Topology Optimization of Flywheel Rotors Using SIMP Method: A Preliminary Study

Abstract

Flywheels are kinetic energy storage and retrieval devices as chemical batteries. However, the high charge and discharge rates, as well as the high cycling capability make flywheels attractive as compared to other energy storage devices. This research serves as a preliminary study that aims for developing a technique in designing a flywheel rotor based on the solid isotropic method with penalization (SIMP) method. Examples are presented to illustrate the optimum structural layouts obtained given various design objectives. For a static rotor, the objectives are maximizing the first torsional natural frequency, maximizing the moment of inertia and maximizing both of them, respectively. The problem is formulated using bound formulation and the method of moving asymptotes (MMA), a first-order optimization technique, was employed. Therefore the design sensitivity becomes a necessity. The so-called checkerboard problem in the topology optimization is avoided using the nodal design variable. Also, a threshold is used to reduce the numerical imperfection in each iteration. For the topology design of a rotating rotor, the centrifugal force induced in the high-speed rotation is considered. The objective is to maximize the rotor stiffness and is demonstrated in the last example. Results show clear topology layout of flywheel was obtained using proposed method.