涡轮增压器喷嘴叶栅的流动特性

摘要

The clearance leakage flow has significant influence on the performances of variable nozzle turbine.In the other hand,the shock wave near the nozzle vane trailing edge can cause a forced response on the impeller,which can frequently lead to the impeller high-cycle fatigue failure.The interaction of the shock wave and the clearance leakage flow not only causes the loss of the flow,but also has significant influences on the reliability and lifetime of the tur bine.The schlieren experiment and numerical simulations were carried out to describe the formation and developing processes of the clearance leakage flow and the shock wave under different clearance and expansion ratios in a linear turbine nozzle.Results indicate that the expansion ratio and clearance configurations have significant influences on the shock wave and the leakage flow.And the influence range of the clearance flow on the shock wave is increased with the increase of the expansion ratio or the clearance ratio.Furthermore,the shock wave is squeezed and bent in the opposite direction of the main flow in the interaction region.Results also show that with the increase of clearance ratio,the influence range of the clearance leakage flow is extended while the shock wave intensity near mid-span is increased.%可调喷嘴涡轮喷嘴叶片端部的间隙泄漏流会对涡轮的性能产生较大的影响,同时喷嘴尾缘激波会造成转子叶片强迫响应,导致转子叶片出现高周疲劳失效现象.当喷嘴叶片间隙泄漏流与激波相互干涉时,不仅会造成流动损失加剧,同时也会显著影响转子叶片的可靠性以及使用寿命.通过纹影试验和数值仿真方法研究了喷嘴叶片平面叶栅在不同膨胀比和不同叶端间隙情况下的激波和间隙泄漏流流动特性.结果表明:膨胀比和间隙比对泄漏流和激波的影响较大,泄漏流对激波的影响范围随着膨胀比或间隙比的增加而增加.在泄漏流影响的范围内,受泄漏流对流场的推动作用,激波被挤压变形,激波形状向逆着气流流动的方向弯曲.随着叶端间隙比增加,泄漏流对激波的影响范围扩大,同时中间叶高位置的激波强度加强.