Power machinery as drive units take a decisive role in the development of work machinery and means of transportation; be it by land, by sea or in the air, but also as electrical generators. They were and are major drivers of all technical, economic and social development.
They are here divided in the following categories:
- Muscle power
- Wind power
- Water power
- Steam engines
- Internal-combustion engines
- Steam turbines
Muscle power machines are called those units with which human or animal power is converted into work.
Initially, the men of the past used only the strength of their muscles. Activities that went beyond the powers of an individual, such as e.g. watering the fields and the transport of large loads were handled by pooling resources from several.
But more than 8000 years ago simple machine elements such as the lever and the wedge were created. As tools and auxiliary means they served to convert and guide physical quantities such as forces, torques and speeds. The combination of such machine elements led over 2000 years ago to the first muscle power machines as horse-gin and treadmills. Early as the third millennium BC, probably the first machine tool have been invented with muscle power: the fiddle bow, which served the drilling of holes and the ignition of fire.
Winds - flowing air masses - are caused by variable heating of the earth's surface. The flow of the wind is a clean, inexhaustible energy source, just like the flow of water. Their technical use however, is limited. Winds are erratic and unbalanced or develop into strong, no longer usable forces. Technically speaking, wind power machines - Windmills and wind turbines - are power converters, in which mechanical energy is generated. In windmills it is used to drive the mill facilities or pumping stations; in wind turbines to drive generators whose electrical energy is fed into the grid.
The first machines, working without muscle force, were water power (hydro) machines. This term summarizes water wheels, water turbines and as a special form of the water column machines.
The oldest water power machines, the water wheel, uses the weight and/or the flow energy of water, depending on building type, to produce a torque. Together with the windmill it was the main energy source before the industrial revolution. It was used to drive machines such as pumping stations, mills, boring mills, chain and wire rope hoists.
The most important water power machine type is nowadays the water turbine. Turbines run at much higher speeds than water wheels and thus provide a much higher performance.
Water column machines use specifically the hydrostatic pressure of a column of water and convert it into work, similar to the pressure of the steam in a steam engine. In the 19th and 20th centuries they were mostly used for pumping purposes.
New mechanical devices require more energy than the natural energy sources water and wind could cover, especially since they are not available everywhere. Only the steam engine - a result of the new scientific findings - provided the solution to both problems: It was now possible to provide mechanical energy almost anywhere and in almost any quantity for driving various machines, given that fuel transportation was provided.
The reciprocating steam engine was the first steam engine. Its invention in the 18th century if not triggered, but allowed the industrial revolution - that is, the transition from artisanal to industrial production. At the end of the 19th century the construction of the much more powerful steam turbine succeeded: Steam power could now be put directly into a rotary motion.
The energy source of all steam engines is heat that e.g. is released by burning coal, natural gas, refined oil or by nuclear fission.
Combustion engines are today and probably in the long run the most important heat engines. They cover an output range of about 100 W at small Model engines to nearly 100 MW in large marine diesel engines. They all operate on a similar principle: the fuel-air mixture must be incorporated into a cylinder to be compressed therein and then ignited. The inflammation causes an explosive combustion and thereby liberated heat is converted into mechanical energy on the bulk or on the crank mechanism respectively.
Although the piston engines of Otto and Diesel improved in the course of their approximately 130-year development history, they could not solve a fundamental problem: Due to the reciprocating motion of the piston, inertial forces arise that limit the efficiency. The rotary engine was developed by Felix Wankel in the 1950s to series production, where these disturbing forces do not occur.
Gas turbines are the latest type of power machines. They belong to the group of high-speed internal combustion engines and are operated with the gases of liquid fuels. Depending on the construction type gas turbines provide mechanical energy in the form of shaft power or thrust as the jet engines. In contrast to the steam turbines, the gas turbines operate at substantially lower pressures (max. 40 bar, steam turbine up to 280 bar), substantially higher temperatures (up to 1500°C, steam turbines less than 580°C) and much smaller number of stages (about 3 to 8 , steam turbines 20-40). Due to great technological advances, particularly by powerful compressors, but also through the development of new heat resistant materials and blade cooling, the gas turbine has advanced in application areas that were previously dominated by steam, diesel and electric motors. The gas turbine is distinguished from the steam turbine by a lower power to weight ratio and less space. It requires less maintenance and staff and requires especially lower investments (steam turbine about 2000 € / kW, gas turbine € 600 / kW).
Gas turbines are therefore used particularly in the following areas:
- as a turboshaft engine in power plants to generate electricity, to power rail and maritime vessels and within certain limits for road vehicles and helicopters;
- As a turbojet in almost all major traffic and transport machinery of civil aviation worldwide and in most military aircraft.
Kurator — Karl Allwang
Kurator — Thomas Röber