Study on Vibration of Turbo-Generator Shaft System Based on Spin Softening

A turbo-generator shaft model was established using finite element method, with which the effects of gyroscopic moment, stress stiffening and spin softening on lateral-torsional vibration mode of the shaft system were analyzed, and subsequently corresponding dynamic equations were deduced, while the torsional, lateral and coupled lateral-torsional vibration calculated with computer programs. Results show that the torsional vibration has a certain influence on safe operation of the system; there are several forms of coupled lateral-torsional vibration; the spin softening has significant influence on the first and second backward whirl mode; the stress stiffening further increases the frequency of the third forward whirl mode; the torsional vibration frequency and critical speed can be obtained in consideration of both the effects of stress stiffening and spin softening. In comparison with beam model, the solid element model has higher simulation degrees, resulting in more accurate calculation results.