A turbine–electric transmission or turbine–electric powertrain system includes a

turboshaft A turboshaft engine is a form of gas turbine that is optimized to produce shaft horsepower rather than jet thrust. In concept, turboshaft engines are very similar to turbojets, with additional turbine expansion to extract heat energy from the ex ...

gas turbine A gas turbine or gas turbine engine is a type of Internal combustion engine#Continuous combustion, continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas gene ...

connected to an

electrical generator In electricity generation, a generator, also called an ''electric generator'', ''electrical generator'', and ''electromagnetic generator'' is an electromechanical device that converts mechanical energy to electrical energy for use in an extern ...

, creating

electricity Electricity is the set of physical phenomena associated with the presence and motion of matter possessing an electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described by Maxwel ...

that powers

electric Electricity is the set of physical phenomena associated with the presence and motion of matter possessing an electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described by Maxwel ...

traction motor A traction motor is an electric motor used for propulsion of a vehicle, such as locomotives, electric vehicle, electric or hydrogen vehicles, or electric multiple unit trains. Traction (engineering), Traction motors are used in electrically powe ...

s. No

clutch A clutch is a mechanical device that allows an output shaft to be disconnected from a rotating input shaft. The clutch's input shaft is typically attached to a motor, while the clutch's output shaft is connected to the mechanism that does th ...

is required. Turbine–electric transmissions are used to drive both

gas turbine locomotive A gas turbine locomotive is a type of railway locomotive in which the prime mover is a gas turbine. Several types of gas turbine locomotive have been developed, differing mainly in the means by which mechanical power is conveyed to the driving ...

s (rarely) and

warship A warship or combatant ship is a naval ship that is used for naval warfare. Usually they belong to the navy branch of the armed forces of a nation, though they have also been operated by individuals, cooperatives and corporations. As well as b ...

Locomotive applications

A handful of experimental locomotives from the 1930s and 1940s used gas turbines as

prime mover Prime mover may refer to: Philosophy *Unmoved mover, a concept in Aristotle's writings Engineering * Prime mover (engine or motor), a machine that converts various other forms of energy (chemical, electrical, fluid pressure/flow, etc.) into ener ...

s. These turbines were based on stationary practice, with single large reverse-flow

combustor A combustor is a component or area of a gas turbine, ramjet, or scramjet engine where combustion takes place. It is also known as a burner, burner can, combustion chamber or flame holder. In a gas turbine engine, the ''combustor'' or combustion ...

heat exchanger A heat exchanger is a system used to transfer heat between a source and a working fluid. Heat exchangers are used in both cooling and heating processes. The fluids may be separated by a solid wall to prevent mixing or they may be in direct contac ...

s and using low-cost heavy oil

bunker fuel Heavy fuel oil (HFO) is a category of fuel oils of a tar-like consistency. Also known as bunker fuel, or residual fuel oil, HFO is the result or remnant from the distillation and cracking process of petroleum. For this reason, HFO contains sev ...

. In the 1960s the idea re-emerged, using developments in light weight engines developed for helicopters and using lighter

kerosene Kerosene, or paraffin, is a combustibility, combustible hydrocarbon liquid which is derived from petroleum. It is widely used as a fuel in Aviation fuel, aviation as well as households. Its name derives from the Greek (''kērós'') meaning " ...

fuels. As these turbines were compact and lightweight, the vehicles were produced as

railcar A railcar (not to be confused with the generic term railroad car or railway car) is a self-propelled railway vehicle designed to transport passengers. The term "railcar" is usually used in reference to a train consisting of a single coa ...

s rather than separate locomotives.

Naval applications

Turboelectric powertrains are a subset of what is referred to in marine nomenclature as

integrated electric propulsion Integrated electric propulsion (IEP), full electric propulsion (FEP) or integrated full electric propulsion (IFEP) is an arrangement of marine propulsion systems such that gas turbines or diesel generators or both generate three-phase electricity ...

or IEP where generated power is converted into electricity before being used to power

propeller A propeller (often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon a working flu ...

s or

pump-jet A pump-jet, hydrojet, or water jet is a marine system that produces a jet of water for propulsion. The mechanical arrangement may be a ducted propeller (axial-flow pump), a centrifugal pump, or a mixed flow pump which is a combination of bot ...

s. Power can be provided by

diesel engine The diesel engine, named after the German engineer Rudolf Diesel, is an internal combustion engine in which Combustion, ignition of diesel fuel is caused by the elevated temperature of the air in the cylinder due to Mechanics, mechanical Compr ...

nuclear reactors A nuclear reactor is a device used to initiate and control a fission nuclear chain reaction. They are used for commercial electricity, marine propulsion, weapons production and research. Fissile nuclei (primarily uranium-235 or plutonium-2 ...

, or

s in which case it is called turboelectric propulsion. As gas and steam turbines are most efficient at thousands of revolutions per minute, when lower turbine speeds are needed in purely mechanical systems this necessitates extensive, and often heavy, reduction gearing. This is especially important on warship as they often require high electrical power independent of travel speed as well as the ability to perform efficient low speed cruise whilst maintaining the ability to perform less efficient sprints. For that reason warships often use combined power systems where an efficient prime mover, such as a

or a small gas turbine, is used for cruising while large gas turbines can be activated for high speed. When such a system uses gearboxes and clutches to accomplish a mechanical combination of power they are referred to as '' CODOG'' (''combined diesel or gas'') or ''

COGAG Combined gas turbine and gas turbine (COGAG) is a type of propulsion system for ships using two gas turbines connected to a single propeller shaft. A gearbox and clutches allow either of the turbines to drive the shaft or both of them combined. Ma ...

'' (''combined gas and gas'') respectively. This further increases the complexity and size of the mechanical power transmission systems. Integrated electric propulsion systems offer the ability to simplify such systems by combining power electrically instead of mechanically. By discarding mechanical power transmission these systems can improve efficiency by allowing each system to operate at its most efficient speed, improve reliability by cutting down on the number of components, and simplify ship layout as without the need for direct mechanical linkages to the propellers engines can be placed optimally. And while turboelectric systems are often heavy compared to simple mechanical systems, they are similar in weight to the complex mechanical systems use to link different engines whilst generating electrical power. An extension of the standard turboelectric propulsion scheme is COGES, or combined gas–electric and steam. In COGES a gas-turbine–electric primary transmission is used with a

heat-recovery boiler A heat recovery steam generator (HRSG) is a heat exchanger that recovers heat from a hot gas stream, such as a combustion turbine or other waste gas stream. It produces steam that can be used in a process (cogeneration) or used to drive a steam ...

in the exhaust flow to generate steam that drives a

steam turbine A steam turbine or steam turbine engine is a machine or heat engine that extracts thermal energy from pressurized steam and uses it to do mechanical work utilising a rotating output shaft. Its modern manifestation was invented by Sir Charles Par ...

that also generates electricity. Thus the system is thus even more efficient, as it converts what would normally be rejected as waste heat into useful power.

Locomotive applications

Naval applications

See also

References

Further reading