平流层长航时气球上升过程超冷现象影响因素分析

平流层长航时气球超冷现象是指内部浮升气体温度低于外界大气温度,超冷会引起浮力损失进而阻碍气球上升过程。建立了长航时气球辐射、对流等热模型和上升过程动力学模型,仿真分析了初始净浮力、蒙皮热物性参数、放飞时间和放飞日期等因素对超冷现象的影响规律。研究结果表明,上升过程内外温差随初始净浮力增大而增大且变化显著,可见光吸收率和红外吸收率增大时,内外温差值总体上呈减小趋势;放飞时刻和放飞日期对超冷现象影响较小,但放飞时间不同,气球上升至设计驻空高度的时间差别较大。该结论可为平流层浮空器总体方案设计和放飞试验提供有益参考。

Analysis of Influential Factors to Supercooling Phenomenon during Ascent Stage of Stratospheric Long Duration Balloons

Supercooling phenomenon of stratospheric long duration balloons means that the temperature of helium gas inside is lower than that of atmosphere outside, this will cause loss of buoyancy and effect ascent process of the balloon as a result. Thermal model and vertical dynamic model of long duration balloons were established, influence regularity of some important factors on supercooling phenomenon is analyzed, including initial net buoyancy, radiation performance of the film, launch time and launch date. Simulation results show that temperature difference between helium gas and outside atmosphere enlarges remarkably along with the increase of initial net buoyancy, and temperature difference decrease when absorptivity for visible light and infrared radiation increases. Simulation results also show that influence of launch time and launch date on supercooling phenomenon is much smaller, while flight time from ground to designed altitude has great difference when launch time is different. All those can provide theoretical reference for conceptual design and flight test