封严腔体出口流场的非定常数值研究

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%.