Piston Engines of the New Generation (Without turbo – supercharging). Anatoly Matveevich Druzhinin

formula, we take the height of the piston ring as an unknown quantity, because we have proved that the standards recommend us incorrect data. Let’s try to correct them, for this we equate both areas of these different surfaces of the piston ring π (r₁²– r₂²) = 2πr₂h. The size of the height of the ring h is unknown, in this equation, it is easily determined by the formula: h = (r₁²-r₂²) /2r₂. Substitute the values and get: h = (20.25—16.81) /2 × 4.1 = 3.44/8.2 = 0.4195 cm = 4.195 mm.

      Define the values of the areas S₁ and S₂:

      S₁ = 3.14 (20.25—16.81) = 3.14 × 3.44 = 10.8016 cm²;

      S₂ = 2 × 3.14 × 4.1 × 0.4195 = 10.801286 cm².

      Now we can accurately calculate the value of the gas-dynamic forces F_o and F_rad acting on the piston compression ring intended for the engine cylinder with a diameter of 90 mm. For this, we multiply the value of the maximum working pressure in the cylinder and in the piston groove by the dimensions of certain surface areas:

      F_o = P_work × S₁ = 80 kg / cm² × 10.8016 cm² = 864.128 kgf;

      F_rad = P_work × S₂ = 80 kg / cm² × 10.801286 cm² = 864.103 kgf.

      The difference F_rad – F₀ = 0.025 kgf, can be negligible, lying within the limits of measurement error.

      We can assume that the effect of the gas dynamic forces are balanced, therefore, the negative effect of gas dynamics on the operation of the piston compression ring is neutralized. The working capacity of the piston ring is provided by the force of pressing the working surface of the ring against the wall of the cylinder, that is, by the elasticity of the piston ring. The necessary magnitude of this force can be achieved not only due to the geometric dimensions of the piston ring, but also the determination of the properties of the material from which the piston ring is made and the heat treatment, the gap in the lock of the ring in the free state.

      So, we got all the necessary sizes, let’s see how the design will look on the sketch of Fig. 3. The difference from the gas-dynamic scheme shown in Fig. 1 is fundamental, both in form and content. The main thing, to what the taken measures have resulted, is clearing of a compression ring from any overloads connected with gas dynamics. To the piston ring was returned to its elastic qualities, the normal position relative to the flanges of the piston groove and the cylinder wall, normal operability. The form, content (material, thermal operations) and dimensions provided favorable conditions for function execution assigned to the piston compression ring.

      The piston compression ring is designed to execution: the following tasks:

      – reliable consolidation of the space between the movable piston and the stationary cylinder, excluding any gas-dynamic losses, or reducing them to an insignificant minimum;

      – heat transfer from an overheated piston head to a cooled cylinder;

      – minimum mechanical losses due to friction of the working surface of the piston ring against the wall of the cylinder.