轮毂封严与高负荷涡轮端区流动的非定常相互作用

Unsteady Interaction Between Purge Flow and Endwall Flow in Highly-Loaded Turbine

关键词:  轮毂封严  非定常相互作用  上游尾迹  二次流  压力场

Key words:  Purge flow  Unsteady interaction  Upstream wake  Secondary flow  Pressure field

摘要:

为了研究轮毂封严出流与高负荷涡轮端区流动非定常作用的物理机制，对转/静叶片之间带有封严腔的高负荷单级涡轮的流场进行了三维非定常数值模拟。数值模拟结果表明，封严气流对上游导叶的影响表现为对端区流动的堵塞作用，这种堵塞作用减弱了吸力面的压力扰动和加速膨胀，减小了吸力面的分离损失。封严流量较小时，封严腔内存在尺度大、频率低的压力扰动，压力扰动的强度向主流传播的过程中不断减弱。这种沿周向分布不均匀的封严气流直接导致了转子叶片通道出口二次流分布的不均匀性。封严流量增大后，压力扰动的影响程度和二次流分布的不均程度均有所减弱。

Abstract:

Three-dimensional annulus time-accurate numerical simulation of endwall flow in highly-loaded turbine stage with inter-stage cavity has been carried out for the purpose of exploring the physical mechanisms of unsteady interaction between purge flow and mainstream near the hub. Simulation results show that upstream vane flow is blocked by the purge flow. Pressure disturbance and accelerating of upstream vane suction side is suppressed by this blockage effect and separation loss is also reduced. There is a large-scale， low-frequency pressure disturbance inside the cavity which is weakened during the propagation to the mainstream. This circumference non-uniform of purge flow directly leads to the non-uniformity of secondary flow at the exit of blade passage when the purge flow rate is relatively low. The pressure disturbance inside the cavity and the non-uniformity of secondary flow at the exit of blade passage are both weakened when the purge flow rate is increased.