The first jets. Jet engine: modern versions

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. The working fluid, in relation to engines, is understood as a substance (gas, liquid, solid), with the help of thermal energy released during fuel combustion is converted into useful mechanical work. As a result of the outflow of the working fluid from the engine nozzle, a reactive force is generated in the form of a reaction (recoil) of the jet, directed in space in the direction opposite to the outflow of the jet. 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 propulsion device, i.e., 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; myself jet engine– 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. There is a distinction between internal thrust (jet thrust) - the result of all gas-dynamic forces applied to the engine, without taking into account external resistance, and effective thrust, which takes into account the external resistance of the power plant. The initial energy is stored on board an aircraft or other vehicle equipped with a jet engine (chemical fuel, nuclear fuel), or (in principle) can come from outside (energy from the Sun).

To obtain the working fluid in a jet engine, a substance taken from environment(for example, air or water); a substance located in the tanks of an 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 their primary energy. In this case, the working fluid is hot gases - products of combustion of chemical fuels. When a jet engine operates, the chemical energy of burning substances is converted into thermal energy of combustion products, and the thermal energy of hot gases is converted into mechanical energy of the translational motion of the 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 stream of air enters the engine and meets the turbines rotating at high speed compressor , which sucks air from external environment(using built-in fan). Thus, two problems are solved - primary air intake and cooling of the entire engine as a whole. Compressor turbine blades compress air approximately 30 times or more and “push” it (pump) into the combustion chamber (generating the working fluid), which is the main part of any jet engine. The combustion chamber also acts as a carburetor, mixing fuel with air. This could be, for example, a mixture of air and kerosene, as in the turbojet engine of a modern jet aircraft, or a mixture of liquid oxygen and alcohol, as in some liquid rocket engines, or some kind of solid fuel for powder rockets. After the formation of the fuel-air mixture, it is ignited and energy is released in the form of heat, i.e., only those substances that can serve as fuel for jet engines chemical reaction in the engine (combustion) they release quite a lot of heat, and also form a large number of gases

During the combustion process, significant heating of the mixture and surrounding parts occurs, as well as volumetric expansion. In effect, a jet engine uses a controlled explosion to propel itself. The combustion chamber of a jet engine is one of its hottest parts (the temperature in it reaches 2700° C), it must be constantly intensively cooled. A 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, gases after the combustion chamber first pass through turbine , to which they give part of their thermal energy to drive the compressor, which serves to compress the air in front of the combustion chamber. But, one way or another, the nozzle is the last part of the engine - gases flow through it before leaving the engine. It directly forms the jet stream. Cold air is directed into the nozzle, pumped by the compressor to cool the internal parts of the engine. The jet nozzle may have various shapes and design depending on the type of engine. If the exhaust speed must exceed the speed of sound, then the nozzle is shaped like 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 and step over the “sound barrier.”

Depending on whether or not the environment is used when operating a jet engine, they are divided into two main classes - air-breathing engines(WRD) and rocket engines(RD). All WFD – heat engines, the working fluid of which is formed during the oxidation reaction of a flammable substance with atmospheric oxygen. The air coming from the atmosphere makes up the bulk of the working fluid of the WRD. Thus, a device with a propellant engine carries an energy source (fuel) on board, and draws most of the working fluid from the environment. These include a turbojet engine (TRE), a ramjet engine (ramjet engine), a pulsed airjet engine (Pvjet engine), and a hypersonic ramjet engine (scramjet engine). In contrast to the VRD, all components of the RD working fluid are located on board the vehicle equipped with the RD. The absence of a propulsion device interacting with the environment and the presence of all components of the working fluid on board the vehicle make the rocket launcher suitable for operation in space. There are also combined rocket engines, representing a combination of both main types.

Main characteristics of jet engines

Main technical parameter characterizing a jet engine is thrust - the force that the engine develops in the direction of movement of the vehicle, specific impulse - the ratio of engine thrust to mass rocket fuel(working fluid) consumed in 1 s, or an identical characteristic - specific consumption fuel (the amount of fuel consumed per 1 s per 1 N of thrust developed by a jet engine), specific mass of the engine (the mass of a jet engine in operating 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 sophistication or quality of an engine. The above diagram (Fig. 2) shows in graphical form the upper values ​​of this indicator for different types jet engines depending on flight speed, expressed in the form of Mach number, which allows you to see the range of applicability of each type of engine. This indicator is also a measure of engine efficiency.

Thrust - the force with which a jet engine acts on a vehicle equipped with this engine - is determined by the formula: $$P = mW_c + F_c (p_c – p_n),$$ where $m$ is the mass flow (mass flow) of the working fluid in 1 s; $W_c$ is the speed of the working fluid in the nozzle cross section; $F_c$ is the area of ​​the nozzle exit section; $p_c$ is the gas pressure in the nozzle cross section; $p_n$ – ambient pressure (usually Atmosphere 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 in the densest layers of the atmosphere, i.e., it varies depending on the flight altitude of a vehicle 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 flow of the working fluid from the nozzle. The flow rate increases with increasing temperature of the flowing 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 speed of their flow). Since the flow rate of combustion products (working fluid) is determined by the physical and chemical properties of the fuel components and design features engine, being a constant value with not very large changes in the operating mode of the jet engine, the magnitude of the reactive force is determined mainly by the mass per second fuel consumption and fluctuates within very wide limits (minimum for electric - maximum for liquid and solid propellant rocket engines). Low thrust jet engines are used mainly in stabilization and control systems aircraft. In space, where gravitational forces are felt weakly and there is practically no environment whose resistance would have to be overcome, they can also be used for acceleration. Taxi engines with maximum thrust are necessary for launching missiles at long ranges and altitudes and especially for launching aircraft into space, i.e., for accelerating them to the first escape velocity. Such engines consume a very large amount of fuel; they usually work very well a short time, accelerating the rockets to a given speed.

WRDs use ambient air as the main component of the working fluid, which is much more economical. WFDs can operate continuously for many hours, which makes them convenient for use in aviation. Different designs made it possible to use them for aircraft operating in different flight modes. Turbojet engines (TRD) are widely used and are installed on almost all modern aircraft without exception. Like all engines using atmospheric air Turbojet engines require a special device to compress the air before it is fed into the combustion chamber. In a turbojet engine, a compressor is used to compress air, and the design of the engine largely depends on the type of compressor. Non-compressor air-breathing engines are much simpler in design, in which the necessary increase in pressure is achieved by other means; These are pulsating and ramjet engines. In a pulsating air-breathing engine (PvRE), this is usually done by a valve grid 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 increases, and the gases rush out through the jet nozzle, after which the whole process is repeated. In a non-compressor engine of another type, a ramjet (ramjet), there is not even this valve grid and atmospheric air, entering the engine inlet at a speed equal to the flight speed, is compressed due to the velocity pressure and enters the combustion chamber. The injected fuel burns, increasing the heat content of the flow, which flows through the jet nozzle at a speed greater than the flight speed. Due to this, the ramjet jet thrust is created. The main disadvantage of ramjet engines is their inability to independently ensure takeoff and acceleration of an aircraft. It is necessary to first accelerate the aircraft to a speed at which the ramjet starts and ensures its stable operation. The peculiarity of the aerodynamic design of supersonic aircraft with ramjet engines (ramjet engines) is due to the presence of special accelerator engines that provide the speed necessary to begin stable operation of the ramjet engine. This makes the tail section 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. The ancestor of the jet engine can be considered Heron's ball. Solid rocket motors(solid propellant rocket motor solid fuel) - gunpowder 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, and combat missiles. An important step In the development of the idea of ​​jet propulsion, there was the idea of ​​​​using 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 design for an aircraft (rocket plane) using jet propulsion from explosive powder gases. Solid propellant rocket motors are used in all classes of military missiles (ballistic, anti-aircraft, anti-tank, etc.), in space (for example, as launch and sustainer engines) and aviation technology (aircraft take-off accelerators, in systems ejection) etc. Small solid fuel engines are used as boosters during aircraft takeoff. Electric rocket motors and nuclear rocket motors can be used on spacecraft.

Most military and civil aircraft around the world are equipped with turbojet engines and bypass turbojet engines, and they are used on helicopters. These jet engines are suitable for flight 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.

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

Back at the beginning of the 20th century. Russian scientist K.E. Tsiolkovsky predicted that after the era of propeller-driven airplanes, the era of jet airplanes would come. He believed that only with a jet engine could supersonic speeds be achieved.

In 1937, the young and talented designer A.M. Lyulka proposed a design for the first Soviet turbojet engine. According to his calculations, such an engine could accelerate the plane to speeds unprecedented at that time - 900 km/h! It seemed fantastic, and the young designer’s proposal was treated with caution. But, nevertheless, work on this engine began, and by mid-1941 it was almost ready. However, the war began, and the design bureau where A.M. worked. Lyulka, was evacuated deep into the USSR, and the designer himself was switched to work on tank engines.

But A.M. Lyulka was not alone in his desire to create a jet aircraft engine. Just before the war, engineers from the design bureau of V.F. Bolkhovitinova - A.Ya. Bereznyak and A.M. Isaev - proposed a project for a fighter-interceptor "BI-1" with a liquid jet engine.

The project was approved and the designers began work. Despite all the difficulties of the first period of the Great Patriotic War, the experimental “BI-1” was nevertheless built.

On May 15, 1942, the world's first rocket fighter was lifted into the air by test pilot EY. Bakhchivandzhi. The tests continued until the end of 1943 and, unfortunately, ended in disaster. In one of the test flights, Bakhchivandzhi reached a speed of 800 km/h. But at this speed the plane suddenly lost control and rushed towards the ground. The new car and its brave tester were killed.

The first aircraft with a Messer-schmitt Me-262 jet engine appeared in the skies just before the end of the Second World War. It was produced in well-camouflaged factories located in the forest. One of these plants in Gorgau - 10 km south of Augsburg along the autobahn - supplied the wings, nose and tail sections of the aircraft to another "timber" plant nearby, which carried out final assembly and picked up the finished aircraft directly from the autobahn. The roof of the buildings was painted in green color, and it was almost impossible to detect such a “timber” plant from the air. Although the Allies managed to detect the takeoffs of the Me-262 and bomb several uncovered aircraft, they were able to establish the location of the plant only after they occupied the forest.

The discoverer of the jet engine, the Englishman Frank Whittle, received his patent back in 7930. The first jet The Gloster aircraft was built in 1941 and was tested in May. The government abandoned it - it was not powerful enough. Only the Germans fully revealed the potential of this invention, in 1942 they assembled the Messerschmitt Me-262, which they used to fight until the end of the war. The first Soviet jet aircraft was the MiG-9, and its “descendant”, the MiG-15, wrote many glorious pages in history. battle history war in Korea (1950-1953).

During these same years in fascist Germany, having lost air superiority on the Soviet-German front, work on jet aircraft is being increasingly intensive. Hitler hoped that with the help of these aircraft he would again seize the initiative in the war and achieve victory.

In 1944, the Messerschmitt Me-262 aircraft, equipped with a jet engine, was put into mass production and soon appeared at the front. German pilots were very wary of this unusual machine, which did not have the usual propeller. In addition, at a speed close to 800 km/h, it was pulled into a dive, and it was impossible to get the car out of this state. The aviation units then issued strict instructions - under no circumstances should the speed be increased to 800 km/h.

However, even with this limitation, the Me-262 was superior in speed to all other fighters of those years. This allowed the commander of Hitler's fighter aviation, General Holland, to declare that the Me-262 was “the only chance to organize real resistance to the enemy.”

On the Eastern Front, the Me-262 appeared at the very end of the war. In this regard, design bureaus received an urgent task to create devices to combat German jet aircraft.

A.I. Mikoyan and P.O. Sukhoi, to help the conventional piston engine located in the bow of the device, added a motor-compressor motor designed by K.V. Kholshchevnikov, installing it in the tail of the plane. The additional engine had to be started when the aircraft needed to give significant acceleration. This was dictated by the fact that the K.V. engine Kholshchevnikov worked no more than three to five minutes.

The first to finish work on a high-speed fighter was A.I. Mikoyan. His I-250 aircraft took flight in March 1945. During testing of this aircraft, a record speed of 820 km/h was recorded, first achieved in the USSR. Fighter P.O. The Sukhoi Su-5 entered testing in April 1945, and after switching on the additional tail engine, a speed exceeding 800 km/h was achieved.

However, the circumstances of those years did not allow the launch of new high-speed fighters into mass production. Firstly, the war is over, even the vaunted Me-262 did not help restore lost air superiority to the Nazis.

Secondly, the skill of Soviet pilots made it possible to prove to the whole world that even jet aircraft can be shot down while flying an ordinary production fighter.

In parallel with the development of an aircraft equipped with a “pushing” motor-compressor engine, in the design bureau of P.O. Sukhoi created the Su-7 fighter, in which the liquid-jet RD-1, developed by designer V.P., worked together with a piston engine. Glushko.

Flights on the Su-7 began in 1945. It was tested by pilot G. Komarov. When RD-1 was turned on, the aircraft's speed increased by an average of 115 km/h. This was a good result, but soon the tests had to be stopped due to frequent exit jet engine failure.

A similar situation arose in the design bureaus of S.A. Lavochkin and AS. Yakovleva. On one of the experimental La-7R aircraft, the accelerator exploded in flight; the test pilot miraculously managed to escape. But when testing the Yak-3 with the RD-1 booster, the plane exploded and its pilot died. The increasing frequency of accidents led to the fact that testing of aircraft with the RD-1 was stopped. In addition, it became clear that piston engines were to be replaced by new engines—jet engines.

After the defeat of Germany, the USSR received German jet aircraft with engines as trophies. The Western allies received not only samples of jet aircraft and their engines, but also their developers and equipment from fascist factories.

To gain experience in jet aircraft construction, it was decided to use German JUMO engines. 004" and "BMW-003", and then create your own based on them. These engines were named “RD-10” and “RD-20”. In addition, the designers of A.M. Lyulke, A.A. Mikulin, V.Ya. Klimov was tasked with creating a “fully Soviet” aircraft jet engine.

While the “engine guys” were working, P.O. Sukhoi developed the Su-9 jet fighter. Its design was made according to the scheme of twin-engine aircraft - two captured JUMO-004 (RD-10) engines were placed under the wings.

Ground tests of the RA-7 jet engine were carried out on the airfield of the airfield in Tushino. During operation, it made a terrible noise and emitted clouds of smoke and fire from its nozzle. The roar and glow from the flames were noticeable even at the Moscow Sokol metro station. There was also some curiosity. One day, several fire engines rushed to the airfield, called by Muscovites to put out the fire.

The Su-9 aircraft could hardly be called just a fighter. Pilots usually called it a “heavy fighter,” since a more accurate name—fighter-bomber—appeared only in the mid-50s. But due to its powerful cannon and bomb armament, the Su-9 could well be considered a prototype of such an aircraft.

This placement of motors had both disadvantages and advantages. The disadvantages include the high drag created by the motors located under the wings. But on the other hand, placing the engines in special outboard engine nacelles allowed unhindered access to them, which was important for repairs and adjustments.

In addition to jet engines, the Su-9 aircraft contained many “fresh” design solutions. So, for example, P.O. Sukhoi installed on his plane a stabilizer controlled by a special electromechanism, starting powder accelerators, an ejection seat for the pilot and a device for emergency release of the canopy covering the pilot's cockpit, air brakes with a landing flap, and a braking parachute. We can say that the Su-9 was created entirely from innovations.

Soon, a prototype version of the Su-9 fighter was built. However, attention was drawn to the fact that performing turns on it is physically difficult for the pilot.

It became obvious that with increasing speeds and flight altitude, it would become increasingly difficult for the pilot to cope with the controls, and then a new device was introduced into the aircraft control system - a booster amplifier, similar to power steering. But in those years, the use of a complex hydraulic device on an airplane caused controversy. Even experienced aircraft designers were skeptical about it.

And yet the booster was installed on the Su-9. Sukhoi was the first to completely shift the effort from the aircraft control stick to the hydraulic system. The pilots' positive reaction was not long in coming. Flying the plane has become more enjoyable and less tiring. The maneuver was simplified and became possible at all flight speeds.

It should be added that in achieving design perfection, P.O. Sukhoi “lost” in the competition between the bureaus of Mikoyan and Yakovlev. The first jet fighters of the USSR - MiG-9 and Yak-15 - took off on the same day - April 26, 1946. They took part in the air parade in Tushino and were immediately put into production. And the Su-9 appeared in the air only in November 1946. However, the military really liked it and in 1947 it was recommended for mass production. But it did not go into production - the aircraft factories were already busy producing MiG and Yakov jets. Yes and P.O. By that time, Sukhoi was already finishing work on a new, more advanced machine - the Su-11 fighter.

By the end of the first decade of the 20th century. The British lagged significantly behind their French colleagues in the field of aircraft manufacturing. By the time mobilization was announced in 1914, most of the country's aviation fleet consisted of foreign-made aircraft, mainly French. However, this lag was short-lived. The country’s great economic, technical and scientific potential made it possible by the middle of the First World War...

The second half of the 20th century has arrived. The design of the aircraft, having undergone many changes, finally acquired its familiar appearance. Quadplanes and triplanes have gone into oblivion, and devices built according to the biplane design are practically not used. And therefore, if the term “wing” appears in the text, we will not imagine in our imagination the fantastic “whatnots” that rose into the sky at the beginning of the 20th century, but...

In addition to the love of flying, pilots all over the world are united by one more circumstance - regardless of whether they are now serving in military or civil aviation, their journey into the sky began with flying a small training teacher plane. The AIR-14 aircraft was created under the leadership of A.S. Yakovlev in 1937. It was a single-seat trainer and sports aircraft that went into…

Further development of helicopter manufacturing was interrupted by the First World War. Since this amazing device did not have time to prove its “usefulness” for the military before it began, they forgot about rotary-wing aircraft for a while and devoted all their efforts to the development of aircraft construction. But as soon as humanity ended the bloody war, different countries around the world, information about...

“A man will fly relying not on the strength of his muscles, but on the strength of his mind.” NOT. Zhukovsky The term “aeronautics” also meant flying on heavier-than-air vehicles (airplanes, gliders). However, people began to dream about flying much earlier. Having built machines capable of moving on land, overtaking the fastest animals, and ships that argued with the inhabitants of the water element, he long time continued with...

Having survived the horrors of the bloody First World War, people believed that now peace on earth would be established for a long time, because a very high price was paid for it. But this was just an attempt to pass off wishful thinking. Historians, politicians, and military men understood that this was not peace yet, but, most likely, a respite between two wars. And there were reasons for this. At first…

If any of you have ever shot a rifle at a shooting range, then you know what the term “recoil” means. Let me explain for others. You've probably seen more than once how a diver, jumping into the water from a boat, pushes it in the opposite direction. A rocket flies using the same, but more complex principle, and a simplified version of this process is exactly what it represents...

The surface area of ​​our planet is 510.2 million km2, of which only 29.2% is land. The rest of the Earth's territory is covered by the World Ocean, which creates a perfectly flat surface with an area of ​​hundreds of millions of square kilometers. It’s hard to even imagine a runway of such gigantic proportions. And most importantly - no obstacles: take off where it’s most convenient for you, don’t land...

First soviet helicopter was built within the walls of TsAGI under the leadership of A.M. Cheremukhin in August 1930. There, in the presence of firefighter A.M. Cheremukhin, part-time pilot of the TsAGI 1-EA experimental vehicle, conducted the first ground tests. After this, the device was transported to one of the military airfields near Moscow. In the spring of 1925, one of the oldest helicopter pilots in Russia...

Unfortunately, no one knows when a person first raised his head to the sky and noticed its frightening size and at the same time fantastic beauty. We also do not know the time when a person first noticed birds soaring in the air and the idea of ​​following them arose in his head. Like any journey, even the longest one, begins with...

There is a fan at the front of the jet engine. It takes air from the external environment, sucking it into the turbine. In rocket engines, air replaces liquid oxygen. The fan is equipped with many titanium blades that have a special shape.

They try to make the fan area large enough. In addition to air intake, this part of the system also participates in cooling the engine, protecting its chambers from destruction. Behind the fan is a compressor. It forces air into the combustion chamber under high pressure.

One of the main structural elements of a jet engine is the combustion chamber. In it, fuel is mixed with air and ignited. The mixture ignites, accompanied by strong heating of the housing parts. The fuel mixture expands under high temperature. In fact, a controlled explosion occurs in the engine.

From the combustion chamber, a mixture of fuel and air enters the turbine, which consists of many blades. The jet stream puts pressure on them and causes the turbine to rotate. The force is transmitted to the shaft, compressor and fan. A closed system is formed, the operation of which only requires a constant supply of the fuel mixture.

The last part of a jet engine is the nozzle. A heated flow enters here from the turbine, forming a jet stream. Cold air is also supplied to this part of the engine from the fan. It serves to cool the entire structure. The air flow protects the nozzle cuff from the harmful effects of the jet stream, preventing parts from melting.

How does a jet engine work?

The working fluid of the engine is a jet. It flows out of the nozzle at a very high speed. This creates a reactive force that pushes the entire device in the opposite direction. The traction force is created solely by the action of the jet, without any support from other bodies. This feature of the jet engine allows it to be used as a power plant for rockets, aircraft and spacecraft.

In part, the operation of a jet engine is comparable to the action of a stream of water flowing from a hose. Under enormous pressure, the liquid is supplied through the hose to the narrowed end of the hose. The speed of water leaving the nozzle is higher than inside the hose. This creates a back pressure force that allows the firefighter to hold the hose only with 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 of high-strength metals and materials that are resistant to melting. Individual parts of jet engines are made, for example, from special ceramic compounds.

Video on the topic

The function of heat engines is to convert thermal energy into useful mechanical work. The working fluid in such installations is gas. It presses forcefully on the turbine blades or on the piston, causing them to move. The simplest examples of heat engines are steam engines, as well as carburetor and diesel internal combustion engines.

Instructions

Piston heat engines They consist of one or more cylinders, inside of which there is a piston. Hot gas expands in the volume of the cylinder. In this case, the piston moves under the influence of gas and performs mechanical work. Such a heat engine converts the reciprocating motion of the piston system into shaft rotation. For this purpose, the engine is equipped with a crank mechanism.

External combustion heat engines include steam engines in which the working fluid is heated when fuel is burned outside the engine. Heated gas or steam under high pressure and high temperature fed into the cylinder. At the same time, the piston moves, and the gas gradually cools, after which the pressure in the system becomes almost equal to atmospheric pressure.

The exhaust gas is removed from the cylinder, into which the next portion is immediately supplied. To return the piston to its initial position, flywheels are used, which are attached to the crank shaft. Such heat engines can provide single or double action. In double-acting engines, there are two stages of piston stroke per shaft revolution; in single-acting engines, the piston makes one stroke in the same time.

The difference between internal combustion engines and the systems described above is that the hot gas here is obtained by burning the fuel-air mixture directly in the cylinder, and not outside it. Supplying the next portion of fuel and

In science jet propulsion call the movement of a body that occurs when some part of it is separated from it. What does this mean?

Simple examples can be given. Imagine that you are in a boat in the middle of a lake. The boat is motionless. But now you take a heavy stone from the bottom of the boat and forcefully throw it into the water. What will happen then? The boat will begin to move slowly. Another example. Let's inflate the rubber ball and then let the air come out of it freely. The deflating ball will fly in the direction opposite to that in which the stream of air will rush. The action force is equal to the reaction force. You threw a stone with force, but the same force made the boat move in the opposite side.

A jet engine is built on this law of physics. Fuel is burned in a heat-resistant chamber. The hot, expanding gas formed during combustion violently escapes from the nozzle. But the same force pushes the engine itself (along with the rocket or airplane in the opposite direction). This force is called thrust.

The principle of jet propulsion has been known to mankind for a long time — simple rockets were made by the ancient Chinese. But in order for modern airplanes and rockets to take to the skies, engineers had to solve many technical problems, and today's jet engines are quite complex devices.

Let's try to look inside the jet engines used in aviation. We'll talk about space rocket engines some other time.

So today Jet aircraft fly with three types of engines:

Turbojet engine;

Turbofan engine;

Turboprop.

How are they structured and how do they differ from each other? Let's start with the simplest - turbojet . The very name of this device tells us keyword — "turbine". A turbine is a shaft around which metal blades are attached. "petals" turned at an angle. If a flow of air (or water, for example) is directed at the turbine along the shaft, it will begin to rotate. If, on the contrary, you begin to rotate the turbine shaft, its blades will begin to drive a stream of air or water along the shaft.

Combustion is the combination of fuel with oxygen, a gas that is not very abundant in ordinary air. More precisely, it is quite enough for you and me to breathe it. But For "breathing" combustion chambers of a jet engine, oxygen is too much dissolved in the air.

What needs to be done to rekindle a dying fire? Right! Blow on it or wave it over it, for example, with a sheet of plywood. By forcefully pumping air, you "feed" The smoldering coals are supplied with oxygen and the flame ignites again. The turbine in a turbojet engine does the same thing.

As the plane moves forward, a stream of air enters the engine. Here the air meets the compressor turbines rotating at high speed. Word "compressor" can be translated into Russian as "compressor". Compressor turbine blades compress air approximately 30 times and "pushing" it into the combustion chamber. The hot gas produced during fuel combustion rushes further to the nozzle. But another turbine gets in his way. Getting on its blades, a stream of gas causes its shaft to rotate. But the compressor turbines are attached to the same shaft. It turns out so peculiar "push-pull". The compressor pumps air into the engine, the mixture of compressed air and fuel burns, releasing hot gas, and the gas rotates the compressor turbines on its way to the nozzle.

An interesting question arises - how to start such an engine? After all, until compressed air enters the combustion chamber, the fuel will not begin to burn. This means there will be no hot gas that will rotate the compressor turbine. But until the compressor turbine spins, there will be no compressed air.

Turns out, the engine is started using an electric motor, which is connected to the turbine shaft. The electric motor causes the compressor to rotate, and as soon as the required air pressure appears in the combustion chamber, fuel enters it and the ignition is triggered. The jet engine has started!

The design of a turbojet engine.

Turbojet engines are very powerful and weigh relatively little. Therefore, they are usually installed on supersonic military aircraft, as well as on supersonic passenger airliners. But such motors also have serious shortcomings- They make a lot of noise and burn too much fuel.

Therefore, on airplanes flying at subsonic speeds (less than 1200 kilometers per hour) so-called ones are installed.

Turbofan engine design.

Are different They are different from a turbojet engine in that in front of the compressor, another turbine with large blades is attached to the shaft - a fan. It is she who is the first to meet the flow of oncoming air and forcefully drives it back. Part of this air, as in a turbojet engine, enters the compressor and further into the combustion chamber, and the other part "flows around" camera and is also thrown back, creating additional thrust. More precisely, for turbofan engine the main jet thrust (about 3/4) is created precisely by this very air flow that the fan drives. And only 1/4 of the thrust comes from hot gases escaping from the nozzle.

Such an engine makes much less noise and burns significantly less fuel, which is very important for aircraft used to transport passengers.

The design of a turboprop engine.

The rotation of the turbine shaft is transmitted to the propeller - a propeller that pushes the aircraft forward. A propeller with huge blades cannot rotate at the same breakneck speed as a turbine shaft. Therefore, the propeller is connected to the shaft by a gearbox that reduces the rotation speed. And although the turboprop engine "eats" there is little fuel, which means it makes the cost of the flight cheaper, it cannot accelerate the plane to high speed. Therefore, these days such motors are mainly used in transport aviation and on small passenger aircraft operating on local routes.

For the experience you will need:

1. stronger thread;

2. wide straw for cocktail;

3. balloon oblong shape;

4. a roll of tape;

5. clothespin.

Pull the thread (can be at an angle), first threading it through the straw. Inflate the balloon, and to prevent it from deflating, pinch it with a clothespin as shown in the picture on the left. Now tape the ball to the straw with tape. The jet engine is ready!

On your marks! Unclench the clothespin. A stream of air will escape from the ball, and it itself, together with the straw, will slide forward along the thread.

©When using this article partially or fully - an active hyperlink link to the site is MANDATORY

Inventor: Frank Whittle (engine)
A country: England
Time of invention: 1928

Turbojet aviation originated during the Second World War, when the limit of perfection of previous propeller-equipped aircraft was reached.

Every year the race for speed became more and more difficult, since even a slight increase in speed required hundreds of additional horsepower of the engine and automatically made the aircraft heavier. On average, an increase in power of 1 hp. led to an increase in the mass of the propulsion system (the engine itself, the propeller and auxiliary equipment) by an average of 1 kg. Simple calculations showed that it is almost impossible to create a propeller-driven fighter aircraft with a speed of about 1000 km/h.

The engine power of 12,000 horsepower required for this could only be achieved with an engine weight of about 6,000 kg. In the future, it turned out that a further increase in speed would lead to the degeneration of combat aircraft, turning them into devices capable of carrying only themselves.

There was no longer any room left on board for weapons, radio equipment, armor and fuel supplies. But even this It was impossible to get a big increase in speed at the cost. A heavier engine increased the overall weight, which forced the wing area to increase; this led to an increase in their aerodynamic drag, to overcome which it was necessary to increase engine power.

Thus, the circle was closed and a speed of about 850 km/h turned out to be the maximum possible for an aircraft with . There could be only one way out of this vicious situation - it was necessary to create a fundamentally new design of an aircraft engine, which was done when turbojet aircraft replaced piston aircraft.

The principle of operation of a simple jet engine can be understood by considering the operation of a fire hose. Water under pressure is supplied through a hose to the fire nozzle and flows out of it. The internal cross-section of the nozzle tip tapers towards the end, due to which the stream of flowing water has a higher speed than in the hose.

The force of back pressure (reaction) in this case is so great that the firefighter often has to strain with all your strength in order to keep the fire hose in the required direction. The same principle can be applied to an aircraft engine. The simplest jet engine is the ramjet engine.

Let's imagine a pipe with open ends mounted on a moving airplane. The front part of the pipe, into which air flows due to the movement of the aircraft, has an expanding internal cross-section. Due to the expansion of the pipe, the speed of air entering it decreases, and the pressure increases accordingly.

Let us assume that in the expanding part fuel is injected into the air flow and burned. This part of the pipe can be called the combustion chamber. The highly heated gases rapidly expand and escape through the converging jet nozzle at a speed many times greater than that of the air flow at the inlet. This increase in speed creates a thrust force that pushes the aircraft forward.

It is easy to see that such an engine can only work if it moves in the air with significant speed, but it cannot be activated when it is motionless. An aircraft with such an engine must either be launched from another aircraft or accelerated using a special starting engine. This disadvantage is overcome in a more complex turbojet engine.

The most critical element of this engine is the gas turbine, which rotates the air compressor sitting on the same shaft. The air entering the engine is first compressed in the inlet device - the diffuser, then in the axial compressor and then enters the combustion chamber.

The fuel is usually kerosene, which is sprayed into the combustion chamber through a nozzle. From the chamber, the combustion products, expanding, flow, first of all, onto the gas blades, causing it to rotate, and then into the nozzle, in which they accelerate to very high speeds.

A gas turbine uses only a small part of the energy of the air-gas jet. The rest of the gases are used to create a reactive thrust force, which arises due to the flow of a jet at high speed combustion products from the nozzle. The thrust of a turbojet engine can be boosted, that is, increased by short period time in various ways.

For example, this can be done using so-called afterburning (in this case, additional fuel is injected into the gas flow behind the turbine, which burns due to oxygen not used in the combustion chambers). Afterburning is possible for short term additionally increase engine thrust by 25-30% at low speeds and up to 70% at high speeds.

Since 1940, gas turbine engines have made a real revolution in aviation technology, but the first developments to create them appeared ten years earlier. Father of the turbojet engine English inventor Frank Whittle is rightfully considered. Back in 1928, while a student at the Cranwell Aviation School, Whittle proposed the first design of a jet engine equipped with a gas turbine.

In 1930 he received a patent for it. The state at that time was not interested in his developments. But Whittle received help from some private firms, and in 1937, based on his design, the British Thomson-Houston company built the first turbojet engine in history, designated “U”. Only after this did the Ministry of Aviation pay attention to Whittle's invention. To further improve the engines of its design, the Power company was created, which had support from the state.

At the same time, Whittle's ideas fertilized the design thought of Germany. In 1936, the German inventor Ohain, then a student at the University of Göttingen, developed and patented his turbojet engine. Its design was almost no different from Whittle's. In 1938, the Heinkel company, which hired Ohain, developed under his leadership the HeS-3B turbojet engine, which was installed on the He-178 aircraft. On August 27, 1939, this aircraft made its first successful flight.

The design of the He-178 largely anticipated the design of future jet aircraft. The air intake was located in the forward part of the fuselage. The air, branching, went around the pilot's cockpit and entered the engine in a direct flow. Hot gases flowed out through a nozzle in the tail section. The wings of this plane were still wooden, but the fuselage was made of duralumin.

The engine, installed behind the cockpit, ran on gasoline and developed a thrust of 500 kg. Maximum the plane's speed reached 700 km/h. At the beginning of 1941, Hans Ohain developed a more advanced HeS-8 engine with a thrust of 600 kg. Two of these engines were installed on the next He-280V aircraft.

Its tests began in April of the same year and showed good result- the plane reached speeds of up to 925 km/h. However, serial production of this fighter never began (a total of 8 were produced) due to the fact that the engine still turned out to be unreliable.

Meanwhile, British Thomson-Houston released the W1.X engine, specially designed for the first English turbojet aircraft, the Gloucester G40, which made its first flight in May 1941 (the aircraft was then equipped with an improved Whittle W.1 engine). The English first-born was far from German. Its maximum speed was 480 km/h. In 1943, the second Gloucester G40 was built with a more powerful engine, reaching speeds of up to 500 km/h.

In its design, the Gloucester was surprisingly reminiscent of the German Heinkel. G40 had all-metal structure with an air intake in the forward part of the fuselage. The air supply duct was divided and went around the pilot's cabin on both sides. The outflow of gases occurred through a nozzle in the rear of the fuselage.

Although the parameters of the G40 not only did not exceed those of high-speed propeller-engined aircraft at that time, but were also noticeably inferior to them, the prospects for the use of jet engines turned out to be so promising that the British Ministry of Aviation decided to begin serial production of turbojet fighter-interceptors. The Gloucester company received an order to develop such an aircraft.

In subsequent years, several English companies began to produce various modifications of the Whittle turbojet engine. The Rover company, taking the W.1 engine as a basis, developed engines W2B/23 and W2B/26. These engines were then purchased by Rolls-Royce, which used them to create their own models, the Welland and Derwent.

The first serial turbojet aircraft in history was, however, not the English Gloucester, but the German Messerschmitt Me-262. In total, about 1,300 of these aircraft of various modifications were manufactured, equipped with the Junkers Yumo-004B engine. The first aircraft of this series was tested in 1942. It had two engines with a thrust of 900 kg and a speed of 845 km/h.

The English production aircraft Gloucester G41 Meteor appeared in 1943. Equipped with two Derwent engines with a thrust of 900 kg each, the Meteor reached speeds of up to 760 km/h and had a flight altitude of up to 9000 m. Subsequently, more powerful Derwents with a thrust of about 1600 kg began to be installed on aircraft, which made it possible to increase the speed to 935 km/h. This aircraft performed well, so production of various modifications of the G41 continued until the end of the 40s.

The United States initially lagged far behind European countries in the development of jet aviation. Until World War II, there were no attempts at all to create a jet aircraft. Only in 1941, when samples and drawings of Whittle engines were received from England, did this work begin in full swing.

General Electric, using Whittle's model as a basis, developed the I-A turbojet engine, which was installed on the first American jet aircraft, the P-59A Ercomet. The American first-born flew for the first time in October 1942. It had two engines, which were located under the wings close to the fuselage. It was still an imperfect design.

According to the American pilots who tested the aircraft, the P-59 was good to fly, but its flight characteristics remained unimportant. The engine was too underpowered, so it was more of a glider than a real combat aircraft. A total of 33 such machines were built. Their maximum speed was 660 km/h, and the flight altitude was up to 14,000 m.

The first serial turbo jet fighter in the USA became the Lockheed F-80 Shooting Star with an engine General Electric I-40 (modification I-A). Until the end of the 40s, about 2,500 of these fighters of various models were produced. Their average speed was about 900 km/h. However, on June 19, 1947, on one of the modifications of this aircraft, the XF-80B, a speed of 1000 km/h was achieved for the first time in history.

At the end of the war, jet aircraft were still inferior in many respects to mature models of propeller-driven aircraft and had many of their own specific disadvantages. In general, during the construction of the first turbojet aircraft, designers in all countries encountered significant difficulties. Every now and then the combustion chambers burned out, the blades and compressors broke and, separating from the rotor, turned into projectiles that crushed the engine body, fuselage and wing.

But, despite this, jet aircraft had a huge advantage over propeller-driven aircraft - The increase in speed with increasing power of a turbojet engine and its weight occurred much more rapidly than that of a piston engine. This decided the future fate of high-speed aviation - it is becoming jet-powered everywhere.

The increase in speed soon brought about a complete change appearance airplane. At transonic speeds, the old shape and profile of the wing turned out to be unable to carry the aircraft - it began to “nod off” and entered an uncontrollable dive. The results of aerodynamic tests and analysis of flight accidents gradually led designers to a new type of wing - thin, swept.

This type of wing shape first appeared on Soviet fighters. Despite the fact that the USSR was later than the Western states began to create turbojet aircraft, Soviet designers very quickly managed to create high-quality combat vehicles. The first Soviet jet fighter to enter production was the Yak-15.

It appeared at the end of 1945 and was a converted Yak-3 (a piston-engine fighter known during the war), which was equipped with an RD-10 turbojet engine - a copy of the captured German Yumo-004B with a thrust of 900 kg. It reached a speed of about 830 km/h.

In 1946 entered service Soviet army The MiG-9 arrived, equipped with two Yumo-004B turbojet engines (official designation RD-20), and in 1947 the MiG-15 appeared - the first in history, a combat jet aircraft with a swept wing, equipped with an RD-45 engine (this was the designation for the Nin engine from Rolls-Royce, purchased under license and modernized by Soviet aircraft designers) with a thrust of 2200 kg.

The MiG-15 was strikingly different from its predecessors and surprised combat pilots with its unusual backward-sloping wings, a huge fin topped with the same swept stabilizer, and a cigar-shaped fuselage. The plane also had other new features: an ejection seat and hydraulic power steering.

He was armed with a rapid-fire weapon and two (in later modifications - three guns). With a speed of 1,100 km/h and a ceiling of 15,000 m, this fighter remained the world's best combat aircraft for several years and attracted enormous interest. (The MiG-15 design later had a significant influence on fighter design in Western countries.)

In a short time, the MiG-15 became the most common fighter in the USSR, and was also adopted by the armies of its allies. This aircraft has proven itself well during Korean War. In many respects it was superior to the American Sabers.

With the advent of the MiG-15, the childhood of turbojet aviation ended and a new stage in its history began. By this time, the jet aircraft had mastered all subsonic speeds and were very close to the sound barrier.