Non-axisymmetric endwall profiling (NAEP) has been widely utilized in reducing secondary flow loss of turbines. However, most of NAEP are designed for the endwall of the entire blade passage, which presents challenges to the design of cooling structures of turbine endwall. This study aims to explore the local concave non-axisymmetric endwall profiling (LCNP) method with the same effect as whole passage NAEP, and reveal the influence mechanism of LCNP on endwall secondary flow structures of a highly-loaded turbine cascade. Under the condition that the maximum depth of LCNP is unchanged, the axial length effect and pitchwise location effect of LCNP are studied, the influence mechanism of LCNP on the secondary flow loss is analyzed, and the genetic algorithm is utilized to optimize LCNP at the optimal position. Results show that as the axial length of the LCNP increases and the pitchwise location gets closer to the suction surface, the intensity and range of the passage vortex are decreased, and the total pressure loss coefficient (loss coefficient) of the turbine cascade is decreased. When LCNP is 100% axial chord in length and at the position of 2/9 pitch, the loss coefficient is reduced by 5.49%. LCNP was optimized at the optimal position, and the optimal LCNP reduced the loss coefficient of the turbine cascade by 6.73%. After the local concave endwall profiling, the loading in the middle of the endwall of the turbine cascade is reduced, and the intensity of the passage vortex is effectively inhibited, which is the mechanism that the loss coefficient of the turbine cascade is reduced. However, after the local concave endwall profiling, the loading in the trailing of the endwall of the turbine cascade is increased, the transverse migration of the new boundary layer in the endwall is accelerated, and the loss coefficient of the near endwall is increased.

中文翻译：

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局部凹面非轴对称端壁剖面对高负荷涡轮机级联端壁二次流的影响


非轴对称端壁剖面 （NAEP） 已广泛用于减少涡轮机的二次流损失。然而，NAEP 大部分是针对整个叶片通道的端壁设计的，这给涡轮端壁的冷却结构设计带来了挑战。本研究旨在探索与全通道 NAEP 效果相同的局部凹面非轴对称端壁剖面 （LCNP） 方法，并揭示 LCNP 对高负荷涡轮机级联端壁二次流结构的影响机制。在 LCNP 最大深度不变的情况下，研究了 LCNP 的轴向长度效应和节距位置效应，分析了 LCNP 对二次流损失的影响机制，并利用遗传算法优化了最优位置的 LCNP。结果表明，随着LCNP轴向长度的增加和节距位置越来越接近吸气面，通道涡流的强度和范围减小，涡轮机级联的总压力损失系数（loss coefficient）减小。当 LCNP 长度为 100% 轴向弦杆且在 2/9 节距位置时，损耗系数降低了 5.49%。在最优位置对 LCNP 进行优化，最优 LCNP 使涡轮机级联损耗系数降低了 6.73%。局部凹形端壁剖面后，汽轮机级联端壁中部的载荷减小，通道涡流强度得到有效抑制，是汽轮机级联损耗系数降低的机理。 然而，在局部凹形端壁剖面之后，涡轮机级联端壁拖曳处的载荷增加，加速了端壁中新边界层的横向迁移，增加了近端壁的损耗系数。