Abstract

Background: When an unbalanced flexible rotor passes through its critical speed, it is very easy to result in great vibration amplitude, even the destruction of rotor and bearings. Therefore, it is significant for high-speed rotating machines to reduce the vibration amplitude of flexible rotor. Various patents have been discussed in this article.

Objective: The purpose of this study is to find out the amplitude reduction method and simulate the feasibility of flexible rotor passing through critical speed.

Methods: On the basis of the model of single disk rotor system with eccentric mass, a novel method is presented to reduce the vibration amplitude passing through critical speed by modulating the acceleration and stiffness simultaneously. Firstly, the amplitude characteristic of a flexible rotor with different acceleration and supporting stiffness was investigated. Then, the method of changing the stiffness during variable acceleration was carried out by numerical simulation based on Newmark algorithm. Furthermore, the strain energy of rotor and input power were also analyzed by using the method of simultaneous modulation of acceleration and stiffness.

Results: The simulation results revealed that the simultaneous modulation of acceleration and stiffness could reduce the vibration amplitude of rotor effectively, which was reduced by 44% and 13%, comparing with the single variable acceleration and the single variation of stiffness, respectively. Moreover, the variation tendency of total energy was similar to that of the rotor amplitude, which could be controlled at a very small level. The input power was mainly dependent on the acceleration, but had very little to do with the stiffness.

Conclusion: The method was suitable for the model of single disk rotor system, and it could also be applied to complex rotor systems, which was very useful for the security of high speed rotating machine.

Keywords: Acceleration, amplitude reduction, critical speed, flexible rotor, Newmark algorithm, stiffness.