Description of design

Diesel engine is a reciprocating piston engine that has the same basic design and duty cycle as a gasoline engine. The main difference between a diesel engine and a gasoline engine is the fuel used and the way the fuel is ignited to ensure combustion.

Job

In diesel engines for ignition air-fuel mixture The combustion chamber uses the heat of compression. This ignition is performed using high compression pressure and diesel fuel, injected into the combustion chamber under very high pressure. The combination of diesel fuel and high compression pressure ensures auto-ignition, allowing the combustion cycle to begin.

Cylinder block

Diesel and gasoline engine are similar to each other, but there are some differences in their design. Most diesel engines use cylinder liners rather than cylinders made as part of a block. By using cylinder liners, repairs can be made to allow the engine to be used for a long time. On those diesel engines that do not use cylinder liners, the cylinder walls are thicker than those on a gasoline engine of similar displacement. To increase the supporting surface crankshaft Diesel engines have heavier and thicker main bars.

Wet cylinder liners

The wet cylinder liners used in diesel engines are similar to those used in gasoline engines. The physical dimensions of liners may vary to suit diesel engine operating conditions.

Crankshaft

The crankshaft used in diesel engines has a design similar to the crankshaft used in gasoline engines, but with two differences:

Diesel engine crankshafts are usually forged rather than cast. Forging does crankshaft more durable.
. Diesel engine crankshaft journals are typically larger in size than gasoline engine crankshaft journals.
Enlarged journals allow the crankshaft to withstand greater loads.

Connecting rods

Connecting rods used in diesel engines are typically made from forged steel. Diesel engine connecting rods differ from gasoline engine connecting rods in that the caps are offset and have small teeth on the mating surface with the connecting rod. The offset, fine-tooth design helps hold the cap in place and reduces stress on the connecting rod bolts.

Pistons and piston rings

The pistons used in light-duty diesel engines look similar to the pistons used in gasoline engines. Diesel pistons are heavier than gasoline engine pistons because diesel pistons usually made of forged steel rather than aluminum, and the internal thickness of the material is greater.

Compression rings used in diesel engines are usually made of cast iron and are often coated with chromium and molybdenum to reduce friction.

Cylinder head

Externally, the cylinder head of a diesel engine looks much like the cylinder head of a gasoline engine. But there are many internal design differences that make diesel engines different and original.

On a diesel engine, the cylinder head itself must be much stronger and heavier to withstand greater heat and pressure loads. The design of the combustion chamber and air passages on diesel engines can be more complex than on a gasoline engine.

Diesel engines use several combustion chamber designs, but two designs are the most common: the undivided combustion chamber and the swirl chamber.

Undivided combustion chamber design

The most common type of combustion chamber for a diesel engine is the unsplit chamber, also known as a direct injection combustion chamber. In an undivided design, turbulence (swirl) of the incoming air is ensured due to the shape of the air inlet channel. Fuel is injected directly into the combustion chamber.

Vortex chamber design

The swirl chamber design uses two combustion chambers for each cylinder. The main chamber is connected by a narrow channel to a smaller vortex chamber. The swirl chamber contains a fuel injector. The vortex chamber is designed to ensure the start of the combustion process. The inlet air is introduced into the vortex chamber through a narrow channel. Fuel is then injected into the vortex chamber and the resulting mixture ignites. After this, the burning mixture enters main camera combustion, where it ends its combustion, causing the piston to move down.

Valves and valve seats

Diesel engine valves are made from special alloys that are able to perform well under the high heat and pressure that is typical of a diesel engine. Some valves are partially filled with sodium, which helps dissipate heat. Big percentage heat is transferred from the valve head to the valve seat. To ensure adequate heat transfer Special attention should be given to the width of the valve seat.

A wide valve seat has the advantage of being able to transfer more heat. However, a wide valve seat also has a greater potential for the accumulation of carbon deposits, which can cause leaks in the valve. A narrow valve seat provides a better seal than a wide valve seat, but does not transfer the same amount of heat. In a diesel engine, a compromise is required between wide and narrow valve seats.

Diesel engines often use push-in valve seats. The inserts have the advantage of being replaceable. Insert valve seats are made from special metal alloys that can withstand the heat and pressure of a diesel engine.

Fuel supply system

Conventional design

In a conventional diesel fuel supply system, fuel is drawn from fuel tank, is filtered and supplied to the high pressure pump. High pressure fuel is brought to the required pressure and supplied to the fuel manifold, which feeds fuel injectors. The injection control system at appropriate times activates the injectors, which during the compression of the piston inject fuel for its subsequent combustion.

Common rail design

Common rail diesel engines use independent fuel pressure and fuel injection systems. The high pressure fuel pump pulls fuel from the tank and delivers it through the pressure regulator to the common fuel manifold. The high pressure pump consists of a transfer pump low pressure and high pressure chambers. Fuel injection is controlled by the powertrain control module (PCM) and the injector control module (IDM), which regulates the timing open state injectors depending on the operating conditions of the engine.

In a design with a common fuel manifold, the level of toxicity of exhaust gases is significantly reduced and noise during operation is minimized. All this is a consequence of greater control of the combustion process. Adjustment of fuel pressure and injector operating phases is controlled by YUM and RSM. The injector design has also been redesigned to allow pre-injection and post-injection fuel injection at various stages of the compression and power strokes.

Improved fuel management allows for cleaner, more consistent combustion and proper cylinder pressure. This has the effect of reducing exhaust toxicity and noise during operation.

Lubrication system

The lubrication system used in diesel engines is similar in principle to the systems of gasoline engines. Most diesel engines have some type of oil cooler to help remove heat from the oil. Oil flows under pressure through the engine passages and returns to the engine crankcase.

The lubricating oil used in diesel engines is different from the oil used in gasoline engines. Special oil This is necessary because when a diesel engine is running, the oil becomes more contaminated than in a gasoline engine. The high carbon content of diesel fuel causes the oil used in diesel engines to change color soon after it is used. Only this should be used engine oil, which is designed specifically for diesel engines.

Cooling system

The cooling system of a diesel engine usually has a larger filling volume than the cooling system of a gasoline engine. The temperature inside a diesel engine must be carefully controlled because heat is used to auto-ignite the fuel.

If the engine temperature is too low, the following problems may occur:

Increased wear
. Poor fuel economy
. Accumulation of water and sludge in the engine crankcase
. Power Loss

If the engine temperature is too high, the following problems may occur:

Increased wear
. Badasses
. Detonation
. Burnout of pistons and valves
. Lubrication problems
. Jamming of moving parts
. Power Loss

Fuel injection system

The diesel engine operates on the principle of self-ignition. The incoming air and fuel are compressed in the combustion chamber so much that the molecules heat up and ignite without the aid of an external ignition spark. The compression ratio of a diesel engine is much higher than that of a gasoline engine. The compression ratio in diesel engines with direct air intake is approximately 22:1. Turbodiesel engines have a compression ratio in the range of 16.5-18.5:1. Compression pressure is created and the air temperature rises from approximately 500 °C to 800 °C (932 °F to 1,472 °F).

Diesel engines can only be operated with a fuel injection system. Mixture formation occurs only in the phase of fuel injection and combustion.

At the end of the compression stroke, fuel is injected into the combustion chamber, where it mixes with hot air and ignites. The quality of this combustion process depends on the quality of mixture formation. Because The fuel is injected so late it doesn't have much time to mix with the air. In a diesel engine, the air-fuel ratio is constantly maintained at a level greater than 17:1, thus ensuring that all the fuel is burned. For more detailed information refer to the publication "Operation of the Engine and Its Systems".

Features of the diesel engine such as efficiency and high torque make it a preferred option. Modern diesel engines are close to gasoline engines in terms of noise, while maintaining advantages in efficiency and reliability.

Design and structure

The design of a diesel engine is no different from a gasoline engine - the same cylinders, pistons, connecting rods. True, the valve parts are reinforced to accept high loads- after all, the compression ratio of a diesel engine is much higher (19-24 units versus 9-11 for gasoline engine). This explains the large weight and dimensions diesel engine compared to gasoline.

The fundamental difference lies in the methods of forming a mixture of fuel and air, its ignition and combustion. In a gasoline engine, the mixture is formed during intake system, and is ignited in the cylinder by a spark plug spark. In a diesel engine fuel and air are supplied separately. First, air enters the cylinders. At the end of the compression stroke, when it is heated to a temperature of 700-800 o C, diesel fuel is injected into the combustion chamber by nozzles under high pressure, which almost instantly ignites spontaneously.

Mixture formation in diesel engines occurs in a very short period of time. To obtain a combustible mixture capable of quickly and completely burning, it is necessary that the fuel be atomized into the smallest particles possible and that each particle has a sufficient amount of air for complete combustion. For this purpose, fuel is injected into the cylinder by a nozzle at a pressure several times higher than the air pressure during the compression stroke in the combustion chamber.

Diesel engines use undivided combustion chambers. They represent a single volume limited by the bottom piston 3 and surfaces of the cylinder head and walls. For better mixing of fuel with air, the shape of the undivided combustion chamber is adapted to the shape of the fuel torches. Recess 1, made in the piston bottom, contributes to the creation of vortex air movement.

Finely atomized fuel is injected from injectors 2 through several holes directed to certain recess locations. So that the fuel burns completely and the diesel has best capacities and economic indicators, fuel must be injected into the cylinder before the piston reaches TDC.

Self-ignition is accompanied by a sharp increase in pressure - hence the increased noise and harshness of operation. This organization of the work process allows you to work on very lean mixtures, which determines high efficiency. Environmental characteristics are also better - emissions when running on lean mixtures harmful substances less than gasoline engines.

Disadvantages include increased noise and vibration, less power, difficulties with cold starting, problems with winter diesel fuel. U modern diesels these problems are not so obvious.

Diesel fuel must meet certain requirements. The main indicators of fuel quality are purity, low viscosity, low temperature self-ignition, high cetane number(not lower than 40). The higher the cetane number, the shorter the auto-ignition delay period after it is injected into the cylinder and the engine runs smoother (without knocking).

Types of diesel engines

There are several types of diesel engines, the difference between which lies in the design of the combustion chamber. In diesel engines with an undivided combustion chamber- I call them diesels with direct injection- fuel is injected into the space above the piston, and the combustion chamber is made in the piston. Direct injection is used on low-speed, large-displacement engines. This is due to difficulties in the combustion process, as well as increased noise and vibration.

Thanks to the introduction of high pressure fuel pumps (HPFP) with electronically controlled, two-stage fuel injection and optimization of the combustion process, it was possible to achieve stable operation of a diesel engine with an undivided combustion chamber at speeds up to 4500 rpm, improve efficiency, reduce noise and vibration.

The most common is another type of diesel - with separate combustion chamber. Fuel injection is carried out not into the cylinder, but into an additional chamber. Typically, a vortex chamber is used, made in the cylinder head and connected to the cylinder by a special channel so that when compressed, air entering the vortex chamber is intensively swirled, which improves the process of self-ignition and mixture formation. Autoignition begins in the vortex chamber and then continues in the main combustion chamber.

With a separate combustion chamber, the rate of increase in pressure in the cylinder is reduced, which helps reduce noise and increase maximum speed. Such engines make up the majority of those installed on modern cars.

Fuel system design

The most important system is the fuel supply system. Its function is to supply a strictly defined amount of fuel at a given moment and with a given pressure. High fuel pressure and precision requirements make the fuel system complex and expensive.

The main elements are: high pressure fuel pump (HPF), injectors and fuel filter.

injection pump

The injection pump is designed to supply fuel to the injectors according to a strictly defined program, depending on the engine operating mode and driver actions. At its core, a modern injection pump combines the functions of a complex system automatic control engine and main actuator, fulfilling the driver's commands.

By pressing the gas pedal, the driver does not directly increase the fuel supply, but only changes the program of operation of the regulators, which themselves change the supply according to strictly defined dependencies on the speed, boost pressure, position of the regulator lever, etc.

On modern cars Distribution type fuel injection pumps are used. Pumps of this type are widely used. They are compact, characterized by high uniformity of fuel supply to the cylinders and excellent performance. high speed thanks to the speed of the regulators. At the same time, they place high demands on the purity and quality of diesel fuel: after all, all their parts are lubricated with fuel, and the gaps in precision elements are small.

Injectors.

Another important element fuel system is the nozzle. Together with the injection pump, it ensures the supply of a strictly dosed amount of fuel into the combustion chamber. Adjusting the injector opening pressure determines operating pressure in the fuel system, and the type of atomizer determines the shape of the fuel spray, which has important for the process of self-ignition and combustion. Two types of nozzles are usually used: with a type or multi-hole distributor.

The injector on the engine operates in harsh conditions: The nozzle needle reciprocates at half the engine speed, and the nozzle is in direct contact with the combustion chamber. Therefore, the nozzle nozzle is made of heat-resistant materials with extreme precision and is a precision element.

Fuel filters.

The fuel filter, despite its simplicity, is the most important element diesel engine. Its parameters, such as filtration fineness, throughput, must strictly correspond to a specific engine type. One of its functions is to separate and remove water, for which the lower one is usually used drain plug. A manual priming pump is often installed on the top of the filter housing to remove air from the fuel system.

Sometimes an electric heating system is installed fuel filter, which makes starting the engine somewhat easier and prevents the filter from clogging with paraffins formed during the crystallization of diesel fuel in winter conditions.

How does the launch happen?

Cold start of the diesel engine is ensured by the system preheating. For this purpose, electric heating elements - glow plugs - are inserted into the combustion chambers. When the ignition is turned on, the spark plugs warm up to 800-900 o C in a few seconds, thereby heating the air in the combustion chamber and facilitating self-ignition of the fuel. A control lamp indicates the operation of the system to the driver in the cabin.

Extinction warning lamp indicates readiness for launch. The power supply from the spark plug is removed automatically, but not immediately, but 15-25 seconds after starting, to ensure stable operation of a cold engine. Modern systems pre-heating ensure easy start-up of a serviceable diesel engine to a temperature of 25-30 o C, of ​​course, subject to the oil and diesel fuel season.

Turbocharging and Common-Rail

An effective means of increasing power is turbocharging. It allows additional air to be supplied to the cylinders, resulting in increased power. Pressure exhaust gases diesel engine is 1.5-2 times higher than that of a gasoline engine, which allows the turbocharger to provide effective boost from the very low revs, avoiding the failure characteristic of gasoline turbo engines - “turbo lag”.

Computer control of fuel supply made it possible to inject it into the combustion chamber of the cylinder in two precisely dosed portions. First, a tiny dose arrives, only about a milligram, which, when burned, increases the temperature in the chamber, and then comes the main “charge”. For a diesel engine - an engine with fuel ignition by compression - this is very important, since in this case the pressure in the combustion chamber increases more smoothly, without a “jerk”. As a result, the motor runs smoother and less noisy.

As a result, in diesel engines with Common-Rail system Fuel consumption is reduced by 20%, and torque at low crankshaft speeds increases by 25%. The soot content in the exhaust is also reduced and the engine noise is reduced.

Over the past ten years diesel technologies developed rapidly. Most of modern cars, which are produced in Europe, are produced with diesel engines. Of course, the working principle of this device did not change. However, a modern diesel engine is much quieter. It has become more environmentally friendly. In the distant past there remained strong rumbling, thick black smoke and bad smell during operation of the device. So, what is the working principle of a diesel engine?

How does a diesel engine work?

The principle of operation of a diesel engine is as follows: into the cylinder

Clean air is sucked in as the piston moves downwards. And when the valve moves up, it heats up. It is worth noting that the temperature during operation of a diesel engine can be from 700 to 900°. This is achieved with strong compression. When the piston moves to its dead top point, diesel fuel is injected into the combustion chamber under sufficiently high pressure. When it comes into contact with hot air, the fuel ignites. As a result, the pressure in the cylinder increases as the self-ignited fuel expands. This is what causes loud noise during operation of the unit.

Advantages and disadvantages

This principle of operation of a diesel engine allows the use lean mixture. Fuel for such devices is relatively inexpensive. This makes diesel engines unpretentious and economical. It is worth noting that, unlike gasoline units, such units have greater torque and efficiency is 10% higher. On to the cons

diesel engine should be attributed increased level noise, vibration, low power per unit of volume, difficulty in cold starting. More modern models are practically devoid of such shortcomings.

Design and features of some components

Taking into account the operating principle of a diesel engine, the parts for such units are significantly strengthened, since they must withstand high loads. Among the main parts of the unit, it is worth highlighting the piston. The shape of its bottom depends on the type of combustion chamber that may be built into the valve bottom. In a diesel engine piston, the bottom usually extends beyond the top of the cylinder block. There is no conventional ignition system in units of this type. Although they also use candles.

Turbine

The power that a motor can develop depends on the amount of fuel and air that enters it. To increase the capabilities of the unit, it is necessary to increase the content of the listed components. To allow more fuel to enter the combustion chamber, the air level must be raised, which

hits the cylinder. For this purpose it is used optional equipment. The operating principle of a diesel engine turbine is quite simple. The part allows you to pump more air. Due to this, the volume of fuel burned increases, which significantly increases the amount of energy released.

Combustion chambers

Diesel engines can use several types of combustion chambers: split and non-split. The first type was used in passenger engineering, but has recently been replaced by a simpler one. Indeed, when using divided compartments, fuel was injected into the combustion chamber, which was located in the cylinder head, and not into the piston cavity. Similar parts were also made in different ways and this depended on the processes of mixture formation: vortex chamber or pre-chamber.

In the latter case, fuel is injected into the preliminary compartment, which

communicates with the cylinder by small valves or holes. In this case, the fuel mixes with air, hitting the walls. Self-igniting fuel enters the main chamber, where it burns completely. As for the vortex chamber combustion process, it, as in the first case, begins in a separate compartment, which is a hollow sphere. Through the connecting channels, air enters the chamber during the compression stroke. It swirls in it and forms a vortex. As a result, the combustible mixture injected into the compartment is well mixed with air. This structure of combustion chambers has several disadvantages. Firstly, more fuel is consumed, as large losses occur due to the volume of the compartments. Secondly, significant losses when air flows into the additional chamber from the air cylinder, as well as reverse process: movement of fuel into the cylinder. It is worth noting that this principle of operation of a diesel engine is rarely used, as the starting characteristics of the unit deteriorate.

Undivided combustion chambers

In a direct injection engine, the combustion chamber is shaped and is a cavity. Such a combustion chamber is built directly into the bottom

piston In this case, fuel is injected directly into the cylinder. Despite the simplicity of the design, this system also has disadvantages. Diesel engines of this type are almost impossible to use if the car has a small displacement. When accelerating at this vehicle There is an increase in noise levels, and vibration also increases.

New developments

Today they are more often used electronic systems, which control the amount of fuel entering the combustion chamber. This made it possible to reduce the noise level, as well as vibration of the unit during operation. Today, completely new diesel engines are being developed, the designs of which use direct injection of a combustible mixture.

In the last century, the operation of a diesel engine was associated with an unpleasant odor, noise and thick black smoke pouring from the chimney. But in the last decade, diesel technology has developed by leaps and bounds.

The engines became quieter, the smell of exhaust gases almost completely disappeared, and the harm caused to the environment began to be reduced to zero. However, the operating principle has not changed.

Operating principle of a diesel engine

The difference between a diesel engine and a gasoline engine is due to the fact that mixing of fuel with air occurs not outside, but inside the cylinder.

In addition, the mixture ignites on its own, without a spark plug. The engine design includes:

1. Cylinder.
2. Inlet and outlet valves.
3. Piston.
4. Fuel injector.

From this video you will learn how a diesel engine works. Let's take a look and take note!

The principle of operation of the motor can be described by considering the actions of the piston, valves and injectors during each stroke. Usually there are four.

stroke – fuel intake

The piston has two dead points: top (TDC) and bottom (BDC). During the first stroke, the intake valves open and the exhaust valves close. A vacuum is created in the cylinder. Air rushes in.

stroke - compression

All valves are closed. The piston moves from BDC to TDC, compressing the air entering during stroke 1 to 5 MPa. Its temperature increases to 700 C o.

Tact – power stroke (expansion)

The piston is at TDC. The high pressure fuel pump delivers fuel into the cylinder through the injector. When sprayed, it mixes with heated air and spontaneously ignites.

During combustion, the temperature increases to 1800 C o, and the pressure to 11 MPa. The piston begins to move from TDC to BDC, making useful work. At the end of the working stroke, the temperature inside the cylinder drops to 700-800 C o, and the pressure drops to 300-500 kPa.

stroke - release of gases

The inlet valve is closed, the outlet valve is open. The piston pushes exhaust gases through it. The temperature inside drops to 500 C, and the pressure to 100 kPa.

Advantages of diesel engines

In this video, they will tell you the differences and advantages of diesel engines from gasoline ones.

Motors that perform useful work by burning diesel fuel have several advantages over gasoline devices:

1. Reduced fuel consumption by a third.
2. Lack of ignition system.
3. Increased motor life by one and a half times.
4. Stability of adjustment parameters.
5. Average efficiency is 40%, for turbocharged engines it is above 50%.
6. High torque.
7. Low saturation of exhaust gases with carbon dioxide (less harm to the environment).
8. Fire safety due to the fact that diesel fuel cannot spontaneously ignite.

Among the disadvantages of the diesel engine, the difficulty of cold starting is noteworthy. The motor is the source strong vibration and loud noise. However, modern models do not have these disadvantages.

Scheme of operation of individual nodes

The design of a modern diesel engine includes the following components:

1. Turbocharger (turbocharger, turbine).
2. Intercooler.
3. Fuel burner.

Let's look at the operation diagrams of the component units.

Turbocharger

Cross-sectional view of a turbocharger

Experience has shown that the fuel does not have time to burn at the moment when the piston moves to the dead center. Therefore, if you force it to burn completely, the engine power will increase sharply.

For this purpose, a turbocharger was created to supply fuel under overpressure and facilitating it complete combustion. The turbocharger design includes:

• Two casings (one for the turbine, the other for the compressor);
• Bearing housing with a shaft connecting the turbine rotor and the compressor wheel;
• Bearings - support for the unit;
• Steel protective mesh.

The scheme of its work is as follows:

1. The compressor draws in air from the outside atmosphere;
2. The compressor rotor, driven by the turbine rotor, compresses it;
3. The compressed air is cooled by an intercooler;
4. The air is purified by a filter and supplied through intake manifold motor, after which the exhaust valve closes. It will open after the working stroke is completed;
5. Exhaust gases entering through an exhaust manifold, when passing through the tapering channel of the turbine housing, the speed increases and affects the rotor;
6. The turbine rotation speed increases to approximately 1500 rpm, as a result of which the compressor rotor is rotated (they are connected by a shaft);
7. The cycle repeats.

As air cools, its density increases. Therefore, more of it is supplied to the engine cylinder. A large amount of air promotes complete combustion of fuel, which increases the power of a diesel engine. At the same time, the negative impact on the environment is reduced.

Type of diesel engine intercooler

Intercooler

When air is compressed, not only does its density increase, but also its temperature. On the one hand, the flow of a large amount of oxygen into the cylinder has a positive effect on fuel combustion. But on the other hand, the intake of hot air contributes to the rapid destruction of the structure.

Therefore, a device is needed that reduces the temperature of the compressed air. This is what an intercooler is. The principle of operation of the intercooler is to cool a hot substance with a cold one by heat exchange between them.

It is possible to use two types of intercooler:

• Air-to-air. The device's radiator transfers the heat of heated air to the atmosphere. The design is extremely simple, therefore it is widespread;
• Air-water. First, the exhaust gases enter the compressor, then they pass through the intercooler radiator, which is washed with water. The devices are highly efficient and compact. But additionally, a radiator is required to cool the water, a pump to circulate it, and a control unit.

It doesn't matter what type of device the intercooler is.

The result of the work is unchanged: the temperature of the air compressed by the compressor is reduced by the radiator.

The intercooler itself can be called a cooling radiator, consisting of tubes made of materials with a high thermal conductivity coefficient.

Nozzle

The design of a diesel engine provides for the presence of one or more injectors. These parts are designed for dosing and atomizing fuel.

Diesel engine injector operation diagram

With their help, the combustion chamber is sealed. Modern injectors operate from a cam camshaft through the pusher. Fuel is supplied and drained through channels located in the cylinder head.

Its dosage is provided by the control unit, which sends signals shut-off valves with electromagnetic properties. The injectors operate in pulse mode. This means that before the main injection of fuel, it is pre-supplied.

At the same time, the operation of the diesel engine becomes softer, and the level of toxic emissions into the atmosphere decreases.

Thus, a diesel engine is a set of interconnected components.

The turbocharger supplies compressed air cooled by an intercooler into the combustion chamber. Fuel is supplied to it through an injector. If at least one of the components fails, the operation of the motor is impossible.

Greetings friends! The diesel power unit has long won love and respect among car enthusiasts! It is more economical, more reliable, and the overall efficiency is an order of magnitude higher than that of its gasoline counterpart. However, the more complex design and operating principle of a diesel engine prevent many domestic drivers from deciding to buy a car of this type. It’s not strange, it makes you pay attention to the cost of vehicle maintenance, and rightly so! But still, in order to dispel the fears of my colleagues, today I will try to describe to you in an understandable form all the features of such a unit. But first things first, as usual...

A little background

The first engine of this type was created by the French engineer Rudolf Diesel, who lived in the 19th century. As you yourself understand, the master did not think long about the name of his invention and followed in the footsteps of the great inventors, calling it his own name. The engine ran on kerosene and was used exclusively among ships and stationary machines. Why? Everything is very simple, the huge weight and increased noise of the engine did not allow increasing the range of its applications.

And so it was until 1920, when the first copies of the already significantly modernized diesel engine began to be used in public and freight transport. True, only 15 years later, the first models appeared passenger cars, running on diesel fuel, but the presence of the same disadvantages did not allow the power unit to be used everywhere. Only in the 70s did truly compact diesel engines see the light of day; by the way, many experts link this event to a sharp jump in oil prices. Be that as it may, the diesel power unit did not work on anything during its formation. The experimenters poured into it everything they could get their hands on: rapeseed oil, crude oil, fuel oil, kerosene and finally diesel fuel. Nowadays, we all see what this has led to - in the background expensive gasoline, diesel is conquering not only Europe, but the whole world!

Design Features

The design of a diesel engine, by and large, does not have many differences in comparison with its gasoline counterpart. It's still the same piston engine internal combustion, in which the fuel is ignited not by a spark, but by compression or heating. There are several main elements in its design:

• Pistons;
• Cylinders;
• Fuel injectors;
• Glow plugs;
• Inlet and outlet valve;
• Turbine;
• Intercooler.

For comparison: the efficiency of a gasoline engine is on average about 30%, in the case of diesel version this figure increases to 40%, and with turbocharging up to 50%!

Moreover, the operating patterns are also very similar to each other. Only the creation processes differ air-fuel mixture and its combustion. Well, another global difference is the strength of the parts. This moment is determined by a significantly higher level of compression ratio, because if in “lighters” a small gap is allowed between parts, then in a diesel engine everything should be as tight as possible.

Principle of operation

Let's finally understand how a diesel engine works. If we talk about the four-stroke version, then here you can observe a combustion chamber separate from the cylinder, which is nevertheless connected to it by a special channel. This type engines were promoted to the masses much earlier than the two-stroke modification, due to the fact that they were quieter and had an increased speed range. If you follow the logic, it becomes clear that if there are 4 clock cycles, then the work cycle accordingly consists of 4 phases, let’s consider them.

1. Intake - when the crankshaft is rotated between 0-180 degrees, air enters the cylinder through the intake valve, which opens 345-355 degrees. Simultaneously with the intake valve, the exhaust valve opens when the crankshaft is turned by 10-15 degrees.
2. Compression - moving upward at 180-360 degrees, the piston compresses the air 16-25 times, in turn, at the beginning of the stroke at 190-210 degrees, the intake valve closes.
3. Power stroke - when the stroke just begins, the fuel mixes with hot air and ignites, naturally all this happens before the piston reaches dead center. In this case, combustion products are released, which put pressure on the piston and it moves down. Please note that the gas pressure is constant, so fuel combustion lasts exactly as long as the diesel engine injector supplies liquid. It is thanks to this that greater torque is developed compared to gasoline units. All this action is carried out at 360-540 degrees.
4. Exhaust - when the crankshaft rotates 540-720 degrees, the piston moves upward and pushes out traffic fumes through an open outlet valve.

The operating principle of a two-stroke diesel engine is characterized by faster phases, a single gas exchange process and direct injection. For those who are not in the know, let me remind you: in such designs, the combustion chamber is located directly in the piston, and the fuel enters the space above it. When the piston moves down, combustion products leave the cylinder through exhaust valves. Next, they open intake valves and fresh air comes in. When the piston moves upward, all valves are closed, and compression occurs at this time. The fuel is injected by sprayers and ignition begins before the piston reaches top dead points.

Optional equipment

If we put the internal combustion engine itself aside, it comes to the general plan whole line fully trained assistants. Let's take a look at the top professionals!

Fuel system

The design of the fuel system of a diesel engine is much more complex than in petrol modifications. This nuance is explained easily and simply - the requirements for fuel supply pressure, quantity and accuracy are very high, you understand why. The fuel injection pump of a diesel engine, the fuel filter, injectors and sprayers are all the main elements of the system. Not only the equipment, but also the design of the fuel filter deserves a separate article. Perhaps we will soon examine them under a microscope.

Turbocharging

A turbine on a diesel engine significantly increases its performance due to the fact that the fuel is supplied under high pressure and, accordingly, burns out completely. The design of this unit is, in principle, not so complicated; it consists of only two casings, bearings and protective mesh made of metal. The operating principle of a diesel engine turbine is as follows:

• The compressor, to which one casing is connected, sucks air into the turbocharger.
• Next, the rotor is activated.
• Afterwards, it’s time to cool the air; the intercooler handles this task.
• Having passed several filters along the way, the air enters the engine through the intake manifold, after which the valve closes, and its subsequent opening occurs at the final stage of the power stroke.
• Just then, exhaust gases leave the engine through the turbine, which also exert a certain pressure on the rotor.
• At this moment, the rotation speed of the turbine can reach 1500 revolutions per second, and the rotor rotates through the shaft.

Turbine operating cycle power unit repeats itself over and over again, and it is thanks to this stability that the engine power grows!

Injectors and intercooler

The operating principle of the intercooler, as well as the injectors, and indeed their purpose, are, of course, radically different. The first, by heat exchange, reduces the temperature of the air, which, when hot, greatly affects the durability of the engine. The injector is responsible for dosing and atomizing the fuel.

It operates in pulse mode due to a cam extending from the camshaft and the nozzles themselves.

Diesel operating temperature

Don’t be alarmed if the usual 90 degrees are missing on the instrument panel. The fact is that working temperature diesel engine is quite specific and depends on the specific brand of car, the engine itself and the thermostat. So, if for a Volkswagen the normal value is in the range of 90-100 degrees, then an ordinary Mercedes operates at 80-100, and an Opel generally in the region of 104-111 degrees. Domestic truck KAMAZ, for example, operates at 95-98 degrees.

Whatever the operating temperature of your power unit, one thing is obvious - diesel engines are more relevant today than ever. Don't believe me? Look around, today you can even find a diesel engine on a Niva, and I’ll tell you this, this is not an isolated case. From this alone we can conclude that such an engine is much better than a gasoline engine.

Yes, it is unlikely to be able to compare with gasoline engines in terms of speed, although modern models with turbines can definitely create competition.

If you don’t want to change the car, much less the engine, I recommend it with my own hands wash the engine, because we don’t do this as often as the procedure I described looks like. In general, I expressed my opinion, I’m waiting for yours in the comments! All the best!