闪沸工况下过热度对水喷雾雾化效果的影响

针对空间及高空环境中航天器、空天飞行器热载荷不断提升而热耗散能力低下的严峻问题，研究水喷雾在低压闪沸工况（又称过热状态）下的雾化效果，雾化效果会直接影响到喷雾的冷却效果。首先，建立了单个液滴在低压环境下由于气泡生长、气动力造成的二次雾化（液滴破裂）模型以及沸腾传质传热模型。其次，通过拉格朗日法综合喷雾中所有液滴，利用MATLAB仿真计算不同过热度对喷雾雾化及液滴温度的影响。进而分析过热度对喷雾冷却效果的影响。计算结果表明，闪沸工况下雾化效果远优于过冷状态；液滴在闪沸工况下温度总会快速趋近饱和温度；过热度越高液滴的雾化效果越好，理论上能够带来更好的冷却效果。

Effect of overheat degree on water spray atomization under flash boiling condition

Heat load in spacecraft and aerospace shuttles, which generally work in space and upper atmosphere, is increasing, while the cooling ability of these vehicles is poor. This study researchs the atomization degree of water spray under the superheated condition, which can exert direct influence on the cooling ability of aerospace vehicles. A model for breakup of a single water droplet caused by bubble growth and aerodynamic force under the superheated condition is established, and a model for mass transfer and heat transfer is also proposed. The Lagrangian method is used to track and integrate all the droplets in the system. The effect of different degrees of superheat on spray atomization and droplet temperature is calculated using MATLAB. Then the degree of effect superheat degree on spray cooling is concluded. The calculation results indicate that the atomization degree under the flash boiling condition is much better than that under the sub-cooled condition. The droplet temperature will rapidly approach the boiling temperature under the superheated condition. The higher degree of superheat, the higher atomization degree, and thus the better spray cooling ability theoretically.