The engine piston is a detail having a cylindrical shape and performing reciprocating movements inside the cylinder. It belongs to the number of details most characteristic of the engine, since the implementation of the thermodynamic process occurring in the DVS occurs precisely when it is assisted. Piston:
- perceiving gases pressure transmits the emerging force on;
- seals the combustion chamber;
- warning from her overwhelming heat.
The photo above shows four tact of engine piston.
Extreme conditions determine the material of the manufacture of pistons
The piston is operated in extreme conditions, characteristic features which are high: pressure, inertial loads and temperatures. That is why the basic requirements for the materials for its manufacture are referred to:
- high mechanical strength;
- good thermal conductivity;
- low density;
- minor linear expansion coefficient, antifriction properties;
- good corrosion resistance.
Pistons can be:
- licenses;
- forged.
The design features of the piston are determined by its purpose
The main conditions defining the design of the piston are the type of engine and the form of the combustion chamber, the peculiarities of the combustion process passing in it. Constructively, the piston is a one-piece element consisting of:
- heads (bottoms);
- sealing part;
- skirts (guide part).
Is there a piston of a gasoline engine from diesel? The surfaces of the heads of the pistons of gasoline and diesel engines are distinguished constructively. In the gasoline engine, the head surface is flat or close to it. Sometimes there are grooves that contribute to the full opening of the valves. For the pistons of engines equipped with a system direct injection Fuel (START), characteristic of a more complex form. The head of the piston in the diesel engine is significantly different from the gasoline, due to the combustion chamber of the specified form in it, a better twist and mixture formation is ensured.
In the photo of the engine piston scheme.
Piston rings: types and composition
The sealing part of the piston includes piston rings that ensure the density of the piston connection with the cylinder. Technical condition The engine is determined by its sealing ability. Depending on the type and purpose of the engine, the number of rings and their location are selected. The most common scheme is a diagram of two compression and one carbonic rings.
Piston rings are manufactured mainly from a special gray high-strength cast iron having:
- high stable strength and elasticity indicators in operating temperatures throughout the entire rings service period;
- high wear resistance under intensive friction;
- good antifriction properties;
- the ability of fast and efficient processing to the surface of the cylinder.
The main purpose of the compression ring is to obstruct the gas engine from the combustion chamber. Especially large loads come on the first compression ring. Therefore, when making rings for pistons of some forced gasoline and all diesel engines Install steel insert, which increases the strength of the rings and allows you to ensure the maximum degree of compression. In the form of compression rings can be:
- trapezoidal;
- tBCH;
- tconic.
The oil-chain ring is placed on the removal of excess oil from the walls of the cylinder and the obstruction of its penetration into the combustion chamber. It is distinguished by the presence of a plurality of drainage holes. In the designs of some rings there are spring expansion.
The shape of the guide part of the piston (otherwise, skirts) may be a cone-shaped or barrel-shapedthat allows you to compensate for its expansion when high operating temperatures achieve. Under their influence, the piston shape becomes cylindrical. The side surface of the piston in order to reduce the thread caused by friction is coated with a layer of antifriction material, for this purpose graphite or molybdenum disulfide is used. Thanks to the holes with tides made in the piston skirt, the piston finger is fixed.
A node consisting of a piston, compression, oil-chained rings, and the piston finger is called a piston group. The function of its connection to the connecting rod is assigned on a steel piston finger having a tubular shape. The requirements are presented to it:
- minimal deformation when working;
- high strength with variable load and wear resistance;
- good impact resistance;
- small mass.
- fixed in the piston bosses, but rotate in the head of the rod;
- fixed in the head of the rod and rotate in the piston bosses;
- freely rotating in the piston buses and in the rod head.
The fingers installed in the third option are called floating. They are the most popular because their wear in length and circle is insignificant and uniform. Upon their use, the danger of jamming is minimized. In addition, they are convenient when mounting.
Distraction of excess heat from the piston
Along with significant mechanical loads, the piston is also subject to the negative effects of extremely high temperatures. Heat OT piston group Assigned:
- cooling system from the walls of the cylinder;
- the inner cavity of the piston, then a piston finger and connecting rod, as well as oil circulating in the lubrication system;
- partially cold fuel-air mixture supplied to cylinders.
- splashing oil through a special nozzle or hole in the connecting rod;
- oil fog in the cylinder cavity;
- oil injection into the zone of the rings, in a special channel;
- circulation of oil in the piston head on a tubular coil.
Video about the four-stroke engine - the principle of operation:
Definition.
Piston Engine - one of the embodiments of the internal combustion engine, working through the transformation of the internal energy of the combusting fuel in mechanical work progressive movement of piston. The piston comes in motion when expanding the working fluid in the cylinder.
The crank-connecting mechanism converts the translational movement of the piston into the rotational motion of the crankshaft.
The operating cycle of the engine consists of a sequence of tact of one-sided translational strokes of the piston. The engines with two and four clocks of work are subdivided.
The principle of operation of the two-stroke and four-stroke piston engines.
Number of cylinders B. piston engines It may vary depending on the design (from the 1st to 24). The engine volume is considered to be equal to the sum of the volumes of all cylinders, the capacity of which is found on the work. cross section on the stroke of the piston.
IN piston engines Different designs in different ways are the process of fuel ignition:
Electrical dischargewhich is formed on the ignition candlelight. Such engines can operate both on gasoline and other types of fuel (natural gas).
Squeezing of the working body:
IN diesel enginesworking on diesel fuel or a gas (with a 5% addition of diesel fuel), air is compressed, and when the piston is reached the maximum compression point, the fuel injection occurs, which flammives from the heated air contact.
Engines compression model. Fuel supply in them exactly the same as in gasoline engines. Therefore, for their work, a special composition of fuel is needed (with impurities of air and diethyl ether), as well as accurate adjustment of the degree of compression. Compressor engines found their distribution in aircraft and automotive industry.
Kalil engines. The principle of their action is largely similar to the engines of the compression model, but it did not cost without construction features. The role of the ignition in them is performed - a calil candle, the intensity of which is maintained by the energy of the combusting fuel on the previous tact. The composition of the fuel is also special, the basis is taken by methanol, nitromethane and castor oil. Engines are used, both on cars and on airplanes.
Calorizator engines. In these engines, ignition occurs when fuel contact with hot engine parts (usually - the bottom of the piston). Martin gas is used as fuel. They are used as drive engines on rolling mills.
Fuel types used in piston engines:
Liquid fuel - diesel fuel, gasoline, alcohols, biodiesel;
Gaza - natural and biological gases, liquefied gases, hydrogen, gaseous oil cracking products;
Produced in a gas generator from coal, peat and wood, carbon monoxide is also used as fuel.
Work of piston engines.
Engine operation cycles Details are painted in technical thermodynamics. Various cyclics are described by various thermodynamic cycles: Otto, diesel engine, atkinson or miller and trinker.
Causes of breakdowns of piston engines.
PDD piston engine.
Maximum efficiency that managed to get on piston Engine is 60%, i.e. a little less than half of the combusting fuel is spent on the heating of the engine parts, and also comes out with heat exhaust gases. In this connection, it has to equip the engine cooling systems.
Classification of cooling systems:
Air S. - Give heat air due to the ribbed outer surface of the cylinders. Lie applied
bo on weak engines (dozens of hp), or on powerful aircraft engines, which are cooled by a rapid air flow.
Liquid SO - The liquid (water, antifreeze or oil) is used as a cooler, which pumps through the cooling shirt (channels in the cylinder block walls) and enters the cooling radiator in which it is cooled by air flows, natural or fans. Rarely, but a metal sodium is also used as a coolant, which is melted from heat heating engine.
Application.
Piston enginesThanks to its power range, (1 watt - 75,000 kW) have gained more popularity not only in the automotive industry, but also aircraft and shipbuilding. They are also used to drive combat, agricultural and construction equipment, electric generators, water pumps, chainsaws and other machines, both mobile and stationary.
The main types of internal combustion engines and steam machines have one common drawback. It is that the reciprocating movement requires a transformation into a rotational movement. This, in turn, causes low productivity, as well as a sufficiently high wear of the details of the mechanism included in different types engines.
Pretty many people thought about creating such a motor in which the moving elements were only rotating. However, it was possible to solve this task only to one person. Felix Vankel - self-taught mechanic - became the inventor of a rotary-piston engine. For your life, this person did not receive any specialty, nor higher education. Consider the further rotary-piston vankel engine.
Brief biography of the inventor
Felix Vankel was born in 1902, on August 13, in the small town of Lar (Germany). In the first world father of the future inventor died. Because of this, Vankel had to throw his studies in the gymnasium and make a seller's assistant in the shop selling books under the publisher. Thanks to this, he was addicted to reading. Felix studied specifications Engines, automotive, mechanics independently. Knowledge he screamed from books that were sold in the shop. It is believed that the scheme of the Vankiel engine (more precisely, the idea of \u200b\u200bits creation) visited in a dream. It is not known, the truth is or not, but it can be said that the inventor possessed outstanding abilities, a burner for mechanics and peculiar
Pros and cons
The convertible movement of a reciprocating character is completely absent in the rotary engine. The pressure formation occurs in those chambers that are created using the convex surfaces of the rotor of the triangular shape and various parts of the case. Rotational motion rotor provides combustion. It can lead to a decrease in vibration and increase the speed of rotation. Due to the efficiency of efficiency, which is due to the rotary engine has dimensions much less than a conventional piston equivalent power engine.
The rotary engine has one main of all its components. This important component is called a triangular rotor that performs rotational movements within the stator. All three peaks of the rotor, thanks to this rotation, have a permanent connection with the inner wall of the housing. With this contact, combustion chambers are formed, or three volumes of closed type with gas. When rotational rotor movements occur inside the case, the volume of all three formed combustion chambers changes all the time, reminding the action of a conventional pump. All three side surfaces of the rotor work like a piston.
Inside the rotor is a small gear with external teeth, which is attached to the housing. A gear that is more in diameter is connected to this fixed gear, which sets the trajectory of rotational rotor movements inside the housing. Teeth in the greater gear internal.
For the reason that, together with the output shaft, the rotor is associated eccentric, the rotation of the shaft occurs like the handle will rotate the crankshaft. The output shaft will make turnover three times for each of the rotor revolutions.
The rotary engine has such an advantage as a small mass. The most basic engine of the rotary engine has small size and mass. In this case, the handling and characteristics of such an engine will be better. It turns out less weight due to the fact that the need for crankshaft, rods and pistons is simply absent.
The rotary engine has such dimensions that are much less conventional Engine appropriate power. Due to the smaller engine size, the handling will be much better, as well as the machine itself will become more spacious, both for passengers and for the driver.
All parts of the rotary engine are carried out continuous rotational movements in the same direction. The change in their movement occurs just as in the pistons of the traditional engine. Rotary engines are internally balanced. This leads to a decrease in the level of vibration itself. The power of the rotary engine seems much smoother and evenly.
The Vankel engine has a convex special rotor with three faces, which can be called its heart. This rotor performs rotational motions inside the cylindrical surface of the stator. The Mazda rotary engine is the world's first rotary engine, which was designed specifically for the production of serial nature. This development was made early in 1963.
What is RPD?
In the classic four-stroke engine, the same cylinder is used for various operations - injection, compression, combustion and release.In the Rotary Engine, each process is performed in a separate compartment of the camera. The effect is not much different from the separation of the cylinder by four compartments for each of the operations.
In the piston engine, the pressure occurs during the combustion of the mixture causes the pistons to move forward and backward in their cylinders. Rollers I. crankshaft Converts this pushing movement into the rotational, necessary for the movement of the car.
IN rotor engine There is no rectilinear movement that it would be necessary to translate into the rotational. The pressure is formed in one of the compartments of the chamber forcing the rotor rotate, it reduces the vibration and increases the potential magnitude of the engine. As a result, great efficiency, and smaller sizes at the same power as the conventional piston engine.
How does the RPD work?
The function of the piston in the RAP is performed by the scholarships of the rotor, which converts the power of the pressure of gases into the rotational motion of the eccentric shaft. The rotor movement relative to the stator (outer case) is provided by a pair of gears, one of which is rigidly fixed on the rotor, and the second on the lateral lid of the stator. The gear itself is fixed on the engine housing. With her, the gear of the rotor from the gear wheel is rolling around it.
The shaft rotates in the bearings placed on the housing, and has a cylindrical eccentric on which the rotor rotates. The interaction of these gears ensures the expedient movement of the rotor relative to the housing, as a result of which three broken alternating volume cameras are formed. The gear ratio of gears 2: 3, so in one turnover of the eccentric shaft rotor returns to 120 degrees, and for the complete turnover of the rotor in each of the chambers there is a full four-stroke cycle. 
Gas exchange is regulated by the peak of the rotor when it passes through the intake and exhaust window. This design allows a 4-stroke cycle without the use of a special gas distribution mechanism.
The sealing of the chambers is provided by radial and end sealing plates, pressed against the cylinder by centrifugal forces, gas pressure and tape springs. The torque is obtained as a result of the operation of the gas forces through the rotor on the eccentric of the shaft of the mixing formation, inflammation, lubrication, cooling, launch - are fundamentally the same as the conventional piston internal combustion engine
Matching
In the theory in the RAP, several varieties of mixture formation are used: external and internal, based on liquid, solid, gaseous fuels.
Regarding solid fuels it is worth noting that they are initially gasified in gas generators, as they lead to elevated ash formation in the cylinders. Therefore, gaseous and liquid fuels received greater distribution in practice.
The mechanism of formation of the mixture in Vankel engines will depend on the type of fuel used.
When using gaseous fuel, its mixing with air occurs in a special compartment at the input to the engine. Fuel mixture The cylinders enters the finished form.
From liquid fuel, the mixture is prepared as follows:
- The air is mixed with liquid fuel before entering the cylinders, where the combustible mixture comes.
- In the engine cylinders, the liquid fuel and air come separately, and mixing them inside the cylinder. The working mixture is obtained by contacting them with residual gases.
Accordingly, the fuel and air mixture can be prepared outside the cylinders or inside them. From this there is a separation of engines with internal or external formation of the mixture.
Technical characteristics of a rotary-piston engine
| parameters | VAZ-4132. | VAZ-415. |
| number of sections | 2 | 2 |
| Engine chamber work volume, ccm | 1,308 | 1,308 |
| compression ratio | 9,4 | 9,4 |
| Rated power, kW (hp) / min-1 | 103 (140) / 6000 | 103 (140) / 6000 |
| Maximum torque, n * m (kgf * m) / min-1 | 186 (19) / 4500 | 186 (19) / 4500 |
| The minimum frequency of rotation of the eccentric shaft on idlingmin-1 | 1000 | 900 |
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Engine mass, kg |
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Overall dimensions, mm |
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Oil consumption in% of fuel consumption |
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Engine resource to first overhaul, thousand km |
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purpose |
VAZ-21059/21079 |
VAZ-2108/2109/21099/2115/2110 |
models are produced
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engine RPD |
Acceleration time 0-100, sec |
Maximum speed, km \\ h |
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Efficiency of rotary-piston design
Despite the number of flaws, the studies have shown that the general Efficiency engine Vankel is pretty high in modern standards. Its value is 40 - 45%. For comparison, the piston engines of the internal combustion of the efficiency is 25%, in modern turbo diesel engines - about 40%. The highest efficiency in piston diesel engines is 50%. So far, scientists continue to find reserves to enhance the efficiency of the engines.
The final efficiency of the motor operation consists of three main parts:
Studies in this area show that only 75% flammable burns in full. It is believed that this problem is solved by separating the combustion and expansion of gases. It is necessary to provide arrangement of special chambers under optimal conditions. The combustion should occur in a closed volume, subject to increasing temperature indicators and pressure, the expansion process should occur at low temperature indicators.
- The efficiency is mechanical (characterizes the work, the result of which was the formation of the main axis transmitted to the torque consumer).
About 10% of the motor operation is spent on bringing the auxiliary nodes and mechanisms. You can correct this flawping by making changes to the engine device: when the main moving working element does not touch the fixed body. The permanent torque should be present throughout the path of the main working element.
- Thermal efficacy (indicator reflecting the amount of thermal energy formed from combustion combustion, transforming into useful work).
In practice, 65% of the resulting thermal energy is destroyed with spent gases into an external environment. A number of studies showed that it is possible to increase thermal efficiency indicators when the engine design can allow combustion of a fuel in the heat insulated chamber so that the maximum temperature indicators be achieved, and at the end this temperature decreased to the minimum values \u200b\u200bby turning on the steam phase.
Rotary-piston vankiel engine
