Influence of Supercharging on Biodiesel Combustion in a Small Single Cylinder DI Diesel Engine

The present study investigated the effect of boost pressure on the operation of a small single cylinder DI diesel engine equipped with a jerk type injection system fueled by different biodiesel fuels. The study employed a Roots blower type supercharger driven by a motor, and the boost pressures were varied from 100 kPa (naturally aspirated condition) to 140 kPa. The experiments used three kinds of biodiesel: rapeseed oil methyl ester (RME), soybean oil methyl ester (SME), and coconut oil methyl ester (CME). Further, a blended fuel with 60% (mass) CME and 40% 1-butanol (represented as CMEB) was also used. The influence of the boost pressure on the engine performance, combustion characteristics, and exhaust emissions with the abovementioned four biofuels were examined and compared with standard JIS No. 2 diesel fuel. The results show that at high loads, the brake thermal efficiency with all the tested fuels increased considerably with increasing boost pressure while the smoke and CO emissions decreased significantly. At the naturally aspirated condition, the ignition delay of CMEB is much longer than with diesel fuel and the biodiesels. But the ignition delay with CMEB decreased remarkably with increasing boost pressures and the combustion was smokeless. At all boost pressures, it was established that all of the investigated biodiesel emission characteristics other than the NOx emissions with RME and SME were superior to those of ordinary diesel fuel.