Investigation of the resonant response of mistuned rotors

Yoon S Choi, Purdue University

Abstract

The resonant response of turbomachinery rotors, in particular IBRs, is a significant problem throughout the gas turbine industry because of mistuning and mechanical damping issues. To minimize or avoid these problems, experimentally validated design systems which predict the resonant response of mistuned rotors are required. Unfortunately, there is a dearth of appropriate mistuned IBR resonant response data for this validation. Also, adding friction dampers to IBRs to decrease large amplitude vibrations is only a very limited option. Hence techniques for control of IBR resonant response must be considered. This research addresses these issues through experiments in the Purdue Transonic Compressor, the Purdue 3-Stage Highly Loaded Compressor and the Purdue High Speed Centrifugal Compressor. The primary instrumentation for these experiments is a state-of-the-art NSMS, thereby enabling benchmark resonant response data to be acquired. The mistuning of the baseline IBR in the Purdue Transonic Compressor is measured, with the effects of steady loading on the IBR 2nd bending resonant response then experimentally quantified. A mistuning model is then utilized to select mistuning distributions which alter the resonant response of this IBR, with three mistuned IBR configurations subsequently selected. This intentional mistuning is accomplished by inserting tip-radial holes into selected blades. After measuring the mistuning of each IBR, the effects of steady loading on the 2nd bending resonant response of each IBR are experimentally investigated. The nominal loading data are then correlated with predictions from a model which includes aerodynamic damping. Vane clocking as a passive technique for control of resonant response is demonstrated through experiments in the Purdue 3-Stage Highly Loaded Compressor. The 1st torsion resonant response of IBR-2 and IBR-3 is investigated with the upstream and downstream vane rows clocked to six configurations and the effects of steady loading also addressed. Finally, the resonant response of a high-speed centrifugal compressor impeller is investigated in the Purdue High Speed Centrifugal Compressor. The forcing function to the impeller is the potential field from the downstream diffuser vanes.

Degree

Ph.D.

Advisors

Fleeter, Purdue University.

Subject Area

Mechanical engineering

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