A turboprop engine is a turbine engine that drives an aircraft propeller.
In its simplest form a turboprop consists of an intake, compressor, combustor, turbine, and a propelling nozzle.Air is drawn into the intake and compressed by the compressor. Fuel is then added to the compressed air in the combustor, where the fuel-air mixture then combusts. The hot combustion gases expand through the turbine. Some of the power generated by the turbine is used to drive the compressor. Thrust is obtained by the combusting gases, pushing toward a (vectored) surface in front of the expanding gas.
The rest is transmitted through the reduction gearing to the propeller. Further expansion of the gases occurs in the propelling nozzle, where the gases exhaust to atmospheric pressure. The propelling nozzle provides a relatively small proportion of the thrust generated by a turboprop.
In contrast to a turbojet, the engine's exhaust gases do not generally contain enough energy to create significant thrust, since almost all of the engine's power is used to drive the propeller.
Exhaust thrust in a turboprop is sacrificed in favour of shaft power, which is obtained by extracting additional power (up to that necessary to drive the compressor) from turbine expansion. Owing to the additional expansion in the turbine system, the residual energy in the exhaust jet is low.Consequently, the exhaust jet typically produces around or less than 10% of the total thrust. A higher proportion of the thrust comes from the propeller at low speeds and less at higher speeds.
Turboprops can have bypass ratios up to 50-100although the propulsion airflow is less clearly defined for propellers than for fans.
The propeller is coupled to the turbine through a reduction gear that converts the high RPM/low torque output to low RPM/high torque. The propeller itself is normally a constant-speed (variable pitch) propeller type similar to that used with larger aircraft reciprocating engines.[ citation needed ]
Unlike the small diameter fans used in turbofan jet engines, the propeller has a large diameter that lets it accelerate a large volume of air. This permits a lower airstream velocity for a given amount of thrust. As it is more efficient at low speeds to accelerate a large amount of air by a small degree than a small amount of air by a large degree,a low disc loading (thrust per disc area) increases the aircraft's energy efficiency, and this reduces the fuel use.
Propellers lose efficiency as aircraft speed increases, so turboprops are normally not used on high-speed aircraftabove 0.6-0.7 Mach. However, propfan engines, which are very similar to turboprop engines, can cruise at flight speeds approaching 0.75 Mach. To increase propeller efficiency across a wider range of airspeeds, turboprops are typically equipped with constant-speed (variable-pitch) propellers. The blades of a constant-speed propeller increase pitch as aircraft speed increases, allowing for a wider range airspeeds than a fixed-pitch propeller. Another benefit of this type of propeller is that it can also be used to generate negative thrust while decelerating on the runway. Additionally, in the event of an engine failure, the propeller can be feathered, thus minimizing the drag of the non-functioning propeller.
While most modern turbojet and turbofan engines use axial-flow compressors, turboprop engines usually contain at least one stage of centrifugal compressor which have the advantage of being simple and lightweight, at the expense of a streamlined shape.[ citation needed ]
While the power turbine may be integral with the gas generator section, many turboprops today feature a free power turbine on a separate coaxial shaft. This enables the propeller to rotate freely, independent of compressor speed. degrees, to produce two opposing jets. Apart from the above, there is very little difference between a turboprop and a turboshaft.Residual thrust on a turboshaft is avoided by further expansion in the turbine system and/or truncating and turning the exhaust 180
Alan Arnold Griffith had published a paper on turbine design in 1926. Subsequent work at the Royal Aircraft Establishment investigated axial turbine designs that could be used to supply power to a shaft and thence a propeller. From 1929, Frank Whittle began work on centrifugal turbine designs that would deliver pure jet thrust.
The world's first turboprop was designed by the Hungarian mechanical engineer György Jendrassik. kW) experimental gas turbine. The larger Jendrassik Cs-1, with a predicted output of 1,000 bhp, was produced and tested at the Ganz Works in Budapest between 1937 and 1941. It was of axial-flow design with 15 compressor and 7 turbine stages, annular combustion chamber and many other modern features. First run in 1940, combustion problems limited its output to 400 bhp. In 1941, the engine was abandoned due to war, and the factory was turned over to conventional engine production. The world's first turboprop engine that went into mass production[ specify ] was designed by a German engineer, Max Adolf Mueller, in 1942.Jendrassik published a turboprop idea in 1928, and on 12 March 1929 he patented his invention. In 1938, he built a small-scale (100 Hp; 74.6
The first mention of turboprop engines in the general public press was in the February 1944 issue of the British aviation publication Flight , which included a detailed cutaway drawing of what a possible future turboprop engine could look like. The drawing was very close to what the future Rolls-Royce Trent would look like. 7 ft 11 in (2.41 m) five-bladed propeller. Two Trents were fitted to Gloster Meteor EE227— the sole "Trent-Meteor" — which thus became the world's first turboprop-powered aircraft, albeit a test-bed not intended for production. It first flew on 20 September 1945. From their experience with the Trent, Rolls-Royce developed the Rolls-Royce Clyde, the first turboprop engine to be fully type certificated for military and civil use, and the Dart, which became one of the most reliable turboprop engines ever built. Dart production continued for more than fifty years. The Dart-powered Vickers Viscount was the first turboprop aircraft of any kind to go into production and sold in large numbers. It was also the first four-engined turboprop. Its first flight was on 16 July 1948. The world's first single engined turboprop aircraft was the Armstrong Siddeley Mamba-powered Boulton Paul Balliol, which first flew on 24 March 1948.The first British turboprop engine was the Rolls-Royce RB.50 Trent, a converted Derwent II fitted with reduction gear and a Rotol
The Soviet Union built on German World War II development by Junkers Motorenwerke, while BMW, Heinkel-Hirth and Daimler-Benz also developed and partially tested designs.[ citation needed ] While the Soviet Union had the technology to create the airframe for a jet-powered strategic bomber comparable to Boeing's B-52 Stratofortress, they instead produced the Tupolev Tu-95 Bear, powered with four Kuznetsov NK-12 turboprops, mated to eight contra-rotating propellers (two per nacelle) with supersonic tip speeds to achieve maximum cruise speeds in excess of 575 mph, faster than many of the first jet aircraft and comparable to jet cruising speeds for most missions. The Bear would serve as their most successful long-range combat and surveillance aircraft and symbol of Soviet power projection throughout the end of the 20th century. The USA would incorporate contra-rotating turboprop engines, such as the ill-fated twin-turbine Allison T40 — essentially a twinned up pair of Allison T38 turboprop engines driving contra-rotating propellers — into a series of experimental aircraft during the 1950s, with aircraft powered with the T40, like the Convair R3Y Tradewind flying boat never entering U.S. Navy service.
The first American turboprop engine was the General Electric XT31, first used in the experimental Consolidated Vultee XP-81. [ citation needed ]The XP-81 first flew in December 1945, the first aircraft to use a combination of turboprop and turbojet power. The technology of the Allison's earlier T38 design evolved into the Allison T56, with quartets of the T56s being used to power the Lockheed Electra airliner, its military maritime patrol derivative the P-3 Orion, and the widely produced C-130 Hercules military transport aircraft. One of the most produced turboprop engines used in civil aviation is the Pratt & Whitney Canada PT6 engine.
The first turbine-powered, shaft-driven helicopter was the Kaman K-225, a development of Charles Kaman's K-125 synchropter, which used a Boeing T50 turboshaft engine to power it on 11 December 1951.
Compared to turbofans, turboprops are most efficient at flight speeds below 725 km/h (450 mph; 390 knots) because the jet velocity of the propeller (and exhaust) is relatively low. Modern turboprop airliners operate at nearly the same speed as small regional jet airliners but burn two-thirds of the fuel per passenger. However, compared to a turbojet (which can fly at high altitude for enhanced speed and fuel efficiency) a propeller aircraft has a lower ceiling.
Compared to piston engines, their greater power-to-weight ratio (which allows for shorter takeoffs) and reliability can offset their higher initial cost, maintenance and fuel consumption. As jet fuel can be easier to obtain than avgas in remote areas, turboprop-powered aircraft like the Cessna Caravan and Quest Kodiak are used as bush airplanes.
Turboprop engines are generally used on small subsonic aircraft, but the Tupolev Tu-114 can reach 470 kn (870 km/h, 541 mph). Large military aircraft, like the Tupolev Tu-95, and civil aircraft, such as the Lockheed L-188 Electra, were also turboprop powered. The Airbus A400M is powered by four Europrop TP400 engines, which are the second most powerful turboprop engines ever produced, after the 11 MW (15,000 hp) Kuznetsov NK-12.
In 2017, the most widespread turboprop airliners in service were the ATR 42/72 (950 aircraft), Bombardier Q400 (506), De Havilland Canada Dash 8-100/200/300 (374), Beechcraft 1900 (328), de Havilland Canada DHC-6 Twin Otter (270), Saab 340 (225).Less widespread and older airliners include the BAe Jetstream 31, Embraer EMB 120 Brasilia, Fairchild Swearingen Metroliner, Dornier 328, Saab 2000, Xian MA60, MA600 and MA700, Fokker 27 and 50.
Turboprop business aircraft include the Piper Meridian, Socata TBM, Pilatus PC-12, Piaggio P.180 Avanti, Beechcraft King Air and Super King Air. In April 2017, there were 14,311 business turboprops in the worldwide fleet.
Between 2012 and 2016, the ATSB observed 417 events with turboprop aircraft, 83 per year, over 1.4 million flight hours: 2.2 per 10,000 hours. Three were “high risk” involving engine malfunction and unplanned landing in single‑engine Cessna 208 Caravans, four “medium risk” and 96% “low risk”. Two occurrences resulted in minor injuries due to engine malfunction and terrain collision in agricultural aircraft and five accidents involved aerial work: four in agriculture and one in an air ambulance.
Jane's All the World's Aircraft . 2005–2006.
|Manufacturer||Country||Designation||Dry weight (kg)||Takeoff rating (kW)||Application|
|DEMC||WJ5E||720||2130||Harbin SH-5, Xi'an Y-7|
|Europrop International||TP400-D6||1800||8203||Airbus A400M|
|General Electric||CT7-9||365||1447||CASA/IPTN CN-235, Let L-610, Saab 340, Sukhoi Su-80|
|General Electric||H80 Series||200||550 - 625||Thrush Model 510, Let 410NG, Let L-410 Turbolet UVP-E, CAIGA Primus 150, Nextant G90XT|
|General Electric||T64-P4D||538||2535||Aeritalia G.222, de Havilland Canada DHC-5 Buffalo, Kawasaki P-2J|
|Honeywell||TPE331 Series||150 - 275||478 - 1650||Aero/Rockwell Turbo Commander 680/690/840/960/1000, Antonov An-38, Ayres Thrush, BAe Jetstream 31/32, BAe Jetstream 41, CASA C-212 Aviocar, Cessna 441 Conquest II, Dornier Do 228, Fairchild Swearingen Metroliner, General Atomics MQ-9 Reaper, Grum Ge man, Mitsubishi MU-2, North American Rockwell OV-10 Bronco, Piper PA-42 Cheyenne, RUAG Do 228NG, Short SC.7 Skyvan, Short Tucano, Swearingen Merlin, Fairchild Swearingen Metroliner|
|Honeywell||LTP 101-700||147||522||Air Tractor AT-302, Piaggio P.166|
|KKBM||NK-12MV||1900||11033||Antonov An-22, Tupolev Tu-95, Tupolev Tu-114|
|Klimov||TV7-117S||530||2100||Ilyushin Il-112, Ilyushin Il-114|
|Progress||AI20M||1040||2940||Antonov An-12, Antonov An-32, Ilyushin Il-18|
|Progress||AI24T||600||1880||Antonov An-24, Antonov An-26, Antonov An-30|
|LHTEC||LHTEC T800||517||2013||AgustaWestland Super Lynx 300 (CTS800-4N), AgustaWestland AW159 Lynx Wildcat (CTS800-4N), Ayres LM200 Loadmaster (LHTEC CTP800-4T) (aircraft not built), Sikorsky X2 (T800-LHT-801), TAI/AgustaWestland T-129 (CTS800-4A)|
|OMKB||TVD-20||240||1081||Antonov An-3, Antonov An-38|
|Pratt & Whitney Canada||PT-6 Series||149 - 260||430 - 1500||Air Tractor AT-502, Air Tractor AT-602, Air Tractor AT-802, Beechcraft Model 99, Beechcraft King Air, Beechcraft Super King Air, Beechcraft 1900, Beechcraft T-6 Texan II, Cessna 208 Caravan, Cessna 425 Corsair/Conquest I, de Havilland Canada DHC-6 Twin Otter, Harbin Y-12, Embraer EMB 110 Bandeirante, Let L-410 Turbolet, Piaggio P.180 Avanti, Pilatus PC-6 Porter, Pilatus PC-12, Piper PA-42 Cheyenne, Piper PA-46-500TP Meridian, Shorts 360, Daher TBM 700, Daher TBM 850, Daher TBM 900, Embraer EMB 314 Super Tucano|
|Pratt & Whitney Canada||PW120||418||1491||ATR 42-300/320|
|Pratt & Whitney Canada||PW121||425||1603||ATR 42-300/320, Bombardier Dash 8 Q100|
|Pratt & Whitney Canada||PW123 C/D||450||1603||Bombardier Dash 8 Q300|
|Pratt & Whitney Canada||PW126 C/D||450||1950||BAe ATP|
|Pratt & Whitney Canada||PW127||481||2051||ATR 72|
|Pratt & Whitney Canada||PW150A||717||3781||Bombardier Dash 8 Q400|
|Rolls-Royce||Dart Mk 536||569||1700||Avro 748, Fokker F27, Vickers Viscount|
|Rolls-Royce||Tyne 21||569||4500||Aeritalia G.222, Breguet Atlantic, Transall C-160|
|Rolls-Royce||250-B17||88.4||313||Fuji T-7, Britten-Norman Turbine Islander, O&N Cessna 210, Soloy Cessna 206, Propjet Bonanza|
|Rolls-Royce||Allison T56||828 - 880||3424 - 3910||P-3 Orion, E-2 Hawkeye, C-2 Greyhound, C-130 Hercules|
|Rolls-Royce||AE2100D2, D3||702||3424||Alenia C-27J Spartan, Lockheed Martin C-130J Super Hercules|
|Turbomeca||Arrius 1D||111||313||Socata TB 31 Omega|
|Walter||M601 Series||200||560||Let L-410 Turbolet, Aerocomp Comp Air 10 XL, Aerocomp Comp Air 7, Ayres Thrush, Dornier Do 28, Lancair Propjet, Let Z-37T, Let L-420, Myasishchev M-101T, PAC FU-24 Fletcher, Progress Rysachok, PZL-106 Kruk, PZL-130 Orlik, SM-92T Turbo Finist|
A jet engine is a type of reaction engine discharging a fast-moving jet that generates thrust by jet propulsion. While this broad definition can include rocket, water jet, and hybrid propulsion, the term "jet engine" typically refers to an airbreathing jet engine such as a turbojet, turbofan, ramjet, or pulse jet. In general, jet engines are combustion engines.
The turbofan or fanjet is a type of airbreathing jet engine that is widely used in aircraft propulsion. The word "turbofan" is a portmanteau of "turbine" and "fan": the turbo portion refers to a gas turbine engine which achieves mechanical energy from combustion, and the fan, a ducted fan that uses the mechanical energy from the gas turbine to accelerate air rearwards. Thus, whereas all the air taken in by a turbojet passes through the turbine, in a turbofan some of that air bypasses the turbine. A turbofan thus can be thought of as a turbojet being used to drive a ducted fan, with both of these contributing to the thrust.
An aircraft engine is a component of the propulsion system for an aircraft that generates mechanical power. Aircraft engines are almost always either lightweight piston engines or gas turbines, except for small multicopter UAVs which are almost always electric aircraft.
A jet aircraft is an aircraft propelled by jet engines.
The turbojet is an airbreathing jet engine, typically used in aircraft. It consists of a gas turbine with a propelling nozzle. The gas turbine has an air inlet, a compressor, a combustion chamber, and a turbine. The compressed air from the compressor is heated by the fuel in the combustion chamber and then allowed to expand through the turbine. The turbine exhaust is then expanded in the propelling nozzle where it is accelerated to high speed to provide thrust. Two engineers, Frank Whittle in the United Kingdom and Hans von Ohain in Germany, developed the concept independently into practical engines during the late 1930s.
A motorjet is a rudimentary type of jet engine which is sometimes referred to as thermojet, a term now commonly used to describe a particular and completely unrelated pulsejet design.
An afterburner is a component present on some jet engines, mostly those used on military supersonic aircraft. Its purpose is to provide an increase in thrust, usually for supersonic flight, takeoff, and combat situations. Afterburning is achieved by injecting additional fuel into the jet pipe downstream of the turbine. Afterburning significantly increases thrust without the weight of an additional engine, but at the cost of very high fuel consumption and decreased fuel efficiency, limiting its practical use to short bursts.
The bypass ratio (BPR) of a turbofan engine is the ratio between the mass flow rate of the bypass stream to the mass flow rate entering the core. A 10:1 bypass ratio, for example, means that 10 kg of air passes through the bypass duct for every 1 kg of air passing through the core.
A propfan, also called an open rotor engine, unducted fan, or ultra high-bypass turbofan, is a type of aircraft engine related in concept to both the turboprop and turbofan, but distinct from both. The design is intended to offer the speed and performance of a turbofan, with the fuel economy of a turboprop. A propfan is typically designed with a large number of short, highly twisted blades, similar to a turbofan's bypass compressor. For this reason, the propfan has been variously described as an "unducted fan" or an "ultra-high-bypass (UHB) turbofan."
A turboshaft engine is a form of gas turbine that is optimized to produce shaftpower rather than jet thrust.
A propelling nozzle is a nozzle that converts the internal energy of a working gas into propulsive force; it is the nozzle, which forms a jet, that separates a gas turbine, being gas generator, from a jet engine.
This article outlines the important developments in the history of the development of the air-breathing (duct) jet engine. Although the most common type, the gas turbine powered jet engine, was certainly a 20th-century invention, many of the needed advances in theory and technology leading to this invention were made well before this time.
The General Electric CJ805 is a jet engine which was developed by GE Aviation in the late 1950s. It was a civilian version of the J79 and differed only in detail. It was developed in two versions. The basic CJ805-3 was a turbojet and powered the Convair 880, while CJ805-23, a turbofan derivative, powered the Convair 990 airliners.
The Rolls-Royce RB.50 Trent was the first Rolls-Royce turboprop engine.
A number of aircraft have been claimed to be the fastest propeller-driven aircraft. This article presents the current record holders for several sub-classes of propeller-driven aircraft that hold recognized, documented speed records in level flight. Fédération Aéronautique Internationale (FAI) records are the basis for this article. Other contenders and their claims are discussed, but only those made under controlled conditions and measured by outside observers. Pilots during World War II sometimes claimed to have reached supersonic speeds in propeller-driven fighters during emergency dives, but these speeds are not included as accepted records. Neither are speeds recorded in a dive during high-speed tests with the Supermarine Spitfire, including Squadron Leader J.R. Tobin's 606 mph in a 45° dive in a Mark XI Spitfire and Squadron Leader Anthony F. Martindale's breaking 620 mph in the same aircraft in April 1944. Flight Lieutenant Edward Powles' 690 mph in Spitfire PR.XIX PS852 during an emergency dive while carrying out spying flights over China on 5 February 1952 is also discounted. This would otherwise be the highest speed ever recorded for a piston-engined aircraft.
The air turborocket is a form of combined-cycle jet engine. The basic layout includes a gas generator, which produces high pressure gas, that drives a turbine/compressor assembly which compresses atmospheric air into a combustion chamber. This mixture is then combusted before leaving the device through a nozzle and creating thrust.
An airbreathing jet engine is a jet engine propelled by a jet of hot exhaust gases formed from air that is forced into the engine by several stages of centrifugal, axial or ram compression, which is then heated and expanded through a nozzle. They are typically gas turbine engines. The majority of the mass flow through an airbreathing jet engine is provided by air taken from outside of the engine and heated internally, using energy stored in the form of fuel.
A powered aircraft is an aircraft that uses onboard propulsion with mechanical power generated by an aircraft engine of some kind.
The familiar study of jet aircraft treats jet thrust with a "black box" description which only looks at what goes into the jet engine, air and fuel, and what comes out, exhaust gas and an unbalanced force. This force, called thrust, is the sum of the momentum difference between entry and exit and any unbalanced pressure force between entry and exit, as explained in "Thrust calculation".
Aircraft engines are a mechanical component of the propulsion system on an airplane, helicopter, rocket or UAV which produces rotary energy to be transferred to a propeller or kinetic energy as a high pressure air exhaust stream. The most common aircraft engine types are turboprop, turbojet, turbofan and turboshaft, however electric engines and piston engines, both used more predominantly in recreational personal aircraft and older model aircraft also exist. Aircraft engine performance has improved dramatically since the advent of the first powered flight in 1848 by John Stringfellow. Aircraft engine manufacturers are constantly innovating to produce more efficient and more reliable engines for aircraft manufacturers. The first jet aircraft and subsequent powered flight occurred on the 27th of August 1939 by a Heinkel He 178. Today, most commercial aircraft are powered by jet engines for long-haul journeys. Efficient aircraft engines have significant positive economic impacts, as they reduce fuel costs for airline companies, enabling cheaper ticket prices and greater flight distances.
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