基于端壁造型优化的高压涡轮导向器流场分析

Analysis of Flow Structures in a High Pressure Turbine Stator Based on Optimized Endwalls

关键词:  流场结构  高压涡轮  非轴对称端壁  数值优化  流动损失  通道涡

Key words:  Flow structure  High pressure turbine  Non-axisymmetric endwall  Numerical optimization  Flow loss  Passage vortex

摘要:

为进一步提升非轴对称端壁造型技术在改善高压涡轮导向器叶栅通道内流场结构的能力，借助数值优化手段对一高压涡轮导向器上、下端壁进行了基于Bezier曲线的非轴对称端壁曲面造型优化，为揭示非轴对称端壁在改善高压涡轮导向器流场方面的流动机理，借助三维空间流线对比分析了优化前后导向器通道内端区的流场结构。优化结果表明:非轴对称端壁有效地降低了导向器出口的流动损失，总压损失降低了9.93%，而出口流量最大增幅不到0.13%，同时，出口气流角分布也更加均匀；流场分析表明:高压涡轮导向器中的通道涡主要是由端壁附面层内的低能流体组成，其强度主要是由端壁附面层横向迁移强度及马蹄涡压力面分支强度所决定；优化后得到的非轴对称端壁通过改变端区局部静压场分布，实现了对端壁附面层迁移的控制，从而达到改善端区流场结构、降低流动损失的目的。

Abstract:

To further enhance the ability of the non-axisymmetric endwalls profiling technique to improve the flow field structure in the high pressure turbine stator passage，numerical optimization methods based on Bezier curves were applied to design non-axisymmetric endwalls for the hub and shroud of a high pressure turbine stator. In order to investigate the flow mechanism of the improvement in flow field by non-axisymmetric endwalls，the flow structures in the passage of stator were compared pre and post optimization by using 3-D streamlines in the vicinity of endwalls. By compared with the results of aerodynamic performance，after using non-axisymmetric endwalls，the total pressure loss coefficient at the stator exit is markedly reduced by 9.93%，while the mass flow increased no more than 0.13%，at the same time，the distribution of exit flow yaw angle becomes more uniform. The analyses of flow field show that the passage vortex in the stator mainly consists of the low-energy fluid from the endwall boundary layer，and the strength of passage vortex is primarily determined by both the migration of endwall boundary layer and the strength of pressure side of horseshoe vortex. And by modifying local static pressure distribution，the non-axisymmetric endwalls accomplish to control the boundary layer movement and achieve the goals of improvement in flow structures and reduction of flow loss.