Method of specific friction resistance control for coating to be flowed around with liquid

FIELD: processes for applying fluent materials to surfaces to obtain anti-friction surface with the purpose to reduce hydraulic and aerodynamic friction of vehicle moving in liquid and to reduce friction in friction assemblies of machines and mechanisms working in aqueous medium.

SUBSTANCE: method involves obtaining and applying antifriction coating on vehicle body so that specific coating surface energy along liquid streamlines (streamline surface) has negative gradient.

EFFECT: reduced friction due to provision of friction resistance control.

 

The invention relates to the production of anti-friction coating to reduce the coefficient of hydro - and aerodynamic drag of vehicles moving in a fluid, as well as in friction units of machines and mechanisms operating in aqueous media.

Close analogues directly related to the ways to control the coefficient of friction of the coating, the streamlined fluid could not be found.

Known anti-friction materials used in friction units of machines and mechanisms operating in aqueous media (USSR author's certificate No. 1654306 from 30.12.1987 year). To achieve lower friction resistance offered by the new composition of the material and the specific ratio of components. However, the achieved results and the results of the experiments are far from the coefficient of friction self polishing coatings, close to theoretical value of Blasius.

Known composite material mounted on the hull of ships, to minimize resistance to movement (France application No. 2615788, 1988). The outer layer is hydrophilic and soluble in water. Soluble paint particles fall within the laminar sublayer and reduce the thickness of the boundary layer. The disadvantage of this material is the short duration of the effect of reducing friction, namely, up until dissolve the paint.

There are various device is tion to reduce the friction of moving the vessel by management in function of time the shape of the surface of the damping coating, pasted on the underwater part of the hull, for example, to create a traveling wave along the body (ed. the certificate of the USSR No. 1726308 from 22.06.1986 year). The disadvantages of such devices is the complexity of construction, low maintainability.

A device for feeding a solution of high-molecular polymer on the surface of the hull (ed. the certificate of the USSR No. 1068325 1982) for the laminar < / span > ambient ship thread. The main disadvantage is the large expenses of the polymer, which have to carry on Board.

The known method of reducing the hydrodynamic resistance to movement of solids (ed. certificate No. 364493 from 22.06.1970 g), which consists in creating in the boundary layer of the electromagnetic field (using aluminum or other electrodes) to generate it complexes of molecules instead of filing in the boundary layer of polymers. The disadvantages of the method is the difficulty of replacement of consumable electrodes and homogeneous (with complexes of molecules) of the boundary layer.

The technical result of the invention is to reduce the friction anti-friction coatings in the liquid by controlling the coefficient of friction is achieved by the fact that in the manufacture of anti-friction coatings specific surface energy along the flow line (surface current) form with a negative gradient.

Modern approaches studied what I hydro - and aerodynamic drag of friction are limited to consideration of internal friction streamlined environment, accepting the hypothesis that the adhesion of the particles of the medium to the wall. On the basis of theoretical and experimental studies (Third international conference "Navy and shipbuilding nowadays". Prospects of shipbuilding and naval fleets in the XXI century, June 26-28, 2003, Proceedings, section a, Section B) shows that the material properties of the wall significantly change the picture of the surface of interaction between the environment and the sides of the body. To the surface of the body having a heterogeneous structure combining hydrophilic and hydrophobic properties on the boundary of contact of dissimilar molecules identified "drip" effect, i.e. the medium under continuous flow in these areas behaves like a drop. On these surfaces there are three zones. The first area with a high activation energy and zero tangential velocity environment in the areas of body surface with hydrophilic properties. The second area with a low activation energy and zero tangential velocity environment in the areas of body surface with hydrophobic properties. The third area with activation energy equal to the activation energy of the molecules of the medium, and a non-zero tangential velocity in the adjacent hydrophilic and hydrophobic areas. Proven dual mechanism of reducing the hydrodynamic friction of these surfaces by reducing the coefficient of viscosity of the medium in the Prip the surface layer, due to the decrease in activation energy, and due to possible slippage of the particles of the medium due to "drip" the behavior of particles of the medium in the flow. Analytical expressions are obtained values of the coefficient of viscosity depending on the type of environment and material properties of the surface. Formulated in terms of slippage of the particles of the medium on the surface of the wall body. theoretical results are in good qualitative agreement with the experimental data, obtained by wrapping water plates coated with a polymeric dye with fullerensoderzhashchikh additives. If (1.0 to 1.5)% content of hydrophobic additives achieved (15-20)% the decrease in the value of the coefficient of friction.

The method of controlling the coefficient of friction anti-friction coatings, streamlined fluid (in this case water), tested on the specialized hydrodynamic stand NS-83 CRI name Krylov shipbuilding.

The stand (see figure 1) has a measuring channel 1 with a rectangular cross-section. In the upper part of the stand there is a sight glass 2. Inside the channel is removable plate 3 (length 1800 mm, width 30 mm, thickness 10 mm) coated on the upper part of the plate-friction coating 4. Measuring channel has a flow meter 6 (IL-61, an error of 1%) and differential manometers 7 (mark DS-EB, measurement error Yes the population is 0.5%).

Coming into the channel, the water flows around the floor 4 of the plate 3 at a given speed (12 m/s). The readings of the flow meter (preset flow rate and differential pressure gauges are calculated ow losses due to friction of water on the coating surface and the corresponding coefficient of friction.

To create anti-friction coating with a negative gradient is selected from polystyrene, which was dissolved fullerene C60. Next was the experimental curve of the coefficient of friction coating on the concentration of fullerenes. The greatest factor corresponds to zero concentration and the lowest value of the concentration of fullerenes 1%. The strip along the length of the plate was divided into 20 parts. Each portion was applied a coating of the same thickness (150 μm) with a given concentration of the fullerene. The first part of the plate concentration was 0%, the twentieth - 1%. At the intermediate parts is linear from 0 to 1%.

The results of measurements and calculations of the coefficient of friction of the coating depending on the Reynolds number are presented in figure 2.

In the beginning was measured plate No. 22 with the addition of fullerenes constant concentration along the length of the strip. Then the second plate (No. 6-1-2), the flow of which water began with the side part with a zero concentration of fullerene (reverse), then the opposite is from, with a concentration of 1% (straight line). Clearly visible is a noticeable difference in the coefficients of friction for forward and reverse, i.e. the influence of the gradient of the specific surface energy of the anti-friction coating.

The method of controlling the coefficient of friction anti-friction coatings, streamlined fluid, characterized in that along the current lines or surfaces of a liquid specific surface energy coatings provide a negative gradient.



 

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