涡轮叶片内部冷却结构流动换热特性的数值研究

Numerical Study on Flow and Heat Transfer Characteristics of Internal Cooling Configurations of Turbine Vane

为了在限制冷气消耗量的情况下提高涡轮叶片综合冷却性能,在叶片冲击冷却的靶面引入不同的肋、凸起和凹坑,采用耦合传热进行叶片真实工况下的数值模拟,从不同方面分析了内部结构改变对内部换热性能、冲击孔和气膜孔流量系数的影响,最终得到受内外换热性能制约的叶片整体冷却性能,总结了叶片优化思路,可供指导叶片设计。本文得到了以下结论:冷却结构的引入可以阻碍横流的发展,增加冲击孔的流量系数,增强流场的扰动,从而强化内部换热,但会减小气膜孔的流量系数,恶化外部气膜冷却。内部换热的增强作用和外部气膜冷却削弱的综合作用使得叶片外壁温降低。通过比较,肋的作用强于凸起/凹坑,在肋间布置凸起/凹坑有利于进一步强化换热,扰流直肋+凹坑结构在冷气消耗量降低1.19%~1.81%的情况下,综合冷却效率提高了1.96%~4.09%,是最优结构。

Different types of ribs,protrusions and dimples were installed on the target surface with impingement cooling in order to improve the cooling performance of the turbine vane with limited influence on the coolant consumption.Conjugate heat transfer was adopted to analyze the influence of different turbulators on the internal heat transfer and discharge coefficient of jet and film holes in real working conditions.Then the overall cooling performance was obtained and optimization thoughts was summarized,which serves as guidance for the vane design.The results show that,the introduction of cooling structure can hinder the development of cross flow,increase the discharge coefficient of impingement holes and enhance the disturbance of the flow field,thus enhance the internal heat transfer,whereas,the external film cooling deteriorates for the reason of decreasing discharge coefficient of film holes.The combined effect of the enhancement of internal heat transfer and the weakening of external film cooling reduces the outer wall temperature of the vane.Through optimization,the effect of rib is stronger than that of the dimples or protrusions,when arranged them between the ribs help to further strengthen the heat transfer.The orthogonal rib+dimple structure mostly increases the overall cooling efficiency by 1.96%~4.09%while reducing the consumption of cooling air by 1.19%~1.81%,so is the optimal structure.