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Brigham Young UniversityBYU ScholarsArchive
All Theses and Dissertations
1969-8
Water Injection in an Automobile Gas TurbineCombustion SystemBilly Ray JacksonBrigham Young University - Provo
Follow this and additional works at: https://scholarsarchive.byu.edu/etd
Part of the Mechanical Engineering Commons
This Thesis is brought to you for free and open access by BYU ScholarsArchive. It has been accepted for inclusion in All Theses and Dissertations by anauthorized administrator of BYU ScholarsArchive. For more information, please contact [email protected], [email protected].
BYU ScholarsArchive CitationJackson, Billy Ray, "Water Injection in an Automobile Gas Turbine Combustion System" (1969). All Theses and Dissertations. 7138.https://scholarsarchive.byu.edu/etd/7138
WATER INJECTION IN AN AUTOMOBILE GAS
TURBINE COMBUSTION SYSTEM
A Thesis
Presented to the
Department of Mechanical Engineering
Brigham Young University
In Partial Fulfillm ent
of the Requirements for the Degree
Master of Science
by
B illy Ray Jackson
August 1969
This th esis , by B illy Ray Jackson, i s accepted in i t s
present form by the Department of Mechanical Engineering of
Brigham Young University as satisfy ing the thesis requirement
for the degree of Master of Science.
' J e d - ,r'-/ Date
APPROVED:
DEDICATION
To Karlene, my school-widowed wife
i i i
ACKNOWLEDGEMENTS
The sage and stimulating counsel of Dr. Milton G. Wille
i s not recompensible, but i t has been greatly appreciated.
The author would also lik e to acknowledge the kindness of
Mr. William 0. Hayes in sharing his s k i l l and knowledge to save
many hours in equipment development.
iv
TABLE OF CONTENTS
CHAPTER TITLE PAGE
ACKNOWLEDGEMENTS................................................................. ±v
TABLE OF CONTENTS . . . . . ....................................... v
LIST OF TABLES..................................................................... v i
LIST OF FIGURES..................................................................v i i
I INTRODUCTION ....................................................................... 1Background ................................................ 3General Problem ............................................ 4Specific Problem ........................................................... 5
II WATER INJECTION AND GAS TURBINE PERFORMANCE . . 8Gas Turbine Efficiency . . . . . ........................... 9Water Injection ..................................... . . . . . 13
III COMPUTER SOLUTION ........................................................... 15
IV EXPERIMENTAL COMBUSTION RESULTSWITH WATER INJECTION....................... ............................. 22
Combustion Chamber Development ............................... 23R e s u l t s ................................................... 26
V DISCUSSION OF RESULTS ................................................... 29Temperature Effect ................................. . . . . . 30Efficiency Effect . . . . . . . . . ................... 31
VI CONCLUSIONS AND RECOMMENDATIONS ................................ 36Conclusions ................................................... 37Recommendations ........................................................... 37
APPENDIX A. ADVANTAGES OF AUTOMOTIVEGAS TURBINES..............................................38
APPENDIX B. COMPUTER PROGRAMS DEVELOPMENT . . . 43
APPENDIX C. COMBUSTION CHAMBER DESIGN ..................... 46
LIST OF REFERENCES......................................... 50
v
iv
v
viv ii
1345
8913
15
222326
293031
363737
38
43
46
50
LIST OF TABLES
TABLE PAGE
1. Combustion Program Resultsfor 3 si Pressure Ratio ........................ 18
2. Combustion Program Resultsfor Atmospheric Pressure . . . . . . ......................... . . 18
3. Frozen Gas Program R e su lts .................... 19
4. Test R e su lts ................................................................... 28
5. Water Injection Effect on Efficiency . . . . .................. 35
6. Smog Comparison ............................. . . . . . . . . . . . 40
vi
28
LIST OF FIGURES
FIGURE PAGE
1. Cost of Metals to Have Sufficien tStrength at Elevated Temperatures ................................... 6
2. Cost of Metals to WithstandCorrosion at Elevated Temperatures ............................ 7
3. Simple Gas Turbine Qycle . . . . . . . ........................... 10
4 . Brayton Cycla . . . . . . . . . . . . . . . . . . . . 10
5. Temperature Reduction for Water Injection . . . . . . 20
6. Specific Impulse for Water Injected . . . . . . . . . 21
7. Combustion Chamber ......................................... . . . . . . 25
8. Control Board . . . . . . . . . . . . ............................... 27
9. Combustor..........................................................................................27
10. Temperature Reduction for Water Injection ......................... 34
11. Water Injection and Efficiency . . . . . . . . . . . 35
vi i
7
CHAPTER I
INTRODUCTION
CHAPTER I
INTRODUCTION
"GENTLEMEN, JUNK YOUR ENGINES!" This t i t l e o f a recenti
periodical a r tic le [ l ] * catches some of the expectation for the
wedding of the Automobile and the Gas Turbine, The nuptials
cannot be completed though, unless two problems are overcome:
1) high fu e l consumption, and 2) high operating temperature. The
f i r s t problem i s solvable by the use of heat regeneration and
much work has been done in th is area [2] [ 3] [4] . The solution of
the second problem of high operating temperature was the basis
for th is th esis . The method of solution was by water in jection /
into the combustion gases prior to entrance into the turbine. /
The injection of water reduces th e_turbine in le t temperature, 1/
which allows the production of gas turbines from le ss expensive ^
materials. This reduces the production cost of gas turbines and^
makes them more competitive in automotive applications. Also , i /
water in jection increases the mass flow rate through the turbine ^
without a sign ifican t decrease in to ta l volume flow, which resu lts /
in only a very small lo ss in overall thermal e ffic ien cy . /
^Bracketed numbers indicate references cited in LIST OF REFERENCES.
2
3
This investigation included 1) a theoretical investigation
of water injection and gas turbine combustion; 2 ) a computer
solution for the combustion model; and 3) development and testing
of an actual combustion model.
Background
The basic mechanics o f gas turbines i s by no means a new
concept. The engendering of the basic gas turbine principle is
attributed to Hero of Alexandria approximately 130 B.C. There
have been many configurations proposed since then, but i t wasn't
u n til 1936 that a gas turbine was b u ilt that achieved a useful
output, Ihe Brown-Boveri Company put one to work that year in
an o i l refinery. Since 1936 the development and application of
gas turbines has accelerated sw iftly , especia lly in the a ircraft
industry.
The gas turbine has many q u a lities that make i t very ----- ...
inviting as a source of motive power for automobiles. Some of
the advantages are: 1) smoother operation; 2 ) simpler construction;
3) large power-to-weight ratio; 4) nearly complete combustion
(only about two per cent the smog problem of an internal /combustion engine); 5) absence of water cooling; 6) simpler
ignition; 7 ) low o i l consumption; 8) low operating pressure;
9) simpler transmission; and 10) le s s maintenance. These advantages
are covered in d e ta il in APPENDIX A.
With th is sign ifican t l i s t of advantages, why aren't we 1/
driving gas turbine cars? A current periodical explains i t 1/
beautifully:
The many virtues of the turbine engine—notably i t s sim plicity, durability and high power-to-weight ratio—provoke the obvious question: phy aren't there two turbine-poweredcars in every American garage today? The principal reason i s that man, the inventive ape, has not always advanced at the same pace on a l l fronts.
Generally speaking, in a simple turbine the fu e l consumption i s too high for ordinary highway use, and exhaust temperatures are also too high, particularly i f you consider the excess heat already generated in the public streets by placard bearers and window smashers. [5]
General Problem
The problem of high fu e l consumption i s being attacked
quite h eartily [2] [3] (V] and i t now appears that gas turbines can
be b u ilt in the near future that w ill have a fu e l consumption that
w ill be competitive with current medium-sized passenger cars.
ihe need to operate a gas turbine at high temperature i s
being met on two fronts: 1) find new exotic materials that have
su ffic ien t strength at the extreme temperatures encountered, and
2 ) develop means of cooling that make the high temperatures
tolerable. ■
High Temperature Materials
M etallurgists have made a tremendous contribution to the
development of gas turbines by ta ilo r making metals that can:
1 ) maintain su ffic ien t structural strength at elevated temperatures
and 2 ) withstand the extreme corrosion encountered in gas turbines.
For the automotive gas turbine, th is approach i s lik e going from
5
tha “frying pan into the f ir e ." As Figures 1 and 2 show, the
cost of the exotic materials that withstand higher temperatures
in fla te the price of a turbine. These costs are d if f ic u lt to
absorb into consumer automobile prices.
Turbine Cooling
Some work has been done in the area of turbine cooling,
notably in the areas of blade, gas in jection and blade liquid
in jection [6 ][7 j. Results o f these e fforts have generally been
p ositive , but they have brought with them complicated and expensive
design problems.
Specific Problem
The intent of th is th esis was to investigate the good and
bad e ffects o f in jecting water into a gas turbine's combustion
gases prior to where they are exhausted into the turbine. The
sp ec ific areas of in terest were: 1 ) the e ffe c t on turbine in le t
temperature from water in jection , and 2) the e ffe c t on thermal
effic ien cy due to water in jection .
/
6
Cost($/Lb)
7.0
6.0
4.0
•3.0
2.0
1.0
1. 'AISI 41302. 17.7 PH3. AISI 3214. AISI 3105. 19-9 DL
I___ , 6. Hastelloy X7. Inconnel X8. Hastelloy C9. Multimet (N-155)
10. H.S. 25(L-605)
10 )
8 >:
6 ,7 ) ( 9 >(
1 X
2 )( 3'4 )
(f
400 800 1200 1600 2000
Temperature F.
Figure 1*— Cost of Metals to Have Suffic ien t Strength, at Elevated Temperatures [l4]
5.0
00
7
Cost($/Lb)
1. 410 ss2. 405 SS3. 430 SS4. 321 SS5. 309 ss6. 446 SS7. Inconnel 6008. Hastelloy X
q, VX
7 X
_ ii
6 ;
5X
f
IX2XX
"A------
3
0 400 800 1200 1600 2000
Temperature F.
Figure 2^~ Cost of Metals to Withstand Corrosion at Elevated Temperatures. [15]
3.0
2 .0
1.0
0
CHAPTER II
WATER INJECTION AND
GAS TURBINE PERFORMANCE
CHAPTER II
WATER INJECTION AND GAS TURBINE PERFORMANCE
To understand the e ffe c t of water in jection on the
performance of a gas turbine, i t is necessary: 1 ) to investigate
the factors that a ffect the thermal e ffic ien cy of a gas turbine,
and 2 ) determine the change in these factors by injecting water
into the hot gases before they enter the turbine.
Thermal Efficiency Of A Simple Gas Turbine
The simple gas turbine cycle i s represented in Figure 3.
Air at atmospheric pressure enters the compressor (C) at (1),
has fu e l added and i s burned in the burner (B), enters the turbine
(T) at (3) and ex its to the atmosphere at (^).
This steady flow process can be represented by the Brayton
Cycle in Figure 4. The air entering at atmospheric pressure P ,
temperature Tj_, and volume Vj i s compressed, adiabatically, along
1-2, to a pressure P2, temperature T2# and volume Yzm Heat is
added along 2- 3, at constant pressure P2 , raising the temperature
from T2 to T3. The gas then expands adiabatically along 3-^» with
decreasing pressure to atmospheric pressure P , temperature H4.,
and volume V .-
9
10
Figure 3 .— Simple Gas Turbine Cycle
4Figure Brayton Cycle
11
For the adiabatic process 1-2, assuming an ideal gas of
constant sp ec ific heat and an ideal compressor,
, k k-1t2 _ (p2\ kTl " \P l) (1)
where k i s the ratio of sp ec ific heats CP/CV for constant pressure
and volume. Reorganizing equation (1), the temperature r ise
during compression is
T2 - Ti = TXk-1
1 (2 )
The heat added per pound mass of compressed gas (2-3)
i s equal to
Cp (t3 - T2 ) (3)
For the adiabatic expansion (3-^)» assuming an ideal
turbine
m . k-1
$ - t3 \p3 JBut P = P-j_ and P =
\ = t3 ____i ___ ’. k-1 (P2/P1) k
The heat rejected at
P2, hence
<*0
(5)
the end of the cycle i s equal to
Cp (fy - Tx ) (6)
The work done by the turbine during the expansion (3-^)
i s equal to
Cp (T3 - fy) (7)
The work absorbed by the compressor during compression
(1- 2 ) i s equal to
Cp (T2 - TX) (8 )
12
The useful work of the cycle i s equal to
Cp (T3 - \ - T2 + T± ) (9)
The thermal e ffic ien cy of the cycle (Eth) i s equal to
Useful Work Heat Supplied
E.th
Eth = 1
= Cp (t 3 - Th .. t 2 + Tl ) Cp“ (T3 - T2)
^ - TfT3 - T2
But since P = P}_ and P3 = P2
m , . k-1h J h \ — -a*
h -12 '
Hence
-t2
A ,
1 „?1
- 1
T3 _ T2 _ T4 _ Tl t2 " Tl
and
% - Tl £T2t3 - t2
Therefore
Eth = 1 - ^ = 1 -t2
1Ti7Tl
= 1 -t «k-1
i r
(10)
(11)
= t2*1
(13)
W
(15)
(16)
(17)
I t can be observed that to determine the effic iency equation
(17) we have assumed that we have a one hundred per cent e ff ic ie n t
compressor, burner, and turbine. I f the e ff ic ie n c ie s of these
components are considered, equation (17) becomes . !/i)
(12 )
13
1 - 1 CPT1 k-1
CpT3Etk-1
( h ) *U u J
- EC© k ■ ■ ■ .
CP- (T3 - t2)Eb (18)
where Eb, Ec, and E are e ffic ien c ies o f the turbine, compressor,
and burner respectively. Simplifying equation (18)
( ... t 3.... _ \ Eb k -1E - EbEt ^ t3 - t2 J i - l
. , k -1
_
Ec ( t3 - t2 JB l *
(1 9 )
Water Injection
I t was the expectation of th is work to show that the e ffe c t
of water injection into combusted gases o f a gas turbine i s to:
1) lower the gas temperature, and 2) increase the mass flow and
minimize the decrease in volume flow rate and, consequently, the
thermal e ffic ien cy would be maintained.
Lower Temperature
The lower gas temperature i s a d irect consequence of the
heat capacity and the heat of vaporization of the water injected.
I f there were no accompanying lo ss in effic ien cy , lower gas temp
eratures would be a sign ifican t benefit because turbines could
be made of le ss expensive materials and could be marketed
competitively with internal-combustion engines. A quantitative
determination of the reductions in temperature per amount of water
injected w ill be determined.
E =
Maintaining Efficiency
It* equations (LI) and (19) are scrutinized, i t can be
observed that the way to improve effic ien cy of a gas turbine i s
to: 1) increase the e ffic ien cy of the compressor, burner and
turbine, and 2) increase the turbine in le t temperature T , This
has been the c la ss ica l approach and most e ffo r t has been applied
in these two areas.
Another way of illu stra tin g the thermal effic ien cy of a
turbine i s to look at the power output of an ideal turbine. For a
reversible adiabatic expansion, one can sta te the property relation
where U i s the internal energy, P i s the pressure and v i s the
sp ecific volume. For enthalpy (fl) ~ U + Pv and a mass flow of
m in equation (20) becomes
V i s the to ta l volume flow rate. Thus, for the same pressure ratio ,
sim ilar to ta l volume flow rates w ill produce similar power le v e ls .
Injecting water into the combustion gases before they enter
the turbine lowers v (because i t causes a decrease in temperature)
re la tiv e ly unaffected, yielding the benefit of reduced temperature
without reducing power for the same rate of fu e l consumption*
Therefore, the ratio of power-to«fuel consumption rate, or in
other words, the thermal e ffic ien cy , would be l i t t l e affected by
water injection .
0 - dU Jr P dv (2 0 )
vd? ~ dU + dPv « dK
mvdP = c:dH ~ R (power output)
R = Vdp<#
(2-1 )
(22 )
(23)
• • •but i t also increases m« Hopefully, the product of mv or V w ill bo
CHAPTER III
COMPUTER SOLUTION
CHAPTER I I I
COMPUTER SOLUTION
Throe computer s o lu tio n s were developed to i s o l a t e the
e f f e c t of w ater in je c t io n on gas tu rb in e tem pera tu re and efficiency.
f i r s t , an ad ap tio n was made to th e U nited S ta te s A ir Force
Rocket p ro p u ls io n L ab ora to ry T h e o re tic a l ISP Program to determ ine
th e tem y sra tu re re d u c tio n and s p e c i f ic im pulse change (which w il l ,
l a t e r to used to caJ.cu.late therm al e f f ic ie n c y ) fo r w ater >to~fuel
ra t.re s o f zero to *to5?l and a th ro e -to ~ o n s p re s su re r a t i o . This
program c a lc u la te s i s e n t r o p ic flow through ro c k e t n o z z le s , fo r
g iven proscur* , le v e l s and r a t i o s , and p r in t s o u t r e s u l t in g s p e c i f ic
.impulses (lsp )» An is o n tro p ic gas tu rb in e o p e ra tin g between
s m a la r p re s su re s w ith th e same gas t-d.ll ex p erien ce the same
en th a lp y change as th e n o zz le . For s im ila r o p e ra tin g c o n d itio n s ,
th e kino t i c energy produced by th e no zz le i s eq u al to the work
produced 'ey the tu rb in e s in c e t h e i r en th a lp y changes a re eq u a l.
I t i s a. sim ple p rocedure to r e l a t e no zz le e x i t k in e t ic energy to
s p e c i f ic im pulse . The method o f c a lc u la t io n i s g iven in Chapter V.
The second -so lu tio n was a r e p e a t o f th e f i r s t to see what
o j.rc c t occu rred !f th e com bustion was c a r r ie d on a t atm ospheric
p re s su re .
'lee c ru ra s o lu t io n was a d e te rm in a tio n o f the fro z e n
temperature e f f e c t as a chock on the fir s t- two prog rams. All
16
17
calculations were made for propane combusting with two hundred
per cent theoretical air and water to fu e l ratios of zero to
^ .5 :1 .
The resu lts o f the three solutions are tabulated in
Tables 1, 2 and 3 and represented graphically on Figures 5 and 6.
A discussion on the computer programs is contained in
APPENDIX B.
TABLE 1
Combustion Program Results for 3:1 Pressure Ratio
H20/FuelRatio—
Temp°R
Ta2y s' To
IspL b f-sec/
/jLbmPressure (Psia)
0.0 2710 1.0 94.176 37.5 : 12.50.5 2600 0.962 92.705 37.5 : 12.51.0 2500 0.925 91.273 37.5 : 12.51 .5 2400 0.889 90.826 37.5 : 12.52.0 2315 0.858 88.461 37.5 : 12.52.5 2225 0.823 87.079 37.5 : 12.53.0 2140 0.792 85.720 37.5 : 12.53.5 2060 0.763 84.374 37.5 : 12.54.0 1985 0.736 83.043 37.5 : 12.5^.5 1910 0.709 81.775 37.5 : 12.5
TABLE 2
Combustion Program Results for Atmospheric Pressure
H20/FuelRatio
TempOR / T o
IspL b f-sec /
/^LbmPressure (Psia)
0.0 2710 1.0 NA 12.5 12.50.5 2600 0.962 NA 12.5 12.51.0 2500 0.925 NA 12.5 12.51.5 2400 0.889 NA 12.5 12.52.0 2315 O.858 NA 12.5 12.52.5 2225 0.823 NA 12.5 12.53.0 2140 0.792 NA 12.5 12.53.5 2060 0.763 NA 12.5 12.54 .0 1985 0.736 NA 12.5 12.5^•5 1910 0.709 NA 12.5 12.5
19
TABLE 3
Frozen Gas Program Results
H20/FuelRatio
Temp°R
Th?0 //To
0.0 2710 1.000.5 2660 0.9831.0 2620 0.9681.5 2570 0.9472.0 2540 0.9392.5 2490 0.9223.0 2460 0.9093.5 2420 0.8934.0 2370 O.874^.5 2340 0.865
20
TH20^ in it ia l
Figure 5 .—Temperature Reduction for Water Injection
21
Water/Fuel Ratio
Figure 6.— Specific Impulse for Water Injected
CHAPTER IV
EXPERIMENTAL COMBUSTION RESULTSWITH WATER INJECTION
CHAPTER IV
EXPERIMENTAL COMBUSTION RESULTS WITH WATER INJECTION
Combustion Chamber Development
I t was desired to develop an actual combustion chamber with
water in jection , and to run te s ts to verify the actual e ffe c t of
water injection on turbine in le t temperature#
The experimental apparatus design procedure consisted of
1) fu e l selection; 2) combustion chamber design and fabrication;
3) mixing section design and fabrication; 4) flame holder design
and fabrication; 5) controls, gauges and connections; and
6) supporting assembly.
Tests were run with the same parameters as the second
computer solution# Test resu lts for water in jection produced the
same per cent reduction in the absolute temperature as the computer
solution.
Fuel Selection
A fu el was required that was 1) available; 2) safe to ' .. '
handle and combust; 3) adaptable to chamber burning; and 4) clean,
burning. The only fu e l that met a l l of these requirements was , '
propane.
23
zh
Combustion Chamber Design and Fabrication
The combustion chamber was designed to have a safety factor
of fiv e for the worst possible catastrophic condition. The worst
condition was concluded to be combustion with 1 ) fu l l lin e air
pressure; 2 ) chamber containing a stoichiom etric mixture; and
3) a l l connections blocked.
The calculations were carried out as shown in APPENDIX C.
The chamber was fabricated and assembled out of sta in less
s te e l and i s shown graphically in Figure 7»
Mixing Section Design and Fabrication
In designing the mixing sections, advantage was taken of
turbulence and eddy theory j lo ] [ll] to mix the fu e l and air; and the
water and combustion gases. Vortex mixers were selected and fabri
cated from sta in less steel.- Their configuration can be seen in
Figure 7.
Flame Holder Design and Fabrication
Flame holder design involves b asica lly two opposing concepts:
1) turbulence generation increases the flame velocity by an order of
magnitude and i s tantamount to attaching a flame; and 2 ) too much
turbulence can cause an excessive pressure lo ss [l2] . For the
combustion apparatus in question, pressure lo ss was not an important
consideration; hence, the design was the one that produced a great
amount of turbulence. I t was fabricated from sixteen gauge sta in less
s te e l wire mesh. The f in a l design i s shown in Figure 7. Test
resu lts showed that the wire mesh held the flame w ell, and since
i t was cooled by the reactants, i t suffered no lo ss in in tegrity .
25
Figure 7 .— Combustion Chamber
26
Controls and Assembly
The proper range flow meters, gauges, valves and connectors
were selected , calibrated and assembled as seen in Figures 8 and 9.
The flow meters used were
a. Air—ro tome ter (SN F & P BA-21 - 600/70),range 0-3 CFM at 70 F and 25 psig
b. Propane—rotometer (SN F & P FP-l/8-25-2/81 t r i f la t ) ,range 0 - 0.2 CFM at 70 F and 35 psig
c. Water—rotometer (SN F & P FP 1/8-16-G-5/81 t r i f la t ) ,range 0 - 0.07 CFH
The air and propane flow meters were calibrated with a wet te s t
meter and the water meter was calibrated with timed water
measurements. The chamber pressure gauge was a U. S. Gauge,
SN 10958-1, range 0.30 psig , that was calibrated with a dead weight
calibrator. The temperature was determined by a shielded chromel-
alumel thermocouple.
Results
Combustion runs were completed to duplicate the second
computer solution with the same pressure ra tio , two hundred per
cent theoretical air and water to fu e l ratio of zero to 4 .5 :1 .
Test flow meters were used to match the computer solution
conditions. When the conditions were matched and equilibrium was
indicated by steady temperature, an eight point traverse was made
of the flow stream to determine the maximum flow temperature. As
would be expected, with wall quenching and heat transfer, the
maximum temperature occurred at the center of the flow. The resu lts
are tabulated in Table 4 and represented graphically on Figure 10.
A discussion of the resu lts i s contained in Chapter V.
2?
Figure 8.— Control Board
Figure 9. —Combustor
28
TABLE 4
Test Results—
H20/FuelRatio
TempOr \ < y
/ToPressure
PsiaComments
0.0 1350 1.0 12.50.5 1246 0.923 12.51.0 1227 0.910 12.51.5 1161 0.861 12.52.0 1126 0.835 12.52.5 105? 0.783 12.53.0 1040 0.771 12.53 .5 1031 0.764 12.54.0 1007 0.747 12.54 .5 994 0.736 12.5
0.0 1521 1.0 19.5 Check Pressure Effect
0.0 I 625 1.0 12.5 Insulated Combustion Chamber With. 1" Glass Wool
CHAPTER V
DISCUSSION OF RESULTS
CHAPTER V
DISCUSSION OF RFSULIS
lue r e s u l t th a t was o f s p e c i f ic i n t e r e s t in t h i s work was
th e e f f e c t o f in je c t in g w ater in to gas tu rb in e com bustion gases
on 1) gas tem p e ra tu re , and 2) gas tu rb in e e f f ic ie n c y , The a re a
i n k y3s 303 i f w ater in je c t io n would make gas tu rb in e
m otive power more su it-ab le to autom obile a p p l ic a t io n .
Temperature E f fe c t
r ig u ro 10 snows c le a r ly th a t The tem peratu re re d u c tio n from
vtatar in je c t io n was -rea lized . W ater in je c t io n can s ig n i f ic a n t ly
i educe tue uovnpsratwue o f gas tu rb in e com bustion gases and,
suosoquon tly , th e c o s t o f m arketing a gas tu rb in e . As an example,
a b ; l waceiwco-fue]. r a t i o could reduce a combustion gas tem peratu re
:a\xm IfuO £ , where adequate m a te r ia ls cost. $2„00 p e r pound down
to 1050 Fo where ad.equa+e m a te r ia ls c o s t only $ ,85 p e r pound.
1.1- .macula hm sio c-eu th a t the ac tu a l, measured tem peratu re
itcu.ceio.-•. ana m.ve coifpueoo p re d ic te d tem pera tu re re d u c tio n
Cui.irflai.eG c lo o o ly , id© range o f vhs measnpad tem p era tu res was
iowox1 th an th e a d ia b a tic computer p re d ic t io n s . This was to be
expecxec. m xh .1) tho b o a t lo s s from, th e a c tu a l chamber, and 2) w a ll
quench to tho com bustion p ro c e s s , keasm ..ren te wore token w ith the
exp erim en ta l G#a]:>usUon chamber in su la ted . a id the expected h ig h e r
hemps i ,■ tv.ro s rc s u l.ted .
S o
too f
31
E ffic iency E ffec t
The thermal e ffic iency fo r a gas turb ine power p lan t i s
determined by the n e t output power divided by the input hea t or
fu e l energy. Since the input heat or fu e l energy was assumed to
be the same fo r systems w ith and without water in je c tio n , the r a t io
of thermal e ff ic ie n c ie s i s equal to the ra t io of n e t output powers.
Using equation (22)
Eth.T „ (water) - WCcompressor)m(air)h2q = r
Eth0 & J vdP (no water) - W(compressor)ft (air) (24-)
solving fo r the thermal e ffic ien cy with water in je c tio n
Eth■h2o_ E ^ x mH2 0 % 2q - ¥ (compressor) m(air)
m o W0 - W(compressor) m( air) (2 5 )
■'th•h2o =Ethr x -
% 2 0 WH2 °" - m a ir ¥ comp. % I *0 ^0
1 - m air ¥ comp hr, (2 6 )
where W i s the work per pound.
Equation (25) was used to determine the thermal e ffic ien cy
fo r each water in je c tio n condition. Eth0 was s e t equal to the
id ea l thermal e ffic ien cy calcu lated with equation (1 ? ) , fo r a
pressure ra t io of 3 : 1 and the computer calcu lated sp e c if ic heat
ratio (1.30).
1 1 Ethc = 1 = 1 “ 0.231 = 0.225 = 22.5$
W K (3)
The compressor work (W comp) was determined with an air
properties table [2l] for a 3:1 pressure ratio and air entering at 530 R.
W comp = 46.91 BTU/Lb = 36,496Ft-Lb/Lb
32
The turbine work without water in jection (W0 ) was determined
for the ideal turbine expansion
WD = Cp(T3 - Th)
from the computer solution To-T . = 369 R. and Cp = 0.315 BTU/Lb R.
W0 = 0.315(369) = 117 BTU/Lb - 91,000 Ft-Lb/Lb
The work output ratio (%£0/Wo ) was determined by relating
i t to the sp ec ific impulse calculated by the Edwards-Isp Program.
For a rocket
H1 “ h2 = = ( I s p /g c )22gc 2gc
For an ideal turbine
- 22 = W
So the wTork output ratio can be determined by2%20 _ (IsPH20)
W0 " 2(Ispo)
The determined values are tabulated on Table 5 and
represented graphically on Figure 11.
Figure 11 shows that for each pound of water injected per
pound of fu e l, there was only a 1 .1 per cent reduction in e ffic ien cy
for water flows up to h .5:1. The resu lts show that while injecting
water into a gas turbine brings down the temperature, the increased
mass flow of the water in the products of combustion keeps the
effic ien cy from going down s ign ifican tly . Also, an important
contribution of the water i s that as i t combines with the products
of combustion and brings the temperature down, i t s low molecular
weight keeps the volume flow rate o f the gas products from
decreasing sign ifican tly . As equation (22) shows, i f the sp ec ific
33
volume i s maintained, the power output and, consequently, the thermal
effic ien cy are maintained.
I t should be noted at th is point that since the volume
flow rate is not changed considerably, there i s no need to increase
the size of a turbine to handle water in jection , and thus the
cost savings in lower temperature materials can be realized .
In summary, water in jection achieves the desired e ffe c t
of decreasing the gas temperature while minimizing the reduction
in thermal effic ien cy .
1.4
1.2
0 .8
Tit■H2°T in i t ia l
0.6
0.4
0.2
! i 11 1
X 3 si Pressure Ratio Computer Solution
L_____________
-f- Ex
A Is.
perimental T
I Pressure R
est Data
atio Computer Solution
* *
*
^4-
-----A+ 4S 7 ~
Av &* A
1.0 2 .0 3 .0
Water-Fuel Ratio
4.0 5.0
Figure 10.— Temperature Reduction for Water Injection
1 .0
35
TABLE 5
Water Injection E ffect on Efficiency
H20/FuelRatio % 0 / WQ
mh2o ftair W.comp
&o WoBTEh2o
*0
0.0 1.00 . 1.00 0.385 22.5000.5 0.9690 1.0154 0.385 21.9111.0 0.9393 1.0309 0.385 21.3401.5 0.9103 1.0464 0.385 20.7622.0 0.8822 1.0619 0.385 20.1882.5 0.8549 1.0774 0.385 19.9793.0 0.8284 1.0929 0.385 19.0393.5 0.8026 1.1084 0.385 18.4614.0 0.7775 1.1239 0.385 17.8834 .5 0.7530 1.1394 0.38 5 17.305
60
50
40
BTE ($ Eff)30
10
f
' X ) <________X _________ ,' — X J
' — K — • < X
1.0 2 . 0 3 .0
Water/Fuel Ratio
4.0 5.0
Figure 1 1 .—Water Injection and Efficiency
CHAPTER VI
CONCLUSIONS AND RE COMMENDATIONS
CKAFTmR VI
INCLUSIONS AND RECOIdddMMTIOHS
C onclusions
Water in je c t io n in to the com bustion gases o f a gas tu rb in e
can have vary fa v o ra b le a p p lic a t io n to the autom otive f i e l d . The
m ajor e f f e c t o f w ater in je c t io n i s to 1 ) reduce th e tu rb in e i n l e t
ab so lu te tem p era tu re approxim ately 7 .1 p e r cen t f o r each pound
o f w ater added p e r pound o f f u e l , and 2) m a in ta in the therm al
e i i ic ie n c y w ith only approxim ately .1,1 p e r c en t lo s s f o r each pound
o f w ater a ided p e r pound o f f u e l . These numbers a re based, upon two
hundred p e r c e n t th e o r e t ic a l a i r u s in g propane as th e f u e l .
Ihe a a jo r a p p lic a t io n i s th a t gas tu rb iv .es can be
fa b r ic a te d from much le s s expensive m a te r ia ls because o f th e
re d u c tio n in tem p era tu re . This makes the gas tu rb in e very
co m p etitiv e in tiio autom otive m arket.
Recommendations
as soon as tho g a s~ tu rb in e s t a t e o f th e a r t i s developed
to in s e x te n t th a t th e f u e l consum ption o f g® tu rb in e s i s
o .up?i/.i,i.vo vrAi.u Ciiteriial. ooiabustion enganes, tho p rlncio io of
w ater in je c t io n could b f p u t to good u se .
vpas cn.ee:i" has not. irv o o iig a e e d the need fo r w ater
Svooa,AD on 5 1 ccmoblies 2 o r x n jeo txon . Fu ture works in t h i s a re a
may jn v u i '.ig a to tho added c o s t fo r th e se req u irem en ts .
3 V
APPENDIX A
ADVANTAGES OF AUTOMOTIVE GAS TURBINES
APPENDIX A
ADVANTAGES OF AUTOMOTIVE GAS TURBINES
Much in te re s t has been generated recen tly fo r the use of
gas turb ines as the motive power fo r automobiles. This in te r e s t
i s not without warrant, fo r the gas turbine has many advantages
th a t make i t very desirab le fo r automobiles. Some of these
advantages are: 1 ) smoother operation; 2 ) simpler construction;
3) relative lightness and small bulk; 4) nearly complete combustion;
5) absence of water cooling; 6) simpler ignition; 7) very low o i l
consumption; 8) low operating pressure; and 9) le s s maintenance.^]
Smoother Operation
A ll of the power-generating components of a gas turbine
are in pure ro ta tio n and there i s no rec ip roca ting motion th a t
accompanies internal-com bustion engines, and hence, the operation
i s much smoother.
Simpler Construction
C h arac te ris tic a lly , gas turb ines have about one-sixth the
number of moving p a rts .
Relative Lightness
Due to the basic cy lin d ric a l shape, gas turb ines can be
made more compact than other engines, and generally the weight
39
40
per horsepower output i s about one-fourth to one-sixth that of
an internal-combustion engine.
Complete Combustion
With the ever increasing smog problem in our urban areas,
smog emission i s an expanding problem. With the large excess of
air used in gas turbines for combustion and cooling, combustion i s
more complete. Therefore, the smog production from gas turbines
i s a great deal lower than internal combustion engines. A current
investigation [17] .resu lts are tabulated in Table 6.
TABLE 6
Smog Comparison
a Emissions gr/mile Emission Noise FuelCal Driving Cycle Index Index Cons.Hydrc. CO NO Lb/HpHr
Gas Engine13 i 960 11.0 80.0 4.0 High Med 0.451970 2.2 23.0 4.0 Low Med 0.50197 x S t i l l Lower Low Med 0.50
Diesel — 3.5 5.0 4.0 Med ■ High 0.40Regen GTC 0.22 2.4 1.0 Low Med 0.45Steam 0.62 2.8 1 .0 Low Low 0. 70+Elect — — — Low Low ?
aProposed 1970 Fed. Stand Hydroc 2.2 gr/m ile, CO 23 gr/mile
bSpark ign ition
°Gas turbine
A recent periodical measures the current impetus against
the smog produced by internal-combustion engines and makes a plea
for gas turbines.
The International Automobile Show, i t i s called , but i t might also be known as the International Smog Machine Show.I t i s well known, of course, that the gasoline-powered car
is the major polluter of U.S. a ir—a problem for which neither Washington nor Detroit has yet managed to find a solution. Short of reverting to the horse and buggy, the obvious answer is to develop a new propulsion system for automobiles that is as e ff ic ie n t as but le s s noxious than the internal-
Absence of Water Cooling
The gas turbine being air cooled avoids the additional
weight and complication of water cooling systems.
Simpler Ignition
Once ign ition has been in itia ted in a gas turbine, the
flame i s maintained by a flame holder. This eliminates a major
source of breakdown.
Low Oil Consumption
The only o i l required by a gas turbine i s a small amount
used to lubricate re la tiv e ly few bearings and gears.
Low Pressures
Gas turbines characteristica lly operate at from three to
f iv e atmospheres. Internal-combustion engines operate up to f i f t y
atmospheres and d iese l engines operate up to seventy atmospheres.
This allows gas turbines to be fabricated with le s s material.
Low Maintenance
The above advantages have indicated that there are le ss
parts to maintain. Also, because of the.simple shape of gas
turbines, parts can be made more accessib le.
combustion engine. [18]
Simpler Transmission
Gas turbines characteristica lly have a f la tte r horsepower
speed curve and, subsequently, they require le s s gear changing.
42
APPENDIX B
COMPUTER PROGRAMS DEVELOPMENT
APPENDIX 3
COMPUTER PROGRAMS DEVELOPMENT
Two programs were used to solve the combustion of
C3H8 + 502 + 5(3.76)N2 + X H20 (27)
Tito hundred per cent theoretical air was used because
i t i s typ ical of gas turbine operation. The range of computer
c3h8 — 1.0 Lbs.
°2 - - 7.2568 Lbs.
n2 — 24,0226 Lbs
(x)h2o — 0.0 Lbs.0.5 ' 1.01.5 2.02.53.03.54 .04 .5
The above numbers were input into the Edwards—U.S. Air
Force Rocket Propulsion Laboratory Theoretical Isp Program.
Calculations were made for pressure ratios of 3 s i and 1:1 with
an exhaust pressure of 12.5 psia .
44
inputs included the following:
The second program considered frozen flow to estim ate the
e ffe c ts of non-equilibrium expansion through the tu rb ine . The
program was as follow s:
123.456789
10
C PROGRAM TO CALCULATE GAS TURBINE COMBUSTION GAS C TEMPERATURE FOR POST COMBUSTION WATER INJECTION CC TI=INITIAL TEMP(K) (FROM EDWARDS PROGRAM)=1503.7 K C TF=FINAL TEMP(X) AFTER WATER INJECTION C W=GRAMS H20 INJECTED C QUANTITY GAS = 100.0 GRAMS C CP=0.313 G-CAL/C C HoO TEMP=288.l6 K CC CALCULATION MADE BY RELATIONSHIP CC (373.16-288.16) *W*1.0+539.0*W+(IF-373.16)#W*0.540=C =(1 5 0 3 .7 - TF)*10Q.0 *0 .3 1 3C
1 WRITE(6,100)2 READ(5,101) W3 TF=(L7065.81-422.4936*W)/(31.3+0.540*W)4 WRITE(6,102) W, IF5 GO TO 2
100 FORMAT(40H0 GRAMS H£0 TEMP (K) )101 FORI'IAT (1F15. 8 )102 FORMAT(2E20.8)
CALL EXIT. END
The experimental re s u l ts tended to agree more with the
equilibrium calcu lations than xclth the frozen-flow calcu lations
GRATIS H20 TEMP (K) )
APPENDIX C
COMBUSTION CHAMBER DESIGN
APPENDIX C
COMBUSTION CHAMBER DESIGN
The combustion chamber was designed to have a sa fe ty fac to r
of five with the worst pressure condition. A ca lcu la tion was
made fo r 1 ) the cy lin d rica l hoop s tre s s ; 2 ) the long itud ina l s tre s s ;
and 3) the b o lt area required . The worst possib le condition was
determined to be fo r
a. F u ll l in e a ir pressure - 60 psigb. Stoichiom etric fu e l mixturec. Combustion with a l l connections blockedd. T max = 3960 R. (Ad. FI. Temp.) [l2]e . T i n i t i a l = 540 R.f . Volume = 0.01 fT^ - s e t
^max ^line
k = 1 . 3 (computer run)
pmax = 60/3960\ 1.3 = 5500 Psig \54Q ) 3
(28)
(29)
C ylindrical Hoop S tress
—— F
FThe force (F) try ing to separate one side of a cylinder
can be described by
F = p r l (30)
where p i s the p ressure, r i s the rad iu s , and 1 i s the length
perpendicular to the paper.
4?
48
The s tre ss (S) in the connecting ends i s
S tress (S) = F_(3D
where t i s the thickness of the w all.
Combining equations (30) and (31)
t = PrS (3 2)
where S = 80,000 Psi fo r s ta in le s s s te e l [2o] solving
t = (5500) (.50) = 0.0343 inches80,000 ’ (3 3 )
Longitudinal S tress
The long itud inal s tre s s was determined by equating the
forces in the l a te r a l elements to the end forces
2irrts = 2irr2P (3 4 )
or
t = itr^P _ rP2nrs S (3 5 )
t = (0.5)(5500) _ 0.0343 inches (3 6 )(80,000)
B o lt Area R equired
The b o lts required were determined by equating the end
forces to the b o lt area.
Abs = 2irr2P (37)
2Trt PS (38)
(39)Afc = 2ir(. 5)2 5500 _ .108 sq. inch 80,000
Using four bolts for l /h ” and 3/18” diameter
A ~ ^T?(.2 5)2 _ 0.196 sq. inch (40)4
A = 4ir(.1875)2 _ 0.111 sq. inch4
(41)
Ab -
^9
LIST OF REFERENCES
LIST OF REFERENCES
1. Ottum, B. "Gentlemen, Junk Your Engines." Sports I l lu s t r a te d .26: p 30-33. 12 June I 9 6 7 .
2. Weatherston, R. C., Hertzberg, A. "Tne Energy Exchanger, ANew Concept fo r High E fficiency Gas Turbine Cycles." Transactions o f the ASME. V 8 8 - 8 9 . A pril 196?.
3. Mondt, J . R. "Vehicular Gas Turbine Periodic-Flow HeatExchanger Solid and F luid Temperature D is tr ib u tio n ." Transactions of the ASMS. V 86. A pril I 96L.
— Judge, A. W. Small Gas Turbines. The Macmillan Company,New York.’ i 9 6 0 .
5. Phinizy, Coles. "Mob of Fiery L i t t le Rebels Makes I t Go."Sports I l lu s t r a te d , p 50-53. 13 May 1 9 6 8 .
6. Hawthorne, W. R. "Thermodynamics of Cooled Turbines."Transactions of the ASME. V 78. 1956.
7. Smith, A. G. "The Cooled Gas Turbine." Proc. In stn . Mech..E ngrs.. 163. 1950.
8. Edkins, Denis. "Helicopter Engine Augmentation Systems ForHot Day A ltitude and Emergency Power." American H elicopter Society. 2Lth Annual National Forum Procedings. Washington, D.C., 8-10. May 1968.
9. Hendrickson, R. L. "Thermodynamic Cycles." Paper G£R-2180c.General E le c tr ic Gas Turbine S tate of the Art Engineering Seminar. June 1 9 6 8 .
10. Vennard, J . K. Fluid Mechanics. John Wiley and Sons In c .,New York, New York. 1968.
11. Schlichting, H. Boundary Layer Theory. McGraw-Hill Company,New York, New York. 1 9 6 8 ,
12. Strehlow, R. A. Fundamentals of Combustion. In te rn a tio n a lTextbook Company, Scranton, Pennsylvania. I 9 6 8 .
13. Foster, A. D. "Gas Turbine M ateria ls ." Paper GER-2182c.General E le c tr ic Gas Turbine S tate of the Art Engineering Seminar. ' June 1968.
51
4.
52
3A. Levy, A. V. "Application of High-Temperature Materials to Aircraft Powerplants in the Temperature Range 1200-2^00 F ." 5AE Transactions V 6k, p 3^6. 1956.
15. Schmid and Cubbler. "Pick Right Alloy to R esist Hotdorrosion." Mater ia ls Engineering, p 31, September1968.
16. Zucrow, M, J. Jet Propulsion and Gas Turbines. John Wileyand Sons, In c ., New York, New York, 1952.
17. Schmidt, J. G. "Here Come Th* Judge.” Motor Trend.January 1969.
18. "Transportation.” Time Magazine, p r/k, 11 April 1969.
19. Horlock, J. H. Axial Flow Turbines. Butterworths, London,England. 19667”
20. Spotts, M. F, Design of Machine Elements. Prentice-HallIn c ., Englewood C liffs , Now Jersey. 1965.
21. Fan Vivien, G. J, Thermodynamics. John Wiley and Sons, In c.,V 9 ■ w . u . a w j r . m H V . W j * w « u ..—vw » v w *
New York, New York, p 552. 1959.
ABSTRACT
The purpose of th is th e s is was an in v estig a tio n in to the
e ffe c t of in jec tin g water in to the combustion gases of a gas-
turbine engine. The sp ec ific area of in te r e s t was to see i f water
in je c tio n would make gas turbine engines more su itab le and
competitive as a source of propulsion power fo r automobiles.
The in vestiga tion included combustion ca lcu la tions, with
various degrees of water in je c tio n , and the development and te s tin g
of an experimental combustion chamber. The re s u lts showed th a t
water in jec tio n decreases the operating temperature while not
s ig n if ic a n tly reducing the engine thermal e ffic ien cy fo r two hundred
per cent th e o re tic a l a ir and propane. This reduction in temperature
would allow gas turb ines to be fab rica ted from le s s expensive m ateria ls ,
thus reducing th e ir marketing cost and making them more competitive
with other engines. The re s u l ts a lso showed th a t water in je c tio n
increases the mass flow of a gas turb ine and thus tends to keep the
volume flow ra te of combustion gases from decreasing s ig n if ic a n tly .
This r e s u l t kept the thermal e ffic iency from reducing s ig n if ic a n tly .
APPROVED: