Engine internal combustion on liquid fuel, developed and first applied in practice in the second half of the 19th century, was the second in history, after steam engine, an example of creating an aggregate that converts energy into useful work. Without this invention, it is impossible to imagine modern civilization, because vehicles with internal combustion engines of various types are widely used in any industry that ensures human existence.

Combustion engine-driven transport plays a decisive role in a global logistics system that is gaining more and more importance against the backdrop of globalization processes.

All modern vehicles can be divided into three large groups, depending on the type of engine used. The first group of vehicles uses electric motors. This includes the usual urban public transport - trolleybuses and trams, and electric trains with electric vehicles, and huge ships and ships that use atomic energy - after all, modern icebreakers, nuclear submarines, and aircraft carriers of NATO countries use electric motors. The second group is equipment equipped with jet engines.

Of course, this type of engine is used primarily in aviation. The most numerous, familiar and significant is the third group vehiclewhich uses internal combustion engines. This is the largest group in terms of quantity, diversity, and influence on human economic life. The principle of operation of the internal combustion engine is the same for any vehicles equipped with such an engine. What is it?

As you know, energy does not come from anywhere and does not go anywhere. The principle of operation of a car engine is fully based on this postulate of the law of conservation of energy.

In the most generalized way we can say that the energy of molecular bonds of liquid fuel burned during engine operation is used to perform useful work.

Several unique properties of the fuel itself contributed to the spread of ICEs using liquid fuel. It:

• high potential energy of molecular bonds used as a fuel for a mixture of light hydrocarbons "for example, gasoline"
• quite simple and safe, in comparison, for example, with atomic energy, the way of its release
• the relative abundance of light hydrocarbons on our planet
• natural state of aggregation such fuel, which makes it convenient to store and transport it.

Another important factor is that oxygen acts as an oxidizing agent necessary for the process of energy release, of which more than 20 percent consists of the atmosphere. This eliminates the need to carry not only the fuel supply, but also the catalyst supply.

Ideally, all molecules of a certain volume of fuel and all molecules of a certain volume of oxygen should enter into a reaction. For gasoline, these indicators are correlated as 1 to 14.7, i.e., almost 15 kg of oxygen is needed to burn a kilogram of fuel. However, such a process, called stoichiometric, is unrealizable in practice. In reality, there is always some part of the fuel that does not combine with oxygen during the reaction.

Moreover, for certain operating modes of the internal combustion engine, stoichiometry is even harmful.

Now that the chemical process is understood in general terms, it is worth considering the mechanics of the process of converting fuel energy into useful work, using the example of a four-stroke internal combustion engine operating according to the so-called Otto cycle.

The most famous and what is called the classic cycle of work is the process of engine operation, patented in 1876 by Nikolaus Otto, consisting of four parts. "Strokes, hence the four-stroke internal combustion engines." The first stroke is the creation of a vacuum in the cylinder by the piston by its own movement under the influence of weight. As a result, the cylinder is filled with a mixture of oxygen and gasoline vapors "nature abhors a void." The piston that continues to move squeezes the mixture - we get the second stroke. On the third stroke, the mixture ignites "Otto used a conventional burner, now the spark plug is responsible for this."

Ignition of the mixture creates the release of a large amount of gas, which presses on the piston and makes it rise - to do useful work. The fourth stroke is the opening of the exhaust valve and the displacement of the combustion products by the returning piston.

Thus, only starting the engine requires external action - scrolling the crankshaft connected to the piston. Now this is done using the power of electricity, and on the first cars the crankshaft had to be cranked manually "the same principle is used in cars in which a forced manual start of the engine is provided."

Since the release of the first cars, many engineers have tried to invent a new ICE cycle. At first, this was due to the operation of the patent, which many wanted to get around.

As a result, at the beginning of the last century, the Atkinson cycle was created, which changed the design of the engine in such a way that all piston movements were made in one crankshaft revolution. This improved the efficiency of the engine, but reduced its power. In addition, the engine operating on this cycle does not need a separate camshaft and gearbox. However, this engine did not become widespread due to a decrease in the power of the unit and a rather complex design.

Instead, the Miller cycle is often used on modern cars.

If Atkinson reduced the compression stroke, increasing efficiency, but making the engine much more difficult, then Miller suggested reducing the intake stroke. This made it possible to reduce the actual compression time of the mixture without reducing its geometric compression. Thus, the efficiency of each operation cycle of the internal combustion engine increases, thereby reducing the consumption of fuel burned "in vain".

However, most engines work on the Otto cycle, so it is necessary to consider it in more detail.

Even the simplest ICE version includes fourteen essential elementsrequired for its work. Each element has specific functions.

So, the cylinder performs a double role - the air mixture is activated in it and the piston moves. In the part called the combustion chamber, a plug is installed, and two valves, one of which blocks the flow of fuel, the other - the release of exhaust gases.

A candle is a device that ignites the mixture with the required cycle. In fact, it is a device for producing a sufficiently powerful electric arc for a short period of time.

The piston moves in the cylinder under the action of expanding gases or from the action of the crankshaft transmitted through the crank mechanism. In the first case, the piston converts the energy of fuel combustion into mechanical work, in the second, it compresses the mixture for better ignition or creates pressure to remove the spent residues of the mixture from the cylinder.

The crank mechanism transfers torque from the piston to the shaft and vice versa. The crankshaft, due to its design, converts the translational "up-down" movement of the piston into a rotary one.

The inlet where the inlet valve, ensures that the mixture enters the cylinder. The valve provides a cyclic flow of the mixture.

The exhaust valve, respectively, removes the accumulated combustion products of the mixture. To provide normal work the engine at the time of pressure build-up and ignition of the mixture, it is closed.

The work of a gasoline engine. Detailed analysis

The piston moves down during the suction stroke. At the same time, the intake valve opens and fuel is supplied to the cylinder. Thus, the fuel-air mixture is in the cylinder. In certain types of gasoline engines, this mixture is prepared in a special device - a carburetor; in others, mixing occurs directly in the cylinder.

Further, the piston begins to rise. At the same time, the intake valve is closed, which ensures that a sufficiently large pressure is generated inside the cylinder. When the piston reaches the extreme upper point, the entire fuel-air mixture is compressed in a part of the cylinder called the combustion chamber. At this point, the candle gives off an electrical spark and the mixture ignites.

As a result of the combustion of the mixture, a large amount of gases is released, which, trying to fill the entire provided volume, press on the piston, forcing it to fall. This work of the piston is transmitted through the crank mechanism to the shaft, which begins to rotate and rotate the drive of the wheels of the car.

As soon as the piston completes its downward movement, the exhaust manifold valve opens.

The remaining gases rush there, as they are pressed by the piston, which goes up under the influence of the shaft. The cycle is over, then the piston goes down again, starting a new cycle.

As you can see, only one phase of the cycle performs useful work. The rest of the phases are the work of the engine "for itself". Even this state of affairs makes the internal combustion engine one of the most efficient systems introduced into production in terms of efficiency. At the same time, the possibility of reducing the "idle" in terms of the efficiency of cycles leads to the emergence of new, more economical systems. In addition, engines are being developed and limitedly introduced, which are generally devoid of a piston system. For example, some japanese cars equipped with rotary motors with a higher efficiency.

At the same time, such engines have a number of disadvantages associated mainly with the high cost of production and the complexity of maintenance of such motors.

Supply system

In order for the combustible mixture entering the combustion chamber to be properly burned and to ensure the smooth operation of the engine, it must be injected in clearly measured portions and be properly prepared. For this purpose, the fuel system serves, the most important parts of which are the gas tank, fuel line, fuel pumps, a device for mixing fuel and air, a manifold, various filters and sensors.

It is clear that the purpose of a gas tank is to store the required amount of fuel. Fuel water is used as lines for pumping with a gasoline pump, gasoline and air filters are needed to prevent clogging of thin manifolds, valves and fuel lines.

It is worth dwelling on the work of the carburetor in more detail. Despite the fact that cars with such devices are no longer produced, many cars with a carburetor type of engine are still in operation in many countries of the world. The carburetor mixes fuel with air as follows.

The float chamber is maintained at a constant level of fuel and pressure thanks to a balancing hole that bleeds off excess air and a float that opens the fuel line valve as soon as the fuel level in the carburetor chamber drops. The carburetor is connected to the cylinder through a jet and diffuser. When the pressure in the cylinder decreases, the precisely metered quantity of fuel thanks to the nozzle rushes into the diffuser of the air chamber.

Here, due to the very small diameter of the hole, it passes into the cylinder under high pressure, gasoline is mixed with atmospheric air that has passed through the filter, and the resulting mixture enters the combustion chamber.

The problem with carburetor systems is the impossibility of accurately measuring the amount of fuel and the amount of air entering the cylinder. Therefore all modern cars equipped with an injection system, also called injection.

IN injection engine Instead of a carburetor, injection is carried out by a nozzle or nozzles - a special mechanical spray, the most important part of which is a solenoid valve. These devices, especially when paired with special computing microchips, allow injecting an accurately measured amount of fuel at the right moment. As a result, the engine runs smoother, starts easier, and uses less fuel.

Gas distribution mechanism

It is clear how the carburetor prepares a combustible mixture of gasoline and air. But how do the valves work to ensure the timely supply of this mixture to the cylinder? The gas distribution mechanism is responsible for this. It is he who performs the timely opening and closing of the valves, and also provides the necessary duration and height of their lift.

It is these three parameters that are collectively the valve timing.

Modern engines have a special device for changing these phases, called an internal combustion engine phase shifter, the principle of operation of which is based on turning the camshaft if necessary. With an increase in the amount of injected fuel, this clutch turns camshaft at a certain angle in the direction of rotation. This change in its position leads to the fact that the intake valves open earlier and the combustion chambers are filled with the mixture better, compensating for the constantly increasing demand for power. On the most technically advanced models, there are several such couplings, they are controlled by rather complex electronics and can regulate not only the valve opening frequency, but also its stroke, which has an excellent effect on the engine's operation at maximum speed.

The principle of operation of the engine cooling system

Of course, not all of the energy released from the bonds of fuel molecules is converted into useful work. Most of it is lost, turning into heat, and the friction of the internal combustion engine parts also creates thermal energy. Excess heat must be removed. The cooling system serves this very purpose.

Share air system, liquid and combined. The most common liquid cooling system, although there are cars with an air one - it was used to simplify the design and reduce the cost of budget cars, or to reduce weight when it comes to sports cars.

The main elements of the system are represented by a heat exchanger, a radiator, a centrifugal pump, an expansion tank and a thermostat. In addition, the cooling system includes an oil cooler, a radiator fan, and a coolant temperature sensor.

The liquid circulates through the heat exchanger under the influence of the pump, removing the temperature from the engine. Until the engine warms up, a special valve closes the radiator - this is called a "small circle" of movement. This system operation allows the engine to warm up quickly.

As soon as the temperature rises to operating temperature, the temperature sensor gives a command to open the valve, and the coolant begins to move through the radiator. The thin tubes of this unit are blown by a stylish flow of headwind, thus cooling the liquid, which again enters the collector, starting the cooling cycle again.

If the exposure to the incoming air is not enough for normal cooling - the car is operating under heavy load, moving at a low speed or in very hot weather, the cooling fan turns on. It blows over the radiator, forcibly cooling the working fluid.

Turbocharged cars have two cooling circuits. One is for cooling the internal combustion engine directly, the second is for removing excess heat from the turbine.

Electrician

The first cars made do with a minimum of electrics. IN modern machines more and more electrical circuits appear. Electricity is consumed by the fuel supply system, ignition, cooling and heating systems, lighting. In the presence of a lot of energy, the air conditioning system, engine management, electronic security systems consume. Aggregates such as the starter system and glow plugs consume energy for a short time, but in large quantities.

Power sources, electrical wiring, control elements and fuse boxes are used to provide all these elements with the necessary electricity.

Vehicle power sources - accumulator batterycoupled with a generator. When the engine is running, the shaft drive turns the generator to produce the required energy.

The generator works by converting the rotational energy of the shaft into electrical energy using the principles of electromagnetic induction. In order to start the internal combustion engine, battery energy is used.

During starting, the main consumer of energy is the starter. This device is a motor direct currentdesigned to scroll crankshaft, providing the beginning of the ICE cycle. The principle of operation of a DC motor is based on the interaction that occurs between the magnetic field generated in the stator and the current flowing in the rotor. This force affects the rotor, which begins to rotate, and its rotation coincides with the rotation of the magnetic field characteristic of the stator. Thus, electrical energy is converted into mechanical energy, and the starter starts to spin the motor shaft. As soon as the engine starts and the generator starts to work, the battery stops giving off energy and starts storing it. If the generator does not work or, for some reason, its power is insufficient, the battery continues to give off energy and discharge.

This type of engine is also an internal combustion engine, but it has distinctive features, allowing to sharply separate the engines operating according to the principle invented by Rudolf Diesel from other ICEs running on "light" fuel like gasoline "in automobiles" or kerosene "in aviation".

Differences in the fuel used determine the design differences. The fact is that "diesel fuel" is relatively difficult to ignite and achieve its instant combustion under normal conditions, so the method of ignition from a candle is not suitable for this fuel. The diesel engine is ignited due to its contact with air heated to a very high temperature. For this purpose, the property of gases is used to heat up during compression. Therefore, the piston, powered by a diesel engine, does not compress the fuel, but the air. When the compression ratio reaches its maximum, and the piston itself reaches the extreme upper point, the "electromagnetic pump" nozzle instead of the candle injects dispersed fuel. It interacts with hot oxygen and ignites. Further, work occurs, which is typical for a gasoline internal combustion engine.

At the same time, the power of the internal combustion engine does not change by the proportion of the mixture of air and fuel, as in gasoline engines, but exclusively by the amount of injected diesel, while the amount of air does not change constantly. At the same time, the principle of operation of a modern gasoline unit equipped with a nozzle is absolutely not similar to the principle of operation of a diesel internal combustion engine.

Gasoline powered electromechanical spray pumps are designed primarily for more accurate metering of the injected fuel and interact with spark plugs. What these two types of internal combustion engines are similar in is the increased demands on fuel quality.

Since the air pressure created by the operation of the piston of a diesel engine is much higher than the pressure exerted by the compressed air-gasoline mixture, such an engine is more demanding on the clearances between the piston and the cylinder walls. In addition, it is more difficult to start a diesel engine in winter, since the diesel fuel thickens under the influence of low temperature indicators, and the nozzle cannot spray it with sufficient quality.

And modern gasoline engine, and its diesel "relative" is extremely reluctant to run on DT gasoline of inadequate quality, and even its short-term use is fraught with serious problems with the fuel system.

Modern internal combustion engines are the most efficient devices for converting thermal energy into mechanical energy. Despite the fact that most of the energy is spent not on directly useful work, but on maintaining the cycle of the engine itself, humanity has not yet learned to mass-produce devices that would be more practical, more powerful, more economical and more convenient than an internal combustion engine. At the same time, the rise in the cost of hydrocarbon energy sources and concern for the environment force us to look for new engine options for passenger cars and public transport... The most promising at the moment is the use of autonomous, equipped with large-capacity batteries, electric motors, the efficiency of which is much higher, and hybrids of such engines with gasoline options. After all, the time will surely come when it will become absolutely unprofitable to use hydrocarbons to propel personal vehicles, and internal combustion engines will take place on museum shelves, like steam engines did half a century ago.

(internal combustion engine) is a heat engine and works on the principle of burning a mixture of fuel and air in a combustion chamber. The main task of such a device is to convert the energy of combustion of a fuel charge into mechanical useful work.

In spite of general principle actions, today there are a large number of units that differ significantly from each other due to a number of individual design features. In this article we will talk about what types of internal combustion engines are, as well as what are their main features and differences.

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Internal combustion engine types

Let's start with the fact that the internal combustion engine can be two-stroke and four-stroke. As for automobile engines, these units are four-stroke. Engine strokes are:

• intake of a fuel-air mixture or air (depending on the type of internal combustion engine);
• compression of a mixture of fuel and air;
• combustion of fuel charge and working stroke;
• exhaust from the combustion chamber;

Both gasoline and diesel piston engines, which are widely used in cars and other equipment, work according to this principle. It is also worth mentioning and, in which gas fuel is burned in the same way as diesel fuel or gasoline.

Gasoline power units

Such a power supply system, especially distributed injection, allows you to increase engine power, while achieving fuel efficiency and reducing the toxicity of exhaust gases. This is made possible by precise metering of the supplied fuel under control (electronic engine management).

Further development of fuel supply systems led to the emergence of engines with direct (direct) injection. Their main difference from their predecessors is that air and fuel are supplied to the combustion chamber separately. In other words, the injector is not installed above the intake valves, but is mounted directly in the cylinder.

This solution makes it possible to supply fuel directly, and the supply itself is divided into several stages (post-injection). As a result, it is possible to achieve the most efficient and complete combustion of the fuel charge, the engine is able to run on a lean mixture (for example, engines of the GDI family), fuel consumption decreases, exhaust toxicity decreases, etc.

Diesel motors

It runs on diesel fuel, and also differs significantly from gasoline. The main difference is the absence of a spark ignition system. The combustion of a mixture of fuel and air in a diesel engine occurs from compression.

Simply put, first air is compressed in the cylinders, which heats up a lot. At the last moment, it is injected directly into the combustion chamber, after which the heated and highly compressed mixture ignites on its own.

If we compare diesel and gasoline internal combustion engines, diesel is distinguished by higher efficiency, better efficiency and the maximum that is available on low revs... Taking into account the fact that diesels develop more traction at lower crankshaft speeds, in practice such a motor does not need to be "turned" at the start, and you can also count on a confident pickup from the very bottom.

However, in the list of disadvantages of such units, one can single out, as well as greater weight and lower speeds at maximum revolutions. The fact is that a diesel engine is initially “slow-moving” and has a lower rotational speed compared to gasoline internal combustion engines.

Diesel engines are also distinguished by a greater mass, since the features of compression ignition imply more serious loads on all elements of such a unit. In other words, the parts in a diesel engine are stronger and heavier. Also diesel motors more noisy, due to the process of ignition and combustion of diesel fuel.

Rotary engine

The Wankel engine (rotary piston engine) is a fundamentally different power plant. In such an internal combustion engine, the usual pistons that reciprocate in the cylinder are simply absent. The main element of a rotary motor is the rotor.

The specified rotor rotates along a predetermined path. Rotary internal combustion engines are gasoline, since such a design is not able to provide high degree compression of the working mixture.

The advantages include compactness, high power with a small working volume, as well as the ability to quickly spin up to high revs. As a result, cars with such an internal combustion engine have outstanding acceleration characteristics.

If we talk about the minuses, then it is worth highlighting a noticeably reduced resource compared to piston units, as well as high fuel consumption. Also, the rotary engine is highly toxic, that is, it does not quite fit into modern environmental standards.

Hybrid engine

On some internal combustion engines, to obtain the required power, it is used in combination with a turbocharger, while on others with exactly the same displacement and layout, such solutions are absent.

For this reason, in order to objectively assess the performance of an engine at different speeds, and not on the crankshaft, but on the wheels, it is necessary to carry out special complex measurements on a dynamometer.

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The invention of the internal combustion engine allowed humanity to step forward significantly in development. Now engines, which use the energy released during the combustion of fuel to perform useful work, are used in many areas of human activity. But these engines are most widely used in transport.

All power plants consist of mechanisms, assemblies and systems that interact with each other to convert the energy released during the combustion of flammable products into the rotational motion of the crankshaft. It is this movement that is his useful work.

To make it clearer, you should understand the principle of operation of an internal combustion power plant.

Principle of operation

When a combustible mixture consisting of flammable products and air is burned, more energy is released. Moreover, at the moment of ignition of the mixture, it significantly increases in volume, the pressure at the epicenter of ignition increases, in fact, a small explosion occurs with the release of energy. This process is taken as a basis.

If combustion is carried out in a closed space, the pressure arising during combustion will press on the walls of this space. If one of the walls is made movable, then the pressure, trying to increase the volume of the enclosed space, will move this wall. If you attach a rod to this wall, then it will already perform mechanical work - moving away, it will push this rod. By connecting the rod to the crank, when moving, it will make the crank rotate about its axis.

This is how it works power unit with internal combustion - there is a closed space (cylinder liner) with one movable wall (piston). The wall is connected by a rod (connecting rod) with a crank ( crankshaft). Then the opposite action is performed - the crank, making a full revolution around the axis, pushes the wall with the rod and so it comes back.

But this is only the principle of working with an explanation of simple components. In fact, the process looks somewhat more complicated, because you must first ensure the flow of the mixture into the cylinder, compress it for better ignition, and also remove the combustion products. These actions are called bars.

Total clock cycles 4:

• inlet (the mixture enters the cylinder);
• compression (the mixture is compressed by reducing the volume inside the liner by the piston);
• working stroke (after ignition, the mixture, due to its expansion, pushes the piston down);
• outlet (removal of combustion products from the liner to supply the next portion of the mixture);

Reciprocating engine strokes

It follows from this that only the working stroke has a useful effect, the other three are preparatory. Each stroke is accompanied by a certain movement of the piston. It moves down during intake and stroke, and up during compression and exhaust. And since the piston is connected to the crankshaft, each stroke corresponds to a certain angle of rotation of the shaft around the axis.

The implementation of strokes in the engine is done in two ways. The first is with overlapping measures. In such a motor, all strokes are performed in one complete cranking of the crankshaft. That is, half a turn of the knees. shaft, in which the movement of the piston up or down is accompanied by two strokes. These engines are called 2-stroke engines.

The second way is separate measures. One piston movement is accompanied by only one stroke. As a result, for a full cycle of work to occur, it takes 2 turns of the knees. shaft around the axis. Such engines received the designation 4-stroke.

Cylinder block

Now the very structure of the internal combustion engine. The basis of any installation is the cylinder block. All the components are located in it and on it.

The design features of the block depend on certain conditions - the number of cylinders, their location, cooling method. The number of cylinders, which are combined in one block, can vary from 1 to 16. Moreover, blocks with an odd number of cylinders are rare, from the currently produced engines you can find only one- and three-cylinder units. Most units come with a paired number of cylinders - 2, 4, 6, 8 and less often 12 and 16.

Four-cylinder block

Power plants with 1 to 4 cylinders usually have in-line cylinders. If the number of cylinders is greater, they are arranged in two rows, while with a certain angle of position of one row relative to the other, the so-called power plants with a V-shaped position of the cylinders. This arrangement made it possible to reduce the size of the block, but at the same time their manufacture is more difficult than in-line arrangement.

Eight-cylinder block

There is another type of blocks in which the cylinders are arranged in two rows and with an angle between them of 180 degrees. These engines are named. They are found mainly on motorcycles, although there are cars with this type of power unit.

But the condition of the number of cylinders and their location is optional. There are 2-cylinder and 4-cylinder engines with V-shaped or opposed cylinders, as well as 6-cylinder in-line engines.

Two types of cooling are used, which are applied to power plants - air and liquid. It depends on it design feature block. Block with air cooled smaller and simpler in design, since the cylinders are not included in its design.

The liquid-cooled block is more complex, its design includes cylinders, and a cooling jacket is located on top of the block with cylinders. Liquid circulates inside it, removing heat from the cylinders. In this case, the block together with the cooling jacket represent one whole.

From above, the block is covered with a special plate - a head cylinder block (Cylinder head). It is one of the components that provide a closed space in which the combustion process takes place. Its design can be simple, not including additional mechanisms, or complex.

crank mechanism

Part of the design of the motor, it converts the reciprocating movement of the piston in the sleeve into the rotational movement of the crankshaft. The main element of this mechanism is the crankshaft. It has a flexible connection to the cylinder block. Such a connection allows the rotation of this shaft about an axis.

A flywheel is attached to one end of the shaft. The task of the flywheel is to transfer torque from the shaft further. Since a 4-stroke engine has only one half-turn with a useful action - a working stroke for two crankshaft revolutions, the rest require a reverse action, which is performed by the flywheel. Having a significant mass and rotating, due to its kinetic energy, it provides knee cranking. shaft during the preparatory measures.

The flywheel circumference has a ring gear, with the help of which the power plant is started.

On the other side of the shaft is the drive gear of the oil pump and the gas distribution mechanism, as well as a flange for attaching the pulley.

This mechanism also includes connecting rods that transfer power from the piston to the crankshaft and vice versa. Mounting to the connecting rod shaft is also movable.

Cylinder block surfaces, knees. the shaft and connecting rods at the joints do not directly contact each other, between them there are plain bearings - liners.

Cylinder-piston group

This group consists of cylinder liners, pistons, piston rings and fingers. It is in this group that the combustion process and the transfer of the released energy take place for transformation. Combustion occurs inside the liner, which is closed on the one side by the block head, and on the other - by the piston. The piston itself can move inside the liner.

To ensure maximum tightness inside the liner, piston rings are used to prevent the mixture and combustion products from leaking between the liner walls and the piston.

The piston is movably connected to the connecting rod by means of a pin.

Gas distribution mechanism

The task of this mechanism is the timely supply of the combustible mixture or its components into the cylinder, as well as the removal of combustion products.

Two-stroke engines have no mechanism as such. In it, the supply of the mixture and the removal of combustion products are made by technological windows, which are made in the walls of the sleeve. There are three such windows - inlet, bypass and outlet.

The piston, while moving, opens and closes one or another window, this is how the liner is filled with fuel and the exhaust gases are removed. The use of such a gas distribution does not require additional units, therefore the cylinder head of such an engine is simple and its task is only to ensure the tightness of the cylinder.

The 4-stroke engine has a timing mechanism. Fuel in such an engine is supplied through special holes in the head. These openings are closed with valves. If it is necessary to supply fuel or exhaust gases from the cylinder, the corresponding valve is opened. The opening of the valves is provided by the camshaft, which, with its cams, at the right time presses on the required valve and that opens the hole. The camshaft is driven by the crankshaft.

Timing with belt and chain drive

The timing may vary. Engines are produced with a lower camshaft (it is located in the cylinder block) and an upper valve arrangement (in the cylinder head). The transfer of force from the shaft to the valves is carried out by means of rods and rocker arms.

Motors are more common where both the shaft and valves are overhead. With this arrangement, the shaft is also located in the cylinder head and acts directly on the valve, without intermediate elements.

Supply system

This system provides fuel preparation for its further supply to the cylinders. The design of this system depends on the fuel used by the engine. The main one now is the fuel separated from oil, with different fractions - gasoline and diesel fuel.

There are two types of engines using gasoline fuel system - carburetor and injection. In the first system, the mixture is generated in the carburetor. It dosages and delivers fuel to the air flow passing through it, then this mixture is fed into the cylinders. Such a system consists and fuel tank, fuel lines, vacuum fuel pump and carburetor.

Carburetor system

The same is done in injection cars, but their dosage is more accurate. Also, fuel in the injectors is added to the air flow already in the intake manifold through the nozzle. This nozzle atomizes the fuel, which ensures better mixture formation. The injection system consists of a tank, a pump located in it, filters, fuel lines, and a fuel rail with injectors installed on the intake manifold.

For diesel engines, the supply of components fuel mixture produced separately. The gas distribution mechanism supplies only air to the cylinders through the valves. The fuel is supplied to the cylinders separately, by nozzles and under high pressure. This system consists of a tank, filters, a high-pressure fuel pump (injection pump) and nozzles.

Recently, injection systems have appeared that work on the principle of a diesel fuel system - a direct injection injector.

The exhaust gas removal system ensures the removal of combustion products from the cylinders, partial neutralization of harmful substances, and a decrease in sound when exhausting the exhaust gas. Consists of an exhaust manifold, a resonator, a catalyst (not always) and a muffler.

Lubrication system

The lubrication system reduces friction between the interacting surfaces of the engine by creating a special film that prevents direct contact between the surfaces. Additionally, it removes heat, protects engine elements from corrosion.

The lubrication system consists of an oil pump, an oil container - a pallet, an oil intake, oil filter, channels through which oil moves to rubbing surfaces.

Cooling system

Maintaining optimal working temperature the cooling system is provided during engine operation. Two types of system are used - air and liquid.

The air system produces cooling by blowing air over the cylinders. For better cooling, cooling fins are made on the cylinders.

In a liquid system, cooling is produced by a liquid that circulates in a cooling jacket in direct contact with the outer wall of the liners. Such a system consists of a cooling jacket, a water pump, a thermostat, pipes and a radiator.

Ignition system

Ignition system applies only to gasoline engines. On diesel engines, the mixture is ignited by compression, so he does not need such a system.

In gasoline cars, ignition is performed from a spark that skips at a certain moment between the electrodes of the glow plug installed in the block head so that its skirt is in the combustion chamber of the cylinder.

The ignition system consists of an ignition coil, distributor (distributor), wiring and spark plugs.

Electrical equipment

This equipment provides the on-board network of the car with electricity, including the ignition system. This equipment also starts the engine. It consists of a battery, generator, starter, wiring, all kinds of sensors that monitor the operation and condition of the engine.

This is the whole device of the internal combustion engine. Although he is constantly improving, his principle of operation does not change, only individual nodes and mechanisms.

Modern developments

The main task over which automakers are fighting is to reduce fuel consumption and emissions of harmful substances into the atmosphere. Therefore, they are constantly improving the nutritional system, the result is the recent appearance injection systems with direct injection.

Alternative fuels are being looked for, the latest development in this direction is the use of alcohols and vegetable oils as fuel.

Also, scientists are trying to establish the production of engines with a completely different principle of operation. Such, for example, is the Wankel engine, but so far there has been no particular success.

Autoleek

You can ask your questions on the topic of the presented article by leaving your comment at the bottom of the page. The deputy general director of the Mustang driving school for academic affairs will answer you Higher school teacher, candidate of technical sciences Kuznetsov Yuri Alexandrovich

Part 1. ENGINE AND ITS MECHANISMS

The engine is a source of mechanical energy.

The vast majority of vehicles use an internal combustion engine.

An internal combustion engine is a device in which the chemical energy of a fuel is converted into useful mechanical work.

Automotive internal combustion engines are classified:

By the type of fuel used:

Light liquid (gas, gasoline),

Heavy liquids (diesel).

Petrol engines

Gasoline carburetor.Fuel-air mixture preparing incarburetor or in the intake manifold using spray nozzles (mechanical or electrical), then the mixture is fed into the cylinder, compressed, and then ignited with the help of a spark slipping between the electrodescandles .

Gasoline injection Mixing occurs by injecting gasoline into the intake manifold or directly into the cylinder using sprayinginjectors ( injector s). There are single-point and multipoint injection systems of various mechanical and electronic systems... In mechanical injection systems, the fuel is dosed by a plunger-lever mechanism with the possibility of electronic adjustment of the mixture composition. In electronic systems, mixture formation is carried out under the control electronic unit control (ECU) injection, which controls the electric petrol valves.

Gas engines

The engine burns hydrocarbons in a gaseous state as fuel. More often gas engines I work on propane, but there are others working on associated (oil), liquefied, blast furnace, generator and other types of gaseous fuel.

The fundamental difference between gas engines and gasoline and diesel engines in a higher compression ratio. The use of gas makes it possible to avoid unnecessary wear of parts, since the combustion processes of the fuel-air mixture occur more correctly, due to the initial (gaseous) state of the fuel. Also, gas engines are more economical, since gas is cheaper than oil and is easier to extract.

The undoubted advantages of gas engines include safety and smokeless exhaust.

By themselves, gas engines are rarely mass-produced, most often they appear after the alteration of traditional internal combustion engines, by equipping them with special gas equipment.

Diesel Engines

Special diesel fuel is injected at a certain point (before reaching top dead center) into the cylinder under high pressure through an injector. A combustible mixture forms directly in the cylinder as fuel is injected. The movement of the piston into the cylinder causes heating and subsequent ignition of the air-fuel mixture. Diesel engines are low-speed and high torque on the motor shaft. An additional advantage of a diesel engine is that, unlike positive ignition engines, it does not need electricity to operate (in automotive diesel engines electrical system used only for starting), and, as a result, is less afraid of water.

By ignition method:

Spark (petrol)

From compression (diesel).

By the number and arrangement of cylinders:

In-line,

Opposed,

V - shaped,

VR - shaped,

W - shaped.

Inline engine

This engine has been known since the very beginning of automobile engine building. The cylinders are located in one row perpendicular to the crankshaft.

Dignity: simplicity of design

Disadvantage: at a large number cylinders, a very long unit is obtained, which cannot be positioned transversely relative to the longitudinal axis of the vehicle.

Boxer engine

Horizontally opposed engines have a lower headroom than in-line or V-type engines, which reduces the center of gravity of the entire vehicle. Light weight, compact design and symmetrical layout reduce the yaw moment of the vehicle.

V-shaped engine

To shorten the length of the engines, this engine has cylinders angled between 60 and 120 degrees, with the longitudinal axes of the cylinders passing through the longitudinal axis of the crankshaft.

Dignity: relatively short motor

Disadvantages: the engine is relatively wide, has two separate block heads, increased manufacturing cost, too large a displacement.

VR engines

In search of a compromise solution for engine performance passenger cars the middle class came to the creation of VR engines. Six cylinders at 150 degrees form a relatively narrow and generally short engine. In addition, such an engine has only one block head.

W-motors

In the W-family engines, two cylinder banks in VR design are connected in one engine.

The cylinders of each row are placed at an angle of 150 to one another, and the rows of cylinders themselves are located at an angle of 720.

A typical automotive engine has two mechanisms and five systems.

Engine mechanisms

Crank mechanism,

Gas distribution mechanism.

Engine systems

Cooling system,

Lubrication system,

Supply system,

Ignition system,

Exhaust system.

crank mechanism

The crank mechanism is designed to convert the reciprocating movement of the piston in the cylinder into the rotational movement of the engine crankshaft.

The crank mechanism consists of:

Cylinder block with crankcase,

Cylinder head,

Engine oil pan,

Pistons with rings and pins,

Shatunov,

Crankshaft,

Flywheel.

Cylinder block

It is a one-piece part that unites the engine cylinders. The cylinder block has supporting surfaces for mounting the crankshaft, the cylinder head is usually attached to the top of the block, and the lower part is part of the crankcase. Thus, the cylinder block is the basis of the engine on which the rest of the parts are hung.

Cast as a rule - from cast iron, less often - from aluminum.

Blocks made from these materials are by no means equal in their properties.

So, a cast iron block is the most rigid, which means that, all other things being equal, it withstands the highest degree of forcing and is least sensitive to overheating. The heat capacity of cast iron is about half that of aluminum, which means that an engine with a cast iron block warms up faster to operating temperature. However, cast iron is very heavy (2.7 times heavier than aluminum), prone to corrosion, and its thermal conductivity is about 4 times lower than that of aluminum, so the cooling system of an engine with a cast iron crankcase works in a more intense mode.

Aluminum cylinder blocks are lightweight and cool better, but in this case there is a problem with the material from which the cylinder walls are made directly. If the pistons of an engine with such a block are made of cast iron or steel, they will very quickly wear out the aluminum cylinder walls. If the pistons are made of soft aluminum, they will simply "grab" the walls, and the engine will instantly jam.

The cylinders in the cylinder block can be either part of the cylinder block casting or can be separate replaceable bushings that can be "wet" or "dry". In addition to the generating part of the engine, the cylinder block carries additional functions, such as the basis of the lubrication system - through the holes in the cylinder block, oil is supplied under pressure to the lubrication points, and in liquid-cooled engines the basis of the cooling system - through similar holes the liquid circulates through the cylinder block.

The walls of the inner cavity of the cylinder also serve as guides for the piston when it moves between the extreme positions. Therefore, the length of the cylinder generatrix is \u200b\u200bpredetermined by the length of the piston stroke.

The cylinder works under conditions of variable pressures in the above-piston cavity. Its inner walls are in contact with flames and hot gases heated to temperatures of 1500-2500 ° C. In addition, the average sliding speed of the piston set along the cylinder walls is car engines reaches 12-15 m / sec with insufficient lubrication. Therefore, the material used for the manufacture of cylinders must have high mechanical strength, and the structure of the walls itself must have increased rigidity. The cylinder walls must withstand good abrasion with limited lubrication and have an overall high resistance against other possible types of wear

In accordance with these requirements, pearlitic gray cast iron with small additions of alloying elements (nickel, chromium, etc.) is used as the main material for the cylinders. High-alloy cast iron, steel, magnesium and aluminum alloys are also used.

Cylinder head

It is the second most important and largest component of the engine. The head contains combustion chambers, valves and cylinder plugs, in which a camshaft with cams rotates on bearings. Just like in the cylinder block, there are water and oil channels and cavities in its head. The head is attached to the cylinder block and, when the engine is running, forms a single whole with the block.

Oil sump

It closes the bottom of the engine crankcase (molded as a unit with the cylinder block) and is used as a reservoir for oil and protects engine parts from contamination. There is a drain plug at the bottom of the pallet engine oil... The pallet is bolted to the crankcase. To prevent oil leakage, a gasket is installed between them.

Piston

A piston is a cylindrical part that reciprocates inside the cylinder and serves to convert a change in gas, vapor or liquid pressure into mechanical work, or vice versa - a reciprocating movement into a pressure change.

The piston is divided into three parts with different functions:

Bottom,

Sealing part,

Guide part (skirt).

The shape of the bottom depends on the function performed by the piston. For example, in internal combustion engines, the shape depends on the location of the spark plugs, injectors, valves, engine design, and other factors. With the concave shape of the bottom, the most rational combustion chamber is formed, but carbon deposits are more intense in it. With a convex bottom, the strength of the piston increases, but the shape of the combustion chamber deteriorates.

The bottom and the sealing part form the piston head. Compression and oil scraper rings are located in the sealing part of the piston.

The distance from the piston crown to the groove of the first compression ring is called the piston fire belt. Depending on the material from which the piston is made, the fire belt has a minimum permissible height, a decrease in which can lead to burnout of the piston along the outer wall, as well as the destruction of the seat of the upper compression ring.

The sealing function performed by the piston group is of great importance for the normal operation of piston engines. ABOUT technical condition the engine is judged by the sealing ability of the piston group. For example, in automobile engines it is not allowed that the oil consumption due to its burnout due to excessive penetration (suction) into the combustion chamber exceeds 3% of the fuel consumption.

The piston skirt (trunk) is its guiding part when moving in the cylinder and has two lugs (lugs) for installing the piston pin. To reduce the temperature stresses of the piston from both sides, where the bosses are located, metal is removed from the surface of the skirt to a depth of 0.5-1.5 mm. These recesses, which improve the lubrication of the piston in the cylinder and prevent the formation of scoring from thermal deformation, are called "coolers". An oil scraper ring can also be located at the bottom of the skirt.

For the manufacture of pistons, gray cast irons and aluminum alloys are used.

Cast iron

Advantages: Cast iron pistons are durable and wear resistant.

Due to their low coefficient of linear expansion, they can operate with relatively small clearances, providing a good cylinder seal.

Disadvantages: Cast iron has a fairly large specific gravity. In this regard, the scope of application of cast iron pistons is limited to relatively low-speed engines, in which the inertial forces of the reciprocating masses do not exceed one-sixth of the force of gas pressure on the piston crown.

Cast iron has low thermal conductivity; therefore, the heating of the bottom of cast iron pistons reaches 350-400 ° C. Such heating is undesirable, especially in carburetor engines, as it causes glow ignition.

Aluminum

The vast majority of modern automobile engines have aluminum pistons.

Advantages:

Low weight (at least 30% less compared to cast iron);

High thermal conductivity (3-4 times higher than the thermal conductivity of cast iron), which ensures the heating of the piston crown no more than 250 ° C, which contributes to better filling of the cylinders and allows to increase the compression ratio in gasoline engines;

Good anti-friction properties.

Connecting rod

The connecting rod is a part connectingpiston (throughpiston pin) and connecting rod journalcrankshaft... Serves to transfer reciprocating movements from the piston to the crankshaft. For less wear on the crankshaft connecting rod journals, place between them and the connecting rodsspecial liners that have an anti-friction coating.

Crankshaft

The crankshaft is a complex part with journals for fasteningconnecting rods , from which it perceives efforts and transforms them intotorque .

Crankshafts are made of carbon, chromium-manganese, chromium-nickel-molybdenum, and other steels, as well as from special high-strength cast irons.

The main elements of the crankshaft

Root neck - shaft support lying in the mainbearing hosted incrankcase engine.

Connecting rod journal - a support with which the shaft is connected toconnecting rods (There are oil channels for lubricating the connecting rod bearings).

Cheeks - connect the main and connecting rod journals.

Front output shaft part (nose) - the part of the shaft on which thegear orpulley power take-off for drivegas distribution mechanism (timing) and various auxiliary units, systems and assemblies.

Rear output part of the shaft (shank) - the part of the shaft connecting withflywheel or a massive main power take-off gear.

Counterweights - provide unloading of the main bearings from the centrifugal forces of inertia of the first order of unbalanced masses of the crank and the lower part of the connecting rod.

Flywheel

Massive toothed disc. The ring gear is required to start the engine (the starter gear engages with the flywheel gear and spins the engine shaft). Also, the flywheel serves to reduce uneven rotation of the crankshaft.

Gas distribution mechanism

Designed for the timely admission of the combustible mixture into the cylinders and the release of exhaust gases.

The main parts of the gas distribution mechanism are:

Camshaft,

Intake and exhaust valves.

Camshaft

Engines are distinguished by the location of the camshaft:

With a camshaft located incylinder block (Cam-in-Block);

With a camshaft located in the cylinder head (Cam-in-Head).

In modern automotive engines, it is usually located at the top of the block headcylinders and connected topulley or a toothed sprocketcrankshaft belt or timing chain, respectively, and rotates at half the frequency than the latter (on 4-stroke engines).

An integral part of the camshaft is itscams , the number of which corresponds to the number of inlet and outletvalves engine. Thus, each valve has an individual cam, which opens the valve by running on the lever of the valve tappet. When the cam “escapes” from the lever, the valve is closed by a powerful return spring.

Engines with an in-line configuration of cylinders and one pair of valves per cylinder usually have one camshaft (in the case of four valves per cylinder, two), and V-shaped and opposed - either one in the collapse of the block, or two, one for each half-block ( in each block head). Engines with 3 valves per cylinder (most often two inlet and one outlet) usually have one camshaft per cylinder head, while engines with 4 valves per cylinder (two inlet and 2 outlet) have 2 camshafts in each cylinder head.

Modern engines sometimes have variable valve timing systems, that is, mechanisms that allow the camshaft to be rotated relative to the drive sprocket, thereby changing the opening and closing (phase) of the valves, which makes it possible to more efficiently fill the cylinders with the working mixture at different speeds.

Valve

The valve consists of a flat head and a stem, connected by a smooth transition. For better filling of the cylinders with a combustible mixture, the diameter of the head of the inlet valves is made much larger than the diameter of the outlet. Because the valves operate at high temperatures, they are manufactured from high quality steels. The intake valves are made of chromium steel, the exhaust valves are heat-resistant, since the latter come into contact with combustible exhaust gases and heat up to 600 - 800 0 C. The high heating temperature of the valves makes it necessary to install special inserts of heat-resistant cast iron in the cylinder head, which are called seats.

How the engine works

Basic concepts

Top dead center - extreme top position piston in the cylinder.

Bottom dead center - the lowest position of the piston in the cylinder.

Piston stroke - the distance that the piston travels from one dead center to another.

The combustion chamber - the space between the cylinder head and the piston when it is at top dead center.

Cylinder displacement - the space freed by the piston when it moves from top dead center to bottom dead center.

Engine displacement - the sum of the working volumes of all engine cylinders. It is expressed in liters, therefore it is often called the engine displacement.

Full cylinder volume - the sum of the volume of the combustion chamber and the working volume of the cylinder.

Compression ratio - shows how many times the total volume of the cylinder is greater than the volume of the combustion chamber.

Compression -pressure in the cylinder at the end of the compression stroke.

Tact - a process (part of the working cycle) that takes place in the cylinder during one piston stroke.

Engine duty cycle

1st stroke - intake... When the piston moves down in the cylinder, a vacuum is formed, under the action of which a combustible mixture (a mixture of fuel with air) enters the cylinder through the open intake valve.

2nd measure - compression ... The piston moves upward under the action of the crankshaft and connecting rod. Both valves are closed and the combustible mixture is compressed.

3rd cycle - working stroke ... At the end of the compression stroke, the combustible mixture ignites (from compression in diesel engine, from the spark of a candle in gasoline engine). Under the pressure of the expanding gases, the piston moves downward and through the connecting rod drives the crankshaft into rotation.

4th measure - release ... The piston moves upward and exhaust gases escape through the opened exhaust valve.

The internal combustion engine (ICE) is by far the most common type of engine. The list of vehicles in which it is installed is simply huge. ICEs can be found on cars, helicopters, tanks, tractors, boats, etc.

An internal combustion engine is a heat engine that converts part of the chemical energy of the combustion fuel into mechanical energy. A significant division of engines into categories is the division according to the duty cycle into 2 and 4-stroke; according to the method of preparing the combustible mixture - with external (in particular, carburetor) and internal (for example, diesel engines) mixture formation; according to the type of energy converter, internal combustion engines are divided into piston, turbine, jet and combined.

The efficiency of the internal combustion engine is 0.4-0.5. The first internal combustion engine was designed by E. Lenoir in 1860. We will consider in this article the four-stroke internal combustion engine, which is most often used in the automotive industry.

The four-stroke engine was first introduced by Nikolaus Otto in 1876 and is therefore also called the Otto cycle engine. A more literate name for such a cycle is a four-stroke cycle. It is currently the most common type of engine for cars.

The principle of operation of an internal combustion engine (ICE)

The action of a piston internal combustion engine is based on the use of the thermal expansion pressure of heated gases during the movement of the piston. The gases are heated as a result of combustion of the fuel-air mixture in the cylinder. To repeat the cycle, the spent gas mixture must be released at the end of the piston movement and filled with a new portion of fuel and air. In the extreme position, the fuel is ignited by a spark plug. The intake and exhaust of fuel and combustion products occurs through valves controlled by the gas distribution mechanism and the fuel supply system.

Thus, the engine cycle is divided into the following stages:

• Intake stroke.
• Compression cycle.
• Expansion stroke, or working stroke.
• Release cycle.

The force from the moving piston of the cylinder through the crankshaft is converted into rotational motion of the engine shaft. Part of the rotational energy is spent on returning the pistons to their original state to perform a new cycle. The design of the shaft determines the different positions of the pistons in different cylinders at any given time. Thus, the more cylinders in the engine, the, in general, the more uniform the rotation of its shaft.

According to the arrangement of the cylinders, engines are divided into several types:

a) Engines with vertical or tilted cylinders in one row

B) V-shaped with the mutual arrangement of the cylinders at an angle in the form of the Latin letter V:

D) Engines with opposing cylinders. It is called "opposed", the cylinders in it are located at an angle of 180 degrees:

The engine gas distribution mechanism at the exhaust stroke cleans the cylinders from combustion products (exhaust gases) and fills the cylinders with a new portion of the fuel-air mixture at the intake stroke.

The ignition system produces a high-voltage discharge and transfers it to the cylinder plug through high voltage wire... The ignition is controlled by a distributor, the wires from which go to each candle. The distributor is designed in such a way that the discharge occurs precisely in the cylinder where the piston is currently passing the point of greatest compression of the fuel mixture. If the mixture ignites earlier, then the gas pressure will work against its course, if later - the power released by the expansion of gases will not be fully used.

To start the engine, it must be given an initial motion. For this, a start system is used (see the article "how the starter works") from an electric motor - starter.

The advantages of gasoline engines

• More low level noise and vibration compared to diesel;
• More power with equal engine volume;
• Ability to work on high revs, without serious consequences for the engine.

Disadvantages of gasoline engines

• Higher fuel consumption than a diesel engine, and higher requirements for its quality;
• The need for and permanent work fuel ignition systems;
• Highest power gasoline internal combustion engines achieved in a narrow rev range.