Multi-objective optimization of the three-way catalytic converter on the combustion and emission characteristics for a gasoline engine

Three-way catalytic converters have shown superiority in redox exhaust gases. However, how to improve its redox capability is a huge challenge in gasoline engines fueled by gasoline-ethanol blended fuels. This paper investigated the effect of a Palladium/cerium dioxide (Pd/CeO2) three-way catalytic converter on the combustion and emission characteristics of a gasoline engine. The emission characteristic of gasoline oxidation catalyst was investigated in terms of total hydro carbons (THC), carbon monoxide (CO), and nitrogen oxides (NOx) emissions. Engine combustion characteristic was also studied in terms of brake specific fuel consumption (BSFC), brake power, fuel consumption rate, and exhaust gas temperature. The experiments were conducted on a four-cylinder direct injection gasoline engine with rotational speed between 2000r/min and 3000r/min, gasoline-ethanol blending ratio not exceeding 30%, and torque not exceeding 100 N·m. In addition, an optimization method integrated with the response surface method (RSM) and non-dominated sorted genetic algorithm II (NSGA II) was used to optimize the objective functions including BSFC and NOx emission. The regression equation of the response was obtained by RSM and brought into NSGA II to obtain Pareto optimal solutions. Different frontiers were implemented and the 100th iteration number was chosen as the Pareto frontier. The findings indicated that the optimal BSFC and NOx emission values were 380 g/(kW·h) and 350 ppm, respectively, which were attained with a torque of 45 N·m, a gasoline-ethanol blending ratio of 17%, and a rotational speed of 2027r/min.