微重力环境下层流扩散火焰实验和数值模拟

Experimental and Numerical Study of Laminar Diffusion Flames in Microgravity Environments

摘要

通过在中国空间站上进行的不同燃料流量和环境氧气体积分数(21%～30%)的层流射流扩散火焰实验,获得了火焰形貌、OH^*和 CH^*分布的实验数据,并结合数值模拟分析了不同工况下的火焰特性,以及环境氧浓度和燃料流量对火焰形态的作用机制．结果表明:随着燃料流量的逐渐增大,火焰依次呈现出“半球形-锥形-圆柱形”形态,火焰辐射分数过大是导致火焰顶部开口的主要原因,环境氧浓度的增加会促进火焰顶部的闭合．与常重力相比,微重力下火焰的流速更低,这导致了较高的火焰辐射和较低的火焰温度．

Abstract

Experiments on laminar jet diffusion flames were conducted aboard China's Space Station under varying fuel flow rates and ambient oxygen concentrations(21%—30%). Measurements of flame morphology and the distributions of OH^* and CH^* was obtained. By combining these data with numerical simulations, the flame characteristics under different operating conditions were analyzed, along with and the influencing mechanisms of ambient oxygen concentration and fuel flow rate on flame morphology. The results show that as the fuel flow rate gradually increases, the flame morphology undergoes a transition from hemispherical to conical and finally cylindrical. An excessively large flame radiation fraction is the primary reason for flame opening at the tip, while an increase in ambient oxygen concentration promotes the closure of the flame tip. Compared to normal gravity, flames in microgravity exhibit lower flow velocities, which leads to higher flame radiation and lower flame temperature.

关键词

微重力 / 扩散火焰 / 环境氧浓度 / 火焰形态 / 辐射分数

Key words

microgravity / diffusion flame / ambient oxygen concentration / flame morphology / radiation fraction

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基金资助

中国载人航天工程空间应用系统项目