INTERNAL COMBUSTION ENGINE CYCLES

The idea of \u200b\u200busing organic fuel combustion products as a working fluid belongs to Sadi Carnot. He substantiated the principle of operation of an internal combustion engine (ICE) with preliminary air compression in 1824, but due to the limited technical capabilities, the creation of such a machine could not be realized.

In 1895 in Germany, engineer R. Diesel built an engine with internal mixing of air and liquid fuel. In such an engine, only air is compressed, and then fuel is injected into it through a nozzle. Due to the separate compression of the air in the cylinder of such an engine, a high pressure and temperature were obtained, and the fuel injected there ignited spontaneously. Such engines were named diesel engines in honor of their inventor.

The main advantages of piston internal combustion engines in comparison with STUs are their compactness and high temperature level of heat supply to the working fluid. The compactness of the internal combustion engine is due to the combination of three elements of a heat engine in the engine cylinder: a hot source of heat, compression and expansion cylinders. Since the ICE cycle is open, the external environment (exhaust of combustion products) is used as a cold source of heat. The small dimensions of the internal combustion engine cylinder practically remove the restrictions on the maximum temperature of the working fluid. The cylinder of the internal combustion engine has forced cooling, and the combustion process is fast, therefore the metal of the cylinder has an acceptable temperature. The efficiency of such motors is high.

The main disadvantage of piston internal combustion engines is the technical limitation of their power, which is in direct proportion to the volume of the cylinder.

The principle of operation of piston internal combustion engines

Let us consider the principle of operation of a piston internal combustion engine using the example of a four-stroke carburetor engine (Otto engine). A diagram of a cylinder with a piston of such an engine and a diagram of the change in gas pressure in its cylinder depending on the position of the piston (indicator diagram) are shown in Fig. 11.1.

The first stroke of the engine is characterized by the opening of the intake valve 1k and by moving the piston from top dead center (TDC) to bottom dead center (BDC) by drawing air or the air-fuel mixture into the cylinder. On the indicator diagram, this is the line 0-1, going from the ambient pressure P o to the vacuum area created by the piston when it moves to the right.

The second stroke of the engine begins with closed valves by the movement of the piston from BDC to TDC. In this case, the working fluid is compressed with an increase in its pressure and temperature (line 1-2). Before the piston reaches TDC, the fuel ignites, resulting in a further increase in pressure and temperature. The very process of fuel combustion (line 2-3) is completed already when the piston passes TDC. The second stroke of the engine is considered completed when the piston reaches TDC.

The third stroke is characterized by the movement of the piston from TDC to BDC, (working stroke). Only in this measure is useful mechanical work done. The complete combustion of the fuel ends in (3) and on (3-4) the combustion products expand.

The fourth stroke of the engine begins when the piston reaches BDC and the exhaust valve 2k opens. In this case, the pressure of the gases in the cylinder drops sharply and when the piston moves towards the TDC, the gases are pushed out of the cylinder. When gases are pushed out in the cylinder, the pressure is higher than atmospheric, because gases need to overcome the resistance of the exhaust valve, exhaust pipe, muffler, etc. in the exhaust tract of the engine. Having reached the TDC position by the piston, the 2k valve closes and the internal combustion engine cycle begins anew with the 1k valve opening, etc.

The area bounded by the indicator diagram 0-1-2-3-4-0 corresponds to two revolutions of the engine crankshaft (full 4 engine strokes). To calculate the power of the internal combustion engine, the average indicator pressure of the engine P i is used. This pressure corresponds to the area 0-1-2-3-4-0 (Fig. 11.1) divided by the piston stroke in the cylinder (the distance between TDC and BDC). Using the indicator pressure, the operation of the internal combustion engine for two revolutions of the crankshaft can be represented as the product of P i and the piston stroke L (the area of \u200b\u200bthe shaded rectangle in Figure 11.1) and the cross-sectional area of \u200b\u200bthe cylinder f. The indicator power of the internal combustion engine per cylinder in kilowatts is determined by the expression

, (11.1)

where Р i is the average indicator pressure, kPa; f is the cross-sectional area of \u200b\u200bthe cylinder, m 2; L is the piston stroke, m; n is the number of revolutions of the crankshaft, s -1; V \u003d fL is the useful volume of the cylinder (between TDC and BDC ), m 3.

At present, the internal combustion engine is the main type of automobile engine. An internal combustion engine (abbreviated name - ICE) is a heat engine that converts the chemical energy of a fuel into mechanical work.

There are the following main types of internal combustion engines: piston, rotary-piston and gas turbine. Of the types of engines presented, the most common is a piston internal combustion engine, therefore, the device and the principle of operation are considered on its example.

Merits piston internal combustion engine, which ensured its widespread use, are: autonomy, versatility (combination with various consumers), low cost, compactness, low weight, the ability to quickly start, multi-fuel.

At the same time, internal combustion engines have a number of essential disadvantages, which include: high noise level, high speed of the crankshaft, toxicity of exhaust gases, low resource, low efficiency.

Gasoline and diesel engines are distinguished depending on the type of fuel used. Alternative fuels used in internal combustion engines are natural gas, alcohol fuels - methanol and ethanol, hydrogen.

The hydrogen engine is promising from the point of view of ecology, because does not create harmful emissions. Along with the internal combustion engine, hydrogen is used to create electrical energy in fuel cells in cars.

Internal combustion engine device

A piston internal combustion engine includes a body, two mechanisms (crank and gas distribution) and a number of systems (intake, fuel, ignition, lubrication, cooling, exhaust and control system).

The engine body integrates the cylinder block and the cylinder head. The crank mechanism converts the reciprocating motion of the piston into rotational motion of the crankshaft. The gas distribution mechanism ensures timely supply of air or a fuel-air mixture to the cylinders and the release of exhaust gases.

The engine management system electronically controls the operation of the combustion engine systems.

Internal combustion engine operation

The principle of operation of the internal combustion engine is based on the effect of thermal expansion of gases that occurs during the combustion of the fuel-air mixture and ensures the movement of the piston in the cylinder.

The piston internal combustion engine operates cyclically. Each working cycle takes place in two crankshaft revolutions and includes four strokes (four-stroke engine): intake, compression, power stroke and exhaust.

During inlet and power strokes, the piston moves downward, while compression and exhaust strokes move upward. The working cycles in each of the engine cylinders are out of phase, which ensures the uniformity of the ICE operation. In some designs of internal combustion engines, the working cycle is realized in two strokes - compression and working stroke (two-stroke engine).

Intake stroke the intake and fuel systems provide an air / fuel mixture. Depending on the design, the mixture is formed in the intake manifold (central and multipoint injection for petrol engines) or directly in the combustion chamber (direct injection for petrol engines, injection for diesel engines). When the intake valves of the gas distribution mechanism are opened, air or the fuel-air mixture is supplied to the combustion chamber due to the vacuum generated by the downward movement of the piston.

On the compression stroke the intake valves close and the air / fuel mixture is compressed in the engine cylinders.

Cycle working stroke accompanied by ignition of the fuel-air mixture (forced or self-ignition). As a result of the ignition, a large amount of gases are formed, which press on the piston and make it move downward. The movement of the piston through the crank mechanism is converted into rotational movement of the crankshaft, which is then used to drive the vehicle.

At beat release the exhaust valves of the gas distribution mechanism are opened, and the exhaust gases are removed from the cylinders to the exhaust system, where they are cleaned, cooled and noise reduced. Then gases enter the atmosphere.

The considered principle of operation of an internal combustion engine makes it possible to understand why the internal combustion engine has a low efficiency - about 40%. At a given moment in time, as a rule, useful work is performed only in one cylinder, in the rest - providing strokes: intake, compression, exhaust.

Currently, the vehicle uses mainly four-stroke piston internal combustion engines.

A single-cylinder engine (Fig. A) contains the following main parts: cylinder 4, crankcase 2, piston 6, connecting rod 3, crankshaft 1 and flywheel 14. At one end, the connecting rod is pivotally connected to the piston by means of a piston pin 5, and the other end also articulated with the crankshaft crank.

When the crankshaft rotates, the piston reciprocates in the cylinder. For one revolution of the crankshaft, the piston makes one stroke down and up. The change in the direction of movement of the piston occurs at the dead points - upper (TDC) and lower (BDC).

Top dead center is the piston position farthest from the crankshaft (uppermost when the engine is vertical), and bottom dead center is the piston position closest to the crankshaft (lowest when the engine is vertical).

Figure: Schematic diagram (a) of a single-cylinder four-stroke piston internal combustion engine and its diagram (b) for determining the parameters:
1 - crankshaft; 2 - crankcase; 3 - connecting rod; 4 - cylinder; 5 - piston pin; 6 - piston; 7 - inlet valve; 8 - inlet pipeline; 9 - a camshaft; 10 - spark plug (petrol and gas engines) or fuel injector (diesels); 11 - outlet pipeline; 12 - outlet valve; 13 - piston rings; 14 - flywheel; D - cylinder diameter; r is the radius of the crank; S - piston stroke

The distance S (Fig. B) between TDC and BDC is called the piston stroke. It is calculated by the formula:

S \u003d 2r,
where r is the radius of the crankshaft crank.

The stroke and bore D determine the main dimensions of the engine. In transport engines, the S / D ratio is 0.7 -1.5. At S / D< 1 двигатель называется короткоходным, а при S/D > 1 - long stroke.

When the piston moves down from TDC to BDC, the volume above it changes from minimum to maximum. The minimum volume of the cylinder above the piston when it is at TDC is called the combustion chamber. The volume of the cylinder released by the piston when it moves from TDC to BDC is called working volume. The sum of the working volumes of all cylinders represents the engine displacement. Expressed in liters, it is called the engine displacement. The total volume of a cylinder is determined by the sum of its working volume and the volume of the combustion chamber. This volume is enclosed above the piston in its position at BDC.

An important characteristic of the engine is the compression ratio, which is determined by the ratio of the total cylinder volume to the combustion chamber volume. The compression ratio shows how many times the charge entering the cylinder (air or fuel-air mixture) is compressed when the piston moves from BDC to TDC. For gasoline engines, the compression ratio is 6-14, while for diesel engines it is 14-24. The adopted compression ratio largely determines the engine power and efficiency, and also significantly affects the toxicity of exhaust gases.

The operation of a piston internal combustion engine is based on the use of pressure on the piston of gases formed during combustion of mixtures of fuel and air in the cylinder. In gasoline and gas engines, the mixture is ignited by the spark plug 10, and in diesel engines due to compression. Distinguish between the concepts of combustible and working mixtures. The combustible mixture consists of fuel and clean air, and the working mixture also includes the exhaust gases remaining in the cylinder.

The set of sequential processes that are periodically repeated in each cylinder of the engine and ensure its continuous operation is called a duty cycle. The working cycle of a four-stroke engine consists of four processes, each of which occurs in one piston stroke (cycle), or half a revolution of the crankshaft. A full working cycle is carried out in two revolutions of the crankshaft. It should be noted that in the general case, the concepts of "workflow" and "stroke" are not synonymous, although for a four-stroke piston engine they practically coincide.

Consider the duty cycle of a gasoline engine.

The first stroke of the working cycle is intake. The piston moves from TDC to BDC, while the inlet valve 7 is open, and the outlet valve 12 is closed, and the combustible mixture under the action of vacuum enters the cylinder. When the piston reaches BDC, the intake valve closes and the cylinder is filled with working mixture. In most gasoline engines, the combustible mixture forms outside the cylinder (in the carburetor or intake manifold 8).

The next measure is compression. The piston moves back from BDC to TDC, compressing the working mixture. This is necessary for its faster and more complete combustion. The inlet and outlet valves are closed. The compression ratio of the working mixture during the compression stroke depends on the properties of the gasoline used, and first of all on its anti-knock resistance, characterized by the octane number (for gasoline it is 76 - 98). The higher the octane number, the greater the anti-knock resistance of the fuel. With an excessively high compression ratio or low anti-knock resistance of gasoline, knock (as a result of compression) ignition of the mixture can occur and the normal operation of the engine can be disrupted. By the end of the compression stroke, the pressure in the cylinder increases to 0.8 ... 1.2 MPa, and the temperature reaches 450 ... 500 ° C.

The compression stroke is followed by expansion (stroke) as the piston moves back down from TDC. At the beginning of this stroke, even with some advance, the combustible mixture is ignited by the spark plug 10. At the same time, the intake and exhaust valves are closed. The mixture burns very quickly with the release of a large amount of heat. The pressure in the cylinder rises sharply, and the piston moves to the WTC, driving the crankshaft 1 into rotation through the connecting rod 3. At the moment of combustion of the mixture, the temperature in the cylinder rises to 1800 ... 2000 ° C, and the pressure - up to 2.5 ... 3.0 MPa ...

The last tick of the working cycle is release. During this stroke, the intake valve is closed and the exhaust valve is open. The piston, moving upwards from BDC to TDC, pushes the exhaust gases remaining in the cylinder after combustion and expansion through the open exhaust valve into the exhaust pipe 11. Then the operating cycle is repeated.

The operating cycle of a diesel engine has some differences from the considered cycle of a gasoline engine. During the intake stroke, through the pipeline 8, not a combustible mixture enters the cylinder, but clean air, which is compressed during the next stroke. At the end of the compression stroke, when the piston approaches TDC, diesel fuel is injected into the cylinder through a special device - a nozzle screwed into the upper part of the cylinder head, under high pressure in a finely atomized state. Coming into contact with air, which has a high temperature due to compression, the fuel particles quickly burn. A large amount of heat is released, as a result of which the temperature in the cylinder rises to 1700 ... 2000 ° C, and the pressure - up to 7 ... 8 MPa. Under the action of the gas pressure, the piston moves downwards - a working stroke occurs. The exhaust cycles for a diesel engine and a gasoline engine are similar.

In order for the working cycle in the engine to occur correctly, it is necessary to coordinate the moments of opening and closing of its valves with the crankshaft speed. This is done as follows. The crankshaft with the help of a gear, chain or belt drive drives another engine shaft - the camshaft 9, which should rotate twice as slow as the crankshaft. The camshaft has profiled lugs (cams), which directly or through intermediate parts (pushers, rods, rocker arms) move the intake and exhaust valves. In two revolutions of the crankshaft, each valve, intake and exhaust, opens and closes only once: during the intake and exhaust strokes, respectively.

The seal between the piston and the cylinder, as well as the removal of excess oil from the cylinder walls, is provided by special piston rings 13.

The crankshaft of a single-cylinder engine rotates unevenly: with acceleration during the working stroke and deceleration during the rest, auxiliary strokes (intake, compression and exhaust). To increase the uniformity of rotation of the crankshaft, a massive disk is installed at its end - a flywheel 14, which accumulates kinetic energy during the working stroke, and during the rest of the cycles gives it away, continuing to rotate by inertia.

However, despite the presence of a flywheel, the crankshaft of a single-cylinder engine does not rotate evenly enough. At the moments of ignition of the working mixture, significant shocks are transmitted to the engine crankcase, which quickly destroys the engine itself and its mounting parts. Therefore, single-cylinder engines are rarely used, mainly on two-wheeled vehicles. On other machines, multi-cylinder engines are installed, which provide a more uniform rotation of the crankshaft due to the fact that the working stroke of the piston in different cylinders does not occur simultaneously. The most widely used are four-, six-, eight- and twelve-cylinder engines, although three- and five-cylinder engines are also used on some vehicles.

Multi-cylinder engines are usually in-line or V-shaped. In the first case, the cylinders are installed in one line, and in the second - in two rows at some angle to each other. This angle for various designs is 60 ... 120 °; for four- and six-cylinder engines, it is usually 90 °. Compared to in-line V-engines of the same power, they are shorter in length, height and weight. The cylinders are numbered sequentially: first, the cylinders of the right (in the direction of travel of the machine) half of the engine are numbered from the front (toe), and then, starting from the front, the left half.

Uniform operation of a multi-cylinder engine is achieved if the alternation of the working stroke in its cylinders occurs through equal angles of rotation of the crankshaft. The angular interval through which the same strokes will be uniformly repeated in different cylinders can be determined by dividing 720 ° (the angle of rotation of the crankshaft at which a full working cycle is performed) by the number of engine cylinders. For example, an eight-cylinder engine has an angular spacing of 90 °.

The sequence of alternating strokes of the same name in different cylinders is called the engine operation order. The order of work should be such as to reduce to the greatest extent the negative effect on the operation of the engine of inertial forces and moments arising from the fact that the pistons move unevenly in the cylinders and their acceleration changes in magnitude and direction. For four-cylinder in-line and V-shaped engines, the operating procedure can be as follows: 1 - 2 - 4 - 3 or 1 - 3 - 4-2, for six-cylinder in-line and V-shaped engines - respectively 1 - 5-3 - 6 - 2- 4 and 1 - 4 - 2 - 5 - 3 - 6, and eight-cylinder V-engines - 1 - 5 - 4 - 2 - 6 - 3 - 7 - 8.

In order to more efficiently use the working volume of the cylinders and increase their power in some designs of piston engines, air is pressurized with a corresponding increase in the amount of injected fuel. Gas turbine compressors (turbocompressors) are most often used to provide pressurization, i.e. to create excess pressure at the cylinder inlet. In this case, the energy of the exhaust gases is used for air injection, which, leaving the cylinders at high speed, rotate the turbine wheel of the turbocharger, mounted on the same shaft with the impeller. In addition to turbochargers, mechanical superchargers are also used, the working elements of which (pump wheels) are driven from the engine crankshaft using a mechanical transmission.

For better filling of the cylinders with a combustible mixture (gasoline engines) or clean air (diesel engines), as well as more complete cleaning of exhaust gases, the valves should open and close not at the moments when the pistons are at TDC and BDC, but with some advance or lag. The valve opening and closing times, expressed in degrees through the angles of rotation of the crankshaft relative to TDC and BDC, are called valve timing and can be represented in the form of a pie chart.

The intake valve begins to open during the exhaust stroke of the previous working cycle, when the piston has not yet reached TDC. At this time, the exhaust gases exit through the exhaust pipe, and due to the inertia of the flow, they entrain fresh charge particles from the opened inlet pipe, which begin to fill the cylinder even in the absence of a vacuum in it. By the time the piston comes to TDC and begins to move down, the intake valve is already open to a significant amount, and the cylinder is quickly filled with fresh charge. The angle a of advancing the opening of the intake valve for various engines ranges from 9 ... 33 °. The inlet valve will close when the piston passes BDC and begins to move upward on the compression stroke. Until this time, the fresh charge fills the cylinder by inertia. The angle p of the intake valve closing delay depends on the engine model and is 40 ... 85 °.

Figure: Camshaft timing of a four-stroke engine:
a - advance angle of the intake valve opening; p - angle of retardation of closing the intake valve; y is the advance angle of the exhaust valve opening; b - angle of retardation of closing the exhaust valve

The exhaust valve opens during the stroke when the piston has not yet reached BDC. At the same time, the work of the piston required to displace the exhaust gases is reduced, compensating for some loss of work of gases due to the early opening of the exhaust valve. The exhaust valve opening advance angle Y is 40 ... 70 °. The exhaust valve closes a little later than the arrival of the piston at TDC, i.e., during the intake stroke of the next working cycle. When the piston starts to descend, the remaining gases will still leave the cylinder by inertia. The angle 5 of the exhaust valve closing delay is 9 ... 50 °.

The angle a + 5, at which the intake and exhaust valves are simultaneously slightly open, is called the valve overlap angle. Due to the fact that this angle and the clearances between the valves and their seats in this case are small, there is practically no charge leakage from the cylinder. In addition, the fresh charge in the cylinder is improved by the high flow rate of the exhaust gas through the exhaust valve.

The lead and lag angles, and, consequently, the duration of the valve opening should be the greater, the higher the engine speed. This is due to the fact that in high-speed engines all gas exchange processes occur faster, and the inertia of the charge and exhaust gases does not change.

Figure: Gas turbine engine schematic diagram:
1 - compressor; 2 - combustion chamber; 3 - compressor turbine; 4 - power turbine; M is the torque transmitted to the machine transmission

The principle of operation of a gas turbine engine (GTE) is explained in the figure. Air from the atmosphere is sucked in by the compressor 2, compressed in it and supplied to the combustion chamber 2, where fuel is also supplied through the nozzle. In this chamber, the fuel combustion process takes place at a constant pressure. The gaseous products of combustion are fed to the turbine compressor 3, where part of their energy is spent on driving the compressor, which pumps air. The rest of the energy of the gases is converted into mechanical work of rotation of a free or power turbine 4, which is connected through a gearbox to the transmission of the machine. In this case, gas expansion occurs in the compressor turbine and the free turbine with a decrease in pressure from the maximum value (in the combustion chamber) to atmospheric.

The working parts of a gas turbine engine, in contrast to similar elements of a piston engine, are constantly exposed to high temperatures. Therefore, to reduce it, it is necessary to supply much more air into the combustion chamber of the GTE than is required for the combustion process.

It will not be an exaggeration to say that most self-propelled devices today are equipped with internal combustion engines of various designs, using different operating principles. In any case, if we talk about road transport. In this article we will take a closer look at the internal combustion engine. What it is, how this unit works, what are its pros and cons, you will learn by reading it.

The principle of operation of internal combustion engines

The main principle of ICE operation is based on the fact that fuel (solid, liquid or gaseous) burns in a specially allocated working volume inside the unit itself, converting thermal energy into mechanical energy.

The working mixture entering the cylinders of such an engine is compressed. After it is ignited with the help of special devices, an excess pressure of gases arises, forcing the pistons of the cylinders to return to their original position. This creates a constant working cycle that transforms kinetic energy into torque with the help of special mechanisms.

Today, the ICE device can have three main types:

• often called lung;
• four-stroke power unit, allowing to achieve higher power indicators and efficiency values;
• with increased power characteristics.

In addition, there are other modifications of the basic schemes that make it possible to improve certain properties of power plants of this type.

The advantages of internal combustion engines

Unlike power units with external chambers, the ICE has significant advantages. The main ones are:

• much more compact dimensions;
• higher power indicators;
• optimal values \u200b\u200bof efficiency.

It should be noted, speaking of the internal combustion engine, that this is a device that in the overwhelming majority of cases allows the use of various types of fuel. It can be gasoline, diesel fuel, natural or kerosene and even ordinary wood.

This versatility has earned this engine concept a well-deserved popularity, ubiquity and truly world leadership.

A brief historical excursion

It is generally accepted that the internal combustion engine dates back to its history since the creation of a piston unit by the French de Rivas in 1807, which used hydrogen in a gaseous aggregate state as fuel. And although the ICE device has undergone significant changes and modifications since then, the basic ideas of this invention continue to be used today.

The first four-stroke internal combustion engine was released in 1876 in Germany. In the mid-80s of the 19th century, a carburetor was developed in Russia, which made it possible to meter the supply of gasoline into the engine cylinders.

And at the very end of the century before last, the famous German engineer proposed the idea of \u200b\u200bigniting a combustible mixture under pressure, which significantly increased the power characteristics of the internal combustion engine and the efficiency indicators of units of this type, which previously left much to be desired. Since then, the development of internal combustion engines has proceeded mainly along the path of improvement, modernization and implementation of various improvements.

The main types and types of internal combustion engines

Nevertheless, the more than 100-year history of units of this type has made it possible to develop several main types of power plants with internal combustion of fuel. They differ among themselves not only in the composition of the working mixture used, but also in design features.

Petrol engines

As the name implies, the units of this group use various types of gasoline as fuel.

In turn, such power plants are usually divided into two large groups:

• Carburetor. In such devices, the fuel mixture is enriched with air masses in a special device (carburetor) before entering the cylinders. After which it is ignited with an electric spark. Among the most prominent representatives of this type are the VAZ models, the internal combustion engine of which for a very long time was exclusively of the carburetor type.
• Injection. This is a more complex system in which fuel is injected into the cylinders by means of a special manifold and injectors. It can occur both mechanically and by means of a special electronic device. Common Rail direct injection systems are considered the most productive. Installed on almost all modern cars.

Injection gasoline engines are considered to be more economical and provide higher efficiency. However, the cost of such units is much higher, and maintenance and operation are much more difficult.

Diesel Engines

At the dawn of the existence of units of this type, one could very often hear a joke about an internal combustion engine, that it is a device that eats gasoline like a horse, but moves much slower. With the invention of the diesel engine, this joke partially lost its relevance. Mainly because diesel is capable of running on much lower quality fuel. This means, and much cheaper than gasoline.

The main fundamental difference between internal combustion is the absence of forced ignition of the fuel mixture. Diesel fuel is injected into the cylinders with special nozzles, and individual drops of fuel are ignited due to the force of the piston pressure. Along with the advantages, the diesel engine has a number of disadvantages. Among them are the following:

• much less power compared to gasoline power plants;
• large dimensions and weight characteristics;
• difficulties with starting in extreme weather and climatic conditions;
• insufficient traction and a tendency to unjustified losses of power, especially at relatively high revs.

In addition, repairing a diesel-type internal combustion engine is usually much more complicated and costly than adjusting or restoring the working capacity of a gasoline unit.

Gas engines

Despite the low cost of natural gas used as fuel, the device of an internal combustion engine running on gas is incomparably more complicated, which leads to a significant increase in the cost of the unit as a whole, its installation and operation in particular.

On power plants of this type, liquefied or natural gas enters the cylinders through a system of special reducers, manifolds and nozzles. The fuel mixture is ignited in the same way as in carburetor gasoline installations - with the help of an electric spark emanating from the spark plug.

Combined types of internal combustion engines

Few people know about combined ICE systems. What is it and where is it applied?

We are, of course, not talking about modern hybrid vehicles capable of running on both fuel and an electric motor. Combined internal combustion engines are usually called such units that combine elements of different principles of fuel systems. The most prominent representative of the family of such engines are gas-diesel units. In them, the fuel mixture enters the ICE block in almost the same way as in gas units. But the fuel is ignited not with the help of an electric discharge from a candle, but with an ignition portion of diesel fuel, as it happens in a conventional diesel engine.

Maintenance and repair of internal combustion engines

Despite a fairly wide variety of modifications, all internal combustion engines have similar basic designs and schemes. Nevertheless, in order to carry out high-quality maintenance and repair of an internal combustion engine, it is necessary to thoroughly know its structure, understand the principles of operation and be able to identify problems. For this, of course, it is necessary to carefully study the design of various types of internal combustion engines, to understand for yourself the purpose of certain parts, assemblies, mechanisms and systems. This is not an easy task, but very exciting! And most importantly, the right thing.

Especially for inquisitive minds who want to independently comprehend all the mysteries and secrets of almost any vehicle, an approximate schematic diagram of the internal combustion engine is shown in the photo above.

So, we found out what this power unit is.

Internal combustion. Its device is quite complex, even for a professional.

When buying a car, first of all they look at the characteristics of the engine. This article will help you understand the basic parameters of the engine.

Number of cylinders. Modern cars have up to 16 cylinders. This is a lot. But the fact is that piston internal combustion engines with the same power and volume may differ significantly in other parameters.

How are the cylinders located?

Cylinders can be arranged in two types: in-line (sequential) and V-shaped (double-row).

At a large camber angle, the dynamic characteristics are significantly reduced, but at the same time the inertia increases. At a low camber angle, inertia and weight are reduced, but this leads to rapid overheating.

Boxer engine

There is also a radical boxer engine with a 180 degree camber angle. In such an engine, all the disadvantages and advantages are maximized.

Let's consider the advantages of such a motor. This engine is easily integrated into the very bottom of the engine compartment, which allows to lower the center of mass and, as a result, increases the stability of the car and its handling, which is important.

Boxer piston combustion engines are less vibration-loaded and fully balanced. They are also shorter in length than single row engines. There are also disadvantages - the width of the car's engine compartment itself is increased. The boxer engine is installed on cars of the Porsche and Subaru brands.

Engine types - W-shaped

At the moment, the W-engine that Volkswagen produces includes two piston groups from the VR type engines, which are at an angle of 72 ° and due to this, an engine with four rows of cylinders is obtained.

Now they make W-shaped engines with 16, 12 and 8 cylinders.

W8 engine - four-row, two cylinders in each row. It has two balance shafts that rotate twice as fast as the crankshaft, they are needed to balance the inertial forces. This motor takes place on a car - VW Passat W8.

W12 engine - four-row, but already three cylinders in each row. It is found on VW Phaeton W12 and Audi A8 W12 cars.

W16 engine - four-row, four cylinders in each row, it is only on the Bugatti Veyron 16.4. This 1000 hp engine and in it the strong influence of inertial moments negatively acting on the connecting rods was reduced by increasing the camber angle to 90 °, and at the same time the piston speed was reduced to 17.2 m / s. True, the size of the engine has increased from this: its length is 710, width is 767 mm.

And the rarest type of engine is inline-V-shaped (also called VR, see the top right picture), which is a combination of the two. VR engines have a small camber between the cylinder banks, only 15 degrees, which made it possible to use one common head on them.

Engine capacity. Almost all other characteristics of the engine depend on this parameter of a piston internal combustion engine. In the case of an increase in engine volume, an increase in power occurs, and as a result, fuel consumption increases.

Engine material. Engines are usually made of three types of material: aluminum or its alloys, cast iron and other ferroalloys, or magnesium alloys. In practice, only the resources and engine noise depend on these parameters.

The most important engine parameters

Torque. It is generated by the engine at maximum tractive effort. The unit of measurement is new meters (nm). Torque directly affects the “elasticity of the engine” (the ability to accelerate at low revs).

Power. The unit of measurement is horsepower (hp). Acceleration time and car speed depend on it.
Maximum revolutions of the crankshaft (rpm). Indicate the number of revolutions that the engine can withstand without losing the strength of the resources. A large number of revs indicates a sharpness and dynamism in the character of the car.

Important in the car and consumption characteristics

Butter. Its consumption is measured in liters per thousand kilometers. The oil grade is designated xxWxx, where the first number indicates the density, the second is the viscosity. Oils with a high density and viscosity significantly increase the reliability and strength of the engine, while oils with a low density give good dynamic characteristics.

Fuel. Its consumption is measured in liters per hundred kilometers. In modern cars, you can use almost any brand of gasoline, but it is worth remembering that a low octane number affects the drop in strength and power, and an octane number above the norm reduces the resource, but increases power.