Performance characteristics of a supercharged variable compression ratio diesel engine fueled by biodiesel blends

Massive pressure was recently exerted on the automotive industry to explore sustainable and eco-friendly fuels. Biodiesel has attracted many researchers over the last decades as an important source of alternative fuel. The redeeming feature of biodiesel is that it reduces the emission of exhaust harmful gases, however, this feature comes at engine performance penalty. Therefore, this study was carried out to investigate the effect of varying the air flow and compression ratios on the performance of biodiesel-diesel fuel engines. The biodiesel was sourced from the transesterification of waste frying oil and was used in selected blends with ratios, by volume ranging from a volume of 0-50% biodiesel-diesel blend. A four strokes naturally-aspirated direct injection diesel engine was investigated in this study. The engine was equipped with a supercharger to increase the density of air supplied to the engine, and with another device to change the compression ratios. The engine brake power, brake specific fuel consumption and brake thermal efficiency were the performance parameters of the present work. The engine was kept running over a speed range from 1000 to 2000 rpm at 250 rpm intervals and three compression ratios (14, 16 and 18) under full load mode of operation, and different intake air pressures. The result indicated that forced induction operation using the supercharger increased the performance of the dual fuel mode by 25% at the highest compression ratio (18) compared to that of natural aspiration. On the other hand, it was revealed that the higher the compression ratio of the engine, the higher the performance obtained from the blend. In fact, supercharging the engine along with the higher compression ratio improved the penetration of the forced air into the fuel charge despite the biodiesel higher viscosity. The appropriate penetration of the biodiesel warranted the higher temperature and pressure in the engine cylinder, which in turn improved the combustion and performance of the dual fuel engine. (C) 2018 Faculty of Engineering, Alexandria University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).