Analysis of mechanisms affecting the compressor rotor stability due to self-recirculating casing treatment with varying circumferential coverage ratios

In this paper, a single passage unsteady numerical simulation is carried out. Three different self-recirculating casing treatment structures with circumferential coverage ratios of 20%, 40% and 60% were designed. The calculation results show that as the circumferential coverage ratio increases, the stability enhancement ability of the self-recirculating casing also increases. Especially when the circumferential coverage ratio increases to 60%, the self-recirculating casing achieves the largest increase in stall margin, with an increase of 49.05%, but the decrease in the peak efficiency is 1.33%. An increase in the circumferential coverage ratio enhances the suction capacity of the self-recirculating casing. This enables it to better suppress the expansion of the leakage flow and reduce the degree of blockage within the passage. The self-recirculating casing can inhibit the occurrence of vortex breakdown in the tip passage. However, at the low flow rate point, it cannot effectively eliminate the interaction between the leakage streamlines. When the circumferential coverage ratio is relatively large, it can suppress the airflow separation phenomenon. The flow separation near the blade trailing edge and the mixing of the leakage flow within the tip passage are important reasons for the internal flow instability of the self-recirculating casing compressor.