超临界压力下浮升力对航空煤油流动换热影响

通过RNG两方程模型结合增强壁面处理法的数值方法,研究了不同重力加速度下,浮升力对超临界压力下水平圆管内RP-3煤油流动换热的影响。建立、验证了计算模型;分析了RP-3煤油在拟临界区热物性变化,并对流动换热受浮升力影响判别准则的适用性进行了比较分析。结果表明:在拟临界温度附近煤油热物性的剧烈变化导致的浮升力作用下,水平圆管内产生较强的二次流动;二次流动减弱上壁对流换热,增强下壁对流换热,增大下壁摩擦阻力,减小上壁摩擦阻力,流动压力损失略有增大;随着重力加速度的增大,浮升力对换热和流动的影响更加显著;最后分析得出Protopopov准则能较好地描述浮升力对超临界压力煤油换热的影响规律和程度。

Buoyancy Influence on Flow and Heat Transfer Characteristics of Aviation Kerosene under Condition of Super Critical Pressure

This paper studies the influence of buoyancy on the heat transfer of the super critical pressure level under different gravitational acceleration by the method of enhanced wall treatment combined with the RNG two equations, establishes and verifies a calculation model, and analyzes the thermal physical property of RP-3 aviation kerosene within the pseudo critical temperature. The applicability of the discriminate criterion of convective heat transfer is also analyzed. The results indicate that the drastic change of the thermal properties of kerosene within the pseudo critical temperature will cause a stronger secondary flow in the horizontal circular tube because of the effect of buoyancy lift. In the secondary flow, the convective heat transfer of the upper wall decreases, the convective heat transfer of the lower wall enhances, the friction resistance of the lower wall increases and the friction resistance of the upper wall reduces, and at last the loss of flow pressure increases. With the acceleration of gravity increases, the influence of floating lift on heat transfer and flow is more significant. From simulation it can be seen that the laws of the influence of floating lift force on heat exchange of the super critical pressure coal oil can be described by Protopopov criterion.