In September 1913, Rudolf Diesel was among the passengers on the Dresden ferry bound for England. It is known that he boarded the ship, and ... no one else saw him. The mysterious disappearance of the famous German engineer is still one of the most intriguing and mysterious stories of the 20th century.
The birth and childhood of a genius
On March 18, 1858, the future great German engineer was born into a family of emigrants from Germany. The man whose invention put him on a par with famous people late 19th and early 20th centuries. It was to Paris that Theodor Diesel and Elise Strobel moved from Augsburg (Germany).
Rudolf's father was a hereditary bookbinder, one of his passions was the invention of toys. So, from early childhood, Rudolf Diesel begins to join the work, delivering books bound by his father to customers around the French capital. It is possible that Rudolf Diesel's first acquaintance with the world of technology took place in a technical museum, which was located not far from his home.
Every weekend, the father took the boy to the museum hall, where there were steam engines, the history of which began in 1770. Life went on as usual, measured and calm. The family of hardworking Germans did not have much wealth, but they did not live in poverty either.
Forced departure
It all ended in 1870 with the outbreak of the Franco-Prussian War. It is becoming unsafe for ethnic Germans in Paris to live. Theodor Diesel was forced to leave all his property, and together with his wife and 12-year-old son Rudolph, move to London. German troops at that time completely occupied the capital of France. The capital of Great Britain greeted the new residents unfriendly.
The Diesel family was in great need. There was no work, I had to survive on random orders for book binding. Then, in 1871, the family decided to send the young Rudolf Diesel to Augsburg to continue his studies, to his mother's brother, mathematics professor Christoph Barnekel.
Rudolf Diesel: biography of the future inventor
Before leaving, Rudolf firmly promised his parents that after graduation he would return home to help his father. However, following his son, two years later, his parents moved to Augsburg.
The family of Professor Barnekel met their nephew with warmth, the boy was surrounded by care and attention. Rudolf's abilities fascinated the professor, for which his uncle allowed him to use his extensive library. Rudolf's first occupation in the professor's family was the binding of all old books, an art taught to him by his father. Communication with an educated relative undoubtedly benefited the young man. Today the whole world knows who invented diesel engine. And then everything was just beginning.
Upon the arrival of his nephew in Germany, Professor Barnekel arranges the boy in a real school, which Rudolf Diesel graduates as the best student. After primary education, the young talent entered the Augsburg Polytechnic School in 1873, from which he graduated two and a half years later. top scores. The next step for the young scientist is to enter the Munich Higher Technical School, which was successfully completed in 1880.
The Technical University of Munich in Bavaria (Germany) still keeps in its museum the results of the final exams of the student Rudolf Diesel, which no student in the entire almost one and a half century history of the university can surpass.
The meeting that changed his life
During his studies, Rudolf Diesel met a famous German engineer, a developer of refrigeration equipment, Professor Carl von Linde. It so happened that due to the disease of typhoid fever, student Diesel did not manage to pass the exams to the professor on time. Rudolph was forced to leave the university for a while and go to practice in Switzerland, getting a job at the engineering company of the Schulzer brothers.
A year later, Diesel returns to Germany, where he successfully completes the educational process by passing the final exams to Professor Carl von Linde. By that time, the mentor decides to leave teaching and come to grips with applied research in the Linde Refrigerators company organized by him. Rudolf Diesel gets a job in the Paris branch of the company as a manager.
For ten years, Rudolf Diesel has improved his knowledge in the field of thermodynamics. A mechanical refrigerator - that's what German inventors have been working on all this time in the company of Karl Linde. The principle of operation of the refrigeration plant was the evaporation and condensate of ammonia using a mechanical pump.
Even while studying at the University, R. Diesel was worried about the problem of an autonomous power source for production. The Industrial Revolution was based on inefficient and unwieldy steam engines whose 10 percent performance factor (COP) clearly did not meet growing energy needs. The world needed compact and cheap energy sources.
Diesel engine: first working copy
In addition to the main work, Rudolf Diesel conducted Scientific research to create an efficient thermal device that would convert thermal energy into mechanical energy. In his laboratory experiments, Rudolf initially used ammonia as the working fluid of the installation. Coal powder was used as fuel.
According to theoretical calculations, the engine of Rudolf Diesel was supposed to work from compression in the working chamber of the body, which, when combined with fuel, would create a critical temperature for ignition.
Already during the experiments, it was found that the diesel engine prototypes had a slight advantage over steam plants. This inspired the inventor for further work and experiments.
One day, work on the creation of a diesel engine almost became fatal for its inventor. The explosion of the car almost led to the death of Rudolf Diesel. The German engineer was hospitalized in one of the Parisian clinics. During the explosion, Rudolph received damage to the eyeball. Until the end of his life, this problem accompanied the inventor.
Looking ahead, it should be noted that in 1896 Rudolf Diesel invented his first working copy, which he presented to the public. With the financial support of the Schulzer brothers and Friedrich Krupp, the world saw an engine with a power of 20 Horse power with an efficiency of 26% with a weight of a mechanical unit of five tons. Today, this miracle of technological progress can be contemplated among the exhibits of the Machine-Building Museum in the city of Augsburg (Germany).
Berlin branch
After a partial restoration of vision in a Paris clinic, Rudolf, at the invitation of his teacher Carl von Lind, headed the Berlin branch of the company. Inspired by success, Rudolf Diesel creates an industrial design of the engine, which was a commercial success. The inventor called the new power plant an atmospheric gas engine.
However, this name did not take root for a long time, and the invention was simply called "diesel" in honor of the creator of the unit. Numerous contracts, financial flows and steady demand for a new invention force Diesel to leave the Karl von Lind branch and open his own diesel engine factory.
financial success
Could the parents, sending their son to study with his uncle, imagine that by the age of 40 he would become known to the whole world? In the autumn of 1900 in London appears new company for the industrial production of diesel engines.
The further chronology of events unfolds very rapidly:
- In 1903, the world saw the first ship powered by Rudolf Diesel.
- In 1908, the automobile industry received a compact diesel engine for commercial vehicles.
- In 1910, the first locomotive with a diesel engine left the railway depot in England.
- The German company "Mercedes" began to produce its cars exclusively with diesel engines.
By that time, Rudolf Diesel had achieved success not only in work. The personal life of the inventor has developed quite successfully. loving wife and three children inspired him to further work.
world crisis
The largest engineering companies in Europe and the United States of America were in line to acquire licenses for the production of diesel engines. The world press constantly fueled interest in the invention of Rudolf Diesel, giving flattering characteristics to the advantages of the new unit over other power plants.
R. Diesel became very rich. Alphonse Bush, an American beer tycoon, offered the designer one million dollars for the right to manufacture engines in the United States. But it all ended overnight.
In 1913, a global crisis broke out. The inept distribution of financial flows led to the gradual bankruptcy of Diesel's enterprises.
The mystery of the disappearance
On September 29, 1913, the Dresden steamer departed Antwerp for London. Among the passengers was Rudolf Diesel. How the great industrialist and inventor of the engine died is still a mystery.
It is known that R. Diesel went to England to open a new plant of Consolidated Diesel Manufacturing, where his engines were to be produced. However, there was no passenger with the surname Diesel at the final destination ...
The same year it was successfully tested. Diesel actively engaged in the sale of licenses for new engine. Despite the high efficiency and ease of use compared to a steam engine, the practical use of such an engine was limited: it was inferior to steam engines of that time in terms of size and weight.
The first Diesel engines ran on vegetable oils or light petroleum products. Interestingly, he initially proposed 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 of both the dust itself and the ash resulting from combustion; there were also big problems with the supply of dust to the cylinders.
Principle of operation
Four stroke cycle
- 1st measure. Inlet. Corresponds to 0° - 180° crankshaft rotation. Through the open ~345-355° inlet valve, air enters the cylinder, at 190-210° the valve closes. At least up to 10-15 ° of rotation of the crankshaft, the exhaust valve is simultaneously open, the time of joint opening of the valves is called valve overlap .
- 2nd beat. Compression. Corresponds to 180° - 360° crankshaft rotation. The piston, moving to the TDC (top dead center), compresses the air 16 (in low-speed) -25 (in high-speed) times.
- 3rd beat. Working stroke, extension. Corresponds to 360° - 540° crankshaft rotation. When fuel is sprayed into hot air fuel combustion is initiated, that is, its partial evaporation, the formation of free radicals in the surface layers of droplets and in vapors, and finally, it flares up and burns out as it comes from the nozzle, combustion products, expanding, move the piston down. The injection and, accordingly, the ignition of the fuel occurs a little earlier than the moment the piston reaches the dead center due to some inertia of the combustion process. The difference from ignition timing in gasoline engines is that the delay is necessary only because of the presence of the initiation time, which in each particular diesel engine is a constant value and cannot be changed during operation. Combustion of fuel in a diesel engine thus occurs for a long time, as long as the supply of a portion of fuel from the nozzle lasts. As a result, the working process proceeds at a relatively constant gas pressure, due to which the engine develops a large torque. Two important conclusions follow from this.
- 1. The combustion process in a diesel engine lasts exactly as long as it takes to inject a given portion of fuel, but not longer than the working stroke.
- 2. The fuel/air ratio in the diesel cylinder can differ significantly from the stoichiometric one, and it is very important to provide an excess of air, since the flame of the torch occupies a small part of the volume of the combustion chamber and the atmosphere in the chamber must provide the required oxygen content to the last. If this does not happen, there is a massive release of unburned hydrocarbons with soot - "the diesel locomotive" gives "bear".).
- 4th beat. Release. Corresponds to 540° - 720° crankshaft rotation. The piston goes up, through the exhaust valve open at 520-530 °, the piston pushes the exhaust gases out of the cylinder.
Depending on the design of the combustion chamber, there are several types of diesel engines:
- Diesel with undivided chamber: the combustion chamber is made in the piston, and the fuel is injected into the space above the piston. The main advantage is the minimum fuel consumption. Flaw - increased noise("hard work"), especially on Idling. Currently, intensive work is underway to eliminate this shortcoming. For example, a Common Rail system uses (often multi-stage) pre-injection to reduce harshness.
- Split chamber diesel: fuel is supplied to the additional chamber. In most diesel engines, such a chamber (it is called a vortex or prechamber) is connected to the cylinder by a special channel so that when compressed, the air entering this chamber swirls intensively. This contributes to good mixing of the injected fuel with air and more complete combustion of the fuel. Such a scheme has long been considered optimal for light diesel engines and has been widely used in passenger cars. However, due to the worse efficiency, the last two decades have been actively replacing such diesel engines with single-chamber engines and Common Rail fuel supply systems.
push cycle
Purge of a two-stroke diesel engine: at the bottom - purge windows, the exhaust valve at the top is open
In addition to the four-stroke cycle described above, a two-stroke cycle can be used in a diesel engine.
During the working stroke, the piston goes down, opening the outlet windows in the cylinder wall, exhaust gases exit through them, the inlet windows open at the same time or somewhat later, the cylinder is blown with fresh air from the blower - carried out purge combining the intake and exhaust strokes. When the piston rises, all windows close. From the moment the inlet windows close, compression begins. Just before reaching TDC, fuel is sprayed from the nozzle and lights up. An expansion occurs - the piston goes down and opens all the windows again, etc.
Purge is innate weak link two stroke cycle. The purge time, in comparison with other cycles, is small and cannot be increased, otherwise the efficiency of the stroke will decrease due to its shortening. In a four-stroke cycle, half of the cycle is allotted for the same processes. It is also impossible to completely separate the exhaust and fresh air charge, so part of the air is lost, going straight into exhaust pipe. If the change of cycles is provided by the same piston, there is a problem associated with the symmetry of opening and closing windows. For better gas exchange, it is more advantageous to have an advance opening and closing of the exhaust windows. Then the exhaust, starting earlier, will provide a decrease in the pressure of the residual gases in the cylinder by the beginning of the purge. With the exhaust windows closed earlier and the intake windows still open, the cylinder is recharged with air, and if the blower provides excess pressure, it becomes possible to pressurize.
Windows can be used both for exhaust gases and for fresh air intake; such a purge is called slot or window. If the exhaust gases are vented through a valve in the cylinder head and the windows are only used to let in fresh air, the purge is called valve-slot. There are engines where in each cylinder there are two counter-moving pistons; each piston controls its windows - one inlet, the other outlet (Fairbanks-Morse - Junkers - Koreyvo system: diesel engines of this system of the D100 family were used on diesel locomotives TE3, 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 strokes occur twice as often as in a four-stroke, but due to the presence of a purge, 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 slow moving two-stroke diesels very widely used on large marine vessels with direct (gearless) drive propeller. Due to the doubling of the number of strokes at the same speed, the two-stroke cycle is beneficial when it is impossible to increase the speed, in addition, a two-stroke diesel engine is technically easier to reverse; such low-speed diesel engines have a power of up to 100,000 hp.
Due to the fact that it is difficult to organize a purge of the vortex chamber (or prechamber) in a two-stroke cycle, 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 typical, which uses a steel head and an duralumin skirt. The main purpose of this complication of the design is to reduce total weight piston while maintaining the maximum possible heat resistance of the bottom. Oil-cooled liquid-cooled designs are very often used.
In a separate group are four-stroke engines, containing in the design of the crosshead . In crosshead engines, the connecting rod is connected to the crosshead - a slider connected to the piston by a rod (rolling pin). The crosshead works on its guide - the crosshead, without impact elevated temperatures, completely eliminating the effect of lateral forces on the piston. This design is typical for large long-stroke marine engines, often - double action, the piston stroke in them can reach 3 meters; trunk pistons of such dimensions would be overweight, trunks with such a friction area would significantly reduce the mechanical efficiency of a diesel engine.
Reversible motors
The combustion of the fuel injected into the diesel cylinder occurs as it is injected. Because the diesel engine produces a high torque at low revs, which makes a diesel-powered vehicle more responsive in motion than the same gasoline-powered vehicle. For this reason, and due to the higher efficiency, most trucks are currently equipped with diesel engines.. For example, in Russia in 2007, almost all trucks and buses were equipped with diesel engines (the final transition of this vehicle segment from gasoline engines to diesel engines was planned to be completed by 2009) . This is also an advantage in marine engines, as high torque at low rpm makes it easier to use the engine's power efficiently, and higher theoretical efficiency (see Carnot cycle) gives higher fuel efficiency.
Compared to gasoline engines, exhaust gases diesel engines tend to have less carbon monoxide (CO), but now, due to 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 (HC or CH), oxides (oxides) of nitrogen (NOx) and soot (or its derivatives) in the form of black smoke. The most polluting vehicles in Russia are truck and bus diesels, which are often old and unregulated.
Other important aspect A safety concern is that diesel fuel is non-volatile (i.e. does not evaporate easily) and thus diesel engines are much less likely to catch fire, especially since they do not use an ignition system. Together with high fuel efficiency, this has led to wide application diesel engines on tanks, since in everyday non-combat operation the risk of a fire in the engine compartment due to fuel leaks was reduced. The lower fire hazard of a diesel engine in combat conditions is a myth, since when penetrating armor, a projectile or its fragments have a temperature that is much higher than the flash point of diesel fuel vapors and can also quite easily set fire to the leaked fuel. Detonation of a mixture of diesel fuel vapors with air in a punched fuel tank in its consequences, it is comparable to the explosion of ammunition, in particular, in T-34 tanks, it led to a rupture welds and knocking out the upper frontal part of the armored hull. On the other hand, a diesel engine in tank building is inferior to a carburetor in terms of specific power, and therefore in a number of cases ( high power with a small volume of the engine compartment) it may be more advantageous to use a carburetor power unit(although this is typical for too light combat units).
Of course, there are also disadvantages, among which is the characteristic knock of a diesel engine during its operation. However, they are noticed mainly by owners of cars with diesel engines, and are almost invisible to an outsider.
The obvious disadvantages of diesel engines are the need to use a starter high power, turbidity and hardening (waxing) of summer diesel fuel at low temperatures, the complexity and higher price in the repair of fuel equipment, since pumps high pressure are precision devices. Also, diesel engines are extremely sensitive to fuel contamination with mechanical particles and water. Repair of diesel engines, as a rule, is much more expensive than the repair of gasoline engines of a similar class. The liter capacity of diesel engines is also usually inferior to that of gasoline engines, although diesel engines have more even and higher torque in their displacement. 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 operating at exhaust gas temperatures above 300 ° C, which oxidize only CO and CH to carbon dioxide (CO 2) and water that are harmless to humans. Also, these converters used to fail due to poisoning with sulfur compounds (the amount of sulfur compounds in 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 electronically controlled nozzles. The supply of a control electrical impulse is carried out by an electronic control unit 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 parameters (complexity) 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 (approximately equivalent to "atmospheres"), 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 in conditions of an unstable composition. exhaust gases, and in some cases, the introduction of the so-called " particulate filter» (DPF - particulate filter). The "particulate filter" is similar to the conventional catalytic converter structure between exhaust manifold diesel and catalyst in the exhaust stream. A high temperature develops in the particulate filter, at which soot particles can 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, 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 - and " intercooler" - a device that cools the air after turbocharger compression - so that after cooling to get a large mass air (oxygen) in the combustion chamber at the same bandwidth collectors, and 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.
Basically, the design of a diesel engine is similar to that of a gasoline engine. However, similar parts of a diesel engine are heavier and more resistant to high compression pressures that occur in a diesel engine, in particular, the hone on the surface of the cylinder mirror is rougher, but the hardness of the cylinder block walls is higher. Piston heads, however, are specially designed for the combustion characteristics of diesel engines and are almost always designed for higher compression ratios. In addition, the piston heads in a diesel engine are higher (for automotive diesel) of the upper plane of the cylinder block. In some cases - in older diesel engines - the piston heads contain a combustion chamber ("direct injection").
Applications
Diesel engines are used to drive stationary power plants, on rail (diesel locomotives, diesel locomotives, diesel trains, railcars) and trackless (cars, buses, trucks) Vehicle Oh, self-propelled vehicles and mechanisms (tractors, asphalt rollers, scrapers, etc.), as well as in shipbuilding as main and auxiliary engines.
Myths about diesel engines
Turbocharged diesel engine
- 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 of the same displacement. This is evidenced by the Audi R10 diesel prototype, which won the 24-hour race at Le Mans, and the new BMW engines, which are not inferior in power to naturally aspirated (non-turbocharged) gasoline engines and at the same time have huge torque.
- The diesel engine is too loud.
Loud engine operation indicates improper operation and possible malfunctions. In fact, some old diesels with direct injection really different very hard work. With the advent of high-pressure common-rail fuel systems, diesel engines have been able 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 main economy 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 longer than a gasoline engine and can reach 400-600 thousand kilometers. Spare parts for diesel engines are somewhat more expensive, the cost of repairs is also higher, especially for fuel equipment. For the above reasons, the cost of operating a diesel engine is somewhat less than that of a gasoline engine. Savings compared to gasoline engines increase in proportion to power, which determines the popularity of diesel engines in commercial vehicles and heavy vehicles.
- A diesel engine cannot be converted to use cheaper gas as fuel.
From the first moments of the construction of diesel engines, a huge number of them were built and are being built, designed to work on gas of different composition. There are basically two ways to convert diesel engines to gas. The first method is that a lean gas-air mixture is supplied to the cylinders, compressed and ignited by a small pilot jet of diesel fuel. An engine operating in this way is called a gas-diesel engine. The second way is to convert a diesel engine with a reduction in the compression ratio, install an ignition system and, in fact, build a gas engine instead of a diesel engine based on it.
record holders
Largest/Most Powerful Diesel Engine
Configuration - 14 cylinders in line
Working volume - 25 480 liters
Cylinder diameter - 960 mm
Piston stroke - 2500 mm
Average effective pressure - 1.96 MPa (19.2 kgf / cm²)
Power - 108,920 hp at 102 rpm. (recoil per liter 4.3 hp)
Torque - 7 571 221 Nm
Fuel consumption - 13,724 liters per hour
Dry weight - 2300 tons
Dimensions - length 27 meters, height 13 meters
The largest diesel engine for a truck
MTU 20V400 designed for installation on a BelAZ-7561 mining dump truck.
Power - 3807 hp at 1800 rpm. ( Specific consumption fuel at rated power 198 g/kW*h)
Torque - 15728 Nm
The largest / most powerful serial diesel engine for a serial passenger car
Audi 6.0 V12 TDI since 2008 it has been installed on the Audi Q7.
Configuration - 12 cylinders V-shaped, camber angle 60 degrees.
Working volume - 5934 cm³
Cylinder diameter - 83 mm
Stroke - 91.4 mm
Compression ratio - 16
Power - 500 hp at 3750 rpm. (return per liter - 84.3 hp)
Torque - 1000 Nm in the range of 1750-3250 rpm.
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 fuel ignition occurs 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 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 high levels of vibration and noise, so engines diesel type are noisier than their petrol 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. The main task of the 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 set parameters(depending on the speed, the operating position of the control lever and the turbocharging 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 electric heating elements - glow plugs, which are equipped with a combustion chamber. 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 provide it safe launch 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. To provide desired pressure pressurization of the air mixture in all operating modes of the engine, a special turbocharger is used.
It remains only to say that disputes over what is better for an ordinary motorist to choose as power plant in your car, petrol or diesel, do not subside until now. Both types of engine have advantages and disadvantages and it is necessary to choose based on the specific operating conditions of the car.
Very common in cars. Many models have at least one option in the engine range. And this is without taking into account trucks, buses and construction equipment, where they are used everywhere. Next, we consider what a diesel engine is, design, principle of operation, features.
Definition
This unit is the operation of which is based on the self-ignition of atomized fuel from heating or compression.
Design features
The gasoline engine has the same structural elements as diesel. The scheme of functioning as a whole is also similar. The difference lies in the processes of formation of the air-fuel mixture and its combustion. In addition, diesel engines are more durable parts. This is due to about twice the compression ratio of gasoline engines (19-24 versus 9-11).
Classification
According to the design of the combustion chamber, diesel engines are divided into options with a separate combustion chamber and with direct injection.
In the first case, the combustion chamber is separated from the cylinder and connected to it by a channel. When compressed, the air entering the vortex-type chamber is twisted, which improves mixture formation and self-ignition, which begins there and continues in the main chamber. Diesel engines of this type were previously common in passenger cars due to the fact that they were distinguished by a reduced noise level and a large speed range from the options discussed below.
In direct injection, the combustion chamber is located in the piston, and the fuel is supplied to the over-piston space. This design was originally used on low-speed high-volume engines. They have a high level of noise and vibration and low flow fuel. Later, with the advent of electronic control and by optimizing the combustion process, the designers have achieved stable operation up to 4500 rpm. In addition, increased efficiency, decreased noise and vibration levels. Among the measures to reduce the rigidity of the work is a multi-stage pre-injection. Due to this, engines of this type have become widespread in the last two decades.
According to the principle of operation, diesel engines are divided into four-stroke and two-stroke, as well as gasoline engines. Their features are discussed below.
Operating principle
To understand what a diesel engine is and what determines its functional features, it is necessary to consider the principle of operation. The above classification of piston internal combustion engines is based on the number of strokes included in the working cycle, which are distinguished by the magnitude of the angle of rotation of the crankshaft.
Therefore, it includes 4 phases.
- Inlet. Occurs when the crankshaft rotates from 0 to 180°. In this case, the air passes into the cylinder through the inlet valve open at 345-355 °. At the same time, during the rotation of the crankshaft by 10-15 °, the exhaust valve is opened, which is called overlap.
- Compression. The piston, moving up at 180-360°, compresses the air 16-25 times (compression ratio), and the intake valve closes at the beginning of the cycle (at 190-210°).
- Workflow, extension. Occurs at 360-540°. At the beginning of the stroke until the piston reaches top dead point, the fuel is injected into the hot air and ignited. This is a feature of diesel engines that distinguishes them from gasoline engines, where ignition advance occurs. The resulting combustion products push the piston down. In this case, the fuel combustion time is equal to the time of its supply by the nozzle and lasts no longer than the duration of the working stroke. That is, during the working process, the gas pressure is constant, as a result of which diesel engines develop more torque. Also an important feature of such motors is the need to provide excess air in the cylinder, since the flame occupies a small part of the combustion chamber. That is, the proportion of the air-fuel mixture is different.
- Release. At 540-720 ° of crankshaft rotation, the open exhaust valve, the piston, moving up, displaces the exhaust gases.
The two-stroke cycle is distinguished by shortened phases and a single process of gas exchange in the cylinder (purge) occurring between the end of the stroke and the start of compression. When the piston moves down, the products of combustion are removed through the exhaust valves or windows (in the cylinder wall). Later, the inlet windows are opened to let in fresh air. As the piston rises, all windows close and compression begins. A little before TDC is reached, fuel is injected and ignited, and expansion begins.
Due to the difficulty of purging the swirl chamber, two-stroke engines are only available with direct injection.
The performance of such engines is 1.6-1.7 times higher than the characteristics of a four-stroke diesel engine. Its growth is ensured by twice as frequent implementation of working strokes, but is partially reduced due to their smaller size and blowing. Due to the double number of working strokes, the two-stroke cycle is especially relevant if it is impossible to increase the speed.
The main problem with such engines is the scavenging due to its short duration, which cannot be compensated without reducing efficiency by shortening the stroke. In addition, it is impossible to separate the exhaust and fresh air, due to which part of the latter is removed with the exhaust gases. This problem can be solved by providing advance exhaust windows. In this case, the gases begin to be removed before the purge, and after the outlet is closed, the cylinder is supplemented with fresh air.
In addition, when using one cylinder, difficulties arise with the synchronism of opening / closing windows, so there are engines (PDP) in which each cylinder has two pistons moving in the same plane. One of them controls the intake, the other controls the exhaust.
According to the mechanism of implementation, the purge is divided into slotted (window) and valve-slotted. In the first case, the windows serve as both inlet and outlet openings. The second option involves using them as intake ports, and a valve in the cylinder head is used for exhaust.
Typically, two-stroke diesel engines are used on heavy vehicles such as ships, diesel locomotives, tanks.
Fuel system
The fuel equipment of diesel engines is much more complicated than that of gasoline engines. This is due to the high requirements for the accuracy of fuel supply in terms of time, quantity and pressure. The main components of the fuel system - injection pump, nozzles, filter.
A computer-controlled fuel supply system (Common-Rail) is widely used. She squirts it in two shots. The first of them is small, serving to increase the temperature in the combustion chamber (pre-injection), which reduces noise and vibration. In addition, this system increases torque at low speeds by 25%, reduces fuel consumption by 20% and soot content in exhaust gases.
Turbocharging
Turbines are widely used in diesel engines. This is due to the higher (1.5-2) times the pressure of the exhaust gases that spin the turbine, which makes it possible to avoid turbo lag by providing boost from lower revs.
Cold start
You can find many reviews that at low temperatures The difficulty of starting such motors in cold conditions is due to the fact that this requires more energy. To facilitate the process, they are equipped with a preheater. This device is represented by glow plugs placed in the combustion chambers, which, when the ignition is turned on, heat the air in them and work for another 15-25 seconds after starting to ensure the stability of the cold engine. Thanks to this, diesel engines are started at temperatures of -30 ... -25 ° С.
Service features
To ensure durability during operation, it is necessary to know what a diesel engine is and how to maintain it. The relatively low prevalence of the engines under consideration in comparison with gasoline engines is explained, among other things, by more complex maintenance.
First of all, this concerns the fuel system of high complexity. Because of this, diesel engines are extremely sensitive to the content of water and mechanical particles in the fuel, and its repair is more expensive, as well as the engine as a whole, compared to gasoline of the same level.
In the case of a turbine, the quality requirements are also high. engine oil. Its resource is usually 150 thousand km, and the cost is high.
In any case, diesel engines should be changed oil more often than gasoline engines (2 times according to European standards).
As noted, these engines have cold start problems when at low temperatures. In some cases, this is caused by the use of unsuitable fuel (depending on the season, different grades are used on such engines, since summer fuel solidifies at low temperatures).
Performance
In addition, many do not like such qualities of diesel engines as lower power and operating speed range, higher noise and vibration levels.
A gasoline engine is indeed usually superior in performance, including liter power, to a similar diesel. The motor of the type in question at the same time has a higher and even torque curve. A higher compression ratio, which provides more torque, forces the use of stronger parts. Since they are heavier, power is reduced. In addition, this affects the mass of the engine, and consequently, the car.
A small range of operating speeds is due to a longer ignition of the fuel, as a result of which high revs it doesn't burn out.
An increased level of noise and vibration causes a sharp increase in pressure in the cylinder during ignition.
The main advantages of diesel engines are considered higher traction, efficiency and environmental friendliness.
Tyagovity, that is, high torque at low speeds, is explained by the combustion of fuel as it is injected. This provides greater responsiveness and facilitates efficient use of power.
The cost-effectiveness is due to both low consumption and the fact that diesel fuel is cheaper. In addition, it is possible to use low-grade heavy oils as it due to the absence of strict requirements for volatility. And the heavier the fuel, the higher the efficiency of the engine. Finally, diesel engines run on lean mixtures compared to gasoline engines and at high degree compression. The latter provides less heat loss with exhaust gases, that is, greater efficiency. All these measures reduce fuel consumption. Diesel, thanks to this, spends it 30-40% less.
The environmental friendliness of diesel engines is explained by the fact that their exhaust gases have a lower content of carbon monoxide. This is achieved by the use of complex cleaning systems, thanks to which the gasoline engine now meets the same environmental regulations as diesel. A motor of this type was previously significantly inferior to gasoline in this regard.
Application
As is clear from what a diesel engine is and what its characteristics are, such motors are most suitable for those cases where high traction at low revs is needed. Therefore, they are equipped with almost all buses, trucks and construction equipment. As for private vehicles, among them such parameters are most important for SUVs. Due to the high efficiency, urban models are also equipped with these motors. In addition, they are more convenient to manage in such conditions. Diesel test drives testify to this.
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 technology diesel units 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, which types of fuel were not used in order to achieve the 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 compete seriously. gasoline analogues.
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 represent by-product from 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 a truck 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 point is that if there significant benefits the unit had whole line disadvantages, such as increased noise during operation and high 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 of this process, a swirl of air masses occurs.
Attention! The intake flaps can only be opened at high crankshaft speed.
When the piston reaches 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 the 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. Nevertheless 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 you to achieve complete combustion 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 this action 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.
Increasing the density of air allows it to be delivered to a much more 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 pulse 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.
