Editor's Note: The following paper was presented at ASME Turbo Expo 2007: Power for Land, Sea and
Air May 14-17, 2007, Montreal Canada.

ABSTRACT Improved rotordynamic stability is desired by end users, and centrifugal compressor manufacturers are expected to meet, if not exceed, this expectation. Compressor manufacturers are required to design and build machines that are rotordynamically stable on the test stand and in the field. Confidence has been established in predicting the excitation forces from seals and bearings, but impeller aerodynamic excitation forces continue to be a challenge. While much attention is paid to impellers from an aerodynamic performance point of view, more efforts are needed from a rotordynamic standpoint. A high-pressure, re-injection centrifugal compressor is analyzed in order to predict rotordynamic stability using the best available resources for seals and bearings. Impeller shroud forces are predicted using the bulkflow model developed by Gupta and Childs [1]. Each impeller stage is analyzed and an attempt is made to improve the estimation of impeller aerodynamic excitation forces.
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