AN INTER-IMPINGEMENT SPRAY MODEL CONSIDERING BINARY DROPLET COLLISION BASED ON OPENFOAM

Collision and breakup are the two main processes of the inter-impingement spray within internal combustion engines. Previous models did not comprehensively account for five collision regimes that delineate collision dynamics under high-pressure conditions, leading to deviations in the prediction of Sauter mean diameter (SMD) and frequency of bouncing regime. Hence, this article integrates an improved composite collision model for high-pressure conditions, incorporating all collision regimes, as well as the generation of satellite droplets. Due to the significant dependence of collision regimes on the geometric relationships between collision pairs, this article advocates the combined utilization of the composite collision model with the absolutely deterministic trajectory (ADT) model. Furthermore, the calculation method of the breakup length B_l that separates the primary and secondary breakup is modified for high-speed inter-impingement sprays. Extensive validation of binary droplet collisions and inter-impingement sprays are conducted. The comparative analysis reveals that the conventional B_l overestimates the penetration, the simplified collision model overestimates the SMD, while the present model agrees well with experimental results. Results show that a slight increase in global SMD and a significant reduction in velocity after the impingement point. Downstream of the impingement point, SMD at the ends exceeds that in the middle when the impinging distance S_z > B_l, contrasting with the situation when S_z < B_l and closer to the impingement point. Moreover, the occurrence of the coalescence regime is more frequent during secondary breakup than in primary breakup before the impingement point.