直喷内燃机高压喷雾碰壁模型的开发

Development of a High Pressure Spray/Wall Interaction Model for Direct-Injection Engine Simulations

基于低压和高压喷雾碰壁后液滴运动形态的差异,分析了现有喷雾碰壁模型在模拟高压喷雾时的不足,提出了针对高压喷雾碰壁模拟的数值模型.该模型基于柴油喷雾碰壁的试验数据,并引入了壁面射流理论来估计靠近壁面的气相速度.针对高压喷雾碰壁后壁面喷雾的运动特点,增加了液滴升力的计算.通过与柴油喷雾碰壁试验进行对比,结果表明:新模型对高压喷雾碰壁液滴运动轨迹的计算更准确,并成功地再现了壁面喷雾前端的涡旋.此外,新模型的网格依赖性也被极大地降低.与传统喷雾碰壁模型相比,新模型更适合直喷发动机中的喷雾碰壁模拟,具有很强的工程实用价值.

Based on the difference between post-impingement movements of low and high pressure sprays and through the analysis of the disadvantages of traditional spray/wall interaction models,a new spray/wall interaction model was developed with emphasis on the simulation of spray impingements generated by high injection pressures.This proposed model was based on experimental measurements from diesel spray impingements.The wall jet theory was introduced to estimate the gas-phase velocity in the near wall region and lift force was considered for the sliding droplets.Extensive validations were performed against measurements from diesel spray impingement experiments.Results show that the new model well matches the measurements and the dependency on grid is significantly reduced.The new model provides a good alternative for the prediction of spray/wall interaction,especially under the conditions relevant to the direct-injection engines.