use of hydrogen to enhance the performance of a vegetable oil fuelled compression ignition engine

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International Journal of Hydrogen Energy 28 (2003) 1143–1154

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Use of hydrogen to enhance the performance of a vegetableoil fuelled compression ignition engine

M. Senthil Kumar∗, A. Ramesh, B. NagalingamDepartment of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600 036, India

Accepted 27 September 2002

Abstract

Use of vegetable oils in unmodi1ed diesel engines leads to reduced thermal e2ciency and increased smoke levels. In thiswork, experiments were conducted to evaluate the performance while using small quantities of hydrogen in a compressionignition engine primarily fuelled with a vegetable oil, namely Jatropha oil. A single cylinder water-cooled direct-injectiondiesel engine designed to develop a power output of 3:7 kW at 1500 rev=min was tested at its rated speed under variableload conditions, with di8erent quantities of hydrogen being inducted. The Jatropha oil was injected into the engine in theconventional way.

Results indicated an increase in the brake thermal e2ciency from 27.3% to a maximum of 29.3% at 7% of hydrogen massshare at maximum power output. Smoke was reduced from 4.4 to 3.7 BSU at the best e2ciency point. There was also areduction in HC and CO emissions from 130 to 100 ppm and 0.26–0.17% by volume respectively at maximum power output.With hydrogen induction, due to high combustion rates, NO level was increased from 735 to 875 ppm at full output. Ignitiondelay, peak pressure and maximum rate of pressure rise were also increased in the dual fuel mode of operation. Combustionduration was reduced due to higher ?ame speed of hydrogen. Higher premixed combustion rate was observed with hydrogeninduction.

Comparison was made with diesel being used as the pilot fuel instead of vegetable oil. In the case of diesel the brake thermale2ciency was always higher. At the optimum hydrogen share of 5% by mass, the brake thermal e2ciency went up from30.3–32%. Hydrocarbon, carbon monoxide, smoke emission and ignition delay were also lower with diesel as compared tovegetable oil. Smoke level decreased from 3.9 to 2.7 BSU with diesel as pilot at the optimum hydrogen share. Peak pressure,maximum rate of pressure rise, heat release rate and NO levels were higher with diesel than Jatropha oil. On the whole, it isconcluded that induction of small quantities of hydrogen can signi1cantly enhance the performance of a vegetable (Jatropha)oil/diesel fuelled diesel engine.? 2003 International Association for Hydrogen Energy. Published by Elsevier Science Ltd. All rights reserved.

Keywords: Vegetable oil fuel for engines; Jatropha oil; Hydrogen; Dual fuel engines; Renewable fuels for engines

1. Introduction

Environmental concerns and depletion in petroleum re-sources have forced researchers to concentrate on 1ndingrenewable alternatives to conventional petroleum fuels. Hy-drogen is thought to be a major energy resource of thefuture due to its clean burning nature and eventual avail-ability from renewable sources. Combustion of hydrogen

∗ Corresponding author.E-mail address: [email protected] (M. Senthil Kumar).

can lead to higher thermodynamic e2ciency on account ofits higher ?ame speed when compared to conventional liq-uid fuels. Thus, hydrogen can also be used to enhance thecombustion rate of slow burning fuels. The wide ?amma-bility limits of hydrogen can lead to low hydrocarbon andcarbon monoxide emissions when it is used along with otherfuels. On the other hand, vegetable oils have long been con-sidered attractive alternatives to diesel [1]. They have theadvantage of being able to be produced from a range of re-newable sources. Vegetable oils o8er almost the same poweroutput with slightly lower thermal e2ciency when used in

0360-3199/03/$ 30.00 ? 2003 International Association for Hydrogen Energy. Published by Elsevier Science Ltd. All rights reserved.PII: S0360 -3199(02)00234 -3

mailto:[email protected]

1144 M. Senthil Kumar et al. / International Journal of Hydrogen Energy 28 (2003) 1143–1154

Table 1Properties of diesel and hydrogen (6& 9)

Properties Diesel Jatropha oil Hydrogen

1. Density (kg=m3) 840 917 822. Calori1c value (kJ/kg) 42490 39774 1198103. Flame velocity (m/s) 0.3 — 2.704. Cetane number 45–55 40–455. Auto ignition temp (◦C) 280 — 5856. Carbon residue (%) 0.1 0.54 0.07. W/Lpm 681:28 W=mLpm 212:7 W=Lpm

diesel engines [2]. However, research 1ndings also revealthat long-term engine durability is adversely a8ected by theuse of vegetable oil fuels. These problems can be tracedback to the high viscosity, low volatility and reactivity ofthe unsaturated hydrocarbon chains in vegetable oil fuels.Of these factors, the high viscosity of vegetable oils posesa predominant hurdle as it causes excessive carbon depositsand ring sticking [3,4].

A number of vegetable oils like karanji oil, rapeseed oil,rice bran oil, cottonseed oil, Jatropha oil etc. have been usedas fuels in diesel engines [5]. Among these, Jatropha oil ex-hibits very good properties. It is a non-edible oil, its calori1cvalue and cetane number are higher compared to many oth-ers. The Jatropha plant can grow almost anywhere, even ongravely, sandy and saline soils. Its water requirement is ex-tremely low [6].

Dual fuel operation in diesel engines o8ers the potential ofreduced smoke emissions with improved performance [7].It can also result in good thermal e2ciency and extremelylow smoke emissions at high power outputs [8]. However,dual fuel operation normally poses problems of low e2-ciency when the concentration of the inducted fuel is lessthan a minimum value. This is because a lean mixture ofthe inducted fuel with air does not burn well. Use of fuelswith wide ?ammability limits and high ?ame velocity canreduce these e8ects. Since vegetable oils usually producehigh smoke emissions from diesel engines, dual fuel opera-tion can be adopted as a method for improving their perfor-mance. A small quantity of hydrogen can be inducted withair while using vegetable oil as the pilot fuel [most of theenergy can be derived from the vegetable oil]. Some of theimportant properties of petroleum diesel, Jatropha oil andhydrogen are shown in Table 1 (from Refs. [9,10]). Due tothe absence of carbon, use of hydrogen in dual fuel engineswill often reduce hydrocarbon and carbon monoxide emis-sions [10,11].

In this work, a single cylinder direct injection diesel en-gine was modi1ed to work in the dual fuel mode with hy-drogen as an inducted fuel. Jatropha oil was used as theinjected fuel and most of the engine’s energy was derivedfrom it. It was injected by the conventional fuel injectionsystem. Experiments were conducted at a constant speed of

Table 2Engine details

1. Name of the engine Kirloscar AV12. General details Four stroke, CI, water-cooled.

single cylinder3. Bore & stroke 80 × 120 mm4. Compression ratio 15:15. Rated output 3:7 kW at 1500 rpm6. Fuel injection opening

pressure170 bar

7. Injection timing 29 BTDC static (Jatropha oil)

1500 rpm, load conditions and the amount of hydrogen andvegetable oil were varied. Comparison has been made withresults obtained while using diesel as the pilot fuel insteadof the vegetable oil.

2. Experimental setup and experiments

A single cylinder four stroke water-cooled diesel en-gine developing 3:7 kW at 1500 rpm when fuelled withpetroleum diesel fuel was used. Details of the enginespeci1cations are given in Table 2. A schematic of theexperimental arrangement is shown in Fig. 1. A high-speeddigital data acquisition system recorded the output signal ofpressure. A piezoelectric transducer and crankshaft positionoptical encoder were used for the measurement of cylinderpressure as a function of crank angle. An infrared exhaustgas analyzer ( HORIBA—MEXA—324 FB ) was usedfor the measurement of HC/CO levels in the exhaust. Formeasuring NOx emissions, a chemiluminescent NO/NOx(rosemount analytical—951 A) Analyzer was utilized.Smoke levels were obtained using a Bosch system.

The injection timing was optimized at the value of29◦before TDC [static] for Jatropha oil. The same timingwas used in the dual fuel mode also. Cooling water out-let temperature was maintained at 70◦C. The engine wastested at various constant outputs at the rated speed of1500 rev=min.

M. Senthil Kumar et al. / International Journal of Hydrogen Energy 28 (2003) 1143–1154 1145

3

19

1 2

6

12

11

13 1514

16 1817

10

20

21

4

LEGEND

1.Engine 9. Dynamometer panel 17.Lub oil Temp. Indictr2.Dynamometer 10. Silencer 18. Rotameter3.Gas flow meter 11. Smoke Pump 19.Pressure Sensor4.Diesel Tank 12. HC/CO Analyzer 20. Charge Amplifier5.Hydrogen Cylinder 13. Stop Watch 21.DDA.System6.Burette ( Diesel ) 14. RPM Indicator 22. Flame Trap7. Air Tank 15. Ext Temp Indicator8. Air Flow meter 16. Coolant Temp. Indr

78

5

22

3

9

Fig. 1. Experimental setup.

2.1. Heat release analysis

The heat release rate was calculated by making a 1rst lawanalysis of the average pressure versus crank angle variationfor 100 cycles using the equation given below

Qapp =�

�− 1[P dv] +

1�− 1

[V dp] + qw ;

where Qapp is the apparent heat release rate, � the ratio ofspeci1c heats, v the instantaneous volume of the cylinder, pthe cylinder pressure and qw in the Hohenberg equation forwall heat transfer.

For this calculation the contents of the cylinder were as-sumed to behave as an ideal gas (air) with the speci1c heatbeing dependent on temperature [12]. The heat transfer wascalculated based on Hohenberg equation [13] and the walltemperature was assumed to be 723 K [12].

The cumulative heat release was then calculated. The startof combustion was determined from the rate of pressurerise variation. This shows a sudden rise in the slope at thepoint of ignition due to the high premixed heat release rate.The end of combustion was taken as the point where 90%of the heat release had occurred [14]. The ignition delay

period was calculated based on the dynamic injection timing.The duration between the point of injection to the pointof ignition was taken as the ignition delay. The point offuel injection was found by using an inductive needle lifttransducer.

3. Results and discussion

3.1. Performance

Figs. 2–8 show the results of all experiments. Shown inFig. 2 is the variation of brake thermal e2ciency with di8er-ent percentage loads and hydrogen mass shares. Hydrogenmass share is de1ned below

Hydrogen mass share =mH2

mH2 + mf;

where mH2 is the mass ?ow rate of hydrogen that is inductedalong with air, mf the mass ?ow rate of liquid fuel, i.e.vegetable oil or petroleum diesel that is injected as the pilotfuel.

Induction of hydrogen improves the brake thermal e2-ciency at medium and high outputs, i.e. above 60% of load.


0 5 10 15 20 25 30 35 40

Hydrogen Mass Share ( % )

5

10

15

20

25

30

35

40

Bra

ke T

her

mal

Eff

icie

ncy

( %

)

100%

80%

60%

40%

20%

Speed 1500 rpmInj.Timing 29BTDCFuel : Jatropha oil

Fig. 2. Variation of brake thermal e2ciency with hydrogen massshare.

0 5 10 15 20 25 30 35 40


707274767880828486889092949698

100

Vo

lum

etri

c E

ffic

ien

cy (

% )

100%

80%

60%

40%

20%


Fig. 3. Variation of volumetric e2ciency with hydrogen mass share.

This is mainly due to the enhanced combustion rate. Thebrake thermal e2ciency is increased from 27.3% with pureJatropha oil [i.e. at 0% of hydrogen mass share] to a max-imum of 29.4% at 7% hydrogen mass share at 100% load.Flame propagation through the hydrogen–air mixture leadsto rapid heat release rates and increases the brake thermale2ciency. Thus the high ?ame speed and wide ?ammabil-ity limits of hydrogen are helpful. However, at high ratesof hydrogen admission the combustion becomes too rapidand hence the thermal e2ciency decreases. At light loads,

0 5 10 15 20 25 30 35 40


0

50

100

150

200

250

300

350

400

450

Exh

aust

Gas

Tem

p (

Deg

C )

100%

80%

60%

40%

20%


Fig. 4. Variation of exhaust gas temp with hydrogen mass share.

0 5 10 15 20 25 30 35 40


0

1

2

3

4

5

Sm

oke

No

( B

osc

h S

mo

ke U

nit

s )

100%

80%

60%

40%

20%


Fig. 5. Variation of smoke no with hydrogen mass share.

dual fuel operation with hydrogen induction showed infe-rior performance than the pure Jatropha oil. This is due topoor combustion e2ciency of the dual fuel engine underpart load conditions. At light loads, the inducted hydrogen–air mixture is too lean to get ignited properly and burn witha su2ciently high ?ame speed. This is signi1cant when thehydrogen mass share is very low. On the other hand, thepilot quantity being very small, it leads to poor ignitionand combustion when the hydrogen share is high at lightload. However, beyond half load the e2ciency of dual fuel


0 5 10 15 20 25 30 35 40Hydrogen Mass Share ( % )

0

20

40

60

80

100

120

140

160

HC

( p

pm

)

Speed 1500 rpmInj.Timing 29 BTDCFuel : Jatropha oil

100%

80%

60%

40%

20%

Fig. 6. Variation of HC with hydrogen mass share.


0.00

0.10

0.20

0.30

CO

( %

)

100%

80%

60%

40%

20%


Fig. 7. Variation of CO with hydrogen mass share.

operation improved su2ciently to surpass pure vegetable oiloperation.

The variation of volumetric e2ciency with hydrogenmassshare is shown in Fig. 3. With pure Jatropha oil operationthe volumetric e2ciency is lower mainly at higher poweroutputs due to the high exhaust and component tempera-ture, which increases the temperature of the charge. Thevolumetric e2ciency is further reduced at all power outputsin the dual fuel operation with hydrogen induction. This isbecause the light hydrogen, which is inducted, displacessome of the air.

0 5 10 15 20 25 30 35


0

100

200

300

600

700

800

900

1000

1100

1200

NO

( p

pm

)

Speed 1500 rpmInj.Timing :29 BTDCFuel : Jatropha oil

100 %

80 %

60 %

40 %

20 %

500

400

Fig. 8. Variation of NO with hydrogen mass share.

In the dual fuel mode of operation with hydrogen induc-tion, there is an increase in exhaust gas temperature partic-ularly at higher power outputs due to faster combustion andhigh temperature reached in the cylinder as seen in Fig. 4.At high outputs, say 100% the brake thermal e2ciency islow with hydrogen beyond the mass share of 7%. This isbecause of high combustion rates. The low e2ciency at theseconditions leads to the use of higher quantities of fuel. Thiscoupled with the high combustion rate results in increasedgas temperature and pressure.

3.2. Emissions

With pure Jatropha oil operation smoke emission is in-creased particularly at higher power outputs due to poor at-omization of the fuel. Smoke levels are shown in Fig. 5.The smoke level is 4:4 BSU with neat Jatropha oil at peakpower output. However, there is a signi1cant reduction ofsmoke emission in dual fuel operation. It is reduced from4.4 to 3:7 BSU at the maximum e2ciency point [i.e. at 7%hydrogen mass share] when producing peak power output.The introduction of hydrogen reduces the quantity of in-jected fuel and lowers the smoke level at all power outputs.Further, it is speculated that the inducted hydrogen forms ahomogeneous mixture that burns more rapidly and the over-all mixture contains less carbon from which smoke canform. Thus, it is concluded from interpreting these data thathydrogen can be used to control the smoke level and alsoincrease the brake thermal e2ciency with vegetable oil fuelsat high outputs.

The unburned hydrocarbon level increases with load in theneat Jatropha oil operation as seen in Fig. 6. The hydrocar-bon emission was 130 ppm with pure Jatropha oil operation


at maximum output. Since, the viscosity of the vegetableoil is higher than diesel the sauter mean diameter (SMD)of vegetable oil becomes large and hence the vegetable oilspray becomes much courser than the diesel spray [15]. Dueto the poor mixing of pure Jatropha oil with air as a result ofthis higher viscosity and density the hydrocarbon emissionis high. However, dual fuel operation reduces the hydrocar-bon emissions considerably. Since hydrogen has no carbon,burning of hydrogen along with Jatropha oil leads to reducedhydrocarbon emission levels. Further, burning of hydrogenincreases the combustion temperature and presumably leadsto more complete oxidation of the injected vegetable oil.

CO emission, as shown in Fig. 7 is higher with pureJatropha oil operation mainly at higher power outputs. How-ever, in the dual fuel mode there is a signi1cant reduction ofCO emission. It is reduced from 0.26% with pure Jatrophaoil to 0.17% at the maximum e2ciency point at peak powerout put with the induction of 7% hydrogen.

NO emission is 735 ppm at maximum output with pureJatropha oil operation as seen in Fig. 8. In dual fuel operationwith hydrogen induction, there is an increase in NO emis-sions. The NO emission is increased from 735 to 875 ppmwhen hydrogen contributed 7% of total mass of the fuelsupplied, which is the best e2ciency point at maximumpower output. When hydrogen is inducted, the enhancedcombustion rate increases the temperature and thus the NOemission. This is the main environmental problem with hy-drogen induction. Thus, measures have to be taken to controlNO at high outputs when inducting hydrogen. However, atlow power outputs with hydrogen induction there was onlya small change in NO emission.

4. Combustion parameters

Fig. 9 shows the measured cylinder pressure versus crankangle variation at full load and di8erent hydrogen massshares. As the hydrogen quantity varies from 0% to thebest e2ciency point there is a rise in the peak pressure andreduction in the expansion pressure. However, when thehydrogen share is increased beyond this value the peak pres-sure becomes very high and also occurs earlier even thoughthe ignition delay is increased. The pressure and temperatureduring the expansion process are higher and more chemicalenergy is converted into mechanical energy.

The ignition delay period of the pilot fuel in a dual fuelengine is generally higher than in single fuel operation. It isnoted from Fig. 10 that the ignition delay of the pilot fuel(Jatropha oil) at all pilot quantities increases considerably inthe presence of the gaseous fuel. In the dual fuel combustionsystem, the pilot spray is surrounded by air and gas mixturesand the reaction with this gaseous mixture can a8ect theignition of the pilot fuel. In some cases dual fuel operationwith hydrogen induction has lowered the ignition delay [8].

The variation of measured cylinder peak pressure and themaximum rate of pressure rise at constant load for various

340 350 360 370 380 390 400

Crank Angle ( deg )

20

30

40

50

60

70

80

Cyl

ind

er P

ress

ure

( b

ar )

At maximum rate

Speed 1500 rpmInj.Timing :29 BTDCFuel : Jatropha oil

0 % Hydrogen

At max.efficiency

Fig. 9. Variation of cylinder pressure with crank angle.


6

8

10

12

14

16

18

20

Ign

itio

n D

elay

( d

eg C

A )


100 %

80 %

60 %

40 %

20 %

Fig. 10. Variation of ignition delay with hydrogen mass share.

amounts of hydrogen mass share are shown Figs. 11 and 12,respectively. The peak pressure is about 62:3 bar at maxi-mum power with pure Jatropha oil. Peak pressure is furtherincreased in dual fuel operation with hydrogen induction.In a dual fuel engine the trend of increase in peak pressureis due to higher energy release rate. There is an increase toabout 64 bar at 7% of hydrogen mass share at maximumpower. The trend of the maximum rate of pressure rise isalso similar. However, as the load is reduced there is a dropin peak pressure and maximum rate of pressure rise withincreasing hydrogen admission. At low loads, the gaseousfuel air mixture is lean and the ignition source is also weak,


0 10


30

35

40

45

50

55

60

65

70

Cyl

ind

er P

eak

Pre

ssu

re (

bar

)


100 %

80 %

60 %

40 %

20 %

403020

Fig. 11. Variation of peak pressure with hydrogen mass share.

0 5 10 15 20 25 30 35 40


0

1

2

3

4

5

6

7

8

Max

.Rat

e o

f Pr.

Ris

e ( b

ar/d

eg C

A )

100%

80%

60%

40%

20%

Speed 1500 rpminj.Timing 29BTDCFuel : Jatropha oil

Fig. 12. Variation of MRPR with hydrogen mass share.

as the pilot quantity is low. This will result in slower com-bustion rates and lower rates of pressure rise. This is alsobelieved to be one of the reasons for the reduced brake ther-mal e2ciency at this condition.

Combustion duration was calculated from the cumula-tive heat release data computed from the heat release rateas explained earlier. 0–90% heat release was taken as thecombustion duration. It increases when the load rises withneat Jatropha oil operation (Fig. 13) due to increase in thequantity of fuel injected. However, with hydrogen admission

0 5 10 15 20 25 30 35 40


20

30

40

50

60

Co

mb

ust

ion

Du

rati

on

( d

eg C

A )


100%

80%

60%

40%

20%

Fig. 13. Variation of combustion duration with hydrogen massshare.

340 350 360 370 380 390 400

Crank Angle ( Deg )

-10

0

10

20

30

40

50

60

70

80

Hea

t Rel

ease

rate

( J/

Deg

CA

)

0% hydrogen

Speed 1500 rpmInj. Timing : 29 BTDC

Fuel : Jatropha oilLoad 60 %

Max. Hydrogen

Max.Efficiency

Fig. 14. Variation of heat release rate as a function of Crank angleat various hydrogen admissions.

there is a reduction in combustion duration due to higher?ame speed of hydrogen.

The heat release rates in the Jatropha oil hydrogen dualfuel engine are indicated at 60% and 100% loads in Figs. 14and 15, respectively. We 1nd that in the dual fuel mode theinitial heat release phase [namely premixed phase] whichis due to the combustion of a portion of the pilot fuel andinducted hydrogen dominates as the inducted hydrogenquantity is increased. This is believed to be the reason for the


340 350 360 370 380 390 400 410 420

Crank Angle ( Deg )

-10

0

10

20

30

40

50

60

70

80

Hea

t Rel

ease

Rat

e ( J

/ CA

)

At 0 % Admission

At Maximum Rate At Maximum Efficiency


Load : 100 %

Fig. 15. Variation of heat release rate as a function of Crank angleat various hydrogen substitutions.

rise in peak pressure and maximum rate of pressure rise andalso the brake thermal e2ciency under certain conditions.We also can 1nd that the peak heat release can reach veryhigh values when the quantity of hydrogen inducted is high.This can lower the thermal e2ciency. The high rate of heatrelease will also lead to increased NO emission and gas tem-peratures. It will also lead to knock. However, at low

Table 3Petroleum diesel

Load (%) BTE ( % ) EXT (◦C) Smoke (BSU) HC (ppm) CO (%) NO (ppm)

0 0 151 0.2 20 0.07 13020 15.5 184 0.9 20 0.07 18240 23.4 238 1.5 30 0.09 21660 27.9 297 2.2 40 0.1 49880 29.7 358 3.0 70 0.13 630100 30.3 404 3.9 100 0.2 785

Table 4Jatropha oil

Load (%) BTE (%) EXT (◦C) Smoke (BSU) HC (ppm) CO (%) NO (ppm)

0 0 158 0.4 40 0.1 8220 13.5 214 1.2 40 0.1 10340 22.6 272 2.1 60 0.12 20860 26.2 331 2.8 70 0.13 40380 27.2 379 3.6 80 0.18 552100 27.3 428 4.4 130 0.26 735

BTE—brake thermal e2ciency (%); EXT—exhaust gas temperature (◦C); SMOKE—smoke number (BSU); HC—hydrocarbon (ppm);CO—carbon monoxide (%); NO—nitric oxide (ppm).

340 360 380 400 420

Crank Angle ( Deg )

-10

0

10

20

30

40

50

60

Hea

t Rel

ease

rate

( J/

Deg

CA

)

0% HydrogenSpeed 1500 rpmInj.Timing 29 BTDCFuel : Jatropha oil

Load : 40 % 27 % Hydrogen

12 % Hydrogen

Fig. 16. Heat release rate as a function of Crank angle at varioushydrogen admissions.

power outputs, induction of hydrogen leads to lower heatrelease rate (Fig. 16).

4.1. Comparison of diesel and Jatropha oil as pilot fuels

Tables 3 and 4 indicate the performance and emissionsof the engine at di8erent loads when pure Jatropha oil andpetroleum diesel were used as the sole fuel. It is clear thatoperation with Jatropha oil is generally inferior to diesel.


0 5 10 15 20 25 30


10

15

20

25

30

35

Bra

ke T

her

mal

Eff

icie

ncy

( %

)

100 % - Jatropha oil

Speed : 1500 rpmInj. Timing

Std diesel : 27 BTDCJatropha oil : 29 BTDC40 % - Jatropha oil

40 % - Std diesel100 % - Std diesel

Fig. 17. Variation of brake thermal e2ciency with hydrogen massshare.

Fig. 17 shows the variation of brake thermal e2ciencywhen diesel and Jatropha oil are used as pilot fuels at 2 dif-ferent loads. 40% load is used to represent part load opera-tion. The brake thermal e2ciency is higher with diesel whencompared to neat Jatropha oil (i.e. at 0% hydrogen admis-sion). In dual fuel operation with hydrogen induction thereis a further increase in brake thermal e2ciency with bothdiesel and Jatropha oil as pilot fuels. It increased from 30.3%with neat diesel to 32% at a mass share of 5% of hydrogenat peak power output. The optimum hydrogen mass sharewas found as 7% with Jatropha oil. However, at higher ratesof hydrogen admission the combustion becomes too rapidand hence the thermal e2ciency is decreased. It is seen thatthe maximum brake thermal e2ciency occurs when morehydrogen is admitted in the case of Jatropha oil as comparedto diesel. But at all rates, diesel hydrogen dual fuel opera-tion showed higher brake thermal e2ciency than Jatrophaoil hydrogen operation. However, at part load (40% load)dual fuel operation showed inferior performance with bothpilot fuels due to reasons explained earlier.

Smoke level is 3:9 BSU with neat diesel, which is lowerthan neat Jatropha oil (Fig. 18). In dual fuel operation withJatropha oil and diesel as pilot fuels there is a signi1cantreduction in smoke level at all rates of hydrogen admission.The smoke is reduced from 3.9 to 2:7 BSU with diesel atmaximum e2ciency point (5% mass share of hydrogen) at100% load. The introduction of hydrogen reduces the in-jected fuel and lowers the smoke level. The same trend wasseen at 40% load also with both the fuels. It is seen fromthe Figs. 19 and 20 that neat Jatropha oil operation showedhigher unburned fuel and carbon monoxide emissions com-pared to neat diesel operation at all loads. The hydrocarbon

0 5 10 15 20 25 30


0

1

2

3

4

5

6

Sm

oke

No

( B

osc

h S

mo

ke U

nit

s )

Speed 1500 rpmInj.Timing

Std diesel : 27 BTDCJatropha oil : 29 BTDC

100 % - Std diesel


40 % - Std diesel

40 % - Jatropha oil

Fig. 18. Variation of smoke no with hydrogen mass share.

0 5 10 15 20 25 30


0

20

40

60

80

100

120

140

160

180

HC

( p

pm

)


Std diesel :27 BTDCJatropha oil :29BTDC

100 % - Std diesel

40 %- Jatrophaoil

40 %- Std diesel


Fig. 19. Variation of HC with hydrogen mass share.

emission is 100 ppm with diesel and 130 ppm with Jatrophaoil in the single fuel operation at full load. In the dual fueloperation with hydrogen induction there is a signi1cantreduction of hydrocarbon and carbon monoxide emis-sion with diesel and Jatropha oil. It was reduced to70 ppm with diesel and 100 ppm with Jatropha oil atthe maximum e2ciency point at full load. The carbonmonoxide emission is reduced from 0.2% to 0.1% atmaximum e2ciency point with diesel. At 40% load alsothere is a reduction of hydrocarbon and carbon monox-ide emissions with both the pilot fuels. CO levels are


0 5 10 15 20 25 30


0.35

CO

( %

)

100 % - Std diesel100 % - Jatropha oil

40 % - Jatropha oil40 % - Std diesel


Std diesel : 27BTDCJatropha oil : 29 BTDC

0.30

0.25

0.20

0.15

0.10

0.05

0.00

Fig. 20. Variation of CO with hydrogen mass share.

0 5 10 15 20 25 30


0

200

400

600

800

1000

1200

NO

( p

pm

)


Speed : 1500 rpmInj.Timing

Std diesel : 27 BTDCJatropha oil : 29 BDC

40 % - Std diesel

40 % - Jatropha oil

100 % - Std diesel

Fig. 21. Variation of NO with hydrogen mass share.

higher with Jatropha oil. Neat Jatropha oil emits lowerNO levels compared to standard diesel (Fig. 21). Whenhydrogen is inducted the NO level rises due to enhancedcombustion rate with both the fuels. At the maximum ef-1ciency point the NO level is 894 ppm with diesel and875 ppm with Jatropha oil.

Jatropha oil leads to longer ignition delay as comparedto diesel in the single fuel operation as seen in the Fig. 22.Increasing the hydrogen admission rises the delay furtherwith both diesel and Jatropha oil at all loads. The peak

0 5 10 15 20 25 30


6

8

10

12

14

16

18

20

Ign

itio

n D

elay

( d

eg C

A )

100 % - Std diesel



40 % - Jatropha oil


Fig. 22. Variation of ignition delay with hydrogen mass share.

0 5 10 15 20 25 30


35

40

45

50

55

60

65

70

75

80

Cyl

ind

er P

eak

Pre

ssu

re (

bar

)

40 % - Jatropha oil


Std diesel : 27 BTDCJatropha oil : 29 BTDC100 % - Jatropha oil

100 % - Std diesel

40 % - Std diesel

Fig. 23. Variation of peak pressure with hydrogen mass share.

pressure and maximum rate of pressure rise as seen in Figs.23 and 24 are highest with diesel followed by Jatropha oilat both loads. The peak pressure is 64 bar with diesel and62 bar with Jatropha oil in the single fuel operation. It isseen from the 1gures that the peak pressure and maximumrate of pressure rise are higher in dual fuel operation whenhydrogen is inducted. It is increased to a maximum of 66 barwith diesel and 64 bar with Jatropha oil at the maximume2ciency points. However, at low load peak pressure and


0 5 10 15 20 25 30


0

1

2

3

4

5

6

7

Max

.Rat

e o

f Pr.

Ris

e ( b

ar/d

eg C

A )

100 % - Std diesel



40 % - Jatropha oil40 % - Std diesel100 % - Jatropha oil

Fig. 24. Variation of MRPR with hydrogen mass share.

0 5 10 15 20 25 30Hydrogen Mass Share ( % )

10

20

30

40

50

60

Co

mb

ust

ion

Du

rati

on

( d

eg C

A )

100 % - Std diesel


Std diesel : 27 BTDCJatropha oil :29 BTDC

40 % - Jatropha oil


Fig. 25. Variation of combustion duration with hydrogen massshare.

maximum rate of pressure rise were reduced with both dieseland Jatropha oil when hydrogen was inducted. This indicatesthe deterioration in combustion in the dual fuel operationmode at low outputs. The combustion duration is higherwith Jatropha oil as compared to diesel as seen in (Fig. 25).However, in dual fuel operation there is a reduction withboth the pilot fuels due to the high ?ame speed of hydrogen.

5. Conclusion

A single cylinder compression ignition engine was oper-ated successfully using hydrogen as the inducted fuel andJatropha oil and diesel as pilot fuels. The following conclu-sions are made based on the experimental results.

Inducting small quantities of hydrogen along with airwhen Jatropha oil and diesel are used as the main injectedpilot fuels:

• Signi1cantly enhances the brake thermal e2ciency. Thevalue rises from 27.3% with neat Jatropha oil operation to29.4% at full load. The optimum hydrogen mass share wasfound to be 7%. With diesel the brake thermal e2ciencywas increased from 30.3% to 32% at 5% hydrogen massshare. However, hydrogen induction reduces the brakethermal e2ciency at low power outputs.

• Resulted in a good reduction in smoke level. It droppedfrom 4.4 to 3:7 BSU with Jatropha oil and 3.9 to 2:2 BSUwith diesel at the optimum hydrogen mass share.

• Reduced hydrocarbon and the carbon monoxide emis-sions with Jatropha oil and diesel. The reduction in HCand CO emissions with Jatropha oil were 130 to 100 ppmand 0.26% to 0.17%, respectively, at maximum e2ciencypoint at peak power output. The corresponding reduc-tion in hydrocarbon and carbon monoxide emissions withdiesel as the pilot fuel were 100 to 70 ppm and 0.2% to0.1%, respectively.

• Lead to a signi1cant rise in NO level from 735 to 875 ppmwith Jatropha oil and 785–894 ppm with diesel at theoptimum e2ciency point. This is e8ect is believed to bethe due the higher combustion temperatures attained.

• Increases the ignition delay of both diesel and Jatrophaoil. It increased from 10◦CA to 13◦CA with Jatropha oiland 9◦ to 11◦ CA with diesel at full load.

• Increases the peak cylinder pressure and rate of pressurerise mainly at higher power outputs.

• Increases the premixed combustion rate at high poweroutputs. At low power outputs the heat release rate isreduced due to poor combustion.

On the whole it is concluded that hydrogen can beinducted along with air to improve the performance andreduce hydro and smoke emissions of a Jatropha oil fuelledcompression ignition engine. The most signi1cant environ-mental penalty will be an increase of NO emission. Theamount of hydrogen that can be added depends on the out-put. At full load 7% of the total mass of fuel admitted hasto be hydrogen for optimal performance. At low outputs itis not advantages to use hydrogen induction.

Acknowledgements

The authors thank Mr. K. Chandrasekar consultant, Jat-ropha plantations and oil extractions, JATROPHA OIL seed


development & research, Hyderabad, for his support and forsupplying the oil for this work.

References

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use of hydrogen to enhance the performance of a vegetable oil fuelled compression ignition engine

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