Optimization Design of Flywheel Rotor Diameter Increase Based on Fixed Moment of Inertia

Flywheel energy storage systems (FESS) are widely favored in fields such as power systems, new energy, rail transit, UPS power supplies, etc. due to their high energy storage density, fast response speed, and long service life. Energy storage density and energy storage are two important indicators for evaluating the performance of energy storage flywheels. For FESS determined based on design indicators such as speed and energy storage, in order to improve the energy storage density of the system while meeting stress and deformation conditions, this paper proposes an optimization approach of “internal cutting and external supplementation” under fixed moment of inertia conditions. Firstly, two stress analysis formulas were analyzed, and the circular axis stress analysis expression was selected to estimate the stress of the rotor to be optimized; Secondly, mathematical models of “increasing diameter method” and “increasing height method” were established, and the effects of the two optimization models were compared. We have obtained a rotor optimization method that can significantly improve the energy storage density during flight. Compared with traditional solid equally thick rotors, the optimized rotor can increase energy storage density by 36.8 % and reduce mass by 26.9%, which helps to improve the energy storage capacity of flywheel rotors per unit mass and effectively enhance the application performance of flywheels in energy and transportation systems.