发动机不稳定燃烧化学反应机理及其抑制方法研究

The phenomenon of engine combustion instability is widely existed in the working process of various engines, which has a serious impact on the function and life-span of engine. Generally, the phenomenon of combustion instability is attributed to the influence of the physical processes such as spray and evaporation, while the chemical reaction in combustion process is considered very little. In the numerical simulation of combustion, two important conclusions can be found: one is the difference of chemical reaction mechanisms will affect the appearance of the unstable combustion, and the conclusion that the chemical reaction has important influence on unstable combustion can be obtained by analysis; another is the mode of unstable oscillatory combustion will sudden change when a geometrical parameter changes. Both of these two important conclusions are also the basis for the study of this project. This project is prone to establish a numerical simulations of combustion engine research platform, which is based on “ non-equilibrium, turbulence, two-phase flow unified algorithm”. This project mainly studies the internal relations between chemical reaction and instability phenomenon, and optimizes the chemical dynamics model. In this platform, research on the influence of the engine geometric distortion on the unstable combustion is carried out, and feasible unstable combustion suppression scheme is formulated.

发动机不稳定燃烧现象广泛存在于各类发动机工作过程中，对发动机性能以及发动机寿命具有严重影响。通常，不稳定燃烧现象被认为是喷雾和蒸发等物理过程的影响，对于燃烧过程中的化学反应的影响考虑的很少。在对不稳定燃烧现象数值模拟过程中发现两个重要结论：一是化学反应反应机理选取的不同可以影响到不稳定燃烧现象是否出现，通过分析得出“化学反应对不稳定燃烧具有重要影响”的结论；二是不稳定振荡燃烧的模态在某一几何参数改变时会发生突变。这两个重要结论也是构成本项目研究的基础。本项目拟建立基于“化学非平衡、湍流、两相流统一算法”的发动机燃烧研究的数值仿真平台，着重研究化学反应与燃烧不稳定现象之间的内在联系，优化化学动力学模型。在平台的基础上，开展发动机几何变形对不稳定燃烧影响的研究，制定可行的不稳定燃烧抑制方案。

本课题以发动机内部不稳定燃烧现象为研究背景，采用化学非平衡流模拟方法结合非结构网格技术，对发动机内部燃烧现象进行数值模拟。通过建立基于“非平衡、湍流、两相流”的发动机燃烧研究的数值仿真平台，对现有计算方法进行创新，以提高该计算平台的适用范围和计算效率；在该平台的基础上对存在C/H燃料燃烧的发动机燃烧室模型进行模拟，开展发动机几何变形对不稳定燃烧影响的研究，制定可行的不稳定燃烧抑制方案。