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氢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。
For developing high efficiency and clean automobile engine, the compression ratio of the engine should be further increased. However, the increasing compression ratio makes the knock inevitable, for the SI engine, the generally accepted mechanism of knock is the end-gas autoignition, but the detailed mechanism on how can end-gas autoignition induces knock is not clear. In view of this, we chose three essential elements of knock as our physical model, namely, tile central spark ignited flame, end-gas autoignition zone, left, and right reflective boundary. Based on tile detailed chemistry, using the one-dimensional reactive compressible flow nmthenmtical model, we obtained the knock under both two abnormal combustion modes, pre-ignition and autoignition, in our calculations. The different physical mechanisms of the initial induced pressure wave were identified between this two abnormal combustion modes, and the mechanism of coupling interaction between flame and pressure wave was revealed. This coupling effect makes the diffusion-controlled flame propagating becomes diffusion and pressure wave co-controlled process.
参考文献
| [1] | Juan Li;Zhenwei Zhao;andreiKazakov;Frederick L.Dryer .An Updated Comprehensive Kinetic Model of Hydrogen Combustion[J].International Journal of Chemical Kinetics,2004(10):566-575. |
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