A fluid flywheel is a hydraulic device. In 1905 Dr. Hermann Föttinger, a chief engineer of the Vulkan Werke AG in Germany, invented the fluid flywheel. The fluid flywheel is now a fundamental part of modern car design and is used in other applications including diesel locomotives.
The Hydraulic Fluid
Fluid flywheels store kinetic energy in rotation. A fluid flywheel transmits rotation between shafts using acceleration and deceleration of a hydraulic fluid. Without hydraulic fluid a fluid flywheel would not work. The hydraulic fluid enhances the smooth running of a liquid flywheel. In simple liquid flywheels, such as those used in bicycles, the hydraulic fluid could be water.
A shell or housing must be part of a liquid flywheel system. An oil-tight seal around the shafts is also mandatory. The housing contains the fluid and the turbines. The housing must be very solid; flywheels can explode from overload. Safety valves reduce the need for heavy and expensive shells in such applications as the liquid flywheel components used in helicopters. Safety valves vent fluid to protect against explosion. The housing can be made from stamped or forged steel.
A turbine is a rotary engine actuated by a current of hydraulic fluid subject to pressure. The turbine is usually made with a series of curved vanes on a central rotating spindle. This fan-like component is connected to the input shaft. The turbine is also known as the pump or the impellor.
Runner is connected to the output shaft; it is also called the output turbine, runner or secondary wheel. This driving turbine is rotated by a mover, which can be an electric motor. The impellor's motion imparts both outwards linear and rotational motion to the fluid. The impellor and runner are an assembly of rotating blades. The hydraulic fluid comes out at high velocity from the pump, impinges the runner blades and leaves the runner at slow speed.