Consider the history of creation, the principle of operation diesel engine, let's try to understand the reasons for its popularity, its design features, advantages, disadvantages and scope.
Rudolf Diesel assembled his brainchild in 1897. It was a smoothly running, extremely simple, easy-to-operate mechanism.
The technical documentation for the invention fit on 13 pages - Rudolf Diesel drew and described the engine on them, which was then named after him.
Thus began the story, as a result of which we now have millions of trucks, cars and ships with diesel engines.
Working principle of diesel engine
And yet, what is the principle of operation of a diesel engine? The principle of operation of a diesel engine is the compression ignition of fuel in the combustion chamber when mixed with a heated air mixture.
The mixture is supplied separately - first air is injected, then the piston compresses it and at top dead center fuel is injected through the nozzle
Air, in the process of compression, is heated to 800ºС, fuel is supplied with a pressure of up to 30 MPa, self-ignition occurs.
This process is accompanied by vibrations and noise. That is, a diesel engine is noisier than a gasoline engine.
The principle of operation of a diesel engine allows engines to be both two-stroke and four-stroke, but the majority of cars are still equipped with four-stroke engines.
In a two-stroke diesel engine, compared to a four-stroke one, due to a different principle of operation, the combination of two cycles, intake and exhaust (purge).
The two-stroke version is about one and a half times more powerful than the four-stroke version of the same size.
Diesel engine design
A diesel engine is almost the same as a gasoline engine - it only does not have an ignition system, and the principle of operation of a diesel engine is to ignite the fuel mixture not from a spark plug, but from air heated by high pressure.
True, high pressure (up to 30 atm.) in the combustion chamber implies increased requirements for details.
According to the design of the combustion chambers, diesel engines are divided into 3 types:
- Divided vortex combustion chamber;
- Undivided combustion chamber;
- Divided prechamber.
In such a device, the fuel mixture is supplied not to the main, but to an additional vortex chamber.
It is located in the cylinder head and is connected to the cylinder through a special channel. Ignition occurs in the vortex chamber and spreads to the main chamber. 
Undivided combustion chamber
With this design, the chamber is located in the piston, and the fuel mixture enters the cavity above the piston.
This version of the chamber allows you to reduce fuel consumption, but increases the noise level during engine operation. 
Divided prechamber
The diesel engine is equipped with a plug-in prechamber, it is connected to the cylinder by channels of small cross section.
The size and shape of the channels affect the speed of movement of gases during the combustion of fuel, while reducing noise and toxicity, increasing the resource. 
Any diesel engine has a special fuel system. The high-pressure system delivers the right amount of fuel mixture to the cylinders. Let's look at its elements.
The main elements of the fuel system
- high pressure fuel pump ();
- fuel filter;
injection pump
Pump supplies fuel to the injectors in an amount that depends on the speed, the position of the regulator lever and the turbo boost pressure indicators.
In modern diesel engines, two systems of fuel pumps are used - in-line (plunger) or distribution. More about pumps.
Several other pumps are used in a modern injection system, they are called main.
In the Common Rail system, the injection pump pumps fuel into the rail, where pressure is maintained in all channels up to the injectors.
Special nozzles are electronically controlled and open at the right time to inject fuel into the combustion chamber. You can read about this system.
Fuel filter
The filter is set based on the engine model. Its function is to separate and remove water from diesel fuel and excess air from the system.
nozzles
To supply the fuel mixture to the combustion chambers, two types of nozzles are used - with multi-hole and font distributors.
The nozzle distributor determines the shape of the flame required for a more efficient ignition process.
Preheating
For a cold start of a diesel engine, preheating is used. It is provided by glow plugs installed in the combustion chamber.
When starting, the glow plugs heat up to 900ºС, heating the air mixture that enters the chamber.
The heating system makes it possible to safely start even at the lowest temperatures.
Turbocharging
Turbocharging in diesel engines increases power and efficiency.
With an increase in air supply, an increased pressure in the cylinders is provided, respectively, the combustion of the mixture improves, thereby increasing engine power.
To obtain optimum pressure supercharging in all operating modes, a turbocharger (turbine) is used.
Diesel advantages and disadvantages
Advantages
The main advantage of a diesel engine is its high-torque power.. It is able to develop high power low revs, easily tolerates overloads, sudden braking and starts.
The second plus is economy.. A liter of diesel costs a little less than a liter of high-octane gasoline, although fuel sellers shamelessly equate it with the most expensive gasoline.
Coefficient useful action for a diesel engine at medium speeds it reaches 45 percent, and with a turbocharger it goes up to 50, for a gasoline engine such figures are not realistic at all. In addition, diesel consumes less fuel.
The third plus is environmental friendliness. The diesel engine has lower toxicity of exhaust gases.
The next advantage is durability and reliability., since diesel fuel at the same time and lubricant protecting engine parts from wear.
disadvantages
As for the shortcomings, one of the most significant is poor frost resistance. Summer fuel becomes thick at minus 5°C, winter fuel at minus 35°C.
Repair of a diesel and gasoline engine is approximately equivalent in cost if the high-pressure fuel pump does not fail. In this case, the owner gets into serious money. And it breaks down from low-quality domestic diesel fuel. In turn, good imported fuel is already a slightly different price.
Diesel engine is good at low and medium speeds. The desire to squeeze the maximum speed out of it brings rapid wear of components and parts.
And a car in a diesel version can cost a third more than a gasoline counterpart.
The turbodiesel has its drawbacks - the resource of the turbocharger is less than the resource of the engine itself. Usually it is no more than 150,000 kilometers. In addition, the turbine makes high demands on the quality of engine oil.
Well, at the expense of the smell of exhaust from diesel engine. Perhaps for someone this is not critical, but the smell is there, and at the same time quite unpleasant.
Areas of use
Diesel engines currently use:
- on heavy trucks;
- on stationary power plants;
- on cars and trucks;
- on diesel locomotives and ships;
- on agricultural, special and construction equipment.
Well, you have learned what a diesel engine is, how many big pluses and small minuses it has.
Now, knowing how a diesel engine works, you will wonder what next car buy: .
Just visit the site!
It’s worth starting with the fact that the efficiency of a diesel engine is much higher than that of a gasoline counterpart. Simply put, this engine consumes much less fuel. The designers managed to achieve a similar result by creating a unique design.
Important! The principle of operation of a diesel engine is very different from a gasoline engine.
Of course, modern gasoline engines have a wide variety of technological innovations. Suffice it to recall direct injection. Despite this, the efficiency of a gasoline engine is about 30 percent. For a diesel engine, this parameter reaches 40. If we recall turbocharging, then the figure can reach up to 50%.
It is not surprising that diesel engines are gradually conquering Europe. Expensive gasoline encourages buyers to buy more economical cars. Manufacturers monitor changes in consumer preferences in real time, introducing appropriate adjustments to the production process.
Unfortunately, the design of a diesel engine is not without flaws. One of the most significant is a lot of weight. Of course, engineers have come a long way, gradually reducing the weight of the motor, but everything has a limit.
The fact is that in the device of a diesel engine, all parts must be adjusted to each other as accurately as possible. If in gasoline analogues the possibility of a slight backlash is allowed, then everything is different here. As a result, at the very beginning of the introduction of the technology, diesel units were installed only on big cars. Suffice it to recall the same trucks of the beginning of the last century.
History of creation
It's hard to imagine, but the first workable diesel engine was designed by engineer Rudolf Diesel back in the 19th century. Then ordinary kerosene was used as fuel.
With the development of technology, scientists began to experiment. As a result, what kinds of fuels were not used to achieve best results. For example, for some time the engines were fueled with rapeseed oil and even crude oil. Of course, such an approach could not give really serious achievements.
Many years of research led scientists to the idea of using fuel oil and diesel fuel. Their low cost and good flammability made it possible to seriously compete with gasoline counterparts.
Attention! Fuel oil and diesel fuel are made without the use of complex technological processes. This is the reason for their low prices. In fact, they are a by-product of oil refining.
Initially, fuel injection systems in diesel engines were extremely imperfect. This did not allow the use of units in machines that worked at high speeds.
The first samples of cars equipped with diesel engines appeared in the 20s of the last century. It was freight and public transport. Prior to this, motors of this class were used only on stationary machines or ships.
Only 15 years later, the first cars appeared that were powered by a diesel engine. Despite this, for a very long time, diesel, being powerful and immune to detonation, was not widely used in the automotive industry. The fact is that in the presence of significant advantages, the unit had a number of disadvantages, such as increased noise during operation and heavy weight.
Only in the 1970s, when oil prices began to rise, did everything change dramatically. Automakers and consumers have turned their eyes to cars, in their arrangement, having diesel engines. It was then that compact diesel engines first appeared.
diesel engine
Diesel engine device
The device of a diesel engine consists of four main elements:
- cylinders,
- pistons
- fuel injector,
- inlet and outlet valve.
Each structural element performs its task and has its own design features. In the process of development, this technology was supplemented with many details that made it possible to achieve much greater productivity, here are the main ones:
- fuel burner,
- intercooler.
Each of these parts has significantly increased the efficiency of the diesel engine.
Principle of operation
The diesel engine works by compression. Through this process, liquid under pressure enters the combustion chamber. Passing elements are injector nozzles.
Important! Fuel gets inside only when the air has the right compression force and high temperature.
The air must be hot enough for the fuel to ignite. Before getting inside, the liquid passes through a series of filters that trap foreign particles that can harm the system.
To understand the principle of operation of a diesel engine, you need to consider the entire process of supplying and igniting fuel from start to finish. At the initial stage, air is supplied through the intake valve. In this case, the piston moves down.
Some intake systems are additionally equipped with dampers. Thanks to them, two channels are created in the design through which air enters. As a result this process air masses are swirling.
Attention! The intake flaps can only be opened at high crankshaft speed.
When the piston reaches its top point, air is compressed 20 times. The maximum pressure is about 40 kilograms per square centimeter. In this case, the temperature reaches 500 degrees.
The nozzle injects fuel into the chamber in a strictly specified amount. Ignition occurs solely due to high temperature. It is this fact that explains the fact that there are no candles in the diesel engine device. Moreover, there is no ignition system as such.
Absence in design throttle valve allows you to develop a large torque. But the number of revolutions at the same time is at a consistently low level. In one cycle, several liquid injections can be carried out.
Down the piston pushes the pressure of expanding gases. The result of this process is that the crankshaft rotates. The connecting link in this microprocess is the connecting rod.
Having reached the bottom point, the piston rises again, thereby pushing out the already exhaust gases. They go out through the exhaust valve. This cycle is repeated over and over again in a diesel engine.
To reduce the percentage of soot in the gases that exit through exhaust system there is a special filter. It allows you to significantly reduce the harm caused to the environment.
Additional nodes
How a turbine works
The turbine in the device of a diesel engine can significantly increase the overall performance of the system. However, automotive engineers did not immediately come to this decision.
The impetus for the creation of a turbine and its implementation in general device diesel engine was that the fuel does not have time to completely burn out while the piston moves to the dead center.
The principle of operation of the turbine on a diesel engine is that this structural element allows for complete combustion of fuel. As a result, the power of the motor increases significantly.
The turbocharger device consists of the following elements:
- Two casings - one is attached to the turbine, the second to the compressor.
- Bearings are the support of the assembly.
- The protective function is performed by a steel mesh.
The entire cycle of the turbine of a diesel engine consists of the following stages:
- Air is sucked in by a compressor.
- The rotor is connected, which is driven by the turbine rotor.
- The intercooler cools the air.
- Air passes through several filters and enters through the intake manifold. At the end of this action, the valve closes. Opening occurs at the end of the working stroke.
- Exhaust gases pass through the turbine of a diesel engine, thereby exerting pressure on the rotor.
- At this stage, the speed of rotation of the turbine of a diesel engine can reach about 1500 revolutions per second. This causes the compressor rotor to rotate through the shaft.
This cycle is repeated over and over. Thanks to the use of a turbine, the power of a diesel engine increases.
Important! As the air cools, the density of the air increases.
The increase in air density allows it to be supplied in a much larger amount inside the engine. The increase in flow contributes to the fact that the fuel inside the system burns out completely.
Intercooler and nozzle
During compression, not only the density of the air increases, but also its temperature. Unfortunately, this greatly affects the durability of the diesel engine. Therefore, scientists invented such a device as an intercooler. It effectively reduces the temperature of the air stream.
Important! The intercooler works by cooling the air by heat transfer.
The device may have one or two nozzles. Their task is to spray and dose fuel. The principle of operation of the diesel engine injector is implemented due to the cam, which moves away from camshaft.
Attention! Diesel engine injectors operate in pulsed mode.
Results
Through the use of new technologies and additional components, a diesel engine allows you to achieve an amazing rate of efficiency from fuel combustion. This figure reaches 40-50 percent. Which is almost twice as much as in the gasoline counterpart.
Diesel engines for cars are different, and it's not just the volume and number of cylinders, so let's try to briefly review the modern market and find out which of the engines are the most reliable.
To whom did the ratings give leadership?
Associations with the word "diesel" among a resident of Russia are always unambiguous: the smell of diesel fuel from a passenger bus, black smoke from a passing truck, vintage jeans and watches of the brand of the same name. Nevertheless, for most Europeans, the word derived from the name of a German inventor is a synonym for a reliable, inexpensive and powerful “heart” of a car. In our country, its popularity is not so high, apparently due to weather conditions and knowledge that diesel fuel thickens in the cold.
Reliability ratings, and especially for cars, are a thankless task. How many opinions, so many lists, in which the compiler simply expresses his view on a particular subject. That is why we want to draw your attention to the fact that the rating below does not claim to become an indisputable truth, but is just an attempt to systematize the data, knowledge and (partially) personal point of view of the compiler.
In search of an answer to the question of which diesel engine occupies a leading position in the configuration of passenger cars, you can see that some ratings call the best products from Mercedes and BMW concerns. However, the situation in the world of the automotive industry today is somewhat different, let's try to figure it out.
As the ratings of the world's major car dealerships show, the days when passenger car diesel engines were reduced copies of units installed on heavy trucks are a thing of the past. The well-known Volkswagen concern, which developed the 1.9 TDI engine, was especially successful in the production of such engines. To date, it ranks first and is considered the most balanced in terms of dynamics and power.
Thanks to the latest engineering solutions, in particular, an updated turbine and an increase in pressure in the combustion chambers, managed not only to achieve unique environmental performance, but also to reduce. Moreover, the power remained at the same level (90–120 hp). The newest cars in the Passat series are now equipped with the highest performance engine (BlueMotion package). Fuel consumption is 3.3 liters per 100 km.
Diesel winners of the car market
The second place is occupied by a modification of the engine with three turbines, owned by the German company BMW. The first time this unit was introduced a few years ago. It has 6 cylinders and, having a volume of 3.0 liters, is capable of developing a power of 381 hp. with. Complete with these engines latest cars 5 and 7 series, as well as heavy crossovers with X5 and X6 indices. Convertibles with serial number 6 are equipped with a modification of it. True, it has two turbines, due to which the power is reduced to 313 hp. with.
Not so long ago, cars were presented to the court of potential buyers, whose engines have four turbines, and with a torque of 800 Nm, the power will be within 390–406 hp. with.
A car with a four-turbine engine
The third place in our rating was occupied by the American company of industrial diesel engines Cummins, which produced a super-powered engine commissioned by the well-known company Dodge. In fairness, it should be noted that overseas manufacturers did not pay too much attention to diesel engines, preferring to develop gasoline ones. However, the recent increasing demand for cars with units that consume diesel fuel has forced them to pay attention to the production of diesel engines.
The model proved to be quite powerful (240–275 hp), but in an attempt to occupy the “diesel” niche in the market, the Americans were cunning and passed off as their development by the Italian concern Fiat. The Maserati Ghibli was equipped with a model of such an engine, but due to the crisis, production was given to US industrialists.
This engine was recognized not only as the most environmentally friendly, but also the most innovative: in its production, metals used in the space industry and plasma fuel filters were used. The fact that the engine took only third place is a "merit" of a narrow focus. It is installed only on sports cars and pickups. dodge ram. In terms of efficiency, it can give odds to its competitors: the consumption is only 8.5 liters per 100 kilometers.
Who is not far behind the top three?
Bursting 20 years ago on the world automotive market the Koreans not only managed to take a worthy place on it, but also “move” the Japanese giants in the ranking. Having come a long way "from electric kettles to mining trucks", they also do not want to miss their benefits, which promises an increased demand for cars equipped with diesel engines.
As always, Asian manufacturers acted very cunningly: not wanting to overhaul production and compete with Europeans and Americans in the power of units, they managed to create a 1.7-liter engine that can produce 110–136 hp. with. Do not rush to wrinkle your nose contemptuously! With such rather modest (compared to products from other manufacturers) data, diesel Hyundai has such incredible torque that it is not inferior in dynamics gasoline units having a capacity of 150-170 liters. with.
I must say that such a unit is equipped Hyundai car i40 supplied to the European market. In Korea, diesel engines have somehow not found wide application (or the wave of “fashion” has not yet reached there), and therefore they are still installed only on export cars. Recently, the same unit appeared on a crossover with the ix35 index, and now it is equipped with such popular cars like Grandeur and Sonata. Fuel consumption, however, is more than that of competitors, but the Koreans do not seek to surprise anyone. Their mission is to deliver reliable workhorses capable of average fuel consumption, in this case 5.5 liters per 100 km.
Having “squeezed out” enough power from cars and won its cell on the market, the Japanese concern Toyota now makes no sense to prove something to anyone. The concept that manufacturers have thrown all their efforts into is ecology and economy while maintaining sufficient power. And they succeeded. Creating an engine for their compact car named Urban Cruiser, they thought that the residents of megacities would not only be convenient to move around the city, but also that a “calculator” would not turn on in their heads, calculating fuel costs.
One of the smallest to date diesel units- This is a 1.4 liter engine with a power of only 90 hp. with. This is the fifth place in our ranking. Such parameters, however, do not interfere with the creation of torque, which makes it easy to “pull” an all-wheel drive car. The consumption of diesel fuel, depending on the mode of travel, ranges from 4 to 6 liters per 100 km.
So which one is the most reliable?
Such a question is a bit naive, since this parameter depends on many factors, including driving style. But if you choose the best from the above list, then the reliability will be given to the Americans Cummins with a Dodge engine.
And it's not about power or fuel consumption per 100 km. Most likely, the materials used in production play a role. The cylinder block is made of high-carbon cast iron, capable of withstanding not only high pressure, but also significant temperature conditions. And its pistons are made of a special aluminum alloy, which is used in the details of spacecraft. This means that they are able to withstand both long-term operation under extreme conditions, and a sharp increase in load when changing speeds.
Also, the engine is equipped with a Common Rail fuel injection system, which, despite a rather capricious attitude to the quality of diesel fuel, not only significantly saves its consumption, but also plays a decisive role in reducing engine noise. It is with these engines that both sports cars and cars are equipped. off-road. That is, precisely those instances of the automotive industry, the operation of which takes place in extreme conditions, requiring from the motor not only unsurpassed power, but also impeccable reliability.
If we talk about the rating of cars that are suitable for Russian roads, it is best to pay attention to samples of Japanese production. Optionally, it will be Toyota (which, by the way, not a single Russian motorist has any complaints about the engine).
For our vast expanses, Mazda, Honda, Nissan or the newly revived Datsun will do just fine. The Subaru performed quite well.
The fact is that European cars equipped with a diesel engine are very sensitive to our diesel fuel, the cleaning quality of which leaves much to be desired. As numerous reviews of car owners show, japanese cars are less prone to malfunctions when using diesel fuel, thanks to numerous cleaning devices, electronic devices and built-in starting preheaters, which does not allow diesel fuel to solidify at low temperatures.
The principle of operation of which is based on the self-ignition of fuel when exposed to hot compressed air.
The design of a diesel engine as a whole is not much different from a gasoline engine, except that the diesel engine does not have an ignition system as such, since the fuel is ignited according to a different principle. Not from a spark, as in a gasoline engine, but from high pressure, which compresses air, causing it to become very hot. The high pressure in the combustion chamber imposes special requirements for the manufacture of valve parts that are designed to withstand more serious loads (from 20 to 24 units).
Diesel engines are used not only in trucks, but also in many models of cars. Diesels can run on various types of fuel - on rapeseed and palm oil, on fractional substances and on pure oil.
The principle of operation of a diesel engine
The principle of operation of a diesel engine is based on the compression ignition of fuel that enters the combustion chamber and mixes with a hot air mass. The working process of a diesel engine depends solely on the heterogeneity of fuel assemblies (fuel air mixture). The supply of fuel assemblies in this type of engine occurs separately.
First, air is supplied, which during the compression process is heated to high temperatures (about 800 degrees Celsius), then fuel is supplied to the combustion chamber under high pressure (10-30 MPa), after which it self-ignites.
The process of fuel ignition itself is always accompanied by a high level of vibration and noise, so diesel-type engines are noisier than gasoline counterparts.
A similar principle of operation of a diesel engine allows the use of more affordable and cheaper (until recently :)) types of fuel, reducing the level of costs for its maintenance and refueling.
Diesels can have both 2 and 4 working strokes (intake, compression, stroke and exhaust). Most cars are equipped with 4-stroke diesel engines.
Types of diesel engines
According to the design features of the combustion chambers, diesel engines can be divided into three types:
- With split combustion chamber. In such devices, fuel is supplied not to the main, but to the additional, the so-called. a swirl chamber, which is located in the head of the cylinder block and is connected to the cylinder by a channel. When it enters the vortex chamber, the air mass is compressed as much as possible, thereby improving the process of fuel ignition. The self-ignition process begins in the vortex chamber, then passes into the main combustion chamber.
- With undivided combustion chamber. In such diesel engines, the chamber is located in the piston, and fuel is supplied to the space above the piston. On the one hand, inseparable combustion chambers allow saving fuel consumption, on the other hand, they increase the noise level during engine operation.
- Prechamber engines. Such diesel engines are equipped with a plug-in prechamber, which is connected to the cylinder by thin channels. The shape and size of the channels determine the speed of movement of gases during the combustion of fuel, reducing the level of noise and toxicity, increasing the life of the engine.
Fuel system in a diesel engine
The basis of any diesel engine is its fuel system. Main task fuel system is the timely supply of the required amount of the fuel mixture under a given operating pressure.
Important elements of the fuel system in a diesel engine are:
- high pressure fuel pump (TNVD);
- fuel filter;
- nozzles
Fuel pump
The pump is responsible for supplying fuel to the injectors according to the set parameters (depending on the speed, the operating position of the control lever and the turbo boost pressure). In modern diesel engines, two types of fuel pumps can be used - in-line (plunger) and distribution.
The filter is an important part of a diesel engine. The fuel filter is selected strictly in accordance with the type of engine. The filter is designed to isolate and remove water from the fuel, and excess air from the fuel system.
nozzles
Nozzles are equally important elements of the fuel system in a diesel engine. Timely supply of the fuel mixture to the combustion chamber is possible only with the interaction of the fuel pump and injectors. In diesel engines, two types of nozzles are used - with a multi-hole and font distributor. The nozzle distributor determines the shape of the flame, providing a more efficient self-ignition process.
Cold start and turbocharged diesel engine
Cold start is responsible for the mechanism preheating. This is ensured by electrical heating elements- glow plugs that the combustion chamber is equipped with. When starting the engine, glow plugs reach a temperature of 900 degrees, heating the air mass that enters the combustion chamber. The glow plug is de-energized 15 seconds after the engine starts. Heating systems before starting the engine ensure its safe start even at low atmospheric temperatures.
Turbocharging is responsible for increasing the power and efficiency of a diesel engine. It provides the supply of more air for a more efficient process of combustion of the fuel mixture and increase the working power of the engine. A special turbocharger is used to ensure the required boost pressure of the air mixture in all operating modes of the engine.
It only remains to say that the debate over what is better for an ordinary motorist to choose as a power plant in his car, gasoline or diesel, has not subsided so far. Both types of engine have advantages and disadvantages and it is necessary to choose based on the specific operating conditions of the car.
Good day. I think a lot of people will be interested in this topic. Advantages and disadvantages ... All below.
In 1890, Rudolf Diesel developed the theory of the "economical thermal engine", which, due to the strong compression in the cylinders, greatly improves its efficiency. He received a patent for his engine on February 23, 1893. The first functioning example was built by Diesel by the beginning of 1897, and on January 28 of the same year it was successfully tested.
It is interesting that Diesel in his book, instead of the diesel fuel familiar to us, described coal dust as an ideal fuel. Experiments also showed the impossibility of using coal dust as a fuel - primarily because of the high abrasive properties.
But Ackroyd Stewart also considered the theory of the diesel engine. He did not consider the benefits of running from a high compression ratio, he simply experimented with the possibilities of eliminating spark plugs from the engine, i.e. he did not pay attention to the most great advantage- fuel efficiency. Perhaps this was the reason why the term “Diesel engine”, “diesel engine” or simply “diesel engine” is currently used, since the theory of Rudolf Diesel became the basis for creating modern engines with compression ignition. In the future, for about 20-30 years, such engines were widely used in stationary mechanisms and power plants of marine vessels, however, the fuel injection systems that existed at that time did not allow the use of diesel engines in high-speed units. The low speed of rotation, the significant weight of the air compressor necessary for the operation of the fuel injection system made it impossible to use the first diesel engines in vehicles.
In the 1920s, the German engineer Robert Bosch improved the built-in high-pressure fuel pump, a device that is still widely used today. Usage hydraulic system for pumping and fuel injection eliminated the need for a separate air compressor and made possible a further increase in rotational speed. High-speed diesel demanded in this form has become increasingly popular as power unit for auxiliary and public transport, however, the arguments in favor of electric ignition engines (traditional principle of operation, lightness and low cost of production) allowed them to be in great demand for installation in passenger and small trucks. In the 50s and 60s, diesel was installed in large quantities in trucks and vans, and in the 70s, after a sharp increase in fuel prices, the world's manufacturers of inexpensive small passenger cars are paying serious attention to it.
Work principles:
Four stroke cycle.
At first bar(intake stroke, piston down) Fresh air is drawn into the cylinder through the open intake valve.
At second measure(compression stroke, piston going up) the intake and exhaust valves are closed the air is compressed in volume by about 17 times (from 14:1 to 24:1), i.e. the volume becomes 17 times smaller than the total volume of the cylinder, and the air becomes very hot.
Right before the start third bar(stroke stroke, piston goes down) fuel is injected into the combustion chamber through the injector nozzle. During injection, the fuel is atomized into fine particles, which are evenly mixed with compressed air to create a self-igniting mixture. Energy is released during combustion when the piston begins its movement in the stroke of the power stroke.
The exhaust valve opens when fourth measure(exhaust stroke, the piston goes up) and the exhaust gases pass through the exhaust valve.
Duplex cycle.
The piston is at bottom dead center and the cylinder is filled with air. During the upward stroke of the piston, the air is compressed; near the top dead center, fuel is injected, which spontaneously ignites. Then there is a working stroke - the combustion products expand and transfer energy to the piston, which moves down. Near the bottom dead center, a purge occurs - the combustion products are replaced by fresh air. The cycle ends.
To carry out purge, purge windows are arranged in the lower part of the cylinder. When the piston is down, the windows are open. When the piston rises, it closes the windows.
Since the strokes are twice as frequent in a two-stroke cycle, you can expect a twofold increase in power compared to a four-stroke cycle. In practice, this cannot be realized, and a two-stroke diesel engine is more powerful than a four-stroke diesel of the same volume by a maximum of 1.6 - 1.7 times.
Currently, two-stroke diesel engines are widely used only on large marine vessels with a direct (gearless) propeller drive. When it is impossible to increase the speed of rotation, the two-stroke cycle is beneficial; such low-speed diesel engines have a power of up to 100,000 hp.
Advantages and disadvantages.
A gasoline engine is rather inefficient and is only capable of converting about 20-30% of the fuel's energy into useful work. A standard diesel engine, however, typically has an efficiency of 30-40%, turbocharged and intercooled diesels in excess of 50% (e.g. MAN S80ME-C7 consumes only 155g per kW, achieving an efficiency of 54.4%). The diesel engine, due to the use of high pressure injection, does not impose requirements on the volatility of the fuel, which allows the use of low-grade heavy oils in it.
Diesel engine cannot develop high revs- the mixture does not have time to burn out in the cylinders. This leads to a decrease in the specific power of the engine per 1 liter of volume, and hence to a decrease in the specific power per 1 kg of engine weight.
The diesel engine does not have a throttle valve, power control is carried out by regulating the amount of fuel injected. This results in no reduction in pressure in the cylinders at low speeds. This is why a diesel produces high torque at low rpm, which makes a car with a diesel engine more "responsive" in motion than the same car with gasoline engine. For this reason, at present most trucks equipped with diesel engines.
The obvious disadvantages of diesel engines are the need to use a high-power starter, turbidity and solidification of summer diesel fuel at low temperatures, the difficulty in repairing fuel equipment, since high-pressure pumps are devices made with high precision. Also, diesel engines are extremely sensitive to fuel contamination with mechanical particles and water. Such contaminants very quickly disable the fuel equipment. Repair of diesel engines, as a rule, is significantly more expensive than repair gasoline engines of the same class. Liter power diesel engines also generally inferior to those of gasoline engines, although diesel engines have more even torque in their operating range. The environmental performance of diesel engines was significantly inferior to gasoline engines until recently. On classic diesel engines with mechanically controlled injection, it is only possible to install oxidative exhaust gas converters (“catalyst” in common parlance), operating at exhaust gas temperatures above 300 ° C, which oxidize only CO and CH to carbon dioxide (CO2) harmless to humans and water. Also, these converters used to fail due to poisoning with sulfur compounds (the amount of sulfur compounds in the exhaust gases directly depends on the amount of sulfur in diesel fuel) and the deposition of soot particles on the catalyst surface. The situation began to change only in recent years in connection with the introduction of diesel engines of the so-called "Common-rail" system. In this type of diesel engines, fuel injection is carried out by electrically controlled nozzles. The supply of a control electrical impulse is carried out by the electronic unit control that receives signals from a set of sensors. The sensors monitor various engine parameters that affect the duration and timing of the fuel pulse. So, in terms of complexity, a modern - and as environmentally friendly as a gasoline - diesel engine is in no way inferior to its gasoline counterpart, and in a number of complexity parameters it significantly surpasses it. So, for example, if the fuel pressure in the injectors of a conventional diesel engine with mechanical injection is from 100 to 400 bar, then in latest systems"Common-rail" it is in the range from 1000 to 2500 bar, which entails considerable problems. Also, the catalytic system of modern transport diesel engines is much more complicated than gasoline engines, since the catalyst must “be able” to work under conditions of an unstable exhaust gas composition, and in some cases, the introduction of the so-called “ particulate filter". The "particulate filter" is similar to the conventional catalytic converter a structure installed between the diesel exhaust manifold and the catalyst in the exhaust gas stream. In the particulate filter develops heat, at which soot particles are able to be oxidized by residual oxygen contained in the exhaust gases. However, part of the soot is not always oxidized and remains in the "particulate filter", so the control unit program periodically switches the engine to the "particulate filter" cleaning mode by the so-called "post-injection", that is, the injection of additional fuel into the cylinders at the end of the combustion phase in order to raise the temperature of the gases, and, accordingly, clean the filter by burning the accumulated soot. The de facto standard in the design of transport diesel engines has become the presence of a turbocharger, and in recent years, the so-called "intercooler" - that is, a device that cools the air compressed by a turbocharger. The supercharger made it possible to raise the specific power characteristics of mass diesel engines, as it allows more air to pass through the cylinders during the working cycle.
And finally, the most interesting. MYTHS about diesel engines.
Diesel engine is too slow.
Modern turbocharged diesel engines are much more efficient than their predecessors, and sometimes outperform their naturally aspirated (non-turbocharged) gasoline counterparts with the same engine size. This is evidenced by the diesel prototype Audi R10, which won the 24-hour race at Le Mans, and new BMW engines, which are not inferior in power to atmospheric (non-turbocharged) gasoline and at the same time have huge torque.
The diesel engine is too loud.
A properly tuned diesel engine is only slightly “louder” than a gasoline one, which is noticeable only on idling. There is practically no difference in operating modes. A loud running engine indicates correct operation and possible malfunctions. In fact, the old diesels with mechanical injection really have a very tough job. Only with the advent of high-pressure common-rail fuel systems for diesel engines was it possible to significantly reduce noise, primarily by dividing one injection pulse into several (typically from 2 to 5 pulses).
The diesel engine is much more economical.
The times when diesel fuel was three times cheaper than gasoline are long gone. Now the difference is only about 10-30% in terms of fuel prices. Despite the fact that the specific heat of combustion of diesel fuel (42.7 MJ/kg) is less than that of gasoline (44-47 MJ/kg), the main efficiency is due to the higher efficiency of the diesel engine. On average, a modern diesel consumes up to 30% less fuel. The service life of a diesel engine is indeed much longer than a gasoline engine and can reach 400-600 thousand kilometers. [source not specified 211 days] Spare parts for diesel engines are also somewhat more expensive, as is the cost of repairs. Despite all of the above reasons, the cost of operating a diesel engine, if properly maintained, will not be much less than that of a gasoline engine. [source not specified 211 days]
The diesel engine does not start well in cold weather.
With proper operation and preparation for winter, there will be no problems with the engine. For example, the VW-Audi 1.9 TDI diesel engine (77 kW/105 hp) is equipped with a quick start: heating of glow plugs up to 1000 degrees is carried out in 2 s. The system allows you to start the engine in any climatic conditions without preheating.
A diesel engine cannot be converted to use cheaper gas as fuel.
The first examples of diesel engines running on cheaper fuel - gas, were pleased back in 2005 by Italian tuning companies that used methane as fuel. At present, options for the use of propane gas diesel engines have successfully proven themselves, as well as cardinal solutions for the conversion of a diesel engine into gas engine, which has an advantage over a similar engine converted from gasoline due to an initially higher compression ratio.
What about a diesel engine?