The rotating propeller pulls the aircraft forward. But the jet engine high speed ejects hot exhaust gases to the rear and thereby creates a reactive thrust force directed forward.

Types of jet engines

There are four types of jet or gas turbine engines:

Turbojet;

Turbofans- such as those used on Boeing-747 passenger liners;

Turboprop where propellers driven by turbines are used;

and Turboshaft that put on helicopters.

turbofan engine consists of three main parts: a compressor, a combustion chamber and a turbine that provides energy. First, air enters the engine and is compressed by a fan. Then, in the combustion chamber, compressed air mixes with fuel and burns, forming gas at high temperature and high pressure. This gas passes through the turbine, causing it to rotate at a tremendous speed, and is thrown back, thus creating a forward thrust force.

Image is clickable

Once in the turbine engine, the air goes through several stages of compression. The pressure and volume of the gas increase especially strongly after passing through the combustion chamber. The thrust generated by the exhaust gases allows jet aircraft to travel at altitudes and speeds far in excess of those available to piston-engined rotorcraft.

In a turbojet engine, air is taken in from the front, compressed, and combusted along with the fuel. resulting from combustion traffic fumes generate reactive thrust.

Turboprops connect jet thrust exhaust gases with forward thrust generated by the rotation of the propeller.

Gas turbine engines are quite high-tech and significantly outperform traditional (conventional) engines in terms of their characteristics. internal combustion. Gas turbine engines have received their main distribution in the aviation industry. But in automotive industry engines of this type have not gained distribution, which is associated with problems with their consumption of aviation fuel, which is too expensive for land vehicles. But nevertheless, in the world there are various and which are equipped with jet engines. Our online publication for its regular readers decided today to publish the Top 10 (top ten) of this amazing in our opinion and powerful vehicles.

1) Tractor Pulling Putten

This tractor can be safely called the pinnacle of human achievement. Engineers have created a vehicle that is capable of towing a 4.5-ton at breakneck speed, and this is thanks to just a few gas turbine engines.

2) Railway locomotive with a gas turbine engine

This experiment of engineers never received the expected commercial fame. A pity of course. Such a railway train used, in particular, an engine from the Convair B-36 "Peacemaker" strategic bomber ("Peacemaker" - made in the USA). Thanks to this motor, the railway locomotive was able to accelerate to a speed of 295.6 km / h.

3) Thrust SSC

At the moment, the engineers of the company "SSC Program Ltd" are preparing for tests, which will have to set a new speed record on the ground. But, despite the design of this new car, the original Thrust SSC, which previously officially set the world speed record among all land vehicles also very impressive.

The power of this Thrust SSC is 110 thousand hp, which is achieved by two Rolls-Royce gas turbine engines. We remind our readers that this jet car in 1997, it accelerated to a speed of 1228 km / h. Thus Thrust SSC became the first car in the world to break the sound barrier on earth.

4) Volkswagen New Beetle

47-year-old car enthusiast Ron Patrick installed in his car Volkswagen models Beetle rocket engine. The power of this machine after its modernization was 1350 hp. Now maximum speed car is 225 km/h. But in the operation of such a motor there is one very significant drawback. This jet leaves behind a hot plume 15 meters long.

5) Russian fire extinguisher "Big Wind"

And how do you like the old Russian proverb - "The wedge is knocked out with a wedge," remember this one? In our example, this proverb, oddly enough, specifically works. We present to you, dear readers, the Russian development - "Extinguishing fire with fire." Don't believe? But it's true. Similar installation actually used in Kuwait to put out oil fires during the Gulf War.

This vehicle was created on the basis of the T-34, on which two jet engines from the MIG-21 fighter were installed (delivered). The principle of operation of this fire extinguishing vehicle is quite simple - extinguishing occurs with the help of jet streams of air along with water. The engines from the jet aircraft were slightly modified, this was done with the help of hoses through which water was supplied under high pressure. During the operation of the gas turbine engine, water fell on the fire coming out of the nozzles of the jet engine, as a result of which a strong steam was formed, which moved in large streams of air at great speed.

This method made it possible to put out oil rigs. The streams of the steam itself were cut off from the burning layer.

6) STP-Paxton Turbocar racing car

This race car was designed by Ken Wallis for the Indianapolis 500. For the first time this sports car took part in the "Indy 500" in 1967. The car's gas turbine and the pilot's seat were located next to each other. Torque with the help of the converter was immediately transmitted to all four wheels.

In 1967, during the main event, this car was a contender for victory. But 12 kilometers before the finish line due to the failure of the bearings, the car left the race.

7) American polar icebreaker USCGC Polar-Class Icereaker

This powerful icebreaker can move through the ice, the thickness of which can reach up to 6 meters. The icebreaker is equipped with 6 diesel engines with a total capacity of 18 thousand hp, as well as three Pratt & Whitney gas turbine engines with a total capacity of 75 thousand hp. But despite the enormous power of all its power plants, the speed of the icebreaker is not great. But for this vehicle, speed is not the main thing -.

8) Summer Luge Vehicle

If you have no sense of self-preservation at all, then this vehicle can be perfect for you to get a huge dose of adrenaline. This unusual vehicle is equipped with a small gas turbine engine. Thanks to him, in 2007, one fearless athlete managed to accelerate to a speed of 180 km / h. But that's nothing. compared to another Australian that is preparing a similar vehicle for itself, all in order to set a world record. This person plans to accelerate on a board with a gas turbine engine to a speed of 480 km / h.

9) MTT Turbine Superbike

The company "MTT" decided to equip its motorcycle gas turbine engine. Ultimately on rear wheel 286 hp power is transmitted. Such a jet engine was produced by the company " Rolls Royce". Jay Leno today already owns such a superbike. According to him, driving such a thing is both scary and interesting at the same time.

The biggest danger for any motorcycle racer who is behind the wheel of such a bike is to keep its stability during acceleration and be sure to slow down in time.

10) Snowplow

Do you know, dear friends, where old jet engines mostly end up after they have been removed from aircraft? Do not know? Very often in many countries of the world they are used in the railway industry, they are used for cleaning railway tracks from the falling snow.

In addition, similar snowplows vehicles are also used on the runways of airfields and wherever required for short term remove snow drift from a certain area.

A jet engine is an engine that creates the traction force necessary for movement by converting the internal energy of the fuel into the kinetic energy of the jet stream of the working fluid.

The working fluid flows out of the engine at high speed, and, in accordance with the law of conservation of momentum, a reactive force is formed that pushes the engine in the opposite direction. To accelerate the working fluid, both the expansion of a gas heated in one way or another to a high thermal temperature (the so-called thermal jet engines) and other physical principles, for example, the acceleration of charged particles in an electrostatic field (see ion engine), can be used.

A jet engine combines the engine itself with a propeller, that is, it creates traction only through interaction with the working fluid, without support or contact with other bodies. For this reason, it is most commonly used to propel aircraft, rockets, and spacecraft.

In a jet engine, the thrust force necessary for movement is created by converting the initial energy into the kinetic energy of the working fluid. As a result of the expiration of the working fluid from the engine nozzle, a reactive force is formed in the form of recoil (jet). The recoil moves the engine and the device structurally connected with it in space. The movement occurs in the direction opposite to the outflow of the jet. The kinetic energy of the jet stream can be converted different kinds energy: chemical, nuclear, electrical, solar. The jet engine provides its own movement without the participation of intermediate mechanisms.

For creating jet thrust a source of initial energy is needed, which is converted into the kinetic energy of a jet stream, a working fluid ejected from the engine in the form of a jet stream, and the jet engine itself, which converts the first type of energy into the second.

The main part of a jet engine is the combustion chamber, in which the working fluid is created.

All jet engines are divided into two main classes, depending on whether they use the environment in their work or not.

The first class is jet engines (WFD). All of them are thermal, in which the working fluid is formed during the oxidation reaction of a combustible substance with oxygen from the surrounding air. The main mass of the working fluid is atmospheric air.

In a rocket engine, all components of the working fluid are on board the apparatus equipped with it.

There are also combined engines, combining both of the above types.

For the first time, jet propulsion was used in Heron's ball, the prototype of a steam turbine. jet engines solid fuels appeared in China in the 10th century. n. e. Such rockets were used in the East, and then in Europe for fireworks, signaling, and then as combat ones.

An important stage in the development of the idea jet propulsion there was an idea to use a rocket as an engine for an aircraft. It was first formulated by the Russian revolutionary N. I. Kibalchich, who in March 1881, shortly before his execution, proposed a scheme for an aircraft (rocket plane) using jet thrust from explosive powder gases.

N. E. Zhukovsky in his works "On the reaction of outflowing and inflowing fluid" (1880s) and "On the theory of ships set in motion by the reaction force of outflowing water" (1908) first developed the main issues of the theory of a jet engine.

Interesting work on the study of rocket flight also belongs to the famous Russian scientist I. V. Meshchersky, in particular in the field of the general theory of the motion of bodies of variable mass.

In 1903, K. E. Tsiolkovsky, in his work "Investigation of the World Spaces with Reactive Devices", gave a theoretical justification for the flight of a rocket, as well as a schematic diagram of a rocket engine, which anticipated many of the fundamental and design features of modern liquid-propellant rocket engines (LRE). So, Tsiolkovsky provided for the use of liquid fuel for a jet engine and its supply to the engine with special pumps. He proposed to control the flight of the rocket by means of gas rudders - special plates placed in a jet of gases emitted from the nozzle.

A feature of a liquid-propellant engine is that, unlike other jet engines, it carries with it the entire supply of oxidizer along with the fuel, and does not take the oxygen-containing air necessary for burning fuel from the atmosphere. This is the only engine that can be used for ultra-high-altitude flight outside the earth's atmosphere.

The world's first rocket with a liquid-propellant rocket engine was created and launched on March 16, 1926 by the American R. Goddard. It weighed about 5 kilograms, and its length reached 3 m. Goddard's rocket was fueled by gasoline and liquid oxygen. The flight of this rocket lasted 2.5 seconds, during which it flew 56 m.

Systematic experimental work on these engines began in the 30s of the XX century.

The first Soviet rocket engines were designed and built in 1930–1931. in the Leningrad Gas Dynamic Laboratory (GDL) under the guidance of the future academician V.P. Glushko. This series was called ORM - an experienced rocket motor. Glushko applied some novelties, for example, cooling the engine with one of the fuel components.

In parallel, the development of rocket engines was carried out in Moscow by the Jet Propulsion Study Group (GIRD). Its ideological inspirer was F. A. Zander, and the organizer was the young S. P. Korolev. Korolev's goal was to build a new rocket apparatus - a rocket plane.

In 1933, F.A. Zander built and successfully tested the OR1 rocket engine, which ran on gasoline and compressed air, and in 1932–1933. - engine OP2, on gasoline and liquid oxygen. This engine was designed to be installed on a glider that was supposed to fly as a rocket plane.

In 1933, the first Soviet liquid-fuel rocket was created and tested at GIRD.

Developing the work begun, Soviet engineers subsequently continued to work on the creation of liquid-propellant jet engines. In total, from 1932 to 1941, 118 designs of liquid-propellant jet engines were developed in the USSR.

In Germany in 1931, rockets were tested by I. Winkler, Riedel, and others.

The first flight on a rocket-propelled aircraft with a liquid-propellant engine was made in the Soviet Union in February 1940. As power plant aircraft was used rocket engine. In 1941, under the leadership of the Soviet designer V.F. Bolkhovitinov, the first jet aircraft was built - a fighter with a liquid-propellant engine. His tests were carried out in May 1942 by pilot G. Ya. Bakhchivadzhi.

At the same time, the first flight of a German fighter with such an engine took place. In 1943, the United States tested the first American jet aircraft, on which a liquid-propellant engine was installed. In Germany, in 1944, several fighters with these Messerschmitt-designed engines were built and in the same year they were used in a combat situation on the Western Front.

In addition, liquid propellant rocket engines were used on German V2 rockets, created under the direction of W. von Braun.

In the 1950s, liquid rocket engines were installed on ballistic missiles, and then on artificial satellites of the Earth, the Sun, the Moon and Mars, automatic interplanetary stations.

The rocket engine consists of a combustion chamber with a nozzle, a turbopump unit, a gas generator or a steam gas generator, an automation system, control elements, an ignition system and auxiliary units(heat exchangers, mixers, drives).

The idea of ​​jet engines has been repeatedly put forward in different countries. The most important and original works in this respect are the studies carried out in 1908–1913. French scientist R. Loren, who, in particular, in 1911 proposed a number of schemes for ramjet engines. These engines use atmospheric air as an oxidizer, and the air in the combustion chamber is compressed by dynamic air pressure.

In May 1939, the first test of a rocket with a ramjet engine designed by P. A. Merkulov took place in the USSR. It was a two-stage rocket (the first stage was a powder rocket) with a takeoff weight of 7.07 kg, and the weight of fuel for the second stage of a ramjet engine was only 2 kg. During the test, the rocket reached a height of 2 km.

In 1939–1940 for the first time in the world in the Soviet Union, summer tests of jet engines installed as additional engines on an aircraft designed by N.P. Polikarpov were carried out. In 1942, ramjet engines designed by E. Senger were tested in Germany.

The jet engine consists of a diffuser in which air is compressed due to the kinetic energy of the oncoming air flow. Fuel is injected into the combustion chamber through the nozzle and the mixture ignites. The jet stream exits through the nozzle.

The operation of the WFD is continuous, so there is no starting thrust in them. In this regard, at flight speeds less than half the speed of sound, jet engines are not used. The use of WFD is most effective at supersonic speeds and high altitudes. The takeoff of an aircraft with a jet engine is carried out using solid or liquid propellant rocket engines.

Another group of jet engines, turbocompressor engines, has received more development. They are divided into turbojet, in which thrust is created by a jet of gases flowing from a jet nozzle, and turboprop, in which the main thrust is created by a propeller.

In 1909, the design of a turbojet engine was developed by engineer N. Gerasimov. In 1914, Lieutenant of the Russian Navy M.N. Nikolskoy designed and built a model of a turboprop aircraft engine. The gaseous combustion products of a mixture of turpentine and nitric acid served as the working fluid for driving the three-stage turbine. The turbine worked not only on the propeller: the exhaust gaseous products of combustion, directed to the tail (jet) nozzle, created jet thrust in addition to the thrust force of the propeller.

In 1924, V. I. Bazarov developed the design of an aircraft turbocompressor jet engine, which consisted of three elements: a combustion chamber, a gas turbine, and a compressor. Flow compressed air here for the first time it was divided into two branches: the smaller part went into the combustion chamber (to the burner), and the larger part was mixed with the working gases to lower their temperature in front of the turbine. This ensured the safety of the turbine blades. The power of the multistage turbine was used to drive the centrifugal compressor of the engine itself and partly to rotate the propeller. In addition to the propeller, thrust was created by the reaction of a jet of gases passed through the tail nozzle.

In 1939, the construction of turbojet engines designed by A. M. Lyulka began at the Kirov Plant in Leningrad. His trials were interrupted by the war.

In 1941, in England, the first flight was made on an experimental fighter aircraft equipped with a turbojet engine designed by F. Whittle. It was equipped with an engine gas turbine, which actuated a centrifugal compressor that supplies air to the combustion chamber. Combustion products were used to create jet thrust.

Whittle's Gloster aircraft (E.28/39)

In a turbojet engine, air entering during flight is compressed first in the air intake and then in the turbocharger. Compressed air is fed into the combustion chamber, where liquid fuel (most often aviation kerosene) is injected. Partial expansion of the gases formed during combustion occurs in the turbine that rotates the compressor, and the final expansion occurs in the jet nozzle. An afterburner can be installed between the turbine and the jet engine, designed for additional combustion of fuel.

Today, most military and civil aircraft, as well as some helicopters, are equipped with turbojet engines.

In a turboprop engine, the main thrust is created by a propeller, and an additional (about 10%) - by a jet of gases flowing from a jet nozzle. The principle of operation of a turboprop engine is similar to a turbojet engine, with the difference that the turbine rotates not only the compressor, but also the propeller. These engines are used in subsonic aircraft and helicopters, as well as for the movement of high-speed ships and cars.

The earliest solid propellant jet engines were used in combat missiles. Them wide application began in the 19th century, when missile units appeared in many armies. At the end of the XIX century. the first smokeless powders were created, with more stable combustion and greater efficiency.

In the 1920s-1930s, work was underway to create jet weapons. This led to the appearance of rocket launchers - "Katyusha" in the Soviet Union, six-barreled rocket mortars in Germany.

Obtaining new types of gunpowder made it possible to use solid-propellant jet engines in combat missiles, including ballistic ones. In addition, they are used in aviation and astronautics as engines of the first stages of launch vehicles, starting engines for aircraft with ramjet engines and brake engines for spacecraft.

A solid propellant jet engine consists of a body (combustion chamber) in which the entire supply of fuel and a jet nozzle are located. The body is made of steel or fiberglass. Nozzle - made of graphite, refractory alloys, graphite.

The fuel is ignited by an igniter.

Thrust is controlled by changing the combustion surface of the charge or the area of ​​the critical section of the nozzle, as well as by injecting liquid into the combustion chamber.

The direction of thrust can be changed by gas rudders, a deflecting nozzle (deflector), auxiliary control engines, etc.

Jet solid propellant engines are very reliable, can be stored for a long time, and therefore, are constantly ready for launch.

Have you ever wondered how a jet engine works? The jet thrust that powers it has been known since ancient times. But they were only able to put it into practice at the beginning of the last century, as a result of the arms race between England and Germany.

The principle of operation of a jet aircraft engine is quite simple, but it has some nuances that are strictly observed in their production. In order for the plane to be able to stay in the air reliably, they must work perfectly. After all, the lives and safety of all who are on board the aircraft depend on it.

It is driven by jet thrust. It needs some kind of fluid pushed out from the back of the system and giving it forward motion. Works here Newton's third law which says: "For every action there is an equal and opposite reaction."

At the jet engine air instead of liquid. It creates a force that provides movement.

It uses hot gases and a mixture of air with combustible fuel. This mixture comes out of it at high speed and pushes the plane forward, allowing it to fly.

If we talk about the device of a jet aircraft engine, then it is combination of the four important details:

• compressor;
• combustion chambers;
• turbines;
• exhaust.

The compressor consists from several turbines, which suck in air and compress it as it passes through the angled blades. When compressed, the temperature and pressure of the air increase. Part of the compressed air enters the combustion chamber, where it is mixed with fuel and ignited. It increases thermal energy of the air.

Jet engine.

hot mix on high speed exits the chamber and expands. There she goes through yet one turbine with blades that rotate due to the energy of the gas.

The turbine is connected to the compressor at the front of the engine., and thus sets it in motion. Hot air exits through the exhaust. At this point, the temperature of the mixture is very high. And it keeps growing thanks to throttling effect. After that, the air comes out of it.

Development of jet-powered aircraft has begun in the 30s of the last century. The British and Germans began to develop similar models. This race was won by German scientists. Therefore, the first aircraft with a jet engine was "Swallow" in the Luftwaffe. "Gloucester Meteor" took to the air a little later. The first aircraft with such engines are described in detail

The engine of a supersonic aircraft is also jet, but in a completely different modification.

How does a turbojet engine work?

Jet engines are used everywhere, and turbojet engines are installed large. Their difference is that the first carries with it a supply of fuel and oxidizer, and the design ensures their supply from the tanks.

aircraft turbojet engine carries with it only fuel, and the oxidizing agent - air - is forced by the turbine from the atmosphere. Otherwise, the principle of its operation is the same as that of the reactive one.

One of their most important details is This is the turbine blade. It depends on the power of the engine.

Scheme of a turbojet engine.

It is they who develop the traction forces necessary for the aircraft. Each of the blades produces 10 times more energy than a typical car engine. They are installed behind the combustion chamber, in the part of the engine where the most high pressure, and the temperature reaches up to 1400 degrees Celsius.

During the production of blades, they pass through the process of monocrystallization which gives them strength and durability.

Each engine is tested for full thrust before being installed on an aircraft. He must pass certification by the European Safety Council and the company that produced it. One of the most large firms their production is Rolls-Royce.

What is a nuclear powered aircraft?

During the Cold War attempts were made to create a jet engine not on chemical reaction, but on the heat that would be produced by a nuclear reactor. It was put in place of the combustion chamber.

Air passes through the reactor core, lowering its temperature and raising its own. It expands and flows out of the nozzle at a speed greater than the flight speed.

Combined turbo-nuclear engine.

In the USSR, it was tested based on TU-95. In the USA, too, they did not lag behind scientists in the Soviet Union.

In the 60s studies in both sides gradually ceased. The main three problems that hindered the development were:

• safety of pilots during the flight;
• release of radioactive particles into the atmosphere;
• in the event of a plane crash, a radioactive reactor can explode, causing irreparable harm to all living things.

How are jet engines for model airplanes made?

Their production for aircraft models takes about 6 hours. Turned first aluminum base plate to which all other parts are attached. It is the same size as a hockey puck.

Attached to it is a cylinder., so it turns out something like a tin can. it future engine internal combustion. Next, the supply system is installed. To fix it, screws are screwed into the main plate, previously lowered into a special sealant.

Aircraft model engine.

Starter channels are mounted on the other side of the chamber to redirect gas emissions to the turbine wheel. Installed in the hole on the side of the combustion chamber incandescent spiral. It ignites the fuel inside the engine.

Then they put the turbine and the central axis of the cylinder. They put on it compressor wheel which forces air into the combustion chamber. It is checked with a computer before the launcher is fixed.

The finished engine is once again checked for power. Its sound is slightly different from the sound of an aircraft engine. He, of course, of lesser strength, but completely resembles him, giving more similarity to the model.

JET ENGINE, an engine that creates the traction force necessary for movement by converting potential energy into kinetic energy of the jet stream of the working fluid. Under the working fluid m, in relation to engines, is understood a substance (gas, liquid, solid body), with the help of which the thermal energy released during the combustion of fuel is converted into useful mechanical work. As a result of the expiration of the working fluid from the engine nozzle, a reactive force is formed in the form of a reaction (recoil) of a jet directed in space in the direction opposite to the outflow of the jet. Various types of energy (chemical, nuclear, electrical, solar) can be converted into the kinetic (speed) energy of a jet stream in a jet engine.

A jet engine (direct reaction engine) combines the engine itself with a propeller, that is, it provides its own movement without the participation of intermediate mechanisms. To create jet thrust (engine thrust) used by a jet engine, you need: a source of initial (primary) energy, which is converted into the kinetic energy of the jet stream; the working fluid, which is ejected from the jet engine in the form of a jet stream; the jet engine itself is an energy converter. Engine thrust - this is a reactive force, which is the result of gas-dynamic forces of pressure and friction applied to the internal and external surfaces of the engine. Distinguish between internal thrust (reactive thrust) - the resultant of all gas-dynamic forces applied to the engine, without taking into account external resistance and effective thrust, taking into account the external resistance of the power plant. The initial energy is stored on board an aircraft or other apparatus equipped with a jet engine (chemical fuel, nuclear fuel), or (in principle) can come from outside (solar energy).

To obtain a working fluid in a jet engine, a substance taken from the environment (for example, air or water) can be used; a substance located in the tanks of the apparatus or directly in the chamber of a jet engine; a mixture of substances coming from the environment and stored on board the vehicle. Modern jet engines most often use chemical energy as primary energy. In this case, the working fluid is incandescent gases - combustion products of chemical fuel. During the operation of a jet engine, the chemical energy of the burning substances is converted into the thermal energy of the combustion products, and the thermal energy of the hot gases is converted into the mechanical energy of the forward motion of the jet and, consequently, the apparatus on which the engine is installed.

The principle of operation of a jet engine

In a jet engine (Fig. 1), a jet of air enters the engine, meets with turbines rotating at great speed compressor , which sucks in air from the external environment (using a built-in fan). Thus, two tasks are solved - the primary air intake and the cooling of the entire engine as a whole. Compressor turbine blades compress the air by about 30 times or more and "push" it (inject) into the combustion chamber (the working fluid is generated), which is the main part of any jet engine. The combustion chamber also acts as a carburetor, mixing fuel with air. This may be, for example, a mixture of air and kerosene, as in a modern turbojet engine. jet aircraft, or a mixture of liquid oxygen with alcohol, as in some liquid rocket engines, or some kind of solid propellant for powder rockets. After education fuel-air mixture it is ignited and energy is released in the form of heat, i.e., jet engines can only be fueled by substances that, during a chemical reaction in the engine (combustion), release a lot of heat, and also form a large amount of gases.

In the process of ignition, there is a significant heating of the mixture and surrounding parts, as well as volumetric expansion. In fact, the jet engine uses a controlled explosion for propulsion. The combustion chamber of a jet engine is one of its hottest parts (the temperature in it reaches 2700 ° C), it must be constantly cooled intensively. The jet engine is equipped with a nozzle through which hot gases, the products of fuel combustion in the engine, flow out of the engine at great speed. In some engines, gases enter the nozzle immediately after the combustion chamber, for example, in rocket or ramjet engines. In turbojet engines, the gases after the combustion chamber first pass through turbine , which is given part of its thermal energy to drive a compressor that compresses air in front of the combustion chamber. But anyway, the nozzle is the last part of the engine - gases flow through it before leaving the engine. It creates directly jet stream. The nozzle is sent cold air, forced by the compressor for cooling internal details engine. The jet nozzle may have various forms and design depending on the type of engine. If the outflow velocity must exceed the speed of sound, then the nozzle is given the shape of an expanding pipe, or first narrowing and then expanding (Laval nozzle). Only in a pipe of this shape can gas be accelerated to supersonic speeds, to step over the "sonic barrier".

Depending on whether or not the environment is used during the operation of a jet engine, they are divided into two main classes - jet engines(WFD) and rocket engines(RD). All WFD - heat engines, the working fluid of which is formed during the oxidation reaction of a combustible substance with atmospheric oxygen. The air coming from the atmosphere makes up the bulk of the working fluid of the WFD. Thus, an apparatus with a WFD carries a source of energy (fuel) on board, and draws most of the working fluid from the environment. These include turbojet engine (TRD), ramjet engine (ramjet), pulsed jet engine (PuVRD), hypersonic ramjet engine (scramjet). Unlike the WFD, all components of the working fluid of the RD are on board the vehicle equipped with the RD. The absence of a propeller interacting with the environment and the presence of all components of the working fluid on board the vehicle make the RD suitable for space operation. There are also combined rocket engines, which are, as it were, a combination of both main types.

Main characteristics of jet engines

Main technical parameter characterizing a jet engine is thrust - the force that develops the engine in the direction of movement of the device, specific impulse - the ratio of engine thrust to the mass of rocket fuel (working fluid) consumed in 1 s, or an identical characteristic - specific consumption fuel (the amount of fuel consumed in 1 s per 1 N of thrust developed by a jet engine), engine specific gravity (mass of a jet engine in working condition per unit of thrust developed by it). For many types of jet engines important characteristics are dimensions and resource. Specific impulse is an indicator of the degree of perfection or quality of the engine. The above diagram (Fig. 2) graphically presents the upper values ​​of this indicator for different types jet engines depending on the flight speed, expressed in the form of a Mach number, which allows you to see the scope of each type of engine. This indicator is also a measure of the efficiency of the engine.

Thrust - the force with which a jet engine acts on a device equipped with this engine - is determined by the formula: $$P = mW_c + F_c (p_c - p_n),$$ where $m$ is mass flow(mass consumption) of the working fluid for 1 s; $W_c$ is the speed of the working fluid in the nozzle section; $F_c$ is the area of ​​the outlet section of the nozzle; $p_c$ – gas pressure in the nozzle section; $p_n$ – ambient pressure (usually atmospheric pressure). As can be seen from the formula, the thrust of a jet engine depends on the ambient pressure. It is greatest in emptiness and least of all in the densest layers of the atmosphere, i.e., it varies depending on the flight altitude of an apparatus equipped with a jet engine above sea level, if flight in the Earth’s atmosphere is considered. The specific impulse of a jet engine is directly proportional to the speed of the outflow of the working fluid from the nozzle. The outflow rate increases with an increase in the temperature of the outgoing working fluid and a decrease in the molecular weight of the fuel (the lower the molecular weight of the fuel, the greater the volume of gases formed during its combustion, and, consequently, the rate of their outflow). Since the rate of exhaust of combustion products (working fluid) is determined by the physicochemical properties of the fuel components and design features engine, being a constant value at not very big changes mode of operation of a jet engine, then the magnitude of the reactive force is determined mainly by the mass per second fuel consumption and varies over a very wide range (a minimum for electric ones - a maximum for liquid and solid rocket engines). Low-thrust jet engines are mainly used in aircraft stabilization and control systems. In space, where gravitational forces are felt weakly and there is practically no medium, the resistance of which would have to be overcome, they can also be used for overclocking. RD with maximum thrust is necessary for launching rockets at long ranges and altitudes, and especially for launching aircraft into space, i.e., for accelerating them to first space velocity. Such engines consume a very large amount of fuel; they usually work for a very short time, accelerating the rockets to a given speed.

WFD is used as the main component of the working fluid ambient air, much more economical. WJDs can operate continuously for many hours, making them suitable for aviation use. Different schemes allowed them to be used for aircraft operated on different modes flight. Turbojet engines (TRDs) are widely used, which are installed on almost all modern aircraft without exception. Like all engines that use atmospheric air, turbojet engines need special device to compress air before it enters the combustion chamber. In a turbojet engine, a compressor is used to compress the air, and the design of the engine largely depends on the type of compressor. Uncompressor jet engines are much simpler in design, in which the necessary pressure increase is carried out in other ways; it's pulsating and direct-flow motors. In a pulsating jet engine(PuVRD) this is usually done by a valve grill installed at the engine inlet, when a new portion of the fuel-air mixture fills the combustion chamber and a flash occurs in it, the valves close, isolating the combustion chamber from the engine inlet. As a result, the pressure in the chamber rises, and the gases rush out through the jet nozzle, after which the whole process is repeated. In a compressorless engine of another type, a ramjet, there is not even this valve grid and atmospheric air, entering the engine inlet at a speed equal speed flight, is compressed due to the velocity pressure and enters the combustion chamber. The injected fuel burns, the heat content of the stream increases, which flows out through the jet nozzle at a speed more speed flight. Due to this, the jet thrust of the ramjet is created. The main disadvantage of the ramjet is the inability to independently provide takeoff and acceleration of the aircraft (LA). It is required first to accelerate the aircraft to a speed at which the ramjet is launched and its stable operation is ensured. The peculiarity of the aerodynamic scheme of supersonic aircraft with ramjet engines (ramjet engines) is due to the presence of special accelerating engines that provide the speed necessary to start stable operation of the ramjet. This makes the tail part of the structure heavier and requires the installation of stabilizers to ensure the necessary stability.

History reference

The principle of jet propulsion has been known for a long time. Heron's ball can be considered the ancestor of the jet engine. Solid rocket motors(RDTT - solid fuel rocket engine) - powder rockets appeared in China in the 10th century. n. e. For hundreds of years, such missiles were used first in the East, and then in Europe as fireworks, signal, combat. An important stage in the development of the idea of ​​jet propulsion was the idea of ​​using a rocket as an engine for an aircraft. It was first formulated by the Russian revolutionary Narodnaya Volya N. I. Kibalchich, who in March 1881, shortly before his execution, proposed a scheme for an aircraft (rocket plane) using jet propulsion from explosive powder gases. Solid propellant rocket engines are used in all classes of military missiles (ballistic, anti-aircraft, anti-tank, etc.), in space (for example, as starting and sustainer engines) and aviation technology (aircraft take-off boosters, in systems ejection), etc. Small solid propellant engines are used as boosters for aircraft takeoff. Electric rocket engines and nuclear rocket engines can be used in spacecraft.

Turbojet engines and dual-circuit turbojet engines are equipped with most military and civil aircraft around the world, they are used in helicopters. These jet engines are suitable for flights at both subsonic and supersonic speeds; they are also installed on projectile aircraft, supersonic turbojet engines can be used in the first stages aerospace aircraft, rocket and space technology, etc.

Of great importance for the creation of jet engines were the theoretical works of Russian scientists S. S. Nezhdanovsky, I. V. Meshchersky, N. E. Zhukovsky, the works of the French scientist R. Enot-Peltri, the German scientist G. Oberth. An important contribution to the creation of the VRD was the work of the Soviet scientist B. S. Stechkin, The Theory of an Air Jet Engine, published in 1929. Practically more than 99% of aircraft use a jet engine to one degree or another.