Non-uniform stator loss reduction design strategy in a transonic axial-flow compressor stage under inflow distortion

Abstract

In a boundary layer ingesting (BLI) propulsion system, the fans/compressors continuously operate at a highly distorted inflow condition due to ingesting the boundary layers on the aircraft fuselage. The BLI inlet distortion induces non-uniform whirl and axial velocities at the rotor outlet, leading to a circumferential and radial non-uniform incidence distribution for the downstream stator. One of the main challenges for the compressor performance is a bad match between the rotor outflow and the stator inlet geometry, which would cause flow separations in blade passages. This paper has employed a non-uniform stator loss reduction design strategy to make a redistribution of stator incidence at the compressor off-design working point so as to reduce the potential separation loss and enhance the stage aerodynamic performance. Firstly, three-dimensional full-annulus unsteady numerical simulations are carried out to reveal the specific flow features of the non-uniform incidence distribution at the stator inlet. Then, according to the circumferential and radial non-uniform incidence distribution, a spatial non-uniform stator loss reduction design strategy based on adjusting the local inlet metal angles of the blade airfoil sections is utilized to make it a good match between the rotor outflow and the stator inlet geometry. Finally, the inner flow fields are analyzed to test the effectiveness of the non-uniform loss reduction design strategy. The computational results indicate that the high-incidence regions at the stator inlet are notably reduced and a more uniform incidence distribution has been achieved along both the circumferential and radial directions. Moreover, the non-uniform loss reduction design has successfully suppressed the flow separations at both the hub and tip regions. As a result, the stator has achieved an 18.2% reduction of the aerodynamic loss at the re-designed point and the stage efficiency has been improved by 0.83%. In the meanwhile, the re-designed stator has decreased the aerodynamic losses over the whole compressor operating range, and the re-designed stage has also achieved a higher efficiency than the baseline one while maintaining the total pressure ratio.