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63-408: The Power Jets WU (Whittle Unit) was a series of three very different experimental jet engines produced and tested by Frank Whittle and his small team in the late 1930s. The WU "First Model", also known by Whittle as the first "experimental" engine, and the "1st edition", was the first turbojet engine to be built and run in the world. Although an experimental engine and not intended for flight it

126-399: A convergent-divergent nozzle is needed on high-speed aircraft. The engine thrust is highest if the static pressure of the gas reaches the ambient value as it leaves the nozzle. This only happens if the nozzle exit area is the correct value for the nozzle pressure ratio (npr). Since the npr changes with engine thrust setting and flight speed this is seldom the case. Also at supersonic speeds

189-417: A de Laval nozzle , is used in modern rocket engine nozzles . De Laval turbines can run at up to 30,000 rpm. The turbine wheel was mounted on a long flexible shaft, its two bearings spaced far apart on either side. The higher speed of the turbine demanded that he also design new approaches to reduction gearing, which are still in use today. Since the materials available at the time were not strong enough for

252-844: A turbojet , turbofan , ramjet , pulse jet , or scramjet . In general, jet engines are internal combustion engines . Air-breathing jet engines typically feature a rotating air compressor powered by a turbine , with the leftover power providing thrust through the propelling nozzle —this process is known as the Brayton thermodynamic cycle . Jet aircraft use such engines for long-distance travel. Early jet aircraft used turbojet engines that were relatively inefficient for subsonic flight. Most modern subsonic jet aircraft use more complex high-bypass turbofan engines . They give higher speed and greater fuel efficiency than piston and propeller aeroengines over long distances. A few air-breathing engines made for high-speed applications (ramjets and scramjets ) use

315-399: A central gas turbine which drives open-air contra-rotating propellers . Unlike turboprop engines, in which the propeller and the engine are considered two separate products, the propfan’s gas generator and its unshrouded propeller module are heavily integrated and are considered to be a single product. Additionally, the propfan’s short, heavily twisted variable pitch blades closely remember

378-401: A centrifugal separator was the most affordable and effective method. He developed several types, and their success established the centrifugal separator as a useful device in a variety of applications. De Laval also made important contributions to the dairy industry, including the first centrifugal milk - cream separator and early milking machine , the first of which he patented in 1894. It

441-402: A combustion rig. Owing to a shortage of funds, many of the components would be modified or repaired for testing on later engines. Whittle and his team experienced many problems developing the three models. Compressor and turbine efficiencies and durability were improved. Poor fuel system and combustion performance no longer limited the testing of other parts of the engine. The general design of

504-408: A compressor ( axial , centrifugal , or both), mixing fuel with the compressed air, burning the mixture in the combustor , and then passing the hot, high pressure air through a turbine and a nozzle . The compressor is powered by the turbine, which extracts energy from the expanding gas passing through it. The engine converts internal energy in the fuel to increased momentum of the gas flowing through

567-462: A higher priority than fuel efficiency, fans tend to be smaller or absent. Because of these distinctions, turbofan engine designs are often categorized as low-bypass or high-bypass , depending upon the amount of air which bypasses the core of the engine. Low-bypass turbofans have a bypass ratio of around 2:1 or less. A propfan engine is a type of airbreathing jet engine which combines aspects of turboprop and turbofan . It’s design consists of

630-406: A jet of water. The mechanical arrangement may be a ducted propeller with nozzle, or a centrifugal compressor and nozzle. The pump-jet must be driven by a separate engine such as a Diesel or gas turbine . All jet engines are reaction engines that generate thrust by emitting a jet of fluid rearwards at relatively high speed. The forces on the inside of the engine needed to create this jet give

693-426: A large number of different types of jet engines, all of which achieve forward thrust from the principle of jet propulsion . Commonly aircraft are propelled by airbreathing jet engines. Most airbreathing jet engines that are in use are turbofan jet engines, which give good efficiency at speeds just below the speed of sound. A turbojet engine is a gas turbine engine that works by compressing air with an inlet and

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756-486: A member of the senate. De Laval died in Stockholm in 1913 at the age of 67. In 1882 he introduced his concept of an impulse steam turbine and in 1887 built a small steam turbine to demonstrate that such devices could be constructed on that scale. In 1890, Laval developed a nozzle to increase the steam jet to supersonic speed, working from the kinetic energy of the steam, rather than its pressure. The nozzle, now known as

819-728: A powerplant for the world's first jet- fighter aircraft , the Messerschmitt Me 262 (and later the world's first jet- bomber aircraft, the Arado Ar 234 ). A variety of reasons conspired to delay the engine's availability, causing the fighter to arrive too late to improve Germany's position in World War II , however this was the first jet engine to be used in service. Meanwhile, in Britain the Gloster E28/39 had its maiden flight on 15 May 1941 and

882-405: A run on 23 August up to 13,600 r.p.m. The 31st and final run was on 24 August 1937. A significantly different, symmetrical design was adopted for the second model. Ten spiral ducts connected the compressor outlet to a single, large, reverse-flow combustion chamber, the outlet of which discharged forward through the turbine before turning rearwards to exhaust through ten jet pipes. Some heat exchange

945-445: A single-sided one. The smaller impeller allowed a higher turbine speed which reduced the loading on the single stage turbine and improved its efficiency. The 16.5 in (419 mm) diameter turbine had to develop 3,000 hp (2,237 kW) to drive the compressor. One disadvantage of a double-sided impeller is the requirement, in an aircraft installation, for an intake with a plenum with its higher pressure losses. A disadvantage for

1008-530: A strong thrust on the engine which pushes the craft forwards. Jet engines make their jet from propellant stored in tanks that are attached to the engine (as in a 'rocket') as well as in duct engines (those commonly used on aircraft) by ingesting an external fluid (very typically air) and expelling it at higher speed. A propelling nozzle produces a high velocity exhaust jet . Propelling nozzles turn internal and pressure energy into high velocity kinetic energy. The total pressure and temperature don't change through

1071-421: A supersonic afterburning engine or 2200 K with afterburner lit. The pressure entering the nozzle may vary from 1.5 times the pressure outside the nozzle, for a single stage fan, to 30 times for the fastest manned aircraft at Mach 3+. Convergent nozzles are only able to accelerate the gas up to local sonic (Mach 1) conditions. To reach high flight speeds, even greater exhaust velocities are required, and so

1134-461: A two-stage axial compressor feeding a single-sided centrifugal compressor . Practical axial compressors were made possible by ideas from A.A.Griffith in a seminal paper in 1926 ("An Aerodynamic Theory of Turbine Design"). Whittle would later concentrate on the simpler centrifugal compressor only. Whittle was unable to interest the government in his invention, and development continued at a slow pace. In Spain, pilot and engineer Virgilio Leret Ruiz

1197-444: Is a twin-spool engine, allowing only two different speeds for the turbines. Ram compression jet engines are airbreathing engines similar to gas turbine engines in so far as they both use the Brayton cycle . Gas turbine and ram compression engines differ, however, in how they compress the incoming airflow. Whereas gas turbine engines use axial or centrifugal compressors to compress incoming air, ram engines rely only on air compressed in

1260-500: Is documented in the story of Ottoman soldier Lagâri Hasan Çelebi , who reportedly achieved flight using a cone-shaped rocket in 1633. The earliest attempts at airbreathing jet engines were hybrid designs in which an external power source first compressed air, which was then mixed with fuel and burned for jet thrust. The Italian Caproni Campini N.1 , and the Japanese Tsu-11 engine intended to power Ohka kamikaze planes towards

1323-400: Is the propellant flow in kg/s, A e {\displaystyle A_{e}} is the cross-sectional area at the exit of the exhaust nozzle, and p {\displaystyle p} is the atmospheric pressure. Combined-cycle engines simultaneously use two or more different principles of jet propulsion. A water jet, or pump-jet, is a marine propulsion system that uses

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1386-566: Is used for launching satellites, space exploration and crewed access, and permitted landing on the Moon in 1969. Rocket engines are used for high altitude flights, or anywhere where very high accelerations are needed since rocket engines themselves have a very high thrust-to-weight ratio . However, the high exhaust speed and the heavier, oxidizer-rich propellant results in far more propellant use than turbofans. Even so, at extremely high speeds they become energy-efficient. An approximate equation for

1449-867: The Gloster Meteor finally entered service with the RAF in July 1944. These were powered by turbojet engines from Power Jets Ltd., set up by Frank Whittle. The first two operational turbojet aircraft, the Messerschmitt Me 262 and then the Gloster Meteor entered service within three months of each other in 1944; the Me 262 in April and the Gloster Meteor in July. The Meteor only saw around 15 aircraft enter World War II action, while up to 1400 Me 262 were produced, with 300 entering combat, delivering

1512-458: The Power Jets W.1 . Design Data None. Jet engine A jet engine is a type of reaction engine , discharging a fast-moving jet of heated gas (usually air) that generates thrust by jet propulsion . While this broad definition may include rocket , water jet , and hybrid propulsion, the term jet engine typically refers to an internal combustion air-breathing jet engine such as

1575-500: The aeolipile , a device described by Hero of Alexandria in 1st-century Egypt . This device directed steam power through two nozzles to cause a sphere to spin rapidly on its axis. It was seen as a curiosity. Meanwhile, practical applications of the turbine can be seen in the water wheel and the windmill . Historians have further traced the theoretical origin of the principles of jet engines to traditional Chinese firework and rocket propulsion systems. Such devices' use for flight

1638-655: The gasoline -fuelled HeS 3 of 5 kN (1,100 lbf), which was fitted to Heinkel's simple and compact He 178 airframe and flown by Erich Warsitz in the early morning of August 27, 1939, from Rostock -Marienehe aerodrome , an impressively short time for development. The He 178 was the world's first jet plane. Heinkel applied for a US patent covering the Aircraft Power Plant by Hans Joachim Pabst von Ohain on May 31, 1939; patent number US2256198, with M Hahn referenced as inventor. Von Ohain's design, an axial-flow engine, as opposed to Whittle's centrifugal flow engine,

1701-402: The ram effect of the vehicle's speed instead of a mechanical compressor. The thrust of a typical jetliner engine went from 5,000 lbf (22 kN) ( de Havilland Ghost turbojet) in the 1950s to 115,000 lbf (510 kN) ( General Electric GE90 turbofan) in the 1990s, and their reliability went from 40 in-flight shutdowns per 100,000 engine flight hours to less than 1 per 100,000 in

1764-532: The 1950s, the jet engine was almost universal in combat aircraft, with the exception of cargo, liaison and other specialty types. By this point, some of the British designs were already cleared for civilian use, and had appeared on early models like the de Havilland Comet and Avro Canada Jetliner . By the 1960s, all large civilian aircraft were also jet powered, leaving the piston engine in low-cost niche roles such as cargo flights. The efficiency of turbojet engines

1827-512: The British embassy in Madrid a few years later by his wife, Carlota O'Neill , upon her release from prison. In 1935, Hans von Ohain started work on a similar design to Whittle's in Germany, both compressor and turbine being radial, on opposite sides of the same disc, initially unaware of Whittle's work. Von Ohain's first device was strictly experimental and could run only under external power, but he

1890-526: The Pratt & Whitney J57 and J75 models. There is also a derivative of the P&;W JT8D low-bypass turbofan that creates up to 35,000 horsepower (HP) . Jet engines are also sometimes developed into, or share certain components such as engine cores, with turboshaft and turboprop engines, which are forms of gas turbine engines that are typically used to power helicopters and some propeller-driven aircraft. There are

1953-644: The Swedish mining company, Stora Kopparberg . From there he returned to Uppsala University and completed his doctorate in 1872. He was further employed in Kloster Iron works in Husby parish, Sweden. de Laval was a member of the Royal Swedish Academy of Sciences from 1886. He was a successful engineer and businessman. He also held national office, being elected to Swedish parliament, from 1888 to 1890 and later became

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2016-476: The chambers could be easily removed for inspection and modifications to the combustor components. Whittle had assumed the use of vortex flow in the turbine blades however BTH engineers had not incorporated this and had manufactured the blades with insufficient twist. Whittle's subsequent insistence on this subsequently led to deteriorating relations with BTH engineers. The WU was effectively destroyed by turbine disc failure on 22 February 1941. Work continued with

2079-486: The design of the rotor thrust bearing is no axial load from the impeller to balance that from the turbine. Whittle sought help in designing the combustion system and had visited the British Industries Fair . When he discussed the requirements for his combustion chamber with various exhibitors he had been "practically laughed off every stand" until he discovered Laidlaw, Drew and Company, a firm prepared to tackle

2142-493: The difficult problem of combustion at intensities 20x those in refractory-lined industrial applications. By the end of 1936 total expenditure on design and manufacture of the engine amounted to £2,000. Testing of the first model started on 12 April 1937 at Rugby . During the testing the British Thomson-Houston (BTH) Chief Engineer considered it unwise to exceed 12,000 r.p.m. in the open factory for safety reasons after

2205-604: The divergent area is less than required to give complete internal expansion to ambient pressure as a trade-off with external body drag. Whitford gives the F-16 as an example. Other underexpanded examples were the XB-70 and SR-71. The nozzle size, together with the area of the turbine nozzles, determines the operating pressure of the compressor. This overview highlights where energy losses occur in complete jet aircraft powerplants or engine installations. Gustaf de Laval Gustaf de Laval

2268-510: The ducted fan blades of turbofan engines. Propfans are designed to offer the speed and performance of turbofan engines with fuel efficiency of turboprops. However, due to low fuel costs and high cabin noise, early propfan projects were abandoned. Very few aircraft have flown with propfans, with the Antonov An-70 being the first and only aircraft to fly while being powered solely by propfan engines. The term Advanced technology engine refers to

2331-473: The earlier type. The "fir-tree" design would be used on all Whittle's subsequent engines. After severe initial combustion problems, in late 1940 a new design of combustion chamber designed by Isaac Lubbock of the Shell Fulham Laboratory was incorporated. This 'Lubbock' chamber/burner proved the answer to many of the combustion problems. The reverse-flow type of combustion chamber, as implemented on

2394-405: The end of World War II were unsuccessful. Even before the start of World War II, engineers were beginning to realize that engines driving propellers were approaching limits due to issues related to propeller efficiency, which declined as blade tips approached the speed of sound . If aircraft performance were to increase beyond such a barrier, a different propulsion mechanism was necessary. This

2457-650: The engine, producing thrust. All the air entering the compressor is passed through the combustor, and turbine, unlike the turbofan engine described below. Turbofans differ from turbojets in that they have an additional fan at the front of the engine, which accelerates air in a duct bypassing the core gas turbine engine. Turbofans are the dominant engine type for medium and long-range airliners . Turbofans are usually more efficient than turbojets at subsonic speeds, but at high speeds their large frontal area generates more drag . Therefore, in supersonic flight, and in military and other aircraft where other considerations have

2520-463: The first ground attacks and air combat victories of jet planes. Following the end of the war the German jet aircraft and jet engines were extensively studied by the victorious allies and contributed to work on early Soviet and US jet fighters. The legacy of the axial-flow engine is seen in the fact that practically all jet engines on fixed-wing aircraft have had some inspiration from this design. By

2583-498: The follow-on W1 engine was very similar to the third model of the experimental engine. The team demonstrated that the turbojet had the potential to compete with the large reciprocating aero-engines then being mass-produced for the UK Re-armament Programme. The initial rounded "bulb" de Laval -type turbine blade root fixing was later replaced with a new triangular "fir-tree" design after repeated stress/fatigue failures of

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2646-712: The form of rocket engines they power model rocketry , spaceflight , and military missiles . Jet engines have propelled high speed cars, particularly drag racers , with the all-time record held by a rocket car . A turbofan powered car, ThrustSSC , currently holds the land speed record . Jet engine designs are frequently modified for non-aircraft applications, as industrial gas turbines or marine powerplants . These are used in electrical power generation, for powering water, natural gas, or oil pumps, and providing propulsion for ships and locomotives. Industrial gas turbines can create up to 50,000 shaft horsepower. Many of these engines are derived from older military turbojets such as

2709-507: The immense centrifugal forces, the output from the turbine was limited, and large scale electric steam generators were dominated by designs using the alternative compound steam turbine approach of Charles Parsons . Using high pressure steam in a turbine that had oil-fed bearings meant that some of the steam contaminated the lube-oil, and as a result, perfecting commercial steam-turbines required that he also develop an effective oil/water separator. After trying several methods, he concluded that

2772-490: The inlet or diffuser. A ram engine thus requires a substantial initial forward airspeed before it can function. Ramjets are considered the simplest type of air breathing jet engine because they have no moving parts in the engine proper, only in the accessories. Scramjets differ mainly in the fact that the air does not slow to subsonic speeds. Rather, they use supersonic combustion. They are efficient at even higher speed. Very few have been built or flown. The rocket engine uses

2835-458: The late 1990s. This, combined with greatly decreased fuel consumption, permitted routine transatlantic flight by twin-engined airliners by the turn of the century, where previously a similar journey would have required multiple fuel stops. The principle of the jet engine is not new; however, the technical advances necessary to make the idea work did not come to fruition until the 20th century. A rudimentary demonstration of jet power dates back to

2898-433: The modern generation of jet engines. The principle is that a turbine engine will function more efficiently if the various sets of turbines can revolve at their individual optimum speeds, instead of at the same speed. The true advanced technology engine has a triple spool, meaning that instead of having a single drive shaft, there are three, in order that the three sets of blades may revolve at different speeds. An interim state

2961-394: The net thrust of a rocket engine is: Where F N {\displaystyle F_{N}} is the net thrust, I sp,vac {\displaystyle I_{\text{sp,vac}}} is the specific impulse , g 0 {\displaystyle g_{0}} is a standard gravity , m ˙ {\displaystyle {\dot {m}}}

3024-404: The nozzle but their static values drop as the gas speeds up. The velocity of the air entering the nozzle is low, about Mach 0.4, a prerequisite for minimizing pressure losses in the duct leading to the nozzle. The temperature entering the nozzle may be as low as sea level ambient for a fan nozzle in the cold air at cruise altitudes. It may be as high as the 1000 Kelvin exhaust gas temperature for

3087-424: The same basic physical principles of thrust as a form of reaction engine , but is distinct from the jet engine in that it does not require atmospheric air to provide oxygen; the rocket carries all components of the reaction mass. However some definitions treat it as a form of jet propulsion . Because rockets do not breathe air, this allows them to operate at arbitrary altitudes and in space. This type of engine

3150-531: The state of the art in compressors. Alan Arnold Griffith published An Aerodynamic Theory of Turbine Design in 1926 leading to experimental work at the RAE . In 1928, RAF College Cranwell cadet Frank Whittle formally submitted his ideas for a turbojet to his superiors. In October 1929, he developed his ideas further. On 16 January 1930, in England, Whittle submitted his first patent (granted in 1932). The patent showed

3213-407: The third engine, was necessary to allow the continued use of the more expensive components, e.g. rotor assembly, which had been designed for the completely different straight-through combustion chamber used on the first engine. The reverse-flow arrangement had no thermal expansion problems, it allowed the continued use of a very short shaft between the impeller and turbine, the end covers at the rear of

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3276-460: The third model. It had ten reverse-flow combustion chambers giving a similar configuration to that of the later Power Jets W.1 and Power Jets W.2 turbojet engines. This configuration was also adopted for the Rolls-Royce Welland and General Electric J31 jet engines. One advantage of using 10 combustion chambers, smaller by a factor of (1/sqrt10), was they could be more easily be tested on

3339-600: Was able to demonstrate the basic concept. Ohain was then introduced to Ernst Heinkel , one of the larger aircraft industrialists of the day, who immediately saw the promise of the design. Heinkel had recently purchased the Hirth engine company, and Ohain and his master machinist Max Hahn were set up there as a new division of the Hirth company. They had their first HeS 1 centrifugal engine running by September 1937. Unlike Whittle's design, Ohain used hydrogen as fuel, supplied under external pressure. Their subsequent designs culminated in

3402-557: Was born at Orsa in Dalarna in the Swedish de Laval Huguenot family (immigrated 1622 - Claude de Laval, soldier - knighted de Laval 1647). He enrolled at the Institute of Technology in Stockholm (later the Royal Institute of Technology, KTH) in 1863, receiving a degree in mechanical engineering in 1866, after which he matriculated at Uppsala University in 1867. He was then employed by

3465-406: Was built in 1903 by Norwegian engineer Ægidius Elling . Such engines did not reach manufacture due to issues of safety, reliability, weight and, especially, sustained operation. The first patent for using a gas turbine to power an aircraft was filed in 1921 by Maxime Guillaume . His engine was an axial-flow turbojet, but was never constructed, as it would have required considerable advances over

3528-441: Was connected to the compressor outlet by a very large single spiral duct giving the engine an asymmetrical appearance. Whittle designed the centrifugal compressor to develop about 4:1 pressure ratio when, as far as he was aware, the best previously demonstrated performance in a single stage was about 2.5:1. He specified a double sided impeller to give his required air flow from a smaller diameter impeller than could be obtained from

3591-437: Was designed to be very light by normal engineering standards. The engine had four basic components: a single stage centrifugal compressor with double-sided impeller, a single straight-through combustion chamber , a single stage, axial flow turbine and a convergent propelling nozzle attached to a jet pipe. The shaft connecting the turbine to the compressor was made as short as possible to avoid whirling. The combustion chamber

3654-571: Was eventually adopted by most manufacturers by the 1950s. Austrian Anselm Franz of Junkers ' engine division ( Junkers Motoren or "Jumo") introduced the axial-flow compressor in their jet engine. Jumo was assigned the next engine number in the RLM 109-0xx numbering sequence for gas turbine aircraft powerplants, "004", and the result was the Jumo 004 engine. After many lesser technical difficulties were solved, mass production of this engine started in 1944 as

3717-577: Was expected from the exhaust pipes to the ten ducts delivering air to the combustion chamber as they were all enclosed by the outer casing. Testing began with a reconstructed engine at the premises of the BTH's redundant Ladywood foundry at nearby Lutterworth in Leicestershire on 16 April 1938 and continued until the turbine was damaged on 6 May 1938. A third reconstructed engine was ready for testing on 26 October 1938. Significant changes were also introduced in

3780-574: Was granted a patent for a jet engine design in March 1935. Republican president Manuel Azaña arranged for initial construction at the Hispano-Suiza aircraft factory in Madrid in 1936, but Leret was executed months later by Francoist Moroccan troops after unsuccessfully defending his seaplane base on the first days of the Spanish Civil War . His plans, hidden from Francoists, were secretly given to

3843-406: Was not until after his death, however, that the company he founded marketed the first commercially practical milking machine, in 1918. Together with Oscar Lamm, de Laval founded the company Alfa Laval in 1883, which was known as AB Separator until 1963 when the present name was introduced. In 1991, Alfa Laval Agri, a company producing dairy and farming machinery was split from Alfa Laval when it

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3906-427: Was still rather worse than piston engines, but by the 1970s, with the advent of high-bypass turbofan jet engines (an innovation not foreseen by the early commentators such as Edgar Buckingham , at high speeds and high altitudes that seemed absurd to them), fuel efficiency was about the same as the best piston and propeller engines. Jet engines power jet aircraft , cruise missiles and unmanned aerial vehicles . In

3969-409: Was the motivation behind the development of the gas turbine engine, the most common form of jet engine. The key to a practical jet engine was the gas turbine , extracting power from the engine itself to drive the compressor . The gas turbine was not a new idea: the patent for a stationary turbine was granted to John Barber in England in 1791. The first gas turbine to successfully run self-sustaining

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