Effect of advancing fuel injection point on performance of Low speed IDI engine fueled with Jatropha straight vegetable oil

Abstract

The diminishing reserves of fossil fuels coupled with spiraling prices and higher environmental degradation has led to the interest in development of environment friendly alternate fuel. This has led to increasing interest in alternative sources of energy. One of the sources is Straight Vegetable Oil (SVO). Many researchers have reported that the brake thermal efficiency of engine with JSVO fuel is lower than the diesel fuel under design operating parameter for almost all the engine. This effect is due many reasons; one prime reason is very high viscosity of JSVO in comparison with diesel. The surface tension is also almost twice than the diesel where as the calorific value of JSVO (39000kJ/kg) is comparable with diesel (42000 kJ/kg). The high viscosity leads to poor atomization characteristics because of release of bigger fuel particle from fuel injector in the combustion chamber. The bigger fuel particles need more time for getting atomized properly. This can be attained by advancing the fuel injection point thereby increasing the time delay. In this work low speed IDI engine is used for investigation. The experiment was done in two phases, first the engine was run with diesel fuel and second it was run with neat JSVO. The design fuel injection point with diesel fuel for this engine is 200 BTDC. During the experiments the fuel injection advance angle in changed to 220 BTDC, 240 BTDC and 260 BTDC and the performance was evaluated. The BTE of engine with diesel fuel at its design operating parameter 200 BTDC and fuel injection pressure 175 kgf/cm2was found 32.96% in comparison with BTE with JSVO 30.62% at same operating parameters. As the advance angle of fuel injection was increased to 220, 240 and 260 BTDC the BTE of diesel fuel was decreased to 31.25% where as the BTE of JSVO was increased to 31.04% at 240 BTDC but decreased to 30.21% at 260 BTDC. Substantial improvement in BTE is achieved by changing the fuel injection point of this engine to 240 BTDC for JSVO.