Experimental and mathematical study on jet atomization and flash evaporation characteristics of droplets in a depressurized environment

Abstract The effect of depressurized ambient condition on spray flash atomization process was of great importance. However, the process of droplet atomization and flash in depressurized environment was complex and coupled with a variety of physical and thermal behaviors. Thus, characteristics of jet flash atomization evaporation under a depressurized condition were mainly investigated in our present work. The experimental analysis and mathematical method were both adopted in order to consider the influence of factors (vacuum degree and superheat degree) on the spatial distribution of near-field region and the flash evaporation characteristics of far-field region. In particular, a laser particle sizer instrument was used to measure the droplets characteristics in the near-field region and a single sphere model of droplet was established to reveal features of flash evaporation process in the far-field region by the analysis of momentum transfer, heat transfer and mass transfer. The results showed that the droplets size distribution in the axial direction exhibited a fine uniform state, while it showed a disordered distribution in the radial direction of the near-field region analysis. In terms of the far-field region, velocity gradient still existed in far field according to the model analysis. The initial diameter had a more significant impact on drop rate of temperature reported at the initial temperature. Moreover, droplets with smaller diameter had a tendency to possess greater evaporation rate and this progress could be enhanced as decreasing the ambient pressure. The coupling process of jet atomization and flash evaporation could accelerate the temperature change process obviously and simultaneously thus promote the mass transfer.