Comparison behavior of a large turbon machine vibration between unbalance and bent shaft

Abstract

Recently, large capacity steam turbines have come into wider use and have been designed to perform at even higher performance specifications. As we all know, it’s hard to maintain the concentricity of rotor-bearing system during operating, especially for multi-rotors within specified levels of vibration. Rotor vibration could be caused by many reasons. Mass unbalance and bent shaft are amongst the most frequently occurring of these reasons. Mass unbalance and bent shafts both give force excitation at a frequency coưesponding to once per revolution. Taking a LP B rotor of a 1000 MW use steam turbine as an example, this paper studies the lateral vibration of the LP B rotor based on finite element. Responses of mass unbalance and bent shaft are analyzed and compared.