
spray was
initially
increasing the bomb pressure
of the fuels tested.
the penetration time
pressure.
tended to
injection pressure
for
increased with increasing bomb
in the
bomb, the
more gas
in the spray which both widens the
spray (cone angle)
and consequently slows
The AMAX slurries appeared to have
angles than the REI slurry at
as with the
wall
This tendency also explains why
The denser the gas
becomes entrained
impacted the
still at a steady state.
increase the cone angle at a given
all
in the
it.
larger cone
identical conditions, but
penetration times, no trend was observable
based on the viscosity differences of the three AMAX
slurries.
As with the effect of
angle analysis, the
injection pressure on the
cone
overall cone angle analyses were
subject to considerable data scatter and were relatively
inconclusive. This
may have been caused to a
large extent
by the nozzle with which the tests were conducted.
The
ADN-4S-1 nozzle was not designed to produce a spray with
59
a
large cone angle and therefore may not have produced
marked differences
fuels and at
B.
in the cone angles of the various
the various conditions tested.
STILL PHOTOGRAPHS
The droplet sizes were
manually measured and counted
for each of the higher magnification still photographs
which were enlarged to 20 times actual
Representative photographs are shown
general,
size.
in Plate
3.
In
the results showed that the atomization of the
slurry was poor with the
in the range
largest percentage of droplets
of 50-75 microns.
In addition to a
numerical average, a mass average
was calculated for
each still
photograph as the
importance
of the volume and thus the
particle.
These are shown
mass average reflects the
in Table
mass will ultimately determine
4.
mass of the
The particles
the amount of water
in
each droplet that will have
to be evaporated before the
coal can begin to combust.
As was clearly seen
lower magnification pictures, the
in the
majority of the
injected fuel did not form droplets at all but remained
in a fairly concentrated core and traveled relatively
straight down until
contact was made with the opposite
wall.
60
TABLE 4
SLURRY
AMAX
AMAX
AMAX
AMAX
AMAX
AMAX
AMAX
AMAX
AMAX
AMAX
AMAX
AMAX
AMAX
AMAX
AMAX
AMAX
AMAX
AMAX
INJECTION APPROXIMATE
BOMB LOC.
CONDITIONS
inj/bomb psi
3000/600
3000/600
3000/600
3000/600
3000/600
3000/600
3000/600
3000/600
3000/600
3000/600
3000/600
4200/600
4200/600
4200/600
3000/600
3000/600
3000/600
3000/600
TOP
TOP
MIDDLE
MIDDLE
MIDDLE
MIDDLE
MIDDLE
MIDDLE
MIDDLE
BOTTOM
BOTTOM
TOP
MIDDLE
MIDDLE
TOP
MIDDLE
MIDDLE
BOTTOM
61
MASS
NUMERICAL
AVERAGE
microns
AVERAGE
microns
55
50
63
65
81
58
67
71
65
78
76
74
90
62
53
70
64
98
72
61
83
98
112
86
84
96
86
101
96
109
120
89
71
86
82
120
From comparisons of
identical conditions,
particle
size
in the
identical
slurries under
it was observed that
injection
top of the bomb, through the
increased from near the
middle of the bomb,
This was not the result
the bottom of the bomb.
smaller droplets agglomerating, but was
some of
the slurry that was
top diffusing outward and
droplets during the
the average
in the
to near
of the
the result of
tight core near the
forming relatively large
course of the
injection.
Particle size distributions were plotted for each
photograph to aid comparisons of
spray.
the droplet
These are enclosed in Appendix B.
sizes
in the
The size
distributions did not vary appreciably from the AMAX A
slurry to the AMAX B slurry at any of the
three
where still
finding was
photographs were taken.
This
locations
general agreement with other results which found no
significant difference
in spray characteristics
attributable to the different viscosities
slurries.
62
of the
in
VI.
1.
CONCLUSIONS
Diesel
injections of coal-water slurry with identical
pressure
traces and needle
a standard diesel
modifications
2.
The
lift traces are
injector to which only minor
were
made.
injection velocities at the nozzle exit may be
correlated to
density of the
the pressure drop across
fuel.
and water from a standard diesel
Most of the
remained
of
slurry
4.
found to be
coal-water slurry,
injector.
is
For the
of a
in terms
0.25.
injected did not atomize well
in the relatively tight core.
injection that did atomize
range
fuel,
used, the correlation
particular nozzle
flow coefficient
the nozzle and the
The correlation was
uniformly valid for No.2 diesel
3.
possible with
and
That part of the
had a mean droplet size
in the
of 50-70 microns.
The droplet size distribution of atomized coal-water
slurry does not appear to be effected by
increasing
injection pressure.
5.
There was no significant difference and no trend
in
comparisons of the
AMAX
slurries
of different
spray properties of the three
viscosities.
63
VII.
FUTURE RESEARCH
There are several recommendations for further
research to be done
in the area of the
in diesel engines.
slurry
recommendations
is an
use of coal-water
least of these
Not the
in-depth study of the effects of
chemical additives on the
and
atomization properties
slurry.
The atomization
is
surface
tension of the
crucial
for combustion to occur even with a pilot
injection, yet
fundamental
indications from this work show that a
trade-off may exist between the
atomization and the need to be able
without excessive
need for good
to handle the
slurry
settling and clogging problems.
More
extensive testing needs to be done to clarify the
observation
has little
Surface
in this work that the
viscosity of the
slurry
effect on the atomization of the slurry.
tension and chemical additives may have more
impact on the atomization than previously believed.
Combustion tests are the next step for the slurry
and tests are being planned on the Rapid Compression
Machine at M.I.T.
A new
to be designed which will
rates
injector and a new nozzle need
provide
the necessary flow
for coal-water slurry and which take
the clogging tendencies of the slurry.
into account
Relatively large
openings and passages along with large clearances between
moving parts are almost necessities.
Finally, bomb
injection tests with multi-hole type
64
nozzles should be conducted to note
similarities of the
types
used
the differences and
injection properties of these two
of nozzles as multi-hole nozzles will
in
actual
engine
tests.
65
eventually be
REFERENCES
1.
Dunlay,J.B.;
DavisJ.P.; Steiger,H.A.;
"Slow-Speed Two-Stroke Diesel Engine
Sources
Technology Conference and Exhibition, Houston,
TX, January,
2.
Tests Using
81-DGP-12, Energy
ASME Paper No.
Coal-Based Fuels,"
Eberle,M.K.
1981.
SiebersD.L.;
Dyer,T.M. "The
Autoignition and
Combustion of Coal-Water Slurry Under Simulated Diesel
Engine
Conditions,"
ASME Paper NO. 85-DGP-15, Energy
Sources and Technology Conference and Exhibition, Dallas,
1985.
TX,
February,
3.
McHaleE.T.; Scheffee,R.S.;
Rossmeissl,N.P.
"Combustion of Coal/Water Slurry,"
Combustion and Flame,
(1982).
45:
121-135
4.
Leonard,G.L.;
Fiske,G.H.
of Coal/Water Mixtures
"Combustion Characteristics
in a Simulated Medium-Speed Diesel
Engine Environment," ASME Paper No.
86-ICE-15, Energy
Sources and Technology Conference and Exhibition, New
Orleans, LA, February, 1986.
66
5.
Bell,S.R.; CatonJ.A. "Numerical
Kishan,S.;
Simulations of Two-Stroke Cycle Engines Using Coal
Fuels,"
ASME Paper No.
86-ICE-13, Energy-Sources and
Technology Conference and Exhibition, New Orleans, LA,
February,
6.
1986.
Tataiah,K;
Wood,C.D. "Performance of Coal Slurry Fuel
in a Diesel Engine,"
7.
Marshall,H.P.;
SAE Paper No.
800329,
1980.
WaltersD.C.,Jr. "An Experimental
Investigation of a Coal-Slurry Fueled Diesel
Paper No.
8.
770795, Sept.,
RyanT.W.,III;
SAE
1977.
DodgeL.G. "Diesel Engine
and Combustion of Slurries of Coal,
Diesel Fuel,"
Engine,"
SAE Paper No.
Charcoal,
Injection
and Coke
840119, SAE International
Congress and Exposition, Detroit, MI,
1984.
67
February-March,
in
APPENDIX A
PLATES
1.
Injection system
2.
High speed movie
Film clips are
to right:
comparison
in the
following order from left
AMAX B Slurry, REI
Diesel Fuel.
of 3000 psi
All were
Slurry, Water, No2.
taken at
identical conditions
injection pressure and 600 psi
bomb
pressure.
3.
Droplet Still Photographs
#1.
3000psi
injection/600psi bomb, AMAX A
#2.
3000psi
injection/600psi
#3.
3000psi
injection/600psi bomb, AMAX A,
#4.
3000psi
injection/600psi
bomb, AMAX A, middle
0.02
inch
2120 microns
z 42 microns
68
bottom
bomb, AMAX B, middle
NOTE:- Scale on Droplet Still Photographs
1 inch =
top
is
PLATE
1
I
69
70
PLATE 3,
#1
i~lwI
*Sir
.
.
71
.'-
PLATE 3, #2
0
F:
P.',
4~.
*
0*
6L
72
PLATE 3,
73
#3
PLATE 3,
#4
*
*
0
0*~
*
-
#
-
*
S
0
S
0
0
5
74
9
APPENDIX B
Droplet
conditions
Size
as
Distribution Bar Graphs
labeled.
75
for various
DROPLET SIZE DISTRIBUTION
3000Yinj/600bomb,AMAX A, +op
30
/7
28
26
2422 -
w
M
z
w
16 -
IL
12 -
14
108-
0-
I
25
40
I
I
m.
I
I
I
1
75 100 125 150 175 200 225250 275 300 325 350 375
SIZE (micrvns)
76
DROPLET SIZE DISTRIBUTION
3000inj/600bombAMAX A, middle
30n
28-
-,7
2624
22
20
18
z
L
16
14
-
12
-f
7
r1--
10
a
6
4
2
0
25
40 50 75 100 125 150 175 200 225 250 275300,325350 375
SIZE (microns)
77
DROPLET SIZE DISTRIBUTION
3000nj/6(00bomb,AMAX A, bot*om
30281
26
24-
22-
2018Lii
0
16-
w
14-
D-
1210-
X--
842-
025 40 50 75 100 125 150 175 200 225 250 275 300 325 350 375
SIZE (mirons)
78
DROPLET SIZE DISTRIBUTION
3000inj/600bomb,AMA'< B, 'op
30268
24
22
w
Li
Li
20
18
16
14
12
10
8
6
4
0
25 40 50 75 100 125 150 175 200 225 250 275 300 325 350 375
SIZE (micron:s)
79
DROPLET SIZE DISTRIBUTION
30
3000nj/60bomb,AMAX B, middIe
'I
2-6
26$
24222018w
w
0
x/F
161412e/
10-7
8 -
F7
62-
025 40
50 75 100 125 150 175.200 225 250 275 300 325 350 375
SIZE (microns)
80
DROPLET SIZE DISTRIBUTION
3000inj/600bomb,AMAX B, bttom
262422 w
20 1814
12 -100
25
40
50
75 100 125 150 175 200 225 250 275 300 325 350 375
SIZE
81
DROPLET SIZE DISTRIBUTION
4200nj/600bomb,AMAX A, top
30
-
28
-
26
-
24
-
22
-
20w
18
z
16-
-
14
LUi
12-
777
10
-e/
4.
2
-
0~
25
V
I
=13
40 50 75 100 125 150 175 200 225 250 275 300 325 350 375
SIZE (microns)
82
DROPLET SIZE DISTRIBUTION
4200'inj/600bombAMAX A, middie
30-
2826242220 -
w
18-
I-
16-
z
Lii
C
14-
Li~I
0~
12-
7;
10 -
8642-
25 40 S0 75 100 125 150 175 200 225 250 275 300 325 350 375
SIZE (microns)
83