小流量下的转静系盘腔传热特征分析

Heat Transfer Characteristic of Rotor-Stator System With Small Radial Outflow

在一些情况下,燃机透平中用于供给轮缘密封的气体流量要小于自由盘的夹带流量。本文采用气热耦合数值计算的方法,并结合轮盘一维导热模型,分析了小流量下(λ_t<0.22)转静腔室传热特点及其中关键的影响因素。研究结果表明,对于小流量下的转静系盘腔系统,可以根据盘面传热系数随冷气量的变化定义一个临界流量λ_(t,c),当冷气流量大于λ_(t,c)时,盘面传热系数随冷气量增加缓慢增大,近似等于自由盘状态;当冷气量小于λ_(t,c)时,盘面传热系数随冷气量减小而迅速减小。文中给出了一种估算动盘面传热系数随冷气量变化的方法。文章同时分析了转速对于轮盘传热(λ_(t,c)<λ_t<λ_(t,fd))的影响,当转速对应的Ecb等于Ecb,c时,轮盘的体平均温度最低。

In some cases,the mass flow rate needed to prevent ingress through rim seals in turbine is smaller than that entrained by free disk.In order to obtain the heat transfer features of the rotor-stator system at such a small mass flow rate,a combined computational and theoretical study is carried out.It is found that the average Nusselt number（Nu_（av））on the rotor drops quickly down to zero with decreasing turbulent flow parameter（λ_t）whenλ_t is smaller thanλ_（t,c）（λ_（t,c）λ_（t,fd））,while Nu_（av）almost keeps constant whenλ_t is larger thanλ_（t,c）.A correlation between Nu_（av）andλ_t is therefore built up.It has been identified that the average temperature of the disk（whenλ_（t,c）λ_tλ_（t,fd）） reaches a minimum at a certain rotating speed which corresponds to Ec_（b,c）under different conditions.