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HISTORY OF TECHNOLOGY, TECHNOLOGY, OBJECTS AROUND US
Turbojet aircraft. History of invention and production
Directory / The history of technology, technology, objects around us Jet aircraft - an aircraft propelled by an air-jet engine (turbojet engine, ramjet engine, pulse jet engine, liquid-propellant engine, etc.) or a rocket engine. Jet aircraft form the basis of modern military and civil aviation.
Turbojet aviation originated during the Second World War, when the limit of perfection of the previous propeller-driven aircraft equipped with internal combustion engines was reached. Every year the race for speed became more and more difficult, since even a slight increase in speed required hundreds of additional horsepower of engine power and automatically led to the weight of the aircraft. On average, an increase in power of 1 hp. led to an increase in the mass of the propulsion system (the engine itself, propeller and auxiliary equipment) by an average of 1 kg. Simple calculations showed that it was practically impossible to create a propeller-driven fighter aircraft with a speed of the order of 1000 km/h. The required engine power of 12000 horsepower could only be achieved with an engine weight of about 6000 kg. In the future, it turned out that a further increase in speed would lead to the degeneration of combat aircraft, turning them into vehicles capable of carrying only themselves. There was no room left for weapons, radio equipment, armor and fuel on board. But even at this price it was impossible to get a big increase in speed. A heavier engine increased the overall weight of the car, which forced an increase in the wing area, this led to an increase in their aerodynamic drag, to overcome which it was necessary to increase engine power. Thus, the circle was closed and the speed of the order of 850 km / h turned out to be the maximum possible for an aircraft with a piston engine. There could be only one way out of this vicious situation - it was necessary to create a fundamentally new design of an aircraft engine, which was done when turbojet aircraft replaced piston aircraft. The principle of operation of a simple jet engine can be understood if we consider the operation of a fire hose. Pressurized water is supplied through a hose to the hose and flows out of it. The internal section of the hose tip tapers towards the end, and therefore the jet of flowing water has a higher speed than in a hose. The force of the back pressure (reaction) in this case is so great that the firefighter often has to exert all his strength in order to keep the hose in the required direction. The same principle can be applied to an aircraft engine. The simplest jet engine is a ramjet.
Imagine a pipe with open ends mounted on a moving aircraft. The front part of the pipe, into which air enters due to the movement of the aircraft, has an expanding internal cross section. Due to the expansion of the pipe, the speed of the air entering it decreases, and the pressure increases accordingly. Let us assume that in the expanding part, fuel is injected and burned into the air stream. This part of the pipe can be called a combustion chamber. Highly heated gases rapidly expand and escape through a narrowing jet nozzle at a speed that is many times greater than that which the air stream had at the entrance. This increase in speed creates a thrust force that pushes the aircraft forward. It is easy to see that such an engine can only work if it is moving through the air at a considerable speed, but it cannot be put into action when it is not moving. An aircraft with such an engine must either be launched from another aircraft or accelerated using a special starting engine. This disadvantage is overcome in a more complex turbojet engine.
The most critical element of this engine is the gas turbine (6), which drives the air compressor (2) sitting on the same shaft with it. The air entering the engine is first compressed in the inlet diffuser (1), then in the axial compressor (2) and then enters the combustion chamber (3). The fuel is usually kerosene, which is sprayed into the combustion chamber through a nozzle. From the chamber, the combustion products, expanding, come first of all to the blades of the gas turbine, causing it to rotate, and then to the nozzle (7), in which they are accelerated to very high speeds. The gas turbine uses only a small part of the energy of the air-gas jet. The rest of the gases goes to create a reactive thrust force, which occurs due to the outflow of a jet of combustion products from the nozzle at high speed. The thrust of a turbojet engine can be boosted, ie increased for a short period of time, in various ways. For example, this can be done using the so-called afterburning (in this case, fuel is additionally injected into the gas stream behind the turbine, which burns due to oxygen not used in the combustion chambers). Afterburning can additionally increase engine thrust by 25-30% at low speeds and up to 70% at high speeds in a short time. Gas turbine engines, starting in 1940, made a real revolution in aviation technology, but the first developments in their creation appeared ten years earlier. Frank Whittle is considered to be the father of the turbojet engine. As early as 1928, while a student at the Cranwell Aviation School, Whittle proposed the first draft of a jet engine equipped with a gas turbine. In 1930 he received a patent for it. The state at that time was not interested in its developments. But Whittle received help from some private firms, and in 1937, according to his design, British Thomson-Houston built the first turbojet engine in history, which received the designation "U". Only after that did the Air Ministry pay attention to Whittle's invention. To further improve the engines of its design, the Power company was created, which had support from the state. At the same time, Whittle's ideas fertilized the design thought of Germany. In 1936, the German inventor Ohain, then a student at the University of Göttingen, developed and patented his turbojet engine. Its design was almost no different from Whittle's. In 1938, the Heinkel firm, which hired Ohain, developed under his leadership the HeS-3B turbojet engine, which was installed on the He-178 aircraft. On August 27, 1939, this aircraft made its first successful flight.
The design of the He-178 largely anticipated the design of future jet aircraft. The air intake was located in the forward fuselage. The air, branching, bypassed the cockpit and entered the engine in a direct stream. Hot gases flowed through a nozzle in the tail section. The wings of this aircraft were still wooden, but the fuselage was made of duralumin. The engine, mounted behind the cockpit, ran on gasoline and developed a thrust of 500 kg. The maximum speed of the aircraft reached 700 km / h. In early 1941, Ohain developed a more advanced HeS-8 engine with a thrust of 600 kg. Two of these engines were installed on the next He-280V aircraft. Its tests began in April of the same year and showed good results - the aircraft reached speeds of up to 925 km / h. However, the serial production of this fighter did not begin (a total of 8 pieces were made) due to the fact that the engine still turned out to be unreliable. In the meantime, British Thomson Houston produced the W1.X engine, specially designed for the first British turbojet aircraft, the Gloucester G40, which made its first flight in May 1941 (the aircraft was then equipped with an improved Whittle W.1 engine). The English first-born was far from the German. Its maximum speed was 480 km / h. In 1943, the second Gloucester G40 was built with a more powerful engine, reaching speeds of up to 500 km / h. In its design, the Gloucester was surprisingly reminiscent of the German Heinkel. The G40 had an all-metal construction with an air intake in the forward fuselage. The inlet air duct was divided and went around the cockpit on both sides. The outflow of gases occurred through a nozzle in the tail of the fuselage. Although the parameters of the G40 not only did not exceed those that high-speed propeller-driven aircraft had at that time, but were noticeably inferior to them, the prospects for the use of jet engines turned out to be so promising that the British Air Ministry decided to start serial production of turbojet interceptor fighters. Firm "Gloucester" received an order to develop such an aircraft. In subsequent years, several English firms at once began to produce various modifications of the Whittle turbojet engine. Based on the W.1 engine, Rover developed the W2B/23 and W2B/26 engines. Then these engines were bought by Rolls-Royce, which based on them created its own models - Welland and Derwent. The first serial turbojet aircraft in history was, however, not the English Gloucester, but the German Messerschmitt Me-262. In total, about 1300 such aircraft of various modifications were manufactured, equipped with the Junkers Yumo-004B engine. The first aircraft of this series was tested in 1942. It had two engines with a thrust of 900 kg and a top speed of 845 km/h.
The English production aircraft "Gloucester G41 Meteor" appeared in 1943. Equipped with two Dervent engines with a thrust of 900 kg each, the Meteor developed a speed of up to 760 km / h and had a flight altitude of up to 9000 m. Later, more powerful Dervents with a thrust of about 1600 kg were installed on the aircraft, which increase speed to 935 km/h. This aircraft proved to be excellent, so the production of various modifications of the G41 continued until the end of the 40s. The United States in the development of jet aviation at first lagged far behind European countries. Until the Second World War, there were no attempts to create a jet aircraft at all. Only in 1941, when samples and drawings of Whittle engines were received from England, did these works begin at full speed. General Electric, based on Whittle's model, developed the IA turbojet engine, which was installed on the first American jet aircraft, the P-59A Ercomet. The American first-born took to the air for the first time in October 1942. It had two engines, which were placed under the wings close to the fuselage. It was still an imperfect design. According to American pilots who tested the aircraft, the P-59 was good to fly, but its flight performance remained unimportant. The engine turned out to be too underpowered, so it was more of a glider than a real combat aircraft. A total of 33 of these machines were built. Their maximum speed was 660 km / h, and the flight altitude was up to 14000 m. The first serial turbojet fighter in the United States was the Lockheed F-80 Shooting Star with a General Electric I-40 engine (modification IA). Until the end of the 40s, about 2500 of these fighters of various models were produced. Their average speed was about 900 km / h. However, on June 80, 19, one of the modifications of this XF-1947B aircraft reached a speed of 1000 km / h for the first time in history.
At the end of the war, jet aircraft were still inferior in many respects to proven models of propeller-driven aircraft and had many of their own specific shortcomings. In general, during the construction of the first turbojet aircraft, designers in all countries faced significant difficulties. Every now and then, the combustion chambers burned out, the blades of turbines and compressors broke and, separated from the rotor, turned into shells that crushed the engine case, fuselage and wing. But, despite this, jet aircraft had a huge advantage over propeller-driven ones - the increase in speed with an increase in the power of a turbojet engine and its weight was much faster than that of a piston one. This decided the future fate of high-speed aviation - it becomes jet everywhere. The increase in speed soon led to a complete change in the appearance of the aircraft. At transonic speeds, the old shape and profile of the wing turned out to be unable to carry the aircraft - it began to “peck” with its nose and entered into an uncontrollable dive. The results of aerodynamic tests and the analysis of flight accidents gradually led the designers to a new type of wing - a thin, swept one. For the first time, this form of wings appeared on Soviet fighters. Despite the fact that the USSR began to create turbojet aircraft later than the Western states, Soviet designers very quickly managed to create high-class combat vehicles. The first Soviet jet fighter put into production was the Yak-15. It appeared at the end of 1945 and was a converted Yak-3 (a famous fighter with a piston engine during the war), on which an RD-10 turbojet engine was installed - a copy of the captured German Yumo-004B with a thrust of 900 kg. He developed a speed of about 830 km / h.
In 1946, the MiG-9 entered service with the Soviet Army, equipped with two Yumo-004B turbojet engines (official designation RD-20), and in 1947 the MiG-15 appeared - the first ever swept-wing combat jet aircraft equipped with an engine RD-45 (as the Rolls-Royce "Nin" engine, purchased under license and modernized by Soviet aircraft designers) with a thrust of 2200 kg was designated. The MiG-15 was strikingly different from its predecessors and surprised combat pilots with unusual, backward-sloping wings, a huge keel topped with the same swept stabilizer, and a cigar-shaped fuselage. The aircraft also had other novelties: an ejection seat and hydraulic power steering. It was armed with a rapid-fire cannon and two machine guns (in later modifications, three cannons). With a speed of 1100 km / h and a ceiling of 15000 m, this fighter for several years remained the best combat aircraft in the world and aroused great interest. (Later, the design of the MiG-15 had a significant impact on fighter design in Western countries.)
In a short time, the MiG-15 became the most common fighter in the USSR, and was also adopted by the armies of its allies. This aircraft proved itself well during the Korean War. In many respects, he was superior to the American Sabers. With the advent of the MiG-15, the childhood of turbojet aviation ended and a new stage in its history began. By this time, jet aircraft had mastered all subsonic speeds and came close to the sound barrier. Author: Ryzhov K.V.
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