Atomization is often accompanied by phase change, which could significantly affect performance parameters such as the cooling efficiency and combustion efficiency of atomization. Nevertheless, the effect of phase change on jet atomization is rarely numerically studied due to the complexity of the coupling of the aerodynamics and the thermodynamics as well as the modelling difficulty caused by the cross-scale flow. In this study, comprehensive direct numerical simulations were carried out to evaluate the effects of phase change on the primary breakup and secondary atomization. Two methods dealing with phase-interface movement and mass transfer across the interface are built to meet the requirements of different modelling scales and Weber numbers. Simulation results indicate that phase change affects the flow behaviours and volume distribution of broken droplets in the primary breakup. In the secondary atomization, phase change leads to significantly different deforming morphologies of droplets with low Weber number and a more thorough breakup of droplets with high Weber number.

Atomization with cryogenic fluids is complicated due to the combined effects of both the mechanical breakup and thermodynamic flashing. However, the weight of the two effects on the atomization has not been determined yet. This paper proposes a hybrid mathematical model to evaluate the weight of the thermodynamic effect and aerodynamic effect. The entire process of jet spray breakup, including the primary breakup and secondary atomization, is described in the model. A linear stability analysis is carried out using the dispersion equations for the primary breakup. In the secondary atomization, the Taylor analogy breakup and bubble micro-explosion models are employed to study aerodynamic and thermodynamic effects on the atomization, respectively. The homogeneous nucleation is implemented in the bubble micro-explosion models. A criterion is obtained which can be evaluated to predict the dominant effect. Accordingly, the influence of factors such as ambient pressure and other physical parameters on the atomization process is analyzed. The results reveal that, under low ambient pressure, thermodynamic flashing is stronger. Besides, the mechanical action is restrained when the surface tension is increased.

One of China’s ambitious hydrogen strategies over the past few years has been to promote fuel cells. A number of hydrogen refueling stations (HRSs) are currently being built in China to refuel hydrogen-powered automobiles. In this context, it is crucial to assess the dangers of hydrogen leaking in HRSs. The present work simulated the liquid hydrogen (LH2) leakage with the goal of undertaking an extensive consequence evaluation of the LH2 leakage on an LH2 refueling station (LHRS). Furthermore, the utilization of an air curtain to prevent the diffusion of the LH2 leakage is proposed and the defending effect is studied accordingly. The results reveal that the Richardson number effectively explained the variation of plume morphology. Furthermore, different facilities have great influence on the gas cloud diffusion trajectory with the consideration of different leakage directions. The air curtain shows satisfactory prevention of the diffusion of the hydrogen plume. Studies show that with the increase in air volume (equivalent to wind speed) and the narrowing of the air curtain width (other factors remain unchanged), the maximum flammable distance of hydrogen was shortened.