Hollow interference fitted multi-ring composite rotor of the superconducting attitude control and energy storage flywheel

The superconducting attitude control and energy storage flywheel is a kind of energy storage flywheel. With respect to this kind of flywheel, a rotor consisting of a hollow hub and three composite cylindrical rings in interference fitted state is presented to achieve high specific energy density. The hollow hub made of high strength steel 18Ni350 is used to change the distribution of centrifugal stress, reduce the maximum radial stress and to ensure the working gap of radial magnetic bearings and motor/generator is constant when the rotor rotates at a high rotary speed. Interference has been introduced between rings or ring and hub to avoid their delamination and eventually increase the maximum speed of the rotor. In order to find out the quantitative relationship among interference, tension force, radial pre-stress and so on, we analyzed the stress distribution of the rotor subjected to centrifugal loads, the initial stresses and displacements of the multi-rings rotor in interference fitted state by mathematical methods and finite element methods. Effects of these factors, such as interference between rings, thickness ratio of rings, different materials of rings and so on, are studied in detail to make clear how they affect the stress distribution of the interference fitted multi-ring composite rotor. The results of this study will give a useful hint for the design, test and manufacture of the composite rotor for the superconducting attitude control and energy storage flywheel.