Dynamics and mechanisms of spray plume interference under flash boiling conditions

Flash boiling spray, recognized as a promising atomization technique, has been proven to achieve superior atomization. However, under flash boiling conditions, plume interference is frequently observed, significantly altering spray morphology. The mechanisms of plume interference are not fully understood and are hard to predict. The purpose of this work is to elucidate the dynamics and mechanisms of plume interference under flash boiling conditions. To simplify the boundary conditions, a symmetrical two-hole injector was employed. Systematic investigations were conducted using three optical diagnostic techniques: planar Mie scattering imaging, particle image velocimetry (PIV), and structured laser illumination planar imaging-laser induced exciplex fluorescence/Mie scattering (SLIPI-LIEF/MIE). These methods captured velocity field and droplet size distributions under various superheat conditions. This study demonstrates that increasing fuel temperature and reducing ambient pressure influence plume expansion dynamics through distinct mechanisms. Quantitative analysis of the velocity field unveils that the plume interference process is fundamentally governed by momentum exchanges. This is characterized by a convergence of axial momentum, coupled with the offsetting of radial momentum. Three primary factors—plume expansion, the Venturi effect, and plume fluctuations—contribute to plume interference. Notably, it was discovered for the first time that plume fluctuations play a pivotal role in plume interactions.