燃烧室热边界对微型发动机瞬态燃烧特性影响数值分析

为了研究燃烧室热边界对微型内燃机微燃烧特性的影响，以指导燃烧室设计，采用层流有限速率模型对微燃烧过程进行了仿真。首先对仿真结果开展了有效性分析，探讨了网格尺寸、时间步长、步长内最大计算步数3个建模因素对仿真结果的影响，结果表明仿真与实验比较吻合。在此基础上探索了散热系数、壁面厚度和材料3个参数对燃烧特性的影响。结果表明，散热系数对燃烧特性有较明显的影响，散热系数从0增加到55 W／（m2·K ）时，压力升高率减小，着火点延后，最高压力值下降了2个大气压。壁面厚度和材料对燃烧特性影响不大，分析表明这是由于在热量从缸内传到外界环境的热流路径中主要传热热阻是外壁面与环境之间的对流换热热阻所致。

Influence numerical analysis of combustion chamber thermal boundary conditions on unsteady combustion characteristics in micro ICE

To research the influence of combustion chamber thermal boundary conditions on micro combustion characteristics in micro ICE, the laminar flow finite rate model is adopted to simulate the micro combustion process. Firstly, the influence of grid scale, the time step length and the maximum iterations per time step on accuracy of simulation results are explored. The results show that simulation results agree well with experimental results. And then, the influences of heat transfer coefficient, wall thickness and material on combustion characteristics are discussed. The results indicate that heat transfer coefficient has obvious influence on combustion characteristics. The pressure rise rate decreases, the ignition delays and the highest pressure value drops 2 atmospheres as heat transfer coefficient increases from 0 to 55 W/(m 2·K). The wall thickness and material have a little effect on combustion characteristics. This is because that the main heat transfer resistance in the heat flow path from cylinder to external environment lies between the outer wall and environment.