关键词: 高压涡轮;主流;封严流;封严回流涡;马蹄涡;Kelvin-Helmholtz不稳定现象

Abstract: In order to advance the understanding of the fundamental mechanism of the interaction between rim sealing flow and mainstream flow in a high-pressure turbine, the influence of sealing flow on the structure of the hub secondary flow and the interaction process between them were analyzed in detail. The numerical simulation method has been verified by experiment to guarantee the accuracy. The study shows that, on the one hand, the mainstream flow ingress occurred at the leading edge of the blade, which leads to a recirculation zone at the outer part of the rim seal and a reverse vortex below it. The position and size of these two vortices influences sealing effectiveness directly. On the other hand, the pressure side leg of horse-shoe vortex and the leakage slot vortex would get merged and develops into passage vortex in the blade passage later, which has the same sense of rotation in streamwise direction. The sealing configuration determines the outflow position and velocity direction of the leakage slot vortex, which affects the loss caused by sealing flow. At the same time, the Kelvin-Helmholtz instability phenomenon is observed to occur at the seal outlet, resulting from a certain circumferential velocity difference between the sealing flow and the mainstream flow with almost the same scale massflow at the interface of the seal outlet. With lots of low-energy boundary layer fluid ingested into the rim seal, the circumferential velocity of the sealing flow would decrease. The pressure side leg of horse-shoe vortex and the leakage slot vortex would subsequently get weakened, which contributes to reducing losses.

Key words: High pressure turbine;Mainstream flow;Sealing flow;Leakage slot vortex;Horse-shoe vortex;Kelvin-Helmholtz instability