Potential of a Low Heat Rejection Diesel Engine with Renewable Fuels

Investigations are carried out to evaluate the performance of a low heat rejection (LHR) diesel engine consisting of air gap insulated piston with ۳-mm air gap, with superni (an alloy of nickel) crown and air gap insulated liner with superni insert with different operating conditions of crude jatropha oil with varied injection timing and injection pressure.  Performance parameters of brake thermal efficiency (BTE), exhaust gas temperature (EGT) and volumetric efficiency (VE) are determined at various magnitudes of brake mean effective pressure. Pollution levels of smoke and oxides of nitrogen (NOx) are recorded at the peak load operation of the engine. Combustion characteristics of the engine of peak pressure (PP), time of occurrence of peak pressure(TOPP), maximum rate of pressure rise (MRPR) and time of occurrence of maximum rate of pressure (TOMRPR) are measured with TDC (top dead centre) encoder, pressure transducer, console and special pressure-crank angle software package. Zero dimensional, multi-zone combustion model is assumed to predict combustion characteristics and validated with experimental results. Conventional engine (CE) showed deteriorated performance, while LHR engine showed improved performance with crude jatropha oil operation at recommended injection timing and pressure and the performance of both version of the engine is improved with advanced injection timing and higher injection pressure when compared with CE with pure diesel operation. Peak brake thermal efficiency increased by ۴%, smoke levels decreased by ۴% and NOx levels increased by ۳۷% with vegetable oil  operation on LHR engine at its optimum injection timing, when compared with pure diesel operation on CE at manufacturer’s recommended injection timing.