On modern tractors and automobiles mainly use piston engines internal combustion. Inside these engines, a combustible mixture burns (a mixture of fuel with air in certain proportions and quantities). Part of the heat released is converted into mechanical work.
Engine classification
Piston engines are classified according to the following criteria:
- according to the method of ignition combustible mixture- from compression (diesels) and from an electric spark
- according to the method of mixture formation - with external (carburetor and gas) and internal (diesel) mixture formation
- according to the method of implementing the working cycle - four- and two-stroke;
- according to the type of fuel used - running on liquid (gasoline or diesel fuel), gaseous (compressed or liquefied gas) fuels and multi-fuel
- according to the number of cylinders - single and multi-cylinder (two-, three-, four-, six-cylinder, etc.)
- according to the location of the cylinders - single-row, or linear (cylinders are located in one row), and double-row, or V-shaped (one row of cylinders is placed at an angle to another)
On tractors and cars heavy duty four-stroke multi-cylinder diesel engines are used, on passenger cars, light and medium-duty vehicles - four-stroke multi-cylinder carburetor and diesel engines, as well as engines running on compressed and liquefied gas.
Main mechanisms and engine systems
The piston internal combustion engine consists of:
- body parts
- crank mechanism
- gas distribution mechanism
- power systems
- cooling systems
- lubrication system
- ignition and starting systems
- speed controller
Four-stroke single-cylinder device carburetor engine shown in the figure:
Drawing. The device of a single-cylinder four-stroke carburetor engine:
1 - drive gears camshaft; 2 - camshaft; 3 - pusher; 4 - spring; 5 - exhaust pipe; 6 - inlet pipe; 7 - carburetor; 8 - exhaust valve; 9 - wire to the candle; 10 - spark ignition candle; eleven - inlet valve; 12 - cylinder head; 13 - cylinder: 14 - water jacket; 15 - piston; 16 - piston pin; 17 - connecting rod; 18 - flywheel; 19 - crankshaft; 20 - oil tank (sump).
crank mechanism(KShM) converts the rectilinear reciprocating motion of the piston into the rotational motion of the crankshaft and vice versa.
Gas distribution mechanism(GRM) is designed for timely connection of the over-piston volume with the intake system fresh charge and the release of combustion products (exhaust gases) from the cylinder at certain intervals.
Supply system serves to prepare a combustible mixture and supply it to the cylinder (in carburetor and gas engines) or fill the cylinder with air and supply high-pressure fuel to it (in a diesel engine). In addition, this system removes exhaust gases to the outside.
Cooling system necessary to maintain the optimal thermal regime of the engine. A substance that removes excess heat from engine parts - the coolant can be a liquid or air.
Lubrication system designed for supply lubricant (engine oil) to friction surfaces in order to separate, cool, protect against corrosion and wash out wear products.
Ignition system serves for timely ignition of the working mixture with an electric spark in the cylinders of carburetor and gas engines.
Launch system is a complex of interacting mechanisms and systems that ensure a stable start of the working cycle in the engine cylinders.
Speed controller- This is an automatically operating mechanism designed to change the supply of fuel or combustible mixture depending on the engine load.
In a diesel engine, unlike a carburetor and gas engines there is no ignition system and in the power system instead of a carburetor or a mixer is installed fuel equipment (fuel pump high pressure, high pressure fuel lines and injectors).
To get acquainted with the main and integral part of any vehicle, consider what is the engine made of? For a full perception of its importance, the engine is always compared with the human heart. As long as the heart works, a person lives. Similarly, the engine, as soon as it stops or does not start, the car with all its systems and mechanisms turns into a pile of useless iron.
During the modernization and improvement of cars, engines have changed a lot in their design in the direction of compactness, efficiency, noiselessness, durability, etc. But the principle of operation has remained unchanged - each car has an internal combustion engine (ICE). The only exceptions are electric motors alternative way receiving energy.
Car engine device presented in a section on figure 2.
The name "internal combustion engine" comes precisely from the principle of obtaining energy. The fuel-air mixture, burning inside the engine cylinder, releases a huge amount of energy and makes the passenger car eventually move through a numerous chain of nodes and mechanisms.
It is fuel vapors mixed with air during ignition that give such an effect in a limited space.
For clarity on figure 3 shows the device of a single-cylinder car engine.
The working cylinder from the inside is closed space. Piston connected through a connecting rod to crankshaft, is the only moving element in the cylinder. When the fuel and air vapors are ignited, all of the released energy pushes against the cylinder walls and the piston, causing it to move downward.
The design of the crankshaft is made in such a way that the movement of the piston through the connecting rod creates a torque, causing the shaft itself to rotate and receive rotational energy. Thus, the released energy from the combustion of the working mixture is converted into mechanical energy.
For cooking fuel-air mixture two methods are used: internal or external mixing. Both methods still differ in the composition of the working mixture and methods of its ignition.
To have a clear concept, it is worth knowing that two types of fuel are used in engines: gasoline and diesel fuel. Both types of energy carriers are obtained on the basis of oil refining. Gasoline evaporates very well in air.
Therefore, for engines running on gasoline, a device such as a carburetor is used to obtain a fuel-air mixture.
In the carburetor, the air flow is mixed with gasoline droplets and fed into the cylinder. There, the resulting air-fuel mixture is ignited when a spark is applied through the spark plug.
Diesel fuel (DF) has a low volatility at normal temperature, but when mixed with air under huge pressure, the resulting mixture ignites spontaneously. This is the principle of operation of diesel engines.
Diesel fuel is injected into the cylinder separately from the air through the nozzle. Narrow injector nozzles, combined with high cylinder injection pressure, convert diesel fuel into fine droplets that mix with air.
For a visual presentation, this is similar to when you press on the cap of a perfume or cologne can: the squeezed out liquid instantly mixes with air, forming a fine mixture, which is immediately sprayed, leaving a pleasant aroma. The same spray effect occurs in the cylinder. The piston, moving up, compresses the air space, increasing the pressure, and the mixture ignites spontaneously, forcing the piston to move in the opposite direction.
In both cases, the quality of the prepared working mixture greatly affects full time job engine. If there is a lack of fuel or air - working mixture does not completely burn out, and the generated engine power is significantly reduced.
How and due to what is the working mixture supplied to the cylinder?
On figure 3 it can be seen that two rods with large caps emerge from the cylinder upwards. This is the inlet and
Exhaust valve s that close and open at certain points in time, providing working processes in the cylinder. They can both be closed, but never both can be open. This will be discussed a little later.
On a gasoline engine, there is the same spark plug in the cylinder that ignites the fuel-air mixture. This is due to the appearance of a spark under the influence of an electric discharge. The principle of operation and operation will be considered in the study
The inlet valve ensures the timely flow of the working mixture into the cylinder, and the exhaust valve ensures the timely release of exhaust gases that are no longer needed. Valves operate at a certain point in time of piston movement. The whole process of converting energy from combustion into mechanical energy is called a work cycle, consisting of four cycles: intake of the working mixture, compression, power stroke and exhaust gases. Hence the name - four stroke engine.
Let's take a look at how this happens figure 4.
The piston in the cylinder makes only reciprocating movements, that is, up and down. This is called piston stroke. The extreme points between which the piston moves are called dead spots: upper (TDC) and lower (BDC). The name "dead" comes from the fact that at a certain moment, the piston, changing direction by 180 degrees, seems to "freeze" in the lower or upper position for thousandths of a second.
TDC is at a certain distance from the top of the cylinder. This area in the cylinder is called the combustion chamber. The area with the piston stroke is called the working volume of the cylinder. You must have heard this concept when listing the characteristics of any car engine. Well, the sum of the working volume and the combustion chamber forms the full volume of the cylinder.
The ratio of the total volume of the cylinder to the volume of the combustion chamber is called the compression ratio of the working mixture. This
enough important indicator for any car engine. The more strongly the mixture is compressed, the more recoil is obtained during combustion, which is converted into mechanical energy.
On the other hand, excessive compression of the air-fuel mixture causes it to explode rather than burn. This phenomenon is called "detonation". It leads to loss of power and destruction or excessive wear of the entire engine.
To avoid modern fuel production produces gasoline that is resistant to high degree compression. Everyone has seen inscriptions like AI-92 or AI-95 at the gas station. The number stands for octane number. The larger its value, the greater the resistance of the fuel to detonation, respectively, it can be used with a higher compression ratio.
Such a marking can often be found on sites dedicated to automotive topics, and it is not in vain that there is nothing complicated in deciphering this abbreviation, which means it is an internal combustion engine familiar to everyone. ICE is its shortened version. This so-called heat engine, main feature which is the transformation of chemical energy into mechanical work, by performing a certain list of works, in the appropriate order.
There are several types of engines: piston, gas turbine and rotary piston. Naturally, the most this moment famous and popular, it is a piston engine. Therefore, disassembly and study of the principle of operation will be considered precisely on his example. Yes and in general scheme and the nature of work for all three types have a similar principle.
Among the main advantages of the presented motor, which received the most wide application, it can be noted: versatility, autonomy, cost, low weight, compactness, multi-fuel.
But despite such an impressive percentage positive aspects, there are also enough shortcomings. These include the noise level high frequency shaft rotation, toxicity of exhaust gases, low resource, low efficiency.
Depending on the type of fuel used, there are diesel and gasoline. The latter are the most in demand and popular. Among the alternative fuels can be used natural gas, fuels of the so-called alcohol group - ethanol, methanol, hydrogen.
The hydrogen engine may become the most promising in the future, given the current increased attention to the environment. After all, this engine missing harmful emissions. In addition to the engine, hydrogen is used to produce electrical energy for the fuel mechanisms of the car.
ICE device
Among the main internal combustion engine elements it is worth distinguishing between the main body, two main mechanisms (gas distribution and crank), as well as a number of related systems such as fuel, intake, ignition, cooling, control, lubrication, exhaust.
The body is integrated with the cylinder block and the block head. The crank mechanism allows you to convert the reciprocating movements of the piston into rotational movements crankshaft. The timing ensures the timely supply of air or fuel to the system, as well as the emission of exhaust gases.
The intake system is responsible for supplying the engine with air, and the fuel system for fuel. Collaboration of these systems or complexes, provides the formation of the so-called fuel-air mass. Main place in fuel system assigned to the injection system.
Ignition performs forced ignition of the above mixture in gasoline engines. In diesel, the process is a little simpler, since the mixture is self-igniting.
Lubrication allows you to relieve stress from parts between which friction occurs. In order to cool the mechanisms in time and engine parts the cooling system is responsible. One of important functions performs exhaust system, which allows you to remove exhaust gases, and also reduces their noise and toxicity.
SUD, that is, the engine management system provides electronic control and control, all motor systems and related complexes.
Principle of operation
The principle of operation is based on the effect of expansion of gases under the influence of heat that occurs during the combustion of the mixture formed by the air-fuel system. Due to this, the movement of the pistons in the cylinders is carried out.
Work on all piston engines is performed cyclically. That is, each cycle occurs in a couple of revolutions of the shaft and, accordingly, includes four cycles. The so-called four-stroke engines. The list of cycles: intake, compression, stroke, exhaust.
When the work of the intake stroke and power stroke is performed, the movement of the piston is carried out in a downward direction. Due to this, the cyclicity does not coincide in each of the cylinders. With this in mind, smoothness and uniformity of engine operation are achieved. There are also two-stroke engines, in which one combustion cycle includes only compression and power stroke.
intake stroke
During this stroke, both systems (intake and fuel) provide the formation of an air-fuel mass. Given the different configuration of motors and design, the formation of a mixture can occur directly in intake manifold or in the combustion chamber itself. At the moment when the intake valves of the timing are opened, air or already a fuel-air mixture moves directly into the combustion chamber, under the influence of a vacuum force, during the movement of the piston.
compression stroke
During compression, the corresponding intake valves close and the air-fuel mixture in the cylinders is compressed.
working stroke
This step is accompanied by the formation of a flame, depending on the type of fuel, as already mentioned forcibly or independently. As a result, the formation a large number gases. And those, in turn, put pressure on the piston itself, forcing it to move down. And thanks to the crank mechanism, the movement of the piston is converted into rotational movements transmitted to the crankshaft, the latter is used in turn to move the car.
Release stroke
During the last cycle, the exhaust valves of the mechanism open, through which exhaust gases are removed. In the future, they are cleaned, noise reduction and cooling. Subsequently, the gases are released into the atmosphere.
If you carefully analyze the information you read, you can understand why ICEs have a small coefficient useful action. Namely, 40%, that is how much work is done at a specific time, during the operation of one cylinder. The rest at the same time provide intake, compression and exhaust, respectively.
The internal combustion engine is the main type of automotive power units today. The principle of operation of an internal combustion engine is based on the effect of thermal expansion of gases that occurs during combustion in the cylinder of the fuel-air mixture.
The most common types of engines
There are three types of internal combustion engines: piston, rotary piston power unit Wankel and gas turbine systems. With rare exceptions on modern cars four-stroke piston engines. The reason lies in the low price, compactness, low weight, multi-fuel capacity and the ability to install on almost any vehicle.
The car engine itself is a mechanism that converts the thermal energy of burning fuel into mechanical energy, the operation of which is provided by many systems, components and assemblies. Piston internal combustion engines are two- and four-stroke. It is easiest to understand the principle of operation of a car engine using the example of a four-stroke single-cylinder power unit.
It is called a four-stroke engine because one working cycle consists of four piston movements (strokes) or two revolutions of the crankshaft:
- inlet;
- compression;
- work stroke;
- release.
General ICE device
To understand the principle of operation of the motor, it is necessary in in general terms imagine his device. The main parts are:
- cylinder block (in our case, there is only one cylinder);
- crank mechanism, consisting of a crankshaft, connecting rods and pistons;
- block head with a gas distribution mechanism (timing).
The crank mechanism provides the conversion of the reciprocating motion of the pistons into the rotation of the crankshaft. The pistons are set in motion thanks to the energy of the fuel burning in the cylinders. 
Job this mechanism is impossible without the operation of the gas distribution mechanism, which ensures the timely opening of the intake and exhaust valves for the intake of the working mixture and the exhaust gases. Timing consists of one or more camshafts, having cams pushing valves (at least two for each cylinder), valves and return springs. 
The internal combustion engine is able to work only with coordinated work auxiliary systems, which include:
- ignition system responsible for igniting the combustible mixture in the cylinders;
- an intake system that provides air supply for the formation of a working mixture;
- a fuel system that provides a continuous supply of fuel and obtaining a mixture of fuel with air;
- lubrication system designed to lubricate rubbing parts and remove wear products;
- exhaust system, which removes exhaust gases from ICE cylinders and reducing their toxicity;
- the cooling system necessary to maintain the optimum temperature for the operation of the power unit.
Motor duty cycle
As mentioned above, the cycle consists of four measures. During the first stroke, the camshaft cam pushes the intake valve, opening it, the piston begins to move from its highest position down. At the same time, a vacuum is created in the cylinder, due to which the finished working mixture enters the cylinder, or air, if the internal combustion engine is equipped with a system direct injection fuel (in this case, the fuel is mixed with air directly in the combustion chamber). 
The piston communicates movement to the crankshaft through the connecting rod, turning it 180 degrees by the time it reaches its lowest position.
During the second stroke - compression - the inlet valve (or valves) closes, the piston reverses its direction of movement, compressing and heating the working mixture or air. At the end of the cycle, the ignition system supplies the spark plug with electrical discharge, and a spark is formed, igniting the compressed air-fuel mixture.
The principle of fuel ignition diesel internal combustion engine another: at the end of the compression stroke, through the nozzle, finely atomized diesel fuel is injected into the combustion chamber, where it mixes with heated air, and the resulting mixture ignites spontaneously. It should be noted that for this reason, the compression ratio of a diesel engine is much higher.
The crankshaft, meanwhile, turned another 180 degrees, making one complete revolution. 
The third cycle is called the working stroke. The gases formed during the combustion of fuel, expanding, push the piston to its lowest position. The piston transfers energy to the crankshaft through the connecting rod and turns it another half turn.
Upon reaching the bottom dead center the final cycle begins - release. At the beginning of this stroke, the camshaft cam pushes and opens the exhaust valve, the piston moves up and drives the exhaust gases out of the cylinder.
ICE installed on modern cars, have not one cylinder, but several. For uniform operation of the motor at the same time in different cylinders different strokes are performed, and every half-turn of the crankshaft, a work stroke occurs in at least one cylinder (with the exception of 2- and 3-cylinder engines). Thanks to this, it is possible to get rid of unnecessary vibrations, balancing the forces acting on the crankshaft and ensuring smooth operation of the internal combustion engine. The connecting rod journals are located on the shaft at equal angles relative to each other. 
For reasons of compactness, multi-cylinder engines are made not in-line, but V-shaped or boxer (Subaru's business card). This saves a lot of space under the hood.
Two stroke motors
In addition to four-stroke piston internal combustion engines there are duplex. The principle of their work is somewhat different from that described above. The device of such a motor is simpler. The cylinder has for the window - inlet and outlet, located above. The piston, being at BDC, closes the inlet window, then, moving up, closes the outlet and compresses the working mixture. When it reaches TDC, a spark forms on the candle and ignites the mixture. At this time, the inlet window is open, and through it the next dose of the fuel-air mixture enters the crank chamber.
During the second stroke, moving down under the influence of gases, the piston opens the outlet window, through which the exhaust gases are blown out of the cylinder with a new portion of the working mixture, which enters the cylinder through the purge channel. At the same time, part of the working mixture also goes into the exhaust window, which explains the voracity of a two-stroke internal combustion engine.
This principle of operation makes it possible to achieve more power engine with a smaller displacement, but this comes at the cost of higher fuel consumption. The advantages of such motors include more uniform operation, simple design, light weight and high power density. Among the shortcomings, mention should be made of a dirtier exhaust, the lack of lubrication and cooling systems, which threatens to overheat and cause the unit to fail.
An internal combustion engine is a heat engine that converts part of the chemical energy of the burning fuel into mechanical energy. An essential division of engines into categories is the division according to the operating cycle into 2-stroke and 4-stroke; according to the method of preparing a combustible mixture - with external (in particular, carburetor) and internal (for example, diesel engines) mixture formation; According to the type of energy converter, internal combustion engines are divided into piston, turbine, jet and combined.
The efficiency of the internal combustion engine is 0.4-0.5. The first internal combustion engine was designed by E. Lenoir in 1860. In this article, we will consider the four-stroke internal combustion engine most commonly used in the automotive industry.
The four-stroke engine was first introduced by Nikolaus Otto in 1876 and is therefore also called the Otto cycle engine. A more literate name for such a cycle is a four-stroke cycle. It is currently the most common type of engine for cars.
The principle of operation of the internal combustion engine (ICE)
Action piston engine internal combustion is based on the use of thermal expansion pressure of heated gases during piston movement. Heating of gases occurs as a result of combustion in the cylinder fuel-air mixture. To repeat the cycle, the exhaust gas mixture must be released at the end of the piston movement and filled with a new portion of fuel and air. IN extreme position fuel is ignited by a spark plug. The intake and exhaust of fuel and combustion products occur through valves controlled by the gas distribution mechanism and the fuel supply system.
Thus, the engine operation cycle is divided into the following stages:
- intake stroke.
- Compression stroke.
- The expansion stroke, or work stroke.
- Release stroke.
The force from the moving piston of the cylinder through the crankshaft is converted into rotational motion of the engine shaft. Part of the rotational energy is spent on returning the pistons to their original state, to complete a new cycle. The design of the shaft determines the different position of the pistons in different cylinders at any given time. Thus, the more cylinders in the engine, the more general case, the rotation of its shaft is more uniform.
According to the location of the cylinders, engines are divided into several types:
a) Engines with vertical or inclined arrangement of cylinders in one row
B) V-shaped with the mutual arrangement of cylinders at an angle in the form of the Latin letter V:
D) Engines with opposed cylinders. It is called "opposite", the cylinders in it are located at an angle of 180 degrees:
The gas distribution mechanism of the engine on the exhaust stroke ensures that the cylinders are cleaned of combustion products (exhaust gases) and the cylinders are filled with a new portion of the fuel-air mixture at the intake stroke.
The ignition system generates a high voltage discharge and transmits it to the cylinder spark plug through high voltage wire. The ignition is controlled by a distributor, the wires from which are suitable for each candle. The distributor is designed in such a way that the discharge occurs precisely in the cylinder where the piston is currently passing the point of greatest compression fuel mixture. If the mixture ignites earlier, then the gas pressure will work against its course, if later, the power released by the expansion of gases will not be fully used.
To start the engine, it must be given initial movement. For this, the start system is used (see the article "how the starter works") from electric motor- starter.
Benefits of gasoline engines
- More low level noise and vibration compared to diesel;
- Great power with equal engine size;
- Ability to work on high revs, without serious consequences for the engine.
Disadvantages of gasoline engines
- Greater than diesel fuel consumption, and higher requirements for its quality;
- The need for and permanent job fuel ignition systems;
- The greatest power of gasoline internal combustion engines is achieved in a narrow speed range.
