Flywheel

A flywheel ( also referred to as a flywheel ) is a machine element. It is used, among other things, as an energy store kinetic energy ( energy of rotation and inertia ) by its rotational motion (rotation) with as little friction loss for use in case of need is stored. Moreover, flywheels to stabilize satellites or airplanes ( Gyro ) in toys and gyros are used.

A flywheel stores rotational energy:

With its moment of inertia with the angular velocity. The moment of inertia is determined by the structure of the flywheel, the larger the diameter and more massive flywheel is designed, the greater the moment of inertia. More details can be found at flywheel storage.

Applications

Energy storage

Applications are among others the reciprocating engines and steam engines. This can direct energy through the crankshaft to the output only in one work cycle. In the remaining cycles they need energy to complete the rotational motion and example to compress the combustion air. This energy is temporarily stored during the power stroke in the flywheel and then discharged again.

Simple little game vehicles do not require spring-loaded and driving alone, flywheel drive typically 3 m wide. The flywheel is composed of 1 to 3 stamped circular discs of from 2 to 4 cm in diameter, from 1 to 2 mm thick iron plate, pressed onto a perforated steel shaft which is mounted in sheet metal or plastic.

Through new, lighter and stronger materials that prevent the rupture at high speeds, keep the flywheels especially in the mobile space feeder to exploit the energy better. Thus, in the test trains of the project LIREX Deutsche Bahn is no longer converted the kinetic energy during braking exclusively into heat energy and released to the environment; instead, a driven flywheel cut off the driving energy and also temporarily stores the majority of the braking energy for further use. These so between stored energy can be used for example to power the onboard electronics or for restarting.

Stabilization

Except for energy storage, the flywheel is used for stabilization. Examples include gyros, gyro ship and satellites.

On the Norwegian island of Utsira an autonomous power supply system was constructed in 2004, with short-term by a flywheel storage (5 kWh) of electricity fluctuations are compensated. The inertias of all current in the power production (synchronous) turbines and generators have a meaning for stabilizing the grid frequency, so energy storage for the period of the order of a phase 1/50 second. Similar means the flywheel of electric motors for the smoothing of the torque output. By flywheels in large stationary machines locally mechanically rather only amounts of energy can be saved, which are depleted in pressing, forging, stamping, rolling and cutting operations in typically half a second to become an electric motor then replenished again in several seconds.

Torsional vibrations, torsional vibrations

In many dynamic processes on machines rotational irregularities occur on ( variations of speed). These are caused by intermittent torques, and can lead to torsional vibrations ( = torsional vibrations ). Flywheels reduce by their inertia, the torsional vibrations by absorbing energy during acceleration and take it to delay again. The nonuniformity is thus low. The disadvantage is that a large mass must be set in motion, which means extra weight in vehicles. Therefore, it is usually trying to keep the non-uniformity low to reduce itself to other types ( for example, in internal combustion engines with more cylinders ) or the torsional vibration ( vibration damping ).

A shock absorber consists of a flywheel and a damping element ( for example, oil and rubber), which transmits the vibration damping forces between the flywheel mass and damping component. The oscillating part " relies " so to speak, on a damping element on the current momentum quiet crowd. The damping member thereby converts kinetic energy into heat and thus cut off the vibrating component, the kinetic energy ( vibration energy).

For vibration damping (actually: amplitude reduction ) was first used a flywheel in the engine of the BMW motorcycle BMW R 69 S from 1960 to prevent the crankshaft breaks previously frequently occurring as a result of vibrations in the highly stressed engine. This caused a small flywheel on the side opposite the clutch side front of the engine for a lower rotational irregularity of the oscillatory system crankshaft flywheel clutch.

A similar special form of the flywheel in the car is the so-called dual-mass flywheel. Here, by the use of a primary - greatly reduced and a secondary flywheel mass with intermediate elastic element, the transmission of engine vibrations to the rest of the drive train ( for example, neutral gear rattle ). Primary and secondary flywheel mass are separated by a precisely tuned Feder-/Dämpfersystem. The transmission side flywheel (secondary flywheel mass ) is heavier than the motor side flywheel (primary flywheel mass ). The moment of inertia of the transmission is thereby increased, whereby the non-uniformity is greatly reduced, especially at low speeds. Torsionsschwingungserregung the force acting on the drive train is greatly reduced.

The balance of the mechanical clock is in interaction with the spiral spring is a torsional vibrator, whose period has a high degree of consistency ( isochronism ).

History

Even in ancient times the inertia was used in the form of rotating masses - for example in pottery wheels spinning wheels or simple flywheels were used to ensure a permanent, uninterrupted and smooth rotation. So around 6000 year old stone disks were found which were used in ancient China as a spindle.

The flywheel as a general machine element for storing kinetic energy is first found in the De diversibus artibus ( via various arts ) of Theophilus Presbyter (ca. 1070-1125 ), who used it in several of his machines. In the Middle Ages wooden flywheels already had speeds of around 100 beats per minute and were able to maintain the rotation part for several minutes. Later flywheels were used to compensate for the non-constant torque at the first steam engines and internal combustion engines.

In the area of ​​early helicopter development found flywheels their use. 1927, the rotors of the aircraft Zaschka rotation of chief engineer Engelbert Zaschka with a twin-rotor effective flywheel were necessarily rotationally connected in contrast to the known till then supporting and helicopters. This arrangement could be carried out with the engine safe vertical glide. Rediscovered they were in space, to ensure the energy supply in the Earth's shadow for a charge on solar power - here they were so used on a large scale for energy storage.

There are applications where flywheels are used as energy storage devices for electromechanical systems, such as converters. These consist of a rapidly rotating wheel, which converts a motor-generator, the electrical energy in its rotational movement or releases it. This system is able to very quickly provide large amounts of energy. So there were applications in sawmills to provide the necessary high initial amounts of current when starting the saw, or in connection with a wave power plant, to smooth the discontinuous energy release of the waves.

In the 1950s, both were in Basel, Switzerland and Austria called Gyrobusse in use. 1955 (then Belgian Congo ) operated a fleet of 12 Gyrobussen in Leopoldville. The flywheels were from the Maschinenfabrik Oerlikon and offered the possibility of regenerative braking. In the 90s buses were used with flywheels in Munich and Bremen. These buses based their power for the electric drive only from a flywheel ( memory contents 9.15 kWh). These buses were able to travel about 20 kilometers without any connection to the power grid. Then they had to each dock to the power supply to charge the flywheel back on breakpoints. This type of energy storage has not been successful at that time or because of technical shortcomings. Today's flywheels work with magnetic bearings and with almost no friction in vacuum housings.