Pressure and velocity fluctuations characteristics of the tip clearance flow in an axial compressor stage at the near-stall condition

Abstract

Pressure and velocity fluctuations characteristics of tip clearance flow in the rotor and stator of the axial compressor are studied by large eddy simulation (LES) at the near stall condition. In this paper, our work mainly emphasizes that the spatiotemporal evolution of complex flow structure, the pressure fluctuation, the velocity fluctuation of tip clearance flows, probability density function (PDF) of velocity and pressure fluctuations in the upstream and downstream of the rotor. Pressure fluctuations of the downstream rotor blade gradually decrease from the tip leading edge to the trailing edge. The motion law of leakage vortex may be related to the passage of the blade channel and the leakage vortexes mainly affect the region from the leading edge to the middle of the blade tip, but has little effect near the trailing edge. The frequency amplitude of suction surface is significantly higher than that of the pressure surface, and the frequency amplitude decreases along the flow direction. The passage shock has a major impact on the space-time correlation for pressure fluctuation. The intensity of space-time correlation of the downstream clearance flow of the rotor tip is similar to that of the upstream scraping vortex flow of the rotor tip. The strong space-time correlation for pressure fluctuation mainly concentrates in the separated flow on both sides of the rotor. Downstream flow has a better local temporal correlation than that of the upstream flow. The space-time correlation decreases more rapidly in velocity fluctuation. The space-time correlations of pressure and velocity fluctuations are vital for understanding the behaviors of unsteady flow characteristics of tip clearances at the near-stall conditions.