Aircraft Anti-icing coating

Abstract

The invention relates to air transport and is intended for preventing the formation of ice on the outer surfaces of aircraft. An anti-icing coating on a protected surface (1) contains a water-soluble adhesive layer (2), and solid particles (3) of a freezing point depressant which have a linear size of not more than 0.2 millimetres. The water-soluble adhesive layer reduces the adhesive strength of ice, and the given size of the particles (3) causes a minimum of added aerodynamic resistance. A method and means for applying the coating are also proposed.

Description

[0001] Aviation anti-icing coating

[0002] AREA OF TECHNOLOGY

[0003] The invention relates to air transport and is intended to prevent the formation of ice on the external surfaces of aircraft.

[0004] LEVEL OF TECHNOLOGY

[0005] It is known that icing-resistant coatings consist of one or more layers providing thermal insulation and a superhydrophobic surface [1].

[0006] A disadvantage of this coating is that superhydrophobic surfaces exhibit limited anti-icing properties due to the following natural phenomena. First, a cooled superhydrophobic surface can become covered with frost due to the condensation and freezing of water vapor [2]. Falling water drops will adhere more readily to the resulting frost, and the adhesion of the ice to the surface will be increased due to its presence in the surface texture. Second, when water droplets hit the surface, some of it can penetrate the surface texture [3,4] and freeze there. This will also lead to further ice growth and increased adhesion of the ice to the superhydrophobic surface. The presence of a heat-insulating layer under the superhydrophobic surface, as proposed by the aforementioned invention, cannot prevent the above-described phenomena.

[0007] Also known is an anti-icing coating containing multiple reservoirs of anti-icing fluid enclosed in a polymer matrix cured by ultraviolet radiation [5].

[0008] The disadvantage of this coating is that after the de-icing fluid is washed out by falling droplets from the cured polymer matrix, a porous structure remains. Due to this porosity, ice will adhere strongly to this surface. The UV-curable polymer matrix complicates its application and removal. Furthermore, the coating lacks dyes to facilitate assessment of the quality of its application or removal.

[0009] DISCLOSURE OF THE INVENTION

[0010] The objective of the invention is to create an anti-icing coating without the disadvantages mentioned in paragraph 2. The technical result of the proposed invention consists of enhancing the anti-icing properties of the coating and expanding the range of aircraft surfaces it can protect. This technical result is achieved by the anti-icing coating containing a water-soluble adhesive layer and a substance that depresses the freezing point of an aqueous solution, in the form of solid particles with a linear dimension of no more than 0.2 millimeters.

[0011] There is a variant in which solid particles of a substance that lowers the freezing point of an aqueous solution are distributed over the thickness of the adhesive layer.

[0012] There is an option in which solid particles of a substance that lowers the freezing point of an aqueous solution are located on the surface of the adhesive layer.

[0013] An option is possible in which the volume fraction of solid particles of a substance that lowers the freezing point of an aqueous solution does not exceed 75%.

[0014] An option is possible where solid particles of a substance that lowers the freezing point of an aqueous solution are colored.

[0015] There is also a variant in which the adhesive layer contains dye.

[0016] Based on the application of the proposed coating, a method for minimizing or preventing icing of the protected surface has been put forward.

[0017] There is an option in which a mixture of a substance that forms a water-soluble adhesive layer with solid particles of a substance that lowers the freezing point of an aqueous solution is applied to the surface to be protected.

[0018] There is also an option in which a substance that forms a water-soluble adhesive layer is first applied to the surface to be protected, and then solid particles of a substance that lowers the freezing point of the aqueous solution are rubbed into the surface of this layer.

[0019] An option is possible in which the surface to be protected is cleaned and degreased before applying the anti-icing coating.

[0020] A product for preventing or minimizing surface icing has also been proposed based on the anti-icing coating. The product contains a substance that forms a water-soluble layer and solid particles of a substance that depresses the freezing point of an aqueous solution.

[0021] There is a version of the product in which these components are mixed.

[0022] It is possible that the components are supplied separately.

[0023] There is a variant in which dye is added to the substance that forms a water-soluble adhesive layer.

[0024] A variant is possible in which the solid particles of the substance that lowers the freezing point of an aqueous solution are colored.

[0025] There is an option that includes separate components for cleaning and degreasing the protected surface with a cleaning material. BRIEF DESCRIPTION OF DRAWINGS

[0026] Fig. 1 shows a schematic diagram of an aircraft anti-icing coating, where a substance that lowers the freezing point of an aqueous solution is distributed over the thickness of the adhesive layer - side view.

[0027] Fig. 2 shows another version of an aviation anti-icing coating, where a substance that lowers the freezing point of an aqueous solution is located on the surface of the adhesive layer - side view.

[0028] IMPLEMENTATION OF THE INVENTION

[0029] The aviation anti-icing coating on the protected surface (1) (Fig. 1, 2) contains a water-soluble adhesive layer (2) and a substance that lowers the freezing point of an aqueous solution in the form of solid particles (3) with a linear size of no more than 0.2 millimeters.

[0030] There is a variant (Fig. 1) in which solid particles (3) of a substance that lowers the freezing point of an aqueous solution are distributed over the thickness of the adhesive layer (2).

[0031] There is an option (Fig. 2) when solid particles (3) of a substance that lowers the freezing point of an aqueous solution are located on the surface of the adhesive layer (2).

[0032] Aircraft anti-icing coatings work as follows. Under icing conditions, supercooled water droplets, present in the atmosphere at temperatures below 0°C, strike the surface of the anti-icing coating as the aircraft and / or its part moves. The impact causes the water droplets to spread and dissolve solid particles (3) of the substance, which depresses its freezing point. After the solid particles (3) dissolve, the water no longer freezes on the surface and is blown away by the airflow generated by the movement of the aircraft and / or its part. The water droplets not only dissolve the solid particles (3) but also the water-soluble adhesive layer (2), thereby reducing the roughness of the resulting surface and revealing the intact protective coating layer.

[0033] For example, a water-soluble adhesive can be used as the water-soluble adhesive layer (2), and the solid particles (3) of a substance that depresses the freezing point of an aqueous solution can be, for example, sodium chloride. To ensure uniform distribution of the particles (3) of the substance that depresses the freezing point of an aqueous solution in the adhesive layer (2) (Fig. 1), they are pre-mixed, and then the resulting mixture is applied to the surface to be protected (1), for example, with a brush. To obtain the second version of the coating (Fig. 2), the adhesive layer (2) is applied, and then solid particles (3) are sprinkled onto the surface of this layer and rubbed in. If the surface to be protected (1) is contaminated before applying the coating, it is pre-cleaned and degreased using, for example, isopropyl alcohol and a paper towel.

[0034] The size of the solid particles (3) of the substance used to depress the freezing point of an aqueous solution can be determined to meet the required criterion, for example, using microscopic examination (for details, see [6]). By analyzing micrographs of the particles, their maximum linear size is determined, which should be no greater than 0.2 millimeters. This particle size allows for the production of an anti-icing coating surface with a minimum level of additional aerodynamic drag. This is based on the general requirements for the quality of the external surface of subsonic aircraft, according to which protrusions should be no larger than 0.2 millimeters [7].

[0035] The volume fraction of particles (3) of a substance that depresses the freezing point of an aqueous solution in the coating is calculated using the formula cp=V_p / (V_p+V_a)хЮ0%, where V_p and V_a are the estimated volume fractions of particles and the adhesion layer, respectively. It should not exceed 75%. The estimate of the maximum fraction of particles is based on two considerations. On the one hand, the higher the fraction of solid particles (3), the stronger the anti-icing properties of the coating. On the other hand, the maximum fraction of particles is limited by the fact that the particles must be well retained on the surface of the adhesion layer (2). Therefore, the maximum fraction of particles (3) in the coating is obtained by considering the thinnest coating with a thickness equal to the diameter of the solid particles (3), in which the adhesion layer (2) is 1 L diameter particles and particles are in a tightly packed manner.

[0036] The adhesion layer (2) can be colored by adding, for example, food coloring. And the solid particles (3) of the freezing point depressant can be colored by adding an aqueous solution of watercolor paint, followed by drying and grinding.

[0037] The proposed anti-icing coating provides protection for aircraft, such as UAVs (unmanned aerial vehicles), and can also be used in other areas, such as protecting antennas.

[0038] Based on the formation of the proposed anti-icing coating, a method for minimizing and preventing icing of the protected surface (1) is proposed. As described above, the method for creating the proposed anti-icing coating may consist of applying a mixture of a substance that forms a water-soluble adhesive layer (2) with solid particles (3) of a substance that depresses the freezing point of an aqueous solution (Fig. 1). Alternatively, the method consists of first applying the substance that forms the water-soluble adhesive layer (2) to the surface (1), then sprinkling and rubbing solid particles (3) into it (Fig. 2). Depending on the degree of contamination, before forming the anti-icing coating, the protected surface (1) may be cleaned and degreased, for example, with isopropyl alcohol.

[0039] Accordingly, the composition for creating the proposed coating contains two main components: a substance that forms a water-soluble adhesive layer (2) and solid particles (3) of a substance that depresses the freezing point of an aqueous solution, with linear dimensions no greater than 0.2 millimeters—supplied either as a mixture or separately (see examples above). These components may contain a dye to ensure application control (see examples above). The composition may also contain separate components for cleaning and degreasing (e.g., isopropyl alcohol) and wiping material (e.g., paper towels).

[0040] The use of a water-soluble adhesion layer reduces surface roughness caused by the collision and spreading of water droplets by dissolving and removing both coating components. This reduced roughness reduces the adhesion of ice to the resulting surface, facilitating its removal by the oncoming airflow generated by the movement of the aircraft and / or its parts. Removing both coating components with water droplets reveals a new layer with anti-icing properties, which also prevents ice formation on the surface. Furthermore, the solubility of both coating components in water allows for easy cleaning of the surface and reapplication.

[0041] The use of solid particles (3) of a substance that depresses the freezing point of an aqueous solution, with a linear size no greater than 0.2 mm, allows for an anti-icing coating surface with minimal additional aerodynamic drag. Furthermore, the small size of the solid particles (3) ensures uniform anti-icing properties across the surface. Distribution of the solid particles (3) across the thickness of the adhesive layer (2) (Fig. 1) enables the production of thick coatings with maximum protection for aircraft components for which additional weight is not critical.

[0042] The presence of solid particles (3) on the surface of the adhesive layer (2) (Fig. 2), on the contrary, makes it possible to obtain thin coatings for aircraft elements that are sensitive to additional weight.

[0043] Using a volume fraction of solid particles (3) of no more than 75% prevents their entrainment in the oncoming air flow due to the adhesion layer (2) being sufficient to hold them together. This, therefore, increases the effectiveness of the anti-icing coating.

[0044] The use of dyes, either in solid particles (3) or in the adhesive layer (2), increases the visual contrast of the coating and thus facilitates quality control of its application or removal. Consequently, this increases the effectiveness of the anti-icing coating.

[0045] Applying a mixture of a substance that forms a water-soluble adhesive layer (2) with solid particles (3) of a substance that depresses the freezing point of an aqueous solution to the surface to be protected (1) creates a thick protective layer for aircraft components that are not sensitive to additional weight. This increases the effectiveness of de-icing protection.

[0046] By first applying a substance (2) to the protective surface (1), followed by rubbing in solid particles (3) of a substance that depresses the freezing point of the aqueous solution, thin protective layers are created for aircraft components that are sensitive to additional weight. This, in turn, expands the range of aircraft components protected by the coating.

[0047] Cleaning the surface to be protected (1) and degreasing it before applying the anti-icing coating improves the uniformity of its application over the surface and the adhesion of the adhesive layer (2) to it.

[0048] A means for preventing or minimizing icing of a protected surface (1) in the form of a mixture of a substance that forms a water-soluble adhesive layer (2) with solid particles (3) of a substance that lowers the freezing point of an aqueous solution, makes it possible to create thick protective layers for aircraft components for which additional weight is not critical.

[0049] A means for preventing or minimizing icing of the protected surface (1) in the form of individual components described above, allows for the formation of thin protective layers on aircraft elements for which additional weight is critical.

[0050] The dye in the product for preventing or minimizing icing of the protected surface (1) facilitates quality control of its application or removal.

[0051] The presence of separate components for cleaning and degreasing with a wiping material in the product allows for improving the quality of application and adhesion of the adhesive layer (2) to the protected surface (1) and, accordingly, the anti-icing protection of the coating.

[0052] Thus, the features of the proposed invention consist of increasing the anti-icing properties of the coating and expanding the range of protected surfaces of the aircraft.

[0053] LITERATURE

[0054] 1. Patent EP 3676178 B1 European Patent Office, IPC B64D 15 / 00 (2006.01), C09K 3 / 18 (2006.01). Non-icing surfaces: N 18852340.1: declared: 09.08.2018: published. 29.06.2022 / Amsalem J., Breuer O., Marmur A.; applicant Rafael Advanced Defense Systems Ltd. - 16 p.: ill. - Text: direct.

[0055] 2. Varanasi KK, Deng T., Smith JD, Hsu M., Bhate N.; Frost formation and ice adhesion on superhydrophobic surfaces. Appl. Phys. Lett. - 2010. - 97 (23): p. 234102-1 - 234102-3: ill. - Text: direct.

[0056] 3. Deng T., Varanasi KK, Hsu M., Bhate N., Keimel C., Stein J., Blohm M.; Nonwetting of impinging droplets on textured surfaces. Appl. Phys. Lett. - 2009. - 94 (13): p. 133109-1 - 133109-3: ill. - Text: direct.

[0057] 4. Kwon H.-M., Paxson A. T., Varanasi K. K., and Patankar N. A. Rapid Deceleration-Driven Wetting Transition during Pendant Drop Deposition on Superhydrophobic Surfaces. Phys. Rev. Lett. - 2011. - 106: p. 036102-1 - 036102-4: ill. - Text: direct.

[0058] 5. Patent EP 3115421 B1 European Patent Office, IPC C09O 5 / 00 (2006.01), Active anti-ice coating, coating material and production method for producing the same: N 15175504.8: declared: 06.07.2015: published 03.03.2021 1 Strobl T., Raps D., Zahouily K., Riess G.; applicant Airbus Helicopters Deutschland GmbH, Airbus Defence and Space GmbH - 17 p.: ill. - Text: direct.

[0059] 6. Gavrilova N. N. Microscopic methods for determining the particle sizes of dispersed materials: textbook, manual / N. N. Gavrilova, V. V. Nazarov, O. V. Yarovaya. - M .: Mendeleyev University of Chemical Technology of Russia, 2012 .-- 52 p. - ISBN 978-5-7237-1055-9. - Text: direct. 7. OCT 1 02507-92. Subsonic aircraft. General requirements for the quality of the external surface: industry standard of the Russian Federation: official publication : approved and registered by TC for standardization No. 323 for No. 874 dated 23.08.92 : introduced to replace : introduced 1993-01-01. - Text: direct.

Claims

CLAUSES OF THE INVENTION 1. An aviation anti-icing coating applied to the surface to be protected (1) and containing: a water-soluble adhesive layer (2), a substance that lowers the freezing point of an aqueous solution, in the form of solid particles (3) with a linear size of no more than 0.2 millimetres.

2. The coating according to paragraph 1, characterized in that the solid particles (3) of the substance that lowers the freezing point of an aqueous solution are distributed over the thickness of the water-soluble adhesive layer (2).

3. The coating according to paragraph 1, characterized in that the solid particles (3) of the substance that lowers the freezing point of an aqueous solution are located on the surface of the water-soluble adhesive layer (2).

4. The coating according to paragraph 2, characterized in that the volume fraction of solid particles (3) of the substance that lowers the freezing point of an aqueous solution does not exceed 75%.

5. The coating according to claim 1, characterized in that the solid particles (3) of the substance that lowers the freezing point of an aqueous solution are colored.

6. The coating according to claim 1, characterized in that the adhesive layer (2) contains a dye.

7. A method for minimizing or preventing icing of a protected surface (1), which consists of forming a coating on it according to paragraph 1.

8. The method according to claim 7, in which a mixture of a substance that forms a water-soluble adhesive layer (2) with solid particles (3) of a substance that lowers the freezing point of an aqueous solution is applied to the surface to be protected (1), wherein the linear size of the particles is no more than 0.2 mm and their volume fraction is no more than 75%.

9. The method according to paragraph 7, in which a substance that forms a water-soluble adhesive layer (2) is applied to the surface to be protected (1), and then solid particles (3) of a substance that lowers the freezing point of an aqueous solution are rubbed into the surface of this layer, wherein the linear size of the particles is no more than 0.2 mm.

10. The method according to claim 7, in which, before applying the anti-icing coating, the surface to be protected (1) is cleaned and degreased.

11. A means for preventing or minimizing icing of a protected surface (1), containing components for forming an anti-icing coating on it according to paragraph 1.

12. The agent according to claim 11, in which the component that forms a water-soluble adhesive layer (2) on the surface to be protected (1) is mixed with solid particles (3) of a substance that lowers the freezing point of an aqueous solution, wherein the linear size of the particles is no more than 0.2 mm and their volume fraction is no more than 75%.

13. The agent according to paragraph 11, in which there is a separate component that forms a water-soluble adhesive layer (2) on the protected surface (1), and solid particles (3) of a substance that lowers the freezing point of an aqueous solution, wherein the linear size of the particles is no more than 0.2 mm.

14. The agent according to claim 11, in which a dye is added to the component that forms the water-soluble adhesive layer (2).

15. The agent according to claim 11, in which the solid particles (3) of the substance that lowers the freezing point of an aqueous solution are colored.

16. The product according to item 11, which contains separate components for cleaning and degreasing the surface with a wiping material.

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