Abstract:

High-speed rotating flywheel rotors for energy storage are key devices of flywheel energy storage technology (FEST). Under normal operating conditions, the flywheel rotor runs stably in the radial gap between the rotor journal and the protective bearing to support the active magnetic suspension bearings at both ends. When the rotor is disturbed (based on several factors) and deviates from a stable trajectory, its journal may collide with the inner ring of the protective bearing, which may cause system instability. Therefore, it is necessary to study the disturbance energy dissipation and the rubbing behavior's influence on the system stability during the rubbing process and subsequently provide a basis for optimizing the system's contact parameters and system stability. In this paper, a set of dynamic equations describing the rubbing process of the flywheel system is established using the two-degrees-of-freedom spring-damping system model, which considers friction after simplification. The fourth-order Runge-Kutta direct integration method was used to numerically solve the system's rubbing behaviors under different contact parameters. The results showed that, within the range of actual contact stiffness, the stability of the rotor system always indicated the trend of first strengthening slowly and then decreasing rapidly with an increase in the friction coefficient. For a given contact stiffness, there was a matching optimal value range and a maximum allowable value for the friction coefficient. Once the friction coefficient exceeded this maximum value, the rubbing effect caused instability behaviors in the flywheel system, such as low-frequency continuous collision or rubbing against the entire circumference. As the contact stiffness increased, the allowable value range of the friction coefficient continued to become narrower. The damping coefficient of the system also restricted the contact parameters' influence on the rubbing process. The calculation results highlighted a feasible solution as enhancing the stability of the flywheel system by optimizing the material of the friction pair during rubbing, as well as the contact parameters between the rotor journal and the inner ring of the protective bearing.

Key words: FEST, rubbing, contact parameter, system stability