A fan is located in front of the jet engine. He takes air from external environment sucking it into the turbine. In engines used in rockets, air replaces liquid oxygen. The fan is equipped with many specially shaped titanium blades.
They try to make the fan area large enough. In addition to air intake, this part of the system is also involved in engine cooling, protecting its chambers from destruction. Behind the fan is the compressor. It pressurizes air into the combustion chamber.
One of the main structural elements jet engine - combustion chamber. In it, the fuel is mixed with air and ignited. The mixture ignites, accompanied by a strong heating of the body parts. fuel mixture expands under high temperature. In fact, a controlled explosion occurs in the engine.
From the combustion chamber, the mixture of fuel and air enters the turbine, which consists of many blades. The jet stream with force presses on them and sets the turbine in rotation. The force is transmitted to the shaft, compressor and fan. A closed system is formed, the operation of which requires only a constant supply of the fuel mixture.
The last detail of a jet engine is a nozzle. A heated stream enters from the turbine here, forming a jet stream. This part of the engine is also supplied from the fan cold air. It serves to cool the entire structure. The airflow protects the nozzle collar from harmful effects jet stream, preventing the parts from melting.
How a jet engine works
The working fluid of the engine is reactive. She is very high speed flows out of the nozzle. This creates a reactive force that pushes the entire device in the opposite direction. The traction force is generated solely by the action of the jet, without any support on other bodies. This feature of the jet engine allows it to be used as power plant for rockets, aircraft and spacecraft.
In part, the operation of a jet engine is comparable to the action of a jet of water flowing from a hose. Under huge pressure liquid is supplied through the sleeve to the narrowed end of the hose. The speed of the water exiting the hose is higher than inside the hose. This creates a back pressure force that allows the firefighter to hold the hose with only great difficulty.
The production of jet engines is a special branch of technology. Since the temperature of the working fluid here reaches several thousand degrees, engine parts are made from high-strength metals and those materials that are resistant to melting. Separate parts of jet engines are made, for example, from special ceramic compositions.
Jet engine was invented Hans von Ohain (Dr. Hans von Ohain), an outstanding German design engineer and Frank Whittle (Sir Frank Whittle). The first patent for a working gas turbine engine was obtained in 1930 by Frank Whittle. However, it was Ohain who assembled the first working model.
On August 2, 1939, the first jet aircraft took to the skies - He 178 (Heinkel 178), equipped with an HeS 3 engine developed by Ohain.
Quite simple and at the same time extremely difficult. Simply according to the principle of operation: outboard air (in rocket engines - liquid oxygen) is sucked into the turbine, where it mixes with fuel and burns, at the end of the turbine it forms the so-called. “ working body” (jet stream), which moves the car.
Everything is so simple, but in fact - this is a whole field of science, because in such engines working temperature reaches thousands of degrees Celsius. One of the most important problems of turbojet engine building is the creation of non-consumable parts, from consumable metals. But in order to understand the problems of designers and inventors, you must first study in more detail principle device engine.
Jet engine device
main parts of a jet engine
At the beginning of the turbine is always fan, which sucks air from the external environment into the turbine. The fan has a large area and a huge number of blades special form made from titanium. There are two main tasks - the primary air intake and cooling of the entire engine as a whole, by pumping air between the outer shell of the engine and internal parts. This cools the mixing and combustion chambers and prevents them from collapsing.
Immediately behind the fan is a powerful compressor which forces air at high pressure into the combustion chamber.
The combustion chamber also acts as a carburetor, mixing fuel with air. After the formation of fuel air mixture she is set on fire. In the process of ignition, there is a significant heating of the mixture and surrounding parts, as well as volumetric expansion. Actually jet engine uses a controlled explosion to move.
The combustion chamber of a jet engine is one of the hottest parts of it - it needs constant intensive cooling. But even this is not enough. The temperature in it reaches 2700 degrees, so it is often made of ceramics.
After the combustion chamber burning fuel-air mixture goes directly to the turbine.
Turbine consists of hundreds of blades, which are pressed by the jet stream, causing the turbine to rotate. The turbine, in turn, rotates the shaft on which the fan and compressor “sit”. Thus, the system is closed and requires only the supply of fuel and air for its functioning.
After the turbine, the flow is directed to the nozzle. The jet engine nozzle is the last but not least part of the jet engine. It forms a direct jet stream. Cool air blown by the fan is directed into the nozzle to cool the internal parts of the engine. This flow restricts the nozzle collar from the super-hot jet stream and allows it to melt.
Rejected thrust vector
Nozzles for jet engines are very different. The most advanced considers a movable nozzle, standing on engines with a deflectable thrust vector. It can contract and expand, as well as deviate to significant angles, adjusting and guiding directly jet stream. This makes aircraft with thrust vectoring engines very manoeuvrable. maneuvering occurs not only due to the mechanisms of the wing, but also directly to the engine.
Types of jet engines
There are several basic types of jet engines.
Classic F-15 jet engine
classic jet engine- the fundamental device of which we described above. It is mainly used on fighters in various modifications.
Turboprop. In this type of engine, the power of the turbine is directed through a reduction gear to rotate the classic propeller. Such engines will allow large aircraft to fly at acceptable speeds and use less fuel. The normal cruising speed of a turboprop aircraft is considered to be 600-800 km/h.
This type of engine is a more economical relative of the classic type. the main difference is that a larger diameter fan is installed at the inlet, which not only supplies air to the turbine, but also creates a sufficiently powerful flow outside it. Thus, increased efficiency is achieved by improving efficiency.
Used on liners and large aircraft.
Scramjet engine (Ramjet)
Works without moving parts. Air is forced into the combustion chamber in a natural way, due to the deceleration of the flow against the inlet fairing.
Used on trains, planes, UAVs, and military missiles, as well as on bicycles and scooters.
And finally - a video of the jet engine:
The pictures are taken from various sources. Russification of pictures - Laboratories 37.
Jet engines are such devices that create the traction force necessary for the process of movement by converting the internal energy of the fuel into the kinetic energy of jet streams in the working fluid. The working fluid rapidly flows out of the engine, and according to the law of conservation of momentum, a reactive force is formed that pushes the engine in the opposite direction. To disperse the working fluid, it can be used as an expansion of gases heated in a variety of ways to high temperatures, as well as in other ways. physical processes, in particular, by the acceleration of charged particles in an electrostatic field.
Jet engines combine the actual engines with propellers. It means that they create tractive effort exclusively by interaction with working bodies, without supports, or by contacts with other bodies. That is, they provide themselves with their own promotion, while the intermediate mechanisms do not take any part. As a result, they are mainly used to propel aircraft, rockets and, of course, spacecraft.
What is engine thrust?
Engine thrust is called reactive force, which is manifested by gas-dynamic forces, pressure and friction applied to internal and external parties engine.
Traction varies by:
- Internal (jet thrust), when external resistance is not taken into account;
- Efficient, taking into account the external resistance of power plants.
The starting energy is stored on board aircraft or other vehicles equipped with jet engines (chemical fuel, nuclear fuel), or can flow in from outside (for example, solar energy).
How is jet thrust formed?
To form jet thrust (engine thrust), which is used by jet engines, you will need:
- Sources of initial energy, which are converted into kinetic energy of jet streams;
- Working fluids that will be ejected from jet engines as jet streams;
- The jet engine itself as an energy converter.
How to get a working body?
To acquire a working fluid in jet engines, the following can be used:
- Substances taken from environment(for example, water or air);
- Substances in the tanks of vehicles or in the chambers of jet engines;
- Mixed substances coming from the environment and stored on board vehicles.
Modern jet engines mainly use chemical energy. The working bodies are a mixture of hot gases, which are products of the combustion of chemical fuel. When a jet engine is running, the chemical energy from the burning substances is converted into thermal energy from the products of combustion. At the same time, thermal energy from hot gases is converted into mechanical energy from the translational movements of jet streams and apparatus on which engines are installed.
In jet engines, jets of air streams that enter the engines meet with compressor turbines that turn at an enormous speed, which suck in air from the environment (using built-in fans). Therefore, two problems are being solved:
- Primary air intake;
- Cooling of the whole engine.
Compressor turbine blades compress the air approximately 30 times or more, “push” it (injection) into the combustion chamber (the working fluid is generated). In general, combustion chambers also perform the role of carburetors, mixing fuel with air.
These can be, in particular, mixtures of air and kerosene, as in turbojet engines of modern jet aircraft, or mixtures of liquid oxygen and alcohol, such as some liquid rocket engines, or some other solid fuel in powder rockets. As soon as the fuel-air mixture is formed, it ignites with the release of energy in the form of heat. Thus, fuel in jet engines can only be substances that, as a result of chemical reactions in engines (during combustion), release heat, while forming a lot of gases.
When ignited, a significant heating of the mixture and parts around with volumetric expansion takes place. As a matter of fact, jet engines use controlled explosions for propulsion. The combustion chambers in jet engines are among the hottest elements ( temperature regime they can reach up to 2700 ° C), and they require constant intensive cooling.
Jet engines are equipped with nozzles through which heated gases, which are products of fuel combustion, flow out of them at great speed. In some engines, the gases are in the nozzles immediately after the combustion chambers. This applies, for example, to rocket or ramjet engines.
Turbojet engines operate somewhat differently. So, gases, after the combustion chambers, first pass through turbines, to which they give up their thermal energy. This is done in order to set in motion the compressors, which will serve to compress the air in front of the combustion chamber. In any case, the nozzles remain last parts engines through which gases flow. Actually, they form a direct jet stream.
Cold air is sent to the nozzles, which is forced by compressors to cool the internal parts of the engines. Jet nozzles may have different configurations and designs based on the types of engines. So, when the flow velocity must be higher than the speed of sound, then the nozzles are given the shape of expanding pipes or, at first, narrowing, and then expanding (the so-called Laval nozzles). Only with pipes of this configuration can gases be accelerated to supersonic speeds, with the help of which jet aircraft step over "sonic barriers".
Based on whether the environment is involved in the operation of jet engines, they are divided into the main classes of air-jet engines (WRD) and rocket engines (RD). All WFDs are heat engines, the working fluids of which are formed when the reaction of the oxidation of combustible substances with oxygen in the air masses occurs. Incoming from the atmosphere air currents form the basis of the working bodies of the WFD. Thus, vehicles with VJD carry sources of energy (fuel) on board, but most of the working fluids are drawn from the environment.
VRD devices include:
- Turbojet engines (TRD);
- Direct-flow air-jet engines (ramjet);
- Pulsating jet engines (PuVRD);
- Hypersonic ramjet engines (scramjet).
In contrast to air-jet engines, all components of the working bodies of the RD are on board vehicles equipped with rocket engines. The absence of propellers interacting with the environment, as well as the presence of all the components of the working bodies on board the vehicles, make rocket engines suitable for operation in outer space. There is also a combination of rocket engines, which is a kind of combination of the two main varieties.
Briefly about the history of the jet engine
It is believed that the jet engine was invented by Hans von Ohain and the outstanding German design engineer Frank Whittle. It was Frank Whittle who received the first patent for a working gas turbine engine in 1930. However, the first working model was assembled by Ohain himself. At the end of the summer of 1939, the first jet aircraft appeared in the sky - He-178 (Heinkel-178), which was equipped with an HeS 3 engine developed by Ohain.
How is a jet engine built?
The device of jet engines is quite simple and at the same time extremely complex. It is simple in principle. So, outboard air (in rocket engines - liquid oxygen) is sucked into the turbine. After that, it begins to mix with fuel there and burn. At the edge of the turbine, a so-called "working body" (previously mentioned jet stream) is formed, which propels the aircraft or spacecraft.
For all its simplicity, in fact, this is a whole science, because in the middle of such engines, the operating temperature can reach more than a thousand degrees Celsius. One of the most important problems in turbojet engine building is the creation of non-consumable parts from metals that can themselves be melted.
At the beginning, in front of each turbine, there is always a fan that sucks air masses from the environment into the turbines. Fans have a large area, as well as a huge number of blades of special configurations, the material for which was titanium. Immediately behind the fans are powerful compressors, which are necessary for forcing air under enormous pressure into the combustion chambers. After the combustion chambers, the burning air-fuel mixtures are sent to the turbine itself.
Turbines consist of many blades, which are subjected to pressure by reactive flows, which cause the turbines to rotate. Further, the turbines rotate the shafts on which the fans and compressors are “mounted”. Actually, the system becomes closed and needs only a supply of fuel and air masses.
Following the turbines, the flows are directed to the nozzles. Jet engine nozzles are the last, but not the least important part in jet engines. They form direct jet streams. Cold air masses are sent to the nozzles, pumped by fans to cool the "insides" of the engines. These streams restrict the collars of the nozzles from super-hot jet streams and do not allow them to melt.
Rejected thrust vector
Jet engines have nozzles of a wide variety of configurations. The most advanced are considered to be movable nozzles placed on engines that have a deflectable thrust vector. They can be compressed and expanded, as well as deflected at significant angles - this is how reactive flows are regulated and directed directly. Due to this, aircraft with engines having a deflectable thrust vector become extremely maneuverable, because the maneuvering processes occur not only due to the actions of the wing mechanisms, but also directly by the engines themselves.
Types of jet engines
There are several main types of jet engines. So, the aircraft engine in the F-15 aircraft can be called a classic jet engine. Most of these engines are used mainly on fighters of a wide variety of modifications.
Two-bladed turboprop engines
In this variety turboprop engines the power of the turbines is directed through reduction gears to rotate classical propellers. The presence of such engines allows large aircraft to fly at the maximum acceptable speeds and at the same time consume less jet fuel. Normal cruising speed turboprop aircraft can have 600-800 km/h.
Turbofan jet engines
This type of engine is more economical in the family of classic types of engines. Home hallmark they are that large-diameter fans are placed at the inlet, which supply air flows not only for the turbines, but also create quite powerful flows outside them. As a result, increased economy can be achieved by improving the efficiency. They are used on liners and large aircraft.
Direct-flow jet engines
This type of engine functions in such a way that it does not need moving parts. Air masses are forced into the combustion chamber in an unconstrained way, thanks to the deceleration of flows against the inlet fairings. In the future, everything is done the same as in ordinary jet engines, namely, air flows are mixed with fuel and exit like jet streams from nozzles. Scramjet engines are used in trains, aircraft, drones, rockets, and can also be mounted on bicycles or scooters.
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. In the kinetic (speed) energy of the jet stream in a jet engine can be converted different kinds energy (chemical, nuclear, electrical, solar).
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 ( jet 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 (the energy of the Sun).
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 thermal energy of combustion products, and the thermal energy of hot gases is converted into mechanical energy. forward movement jet stream 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 the hottest parts of it (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 forms a direct jet stream. The cold air forced by the compressor is directed into the nozzle to cool the internal parts of the 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.
WFDs use ambient air as the main component of the working fluid, which is much more economical. WJDs can operate continuously for many hours, making them suitable for aviation use. Miscellaneous 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 using 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; these are 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 flow increases, which flows out through the jet nozzle at a speed greater than the flight speed. 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.
Historical 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 milestone 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 theoretical work 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.
Reactive is understood as a movement in which one of its parts is separated from the body at a certain speed. The resulting force acts on its own. In other words, it lacks even the slightest contact with external bodies.
in nature
During a summer vacation in the south, almost every one of us, swimming in the sea, met with jellyfish. But few people thought about the fact that these animals move in the same way as a jet engine. The principle of operation in nature of such an aggregate can be observed when moving some types of marine plankton and dragonfly larvae. Moreover, the efficiency of these invertebrates is often higher than that of technical means.
Who else can clearly demonstrate what the principle of operation of a jet engine is? Squid, octopus and cuttlefish. A similar movement is made by many other marine mollusks. Take, for example, cuttlefish. She draws water into her gill cavity and throws it vigorously through a funnel, which she directs back or sideways. In this case, the mollusk is able to make movements in the right direction.
The principle of operation of a jet engine can also be observed when moving the lard. This marine animal takes in water into a wide cavity. After that, the muscles of his body contract, pushing the liquid out through the hole in the back. The reaction of the resulting jet allows the grease to move forward.
Naval missiles
But squids have achieved the greatest perfection in jet navigation. Even the shape of the rocket itself seems to be copied from this particular marine life. When moving at low speed, the squid periodically bends its diamond-shaped fin. But for a quick throw, he has to use his own "jet engine". The principle of operation of all his muscles and body should be considered in more detail.
Squids have a peculiar mantle. This is the muscle tissue that surrounds his body from all sides. During movement, the animal sucks a large volume of water into this mantle, sharply ejecting a jet through a special narrow nozzle. Such actions allow squids to move in jerks backwards at speeds up to seventy kilometers per hour. the animal collects all its ten tentacles in a bundle, which gives the body a streamlined shape. The nozzle has a special valve. The animal turns it with the help of muscle contraction. This allows the marine life to change direction. The role of the steering wheel during the movements of the squid is also played by its tentacles. He directs them to the left or right, down or up, easily dodging collisions with various obstacles.
There is a species of squid (stenoteuthys), which holds the title of the best pilot among mollusks. Describe the principle of operation of a jet engine - and you will understand why, chasing fish, this animal sometimes jumps out of the water, even getting on the decks of ships sailing across the ocean. How does it happen? Pilot squid, being in the water element, develops maximum jet thrust for him. This allows him to fly over the waves at a distance of up to fifty meters.
If we consider a jet engine, the principle of operation of which animal can be mentioned more? These are, at first glance, baggy octopuses. Their swimmers are not as fast as squids, but in case of danger even the best sprinters can envy their speed. Biologists who have studied the migration of octopuses have found that they move like a jet engine has a principle of operation.
With each jet of water thrown out of the funnel, the animal makes a jerk of two or even two and a half meters. At the same time, the octopus swims in a peculiar way - backwards.
Other examples of jet propulsion
There are rockets in the world of plants. The principle of a jet engine can be observed when, even with a very light touch, the “crazy cucumber” with high speed rebounds from the stalk, simultaneously rejecting the sticky liquid with seeds. In this case, the fetus itself flies off a considerable distance (up to 12 m) in the opposite direction.
The principle of operation of a jet engine can also be observed while in a boat. If heavy stones are thrown from it into the water in a certain direction, then movement will begin in the opposite direction. It has the same principle of operation. Only there gases are used instead of stones. They create a reactive force that provides movement both in air and in rarefied space.
Fantastic Journeys
Mankind has long dreamed of flying into space. This is evidenced by the works of science fiction writers, who offered a variety of means to achieve this goal. For example, the hero of the story of the French writer Hercule Savignin, Cyrano de Bergerac, reached the moon on an iron cart, over which a strong magnet was constantly thrown up. The famous Munchausen also reached the same planet. A giant bean stalk helped him make the journey.
Jet propulsion was used in China as early as the first millennium BC. At the same time, bamboo tubes, which were filled with gunpowder, served as a kind of rockets for fun. By the way, the project of the first car on our planet, created by Newton, was also with a jet engine.
The history of the creation of the RD
Only in the 19th century. Mankind's dream of outer space began to acquire concrete features. After all, it was in this century that the Russian revolutionary N.I. Kibalchich created the world's first project with a jet engine. All the papers were drawn up by a Narodnaya Volya in prison, where he ended up after the assassination attempt on Alexander. But, unfortunately, on April 3, 1881, Kibalchich was executed, and his idea did not find practical implementation.
At the beginning of the 20th century. the idea of using rockets for flights into space was put forward by the Russian scientist K. E. Tsiolkovsky. For the first time, his work, containing a description of the movement of a body of variable mass in the form of a mathematical equation, was published in 1903. Later, the scientist developed the very scheme of a jet engine driven by liquid fuel.
Tsiolkovsky also invented a multi-stage rocket and expressed the idea of creating real space cities in near-Earth orbit. Tsiolkovsky convincingly proved that the only means for space flight is a rocket. That is, an apparatus equipped with a jet engine, refueled with fuel and an oxidizer. Only such a rocket is capable of overcoming gravity and flying beyond the Earth's atmosphere.
Space exploration
Tsiolkovsky's idea was implemented by Soviet scientists. Headed by Sergei Pavlovich Korolev, they launched the first artificial Earth satellite. On October 4, 1957, this apparatus was delivered into orbit by a rocket with a jet engine. The work of the RD was based on the conversion of chemical energy, which is transferred by the fuel to the gas jet, turning into kinetic energy. In this case, the rocket moves in the opposite direction.
The jet engine, the principle of operation of which has been used for many years, finds its application not only in astronautics, but also in aviation. But most of all it is used for After all, only RD is able to move the device in a space in which there is no any medium.
liquid jet engine
Anyone who has fired a firearm or simply watched this process from the side knows that there is a force that will certainly push the barrel back. Moreover, when more charge return will certainly increase. The jet engine works the same way. Its principle of operation is similar to how the barrel is pushed back under the action of a jet of hot gases.
As for the rocket, the process during which the mixture is ignited is gradual and continuous. This is the simplest, solid fuel engine. He is well known to all rocket modellers.
In a liquid-propellant jet engine (LRE), a mixture consisting of fuel and oxidizer is used to create a working fluid or a pushing jet. The last, as a rule, is nitric acid, or kerosene serves as fuel in a rocket engine.
The principle of operation of the jet engine, which was in the first samples, has been preserved to this day. Only now it uses liquid hydrogen. When this substance is oxidized, it increases by 30% in comparison with the first liquid-propellant rocket engines. It is worth saying that the idea of using hydrogen was proposed by Tsiolkovsky himself. However, the difficulties of working with this extremely explosive substance at that time were simply insurmountable.
What is the working principle of a jet engine? Fuel and oxidizer enter the working chamber from separate tanks. Next, the components are converted into a mixture. It burns, releasing an enormous amount of heat under pressure of tens of atmospheres.
Components enter the working chamber of a jet engine in different ways. The oxidizing agent is introduced here directly. But the fuel travels a longer path between the walls of the chamber and the nozzle. Here it warms up and, already having high temperature, is thrown into the combustion zone through numerous nozzles. Further, the jet formed by the nozzle breaks out and provides the aircraft with a pushing moment. This is how you can tell what a jet engine has the principle of operation (briefly). IN this description many components are not mentioned, without which the operation of the LRE would be impossible. Among them are compressors necessary to create the pressure required for injection, valves, supply turbines, etc.
Modern usage
Despite the fact that the operation of a jet engine requires a large number fuel, LRE continue to serve people today. They are used as the main propulsion engines in launch vehicles, as well as shunting engines for various spacecraft and orbital stations. In aviation, other types of taxiways are used, which have slightly different performance characteristics and design.
Aviation development
From the beginning of the 20th century, until the period when the Second World War, people flew only on propeller-driven aircraft. These vehicles were equipped with motors internal combustion. However, progress did not stand still. With its development, there was a need to create more powerful and faster aircraft. However, here aircraft designers are faced with a seemingly insoluble problem. The fact is that even with a slight increase, the mass of the aircraft increased significantly. However, the way out of the created situation was found by the Englishman Frank Will. He fundamentally created new engine called reactive. This invention gave a powerful impetus to the development of aviation.
The principle of operation of an aircraft jet engine is similar to the actions of a fire hose. Its hose has a tapered end. Flowing out through a narrow opening, water significantly increases its speed. The back pressure force created in this case is so strong that the firefighter can hardly hold the hose in his hands. This behavior of water can also explain the principle of operation of an aircraft jet engine.
Direct flow taxiways
This type of jet engine is the simplest. You can imagine it in the form of a pipe with open ends, which is installed on a moving plane. In front of its cross section expands. Due to this design, the incoming air reduces its speed, and its pressure increases. The widest point of such a pipe is the combustion chamber. This is where the fuel is injected and then burned. Such a process contributes to the heating of the formed gases and their strong expansion. This creates the thrust of a jet engine. It is produced by all the same gases when they burst out with force from the narrow end of the pipe. It is this thrust that makes the plane fly.
Usage issues
Scramjet engines have some disadvantages. They are able to work only on the aircraft that is in motion. An aircraft at rest cannot be activated by direct-flow taxiways. In order to lift such an aircraft into the air, any other starting engine is needed.
Solution
The principle of operation of a jet engine of a turbojet type aircraft, which is devoid of the shortcomings of a direct-flow taxiway, allowed aircraft designers to create the most advanced aircraft. How does this invention work?
The main element in a turbojet engine is gas turbine. With its help, it is activated air compressor, passing through which compressed air sent to a special chamber. The products obtained as a result of the combustion of fuel (usually kerosene) fall on the blades of the turbine, which drives it. Further, the air-gas flow passes into the nozzle, where it accelerates to high speeds and creates a huge jet thrust force.
Power increase
The reactive thrust force can increase significantly in a short period of time. For this, afterburning is used. It is the injection of an additional amount of fuel into the gas stream escaping from the turbine. Unused oxygen in the turbine contributes to the combustion of kerosene, which increases the engine thrust. On high speeds the increase in its value reaches 70%, and for small ones - 25-30%.
