Effect of initial bending and residual eccentricity of a turbine rotor on its transient vibration amplitudes

Abstract

Based on the mathematical model of a single-span turbine rotor featuring initial bending and residual imbalance, an estimate is made for the vibration amplitudes at the control points of the rotor span at speeds near the lowest critical values on the rundown. Two versions of rotor mounting on anisotropic foil bearings are considered, which simulate bench tests and interaction with the rest of the shafting during operation of the turbine, and two imbalance versions, one with the imbalance concentrated at one point and the other with the imbalance distributed along the rotor span. We present an example of calculations of vibration amplitudes at the lowest critical frequencies during rundown of the high-pressure rotor of a Model K-300-23.5 steam turbine. The rotor here is assumed to have the largest permissible initial deflection and residual imbalance values based on the limits imposed on these values in the operation of turbo units [1]. The results are analyzed.