What a diesel engine is needed. Diesel engine - advantages and disadvantages. Diesel cars safer

The number of vehicles, the characteristic sound of the working force unit of which, is growing annually. It is the diesel engines that will be devoted to this publication in which we will try to describe the most described by their features, some performance and differences from gasoline engines.

Distinctive features of diesel units, such as: efficiency, high working indicators and fuel, which is cheaper, make this kind of motors today still demand. The latest models of diesel engines in terms of their noise and environmental indicators are practically no different from their petrol female , except that they are more economical and durable.

Design features

Constructively operating on diesel engines are no different from gasoline, and have the same details. Except that the valve elements of diesel engines are produced more enhanced, otherwise they will not hold out the entire load. For comparison: the degree of compression of the diesel power unit is 19-24 units, and this is twice as high than the gasoline. For this reason, diesel has a little large dimensions and mass.

The noisy work of this power unit is due to one of its feature. The fact is that the self-ignition of the mixture inside its cylinders occurs only at the moment of increase in pressure. Due to this, it is allowed to use cheap fuel in the motor (not to be confused with poor-quality), and its work on the resemblance of mixtures. Due to this, the savings are achieved. Since the unit works on kindly mixtures, respectively, its harmful emissions The atmosphere is significantly reduced.

The only minuses of diesel engines are considered to be their noisy work, accompanied by vibration, problems with starting in cold and less power in litter. But, such shortcomings of the prerogative of exclusively old engines, in modern diesel engines (in view of their constructive features) These problems are excluded.

Diesel with Direct Injection

There are several designs of diesel engines that differ from each other by the structure of the combustion chamber. The aggregates in which the combustion chamber is inseparable, and the fuel injection is carried out directly into space above the piston, are called direct injection engines. The role of the combustion chamber is played by the piston.

Not so long ago, the immediate injection was used exclusively on low-robust diesel engines with an increased working volume. Such a measure was associated only with problems in combustion of fuel, constant vibration and noisy work.

However, the situation has changed with the advent of high pressure fuel pump, controlled by electronics, innovative system of two-level injection and solving the problem of incomplete combustion of fuel. Such events allowed to obtain a stable work of the unit already at 4500 rpm, made it more economical and low noise.

Diesel with a separate chamber

Today, this type of diesel power units is widespread on passenger vehicles. Fuel in such a motor is injected into a separate chamber, and not in the cylinder. The model of the vortex chamber is widespread, which is located at the base of the cylinder block and through a special channel is connected to the cylinder so that the air, compressing, falling into it, and further twisted inside the vikery. This contributes to a good saturation of the mixture and increases its self-ignition, which occurs in the vortex chamber and further goes into the main one.




With this design of the motor, the pressure in its cylinders increases gradually, as a result of which the noise level of the unit is significantly reduced, and the revolutions are rising. Almost 90% of diesel transport are installed engines with a vortex chamber.

Diesel fuel system

Perhaps this system is the most important part of diesel engine, mostly characterizing its effectiveness. Its work lies in the dosage of fuel supply under certain pressure and at a certain time. Increased requirements for the accuracy of its work, and the presence of high pressure inside the system makes this node of the diesel unit costly and complex.

The fuel feed system is from:

1. which provides diesel fuel to the engine nozzles according to a strictly specified cycle, which depends on the operation of the unit and the driver applied by the driver to the accelerator pedal. The multi-mode TNVD combines the operation of the main executive device, the function of which is the processing of the driver commands, and the automatic power unit control system.

Driving a accelerator pedal, the driver does not reduce either increases the flow of the working mixture, and only sets the appropriate regulators mode, which independently adjust the fuel feed depending on the pressure, the number of revolutions, the position of the feed regulators, etc. Note that most of the diesel SUVs produced today Distribution type TNVD.

Distributive pumps are mostly prerogative of diesel engines installed on the passenger vehicle. They differ correctly adjusted fuel feeds and increased speed, due to which they are achieved. stable work At high speed. However, this type of fuel pumps is too demanding for the quality of the diesel fuel and its purity, because it lubricates the working surfaces of their parts.

1. The diesel engines are no less important than the Element of the fuel supply system, which, together with the fuel pump, carry out uninterrupted dosage of the working mixture into the combustion chamber. The pressure in the fuel feed system depends on the angle of placing the nozzle, and the shape of the fuel torch, on which the entire correct sequence of self-ignition and combustion of the fuel depends, gives the sprayer. Two types of nozzles are found: multi-dimensional or fonts.

The operation of the nozzle in the diesel unit is due to the conditions too heavy for it. This is due to the fact that the working movement of the sprayer needle is two times less than the rotor of the motor, while the sprayer of the nozzle is subjected to a constant effect of high temperature and fuel explosions upon contact with the combustion chamber. Accordingly, such an element must be made of durable and heat-resistant materials.

1. Fuel filter, although it is the simplest element in the diesel fuel system, it still does not be able to ensure full-fledged operation of the motor. Its characteristics (level of filtering and throughput) must necessarily be selected in accordance with the type and power indicators of the power unit. In addition to filtering the diesel fuel, the filter still plays the role of separator of water. To do this, its design provides the bottom plums closed by a plug. Often, a manual pump is installed on the fuel filter, which is necessary for pumping air from the system.

Rarely, but still come fuel filters With electric heating, which many times easier to start the unit in the cold time.

Features of the launch of diesel engines

Thanks to the preheating, a cold start of the engine operating on the diesel engine is possible. Act preheater So: inside the combustion chambers are special electrical heaters - incandescent candles. At the moment of inclusion of ignition, these elements provide instant heating of combustion chambers, facilitating the process of self-ignition of the working mixture. The corresponding indicator in the cabin signals the operation of the system.

As soon as the indicator has the way out - the power unit warmed up and is ready for starting. After starting the motor to the heating element, for 15-20 seconds, the power supply continues to flow. This allows you to stabilize the work of another cold engine. It should be noted that the preheater is able to provide a free launch of the motor (provided that it is complete and the availability of the appropriate diesel fuel) at temperatures up to -30 degrees.

Turbated diesel

Effectively increase the power of the diesel engine is possible only with the use of turbocharging. Thanks to him, more air is supplied to the diesel cylinders with the help of the pump, as a result of which the supply of the mixture increases, its burning improves and increases the power of the motor. Since the exhaust gases of the diesel engine are more than 1.5-2 times the pressure in contrast to gasoline units, their turbocharger works more efficiently even on small speeds, which allows the turbocharged diesel to avoid failures in the work (the so-called "turbists").

However, the turboodiesel is not deprived of the shortcomings that are mainly in the imperfection of the turbocharger design. Its working resource rarely exceeds the mileage of 150 thousand km, which is much less than the resource of the aggregate itself.

Advantages of using the Common-Rail system

Thanks to the electronic control system of fuel feeds, the injection of diesel fuel is provided by two consecutive doses into the combustion chamber. Initially, a small portion is supplied, necessary for heating the chamber, and after it is already the main one. Such a fuel dosage system is very important for diesel power units, since it provides a smooth pressure growth inside combustion chambers, which is due to the smaller noise of the motor and its stable work.

The use of the Common-Rail system allows to reduce fuel consumption by 20%, while 25% increase the crankshaft torque when operating the engine at low revs.

The video will show the device and the principle of operation of the diesel engine:

The video will tell about the operation of modern diesel engines:

Diesel technologies are developing impressive pace especially in the last ten years. Half of new cars sold today in Europe are their modifications having a diesel engine. Despite the fact that the diesel engine remained the same, it became quieter, ecologically cleaner, and an unpleasant smell, thick smoke from the pipe and loud terrain remained far in the past.

Not only economy, but also high power, good dynamics became the main characteristic features of modern diesel engines. It is interesting how the diesel is able to respond to the ever-increasing values \u200b\u200bof the norms of toxicity, not only without losing at the same time in power and efficiency, but constantly improving these indicators. Let's try to consider everything in order.

How does diesel work, which is good, and what is not quite

The main principal distinction of the diesel engine from gasoline is a way to prepare a working combustible mixture and its further inflammation. In most carburetor and injector gasoline engines, the working mixture is prepared in the intake path. Although in some gasoline engines, the mixture is formed, as in the diesel engine directly in the cylinder. The ignition of the mixture in the gasoline engine occurs at the right moment from the electrical breakdown (spark), and in the diesel engine from the high temperature in the air cylinder.

Diesel works like this: when the piston is down, suction is absorbed into the cylinder of clean air, which heats up when the piston is upward. In this case, the temperature of the diesel engine comes to 700-900 ° C, which is caused by a high degree of compression. When the piston is suitable in the upper dead point in the combustion chamber is injected under high pressure diesel fuel and, in contact with heated air, is self-propagated. The self-splashing diesel fuel, expanding, leads to a sharp increase in the pressure in the cylinder than in principle and the increased noise of the diesel engine is caused.

The above-described principle of operation allows diesel to use a very poor mixture with a relatively cheap diesel fuel, and this in turn determines its high efficiency and unpretentiousness. Diesel has 10% higher efficiency and torque more than that gasoline engine. The main disadvantages of diesel engines are the increased noise and vibration, the difficulties of the cold start and, of course, less power per unit volume, although modern models of these shortcomings practically do not have.

Features and device of some nodes

Given that the degree of compression of the diesel engine is about 2 times more, the degree of gasoline compression, similar to its parts is significantly enhanced, as they will have to withstand higher loads. The characteristic detail of the diesel is its piston, the bottom of the bottom of which depends on the combustion chamber or rather from its type, and in many cases the combustion chamber itself is arranged in the bottom of the same piston. Unlike the bottoms of the bottom of the diesel pistons, in the upper dead point, protrude beyond the top plane of the cylinder block. Since the working mixture is self-proposal from compression, the diesel does not have a familiar ignition system, although the candles are used on the diesel.

And these are candles with an elevated incandescent spiral, which are designed to warm the air in the combustion chamber especially in front of the cold start of the engine. The main indicators of the diesel engine both are technical and environmental are determined mainly by the fuel injection system, and the type of combustion chamber.

Principle of operation of the combustion chambers and their types

In diesel engines, combustion chambers can be two types undeveloped and separated. Until recently, diesel engines with separate combustion cameras prevailed in the passenger engineering. The fuel in this case was injected not into the space above the piston, but in the combustion chamber located in the head of the cylinder block. Separate combustion chambers, depending on the process of forming a mixture of a pre-commercial (forkarmic) or a rowed, are structurally performed in different ways.

With the forkar process, the fuel injection is performed in the pre-chamber, communicating small holes or channels with a cylinder, fuel, hovering on its wall, mixed with air. The ignited mixture at high speed through the channels whose cross sections are selected, so that in compression and resolution there was a large pressure difference between the preliminary chamber and the cylinder, it enters the main chamber, where it completely burns.

In the dramatic process, the combustion of the mixture also begins in a separate chamber, which is a hollow sphere. During the compression tact, the air through the connecting channel falls into this chamber and, twisting in it, forms a whirlwind, thanks to which the fuel is injected at the right time, it is thoroughly mixed with air.

As you can see, in the separated chamber, the diagram of the diesel engine is as follows: fuel burns as it were in two stages, which, of course, reduces the load on the pistons, thereby providing a softer engine operation. One of the disadvantages of diesel engines made with a separated combustion chamber, an increased fuel consumption can be called due to the losses of such a chamber due to the large surface, as well as significant losses for the flow of air from the cylinder in additional camar And then already a combustible mixture back into the cylinder. These losses deteriorate in addition to the launch characteristics of the diesel engine.

Well, now about diesel engines with an undivided combustion chamber or how they are also called diesel engines with direct injection. In such an engine, the combustion chamber is the cavity of a certain form, structurally performed in the bottom of the piston, and the fuel injection is made in the cylinder directly. The direct injection has not yet been so long ago was the prerogative of low-robust diesel engines with a large volume and installed on trucks. The cost-effectiveness of diesel engines with immediate injection was very bribed, but their use on diesel engines of small litters was restrained by constructive difficulties in the organization, actually, the combustion process and in addition to even increased vibration and noise appearing in the speed set mode.

The use of the fuel dosing that appeared recently, allowed to optimize the combustion of the working mixture in diesel engines with a direct injection (with an undivided combustion chamber), which in turn led to a decrease in vibration and noise. Today, new diesel engines developed in their design use the direct injection of diesel fuel.

Fuel supply systems

The fuel feed system, being one of the most important links of the diesel engine, is designed to provide it at the desired point in time with the necessary amount of fuel, and.

An important element of the fuel feed system is the high pressure fuel pump (TNVD), which in the desired sequence is charged the necessary quantities diesel fuelcoming from the pumping pump from the tank into the highway hydromechanical nozzles of each cylinder. If there are high pressure in front of the nozzle, it opens, and when it is missing or decreasing, it is closed.

High-pressure fuel pumps are two types: Pumps in line multi-vent and distribution type pumps. An inline pump is a set of individual sections, by the number of cylinders located in one row, from here and such a name. The section consists of a sleeve and a plunger included in it, driven by a shaft with cams, which receives rotation from the engine. Despite different principles of diesel engines in modern carsSuch pumps are now practically not used, because the pressure being created by them is not constantly due to the dependence on the crankshaft revolutions and still because they cannot provide modern requirements for noise and ecology.

Unlike row pumps, distribution pumps are capable of creating a higher pressure during fuel injection and thereby ensure the achievement of regulated, existing standards, values \u200b\u200bof the toxicity of exhaust gases. Such pumps create pressure with the parameters corresponding to the engine operation mode. The distribution pump has a distributor plunger in the design, which performs the rotational and translational movement, with a progressive movement, the fuel is discharged, and with the rotational distribution by the nozzles. These pumps are compact, carried out uniform feeding and distribution of fuel over the cylinders, and also work perfectly on high speeds. The switchgear pumps are very sensitive to the purity and quality of diesel fuel, since all the precision parts of such pumps are lubricated, and the gaps between them are very small.

For fuel injection, another pump-nozzle is used, installed in the engine block head for each cylinder, and is driven camshaft cams through the pusher. At the same time, the tact of the operation of the diesel engine occurs alternately. Fuel lines to the pump pump are made in the block head in the form of channels, due to which the pressure is about 2200 bar. Dosage compressed to such a degree of fuel, control of the injection advance angle is performed using a special electronic unit issuing control commands to electromagnetic or piezoelectric shut-off valves of pumps-injectors.

The ability to operate in pulse mode allows you to perform a pre-injection, feeding a small first portion of fuel, which in turn makes the operation of the engine softer and reduces exhaust toxicity. The main disadvantage of such nozzles is the dependence of pressure from the revolutions of diesel and, of course, their very high cost due to complex manufacturing technology.

Turbochargedow, turbodiesel

Turbocharging is effective way Increased diesel power. With it, you can fill the cylinders with an additional amount of working mixture, thereby increasing the engine power. The presence of an elevated one and a half two times the pressure of the exhaust gases of a diesel engine against gasoline allows the turbocharger to provide turbocharging from very low revolutions, and avoids the failure of the dyed gasoline engines. Since there is no in the diesel throttle valveThe effectful filling of cylinders in different modes does not require complex systems to control the turbocharger. Superior helps to obtain the same turbodiesel power with a conventional diesel engine with a smaller working volume, which in turn reduces its mass.

Turbocaddv allows you to optimize the operation of the engine in highland areas, compensating for the shortage of air and thereby, not allowing the reduction in power. The disadvantages of Turbodizel are mainly associated with the reliable operation of the turbocharger, the resource of which is significantly less than the engine resource due to harsh quality requirements motor oil. The breakdown of the turbocharger can withdraw with standing and the engine itself. It should be said that its own resource of Turbodiesel is still below the same conventional diesel engine mainly due to a large degree of forcing. In such diesel engines with turbocharging, as a rule, the increased temperature of the gases in the combustion chamber, and to ensure reliable work of the pistons, they are cooled by oil, which is supplied through special sprayers from the bottom.

Video - the principle of operation of the diesel engine

CONCLUSION!

Two main tasks: a decrease in toxicity and an increase in power, to solve them are the search for new principles of the diesel engine for cars. Given this, in particular, modern cars are equipped with diesel engines with turbocharging.

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What is a diesel car?

Diesel vehicles uses the engine that does not have a combustion cycle as a gasoline engine.

In the gasoline engine, the fuel mixes with air, enters the cylinder and flammifies the spark plug. In the diesel, the air is injected into the cylinder and compresses first without fuel. This compression heats the air to such a high temperature that when the fuel is then injected into the cylinder, it flammifies.

Using a higher level of compression and higher combustion temperatures, diesel engines work more energy efficiently. As a result, cars with a diesel engine achieve better than their gasoline analogs. In addition, in a liter of diesel fuel by about 10% more energy than in a liter of gasoline. These two factors help modern diesel engines to achieve about 50% of the best fuel economy than their gasoline analogues. Currently, diesel vehicles accounts for almost half of all sales of new cars in Europe, and a small but growing market share in the United States. In Russia, in 2009, the share of the market of new cars engaged in Diesel was only 5.6% according to the Avtostat agency.

Advantages of diesel

• Higher fuel efficiency (20-40% more than gasoline vehicles).
• Diesel engines serve longer and get a higher cost when resale.
• Diesel engines can use biodiesel as fuel.
• Diesel provides greater torque; Great for rapid acceleration and towing.
• Power reserve on one tank more.

Disadvantages of diesel

• In Russia, diesel fuel is very low quality.
• Assortment of models with a diesel engine is small.
• The diesel fuel is not available at all gas stations.
• Diesel vehicles are usually more expensive.
• Emissions of exhaust gases of nitrogen oxides and solid particles, as a rule, more.
• Considering the advantages and disadvantages of a diesel engine, it can be concluded that the latter are not essential and can be overcome.

Dreams of diesel hybrid

"Toyota", "Ford", "Volkswagen", "Peugot" and "Citroën" produce conceptual cars that combine a diesel engine with a hybrid system. Diesel-hybrid "Citroën C-Metisse", represented in 2006 at the Motor Show in Paris, is shown below. Combining two fuel-saving technologies in one vehicle can give a phenomenal result.

Unfortunately, the additional costs of combining a diesel engine with a hybrid system are ocked as expensive. Most analysts predict that diesel-hybrid will be a specialized product.

If in a few words describe the principle of operation of the diesel engine, then we can say that it depends in many respects from the pressure generated in the combustion chamber. Differences from gasoline engines are not very much: there is also a block, and CCC, and nozzles, which are something similar to those used in the injection injection system. The only significant difference is the fuel-air mixture flammable not from the spark, which slips between the candles between the electrodes, and from the colossal compression of the air that heats up and flammifies diesel fuel. Since the cylinders are very high pressure, the valves must withstand heavy loads. Diesel motors are used for majority on trucks, but it is often possible to meet and can be found on a diesel population.

Fuel ignition in diesel engine

The diesel engine is based on compression fuel ignition. Moreover, the diesel fuel, falling into the combustion chamber, connects with heated air. So the difference in the formation of a mixture from the gasoline engine - the diesel fuel and air in the combustion chambers are incorporated independently, mixed immediately before ignition. First comes in some air. When it is compressed, its heating begins (about 800 degrees). The fuel enters the cylinder under pressure from 10 to 30 MPa. After that it flammifies. During operation, there is a lot of noise, and the level of vibration is high enough. By such a simple sign, it is easier to distinguish a car with a diesel engine. By the way, in his design, there are still a candle, that's just the appointment they have completely different. They do not ignite the mixture, and the combustion chambers are warmed so that the engine is easier to start the engine. They are called - incandescent candles.

There are both two and four-stroke diesel engines. The latter are used on most cars and operate in this mode:

1. Tact intake.
2. Air compression and fuel injection occurs.
3. The explosion of the combustible mixture, the piston moves down, performing the work move.
4. Produced out of exhaust gases, the beginning of the first tact.

Diesel Engine Candles

Until some time, diesel fuel had low cost, so saving for owners diesel cars It was essential. But the overhaul, for example, is much more expensive, unlike a gasoline engine. Yes, and the device of a diesel engine for most of the motorists is unfamiliar.

What types of diesel engines exist

If you carry out the design of the design, then only three types can be distinguished:

1. Engines having a separated combustion chamber. The essence is simple - the air mixture does not receive immediately into the combustion chamber. Initially, it enters a separate compartment, called a vortex chamber. This camera is located in the GBC. Between the combustion chamber and this compartment is a small canal. It is in the vortex chamber that the air is able to squeeze to a large pressure. Consequently, its heating will be stronger and fuel ignition improves. In the same compartment there is initial fuel ignition. Then the process smoothly passes into the main combustion chamber.
2. With a combustion chamber, not divided into compartments. Such engines have a maximum noise level, fuel consumes less. The piston has small recesses in which the fuel mixture falls. It flammifies directly above the piston, after which the power of the explosion pushes it down.
3. Pre-commercial DVS have a plug-in forkamir in their design. From it to the main combustion chamber there are several thin channels. Most of the characteristics of a diesel engine of this type (noise level, resource, toxicity, fuel consumption, vibration, power) depend on the number of channels, their thickness and shapes.

Diesel engine nozzles

Basic fuel system nodes

It can be said that the fuel system is the basis of a diesel engine. It serves under a predetermined pressure fuel into the combustion chamber. Moreover, it is necessary for a strictly defined amount of diesel fuel and air. The main elements of the system:

1. TNLD (high pressure fuel pump).
2. Fuel filter.
3. Nozzle.

Consider the device of the diesel engine fuel system in more detail.

High Pressure Fuel Pump

On cars that can be found today on the roads, mostly installed pumps of the following types:

1. Distribution.
2. Plunger (row).

The pump function is to pick up fuel from the tank and transfer it to the nozzles. Moreover, its work depends on many parameters, among which air pressure in the turbine, the number of crankshaft revolutions and other things. The main difference from the pumps installed on simple gasoline cars is that the diesel engine pump needs to create a much greater fuel pressure so that it can still be injected directly into the combustion chamber, in which the air is under high pressure.

High pressure fuel pump diesel engine

Fuel filter

For each motor provided its, indispensable, filter type. As can be seen from the name, it is necessary for cleaning the diesel fuel coming from the tank. They will be detained any, even the smallest, particles. It also removes air and moisture from the system.

Fuel injectors

High pressure pump has a solid connection with nozzles. It is from these two elements that it depends on whether the fuel in the combustion chamber is in a timely manner (and it must be sprayed at the time of finding the piston at the upper dead point). The design of the modern diesel engine use the following types of nozzles:

1. Multi-line.
2. Having a font distributor.

The injector distributor is responsible for the form of a torch that the fuel evenly entered the combustion chamber and its ignition occurred most effectively.

Preheating and turbine

Diesel turbine

The cold start system is necessary for warming up immediately before starting the engine. As already mentioned, in the combustion chamber there are candles that work on the type of soldering iron - they are located in them, under the action of electric current, it heats up to nine hundred degrees. All air entering the combustion chamber is also heated. Such a system is triggered immediately before starting startup and turns off after a quarter of minutes after the engine started. In the process of work, it does not participate. Thanks to this system, the engine is easier to start the engine (if only the diesel fuel in the tank and the fuel line does not acquire a jelly-like type).

But the turbocharger system can significantly increase the power produced by the engine. Due to it, the injection of large amounts of air occurs. As a result, the combustion process of fuel is significantly improved. In order for the air to be under pressure at any mode of operation, a special turbocharger is installed. Consider a diesel engine turbine device in general. The turbine is a two impeller, located on the shaft of steel. Moreover, one of the impellers is in the graduate manifold and is spinning with exhaust gases. At the same time, the shaft begins to transmit the rotational movement of the second impeller, which is already in the intake manifold. With its help, an additional air pressure is created in the inlet path. The turbocharging system is enclosed in a cast iron case. Like all engine aggregates, the hull is susceptible to wear. The inclination of the impeller is very high, it is for this reason that the destruction occurs. The housing of the turbine has a snail shape, so there is a complex movement of the gas stream, which leads the entire supercharger mechanism. In the manufacture of the turbine, precise casting and fitting of all parts are extremely important.

Instead of imprisonment

Disputes about the disadvantages and benefits of diesel engines sound from the moment they appear. It is impossible to definitely say that it is a diesel engine that is right choices. Choose or not a car with a diesel engine - the solution is still everyone takes. Therefore, it is necessary to know how a diesel engine works at various loads and in a specific climate.

The same year he was successfully tested. Diesel actively engaged in selling licenses for a new engine. Despite the high efficiency and ease of operation compared to the steam engine, the practical application of such an engine was limited: he inferior to steam machines of the time in size and weight.

The first diesel engines worked on vegetable oils or lung petroleum products. Interestingly, it was originally as an ideal fuel offered coal dust. Experiments showed the impossibility of using coal dust as fuel - primarily due to the high abrasive properties of both the dust itself and ash, obtained during combustion; Also there were large problems with dust in cylinders.

Principle of operation

Four-stroke cycle

• 1st tact. Inlet. Corresponds to 0 ° - 180 ° rotation of the crankshaft. Through open ~ from 345-355 °, the air intake valve enters the cylinder, on 190-210 ° valve closes. At least up to 10-15 ° crankshaft rotation at the same time, the exhaust valve is open, the joint opening time of the valves is called overlapping valve .
• 2nd tact. Compression. Corresponds to 180 ° - 360 ° rotation of the crankshaft. The piston, moving to the VTT (upper dead point), compresses the air to 16 (in low-speed) -25 (in the speed) times.
• 3rd tact. Working, expansion. Corresponds to 360 ° - 540 ° rotation of the crankshaft. When spraying fuel in hot air, the fuel combustion is initiated, that is, its partial evaporation, the formation of free radicals in surface layers of droplets and in paráh, finally, it flashes and burns as far as the injectors arrived, burning products, expanding, move the piston down. Injection and, accordingly, fuel ignition occurs a little earlier than the moment of reaching the piston of the dead point due to some inertness of the combustion process. The difference from the ignition advance in gasoline engines is that the delay is necessary only due to the presence of initiation time, which in each specific diesel - is not subject to permanent and change during operation. The combustion of fuel in the dieselle occurs, thus, for a long time, so much time, how long is the flow of portion of fuel from the nozzle. As a result, the workflow proceeds with a relatively constant pressure of gases, which is why the engine develops a large torque. Two major output are followed from this.
  • 1. The combustion process in the dieselle lasts exactly so much time as required for the injection of this portion of fuel, but no longer the time of the working stroke.
  • 2. The ratio of fuel / air in a diesel cylinder can differ significantly from stoichiometric, and it is very important to ensure an excess of air, since the flame of the torch occupies a small part of the combustion chamber volume and the atmosphere in the chamber must prior to the latter to ensure the desired oxygen content. If this does not occur, there is a massive release of unburned hydrocarbons with soot - "Temloom" gives a "bear".).
• 4th tact. Release. Corresponds to 540 ° - 720 ° crankshaft rotation. The piston goes up, through open at 520-530 ° exhaust valve piston pushes the spent gases from the cylinder.

Depending on the combustion chamber design, there are several types of diesel engines:

• Diesel with an undivided camera: The combustion chamber is made in the piston, and the fuel is injected into the epipper space. The main advantage is the minimum fuel consumption. Disadvantage - increased noise ("tough work"), especially on idling. Currently, intensive work is underway to eliminate the specified shortage. For example, in the COMMON Rail system to reduce the stiffness of the work (often multistage) antipsychos.
• Diesel with a separated chamber: Fuel is served in an additional chamber. In most diesel engines, such a chamber (it is called a vortex or pre-tariff) is associated with a cylinder with a special channel so that when compressing the air, falling into the camera, it swollen intensively. This contributes to a good mixing of the injected fuel with air and more complete fuel combustion. Such a diagram was considered optimal for light diesel engines and was widely used on passenger cars. However, due to the worst economy, the last two decades there is an active displacement of such diesel engines with an inseparable chamber and with Common Rail fuel systems.

Two-stroke cycle

Purge of the two-stroke diesel engine: down - purge windows, exhaust valve top open

In addition to the above-described four-stroke cycle, in diesel, it is possible to use a two-stroke cycle.

At the working trip, the piston goes down, opening the outlet windows in the cylinder wall, the exhaust gases overlook, at the same time open windows open, the cylinder is blown out with fresh air from the blower - purge combining intake and release tacts. When the piston rises, all windows are closed. From the moment of closing the intake windows, compression begins. A little without reaching the NTT, the fuel is sprayed from the nozzle and lights up. Expansion occurs - the piston goes down and again opens all the windows, etc.

Blowing is a congenital weak point of the two-stroke cycle. The purge time, in comparison with other clocks, it is impossible, it is impossible to increase it, otherwise the efficiency of the working move will fall due to its shortening. In the four-stroke cycle, half of the cycle is given to the same processes. Fully divided exhaust and fresh air charge is also impossible, so part of the air is lost, leaving right in exhaust pipe. If the shift of the clock provides the same piston, the problem arises associated with the symmetry of opening and closing windows. For better gas exchange it is more profitable to have ahead of the opening and closing of exhaust windows. Then the exhaust, starting earlier, will reduce the pressure of residual gases in the cylinder to the beginning of the purge. With the previously closed exhaust windows and open - still - inlets are carried out with a coil of the cylinder with air, and if the blower provides overpressure, it becomes possible to carry out superior.

Windows can be used for exhaust exhaust gases, and for intake fresh air; This purge is called slit or window. If the spent gases are produced through the valve in the cylinder head, and the windows are used only for intake fresh air, purging is called valve-slot. There are engines where in each cylinder there are two meet-moving pistons; Each piston manages its windows - one intake, other graduation (Ferbenx-Morse system - Junkers - Korevo: Diesels of this system of the D100 family were used on TE3 diesel locomotives, TE10, tank engines 4TPD, 5TD (f) (T-64), 6TD (t -80ud), 6TD-2 (T-84), in aviation - on Junkers bombers (Jumo 204, Jumo 205).

IN two-stroke engine Working runs are twice as much as in four-stroke, but due to the presence of purging the two-stroke diesel is more powerful than 1.6-1.7 times in the volume of the four-stroke maximum.

Currently, low-speed two-stroke diesel engines are very widely used on large maritime ships with direct (unprecedented) drive propeller. Due to the doubling of the number of work moves on the same turns, the two-stroke cycle is advantageous if it is impossible to increase the frequency of rotation, in addition, the two-stroke diesel is technically easier to reverse; Such low-speed diesel engines have a capacity of up to 100,000 hp.

Due to the fact that it is difficult to organize the purge of the vortex chamber (or pre-stop) at a two-stroke cycle, the two-stroke diesel engines are built only with undivided combustion chambers.

Design options

For medium and heavy two-stroke diesel engines, the use of composite pistons is characterized in which the steel head and duralum skirt is used. The main purpose of this complication of the design is to reduce the total weight of the piston while maintaining the maximum possible heat resistance of the bottom. Very often used constructions with oil liquid cooling.

Four-stroke engines are allocated to a separate group containing Creicopf in the design. In Creicopful engines, the connecting rod joins the Creiccopfu - the slider connected to the piston rod (rolling pin). Creicopf works in his guide - the crown, without the effects of elevated temperatures, completely eliminating the impact of lateral forces on the piston. This design is typical for large long-term ship engines, often - double action, the stroke of the piston can reach 3 meters; Thrinking pistons of such sizes would be overheated, tries with such a friction area would significantly reduce the mechanical efficiency of the diesel engine.

Reversible engines

The combustion of the fuel injected into the cylinder is occurs as an injection. Therefore, diesel gives a high torque at low revs, which makes a car with a diesel engine more "responsive" in motion than the same car with a gasoline engine. For this reason, and due to higher efficiency at present, most trucks Tools with diesel engines . For example, in Russia in 2007, almost all trucks and buses were equipped with diesel engines (the final transition of this segment of vehicles from gasoline engines to diesel engines was planned to be completed by 2009). This is also an advantage in the engines of sea vessels, since the high torque at low revs makes more easy to efficiently use the engine power, and a higher theoretical efficiency (see Carno cycle) gives higher fuel efficiency.

Compared to gasoline engines, in the exhaust gases of the diesel engine, as a rule, less carbon monoxide (CO), but now, in connection with the use of catalytic converters on gasoline engines, this advantage is not so noticeable. The main toxic gases that are present in the exhaust in noticeable quantities are hydrocarbons (ns or CH), nitrogen oxides (NO) and soot (or derivatives) in the form of black smoke. Most polluted the atmosphere in Russia Diesels of trucks and buses, which are often old and non-regulated.

Another important aspect of security is that diesel fuel is non-volatile (that is, it does not easily evaporate) and, thus, the probability of fire in diesel engines is much smaller, especially since the ignition system is not used. Together with high fuel efficiency, this was the reason for the wide use of diesel engines on tanks, since the risk of fire in the engine compartment was decreased in everyday neborement exploration due to fuel leaks. The smaller fire hazard of the diesel engine in combat conditions is a myth, since when armor breaks, the projectile or its fragments have a temperature that highly exceeds the flash of the vapor of diesel fuel and is also able to simply set fire to the resulting fuel. The detonation of a mixture of vapors of diesel fuel with air in a fuel tank through its consequences is comparable to the explosion of ammunition, in particular, in T-34 tanks, it led to the rupture of welds and knock out the top front desk of the armorpus. On the other hand, a diesel engine in a tank building is inferior to the carburetor in terms of specific power, and therefore in some cases (high power with a small volume of the engine compartment) more advantageous can be the use of precisely carburetor power unit (although it is typical for too light combat units).

Of course, there are disadvantages, among which is a characteristic knock of a diesel engine at its work. However, they are noted mainly by car owners with diesel engines, and for a third-party person almost invisible.

The obvious disadvantages of diesel engines are the need to use a high-power starter, clouding and frosting (sprinkling) of summer diesel fuel at low temperatures, complexity and higher price in the repair of fuel equipment, since high pressure pumps are precision devices. Also, diesel motors are extremely sensitive to fuel contamination with mechanical particles and water. Repair of diesel engines, as a rule, significantly more expensive repair Gasoline engines of a similar class. The liter power of diesel engines also, as a rule, is inferior to similar indicators of gasoline engines, although diesel engines have a faster and high torque in their working volume. Environmental indicators of diesel engines significantly inferior to recently gasoline engines. On classical diesel engines with a mechanically controlled injection, only oxidative neutralizers of exhaust gases operating at a temperature of exhaust gas over 300 ° C are possible, which oxidize only CO and CH to harmful carbon dioxide (CO 2) and water. Also earlier, these neutralizers were out of order due to poisoning by their sulfur compounds (the number of sulfur compounds in the exhaust gases directly depends on the amount of sulfur in diesel fuel) and deposits on the surface of the catalyst of soot particles. The situation began to change only in recent years due to the introduction of the diesel engines of the so-called Common Rail system. In this type of diesel engines, the fuel injection is carried out by electronically controlled nozzles. The control of the control electrical pulse performs an electronic control unit receiving signals from the sensor set. The sensors also track different engine parameters affecting the duration and moment of supplying the fuel pulse. So, the complexity is modern - and environmentally friendly, as well as a gasoline-diesel engine is nothing inferior to its gasoline fellow, but for a number of parameters (complexity) and significantly exceeds it. For example, if the pressure of the fuel in the nozzles of a conventional diesel engine with a mechanical injection ranges from 100 to 400 bar (approximately equivalent to "atmospheres"), then in the newest systems "Common-Rail" it is in the range from 1000 to 2500 bar, which goes for It is considerable problems. Also, the catalytic system of modern transport diesel engines is much more complicated by gasoline engines, since the catalyst must "be able to" work under the conditions of an unstable composition of exhaust gases, and in cases where the introduction of the so-called " squeeze filter"(DPF - Filter of solid particles). The "Syft Filter" is a similar to the usual catalytic neutralizer the structure installed between the exhaust collector of a diesel engine and the catalyst in the exhaust flow. The particulate filter develops a high temperature in which the soot particles are capable of oxidizing residual oxygen contained in exhaust gases. However, part of the soot is not always oxidized, and remains in the "scenic filter", so the control unit program periodically translates the engine into the "cleaning filter cleaning" mode by the so-called "posting", that is, the injection of the additional amount of fuel in the cylinders at the end of the combustion phase with the aim of Raise the temperature of the gases, and, accordingly, clean the filter by burning the accumulated soot. The standard of de facto in the designs of transport diesel engines was the presence of a turbocharger, and in recent years - and "intercooler" - devices, cooling air after compression turbocharger - to get a big one after cooling mass air (oxygen) in the combustion chamber with the former bandwidth of the collectors, and The supercharger made it possible to lift the specific power characteristics of mass diesel engines, as it allows you to skip a larger amount of air through cylinders.

For its basis, the design of the diesel engine is similar to the design of the gasoline engine. However, similar parts in a diesel engine are harder and more resistant to high compression pressures, having a place in a diesel engine, in particular, Hon on the surface of the cylinder mirror is more coarse, but the solidity of the walls of the cylinder block is higher. Piston heads, however, are specially designed to combat the combustion in diesel engines and are almost always designed for an increased degree of compression. In addition, the piston heads in the diesel engine are above (for a car diesel engine) of the upper plane of the cylinder block. In some cases, in obsolete diesel engines - piston heads contain a combustion chamber ("direct injection").

Scope of application

Diesel engines are used to drive stationary power plants, on rail (diesel locomotive, dieselosis, diesel trains, autodresions) and firefight (cars, buses, trucks) vehicles, self-propelled machines and mechanisms (tractors, asphalt rollers, scrapers, etc.), as well as in shipbuilding as the main and auxiliary engines.

Myths about diesel engines

Diesel engine with turbocharged

• The diesel engine is too slow.

Modern diesel engines with a turbocharger system are much more efficient than their predecessors, and sometimes exceed their gasoline atmospheric (without turbocharging) fellow with the same volume. This is talking about this Diesel prototype Audi R10, which won the 24-hour race in Le Mans, and new BMW engines that are not inferior at the power of atmospheric (without turbocharging) gasoline and at the same time have a huge torque.

• The diesel engine works too loudly.

Loud engine operation indicates incorrect operation and possible faults. In fact, some old diesel engines with direct injection are really distinguished by a very rigid job. With the advent of the battery fuel systems of high pressure ("Common-Rail") in diesel engines, it was possible to significantly reduce the noise, primarily due to the separation of one injection pulse to several (typically - from 2 to 5 pulses).

• The diesel engine is much more economical.

The main efficiency is due to a higher efficiency of the diesel engine. On average, modern diesel consumes fuel up to 30% less. The life of the diesel engine is greater than gasoline and can reach 400-600 thousand kilometers. Spare parts for diesel engines are somewhat more expensive, the cost of repair is as higher, especially fuel equipment. According to the above reasons, the cost of operation of the diesel engine is somewhat less than that of gasoline. Saving compared with gasoline engines increases in proportion to power, which determines the popularity of the use of diesel engines in commercial transport and heavy vehicles.

• The diesel engine cannot be converted to the use of cheaper gas as fuel.

From the first moments of the construction of diesel engines, a huge number of them, designed to work on gas of various compositions, was built and built. There are mainly two ways to transfer diesel engines for gas. The first method is that the cylinders are served the depleted gas-air mixture, it is compressed and a small rigorous jet of diesel fuel is mounted. The engine operating in this way is called gas dial. The second method consists in converting a diesel engine with a decrease in the degree of compression, the installation of the ignition system and, in fact, with the construction of a gas engine instead of a diesel engine based on it.

Recordsmen

The largest / powerful diesel engine

Configuration - 14 cylinders in a row

Operating volume - 25,480 liters

Cylinder diameter - 960 mm

Piston stroke - 2500 mm

Average efficient pressure - 1.96 MPa (19.2 kgf / cm²)

Power - 108 920 hp at 102 rpm. (return from liter 4.3 hp)

Torque - 7 571 221 N · m

Fuel consumption - 13,724 liters per hour

Dry mass - 2300 tons

Dimensions - Length 27 meters, Height 13 meters

The largest diesel engine for a truck

MTU 20V400. Designed to install for career dump truck BelAZ-7561.

Power - 3807 hp at 1800 rpm. (Specific fuel consumption at rated power 198 g / kW * h)

Torque - 15728 N · m

The largest / powerful serial diesel engine for serial passenger car

Audi 6.0 V12 TDI Since 2008, it is installed on the Audi Q7 car.

Configuration - 12 cylinders V-shaped, the angle of collapse is 60 degrees.

Operating volume - 5934 cm³

Cylinder diameter - 83 mm

Piston stroke - 91.4 mm

Compression ratio - 16

Power - 500 hp at 3750 rpm. (return from the liter - 84.3 hp)

Torque - 1000 nm in the range of 1750-3250 rpm.