On the role of droplet bouncing in modeling impinging sprays under elevated pressures

Impingement of multiple diesel sprays under an elevated pressure of 30 atm is investigated numerically and experimentally, with the particular interest in illustrating the importance of taking into account of the ambient pressure effects in modeling binary droplet collisions. Specifically, a practical while simplified droplet collision model was proposed by modifying the widely-used Estrade et al.'s model to account for the previous experimental observation that hydrocarbon droplets tend to bounce back upon collision at elevated ambient pressures. The KIVA-3V program code implemented with the model was used to simulate the impinging sprays from the previous and the present experiments. The results show that the present model can produce qualitatively satisfactory predictions to the shape, the penetration length, and the Sauter mean diameter (SMD) of the impinging sprays because it accounts for the increased propensity of droplet bouncing at elevated pressures, which however was not considered in any previous models. Due to the limited experimental data on binary droplet collision at elevated pressures, the present model can be treated as a practical approximation for predicting droplet collision outcomes in sprays under high-pressure engine conditions.