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Renewable Energy 36 (2011) 2635e2640

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Renewable Energy

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Alternative fuel for gas turbine: Esterified jatropha oilediesel blend

A. Rehman a,*, Deepak R. Phalke b, Rajesh Pandey a

aDepartment of Mechanical Engineering, Maulana Azad National Institute of Technology, Bhopal, M.P. 462051, IndiabRDCT, Indore, M.P., India

a r t i c l e i n f o

Article history:Received 27 March 2010Accepted 9 June 2010Available online 10 July 2010

Keywords:BiodieselBiofuelsJatrophaGas turbinesEmissions

* Corresponding author. Tel.: þ91 755 3016386; faxE-mail addresses: manit1963@yahoo.com (A. Re

(R. Pandey).

0960-1481/$ e see front matter � 2010 Elsevier Ltd.doi:10.1016/j.renene.2010.06.013

a b s t r a c t

The oil crisis and the global effort to control the greenhouse effect have forced the researchers to think ofvarious alternative energy sources. This decade has seen increasing importance of chemically treatedvegetable oil biodiesel fuels for various applications in heat engines. Post-Kyoto negotiations refer to highlevel talks attempting to address global warming by limiting greenhouse gas emissions. During ClimateChange Conference in Copenhagen the potential topics discussed were carbon capture and storage,biofuels, adaptation financing, technology transfer, sustainable agriculture, emissions targets, tropicalforests and rural and transport electrification. Our area of interest is biofuels under which nonedibleJatropha oil due to its properties which are very close to diesel fuel is being explored as an alternativefuel. A lot of research is underway in the use of different biodiesel fuels in Internal Combustion engines,but very limited work has been reported in its use in gas turbines. This paper describes the results of anongoing development program aimed at determining the technical feasibility of utilizing biodiesel in IS/60 Rovers gas turbine. The test rig is equipped with a dynamometer for turbine loading and AVL exhaustgas analyzer has been used to record emissions. The test results of 2 blends have been reported in thispaper. Analyzing the results compared with the base line performance using diesel fuel under normalconditions show encouraging outcomes.

� 2010 Elsevier Ltd. All rights reserved.

1. Introduction

During the last decade a lot of work has been undertaken toexplore the feasibility and viability of using biofuels in differentapplications [1]. In the recently concluded Copenhagen December2009 United Nations Climate Change Conference the worldleaders and researchers mainly discussed issues related to bio-fuels, sustainable agriculture, emissions targets, production ofcarbon dioxide and global warming [2e4]. Role of developedcountries and their demand for more energy was a point of greatconcern so that they may shoulder the responsibility of prevent-ing any further environmental degradation. Much can be done toprevent this loss, like using biodiesel fuels which have lowercarbon dioxide percentage on combustion as compared to diesel.Efficient use of fuel is another area of importance for researchersto prevent environmental degradation and delay exhaustion ofthe fossil fuels.

Sufficient level of research in the area of biodiesel as fuel forInternal Combustion Engines has been done [5e10] as comparedto its use in Gas Turbines. There is an increasing amount of

: þ91 755 5206006.hman), rkpmanit@gmail.com

All rights reserved.

literature on gas turbine covering other aspects such as: design,combustion, heat transfer, performance, materials (super alloys,coating); applications (propulsion; power generation, mechanicaldrive; traction); process control. Reported work on gas turbineand specially related to power generation application usuallymentions natural gas and gas oil but they virtually ignore otheralternate fuel. Research and investigations on alternative biofuelsfor the gas turbines along with the effect of varying turbine inletconditions is a very important area of work [10e13]. India is oneamong the largest petroleum consuming nations with its currentyearly consumption of diesel oil touching 40 million tones whichis about 40% of the total petroleum product consumption [1].India and all developing countries of the world need to explorethis area with conviction in a planned manner. A dangerouseffect of burning fuel emissions on environment is a fact whichcannot be left in the research. Gas turbine and InternalCombustion engines running on diesel are a major contributorto air pollution especially within cities and along urban trafficroutes.

Biodiesel can be one of the alternative renewable energy sourcesfor gas turbine. As the properties of biodiesel closely match withthe diesel fuel properties, so it can be used as one of the alternativefuels which is of comparable cost and produce less emissions[5e15].

Nomenclature

d diesel fuel tested under normal inlet conditionsb1 fuel blend of 15% biodiesel in 85% diesel fuelb2 fuel blend of 25% biodiesel in 75% diesel fuelbsfc brake specific fuel consumptionCO carbon monoxideHC hydrocarbonsNOx oxide of nitrogen

Table 2Specifications of IS/60 rovers gas turbine.

Part of test rig Details

Compressor CentrifugalTurbine Single stage axialCombustion Chamber Reverse flowTurbine Speed 46,000 rpm.Pressure Ratio 2.8/1Max BP at 46,000 rpm 44 kW at 3000 rpm

Table 3List of instruments and range, accuracy and percentage uncertainties.

Sr. no Instruments Range Accuracy Percentageuncertainties

1 Gas analyzer NOx

0e500 ppm�10 ppm �0.9

HC �1 ppm �0.1CO �0.01% �0.3CO2 �0.03% �0.15

2 Smoke levelmeasuring instrument

Opacity % �0.2 �0.28

3 EGT indicator 0e900 �C �1 �C �0.154 Speed measuring unit 0e10000 ppm �10 rpm �0.665 Load indicator 0e100 kg �0.1 kg �0.26 Burette for fuel

measuremente �0.2 cm2 �2.0

7 Digital stop watch e �0.2 s �0.28 Manometer e �1 mm �1.09 Pressure pick up 0e110 bar �1 bar �0.110 Encoder e �1� �0.2

A. Rehman et al. / Renewable Energy 36 (2011) 2635e26402636

1.1. Biodiesel and related problems

Many problems are encountered during the use of plain vege-table oil as fuel in diesel engines and gas turbines. Higher viscosityof plain vegetable oils interferes with the fuel atomization. This inturn affects combustion, makes cold starting difficult, clogs thenozzle, and contaminates lubricating oil. Poor volatility makes plainvegetable oil difficult to vaporize and ignite this also results inthermal crackingwhich in turn leads to heavy smoke emissions andcarbon deposits in the combustion chamber. The problem of highviscosity can be overcome to a great extent by various techniques,such as heating, dilution, emulsification and esterification [6e8].

1.2. The effect of water and steam

There are several reasons why water may be present in the airused by a gas turbine engine such as ambient humidity and wateror steam injection. The above are additional to the water vaporproduced by combustion. The amount of water and carbon dioxideproduced are based on fuel properties and fueleair ratio, accountedin performance calculations via modified gas properties. Thepresence of any additional water beyond that produced bycombustion affects performance [10e12].

1.3. Biodiesel (jatropha) availability

Jatropha plant has medicinal and industrial use and can beplanted on a large scale and great profit can be earned from itsplantation. In India various states have sufficient forest area for theplantation of jatropha [1,6,8].

2. Material and methods

Jatropha oil was chemically treated to modify oil properties byway of transesterification. After transesterification process thevegetable oil esters are referred to as biodiesel. Since most vege-table oils and diesel oils are miscible, blends of esters of vegetableoil and diesel oil were prepared. Blending up to 30% of jatropha oilbiodiesel in diesel show good test results on diesel engine as that

Table 1Comparison of evaluated properties of diesel, jatropha, ester and blends b1, b2.

Sr. no Properties ASTM test method Diesel oil

1 Density gm/cc 15 �C D 4052 0.8522 Viscosity cSt D 445 3.383 Calorific value MJ/g D 240 439634 Flash point �C D 93 675 Fire point �C 736 Cloud point �C D 2500 �67 Pour point D 97 �128 Carbon residue wt% D 524 0.289 Sulphur content % D 129 0.03210 Saponification no. mg KOH/gm oil e e

obtained with diesel fuel. Two blends were prepared for testing thebiodiesel in gas turbine, blend 1 e b1: with 15% biodiesel and 85%diesel and blend 2 e b2: with 25% biodiesel and 75% diesel. Prop-erties of diesel, jatropha, ester and their blends b1, b2 evaluated forcomparison with diesel and reported in Table 1.Rover gas turbineIS/60 test rig has been used for testing the performance with dieseland biodiesel. It is a single stage turbine with maximum 44 kWbrake power at rated conditions. Table 2 gives brief specifications ofthe Gas Turbine. The tests were conducted at temperaturesbetween 28 �C and 35 �C. AVL exhaust gas analyzer was used torecord emissions under all test conditions. The tests were con-ducted at speed of about 1500 revolutions perminute on the outputshaft. Fuel flow meter which is part of the test rig was used to notethe fuel consumption. Hydraulic dynamometer, Heenan Froudemake, was used to observe the turbine load variations. Exhaust gastemperature was regularly monitored.

2.1. Error analysis

Although, all efforts have been made to minimize the errors inexperimentation, yet some errors are likely to creep in depending

Jatropha oil Jatropha oil methyl ester Blend e b 1 Blend e b2

0.910 0.884 0.856 0.8630 5.42 3.68 3.8939.4 39.89 42.29 42.89

240 171 82.6 6244 175 88.3 106

7 �1 �5.1 �4.74 3 �10.2 �92.41 1.49 0.461 0.580.006 0.003 0.272 0.24

191 186 e e

Table 5List of instruments and range, accuracy and percentage uncertainties.

Sr. no Instruments Range Accuracy Percentageuncertainties

1 Gas analyzer NOx

0e5000 ppm�20 ppm �0.2

HC �15 ppm �0.2CO �0.02% �0.2CO2 �0.03% �0.15

2 Smoke level measuringinstrument

BSN 0e10 �0.2 �1.0

3 EGT indicator 0e900 �C �1 �C �0.154 Speed measuring unit 0e10,000 ppm �10 rpm �1.05 Load indicator 0e100 kg �0.1 kg �0.26 Burette for fuel

measuremente �0.2 cm2 �1.5

7 Digital stop watch e �0.2 s �0.28 Manometer e �1 mm �1.09 Pressure pick up 0e110 bar �1 bar �0.110 Encoder e �1� �0.2

Table 4List of instruments used for measuring various parameters and measurementtechniques.

Instrument Purpose Make andmodel

Measurementtechniques

Exhaustgas analyzer

Measurement ofHC, CO, CO2 andNOx emissions

AVL 444 DiGasanalyzer

NDIR principle(non-depressive infrared sensor) NOx

electrochemical sensorSmoke meter Measurement of

smoke emissionsAVL 434 Smokeanalyzer

EGT 2 indicator Measurement ofexhaust gastemperature

k-Type(Cr Al)thermocouple

Speed measuringunit

Measurement ofengine speed

Magnetic pick up

Encoder Magnetic pick up typeLoad indicator Loading device BENZ Strain gauge type load

cell

Fig. 2. Effect of brake load on CO emissions with diesel and biodiesel blends.

A. Rehman et al. / Renewable Energy 36 (2011) 2635e2640 2637

upon the accuracy of the instruments used for various measure-ments. In order to determine the extent of this uncertainty, anuncertainty analysis has been carried out.

Effect of uncertainty in case of the single measurement can becalculated as:

Fig. 1. Effect of brake load on brake specific fuel consumption with diesel and biodieselblends.

dR=R ¼ ðdX1=X1Þ (1)

If result R of the experiment is assumed to be calculated froma set of measurements using a data interpretation programmerepresented by

R ¼ Xa1; Xb

2; Xc3.Xn

N (2)

Then the relative uncertainty can be found as:

dR=R ¼hfaðdX1=X1Þg2þfbðdX2=X2Þg2þ.fnðdXN=XNÞg2

i1=2

The uncertainties of the measurements are described inpercentage. The possible uncertainties in the derived results wereexamined before the start of the experimental works, which helpedin the selection of the instruments for experiments and reported inTables 3e5.

Fig. 3. Effect of brake load on HC emissions with diesel and biodiesel blends.

A. Rehman et al. / Renewable Energy 36 (2011) 2635e26402638

Total percentage uncertainty of this experiment is

¼ Square root of ðuncertainty of TFCÞ2þðuncertainty of BPÞ2

þ ðuncertainty of BSFCÞ2

þ ðuncertainty of brake thermal efficiencyÞ2

þ ðuncertainty of COÞ2þðuncertainty of UBHCÞ2

þ ðuncertainty of NOxÞ2 ¼ ð1:41%Þ2þð0:50%Þ2þð1:5%Þ2

þ ð0:6%Þ2þð0:3%Þ2þð1%Þ2þð0:9%Þ2 ¼ 2:59%

3. Results and discussion

The various tests performed with two biodiesel blends used inthe present work were carried out under ambient inlet conditions.Table 2 gives the details of the test rig used in the present work.Also Figs. 5e8 at the end of the paper give the view of the gasturbine used in the present work.

Fig. 4. Effect of brake load on NOx emissions from diesel and biodiesel blends.

3.1. Effect of brake load on brake specific fuel consumption

Fig. 1 shows that bsfc for b1 and b2 is higher than that of diesel.The higher fuel consumption per unit power produced can beattributed to lower calorific value of the blends. As reported byvarious researchers the brake specific fuel consumption is 5e8%higher than that of diesel and improves at higher power output[5,14,15]. Further the figure shows us that at lower loads the bsfcwith biodiesel blends is higher. However, bsfc for b1 and b2reduced marginally below that obtained with diesel for mediumloads. This can be attributed to higher oxygen content of the fuelwhich supports combustion but also marginally increasesblendeair mixture temperature.

Fig. 5. The schematic of ga

3.2. Effect of brake load on CO emissions

As evident from Fig. 2 the CO emissions from different blends ofbiodiesel are lower then diesel. This can be due to higher oxygencontent of jatropha oil which improves combustion. Biodieselcontains 10e12% oxygen on weight basis which lowers the energycontent of the fuel. However, lower energy content of the blendscause reduction in engine torque and power. Better combustion

s turbine test set-up.

Fig. 6. The sectional details of gas turbine.

Fig. 8. The compressor impellor and the turbine blades.

A. Rehman et al. / Renewable Energy 36 (2011) 2635e2640 2639

reduces products of incomplete combustion [16,17]. Again theemissions from b2 are lower than that of b1 which may be due tothe same reason related to more oxygen content in b2 than in b1[5,6,15].

3.3. Effect of brake load on HC emissions

In Fig. 3 it can be seen that the effect of load/brake power on HCemissions with diesel compared with different blends of biodieselare higher. Emissions of HC for b1 and b2 as compare to that

Fig. 7. The end view of the turbine showing turbine blades; picture taken when themodifications were done for water injection etc.

obtained with diesel fuel are lower due to higher fuel oxygencontent of biodiesel as compared to diesel resulting in bettercombustion. Also the HC emissions with b2 are lower than thatwith b1 again due to the same reason related to oxygen in fuel.

3.4. Effect of brake load on NOx emissions

NOx emissions are the major source of pollution from any gasturbine. NOx emissions mainly depend on temperature and oxygenavailable at that temperature. However, fuel properties, engineload, engine type, airefuel mixture ratio and time affect NOx

formation indirectly [13,16,17]. In the present case the higher NOx

emissions may be mainly due to higher temperature in thecombustion zones of the chamber [13,16]. Further, NOx emissionsare due to three mechanisms involved during combustion and theyare thermal NO, Fuel NO and prompt NO [17]. In the presentalternative fuel first twomechanisms aremainly responsible for theformation of higher NOx emissions.

From Fig. 4 it is evident that NOx emissions for b1 and b2 arehigher than that obtained with diesel fuel. Higher combustiontemperatures were observed due to better combustion on accountof higher oxygen in biodiesel fuel as compared to diesel. Highertemperature factor is mainly responsible for higher NOx with bio-diesel blend. Further, the cetane number for the biodiesel is higherthan diesel which may also be another reason for higher NOx

emissions. NOx emission for b2 is higher than that of b1 which canagain be attributed to the same reasons already discussed related tohigher cycle temperature achieved during combustion.

4. Conclusions

Based on the experimental results following conclusions aredrawn.

1. Jatropha oil has characteristics properties very close to dieseloil. However the viscosity is higher which can be reduced bydegumming/esterification of Jatropha oil to form its biodieselfuel.

2. Esterified Jatropha oil is miscible with diesel fuel in anyproportion and can be used as diesel fuel extenders.

A. Rehman et al. / Renewable Energy 36 (2011) 2635e26402640

3. Biodiesel blend of Jatropha oil with diesel oil can be one of thealternate fuels, for gas turbine application.

4. India is Agriculture-based country, large portion of its wasteand unfertile land can be used for growing jatropha plant. Thiswould provide jatropha oil for biodiesel production, which willact as future fuel for gas turbines.

5. Transesterification process can reduce the viscosity of jatro-pha oil to a substantial level and allow it to be used in gasturbine. It also reduces the specific gravity from 0.917 to0.881 at 15 �C.

6. The Calorific value of Jatropha oil is found to be lower in therange 7e9% due to the difference in chemical composition andthe difference of carbonehydrogen content.

7. Experimental results show the fuel consumption of variousblends are initially higher at lower loads due to higher specificgravity, low volatility, high viscosity but improves as thecombustion proceed due to decrease in viscosity.

8. Initially at lower loads the brake specific fuel consumption ishigher for the blends due to lower calorific value and highdensity & viscosity. The bsfc marginally reduced at a point byabout 4% as the viscosity reduced with the increase in cycletemperature at higher loads.

9. Carbon monoxide and Hydrocarbon emissions from theexhaust of turbine for b1 and b2 are lower than that obtainedwith diesel fuel. It may be due to better combustion withoxygenated blends of biodiesel fuel, which can be predictedfrom high exhaust temperature as compared to that obtainedwith diesel.

10. NOx emission from b1 and b2 are higher than diesel due tobetter combustion resulting in higher cycle temperature. AsNOx emissions are temperature dependant and are higher athigh temperature.

11. Above results indicate jatropha can be one of the alternate fuelfor gas turbine. Its cost is comparable based on its level ofproduction and oil extraction technology.

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