Influence of compressor deterioration on engine dynamic behavior and transient stall-margin

This paper presents an experimental and analytical investigation of compres sor stability assessment during engine transient operation. A two-dimension al, 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 commer cial aircraft engines in both undeteriorated and deteriorated states. Un st eady measurements of pressure in these test engines during rapid accelerati ons revealed the growth of pre-stall disturbances, which rotate at rotor sp eed and at approximately half rotor speed. These disturbances are stronger in deteriorated engines. The model showed that the signal at shaft speed wa s the first compressible system mode, whose frequency is near shaft speed, excited by geometric nonuniformities. The computed behavior of this mode du ring throttle transients closely matched engine data. The signal increased in strength as stall was approached and as the engine deteriorated. This wo rk firmly establishes the connection between observed signals in the these engines and first principles stability models. [S0889-504X(00)01603-2].