对置活塞二冲程柴油机燃油系统设计研究

Fuel System Design for Two-Stroke Opposed-Piston Diesel Engine

基于对置活塞二冲程(OP2S)柴油机的特殊结构,开发了高压共轨燃油系统,利用喷射试验获取的共轨压力、喷油脉宽对应的喷油量图谱,实现了对循环喷油量的精确控制,通过燃油单次喷射试验验证了该高压共轨燃油系统的可行性。为进一步考察燃油系统中喷油器雾束形态对柴油机性能的影响,利用单次喷射的喷油速率曲线及三维CFD仿真模型对喷油器喷射雾束夹角进行了研究。结果表明:适当增大喷油雾束角将有利于燃油与缸内气体的混合,从而提高OP2S柴油机的循环热效率;但当喷射雾束夹角过大时则会出现雾束碰壁现象,不利于油气混合及燃油燃烧;另一方面,为避免对置二冲程柴油机燃烧粗暴的隐患,可以通过调节喷射雾束夹角得以改善。

Based on the special structure of the opposed-piston two-stroke(OP2S)diesel engine,a high-pressure common rail fuel system was developed,the accurate control of cycle injection volume was realized by using the MAP of injection volume corresponding to the common rail pressure and injection pulse width obtained from the injection test,and the feasibility of high-pressure common rail fuel system was verified by the fuel single injection test.In order to investigate the effect of injector spray pattern on engine performance,the injection spray angle was analyzed based on engine injection rate and 3D CFD simulation.The results show that the larger spray angle will improve the mixing process of fuel and in-cylinder air and hence promote the thermal efficiency of OP2S diesel engine.However,too large spray angle might lead to the collision of fuel and cylinder wall,which will deteriorate the mixing process of fuel and in-cylinder air and even the combustion conditions.Accordingly,the wild combustion can be prohibited by adjusting the spray angle.