Numerical and optimization modeling of dual-fuel natural gas–diesel engine at the idle load

Abstract

In this article, the modeling and optimization of a dual-fuel diesel engine with the combination of South Pars Refinery gas have been discussed at the idle load. First, using the computational fluid dynamics (CFD) method, the modeling has been validated with experimental data, and the results of the present numerical solution are in acceptable agreement with the experimental data. In order to optimization, the considered objective functions include minimum NO_x emission, maximum power generation, and minimum fuel consumption. Optimization variables include start of injection (SOI) time, the mass fraction of mean natural gas (Y_NG), and inlet air pressure (P_i). The number of tests required by the response surface method for the intervals 5 < SOI < 25 before top dead center (BTDC) crank angle (CA), mass fraction 0.02 < Y_NG < 0.04, and 0.75 < P_i < 1.75 (bar) are considered with 20 numerical solutions using the CFD method. The objective functions are set with confidence 95% that has been calculated. In the following, using the non-dominated sorting genetic algorithm method, the objective functions are optimized and the Pareto front is displayed. In addition, by using TOPSIS, the optimal point has been obtained at SOI = 10 BTDC (CA), Y_NG = 0.02, and P_i = 1.6 (bar). Also, in optimal conditions for three revolutions of 850, 1000, and 1250 rpm, the thermal, fluid, and performance parameters of the engine have been compared.