Experimental and numerical investigation on rotating stall flow pattern in a counter-rotating axial compressor

Rotational stall is a common flow instability phenomenon in axial and centrifugal compressors. The experimental and numerical results of the three-dimensional flow field in a low-speed counter-rotating axial compressor operating in deep rotating stall are presented in this paper. The obtained results provide a detailed description of the flow inside and outside the stall cell. The circumferential flow of the reversed flow upstream and downstream is dominated, respectively, by the counter-rotating front and rear row rotors. The reverse flow downstream reenters the rear row rotor and the front rotor at higher blade heights, undergoing repeated work by the rotors. This leads to the formation of a high-pressure region at the leading edge of stall cell, which is essential for maintaining stall conditions upstream of rotors. Stalls primarily occur in the middle and tip regions with elevated pressure, while the downstream stall cell exhibits significant spreading from hub to tip with some circumferential bias.