An inter-impingement spray model considering binary droplet collision based on an open-source platform

Abstract

Collision and breakup are the two main processes of the inter-impingement spray within internal combustion engines. However, previous models have not comprehensively considered five collision regimes representing collision dynamics under high-pressure conditions, leading to deviations of Sauter mean diameter (SMD) and frequency of bouncing regime. Hence, this paper integrates an improved composite collision model for high-pressure conditions, incorporating all collision regimes and the generation of satellite droplets. Due to the significant dependence of collision regimes on the geometric relationships between collision pairs, this paper advocates the combined utilization of the composite collision model with the absolutely deterministic trajectory model. Furthermore, the calculation method of the breakup length Bl that separates the primary and secondary breakup is adapted to apply the hybrid KH-RT breakup model to inter-impingement sprays. Extensive validation of binary droplet collisions and inter-impingement sprays are conducted. The comparative analysis reveals that the conventional Bl 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 Sz > Bl, contrasting with the situation when Sz < Bl and closer to the impingement point. Moreover, the occurrence of the coalescence regime is more frequent during secondary break before the impingement point.