A jet engine is a reaction engine A reaction engine is an engine which provides propulsion by expelling reaction mass, in accordance with Newton's third law of motion. This law of motion is most commonly paraphrased as: "For every action force there is an equal, but opposite, reaction force" that discharges a fast moving jet A jet is a coherent stream of fluid that is projected into a surrounding medium, usually from some kind of a nozzle or aperture. Jets can travel long distances without dissipating. In the Earth's atmosphere there exist jet streams that travel thousands of miles of fluid A fluid is a substance that continually deforms under an applied shear stress. Fluids are a subset of the phases of matter and include liquids, gases, plasmas and, to some extent, plastic solids to generate thrust by jet propulsion and in accordance with Newton's Sir Isaac Newton FRS was an English physicist, mathematician, astronomer, natural philosopher, alchemist, and theologian who is considered by many scholars and members of the general public to be one of the most influential people in human history. His 1687 publication of the Philosophiæ Naturalis Principia Mathematica (usually called the laws of motion Newton's laws of motion are three physical laws that form the basis for classical mechanics. They have been expressed in several different ways over nearly three centuries, and can be summarised as follows:. This broad definition of jet engines includes turbojets Turbojets are the oldest kind of general-purpose jet engines. 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, although credit for the first turbojet is given to Whittle who was first to conceive, first to formally describe, first to, turbofans A turbofan is a type of aircraft jet engine based around a gas turbine engine . Turbofans provide thrust using a combination of a ducted fan and a jet exhaust nozzle. Part of the airstream from the ducted fan passes through the core, providing oxygen to burn fuel to create power. However, the rest of the air flow bypasses the engine core and mixes, rockets A rocket engine, or simply "rocket," is a jet engine that uses only propellant mass for forming its high speed propulsive jet. Rocket engines are reaction engines and obtain thrust in accordance with Newton's third law. Since they need no external material to form their jet, rocket engines can be used for spacecraft propulsion as well as, ramjets A ramjet, sometimes referred to as a stovepipe jet, or an athodyd, is a form of jet engine using the engine's forward motion to compress incoming air, without a rotary compressor. Ramjets cannot produce thrust at zero airspeed and thus cannot move an aircraft from a standstill, pulse jets A pulse jet engine is a very simple type of jet engine in which combustion occurs in pulses. Pulsejet engines can be made with few or no moving parts, and are capable of running statically and pump-jets A pump-jet, hydrojet, or water jet, is a marine system that creates a jet of water for propulsion. The mechanical arrangement may be a ducted propeller with nozzle, or a Centrifugal pump and nozzle. The first functioning man-made pump-jet engine was created by New Zealand inventor Sir William Hamilton in 1954. In general, most jet engines are internal combustion engines The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber. In an internal combustion engine the expansion of the high temperature and pressure gases, which are produced by the combustion, directly applies force to a movable component of the engine, such as the^[1] but non-combusting forms also exist.

In common parlance, the term jet engine loosely refers to an internal combustion The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber. In an internal combustion engine the expansion of the high temperature and pressure gases, which are produced by the combustion, directly applies force to a movable component of the engine, such as the airbreathing jet engine (a duct engine). These typically consist of an engine with a rotary (rotating) air compressor powered by a turbine A turbine is a rotary engine that extracts energy from a fluid flow and converts it into useful work ("Brayton cycle The Brayton cycle is a thermodynamic cycle that describes the workings of the gas turbine engine, basis of the jet engine and others. It is named after George Brayton , the American engineer who developed it, although it was originally proposed and patented by Englishman John Barber in 1791. It is also sometimes known as the Joule cycle. The"), with the leftover power providing thrust via a propelling nozzle A propelling nozzle is the component of a jet engine that operates to form an exhaust jet and maximise the velocity from the engine. These types of jet engines are primarily used by jet aircraft A jet aircraft is an aircraft propelled by jet engines. Jet aircraft generally fly much faster than propeller-powered aircraft and at higher altitudes — as high as 10,000 to 15,000 meters . At these altitudes, jet engines achieve maximum efficiency over long distances. The engines in propeller powered aircraft achieve their maximum efficiency at for long distance travel. Early jet aircraft used turbojet Turbojets are the oldest kind of general-purpose jet engines. 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, although credit for the first turbojet is given to Whittle who was first to conceive, first to formally describe, first to engines which were relatively inefficient for subsonic flight Flight is the process by which an object moves either through the air, or movement beyond earth's atmosphere , by generating lift, propulsive thrust or aerostatically using buoyancy, or by simple ballistic movement. Modern subsonic jet aircraft usually use high-bypass turbofan engines A turbofan is a type of aircraft jet engine based around a gas turbine engine . Turbofans provide thrust using a combination of a ducted fan and a jet exhaust nozzle. Part of the airstream from the ducted fan passes through the core, providing oxygen to burn fuel to create power. However, the rest of the air flow bypasses the engine core and mixes which give high speeds, as well as (over long distances) better fuel efficiency than many other forms of transport.^{[citation needed]}

Contents 1 History 2 Uses 3 Types 3.1 Airbreathing 3.1.1 Turbine powered 3.1.1.1 Turbojet 3.1.1.2 Turbofan 3.1.1.3 Turboprop and turboshaft 3.1.1.4 Propfan 3.1.2 Ram powered 3.1.2.1 Ramjet 3.1.2.2 Scramjet 3.1.3 Non continuous combustion 3.2 Rocket 3.3 Hybrid 3.4 Water jet 4 General physical principles 4.1 Thrust 4.2 Energy efficiency 4.3 Propulsive efficiency 4.4 Cycle efficiency 4.5 Fuel/propellant consumption 4.6 Thrust-to-weight ratio 4.7 Comparison of types 4.8 Altitude and speed 4.9 Noise 5 See also 6 References 6.1 Notes 6.2 Bibliography 7 External links

History

Main article: History of the jet engine Further information: Timeline of jet power

Jet engines can be dated back to the invention of the aeolipile An aeolipile , also known as a Hero engine, is a rocket style jet engine which spins when heated. In the first century AD, Hero of Alexandria described the device, and many sources give him the credit for its invention before the first century AD. This device used steam power directed through two nozzles to cause a sphere to spin rapidly on its axis. So far as is known, it was not used for supplying mechanical power, and the potential practical applications of this invention were not recognized. It was simply considered a curiosity.

Jet or rocket propulsion only took off, literally and figuratively, with the invention of the gunpowder Gunpowder, also called black powder, is a mixture of sulfur, charcoal, and potassium nitrate. Gunpowder can be made just using potassium nitrate and charcoal, but without the sulfur, the powder is not as strong. It burns rapidly, producing a volume of hot gas made up of carbon dioxide, water, and nitrogen, and a solid residue of potassium sulfide-powered rocket A rocket or rocket vehicle is a missile, spacecraft, aircraft or other vehicle which obtains thrust from a rocket engine. In all rockets, the exhaust is formed entirely from propellants carried within the rocket before use. Rocket engines work by action and reaction. Rocket engines push rockets forwards simply by throwing their exhaust backwards by the Chinese in the 13th century as a type of fireworks Fireworks are a class of low explosive pyrotechnic devices used for aesthetic and entertainment purposes. The most common use of a firework is as part of a fireworks display. A fireworks event is a display of the effects produced by firework devices. Fireworks competitions are also regularly held at a number of places. Fireworks (devices) take, but gradually progressed to propel formidable weaponry; and there the technology stalled for hundreds of years.

The earliest attempts at 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. In one such system, called a thermojet by Secondo Campini but more commonly, motorjet 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. At the heart the motorjet is always an ordinary piston engine , but instead of (or sometimes, as well as) driving a propeller, it drives a compressor. The compressed, the air was compressed by a fan driven by a conventional piston engine. Examples of this type of design were Henri Coandă Henri Marie Coandă was a Romanian inventor, aerodynamics pioneer and the builder of world's first jet powered aircraft, the Coanda-1910. He discovered and gave his name to the Coandă effect's Coandă-1910 aircraft^{[citation needed]} (first jet-propelled aircraft ever built, with the first flight on 16 December 1910^{[citation needed]}), and the much later Caproni Campini N.1, and the Japanese Tsu-11 The Tsu-11 was a primitive, motorjet-style jet engine produced in small numbers in Japan in the closing stages of World War II. It was principally designed to propel the Japanese Ohka flying bomb, a kamikaze weapon engine intended to power Ohka The Yokosuka MXY-7 Ohka, (櫻花 "cherry blossom", Hebon-shiki transcription Ōka, ) was a purpose-built, rocket powered human-guided anti-shipping kamikaze attack plane employed by Japan towards the end of World War II. United States sailors gave the aircraft the nickname Baka (Japanese for "fool" or "idiot") kamikaze planes towards the end of World War II Albania · Australia · Austria · Azerbaijan · Belarus · Belgium · Brazil · Bulgaria · Burma · Cambodia · Canada · Ceylon (Sri Lanka) · Channel Islands · China · Czechoslovakia · Denmark · Dutch East Indies · Egypt · Estonia · Finland · France · Germany · Gibraltar · Greece · Greenland · Hong Kong · Hungary · Iceland ·. None were entirely successful and the N.1 ended up being slower than the same design with a traditional engine and propeller combination.

Albert Fonó Albert Fonó , was a Hungarian mechanical engineer who was one of the early pioneers of turbojet and ramjet propulsion and was first to patent a ramjet engine in 1928, (granted in 1932)'s ramjet A ramjet, sometimes referred to as a stovepipe jet, or an athodyd, is a form of jet engine using the engine's forward motion to compress incoming air, without a rotary compressor. Ramjets cannot produce thrust at zero airspeed and thus cannot move an aircraft from a standstill-cannonball from 1915 The Coandă-1910,first jet-propelled aircraft ever built

Even before the start of World War II, engineers were beginning to realize that the piston engine was self-limiting in terms of the maximum performance which could be attained; the limit was due to issues related to propeller A propeller is a type of fan which transmits power by converting rotational motion into thrust. A pressure difference is produced between the forward and rear surfaces of the airfoil-shaped blade, and air or water is accelerated behind the blade. Propeller dynamics can be modeled by both Bernoulli's principle and Newton's third law efficiency,^[2] which declined as blade tips approached the speed of sound The speed of sound is the rate of travel of a sound wave through an elastic medium. In dry air at 20 °C , the speed of sound is 343 metres per second (1,125 ft/s). This equates to 1,236 kilometres per hour (768 mph), or about one kilometer in three seconds and about one mile in five seconds. This figure increases with temperature (equations are. If engine, and thus aircraft, performance were ever to increase beyond such a barrier, a way would have to be found to radically improve the design of the piston engine, or a wholly new type of powerplant would have to be developed. This was the motivation behind the development of the gas turbine engine, commonly called a "jet" engine, which would become almost as revolutionary to aviation as the Wright brothers The Wright brothers, Orville and Wilbur (April 16, 1867 – May 30, 1912), were two Americans who are generally credited with inventing and building the world's first successful airplane and making the first controlled, powered and sustained heavier-than-air human flight, on December 17, 1903. In the two years afterward, the brothers developed' first flight.

The key to a practical jet engine was the gas turbine, used to extract energy from the engine itself to drive the compressor A gas compressor is a mechanical device that increases the pressure of a gas by reducing its volume. The gas turbine A gas turbine, also called a combustion turbine, is a rotary engine that extracts energy from a flow of combustion gas. It has an upstream compressor coupled to a downstream turbine, and a combustion chamber in-between. Gas turbine may also refer to just the turbine component was not an idea developed in the 1930s: the patent for a stationary turbine was granted to John Barber in England in 1791. The first gas turbine to successfully run self-sustaining was built in 1903 by Norwegian engineer Ægidius Elling. Limitations in design and practical engineering and metallurgy prevented such engines reaching manufacture. The main problems were safety, reliability, weight and, especially, sustained operation.

The first patent for using a gas turbine to power an aircraft was filed in 1921 by Frenchman Maxime Guillaume.^[3] His engine was an axial-flow turbojet. Alan Arnold Griffith published An Aerodynamic Theory of Turbine Design in 1926 leading to experimental work at the RAE.

The Whittle W.2/700 engine flew in the Gloster E.28/39 The Gloster E.28/39, was the first British jet engined aircraft to fly in the United Kingdom. Developed to test the new Whittle jet engine in flight, the test results would influence the development of an operational fighter, the Gloster Meteor, the first British aircraft to fly with a turbojet engine, and the Gloster Meteor The Gloster Meteor was the first British jet fighter and the Allies' first operational jet. Designed by George Carter, it first flew in 1943 and commenced operations on 27 July 1944 with 616 Squadron of the Royal Air Force . The Gloster Meteor was not an aerodynamically advanced aircraft but the Gloster design team succeeded in producing an

In 1928, RAF College Cranwell The Royal Air Force College is the Royal Air Force training and education academy which provides initial training to all RAF personnel who are preparing to be commissioned officers. The College also provides initial training to aircrew cadets and is responsible for all RAF recruiting along with officer and aircrew selection. In recent years it has cadet ^[4] Frank Whittle Air Commodore Sir Frank Whittle, OM, KBE, CB, FRS, Hon FRAeS was a British Royal Air Force (RAF) officer. Frank Whittle invented the jet engine in 1932, but does concede that Germany's Dr. Hans von Ohain independently also "invented" the jet engine years later. Whittle is hailed as a father of jet propulsion formally submitted his ideas for a turbo-jet to his superiors. In October 1929 he developed his ideas further.^[5] On 16 January 1930 in England, Whittle submitted his first patent (granted in 1932).^[6] The patent showed a two-stage axial compressor Axial compressors are rotating, airfoil based compressors in which the working fluid principally flows parallel to the axis of rotation. This is in contrast with other rotating compressors such as centrifugal, axi-centrifugal and mixed-flow compressors where the air may enter axially but will have a significant radial component on exit 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, for a variety of practical reasons. Whittle had his first engine running in April 1937. It was liquid-fuelled, and included a self-contained fuel pump. Whittle's team experienced near-panic when the engine would not stop, accelerating even after the fuel was switched off. It turned out that fuel had leaked into the engine and accumulated in pools. So the engine would not stop until all the leaked fuel had burned off. Whittle was unable to interest the government in his invention, and development continued at a slow pace.

Heinkel He 178, the world's first aircraft to fly purely on turbojet power

In 1935 Hans von Ohain started work on a similar design in Germany A region named Germania, inhabited by several Germanic peoples, has been known and documented before AD 100. Beginning in the 10th century, German territories formed a central part of the Holy Roman Empire, which lasted until 1806. During the 16th century, northern Germany became the centre of the Protestant Reformation. As a modern nation-state,, apparently unaware of Whittle's work.^[7] His first device was strictly experimental and could only run under external power, but he 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 Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of 1.00794 u (1.007825 u for Hydrogen-1), hydrogen is the lightest and most abundant chemical element, constituting roughly 75 % of the Universe's elemental mass. Stars in the main sequence are mainly composed of hydrogen in its as fuel, supplied under external pressure. Their subsequent designs culminated in the gasoline-fuelled HeS 3 of 1,100 lbf (5 kN), 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 Rostock is the largest city in the north German state Mecklenburg-Vorpommern. Rostock is located on the Warnow river; the quarter of Warnemünde 12 km north of the city centre lies directly on the coast of the Baltic Sea-Marienehe aerodrome, an impressively short time for development. The He 178 was the world's first jet plane.^[8]

A cutaway of the Junkers Jumo 004 engine

Austrian Austria /ˈɒstriə/ or /ˈɔːstriə/ (German: Österreich (help·info)), officially the Republic of Austria (German: Republik Österreich), is a landlocked country of roughly 8.3 million people in Central Europe. It borders Germany and the Czech Republic to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and Anselm Franz of Junkers Junkers & Co was a major German aircraft manufacturer. It produced some of the world's most innovative and best-known airplanes over the course of its fifty-plus year history in Dessau, Germany. It was founded there in 1895 by Hugo Junkers, initially manufacturing boilers and radiators. During World War I, and following the war, the company' 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 The Air Ministry was a government department during the period of Nazi Germany (1933–45). It is also the original name of a building in Wilhelmstraße in central Berlin, the capital of Germany, which now houses the German Finance Ministry (see Air Ministry Building) numbering sequence, 4, and the result was the Jumo 004 engine. After many lesser technical difficulties were solved, mass production of this engine started in 1944 as a powerplant for the world's first jet-fighter aircraft, the Messerschmitt Me 262 The Messerschmitt Me 262 Schwalbe was the world's first operational jet-powered fighter aircraft. Design work started before World War II opened, but engine problems meant the aircraft did not reach operational status until the summer of 1944. Compared with Allied fighters of its day, including the jet-powered Gloster Meteor which entered service (and later the world's first jet-bomber aircraft, the Arado Ar 234 The Arado Ar 234 was the world's first operational jet powered bomber, built by the German Arado company in the closing stages of World War II. In the field it was used almost entirely in the reconnaissance role, but in its few uses as a bomber it proved to be nearly impossible to intercept). A variety of reasons conspired to delay the engine's availability, this delay caused the fighter to arrive too late to decisively impact Germany's position in World War II. Nonetheless, it will be remembered as the first use of jet engines in service.

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 A fixed-wing aircraft, typically called an airplane, aeroplane or plane, is an aircraft capable of flight using forward motion that generates lift as the wing moves through the air. Planes include jet engine and propeller driven vehicles propelled forward by thrust, as well as unpowered aircraft . Fixed-wing aircraft are distinct from ornithopters have had some inspiration from this design.

By 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 such low-cost niche roles such as cargo flights.

However, the efficiency of turbojet engines was still rather worse than piston engines, but by the 1970s with the advent of high bypass jet engines, an innovation not foreseen by the early commentators like Edgar Buckingham, at high speeds and high altitudes that seemed absurd to them, only then did the fuel efficiency finally exceed that of the best piston and propeller engines.^[9]

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