燃气透平叶片树状分形内冷微通道的换热特性实验研究

Experimental Research on Heat Transfer Characteristics of Fractal Tree-Like Microchannel for Cooling Gas Turbine Blade

针对燃气透平叶片内部对流冷却特点,基于能量输运原理和分形几何理论生成了适用于叶片内部流体输运的分形网络,并设计了4级T型树状分形分叉微通道内冷结构。在建立的透平叶片内冷微通道对流冷却实验平台上,研究了通道进口雷诺数和加热功率对空气的努塞尔数、摩擦系数和强化换热因子的影响。结果表明:当雷诺数从194增大到19 400时,空气的平均努塞尔数增大148.5%,摩擦系数从0.78减小到0.009,最大强化换热因子在通道进口雷诺数为17 300时获得;加热功率从10 W增大到110 W时,平均努塞尔数降低35.9%,而摩擦系数几乎不变,加热功率为10 W时具有最佳的强化换热特性;分叉结构耦合共轭传热效应显著提高了第2、第3级微通道的当地努塞尔数;相比于前3级通道,末级通道的换热性能受雷诺数和加热功率的影响更为突出。

Following energy transport principle and fractal geometry theory,the fractal network fitted for the fluid flow transport in the blade internal passages was generated,and the fractal tree-like branching microchannel was designed as an internal cooling structure for turbine blade.In the experiment system of convection cooling for gas turbine internal microchannel,the effects of inlet Reynolds number and heating power on the Nusselt number,friction factor and enhancement heat transfer factor of air flow were investigated.The results reveal that as Reynolds number ranges from 194 to 19 400,the average Nusselt number of air increases by148.5%,the friction factor decreases from 0.78 to 0.009 and the maximum value of enhancement heat transfer is obtained at inlet Reynolds number=17 300.When the heating power ranges from10 Wto 110 W,the average Nusselt number reduces by about 35.9%,the friction factor changes slightly and the best enhancement heat transfer factor is observed at P=10 W.The local Nusselt numbers of the first and second level microchannel are greatly promoted by the branchingstructure in combination with the conjugation heat transfer effects.In comparison of the first three levels microchannels,the heat transfer performance of the last level microchannel is more obviously affected by Reynolds number and heating power.