Multi-Objective Optimization of Heterogeneous Non-Uniform Flywheel

Abstract

Rapid prototyping (RP) technologies, such as Laser Engineered net Shaping (LENS), can be used to fabricate heterogeneous objects composed of more than one material, wherein spatially varied microscopic structural details produce continuously or discrete changing macroscopic properties. These heterogeneous or multi-material objects have enhanced functional performance. The application of heterogeneous objects has already been considered in many industries such as aerospace, automotive, electronics, and bio-medical. This study considers optimization problem of heterogeneous non-uniform flywheel. Storing energy in the form of mechanical kinetic energy in flywheels has been known for century, and is now being considered again due to improvements in material properties, power electronics, magnetic bearing technology, and analysis capabilities. Another driving factor for the rebirth of flywheels comes as result of a need for an alternative high performance energy storage system that is more efficient, environmentally friendly, and economic compared to traditional electrochemical batteries. As a result of research and development efforts, flywheel batteries have found acceptance in such applications as uninterruptible power supplies (UPS) and power conditioning units. A UPS can be effectively used to transition smoothly between a primary power source and a backup generator unit when necessary. Although generally more expensive than batteries in terms of first cost, the longer life, simpler maintenance, and smaller footprint of the flywheel systems makes them attractive battery alternatives. In addition, the transportation industry is considering flywheels coupled with internal combustion engines for hybrid electric vehicles (HEV). A gasoline engine can provide a steady supply of power while a flywheel can deliver extra power during acceleration, thus improving fuel economy. Furthermore, in spacecraft applications, the flywheel can serve as dual-functional component providing its rotational kinetic energy for satellite and space station attitude control as well as energy storage. The problem of finding an optimum shape for rotating discs is a classical one and has received considerable attention. Most of the research work is concentrated on the analytical solutions of rotating isotropic disks with simple cross-section geometries of uniform thickness or specifically variable thickness. Christensen and Wu (1977) reported the optimal design for composite material flywheels. They showed that many optimal shapes exist depending on the type of anisotropy of the material chosen. However, they also concluded that the only manufacturable design was that of equal radial and hoop stiffness. Genta and Bassani (1995) applied a GA for design of rotating disk. Eby et al. (1997,1999) studied the optimal design of flywheels using an injection island genetic algorithm scheme which incorporates a finite element scheme. Kress (2000) ∗Research Associate, AIAA Member, e-mail: vbg1975@clemson.edu †Graduate Student, e-mail: stiwari@clemson.edu ‡Professor, AIAA Member, e-mail: fgeorge@clemson.edu §Professor, e-mail: lopatin@krasline.ru Copyright c © 2007 by Vladimir Gantovnik. Published by the American Institute of Aeronautics and Astronautics, Inc. with permission.