基于多目标的二冲程发动机换气过程优化

二冲程航空活塞发动机的换气过程直接影响燃烧效果和发动机性能，以某二冲程航空活塞发动机为例，建立仿真模型，基于动力性能、经济性能、扫气性能进行多目标优化，对扫气道、排气道结构参数的不同组合优化分析。另外，还对不同海拔工况点下（转速为5 600 r/min，100%节气门开度）的气道结构参数进行优化。结论表明:使用NSGA-Ⅱ算法对发动机气道结构的优化可以有效提高扫气效率和功率，优化后（转速为5 600 r/min）分别为0.841 kW和2.712 kW，燃油消耗率降低22.08 $\mathrm{g}/(\mathrm{k}\mathrm{W}?\mathrm{h})$；另外，在不同海拔工况点中，随着海拔高度的增加扫气道长度呈现出减短的趋势，而排气道长度逐渐增加，且在海拔高度大于1 800 m时趋势变化更加明显。 

Gas exchange process of two-stroke engine based on multi-objective optimization

The gas exchange process of two-stroke aviation piston engine directly affects the combustion effect and the performance of the engine.Taking a two-stroke aviation piston engine as an example，a simulation model was established，and multi-objective optimization based on dynamic performance，economic performance，and scavenging performance was conducted.The optimization analysis of structure parameters of scavenging ducts and exhaust ducts was also performed.In addition，the parameters of the ducts structure under different altitude operating conditions （speed of 5 600 r/min，100% throttle opening） were optimized.The conclusion showed that the optimization of the engine ducts structure using the NSGA-Ⅱ algorithm can effectively improve the engine scavenging efficiency and power （speed of 5 600 r/min），by 0.841 kW and 2.712 kW respectively，and reduce the fuel consumption by 22.08 $\mathrm{g}/(\mathrm{k}\mathrm{W}?\mathrm{h})$；in addition，under different altitude operating conditions，as the altitude increased，the length of the scavenging duct showed a trend of decrease，while the length of the exhaust duct gradually increased，and the trend changed more obviously when the altitude was greater than 1 800 m.