可变燃烧室(VCC)活塞设计及其动力学特性

Design of VCC Piston and Its Dynamics Characteristics

介绍了可变燃烧室(VVC)活塞的主要设计特性,包括钢珠-型面结构和连杆复位凸轮。采用VCC活塞的动力学仿真和发动机性能仿真的耦合迭代计算,预测了VCC活塞的动态响应特性;分析了影响VCC活塞动力学特性的关键控制参数及其它们之间的相互关系。研究结果表明:VCC活塞具有控制工作循环内气缸压力的快速动态响应,能有效控制5000r/min范围内100%负荷工况时过高的气缸压力;VCC活塞发动机能够在部分负荷工况保持较高的气缸压力,50%以下负荷工况的气缸压力与压缩比12.0的发动机几乎相同;钢珠-型面设计能够将弹簧变形量放大3倍,有效增加燃烧室容积变化;实际的动态预紧力远大于静态预紧力,适当减小碟簧预紧力可改善VCC活塞的动态特性。

Main design features of variable combustion chamber （VCC） piston, including the ball-pro- file and the reset cam were discussed in detail. Dynamic response characteristics of VCC piston were predicted by VCC engine coupling performance simulation with VCC piston dynamics simulation and iterative com- putation. The main affecting factors on the dynamics characteristics of VCC piston and their correlation were analyzed. It is revealed that the VCC piston possesses fast dynamic response ability to limit effectively excessive combustion pressure in 100% load and below speed of 5000 r/min conditions for every working cycle; it can maintain higher in-cylinder pressures in part load conditions, under 50% load its in-cylinder pressures are almost same as the engine with compression ratio 12.0; disc spring deformation is successfully increased 3 times due to the ball-profile design so that the combustion chamber volume is increased significantly; the dynamic pre-tightening force is much higher than the static one, and reducing properly pre-tightening force of the disc springs can improve dynamic response of VCC piston.