AN INVESTIGATION ON THE PERFORMANCE CHARACTERISTICS OF A DIESEL ENGINE USING DIESEL-RICE BRAN BIODIESEL BLENDS AT DIFFERENT INJECTION PRESSURES

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1 INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING AND TECHNOLOGY (IJMET) International Journal of Mechanical Engineering and Technology (IJMET), ISSN (Print), ISSN (Print) ISSN (Online) Volume 6, Issue 1, January (2015), pp IAEME: Journal Impact Factor (2014): (Calculated by GISI) IJMET I A E M E AN INVESTIGATION ON THE PERFORMANCE CHARACTERISTICS OF A DIESEL ENGINE USING DIESEL-RICE BRAN BIODIESEL BLENDS AT DIFFERENT INJECTION PRESSURES Dr.G VENKATA SUBBAIAH Mechanical Engineering Department, MVSR Engineering College, Nadergul, Hyderabad, India ABSTRACT The depletion of fossil fuels, increasing demand for petroleum fuels prompted extensive research on alternative sources of energy for internal combustion engines. Biodiesel as alternative fuel has been widely studied as alternative for diesel fuel due to its merits such as lower sulfur, lower aromatic hydrocarbon and higher oxygen content. The aim of this study is to investigate the effect of injection pressure on the performance characteristics of a single cylinder diesel using diesel and diesel-rice bran biodiesel blends B10 (90% diesel and 10% rice bran biodiesel), B20 (80% diesel and 20% rice bran biodiesel) and B30 (70% diesel and 30% rice bran biodiesel). The diesel engine was tested at 180, 200, 220 and 240 bar injection pressure by using diesel fuel, diesel-rice bran biodiesel blends. The engine was run at its rated speed of 1500 rpm and the parameters related to performance were measured at the rated power of the engine. The brake thermal efficiency increased with B10 and B20 but reduced with B30. The brake specific fuel consumption and exhaust gas temperature were increasing with the percentage of rice bran biodiesel in the blends. The brake thermal efficiency and exhaust gas temperature increased but brake specific fuel consumption reduced up to 220 bar and reversed trend was observed at 240 bar injection pressure for all the fuels tested. The brake thermal efficiency, brake specific fuel consumption and exhaust gas temperature with the blends B10, B20 and B30 was higher than that of the diesel fuel at all injection pressures. The maximum brake thermal efficiency and minimum brake specific fuel consumption were observed with the blend B20 at 220 bar. Keywords: Diesel Engine, Injection Pressure, Performance and Rice Bran Biodiesel. 20

2 1. INTRODUCTION Diesel engines are greatly used in transportation sector because of their higher thermal efficiency, reliability and fuel economy. Biodiesel is gaining worldwide attention as a solution to environmental problems, energy security, rural employment and improving agricultural economy [1] Rice bran is a brown layer present between rice and the outer husk of the paddy. Rice bran oil is an important derivative of rice. Rice bran oil (RBO) has been difficult to refine because of its high content of free fatty acid (FFA), unsaponifiable matter and dark color. The studies [2-7] on the performance and emission characteristics of a diesel engine using rice bran biodiesel reported that the brake thermal efficiency increased and brake specific fuel consumption reduced up to 20% blending of rice bran biodiesel. The brake thermal efficiency was slightly improved by the use of additives. This literature reveals that the rice bran biodiesel can be used as an alternate fuel for a diesel engine. Jindal al., [8] investigated the change of design parameters such as compression ratio (CR) and fuel injection pressure (IP) on the performance and emissions characteristics with Jatropha methyl ester as biofuel compared to the diesel. It is found that the increase of compression ratio and injection pressure increases the brake thermal efficiency and reduces BSFC and exhaust emissions. Pandian et al [9] investigated the effect of injection system parameters such as injection pressure, injection timing and nozzle tip protrusion on the performance and emission characteristics of a twin cylinder diesel engine fueled with pongamia oil, blended with diesel. The results depicted that the BSEC, CO, HC and smoke opacity were lesser, and BTE and NOx were higher at 2.5 mm nozzle tip protrusion, 225 bar of injection pressure and at 30_ BTDC of injection timing. Optimization of injection system parameters was performed using the desirability approach of the response surface methodology. The studies [10-15] on the effect of injection pressure on performance of a diesel engine reported that the brake thermal efficiency and exhaust gas temperature increased and brake specific fuel consumption reduced with injection pressure in the range of bar. P. Dinesha and P. Mohanan studied the combustion, performance and emission characteristics of a CI engine at 180, 200 and 220 bar injection pressure using biofuel. The optimum pressure for the biofuel blend B20M10 (20% cardanol, 10% methanol, and 70% diesel) is 220 bar. They observed reduction in and brake thermal efficiency [15]. M. Bahattin CELIK and Dogan SIMSEK investigated experimentally the optimum blend rate and injection pressure for a direct injection diesel engine by using soybean biodiesel. They reported that B25 is the optimum blend with respect to the performance and emissions. They tested the blend B25 at 160, 180, 200, 220 and 240 bar injection pressure. The optimum injection pressure observed for B25 is 220 bar which is above the original injection pressure of 200 bar [16]. The above literature reveals that the injection pressure has an influence on the performance and emission characteristics of a diesel engine using biodiesels obtained from jatropha, sesame, chicken fat, mohr oil, pongamia pinnata, rubber seed oil, waste cooking oil, soybean etc. There is no literature found on the study of effect of injection pressure on the performance and emission characteristics of a diesel engine using rice bran biodiesel. Hence the objective of this paper is to investigate the effect of injection pressure on the performance and emission characteristics of a direct injection diesel engine using rice bran biodiesel. 2. MATERIALS & METHODS The diesel fuel and rice bran biodiesel are used in the present investigation. The diesel fuel was purchased from the Bharat Petroleum pump outlet, Nandyal, Andhra Pradesh and the rice bran oil biodiesel (RBD) was supplied by Gaiatech Fuels Pvt Ltd; Hyderabad, India. The fuel properties 21

3 of diesel and rice bran biodiesel such as density, viscosity, calorific value, net heating value, autoignition temperature, pour point, cetane number, iodine number, acid value and oxygen content are measured and shown in the Table 1. Table 1: Properties of Diesel and Rice Bran Biodiesel Property parameters Diesel fuel Rice bran oil biodiesel Density at 20 0 C, g/cm Viscosity at 40 0 C, mm2/s Flash point, 0 C Auto-ignition temperature, 0 C Pour point, 0 C 1 3 Cetane number Iodine number, J2 g/100 g Acid value, mg KOH/g Oxygen content, max wt% Net heating value, MJ/kg The schematic diagram of the engine test rig is shown in Fig1.The set up consists of engine test bed, diesel engine, electrical alternator, fuel and air consumption metering equipments. Fig.1. schematic diagram of experimental setup. The specifications of the engine are given in the Table 2. The combustion chamber of the diesel engine is a direct type without any arrangement for air swirl motion. The engine was connected to electrical dynamometer for measuring brake power. The naturally aspirated engine was provided with water cooling system. The engine oil was provided with a pressure feed system. 22

4 Table 2: Specifications of the Diesel Engine Make No. of Strokes per cycle 4 No. of Cylinders Combustion chamber position Cooling method Starting condition Ignition technique Bore (D) Stroke ( L ) Rated speed Rated power Kirloskar model AV1 single vertical Water cooled Cold start Compression ignition 80 mm 110 mm 1500 rpm Compression ratio 16.5 : 1 Injection opening pressure 5 hp (3.72 kw) 200 bar The engine was first operated on diesel fuel with no load for about 15 minutes until the cooling water and lubricating oil temperatures reaches to 850 C at rated speed of 1500 rpm and the original injection pressure of 200 bar. The baseline parameters were obtained at rated load on the engine with the diesel fuel (Diesel). After this, the diesel fuel was replaced by diesel-rice bran biodiesel blends B10 (90% diesel and 10% rice bran biodiesel), B20 (80% diesel and 20% rice bran biodiesel) and B30 (70% diesel and 30% rice bran biodiesel) one after the other and observations were noted. The injection pressure was adjusted to and calibrated to 180bar, 220 bar and 240 bar in the fuel injector and the same tests were conducted with diesel, B10, B20 and B30 at each of these injection pressures. The results obtained for diesel-rice bran biodiesel blends at different injection pressures were compared with the baseline parameters obtained during engine fuelled with diesel fuel at rated speed of 1500 rpm. The performance parameters such as brake thermal efficiency, brake specific fuel consumption and exhaust gas temperature were determined by measuring fuel consumption, engine torque, engine speed and exhaust gas temperature. The electrical alternator was used for the measurement of brake power. The mass of fuel consumed was measured with the help of a burettee connected to the fuel tank through a three way cock and a stop watch. 3. RESULTS& DISCUSSIONS The results obtained pertaining to the performance and emissions of the engine are demonstrated with the help of graphs. The variation of brake thermal efficiency with injection pressure for diesel and diesel-rice bran biodiesel blends is shown in the Fig.2. The brake thermal efficiency of all the fuels is minimum at lower injection pressure of 180 bar. The brake thermal efficiency (BTE) is increasing with increase in injection pressure. The maximum efficiency for all fuels tested is obtained at 220 bar injection pressure. The reduced BTE is observed at 240 bar. 23

5 Brake Thermal Efficiency (%) 27.7 Diesel 27.6 B B20 B Injection Pressure (bar) Fig. 2. Variation of Brake Thermal Efficiency with Injection Pressure It may be due to reduced fuel droplet size and injection of high fine fuel spray which reduces the penetration of fuel spray and momentum of fuel droplets at higher injection pressures [17]. The maximum brake thermal efficiency of 27.64% is observed with B 20 at an injection pressure of 220 bar which is1.61% higher than that of diesel fuel at original injection pressure of 200 bar. Brake specific fuel consumption (kg/kw-hr) Diesel B B B Injection Pressure (bar) Fig 3. Variation of brake specific fuel consumption with injection pressure The variation of brake specific fuel consumption for diesel, B10, B20 and B30 with injection pressure is shown in the Fig.3. BSFC for all diesel-biodiesel blends B10, B20 and B30 is higher than diesel fuel at all injection pressures. It is found that the BSFC is decreased with increase in injection 24

6 pressure up to 220 bar but increased at 240 bar. This may be due to that, as injection pressure increases the penetration length and spray cone angle increases, so that at optimum pressure, fuel air mixing and spray atomization will be improved. The optimum injection pressure observed is 220 bar instead of original injection pressure of 200 bar for all the fuels tested. At 220 bar the BSFC of B10, B20 and B30 is 1.89%, 2.8% and 3.56% respectively higher than that of diesel fuel. The exhaust gas temperature variation with injection pressure for diesel fuel, B10, B20 and B30 is shown in the Fig.4. Exhaust Gas Temperature (deg C) Diesel B10 B B Injection Pressure (bar) Fig. 4. variation of exhaust gas temperature with injection pressure The exhaust temperature is increasing with injection pressure up to 220 bar and then decreasing for all the fuels tested. The exhaust gas temperature is increasing with the percentage of rice bran biodiesel in the blends. The exhaust gas temperature of B10, B20 and B30 is 2.56%, 3.98% and 9.1% respectively higher than that of diesel fuel at rated injection pressure of 200 bar. The maximum exhaust gas temperature of 3600C, 3690C, 3810C and 3900C is observed respectively for diesel fuel, B10, B20 and B30 at 220 bar. It is due to the better atomization, mixing and combustion of the fuel. 4. CONCLUSION The following conclusions are drawn from the above test on a diesel engine by using diesel and diesel-rice bran biodiesel blends at different injection pressures. The rice bran biodiesel can be used as a substitute for the diesel fuel in diesel engines. The brake thermal efficiency with the blends B10 and B20 was higher than that of diesel fuel at all injection pressure. The brake thermal efficiency was increasing up to 220 bar injection pressure for all the fuels tested. The exhaust gas temperature was increasing with the percentage of rice bran biodiesel in the blends and also with injection pressure. The better performance is observed with the blend B20 at 220 bar which is higher than the original injection pressure of 200 bar 25

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