The purpose of the engine piston. A piston is a part of a car engine. The device, replacement, installation of the piston. Pistons can be
A piston is one of the most significant elements in the conversion of the chemical energy of fuel into heat, and then into mechanical, both literally and figuratively. Motor performance largely depends on how well the piston performs its tasks. This determines the efficiency and, more importantly, the reliability of the motor. This parameter takes on special significance when it comes to car modifications in tuning salons, or about sports applications. Designers always collide with the problem of using special pistonswhen the power rises. The piston can be considered one of the most complex motor parts due to the many functions performed and its rather contradictory properties. This is supremely confirmed by the fact that very few car manufacturers make pistons for their engines using only their own strengths.
Increasing valve size is also a good alternative. They are space limitations of the combustion chamber and the cylinder bore. They were so large that it was necessary to dig out the engine block a bit so that the valves fully opened. Now, if you do not want to spend a lot of money on various controls or even increase the size of the valves, you can still improve the absorption of your engine. Just polishing the valve paws, which usually has sufficient roughness.
This occurs mainly in older engines. A good alternative is also to change the angle of the valve seats. However, this work should be performed by someone who is well versed in the subject. Valves should fit well in their seats, avoiding leaks that could result in loss of power.
In most cases, they resort to the services of firms specializing in this matter. A lot of secrets and conjectures go about pistons, which creates a variety of sizes and shapes of this part. In the appropriate section of our site you can find the article. It is technically difficult, practically impossible, to manufacture a piston under standard engineering conditions in tuning companies, which is why most companies refuse to do this. In addition, the production of such complex parts by the piece can be burdensome from a financial point of view. Intuitively, tuners understand that improved engines must have improved pistons.
Recycling the intake ducts can also improve your engine by adding a few extra horsepower. To do this, you must polish the air ducts, removing all burrs and casting defects. Increasing the diameter of the channels is a reasonable job, because if you increase the diameter of the channel too much, believing that your engine will breathe better, you can actually cause the opposite effect.
The air velocity inside the intake ducts is important, so that the filling of the cylinder is greater. Therefore, if we increase the diameter of the channel incorrectly, we can reduce the gas velocity, and this undermines productivity. Polishing too many channels can also cause another problem, especially in carburized engines. When the carburetor injects fuel, with a quick injection of the injector into accelerations, the fuel enters the intake channels in liquid form. However, before entering the cylinder, it must evaporate.
Piston arrangement
Let’s take a closer look at what requirements are usually placed on pistons and how they are generally arranged.
- First, the piston moves in the cylinder, which makes it possible to perform mechanical work by expanding the combustion products of the fuel, i.e., compressed gases
From this we can conclude that it must resist gas pressure, have heat resistance and seal the cylinder channel.
Thus, if the pipelines are too smooth, fuel can flow as liquid into the cylinder. When this happens, in addition to the deterioration of combustion, since the fuel will not be fully homogenized with air, we will still have the aggravation that fuel in liquid form can literally flush the cylinder wall, cleaning the lubricating oil. This will increase the friction of the piston with the liner. In this case, in addition to power loss due to improper combustion, we will also lose energy by increasing the friction of the piston with the cylinder liner.
And, worst of all, we will have premature wear on the piston, ring and cylinder. An ideal way to work with air ducts is to polish, removing all burrs without a significant increase in diameter, especially in the part closest to the head. We must remove any negative or positive steps that may occur when connecting the intake manifold to the head inlet to avoid turbulence. After polished ducts, we must sandblast them or glass microspheres, thereby causing a fine roughness that will have the effect of retaining the fuel particles until they evaporate under the influence of heat, thus preventing its flow into the cylinder.
- Secondly, the piston must meet the requirements of a friction pair, so that mechanical losses and wear are minimized.
- Thirdly, it must withstand the reaction of the connecting rod and mechanical stress from the combustion chamber.
- Fourth, the piston should minimize the inertial forces of the crank mechanism, making reciprocating movements with high speed.
It turns out that all the problems associated with this significant part of the engine can be divided into two categories:
After the advent of hybrid models, it was more often heard that such an engine was Atkinson, the other was Miller, and so on. And that will make these gas engines no longer have the famous Otto cycle. With this in mind, we monitor the most efficient cycles of the internal combustion engine and explain why they make better use of the energy concentrated in the fuel.
But make no mistake: they told us about all the most effective cycles available today. And the most economical of all can go unnoticed. Among all engine cycles already developed, the most economical is diesel, which we use in capital letters, because it is a cycle, not a fuel. “This high performance is mainly due to the high compression ratios used in these engines, combined with the use of turbochargers,” says Pereira.
- These are mechanical processes.
- Thermal processes, the first being much more extensive than the second. Categories have a fairly close relationship. Let's take a closer look at the first.
As you know, fuel burns in non-piston space, and at the same time emits a very large amount of heat during each cycle of the engine. The temperature of already burnt gases is on average equal to 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 processed 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 working principles of the entire piston group.
Oricassa confirms: The efficiency of internal combustion engines has approximately the following efficiency: diesel fuel and gasoline. High compression ratios provide greater cumulative energy and, consequently, greater strength, - says Orikassa.
Among the improvements, the brand refers to reduced downtime, higher turbocharging pressure, faster closing of the intake valve and additional fuel injection at partial loads. Its variable valve opening system allows the use of a new turbocharged two-stroke engine in Europe to work with the Otto or Atkinson cycle. In fact, since it is muddy, the cycle is Miller.
This is especially important when the motor is forced. With increasing engine power, the amount of heat generated in the combustion chamber per one temporary unit automatically increases. Of course, we see very rarely pistons in the molten one, however, in any of their problems, there is always a mention of temperature, just like the speed is present in any accident. Of course, the fault lies with the driver, but no one would have been hurt if the car stood still. The fact is that high temperatures degrade the performance of all materials. A load of 100 degrees will cause elastic deformation, 300 degrees - it deforms the product completely, and at 450 degrees it deforms. For this reason, you must either use materials that can withstand severe loads from high temperatures, or take measures to prevent the temperature of the piston from rising. Both are usually done. However, the design of the piston must be such that in the right places there is a certain amount of metal that can withstand destruction.
Below is a beautiful brand video to present your little pearl. It is even possible that the internal combustion engine is designed for its own day, but the variety of new technologies to make it more efficient shows that it still has a lot of wood for burning.
It is a synthetic fuel. This process, Bosch says, will allow the production of various fuels, such as gasoline, diesel and kerosene. In addition, the German company says that synthetic fuels can be created so that they do not release soot, which will reduce the need for exhaust gas treatment equipment. Another advantage, according to Bosch, is that these fuels will be almost similar to their natural counterparts, which will make them available through the current distribution network and do not require any adaptation to cars.
The course of general physics is confirmed by the fact that the heat flux 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 significant structural moments that affect its temperature, in other words, to understand how cooling occurs. We know that most of the details are heated by the working fluid, that is, the gases in the combustion chamber. It is clear that in the end the heat will be transferred to the air that surrounds the car - the coldest, but under certain circumstances infinitely heat-intensive. Washing the engine casing and radiator, air draws in the cylinder block, coolant and head housing. We can only find a bridge over which the piston transfers its heat to the antifreeze and the 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 less or greater importance depending on the design of the engine.
This new technology is being tested in Germany and Norway, and the German Ministry of Energy and Business supports biofuel research. Aircraft engines are included in the group of internal combustion engines and can be characterized in various ways in accordance with more or less general characteristics and features. However, the absolute and final characterization becomes complex.
Since they first appeared, piston engines can be classified by cylinder arrangement, crankshaft position, cooling method, number of times each cycle and type of ignition. Regarding the position of the crankshaft can be considered excellent or inverted. For this reason, each of the devices with respect to the cylinders can be combined with the position of the crankshaft.
First way
These are piston rings, it provides the greatest flow. Since the first ring is located closer to the bottom, it plays the main role. This is the shortest path to the coolant through the cylinder wall. At the same time, the rings are pressed against the cylinder walls and to the piston grooves. They provide more than half of the total heat flow.
As for the cooling method, the engines can be cooled by air or through a liquid. As for the number of times per cycle, that is, engines 2 and 4 times per cycle. Regarding the occurrence of ignition, it can be controlled by electric discharge or compression, which occurs spontaneously depending on the thermodynamic and chemical conditions of the mixture inside the cylinder.
The characteristics of the following alternative engines, which are not absolute or final, are nevertheless a common basis for the various types of aircraft engines that are currently in operation or are used in significant quantities. Since this is the one that best shows the different types of alternative engines, a characteristic for the arrangement of the cylinders was adopted.
Second way
Not so obvious, but underestimating it is difficult. The second engine cooling fluid is oil. Despite its poor circulation and relatively small volume, oil mist has access to the warmest parts of the engine. It takes away a significant part of the heat from the hottest spots, and transfers 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 bottom, the oil share in heat transfer often reaches 30 - 40 percent. Of course, if we load the oil more than the degree of coolant function, it will need to be cooled. Overheated oil will not only lose its properties, but it can also lead to bearing malfunction. And the higher the temperature of the oil, the less it will be able to transfer heat through itself.
Thus, the vast majority of aircraft engines are characterized. Internal combustion engines can be either self-igniting or self-igniting. Self-igniting engines have little use. Thus, internal combustion engines and spark ignition are divided into 3 fundamental groups as follows.
Alternative engines are internal combustion engines, usually 4-stroke ones, in which the energy released from combustion, accompanied by the explosion of a gas mixture of air and fuel, causes the cylinders to move linearly in the cylinders, thereby encouraging the crankshaft to be circular. These engines are divided into two groups.
Third way
Through the big bosses into the finger, then into the connecting rod, and 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 coefficient of resistance and a considerable length.
Fourth way
Not associated with coolant or oil. Part of the heat is taken in by the fresh air-fuel mixture received in the cylinder after the intake stroke. The amount of heat that this mixture will take depends on the degree of opening of the throttle and the mode of operation. It should be noted that the heat that is generated during combustion is also proportional to the charge. We can say that this cooling path is transient, has a pulsed nature, highly efficient, proportional to subsequent heating, due to the fact that heat is taken from the same side from which the piston is heated.
Longitudinal motors have a main feature, the cylinders are aligned along the longitudinal axis. These engines, in turn, are subdivided into. Vertical engines are characterized by cylinders aligned along one longitudinal plane and located opposite each other, forcing the movement of the pistons inside the cylinders vertically. Due to the position of the cylinders, this type of engine has large dimensions along the longitudinal axis.
Horizontal engines are characterized in that the cylinders are aligned along one longitudinal plane and are opposed to each other, causing the pistons to move horizontally inside the cylinders in opposite directions. This configuration allows you to create smaller engines with the same power level, but more balanced. In alternative engines, horizons are most widely used in aeronautics.
You should also talk about the standard technique that is used when setting up motors of a sports type. The fact is that the heat capacity of the mixture is largely determined by its composition. Often, to normalize the operation of the motor, it is necessary to reduce the internal temperature quite a bit, by 5 - 10 degrees. This is achieved with a slight enrichment of the mixture. Moreover, this fact in no way affects the combustion process, and the temperature decreases. The detonation threshold is pushed back, ignition ignition disappears. In this case, it would be better a little richer than a little poorer. Motors that run on methanol are much less demanding on the cooling system because of the heat of conversion, which is 3 times more than gasoline.
This type of engine is a compromise between vertical engines and horizontal engines reaching shorter lengths than verticals, shorter widths than horizontal lines, but not as balanced as the latter. Currently, they are little used in aeronautics. Radial engines are more bulky compared to longitudinal engines, they have a smaller crankshaft and are much more balanced. These engines allow you to achieve a power level that is much higher than the longitudinal ones, but they advised against the later development of the weight and dimensions that they require, creating turbotronic engines and dividing them into.
Careful attention should be paid to the process of heat transfer through the piston rings because of its greater importance. It is clear that if you block this path for any reason, the engine will not stand up to long forced modes. The temperature will become very high, the piston will start to melt, and the engine will collapse. Now let's recall such a characteristic as a procession, which, it would seem, does not affect heat transfer in any way. If a person came across a used car, he should clearly understand what it is. This is a very significant parameter that any car owner who wants to know about the state of the engine of his car wants to know about. Compression indirectly indicates the degree of density of the piston group. This is a very important parameter when viewed from the point of view of heat transfer.
Simple star-shaped engines are characterized by a radial arrangement of the cylinders in one plane, forcing the pistons inside them to move radially with respect to the center of the engine, turning this longitudinal motion into rotational motion of the crankshaft.
Engines with several stars are similar to engines with a single star, the main difference being that there can be several groups of cylinders located in several parallel planes, the elements of which move in the radial direction and are connected to the same crankshaft.
Let's imagine the situation that the ring does not fit 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 into the gap. This is equivalent to the fact that you close part of the radiator of the car so that it does not have the opportunity to cool the air.
Rotary engines, like alternating ones, have internal combustion, and they are mainly characterized by the absence of linear movement of any component, which leads to circular motion directly from the energy released during combustion of the air-fuel mixture. This type of engine is divided into 3 groups.
Rotating alternating engines are the same as those of other star-shaped engines, with the feature of a motor housing that rotates solidly with a spiral around the crankshaft, which remains stationary. These engines were used in aircraft soils and preceded both longitudinal and radial engines. These engines were able to achieve high power levels in their time, but the weight and size that they required prevented their further development, creating significant gyroscopic forces and violating the stability of the aircraft, which is motorized, especially takeoff.
If the ring does not have close contact with the groove, we will observe an even more terrible picture. In those places where gases have the opportunity to flow through the groove past the ring, the piston section simply loses the ability to cool, 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 the wear of the grooves and the geometry of the cylinder of the ring. And the main reason is not the deterioration of energy. After all, a small amount of gases that burst into the crankcase does not carry enough energy in itself to affect the loss of pressure in the stroke of the stroke and, accordingly, the loss of engine torque. Especially when it comes to high-speed motor. A little more damage to the engine is caused by a low density in the sense of loss of reliability and rigidity and local thermal overloads. It is for this reason that the pistons that have already failed are restored when they are restored by the method of block re-assembly or ring replacement. That is why, first of all, in sports engines, a cylinder that has less compression is destroyed.
Here, apparently, you 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 will these rings be? From the point of view of mechanics, it is better when the rings are few. 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 piston cooling conditions will deteriorate and the thermal resistance will increase. Therefore, when choosing a design, you always have to compromise. The rigidity of the frame increases with the speed of the motor. In this section of our site you can find an article about. Short processes reduce compaction requirements. Mechanical losses grow along with speed, and they need to 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 should be expanded. From this we obtain that the rings should be both narrow and wide. For speed they need two, and for the efficiency of cooling the piston - three. The designer must find the optimal solution to this problem. The results of his work will show the balance of the engine.
To date, engineers who work in large scientific centers and manufacturing companies have enormous empirical material on the basis of which they create calculation methods that allow us to predict the field of characteristics and temperatures of a particular product with very high accuracy. It is available to very, very few tuning companies. This article does not specifically mention many of the values \u200b\u200bof specific quantities that would encourage some readers to pick up calculators. To do thermal calculations on the fingers is not a promising and absolutely useless occupation. This article reveals the 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 influence 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.
The principle of an internal combustion engine (ICE) is based on the conversion of reciprocating motion into rotational motion. Despite the fact that the process technology is relatively simple, particular attention is paid to the individual parts of the crank mechanism. One of these parts is the piston.
For a typical average owner, a piston is a regular cylinder with slots for piston rings, but this is not entirely true.
Piston - A high-tech component, over which engineers work more than one day. After all, a large number of functions are assigned to the piston:
It should be light and at the same time possess sufficient strength, because during the ignition of the fuel-air mixture it is subjected to a significant load;
It must have high thermal conductivity (transmit heat), to remove excess heat from the combustion chamber;
The dimensions of the piston must be such that during operation the gases under high pressure do not penetrate the crankcase and at the same time it should not adhere very tightly to the cylinder walls, otherwise there is a possibility that it will simply stick due to thermal expansion;
Piston material should be affordable. As a material for a piston for conventional vehicles, aluminum and alloys based on it have been widely used recently. For cars that participate in competitions, more sophisticated materials, such as ceramics, are used as a material.
In mechanical engineering, there are two main methods for manufacturing pistons:
- a method of molding under high pressure;
- forging method.
Piston device
A piston is an all-metal part, cylindrical in shape, conventionally divided into a head (bottom) and a skirt. The shape and arrangement of the piston is highly dependent on the type of engine and fuel used. So the piston installed in a gasoline engine has a flat bottom, or as close to a flat one. For individual gasoline engines, special slots are provided in the piston head for opening the valves. But for diesel engines, the piston head is made with a special recess that acts as a combustion chamber and contributes to optimal mixing and combustion of fuel.
For engines with direct fuel injection, piston head has a more complex shape.
If you pick up a piston, you can see that on its cylindrical walls there are special slots - these are seats for piston and oil scraper rings.
This design is the most optimal in terms of operation and repair. In case of loss of tightness (compression), it is enough to replace only the rings, and the pistons can not be changed with proper operation, thereby saving money. And the contact area of \u200b\u200bthe ring with the walls of the cylinder is much smaller if only the piston walked in the cylinder.
Piston skirt performed curvilinear or cone-shaped, this form allows you to save on weight and at the same time the piston optimally compensates for thermal expansion.
At the base of the skirt there are two tides with a through hole. This hole is intended for the piston pin, which allows the "non-rigid" to connect the piston to the connecting rod.
As we wrote above, the piston removes excess heat from the combustion chamber, now we will consider how the piston itself is cooled. The most common piston cooling methods:
a) due to fog from the lubricant (oil);
b) by spraying oil through special holes in the connecting rod;
c) additional spraying of oil with a separate nozzle;
d) oil supply to a special channel, which is located next to the slots for the piston rings;
e) the special design of the piston allows the oil to circulate in the "body" of the piston.
Lastly, it is worth noting that when tuning the engine, the design and shape of the pistons plays an important role. For example, when replacing the "native" piston group on VAZ family cars with forged ones, it will improve the technical and economic performance of the engine.
