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。
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.
[1] SHANMUGASUNDARAM V, RAMALINGAM M, DONOVAN B. Thermal management system with energy storage for an airborne laser power system application[C]//5th International Energy Conversion Engineering Conference and Exhibit (IECEC), 2007.
[2] 彭治雨, 石义雷, 龚红明, 等. 高超声速气动热预测技术及发展趋势[J]. 航空学报, 2015, 36(1):325-345. PENG Z Y, SHI Y L, GONG H M, et al. Hypersonic aeroheating prediction technique and its trend of development[J]. Acta Aeronautica et Astronautica Sinica, 2015, 36(1):325-345(in Chinese).
[3] 李翔, 傅波. 高超声速飞行器复杂结构热试验技术[J]. 航空学报, 2016, 37(S1):73-79. LI X, FU B. Thermal test technique of complex structure of hypersonic aircraft[J]. Acta Aeronautica et Astronautica Sinica, 2016, 37(S1):73-79(in Chinese).
[4] LEE S H, MUDAWAR I, HASAN MM. Thermal analysis of hybrid single-phase, two-phase and heat pump thermal control system (TCS) for future spacecraft[J]. Applied Thermal Engineering, 2016, 100:190-214.
[5] 侯增祺, 胡金刚. 航天器热控制技术[M]. 北京:中国科学技术出版社, 2007:129-293. HOU Z Q, HU J G. Thermal control technology for spacecraft[M]. Beijing:China Science and Technology Press, 2007:129-293(in Chinese).
[6] 汪新智, 马军军, 彭稳根, 等. 高超声速飞行器主动冷却系统优化设计[J]. 航空学报, 2014, 35(3):624-633. WANG X Z, MA J J, PENG W G, et al. Optimal design for active cooling system of hypersonic vehicle[J]. Acta Aeronautica et Astronautica Sinica, 2014, 35(3):624-633(in Chinese).
[7] WANG J X, LI Y Z, ZHANG H S, et al. Investigation of a spray cooling system with two nozzles for space application[J]. Applied Thermal Engineering, 2015, 89:115-124.
[8] SMAKULSKI P, PIETROWICZ S. A review of the capabilities of high heat flux removal by porous material, microchannels and spray cooling technologies[J]. Applied Thermal Engineering, 2016, 104:636-646.
[9] KIM J. Spray cooling heat transfer:The state of the art[J]. International Journal of Heat and Fluid Flow, 2007, 28(4):753-767.
[10] WANG J X, LI Y Z, YU X K, et al. Investigation of heat transfer mechanism of low environmental pressure large-space spray cooling for near-space flight systems[J]. International Journal of Heat and Mass Transfer, 2018, 119:496-507.
[11] 赵凯璇, 赵建福, 陈淑玲, 等. 液滴真空闪蒸/冻结过程的热动力学研究[J]. 中国空间科学学报, 2011, 31(1):57-62. ZHAO K X, ZHAO J F, CHEN S L, et al. Thermodynamic of flashing/freezing process of a droplet in vacuum[J]. Chinese Journal of Space Science, 2011, 31(1):57-62(in Chinese).
[12] WANG J X, LI Y Z, LI G C, et al. Investigation of a gravity-immune chip-level spray cooling for thermal protection of laser-based wireless power transmission system[J]. International Journal of Heat and Mass Transfer, 2017, 114:715-726.
[13] MUGELE R A, EVANS H D. Droplet size distribution in sprays[J]. Industrial & Engineering Chemistry, 1951, 43(6):1317-1324.
[14] SHER E, BAR-KOHANY T, RASHKOVAN A. Flash-boiling atomization[J]. Progress in Energy and Combustion Science, 2008, 34(4):417-439.
[15] ZENG Y, LEE C F F. An atomization model for flash-boiling sprays[J]. Combustion Science and Technology, 2001, 169(1):45-67.
[16] KAWANO D, ISHⅡ H, SUZUKI H,et al. Numerical study on flash-boiling spray of multicomponent fuel[J]. Heat Transfer-Asian Research, 2006, 35(5):369-385.
CJA