High-speed centrifugal compressor instabilities during speed transients

Quasi-steady instability initiation studies do not model the actual operation of a compressor in an installed engine. Namely, gas turbine engine compressors are subject to transient operation. To provide needed high-speed centrifugal compressor instability initiation information addressing transient operation, an experimental study is performed to characterize the instability behavior of a high-speed centrifugal compressor during accelerations and decelerations at various throttle settings. Data are acquired from high response dynamic pressure transducers at the inlet and exit of the compressor. Analysis of these data shows that three distinct instabilities occur: Deep surge, mild surge, and rotating stall. The rotating stall is consistent with a nine-lobed stall pattern occurring in or near the diffuser. During accelerations, rotating stall occurs prior to surge initiation. During decelerations, all three instabilities are observed. Rotating stall is observed prior to and following both mild and deep surge.