航空活塞二冲程汽油机排气口高度优化研究

针对作为无人机动力的某可变排气二冲程发动机在去掉可变排气系统后对发动机性能的影响，利用Fire仿真软件建立了发动机的缸内工作过程仿真模型，通过仿真和试验的方法研究了去掉可变排气系统后的发动机特性，结果表明:去掉可变排气系统后在2000r/min、10%节气门开度和5500r/min、50%节气门开度条件下，发动机的扫气效率降低，输出功率下降。在此基础上，利用仿真研究的方法对排气口高度参数进行了优化研究。去掉可变系统后排气口高度最优值为36.3mm时可以在保证常用无人机飞行转速范围内，各工况下扫气效率较高，发动机指示功损失最小，输出功率可以满足无人机动力需求。 

ptimization research of the exhaust height on aviation pistontwo-stroke gasoline engine

In order to study the influence on engine performance by a variable-exhaust two-stroke engine as the unmanned aircraft power with removal of the variable exhaust system, the simulation of the cylinder''s working process in the engine was established using Fire simulation software. In the model, the characteristics of the engine after removing the variable exhaust system were studied through simulation and test. The results showed that after removing the variable exhaust system under the condition of 2000r/min, 10% throttle opening and 5500r/min, 50% throttle opening, the scavenging efficiency of the engine and the output power were reduced. On this basis, using the simulation study method to optimize the exhaust outlet height parameters, the results showed that: after removing the variable system, the optimal value of the exhaust outlet height was 36.3mm, which can guarantee the common drone flight speed range. The scavenging efficiency is high under all operating conditions. The loss of engine indicator power is minimal, and the output power can satisfy the drone power demand.