超临界压力下航空煤油RP-3在水平细圆管内对流换热特性实验研究

Experimental study of convective heat transfer of aviation kerosene RP-3 in horizontal tube under supercritical pressures

为探究超临界压力下碳氢燃料在水平管内的对流换热规律,文章针对超临界条件下航空煤油RP-3在水平细圆管内的对流换热,分析了热流密度、进口雷诺数及浮升力对对流换热的影响。研究表明:沿流动方向,管内表面传热系数随热流密度的增大先减小后增大;在低进口温度及低进口雷诺数情况下,管内换热均出现先恶化后强化的现象,而随着进口温度和雷诺数的增加,此现象消失;浮升力对换热的影响随热流密度的增加而增加;浮升力对下表面换热的加强使得入口效应的影响在下表面先于上表面结束;受浮升力影响,上下壁最大温差可达50 K;质量流速的增加会抑制浮升力对换热的影响;准则数Grq/Grth可以很好地反映浮升力的变化趋势。以上研究结果可为采用碳氢燃料作冷却介质的各类飞行器主动热防护技术方案提供技术支撑。

To better understand the convective heat transfer of the hydrocarbon fuel in horizontal tubes under supercritical pressures, an experimental study is carried out for the convective heat transfer of the aviation kerosene RP-3 in a horizontal miniature round tube. Under the working conditions of the air-kerosene heat exchanger, the aviation kerosene is heated up to the supercritical regime. The influences of the heat flux, the fluid inlet temperature, and the buoyancy on the heat transfer of the RP-3 are analyzed. It is found that the heat transfer coefficients decrease with the increase of the heat flux, and the buoyancy causes a large temperature difference of50 K between the top and the bottom surfaces of the test tube under high heat flux conditions, which can be predicted by the non-dimensional parameter Grq/Grth. The effects of the buoyancy on the heat transfer can be suppressed by increasing the mass flux. The results may provide a technological basis for the active thermal protection of the flight vehicles to be cooled by hydrocarbon fuels.