Breakup characteristics of droplets induced by detonation waves under different diameters and Mach numbers

The growing interest of liquid-fueled detonation engines for the next-generation propulsion applications necessitates extensive understanding of the breakup physics of droplets induced by detonation waves. However, current knowledge of this topic still remains very limited. The breakup dynamics of water droplets induced by detonation waves under varying diameters and Mach numbers were experimentally investigated in the present study. High-speed schlieren imaging was used to capture the detailed breakup process of the droplets. Based on the experimentally observed flow instabilities, the detonation-induced droplet breakup can be classified into two stages dominated by the Kelvin-Helmholtz instability (KHI) and Rayleigh-Taylor instability (RTI), respectively. During the KHI-dominated phase, droplets of different Mach numbers and diameters exhibit nearly identical linear growth in non-dimensional cross-stream diameter with non-dimensional time. For the first time, significant differences in droplet acceleration between detonation waves and shock waves have been reported. The dimensionless droplet acceleration induced by shock waves is 11-17 times greater than that induced by detonation waves. Finally, theoretical analysis and experimental results show that decreasing droplet diameter and increasing Mach number can accelerate the instability development and shorten the absolute breakup time.