A turbine–electric transmission system includes a

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

gas turbine A gas turbine, also called a combustion turbine, is a type of continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas generator or core) and are, in the directio ...

connected to an

electrical generator In electricity generation, a generator is a device that converts motive power ( mechanical energy) or fuel-based power ( chemical energy) into electric power for use in an external circuit. Sources of mechanical energy include steam turbines, ...

, creating

electricity Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as describe ...

that powers

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

traction motor A traction motor is an electric motor used for propulsion of a vehicle, such as locomotives, electric or hydrogen vehicles, elevators or electric multiple unit. Traction motors are used in electrically powered rail vehicles ( electric multip ...

s. No

clutch A clutch is a mechanical device that engages and disengages power transmission, especially from a drive shaft to a driven shaft. In the simplest application, clutches connect and disconnect two rotating shafts (drive shafts or line shafts). ...

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 w ...

s (rarely) and

warship A warship or combatant ship is a naval ship that is built and primarily intended for naval warfare. Usually they belong to the armed forces of a state. As well as being armed, warships are designed to withstand damage and are usually faster ...

s. 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), motor, a machine that converts various other forms of energy (chemical, electrical, fluid pressure/flow, etc) into energy ...

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, combustion chamber or flame holder. In a gas turbine engine, the ''combustor'' or combustion chamber is f ...

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 conta ...

s and using low-cost heavy oil bunker fuel. In the 1960s the idea re-emerged, using developments in light weight engines developed for helicopters and using lighter

kerosene Kerosene, paraffin, or lamp oil is a combustible hydrocarbon liquid which is derived from petroleum. It is widely used as a fuel in aviation as well as households. Its name derives from el, κηρός (''keros'') meaning " wax", and was re ...

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

railcar A railcar (not to be confused with a 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 coach (carriage, car), with a dri ...

s rather than separate locomotives.

Naval applications

Gas and steam turbines are most efficient at thousands of revolutions per minute. This is a major drawback because of the need for heavy gears, which drive the engine into one single duty, propulsion. Electric motors provide numerous applications including use of accessories besides that of propulsion. Permanent magnets and even motor generator sets will soon be included into Naval fleets that will have a larger variety of applications. Warships require the ability to cruise efficiently for long distances and also to have high power for intermittent bursts of speed. For that reason they use combined power systems that use an efficient prime mover, such as a

diesel engine The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is a so-cal ...

or a small gas turbine, for cruising and large gas turbines for high speed. Most of these use mechanical combination of power, through gearboxes and clutches, with systems such as CODOG (Combined Diesel or Gas) or COGAG (Combined Gas And Gas). Where electric transmissions are used, this is referred to as

integrated electric propulsion Integrated electric propulsion (IEP) or 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 electri ...

or IEP. A guided missile destroyer—for example the ''Zumwalt''-class—allows a gas driven turbine to run generators. This generator can produce electricity to move the ship and also operate a variety of its instruments and accessories. A lot of these electricity-generating turbines are being produced to include integrated electrical propulsion. Integrated electrical propulsion is when the engine strictly runs off of electricity, without the use of any gasoline, diesel, or fuel for that matter. The electric engine is more efficient due to only being electric and not gasoline based. It allows for less pollution and provides electricity to the naval ships instruments and applications. A lot of these electricity-generating turbines are being produced to include integrated electrical propulsion. A good example of one of these systems is the COGAL (combined gas and electric) system. An alternative approach is to use COGES, Combined Gas–Electric and Steam, to improve overall efficiency. A gas turbine-electric primary transmission is used, with a

heat-recovery boiler A heat recovery steam generator (''HRSG'') is an energy recovery 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 us ...

in the exhaust flow to generate steam and thus electricity via a secondary

steam turbine A steam turbine is a machine that extracts thermal energy from pressurized steam and uses it to do mechanical work on a rotating output shaft. Its modern manifestation was invented by Charles Parsons in 1884. Fabrication of a modern steam tu ...

. Electric driven propulsion allows for movement of the ship and provides power generation on-board of the ship. Heat lost by gas turbines is not practical because it is wasting energy as heat dissipates into the surroundings. The COGES system allows the heat to be captured and converted into steam for the generation of electricity. Unlike diesel and other heavy-fuel turbines, the COGES captures the left over heat and exhaust from the turbine and it reduces pollutants from escaping into the atmosphere. The COGES system allows for practical applications in cruise ships, for example the General Electric LM2500.

Adaptable gas turbine

"The Adaptable Gas Turbine", an article by Lee S. Langston on the many uses of gas turbines, was published in the ''American Scientist'' for July–August 2013.

References

{{Reflist Engine technology Gas turbine locomotives Gas turbine technology Marine propulsion Electric power

Naval applications

Adaptable gas turbine

See also

References