Investigations on a CI Engine Using Animal Fat and Its Emulsions with Water and Methanol as Fuel

Transcription

1 Paper Number 5P-95 Investigations on a CI Engine Using Animal Fat and Its Emulsions with Water and Methanol as Fuel A. Kerihuel, M. Senthil Kumar, J. Bellettre and M. Tazerout Département Systèmes Energétiques et Environnement, Ecole des Mines de Nantes Copyright 24 SAE International ABSTRACT Performance of a compression ignition engine fuelled with animal fat and its emulsions as fuel is evaluated. A single cylinder air-cooled, direct injection diesel engine developing a power output of 2.8 kw at 15 rev/min is used. Base data is generated with standard diesel fuel. Subsequently, animal fat is modified into its emulsions using water and methanol. Comparison is undertaken with diesel, neat animal fat and its emulsion as fuels. Results show improved performance with animal fat emulsions as compared to neat fat. Peak pressure and rate of pressure rise are increased with animal fat emulsions due to improved combustion rate. Heat release pattern shows higher premixed combustion rate with the emulsions. Higher ignition delay and lower combustion duration are found with animal fat emulsions than neat fat. Drastic reduction in black carbon smoke and NO are found with the emulsions as compared to neat animal fat and neat diesel. The reduction in smoke level is from 3.6 m -1 with neat fat to.9 m -1 with animal fat emulsions at peak power output. It is 6.3 m -1 with diesel. NO value is found as 18.7 g/kwh with diesel and 18.3 g/kwh with neat fat whereas it is 2.6 g/kwh with the emulsions. Hydrocarbon and carbon monoxide emissions are found as high with neat animal fat as compared to diesel. These emissions are also reduced considerably with the emulsions of animal fat. On the whole it is concluded that animal fat emulsions with water and methanol can be used as fuel in a compression ignition engine with significant reduction in exhaust emissions and improved performance as compared to neat fat. INTRODUCTION In the contest of fast depletion of petroleum reserves associated with rising vehicle population and stringent emission standards, the development of alternative energy sources has become very important. Animal fats and vegetable oils are found as promising alternative fuels for diesel engines [1-5]. They are renewable and biologically degradable. As a compression ignition engine fuel, animal fats and vegetable oils have cetane number very close to diesel. The flash point is higher as compared to diesel. Due to their high flash point, animal fat and vegetable oil have certain advantages like great safety during storage, handling and transport. However, this may create problems during engine starting. Animal fats and vegetable oils typically have large molecules, with carbon, hydrogen and oxygen being present (Table 1). They have a higher molecular mass and viscosity as compared to diesel. Contrary to fossil fuels, animal fats and vegetable oils are free from sulfur and heavy metals. The main problems associated with the use of animal fats and vegetable oils are their high viscosity and density. Methods like transesterification, blending with diesel/alcohol, dual fuel operation, use of additives etc. were tried in the past to use vegetable oils efficiently in diesel engines [6-8]. Transesterification can result in significant reduction in viscosity and enhancement in physical properties. But it is a time consuming process. It also results in certain by products such as fatty acids and glycerol, which cannot be used as fuels in engines though they have other uses. Blending of vegetable oils with alcohol results in significant improvement in physical properties [9]. However, the maximum quantity of alcohol that can be blended is limited by the presence of water in alcohol and very high quantities lead to separation. Engine

2 modifications like utilization of higher fuel injection pressure, optimized combustion chamber design and multiple injection systems have been adopted for improving alternative fuels performance [1]. However, the long life of the diesel engine makes it a slow process. Water addition to diesel and biodiesel is found as an attractive method of reducing emissions in diesel engines with improved performance. Water can be introduced into the engine combustion chamber in 3 different ways. 1. Spraying water into the intake air by fumigation, 2. Direct water injection into the engine using a separate injector and 3. Water oil emulsion. Fumigation is the method of injecting the liquid water into the upstream air intake manifold. Fumigation has the advantage of reduced NOx and particulate emissions in diesel engines [11]. But it suffers from the drawback of water in the combustion chamber areas where it is less effective in reducing emissions. Presence of liquid water in the combustion chamber results in oil contamination and increased engine wear. Direct water injection has the advantage over fumigation of having the liquid water close to flame and away from the wall. The presence of water in the fuel spray also increases the liquid and vapor penetration. However, the modification in injection system for water injection results in complex design of the engine and very expensive to implement in normal engines. In addition to that further study is needed to find the best fuel/water percentage for various operating conditions because too much of water results in increased soot formation. Significant reduction in emissions (simultaneous reduction in smoke and oxides of nitrogen) without an adverse effect in fuel consumption and engine design is achieved by the addition of water, emulsified with the fuel [12-14]. The added advantage is the result of "microexplosion" phenomenon (breaking of large fuel droplet into smaller droplets when heated). Adding small quantities of methanol with the emulsions further improves emulsions viscosity and stability. Experiments verified that emulsified fuels with alcohols could effectively reduce diesel engine pollution and improve air quality [15-17]. Eventhough a number of studies were carried out on the engine using water diesel emulsions, limited analysis have been done on the use of biofuel emulsions in diesel engines. Moreover, extensive research on animal fat and its emulsions using methanol and water on diesel engine performance does not seem to have been done anywhere in the past. In this work animal fat and its emulsions are investigated for their performance as fuel in diesel engine. Animal fat is emulsified in the laboratory using different ratios of water and methanol in equal proportions and tested as fuel. Experiments are conducted on a single cylinder diesel engine at the rated speed of 15 rev/min with variable load conditions. Performance parameters like specific energy consumption, volumetric efficiency and emission parameters like smoke, unburned hydrocarbon, carbon monoxide and nitric oxide emissions are evaluated. Peak pressure, rate of pressure rise, ignition delay, combustion duration and heat release rate are obtained from pressure crank angle histories. Optimum emulsion is found based on the emission characteristics. In this paper results of optimum emulsion are compared with diesel and neat animal fat. Table 1. Properties of Diesel, Animal Fat and Vegetable Oil [18-2] Properties Diesel Animal Fat Vegetable Oil Density (kg/m 3 ) LHV (kj/kg) Viscosity (cst) Cetane Number Flash Point ( C) Carbon (% by mass) Hydrogen (% by mass) Oxygen (% by mass) Sulphur (% by mass).29 EXPERIMENTAL SETUP AND EXPERIMENTAL PROCEDURE A Single cylinder 4-Stroke air-cooled diesel engine developing a power output of 2.8 kw is used. Engine details are given in Table 2. Make General Details Bore & Stroke Table 2. Engine Details LISTER PETTER TS1 Four Stroke, CI, Air Cooled, NA, Single Cylinder Engine 95.3 mm 88.9 mm Compression Ratio 18:1 Rated Power Output Injector Opening Pressure Displacement Volume Connecting Rod Length Fuel Injection Timing 2.8 kw at 15 rev/min 25 bar 633 cc mm 2 BTDC The Schematic of the experimental set up is shown in Fig.1. An electrical dynamometer is used for loading the engine. The load is adjusted mechanically. An orifice meter connected to a large tank is attached to the

3 engine to make air flow measurements. An optical shaft position encoder is used to give signals at TDC. The fuel flow rate is measured on the volumetric basis using a burette. Chromel alumel thermocouples in conjunction with a slow speed digital data acquisition system is used for measuring the exhaust gas temperature. An another high-speed digital data acquisition system (AVL Indiwin) in conjunction with two piezoelectric transducers is used for the measurement of cylinder pressure and fuel line pressure histories. the entire investigation the injection timing is optimized and set at 2 o before TDC. This optimum injection timing is set for diesel fuel based on the maximum efficiency and minimum emissions. The engine is thermally stabilized before taking all measurements. Readings for engine speed, fuel flow, air flow, exhaust gas temperature etc. are recorded for obtaining performance parameters. Exhaust gas analyzers are calibrated before making measurements. Variation of ambient temperature and humidity are negligible because all the tests occur during a short period of time. Cy linderpressure Transducer Injection Pressure Transducer Diesel Diesel Tank Tank Diesel Tank Fat Tank ExhaustPipe Air Tank Exhaust Gas Analy ser HC CO O2 NOx Charge Amplif ier F.I.P A.D.C Data Acqusition Sy stems A.D.C TDC Position Encoder Single Cy linder Engine DieselFilter Control Valv e Animal Fat Filter Electrical Dynamometer Speed Sensor Fig.1 Experimental Setup An infrared exhaust analyzer (COSMA 5) is used for measuring HC/CO emissions although its not the standard method to measure HC emission. However, estimated HC emission gives accurate trend. NO in the exhaust are measured by using a Beckman chemiluminascent analyzer (model 4). Since the exhaust gas from diesel engines mainly has NO, observations are made only for NO. Black carbon smoke levels are obtained by using a standard Hartridge smoke meter which works on light absorption technique (passing a light beam through the exhaust sample and the fraction of light is absorbed by the exhaust gas). Standard SAE J1667 procedure is followed for the measurement of smoke [21]. Light extinction coefficient K is used as the measure of smoke density per meter. It uses the following relationship, K = (-1/L) *ln (1-N/1), Where, K = Smoke density (m -1 ) L = Optical path length of the smoke measurement (m) N = Smoke Opacity (%). Experiments are initially carried out on the engine using diesel as fuel in order to provide baseline data. During Observations are made for smoke, NO, HC and CO to analyze the emission characteristics. In all cases pressure crank angle data are recorded and processed to get combustion parameters. Subsequently experiments are repeated with animal fat and its emulsions with water and methanol at different fractions. Finally, Performance with the optimum emulsion is compared with neat fat and neat diesel. ESTIMATION OF UNCERTAINTY All experimental results regardless of the care taken to obtain them posses errors. These errors are of systemic and random nature. Systemic errors can be corrected by calibration. The uncertainty in the results due to random errors are obtained statistically. Uncertainties in the measured parameters from the experiments are estimated with confidence limits of ± 2σ (95.5% of measured data lie within the limits of ± 2σ around the mean). The percentage uncertainty in the measured parameter is estimated using the equation (1): x i (%) = 2σx x i i X 1 (1)

4 x Where, i - Mean of the measured quantity σ i - Standard deviation In order to have reasonable limits of uncertainty for the computed values obtained from the measured parameters, the uncertainties are evaluated based on Kline and Mc.Clintock method [22]. The uncertainties for some of the measured and computed quantities from the experiments are estimated as 7.9 ±.8% for air flow rate (g/sec),.36 ± 2% for fuel flow rate (g/sec), 1755 ± 1.2% for power (watts),.22 ± 2.8% for hydrocarbon (g/kwh),.94 ±.7% for carbon monoxide (g/kwh), 6.55 ±.6% for nitric oxide (g/kwh) and 3.5 ± 4% for smoke density K (m -1 ). EMULSION PREPARATION PROCESS Emulsion preparation involves mixing water, methanol and fat in suitable proportions with the help of a surfactant called emulsifier. Specified amounts of animal fat, water, methanol and surfactant are taken in a container. The mixture is stirred vigorously since the fat and water are immisible until a homogeneous phase is obtained. The emulsions are prepared by using a stirrer (Janker and Kunkel model RW 2 DZN) which rotates at maximum 2 rpm. Since the fat is in solid form at low temperatures (less than 3 C) a heater is used to give enough heat to maintain its liquid state. The heat energy is also used to enhance mixing rate and the emulsion formation. The animal fat container is kept in water bath and the emulsification process is carried out at a constant temperature of 5 C during mixing. This method has resulted in very stable emulsions. RESULTS AND DISCUSSION COMBUSTION PARAMETERS: In a compression ignition engine cylinder pressure yields to the information on the combustion efficiency. The cylinder pressure depends on the burned fuel fraction during the initial stage of combustion. Cylinder pressure characterizes the fuel ability to well mix with air and burn in good conditions. Indeed, the combustion of an appropriate fuel for CI engines results in high peak pressure and maximum rate of pressure rise which correspond to a great amount of fuel burned in premixed combustion. The cylinder pressure crank angle histories is obtained by averaging 1 cycles at different power outputs. Peak pressure and maximum rate of pressure rise are obtained at different loads from these measurements. Figure 2 represents the results of cylinder pressure obtained at peak power output with different tested fuels. The pressure reaches up to the maximum value of 95 bars, 89 bars and 86 bars respectively with diesel, animal fat emulsion and neat animal fat. It is seen from the Figs. 3 and 4 that the peak pressure and maximum rate of pressure rise with neat animal fat are lower as compared to neat diesel fuel. These results are mainly due to higher viscosity of animal fat than diesel, which leads to poor atomization. Since animal fat has high viscosity less fuel is mixed well with air and hence a little quantity of fuel/air is in favorable conditions to autoignite at the initial stage. However, animal fat emulsions increase peak pressure and rate of pressure rise and improves the combustion performance. Cylinder Pressure (bar) Inj.Timing : 2 BTDC Load : 1% Crank Angle ( CA) Fig.2 Variation Cylinder Pressure Crank Angle Histories with and its Emulsion Peak Pressure (bar) MRPR (bar/deg CA) Fig.3 Variation of Cylinder Peak Pressure with and its Emulsion Inj.timing : 2 BTDC Inj.timing : 2 BTDC Fig.4 Variation of Maximum Rate of Pressure Rise with and its Emulsion

5 In case of animal fat emulsions, the phenomenon of micro-explosion enhances the fuel atomization by the result of secondary atomization. In addition to that animal fat has longer ignition delay (Fig.5) than standard diesel to ignite. The longer ignition delay with the Ignition Delay ( CA) Inj.timing : 2 BTDC Fig.5 Variation of Ignition Delay with and its Emulsion emulsion implies more fuel to be injected before the ignition and then more fuel consumed during the uncontrolled (i.e. premixed) combustion phase. As a result, animal fat emulsion leads to the rise in cylinder pressure and maximum rate of pressure rise. The combustion duration for each fuel is calculated and differences between the tested fuels are presented in Fig. 6. Neat animal fat burns for a longer period than its emulsions and diesel. In fact, as previously explained, animal fat forms bigger droplets than diesel, so the diffusive combustion period is increased due to a longer time required to burn them. With the emulsion, the presence of surface agent contributes to better atomization characteristics of the fuel on leaving the injection nozzle. Moreover, micro-explosion further enhances the fuel atomization, which increases the premixed combustion and reduces the diffusive combustion phase. Combustion Duration ( CA) Inj.timing : 2 BTDC Fig.6 Variation of Combustion Duration with and its Emulsion The heat release by the combustion of fuel allows to analyze the type of combustion process and the nature of combustion, which is predominant. As indicated in Fig. 7, the heat release varies according to the used fuel. With standard diesel, premixed combustion is the main mechanism, which yields to peak of heat release in the start of combustion. These results are in agreement with the high peaks of cylinder pressure and the high maximum rate of pressure rise obtained (Figs. 3 and 4). Heat Release Rate (kj/m3deg) Fig.7 Variation of Heat Release Rate with and its Emulsion As compared to diesel combustion, neat animal fat shows an inverse trend. In this case, the main mechanism is the diffusion flame combustion. However, animal fat emulsion shows improvement in premixed combustion rate as compared to neat fat. The diffusion flame combustion period is shorter than neat fat. PERFORMANCE PARAMETERS: Figure 8 indicates the measured exhaust gas temperatures for the three tested fuels. Neat animal fat shows higher exhaust gas temperature than neat diesel operation. Exhaust Gas Temperature ( C) Crank Angle ( CA) Ignition Delay Premixed Phase Diffusion Phase Inj.timing : 2 BTDC Neat f at 2 Inj; Timing : 2 BTDC Load : 1% Tail Region Fig.8 Variation of Exhaust Gas Temperature with and its Emulsion The reasons are the bad fuel atomization and vaporization due to high viscosity of animal fat. The

6 injected fuel finishes to burn slowly and some of them are present in the late combustion cycle. This results in higher exhaust gas temperature. However, its emulsion results in reduced exhaust gas temperature at all power outputs. The parameter used to measure the effectiveness of an engine s induction process is the volumetric efficiency. As shown by the curves in Fig. 9, volumetric efficiency decreases when power output increases with all tested fuels. This is due to the higher wall temperature, which leads to the inlet air expansion. Thus, less air is admitted into the combustion chamber and the volumetric efficiency is reduced. It is noted that the volumetric efficiency is highest with animal fat emulsion whereas neat animal fat has the lowest one. The volumetric efficiency of standard diesel fuel is between these two values. The highest volumetric efficiency can be explained by the presence of water and methanol content in the emulsion. In fact, these two liquids have high latent heat of evaporation. When the water and the methanol evaporate, the cylinder temperature considerably decreases and permits to aspirate more air than usual. Hence, the volumetric efficiency is enhanced. Volumetric Efficiency Inj.timing : 2 BTDC Power (watts) Fig.9 Variation of Volumetric Efficiency with and its Emulsion According to the results shown in Fig. 1, the specific energy consumption (SEC) of all the tested fuel are higher at low loads than at high loads. This is caused by the higher heat loss and also a lower mechanical efficiency as a result of more negative work. The measured SEC of neat animal fat is higher than the diesel one. This result finds explanations in the fact that fat is very viscous as compared to diesel. Animal fat is even in a solid state at temperatures below 3 C. Indeed, the mean diameter of droplets produced with animal fat are bigger than diesel. As previously observed, the combustion quality is bad with animal fat. However, animal fat emulsions reduce the specific energy consumption. This reduction is certainly due to the better atomization. The well known micro-explosion enhances fuel atomization by leading to a secondary atomization after injection. Thus, the SEC is lower with emulsions than neat animal fat. SEC(kJ/kW.hr) Inj.timing : 2 BTDC Power (watts) Fig.1 Variation of Specific Energy Consumption with and its Emulsion EMISSION PARAMETERS: In a compression ignition engine oxides of nitrogen, smoke and particulate emissions are considered as main pollutants. Hydrocarbon and carbon monoxide emissions are also considered as the pollutants of diesel engines. In this study, Nitric oxide, black carbon smoke, hydrocarbon and carbon monoxide emissions are measured and analyzed. Hydrocarbons are mainly due to the incomplete combustion. Shown in Fig. 11 is the variation of hydrocarbon emissions with diesel, animal fat and its emulsion. Diesel and neat fat show increasing trend of emissions when the load is increased. This amplified Hydrocarbon (g/kwh),9,8,7,6,5,4,3,2,1 Inj.timing : 2 BTDC Fig.11 Variation of Hydrocarbon Emission with and its Emulsion formation at full load is caused by the excess fuel that enters into the cylinder under high power output conditions. The fuel/air mixture becomes rich and yields higher unburned hydrocarbons. Animal fat hydrocarbon emissions are higher than diesel whereas its emulsion

7 drastically reduces them. At peak power output, hydrocarbon emissions reach respectively.79 g/kwh,.48 g/kwh, and.17 g/kwh with animal fat, standard diesel and animal fat emulsion. The micro-explosion of animal fat emulsion leads to better air/fuel mixing rates than neat animal fat. This mechanism permits to obtain low hydrocarbon emissions at all power outputs. Carbon monoxide emissions are controlled primarily by fuel/air equivalence ratio as hydrocarbons. Carbon monoxides emissions obtained for the tested fuels reveal the same trend of hydrocarbon emissions. It is seen from the Fig.12 that carbon monoxide emission increases when the load is increased. Animal fat and diesel combustion results in high values at high power output. Animal fat emulsion results in drastic reduction in these emissions. This reduction finds explanations again on the improved mixture formation caused by microexplosion. Carbon Monoxides (g/kwh) The principal source of NO is the oxidation of atmospheric nitrogen. The chemical reactions, which yield to the formation of NO are, governed by high temperatures and availability of oxygen. NO are formed in cylinder areas where high temperature peaks appear mainly during the uncontrolled combustion. The variation of NO emission with power output is shown in Fig. 13. Nitric Oxide (g/kwh) Fig.12 Variation of Carbon Monoxide Emission with Neat Animal fat and its Emulsion Inj.timing : 2 BTDC Inj.timing : 2 BTDC NO emission with neat animal fat is close to standard diesel one. Animal fat emulsion combustion results in NO reduction. At full load, NO emissions are 18.7 g/kwh, 18.3 g/kwh and 2.6 g/kwh respectively with diesel, animal fat and its emulsion. NO emissions are relied on the premixed combustion. As mentioned earlier, animal fat combustion leads to lower premixed combustion and results in cylinder temperature lower than diesel combustion. Drastic reduction in NO formation with animal fat emulsion is caused by the presence of water and methanol in the emulsion. The high latent heat of vaporization of these liquids results in significant reduction in cylinder temperature. Hence, NO emissions are decreased. Figure 14 represents the black carbon smoke emitted at different power outputs with the three tested fuels. It can be noted that smoke is high mainly at high power outputs. As explained earlier, high loads imply that more fuel is injected into the combustion chamber and hence incomplete combustion of fuel is amplified. It is noted that the smoke density with animal fat is lower than standard diesel. At full load, the maximum value of 6.3 m -1 is reached with diesel although 3.6 m -1 is obtained with neat animal fat. The reduction in black smoke can be explained by the presence of less carbon (Table 1) with animal fat as compared to diesel. In addition to that, animal fat has more oxygen content contrary to diesel, which has no oxygen. The presence of oxygen in the animal fat is in favour of carbon residual oxidation, which leads to a reduction in smoke density. Animal fat emulsion further reduces the smoke density up to the value of.9 m -1 for the same power output. This is due to the micro-explosion of emulsions, which leads to better atomization. Smoke Density K (m-1) Inj.timing : 2 BTDC -1 Fig.14 Variation of Smoke Density with and its Emulsion The high oxygen contents of animal fat associated with better fuel/air mixing rates enhance the combustion process and yield to reduce unburned carbon particles which form smoke. Fig.13 Variation of Nitric Oxide with and its Emulsion

8 CONCLUSION A single cylinder diesel engine was operated successfully on animal fat and its emulsions with water and methanol as fuels. The following conclusions are made based on the experimental results: The operation of the engine is smooth on animal fat and its emulsion with acceptable performance. Neat animal fat results in reduced peak pressure and maximum rate of pressure rise as compared to neat diesel. Animal fat emulsion increases the peak pressure and rate of pressure rise. Ignition delay is increased with both animal fat and its emulsion as compared to diesel. Animal fat emulsion shows highest ignition delay at all power outputs. Combustion duration is found higher with neat animal fat as compared to diesel. Animal fat emulsion shows improvement in combustion duration due to reduced diffusion combustion rate. Lower heat release rates are found with neat animal fat during the premixed combustion phase. Animal fat emulsion results in improved heat release rates. Increased SEC (specific energy consumption) and exhaust gas temperature are observed with neat fat at all power outputs as compared to diesel. Animal fat emulsion shows improvements in SEC and exhaust gas temperature. Drastic reduction in carbon smoke emission is found with animal fat emulsion mainly at high power outputs as compared to neat fat and neat diesel. The maximum smoke level is 3.6 m -1 with neat fat and.9 m -1 with animal fat emulsion at peak power. It is 6.3 m -1 with diesel. Hydrocarbon emission is higher with animal fat as compared to diesel. The maximum hydrocarbon emission is about.48 g/kwh with diesel and.79 g/kwh with neat animal fat at peak power output. Significant reduction in hydrocarbon emission is found with animal fat emulsion. It is about.17 g/kwh at peak power output. Similar trends are also seen in the case of carbon monoxide emissions. NO emission is lower with both neat fat and its emulsion as compared to neat diesel at maximum power output. The reduction is more significant with animal fat emulsion due to the lowest peak flame temperature. On the whole it is concluded that animal fat emulsions can be used as good alternative fuel for diesel engines. However, the long-term effects of these fuels on wear and corrosion of engine parts have to be evaluated. REFERENCES 1. Gerhard Vellguth. Performance of vegetable oils and their monoesters as fuel for diesel engines, SAE Paper , John W. Goodrum, Daniel P. Geller, Thomas T. Adams. "Rheological characterization of animal fats and their mixtures with # 2 fuel oil, Biomass and Bioenergy", vol. 24, pp , M. S. Graboski, J. D. Ross and R. L. McCormick. Transient emissions from No. 2 diesel and biodiesel blends in DDC series 6 engine, SAE Paper , Da Nian Zheng and Milford Hanna. preparation and properties of methyl esters of beef tallow, Bioresource Technology, vol. 57, pp , M. Senthil Kumar, A. Ramesh B. Nagalingam. Experimental Investigations on a Jatropha oil methanol dual fuel engine, SAE Paper , Abdul Moneyem and Jon H. Van Gerben. The effect of biodiesel oxidation on engine performance and emissions, Biomass and Bioenergy, vol. 2, pp , M. Senthil Kumar, A. Ramesh, B. Nagalingam. Use of Hydrogen to enhance the performance of a vegetable oil fuelled Compression Ignition engine. International Journal of Hydrogen Energy, vol. 28, pp , M. Senthil Kumar, A. Ramesh and B. Nagalingam. An experimental comparison of methods to use methanol and Jatropha oil in a compression ignition engine, Biomass and Bioenergy, vol. 25, no. 3, pp , J. Czerwinski. Performance of HD-DI Diesel engine with addition of Ethanol and Rapeseed oil, SAE Paper 94545, C. Y. Choi and R. D. Reitz. An experimental study on the effects of oxygenated fuel blends and multiple injection strategies on DI diesel engine emissions, Fuel, vol. 78, no. 11, pp , Marwan A A Nazha, Hobina Rajakaruna and S. A. Wagstaff. The Use of Emulsion, Water Induction and Egr for Controlling Diesel Engine Emissions, SAE Paper , Abu-Zaid M, Performance of single cylinder, direct injection Diesel engine using water fuel emulsions, Energy Conversion and Management, vol. 45, no. 5, pp , Cherng-Yuan Lin and Kuo-Hua Wang. Effects of an oxygenated additive on the emulsification characteristics of two and three-phase diesel emulsions, Fuel, vol. 83, no. 4-5, pp , Roy J. Crookes, Fariborz Kiannejad and Marouan A. A. Nazha. Systematic assessment of combustion characteristics of biofuels and emulsions with water for use as diesel engine fuels, Energy Conversion and management, vol.38, pp , 1997.

9 15. Schwab A.W, Bagby M.O. and Freedman B, Preparation and properties of diesel fuels from vegetable oils, Fuel, vol. 66, pp , N. Khan and S.R. Gollahalli, Performance and Emission Characteristics of a Diesel engine burning unstabilized emulsions of diesel fuel with water, methanol and ethanol, SAE Paper 81121, Quentin A. Baker, Use of alcohol-in-diesel fuel emulsions and solutions in a medium speed diesel engine, SAE Paper 81254, A. Kerihuel, M. Senthil Kumar, J. Bellettre and M. Tazerout. Use of Animal Fats as CI Engine fuel by making stable emulsions with water and methanol, Fuel (Under review), M. Senthil Kumar, A. Kerihuel, J. Bellettre and M. Tazerout. Investigations on the use of preheated animal fat as fuel in a diesel engine, Renewable Energy (Accepted), Yasufumi Yoshimoto, Masayuki Onodera and Hirorya Tamaki. Reduction of NOx, smoke and BSFC in a Diesel engine fuelled by biodiesel emulsion with used frying oil, SAE Paper , SAE J1667. "Recommended Practice for Snap Acceleration Smoke Test Procedure for Heavy-Duty Powered Vehicles", SAE report J. P. Holman. Experimental Methods for Engineers, Seventh Edition, New York, McGraw-Hill, 1993.

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