自由活塞发动机进气口参数设计

卜祥祺，肖进^*

上海交通大学动力机械与工程教育部重点实验室，上海  200240

摘要：针对某Curtis型自由活塞发动机扫气性能优化问题，以目标扫气点与轴线的距离、侧向进气口倾角、排气口对侧进气口倾角为设计变量，基于Box-Benhnken响应面法设计试验方案，构建以充气效率、扫气效率、困气效率、给气化为优化目标的响应面模型；在此基础上引入合意度函数实现多指标综合优化，获得兼顾充气、扫气、困气与短路损失的最优端口几何参数组合。仿真结果表明：当目标扫气点与轴线的距离为11.86 mm、排气口对侧进气口倾角为46.01°、侧向进气口倾角为40.37°时，发动机扫气综合性能最佳，对应的充气效率为1.061，扫气效率为0.977，困气效率为0.331，给气比为3.205。研究表明，响应面-合意度一体化方法可为自由活塞发动机进气口几何参数的多目标优化提供有效的设计依据与参数选型参考。

关键词：自由活塞发动机；扫气；三维CFD仿真；响应面法

Design of intake port parameters for a free-piston engine

BU Xiangqi, XIAO Jin^*

Key Laboratory for Power Machinery and Engineering of the Ministry of Education, Shanghai Jiao Tong University, Shanghai 200240,China

Abstract: To address the optimization of scavenging performance in a Curtis-type free-piston engine, the horizontal scavenging target point, the inclination angle of the lateral intake ports, and the inclination angle of the intake ports opposite the exhaust port are selected as design variables. An experimental design is constructed using the Box-Behnken response surface methodology, and response surface models are established with charging efficiency, scavenging efficiency, and trapping efficiency as the optimization objectives. On this basis, a desirability function is introduced to achieve multi-objective comprehensive optimization, yielding optimal port geometric parameters that simultaneously account for charging, scavenging, trapping, and short-circuiting losses.Simulation results indicate that when the horizontal scavenging target point is 11.86 mm, the inclination angle of the intake ports opposite the exhaust port is 46.01°, and the inclination angle of the lateral intake ports is 40.37°, the engine achieves the best overall scavenging performance. Under these conditions, the corresponding charging efficiency, scavenging efficiency, trapping efficiency, and delivery ratio are 1.061, 0.977, 0.331, and 3.205, respectively.The study demonstrates that the integrated response surface-desirability approach provides an effective design framework and parameter selection reference for the multi-objective optimization of scavenging port geometry in free-piston engines.

Keywords: free-piston engine; scavenging; 3D CFD simulation; response surface methodology (RSM)