LAUSR

Abstract In this study, diesel injection parameters of a natural gas/diesel reactivity controlled compression ignition engine were optimized. Seven injection parameters including the mass ratio of diesel in the first injection, the spray angle in the first and second injections, and the non-dimensional initial injection rate and the ramp injection slope in the first and second injections were considered. The objective of the optimization was to simultaneously maximize the engine gross indicated efficiency and minimize exhaust emissions and the maximum pressure rise rate. The optimal space filling design of experiment method was applied to evaluate the effect of seven injection parameters on the objective variables with a minimum number of numerical experiments. The relationships between the injection parameters and objective variables were approximated by the genetic aggregation response surface model. Finally, the non-dominated sorting genetic algorithm II was employed to find the optimum values of the injection parameters. By applying the optimum parameters, the gross indicated efficiency increased by 11.45%, NO x , CO, and unburned hydrocarbons emissions reduced by 22.28%, 44.93%, and 47.10%, respectively, and the maximum pressure rise rate decreased by 37.50%.