柴油机缸内湍流和化学反应共同作用下的混合气形成机理

除了燃油喷射和雾化过程影响混合气形成，缸内的湍流和化学反应也对混合气的形成有着重要的影响，并且这种影响在高强化柴油机中，由于涉及工质跨临界的问题而表现得更加显著。本项目以定容燃烧弹内和柴油机缸内的喷雾和燃烧可视化实验为基础，结合计算流体力学与化学动力学数值模拟，测定和分析柴油机工况下的混合气形成和燃烧特性，测试出缸内各种关键组分的迁移和变化规律，深入系统地研究湍流和化学反应对混合气形成的作用机制。通过以上研究获得高强化柴油机缸内环境下燃油喷雾的精细结构以及蒸发（气化）特性随喷射压力、背压、环境温度、密度等条件的变化规律；揭示湍流对浓度分布、密度分布等的影响规律，获得化学反应对自由基等重要组分迁移和转变的影响规律，阐明湍流和化学反应对混合气形成的作用机制，修正输运方程中的扩散系数，建立更精确的缸内湍流射流扩散燃烧的计算模型，为丰富内燃机燃烧理论和发展新型高性能低污染柴油机做出贡献。

Research results show that in-cylinder turbulence and chemical reactions have important influence on mixture formation besides fuel spray and atomization themselves. Those influences are much more prominent for highly-strengthened diesel engines because it involves the critical problems for working medium. In this project, based on spray and combustion visualization experiments in a constant volume chamber and an optical diesel engine, in combination with computational fluid dynamics and chemical dynamics, mixture formation and combustion characteristics in diesel working conditions will be measured and analyzed. Transfer and change rules for some key components will be measured, and mechanism of the impact of turbulence and chemical reactions on mixture formation will be deeply investigated. By doing so, fine structure of spray in highly-strengthened diesel engines, impact of fuel injection pressure, ambient pressure and temperature, ambient density on fuel evaporation and vaporization will be studied. Impact of turbulence on concentration and density distribution, impact of chemical reaction on law of transfer and change of free radicals will be obtained, and mechanism of mixture formation with turbulence and chemical reactions will be revealed. By revising the diffusion coefficient in the transport equation, a more precise numerical calculation models for turbulent jet diffusion combustion will be founded. All those efforts will enrich combustion theories for internal combustion engines and contribute to development of high efficient and low emission diesel engines.