co-injeção diesel h2 2

11
Int. J. Hydrogen Energy. Vol. 12, No. 3. pp. 177-186, 1987. Printed in Great Britain. 11 36 1) 319 9/8 7 $3.011 + 0.00 Pergamon Journals Ltd. © 1987 International Association for Hydrogen Energy. WATER INDUCTION STUDIES IN A HYDROGEN-DIESEL DUAL-FUEL ENGINE G. P. PRABHUKUMARt, S. SWAMINATHAN*, B. NAGALINGAM* and K. V. GOPALAKR1SHNAN* * nter nal Combustion Engines Laboratory, Indi an Insti tute of Technology, Madras 6 00 036, India t Department of Mechanical Engineerin g, Govern ment B.D.T. College of Engineering , Davangerc 577 004, India (Received[or publication 27 October 1986) Abstract --Po wer output of a hydrogen-diesel dual-fuel engine is limited by the onset of knock as the percentage of heat input derived from hydrogen increases beyond a certain limit. Earlier work carried out at the Internal Combustion Engines Laboratory, Indi an Insti tute of Technology, Madras, indicates that this knock sets in when th e inducted hydrogen exceeds about 60% of inpu t ene rgy at a pilot diesel quantity of 30% of full load diesel amount. At higher rates of hydrogen induction, the richer hydrogen-air mixture is more prone to knocking. Hardl y any information is available on the possibilities of improving the knock limited power output of a hydrogen-diesel because of its high late nt heat. This paper presents the results of ou r investigation on improving the knock limited power output when water is inducted with the intake charge of a hydrogen-diesel dual-fuel engine, The change in the combustion charact eristics are also reported. INTRODUCTION The present energy situation has stimulated active research interest in non-petroleum and non-polluting fuels, particularly for the t ranspo rtation and agricultural sectors. Hydrogen has been suggested as a long term alternative fuel for internal combustion engines [1]. Besides being the cleanest burning chemical fuel, hydro- gen can be produced from water using non-fossil energy sources such as nuclear and solar energy. In India, compression ignition engines play a domi- nant role in transportation and agricultural sectors, because of their superior thermal efficiency and durabil- ity charactersitics. In fact, the diesel consumption at present is about 16 million tonnes per year compared to 1. 7 million tonnes of petrol. It is estimated that the cons umpt ion of di esel in the year 2000 wi ll be ar oun d 45 million tonnes. Hence, there is a need for developing alternative fuels such as hydrogen for diesel engines. An easy method of using hydrogen in diesel engines is the hydrogen-diesel dual-fuel mode. It is possible to trace the origin of the dual-fuel engines back to Dr Rudolf Diesel who patented the engine running essentially on the dual-fuel principle [2]. He stated that the amount of gas used as the main fuel charge was limited to small proportion s due to the loss of combustion control. The significance of his findings, however, was appreciated only at a much later date. Commercial units of the dual-f uel type were actually put in to opera tion in 1935. The dual-fuel combustion system features essentially a homoge neous gas-air mixture compressed to below its auto ign ition conditions and ignited by the injection of a pilot liquid fuel near the top dead centre position. The primary fuel is generally gaseous at atmospheric condi- tions and controls the power output. Th e pilot liquid fuel is injected through the conventional diesel injection equipment. Unlike the spark ignited gas engine which requires an adequate and un interrupted gas supply, the dual-fuel type is capable of being switched over enti rely to conventional diesel dual-fuel operation whenever desired without interruption. Very little information is available about the be- haviour of hydrogen as a fuel in conventional compress- ion ignition engines modified to operate on the dual-fuel type. Earlier work carried out in this laboratory by Gopal and others [3] on the hydrogen-diesel dual-fuel engine indicates that knock sets in when the inducted hydrogen exceeds about 60% of input energy at a pilot diesel quantity of 30% of full load diesel amount. This paper presents some of the findings of our investigaiton on improving the knock limited power output of a single-cylinder hydrogen- diesel dual-fuel engine by in- duction water along with the intake charge. The change in combustion characteristics are also reported. EXPERIMENTAL SET UP A si ngle-cylinder , direct injection, diesel engine of 80 mm bore and 110 mm stroke was used for the ex- perimental work. The details of the engine are given in Appendix A. This engine was chosen for dual4uel operation since it is a widely used type of engine in Indi a and has a robust construction and reliable performance. A schematic lay out of the test set up is given in Fig. 1. Hydrogen, stored at 17.5 MPa in gas cylinders was reduced to 0.1 MPa through a pressure regulator. Then it was passed through a fine control valve, for regulating the am ount of gas, a gas f low meter, a flame trap and a flame arrestor. The flame trap and the flame arrestor were used to suppress the backflash into the intake manifold. Hydrogen was inducted into the engine through the intake manifold. Water was injected into the intake charge in the form of a fine spray and was 177

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Int. J . Hydrogen Energy. Vol. 12, No. 3. pp. 177-186, 1987.Pr in ted in Grea t Br i ta in .

11361) 319 9/8 7 $3.011 + 0.00P e r g a m o n J o u r n a l s L t d .

© 1 9 8 7 I n t e r n a ti o n a l A s s o c i a t i o n f o r H y d r o g e n E n e r g y .

W A T E R I N D U C T I O N S T U D I E S IN A H Y D R O G E N - D I E S E L D U A L - F U E L

E N G I N E

G. P. PRABHUKUMARt,S. S W A M I N A T H A N * , B. NAGALINGAM*and K. V. G O P A L A K R 1 S H N A N *

* nternal Combustion Engines Laboratory, Indian Institute of Technology, Madras 600 036, Indiat Department of Mechanical Engineering, Government B.D.T. College of Engineering, Davangerc 577 004, India

(Received[or publication 27October 1986)

Abstract--Power output of a hydrogen-diesel dual-fuel engine is limited by the onset of knock as the percentage ofheat input derived from hydrogen increases beyond a certain limit. Earlier work carried out at the InternalCombustion Engines Laboratory, Indian Institute of Technology, Madras, indicates that this knock sets in when theinducted hydrogen exceeds about 60% of input energy at a pilot diesel quantity of 30% of full load diesel amount. Athigher rates of hydrogen induction, the richer hydrogen-air mixture is more prone to knocking. Hardly anyinformation is available on the possibilities of improving the knock limited power output of a hydrogen-dieseldual-fuel engine. Water can serve as a powerful internal coolant in decreasing the unburned mixture temperaturebecause of its high latent heat. This paper presents the results of our investigation on improving the knock limitedpower output when water is inducted with the intake charge of a hydrogen-diesel dual-fuel engine, The change in thecombustion characteristics are also reported.

INTRODUCTION

The present energy situation has stimulated active

research interest in non-petroleum and non-polluting

fuels, particularly for the t ranspo rtation and agricultural

sectors. Hydrogen has been suggested as a long term

alternative fuel for internal combustion engines [1].

Besides being the cleanest burn ing chemical fuel, hydro-

gen can be produced from water using non-fossilenergy sources such as nuclear and solar energy.

In In dia, compression ignition engines play a domi-

nant role in transportation and agricultural sectors,

because of their superior thermal efficiency and durabil-ity charactersitics. In fact, the diesel consumption at

present is about 16 million tonnes per year compared to

1.7 million tonnes of petrol. It is estimated that the

cons umpt ion of diesel in the year 2000 will be aroun d 45

million tonnes. Hence, there is a need for developing

altern ative fuels such as hydrogen for diesel engines. An

easy method of using hydrogen in diesel engines is the

hydrogen -diesel dual-fuel mode. It is possible to tracethe origin of the dual-fuel engines back to Dr Rudolf

Diesel who p atented the engine ru nnin g essentially on

the dual-fuel principle [2]. He stated that the amount of

gas used as the main fuel charge was limited to small

proportion s due to the loss of combustio n control. Thesignificance of his findings, however, was appreciated

only at a much later date. Commercial units of thedual-fuel type were actually put in to opera tion in 1935.

The dual-fuel combustion system features essentially

a homoge neous gas-air mixture compressed to below itsauto ign ition conditions and ignited by the inj ection of apilot liquid fuel near the top dead centre position. The

primary fuel is generally gaseous at atmospheric condi-tions and control s the power output. The pilot liquid fuel

is injected through the conventional diesel injectionequipment. Unlike the spark ignited gas engine which

requires an adequate and un inter rupt ed gas supply, the

dual-fuel type is capable of being switched over enti rely

to conventional diesel dual-fuel operation whenever

desired without interruption.

Very little information is available about the be-

haviour of hydrogen as a fuel in con ventional compress-

ion ignition engines modified to operate on the dual-fuel

type. Earlier work carried out in this laboratory byGopal and others [3] on the hydrogen-diesel dual-fuel

engine indicates that knock sets in when the inducted

hydrogen exceeds about 60% of input energy at a pilot

diesel quantity of 30% of full load diesel amount. This

paper presents some of the findings of our investigaiton

on improving the knock limited power output of a

single-cylinder hydrogen- diesel dual-fuel engine by in-

duction water along with the intake charge. The changein combustion characteristics are also reported.

EXPERIMENTAL SET UP

A single-cylinder , direct inj ection, diesel engine of 80

mm bore and 110 mm stroke was used for the ex-

perimental work. The details of the engine are given in

Appendix A. This engine was chosen for dual4uel

operation since it is a widely used type of engine in India

and has a robust construction and reliable performance.

A schematic layout of the test set up is given in Fig. 1.Hydrogen, stored at 17.5 MPa in gas cylinders was

reduced to 0.1 MPa through a pressure regulator. Then

it was passed throu gh a fine control valve, for regulatingthe am oun t of gas, a gas flow meter, a flame trap an d a

flame arrestor. The flame trap and the flame arrestor

were used to suppress the backflash into the intakemanifold. Hydrogen was inducted into the enginethrough the intake manifold. Water was injected intothe intake charge in the form of a fine spray and was

177

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178

( , 4

H 3

, q 2

I1

G. P. PRABHUKUMARe t a l .

5 • I

1 9~ 1 ~ ~ 1 8

f'-120

I-'121

Fig. 1. Schematic layout of the test set up. 1. Pressurised hydrogen gas cylinder. 2. Cylinder gas pressureregulator. 3. Control valve, fine adjustment. 4. Hydrogen gas flow meter. 5. Water flame trap. 6. Flamearrestor. 7. Air flow meter. 8. Water injection nozzle. 9. Water flow control valve. 10. Water flow meter.11. Engine. 12. Hydraulic dynamometer. 13. Pressure pick up. 14. Charge amplifier. 15. Oscilloscope. 16.Signal analyser. 17. Crank angle inductive pick up. 18. Diesel fuel tank. 19. Fuel measuring burette. 20.

Exhaust temperature meter. 21. Exhaust smoke meter.

metered on volumetric basis by the use of a water flow

meter. A Kistler piezo-electric pressure pick up fitted

into the engine combustion chamber, along with a

charge amplifier, oscilloscope and signal analyser en-

ables the measurement of cylinder pressure. Timingmark signals were generated by an electro magnetic

inductive pick up close to the en gine fly wheel. Pressure

crank angle diagrams, averaged for 100 cycles werestored in floppy discs and lat er analysed with the help of

an Iwatsu Signal Analyser to derive important combus-

tion parameters such as ignition delay, maximu m rate of

pressure rise and peak pressure. The power outpu t was

measured by a hydraulic dynamometer. Diesel and air

consumption rates were measured by standard instru-

mentatio n. The exhaust temperatur e was measured by a

thermocouple. The exhaust smoke density was mea-sured using Bosch diesel smoke meter.

EXPERIMENTAL PROCEDURE

Hydrogen was inducted through the intake manifoldkeeping the diesel flow, called the pilot quantity,

constant. This resulted in increased engine output as theengine speed was held constan t at 1500 r.p.m. All theexperimental data were recorded. Hydrogen flow rate

was then increased to a higher value and all theobservaitons were once again recorded. This was con-tinued until knock set in. These experiments wererepeated for three differen t diesel pilot quant ities of 10,

30 and 45% of full load diesel amount (Full load dieselconsumpt ion = 1.06 kg hr -1) and the co rrespondi ngknock limited power outpu t was foun d out at each diesel

pilot quantity without water induction . In order to study

the effect of water in suppressing knocking it wasinducted in the intake manifold simultaneo usly with

hydrogen induction. The above experiments were repe-

ated with water induction. Flow rate of water was varied

from 0.4 x 10 -3 to 5 x 10 -3 m 3 hr -1.

DETECT ION OF THE ONSET OF KNOCK

Dual-fuel engines are said to knock when the rate of

pressure rise following ignition is found to increase

abruptly to very high values, so high in fact that

continu ed operation u nder such conditions can result in

engine damage.

The initial introduction of small quantities of hyd-

rogen with the air charge neither affected the pressure

diagrams nor the power developed. As the hydrogen

concentration was slowly increased, the engine de-

veloped higher power at the same speed. A significant

increase in the ignition delay was observed during this

process. The ignition delay was defined as the periodbetween the start of injec tion and the first detec table risein cylinder pressure due to combustion. Further increase

in gas admission resulted in considerable increase inpower output with higher cylinder pressures. The gasconcentrations could be further increased up to a point

beyond which combustion became very rapid and aslight increase in the gas concent rati on led to ~knocking'.

As soon as it occurred, the audible sound of the enginechanged considerably. Simultaneously, the shape of the

pressure crank angle diagram changed as shown in Fig. 2exhibiting a very sharp pressure rise with much highermaximum pressure accompanied by oscillations on theexpansion curve.

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A H Y D R O G E N - D I E S E L D U A L - F U E L E N G I NE 17 9

1 I I I

TDC

W I T H O U T K N O C K I N G

I I I I

T D C

KNOCKI NGI I I IFig. 2 . Typical pressure crank angle diagram s jus t before and after the onset o f knock.

T h e t r a n s it i o n f ro m " n o r m a l' t o ' k n o c k i n g ' o p e r a t i o n

w a s q u i t e s h a r p a n d c o u l d b e a c h i e v e d b y s m a l l c h a n g e si n m i x t u r e s t r e n g t h . T h e a b r u p t c h a n g e i n t h e s h a p e o f

t h e p r e s s u r e d i a g r a m w a s u s e d a s a m e a n s f o r d e t e c t i n g

t h e o n s e t o f k n o c k [ 4].

R E S U L T S A N D D I S C U S S I O N S

EJfect of pilot quantity on the performance of a normalhydrogen-diesel dual-Juel engine

T h e p e r c e n t a g e o f h e a t i n p u t d e r i v e d f ro m h y d r o g e n

v e r s u s p o w e r o u t p u t a n d b r a k e t h e r m a l e f f i c ie n c y a t th r e e

d i f f e r e n t d i e s e l p i l o t q u a n t i t i e s a r e s h o w n i n F i g . 3. A s

e x p e c t e d a t e a c h p i l o t q u a n t i t y t h e p o w e r o u t p u ti n c r ea s e s w h e n t h e p e r c e n t a g e o f h y d r o g e n i n th e

m i x t u r e in c r e a se s . H o w e v e r , t h e m a x i m u m p o w e r t h a t is

d e v e l o p e d a t a g i v e n p i l o t q u a n t i t y i s l im i t e d b y t h e o n s e t

o f k n o c k in g . K n o c k - l i m i t e d p o w e r o u t p u t a t h i g h e r p i l o t

q u a n t i t i e s o c c u r s w i t h l o w e r p e r c e n t a g e s o f h e a t i n p u t

d e r i v e d f r o m h y d r o g e n . T h i s i s d u e t o t h e f a c t t h a t

g r e a t e r e n e r g y r e l e a s e d b y d i e s e l c o m b u s t i o n a t h i g h e r

p i l o t in j e c t i o n r a t e s , w h i c h e n a b l e s e v e n r e l a t i v e l y l e a n

h y d r o g e n - a i r m i x t u re s t o b u r n f a s t e r.

T h e b r a k e t h e r m a l e f f i c i en c y at d i f f e r e n t d i e s e l p i l o t

. 4 o I I I I3O

~ o 4~ 2 0

m 10

~t .L

aaw O,

3 . ° 0 ,. / ~ f

5

0 15 30 .45 60

I I

/

i I i 1 I75 90

I I I

DI ESEL P I LOT

Q U A N T I T I E S

o 10 % F .L

& 3 0 % F . L

, 4 5 % F . L

C . R = 1 6 . 5

S P E E D - - 1 5 0 0 ( r p r n )o

I N J . T I M I N G - - 2 7 b T D C

~ K N O CK L IMI T

P E R C E N T A G E O F H E A T I NP UT D E R I V E D F R O M H Y D R O G E N

I I

I

Fig. 3 . Effect of diesel pi lot quant i ty on the perform ance.

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180

7 . 0W

u3~n ~ 6.0

L d 0n- ~I.

o. E

x ~ 5 . 0

wo_

0 . 3

o E - < 0 . 2w o

× w~ EO. ~< f n -

35>-

<

~ 30

~ 2 5

20

0 15 30 L5 60

G. P. PR AB HU KU MAR et al.

[

//

I7 5 9 0

40

3O

~ 2 0 - -rr"

U > -- t O

~ - w Z 1 0w ~v

n , " I _

m w 0

I IDI ESEL P I LOT

QUANT I T IES

o 10 % F.L

A 3 0 % F . L

, Z,5 °/o F.L

C . R = 1 6 . 5

S P E E D = 1 5 00 r p m )

INJ. TIM ING = 27 ° bTDC

K N O C K L I M I T

I I 1 IP E R C E N T A G E O F H E AT I NP U T D E R I V E D F R O M H Y D R O G E N

Fig. 4. Effect of diesel pilot quantity on combustion characteristics.

I f ] I ~ [ I l f 1DI ESEL P I LOT

Q U A N T I T Y = I 0 % E L .

C . R . = 16 . 5

S P E E D = 1 5 0 0 ( r p m )

I NJ. T I M I NG = 27 °bT D C

W ATER I NJ . RATE

o N O R M A L

A 0 . 4 x 10 - 3m 3/ h r

• 0 . 7 , ,

V 0 . 9 , ,

K N O C K L I M I T

3.0(3 ~

I I I I I I I0 . 0 0 ~ _ _

76 78 80 82 84 86 88 90 92 94 96P E R C E N T A G E O F H E A T I N PU T D E R I V E D F R O M H Y D R O G E N

F i g . 5. E f f e c t o f w a t e r i n d u c t i o n o n t h e p e r f o r m a n c e a t ] 0 % o f f u l l lo a d d i e s e l a m o u n t .

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181

/.0

quantities is almost constant at the same power output .

The variation of ignition delay, maximum rate of

pressure rise and peak pressure with percentage of heat

input derived from hydrogen at different pilot quantities

are shown in Fig. 4. It is noted that at lower pilot

quantity of 10% full load diesel amount the ignition

delay of the pilot fuel decreases with the addition ofhydrogen. However there is not much change in the

ignition delay with increase in percentage of hydrog en at

higher pilot quanti ties. It can be seen that the maximum

rate of pressure rise and peak pressures increase at

higher percentage of hydrogen because of the greaterinitial energy being released at higher pilot quantities.

It is observed that the knock limited power output

occurs when the percentage of heat i nput derived from

hydrogen is about 84, 60 and 50% at the diesel pilot

quant ities of 10, 30 and 45% of full load diesel amount .

E f f e c t o f w a t e r i n d u c t i o n o n t h e p e r f o r rn a n c e

Fig. 5 compares the power ou tput and brake thermal

efficiency of the hydrogen -diesel dual-fuel engine with

and without the induction of water at a diesel pilot

quantity of 10% of full load diesel amount. Induct ion of

water into the intake manifold along with hydrogen

increases the knock limited power ou tput as it serves as

the powerful internal coolant in decreasing the un-

burned mixture temperature. The percentage of heat

input derived from hydrogen at knock-limited power

output increases to 85.7 and 87.5% for the water

ind uct ion rate of 0.4 x 10 -3 to 0.7 x 10 -3 m3hr -1

respectively. It is observed that the percentage increase

in knock limited power outpu t is about 19 and 39% forthe water in ducti on of 0.4 x 10 -3 and 0.7 x 10 -3 mShr - l

respectively. More than 0.7 × 10 -3 m3hr -~ of water

induction rate did not result in further impro vement inthe knock limited power ou tput.

In comparison to normal hydrogen-diesel dual-fuel

operatio n, power output decreases with water induction

for the same percentage of heat input derived from

hydrogen. The reduction in power is particularly notice-

able at light loads. Water addition is expected to

influence the compress ion stroke characteristics [5]. The

temperature of the mixture is lowered at the start of

compression and this is expected to extend the delay

period. Vaporization of the water decreases the effec-

tive polytropic expone nt of compression resulting in a

greater drop in the temper ature of the mixture at the endof the compression stroke. A drop in overall flame

temperature would be expected with a consequent

decrease in the flame speed. Moreover the flame would

not sweep throughout the combustion chamber and a

layer of a fuel-air mixture adjac ent to the chamber walls

would fail to burn because of quenching. Increasing the

amount of water added to the intake charge is expected

to thicken this quench layer, thereby c ontributi ng to theloss of power.

Brake thermal efficiency decreases with induction of

] T - - T l I T3 0

2 0 - -CXC

~- -Z

w 10

<u_

mm 0

3 . 0 [

2.25

o_

5 -

o ~ 1.50__£XC

W ~

O

a_ 0.75 _ _

0.00

A HYDROGEN-DIESEL DUAL-FUEL ENGINE

D I E S E L P I L O T

O U A N T I T Y = 3 0 % F .L ,

C. R = 1 6 . 5

S P E E D = 1 5 00 ( r p m )

I N J . T I M I N G = 2 7 ° b T D C

W A T E R I N J. R A T E

o N O R M A L

A 0 . Z, X 1 0 3 m 3 / h r _ _

• 0 . 7 0 ,

7 0 . 9 , ,

~ KNOCK LIMIT

1 l I _ 1 _ _ _10 2 0 3 0 Z ,0 5 0 6 0 7 0 8 0 9 0 10 0

P E R C E N T A G E O F H E A T IN P U T D E R I V E D F R OM H Y D R O G E N

Fig. 6. Effect of water induction on the performance at 30% of full load diesel amount.

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l

G. P. PRABHUKUMAR e t a l .

I I I I 10

30

~ 20n.-

~ . - - z

m 10

O2u..

m m 0

3.00

5 2.25

a: ~ 1.50

o 0 . 7 s

I I I 1DIESEL PILOT

QUANTITY : 45% EL.

C.R : 16.5

SPEED = 1500 ( r p m)INJ. TIMING =27°bTDC

WATER INJ. RATE

o NORMAL

& 0.4 x 10-3rn 3/hr

• 0.7 ,,

7 0.9 ,,

I KNO CK LIMIT

o . o o I I I I I I I I10 20 30 Z,0 50 60 70 80

PERCENTAGE OF HEAT INPUT DERIVED FROM HYDROGEN

I I90 100

Fig. 7. Effect of water induction on the performance at 45% of full load diesel amount.

o . 0 I I I I I I(

u3

u~ -- 5.0LLIn,"

0_ E

~'~ /-,.C.<U.l0_ 'A V

~: ~ o.1.

Z

_o

~0 I 1 I76 78 80 82 84 86 88 90 92PERCENTAGE OF HEAT INPUT DERIVED FROM HYDROGEN

I I I lDIESEL PILOT

QUANTITY = 10% F.L.

C.R. = 16.5

SPEED = 1500 ( rpm )o

INJ.T IMING = 27 bTDC

WATER INJ. RATE

o NORMAL

A 0. Z, x 10-3m3/hr

• 0 . 7 ,,

V 0.9 ,,

KNOCK LIMIT

I I94 96

Fig. 8. Effect of water induction on combustion characteristics at 10% of full load diesel amount.

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A HYDROGEN-DIESEL DUAL-FUEL ENGINE 183

7.0k13C~

t ntn~ 6.0LO t3

CI~ O~

a. E" ~ 5 . [<

k13a_

/,.0

laJ

0 . 3 ~LO:__ W °

O_

0.1 __

>-

<

-3

w_ 30C3

<

Z tO

CIo

~ 25__

V

.------- V

V ~ V ~

I 1 I IDI ESEL P I LOT

Q U A N T IT Y = 3 0 % F . L .

C . R . = 16 . 5

S P E E D = 1 5 0 0 ( r p m )

I NJ . T I M I NG = 27°bTDC

W A T E R I N J . R A T E

o N O R M A L

A 0 . / - x l 0 3 r n 3 / h r .

• 0 . 7 ,,

V 0 .9 ,,

KNOCK LIMIT

0 f l I I I I I0 10 20 30 Z,0 50 60 70 80 90 100

P E R C E N T A G E O F H E A T I N PU T D E R I V E D F R O M H Y D R O G E N

Fig. 9. Effect of water induction on combustion characteristics at 30% of full load diesel amount.

water for the same input of hydrogen energy. Wateraddition allows more gaseous fuels to escape the com-

bustion process as a result of the q uenching due to the

reduction in the cycle tempera ture as explained above.

Hence, the br ake thermal efficiency decreases with the

induction of water, However, addition of water in-

creases the brake thermal efficiency in the range beyondthe knock limited power output of the normal

hydrogen -diesel and dual-fuel engine.

As seen in Fig. 6, at the pilot quantity of 30% of full

load diesel amount, the percentage increase in the knock

limited power output is about 8.7 and 11% for theinducted water rate of 0.4 x 10 3 an d 0.7 x 10 -3 m3hr -1

respectively. It is observed that though the increased

water induction results in the impreved knock limitedpower outp ut, the lubricating oil was diluted. The

percentage increase in the knock limited power out put is

6.7 and 10% for the inducted water flow rate of 0.4 x10 3 an d 0.7 x 10 3 m 3 hr . / a t a diesel pilot quant ity of

45% of full load diesel (Fig. 7). At 30 and 45% diesel

pilot quantity also similar trends in the performance areobserved as in the case of 10% diesel pilot quantity.

Effect of water induction on the combustion

characteristics

The effect of water addition on the ignition delay,

maximum rate of pressure rise, and p eak pressures in a

hydrog en-diese l dual-fuel engine is shown in Figs 8, 9

and 10 for three differen t diesel pilot quantities of 10, 30and 45% of full load diesel. Cooling of the compressed

charge due to the water addition increases the ignition

delay at a particular diesel pilot quantity.

In comparison to normal hydrogen-diesel dual-fuel

engine, the maximum rate of pressure rise and peak

pressure decrease with water induct ion due to the slower

combustion rates. Water addition decreases the mixturetemperature at the end of compression, resulting in a

drop in the overall flame temperature with a consequent

decrease in flame speed.The variation of knock limited power output with

water induction is shown in Fig. 11. It is observed that

the knock limited power o utput increases with increased

rate of water induction. The optimum water induction

rate for improved knock limited power o utput is foundto be 0.7 × 10 -3 m3hr -1 at all the th ree diesel pi lot

quant ities of 10, 30 and 45% of full load diesel amount .

Imbricating oil quality was found to deteriorate when

the water induction rate was increased beyond 0.7 ×10 -3 m3hr -1"

Figure 12 shows the typical pressure-crank angle

diagrams at the same operating conditions with andwithout water induction for all the three diesel pilot

quant ities of 10, 30 and 45% of full load diesel amount.

It is clearly seen that water addition suppresses knockingbecause of reduced temperature of the unburned mix-

ture.The exhaust temperat ure with water inductio n of 0.7

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1 8 4 G . P . PRABHUKUMAReta l .

h i

U 3~ 7.0

L d ot3~ d~.

o_ E

~ - - 6 . 0

b J

5 , 0 _ _

W

o ~ oc~0.z,W

>~ ~ E 0 .3

0 .2

> -

<uw ~ 2 5o

z uo o

~ 20

I 1 I I I I

15

I I I ID I E S E L PI L OT

QU AN TIT Y -- 45 % F-. L ,

C . R . = 1 6 . 5

S P E E D - - 1 5 0 0 ( r p m )

I N J . T I M I N G = 2 7 ° b T O C

W A T E R I N J , R A T E

o N O R M A L

z& 0. Z, x 10"3m 31 h r

• 0 . 7 , ,

7 0 . 9 , ,

K N O C K L I M I T

I I I I I I I I I I9O 1000 10 20 30 40 50 60 70 8 0

P E R C E N T A G E OF" H E A T I N PU T D E R I V E D F R O M H Y D R O G E N

F i g. 1 0. E f f e c t o f w a t e r i n d u c t i o n o n c o m b u s t i o n c h a r a c t e r i s ti c s a t 4 5 % o f fu l l l o a d d i e s e l a m o u n t .

3 , 7 5

3 . 0 0

0 _

O

pc .

L U

o 2 . 2 50 _

a

L U

d

u 1.50OZ"- z

I 1 I I

_ _ D I E S E L P I LO T

Q U A N T I T I E S

C .R -- 16. 5 o 10 °/o F. L

S P E E D -- 1 50 0 ( r p m ) A 3 0 % F . L

INJ. T IM ING : 27°bTDC • 45 % F .L

0 7 5 I I I I0 0 .5 1 .0 1 ,5 2 .0

W A T ER F L O W R A T E ( x 1 0 " 3 m 3 / h r )

F i g . I I . V a r i a t i o n o f k n o c k - l i m i t e d p o w e r o u t p u t w i t h w a t e r i n d u c t i o n .

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A HYDROGEN-DIESEL DUAL-FUEL ENGINE

D I E S E L P I L O T

Q U A N T IT Y = 1 0 % F . L

I I I I I i

D

I L I t I I

I 1 1 I I 1

I l i l ) l

I I

D I E S E L P I L O T

Q U A N T I T Y = 3 0 % F . L

1 I I ~ t [

l _ l _K N O C K S

T - [ - - - -

I t t I

N O K N O C K I N G .

I I I I I I I I IW I TH O U T W A T E R A D D I T I O N

] ~ - T - F - F I - - I - - ] ~ - -

I I f I I I I

D I E S E L P I L O T

OUANTITY = /. 5 % F .L

I I

I I I I I I I I

I I I 1 1 I I I

I I I I 1 I I

W A T E R F L O W R A T E s 0.7x 1 0 3 m 3 / h r .

Fig. 12. Typical pressure crank angle diagrams and without the addition of water at the same operatingconditions.

185

× 10 -3 m3hr -I is about 30°C lower t han the norma l

hydrogen-diesel dual-fuel operation. Exhaust smoke

density was found to be almost negligible at all opera ting

conditions in a hydrogen-diesel dual-fuel engine with

and without water induction.

CONCLUSIONS

The following conclusions are drawn based on our

experimental investigations in a h ydrogen~ liesel dual-

fuel engine with water induction.

(1) Under nor mal hydrogen-di esel dual-fuel opera-

tiom the knock-limited power outpu t occurs when the

percentage of heat in put derived from hydrogen is about

84, 60 and 50% at the diesel pilot quant ities of 10, 30 and

45% of full load diesel amount.

(2) Inducti on of water into the intake manifold along

with hydrogen increases the knock-limited power out-

put, as it serves as a powerful internal coolant in

decreasing the unburned mixture temperature. The

percentage of heat input derived from hydrogen atknock-limited power output increases to 87.5, 65 and

53.5% at the diesel pilot quanti ties of 10, 30 and 45% forthe water induc tion rate of 0.7 x 10 3 m3hr-~.

(3) In comparison to normal hydrogen-diesel dual-

fuel operation, the knock-limited power output in-o ~ ~ 1creases by abou t 39, I 1 and 10 g,, with 0.7 x I0-- m- hr -

of full load diesel amount.(4) Brake thermal efficiency as well as power outpu t

decreases with the inductio n of water due to the escape

of gaseous fuel during combustion process as a result of

quenching at the same heat input derived from hyd-

rogen. However, addition of water increases the brake

thermal efficiency beyond the knock-limited power

output of nor mal hydrogen -diesel dual-fuel engine.

(5) Ignition delay increases with the addition of water

due to cooling of the charge at the end of compression .

(6) Maximu m rate of pressure rise and peak pressures

decrease with water induction due to slow combustion

rate.

(7) The optim um water induction rate for improvedknock limited power out put is found to be 0.7 × 10 -3

m3hr -I at all the three diesel pilot quanti ties of 10, 30

and 45%. More than 0.7 x 10 -3 m3hr i of waterinduction causes d eterioration in lubricating oil quality

even though it improves .the knock limited poweroutput.

Acknowledgements--The authors thank the Dept of Science &Technology and Dept of Non-Conventional Energy Sources,Govt. of lndia for the financial assistance to carry out thisresearch work on hydrogen fueled engine studies.

REFERENCES

1. Kenneth E. Cox and K. D. Williamson Jr, ttydrogen--ltsTechnology and Implications, Vol. IV (1979).

2. R. L. Boyer, Status of dual-fuel engine development.SAE Journal 57, 46--48 (1949).

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186 G . P . P R A B H U K U M A R e t al.

3. G. Gopal , P. Srinivasa Rao, K. V. Gopalakri shnan and B.S. Murthy. Use of hydrogen in dual-fuel engines. In t . J .

H y d r o g e n E n e r g y 7,267-272 (1982).4. G. A. Karim, S. R. Klat and N. P. W. Moore, Knock in

dual-fuel engines. Pro c . In s t . Me c h l . En g rs 181, 453-466

(1967).

5. G. A. Karim and N. Amoozegar, Examination of theperformance of dual-fuel diesel engine with particular

reference to the presence of some inert diluents in theengine intake charge. SAE Paper 821222 (1982).

6. G. A. Karim and S. R. Klat, The knock and auto ignition

characteristics of some gaseous fuels and their mixtures. J.Inst . Fue l . 39, 109-119 (1966).

APPENDIX A

En g in e S p e c i f i c a t io n s

Make AV1 Kirloskar EngineType Single cylinder, water cooled, direct injec.

tion vertical diesel engine.

Rated output 3.68 kW at 1500 r.p. m.Bore 80 mm

Stroke 110 mmDisplacement 553 cm3

volume