Evaluation of the influence of the initial deflection curve shape of a two-span rotor with residual imbalance on its vibroactivity during rundown

Abstract

This work is devoted to the evaluation of the influence of the curve shape of the ineradicable initial deflection of a two-span rotor with the residual imbalance on the transition vibration amplitudes at low critical speeds under the rundown. The model corresponds to a high-pressure rotor–combined mid-low-pressure rotor (HPR–MLPR) system of a turbine unit. It is assumed that rotors are connected by a rigid coupling and installed on anisotropic elastic damper supports. It is supposed that the resulting deflection (bend) of this system is formed as a result of the fact that a high-pressure rotor acquires the initial deflection during the operation or because of abnormal launch conditions, the curve shape of which for a load-free rotor is known. The influence of the mutual arrangement of the residual imbalances of rotors and the imbalances caused by the resulting deflection of shafting in a system on the amplitudes of its transition vibration under the rundown of a turbine unit has been studied for two shapes of the initial rotor deflection curve that have the highest and lowest values of the shape parameter. The values of the initial rotor bending deflection and the residual imbalance of both rotors have been set equal to the maximum acceptable values for the operation of a turbine unit. Amplitude calculations have been performed for rotors of a K-300-23.5 Leningrad Mechanical plant (LMZ) turbine.