The Effects of Pilot Injection Timing on The Combustion Process and Exhaust Emissions in Dual-Fuel Diesel Engine using Biodiesel-CNG at High Load

Biodiesel and compressed natural gas (CNG) are alternative fuels that can be used in the dual-fuel engine. In this research, Biodiesel was used as a combustion pilot and CNG was applied as a substitution fuel injected at the intake process. The pilot injection timing has an important role in controlling the initial combustion of dual-fuel combustion. It is caused by the ignition delay of dual-fuel engines longer than single-fuel engines. The engine was kept at a constant speed of 2000 rpm and was given a high load. The single fuel mode used standard injection time of -13 degrees CA ATDC. The time of pilot injection in the dual-fuel engine was varied from -11 to -19 degrees CA ATDC in steps of -2 degrees CA to investigate the combustion process and exhaust emissions. The results show that dual-fuel mode with the standard time of pilot injection produces the cylinder pressure and heat release rate (HRR) greater than the single-fuel mode. Moreover, cylinder pressure increases 21.46% and peak pressure in the range of 10 - 15 degrees CA ATDC with advanced the time of pilot injection in dual-fuel mode. However, HRR slightly increases by 4.79% at high load. The lower exhaust emissions can be achieved with advanced the time of pilot injection -17 degrees CA ATDC at high load.