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Turbojet aircraft


Turbojet aircraft
Turbojet aircraft originated in World War II, when the limit has been reached perfection old propeller planes, equipped with internal combustion engines. race became increasingly difficult for the speed Every year, since even a slight increase in its required hundreds of additional horsepower engine power and automatically leads to the weighting of the aircraft. On average, the increase in power 1HP It led to an increase in weight of the propulsion system (the engine, propeller and aids) on average per 1 kg. A simple calculation shows that to create a propeller fighter with a speed of about 1000 km / h is almost impossible. The necessary engine power of 12,000 horsepower can be achieved only with the weight of the engine of about 6000 kg. In the future, it appeared that further rate increase will lead to the degeneration of combat aircraft, turn them into devices that can only be of themselves. For weapons, radio equipment, armor and reserve fuel on board is not perpetuated. But even at this price it was impossible to get a big speed increase. The heavier the engine increases the overall weight of the machine, which made increase the wing area, this led to an increase of aerodynamic drag, in order to overcome an engine power increase was necessary. Thus, the circle closes, and the speed of the order of 850 km / h provided the maximum possible for aircraft with piston engine. Out of this evil situation could be only one - required to create a fundamentally new design of an aircraft engine, which was done, when to replace piston planes came turbojet.

The operating principle of a simple jet engine it can be understood if we consider the work of a fire hose. Pressurized water is supplied through a hose from a hose and flows out of it. The inner hose section tapering toward the tip end, and therefore the flowing water jet has a higher velocity than in the hose. The strength of the back pressure (reaction) at the same time is so great that a firefighter must often exert every effort to keep the hose in the desired direction. The same principle can be applied in aviation engines. The simplest jet engine is a ramjet.

Imagine a pipe with open ends mounted on a moving airplane. The front part of the pipe that receives the air due to the aircraft, has an internal cross-section widening. Because expansion air inlet pipe velocity therein is reduced and the pressure correspondingly increases. Assume that in the divergent part of the air stream and the injected fuel is burned. This part of the pipe may be called a combustion chamber. Strongly heated gases rapidly expanding and are pulled through the narrowing jet nozzle at a rate many times superior to the one that had the air flow at the inlet. Due to this increase in speed creates a reactive thrust that pushes the plane forward. It is easy to see that such a motor can be operated only if it moves in the air at a significant rate, but it can not be operated when there is no traffic. The plane with the engine must be started or from another aircraft or to be dispersed with a special starter motor. This disadvantage is overcome in a more complicated turbojet.

Most crucial element of a gas turbine engine (6) which drives the air compressor (2) sitting on a shaft with it. The air flowing into the engine is compressed in the first input device - a diffuser (1) and then in the axial compressor (2) and then into the combustion chamber (3). The fuel is usually kerosine which inject into the combustion chamber through the nozzle. From the combustion chamber, expands, coming primarily on the gas turbine blades, causing it to rotate and then to the nozzle (7), which are accelerated to very high velocities. The gas turbine uses only a small part of the energy of the air-gas jet. The remainder of the gas jet is to create a thrust, which is due to expire at a high speed jet combustion gases from the nozzle. Thrust turbojet engine can be forced, that is, to increase for a short period of time in different ways. For example, this can be done with the help of the so-called post-combustion (thus in the gas stream behind the turbine is further injected fuel that is burned by oxygen not used in combustion chambers). Post-combustion can be in the short term to further increase the engine power by 25-30% at low speeds and up to 70% at high speeds.

Gas turbine engines since 1940, have made a real revolution in aviation technology, but the first development to create them appeared ten years before. Father of the turbojet engine is considered to be an English inventor Frank Whittle. Back in 1928, while a student at the aviation school in Krenuelle, Whittle proposed a first draft of a jet engine, equipped with a gas turbine. In 1930 he received a patent for it. State while not interested in its development. But Whittle got help from some private companies, and in 1937 for his design company "British Thomson-Houston" built first in the history of the turbojet engine, designated "U". Only after that the Air Ministry drew attention to the invention Whittle. To further improve its engines design company "Power", which had support from the state was created.

At the same time the idea of ​​the design idea Whittle fertilized Germany. In 1936, German inventor Ohain, while a student of the University of Göttingen, has developed and patented a turbojet engine. Its design is almost no different from Whittle design. In 1938, the company "Heinkel", which took Ohain work, developed under his leadership turbojet HeS-3B, which was installed on the plane He-178. August 27, 1939 the plane made its first successful flight.

Design He-178 much anticipated device of the future of jet planes. The air intake located in the forward fuselage. The air branching out, walked around the cockpit and got direct flow to the engine. Hot expired gases through a nozzle in the tail. The wings of the aircraft were still wooden, but the fuselage - made of aluminum. The engine, mounted behind the cockpit, working on gasoline and developed a thrust of 500 kg. The maximum speed of the aircraft reached 700 km / h. In early 1941, Ohain developed the more advanced engine HeS-8 with a thrust of 600 kg. Two of these engines were installed on the next plane He-280V. Test it began in April of the same year and showed a good result - the plane developed a speed of 925 km / h. However, mass production of this fighter and has not begun (total 8 pieces were produced) due to the fact that the engine is still proved unreliable.

Meanwhile, the "British Thomson-Houston" released W1.X engine, specially designed by the first English turbojet aircraft "Gloucester G40", which made its first flight in May 1941 (on the plane was set then improved engine W.1 Whittle). 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 to reach speeds up to 500 km / h.

By "Gloucester" bore a striking resemblance to its construction the German "Heinkel". G40 has an all-metal construction with air intake in the forward fuselage. The supply air duct has been split and rounding on both sides of the cockpit. Expiration of gas going through a nozzle at the tail of the fuselage. Although the G40 parameters not only superior to those that were at the time of high-speed-rotor aircraft, but much inferior to them, the prospects for the use of jet engines were so promising that the British Air Ministry decided to start serial production of turbojet fighter-interceptors. Firm "Gloucester" received an order to develop such an aircraft. In subsequent years, several British companies have started to make various modifications to the jet engine Whittle. Firm "Rover", based on the engine W.1, developed engines W2B / 23 and W2B / 26. Then, these engines were purchased by the company "Rolls Royce", which is based on them created their models - "Uellend" and "Derwent".

The first in the history of serial turbojet aircraft became, however, not English "Gloucester" and the German "Messerschmitt" Me-262. Total was made about 1300 of these aircraft of various models, equipped with "Junkers" motor company "Jumo-004B». The first aircraft of this series has been tested in 1942. It had two engines with a thrust of 900 kg and a top speed of 845 km / h.

English production aircraft "Gloster Meteor G41" appeared in 1943. Powered by two "Derwent" to thrust each 900 kg, "Meteor" developed a speed of 760 km / h and had a flight altitude of 9000 m. In the future, the planes began to establish a more powerful "Derventa" with a thrust of about 1600 kg, which allowed increase the speed to 935 km / h. This aircraft has proven itself, so the production of various modifications of the G41 continued until the end of the 40s.

US jet aircraft development initially far behind the European countries. Up until World War II, there was generally no attempt to create a jet plane. Only in 1941, when England samples and drawings Whittle engines have been received, the work unfolded in full swing. "General Electric" company, based on a model Whittle developed a turbojet IA, which was installed on the first American jet aircraft P-59A «Erkomet". American firstborn first flew 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 the American pilots who were experiencing a plane, P-59 was good to drive, but its flight characteristics were unimportant. The engine proved to be too small, so that it was more a glider than a real combat aircraft. A total of 33 of these machines were built. Their top speed was 660 km / h and flight altitude up to 14,000 m.

The first serial turbojet fighter in the United States was "Lockheed F-80 Shuting Star" with the engine of the company «General Electric» I-40 (modification IA). about 2,500 of these fighters of different models have been released before the end of the 40s. their speed averaged about 900 km / h. However, in a modification of the plane XF-80B 19 June 1947 for the first time in the history it has reached the speed of 1000 km / h.

At the end of the war jets in many respects even inferior exhaust model propeller planes and we had a lot of their specific shortcomings. In general, the construction of the first turbojet aircraft designers in all countries are faced with considerable difficulties. Every now and then goes bust of the combustion chamber, breaking the blades of turbines and compressors, and separated from the rotor turned into projectiles, lamented the motor housing, the fuselage and the wing. But, despite this, the jets have a huge advantage before-rotor - the increment rate with an increase in power of the turbojet engine, and its weight was going much faster than that of the piston. It further decided the fate of high-speed aircraft - it is everywhere becoming reactive. Increase speed soon led to a complete change in the appearance of the aircraft. At transonic speeds old form and the profile of the wing were unable to carry the plane - he began to "peck" nose and entered into uncontrollable nosedive. The results of aerodynamic tests and analysis of flight accidents gradually led designers to the new wing type - thin, Sweep.

For the first time this form of wings appeared on the Soviet fighters. Despite the fact that the Soviet Union after the Western states began to establish turbojet aircraft, Soviet designers were able to quickly create high-end combat vehicles. The first Soviet jet fighter, running in production, was the Yak-15. He appeared at the end of 1945 and is a converted Yak-3 (known in the fighter with piston engine during the war), which was set turbojet engine RD-10 - a copy of captured German "Jumo-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 turbojet engines "Jumo-004B» (the official designation of RD-20), and in 1947 appeared the MiG-15 - the first in the history of the combat jet with swept wings, equipped with a motor RD-45 (as designated engine "Ning" company "Rolls-Royce", purchased licenses and modernized Soviet aircraft) with a thrust of 2200 kg. MiG-15 is strikingly different from their predecessors, and combat pilots surprised unusual, oblique back wings, a huge keel, topped with the same swept stabilizer and cigar-shaped fuselage. The plane had other news: catapult chair and hydraulic rudder amplifiers. He was armed with a high-velocity gun and two machine guns (in later versions - three guns). With a speed of 1,100 km / h and a ceiling of 15,000 m, this fighter for several years remained the best in the world of combat aircraft and summoned a great interest. (Later, the MiG-15 design had a significant impact on the design of fighter aircraft in the West.) In a short time, the MiG-15 was the most popular fighter in the USSR, and was adopted in the armies of its allies. The aircraft performed well and during the Korean War. In many respects, it was superior to the US "Sabres".

With the advent of the MiG-15 ended childhood turbojet aircraft and began a new phase in its history. By this time the jets have mastered all subsonic speed and very close to the sound barrier.

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