Analysis of Axial Compressor Stall Inception Using Unsteady Casing Pressure Measurements

The unsteady flow in axial compressors during pre-stall and stall inception is often studied using circumferentially distributed pressure sensors. The present investigation utilized a transonic axial compressor facility to acquire time resolved casing static pressure measurements at an axial location upstream of the rotor leading edge. These measurements were processed using a variety of analysis techniques in order to provide insight into the fluid dynamics and compression system dynamics prior to and during stall inception. Specifically, visual inspection of the time series, spatial Fourier decomposition, traveling wave energy, and wavelet transform results will be described and compared for two representative stall inception events. Additionally, a new method was developed based on a windowed, two-point correlation function between adjacent sensors. The intent was to provide a scalar function that was nonzero only when disturbances that rotated around the compressor annulus in the direction of the rotor’s rotation were present. The results indicated that this method highlights many detailed features of the rotating disturbances with both spatial and temporal resolution during both pre-stall and stall inception.