Experimental validation and formation mechanism analysis of tip secondary vortex in a compressor rotor

Pressure variation on a compressor rotor casing wall was detected dynamically and wavelet method was used to analysis the dynamic static pressure signals detected on the rotor casing wall. The results show that there is a high-energy band near the tip secondary vortex frequency on the power spectrum map and the attenuation of the peak value along axial direction is consistent with the motion of tip secondary vortex. It indicates that the tip secondary vortex may exist in real flow field. Full-annulus unsteady simulation was conducted on the same rotor. According to the analysis of the full-annulus computation results, at near stall condition, there are accordant secondary vortexes in all the passages near the blade tip. Tip leakage flow from aft part of the tip gap interacts with the low-energy fluid caused by the breakdown of leakage vortex, which forms a tip secondary vortex in the blocking area. The tip secondary vortex affects the distribution of blade-loading near the blade tip which induces a cyclically self-excited flow phenomenon in the tip flow field.