关键词: 柴油机, 油耗, 排放, 多目标优化

Abstract: Using aftertreatment devices is expensive for nonroad diesel engines. It is one of the economical and effective methods to simultaneously reduce the original engine emissions and maintain reasonable fuel economy by optimizing combustion. Taking a small agricultural diesel engine developed in China IV stage emission regulations for nonroad mobile machinery as the research object, firstly, a onedimensional thermodynamic simulation model was established through GTPower software according to the existing test data. Secondly, after verifying the accuracy of the model, the response surface method was used to carry out experimental design for the previous seven working conditions of the offroad diesel engine steadystate test cycle, and the regression models of the key performance parameters of the diesel engine were obtained by the stepwise method. Thirdly, the multiobjective optimization of fuel consumption and emissions was conducted using NSGA-Ⅱ. The desired optimal solution and its corresponding calibration parameters were determined from the Pareto optimal solution by TOPSIS under each working condition. Finally, the optimization results were verified by bench test. The results show that it was feasible touse NSGA-Ⅱ for multiobjective optimization of fuel consumption and emissions and screen the optimal solution based on TOPSIS, and the optimization results were accurate. Compared with the original diesel engine, the weighted brake specific fuel consumption, NOX, and soot of the eight working conditions of the optimized steadystate test cycle has been reduced by 2.8%, 27.4%, and 18.2%, respectively. The optimized CO, HC+NOX, and PM emissions of this steadystate test cycle are 2.811 g/(kW·h), 3.342 g/(kW·h), and 0.015 g/(kW·h), respectively, which meets China nonroad stage IV emission standards.

Key words: diesel engine, fuel consumption, emissions, multiobjective optimization