Abstract
This paper uses finite element method to analyze the effect of brace stiffness and damping of an electromagnetic bearing on the critical speed of a flexible rotor for the rotor system of a high-speed turbo-expander. Result shows that eight orders of critical speed and eight modal shapes exist in the range of the calculation speed for the flexible rotor system of an electromagnetic bearing. The first six orders of vibrations are swing of rigid body, in which the critical speed increases with increase of the brace stiffness of the bearing. The seventh and eighth orders are first-order bending, in which the stiffness of the bearing has little influence on the critical speed of the rotor. Adjusting the stiffness of magnetic bearing can significantly change the corresponding critical speed of the rotor during rigid body swing. However, doing so has little influence on the critical speed of the first-order bending. The rotor system experimental test results of turbo-expander electromagnetic bearing show that adjusting the brace stiffness and damping of electromagnetic bearing through the control system can change the distribution of each order of the critical speed of the rotor system to maintain a steady working speed of 30000 r/min. Moreover, the movement tracks of the rotor axis center can be maintained within 6 μ m when external influences interfere with the rotor during operation.
Get full access to this article
View all access options for this article.
