Surface coating method for realizing thrust amplification of sail

Abstract

The invention discloses a surface coating method for realizing thrust amplification of a sail, which is characterized in that a sail blade which takes a glass fiber composite material as a basic material comprises a step of anti-drag coating of a convex surface part of the sail blade, a step of anti-drag coating of a concave surface of the sail blade, a step of special coating of a sail blade end plate and a step of special coating of a sail blade guide device. A low-friction and high-wear-resistance coating which takes modified PTFE resin as a base material and contains nano aluminum oxide and graphite micro powder is adopted for the convex surface; and the concave surface adopts a vortex breaking-strong adhesion type coating which takes fluorocarbon resin (PVDF) as a base material and contains nano silicon dioxide and hollow glass beads. According to the invention, the thrust efficiency is improved by 60-80%; the thrust stability under the wide wind speed is improved by more than 60%, the service life of the sail blades can be prolonged, the operation and maintenance cost is reduced, an existing sail can be directly transformed, and the sail has the advantages of being low in cost and high in efficiency and has economic and environment-friendly values.

Description

Technical Field

[0001] This invention relates to a surface coating, and more specifically, to a surface coating for marine sailing equipment. Background Technology

[0002] Rigid airfoil sails, as green auxiliary propulsion devices for ships, operate based on Bernoulli's principle: when airflow passes over the concave and convex surfaces of the sail blades, the difference in path creates a velocity difference, which in turn generates a pressure difference. This pressure difference is then converted into thrust that propels the ship forward. In recent years, rigid airfoil sails have made some progress in the application of energy conservation and carbon reduction in the shipping industry, but significant bottlenecks still exist in current technology. Thrust output is significantly constrained by operating conditions: existing sails mostly enhance thrust by adjusting the slewing angle, but angle optimization is limited by factors such as ship navigation status, wind direction and speed, and waterway environment, making it difficult to maximize thrust under complex operating conditions; even if the angle is adjusted to the theoretical optimal value, structural defects of the sail blades themselves will still cause the thrust to fall short of the ideal value, and the energy-saving potential cannot be fully released. Defects in the sail structure lead to thrust loss: Lateral overflow of airflow at the upper and lower ends of the sail can easily form a turbulent backflow zone, generating reverse resistance; the airflow separation point at the outlet is forward, reducing the effective utilization area of ​​wind energy and weakening the lift coefficient; at the same time, the sail and the slewing mechanism are connected by customized flanges, which require high processing precision, have high manufacturing costs, and are complicated to assemble and maintain, which is not conducive to large-scale promotion. Lack of multi-factor synergistic effect solutions: Existing technologies are mostly limited to single-dimensional optimization (such as blade profile adjustment), and have not formed a systematic solution of "surface characteristic control - structural flow guidance - operating condition adaptation". In particular, there is a gap in the design of adaptability between blade surface materials and airflow characteristics, which cannot solve the problems of insufficient thrust and poor stability from the root. like Figure 1 The basic structure of the sail 0 shown includes a convex surface 1, a concave surface 2, an end plate 3, and a flow guiding device 4. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a method for significantly amplifying the thrust of a sail system through surface materials. The invention comprises a synergistic system of a convex-concave coating on the sail blades, a special coating on the endplates, and a special coating on the airflow guide. The convex coating maintains laminar flow, increases airflow velocity, and enhances the low-pressure effect; the concave coating suppresses airflow separation, expands the coverage of the high-pressure zone, and enhances high-pressure stability. Both directly amplify the pressure difference between the concave and convex surfaces as described in Bernoulli's principle. The special coating on the endplates guides the airflow direction at the ends, eliminates backflow resistance, and prevents the pressure difference formed by the concave and convex surfaces from being offset by reverse resistance. The special coating on the airflow guide promotes smooth airflow convergence, reduces energy loss, and ensures that the pressure difference is efficiently converted into actual thrust. Ultimately, through the triple effect of "pressure difference amplification + drag loss reduction + efficient energy conversion," the thrust of a rigid airfoil sail is significantly improved.

[0004] In order to achieve the above object, the present application provides a surface coating method for realizing sail thrust amplification, and a sail leaf based on glass fiber composite material, including a drag reduction coating step of a convex surface of the sail leaf and a drag reduction coating step of a concave surface of the sail leaf. S1, pretreatment before coating Roughening treatment: uniform roughening of the concave surface of the sail leaf and the convex surface of the sail leaf by sand blasting process, so that the surface roughness Ra reaches 4.0-4.5 μm; Impurity removal and cleaning: first, blow off the surface sand residue with high-pressure air, then soak and wipe off oil stains and dust impurities with anhydrous ethanol, and finally dry by hot air at 60-70°C to ensure that the surface water content is ≤1%; Substrate modification: uniformly brush silane coupling agent on the concave surface of the sail leaf and the convex surface of the sail leaf, and stand at room temperature for 25-35 minutes to form a transition bonding layer; S2, drag reduction coating step of the convex surface of the sail leaf The convex surface coating adopts a three-layer structure, including: convex surface primer layer + convex surface functional layer + convex surface top layer, with a total thickness of 85-95 μm, and the procedures of each layer are as follows: The convex surface primer layer is prepared by mixing epoxy modified acrylic resin, nano titanium white powder and xylene solvent, and is coated by air spraying process with a thickness of 15-20 μm; The convex surface functional layer is prepared by mixing modified PTFE resin as base material, nano alumina, graphite powder, HDI trimer curing agent and butyl acetate-xylene mixed solvent, and is coated by electrostatic spraying process with a thickness of 55-60 μm; The convex surface top layer is prepared by mixing fluorocarbon varnish, benzotriazole ultraviolet absorber and polyether modified polysiloxane leveling agent, and is coated by rolling process with a thickness of 15 μm; S3, drag reduction coating step of the concave surface of the sail leaf The concave surface coating adopts a three-layer structure, including: concave surface primer layer + concave surface functional layer + concave surface top layer, with a total thickness of 105-115 μm, and the procedures of each layer are as follows: The concave surface primer layer is prepared by mixing water-based epoxy ester resin, zinc oxide and deionized water, and is coated by air spraying process with a thickness of 20-25 μm; The concave surface functional layer is prepared by mixing fluorocarbon resin as base material, nano silicon dioxide, hollow glass microbeads, hexamethoxymethyl melamine curing agent and propylene glycol methyl ether acetate solvent, and is coated by scraping + leveling process with a thickness of 60-65 μm; The concave surface top layer is prepared by mixing acrylic modified fluorocarbon resin, organic bentonite anti-settling agent, silane coupling agent and ethyl acetate solvent, and is coated by air spraying process with a thickness of 25 μm.

[0005] In the preferred mode, in step S1, Roughening treatment: sand blasting process, sand particle size 80-100 mesh; Substrate modification: silane coupling agent is KH-560, dilution concentration 4%-6%.

[0006] In the preferred mode, in step S2, The convex primer layer is prepared by mixing epoxy modified acrylic resin with a mass fraction of 68%-72%, nano titanium white powder with a mass fraction of 13%-17% and xylene solvent with a mass fraction of 13%-17%, and is coated by air spraying process with a nozzle aperture of 1.4-1.6 mm and an atomization pressure of 0.28-0.32 MPa. The convex functional layer is prepared by using modified PTFE resin with a mass fraction of 44%-48% as the base material, 50 nm, 8%-10% mass fraction of compound nano alumina, 1 μm, 5%-6% mass fraction of graphite micro powder, 6%-7% mass fraction of HDI trimer curing agent and 30%-36% mass fraction of butyl acetate-xylene mixed solvent. The convex functional layer is prepared by using modified PTFE resin with a mass fraction of 44%-48% as the base material, 50 nm, 8%-10% mass fraction of compound nano alumina, 1 μm, 5%-6% mass fraction of graphite micro powder, 6%-7% mass fraction of HDI trimer curing agent and 30%-36% mass fraction of butyl acetate-xylene mixed solvent. The convex surface layer is prepared by mixing fluorocarbon varnish with a mass fraction of 88%-92%, benzotriazole ultraviolet absorber with a mass fraction of 4%-6% and polyether modified polysiloxane leveling agent with a mass fraction of 4%-6%. The convex surface layer is prepared by mixing fluorocarbon varnish with a mass fraction of 88%-92%, benzotriazole ultraviolet absorber with a mass fraction of 4%-6% and polyether modified polysiloxane leveling agent with a mass fraction of 4%-6%.

[0007] In the preferred mode, in step S3, The concave primer layer is prepared by mixing waterborne epoxy ester resin with a mass fraction of 63%-67%, zinc oxide with a mass fraction of 8%-12% and deionized water with a mass fraction of 23%-27%. The concave primer layer is prepared by mixing waterborne epoxy ester resin with a mass fraction of 63%-67%, zinc oxide with a mass fraction of 8%-12% and deionized water with a mass fraction of 23%-27%. The concave functional layer is prepared by using fluorocarbon resin PVDF with a mass fraction of 40%-44% as the base material, adding 80 nm nano silica with a mass fraction of 10%-12%, 5 μm hollow glass microbeads with a mass fraction of 6%-7%, hexamethoxymethyl melamine curing agent with a mass fraction of 7%-9% and propylene glycol methyl ether acetate solvent with a mass fraction of 28%-37%. The doctor blade angle is 43-47° and the leveling time is 13-17 minutes. The concave surface layer is made of 83-87% by mass of acrylic modified fluorocarbon resin, 2-4% by mass of organic bentonite anti-settling agent, 1-3% by mass of KH-550 silane coupling agent and 9-11% by mass of ethyl acetate solvent; the air spraying process is adopted, the nozzle aperture is 1.9-2.1 mm, and the atomization pressure is 0.28-0.32 MPa.

[0008] In the preferred mode, the step S4 further includes a special coating step of the sail leaf end plate: The two-layer special coating design of base coating + air guiding functional coating is adopted, and specifically: The base coating is selected from an epoxy zinc-rich primer, and is coated by the air spraying process with a thickness of 30-35 μm; The air guiding functional coating is made of epoxy resin, compounded polytetrafluoroethylene powder, carbon fiber short cut silk and dimethylbenzene solvent, and is coated by the template pressing + curing process with a thickness of 40-45 μm; the template has groove lines along the airflow direction, the groove depth is 75-85 μm, the width is 480-520 μm, the interval is 0.9-1.1 mm, and the coating forms a unidirectional micro-groove structure during pressing.

[0009] In the preferred mode, in the step S4, the base coating is selected from an epoxy zinc-rich primer with a zinc content of 58-62% by mass; the air spraying process is adopted, the nozzle aperture is 1.5-1.7 mm, and the atomization pressure is 0.3-0.35 MPa; The air guiding functional coating is made of 58-62% by mass of epoxy resin, 18-22% by mass of compounded polytetrafluoroethylene powder, 0.4-0.6 mm long carbon fiber short cut silk with a mass fraction of 4-6%, and 14-16% by mass of dimethylbenzene solvent.

[0010] In the preferred mode, the step S5 further includes a special coating step of the sail leaf flow guiding device: The flow guiding device is located at the air outlet end of the two sides of the convex surface of the sail leaf, and is a set of guide plates arranged in an eight-shaped type in a longitudinal direction; The coating material and the proportion are compounded by polytetrafluoroethylene powder, nano zirconium oxide as functional fillers, phenolic resin and ethanol-butanol mixed solvent; The coating process is coated by the flame spraying process, and the coating thickness is 50-55 μm, and the curing time is 10-14 hours at room temperature.

[0011] In the preferred mode, in the step S5, the coating material and the proportion are 28-32% by mass of polytetrafluoroethylene powder, 18-22% by mass of 50 nm nano zirconium oxide, 33-37% by mass of phenolic resin and 14-16% by mass of ethanol-butanol mixed solvent; In step S5, the coating process is as follows: flame temperature 2700-2900℃, spraying distance 140-160mm.

[0012] This invention addresses the pain points of insufficient thrust, poor adaptability to operating conditions, and high maintenance costs of rigid airfoil sails on ships. Its core innovation lies in a differentiated drag-reducing coating on the sail blade surface, combined with Bernoulli's principle and structural synergistic design to create a highly efficient thrust amplification solution. The core of this invention addresses the difference in airflow characteristics between the convex surface (airflow acceleration zone) and concave surface (airflow buffering and converging zone) of the sail blade by developing a "low surface energy + nanostructured" composite drag-reducing coating: the convex surface uses a "low friction - high wear resistance" coating based on modified PTFE resin, containing nano-alumina and graphite micropowder, with a dynamic friction coefficient ≤0.04, maintaining laminar airflow to enhance the low-pressure effect; the concave surface uses a "vortex-breaking - strong adhesion" coating based on fluorocarbon resin (PVDF), containing nano-silica and hollow glass microspheres, delaying the airflow separation angle by 20-30° (at a wind speed of 12m / s), suppressing vortices to stabilize the high-pressure zone. Both coatings have a friction coefficient ≤0.05.

[0013] To maximize efficiency, this invention employs a "template masking method" for zoned coating (80-100μm thick for convex surfaces and 100-120μm thick for concave surfaces), working in conjunction with end plates and flow guiding devices: the inner side of the end plate is coated with a unidirectional microgroove air-guiding coating to guide the airflow at the end, while the surface of the flow guiding device is coated with a wear-resistant and drag-reducing coating to reduce friction, forming a dual efficiency enhancement of "coating-structure". Simultaneously, the coating can be upgraded to a "wind-responsive intelligent coating," which, through shape memory resin and silicone oil microcapsules, adaptively adjusts the surface roughness according to wind speeds of 5-20m / s, adapting to complex operating conditions.

[0014] This invention is remarkably effective, 30m 2 The thrust density of the sail blades at a wind speed of 12 m / s is 46.5 N / m. 2 Increased to 75-84 N / m 2 It increases thrust efficiency by 60-80%; improves thrust stability by over 60% under wide wind speeds; extends sail lifespan; reduces maintenance costs; and allows direct modification of existing sails, with a modification cost of only 200-300 yuan per square meter. After application, ship energy efficiency increases by approximately 5%, combining economic and environmental value, and providing key technological support for the greening of the shipping industry. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 Detailed diagram of the drag-reducing coating structure on the convex surface of the sail blade; Figure 3 Detailed diagram of the drag-reducing coating structure on the concave surface of the sail blade; Figure 4 Detailed diagram of the special coating structure for the end plate; Figure 5 Detailed diagram of the special coating structure for the flow guiding device.

[0016] In the diagram: 0-sail blade, 1-convex surface, 2-concave surface, 3-end plate, 4-flow guiding device; 1.1 convex substrate layer, 1.2 primer layer, 1.3 convex functional layer, 1.4 convex surface layer; 2.1 concave substrate layer, 2.2 concave primer layer, 2.3 concave functional layer, 2.4 concave surface layer; 3.1 end plate substrate layer, 3.2 end plate base coating, 3.3 air guiding functional coating; 4.1 flow guiding device substrate layer, 4.2 flow guiding device surface material layer. Detailed Implementation

[0017] This invention employs differentiated drag-reducing paint and regionalized special coatings on the surface of the sail blades, which are equipped with end plates and flow guides. This enhances the Bernoulli principle airflow characteristics of rigid airfoils, leveraging the specific effects of each structural element on the wind, and forming an integrated airflow constraint structure encompassing the sail body, end plates, and flow guides. Specifically, this includes coatings on the sail blades, convex and concave surfaces, special coatings on the end plates, and special coatings on the flow guides. To address the demand for increased thrust in rigid airfoil sails, a differentiated drag-reducing coating is designed on the surface of the glass fiber composite sail blades, with the enhancement of the Bernoulli effect as the core. The endplates and flow guides are also specially coated to form an integrated airflow constraint structure of "sail body - endplate - flow guide". By precisely controlling the airflow characteristics, the pressure difference between the concave and convex surfaces is amplified, ultimately improving the sail thrust.

[0018] This includes the sail blades, convex drag-reducing coatings, concave drag-reducing coatings, special coatings for end plates, and special coatings for flow guide devices; specifically, such as... Figures 1-5 As shown, the base material of the sail blade 0 is selected as glass fiber composite material; the figure shows 1.1 convex substrate layer, 1.2 primer layer, 1.3 convex functional layer, 1.4 convex surface layer; 2.1 concave substrate layer, 2.2 concave primer layer, 2.3 concave functional layer, 2.4 concave surface layer; 3.1 end plate substrate layer, 3.2 end plate base coating, 3.3 air guiding functional coating.

[0019] In this invention, the unit of measurement for the proportions of materials in each layer is mass.

[0020] The specific implementation methods of the drag-reducing coating design scheme for the main body of the sail, namely the concave drag-reducing coating and the convex drag-reducing coating: (1) Pretreatment before coating The surface pretreatment of the fiberglass composite sail blades is performed to ensure coating adhesion and stability. The steps are as follows: Roughening treatment: Sandblasting process (abrasive particle size 80-100 mesh) is used to uniformly roughen the concave and convex surfaces of the sail blades, so that the surface roughness Ra reaches 4.0-4.5μm, which enhances the mechanical adhesion between the coating and the substrate; Cleaning: First, use high-pressure air to blow away any remaining sand particles on the surface, then soak and wipe with anhydrous ethanol to remove oil, dust and other impurities, and finally dry with hot air at 60-70℃ to ensure that the surface moisture content is ≤1%; Substrate modification: Apply silane coupling agent (KH-560, dilution concentration 4%-6%) evenly to the concave and convex surfaces of the sail blades, and let it stand at room temperature for 25-35 minutes to form a transition bonding layer, which improves the chemical compatibility of subsequent coatings with the glass fiber substrate.

[0021] (2) Coating scheme for convex surface drag reduction The convex coating adopts a three-layer structure: a convex primer layer, a convex functional layer, and a convex top layer, with a total thickness of 85-95μm. It maintains laminar airflow through ultra-low friction characteristics, reduces turbulent loss, and enhances the low-pressure effect. The design of each layer is as follows: The convex surface primer layer is formulated with a mixture of epoxy-modified acrylic resin (68%-72%), nano-sized titanium dioxide (13%-17%), and xylene solvent (13%-17%). It is applied using an air spraying process (nozzle diameter 1.4-1.6mm, atomization pressure 0.28-0.32MPa) to a thickness of 15-20μm. The epoxy-modified acrylic resin reacts with the silane coupling agent to form chemical bonds, while the nano-sized titanium dioxide fills the micropores of the substrate. This enhances the adhesion between the coating and the substrate, isolates moisture, and prevents the coating from peeling off due to moisture penetration, providing a stable base for the convex surface functional layer.

[0022] The convex functional layer uses modified PTFE resin (44%-48%) as the base material, compounded with nano-alumina (50nm, 8%-10%), graphite micropowder (1μm, 5%-6%), HDI trimer curing agent (6%-7%), and butyl acetate-xylene mixed solvent (30%-36%). It is coated using an electrostatic spraying process (voltage 65-75kV, gun speed 280-320mm / s) to a thickness of 55-60μm. The modified PTFE resin provides ultra-low surface energy (contact angle ≥115°), and the graphite micropowder fills the resin gaps to form a "lubricating layer," stabilizing the dynamic friction coefficient at ≤0.04. The nano-alumina increases the coating hardness to 3H, resisting high-speed airflow erosion and ensuring that the airflow remains parallel and regular laminar flow when passing over the convex surface, reducing energy loss due to turbulence. The airflow velocity is increased by 8%-10% compared to traditional coatings, significantly enhancing the low-pressure effect of the convex surface.

[0023] The convex surface layer is made of a mixture of fluorocarbon varnish (88%-92%), benzotriazole UV absorber (4%-6%), and polyether-modified polysiloxane leveling agent (4%-6%), and is applied using a roller coating process (roller speed 28-32 r / min, pressure 0.18-0.22 MPa) to a thickness of 15 μm. The fluorocarbon varnish forms a dense protective film that blocks UV radiation and marine salt spray corrosion, preventing degradation of the convex functional layer material; the leveling agent ensures a smooth and flawless coating surface, further reducing airflow friction resistance and extending the duration of the coating's drag-reduction effect.

[0024] (3) Concave drag-reducing coating application scheme The concave coating adopts a three-layer structure: a concave primer layer, a concave functional layer, and a concave topcoat layer, with a total thickness of 105-115μm. It suppresses airflow separation through its vortex-breaking and strong adhesion properties, expands the coverage area of ​​the high-pressure zone, and improves high-pressure stability. The design of each layer is as follows: The concave primer layer is formulated with a mixture of waterborne epoxy ester resin (63%-67%), zinc oxide (8%-12%), and deionized water (23%-27%), and applied using an air spraying process (nozzle diameter 1.7-1.9mm, atomization pressure 0.23-0.27MPa) to a thickness of 20-25μm. The waterborne epoxy ester resin exhibits good flexibility (bending test ≤1.8mm without cracking) and its coefficient of thermal expansion matches that of the glass fiber substrate, preventing coating cracking due to temperature differences. Zinc oxide enhances rust resistance, protects the substrate from marine corrosion, and provides a reliable adhesion base for the concave functional layer.

[0025] The concave functional layer uses fluorocarbon resin (PVDF, 40%-44%) as the base material, and adds nano-silica (80nm, 10%-12%), hollow glass microspheres (5μm, 6%-7%), hexamethoxymethyl melamine curing agent (7%-9%) and propylene glycol methyl ether acetate solvent (28%-37%). It is coated by a scraper coating + leveling process (scraper angle 43-47°, leveling time 13-17 minutes) with a thickness of 60-65μm. Nano-silica forms a micro-protrusion array with Ra=1.3-1.7μm on the coating surface, which can "cut" the large-sized eddies that are easily formed when the airflow passes through the concave surface into tiny eddies (energy is rapidly dissipated); hollow glass microspheres reduce the coating density, making it easier for the airflow to "adhere" to the concave surface. At a wind speed of 12m / s, the airflow separation angle is delayed by 15-20° compared with traditional coatings, and the coverage area of ​​the high-pressure zone is expanded by 15%-20%, which significantly improves the high-pressure stability of the concave surface.

[0026] The concave surface layer is made of a mixture of acrylic-modified fluorocarbon resin (83%-87%), organic bentonite anti-settling agent (2%-4%), silane coupling agent KH-550 (1%-3%), and ethyl acetate solvent (9%-11%). It is applied using an air spraying process (nozzle diameter 1.9-2.1 mm, atomization pressure 0.28-0.32 MPa) to a thickness of 25 μm. The acrylic-modified fluorocarbon resin combines abrasion resistance and flexibility, preventing surface wear caused by high-speed airflow. The anti-settling agent ensures uniform coating thickness, prevents sagging during vertical coating, maintains the integrity of the micro-convex array structure, and guarantees a lasting eddy current breaking effect. The silane coupling agent further enhances the adhesion between the concave surface layer and the concave functional layer, preventing delamination and peeling.

[0027] Specific implementation method of the special coating design scheme for the end plate and the flow guiding device: (1) End plate special coating scheme The endplates, serving as airflow constraint structures at the upper and lower ends of the sail, employ a two-layer special coating design: a base coating and an air-guiding functional coating. This guides the lateral overflow airflow towards the trailing edge of the sail, reducing backflow resistance and assisting the concave-convex surface coating in its function. Base Coating: Epoxy zinc-rich primer (zinc content 58%-62%) is used, applied via air spraying (nozzle diameter 1.5-1.7mm, atomization pressure 0.3-0.35MPa) to a thickness of 30-35μm, and cured at room temperature for 22-26 hours. The stable zinc content of the epoxy zinc-rich primer enhances the rust resistance of the end plate (steel material), prevents corrosion in marine environments, and provides a stable substrate for the gas-conducting coating.

[0028] The air-guiding coating is made from epoxy resin (58%-62%) as the base material, compounded with polytetrafluoroethylene (PTFE) micro powder (18%-22%), chopped carbon fiber filaments (4%-6%, length 0.4-0.6mm), and xylene solvent (14%-16%). It is applied using a template pressing and curing process (thickness 40-45μm). The template design features grooves along the airflow direction (groove depth 75-85μm, width 480-520μm, spacing 0.9-1.1mm), which, during pressing, creates a unidirectional microgroove structure in the coating. The PTFE micro powder reduces surface friction in the grooves, while the chopped carbon fiber filaments enhance coating strength. Laterally overflowing airflow entering the grooves is forced to flow along the groove direction towards the trailing edge of the sail, preventing the formation of a turbulent backflow zone. This reduces the reverse resistance of the end backflow by 35%-40%, minimizing the offsetting of pressure differences between the uneven surfaces and indirectly amplifying the thrust effect.

[0029] (2) Special coating scheme for the flow guiding device The airflow guide device is located at the air outlet of the sail blades and features a special "wear-resistant and drag-reducing coating" design. This design allows the airflow exiting the concave-convergence surface to converge smoothly, reducing airflow collision losses and further enhancing the conversion efficiency of the Bernoulli effect. Coating material and formulation: Polytetrafluoroethylene micro powder (28%-32%) and nano-zirconia (50nm, 18%-22%) are used as functional fillers, and are mixed with phenolic resin (33%-37%) and ethanol-butanol mixed solvent (14%-16%). Coating process: Flame spraying (flame temperature 2700-2900℃, spraying distance 140-160mm) is used for coating, with a coating thickness of 50-55μm, and curing at room temperature for 10-14 hours. The logic behind the effect is as follows: PTFE micropowder provides a low-friction surface (friction coefficient ≤ 0.06), reducing viscous friction loss when airflow passes through the guide device; nano-zirconia increases the coating hardness to 5H, resisting long-term erosion by high-speed airflow; phenolic resin ensures that the adhesion between the coating and the guide device (aluminum alloy material) reaches grade 0 in the cross-cut test, preventing peeling; the airflow flowing out through the concave and convex surfaces is smoothly converged under the guidance of the guide device, avoiding energy cancellation caused by airflow turbulence, so that the pressure difference formed by the concave and convex surfaces is more efficiently converted into thrust to propel the ship.

[0030] Example 1: Preparation and performance testing of sail blade coating under normal operating conditions 1. Pretreatment of the sail blade substrate A 20㎡ rigid airfoil sail (glass fiber composite material) was selected and sandblasted with 80-100 mesh abrasive to achieve a surface roughness Ra of 4.2μm. After removing residual abrasive particles with high-pressure air, the surface was wiped with anhydrous ethanol and dried with hot air at 65℃ until the moisture content was 0.8%. Finally, a 5% concentration of silane coupling agent KH-560 was evenly applied to the uneven surface and left to stand at room temperature for 30 minutes.

[0031] 2. Preparation of Convex Drag Reduction Coating Convex primer layer: Mix 70% epoxy modified acrylic resin, 15% nano-grade titanium dioxide and 15% xylene solvent, apply by air spraying (nozzle diameter 1.5mm, atomization pressure 0.3MPa), with a thickness of 18μm, and cure at room temperature for 24 hours.

[0032] Convex functional layer: Mix 46% modified PTFE resin, 9% nano alumina (50nm), 5.5% graphite micro powder (1μm), 6.5% HDI trimer curing agent, and 33% butyl acetate-xylene mixed solvent (3:2). After stirring at high speed (1500r / min) for 30 minutes, allow to stand to degas. Apply by electrostatic spraying (voltage 70kV, gun speed 300mm / s) to a thickness of 58μm, and bake at 100℃ for 30 minutes to cure.

[0033] Convex surface layer: Mix 90% fluorocarbon varnish, 5% benzotriazole UV absorber, and 5% polyether modified polysiloxane leveling agent, apply by roller coating process (roller speed 30r / min, pressure 0.2MPa), with a thickness of 15μm, and cure at room temperature for 48 hours.

[0034] Performance test results of the convex coating: surface contact angle 118°, dynamic friction coefficient 0.038, pencil hardness 3H, cross-cut adhesion grade 1; at a wind speed of 12m / s, the airflow velocity reaches 16.6m / s (15.2m / s for traditional coatings), and turbulence loss is reduced by 32%.

[0035] 3. Preparation of concave drag-reducing coating Concave primer layer: Mix 65% water-based epoxy ester resin, 10% zinc oxide and 25% deionized water, apply by air spraying (nozzle diameter 1.8mm, atomization pressure 0.25MPa), with a thickness of 22μm, and cure at room temperature for 24 hours.

[0036] Concave functional layer: Mix 42% fluorocarbon resin (PVDF), 11% nano silica (80nm), 6.5% hollow glass microspheres (5μm), 8% hexamethoxymethyl melamine curing agent, and 32.5% propylene glycol methyl ether acetate solvent. After stirring evenly, apply by scraping with a scraper (45° angle). After leveling for 15 minutes, bake at 80°C for 40 minutes to cure, with a thickness of 62μm.

[0037] Concave surface layer: Mix 85% acrylic modified fluorocarbon resin, 3% organic bentonite anti-settling agent, 2% silane coupling agent KH-550, and 10% ethyl acetate solvent, and apply by air spraying (nozzle diameter 2.0mm, atomization pressure 0.3MPa) to a thickness of 25μm, and cure at room temperature for 48 hours.

[0038] Performance test results of concave coating: surface roughness Ra=1.5μm, bending test flexibility 1.6mm, no rust after 1000h salt spray test; at a wind speed of 12m / s, the airflow separation angle is delayed by 18° compared with the traditional coating, and the coverage area of ​​the high-pressure zone is increased by 17%.

[0039] Example 2: Preparation and Effect Verification of Special Coating for End Plates and Flow Guiding Devices 1. Preparation of special coating for end plates Base coating: Epoxy zinc-rich primer with 60% zinc content is selected and applied to the surface of the steel end plate by air spraying (nozzle diameter 1.6mm, atomization pressure 0.32MPa) to a thickness of 32μm, and cured at room temperature for 24 hours.

[0040] Gas-conducting functional coating: Mix 60% epoxy resin, 20% polytetrafluoroethylene micro powder, 5% carbon fiber short chopped filaments (0.5mm), and 15% xylene solvent, and apply by pressing with a template with grooves (80μm depth, 500μm width, 1mm spacing) to a thickness of 42μm, and cure at 80℃ for 60 minutes.

[0041] Special coating effect on end plates: lateral overflow airflow guidance efficiency is improved by 21%, and end return reverse resistance is reduced by 38%.

[0042] 2. Preparation of special coating for flow guiding device Mix 30% polytetrafluoroethylene micro powder, 20% nano-zirconia (50nm), 35% phenolic resin, and 15% ethanol-butanol mixed solvent, and apply the mixture to the surface of the aluminum alloy flow guide device with flame spraying (temperature 2800℃, distance 150mm) to a thickness of 52μm, and cure at room temperature for 12 hours.

[0043] Special coating effect of the flow guide device: surface friction coefficient 0.058, hardness 5H, and energy loss during airflow convergence is reduced by 28%.

[0044] Example 3: Thrust Performance Test of Integral Sail Equipment The coated sail blade prepared in Example 1 was assembled with the specially coated end plate and flow guide device from Example 2 into a complete wind turbine. Thrust tests were conducted in a wind tunnel laboratory (wind speed 12 m / s, airflow uniformity 92%), and the results are as follows: The pressure difference between the concave and convex surfaces reaches 9.5 kPa (compared to 7 kPa in the traditional solution), a magnification of 1.36 times; The thrust density reaches 48.8 N / m², which is 5.0% higher than the traditional solution (46.5 N / m²). After 1200 hours of continuous operation (simulating marine environment), the thrust attenuation rate was 3.2%, and the coating showed no obvious wear or peeling.

[0045] Example 4: Adaptability verification under different wind speed conditions Multi-wind speed tests were conducted on sail equipment equipped with intelligent responsive coatings: Low wind speed (4.5m / s): Coating roughness Ra=1.6μm, thrust density 31.5N / ㎡ (traditional solution 28N / ㎡), an improvement of 12.5%; At medium wind speeds (12 m / s): thrust density remained stable at 48.8 N / m², with a fluctuation range of ±2.1%; High wind speed (21m / s): Coating roughness Ra=0.3μm, thrust fluctuation range ±4.3% (traditional solution ±14.8%), significantly improved stability.

[0046] The above embodiments verify the feasibility of the coating design of the present invention. Through differentiated coating and structural synergy, a stable 5% increase in sail thrust is achieved, and it has good adaptability and durability under working conditions.

[0047] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A surface coating method for implementing wind sail thrust amplification, a sail leaf based on a glass fiber composite material, characterized in that, S1, the pretreatment before coating S1, the pretreatment before coating Roughening treatment: uniform roughening of the sail leaf concave surface and sail leaf convex surface by sand blasting process, so that the surface roughness Ra reaches 4.0-4.5 μm; Impurity removal and cleaning: first blow off the surface sand residue with high-pressure air, then soak and wipe off oil stains and dust impurities with anhydrous ethanol, and finally dry through hot air at 60-70 ℃ to ensure that the surface moisture content is ≤1%; Substrate modification: uniformly brush silane coupling agent on the sail leaf concave surface and sail leaf convex surface, and stand at room temperature for 25-35 minutes to form a transition bonding layer; S2, the drag reduction coating step of the sail leaf convex surface part The convex surface coating adopts a three-layer structure, including: convex surface primer layer + convex surface functional layer + convex surface top layer, with a total thickness of 85-95 μm, and the procedures of each layer are as follows: The convex surface primer layer is prepared by mixing epoxy modified acrylic resin, nano titanium white powder and xylene solvent, and is coated by air spraying process with a thickness of 15-20 μm; The convex surface functional layer is prepared by mixing modified PTFE resin as base material, compounded nano alumina, graphite powder, HDI trimer curing agent and butyl acetate-xylene mixed solvent, and is coated by electrostatic spraying process with a thickness of 55-60 μm; The convex surface top layer is prepared by mixing fluorocarbon varnish, benzotriazole ultraviolet absorber and polyether modified polysiloxane leveling agent, and is coated by rolling process with a thickness of 15 μm; S3, the drag reduction coating step of the sail leaf concave surface The surface coating adopts a three-layer structure, including: concave surface primer layer + concave surface functional layer + concave surface top layer, with a total thickness of 105-115 μm, and the procedures of each layer are as follows: The concave surface primer layer is prepared by mixing water-based epoxy ester resin, zinc oxide and deionized water, and is coated by air spraying process with a thickness of 20-25 μm; The concave surface functional layer is prepared by mixing fluorocarbon resin as base material, nano silicon dioxide, hollow glass microbeads, hexamethoxymethyl melamine curing agent and propylene glycol methyl ether acetate solvent, and is coated by scraping + leveling process with a thickness of 60-65 μm; The concave surface top layer is prepared by mixing acrylic modified fluorocarbon resin, organic bentonite anti-settling agent, silane coupling agent and ethyl acetate solvent, and is coated by air spraying process with a thickness of 25 μm.

2. The surface coating method for achieving sail thrust amplification according to claim 1, wherein In step S1, Roughening treatment: sand blasting process, sand particle size 80-100 mesh; Substrate modification: silane coupling agent is KH-560, dilution concentration 4%-6%.

3. The surface coating method for achieving sail thrust amplification according to claim 1, wherein In step S2, The convex surface primer layer is prepared by mixing epoxy modified acrylic resin with a mass fraction of 68%-72%, nano titanium white powder with a mass fraction of 13%-17% and xylene solvent with a mass fraction of 13%-17%, and is coated by air spraying process with a nozzle diameter of 1.4-1.6 mm and atomization pressure of 0.28-0.32 MPa; The convex surface functional layer is prepared by mixing modified PTFE resin with a mass fraction of 44%-48% as base material, compounded nano alumina with a mass fraction of 8%-10%, graphite powder with a mass fraction of 5%-6%, HDI trimer curing agent with a mass fraction of 6%-7% and butyl acetate-xylene mixed solvent with a mass fraction of 30%-36%; Electrostatic spraying process, voltage 65-75kV, gun speed 280-320mm / s coating; The convex surface layer is made of 88%-92% fluorocarbon varnish, 4%-6% benzotriazole ultraviolet absorber and 4%-6% polyether modified polysiloxane leveling agent; Rolling process, roller speed 28-32r / min, pressure 0.18-0.22MPa coating.

4. The surface coating method for achieving sail thrust amplification according to claim 1, wherein In step S3, The concave primer layer is prepared by mixing 63%-67% water-based epoxy ester resin, 8%-12% zinc oxide and 23%-27% deionized water; Air spraying process, nozzle diameter 1.7-1.9mm, atomization pressure 0.23-0.27MPa; The concave functional layer is made of 40%-44% fluorocarbon resin PVDF as base material, 10%-12% 80nm nano silicon dioxide, 6%-7% 5μm hollow glass beads, 7%-9% hexamethoxymethyl melamine curing agent and 28%-37% propylene glycol methyl ether acetate solvent; The doctor blade angle is 43-47°, and the leveling time is 13-17 minutes; The concave surface layer is made of 83%-87% acrylic modified fluorocarbon resin, 2%-4% organic bentonite anti-settling agent, 1%-3% KH-550 silane coupling agent and 9%-11% ethyl acetate solvent; air spraying process, nozzle diameter 1.9-2.1mm, atomization pressure 0.28-0.32MPa.

5. The surface coating method for achieving sail thrust amplification according to claim 1, wherein It also includes the special coating step of S4 sail leaf end plate: Two layers of special coating design are adopted, namely base coating and air guiding functional coating, specifically: Base coating: epoxy zinc-rich primer is selected, and air spraying process is adopted for coating, with a thickness of 30-35μm; Air guiding functional coating: epoxy resin is used as base material, polytetrafluoroethylene powder, carbon fiber short cut and xylene solvent are compounded, and the coating is coated by template pressing + curing process, with a thickness of 40-45μm; the template has groove lines along the airflow direction, with a groove depth of 75-85μm, a width of 480-520μm, a pitch of 0.9-1.1mm, and a single-direction micro-groove structure formed in the coating during pressing.

6. The surface coating method for realizing wind sail thrust amplification according to claim 5, wherein, In step S4, the base coating: epoxy zinc-rich primer with zinc content of 58%-62%; air spraying process, nozzle diameter 1.5-1.7mm, atomization pressure 0.3-0.35MPa; Air guiding functional coating: 58%-62% epoxy resin, 18%-22% compounded polytetrafluoroethylene powder, 0.4-0.6mm long carbon fiber short cut, 4%-6% and 14%-16% xylene solvent.

7. The surface coating method for achieving sail thrust augmentation according to claim 1, wherein It also includes the special coating step of S5 sail leaf flow guide device: The flow guide device is located at the outflow end of the convex surface of the sail leaf, and is a set of guide plates arranged in an eight-shaped pattern in the longitudinal direction. Coating material and proportion: polytetrafluoroethylene powder, nano zirconium oxide as functional filler, with phenolic resin and ethanol-butanol mixed solvent mixed preparation; Coating process: flame spraying process is adopted, coating thickness is 50-55 μm, room temperature curing 10-14 hours.

8. The surface coating method for realizing the sail thrust amplification according to claim 7, wherein, In step S5, the coating material and proportion: 28%-32% of polytetrafluoroethylene powder, 18%-22% of 50nm nano zirconium oxide, 33%-37% of phenolic resin and 14%-16% of ethanol-butanol mixed solvent; In step S5, the coating process: flame temperature is 2700-2900 ℃, spraying distance is 140-160 mm.

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