Calculation of Rotor´s Torsional Vibration Characteristics Based on Equivalent Diameter of Stiffness

In this paper, ANSYS finite element analysis software is used to simulate the twisted state of turbine integral rotor´s discs. For various stepped shaft structure, the formula of ¿-stiffness influence coefficient is fit by changing the geometric parameters of the equal-thickness disc, then equivalent diameter of stiffness is obtained. For the cone-shaped disc, the equivalent diameter of stiffness is calculated in advance according to equal-thickness disc, and then the diameter is revised by the formula. Taking an integral rotor of a 600 MW air-cooled steam turbine as an example, its first four orders of the torsional vibration frequencies are calculated by using the equivalent stiffness. The calculating results show that the approach proposed in this paper has such features as simple and higher accuracy.