Where does the piston go? Piston rings: types and composition

Definition.

piston engine- one of the engine options internal combustion, which works by converting the internal energy of the burning fuel into mechanical work progressive movement of the piston. The piston is set in motion by the expansion of the working fluid in the cylinder.

The crank mechanism converts the translational motion of the piston into rotational motion of the crankshaft.

The working cycle of the engine consists of a sequence of cycles of one-sided translational piston strokes. Subdivided engines with two and four cycles of work.

The principle of operation of two-stroke and four-stroke piston engines.

Number of cylinders in piston engines may vary depending on the design (from 1 to 24). The volume of the engine is considered to be equal to the sum of the volumes of all cylinders, the capacity of which is found by the product of the cross section and the piston stroke.

IN piston engines different designs, the process of fuel ignition occurs in different ways:

Electric spark discharge, which is formed on spark plugs. Such engines can run on both gasoline and other types of fuel (natural gas).

Compression of the working body:

IN diesel engines working on diesel fuel or gas (with 5% addition of diesel fuel), air is compressed, and when the piston reaches the point of maximum compression, fuel is injected, which ignites from contact with heated air.

Compression model engines. The fuel supply in them is exactly the same as in gasoline engines. Therefore, for their operation, a special fuel composition (with impurities of air and diethyl ether) is required, as well as precise adjustment of the compression ratio. Compressor engines have found their distribution in the aircraft and automotive industries.

glow engines. The principle of their operation is in many respects similar to the engines of the compression model, but not without design features. The role of ignition in them is performed by - glow plug, the glow of which is maintained by the energy of the fuel burned in the previous cycle. The composition of the fuel is also special, based on methanol, nitromethane and castor oil. Such engines are used both on cars and on airplanes.

calorific engines. In these engines, ignition occurs when fuel comes into contact with hot parts of the engine (usually the piston crown). Open-hearth gas is used as fuel. They are used as drive motors in rolling mills.

Fuel types used in piston engines:

Liquid fuel– diesel fuel, gasoline, alcohols, biodiesel;

gases– natural and biological gases, liquefied gases, hydrogen, gaseous products of oil cracking;

Produced in a gas generator from coal, peat and wood, carbon monoxide is also used as a fuel.

Operation of piston engines.

Engine cycles described in detail in technical thermodynamics. Different cyclograms are described by different thermodynamic cycles: Otto, Diesel, Atkinson or Miller and Trinkler.

Causes of piston engine failures.

piston engine efficiency.

The maximum efficiency that could be obtained on piston engine is 60%, i.e. slightly less than half of the burning fuel is spent on heating engine parts, and also comes out with heat exhaust gases. In this connection, it is necessary to equip the engines with cooling systems.

Classification of cooling systems:

Air CO- they give off heat to the air due to the ribbed outer surface of the cylinders. Are the
more on weak engines(tens of hp), or on powerful aircraft engines which are cooled by a fast air flow.

Liquid CO- a liquid (water, antifreeze or oil) is used as a coolant, which is pumped through the cooling jacket (channels in the walls of the cylinder block) and enters the cooling radiator, in which it is cooled air currents, natural or from fans. Rarely, sodium metal is also used as a coolant, which is melted by the heat of a warming engine.

Application.

Piston engines, due to their power range (1 watt - 75,000 kW), have gained great popularity not only in the automotive industry, but also in the aircraft industry and shipbuilding. They are also used to drive combat, agricultural and construction equipment, power generators, water pumps, chainsaws and other machines, both mobile and stationary.

Piston - a part of the piston group of the engine, located inside the cylinder. By means of a connecting rod, the piston is connected to crankshaft. The design is designed in such a way that the piston constantly reciprocates during engine operation, converting the energy of the gases expanding during combustion into rotation of the crankshaft.

Piston device

The piston consists of three parts, although it is made from a single blank: the bottom, the sealing part and the skirt. The piston is connected with a connecting rod. The piston is put on the connecting rod and threaded through the part. The shape of the piston crown of an internal combustion engine is never flat. Depending on the design, the bottom may have a complex configuration. Candles, nozzles and valves can be located above the bottom.

The distance from the piston crown to the first compression ring is called the piston firing zone.

Most often, in the bottom of the piston, you can see the recesses designed so that they do not come into contact with the surface of the piston. Recesses tend to be deeper at one end because the flaps above them are set at an angle. In general, as a rule, the general shape of the bottom is made concave. This is due to the fact that the piston, rising up, is at the same time, and for optimal flame propagation, the concave bottom fits perfectly. This form also has its drawbacks - soot is deposited faster in the lower part of the cavity.

The distance from the piston crown to the first compression ring is called the piston firing zone. Because the piston is operating under extreme conditions high temperatures, the fire belt has a strictly calculated height, which also depends on the material from which the piston is made. Reducing the height below a certain limit can lead to premature burnout of the piston.

In the past, the piston was made entirely of steel, but in modern engines lightweight pistons made of aluminum alloys are often used

The piston is a high-precision part, since one of its tasks is to serve as the basis for the compression rings that seal the combustion chamber at the time of compression. Over time, the piston wears out and burns, which leads to a decrease in sealing - hot gases begin to seep between the piston body and the ring, and enter the crankcase, and oil seeps from the crankcase into the combustion chamber.

From this it follows that it can be a sign of piston wear. In addition, this can be judged by the appearance of smoke in the exhaust gas stream - the smoke is formed as a result of the combustion of oil entering the space above the piston.

The combination of the bottom and the sealing part (which serves as the basis for the rings) is called the piston head. In the past, the piston was made entirely of steel, but modern engines often use lightweight pistons made of aluminum alloys. Aluminum is inferior to steel in strength, therefore, to create the basis for the upper compression ring, it is provided with a rim made of cast iron with high anticorrosion and strength properties. In the cast-iron rim, fused into the piston body, a groove is cut into which it is inserted. This type of cast iron is called niresist.

In the lower part of the head there are channels for oil scraper rings. They are cut on the machine and provided with through holes through which the oil removed from the cylinder mirror flows down the inner wall of the piston into the crankcase sump of the cylinder block.

The skirt or guide part of the piston is equipped with two lugs, or bosses, in which holes are made. Since the piston has the greatest thickness at the location of the bosses, deformations most often occur in it under the influence of temperature. In order to avoid the risk of deformation, part of the metal from the bosses is cut off on a milling machine. The recesses serving for cooling and increasing the intensity of lubrication of the piston are called "refrigerators" in technical slang.

Materials for the production of pistons

High demands are placed on the materials used for the manufacture of pistons. First of all, the material must have high mechanical strength at low density and low coefficient of linear expansion, high thermal conductivity and corrosion resistance, good antifriction properties. Proceeding from this, the pistons are made either from gray cast iron or from an aluminum alloy, often interspersed with cast iron.

Cast iron pistons are durable and wear-resistant, work with small gaps. The disadvantage of cast iron is a lot of weight. Therefore, cast iron pistons are used, as a rule,. Cast iron has low thermal conductivity, so the bottom is very hot. This is a drawback, as the high temperature inside the combustion chamber before ignition can lead to incorrect combustion of the fuel, which is called pre-ignition. This problem was especially acute in previous years, when the carburetor was the predominant injection device.

Aluminum alloy pistons are used much more often in modern engines. Among their advantages are low weight, high thermal conductivity (due to which the temperature of the bottom rarely rises above 250 ° C). It is thanks to this factor that engineers managed to find a way to significantly increase the compression ratio in gasoline engines. The main disadvantage of aluminum is the high coefficient of linear expansion, which forces large gaps, reducing the piston's ability to seal. In addition, the mechanical strength of aluminum during heating drops sharply (up to 50%), which does not happen with cast iron. However, the shortcomings were not fatal, as the engineers managed to come up with ways to level negative properties material. For example, to reduce compression losses, the piston skirt is given an oval-tapered shape. In order to prevent deformation from overheating, the skirt is isolated from the head using a material with low thermal conductivity, etc.

The most "strong" pistons are forged, that is, made from blanks obtained by casting, and subsequently subjected to forging. Forging - mechanical processing of metal heated to forging temperature. Each metal has its own forging temperature; for aluminum, it is not high - only in the region of 500 degrees.

The piston occupies a central place in the process of converting fuel energy into thermal and mechanical energy. Let's talk about engine pistons, what they are and how they work.

What it is?

A piston is a cylindrical part that reciprocates inside an engine cylinder. Needed to change gas pressure into mechanical work, or vice versa - reciprocating movement into a change in pressure. Those. it transmits to the connecting rod the force arising from the gas pressure and ensures the flow of all cycles of the working cycle. It looks like an inverted glass and consists of a bottom, a head, a guide part (skirt).

IN gasoline engines pistons with a flat bottom are used due to ease of manufacture and less heat during operation. Although on some modern cars make special recesses for the valves. This is necessary so that when the timing belt breaks, the pistons and valves do not meet and do not entail a serious repair. The bottom of the diesel piston is made with a recess, which depends on the degree of mixture formation and the location of the valves and injectors. With this shape of the bottom, the air is better mixed with the fuel entering the cylinder.

The piston is exposed to high temperatures and pressures. He moves with high speed inside the cylinder. Therefore, initially for automotive engines they were cast from cast iron. With the development of technology, aluminum began to be used, because. he gave the following benefits: increase in speed and power, less stress on parts, better heat dissipation.

Since then, the power of the motors has increased many times. The temperature and pressure in the cylinders of modern automobile engines (especially diesel engines) have become such that aluminum has reached its limit of strength. Therefore, in last years such motors are equipped with steel pistons that can confidently withstand increased loads. They are lighter than aluminum due to thinner walls and lower compression height, i.e. distance from the bottom to the axis of the aluminum pin. And the steel pistons are not cast, but prefabricated.

Among other things, reducing the vertical dimensions of the piston with the same cylinder block makes it possible to lengthen the connecting rods. This will reduce the lateral loads in the piston-cylinder pair, which will positively affect fuel consumption and engine life. Or, without changing the connecting rods and crankshaft, you can shorten the cylinder block. Thus, we will lighten the engine.

What are the requirements?

• The piston, moving in the cylinder, allows the compressed gases, the product of fuel combustion, to expand and perform mechanical work. Therefore, it must be resistant to high temperature, gas pressure and reliably seal the cylinder bore.
• It must best meet the requirements of the friction pair in order to minimize mechanical losses and, as a result, wear.
• Experiencing loads from the combustion chamber and reaction from the connecting rod, it must withstand mechanical impact.
• Reciprocating at high speed, should load as little as possible crank mechanism inertial forces.

Main purpose

Fuel, burning in the space above the piston, releases a huge amount of heat in each cycle of the engine. The temperature of the burnt gases reaches 2000 degrees. They will transfer only part of the energy to the moving parts of the motor, everything else in the form of heat will heat the engine. What remains, together with the exhaust gases, will fly into the pipe. Therefore, if we do not cool the piston, it will melt after a while. This important point to understand the working conditions of the piston group.

Once again, we repeat the well-known fact that the heat flow is directed from more heated bodies to less heated ones.

The hottest is working body, or, in other words, the gases in the combustion chamber. It is quite clear that the heat will be transferred to the surrounding air - the coldest. Air, washing the radiator and engine housing, will cool the coolant, cylinder block and head housing. It remains to find a bridge through which the piston gives off its heat to the block and antifreeze. There are four ways for this.

So, the first path providing the most flow, are piston rings. Moreover, the first ring plays a major role, as it is located closer to the bottom. This is the shortest path to the coolant through the cylinder wall. The rings are simultaneously pressed against both the piston grooves and against the cylinder wall. They provide more than 50% of the heat flow.

The second way is less obvious. The second coolant in the engine is oil. Having access to the most heated places of the engine, oil mist carries away and gives to the oil pan a significant part of the heat from the hottest points. In the case of using oil nozzles that direct the jet to the inner surface of the piston bottom, the share of oil in heat exchange can reach 30 - 40%. It is clear that when loading the oil with the function of a coolant, we must take care to cool it down. Otherwise, overheated oil may lose its properties. Also, the higher the temperature of the oil, the less heat it can carry.

Third way. Part of the heat is taken away for heating by fresh air-fuel mixture entered into the cylinder. The amount of fresh mixture and the amount of heat that it takes away depends on the mode of operation and the degree of opening of the throttle. It should be noted that the heat obtained during combustion is also proportional to the charge. Therefore, this cooling path is impulsive; it is fast and highly efficient due to the fact that the heat is taken from the side from which the piston is heated.

Due to its greater importance, close attention should be paid to the transfer of heat through the piston rings. It is clear that if we block this path, then it is unlikely that the engine will withstand any long forced regimes. The temperature will rise, the piston material will "float", and the engine will collapse.

Recall such a characteristic as compression. Let us imagine that the ring does not adhere along its entire length to the wall of the cylinder. Then the burnt gases, breaking through into the gap, will create a barrier that prevents the transfer of heat from the piston through the ring to the cylinder wall. This is the same as if you closed part of the radiator and deprived it of the ability to be cooled by air.

The picture is more terrible if the ring does not have close contact with the groove. In those places where gases have the opportunity to flow past the ring through the groove, the piston section is deprived of the opportunity to cool. As a result, burnout and chipping of the part adjacent to the leak.

How many rings do you need for a piston? From a mechanical point of view, the fewer rings, the better. The narrower they are, the less loss in piston group. With a decrease in their number and height, the conditions for cooling the piston worsen, increasing the thermal resistance of the bottom - ring - cylinder wall. Therefore, the choice of design is always a compromise.

IN cylinder-piston group(CPG) occurs one of the main processes due to which the internal combustion engine functions: the release of energy as a result of the combustion of the air-fuel mixture, which is subsequently converted into mechanical action- rotation of the crankshaft. The main working component of the CPG is the piston. Thanks to him, the conditions necessary for the combustion of the mixture are created. The piston is the first component involved in the conversion of the received energy.

The engine piston has a cylindrical shape. It is located in the cylinder liner of the engine, it is a movable element - in the process of operation it performs reciprocating movements and performs two functions.

1. At forward movement the piston reduces the volume of the combustion chamber by compressing fuel mixture, which is necessary for the combustion process (in diesel engines ignition of the mixture does occur from its strong compression).
2. After the ignition of the air-fuel mixture in the combustion chamber, the pressure rises sharply. In an effort to increase the volume, it pushes the piston back, and it makes a return movement, transmitted through the connecting rod to the crankshaft.

What is a car internal combustion engine piston?

The device of the part includes three components:

1. Bottom.
2. Sealing part.
3. Skirt.

These components are available both in solid pistons (the most common option) and in composite parts.

Bottom

Bottom - main working surface, since it, the walls of the sleeve and the head of the block form a combustion chamber in which the fuel mixture is burned.

The main parameter of the bottom is the shape, which depends on the type of internal combustion engine (ICE) and its design features.

IN two-stroke engines pistons are used, in which the bottom of a spherical shape is the protrusion of the bottom, this increases the efficiency of filling the combustion chamber with a mixture and the removal of exhaust gases.

In four-stroke gasoline engines, the bottom is flat or concave. Additionally, technical recesses are made on the surface - recesses for valve plates (eliminate the possibility of a collision between the piston and the valve), recesses to improve mixture formation.

In diesel engines, the recesses in the bottom are the most dimensional and have a different shape. Such recesses are called piston combustion chambers and they are designed to create turbulence when air and fuel are supplied to the cylinder to ensure better mixing.

The sealing part is designed to install special rings (compression and oil scraper), the task of which is to eliminate the gap between the piston and the liner wall, preventing the breakthrough of working gases into the under-piston space and lubricants into the combustion chamber (these factors reduce the efficiency of the motor). This ensures that heat is removed from the piston to the sleeve.

Sealing part

The sealing part includes grooves in the cylindrical surface of the piston - grooves located behind the bottom, and bridges between the grooves. In two-stroke engines, special inserts are additionally placed in the grooves, against which the locks of the rings rest. These inserts are necessary to eliminate the possibility of the rings turning and getting their locks into the inlet and outlet windows, which can cause their destruction.


The jumper from the edge of the bottom to the first ring is called the heat zone. This belt perceives the greatest temperature impact, so its height is selected based on the operating conditions created inside the combustion chamber and the piston material.

The number of grooves made on the sealing part corresponds to the number of piston rings (and 2 - 6 can be used). The most common design with three rings - two compression and one oil scraper.

in the groove under oil scraper ring holes are made for a stack of oil, which is removed by a ring from the wall of the sleeve.

Together with the bottom, the sealing part forms the piston head.

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Skirt

The skirt acts as a guide for the piston, preventing it from changing its position relative to the cylinder and providing only the reciprocating movement of the part. Thanks to this component, a movable connection of the piston with the connecting rod is carried out.

For connection, holes are made in the skirt for installation piston pin. To increase strength at the point of finger contact, with inside skirts are made of special massive influxes, called bosses.

To fix the pin in the piston, grooves for retaining rings are provided in the mounting holes for it.

Piston types

There are two types of pistons used in internal combustion engines. constructive device- integral and composite.

One-piece parts are made by casting, followed by machining. In the process of casting, a blank is created from metal, which is given the general shape of the part. Further, on metalworking machines in the resulting workpiece, working surfaces are processed, grooves are cut for rings, and technological holes and recesses.

IN constituent elements the head and skirt are separated, and they are assembled into a single structure during installation on the engine. Moreover, the assembly in one piece is carried out by connecting the piston to the connecting rod. For this, in addition to holes for the finger in the skirt, there are special eyelets on the head.

The advantage of composite pistons is the possibility of combining materials of manufacture, which increases the performance of the part.

Manufacturing materials

Aluminum alloys are used as the manufacturing material for solid pistons. Parts made of such alloys are characterized by low weight and good thermal conductivity. But at the same time, aluminum is not a high-strength and heat-resistant material, which limits the use of pistons made from it.

Cast pistons are also made of cast iron. This material is durable and resistant to high temperatures. Their disadvantage is a significant mass and poor thermal conductivity, which leads to strong heat pistons during engine operation. Because of this, they are not used on gasoline engines, since high temperatures cause glow ignition (the air-fuel mixture ignites from contact with heated surfaces, and not from a spark plug spark).

The design of composite pistons allows you to combine these materials with each other. In such elements, the skirt is made of aluminum alloys, which ensures good thermal conductivity, and the head is made of heat-resistant steel or cast iron.

However, composite type elements also have disadvantages, including:

• can only be used in diesel engines;
• greater weight compared to cast aluminum;
• the need to use piston rings made of heat-resistant materials;
• higher price;

Due to these features, the scope of use of composite pistons is limited, they are used only on large-sized diesel engines.

Video: The principle of operation of the engine piston. Device

The piston is one of the most significant elements in the conversion of the chemical energy of the fuel into thermal energy, and then into mechanical energy, both literally and figuratively. Motor characteristics largely depend on how well the piston performs its tasks. This determines the efficiency and, more importantly, the reliability of the motor. Special meaning given parameter accepts when it comes to car modifications in tuning salons, or sports applications. Designers always collide with the problem of using special pistons when power increases. The piston can be considered one of the most complex motor parts due to its many functions and rather contradictory properties. It's in the highest degree confirms the fact that very few car builders make pistons for their engines using only their own strength.

In most cases, they resort to the services of firms specializing in this matter. There is a huge amount of mystery and conjecture about pistons, which creates a variety of sizes and shapes of this part. In the relevant section of our site you can find an article. Make a piston standard conditions mechanical engineering in tuning companies is technically difficult, almost impossible, so most companies refuse to deal with this business. Moreover, the production of such intricate details piece by piece can be burdensome financially. Intuitively tuners understand that improved engines must have improved pistons.

Piston device

Let's take a closer look at what requirements are usually placed on pistons, and how they are generally arranged.

• The piston, firstly, moves in the cylinder, which allows mechanical work to be performed by expanding the combustion products of the fuel, that is, compressed gases

From this we can conclude that it must resist the pressure of gases, have heat resistance and seal the cylinder bore.

• Secondly, the piston must meet the requirements of the friction pair so that mechanical losses and wear are minimal.
• Thirdly, it must withstand the reaction of the connecting rod and the mechanical impact from the combustion chamber.
• Fourthly, the piston must minimally load the crank mechanism with inertial forces, making reciprocating movements at high speed.

It turns out that all the problems associated with this significant part of the engine can be divided into two categories:

1. This mechanical processes
2. Thermal processes, and the first is much more extensive than the second. Categories have a fairly close relationship. Let's take a closer look at the first one.

As you know, fuel burns in a non-piston space, and at the same time emits very a large number of heat during each engine cycle. The temperature of already burned gases is on average 2000 degrees. Part of the energy will go to the moving parts of the motor, and the rest will heat the engine. The energy that remains in the end will fly into the pipe along with the treated gases. According to the laws of physics, two bodies can transfer heat to each other until their temperatures are completely equal. Accordingly, if the piston is not periodically cooled, after a while it will simply melt. This is a very significant moment for understanding the principles of operation of the entire piston group.

This is especially important when the motor is boosted. With an increase in engine power, the amount of heat generated in the combustion chamber per one time unit automatically increases. Of course, we see very infrequently melted pistons, however, temperature is always mentioned in any of their problems, just like speed is present in any accident. Of course, the blame here lies with the driver, but no one would have been hurt if the car had stood still. The fact is that high temperatures degrade the characteristics of all materials. A load of 100 degrees will cause elastic deformation, a load of 300 degrees will completely deform the product, and a load of 450 degrees will deform it. For this reason, either materials must be used that can withstand severe stress from high temperatures, or measures must be taken to prevent the piston from rising in temperature. Usually both are done. However, the design of the piston must be such that in the right places there is a certain amount of metal that is able to withstand destruction.

The course of general physics confirms the fact that the heat flow is directed to less heated bodies from more heated ones. Thus, we have the opportunity to see how temperatures are distributed over the piston during its operation, and to determine the significant design points that affect its temperature, in other words, to understand how cooling occurs. We know that the working fluid, that is, the gases in the combustion chamber, heats up more than all the parts. It is quite clear that in the end the heat will be transferred to the air that surrounds the car - the coldest, but under certain circumstances infinitely warm. Washing the engine housing and radiator, the air cools the cylinder block, coolant and head housing. We just have to find a bridge across which the piston gives off its heat to the antifreeze and block. There are four ways to do this. In terms of their contribution, they are completely different, but it is necessary to mention each of them, since they are of lesser or greater importance depending on the design of the engine.

First way

These are the piston rings, it provides the most flow. Since the first ring is located closer to the bottom, it is it that plays the main role. This is the shortest way to the coolant through the cylinder wall. At the same time, the rings are pressed against the cylinder walls and piston grooves. They provide more than half of the total heat flow.

Second way

It is not so obvious, but it is difficult to underestimate it. The second liquid for engine cooling is oil. Despite its poor circulation and relatively small volume, oil mist has access to the hottest parts of the motor. It carries away a significant part of the heat from the hottest spots, and gives it to the oil pan. In this section of our site you can find an article about. When using oil nozzles, which direct the jet to the inner surface of the piston crown, the proportion of oil in heat exchange often reaches 30 - 40 percent. Of course, if we load the oil more than the degree of function of the coolant, it will need to be cooled. Overheated oil will not only lose its properties, but can also lead to bearing failure. And the higher the temperature of the oil, the less it will be able to transfer heat through itself.

third way

Through the big bosses into the finger, then into the connecting rod, and only then into the oil. This method is not so interesting, because on the way there are significant thermal resistances in the form of steel parts and gaps, which have a low resistance coefficient and a significant length.

Fourth way

Not related to coolant or oil. Part of the heat is taken away by the fresh air-fuel mixture entering the cylinder after the intake stroke. The amount of heat that this mixture will take depends on the degree of throttle opening and the mode of operation. It should be noted that the heat that is generated during combustion is also proportional to the charge. It can be said that this cooling path is fast, impulsive, highly efficient, proportional to subsequent heating, due to the fact that heat is taken from the same side from which the piston is heated.

You should also talk about the standard technique that is used when setting up motors sports type. The fact is that the heat capacity of a mixture is largely determined by its composition. Often, to normalize the operation of the motor, you need quite a bit, by 5 - 10 degrees, to lower the internal temperature. This is achieved by slightly enriching the mixture. Moreover, this fact does not affect the combustion process in any way, and the temperature decreases. The detonation threshold is pushed back, the glow ignition disappears. IN this case a little richer is better than a little poorer. Motors that run on methanol make much less demands on the cooling system due to the heat of conversion, which is 3 times greater than that of gasoline.

Close attention should be paid to the process of heat transfer through the piston rings due to its greater importance. It is quite clear that if this path is blocked for any reason, the engine will no longer withstand long forced modes. The temperature will become very high, the piston will begin to melt, and the engine will collapse. Now let's remember such a characteristic as a procession, which, it would seem, does not affect heat transfer in any way. If a person has come across a used car, he must clearly understand what it is. This is a very significant parameter that any car owner who cares about the condition of the engine of his car wants to know about. Compression indirectly indicates the degree of density of the piston group. This is very important parameter, if we consider it from the point of view of heat transfer.

Let's imagine a situation where the ring does not adhere to the cylinder wall along its entire length. In this case, the burnt gases will create a barrier that will interfere with the transfer of heat through the ring to the cylinder wall, starting from the piston, when they break through into the slot. This is equivalent to covering up part of the car's radiator so that it doesn't have a chance to cool with air.

If the ring does not have close contact with the groove, we will see an even more terrible picture. In those places where the gases have the opportunity to flow through the groove past the ring, the piston section simply loses the opportunity to cool down, falling into a kind of heat bag. As a result, we get chipping and burnout of the part of the fire belt, which is adjacent to the leak. It is for this reason that so much attention is paid to groove wear and ring cylinder geometry. AND main reason not at all a deterioration in energy. After all, a small amount of gases that break into the crankcase does not carry enough energy in itself to affect the pressure loss in the stroke of the power stroke and, accordingly, the loss of engine torque. Especially when it comes to high-speed motor. Much more damage to the engine is caused by low density in terms of loss of reliability and rigidity and local thermal overloads. It is for this reason that pistons restored by re-sleeving the block or replacing rings break very quickly, which are already out of order. That is why, first of all, in sports engines, a cylinder that has less compression is destroyed.

Here, apparently, we should touch on the issue that is necessarily discussed in the manufacture of special pistons for tuning or sports applications. How many rings will the new piston have? How thick are these rings? From the point of view of mechanics, it is better when there are few rings. The narrower they are, the less losses will be in the piston group. However, with a decrease in the thickness and height of the rings, the conditions for cooling the piston will worsen, and the thermal resistance will increase. Therefore, when choosing a design, you always have to compromise. The rigidity of the frames increases with the speed of the motor. In this section of our site you can find an article about. The rapidity of the processes reduces the requirements for compaction. Mechanical losses increase with speed, and they must be reduced, otherwise everything that was converted earlier into mechanical power simply will not reach the wheels. Meanwhile, the amount of heat generated becomes larger, so the cooling bridge must be expanded. From this we get that the rings should be both narrow and wide. Two are needed for speed, and three for piston cooling efficiency. The designer must find the optimal solution to this problem. The results of his work will show the balance of the engine.

Today, engineers who work in large scientific centers and manufacturing companies, have a huge empirical material, on the basis of which they create calculation methods that make it possible to predict the field of characteristics and temperatures of a particular product with very great precision. This is available to very, very few tuning companies. This article does not specifically mention many of the values ​​of specific quantities that would encourage some readers to pick up calculators. Do the same thermal calculations on the fingers is not at all promising and absolutely useless occupation. This article reveals that side of the processes occurring in the engine, which is very rarely considered, but always implied. I just wanted to reveal the necessity and importance of the effect of heat on the overall efficiency of the engine. As for the mechanical part of this issue, we will talk about it in detail next time.