Microscopic Measurements of Liquid Rim Formation and Breakup inside a 2D Slit Nozzle under Flash Boiling Conditions

Abstract Flash boiling atomization has been considered a potential technique to enhance state-of-the-art atomization performance. It is usually believed that the phase change during flash boiling atomization can improve the disintegration of the bulk liquid. Many investigations have indicated that flash boiling atomization acts on the secondary breakup of the liquid droplets via micro-explosion mechanisms. However, recent investigations indicated that vapor bubbles inside the nozzle could directly affect the primary atomization of the bulk liquid. Therefore, this investigation focuses on the phase change process inside the nozzle via high-speed microscopic measurements. A two-dimensional slit nozzle with an expansion chamber was used in two dimensions to approximate the nozzle and the near field. Rim structures were observed in the measurements, and the transition from vapor bubbles to liquid rims was presented and analyzed.