Influence of Emulsified Palm Biodiesel as Pilot Fuel in a Biogas Run Dual Fuel Diesel Engine

This study attempts to explore the influence of emulsified palm biodiesel as a pilot fuel in a biogas run dual fuel engine. The intention is to achieve diesel-equivalent performance from a diesel engine, together with a reduction in engine emissions, with complete replacement of fossil diesel with renewable fuels. The results of this study are compared to those for a neat biodiesel (Jatropha)-biogas dual fuel engine run at identical engine settings. For baseline comparison, the results are also compared with a standard diesel run. The results show that with the presence of biogas, emulsified biodiesel as a pilot fuel can present a better dual fuel efficiency (41%) and a lower energy consumption (38%) than neat biodiesel in a piloted study. Also, the presence of a microexplosion of emulsified biodiesel was found to reduce the pilot fuel consumption with the presence of biogas, especially at lower loads, where the burning rate of biogas usually slows down due to the lean gas-air mixture and cooler charge temperature. In addition, emulsified palm biodiesel successfully brings the peak cylinder pressure (PCP) closer (8 degrees ATDC) to top dead center (TDC). This elevates the magnitude of the PCP, which increases the expansion ratio and hence improves engine efficiency. With the presence of emulsified biodiesel, the supply of biogas is found to get reduced, especially at higher loads, which in turn reduces the hydrocarbon emission. However, other emission characteristics are not as exciting, and hence emulsified biodiesel in biogas dual fuel mode needs to be further explored at various engine-operating characteristics in order to obtain a superior emission performance. (C) 2014 American Society of Civil Engineers.