Attempts on the Reduction of Leakage Flow Through the Stator Well in an Axial Compressor

Abstract

As performance improvements of compressors become more difficult to obtain, the optimization of stator well structure to control the reverse leakage flow is a more important research subject. Normally, the stator well can be considered as two rotor–stator cavities linked by the labyrinth seal. The flow with high tangential velocity and high total temperature exited from the stator well interacts with the main flow, which can affect the compressor aerodynamic performance. Based on the flow mechanisms in the basic stator well, four geometries were proposed and studied. For geometry a and geometry b, seal lips were attached to the rotor and stator inside downstream rim seal while impellers were positioned in the cavities for geometry c and geometry d. Leakage flow rates, tangential velocities, and pressure distributions in the cavities were analyzed using validated method of computational fluid dynamics. In the current study, where ω = 8000 rpm, π = 1.05–1.30, the maximum reductions of leakage flow rate for geometry a and geometry b are 7.9% and 15.9%, respectively, compared to the baseline model. In addition, the rotating impellers in the downstream cavity for geometry c contribute to a more significant pressure gradient along radial direction, reducing the leakage flow as much as 46%. Although the stationary impellers in the upstream cavity for geometry d appear to have little effect upon the leakage, these impellers can be used to adjust the tangential velocity of ejected flow from the stator well to the mainstream.