Experimental Investigation to Study the Effect of Properties of Coconut Oil Biodiesel and Castor Oil Biodiesel and its Blending with Diesel on the Performance in a CI Engine

Vegetable oils and its esters are being considered seriously for internal combustion engines. It has many advantages such as it is renewable, nontoxic, sulphur free and biodegradable. But there are several problems associated with its use in diesel engines such as lower thermal efficiency and higher smoke levels compared to diesel. One of the methods by which these problems can be tackled is by blending of diesel (DSL) with biodiesels. In this work coconut oil biodiesel and castor oil biodiesel which are obtained from different sources are chosen, considering the wide variation in properties such as viscosity and degree of unsaturation. For coconut oil biodiesel (COBD) and castor oil biodiesel (CSBD), iodine value, which is an indication of the degree of unsaturation, was determined experimentally. The property influence on the performance of COBD and CSBD and its blends with equal volume with diesel was studied. Due to low viscosity, low density and high cetane value, COBD compared to CSBD has better performance and combustion characteristics. It is observed that higher thermal efficiency of 28.97% was obtained using COBD compared to 26.68% for CSBD. There is a significant reduction in NO emission with the addition of DSL to CSBD compared to CSBD operation. This also improved the performance characteristics due to reduction in viscosity and density of both COBD and CSBD. Compared to the thermal efficiency of COBD and CSBD the thermal efficiency of COBD-DSL and CSBD-DSL has increased to 29.72% and 26.85% respectively indicating improvement in atomization and combustion characteristics.