axial compressor

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Turboshaft Jet Engine Overview

Part of a series of jet engine overviews

Turboshaft engines are a specific, yet widely employed form of the turbojet engine. This type of engine is most commonly used on helicopters and low airspeed airplanes, but it also sees use on some armored vehicles, ships.

Operation

Turboshaft engines are not actually jet engines, as they do not a use a jet of fluid to produce thrust, however they are worth mentioning because of their similarity to turbojet engines and their widespread use. Turboshaft engines are extremely similar to turbojet and turbofan engines. In a turboshaft engine, air is drawn into an intake and compressed by a series of axial flow compressors.

After it is compressed it is injected with fuel and passes into a combustion chamber where it is ignited. After ignition, the hot high energy gas moves rearward past a series of turbines. In a turbojet engine, the turbines would extract a small amount of energy from the gaseous stream, just enough to power the compressors at the fore of the engine. The turboshaft engine instead, extracts most, if not all of the energy from the passing air via the turbines. Whatever energy is not used to power the axial compressors is then used to rotate a shaft which provides mechanical energy.

Uses

Aircraft

Turboshaft engines are used in a variety of aerial application. When used on airplanes to drive props, they are known as turboprop engines.

Turboprop engines are used to achieve high fuel efficiency at low airspeeds. They are used in many commercial aircraft, and large low-airspeed military transports such as the C-130. Other notable applications include the Tupolev Tu-95 Bear, the Super Tucano and the infamous Republic XF-84H, a turboprop plane whose supersonic propellers produced shock waves powerful enough to knock a man over and noise loud enough to cause nausea and fainting among ground crews.

Additionally, turboshaft engines are commonly used to power helicopters. Helicopters commonly use multiple turboshaft engine both for increased power and for redundancy. Most large military and civilian helicopters use turboshaft engines in lieu of piston engines, due to their increased efficiency and reliability. Some notable turboshaft helicopters include the Sikorsky Black Hawk, the Bell Boeing Osprey, and the Mil V-12, the worlds largest helicopter.

Land

The turboshaft engine has seen use on a variety of land vehicles from cars to tanks. Examples of civilian ground application include the Fiat Turbina concept car, the Y2K Turbine Superbike motorcycle and the Howmet TX racecar, the only turbine powered racecar to ever win a race. Military ground application of turbine engines began in 1944 when the Nazis attempted to install a turbine engine in a Panther Tank. In 1954, the British installed a turbine in a Conqueror tank. The Swedish Stridsvagen 103, developed in the 1950s, employed a turboshaft engine as an Auxiliary Power Unit or APU. The American M1 and the Russian T-80 both mount turboshaft engines as their main source of propulsion. Turbine engines allow for more power and for greater fuel flexibility (the M1, for example, can burn gasoline, diesel, jet fuel or kerosene.) However, they are extremely inefficient and vulnerable to sand and dirt.

Sea

Maritime use of turboshaft engines is widespread. Turboshaft engines are commonly used on frigates, destroyers, corvettes and cutters. Among the countries that deploy turboshaft powered ships are the US, Denmark, Sweden, Britain and Finland. Naval turboshaft engines experience high levels of wear due to salt in the air and fuel, and lower grades of fuel.

PSA
As always, I appreciate hearing from yall. Let me know if you have any suggestions for future topics. Finals are coming up so I might be posting with slightly less frequency, but I will hopefully be able to put out pulse jets and rockets by the beginning of next year. I definitely want to do a post on torpedoes in the near future as well.