TAILORING THE FLASH-BOILING SPRAY STRUCTURE THROUGH THE CONTROL OF PLUME-TO-PLUME INTERACTION

Flash-boiling injection has significant advantages in enhancing fuel atomization and vaporization. For multi-hole injectors, flash boiling usually causes the spray to collapse under highly superheated conditions, and the collapsed spray might not match the geometry of the engine cylinder well since its structure changes dramatically from the designed one. Therefore, while benefiting from the performance of flash-boiling spray, it is also desired to tailor it into a favorable structure. Existing studies have pointed out that the flash-boiling induced plume-to-plume interaction is related to the change of spray structure, but the detailed process and mechanism are still unclear. In this work, two customized two-hole injectors were used to thoroughly study the plume interaction by using various optical diagnostic techniques. The initial interaction process near the injector tip was clearly observed. The characteristic behaviors of the interacting plumes and their effects on the subsequent plume merging were carefully analyzed. The spray momentum redistribution during the plume-to-plume interaction process plays a vital role in the plume merging of the two-hole spray. A comparative study was carried out using a more practical six-hole injector, which demonstrates that the momentum redistribution also dominates the collapsing of the multi-hole flash-boiling spray. Finally, based on the correlation between the intensity of plume-to-plume interaction and the spray behavior, the strategy to actively tailor the flash-boiling spray structure was proposed and demonstrated.