Examination of rotating stall precursors in a high-speed axial compressor

The compressor of an aircraft gas turbine engine is one of the many components that have been studied in an effort to increase engine performance. Among the aspects of compressor operation studied is airflow through the compressor at off-design speeds and past the point of maximum compressor performance. One type of airflow that occurs in these conditions is rotating stall, an internal aerodynamic disturbance that limits the performance and operating life of a compressor. The precursors to this type of flow have been studied with the aim of developing techniques to predict and prevent the inception of rotating stall.;Previous studies of high-speed multi-stage compressors have shown both modal and spike-type stall inception at different compressor stages depending on stage matching. Other examinations of the Model 250 compressor have shown stall inception occurring at the first stage of the compressor. Similar results were observed in this study. Inspection of axially distributed pressure trace plots and stage characteristic maps demonstrated that rotating stall occurred at the first rotor stage. Circumferential pressure trace plots and spatial Fourier series phase plots revealed spike-type stall inception at low rotor speeds and modal stall inception at high speeds. Travelling wave energy analysis revealed the presence of a half rotor speed rotating wave at all rotor speeds. Detailed pre-stall signatures are presented in this thesis, and recommendations for follow-on experiments are made.;Keywords. Turbomachinery, Gas Turbines, Axial Compressor, Rotating Stall, Stall Precursors, Model 250.;To further the understanding of rotating stall inception, a test rig was constructed and instrumented with the axial stages of a Rolls-Royce/Allison Model 250-C20B small, high-speed axial compressor as the test article. The goal of this test rig was to evaluate the stalling characteristics of this compressor. A gasoline engine powered the compressor and airflow through the compressor was throttled with a pneumatic valve. Simultaneous static pressure measurements were taken with seven high-speed transducers arranged in two configurations over the operating range of the compressor. The compressor and stage characteristics were mapped with detailed pressure measurements taken between idle and surge operating conditions.