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All Theses and Dissertations

1969-8

Water Injection in an Automobile Gas TurbineCombustion SystemBilly Ray JacksonBrigham Young University - Provo

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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: