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 shouldn’t 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, didn’t 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 621—87 for cylinder diameters of 88 mm and 130 mm “determined” the height of the sealing rings for both 2.0 mm. It’s 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 author’s publications.
To prove the published and patented objective fact, let’s 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.
Let’s 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.
Based on our research, we can use the maximum cylinder size for VAZ engines. Author is a technologist intuitively suggests that the most preferable can be taken as a basis for further calculations – the diameter of the cylinder is 90 mm. The second, the maximum working pressure is very important for further calculations, which we transfer from the previous calculation of the compression ring of the VAZ – 2190 engine, that is 8 MPa, and for our calculations it is more convenient to operate with 80 kg / cm2.
So, we know the size of the outer diameter of the sealing piston ring. Let’s see what size of the inner diameter GOST R 53843—2010 “recommends” to us, “suggesting” the radial thickness of the ring 3.8 +0.1—0.15 mm. Therefore, the internal diameter of the piston ring will be 90.0 – 3.8 = 86.2 mm. GOST offers to take the height of the ring of 2.0 mm. Very elegant ring! Do not prove that the developers ignored the second main task of the compression ring – to transfer heat from the overheated piston head to the cooled cylinder.
Solving this problem with such a “lightweight” piston ring is problematic, since the mass of the transmitting element, i.e. the piston ring, was lost. Due to poor heat transfer between the piston and the cylinder, the author justified the inexpediency of using standard, currently used piston trapezoidal compression rings (for example, on all models of KAMAZ engines) [2].
Nevertheless, the “trapezoidal” piston compression rings continue to be produced by the manufacturer of sets of cylinder-piston group “KOSTROMA-MOTORDETAL”, equipping KAMAZ engines, YAMZ engines and many others. It will be necessary, once again, to prove the absolute axiom shown in Fig. 2, this design does not in any way resemble a piston seal ring and a structural element that, among other things, must provide the best heat dissipation from an overheated piston head to a cooled cylinder.
Figure. 2. A compression ring with a facet at an upper end face in dynamics: 1-A CYLINDER 2-A PISTON; 3-A PISTON RING
Moreover, the initiator of the “twisting”, “wedge-shaped”, and according to our GOST “trapezoidal” piston seal rings, intelligibly explained that the “twisting” rings are obtained as a result of the fact that “… the main axes of inertia formed (after tuck, bevel, facet) of the non-symmetric cross-section of the
