The article describes an analytical model to calculate the stability of axial-flow compressor rotors. It illustrates how stability is related to the ratio of two times. The definitions of both times are obtained in a rational way for high-performance rotors subjected to non-small disturbances, and a theoretical stability margin coefficient is established. This coefficient determines the location of the stability line in the rotor map. The range of validity of this theoretical characterization is supported by several lemmas and theorems, whose proofs are given. These proofs also give physical meaning to the final analytical formula, connect the results with the surge and stall phenomena, and provide the widest area in the rotor map where normal operation can be sustained. The analytical results link the loading and flow coefficients, the tangential Mach number, and the basic rotor geometry. The stability model is validated with the actual data of transonic axial-compressor rotors. Errors lie in the 1—7 per cent range for cases accomplishing the premises of the theorems. Other empirical and numerical evidences that support the theory, as well as its limitations, are discussed. Due to its simplicity and robustness, the model can be easily used for multi-objective optimizations, preliminary performance calculations, and first estimations of axial solidity in new designs.
Theoretical characterization of stability in axial-flow compressor rotors
2009-02-01
18 pages
Aufsatz (Zeitschrift)
Elektronische Ressource
Englisch
performance , stability , surge , stall , rotor map , axial compressor
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