A Comparative Study of Different Methods of Using Animal...

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M. Senthil Kumar A. Kerihuel J. Bellettre 1 e-mail: [email protected] M. Tazerout Département Systèmes Energétiques et Environnement, Ecole des Mines de Nantes, 4 rue Alfred Kastler, BP 10722, 44307 Nantes, Cedex 03, France A Comparative Study of Different Methods of Using Animal Fat as a Fuel in a Compression Ignition Engine This work explores a comparative study of different methods of using animal fat as a fuel in a compression ignition engine. A single-cylinder air-cooled, direct-injection diesel engine is used to test the fuels at 100% and 60% of the maximum engine power output conditions. Initially, animal fat is tested as fuel at normal temperature. Then, it is pre- heated to 70°C and used as fuel. Finally, animal fat is converted into methanol and ethanol emulsions using water and tested as fuel. A drop in cylinder peak pressure, longer ignition delay, and a lower premixed combustion rate are observed with neat animal fat as compared to neat diesel. With fat preheating and emulsions, there is an improvement in cylinder peak pressure and maximum rate of pressure rise. Ignition delay becomes longer with both the emulsions as compared to neat fats. However, preheating shows shorter ignition delay. Improvement in heat release rates is achieved with all the methods as compared to neat fats. At normal temperature, neat animal fat results in higher specific energy consumption and exhaust gas temperature as compared to neat diesel at both power outputs. Preheating and emulsions of animal fat show improvement in performance as compared to neat fat. Smoke is lower with neat fat as compared to neat diesel. It reduces further with all the methods. At peak power output, the smoke level is found as 0.89 m -1 with methanol, 0.28 m -1 with ethanol emulsions, and 1.7 m -1 with fat preheating, whereas it is 3.7 m -1 with neat fat and 6.3 m -1 with neat diesel. Methanol and ethanol emulsions significantly reduce NO emissions due to the vaporization of water and alcohols. However, NO increases with fat preheating due to high in-cylinder tem- perature. Higher unburned hydrocarbon and carbon monoxide emissions are found with neat fat as compared to neat diesel at both power outputs. However, these emissions are considerably reduced with all the methods. It is finally concluded that adopting emulsi- fication with the animal fat can lead to a reduction in emissions and an improvement in combustion characteristics of a diesel engine. DOI: 10.1115/1.2180278 Introduction The main problems associated with the use of animal fats and vegetable oils as fuel in diesel engines are their high viscosity and poor volatility. A number of methods have been tried in the past to use vegetable oils and animal fats efficiently in diesel engines. Some of them are transesterification of vegetable oils, blending the oils with diesel and alcohols, fuel preheating, dual fueling with gaseous and liquid fuels, use of additives, etc. 1–5. Transesterification shows significant reduction in viscosity, en- hancement in cetane number, and other physical properties 5. But, transesterification is a complex and cumbersome process. Dual fueling is a well-established technique to use different types of fuels in diesel engines 6. A dual fuel engine results in good thermal efficiency and low smoke emissions, particularly at high power outputs 7. However, dual fuel operation needs modifica- tion in the engine design. In addition, dual fuel operation with alcohol induction results in higher hydrocarbon and carbon mon- oxide emissions 7. Though blending of oils with alcohols is a simple process, significant improvement in performance and re- duction emissions are not reported in the literature. In addition, more quantities of alcohol addition to the oils leads to phase sepa- ration 8. The fuel preheating technique offers the advantage of easy con- version of the normal diesel engine to work on highly viscous fuels. It needs no modification in the engine. Past investigations showed that preheated animal fat and vegetable oils in diesel en- gines resulted in improved brake thermal efficiency and reduced smoke and particulate emissions 4,9,10. Since animal fats have very high viscosity, the preheating technique can offer significant reduction in viscosity with improved performance and reduced emissions in a diesel engine fueled with animal fats. Emulsions also find attraction to use as fuel in diesel engines due to their simultaneous reduction of smoke and NO x emissions using vegetable oils/diesel as fuel 11–14. Emulsification is a simple process and needs no modification in the engine design. Emulsion properties are further improved by mixing alcohols with oil and water during the emulsion preparation process. Alcohols act as cosurfactants and fuel extenders in making emulsions. They increase the stability and reduce viscosity of emulsions 15–19. Since animal fats mix freely with alcohols, alcohols can be used as cosurfactants to improve the emulsion properties further. Past results obtained from the experiments on diesel engines using emulsions of animal fats/diesel with alcohol showed very good agreement with the engine performance and exhaust smoke emis- sions 15,16,20. In this work, different methods, such as neat fat operation, fat preheating, and emulsions with methanol/ethanol, are studied ex- perimentally to analyze the emissions and combustion character- istics of a diesel engine fueled with animal fat. Experiments are conducted with different fractions of alcohols, water, and fats. 1 To whom correspondence should be addressed. Contributed by the Internal Combustion Division of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received October 4, 2004; final manuscript received October 17, 2005. Review conducted by J. C. Cowart. Journal of Engineering for Gas Turbines and Power OCTOBER 2006, Vol. 128 / 907 Copyright © 2006 by ASME Downloaded 31 Jul 2007 to 18.51.1.222. Redistribution subject to ASME license or copyright, see http://www.asme.org/terms/Terms_Use.cfm

Transcript of A Comparative Study of Different Methods of Using Animal...

Page 1: A Comparative Study of Different Methods of Using Animal ...web.mit.edu/nuwong/Public/Diesohol/Kumar_AnimalFatCIengine_JEn… · Engine This work explores a comparative study of different

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M. Senthil Kumar

A. Kerihuel

J. Bellettre1

e-mail: [email protected]

M. Tazerout

Département Systèmes Energétiques etEnvironnement,

Ecole des Mines de Nantes,4 rue Alfred Kastler,

BP 10722,44307 Nantes,

Cedex 03, France

A Comparative Study of DifferentMethods of Using Animal Fat as aFuel in a Compression IgnitionEngineThis work explores a comparative study of different methods of using animal fat as a fuelin a compression ignition engine. A single-cylinder air-cooled, direct-injection dieselengine is used to test the fuels at 100% and 60% of the maximum engine power outputconditions. Initially, animal fat is tested as fuel at normal temperature. Then, it is pre-heated to 70°C and used as fuel. Finally, animal fat is converted into methanol andethanol emulsions using water and tested as fuel. A drop in cylinder peak pressure,longer ignition delay, and a lower premixed combustion rate are observed with neatanimal fat as compared to neat diesel. With fat preheating and emulsions, there is animprovement in cylinder peak pressure and maximum rate of pressure rise. Ignition delaybecomes longer with both the emulsions as compared to neat fats. However, preheatingshows shorter ignition delay. Improvement in heat release rates is achieved with all themethods as compared to neat fats. At normal temperature, neat animal fat results inhigher specific energy consumption and exhaust gas temperature as compared to neatdiesel at both power outputs. Preheating and emulsions of animal fat show improvementin performance as compared to neat fat. Smoke is lower with neat fat as compared to neatdiesel. It reduces further with all the methods. At peak power output, the smoke level isfound as 0.89 m−1 with methanol, 0.28 m−1 with ethanol emulsions, and 1.7 m−1 with fatpreheating, whereas it is 3.7 m−1 with neat fat and 6.3 m−1 with neat diesel. Methanoland ethanol emulsions significantly reduce NO emissions due to the vaporization of waterand alcohols. However, NO increases with fat preheating due to high in-cylinder tem-perature. Higher unburned hydrocarbon and carbon monoxide emissions are found withneat fat as compared to neat diesel at both power outputs. However, these emissions areconsiderably reduced with all the methods. It is finally concluded that adopting emulsi-fication with the animal fat can lead to a reduction in emissions and an improvement incombustion characteristics of a diesel engine. �DOI: 10.1115/1.2180278�

ntroductionThe main problems associated with the use of animal fats and

egetable oils as fuel in diesel engines are their high viscosity andoor volatility. A number of methods have been tried in the past tose vegetable oils and animal fats efficiently in diesel engines.ome of them are transesterification of vegetable oils, blending

he oils with diesel and alcohols, fuel preheating, dual fueling withaseous and liquid fuels, use of additives, etc. �1–5�.

Transesterification shows significant reduction in viscosity, en-ancement in cetane number, and other physical properties �5�.ut, transesterification is a complex and cumbersome process.ual fueling is a well-established technique to use different typesf fuels in diesel engines �6�. A dual fuel engine results in goodhermal efficiency and low smoke emissions, particularly at highower outputs �7�. However, dual fuel operation needs modifica-ion in the engine design. In addition, dual fuel operation withlcohol induction results in higher hydrocarbon and carbon mon-xide emissions �7�. Though blending of oils with alcohols is aimple process, significant improvement in performance and re-uction emissions are not reported in the literature. In addition,ore quantities of alcohol addition to the oils leads to phase sepa-

ation �8�.

1To whom correspondence should be addressed.Contributed by the Internal Combustion Division of ASME for publication in the

OURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received October, 2004; final manuscript received October 17, 2005. Review conducted by J. C.

owart.

ournal of Engineering for Gas Turbines and PowerCopyright © 20

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The fuel preheating technique offers the advantage of easy con-version of the normal diesel engine to work on highly viscousfuels. It needs no modification in the engine. Past investigationsshowed that preheated animal fat and vegetable oils in diesel en-gines resulted in improved brake thermal efficiency and reducedsmoke and particulate emissions �4,9,10�. Since animal fats havevery high viscosity, the preheating technique can offer significantreduction in viscosity with improved performance and reducedemissions in a diesel engine fueled with animal fats.

Emulsions also find attraction to use as fuel in diesel enginesdue to their simultaneous reduction of smoke and NOx emissionsusing vegetable oils/diesel as fuel �11–14�. Emulsification is asimple process and needs no modification in the engine design.Emulsion properties are further improved by mixing alcohols withoil and water during the emulsion preparation process. Alcoholsact as cosurfactants and fuel extenders in making emulsions. Theyincrease the stability and reduce viscosity of emulsions �15–19�.Since animal fats mix freely with alcohols, alcohols can be usedas cosurfactants to improve the emulsion properties further. Pastresults obtained from the experiments on diesel engines usingemulsions of animal fats/diesel with alcohol showed very goodagreement with the engine performance and exhaust smoke emis-sions �15,16,20�.

In this work, different methods, such as neat fat operation, fatpreheating, and emulsions with methanol/ethanol, are studied ex-perimentally to analyze the emissions and combustion character-istics of a diesel engine fueled with animal fat. Experiments are

conducted with different fractions of alcohols, water, and fats.

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uel inlet temperature is also varied at different temperatures foreat fat operation. Results are optimized based on minimum emis-ion levels. The optimum results obtained with different methodsre compared to their respective fats and neat diesel at two differ-nt power outputs �i.e., 100% load and 60% load�. Comparison isade for the following cases:

�a� neat diesel and neat animal fat at normal temperature�b� animal fat with preheating at 70°C and emulsions of ani-

mal fat with methanol�c� neat animal fat and emulsions of animal fat with ethanol

xperimental Setup and Experimental Procedure

Engine Test Cell. A single-cylinder air-cooled Lister PetterTS1� diesel engine developing a power output of 2.8 kW at500 rpm is used for the work. The schematic of the experimentaletup is shown in Fig. 1, and the engine details are given in Table. An electrical dynamometer is used for loading the engine. Anrifice meter connected to a large tank is attached to the enginentake manifold to make airflow measurements. The fuel flow rates measured on the volumetric basis using a burette and a stop-atch. A chromel-alumel thermocouple in conjunction with a

low-speed digital data acquisition system is used for measuringhe exhaust gas temperature.

Fig. 1 Schematic of experimental setup

Table 1 Engine details

Make Lister Petter—TS 1

General details Four-stroke, compression ignition, air-cooled,naturally aspirated, single-cylinder engine

Bore and stroke 95.3 mm�88.9 mmConnecting rod length 165.3 mm

Compression ratio 18:1ated brake power output 2.8 kW at 1500 rpm

Injector opening pressure 250 barDisplacement volume 630 ccFuel injection timing 20 deg BTDC �static�

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Emission Instrumentation. An infrared �COSMA� exhaustanalyzer is used for measuring hydrocarbon �HC� and carbonmonoxide �CO� emissions. NO in the exhaust is measured byusing a Beckman chemiluminascence NO/NOx analyzer. Smokelevels are measured by using a standard Hartridge smoke meter,which works on a light absorption technique �passing a light beamthrough the exhaust sample and the fraction of light is absorbedby the exhaust gas�. Light extinction coefficient K is used as themeasure of smoke density. Details on smoke measurement can befound in �18,20�.

Combustion Data Acquisition. A high-speed digital data ac-quisition system in connection with AVL 620-Indiwin hardware isused for combustion data acquisition. The AVL INDISET 620consists of a docking station with 16 input channels connected toa PC via a centronics interface. The combustion pressure is mea-sured using a piezoelectric transducer �AVL Model� mounted flushon the cylinder head. The fuel line pressure is measured by ananother piezoelectric transducer �AVL Model� mounted on thefuel line very close to the fuel injector. Both transducers are con-nected with the high-speed data acquisition system to obtain cyl-inder pressure and fuel-line pressure histories. The output signalsgenerated by the transducers are conditioned by the appropriatecharge amplifiers. An AVL �Model 364� crankshaft position en-coder is used to give signals at TDC. Engine in-cylinder pressureand crank-angle signals are sampled for 100 consecutive cycles atthe increments of 0.1 crank-angle intervals.

Experimental Procedure. Animal fats of the same kind �i.e.,duck fat� are collected from several fat industries. The fats usedfor making emulsions are obtained by centrifuging, heating, andseparating the raw waste fat. Before conducting all the experi-ments, preliminary analysis is performed on the animal fat to ob-tain important properties, such as viscosity, density, lower heatingvalue, etc., to find its suitability as fuel for diesel engines. Fattyacid compositions are found from the literature for animal fats�21,22�. The obtained properties of animal fat are compared todiesel and vegetable oil in Table 2. �Further details on animal fatsproperties and their measurement can be found in �19��. Methanolanimal fat emulsions are then prepared in the laboratory by adding2% of surfactant �Span 83 also called as sorbitan sesquiolate� byvolume to animal fat and thereafter adding a water/methanol mix-ture to the animal fat. Span 83 is chosen as the surfactant for allformulations because of the better stability of emulsions. Some ofthe properties can be seen in Table 3. The same procedure isfollowed for ethanol animal fat emulsions also using differentproportions of fat, surfactant, water, and ethanol. A number offormulations are made by varying water, surfactant, alcohol, andfat fractions to obtain the optimum formulation �19,23�. It wasfound that the methanol and ethanol emulsions were stable up to15 days without any phase separation.

Experiments are then carried out on the engine using diesel and

Table 2 Properties of diesel, animal fat, and vegetable oil

Properties Diesel Animal fat Vegetable oil

Density �kg/m3� 840 920 904Lower heating value �kJ/kg� 42,490 39,770 37,000

Viscosity ��10−6 m2/s� at 30°C 4.59 45 40Carbon �% by mass� 84–87 73 77.6

Hydrogen �% by mass� 13–16 12.3 11.6Oxygen �% by mass� 00 12.5 10.8Sulphur �% by mass� 0.29 0.0 0.0

Fatty acid composition �21,22�Oleic acid �% by mass� 42.1 64.1

Palmitic acid �% by mass� 22.7 3.5Linoleic acid �% by mass� 17.1 22.3

Palmitoleic acid �% by mass� 8.3 0.1Stearic acid �% by mass� 5.4 0.9

neat fat as fuels. During the entire investigation, the injection

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iming is optimized and set at 20 deg before top dead centerTDC� based on minimum emission levels. The engine is ther-ally stabilized before taking all measurements. Readings of en-

ine speed, fuel flow, air flow, exhaust gas temperature, etc., areecorded for obtaining performance parameters. Exhaust gas ana-yzers are calibrated carefully before making measurements, basedn the manufacturer’s recommended procedure. Standard spanases and zero gas are used for the calibration of HC, CO, andO. Observations are made for smoke, NO, HC, and CO to ana-

yze the emission characteristics. In all cases, pressure crank angleata are recorded and processed to get combustion parameterssuch as cylinder peak pressure, ignition delay, combustion dura-ion, and heat release rate�. Furthermore, tests are repeated withreheated animal fat prior to injection at different temperatures40°C, 50°C, 60°C, and 70°C� to obtain the optimum tempera-ure for minimum emissions. In the next phase, experiments arearried out with methanol animal fat emulsions with differentractions of water, surfactant, and methanol using animal fat. Fi-ally, experiments are done with ethanol animal fat emulsionsith different fractions of water, surfactant, ethanol, and animal

at. The optimum formulations among them are found based oninimum exhaust emission levels in all cases. Detailed analysis

an be found in the previous study �18,20�. Optimum formulationsith different emulsions can be seen in Table 4. Optimum resultsf the emulsions of ethanol and methanol and fuel preheating �i.e.,0°C� are compared to their respective neat fats and diesel at twoifferent power output conditions �i.e., 60% and 100% load�.

esults and Discusssion

Combustion Parameters. Cylinder pressure crank-angle varia-ions obtained by averaging 100 cycles at peak power output withifferent methods tested are given in Figs. 2 and 3. All the testeduels follow the trend, similar to the diesel pressure diagram. Theylinder peak pressure is highest with diesel followed by animalat emulsion and the neat animal fat as seen in Fig. 2. The samerend is observed in case of fat preheating also in Fig. 3. However,nimal fat emulsion shows a small deviation in occurrence of peakressure as compared to neat fat and neat diesel. The delayed startf combustion and resulting increase in peak pressure over that foreat animal fat due to the strong premixed combustion phase �wille explained later� are clearly seen in Fig. 2. It can be noted thathe occurrence of peak pressure moves further away from topead center for the emulsion in comparison to neat animal fat andiesel fuels. This indicates that the ignition delay �which will bexplained later� is longer with the emulsions as compared to neat

Table 3 Properties of surfactant—Span 83

Chemical name Sorbitan sesquiolate

Molecular formula C66H108O13HLB number 3.7

Molecular weight 1110atty acid composition Oleic acid 70%, balance primarily palmitic acid,

strearic acid and linoleic acid.Vapor pressure 0.81 psi at 20°C

Density 0.989 g/ml at 25°C

Table 4 Formulation of best emulsions

Best emulsion

Waterfraction

�%�

Animal fatfraction

�%�

Alcoholfraction

�%�

SurfactantFraction

�%�

ethanol animal fatbest emulsion

9.8 78.4 9.8 2

Ethanol animal fatbest emulsion

10 50 36 4

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fat.A comparison of cylinder peak pressure and maximum rate of

pressure rise at peak and part �i.e., 100% and 60% load� poweroutputs with different methods are shown in Figs. 4 and 5. Neatanimal fats result in lower peak pressure and rate of pressure riseas compared to neat diesel fuel at normal temperature. In a com-

Fig. 2 Cylinder pressure crank-angle diagram with methanolanimal fat emulsion at maximum power output

Fig. 3 Cylinder pressure crank-angle diagram with preheatedfat at maximum power output

Fig. 4 Variation of cylinder peak pressure with different

methods

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ression ignition engine, the peak pressure depends on the com-ustion rate in the initial stages, which, in turn, is influenced byhe fuel taking part in the uncontrolled combustion. The uncon-rolled or the premixed combustion phase is governed by the delayeriod, the spray envelope, and the air-fuel mixture preparationuring the delay period. Thus, the higher viscosity and poor vola-ility of the neat animal fat at normal temperature result in lowereak pressure and maximum rate of pressure rise as compared toeat diesel. However, there is an improvement in peak pressurend maximum rate of pressure rise with the preheated animal fatnd the emulsions of animal fat with methanol and ethanol. Theaximum cylinder pressures at peak power output are found as

5 bar, 82 bar, 93 bar, 88 bar, and 87 bar, respectively, with neatiesel, neat fat, preheated animal fat, methanol animal fat emul-ion, and ethanol animal fat emulsion. The increase in peak pres-ure with the emulsions is due to the enhanced combustion rate asresult of rapid combustion of emulsions at the premixed com-

ustion period. The dispersed water droplets in the evaporatingpray have much lower boiling temperatures than the surroundinguel. Under certain conditions they become superheated and, sub-equently, expand in a very rapid vaporization event called mi-roexplosion. Presence of water and methanol fractions also low-rs the temperature of the combustion chamber and leads to moreuel being accumulated during the ignition delay period. A strongremixed combustion rate due to a long ignition delay results inigher peak pressure and rate of pressure rise as compared to neatat. With the preheated animal fat, vaporization of the fat becomesetter because of the improved viscosity and combustion becomesaster due to rapid burning of the injected fuel.

The variation of ignition delay with all the methods is shown inig. 6. The ignition delay period of all the fuels tested is calcu-

ated based on the dynamic injection timing. The duration be-ween the point of the start of injection to the point of ignition isaken as the ignition delay. The point of fuel injection is found bysing a piezoelectric pressure sensor that gives the online fuelnjection pressure. The start of combustion is determined from theate of pressure rise variation. This shows a sudden rise in thelope at the point of ignition due to the high premixed heat releaseate. Ignition delay shown in Fig. 6 is longer with neat animal fats compared to neat diesel due to the low cetane number. Witheat animal fat, due to poor atomization and vaporization, physi-al delay becomes longer as compared to neat diesel. The ignitionelay is found as 6 deg CA �crank angle� with neat diesel anddeg CA with neat animal fat at normal temperature. Ignition

elay further increases with both animal fat emulsions as com-ared to neat animal fat and neat diesel fuel. It is found as 9 degA with methanol animal fat emulsion and 10 deg CA with eth-nol animal fat emulsion at peak power output. The increase in

ig. 5 Variation of maximum rate of pressure rise with differ-nt methods

gnition delay with animal fat emulsions is due to the high latent

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heat of vaporization of water and methanol/ethanol in the emul-sions. Vaporization of water and alcohols reduces the temperatureof intake air and fuel. In addition, the presence of water andmethanol/ethanol results in reduction of the overall cetane numberof the emulsions. Hence, the delay is longer with the emulsions ascompared to neat fat. However, ignition delay reduces with fatpreheating. It is found as 7 deg CA at peak power output.

Figure 7 shows the variation of combustion duration. The com-bustion duration is calculated by obtaining the cumulative heatrelease rate. The end of combustion is taken as the point where95% of the heat release had occurred. Longer combustion durationis observed with neat fats than diesel at both power outputs. Thisis due to the injection of larger quantities of animal fat than dieselfor the same load condition �because the heating value of animalfat is lower than diesel fuel�. Since the diffusion burning �will beexplained later� is more pronounced with the animal fat, late burn-ing occurs in the expansion stroke and results in longer combus-tion duration with the neat fats. However, the combustion durationis reduced with both the emulsions of animal fat as compared toneat fat. Because of the long ignition delay, more fuel is physi-cally prepared �evaporation, mixing, etc.� with the emulsions forchemical reaction, and rapid burning occurs in the premixed stageitself. Hence, the heat release during the diffusion burning periodis lowered and results in reduced combustion duration. The mi-croexplosion further accelerates diffusion combustion and de-creases total combustion duration. Preheating also indicates reduc-tion in combustion duration as compared to neat fat at both poweroutputs.

Heat release patterns with neat fat operation and other testedmethods are compared in Figs. 8–11. The heat release rate is

Fig. 6 Variation of ignition delay with different methods

Fig. 7 Variation of combustion duration with different

methods

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alculated by performing the first law analysis of the average pres-ure versus crank-angle variations. As in thermodynamics, a sim-lified calculation process that determines the energy effectivelyelivered to the gas is taken in to account. Fuel vapor and prod-cts are treated as the mixture of ideal gases. The surface heatransfer losses are ignored. The gas mass is taken for determina-ion of the gas temperature and the heat release equation is writtens

dQ = � �

� − 1�PdV + � 1

� − 1�VdP �1�

here � is the ratio of specific heats, P is the cylinder pressurend V is the instantaneous volume.

From the Figs. 8–10, it is seen that the premixed burning isore pronounced with diesel as expected. Neat animal fat shows

ower heat release rate at the initial stage as compared to neatiesel. The high viscosity and density of neat animal fat result inoor atomization and vaporization and lead to reduction in airntrainment and fuel-air mixing rates. Hence, more burning oc-urs in the diffusion phase. With fat preheating, there is an im-rovement in heat release rate as seen in Fig. 10. By raising theemperature, the premixed phase of the heat release curve be-omes high due to the improved atomization and vaporization ofhe animal fat. The low viscosity of the preheated fat leads to form

ig. 8 Variation of heat release rate with methanol emulsion ateak power output

ig. 9 Variation of heat release rate with ethanol emulsion at

eak power output p

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more flammable fuel-air mixture during the delay period and en-hances the combustion process. This results in improved heat re-lease rates.

Animal fat emulsions with methanol and ethanol also showimprovement in heat release rates �both in premixed and diffusioncombustion� as compared to neat fat as shown in Figs. 8 and 9.There is a delay in the start of combustion and an increase in theheat release rate at the premixed burn period with the emulsion ascompared to neat animal fat. The diffusion combustion phase isless with the emulsions as compared to neat fat. When the ignitiondelay is increased, more fuel is accumulated in the combustionchamber and physically prepared for chemical reaction. Once theaccumulated fuel attains its self-ignition temperature, it burns in-stantaneously and raises the peak pressure and the premixed com-bustion rate. In addition, microexplosion of droplets enhances thecombustion rate. The good atomization and vaporization of emul-sions promote rapid mixing with the surrounding air �24�. Theoxygen available in the fuel further improves the overall rate ofcombustion. All these factors contribute to the improved heat re-lease rates with the emulsions as compared to neat fat. However,at part load the improvement in heat release rate is not muchsignificant �Fig. 11�.

Performance Parameters. Neat animal fat as indicated in Fig.12 results in increased specific energy consumption �SEC� as

ig. 10 Variation of heat release rate with preheated animal fatt peak power output

ig. 11 Variation of heat release rate with ethanol emulsion at

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ompared to neat diesel at 100% and 60% of the maximum engineower output. High viscosity and poor volatility of the fats resultn poor atomization and mixture formation and in higher specificnergy consumption than neat diesel. However, there is an im-rovement in specific energy consumption with all the methodsdopted. The reduction in SEC with fat preheating is due to theigh combustion rate. The preheated fat has lower viscosity,hich results in better atomization of the fuel as compared to neat

at at normal temperature. Emulsions of animal fat result in re-uced SEC due to the better fuel atomization. Microexplosion ofhe emulsions leads to secondary atomization �25� and reduces the

ean diameter of the injected fuel. In addition, the presence ofurfactant in the emulsions contributes to better atomization of theuel. Ethanol emulsion reaches the minimum SEC as compared toethanol due to its superior physical characteristics, such as low

iscosity and better miscibility with animal fat than methanol, andesults in overall reduction in viscosity of emulsions �23�. How-ver, SEC is higher with all the methods as compared to neatiesel. The difference becomes more at 60% load. At part loads,ue to heat loss to the walls, SEC becomes high despite the facthat flame temperature is not as high in the case of emulsion �cf.Ox analysis�. This observation is not dramatic because the aim is

o obtain a fuel for CI engines from a waste that is nearly free.The exhaust gas temperature as shown in Fig. 13 is very high

ith neat animal fat as compared to neat diesel due to slow com-ustion. With the emulsions there is a reduction in exhaust gasemperature. Ethanol emulsion shows the highest reduction in ex-aust gas temperature �i.e., 480 °C at the optimum emulsion,here as it is 580 °C with its neat animal fat. This reduction in

xhaust gas temperature is due to the reduction in charge tempera-

ig. 12 Variation of specific energy consumption with differ-nt methods

ig. 13 Variation of exhaust gas temperature with different

ethods

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ture as a result of vaporization of ethanol. A similar trend is seenin the case of methanol emulsion also. The high latent heat ofvaporization of alcohols and water helps in reducing the cylindertemperature with both the emulsions. However, with fat preheat-ing due to the high fuel inlet temperature, exhaust gas temperaturebecomes high mainly at high power output.

Emission Parameters. The smoke level is indicated in Fig. 14.It is interesting to see that neat animal fat result in lower smokelevels than neat diesel mainly at peak power output. It is about3.7 m−1 with neat animal fat and 6.3 m−1 with neat diesel at themaximum power output. This reduction in smoke emission withneat fats is due to the presence of in-built oxygen with the fats.The high oxygen content in the animal fats helps in completeoxidation of the fuel and reduces soot concentration in the exhaustgas. Smoke further reduces with fat preheating and emulsions ofmethanol and ethanol. The values are found as 1.7 m−1 with pre-heated animal fat, 0.89 m−1 with methanol emulsion, and0.28 m−1 with ethanol emulsions. Improved vaporization of thepreheated fat results in lower smoke values than fat at normaltemperature. Emulsions of animal fat promote this reduction dueto the presence of alcohol content. Microexplosion plays a majorrole in drastic reduction in smoke emissions �11,13�. It leads tosecondary atomization and permits one to obtain a better fuel-airmixture formation. Hence, smoke density reaches to very low val-ues with animal fat emulsions. The greatest reduction in smokeemission is seen with ethanol animal fat emulsion than withmethanol and fat preheating. The combustion of ethanol animalfat emulsion produces the minimum smoke emission because ofhigher ethanol content as compared to methanol. However, at partload, the smoke levels are very low with all the fuels and thedifferences are not distinguishable.

Shown in Fig. 15 is the variation of hydrocarbon emission withdifferent methods at 100% and 60% load conditions. The hydro-carbon emission at normal temperature is higher with neat animalfat as compared to neat diesel at both power outputs. Unburnedhydrocarbons are the results of incomplete combustion. High vis-cosity and poor volatility of animal fat result in poor mixing of thefuel with air and lead to more hydrocarbon emissions at normaltemperature. However with the preheated fat, there is a reductionin hydrocarbon emissions. It can be noted that the HC emissionwith animal fat approaches diesel value at a high fuel inlet tem-perature of 70 °C. Because of the improved vaporization and fuel-air mixing rates, combustion becomes complete and results in lowhydrocarbon emissions with the preheated animal fat. Emulsionsof animal fat also indicate lower levels of hydrocarbon emissionsas compared to their parent fuels mainly at 100% power output.This is due to the reduction in the overall amount of carbon ad-mitted into the engine. Secondary atomization provided by themicroexplosion of water droplets increases the surface area ofcontact of fuel droplets with air, improves the fuel-air mixture

Fig. 14 Variation of smoke density with different methods

formation, and leads to lower hydrocarbon emissions as compared

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o neat fat. However, ethanol emulsion shows sight increase in HChan neat animal fat at light load �i.e., 60% of maximum powerutput�. This finds explanation that the larger amount ethanolresent in the emulsion causes lower combustion temperaturesnd leads to partial combustion of the fuel at part loads.

Neat animal fat leads to higher CO emissions than diesel atormal temperature as shown in Fig. 16. As mentioned earlier,uel richness due to low volumetric efficiency contributes to therend of higher CO emissions with neat fats. Rich pockets formedn the cylinder cause more CO emissions with animal fat at nor-

al temperature. It may be noted that the lower heating value ofnimal fat leads to injection of higher quantities of fuel as com-ared to diesel for the same load conditions. However, fuel pre-eating leads to complete combustion of the fuel and reduces COmission. The level becomes lower than diesel with preheatednimal fat at 70 °C at both power outputs. Emulsions of animalat with methanol and ethanol show significant reduction in COmissions as compared to their respective fats. Introduction ofater into the fuel replaces a portion of flammable fuel that con-

ains hydrocarbons. The increase in vaporized fuel jet momentumives great air entrainment to the fuel jet and accelerates the dif-usive burning rate. In addition, the presence of water and metha-ol in the emulsion increases oxygen concentration in the fuel,hich helps in complete oxidation of the fuel. All the factorsarticipate in significant reduction in CO emissions. It is interest-ng to note that the levels with the emulsions are even lower thaneat diesel operation. The trend of CO emissions is also similaror all the methods in part load.

The variation of NO emission with power output is shown inig. 17. NO formation in diesel engine is due to the high combus-

ig. 15 Variation of hydrocarbon emissions with differentethods

ig. 16 Variation of carbon monoxide emissions with different

ethods

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tion temperature and the availability of oxygen. It forms mainly inthe high-temperature regions of the product gases. It is seen thatthe neat animal fat emits lower NO levels as compared to standarddiesel at both power outputs. The reduction in NO emission withanimal fat is mainly associated with the reduced premixed burningrate following the delay period. The lower air entrainment andfuel-air mixing rates with the animal fat result in low peak tem-perature and the resulting NO levels. Fuel preheating shows arising trend in NO emissions due to rapid burning as a result ofincreased fuel inlet temperatures. This is the drawback with fuelpreheating. However, the values are still lower than diesel. NOfurther reduces with the emulsions with methanol and ethanol.This reduction in NO emission is due to the drop in charge tem-perature as a result of vaporization of alcohol and water. Thewater brought in by the emulsified fuel changes the relative quan-tities of fuel, oxygen, and inert during the rich premixed-burnstage of animal fat combustion. Water lowers the peak combustiontemperatures due to its high latent heat of vaporization. This re-duces formation of nitrogen oxides. It must be noted that the NOlevel is very low, even with the increased premixed combustionphase in case of emulsions. In general, with animal fat emulsionsthe NO emissions decrease considerably at both power outputswithout compromising engine performance.

ConclusionThe following conclusions are made based on the above results:

• Neat animal fat results in lower cylinder peak pressure,maximum rate of pressure rise, longer ignition delay, andcombustion duration as compared to neat diesel at 60% and100% power outputs. Increased specific energy consump-tion, exhaust gas temperature, hydrocarbon, and carbonmonoxide emissions are observed with neat fat as comparedto neat diesel at both power output conditions. Lower smokelevels are found with neat fat at both power outputs due thein-built oxygen present in it. NO emissions are also found aslower with neat fat as compared to neat diesel due to slowcombustion.

• Emulsions of animal fat with methanol/ethanol and fat pre-heating show higher peak pressure and maximum rate ofpressure rise as compared to neat fat at both power outputs.But the values are still lower than diesel. Longer ignitiondelay and combustion duration are observed with neat ani-mal fat as compared to neat diesel. Emulsions of animal fatfurther prolong the ignition delay. However, combustion du-ration is shorter with the emulsions. Preheating showsshorter ignition delay and combustion duration as comparedto neat fat. The heat release rate shows improvement withall the methods adopted as compared to neat animal fat.

Fig. 17 Variation of nitric oxide emission with differentmethods

• Emulsions of animal fat with alcohols show considerable

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improvement in SEC and reduction in exhaust gas tempera-ture, hydrocarbon, and carbon monoxide emissions as com-pared to their parent fuels mainly due to microexplosion.Preheating also shows lower SEC, hydrocarbon, and carbonmonoxide emissions. However, the exhaust temperature ishigher with preheating. Animal fat emulsions �both metha-nol and ethanol� and fat preheating show considerable re-duction in smoke density as compared to their neat fats.However, there is no significant difference in smoke emis-sions with all the fuels at low power output. Emulsions fur-ther reduce NO emissions due to the high latent heat ofvaporization of water and alcohols.

From the above results it can be concluded that preheated ani-al fat and emulsions of animal fat with methanol/ethanol can be

sed as fuel in a diesel engine with improved performance andeduced emissions as compared to neat fat. Emulsification of ani-al fat with methanol and/or ethanol can be preferred as betterethods to use animal fat efficiently in a diesel engine with a

rastic reduction in all emissions as compared to fat preheating.reheating can also lead to a slight improvement in engine per-ormance and emissions without modifying the fuel. However,easures must be taken to control NO emissions with fat preheat-

ng. Table 5 presents a summary of the results obtained with dif-erent methods using animal fat as base fuel and their effectselative to neat diesel. Stability of emulsions and the longtermffects of emulsions on engine parts need further study.

omenclatureBTDC � before top dead center

CA � crank angleCO � carbon monoxide

DDAS � digital data acquisition systemHC � Hydrocarbon

P � cylinder pressureV � cylinder volumeQ � heat release� � ratio of specific heats

eferences

able 5 Summary of the results obtained with different fuelsested and their effects relative to base diesel at peak powerutput

Methods Neat fuel operation Emulsified fuel

Fuels Neat fat Preheated fat Methanol EthanolSEC ↑ ↑ ↑ ↑EGT ↑ ↑ ↑ ↑

Smoke ↓ ↓ ↓ ↓NO ↓ ↑ ↓ ↓CO ↑ ↓ ↓ ↓HC ↑ ↑ ↓ ↓PP ↓ ↓ ↓ ↓

MPPR ↓ ↓ ↓ ↓ID ↑ ↑ ↑ ↑CD ↑ ↑ ↑ ↑

HRR ↓ ↑ ↑ ↑

�1� Barsic, N. J., and Humke, A. L., 1981, “Performance and Emission Character-

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istics of a Naturally Aspirated Diesel Engine With Vegetable Oils,” Society ofAutomotive Engineers Paper No. 810262.

�2� Vellguth, G., 1983, “Performance of Vegetable Oils and Their Monoesters asFuel for Diesel Engines,” Society of Automotive Engineers Paper No. 831358.

�3� Senthil Kumar, M., Ramesh, A., and Nagalingam, B., 2001, “Complete Veg-etable Oil Fuelled Compression Ignition Engine,” Society of Automotive En-gineers Paper No. 2001-28-0067.

�4� Senthil Kumar, M., Kerihuel, A., Bellettre, J., and Tazerout, M., 2005, “Inves-tigations on the Use of Preheated Animal Fat as Fuel in a Diesel Engine,”Renewable Energy, 30�9�, pp. 1443–1456.

�5� Senthil Kumar, M., Ramesh, A., and Nagalingam, B., 2000, “PerformanceStudies on a CI Engine Using Methyl Ester of Jatropha oil as Fuel,” Proceed-ings of XVI National Conference on I. C. Engines and Combustion, Calcutta,pp. 89–94.

�6� Karim, G. A., 1987, “The Dual Fuel Engine,” Automotive Engine Alternatives,R. L. Evens, Bleham Press.

�7� Senthil Kumar, M., Ramesh, A., and Nagalingam, B., 2001, “ExperimentalInvestigations on a Jatropha Oil Methanol Dual Fuel Engine,” New Develop-ments in Alternative Fuels for IC Engines �SP-1608�, Society of AutomotiveEngineers, Warrendale, PA, SAE Paper No. 2001-01-0153.

�8� Senthil Kumar, M., Ramesh, A., and Nagalingam, B., 2003, “An ExperimentalComparison of Methods to Use Methanol and Jatropha Oil in a CompressionIgnition Engine,” Biomass Bioenergy, 25�3�, pp. 309–318.

�9� Nwafor, O. M. I., 2003, “The Effect of Elevated Fuel Inlet Temperature onPerformance of Diesel Engine Running on the Neat Vegetable Oil at ConstantSpeed Conditions,” Renewable Energy, 28, pp. 171–181.

�10� Bari, S., Lim, T. H., and Yu, C. W., 2002, “Effect of Preheating of Crude PalmOil �CPO� on Injection System, Performance and Emission of a Diesel En-gine,” Renewable Energy, 27, pp. 339–351.

�11� Marwan, A. A. N., Hobina, R., and Wagstaff, S. A., 2001, “The Use of Emul-sion, Water Induction and Egr for Controlling Diesel Engine Emissions,” So-ciety of Automotive Engineers Paper No. 2001-01-1941.

�12� Yoshimoto, Y., Onodera, M., and Tamaki, H., 1999, “Reduction of NOx,Smoke and BSFC in a Diesel Engine Fuelled by Biodiesel Emulsion WithUsed Frying Oil,” Society of Automotive Engineers Paper No. 999-01-3598.

�13� Hsu, B. D., 1986, “Combustion of Water-in-Diesel Emulsion in an Experimen-tal Medium Speed Diesel Engine,” Society of Automotive Engineers Paper No.860300.

�14� Lin, C. Y., and Wang, K. H., 2004, “Diesel Engine Performance and EmissionCharacteristics Using Three-Phase Emulsions as Fuel,” Fuel, 83, pp. 537–545.

�15� Baker, Q. A., 1981, “Use of Alcohol-in-Diesel Fuel Emulsions and Solutionsin a Medium Speed Diesel Engine,” Society of Automotive Engineers PaperNo. 810254.

�16� Haepp, H. J., and Truong, H. S., 1983, “The Effect of Methanol/Diesel FuelEmulsions on the Mixture Formation in Direct Injection Diesel Engines. ATheory on Spontaneous Evaporation,” Society of Automotive Engineers PaperNo. 830376.

�17� Khan, N., and Gollahalli, S. R., 1981, “Performance and Emission Character-istics of a Diesel Engine Burning Unstabilized Emulsions of Diesel Fuel WithWater Methanol and Ethanol,” Society of Automotive Engineers Paper No.811210.

�18� Kerihuel, A., Senthil Kumar, M., Bellettre, J., and Tazerout, M., 2005, “Ex-perimental Investigations on a Compression Ignition Engine Using Animal FatEmulsions as Fuel With Water and Methanol,” Society of Automotive Engi-neers Paper No. 2005-01-1729.

�19� Kerihuel, A., Senthil Kumar, M., Bellettre, J., and Tazerout, M., 2005, “Use ofAnimal Fats as CI Engine Fuel by Making Stable Emulsions With Water andMethanol,” Fuel, 84, pp. 1713–1716.

�20� Senthil Kumar, M., Kerihuel, A., Bellettre, J., and Tazerout, M., 2005, “Effectof Water/Methanol Fractions on the Performance of a Compression IgnitionEngine,” Asph. Paving Technol. �to appear�.

�21� Goodrum, J. W., Geller, D. P., and Adams, T. T., 2003, “Rheological Charac-terization of Animal Fats and Their Mixtures With # 2 Fuel Oil,” BiomassBioenergy, 24, pp. 249–256.

�22� Demirba, A., 2002, “Biodiesel From Vegetable Oils via Transesterification inSupercritical Methanol,” Energy Convers. Manage., 43, pp. 2349–2356.

�23� Kerihuel, A., Senthil Kumar, M., Bellettre, J., and Tazerout, M., 2005, “Etha-nol Animal Fat Emulsions as a Diesel Engine Fuel—Formulations and Influ-ential Parameters �P. 1�,” Fuel �submitted�.

�24� Musculus, M. P. B., Dec, J. E., Tree, D. R., Daly, D., Langer, D., Ryan, T. W.,and Matheaus, A. C., 2002, “Effects of Water-Fuel Emulsions on Spray andCombustion Processes in a Heavy-Duty DI Diesel Engine,” Society of Auto-motive Engineers Paper No. 02012892.

�25� Adiga, K. C., and Shah, D. O., 1990, “On the Vaporization Behavior of Water-

in-Oil Microemulsions,” Combust. Flame, 80, pp. 412–414.

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