Influence of the Terminal Position of the Rotatable Ring of Controllable Speed Casing on the Flow Stability of a High-Load Compressor Stage

Controllable Speed Casing (CSC) is an innovative casing treatment technology designed to enhance the flow stability of compressors. This technology improves the compressor stage’s flow stability by exerting an additional circumferential force through a rotating ring on the rotor tip region flow. This paper investigates the effect of varying the terminal position of the rotating ring on the stability expansion capability of the CSC, with its initial position fixed at the rotor tip leading edge. The findings indicate that when the rotatable ring’s terminal position is set before the position where the tip leakage vortex begins to break down, the CSC primarily boosts compressor flow stability by suppressing the development of the tip leakage vortex and controlling the tip leakage flow. However, if the rotatable ring’s terminal position is set after the position where the tip leakage vortex begins to break down, the circumferential additional force range exerted by the CSC expands, further diminishing the original driving force of the tip leakage flow. This also causes the leakage vortex to undergo circumferential deflection, distancing it from the adjacent blade pressure surface, thereby enhancing the flow capacity of the compressor stage. As the terminal position of the rotatable ring moves continuously towards the rotor tip trailing edge, the stability expansion capability of the CSC is progressively improved. When the terminal position of the rotatable ring reaches the rotor trailing edge position, the CSC can increase the stable operating margin of the compressor stage by a maximum of 45.11%.