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为了发展高效、清洁的汽车发动机,需要进一步增大缸内压缩比。而压缩比的提高,使得敲缸现象无法规避。对于火花点火发动机,敲缸机理解释普遍接受的观点是末端混气自燃,但这种自燃如何能产生敲缸的机理尚不十分明确。为此,本研究以形成敲缸现象的最基本要素,即中心火花引燃的火焰面、末端壁面高压高温自燃区、两侧可反射压力波的壁面为物理模型,并基于详细化学反应机理和一维可压缩反应流模型,分别在热壁提前点火和末端混合气自燃模式下模拟得到氧燃料火花点燃式发动机的敲缸现象。本文分析了两种不同模式产生初始压力波的不同物理机制,并发现导致初始压力波被放大继而产生强敲缸现象的压力波和火焰的耦合作用机理。这样的耦合作用,使得火焰传播由扩散控制,转变为在敲缸发生时由扩散和压力波共同控制。
In order to develop an efficient, clean car engine, there is a need to further increase the in-cylinder compression ratio. The compression ratio increased, making knocking phenomenon can not be avoided. For a spark-ignition engine, the mechanism of knock mechanism is generally not fully understood at the end of the mix. Therefore, in this study, the most basic elements forming the knocking phenomenon are the flame surface of central spark ignition, the spontaneous combustion zone of high pressure and high temperature in the end wall, and the wall surface of pressure wave on both sides as physical model. Based on the detailed chemical reaction mechanism and One-dimensional compressible reaction flow model was used to simulate the knocking of oxy-fuel spark-ignited engine under hot-wall pre-ignition and end-mixed gas self-ignition mode respectively. In this paper, different physical mechanisms of the initial pressure waves generated by the two different modes are analyzed. The coupling mechanism between the pressure wave and the flame is also found, which leads to the initial pressure wave being amplified and then to a strong knocking cylinder. This coupling causes the propagation of the flame to be controlled by diffusion, converted to a common control of diffusion and pressure waves at the time of knocking.