用特征时间燃烧模型模拟直喷式柴油机的燃烧

为了更好地模拟直喷式柴油机的喷雾及燃烧过程，对Kiva-3程序的喷雾和燃烧模型进行了改进，引入Kelvin-Helmholtz和Rayleigh-Taylor模型来模拟油滴破碎过程，采用改进的SheU自燃模型来模拟着火过程，为了综合考虑化学动力学和湍流对燃烧的影响，采用层流和湍流多重特征时间尺度燃烧模型来模拟燃烧过程．计算结果表明：在不同工况下计算所得的缸内压力、滞燃期和燃烧放热速率与实验结果吻合良好，着火点位于油束下游当量比略小于1的稀混合气区域；用改进的Kiva-3程序可以较好地研究直喷式柴油机的喷雾和燃烧过程，为进一步利用三维数值模拟计算来指导直喷式柴油机的参数优化奠定了基础。

Multidimensional Numerical Simulation of Direct Inject Diesel Engine Combustion via Characteristic Time Combustion Model

Numerical simulations of direct injection diesel engine combustion at different engine operating conditions were conducted using the Kiva-3 code. The spray and combustion models of the code were modified. In the modification, Kelvin-Helmholtz and Rayleigh-Taylor model was applied to describe the breakup process of injection spray and the improved Shell auto-ignition model was adopted to simulate the ignition process. In addition, the post-ignition combustion simulation was performed with a multiple laminar and turbulent characteristic timescale combustion model for taking into account the effects of both turbulence and chemical kinetic on combustion. The predicted values were compared with the engine testing data. The results calculated show good agreement with experimental results in cylinder pressure, in ignition delay period, and in heat release. The ignition site is located at the lower reaches of spray where the equivalent ratio of air-fuel mixture is slightly less than one. The modified Kiva-3 code could successfully predict the essential features of spray ignition and combustion processes. This work laid the foundation for optimizing the system parameters of direct injection diesel engines using multidimensional numerical simulations. .