Municipal educational institution
Secondary school №6
Essay on physics on the topic:
Internal combustion engines. Their advantages and disadvantages.
Pupil 8 "A" class
Butrinova Alexandra
Teacher: Shulpina Taisiya Vladimirovna
1. Introduction……………………………………………………………….. Page 3
1.1. The purpose of the work
1.2 Tasks
2. The main part.
2.1.History of the creation of internal combustion engines………………. Page 4
2.2. General arrangement of internal combustion engines……………… Page 7
2.2.1. The device of two-stroke and four-stroke engines
internal combustion;……………………………………….……………..Page 15
2.3 Modern internal combustion engines.
2.3.1. New design solutions implemented in the internal combustion engine;……………………………………………………………………P. 21
2.3.2. Tasks that designers face……………………P.22
2.4. Advantages and disadvantages over other types of internal combustion engines ……………………………………………………..P.23
2.5. Application of internal combustion engine..…………………….P.25
3. Concluded ………………………………………………………………. Page 26
4. List of references……………………………………………………….. Page 27
5. Applications ……………………………………………………………. Page 28
1. Introduction.
1.1. Goal of the work:
Analyze the discovery and achievements of scientists on the invention and application of the internal combustion engine (D.V.S.), talk about its advantages and disadvantages.
1.2. Tasks:
1. Study the necessary literature and work out the material
2. Conduct theoretical research (D.V.S.)
3. Find out which of the (D.V.S.) is better.
2. The main part.
2.1 .The history of the internal combustion engine .
The project of the first internal combustion engine (ICE) belongs to the famous inventor of the watch anchor, Christian Huygens, and was proposed back in the 17th century. It is interesting that gunpowder was supposed to be used as fuel, and the idea itself was prompted by an artillery gun. All attempts by Denis Papin to build a machine on this principle were unsuccessful. Historically, the first working internal combustion engine was patented in 1859 by the Belgian inventor Jean Joseph Etienne Lenoir. (Fig. No. 1)
The Lenoir engine has a low thermal efficiency, in addition, compared to other reciprocating internal combustion engines, it had an extremely low power taken per unit cylinder displacement.
An 18-liter engine developed only 2 horsepower. These shortcomings were due to the fact that the Lenoir engine does not compress the fuel mixture before ignition. The Otto engine of equal power to it (in the cycle of which a special compression stroke was provided) weighed several times less and was much more compact.
Even the obvious advantages of the Lenoir engine - relatively low noise (a consequence of exhaust at almost atmospheric pressure), and a low level of vibration (a consequence of a more even distribution of power strokes over the cycle) did not help it withstand competition.
However, during the operation of the engines, it turned out that the gas consumption per horsepower is 3 cubic meters. per hour in place of the expected approximately 0.5 cubic meters. The efficiency of the Lenoir engine was only 3.3%, while the steam engines of that time reached an efficiency of 10%.
In 1876, Otto and Langen exhibited a new 0.5 hp engine at the second Paris World Exhibition (Fig. No. 2)
Fig.2 Engine Otto
Despite the imperfection of the design of this engine, reminiscent of the first steam-atmospheric machines, it showed high efficiency for that time; gas consumption was 82 cubic meters / m. per horsepower per hour and efficiency. amounted to 14%. For 10 years, about 10,000 such engines were manufactured for small industry.
In 1878, Otto built a four-stroke engine based on the idea of Boudet-Roche. Simultaneously with the use of gas as a fuel, the idea of using gasoline vapors, gasoline, naphtha as a material for a combustible mixture, and from the 90s, kerosene, began to be developed. Fuel consumption in these engines was about 0.5 kg per horsepower per hour.
Since that time, internal combustion engines (D.V.S.) have changed in design, according to the principle of operation, the materials used in the manufacture. Internal combustion engines have become more powerful, more compact, lighter, but still in the internal combustion engine, out of every 10 liters of fuel, only about 2 liters are used for useful work, the remaining 8 liters are wasted. That is, the efficiency of the internal combustion engine is only 20%.
2. 2. General arrangement of the internal combustion engine.
At the core of every D.V.S. lies the movement of the piston in the cylinder under the influence of the pressure of the gases that are formed during the combustion of the fuel mixture, hereinafter referred to as the working one. In this case, the fuel itself does not burn. Only its vapors mixed with air burn, which are the working mixture for the internal combustion engine. If you set fire to this mixture, it instantly burns out, multiplying in volume. And if you place the mixture in a closed volume, and make one wall movable, then on this wall
there will be an enormous pressure that will move the wall.
D.V.S. used on passenger cars consist of two mechanisms: crank and gas distribution, as well as the following systems:
nutrition;
· release of the fulfilled gases;
· ignition;
cooling;
lubricants.
The main details of the internal combustion engine:
Cylinder head
· cylinders;
· pistons;
· piston rings;
Piston pins
· connecting rods;
· crankshaft;
flywheel
camshaft with cams;
· valves;
· spark plug.
Most modern small and medium class cars are equipped with four-cylinder engines. There are motors of a larger volume - with eight or even twelve cylinders (Fig. 3). The larger the engine, the more powerful it is and the higher the fuel consumption.
The principle of operation of an internal combustion engine is easiest to consider using the example of a single-cylinder gasoline engine. Such an engine consists of a cylinder with an internal mirror surface, to which a removable head is screwed. The cylinder contains a cylindrical piston - a glass, consisting of a head and a skirt (Fig. 4). The piston has grooves in which the piston rings are installed. They ensure the tightness of the space above the piston, preventing gases generated during engine operation from penetrating under the piston. In addition, piston rings prevent oil from entering the space above the piston (oil is intended to lubricate the inner surface of the cylinder). In other words, these rings play the role of seals and are divided into two types: compression (those that do not let gases through) and oil scraper (prevent oil from entering the combustion chamber) (Fig. 5).
Rice. 3. Cylinder layouts in engines of various layouts:
a - four-cylinder; b - six-cylinder; c - twelve-cylinder (α - camber angle)
Rice. 4. Piston
A mixture of gasoline and air, prepared by a carburetor or injector, enters the cylinder, where it is compressed by a piston and ignited by a spark from a spark plug. Burning and expanding, it causes the piston to move down.
Thus, thermal energy is converted into mechanical energy.
Rice. 5. Piston with connecting rod:
1 - connecting rod assembly; 2 - connecting rod cover; 3 - connecting rod insert; 4 - bolt nut; 5 - connecting rod cover bolt; 6 - connecting rod; 7 - connecting rod bushing; 8 - retaining rings; 9 - piston pin; 10 - piston; 11 - oil scraper ring; 12, 13 - compression rings
This is followed by the conversion of the piston stroke into shaft rotation. To do this, the piston, using a pin and a connecting rod, is pivotally connected to the crankshaft crank, which rotates on bearings installed in the engine crankcase (Fig. 6).
Rice. 6 Crankshaft with flywheel:
1 - crankshaft; 2 - connecting rod bearing insert; 3 - persistent half rings; 4 - flywheel; 5 - washer of the flywheel mounting bolts; 6 - liners of the first, second, fourth and fifth main bearings; 7 - insert of the central (third) bearing
As a result of the movement of the piston in the cylinder from top to bottom and back through the connecting rod, the crankshaft rotates.
Top dead center (TDC) is the highest position of the piston in the cylinder (that is, the place where the piston stops moving up and is ready to start moving down) (see Fig. 4).
The lowest position of the piston in the cylinder (that is, the place where the piston stops moving down and is ready to start moving up) is called bottom dead center (BDC) (see Fig. 4).
The distance between the extreme positions of the piston (from TDC to BDC) is called the piston stroke.
As the piston moves from top to bottom (from TDC to BDC), the volume above it changes from minimum to maximum. The minimum volume in the cylinder above the piston when it is at TDC is the combustion chamber.
And the volume above the cylinder, when it is at BDC, is called the working volume of the cylinder. In turn, the working volume of all engine cylinders in total, expressed in liters, is called the working volume of the engine. The total volume of the cylinder is the sum of its working volume and the volume of the combustion chamber at the moment the piston is at BDC.
An important characteristic of an internal combustion engine is its compression ratio, which is defined as the ratio of the total volume of the cylinder to the volume of the combustion chamber. The compression ratio shows how many times the air-fuel mixture entering the cylinder is compressed when the piston moves from BDC to TDC. For gasoline engines, the compression ratio is in the range of 6–14, for diesel engines - 14–24. The compression ratio largely determines the power of the engine and its efficiency, and also significantly affects the toxicity of exhaust gases.
Engine power is measured in kilowatts or horsepower (more commonly used). At the same time, 1 l. With. equals approximately 0.735 kW. As we have already said, the operation of an internal combustion engine is based on the use of the pressure force of the gases formed during the combustion of the air-fuel mixture in the cylinder.
In gasoline and gas engines, the mixture is ignited by a spark plug (Fig. 7), in diesel engines it is ignited by compression.
Rice. 7 Spark plug
When a single-cylinder engine is running, its crankshaft rotates unevenly: at the moment of combustion of the combustible mixture it accelerates sharply, and the rest of the time it slows down. To improve the uniformity of rotation on the crankshaft, coming out of the engine housing, a massive disk is fixed - a flywheel (see Fig. 6). When the engine is running, the flywheel rotates.
2.2.1. Two-stroke and four-stroke device
internal combustion engines;
A two-stroke engine is a piston internal combustion engine in which the working process in each of the cylinders takes place in one revolution of the crankshaft, that is, in two piston strokes. The compression and stroke strokes in a two-stroke engine occur in the same way as in a four-stroke one, but the processes of cleaning and filling the cylinder are combined and are carried out not within individual strokes, but in a short time when the piston is near the bottom dead center (Fig. 8).
Fig.8 Two-stroke engine
Due to the fact that in a two-stroke engine, with an equal number of cylinders and the number of revolutions of the crankshaft, the working strokes occur twice as often, the liter power of two-stroke engines is higher than that of four-stroke engines - theoretically twice, in practice 1.5-1.7 times, since part of the useful stroke of the piston is occupied by gas exchange processes, and the gas exchange itself is less perfect than in four-stroke engines.
Unlike four-stroke engines, where the expulsion of exhaust gases and the suction of a fresh mixture is carried out by the piston itself, in two-stroke engines, gas exchange is carried out by supplying a working mixture or air (in diesel engines) to the cylinder under pressure created by a scavenge pump, and the gas exchange process itself is called - purge. During the scavenging process, fresh air (mixture) forces combustion products out of the cylinder into the exhaust organs, taking their place.
According to the method of organizing the movement of purge air flows (mixtures), two-stroke engines are distinguished with contour and direct-flow purge.
A four-stroke engine is a piston internal combustion engine in which the working process in each of the cylinders is completed in two revolutions of the crankshaft, that is, in four strokes of the piston (stroke). These beats are:
First stroke - inlet:
During this cycle, the piston moves from TDC to BDC. The intake valve is open and the exhaust valve is closed. Through the inlet valve, the cylinder is filled with a combustible mixture until the piston is at BDC, that is, its further downward movement becomes impossible. From what was said earlier, we already know that the movement of the piston in the cylinder entails the movement of the crank, and therefore the rotation of the crankshaft and vice versa. So, for the first stroke of the engine (when the piston moves from TDC to BDC), the crankshaft rotates half a turn (Fig. 9).
Fig.9 First stroke - suction
Second step - compression .
After the air-fuel mixture prepared by the carburetor or injector enters the cylinder, mixes with the remnants of the exhaust gases and the intake valve closes behind it, it becomes working. Now the moment has come when the working mixture has filled the cylinder and there is nowhere for it to go: the intake and exhaust valves are securely closed. At this point, the piston starts moving from bottom to top (from BDC to TDC) and tries to press the working mixture against the cylinder head. However, as they say, he will not succeed in erasing this mixture into powder, since the piston
it cannot, but the internal space of the cylinder is designed in such a way (and accordingly the crankshaft is positioned and the dimensions of the crank are selected) so that above the piston located at TDC, there is always, if not very large, but free space - the combustion chamber. By the end of the compression stroke, the pressure in the cylinder increases to 0.8–1.2 MPa, and the temperature reaches 450–500 °C. (fig.10)
Fig.10 Second cycle - compression
Third cycle - working stroke (main)
The third cycle is the most crucial moment when thermal energy is converted into mechanical energy. At the beginning of the third stroke (and in fact at the end of the compression stroke), the combustible mixture is ignited with the help of a spark plug (Fig. 11)
Fig. 11. Third cycle, working stroke.
Fourth measure - release
During this process, the intake valve is closed and the exhaust valve is open. The piston, moving from bottom to top (from BDC to TDC), pushes the exhaust gases remaining in the cylinder after combustion and expansion through the open exhaust valve into the exhaust channel (Fig. 12)
Fig.12 Release.
All four cycles are periodically repeated in the engine cylinder, thereby ensuring its continuous operation, and are called the duty cycle.
2.3 Modern internal combustion engines.
2.3.1. New design solutions implemented in the internal combustion engine.
From the time of Lenoir to the present, the internal combustion engine has undergone great changes. Their appearance, device, power has changed. For many years, designers around the world have been trying to increase the efficiency of an internal combustion engine, with less fuel, to achieve more power. The first step towards this was the development of industry, the emergence of more accurate machine tools for the manufacture of DVS, equipment, and new (light) metals appeared. The next steps in motor building depended on the ownership of the motors. Powerful, economical, compact, easy to maintain, durable engines were needed in the building's car. In shipbuilding, tractor building, would traction engines with a large power reserve be needed (mainly diesel engines). In aviation, powerful, failure-free, durable engines.
To achieve the above parameters, high-revving and low-revving were used. In turn, on all engines, the compression ratios, cylinder volumes, valve timing, the number of intake and exhaust valves per cylinder, and the methods of supplying the mixture to the cylinder changed. The first engines were with two valves, the mixture was fed through a carburetor, consisting of an air diffuser, throttle valve and a calibrated fuel jet. Carburettors were quickly upgraded, adapting to new engines and their operating modes. The main task of the carburetor is the preparation of a combustible mixture and its supply to the engine manifold. Further, other methods were used to increase the power and efficiency of the internal combustion engine.
2.3.2. Challenges faced by designers.
Technological progress has stepped so far that internal combustion engines have changed almost beyond recognition. The compression ratios in the cylinders of the internal combustion engine have increased to 15 kg/sq.cm for gasoline engines and up to 29 kg/sq.cm for diesel engines. The number of valves has grown to 6 per cylinder, from small engine volumes they remove the power that large-volume engines used to give out, for example: 120 hp is removed from a 1600 cc engine, and 2400 cc from an engine. up to 200 hp With all this, the requirements for D.V.S. increases every year. It has to do with the tastes of the consumer. Engines are subject to requirements related to the reduction of harmful gases. Nowadays, the EURO-3 standard has been introduced in Russia, and the EURO-4 standard has been introduced in European countries. This forced designers around the world to switch to a new way of fuel supply, control, engine operation. In our time, for the work of D.V.S. controls, manages, microprocessor. Exhaust gases are afterburned by different types of catalysts. The task of modern designers is as follows: to please the consumer, by creating motors with the necessary parameters, and to meet the EURO-3, EURO-4 standards.
2.4. Advantage and disadvantages
over other types of internal combustion engines.
Assessing the advantages and disadvantages of D.V.S. with other types of engines, you need to compare specific types of engines.
2.5. The use of an internal combustion engine.
D.V.S. used in many vehicles and in industry. Two-stroke engines are used where small size is important but fuel economy is relatively unimportant, such as motorcycles, small motorboats, chainsaws, and motorized tools. Four-stroke engines are installed on the vast majority of other vehicles.
3. Conclusion.
We analyzed the discovery and achievements of scientists on the issue of the invention of internal combustion engines, found out what their advantages and disadvantages are.
4. List of references.
1. Internal combustion engines, vol. 1-3, Moscow.. 1957.
2. Physics grade 8. A.V. Peryshkin.
3. Wikipedia (free encyclopedia)
4. Magazine "Behind the wheel"
5. A large reference book for students in grades 5-11. Moscow. Drofa Publishing.
5. Application
Fig.1 http://images.yandex.ru
Fig.2 http://images.yandex.ru
Fig.3 http://images.yandex.ru
Fig.4 http://images.yandex.ru
Fig.5 http://images.yandex.ru
Fig.6 http://images.yandex.ru
Fig.7 http://images.yandex.ru
Fig.8 http://images.yandex.ru
Fig.9 http://images.yandex.ru
Fig.10 http://images.yandex.ru
Fig.11 http://images.yandex.ru
Fig.12 http://images.yandex.ru
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-and-rod transmission 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).
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 cycles:
- 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 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.
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 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.
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).
see also
- Philippe Lebon - French engineer who received a patent in 1801 for an internal combustion engine that compresses a mixture of gas and air.
- Rotary engine: designs and classification
- Rotary piston engine (Wankel engine)
Notes
Links
- Ben Knight "Increasing mileage" //Article on technologies that reduce fuel consumption of automotive internal combustion engines
At present, the internal combustion engine is the main type of automobile engine. An internal combustion engine (abbreviated name - ICE) is a heat engine that converts the chemical energy of fuel into mechanical work.
There are the following main types of internal combustion engines: piston, rotary piston and gas turbine. Of the presented types of engines, the most common is a piston internal combustion engine, so the device and the principle of operation are considered using its example.
Virtues piston internal combustion engine, which ensured its wide application, are: autonomy, versatility (combination with various consumers), low cost, compactness, low weight, the ability to quickly start, multi-fuel.
However, internal combustion engines have a number of significant shortcomings, which include: high noise level, high crankshaft speed, exhaust gas toxicity, low resource, low efficiency.
Depending on the type of fuel used, gasoline and diesel engines are distinguished. Alternative fuels used in internal combustion engines are natural gas, alcohol fuels - methanol and ethanol, hydrogen.
From the point of view of ecology, the hydrogen engine is promising, because. does not create harmful emissions. Along with internal combustion engines, hydrogen is used to create electrical energy in the fuel cells of cars.
Internal combustion engine device
A piston internal combustion engine includes a housing, two mechanisms (crank and gas distribution) and a number of systems (inlet, fuel, ignition, lubrication, cooling, exhaust and control system).
The engine housing integrates the cylinder block and the cylinder head. The crank mechanism converts the reciprocating motion of the piston into rotational motion of the crankshaft. The gas distribution mechanism ensures the timely supply of air or a fuel-air mixture to the cylinders and the release of exhaust gases.
The engine management system provides electronic control of the internal combustion engine systems.
The operation of the internal combustion engine
The principle of operation of the internal combustion engine is based on the effect of thermal expansion of gases that occurs during the combustion of the fuel-air mixture and ensures the movement of the piston in the cylinder.
The operation of a piston internal combustion engine is carried out cyclically. Each work cycle occurs in two revolutions of the crankshaft and includes four cycles (four-stroke engine): intake, compression, power stroke and exhaust.
During the intake and power strokes, the piston moves down, while the compression and exhaust strokes move up. The operating cycles in each of the engine cylinders do not coincide in phase, which ensures uniform operation of the internal combustion engine. In some designs of internal combustion engines, the operating cycle is implemented in two cycles - compression and power stroke (two-stroke engine).
On the intake stroke the intake and fuel systems provide the formation of a fuel-air mixture. Depending on the design, the mixture is formed in the intake manifold (central and multipoint injection of gasoline engines) or directly in the combustion chamber (direct injection of gasoline engines, injection of diesel engines). When the intake valves of the gas distribution mechanism are opened, air or a fuel-air mixture is supplied into the combustion chamber due to the vacuum that occurs when the piston moves down.
On the compression stroke The intake valves close and the air-fuel mixture is compressed in the engine cylinders.
Stroke stroke accompanied by ignition of the fuel-air mixture (forced or self-ignition). As a result of ignition, a large amount of gases is formed, which put pressure on the piston and force it to move down. The movement of the piston through the crank mechanism is converted into rotational movement of the crankshaft, which is then used to propel the car.
On tact release the exhaust valves of the gas distribution mechanism open, and the exhaust gases are removed from the cylinders to the exhaust system, where they are cleaned, cooled and noise is reduced. The gases are then released into the atmosphere.
The considered principle of operation of the internal combustion engine makes it possible to understand why the internal combustion engine has a low efficiency - about 40%. At a particular moment in time, as a rule, useful work is performed in only one cylinder, while in the rest - providing cycles: intake, compression, exhaust.
thermal expansion
Reciprocating internal combustion engines
ICE classification
Fundamentals of piston internal combustion engines
Principle of operation
The principle of operation of a four-stroke carburetor engine
The principle of operation of a four-stroke diesel engine
The principle of operation of a two-stroke engine
Four-stroke engine duty cycle
Working cycles of two-stroke engines
INDICATORS CHARACTERIZING ENGINE OPERATION
Average indicated pressure and indicated power
Effective power and average effective pressures
Indicator efficiency and specific indicator fuel consumption
Effective efficiency and specific effective fuel consumption
Motor thermal balance
Innovation
Introduction
The significant growth of all sectors of the national economy requires the movement of a large number of goods and passengers. High maneuverability, cross-country ability and adaptability to work in various conditions makes the car one of the main means of transporting goods and passengers.
An important role is played by road transport in the development of the eastern and non-chernozem regions of our country. The lack of a developed network of railways and the limited use of rivers for navigation make the car the main means of transportation in these areas.
Road transport in Russia serves all sectors of the national economy and occupies one of the leading places in the unified transport system of the country. The share of road transport accounts for over 80% of the goods transported by all modes of transport combined, and more than 70% of passenger traffic.
Road transport was created as a result of the development of a new branch of the national economy - the automotive industry, which at the present stage is one of the main links in the domestic engineering industry.
The beginning of the creation of the car was laid more than two hundred years ago (the name "car" comes from the Greek word autos - "self" and the Latin mobilis - "mobile"), when they began to produce "self-propelled" carts. They first appeared in Russia. In 1752, the Russian self-taught mechanic peasant L. Shamshurenkov created a "self-running carriage" quite perfect for its time, set in motion by the power of two people. Later, the Russian inventor I.P. Kulibin created a "scooter cart" with a pedal drive. With the advent of the steam engine, the creation of self-propelled carts advanced rapidly. In 1869-1870. J. Cugno in France, and a few years later in England, steam cars were built. The widespread use of the car as a vehicle begins with the advent of the high-speed internal combustion engine. In 1885, G. Daimler (Germany) built a motorcycle with a gasoline engine, and in 1886, K. Benz - a three-wheeled cart. Around the same time, in industrialized countries (France, Great Britain, USA), cars with internal combustion engines were created.
At the end of the 19th century, the automobile industry arose in a number of countries. In tsarist Russia, attempts were repeatedly made to organize their own mechanical engineering. In 1908, the production of automobiles was organized at the Russian-Baltic Carriage Works in Riga. For six years, cars were produced here, assembled mainly from imported parts. In total, the plant built 451 cars and a small number of trucks. In 1913, the car park in Russia was about 9,000 cars, most of them - foreign production. After the Great October Socialist Revolution, the domestic automobile industry had to be created almost anew. The beginning of the development of the Russian automotive industry dates back to 1924, when the first AMO-F-15 trucks were built at the AMO plant in Moscow.
In the period 1931-1941. large-scale and mass production of cars is created. In 1931, mass production of trucks began at the AMO plant. In 1932, the GAZ plant went into operation.
In 1940, the Moscow Plant of Small Cars began the production of small cars. A little later, the Ural Automobile Plant was created. During the years of the post-war five-year plans, the Kutaisi, Kremenchug, Ulyanovsk, Minsk automobile plants came into operation. Since the late 60s, the development of the automotive industry has been characterized by a particularly rapid pace. In 1971, the Volga Automobile Plant named after V.I. 50th anniversary of the USSR.
In recent years, automotive industry plants have mastered many samples of modernized and new automotive equipment, including for agriculture, construction, trade, oil and gas and forestry industries.
Internal combustion engines
Currently, there are a large number of devices that use the thermal expansion of gases. Such devices include a carburetor engine, diesel engines, turbojet engines, etc.
Heat engines can be divided into two main groups:
1. External combustion engines - steam engines, steam turbines, Stirling engines, etc.
2. Internal combustion engines. As power plants for automobiles, internal combustion engines are most widely used, in which the combustion process
fuel with the release of heat and its transformation into mechanical work occurs directly in the cylinders. Most modern cars are equipped with internal combustion engines.
The most economical are piston and combined internal combustion engines. They have a fairly long service life, relatively small overall dimensions and weight. The main disadvantage of these engines should be considered the reciprocating movement of the piston, associated with the presence of a crank mechanism, which complicates the design and limits the possibility of increasing the speed, especially with significant engine sizes.
And now a little about the first internal combustion engines. The first internal combustion engine (ICE) was created in 1860 by the French engineer Ethwen Lenoir, but this machine was still very imperfect.
In 1862, the French inventor Beau de Rocha suggested using a four-stroke cycle in an internal combustion engine:
1. suction;
2. compression;
3. combustion and expansion;
4. exhaust.
This idea was used by the German inventor N. Otto, who built the first four-stroke internal combustion engine in 1878. The efficiency of such an engine reached 22%, which exceeded the values obtained when using engines of all previous types.
The rapid spread of internal combustion engines in industry, transport, agriculture and stationary energy was due to a number of their positive features.
The implementation of the internal combustion engine cycle in one cylinder with low losses and a significant temperature difference between the heat source and the refrigerator ensures high efficiency of these engines. High efficiency is one of the positive qualities of internal combustion engines.
Among internal combustion engines, diesel is currently such an engine that converts the chemical energy of fuel into mechanical work with the highest efficiency over a wide range of power changes. This quality of diesel engines is especially important, given that the reserves of petroleum fuels are limited.
The positive features of internal combustion engines should also include the fact that they can be connected to almost any consumer of energy. This is due to the wide possibilities of obtaining the appropriate characteristics of the change in power and torque of these engines. The engines in question are successfully used on cars, tractors, agricultural machines, diesel locomotives, ships, power plants, etc., i.e. Internal combustion engines are distinguished by good adaptability to the consumer.
The relatively low initial cost, compactness and low weight of internal combustion engines have made it possible to widely use them in power plants that are widely used and have a small engine compartment.
Installations with internal combustion engines have a large autonomy. Even aircraft with internal combustion engines can fly for tens of hours without refilling fuel.
An important positive quality of internal combustion engines is the ability to quickly start them under normal conditions. Engines operating at low temperatures are equipped with special devices to facilitate and accelerate starting. After starting, the motors can take full load relatively quickly. Internal combustion engines have a significant braking torque, which is very important when using them in transport installations.
The positive quality of diesels is the ability of one engine to run on many fuels. So known are the designs of automotive multi-fuel engines, as well as high-power marine engines that operate on various fuels - from diesel to boiler oil.
But along with the positive qualities of internal combustion engines, they have a number of disadvantages. Among them, the aggregate power is limited compared to, for example, with steam and gas turbines, a high noise level, a relatively high crankshaft speed at start-up and the impossibility of directly connecting it to the consumer's drive wheels, exhaust gas toxicity, reciprocating piston movement, limiting the speed and are the cause of the appearance of unbalanced inertia forces and moments from them.
But it would be impossible to create internal combustion engines, their development and application, if not for the effect of thermal expansion. After all, in the process of thermal expansion, gases heated to a high temperature perform useful work. Due to the rapid combustion of the mixture in the cylinder of an internal combustion engine, the pressure rises sharply, under the influence of which the piston moves in the cylinder. And this is the very necessary technological function, i.e. force action, the creation of high pressures, which is performed by thermal expansion, and for which this phenomenon is used in various technologies, and in particular in internal combustion engines.
Subject: INTERNAL COMBUSTION ENGINES.
Lecture plan:
2. Classification of internal combustion engines.
3. The general arrangement of the internal combustion engine.
4. Basic concepts and definitions.
5. ICE fuels.
1. Definition of internal combustion engines.
Internal combustion engines (ICE) are called a reciprocating heat engine, in which the processes of fuel combustion, heat release and its transformation into mechanical work occur directly in its cylinder.
2. Classification of internal combustion engines
According to the method of implementation of the working cycle of the internal combustion engine fall into two broad categories:
1) four-stroke internal combustion engines, in which the working cycle in each cylinder takes four strokes of the piston or two revolutions of the crankshaft;
2) two-stroke internal combustion engines, in which the working cycle in each cylinder takes place in two piston strokes or one revolution of the crankshaft.
According to the method of mixing four-stroke and two-stroke internal combustion engines distinguish between:
1) Internal combustion engines with external mixing, in which the combustible mixture is formed outside the cylinder (these include carburetor and gas engines);
2) ICE with internal mixing, in which the combustible mixture is formed directly inside the cylinder (these include diesel engines and engines with light fuel injection into the cylinder).
According to the method of ignition combustible mixture are distinguished:
1) ICE with ignition of a combustible mixture from an electric spark (carburetor, gas and light fuel injection);
2) ICE with fuel ignition in the process of mixture formation from the high temperature of compressed air (diesel engines).
By type of fuel used distinguish:
1) internal combustion engines operating on light liquid fuel (gasoline and kerosene);
2) internal combustion engines operating on heavy liquid fuel (gas oil and diesel fuel);
3) internal combustion engines operating on gas fuel (compressed and liquefied gas; gas coming from special gas generators, in which solid fuel - firewood or coal - is burned with a lack of oxygen).
According to the cooling method distinguish:
1) liquid-cooled internal combustion engine;
2) ICE with air cooling.
According to the number and arrangement of cylinders distinguish:
1) single and multi-cylinder internal combustion engines;
2) single row (vertical and horizontal);
3) two-row (-shaped, with opposite cylinders).
By appointment distinguish:
1) transport internal combustion engines installed on various vehicles (cars, tractors, construction vehicles and other objects);
2) stationary;
3) special internal combustion engines, which usually play an auxiliary role.
3. General arrangement of the internal combustion engine
Widely used in modern technology, internal combustion engines consist of two main mechanisms: crank and gas distribution; and five systems: power supply, cooling, lubrication, start-up and ignition systems (in carburetor, gas and engines with light fuel injection).
crank mechanism designed to perceive the pressure of gases and convert the rectilinear movement of the piston into the rotational movement of the crankshaft.
Gas distribution mechanism designed to fill the cylinder with a combustible mixture or air and to clean the cylinder from combustion products.
The gas distribution mechanism of four-stroke engines consists of intake and exhaust valves driven by a camshaft (camshaft, which is driven from the crankshaft through a gear block. The camshaft rotation speed is half that of the crankshaft rotation speed.
Gas distribution mechanism two-stroke engines are usually made in the form of two transverse slots (holes) in the cylinder: exhaust and intake, opened sequentially at the end of the piston stroke.
Supply system is designed to prepare and supply a combustible mixture of the required quality (carburetor and gas engines) or portions of atomized fuel at a certain moment (diesel engines) into the piston space.
In carburetor engines, fuel enters the carburetor by means of a pump or by gravity, where it mixes with air in a certain proportion and enters the cylinder through an inlet valve or hole.
In gas engines, air and combustible gas are mixed in special mixers.
In diesel engines and internal combustion engines with light fuel injection, fuel is supplied to the cylinder at a certain moment, usually using a plunger pump.
Cooling system is designed for forced heat removal from heated parts: cylinder block, cylinder head, etc. Depending on the type of heat-removing substance, liquid and air cooling systems are distinguished.
The liquid cooling system consists of channels surrounding the cylinders (liquid jacket), a liquid pump, a radiator, a fan and a number of auxiliary elements. The liquid cooled in the radiator is pumped into the liquid jacket by means of a pump, cools the cylinder block, heats up and enters the radiator again. In the radiator, the liquid is cooled due to the oncoming air flow and the flow created by the fan.
The air cooling system is the fins of the engine cylinders, blown by an incoming or fan-generated air flow.
Lubrication system serves for continuous supply of lubricant to the friction units.
Launch system is designed for quick and reliable engine starting and is usually an auxiliary engine: electric (starter) or low-power gasoline).
Ignition system used in carburetor engines and serves to ignite the combustible mixture by means of an electric spark created in a spark plug screwed into the engine cylinder head.
4. Basic concepts and definitions
top dead center- TDC, call the position of the piston, the most distant from the axis of the crankshaft.
bottom dead center- BDC, call the position of the piston, the least distant from the axis of the crankshaft.
At dead points, the piston speed is , because they change the direction of movement of the piston.
The movement of the piston from TDC to BDC or vice versa is called piston stroke and is denoted.
The volume of the cylinder cavity when the piston is at BDC is called the total volume of the cylinder and is denoted by .
The compression ratio of an engine is the ratio of the total volume of the cylinder to the volume of the combustion chamber.
The compression ratio shows how many times the volume of the piston space decreases when the piston moves from BDC to TDC. As will be shown in the future, the compression ratio largely determines the efficiency (efficiency) of any internal combustion engine.
The graphical dependence of the pressure of gases in the piston space on the volume of the piston space, the movement of the piston or the angle of rotation of the crankshaft is called engine indicator chart.
5. ICE fuel
5.1. Fuel for carburetor engines
Gasoline is used as fuel in carbureted engines. The main thermal indicator of gasoline is its lower calorific value (about 44 MJ/kg). The quality of gasoline is evaluated by its main operational and technical properties: volatility, anti-knock resistance, thermal-oxidative stability, absence of mechanical impurities and water, stability during storage and transportation.
The volatility of gasoline characterizes its ability to move from a liquid phase to a vapor phase. The volatility of gasoline is determined by its fractional composition, which is found by distilling it at different temperatures. The volatility of gasoline is judged by the boiling points of 10, 50 and 90% of gasoline. So, for example, the boiling point of 10% of gasoline characterizes its starting qualities. The greater the volatility at low temperatures, the better the quality of gasoline.
Gasolines have different antiknock resistance, i.e. different propensity to detonate. The antiknock resistance of gasoline is estimated by the octane number (OC), which is numerically equal to the percentage by volume of isooctane in a mixture of isooctane and heptane, which is of different knock resistance to this fuel. The octane of isooctane is taken as 100, and that of heptane is taken as zero. The higher the octane of gasoline, the lower its tendency to detonate.
To increase the OCh, ethyl liquid is added to gasoline, which consists of tetraethyl lead (TES) - an antiknock agent and dibromoethene - a scavenger. Ethyl liquid is added to gasoline in the amount of 0.5-1 cm 3 per 1 kg of gasoline. Gasolines with the addition of ethyl liquid are called leaded gasolines, they are poisonous, and precautions must be taken when using them. Leaded gasoline is colored red-orange or blue-green.
Gasoline must not contain corrosive substances (sulphur, sulfur compounds, water-soluble acids and alkalis), since their presence leads to corrosion of engine parts.
Thermal-oxidative stability of gasoline characterizes its resistance to resin and carbon formation. Increased soot and tar formation causes a deterioration in heat removal from the walls of the combustion chamber, a decrease in the volume of the combustion chamber and a disruption in the normal supply of fuel to the engine, which leads to a decrease in engine power and efficiency.
Gasoline must not contain mechanical impurities and water. The presence of mechanical impurities causes clogging of filters, fuel lines, carburetor channels and increases wear on cylinder walls and other parts. The presence of water in gasoline makes it difficult to start the engine.
The storage stability of gasoline characterizes its ability to retain its original physical and chemical properties during storage and transportation.
Automobile gasolines are marked with the letter A with a digital index, they show the value of the OC. In accordance with GOST 4095-75, gasoline grades A-66, A-72, A-76, AI-93, AI-98 are produced.
5.2. Fuel for diesel engines
Diesel engines use diesel fuel, which is a product of petroleum refining. The fuel used in diesel engines must have the following basic qualities: optimal viscosity, low pour point, high ignition tendency, high thermal and oxidative stability, high anti-corrosion properties, absence of mechanical impurities and water, good storage and transportation stability.
The viscosity of diesel fuel affects fuel delivery and atomization. If the viscosity of the fuel is insufficient, leakage is crowned through the gaps in the injector nozzles and in the inert pairs of the fuel pump, and at high viscosity, the processes of fuel supply, atomization and mixture formation in the engine worsen. The viscosity of the fuel depends on the temperature. The pour point of the fuel affects the process of fuel supply from the fuel tank. into the engine cylinders. Therefore, the fuel must have a low pour point.
The tendency of fuel to ignite affects the course of the combustion process. Diesel fuels, which have a high tendency to ignite, provide a smooth flow of the combustion process, without a sharp increase in pressure, the flammability of the fuel is estimated by the cetane number (CN), which is numerically equal to the percentage by volume of cetane in a mixture of cetane and alphamethylnaphthalene, equivalent in flammability to this fuel. For diesel fuels CCH = 40-60.
Thermal-oxidative stability of diesel fuel characterizes its resistance to resin and carbon formation. Increased soot and tar formation causes a deterioration in heat removal from the walls of the combustion chamber and a disruption in the supply of fuel through the nozzles to the engine, which leads to a decrease in engine power and efficiency.
Diesel fuel must not contain corrosive substances, since their presence leads to corrosion of parts of the fuel supply equipment and the engine. Diesel fuel must not contain mechanical impurities and water. The presence of mechanical impurities causes clogging of filters, fuel lines, injectors, channels of the fuel pump, and increases the wear of parts of the fuel equipment of the engine. The stability of diesel fuel characterizes its ability to retain its initial physical and chemical properties during storage and transportation.
For autotractor diesel engines, industrially produced fuels are used: DL - diesel summer (at temperatures above 0 ° C), DZ - diesel winter (at temperatures up to -30 ° C); YES - diesel arctic (at temperatures below -30 ° C) (GOST 4749-73).
