Investigating the performance and emission of RCCI engines with different compositions ‎and percentages of natural gas

The RCCI method is used in dual-fuel diesel-gas engines in this study. Previous studies have shown that different natural gas compounds and their percentages have a significant effect on the performance of dual-fuel engines. This research aims to investigate the combustion behavior of the OM-355 engine in dual-fuel (diesel/gas) mode using computational fluid dynamics. For this purpose, the dual-fuel engine is simulated using CONVERGE software. The simulation was performed at 1400 rpm, and different combinations of CNG gas and their various percentages and the output parameters of engine performance and pollution were studied. The simulation results show that natural gas compounds with a higher methane content increase the combustion quality and reduce unburned hydrocarbons and smoke pollutants. Additionally, in the combustion of this mixture, the temperature inside the combustion chamber increases, and the amount of NOX pollutants in the exhaust gases increases. The investigation of different percentages of natural gas in the dual-fuel engine shows that an increase in the amount of natural gas until 70% reduces the maximum temperature inside the combustion chamber, and beyond this amount, it increases. Therefore, for natural gas ratios up to 70%, the NOX pollutant is reduced by 75% compared to a diesel engine, and with further increases in the amount of natural gas, the NOX pollutant increases due to the rise in the temperature of the combustion chamber.