Experiment investigation on the effect of inlet circumferential non-uniformity on the stall behaviours in a transonic axial compressor with axisymmetric stall precursor

Abstract

The circumferential non-uniformity is becoming a high risk for jet engines in the future with cutting-edge intake design and undesirable inflow, like crosswind and highly turbulence. This leads to the requirement of a well-designed non-uniformity-tolerant compressor. In those research, the test rigs are mainly low-speed compressors whose stalls are triggered by small length scale disturbance of several blade pitches. The load achieves its maximum value at the trailing edge of the distortion, and spikes tend to emerge from this region. Thus, the circumferential non-uniformity usually deteriorates the stall margin. Unlike the spike, the partial surge shows axisymmetric features in both phase and amplitude since the embryonic period. It is interesting to find out the influence of circumferential uniformity of local disturbance at the hub on the propagation of partial surge. Thus, this paper implemented an experimental method on a transonic axial compressor with an axisymmetric stall precursor originating from the hub, partial surge. The non-uniformity patterns are varied by adjusting the distortion sector with different angles. The stall margin decreased with the sector angle of 90 degrees. In contrast, an unexpected result indicated that the stall margin increased with the sector angle of 120 degrees and 180 degrees, which were affected by two mechanisms, i.e., partial-surge-suppression and embryo-stall-cells-motivation. First, when the sector angle was 90 degrees and 120 degrees, the non-uniformity suppressed the partial surge and the formation of embryo rotating stall cells in the distorted region. With the development of partial surge, the embryo rotating stall cells in the undistorted region grew larger than those in the uniform case. Secondly, the partial surge inception disappeared when the sector angle was further enlarged to 180 degrees. The embryo rotating stall cells at the rotor tip emerged from the distorted region and died out in the undistorted region.