A New Vibration Criteria For High Speed Large Capacity Turbomachinery

Abstract

This paper presents the development and analysis of new critical speed criteria. The critical speed has been defined as the resonant speed of the rotor bearing system at which large response amplitudes can occur. However, recent observations of actual rotor vibrations show that the sensitivity of the critical speed is not so high for many types of turbomachinery. This new critical speed criteria, considering damping, Q-factor criteria, and model mass consideration, is developed based on operating experience, analysis and physical considerations. The procedure that is followed in the analysis is shown and the approximate modal analysis used is introduced. Typical low sensitive rotors are used as examples to illustrate the application of the analysis.