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为了研究竖直管道内压力对超临界碳氢燃料换热恶化的影响,采用数值模拟的方法,选择RP-3的四组分替代模型和LS低雷诺数湍流模型,分别从浮升力和物性的角度深入分析压力作用机理,并对比了直径2mm与10mm管道内压力的作用效果。各工况下计算结果与实验数据基本吻合,证实了计算方法的准确性。数值模拟结果表明:不考虑裂解结焦的情况下,系统压力超过5MPa后,碳氢燃料物性随温度变化趋于平缓,密度及比热容在管内不均匀性得到改善,同时壁面附近比热容平均值增大,使得管内换热恶化得到有效缓解;而在直径10mm管道内,热流从壁面到主流区传播减慢,管壁与管道轴心处流体温差最大可达300K,物性不均匀现象加剧,增大压力对换热恶化的缓解效果被削弱。
In order to study the effect of pressure in the vertical pipe on the heat transfer deterioration of supercritical hydrocarbon fuel, four-component RP-3 and LS low Reynolds number turbulence models were selected by numerical simulation. Analyze the mechanism of pressure action in depth, and compare the effect of the pressure inside pipe with diameter of 2mm and 10mm. The calculated results under each condition are in good agreement with the experimental data, which confirms the accuracy of the calculation method. The numerical simulation results show that the physical property of hydrocarbon fuel tends to be gentle with temperature when the system pressure exceeds 5MPa, the inhomogeneity of density and specific heat capacity is improved in the tube, meanwhile the average specific heat capacity of wall near the wall increases, So that the deterioration of heat transfer in the tube can be effectively alleviated. However, in the 10mm diameter pipe, the propagation of heat flow from the wall to the mainstream decreases. The maximum temperature difference between the pipe wall and the pipe axis can reach 300K. Mitigating effect of deterioration of heat exchange is weakened.