涡轮盘腔燃气入侵及间隙剪切涡特性分析

Analysis of Gas Ingestion and Seal Shear Vortex Characteristics in Turbine Cavity

关键词:  涡轮盘腔  燃气入侵  间隙剪切涡  轮缘非定常效应  轮缘密封性能

Key words:  Turbine cavity  Gas ingestion  Seal shear vortex  Unsteady rim seal effect  Rim sealing performance

摘要:

为揭示转-静相互作用下的非定常燃气入侵机理及轮缘大尺度涡结构的产生机制，对带有轴向封严结构的1.5级高压涡轮装置进行三维非定常数值模拟，结合实验结果和盘腔内的经典流动理论对数值方法进行了验证。研究结果表明：转子前缘压力势场是造成旋转燃气入侵的主导因素。轮缘间隙内的间隙剪切涡是构成轮缘三维非定常流动的主要原因，其强度受到入侵燃气和出流冷气的径向速度、切向速度梯度以及上游边界层共同影响；间隙剪切涡周向方向的旋转有利于加快入侵燃气从动盘侧迁移至静盘侧，缩小动、静盘封严效率差异，当封严流量从0.5%降低到0.25%时，盘腔出口动静盘侧封严效率差值增大175%；间隙剪切涡与旋转泵效应的相互作用对于主流高温燃气在径向方向入侵盘腔具有抑制作用；由燃气入侵机制和间隙涡特性可以得出：文中盘腔出口设置在更靠近转子前缘位置对于提升轮缘密封性能具有正向意义。

Abstract:

In order to reveal the mechanism of unsteady gas ingestion and the generation mechanism of large-scale vortex structure on sealing clearance under stator-rotor interaction， the three-dimensional unsteady numerical simulation of a 1.5-stage high-pressure turbine with an axial sealing structure was carried out. Firstly， the numerical method was verified by combining the experimental results and the classical flow theory in the cavity. The results show that the pressure potential field at the leading edge of the rotor is the main cause of the rotary gas ingestion. The seal shear vortex in the rim clearance is the main reason for the three-dimensional unsteady flow of the turbine rim， and its strength is mainly affected by the radial velocity and tangential velocity gradient of the ingested gas and the purged flow， as well as the upstream boundary layer. The circumferential rotation of the seal shear vortex is conducive to accelerating the migration of the ingested gas from the rotor wall side to the stator wall side， reducing the difference of the sealing efficiency between the two wall sides. The sealing efficiency difference between the rotor and stator sides of the cavity outlet increases by 175% when the sealing flow rate is reduced from 0.5% to 0.25%.The interaction between the seal shear vortex and the rotary pump effect can restrain the mainstream high-temperature gas from ingesting the rotor cavity in the radial direction. Finally， it can be concluded that the axial position of the cavity outlet closer to the leading edge of the rotor has a positive significance for improving the sealing performance in this paper， according to the gas ingestion mechanism and the characteristics of the seal shear vortex.