Focusing on the spray simulation in engines using the Lagrangian-Drop Eulerian-Fluid (LDEF) approach, a new hybrid stochastic/trajectory (HST) droplet collision model with the improved collision frequency, the redivided collision cell, and an updated method for selection of the candidate collision pairs was developed in this study. The stochastic method used in the HST model was based on the theoretical framework of the time-counter (TC) direct simulation Monte Carlo (DSMC) method. Besides the stochastic method, the trajectory method was also introduced for the cases with sparse spray conditions in order to improve the reliability of the model predictions. The factor of “every parcel represents a certain number of droplets” was well considered in the calculations of the droplet collision frequency in the present model, which has not been attracted enough attention in previous models. Moreover, an adaptive collision cell technique was used for reducing the dependence of the calculation results on the computational mesh. The formula for selecting the collision pairs was updated in order to accurately reproduce the spatial distribution of the spray droplets after collision. To assess the performance of the droplet collision model, the experimental data with the direct spray-to-spray impingement under wide operating conditions were used for model validations. In addition, the numerical results by the droplet collision models including O'Rourke model, Nordin model, and no-time-counter (NTC) model were presented for comparison. The results indicate that the HST model is capable of satisfactorily reproducing the spray morphology, collision frequency, and Sauter mean diameter (SMD) of the droplets during the spray process. Meanwhile, good independence on the computational grid size, time step, and parcel number can be achieved by the HST model.

专注于使用拉格朗日·德·欧拉流体（LDEF）方法进行的发动机喷雾模拟，具有改进的碰撞频率的新的混合随机/轨迹（HST）液滴碰撞模型，重新设计的碰撞单元以及更新的选择方法本研究开发了候选碰撞对。HST模型中使用的随机方法基于时间计数器（TC）直接模拟蒙特卡洛（DSMC）方法的理论框架。除了随机方法外，还针对喷射条件稀疏的情况引入了轨迹法，以提高模型预测的可靠性。在本模型的液滴碰撞频率计算中，考虑了“每个包裹代表一定数量的液滴”的因素，在以前的模型中没有引起足够的重视。此外，使用自适应碰撞单元技术来减少计算结果对计算网格的依赖性。更新了用于选择碰撞对的公式，以便精确地再现碰撞后喷雾液滴的空间分布。为了评估液滴碰撞模型的性能，将在宽工作条件下具有直接喷雾到喷雾撞击的实验数据用于模型验证。此外，还给出了液滴碰撞模型（包括O'Rourke模型，Nordin模型和无时间计数器（NTC）模型）的数值结果进行比较。结果表明，HST模型能够令人满意地再现喷雾形态，碰撞频率，喷雾过程中液滴的Sauter平均直径（SMD）。同时，HST模型可以在计算网格大小，时间步长和宗地数量上实现良好的独立性。