The main disadvantage of piston internal combustion engines. Working processes in reciprocating and combined engines classification of internal combustion engines

26.06.2020

The reciprocating internal combustion engine has been known for over a century, and almost as many, or rather since 1886, it has been used in cars. The fundamental solution to this type of engine was found by German engineers E. Langen and N. Otto in 1867. It turned out to be quite successful in order to provide this type of engine with a leading position that has been preserved in the automotive industry to this day. However, the inventors of many countries tirelessly sought to build a different engine capable of surpassing the piston internal combustion engine in terms of the most important technical indicators. What are these indicators? First of all, this is the so-called effective coefficient of performance (COP), which characterizes how much heat that was in the consumed fuel is converted into mechanical work. The efficiency for a diesel internal combustion engine is 0.39, and for a carburetor - 0.31. In other words, the effective efficiency characterizes the efficiency of the engine. Specific indicators are no less significant: specific occupied volume (hp / m3) and specific gravity (kg / hp), which indicate compactness and lightness of the design. Equally important is the ability of the engine to adapt to various loads, as well as the complexity of manufacturing, the simplicity of the device, the noise level, and the content of toxic substances in the combustion products. With all the positive aspects of a particular concept of a power plant, the period from the beginning of theoretical development to its introduction into mass production sometimes takes a very long time. Thus, the creator of the rotary piston engine, the German inventor F. Wankel, took 30 years, despite his continuous work, in order to bring his unit to an industrial design. By the way, it will be said that it took almost 30 years to introduce a diesel engine on a production car (Benz, 1923). But it was not technical conservatism that caused such a long delay, but the need to exhaustively work out a new design, that is, to create the necessary materials and technology to enable its mass production. This page contains a description of some types of non-traditional engines, but which have proven their viability in practice. A piston internal combustion engine has one of its most significant drawbacks - it is a rather massive crank mechanism, because the main friction losses are associated with its operation. Already at the beginning of our century, attempts were made to get rid of such a mechanism. Since that time, many ingenious designs have been proposed that convert the reciprocating motion of a piston into the rotational motion of a shaft of this design.

Connecting rodless engine S. Balandin

The transformation of the reciprocating motion of the piston group into rotational motion is carried out by a mechanism based on the kinematics of the "exact straight line". That is, two pistons are rigidly connected by a rod acting on a crankshaft rotating with gear rims in the cranks. A successful solution to the problem was found by the Soviet engineer S. Balandin. In the 1940s and 1950s, he designed and built several models of aircraft engines, where the rod that connected the pistons to the converting mechanism did not oscillate. Such a connecting rodless design, although to some extent more complicated than the mechanism, occupied a smaller volume and provided less friction losses. It should be noted that an engine similar in design was tested in England at the end of the twenties. But the merit of S. Balandin is that he considered the new possibilities of a transforming mechanism without a connecting rod. Since the rod in such an engine does not swing relative to the piston, then it is also possible to attach a combustion chamber on the other side of the piston with a structurally simple seal of the rod passing through its cover.

1 - piston rod 2 - crankshaft 3 - crank bearing 4 - crank 5 - power take-off shaft 6 - piston 7 - rod slider 8 - cylinder Such a solution makes it possible to almost double the power of the unit with the same dimensions. In turn, such a two-way workflow requires the need for a gas distribution mechanism on both sides of the piston (for 2 combustion chambers) with due complication, and, therefore, an increase in the cost of the design. Apparently, such an engine is more promising for machines where high power, low weight and small size are of primary importance, while cost and labor intensity are of secondary importance. The last of the connecting rodless aircraft engines of S. Balandin, which was built in the 50s (double-acting with fuel injection and turbocharging, the OM-127RN engine), had very high performance for that time. The engine had an effective efficiency of about 0.34, specific power - 146 liters. s./l and specific gravity - 0.6 kg/l. With. According to these characteristics, it was close to the best racing car engines.

At the beginning of the last century, Charles Yale Knight decided that it was time to bring something new to the design of engines, and came up with a valveless engine with sleeve distribution. To everyone's surprise, the technology turned out to be working. These engines were very efficient, quiet and reliable. Among the minuses can be noted the consumption of oil. The engine was patented in 1908 and later appeared in many cars, including Mercedes-Benz, Panhard and Peugeot. Technology took a backseat as engines started to rev faster, which the traditional valve system did much better.

Rotary piston engine F. Wankel

It has a trihedral rotor, which makes a planetary movement around the eccentric shaft. The changing volume of the three cavities formed by the walls of the rotor and the internal cavity of the crankcase allows the operating cycle of the heat engine with the expansion of gases to be carried out. Since 1964, on mass-produced cars in which rotary piston engines are installed, the piston function is performed by a trihedral rotor. The movement of the rotor required in the housing relative to the eccentric shaft is provided by a planetary-gear matching mechanism (see figure). Such an engine, with equal power to a piston engine, is more compact (has a 30% smaller volume), 10-15% lighter, has fewer parts and is better balanced. But at the same time, it was inferior to a piston engine in terms of durability, reliability of seals in working cavities, it consumed more fuel, and its exhaust gases contained more toxic substances. But, after many years of fine-tuning, these shortcomings were eliminated. However, mass production of cars with rotary piston engines is currently limited. In addition to the design of F. Wankel, numerous designs of rotary piston engines by other inventors (E. Cauertz, G. Bradshaw, R. Seyrich, G. Ruzhitsky, etc.) are known. However, objective reasons did not give them the opportunity to leave the experimental stage - often due to insufficient technical merit.

Gas twin-shaft turbine

From the combustion chamber, gases rush to two turbine impellers, each connected to independent shafts. A centrifugal compressor is driven from the right wheel, and power directed to the wheels of the car is taken from the left. The air injected by it enters the combustion chamber passing through the heat exchanger, where it is heated by the exhaust gases. A gas turbine power plant with the same power is more compact and lighter than a piston internal combustion engine, and is also well balanced. Less toxic and exhaust gases. Due to the peculiarities of its traction characteristics, a gas turbine can be used on a car without a gearbox. The technology for the production of gas turbines has long been mastered in the aviation industry. For what reason, taking into account the experiments with gas turbine machines that have been going on for over 30 years, do they not go into mass production? The main reason is the low effective efficiency and low efficiency in comparison with piston internal combustion engines. Also, gas turbine engines are quite expensive to manufacture, so that they are currently only found on experimental cars.

Steam piston engine

Steam is alternately supplied to the two opposite sides of the piston. Its supply is regulated by a spool that slides over the cylinder in the steam distribution box. In the cylinder, the piston rod is sealed with a sleeve and connected to a fairly massive crosshead mechanism, which converts its reciprocating motion into rotational.

R. Stirling engine. External combustion engine

Two pistons (lower - working, upper - displacing) are connected to the crank mechanism by concentric rods. The gas located in the cavities above and below the displacement piston, being heated alternately from the burner in the cylinder head, passes through the heat exchanger, cooler and back. A cyclic change in the temperature of the gas is accompanied by a change in volume and, accordingly, an effect on the movement of the pistons. Similar engines ran on fuel oil, wood, coal. Their advantages include durability, smooth operation, excellent traction characteristics, which makes it possible to do without a gearbox at all. The main disadvantages: the impressive mass of the power unit and low efficiency. Experimental developments of recent years (for example, the American B. Lear and others) made it possible to design closed-cycle units (with complete condensation of water), to select the compositions of vapor-forming liquids with indicators more favorable than water. Nevertheless, not a single plant has dared to mass-produce cars with steam engines in recent years. The hot-air engine, the idea of which was proposed by R. Stirling back in 1816, belongs to external combustion engines. In it, the working fluid is helium or hydrogen, which is under pressure, alternately cooled and heated. Such an engine (see figure) is simple in principle, has a lower fuel consumption than internal combustion reciprocating engines, does not emit gases that have harmful substances during operation, and also has a high effective efficiency equal to 0.38. However, the introduction of the R. Stirling engine into mass production is hindered by serious difficulties. It is heavy and very bulky, slowly gaining momentum compared to a reciprocating internal combustion engine. Moreover, it is technically difficult to ensure reliable sealing of working cavities. Among non-traditional engines, ceramic stands apart, which does not differ structurally from a traditional four-stroke piston internal combustion engine. Only its most important parts are made of a ceramic material that can withstand temperatures 1.5 times higher than metal. Accordingly, the ceramic engine does not require a cooling system and thus there are no heat losses that are associated with its operation. This makes it possible to design an engine that will operate on the so-called adiabatic cycle, which promises a significant reduction in fuel consumption. Meanwhile, similar work is being carried out by American and Japanese specialists, but so far they have not left the stage of searching for solutions. Although there is still no shortage of experiments with a variety of non-traditional engines, the dominant position in cars, as noted above, is retained and, possibly, will remain for a long time to be reciprocating four-stroke internal combustion engines.

8 Combined combustion engine

History of creation

The first practical gas internal combustion engine was designed by the French mechanic Etienne Lenoir (1822-1900) in 1860. Engine power was 8.8 kW (12 hp). The engine was a single-cylinder horizontal double-acting machine, running on a mixture of air and lighting gas with electric spark ignition from an external source. efficiency engine did not exceed 4.65%. Despite the shortcomings, the Lenoir engine received some distribution. Used as a boat engine.

Having become acquainted with the Lenoir engine, the outstanding German designer Nikolai August Otto (1832-1891) created in 1863 a two-stroke atmospheric internal combustion engine. The engine had a vertical cylinder, open flame ignition and efficiency. up to 15 %. Displaced the Lenoir engine.

In 1876, Nikolaus August Otto built a more advanced four-stroke gas internal combustion engine.

Daimler motorcycle with ICE 1885

In 1885, German engineers Gottlieb Daimler and Wilhelm Maybach developed a lightweight gasoline carburetor engine. Daimler and Maybach used it to build their first motorcycle in 1885, and in 1886 on their first car.

In 1896, a two-cylinder gasoline engine was developed by Charles W. Hart and Charles Parr. In 1903, their firm built 15 tractors. Their six-ton is the oldest internal combustion engine tractor in the United States and is housed in the Smithsonian's National Museum of American History in Washington, DC. The gasoline two-cylinder engine had a completely unreliable ignition system and a power of 30 liters. With. at idle and 18 liters. With. under load.

Dan Albon with his Ivel farm tractor prototype

The first practical tractor powered by an internal combustion engine was Dan Elborn's 1902 American Ivel three-wheeled tractor. About 500 of these light and powerful machines were built.

Types of internal combustion engines

piston engine

rotary internal combustion engine

Gas turbine internal combustion engine

Piston engines - the combustion chamber is contained in a cylinder, where the thermal energy of the fuel is converted into mechanical energy, which is converted from the translational movement of the piston into rotational motion using a crank mechanism.

ICEs are classified:

a) By purpose - are divided into transport, stationary and special.

b) By the type of fuel used - light liquid (gasoline, gas), heavy liquid (diesel fuel, marine fuel oil).

c) According to the method of formation of a combustible mixture - external (carburetor) and internal (in the engine cylinder).

d) According to the method of ignition (with forced ignition, with compression ignition, calorising).

e) According to the location of the cylinders, they are divided into in-line, vertical, opposed with one and two crankshafts, V-shaped with an upper and lower crankshaft, VR-shaped and W-shaped, single-row and double-row star-shaped, H-shaped, double-row with parallel crankshafts, "double fan", diamond-shaped, three-beam and some others.

Petrol

Petrol carburetor

The working cycle of four-stroke internal combustion engines takes two complete revolutions of the crank, consisting of four separate strokes:

intake,
charge compression,
working stroke and
release (exhaust).

The change in working cycles is provided by a special gas distribution mechanism, most often it is represented by one or two camshafts, a system of pushers and valves that directly provide a phase change. Some internal combustion engines have used spool sleeves (Ricardo) for this purpose, having inlet and/or exhaust ports. The communication of the cylinder cavity with the collectors in this case was provided by the radial and rotational movements of the spool sleeve, opening the desired channel with windows. Due to the peculiarities of gas dynamics - the inertia of gases, the time of occurrence of the gas wind, the intake, power stroke and exhaust strokes in a real four-stroke cycle overlap, this is called valve timing overlap. The higher the operating speed of the engine, the greater the phase overlap and the larger it is, the lower the torque of the internal combustion engine at low speeds. Therefore, modern internal combustion engines are increasingly using devices that allow you to change the valve timing during operation. Particularly suitable for this purpose are engines with solenoid valve control (BMW, Mazda). Variable compression ratio (SAAB) engines are also available for greater flexibility.

Two-stroke engines have many layout options and a wide variety of structural systems. The basic principle of any two-stroke engine is the performance by the piston of the functions of a gas distribution element. The working cycle consists, strictly speaking, of three cycles: the working stroke, lasting from the top dead center ( TDC) up to 20-30 degrees to the bottom dead center ( NMT), purge, which actually combines intake and exhaust, and compression, lasting from 20-30 degrees after BDC to TDC. Purging, from the point of view of gas dynamics, is the weak link of the two-stroke cycle. On the one hand, it is impossible to ensure complete separation of the fresh charge and exhaust gases, therefore, either the loss of the fresh mixture is inevitable, literally flying out into the exhaust pipe (if the internal combustion engine is a diesel, we are talking about air loss), on the other hand, the working stroke does not last half turnover, but less, which in itself reduces efficiency. At the same time, the duration of the extremely important process of gas exchange, which in a four-stroke engine takes half the working cycle, cannot be increased. Two-stroke engines may not have a gas distribution system at all. However, if we are not talking about simplified cheap engines, a two-stroke engine is more complicated and expensive due to the obligatory use of a blower or a pressurization system, the increased heat stress of the CPG requires more expensive materials for pistons, rings, cylinder liners. The performance by the piston of the functions of the gas distribution element obliges to have its height not less than the piston stroke + the height of the purge windows, which is uncritical in a moped, but significantly makes the piston heavier even at relatively low powers. When the power is measured in hundreds of horsepower, the increase in piston mass becomes a very serious factor. The introduction of vertically stroked distributor sleeves in Ricardo engines was an attempt to make it possible to reduce the size and weight of the piston. The system turned out to be complicated and expensive in execution, except for aviation, such engines were not used anywhere else. Exhaust valves (with direct-flow valve scavenging) have twice the heat density compared to four-stroke exhaust valves and worse conditions for heat removal, and their seats have a longer direct contact with the exhaust gases.

The simplest in terms of the order of operation and the most complex in terms of design is the Koreyvo system, presented in the USSR and Russia, mainly by diesel locomotive diesel engines of the D100 series and tank diesel engines KhZTM. Such an engine is a symmetrical two-shaft system with diverging pistons, each of which is connected to its own crankshaft. Thus, this engine has two crankshafts mechanically synchronized; the one connected to the exhaust pistons is ahead of the intake by 20-30 degrees. Due to this advance, the quality of the scavenging is improved, which in this case is direct-flow, and the filling of the cylinder is improved, since the exhaust windows are already closed at the end of the scavenging. In the 30s - 40s of the twentieth century, schemes with pairs of diverging pistons were proposed - diamond-shaped, triangular; There were aviation diesel engines with three radially diverging pistons, of which two were inlet and one exhaust. In the 1920s, Junkers proposed a single-shaft system with long connecting rods connected to the fingers of the upper pistons with special rocker arms; the upper piston transmitted forces to the crankshaft by a pair of long connecting rods, and there were three crankshafts per cylinder. There were also square pistons of the scavenging cavities on the rocker arms. Two-stroke engines with divergent pistons of any system have, basically, two drawbacks: firstly, they are very complex and large, and secondly, exhaust pistons and sleeves in the area of exhaust windows have significant thermal tension and a tendency to overheat. Exhaust piston rings are also thermally stressed, prone to coking and loss of elasticity. These features make the design of such engines a non-trivial task.

Direct-flow valve-scavenged engines are equipped with a camshaft and exhaust valves. This significantly reduces the requirements for materials and execution of the CPG. The intake is carried out through the windows in the cylinder liner, opened by the piston. This is how most modern two-stroke diesels are assembled. The window area and the sleeve in the lower part are in many cases cooled by charge air.

In cases where one of the main requirements for the engine is its reduction in cost, different types of crank-chamber contour window-window purge are used - loop, reciprocating-loop (deflector) in various modifications. To improve the parameters of the engine, a variety of design techniques are used - a variable length of the intake and exhaust channels, the number and location of bypass channels can vary, spools, rotating gas cutters, sleeves and curtains are used that change the height of the windows (and, accordingly, the moments of the start of intake and exhaust). Most of these engines are air-cooled passively. Their disadvantages are the relatively low quality of gas exchange and the loss of the combustible mixture during purging; in the presence of several cylinders, the sections of the crank chambers have to be separated and sealed, the design of the crankshaft becomes more complicated and more expensive.

Additional units required for internal combustion engines

The disadvantage of an internal combustion engine is that it develops its highest power only in a narrow rev range. Therefore, an integral attribute of the internal combustion engine is /mirtesen.ru/market/avto/zapchasti/transmissiya" id="marketCategoryTag" class="categoryTag" target="_blank">Transmission" href="http://ru.wikipedia.org /wiki/%D0%A2%D1%80%D0%B0%D0%BD%D1%81%D0%BC%D0%B8%D1%81%D1%81%D0%B8%D1%8F">transmission . Only in some cases (for example, in airplanes) can a complex transmission be dispensed with. The idea of a hybrid car is gradually conquering the world, in which the engine always works in the optimal mode.

In addition, an internal combustion engine needs a power system (for supplying fuel and air - preparing a fuel-air mixture), an exhaust system (for exhaust gases), and a lubrication system (designed to reduce friction forces in engine mechanisms, protect parts engine from corrosion, as well as together with the cooling system to maintain optimal thermal conditions), cooling systems (to maintain optimal thermal conditions of the engine), starting system (starting methods are used: electric starter, with the help of an auxiliary starting engine, pneumatic, with the help of human muscle power ), ignition system (for igniting the air-fuel mixture, used in positive ignition engines).

It would not be an exaggeration to say that most self-propelled devices today are equipped with internal combustion engines of various designs, using various operating principles. In any case, if we talk about road transport. In this article, we will take a closer look at ICE. What it is, how this unit works, what are its pros and cons, you will learn by reading it.

The principle of operation of internal combustion engines

The main principle of operation of an internal combustion engine is based on the fact that fuel (solid, liquid or gaseous) burns in a specially allocated working volume inside the unit itself, converting thermal energy into mechanical energy.

The working mixture entering the cylinders of such an engine is compressed. After its ignition, with the help of special devices, an excess pressure of gases arises, forcing the pistons of the cylinders to return to their original position. This creates a constant working cycle that converts kinetic energy into torque with the help of special mechanisms.

To date, the ICE device can have three main types:

often called easy;
four-stroke power unit, allowing to achieve higher power and efficiency values;
with enhanced power characteristics.

In addition, there are other modifications of the main circuits that improve certain properties of power plants of this type.

Benefits of internal combustion engines

Unlike power units that provide for the presence of external chambers, the internal combustion engine has significant advantages. The main ones are:

much more compact dimensions;
higher power ratings;
optimal efficiency values.

It should be noted, speaking of an internal combustion engine, that this is a device that in the vast majority of cases allows the use of various types of fuel. It can be gasoline, diesel fuel, natural or kerosene, and even ordinary wood.

Such versatility has given this engine concept its well-deserved popularity, ubiquity and truly world leadership.

Brief historical excursion

It is generally accepted that the internal combustion engine has been counting its history since the creation by the Frenchman de Rivas in 1807 of a piston unit that used hydrogen in a gaseous state of aggregation as fuel. And although since then the ICE device has undergone significant changes and modifications, the main ideas of this invention continue to be used today.

The first four-stroke internal combustion engine saw the light in 1876 in Germany. In the mid-80s of the XIX century, a carburetor was developed in Russia, which made it possible to dose the supply of gasoline to the engine cylinders.

And at the very end of the century before last, the famous German engineer proposed the idea of igniting a combustible mixture under pressure, which significantly increased the power characteristics of internal combustion engines and the efficiency indicators of units of this type, which had previously left much to be desired. Since then, the development of internal combustion engines has been mainly along the path of improvement, modernization and the introduction of various improvements.

The main types and types of internal combustion engines

Nevertheless, more than 100 years of history of this type of units has made it possible to develop several main types of power plants with internal combustion of fuel. They differ from each other not only in the composition of the working mixture used, but also in design features.

Gasoline engines

As the name implies, the units of this group use various types of gasoline as fuel.

In turn, such power plants are usually divided into two large groups:

Carburetor. In such devices, the fuel mixture is enriched with air masses in a special device (carburetor) before entering the cylinders. Then it is ignited by an electric spark. Among the most prominent representatives of this type are the VAZ models, the internal combustion engine of which for a very long time was exclusively of the carburetor type.
Injection. This is a more complex system in which fuel is injected into the cylinders through a special manifold and injectors. It can occur both mechanically and through a special electronic device. Common Rail direct injection systems are considered the most productive. Installed on almost all modern cars.

Injected gasoline engines are considered to be more economical and provide higher efficiency. However, the cost of such units is much higher, and maintenance and operation are much more difficult.

Diesel engines

At the dawn of the existence of units of this type, one could very often hear a joke about the internal combustion engine, that this is a device that eats gasoline like a horse, but moves much more slowly. With the invention of the diesel engine, this joke has partially lost its relevance. Mainly because diesel is able to run on much lower quality fuel. This means that it is much cheaper than gasoline.

The main fundamental difference between internal combustion is the absence of forced ignition of the fuel mixture. Diesel fuel is injected into the cylinders by special injectors, and individual drops of fuel are ignited due to the pressure force of the piston. Along with the advantages, the diesel engine has a number of disadvantages. Among them are the following:

much less power compared to gasoline power plants;
large dimensions and weight characteristics;
difficulties with starting under extreme weather and climatic conditions;
insufficient traction and a tendency to unjustified power losses, especially at relatively high speeds.

In addition, repairing a diesel-type internal combustion engine is usually much more complicated and costly than adjusting or restoring the performance of a gasoline unit.

gas engines

Despite the cheapness of natural gas used as fuel, the construction of gas-fired internal combustion engines is incommensurably more complicated, which leads to a significant increase in the cost of the unit as a whole, its installation and operation in particular.

On power plants of this type, liquefied or natural gas enters the cylinders through a system of special gearboxes, manifolds and nozzles. The ignition of the fuel mixture occurs in the same way as in carburetor gasoline installations - with the help of an electric spark emanating from a spark plug.

Combined types of internal combustion engines

Few people know about combined ICE systems. What is it and where is it applied?

This, of course, is not about modern hybrid cars that can run both on fuel and on an electric motor. Combined internal combustion engines are usually called such units that combine elements of various principles of fuel systems. The most prominent representative of the family of such engines are gas-diesel plants. In them, the fuel mixture enters the internal combustion engine block in almost the same way as in gas units. But the fuel is ignited not with the help of an electric discharge from a candle, but with an ignition portion of diesel fuel, as happens in a conventional diesel engine.

Maintenance and repair of internal combustion engines

Despite a fairly wide variety of modifications, all internal combustion engines have similar basic designs and diagrams. Nevertheless, in order to carry out high-quality maintenance and repair of internal combustion engines, it is necessary to thoroughly know its structure, understand the principles of operation and be able to identify problems. To do this, of course, it is necessary to carefully study the design of internal combustion engines of various types, to understand for yourself the purpose of certain parts, assemblies, mechanisms and systems. This is not easy, but very exciting! And most importantly, necessary.

Especially for inquisitive minds who want to independently comprehend all the mysteries and secrets of almost any vehicle, an approximate schematic diagram of an internal combustion engine is presented in the photo above.

So, we found out what this power unit is.

However, lighting gas was suitable not only for lighting.

The credit for creating a commercially successful internal combustion engine belongs to the Belgian mechanic Jean Étienne Lenoir. While working at an electroplating plant, Lenoir came up with the idea that the air-fuel mixture in a gas engine could be ignited by an electric spark, and decided to build an engine based on this idea. Having solved the problems that arose along the way (tight stroke and overheating of the piston, leading to jamming), having thought through the engine cooling and lubrication system, Lenoir created a workable internal combustion engine. In 1864, more than three hundred of these engines of various capacities were produced. Having grown rich, Lenoir stopped working on further improvement of his car, and this predetermined her fate - she was forced out of the market by a more advanced engine created by the German inventor August Otto and who received a patent for the invention of his gas engine model in 1864.

In 1864, the German inventor Augusto Otto entered into an agreement with the wealthy engineer Langen to implement his invention - the company "Otto and Company" was created. Neither Otto nor Langen had sufficient knowledge of electrical engineering and abandoned electric ignition. They ignited with an open flame through a tube. The cylinder of the Otto engine, unlike the Lenoir engine, was vertical. The rotating shaft was placed above the cylinder on the side. Principle of operation: a rotating shaft raised the piston by 1/10 of the height of the cylinder, as a result of which a rarefied space formed under the piston and a mixture of air and gas was sucked in. The mixture then ignited. During the explosion, the pressure under the piston increased to approximately 4 atm. Under the action of this pressure, the piston rose, the volume of gas increased and the pressure fell. The piston, first under gas pressure, and then by inertia, rose until a vacuum was created under it. Thus, the energy of the burnt fuel was used in the engine with maximum completeness. This was Otto's main original find. The downward working stroke of the piston began under the influence of atmospheric pressure, and after the pressure in the cylinder reached atmospheric pressure, the exhaust valve opened, and the piston displaced the exhaust gases with its mass. Due to the more complete expansion of the combustion products, the efficiency of this engine was significantly higher than the efficiency of the Lenoir engine and reached 15%, that is, it exceeded the efficiency of the best steam engines of that time. In addition, Otto engines were almost five times more economical than Lenoir engines, they immediately became in great demand. In subsequent years, about five thousand of them were produced. Despite this, Otto worked hard to improve their design. Soon, a crank gear was used. However, the most significant of his inventions came in 1877, when Otto received a patent for a new four-stroke cycle engine. This cycle still underlies the operation of most gas and gasoline engines to this day.

Types of internal combustion engines

piston engine

rotary internal combustion engine

Gas turbine internal combustion engine

Piston engines - the combustion chamber is contained in a cylinder, where the thermal energy of the fuel is converted into mechanical energy, which is converted from the translational movement of the piston into rotational motion using a crank mechanism.

ICEs are classified:

a) By purpose - are divided into transport, stationary and special.

b) By the type of fuel used - light liquid (gasoline, gas), heavy liquid (diesel fuel, marine fuel oil).

c) According to the method of formation of a combustible mixture - external (carburetor, injector) and internal (in the engine cylinder).

d) According to the method of ignition (with forced ignition, with compression ignition, calorising).

Petrol

Petrol carburetor

The working cycle of four-stroke internal combustion engines takes two complete revolutions of the crank, consisting of four separate strokes:

intake,
charge compression,
working stroke and
release (exhaust).

The simplest in terms of the order of operation and the most complex in terms of design is the Fairbanks-Morse system, presented in the USSR and Russia, mainly by diesel locomotives of the D100 series. Such an engine is a symmetrical two-shaft system with diverging pistons, each of which is connected to its own crankshaft. Thus, this engine has two crankshafts mechanically synchronized; the one connected to the exhaust pistons is ahead of the intake by 20-30 degrees. Due to this advance, the quality of the scavenging is improved, which in this case is direct-flow, and the filling of the cylinder is improved, since the exhaust windows are already closed at the end of the scavenging. In the 30s - 40s of the twentieth century, schemes with pairs of diverging pistons were proposed - diamond-shaped, triangular; There were aviation diesel engines with three radially diverging pistons, of which two were inlet and one exhaust. In the 1920s, Junkers proposed a single-shaft system with long connecting rods connected to the fingers of the upper pistons with special rocker arms; the upper piston transmitted forces to the crankshaft by a pair of long connecting rods, and there were three crankshafts per cylinder. There were also square pistons of the scavenging cavities on the rocker arms. Two-stroke engines with divergent pistons of any system have, basically, two drawbacks: firstly, they are very complex and large, and secondly, exhaust pistons and sleeves in the area of exhaust windows have significant thermal tension and a tendency to overheat. Exhaust piston rings are also thermally stressed, prone to coking and loss of elasticity. These features make the design of such engines a non-trivial task.

Additional units required for internal combustion engines

The disadvantage of an internal combustion engine is that it develops its highest power only in a narrow rev range. Therefore, an essential attribute of an internal combustion engine is a transmission. Only in some cases (for example, in airplanes) can a complex transmission be dispensed with. The idea of a hybrid car is gradually conquering the world, in which the engine always works in the optimal mode.

Notes

Links

Ben Knight "Increasing mileage" //Article on technologies that reduce fuel consumption of automotive internal combustion engines

internal combustion. Its device is very complex, even for a professional.

When buying a car, first of all look at the characteristics of the engine. This article will help you understand the basic parameters of the engine.

Number of cylinders. Modern cars have up to 16 cylinders. This is a lot. But the fact is that piston internal combustion engines with the same power and volume can differ significantly in other parameters.

How are the cylinders arranged?

Cylinders can be arranged in two types: in-line (sequential) and V-shaped (two-row).

With a large camber angle, the dynamic characteristics are significantly reduced, but the inertia increases. With a small camber angle, inertia and weight are reduced, but this leads to rapid overheating.

boxer engine

There is also a radical boxer engine with a camber angle of 180 degrees. In such an engine, all the disadvantages and advantages are maximum.

Consider the advantages of such a motor. This engine is easily built into the very bottom of the engine compartment, which allows you to lower the center of mass and, as a result, increases the stability of the car and its handling, which is no less important.

Opposed reciprocating internal combustion engines have reduced vibration load and are fully balanced. They are also shorter than single row motors. There are also disadvantages - the very width of the engine compartment of the car is increased. The boxer engine is installed on cars of Porsche brands, as well as Subaru.

Varieties of the engine - W-shaped

At the moment, the W-shaped engine that Volkswagen produces includes two piston groups from VR-type engines, which are at an angle of 72 ° and due to this, it turns out an engine with four cylinder banks.

Now they make W-shaped engines with 16, 12 and 8 cylinders.

W8 engine- four-row with two cylinders in each row. It has two balance shafts that rotate twice as fast as the crankshaft, they are needed to balance the forces of inertia. This motor has a place to be on a car - VW Passat W8.

W12 engine - four-row, but already three cylinders in each row. It is found on VW Phaeton W12 and Audi A8 W12 cars.

W16 engine - four-row, four cylinders in each row, it is only on the Bugatti Veyron 16.4 car. This 1000 hp engine and in it the strong influence of inertial moments negatively affecting the connecting rods was reduced by increasing the camber angle to 90 °, and at the same time, the piston speed was reduced to 17.2 m / s. True, the dimensions of the engine have increased from this: its length is 710, width 767 mm.

And the rarest type of engine is row-V-shaped (also called - VR, see the top right picture), which is a combination of two varieties. VR engines have a small camber between the cylinder banks, only 15 degrees, which made it possible to use one common head on them.

Engine capacity. Almost all other characteristics of the engine depend on this parameter of a piston internal combustion engine. In the case of an increase in engine size, there is an increase in power, and as a result, fuel consumption increases.

engine material. Engines are usually made of three types of material: aluminum or its alloys, cast iron and other ferroalloys, or magnesium alloys. In practice, only resources and engine noise depend on these parameters.

The most important engine parameters

Torque. It is generated by the engine at maximum tractive effort. The unit of measurement is new meters (nm). Torque directly affects the “engine elasticity” (ability to accelerate at low speeds).

Power. The unit of measurement is horsepower (hp). The acceleration time and speed of the car depend on it.
Maximum revolutions of the crankshaft (rpm). They indicate the number of revolutions that the engine is able to withstand without losing the strength of resources. A large number of revolutions indicates sharpness and dynamism in the character of the car.

Important in the car and consumption characteristics

Oil. Its consumption is measured in liters per thousand kilometers. The brand of oil is indicated by xxWxx, where the first number indicates the density, the second the viscosity. Oils with high density and viscosity significantly increase the reliability and durability of the engine, and oils with low density give good dynamic characteristics.

Fuel. Its consumption is measured in liters per hundred kilometers. Almost any brand of gasoline can be used in modern cars, but it is worth remembering that a low octane number affects the drop in strength and power, and an octane number above the norm reduces the resource, but increases power.