What are the main parts of an internal combustion engine? ICE: device, work, efficiency

23.09.2019

We all drive cars of completely different makes and models. But, few of us even think about how the engine of our car works. By and large, it is not necessary to know 100% the device of a car engine. After all, we all use, for example, mobile phones, but this does not mean that we must be radio electronics geniuses. There is a button "On", pressed and speak. But the car is a different story.

After all, a faulty phone is just a lack of communication with friends. A faulty car engine is our life and health. Many aspects of the movement of the car in general and the safety of people in particular depend on the proper maintenance of the car engine. Therefore, most likely, it will be right to take ten minutes to understand what a car engine consists of and how the engine works.

A couple of steps in the history of the creation of a car engine

Motor (motor) translated from Latin motor, means - setting in motion. In the modern sense, an engine is a device that converts any energy into mechanical energy. In the automotive industry, the most common engines are ICEs (internal combustion engines) of various types. The year of birth of the first internal combustion engine is considered to be 1801. Then the Frenchman Philippe Lebon patented the first engine running on lighting gas. Then there were Jean Etienne Lenoir and August Otto. It was August Otto who in 1877 received a patent for a four-stroke engine. And to this day, the operation of a car engine basically works on this principle.

In 1872, the American Brighton presented the first liquid fuel engine - kerosene. The attempt was unsuccessful. Kerosene did not want to actively explode inside the cylinders. And in 1882, the Gottlieb Daimler engine appeared, gasoline and efficient.

And now let's figure out what types of car engine there are and what type, first of all, your car can be attributed to.

What type of car engine do you have?

Taking into account the fact that the most popular in the automotive industry is the internal combustion engine, let's consider what types of engines are installed on our cars. The internal combustion engine is not the most perfect type of engine, but due to its 100% autonomy, it is he who is used in most modern cars. Traditional types of car engines:

Gasoline engines. They are divided into injection and carburetor. There are different types of carburetors and injection systems. The type of fuel is gasoline.
Diesel engines. Diesel fuel enters the cylinders through injectors. The advantage of diesel engines is that they do not need electricity to run. For engine start only.
gas engines. The fuel can be both liquefied and compressed natural gases, and generator gases obtained by converting solid fuels (coal, wood, peat) into gaseous.

We disassemble the device and the principle of operation of the car engine

How does a car engine work? At the first glance at the section of the engine, an ignorant person wants to run away. Everything seems so complicated and confusing. In fact, with a deeper study, the structure of a car engine is simple and understandable in order to know the principle of its operation. Know and, if necessary, apply this knowledge in life.

Cylinder block- it can be called a frame or engine housing. Inside the block there is a system of channels for lubrication and cooling of the engine. It serves as the basis for attachments: cylinder head, crankcase, etc.
Piston- a hollow metal glass. The upper part of the piston (skirt) has special grooves for piston rings.
Piston rings. The upper rings are compression, to ensure a high degree of compression of the air-fuel mixture (compression). The lower rings are oil scraper. The rings perform two functions: they ensure the tightness of the combustion chamber and act as seals so that oil does not enter the combustion chamber.
crank mechanism. Transfers the reciprocating energy of the piston movement to the crankshaft.
The principle of operation of the internal combustion engine is quite simple. From the injectors, fuel is fed into the combustion chamber and enriched with air there. The spark from the spark plug ignites the air/fuel mixture and an explosion occurs. The resulting gases push the piston down, thereby forcing it to transfer its translational motion to the crankshaft. The crankshaft, in turn, transmits the rotational movement of the transmission. Further, the gear system transmits the movement to the wheels.

And already the wheels of the car are carrying the load-bearing body with us in the direction we need. This is the principle of the engine, we are sure you will understand. And you will know what to answer when unscrupulous workers in a car service say that you need to change the compression, but there is only one left in the warehouse, and that one is imported. Good luck in understanding the device and the principle of operation of the car engine.

The modern internal combustion engine has gone far from its forefathers. It has become larger, more powerful, more environmentally friendly, but at the same time, the principle of operation, the structure of the car engine, as well as its main elements, have remained unchanged.

Internal combustion engines, widely used in automobiles, are of the piston type. This type of internal combustion engine got its name due to the principle of operation. Inside the engine is a working chamber called a cylinder. It burns the working mixture. When the mixture of fuel and air is burned in the chamber, the pressure that the piston perceives increases. Moving, the piston converts the received energy into mechanical work.

How is the internal combustion engine

The first piston engines had only one cylinder of small diameter. In the process of development, to increase power, the cylinder diameter was first increased, and then their number. Gradually, internal combustion engines took on the form familiar to us. The motor of a modern car can have up to 12 cylinders.

The modern ICE consists of several mechanisms and auxiliary systems, which, for ease of perception, are grouped as follows:

KShM - crank mechanism.
Timing - a mechanism for adjusting the valve timing.
Lubrication system.
Cooling system.
Fuel supply system.
Exhaust system.

ICE systems also include electrical starting and engine control systems.

KShM - crank mechanism

KShM is the main mechanism of a piston motor. It performs the main work - it converts thermal energy into mechanical energy. The mechanism consists of the following parts:

Cylinder block.
Cylinder head.
Pistons with pins, rings and connecting rods.
Crankshaft with flywheel.

Timing - gas distribution mechanism

In order for the required amount of fuel and air to enter the cylinder, and the combustion products to be removed from the working chamber in time, the internal combustion engine has a mechanism called gas distribution. It is responsible for opening and closing the intake and exhaust valves, through which the fuel-air combustible mixture enters the cylinders and exhaust gases are removed. Timing parts include:

Camshaft.
Inlet and outlet valves with springs and guide bushings.
Valve drive parts.
Timing drive elements.

The timing is driven from the crankshaft of the car engine. With the help of a chain or belt, rotation is transmitted to the camshaft, which, through cams or rocker arms, presses the intake or exhaust valve through the pushers and opens and closes them in turn

Depending on the design and number of valves, one or two camshafts can be installed on the engine for each bank of cylinders. With a two-shaft system, each shaft is responsible for the operation of its own series of valves - intake or exhaust. The single-shaft design has the English name SOHC (Single OverHead Camshaft). The dual shaft system is called DOHC (Double Overhead Camshaft).

During engine operation, its parts come into contact with hot gases that are formed during the combustion of the fuel-air mixture. In order for the parts of an internal combustion engine not to collapse due to excessive expansion when heated, they must be cooled. You can cool the car engine with air or liquid. Modern motors, as a rule, have a liquid cooling scheme, which is formed by the following parts:

Engine cooling jacket
Pump (pump)
Radiator
Fan
Expansion tank

The cooling jacket of internal combustion engines is formed by cavities inside the BC and cylinder head, through which the coolant circulates. It removes excess heat from engine parts and carries it to the radiator. Circulation is provided by a pump driven by a belt from the crankshaft.

The thermostat provides the necessary temperature conditions for the car engine, redirecting the fluid flow to the radiator or bypassing it. The radiator, in turn, is designed to cool the heated liquid. The fan enhances the air flow, thereby increasing the cooling efficiency. An expansion tank is necessary for modern engines, since the coolants used expand greatly when heated and require additional volume.

Engine lubrication system

In any motor, there are many moving parts that need to be constantly lubricated to reduce frictional power loss and avoid increased wear and jamming. There is a lubrication system for this. Along the way, with its help, several more tasks are solved: protection of internal combustion engine parts from corrosion, additional cooling of engine parts, and removal of wear products from the points of contact of rubbing parts. The lubrication system of a car engine is formed by:

Oil sump (pan).
Oil supply pump.
Oil filter with .
Oil pipelines.
Oil dipstick (oil level indicator).
System pressure gauge.
Oil filler neck.

The pump takes oil from the oil sump and delivers it to the oil lines and channels located in the BC and cylinder head. Through them, oil enters the points of contact of rubbing surfaces.

Supply system

The supply system for internal combustion engines with spark ignition and compression ignition differ from each other, although they share a number of common elements. Common are:

Fuel tank.
Fuel level sensor.
Fuel filters - coarse and fine.
Fuel pipelines.
Intake manifold.
Air pipes.
Air filter.

Both systems have fuel pumps, fuel rails, fuel injectors, but due to the different physical properties of gasoline and diesel fuel, their design has significant differences. The principle of supply is the same: the fuel from the tank is fed through the filters through the filters into the fuel rail, from which it enters the injectors. But if in most gasoline internal combustion engines the nozzles feed it into the intake manifold of the car's engine, then in diesel engines it is fed directly into the cylinder, and already there it mixes with air. The parts that clean the air and supply it to the cylinders - the air filter and pipes - also belong to the fuel system.

Exhaust system

The exhaust system is designed to remove exhaust gases from the cylinders of a car engine. The main details, its components:

An exhaust manifold.
Muffler intake pipe.
Resonator.
Muffler.
Exhaust pipe.

In modern internal combustion engines, the exhaust structure is supplemented with devices for neutralizing harmful emissions. It consists of a catalytic converter and sensors that communicate with the engine control unit. Exhaust gases from the exhaust manifold through the exhaust pipe enter the catalytic converter, then through the resonator into the muffler. Then they are released into the atmosphere through the exhaust pipe.

In conclusion, it is necessary to mention the start-up and engine control systems of the car. They are an important part of the engine, but they need to be considered together with the car's electrical system, which is beyond the scope of this article on the internals of the engine.

Most drivers have no idea what a car engine is. And it is necessary to know this, because it is not in vain that when studying in many driving schools, students are told the principle of operation of internal combustion engines. Every driver should have an idea about the operation of the engine, because this knowledge can be useful on the road.

Of course, there are different types and brands of car engines, the operation of which differs from each other in small things (fuel injection systems, cylinder arrangement, etc.). However, the basic principle for all types of internal combustion engines remains unchanged.

The device of a car engine in theory

It is always appropriate to consider the internal combustion engine device using the example of the operation of one cylinder. Although most often cars have 4, 6, 8 cylinders. In any case, the main part of the motor is the cylinder. It contains a piston that can move up and down. At the same time, there are 2 boundaries of its movement - upper and lower. Professionals call them TDC and BDC (top and bottom dead center).

The piston itself is connected to the connecting rod, and the connecting rod is connected to the crankshaft. When the piston moves up and down, the connecting rod transfers the load to the crankshaft, and it rotates. The loads from the shaft are transferred to the wheels, causing the car to start moving.

But the main task is to make the piston work, because it is he who is the main driving force of this complex mechanism. This is done using gasoline, diesel fuel or gas. A drop of fuel ignited in the combustion chamber throws the piston down with great force, thereby setting it in motion. Then, by inertia, the piston returns to the upper limit, where the explosion of gasoline again occurs and this cycle is repeated constantly until the driver turns off the engine.

This is what a car engine looks like. However, this is just a theory. Let's take a closer look at the cycles of the motor.

Four stroke cycle

Almost all engines operate on a 4-stroke cycle:

Fuel inlet.
Fuel compression.
Combustion.
Output of exhaust gases outside the combustion chamber.

Scheme

The figure below shows a typical diagram of a car engine (one cylinder).

This diagram clearly shows the main elements:

A - Camshaft.

B - Valve cover.

C - Exhaust valve through which gases are removed from the combustion chamber.

D - Exhaust port.

E - Cylinder head.

F - Coolant chamber. Most often there is antifreeze, which cools the heating motor housing.

G - Motor block.

H - Oil sump.

I - Pan where all the oil flows.

J - A spark plug that generates a spark to ignite the fuel mixture.

K - The intake valve through which the fuel mixture enters the combustion chamber.

L - Inlet.

M - A piston that moves up and down.

N - Connecting rod connected to the piston. This is the main element that transmits force to the crankshaft and transforms the linear movement (up and down) into rotational.

O - Connecting rod bearing.

P - Crankshaft. It rotates due to the movement of the piston.

It is also worth highlighting such an element as piston rings (they are also called oil scraper rings). They are not shown in the figure, but they are an important component of the car engine system. These rings wrap around the piston and create a maximum seal between the walls of the cylinder and the piston. They prevent fuel from entering the oil pan and oil from entering the combustion chamber. Most old VAZ car engines and even engines from European manufacturers have worn rings that do not create an effective seal between the piston and cylinder, which can cause oil to enter the combustion chamber. In such a situation, there will be an increased consumption of gasoline and "zhor" oil.

These are the basic design elements that take place in all internal combustion engines. In fact, there are many more elements, but we will not touch on the subtleties.

How does an engine work?

Let's start with the initial position of the piston - it is at the top. At this point, the inlet port is opened by a valve, the piston begins to move down and sucks the fuel mixture into the cylinder. In this case, only a small drop of gasoline enters the cylinder capacity. This is the first cycle of work.

During the second stroke, the piston reaches its lowest point, while the inlet closes, the piston begins to move upward, as a result of which the fuel mixture is compressed, since it has nowhere to go in a closed chamber. When the piston reaches its maximum upper point, the fuel mixture is compressed to its maximum.

The third stage is the ignition of the compressed fuel mixture using a spark plug that emits a spark. As a result, the combustible composition explodes and pushes the piston down with great force.

At the final stage, the part reaches the lower boundary and returns to the upper point by inertia. At this time, the exhaust valve opens, the exhaust mixture in the form of gas leaves the combustion chamber and enters the street through the exhaust system. After that, the cycle, starting from the first stage, repeats again and continues for the entire time until the driver turns off the engine.

As a result of the explosion of gasoline, the piston moves down and pushes the crankshaft. It spins and transfers the load to the wheels of the car. This is what a car engine looks like.

Differences in gasoline engines

The method described above is universal. By this principle, the work of almost all gasoline engines is built. Diesel engines are distinguished by the fact that there are no candles - an element that ignites the fuel. Detonation of diesel fuel is carried out due to the strong compression of the fuel mixture. That is, in the third cycle, the piston rises, strongly compresses the fuel mixture, and it explodes naturally under pressure.

ICE alternative

It should be noted that recently electric cars have appeared on the market - cars with electric motors. There, the principle of operation of the motor is completely different, since the source of energy is not gasoline, but electricity in batteries. But so far, the automotive market belongs to cars with internal combustion engines, and electric motors cannot boast of high efficiency.

A few words in conclusion

Such an internal combustion engine device is almost perfect. But every year new technologies are being developed that increase the efficiency of the engine, and the characteristics of gasoline are improved. With proper maintenance, a car engine can last for decades. Some successful engines of Japanese and German concerns "run" a million kilometers and become unusable solely due to mechanical obsolescence of parts and friction pairs. But many engines, even after a million run, successfully undergo overhaul and continue to fulfill their intended purpose.

Internal combustion engines

Part I of the basics of the theory of engines

1. CLASSIFICATION AND OPERATING PRINCIPLE OF INTERNAL COMBUSTION ENGINES

1.1. General information and classification

1.2. Operating cycle of a four-stroke internal combustion engine

1.3. Working cycle of a two-stroke internal combustion engine

2. THERMAL CALCULATION OF INTERNAL COMBUSTION ENGINES

2.1. Theoretical thermodynamic cycles of internal combustion engines

2.1.1. Theoretical cycle with heat input at constant volume

2.1.2. Theoretical cycle with heat input at constant pressure

2.1.3. Theoretical cycle with heat input at constant volume and constant pressure (mixed cycle)

2.2. Valid ICE cycles

2.2.1. Working bodies and their properties

2.2.2. intake process

2.2.3. Compression process

2.2.4. combustion process

2.2.5. Expansion process

2.2.6. Release Process

2.3. Indicator and effective indicators of the engine

2.3.1. Engine indicators

2.3.2. Efficient indicators of engines

2.4. Features of the working cycle and thermal calculation of two-stroke engines

3. PARAMETERS OF INTERNAL COMBUSTION ENGINES.

3.1. Thermal balance of engines

3.2. Determination of the main dimensions of engines

3.3. The main parameters of the engines.

4. CHARACTERISTICS OF INTERNAL COMBUSTION ENGINES

4.1. Regulating characteristics

4.2. Speed characteristics

4.2.1. External speed characteristic

4.2.2. Partial speed characteristics

4.2.3. Construction of speed characteristics by the analytical method

4.3. Regulatory characteristic

4.4. Load characteristic

Bibliography

1. Classification and principle of operation of internal combustion engines

General information and classification

A piston internal combustion engine (ICE) is a heat engine in which the conversion of the chemical energy of the fuel into heat and then into mechanical energy occurs inside the working cylinder. The transformation of heat into work in such engines is associated with the implementation of a whole complex of complex physicochemical, gas-dynamic and thermodynamic processes that determine the difference in operating cycles and design.

The classification of reciprocating internal combustion engines is shown in fig. 1.1. The type of fuel on which the engine runs is taken as the initial sign of the classification. Gaseous fuel for internal combustion engines are natural, liquefied and generator gases. Liquid fuel is a product of oil refining: gasoline, kerosene, diesel fuel, etc. Gas-liquid engines run on a mixture of gaseous and liquid fuels, with the main fuel being gaseous, and liquid is used as a pilot in small quantities. Multi-fuel engines are capable of long-term operation on a variety of fuels ranging from crude oil to high-octane gasoline.

Internal combustion engines are also classified according to the following criteria:

according to the method of ignition of the working mixture - with forced ignition and with compression ignition;

according to the method of implementing the working cycle - two-stroke and four-stroke, with and without supercharging;

Rice. 1.1. Classification of internal combustion engines.

according to the method of mixture formation - with external mixture formation (carburetor and gas) and with internal mixture formation (diesel and gasoline with fuel injection into the cylinder);

according to the method of cooling - with liquid and air cooling;

according to the location of the cylinders - single-row with a vertical, inclined horizontal arrangement; double-row with V-shaped and opposite arrangement.

The conversion of the chemical energy of the fuel burned in the engine cylinder into mechanical work is carried out with the help of a gaseous body - the products of combustion of liquid or gaseous fuel. Under the influence of gas pressure, the piston performs a reciprocating motion, which is converted into rotational motion of the crankshaft using the crank mechanism of the internal combustion engine. Before considering workflows, let's dwell on the basic concepts and definitions adopted for internal combustion engines.

For one revolution of the crankshaft, the piston will twice be in the extreme positions, where the direction of its movement changes (Fig. 1.2). These piston positions are called dead spots, since the force applied to the piston at this moment cannot cause the rotational movement of the crankshaft. The position of the piston in the cylinder, at which its distance from the axis of the engine shaft reaches a maximum, is called top dead center(TDC). bottom dead center(BDC) is the position of the piston in the cylinder at which its distance from the axis of the engine shaft reaches a minimum.

The distance along the axis of the cylinder between the dead points is called the piston stroke. Each stroke of the piston corresponds to a rotation of the crankshaft by 180°.

The movement of the piston in the cylinder causes a change in the volume of the over-piston space. The volume of the internal cavity of the cylinder when the piston is at TDC is called combustion chamber volumeV c .

The volume of the cylinder formed by the piston as it moves between dead points is called cylinder displacementV h .

Where D- cylinder diameter, mm;

S – piston stroke, mm

The volume of the above-piston space when the piston is at BDC is called full cylinder volumeV a .

Fig 1.2. Scheme of a piston internal combustion engine

The displacement of an engine is the product of the displacement of a cylinder by the number of cylinders.

The ratio of the total volume of the cylinder V a to the volume of the combustion chamber V c called compression ratio

When the piston moves in the cylinder, in addition to changing the volume of the working fluid, its pressure, temperature, heat capacity, and internal energy change. The work cycle is a set of successive processes carried out in order to convert the thermal energy of the fuel into mechanical energy.

Achieving the periodicity of work cycles is ensured with the help of special mechanisms and engine systems.

The working cycle of any reciprocating internal combustion engine can be carried out according to one of the two schemes shown in Fig. 1.3.

According to the scheme shown in Fig. 1.3a, the working cycle is carried out as follows. Fuel and air in certain proportions are mixed outside the engine cylinder and form a combustible mixture. The resulting mixture enters the cylinder (inlet), after which it is compressed. The compression of the mixture, as will be shown below, is necessary to increase the work per cycle, since this expands the temperature limits in which the working process proceeds. Pre-compression also creates better conditions for the combustion of the air-fuel mixture.

During the intake and compression of the mixture in the cylinder, additional mixing of fuel with air occurs. The prepared combustible mixture is ignited in the cylinder by an electric spark. Due to the rapid combustion of the mixture in the cylinder, the temperature and, consequently, the pressure rise sharply, under the influence of which the piston moves from TDC to BDC. In the process of expansion, the gases heated to a high temperature perform useful work. The pressure, and with it the temperature of the gases in the cylinder, decreases. After the expansion, the cylinder is cleaned of combustion products (exhaust), and the working cycle is repeated.

Rice. 1.3. Schemes of the working cycle of engines

In the considered scheme, the preparation of an air-fuel mixture, i.e., the mixing process, occurs mainly outside the cylinder, and the cylinder is filled with a ready-made combustible mixture, therefore, engines operating according to this scheme are called engines with external mixing. These engines include carbureted gasoline engines, gas engines, and engines with fuel injection into the intake manifold, that is, engines that use fuel that evaporates easily and mixes well with air under normal conditions.

The compression of the mixture in the cylinder in engines with external carburetion must be such that the pressure and temperature at the end of compression do not reach values at which premature flashing or too rapid (knocking) combustion could occur. Depending on the fuel used, the composition of the mixture, the conditions of heat transfer to the cylinder walls, etc., the pressure of the end of compression in engines with external mixture formation is in the range of 1.0–2.0 MPa.

If the engine cycle occurs according to the scheme described above, then good mixture formation and use of the working volume of the cylinder are ensured. However, the limited degree of compression of the mixture does not improve the efficiency of the engine, and the need for forced ignition complicates its design.

In the case of the implementation of the working cycle according to the scheme shown in Fig. 1.3b , the process of mixture formation occurs only inside the cylinder. The working cylinder in this case is filled not with a mixture, but with air (inlet), which is compressed. At the end of the compression process, fuel is injected into the cylinder through the nozzle under high pressure. When injected, it is finely sprayed and mixed with the air in the cylinder. Fuel particles, in contact with hot air, evaporate, forming an air-fuel mixture. The ignition of the mixture during engine operation according to this scheme occurs as a result of heating the air to temperatures exceeding the self-ignition of the fuel due to compression. Fuel injection only starts at the end of the compression stroke to prevent pre-flash. By the time of ignition, fuel injection is usually not finished yet. The fuel-air mixture formed during the injection process is heterogeneous, as a result of which complete combustion of the fuel is possible only with a significant excess of air. As a result of the higher compression ratio allowed when the engine is operated according to this scheme, a higher efficiency is also provided. After the combustion of the fuel, the process of expansion and cleaning of the cylinder from combustion products (exhaust) follows. Thus, in engines operating according to the second scheme, the entire process of mixture formation and preparation of the combustible mixture for combustion occurs inside the cylinder. Such motors are called motors. with internal mixing. Engines in which fuel ignition occurs as a result of high compression are called compression ignition engines or diesel engines.

Operating cycle of a four-stroke internal combustion engine

An engine whose duty cycle is completed in four strokes, or two revolutions of the crankshaft, is called four stroke. The operating cycle in such an engine is as follows.

First measure - inlet(Fig. 1.4). At the beginning of the first stroke, the piston is in a position close to TDC. The inlet starts from the moment the inlet is opened, 10–30 ° before TDC.

Rice. 1.4. Inlet

The combustion chamber is filled with combustion products from the previous process, the pressure of which is slightly greater than atmospheric pressure. On the indicator diagram, the initial position of the piston corresponds to the point r. When the crankshaft rotates (in the direction of the arrow), the connecting rod moves the piston to BDC, and the camshaft fully opens the intake valve and connects the over-piston space of the engine cylinder to the intake manifold. At the initial moment of inlet, the valve is just beginning to rise and the inlet is a round narrow slot a few tenths of a millimeter high. Therefore, at this moment of intake, the combustible mixture (or air) hardly passes into the cylinder. However, advancing the opening of the inlet is necessary so that by the time the piston starts lowering after it has passed the TDC, it would be open as much as possible and would not impede the flow of air or mixture into the cylinder. As a result of the movement of the piston to the BDC, the cylinder is filled with a fresh charge (air or combustible mixture).

At the same time, due to the resistance of the intake system and intake valves, the pressure in the cylinder becomes 0.01–0.03 MPa less than the pressure in the intake pipeline . On the indicator diagram, the intake stroke corresponds to the line ra.

The intake stroke consists of the intake of gases, which occurs when the movement of the descending piston accelerates, and the intake when its movement slows down.

Intake during piston acceleration begins at the moment the piston starts to descend and ends at the moment the piston reaches maximum speed at approximately 80 ° of shaft rotation after TDC. As the piston begins to descend, little air or mixture enters the cylinder due to the small opening of the inlet, and therefore the residual gases remaining in the combustion chamber from the previous cycle expand and the pressure in the cylinder drops. When the piston is lowered, the combustible mixture or air, which was at rest in the intake manifold or moved in it at a low speed, begins to pass into the cylinder at a gradually increasing speed, filling the volume released by the piston. As the piston descends, its speed gradually increases and reaches a maximum when the crankshaft rotates by about 80°. In this case, the inlet opening opens more and more and the combustible mixture (or air) passes into the cylinder in large quantities.

Intake with slow piston movement begins from the moment the piston reaches its maximum speed and ends at BDC , when its speed is zero. As the piston speed decreases, the speed of the mixture (or air) passing into the cylinder decreases somewhat, but at BDC it is not zero. When the piston moves slowly, the combustible mixture (or air) enters the cylinder due to an increase in the volume of the cylinder released by the piston, as well as due to its inertia force. At the same time, the pressure in the cylinder gradually increases and in the BDC it can even exceed the pressure in the intake pipeline.

The pressure in the inlet pipeline can be close to atmospheric in naturally aspirated engines or higher depending on the degree of boost (0.13–0.45 MPa) in supercharged engines.

The inlet will end at the moment the inlet is closed (40–60°) after BDC. The delay in closing the intake valve occurs with a gradually rising piston, i.e. decreasing volume of gases in the cylinder. Consequently, the mixture (or air) enters the cylinder due to the previously created rarefaction or inertia of the gas flow accumulated during the flow of the jet into the cylinder.

At low shaft speeds, for example, when starting the engine, the gas inertia force in the intake manifold is almost completely absent, therefore, during the intake delay, the mixture (or air) that entered the cylinder earlier during the main intake will be thrown back.

At medium speeds, the inertia of the gases is greater, therefore, at the very beginning of the piston rise, recharging occurs. However, as the piston rises, the gas pressure in the cylinder will increase and the recharging that has begun can turn into a reverse ejection.

At high speeds, the inertia force of the gases in the intake manifold is close to the maximum, so the cylinder is intensively recharged, and the reverse ejection does not occur.

Second measure - compression. When the piston moves from BDC to TDC (Fig. 1.5), the charge entering the cylinder is compressed.

At the same time, the pressure and temperature of the gases increase, and with some movement of the piston from BDC, the pressure in the cylinder becomes the same as the intake pressure (point T on the indicator chart). After the valve closes, as the piston moves further, the pressure and temperature in the cylinder continue to rise. Pressure value at the end of compression (point With) will depend on the degree of compression, tightness of the working cavity, heat transfer to the walls, and also on the value of the initial compression pressure.

Fig 1.5. Compression

The ignition and combustion process of the fuel, both with external and internal mixture formation, takes some time, although very little. For the best use of the heat released during combustion, it is necessary that the combustion of the fuel ends at a piston position as close to TDC as possible. Therefore, the ignition of the working mixture from an electric spark in engines with external carburetion and fuel injection into the cylinder of engines with internal carburetion is usually carried out before the piston reaches TDC.

Thus, during the second stroke, the charge is mainly compressed in the cylinder. In addition, at the beginning of the stroke, cylinder charging continues, and fuel combustion begins at the end. On the indicator diagram, the second measure corresponds to the line ac.

Third beat - combustion and expansion. The third stroke occurs during the piston stroke from TDC to BDC (Fig. 1.6). At the beginning of the stroke, the fuel that entered the cylinder and prepared for this at the end of the second stroke burns intensively.

Due to the release of a large amount of heat, the temperature and pressure in the cylinder rise sharply, despite a slight increase inside the cylinder volume (section сz on the indicator chart).

Under the action of pressure, the piston moves further to the BDC and the gases expand. During expansion, the gases do useful work, so the third cycle is also called working move. On the indicator diagram, the third measure corresponds to the line сzb.

Rice. 1.6. Extension

Fourth beat - release. During the fourth stroke, the cylinder is cleaned of exhaust gases (Fig. 1.7 ). The piston, moving from BDC to TDC, displaces gases from the cylinder through the open exhaust valve. In four-stroke engines, the exhaust port is opened by 40–80 ° until the piston arrives at BDC (point b) and close it 20-40° after the piston has passed TDC. Thus, the duration of cleaning the cylinder from exhaust gases in different engines is from 240 to 300 ° of the angle of rotation of the crankshaft.

The exhaust process can be divided into the pre-exhaust, which occurs with the descending piston from the moment the exhaust port opens (point b) to BDC, i.e., within 40–80 °, and the main exhaust, which occurs when the piston moves from BDC until the outlet is closed, i.e., during 200–220 ° of crankshaft rotation.

During pre-release, the piston descends and cannot remove exhaust gases from the cylinder.

However, at the beginning of pre-exhaust, the pressure in the cylinder is much higher than in the exhaust manifold.

Therefore, the exhaust gases are ejected from the cylinder at critical speeds due to their own excess pressure. The outflow of gases at such high speeds is accompanied by a sound effect, to absorb which silencers are installed.

The critical exhaust gas flow rate at temperatures of 800–1200 K is 500–600 m/s.

Rice. 1.7. Release

When the piston approaches the BDC, the pressure and temperature of the gas in the cylinder decrease and the exhaust gas flow rate decreases.

When the piston reaches BDC, the pressure in the cylinder will decrease. In this case, the critical expiration will end and the main release will begin.

The outflow of gases during the main outlet occurs at lower velocities, reaching 60–160 m/s at the end of the outlet.

Thus, the pre-release is shorter, the gas velocities are very high, and the main exhaust is about three times longer, but the gases at this time are removed from the cylinder at lower velocities.

Therefore, the amounts of gases leaving the cylinder during the pre-exhaust and the main exhaust are approximately the same.

As the engine speed decreases, all cycle pressures decrease, and hence the pressures at the moment the exhaust port opens. Therefore, at medium speeds, it is reduced, and in some modes (at low speeds), the outflow of gases with critical speeds characteristic of pre-release completely disappears.

The temperature of the gases in the pipeline varies according to the angle of rotation of the crank from the maximum at the beginning of the outlet to the minimum at the end. Preliminary opening of the outlet slightly reduces the usable area of the indicator diagram. However, a later opening of this hole will cause high pressure gases to be trapped in the cylinder and additional work will have to be expended to remove them when the piston moves.

A slight delay in closing the exhaust port makes it possible to use the inertia of the exhaust gases previously released from the cylinder to better clean the cylinder from burnt gases. Despite this, part of the combustion products inevitably remains in the cylinder head, passing from each given cycle to the next in the form of residual gases. On the indicator diagram, the fourth measure corresponds to the line zb.

The fourth stroke ends the working cycle. With further movement of the piston, all cycle processes are repeated in the same sequence.

Only the combustion and expansion stroke is working, the remaining three strokes are carried out due to the kinetic energy of the rotating crankshaft with a flywheel and the work of other cylinders.

The more completely the cylinder is cleaned of exhaust gases and the more fresh charge enters it, the more, therefore, it will be possible to obtain useful work per cycle.

To improve the cleaning and filling of the cylinder, the exhaust valve closes not at the end of the exhaust stroke (TDC), but somewhat later (when the crankshaft is rotated 5–30 ° after TDC), i.e. at the beginning of the first stroke. For the same reason, the intake valve also opens with some advance (10–30 ° before TDC, i.e., at the end of the fourth cycle). Thus, at the end of the fourth stroke, both valves can be open for a certain period. This valve position is called valve overlap. It helps to improve the filling as a result of the ejecting action of the flow of gases in the exhaust pipeline.

From a consideration of the four-stroke cycle of operation, it follows that the four-stroke engine only works as a heat engine (compression and expansion strokes) for only half the time spent on the cycle. The second half of the time (intake and exhaust strokes) the engine works like an air pump.

For about a hundred years, everywhere in the world, the main power unit on cars and motorcycles, tractors and combines, and other equipment has been an internal combustion engine. Coming at the beginning of the twentieth century to replace external combustion engines (steam), it remains the most cost-effective type of motor in the twenty-first century. In this article, we will consider in detail the device, the principle of operation of various types of internal combustion engines and its main auxiliary systems.

Definition and general features of the internal combustion engine

The main feature of any internal combustion engine is that the fuel ignites directly inside its working chamber, and not in additional external carriers. During operation, chemical and thermal energy from fuel combustion is converted into mechanical work. The principle of operation of the internal combustion engine is based on the physical effect of thermal expansion of gases, which is formed during the combustion of the fuel-air mixture under pressure inside the engine cylinders.

Classification of internal combustion engines

In the process of evolution of internal combustion engines, the following types of these motors have proven their effectiveness:

Piston internal combustion engines. In them, the working chamber is located inside the cylinders, and the thermal energy is converted into mechanical work by means of a crank mechanism that transfers the energy of motion to the crankshaft. Piston engines are divided, in turn, into
carburetor, in which the air-fuel mixture is formed in the carburetor, injected into the cylinder and ignited there by a spark from a spark plug;

injection, in which the mixture is fed directly into the intake manifold, through special nozzles, under the control of the electronic control unit, and is also ignited by means of a candle;
diesel, in which the ignition of the air-fuel mixture occurs without a candle, by compressing air, which is heated by pressure from a temperature exceeding the combustion temperature, and fuel is injected into the cylinders through nozzles.
Rotary piston internal combustion engines. In motors of this type, thermal energy is converted into mechanical work by rotating the working gases of a rotor of a special shape and profile. The rotor moves along a "planetary trajectory" inside the working chamber, which has the shape of a "eight", and performs the functions of both a piston and a timing (gas distribution mechanism), and a crankshaft.
gas turbine internal combustion engines. In these motors, the transformation of thermal energy into mechanical work is carried out by rotating the rotor with special wedge-shaped blades, which drives the turbine shaft.

The most reliable, unpretentious, economical in terms of fuel consumption and the need for regular maintenance are piston engines.

Equipment with other types of internal combustion engines can be included in the Red Book. Nowadays only Mazda makes cars with rotary piston engines. An experimental series of cars with a gas turbine engine was produced by Chrysler, but it was in the 60s, and none of the automakers returned to this issue. In the USSR, T-80 tanks and Zubr landing ships were equipped with gas turbine engines, but later it was decided to abandon this type of engine. In this regard, let us dwell in detail on the "world-dominated" reciprocating internal combustion engines.

The engine housing combines into a single organism:

cylinder block, inside the combustion chambers of which the fuel-air mixture ignites, and the gases from this combustion drive the pistons;
crank mechanism, which transfers the energy of movement to the crankshaft;
gas distribution mechanism, which is designed to ensure the timely opening / closing of valves for the inlet / outlet of the combustible mixture and exhaust gases;
supply system ("injection") and ignition ("ignition") of the fuel-air mixture;
combustion products removal system(exhaust gases).

Cross section of a four-stroke internal combustion engine

When the engine is started, an air-fuel mixture is injected into its cylinders through the intake valves and ignites there from a spark plug spark. During combustion and thermal expansion of gases from excess pressure, the piston sets in motion, transferring mechanical work to the rotation of the crankshaft.

The operation of a piston internal combustion engine is carried out cyclically. These cycles are repeated at a frequency of several hundred times per minute. This ensures continuous translational rotation of the crankshaft exiting the engine.

Let's define terminology. A stroke is a work process that occurs in an engine in one stroke of the piston, more precisely, in one of its movements in one direction, up or down. A cycle is a set of cycles that repeat in a certain sequence. According to the number of strokes within one working cycle, internal combustion engines are divided into two-stroke (the cycle is carried out in one revolution of the crankshaft and two strokes of the piston) and four-stroke (for two revolutions of the crankshaft and four pistons). At the same time, both in those and in other engines, the working process goes according to the following plan: intake; compression; combustion; expansion and release.

The principles of operation of the internal combustion engine

- The principle of operation of a two-stroke engine

When the engine starts, the piston, entrained by the rotation of the crankshaft, begins to move. As soon as it reaches its bottom dead center (BDC) and proceeds to move up, a fuel-air mixture is supplied to the combustion chamber of the cylinder.

In its upward movement, the piston compresses it. When the piston reaches its top dead center (TDC), a spark from the electronic spark plug ignites the air-fuel mixture. Instantly expanding, the vapors of burning fuel rapidly push the piston back to the bottom dead center.

At this time, the exhaust valve opens, through which hot exhaust gases are removed from the combustion chamber. Having passed BDC again, the piston resumes its movement to TDC. During this time, the crankshaft makes one revolution.

With a new movement of the piston, the inlet channel of the fuel-air mixture opens again, which replaces the entire volume of exhaust gases, and the whole process is repeated anew. Due to the fact that the work of the piston in such motors is limited to two strokes, it makes a much smaller number of movements per unit of time than in a four-stroke engine. Friction losses are minimized. However, a lot of heat energy is released, and two-stroke engines heat up faster and more strongly.

In two-stroke engines, the piston replaces the gas distribution valve mechanism, during its movement at certain moments, opening and closing the intake and exhaust working openings in the cylinder. Worse, compared with a four-stroke engine, gas exchange is the main drawback of a two-stroke ICE system. At the moment of removal of exhaust gases, a certain percentage of not only the working substance, but also power is lost.

The areas of practical application of two-stroke internal combustion engines are mopeds and scooters; outboard motors, lawn mowers, chainsaws, etc. low power technology.

Four-stroke internal combustion engines are deprived of these shortcomings, which, in various versions, are installed on almost all modern cars, tractors and other equipment. In them, the intake / exhaust of a combustible mixture / exhaust gases are carried out as separate workflows, and not combined with compression and expansion, as in two-stroke ones. With the help of the gas distribution mechanism, the mechanical synchronization of the operation of the intake and exhaust valves with the crankshaft speed is ensured. In a four-stroke engine, the injection of the fuel-air mixture occurs only after the complete removal of exhaust gases and the closing of the exhaust valves.

The working process of an internal combustion engine

Each stroke of work is one stroke of the piston in the range from top to bottom dead center. In this case, the engine goes through the following phases of operation:

Stroke one, inlet. The piston moves from top dead center to bottom dead center. At this time, a vacuum occurs inside the cylinder, the intake valve opens and the fuel-air mixture enters. At the end of the intake, the pressure in the cylinder cavity is in the range from 0.07 to 0.095 MPa; temperature - from 80 to 120 degrees Celsius.
Bar two, compression. When the piston moves from bottom to top dead center and the intake and exhaust valves are closed, the combustible mixture is compressed in the cylinder cavity. This process is accompanied by an increase in pressure up to 1.2-1.7 MPa, and temperature - up to 300-400 degrees Celsius.
Bar three, expansion. The fuel-air mixture ignites. This is accompanied by the release of a significant amount of thermal energy. The temperature in the cavity of the cylinder rises sharply to 2.5 thousand degrees Celsius. Under pressure, the piston moves quickly to its bottom dead center. The pressure indicator in this case is from 4 to 6 MPa.
Bar four, issue. During the reverse movement of the piston to the top dead center, the exhaust valve opens, through which the exhaust gases are pushed out of the cylinder into the exhaust pipe, and then into the environment. The pressure indicators in the final stage of the cycle are 0.1-0.12 MPa; temperature - 600-900 degrees Celsius.

Auxiliary systems of the internal combustion engine

The ignition system is part of the electrical equipment of the machine and is designed to provide a spark, igniting the fuel-air mixture in the working chamber of the cylinder. The components of the ignition system are:

Power supply. During engine start, this is the battery, and during its operation, the generator.
Switch, or ignition switch. This was previously a mechanical, and in recent years, more and more often an electrical contact device for supplying electrical voltage.
Energy storage. A coil, or autotransformer, is a unit designed to store and convert enough energy to cause the desired discharge between the spark plug electrodes.
Ignition distributor (distributor). A device designed to distribute a high voltage pulse along the wires leading to the candles of each of the cylinders.

ICE ignition system

- intake system

The ICE intake system is designed For uninterrupted filing into the motor atmospheric air, for mixing it with fuel and preparing a combustible mixture. It should be noted that in the carburetor engines of the past, the intake system consists of an air duct and an air filter. And that's it. The composition of the intake system of modern cars, tractors and other equipment includes:

air intake. It is a branch pipe of a form convenient for each particular engine. Through it, atmospheric air is sucked into the engine, through the difference in pressure in the atmosphere and in the engine, where vacuum occurs when the pistons move.
Air filter. This is a consumable product designed to clean the air entering the motor from dust and solid particles, their retention on the filter.
throttle valve. An air valve designed to regulate the supply of the desired amount of air. Mechanically, it is activated by pressing the gas pedal, and in modern technology - using electronics.
Intake manifold. Distributes the air flow through the engine cylinders. To give the air flow the desired distribution, special intake flaps and a vacuum booster are used.

The fuel system, or the power supply system of the internal combustion engine, is "responsible" for uninterrupted fuel supply to form a fuel-air mixture. The fuel system includes:

Fuel tank- a container for storing gasoline or diesel fuel, with a device for taking fuel (pump).
Fuel lines- a set of tubes and hoses through which its "food" enters the engine.
Mixing device, i.e. carburetor or injector- a special mechanism for the preparation of the fuel-air mixture and its injection into the internal combustion engine.
Electronic control unit(ECU) mixture formation and injection - in injection engines, this device is “responsible” for synchronous and efficient work on the formation and supply of a combustible mixture to the engine.
Fuel pump- an electrical device for pumping gasoline or diesel fuel into the fuel line.
The fuel filter is a consumable for additional purification of fuel during its transportation from the tank to the engine.

ICE fuel system diagram

- Lubrication system

The purpose of the ICE lubrication system is friction reduction and its destructive effect on parts; abduction parts of the excess heat; removal products soot and wear; protection metal against corrosion. The engine lubrication system includes:

Oil pan- engine oil storage tank. The oil level in the sump is controlled not only by a special dipstick, but also by a sensor.
Oil pump- pumps oil from the sump and delivers it to the necessary engine parts through special drilled channels - "lines". Under the influence of gravity, the oil flows down from the lubricated parts, back into the oil pan, accumulates there, and the lubrication cycle is repeated again.
Oil filter traps and removes solid particles from engine oil formed from soot and wear products of parts. The filter element is always replaced with a new one with every engine oil change.
Oil radiator Designed to cool engine oil using liquid from the engine cooling system.

The exhaust system of the internal combustion engine serves for removing spent gases And noise reduction motor work. In modern technology, the exhaust system consists of the following parts (in order of exhaust gases leaving the engine):

An exhaust manifold. This is a pipe system made of heat-resistant cast iron, which receives hot exhaust gases, dampens their primary oscillatory process and sends them further to the exhaust pipe.
Downpipe- a curved gas outlet made of fire-resistant metal, popularly referred to as "pants".
Resonator, or, in popular language, the “bank” of the muffler is a container in which exhaust gases are separated and their speed is reduced.
Catalyst- a device designed for purification of exhaust gases and their neutralization.
Muffler- a container with a complex of special partitions designed to repeatedly change the direction of gas flow and, accordingly, their noise level.

Exhaust system

- Cooling system

If on mopeds, scooters and inexpensive motorcycles an air cooling system of the engine is still used - with an oncoming air flow, then for more powerful equipment it is, of course, not enough. This is where a liquid cooling system comes into play. For absorbing excess heat at the motor and reduction of thermal loads on its details.

Radiator The cooling system is used to release excess heat to the environment. It consists of a large number of curved aluminum tubes, with fins for additional heat dissipation.
Fan designed to enhance the cooling effect on the radiator from the oncoming air flow.
Water pump(pump) - "drives" the coolant in the "small" and "large" circles, ensuring its circulation through the engine and radiator.
Thermostat- a special valve that ensures the optimum temperature of the coolant by starting it in a "small circle", bypassing the radiator (when the engine is cold) and in a "large circle", through the radiator - when the engine is warm.

The coordinated work of these auxiliary systems ensures maximum efficiency from the internal combustion engine and its reliability.

In conclusion, it should be noted that in the foreseeable future, worthy competitors to the internal combustion engine are not expected to appear. There is every reason to assert that in its modern, improved form, it will remain the dominant type of motor in all sectors of the world economy for several decades to come.