Safety design method of lateral-torsional coupled vibration for high-speed flexible rotor

Aiming at the lateral-torsional coupled vibration of high-speed flexible rotor system under extreme load environment such as blades off， the dangerous evaluation parameter of lateral-torsional coupled zone and the design method of lateral-torsional coupled vibration safety were proposed. This method modifies the bending mode distribution through optimization of rotor structure or support stiffness， thereby adjusting the unstable speed zone of lateral-torsional coupled to avoid the occurrence of lateral-torsional coupled vibration of the rotor in the short period of time when the speed is relatively stable after the blade off. Through the variable stiffness and damping design of the support structure， the lateral-torsional coupled instability speed and dangerous range were reduced and contracted， and the dynamic response of the rotor during the deceleration process was controlled. The results showed that by optimizing the local support stiffness of the turbine and designing a variable stiffness buffer damping structure for the bearing inner ring， the amplification factor of the lateral-torsional coupled zone could be reduced by about 95%， and the amplitude of lateral-torsional vibration response could be reduced by about 64%~87%， which ensured the safety of the high-speed flexible rotor under the extreme load environments， and verified the effectiveness of the method proposed in this paper.