Impact of circumferential inlet distortion on different types of stall inceptions in a transonic compressor

The application of higher bypass ratios and lower pressure ratios significantly reduces specific fuel consumption with the development of turbofan engines. However, it also increases the risk of flow separation at the intake, leading to severe circumferential non-uniform inlet conditions. This study aimed to present an experimental investigation on instability evolutions of the compressor under circumferential non-uniform inlet conditions. Two stall inceptions regarding the different spatial scales and initial locations were selected to investigate this issue. The experiments were carried out on one tested rig, which the stall inceptions verified with the rotational speeds. At 65% design rotational speed (Ω), the stall inception was the spike, which was triggered by disturbances within serval pitches scale at the tip. Consequently, the spike-type stall inception was sensitive to circumferential distortion and led to a shrunk stall margin of the compressor. With the rotational speed increasing to 88%Ω, the stall inception switched to partial surge, which was induced by the flow blockage in the hub region around the full-annular. The results indicated that the partial surge was insusceptible to the circumferential distortion, which caused an extended stall margin with a lower stalled mass flow rate. In summary, the influence of distortion on the stability of the target compressor was found to be determined by the stall inception.