封严腔体出口流场的非定常数值研究

Unsteady Numerical Investigation for Flow Fieldof Rim Seal Cavity Exit

关键词:  转静盘腔  腔体出口  非定常特性  燃气入侵  封严出流

Key words:  Rotor-stator cavity  Cavity exit  Unsteady characteristic  Hot gas ingress  Egress flow

摘要:

为了研究涡轮转静盘腔中轮缘封严气流的非定常特性对主流的影响机制，在不同封严流量下对封严腔体出口的流场进行了三维非定常数值模拟，细致分析了封严腔体出口流场的非定常特性。结果表明封严腔体出口附近流场呈现出强烈的三维非定常性。随着封严流量的增加，燃气入侵作用和转动壁面摩擦的泵吸效应不断减弱。在腔体内部从转动壁面到静止壁面燃气入侵的区域和强度都有所降低。腔体出口燃气入侵和封严出流的周向分布是由静子作用主导，转子转动造成燃气入侵和封严出流的位置发生周期性变化。同时，随着封严气流出现，封严腔体出口流场出现由静子作用主导到转子作用主导的转变。由于燃气入侵和封严出流造成腔体出口附近封严气流和主流之间强烈的流量交换，小封严流量下非定常波动强度较大并出现低频扰动。封严流量IR=0.0%时，低频脉动最大幅值所对应的频率为0.333倍转子通过频率，IR=0.5%时为0.467倍转子通过频率。封严流量增大后非定常波动强度逐渐降低，低频扰动逐渐减弱甚至消失。

Abstract:

In order to investigate the influence mechanism of unsteady characteristic of rim seal flow inside the turbine rotor-stator cavity on the mainstream， 3D unsteady numerical simulations were conducted for the flow field at rim seal cavity exit at different rim seal flow rate， and the unsteady characteristic of flow field at rim seal cavity exit was analyzed in detail. The time-resolved results show that the flow filed near rim seal cavity exit is strongly three-dimensional and unsteady. The ingress effects and pumping effects become weaker with the increase of rim seal flow rate. From the rotating wall to the stationary wall inside the cavity， the extent and strength of ingress are all reduced. The circumferential distribution of ingress and egress at cavity exit are mainly determined by the stator while their locations are changed periodically with the rotor. Besides， the dominated factor of cavity exit flow field is shifted from the stator to the rotor with the rim seal flow. Owing to the strong mass flow exchange between rim seal flow and mainstream caused by the ingress and egress near the cavity exit， the magnitude of unsteady fluctuation keeps high at low rim seal flow rate and consistently decreases with the increase of rim seal flow rate. Meanwhile， the low frequency fluctuation exists at low rim seal flow rate and gradually reduces and disappears at high rim seal flow rate. The corresponding frequencies for the peak amplitude of low frequency fluctuation are 0.333 times of blade passing frequency at injection rate IR=0.0% and 0.467 times of blade passing frequency at IR=0.5%.