In the technical conditions for the production of the the compression piston ring KAMAZ engine 740.1004032 is recorded: The load applied to the arrows K, when the ring is compressed by a flexible tape to the gap in the lock, equal to the gap in the calibre of 120 mm, should be 2.3 3.1 kgf. From this it follows that, despite the obvious difference in the methods of measuring the elasticity of a piston seal ring, the values of the recommended values in the textbook and the developers of the KAMAZ engine are of the same order.
It is worth noting that it makes no sense to rely neither on the recommendations of the scientist nor on the value of the load practiced by the KAMAZ engine manufacturers in the development of engines with cylinder dimensions about 120 mm. When calculating the elements of the kinematic system cylinder-piston ring-piston in modern engines, developers take into account the wear amount of each of them, thereby prolonging the warranty periods of operation of the piston rings.
The permissible value wear of the cylinder 0,15 mm, increases the gap in the lock of the compression ring of the KAMAZ engine to a size of 0.94 mm. When only the working surface of the piston ring is worn by 0.5 mm, the gap in the lock of the ring increases by 3.14 mm. In large engines, wear of the working surface of the piston ring is permitted up to 1.0 mm, which corresponds to an increase in the gap in the ring lock by 6.28 mm. Total allowable increase in the gap in the compression ring lock will be 7.22 mm! This is without thermodynamic, i.e. thermal extensions [4].
It is difficult to imagine how such a thin seal, in the design of which, by definition, there should not be any gaps, or they should be reduced to an insignificant minimum. Unfortunately, its hard to argue with opponents who have disarming arguments. At first, the engines work fine, and secondly, the compression piston rings are made exactly in accordance with the instructions of the domestic standards [8] and [9].
In this case, the question arises, why the modern internal combustion engine is so good? The answer is obvious, if you give an example from everyday life, answering a similar question: can you take a bucket of water with a sieve? Of course you can. It needs to be done very quickly and for a long time, but the efficiency is too small.
Is the engine has a high efficiency? No! Maybe he has a small rotation speed of the crankshaft? Also, no. On the latest models of VAZ engines, small-gas turns are already over 1000 min-1!
The engines of the Formula-1 maximum power reach over 22 000 min -1, while after each race there is a major repair of the engine.
So, what are the conclusions will be drawn?
Proceeding from a purpose of a working step admission, it is necessary to remember, the consolidation between the piston and the cylinder, the excluding, any suction from the crankcase is more reliable, the extent of discharge of space over the piston is more; the more actively there is a fence of an atmospheric air and implementation of rated data.
First of all, it is worth paying attention to the design of the cylinder-piston group and, first of all, the design, shapes and dimensions of the piston rings. Its incomprehensible! With a complete change in the entourage of the car, the famous AvtoVAZ, which is quite competitive with foreign models, for decades the engines are equipped with permanent piston rings, performed at the will of the standards.
It is worth noting that the equipment and technology for the manufacture of piston rings not only for the AvtoVAZ engines but also for KAMAZ, YaMZ and other engines was used by the world famous German company Goetze, which is under the patronage of the equally famous Federal Mogul concern the advanced European manufacturer of the engine gaskets and piston rings. That is, all claims to poor-quality piston engine compaction should be presented not to the main designers of these engines, but to world-famous specialists with whom the main are in solidarity.
To this we must add the following circumstance. From the advertisement of its latest achievement, the manufacturer of the elements of CPG the Kostroma-Motordetal presented ncMDChr (nanochrome) a new generation coating is applied to the working surface of the upper compression and oil-removable piston rings! Especially shocking and oil-removable rings, inefficient, performing a rough operation of removing oil from the cylinder wall, in a continuous oil environment.
It is unclear why to apply nanochrome on them, if the working surface of the oil-removable piston ring does not wear out and without nano. When it is necessary to change the piston rings, along with the compression rings, oil-removable rings also fall into disassembly, but not because they have a worn working surface, but because the waste oil is clogged, sometimes coked, by the spiral extension of the oil-removal ring. This is especially true of the diesel engines. The inefficient oil-removal piston ring becomes generally inoperable.
This is an example of the imperfection of the widely used oil-removable ring with useless nanochrome. Nevertheless, Kostroma is pleased, scientific and technological progress all that is needed for the buyer to appreciate these innovations.
The design of compression piston rings, subjected to rigid analysis by the author, continue to live and improve. The achieved results of the research and the proposed measures for the recognized authorities of the car industry are not so obvious, there may be other reasons that have nothing to do with science.
The low efficiency of consolidation between the piston and cylinder is one of the most important problems of the ICE. The negative consequences of this decision are obvious, the engine can earn and operate normally only at huge speeds of rotation of the crankshaft, boosting the engine work. What leads to forcing should be known even to the motorist.
The problem of gaps is only part of the general problem of the cylinder-piston ring-piston system. In this case, on a working step admission, in the absence of excessive pressure over the piston, the mechanical friction losses of the compression rings affecting the efficiency of the engine or compressor The magnitude of the mechanical losses at the admission step depends on the magnitude of the elastic forces of the piston seal ring and the friction coefficient of the two kinematic elements: Piston ring-cylinder, more specifically, the working surface of the piston ring and the cylinder wall.
The shape and dimensions of the piston seal ring at the admission step depend mainly on the design value of the minimum necessary elastic force of the ring. It is necessary to determine the magnitude of the elastic force of the piston ring and the necessary material from which the ring should be made.
In analysis of the reasons for the low efficiency of internal combustion engines, it was found that in calculating the sizes and permissible deviations in the manufacturing process, in domestic engines, especially in the cylinder-piston group, there is lacks precision; therefore, as one of the measures to increase the efficiency of internal combustion engines, in the system cylinder piston ring piston was held minimization of gaps [10].
The modern piston rings, depending on their size, are mainly made of steel and cast iron. The researches, the developed theory of designing of the piston rings provide an opportunity of manufacturing of rings from other metals and alloys, and also nonmetallic materials. For example, the domestic company LLC Compressor Technologies advertises bronze with various fillers, various plastics as a material for manufacturing sealing and oil-removable piston rings.
The modern piston rings, depending on their size, are mainly made of steel and cast iron. The researches, the developed theory of designing of the piston rings provide an opportunity of manufacturing of rings from other metals and alloys, and also nonmetallic materials. For example, the domestic company LLC Compressor Technologies advertises bronze with various fillers, various plastics as a material for manufacturing sealing and oil-removable piston rings.
At the research stage, to define the shape and dimensions of the sealing (compression) piston rings, using the results of theoretical studies, to recommend various bronze alloys and copper alloys as a material for the preparation of the ring.
Working step compression of a fresh charge of air, fuel-air mix and its ignition
The working step compression is fundamentally different from the previous step admission in that by obtaining a piston ring pressed against the upper flange of the piston groove and to the wall of the cylinder by the force of its own elasticity, at the beginning of the pistons movement to the upper position, the piston ring is shifted downward. The forces of friction of the piston ring working surface against the cylinder wall, as well as the appearing overpressure P0 above the piston and in the piston groove, further enhance the contact of the piston ring with the lower flange of the piston groove and the cylinder wall.
It is important to note, the piston ring being in the lower dead point in rather free state, is fixed in this position, appearing changes and, above all, increasing pressure over the piston. This position of the sealing piston ring relative to the piston and cylinder will remain unchanged on the remaining steps of the engine motoring run.
So, with the beginning of the pistons movement to the upper position on the working step compression, gas dynamics comes into operation, according to the scheme given above to fig. 1. On a working step admission the design of a piston sealing ring, its shape and dimensions, werent of particular importance, solving the main task of effectively consolidation of the free space between the piston and the cylinder with the minimum possible mechanical friction losses.
At this stage, the developer must solve the problem of the correct use of gas-dynamic forces that will preserve the elastic forces of the piston ring, thereby guaranteeing its working capacity [11].
The author to solve this problem developed a formula, the use of which in the calculation of the geometric characteristics of a sealing piston ring allows neutralizing the negative effect of huge gas-dynamic forces on the operation of the piston ring. This formula solved the historical injustice of the subjective decision in assigning the height of the piston ring, although this decision was made by an authoritative German scientist [5].
It was suggested to choose for the engine the free size of the height of the sealing piston ring in an unreasonable range of sizes, relying only on the recommendation of an authoritative scientist: Usually, the ratio of h/a shouldnt be lower than 0,5 0,45 (h height of a piston ring, and the radial thickness of a ring).
The domestic scientists and then developers of the piston cars took these recommendations for an axiom which, obviously, those far sixtieth years of last century, didnt demand any proofs, pilot and other studies which had to be carried out at so basic decision. As a result, instead of an incomprehensible range of sizes of recommendations for the height of the piston ring, there appeared precise indications of the domestic standards. Designers did not have to calculate the height of the sealing ring, thereby removing all responsibility for low-quality products from all general and main ones.
For example, the current GOST 62187 for cylinder diameters of 88 mm and 130 mm determined the height of the sealing rings for both 2.0 mm. Its incomprehensible! Really when developing so responsible document how the technical standard, it was unclear that from the given size of diameter of the cylinder equal to the outer diameter of a piston ring, all other geometrical characteristics of a ring depend?
How can ignore the enormous working pressures in the engine cylinders, reaching 20 MPa (200 kg / cm2) and actively affecting to the free surfaces of the movable piston ring? In these extreme conditions, the minimum change in the height of the sealing ring and its radial thickness is transformed into kilograms of force, reflecting on the performance of the piston ring and, ultimately, on the technical, economic and environmental performance of the engine. Why all this happened in detail described in the authors publications.
To prove the published and patented objective fact, lets show the calculation of the sealing (compression) piston ring, of a virtual motor which could be used for domestic AvtoVAZ models.
§3. The practical solutions from the theoretical conclusions
To comparing two engines of the same purpose KAMAZ and MERCEDES, the author a professional technologist, intuitively (sometimes trusting the designers), was closer the MERCEDES engine. Of course, the importance was not the authority of the firm, but pragmatism, confirmed by many years of searching for the reasons for the low efficiency of the product, the project of which technology is implemented in the metal. Obviously, it is not necessary to convince the designers of the need for difficult searches for a simpler design that is completely would perform the tasks assigned to it.
The main advantage of the German engine, in comparison with the competing engines of KAMAZ OOO (Limited Liability Company) " and YaMZ TMZ of Avtodizel OAO (Open Joint-stock Company), is the size of its cylinder of 128 mm. The difference is small, only 8 mm, but taking into account the huge operating pressures, the power increases significantly, so the competitor was allowed to provide only 6 cylinders, with all the ensuing positive consequences.
Therefore it would be possible to recommend to domestic trucks of a class KAMAZ and YaMZ to use diameter of the cylinder of 130 mm. Kostroma MOTORDETAL OAO(Open Joint-stock Company) is manufactured a similar piston group with a cylinder diameter of 130 mm, for the tractor engines. This measure can be implemented only on condition of fundamental changes in the design of piston devices.
So, back to the calculation of the sealing (compression) piston ring, which could be used for domestic AvtoVAZ models. Considering the strategy of design of similar engines, it was interesting to get acquainted with features of engines of Formula -1. With engine speeds of 18,000 22,500 rpm or more, the engine develops power over 750 PS. with a cylinder diameter of 98 mm, a piston stroke of 39.7 mm, fuel consumption of about 60 litres per 100 km.
It is not enough to copy for our engines from AvtoVAZ series, but the design strategy, taking into account the highest class of skill of the mechanics of Formula-1, should be taken into account. Now we have VAZ engines with diameters of cylinders of 76 82 mm, three and four-cylinder.
Lets finish the interrupted calculation of the effect of gas dynamics on the operation of the compression ring of the VAZ-2190 engine presented above, but already for a virtual engine with the desired initial data.