Simulation of Subcritical Vibrations of a Large Flexible Rotor with Varying Spherical Roller Bearing Clearance and Roundness Profiles

Emil Kurvinen,Jussi Sopanen,Raine Viitala,Tuhin Choudhury,Janne Heikkinen

doi:10.3390/machines8020028

Emil Kurvinen, Jussi Sopanen + Show 3 more

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https://doi.org/10.3390/machines8020028

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Abstract

In large rotor-bearing systems, the rolling element bearings act as a considerable source of subcritical vibration excitation. Simulation of such rotor bearing systems contains major sources of uncertainty contributing to the excitation, namely the roundness profile of the bearing inner ring and the clearance of the bearing. In the present study, a simulation approach was prepared to investigate carefully the effect of varying roundness profile and clearance on the subcritical vibration excitation. The FEM-based rotor-bearing system simulation model included a detailed description of the bearings and asymmetricity of the rotor. The simulation results were compared to measured responses for validation. The results suggest that the simulation model was able to capture the response of the rotor within a reasonable accuracy compared to the measured responses. The bearing clearance was observed to have a major effect on the subcritical resonance response amplitudes. In addition, the simulation model confirmed that the resonances of the 3rd and 4th harmonic vibration components in addition to the well-known 2nd harmonic resonance (half-critical resonance) can be significantly high and should thus be taken into account already in the design phase of large subcritical rotors.

Highlights

Large rotor-bearing systems are commonly used in the industry as a part of, e.g., electric motors and generators, turbines in renewable or fossil energy production, and paper, steel and non-ferrous metal manufacturing machinery
The results suggest that the simulation model output reacts clearly to the varying bearing inner ring roundness profile and the bearing clearance
The frequencies of the subcritical resonance peaks were captured accurately compared to a measurement case used for validating, suggesting that the simulation model is able to predict the critical speeds of the rotor system in horizontal and vertical directions

Summary

Introduction

Large rotor-bearing systems are commonly used in the industry as a part of, e.g., electric motors and generators, turbines in renewable or fossil energy production, and paper, steel and non-ferrous metal manufacturing machinery. The rolling element bearings act as a considerable source of excitation, which is seldom modeled accurately. The simulation of such rotor bearing systems contains major sources of uncertainty contributing to the excitation, namely the roundness profile of the bearing inner ring and the clearance of the bearing. The subcritical vibration excitation originating from the bearings causes response in the rotor system, leading occasionally to a subcritical resonance, when the excitation frequency and the natural frequency coincide. Elevated responses cause increased wear leading to an inclined need for maintenance. The increased vibration responses affect negatively on the end-product in industries, which use large rotors to manipulate the end-product with the rotor surface

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