端壁运动对串列扩压叶栅气动性能与叶尖流动特性的影响

Numerical simulation methods were employed to quantitatively and qualitatively explore the impact of endwall movement on the aerodynamic performance and tip flow characteristics of tandem diffusion cascades from the perspectives of entropy production rate，blockage factor and kinetic energy component of leakage flow. The main conclusions were as follows: firstly，after the endwall movement，the overall loss of tandem cascade was reduced，the blockage in tip area was intensified，and the flow turning angle was decreased， while the lag angle was increased. In the range of −4° to 4° angle of incidence，the loss was reduced by more than 3.9%，and the blockage was increased by more than 30.4%. Secondly，the endwall movement increased the leakage flow of the front and rear blades by 12.3% and 9.9%，respectively，but decreased the gap jet flow. Furthermore，the endwall movement enlarged the ratio of the kinetic energy of the leakage flows of the front and rear blades，with the secondary flow kinetic energy becoming dominant. It also increased the loads on the front and rear blades and made the position of the maximum pressure difference move forward in advance. As a result， the morphology and development of the leakage vortices were changed and the formation of the jet vortices was suppressed. In addition，the endwall movement significantly weakened the endwall shear effect and the mixing effect of the gap jet，expanded the circumferential influence range of the leakage flow of the front blade and caused secondary leakage. This resulted in a significant reduction in the entropy production of the front blade，while the change in the entropy production of the rear blade was relatively small. Moreover，the blockages of both the front and rear blades were intensified. The impact of the endwall movement and the increase in the angle of incidence on the front blade of the tandem cascades was greater than that on the rear blade，which was mainly the result of the regulating effect of the gap jet.