TABLE OF CONTENTS A flywheel is an energy storage device. It absorbs mechanical energy by increasing its angular velocity and delivers energy by decreasing its angular velocity. Commonly, the flywheel is used to smooth the flow of energy between a power source and its load. If the load happens to be a punch press, the actual punching operation requires energy for only a fraction of its motion cycle. If the power source happens to be a two-cylinder four-cycle engine, the engine delivers energy during only about half of its motion cycle. More recent applications under investigation involve using a flywheel to absorb braking energy and deliver accelerating energy for an automobile and to act as energy-smoothing devices for electric utilities as well as solar and wind-power generating facilities. Electric railways have long used regenerative braking by feeding braking energy back into power lines, but newer and stronger materials now make the flywheel more feasible for such purposes.
Figure 21.1 is a mathematical representation of a flywheel. The flywheel, whose motion is measured by the angular coordinate ?, has a mass moment of inertia I. An input torque T i, corresponding to a coordinate ? i, will cause the flywheel speed to increase. A load or output torque T o, with corresponding coordinate ? o, will absorb energy from the flywheel and cause it to slow down. If the work into the system is considered positive and work output is negative, the equation of motion...
