Influence of Compressor Deterioration on Engine Dynamic Behavior and Transient Stall-Margin

Abstract

This paper presents an experimental and analytical investigation of compressor stability assessment during engine transient operation. A two-dimensional, linear, compressible, state-space analysis of stall-inception (Feulner et al., 1996, ASME J. Turbomach., 118, pp. 1–10) was modified to account for engine transients and deterioration, with the latter modeled as increased tip-clearance and flow blockage. Experiments were performed on large commercial aircraft engines in both undeteriorated and deteriorated states. Unsteady measurements of pressure in these test engines during rapid accelerations revealed the growth of pre-stall disturbances, which rotate at rotor speed and at approximately half rotor speed. These disturbances are stronger in deteriorated engines. The model showed that the signal at shaft speed was the first compressible system mode, whose frequency is near shaft speed, excited by geometric nonuniformities. The computed behavior of this mode during throttle transients closely matched engine data. The signal increased in strength as stall was approached and as the engine deteriorated. This work firmly establishes the connection between observed signals in the these engines and first principles stability models. [S0889-504X(00)01603-2]