Book Description

Two single-stage, transonic compressor designs were tested under various undistorted operating conditions to characterize the process leading up to aerodynamic stall. The rig case was instrumented with eight high-response static pressure transducers equally spaced around the annulus for stall development detection. High-response measurements were low-pass filtered and both spatially and temporally analyzed using discrete Fourier techniques. At all speeds tested for both designs, stall inception was characterized by growth of a small amplitude' rotating wave. The waves did not grow significantly until just prior to the instability, when exponential growth into fully-developed rotating stall occurred very rapidly, within 6-10 rotor revolutions. The amount of time the rotating waves could be detected prior to stall varied considerably with compressor operating condition and was largely dependent on the local slope of the compressor speedline characteristics. Stall warning times ranged from less than one-tenth of a second to more than two seconds for the same machine operated at different high speeds (above 60% design speed). The influence of compressibility effects are also discussed.