Abstract The multiple impingement jet system in a high-pressure turbine inner casing has been studied numerically. Four target surface configurations, i.e., smooth, cambered rib, square and round pin-fin are investigated, respectively. Three different boundary conditions (i.e., the maximum, medium and minimum scheme) are set based on the real turbine operating condition. The numerical validation reveals that the selected computational method can provide a good prediction of the impingement heat transfer on both the smooth and roughened surface structures. The results indicate that the roughness elements can significantly improve the heat transfer characteristics of the multiple impingement jet system. And the cambered rib surface displays the best enhancement of the impingement cooling effect. For the turbine inner casing with different target surfaces, local/average heat transfer parameters and the flow structure are obtained and compared under the same boundary condition, and such process has been repeated under three selected boundary conditions. All of the roughened surfaces show the outstanding cooling effect than the smooth surface. Especially, with the cambered rib configuration, the average temperature of the turbine inner casing domain can be decreased by 20 K, and the average Nusselt number can be increased by up to 62.6% than that on the smooth surface. The little temperature difference also demonstrates that the cambered rib configuration can promote the cooling uniformity and decrease the thermal stress in the turbine inner casing. Moreover, the analysis of the flow structure also illustrates that the cambered rib configuration can effectively reduce the crossflow and adjacent jet interaction, which promotes the turbulent mixing and augments the impingement heat transfer. The proposed structure can be used to improve the cooling effect of the turbine inner casing and is expected as the potential design reference for the turbine engine in the future.

中文翻译：

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高压汽轮机内壳光滑粗糙表面冲击传热数值研究

摘要 对高压汽轮机内壳内的多重冲击射流系统进行了数值研究。分别研究了四种目标表面配置，即光滑、弧形肋、方形和圆形针翅。三种不同的边界条件（即最大值、中值和最小值方案）是基于真实的汽轮机运行条件设置的。数值验证表明，所选的计算方法可以很好地预测光滑和粗糙表面结构的冲击传热。结果表明，粗糙度元素可以显着改善多重冲击射流系统的传热特性。并且弧形肋表面显示了对冲击冷却效果的最佳增强。对于不同目标面的涡轮机内壳，在相同的边界条件下获得局部/平均传热参数和流动结构并进行比较，并在三个选定的边界条件下重复该过程。所有粗糙的表面都表现出比光滑表面更出色的冷却效果。特别是采用弧形肋结构，涡轮内壳域的平均温度可降低20 K，平均努塞尔数比光滑表面提高62.6%。微小的温差也表明弧形肋结构可以促进冷却均匀性并降低涡轮机内壳的热应力。而且，流动结构的分析还表明，弧形肋结构可以有效地减少横流和相邻射流相互作用，促进湍流混合并增强冲击传热。所提出的结构可用于提高涡轮内壳的冷却效果，有望成为未来涡轮发动机的潜在设计参考。