Optimization of diesel engine comprehensive economy and emissions based on the RSM-NSGA III-VIKOR method

• RSM–NSGA–III–VIKOR integrated method applied for diesel engine optimization. • High–accuracy RSM models established with R 2 > 0.98 for BSFC, BSUC, NOx, CO 2 and N 2 O. • Optimization reduces BSCC by 0.62 g/kWh, NOx by 13.79%, and N 2 O by 14.40%. In practical applications, modern diesel engines simultaneously consume diesel fuel and urea to meet power output and emissions regulations. To improve the comprehensive liquid consumption and emissions, this study employed an RSM-NSGA III-VIKOR hybrid method to optimize engine control parameters. The objective was to reduce the Brake Specific Comprehensive Liquid Consumption (BSCC) by optimizing the trade-off between Brake Specific Fuel Consumption (BSFC) and Brake Specific Urea Consumption (BSUC). The Box-Behnken design was employed for experimental design with four main control parameters as factors: engine air mass flow (MAF), exhaust gas recirculation (EGR) rate, main injection timing (MIT), and rail pressure. The optimization objectives included BSFC, BSUC, BSCC, raw nitrogen oxides (NOx) and soot emissions, as well as the tailpipe carbon dioxide (CO 2 ) and nitrous oxide (N 2 O) emissions. A mathematical model was first established using RSM based on experimental data. This model was then optimized to generate a Pareto frontier using the NSGA-III algorithm. Subsequently, the VIKOR method was applied to identify the final optimal solution from the Pareto frontier. This final solution was then experimentally verified. The test verification results show that the BSCC was reduced by 0.62 g/(kW·h). NOx and N 2 O emissions were reduced by 13.8% and 14.4%, respectively. However, soot and CO 2 emissions increased by 9.8% and 1.6%, respectively. This study confirms the potential of the proposed approach for reducing operating costs of diesel engine at high load condition.