Air film layer drag reduction device based on porous wetting anisotropic electrode, control method and application

Abstract

The application discloses a porous wetting hetero-electrode-based air film layer drag reduction device, a control method and application, and belongs to the underwater drag reduction technical field.The device comprises a water tank, a porous wetting hetero-electrode and an adjustable direct current power supply; the water tank contains electrolyte; the porous wetting hetero-electrode is installed on the water tank, and the surface and the interior of the electrode on the electrolyte side have superhydrophilicity, and the surface and the interior of the electrode on the working fluid side have superhydrophobicity; and the porous wetting hetero-electrode is powered by the adjustable direct current power supply.The porous wetting hetero-electrode surface and the porous structure inside the electrode have superhydrophobicity and superhydrophilic wetting characteristics; the gas generated by the superhydrophilic electrode part electrolysis of water spontaneously transports to the superhydrophobic part through the porous structure, and then realizes stable storage of a large-area continuous drag reduction air film layer on the surface of the electrode superhydrophobic part; the electrolysis current is controlled to control the gas production rate of the porous wetting hetero-electrode, and then the shape of the drag reduction air film layer is accurately controlled.

Description

Technical Field

[0001] This invention belongs to the field of underwater drag reduction technology, specifically relating to a drag reduction device, control method and application based on a porous wetting anisotropic electrode for gas film layer. Background Technology

[0002] Marine vehicles such as ships and submarines experience various forms of resistance during navigation, increasing energy consumption. It is estimated that approximately 50%-60% of this power is used to resist the shear friction between the vehicle's hull and seawater. Frictional resistance generated by the viscous shear of liquid and solid walls also restricts the development and application of long-distance pipeline transportation. Since gases have much lower viscosity than liquids, forming a uniform gas film layer on the hull of a vehicle or the inner wall of a pipeline can effectively reduce frictional resistance, thereby reducing energy consumption. Therefore, researchers have proposed various gas film layer drag reduction technologies.

[0003] However, existing technologies still have certain shortcomings: Existing technologies for ship drag reduction using air film involve introducing gas into the bottom of the ship via a blower to form a drag-reducing air film. However, this invention cannot achieve stable air film retention, requiring continuous ventilation to maintain the air film's shape, and it is not applicable to pipeline liquid transportation. Existing technologies for drag reduction using wettability-controlled air film utilize the gas-loving properties of superhydrophobic surfaces to effectively retain the air film, but this air film layer requires a stable gas source to maintain it, and lacks reliable and precise means of controlling the air film layer's state. Existing technologies using water electrolysis for gas replenishment utilize the principle of electrolysis gas generation and the binding effect of superhydrophobic structures to achieve the maintenance and shape control of the drag-reducing air film layer. However, due to limitations in the electrode structure, it can only form intermittently separated air film layers in localized areas of the surface, and cannot achieve the generation and maintenance of continuous drag-reducing air film layers, thus limiting the drag reduction effect of the air film layer. Summary of the Invention

[0004] The technical problem to be solved:

[0005] To overcome the shortcomings of existing technologies, this invention provides a drag reduction device and control method for underwater gas film layers based on porous wetting anisotropic electrodes, solving the problem of maintaining stable large-area gas film layers and controlling their morphology in underwater drag reduction technology. This invention utilizes the superhydrophobic and superhydrophilic wetting properties of the porous wetting anisotropic electrode surface and its internal porous structure. Gas generated by water electrolysis in the superhydrophilic electrode portion is spontaneously transported to the superhydrophobic portion through the porous structure, thereby achieving stable sealing of a large-area continuous drag-reduced gas film layer on the surface of the superhydrophobic portion of the electrode. This overcomes the problem of bubble loss due to buoyancy in traditional electrolysis gas generation methods. Furthermore, by controlling the electrolysis current, the gas generation rate of the porous wetting anisotropic electrode is controlled, thereby precisely controlling the morphology of the drag-reduced gas film layer.

[0006] The technical solution of the present invention is: a gas film layer drag reduction device based on a porous wetting anisotropic electrode, characterized in that: it includes a water tank, a porous wetting anisotropic electrode and an adjustable DC power supply; the water tank is filled with electrolyte; the porous wetting anisotropic electrode is installed on the water tank, and its surface and interior on the electrolyte side are superhydrophilic, and its surface and interior on the working fluid side are superhydrophobic.

[0007] The porous wetting anisotropic electrode is powered by an adjustable DC power supply.

[0008] A further technical solution of the present invention is: the preparation method of the porous wetting anisotropic electrode, the specific steps of which are as follows:

[0009] Step 1: A porous titanium plate prepared by powder metallurgy is used as the anode, and a graphite plate with the same area and facing the porous titanium plate is used as the cathode. Sodium chloride solution is used as the reaction solution to generate a micro-nano composite structure on the surface of the porous titanium plate.

[0010] Step 2: After thoroughly cleaning and drying the corroded porous titanium plate with deionized water, partially immerse it in a fluorosilane ethanol solution and heat it to react so that fluorosilane molecules are grafted onto the porous titanium surface to obtain a locally superhydrophobic porous titanium electrode.

[0011] Step 3: Wrap an inert mask layer around the superhydrophobic part of the porous titanium electrode, and treat the porous titanium electrode with an oxygen plasma cleaner to remove excess organic impurities from the surface, so that the static contact angle of the droplets in the superhydrophilic part is less than 10 degrees and penetrates into the interior of the porous structure. After removing the mask, a porous wetting anisotropic electrode with local superhydrophobicity and local superhydrophilicity is obtained.

[0012] A further technical solution of the present invention is: in step 2, the depth to which the dried porous titanium plate is immersed in the fluorosilane ethanol solution is controlled between 1 / 2 and 2 / 3 of the overall thickness.

[0013] A further technical solution of the present invention is: in step 2, the solution concentration and reaction time ensure that the static contact angle of the superhydrophobic part after treatment is greater than 150 degrees and the roll-off angle is less than 10 degrees.

[0014] A further technical solution of the present invention is: the porous wetting anisotropic electrode is composed of one or more sets forming a circuit, and the electrodes are separated by an insulating partition; the upper surface of the insulating partition is superhydrophobic, and the upper surface is flush with the upper surface of the superhydrophobic part of the porous wetting anisotropic electrode.

[0015] A further technical solution of the present invention is: the water tank includes a circulating water pump, a circulating pipe, an electrolytic water tank, and a circulating water tank, wherein the electrolytic water tank and the circulating water tank are both filled with electrolyte and are connected through the circulating water pump and the circulating pipe; the electrolyte enters the electrolytic water tank from the circulating water tank through the circulating water pump;

[0016] The porous wetting anisotropic electrode is installed on the water electrolysis tank to ensure that the superhydrophilic part of the porous wetting anisotropic electrode is completely wetted by the electrolyte, while the superhydrophobic part is not wetted.

[0017] A method for controlling a drag-reducing gas film layer using a gas film layer drag-reducing device based on a porous wetting anisotropic electrode, characterized by the following specific steps:

[0018] Step 1: Connect the DC power supply to produce hydrogen and oxygen through water electrolysis. The gas is generated in the form of bubbles inside the superhydrophilic part of the porous wetting anisotropic electrode and spontaneously transfers and converges from the superhydrophilic part to the superhydrophobic part inside the porous wetting anisotropic electrode, thereby increasing the thickness of the gas film layer sealed in the superhydrophobic porous structure on the surface of the porous wetting anisotropic electrode.

[0019] Step 2: Under the shearing action of water flow in the external flow field, the superhydrophobic coating sprayed on the rear surface of the porous wetting anisotropic electrode will automatically adsorb the gas discharged from the porous wetting anisotropic electrode and spread into a uniform gas film, thereby realizing the generation and stable maintenance of a large-area drag-reducing gas film layer.

[0020] A further technical solution of the present invention is: in step one, the gas production and the thickness of the drag-reducing gas film layer are precisely controlled by controlling the output current of the DC power supply;

[0021] The relationship between the volume of the generated gas and the electric current satisfies the following formula:

[0022] V = (3ItRT) / (2FP)

[0023] Where I represents the current magnitude, t represents the energizing time, and R, T, F, and P are the gas constant, ambient temperature, Faraday constant, and ambient water pressure, respectively.

[0024] The gas generation rate of the porous wetting anisotropic electrode is expressed as Q = (3IRT) / (2FP);

[0025] The thickness of the drag-reducing gas film layer is expressed as H = Q / (Lv);

[0026] Where L is the spanwise width of the superhydrophobic surface, and v is the characteristic velocity of water flow in the external environment;

[0027] The above formulas allow for precise calculation and control of gas production and gas film thickness under different environmental conditions.

[0028] An application of a gas film drag reduction device based on a porous wetting anisotropic electrode, characterized by the following specific steps:

[0029] Step a: Fabricate a porous, wettable, anisotropic electrode;

[0030] Step b: Construct the electrolysis tank;

[0031] Step c: Install the electrolytic water tank and the circulating water tank; install the electrolytic water tank in an embedded manner on the bottom of the hull or the surface of a rectangular pipe, ensuring that the upper surface of the superhydrophobic part of the porous wetting anisotropic electrode is flush with the inner wall of the ship hull / pipe, and use sealing silicone rubber to seal and insulate the circuit and electrode edges; connect the electrolytic water tank and the circulating water tank through a circulation pipeline and a water pump, and use water or other alkaline electrolyte;

[0032] Step d: Spray a superhydrophobic coating; remove rust from the hull or pipe wall behind the electrolytic water tank and the porous wetting anisotropic electrode, and then clean the surface with acetone, anhydrous ethanol and pure water in sequence; spray a superhydrophobic coating with a static contact angle greater than 150 degrees on the cleaned surface and above the insulating partition between the electrodes, and it can be used after the coating has solidified and dried.

[0033] A further technical solution of the present invention is as follows: the method for manufacturing the electrolytic water tank in step b is to use organic glass or PVC material with insulating and corrosion-resistant properties to manufacture a square electrolytic water tank, and to reserve electrode slots and perforation positions on the top of the electrolytic water tank for installing porous wetting anisotropic electrodes and arranging circuits; to install the porous wetting anisotropic electrodes in the reserved slot positions inside the electrolytic water tank to form multiple sets of porous wetting anisotropic electrodes arranged in an array, the superhydrophobic part of the porous wetting anisotropic electrodes is in contact with the working fluid, while the superhydrophilic part is in contact with the inside of the electrolytic water tank; each set of porous wetting anisotropic electrodes consists of a cathode and an anode, separated by an insulating plate; the upper surface of the insulating plate is sprayed with a superhydrophobic coating, and is made flush with the surface of the superhydrophobic part of the porous wetting anisotropic electrodes; the porous wetting anisotropic electrode groups are connected by a parallel circuit and the circuit is connected to the positive and negative terminals of a DC power supply to form a loop.

[0034] Beneficial effects

[0035] The beneficial effects of this invention are as follows:

[0036] (1) This invention utilizes the principle of electrochemical gas generation. By controlling the electrolysis current, the gas generation rate and gas film thickness can be precisely controlled. The calculation formula can quickly calculate the gas film volume and the required electrolysis current and time under different flow rates and water pressures. Figure 3a , 3b As shown, the thickness of the gas film layer under different flow rates was precisely controlled by controlling the power supply current of the electrolysis device in the experiment. The control method is simple and has high precision.

[0037] (2) This invention utilizes a porous, wetting, anisotropic electrode material. The superhydrophobic portion in contact with the working fluid is entirely superhydrophobic, enabling the formation of a large-area continuous gas film layer. This overcomes the shortcomings of other electrolytic gas generation methods, which can only form intermittent gas film layers. Figure 3a , 3b As shown, the experiment achieved long-term stable residence of a continuous gas film layer with sub-millimeter thickness, thus the gas film layer has better stability and drag reduction effect.

[0038] (3) The device of the present invention uses powder metallurgy and liquid phase deposition process to prepare electrode materials. Compared with other electrolysis devices, the materials are inexpensive and the manufacturing process is mature and convenient. Gas is generated inside the porous and heterogeneous electrode, and a large area continuous gas film layer is directly formed by the porous structure. This overcomes the problem of electrolysis bubbles being lost due to buoyancy, and is suitable for large-scale manufacturing and practical application. Attached Figure Description

[0039] Figure 1a This is a schematic diagram illustrating the principle of the gas film layer drag reduction device and control method based on porous wetting anisotropic electrodes of the present invention.

[0040] Figure 1b A schematic diagram illustrating the circuit connection principle of a porous wetting anisotropic electrode.

[0041] Figure 2 A schematic diagram of the fabrication process of a porous wetting anisotropic electrode;

[0042] Figure 3a These are photographs showing the effect of using this invention in a rectangular pipe;

[0043] Figure 3b This invention relates the thickness of the gas film layer generated in a rectangular pipe to the electrolysis current and flow velocity.

[0044] Explanation of reference numerals in the attached drawings: 1. Working fluid; 2. Upper wall of the pipe; 3. Superhydrophobic coating; 4. Lower wall of the pipe; 5. Circulation pipe; 6. Circulation tank; 7. Electrolyte; 8. Circulation pump; 9. Electrolytic tank; 10. Porous wetting anisotropic electrode; 11. Insulating partition; 12. Wire; 13. Adjustable DC power supply; 14. Electrochemical reaction tank; 15. Cathode electrode plate; 16. Sodium chloride solution; 17. Liquid phase deposition reaction tank; 18. Fluorosilane ethanol solution; 19. Oxygen plasma; 20. Mask layer; 21. Drag-reducing gas film layer.

[0045] Caption: Figure 1a The arrows marked on the circulating pipe 5 and the circulating water pump 8 indicate the direction of water flow. Figure 2 The arrows in Figure 19 indicate the direction of plasma irradiation, while the arrows in Figure 3 indicate the direction of water flow in the experiment. Detailed Implementation

[0046] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0047] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0048] This invention provides a drag reduction device and control method for underwater gas film layers based on porous wetting anisotropic electrodes, solving the problem of maintaining stable large-area gas film layers and controlling their morphology in underwater drag reduction technology. This invention utilizes the superhydrophobic and superhydrophilic wetting properties of the porous wetting anisotropic electrode surface and its internal porous structure. Gas generated by water electrolysis in the superhydrophilic electrode portion is spontaneously transported to the superhydrophobic portion through the porous structure, thereby achieving stable sealing of a large-area continuous drag-reduced gas film layer on the surface of the superhydrophobic portion of the electrode. This overcomes the problem of bubble loss due to buoyancy in traditional electrolysis gas generation methods. Furthermore, by controlling the electrolysis current, the gas generation rate of the porous wetting anisotropic electrode is controlled, thereby precisely controlling the morphology of the drag-reduced gas film layer.

[0049] This embodiment discloses a gas film drag reduction device based on a porous wetting anisotropic electrode, comprising an electrolytic water tank, a circulating water tank, a porous wetting anisotropic electrode, an insulating partition, an adjustable DC power supply, and a superhydrophobic coating. The porous wetting anisotropic electrode is mounted on the electrolytic water tank, comprising one or more sets of electrode plates forming a circuit and powered by the DC power supply, with the electrodes separated by insulating partitions. The porous wetting anisotropic electrode exhibits superhydrophobicity on its surface and internal porous structure on the working fluid side, and superhydrophilicity on its surface and internal structure on the electrolyte side. The static contact angle of a droplet on its superhydrophobic surface is greater than 150°. The roll-off angle is less than 10°; to ensure the pressure resistance of the gas film layer sealed by the porous hydrophobic part, the longitudinal thickness of the superhydrophobic part inside the porous wetting anisotropic electrode accounts for 1 / 2 to 2 / 3 of the electrode thickness; the upper surface of the insulating partition between the electrodes is also superhydrophobic, and the upper surface is flush with the upper surface of the superhydrophobic part of the porous wetting anisotropic electrode; relative water droplets are quickly absorbed into the electrode interior by the superhydrophilic part of the porous wetting anisotropic electrode; under initial conditions, the superhydrophilic part of the porous wetting anisotropic electrode is installed in the water electrolysis tank and contacts the electrolyte, while the superhydrophobic part is outside the water electrolysis tank and contacts the external working fluid.

[0050] During device operation, electrolyte enters the electrolysis tank from the circulating water tank via a circulating water pump. The superhydrophilic portion of the porous wetting anisotropic electrode is completely wetted by the electrolyte, while the superhydrophobic portion remains unwetted and stores gas within the porous structure. Upon connection to a DC power source, the electrolysis reaction produces hydrogen and oxygen. These gases are generated as bubbles within the superhydrophilic portion of the porous wetting anisotropic electrode and spontaneously migrate and converge from the superhydrophilic to the superhydrophobic portion, increasing the thickness of the gas film layer sealed within the superhydrophobic porous structure on the electrode surface. Subsequently, under the shearing action of the external water flow, the superhydrophobic coating sprayed on the rear surface of the porous wetting anisotropic electrode automatically adsorbs the gas discharged from the porous electrode and spreads into a uniform gas film, thereby achieving large-scale... The generation and stable maintenance of the drag-reducing gas film layer are discussed. The gas production rate can be precisely controlled by adjusting the current through a DC power supply. The relationship between the generated gas volume and the current satisfies the formula V = (3IRT) / (2FP), where I represents the current magnitude, t represents the energizing time, and R, T, F, and P are the gas constant, ambient temperature, Faraday constant, and ambient water pressure, respectively. The gas production rate of the porous wetted anisotropic electrode can be expressed as Q = (3IRT) / (2FP). Furthermore, the thickness of the drag-reducing gas film layer can be expressed as H = Q / (Lv), where L is the spanwise width of the superhydrophobic surface, and v is the characteristic velocity of water flow in the external environment. These formulas allow for precise calculation and control of the gas production rate and gas film thickness under different environmental conditions.

[0051] The fabrication process of this porous wetting anisotropic electrode and the assembly process of the gas film drag reduction device include the following steps:

[0052] Step 1: Fabricate a porous wetting anisotropic electrode. A porous titanium plate prepared by powder metallurgy was used as the anode, and a graphite plate with the same area facing the porous titanium plate was used as the cathode. Sodium chloride solution was used as the reaction solution to generate a micro-nano composite structure on the surface of the porous titanium plate. After the porous titanium plate was thoroughly cleaned and dried with deionized water, it was partially immersed in a fluorosilane ethanol solution. The immersion depth was controlled between 1 / 2 and 2 / 3 of the thickness of the porous material. The heating reaction caused fluorosilane molecules to branch onto the surface of the porous titanium to obtain a locally superhydrophobic porous titanium electrode. The solution concentration and reaction time ensured that the static contact angle of the superhydrophobic part after treatment was greater than 150 degrees and the roll-off angle was less than 10 degrees. The surface of the superhydrophobic part of the porous titanium electrode was wrapped with an inert mask layer, and the porous titanium electrode was treated with an oxygen plasma cleaner to remove excess fluorosilane molecules and other organic impurities from the surface. This ensured that the static contact angle of the droplets in the superhydrophilic part was less than 10 degrees and that they penetrated into the interior of the porous structure. After removing the mask, a porous wetting anisotropic electrode with local superhydrophobicity and local superhydrophilicity was obtained.

[0053] Step 2: Construct the electrolytic water tank. A square electrolytic water tank is constructed using acrylic or PVC material with insulating and corrosion-resistant properties. Electrode slots and perforations are pre-drilled at the top of the tank for installing porous wetting electrodes and arranging the wiring. The porous wetting electrodes are installed in the pre-drilled slots inside the tank, forming multiple arrays of porous wetting electrodes. The superhydrophobic portion of the electrodes contacts the working fluid, while the superhydrophilic portion contacts the inside of the tank. Each group of porous wetting electrodes consists of a cathode and an anode, separated by an insulating plate. The upper surface of the insulating plate is coated with a superhydrophobic coating, ensuring it is flush with the superhydrophobic surface of the porous wetting electrodes. The groups of porous wetting electrodes are connected in parallel, and the wiring is connected to the positive and negative terminals of a DC power supply to form a circuit.

[0054] Step 4: Install the electrolytic water tank and the circulating water tank. Install the electrolytic water tank in an embedded manner on the bottom of the hull or the surface of a rectangular pipe, ensuring that the upper surface of the porous, wetting, anisotropic electrode's superhydrophobic portion is flush with the hull or the inner wall of the pipe. Use sealing silicone rubber to seal and insulate the wiring and electrode edges. Connect the electrolytic water tank and the circulating water tank via a circulation pipeline and a water pump. The electrolyte can be water or other alkaline electrolytes.

[0055] Step 5: Apply superhydrophobic coating. Remove rust from the ship hull or pipe wall behind the porous wetting anisotropic electrode in the electrolytic water tank, and then clean the surface sequentially with acetone, anhydrous ethanol, and pure water. Apply a superhydrophobic coating with a static contact angle greater than 150 degrees to the cleaned surface and above the insulating partition between the electrodes. The coating is ready for use after it has solidified and dried.

[0056] (1) This invention utilizes the principle of electrochemical gas generation. By controlling the electrolysis current, the gas generation and gas film thickness can be precisely controlled. The gas film volume and the required electrolysis current and electrolysis time under different flow rates and water pressures can be quickly calculated using the calculation formula, as shown in Figure 3. In the experiment, by controlling the power supply current of the electrolysis device, the gas film thickness under different flow rates was precisely controlled. The control method is simple and has high precision.

[0057] (2) The present invention utilizes porous wettable anisotropic electrode material, and the superhydrophobic part in contact with the working fluid is superhydrophobic as a whole, which can form a large area continuous gas film layer. This overcomes the shortcomings of other electrolytic gas generation methods, which can only form intermittent gas film layers. As shown in Figure 3, the experiment achieved long-term stable residence of a sub-millimeter thickness continuous gas film layer. Therefore, the stability and drag reduction effect of the gas film layer are better.

[0058] (3) The device of the present invention uses powder metallurgy and liquid phase deposition process to prepare electrode materials. Compared with other electrolysis devices, the materials are inexpensive and the manufacturing process is mature and convenient. Gas is generated inside the porous and heterogeneous electrode, and a large area continuous gas film layer is directly formed by the porous structure. This overcomes the problem of electrolysis bubbles being lost due to buoyancy, and is suitable for large-scale manufacturing and practical application.

[0059] The following detailed description, in conjunction with the accompanying drawings and embodiments, provides a more comprehensive overview of the drag reduction device and control method for a gas film layer based on a porous wetting anisotropic electrode according to the present invention.

[0060] See Figure 1a The main structure of this invention consists of a superhydrophobic coating (3), a circulation pipe (5), a circulation tank (6), an electrolyte (7), a circulation pump (8), an electrolytic tank (9), a porous wetting anisotropic electrode (10), an insulating partition (11), wires (12), and an adjustable DC power supply (13). The electrode wires, porous wetting anisotropic electrode, electrolyte, and adjustable DC power supply form an electrolytic circuit. When the electrolyte enters the electrolytic tank through the circulation pipe and contacts the superhydrophilic portion of the porous wetting anisotropic electrode, the circuit closes and an electrolytic reaction occurs. Electrolysis produces hydrogen and oxygen, which are transferred from the superhydrophilic portion to the superhydrophobic portion inside the porous wetting anisotropic electrode. A superhydrophobic coating is sprayed onto the insulating partition between the wetting anisotropic electrodes and on the downstream surface. The mixed gas discharged from inside the porous electrode is adsorbed by the superhydrophobic surface and spread into a uniform gas film layer.

[0061] In this system, two wetting, dissimilar electrodes are connected to the positive and negative terminals of the power supply, respectively, forming an electrode circuit. Multiple pairs of electrodes can be placed in the electrolysis tank to form an electrode array. Each pair of electrodes is connected in parallel via a circuit, the principle of which is as follows: Figure 1b As shown; during the electrolysis gas generation process, based on the electrochemical formula and the quantitative relationship between electron transfer and gas generation during the chemical reaction, the gas generation of the porous wetting anisotropic electrode can be calculated by the formula: V=(3ItRT) / (2FP), where I is the electrolysis current, t is the energizing time, and R, T, F and P are the gas constant, ambient temperature, Faraday constant and ambient water pressure, respectively. By controlling the electrolysis current and electrolysis time, the gas generation of the device can be accurately controlled; based on the gas generation rate Q=(3IRT) / (2FP) of the electrolytic water tank, the speed of the external working fluid or the ship's speed v, and the spanwise width L of the superhydrophobic coating, the thickness of the gas film layer on the superhydrophobic surface is controlled according to the calculation formula H=Q / (Lv), thereby achieving different drag reduction effects and fully adapting to various different practical engineering environments.

[0062] Example:

[0063] A drag reduction device, control method, and application in rectangular pipes based on porous wetting anisotropic electrodes for gas film layer:

[0064] (1) A porous titanium plate with dimensions of 60mm×30mm×20mm and an average filtration accuracy of 60 micrometers was used as the anode, and a graphite plate with the same area (60mm×30mm) facing the porous titanium plate was used as the cathode. The plate was etched with a 3% sodium chloride solution at 15V for 30 minutes to generate a micro-nano composite structure on the surface of the porous titanium plate. After the etched porous titanium plate was thoroughly cleaned and dried with deionized water, it was partially immersed in a 2% perfluorooctyltrichlorosilane ethanol solution at a depth of 10mm. After heating at 60℃ for 2 hours, the porous titanium plate was removed and thoroughly dried to obtain a locally superhydrophobic material. A porous titanium electrode was prepared by coating the superhydrophobic portion of the electrode with a polyimide mask layer. The electrode was then treated with oxygen plasma for 5 minutes at a plasma flow rate of 10 ml / s to remove any fluorosilane chains and other organic impurities that might be present in the undeposited portion. After removing the mask, a porous wetting anisotropic electrode with localized superhydrophobicity and localized superhydrophilicity was obtained. In the superhydrophobic portion of this porous wetting anisotropic electrode, the static contact angle of a water droplet was 155 degrees, and the roll-off angle was less than 2 degrees. In the superhydrophilic portion, water droplets could rapidly wet the surface and penetrate the porous structure. The fabrication process of the porous wetting anisotropic electrode is as follows: Figure 2 As shown.

[0065] (2) A square electrolysis tank is made of plexiglass material. The internal dimensions of the electrolysis tank are 50×50×20mm, and the wall thickness of the plexiglass is 5mm. Electrode slots and perforations are reserved in the upper part of the electrolysis tank for the installation of porous wetting anisotropic electrodes and the arrangement of circuits. Specifically, six slots of 60×30mm are reserved, with a spacing of 6mm between adjacent slots. The porous wetting anisotropic electrodes are installed in the reserved slots within the electrolysis tank. Adjacent electrode plates are separated by polytetrafluoroethylene (PTFE) insulating plates, forming multiple electrode arrays. The upper surface of the insulating plates is coated with a superhydrophobic coating to ensure it is flush with the surface of the porous wetting anisotropic electrodes. Each porous electrode consists of a cathode and an anode. The superhydrophobic part of the porous wetting anisotropic electrode faces the inside of the pipe, and the superhydrophilic part faces the inside of the electrolysis tank. The electrode groups are connected in parallel circuits, and the circuits are connected to the positive and negative terminals of the DC power supply to form a loop. The circuit connection principle is as follows: Figure 1b As shown.

[0066] (3) The electrolytic water tank is installed on the surface of the rectangular pipe in an embedded manner, ensuring that the upper surface of the superhydrophobic part of the porous wetting anisotropic electrode on the electrolytic water tank is flush with the inner wall of the pipe. Specifically, the spanwise width of the rectangular pipe is 60mm, the cross-sectional height is 20mm, and the pipe wall is reserved with an installation position for the electrolytic water tank, the size of which meets the size requirements for accommodating the electrolytic water tank; waterproof sealant is used to seal and insulate the circuit and electrodes, and the circuit connection principle is as follows. Figure 1bAs shown; the electrolytic water tank is connected to the circulating water tank via a circulation pipe and a water pump, and the circulating water tank is filled with water; the system schematic diagram and layout of the device are as follows. Figure 1a As shown.

[0067] (4) Remove rust from the pipe wall behind the porous wetting anisotropic electrode, and then clean the surface with acetone, anhydrous ethanol and pure water in sequence; spray superhydrophobic coating on the cleaned rectangular pipe surface and the upper layer of the insulating partition. After the coating solidifies and dries, ensure that the water droplet contact angle is greater than 150 degrees and the roll-off angle is less than 10 degrees.

[0068] In this example, water flows from left to right within the pipe. The porous wetting anisotropic electrode, immersed in the superhydrophobic portion of the working fluid, automatically seals a gas film layer, storing gas within the superhydrophobic porous structure under initial conditions. After turning on the circulating water pump and adjustable DC power supply, the adjustable DC power supply current is kept constant at 10A during electrolysis, at which point the gas production rate is approximately 90 ml / min. Gas is generated in the superhydrophilic portion of the porous wetting anisotropic electrode. Once generated, the electrolytic gas spontaneously transfers from the interior of the porous structure to the porous superhydrophobic structure, increasing the thickness of the gas film layer sealed in the superhydrophobic portion. Under the shearing action of the water flow, the gas is discharged downstream. Upon discharge, the gas contacts the downstream superhydrophobic surface, where it is automatically adsorbed and spread under the gas-affinity effect, forming a large-area, continuous, and uniform gas film layer with drag-reducing properties. The effect is as follows: Figure 3a As shown, numerous experimental studies have demonstrated that a low-viscosity gas film layer adhering to a solid wall surface has a good drag reduction effect. Furthermore, by appropriately increasing or decreasing the current of the power supply, the gas production rate can be directly calculated using the formula V = (3ItRT) / (2FP), and the thickness of the surface drag-reducing gas film layer can be further calculated using the formula H = Q / (Lv). Figure 3b As shown, different sizes of air film states are obtained to achieve different drag reduction effects.

[0069] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A drag reduction device for a gas film layer based on a porous wetting anisotropic electrode, characterized in that: It includes a water tank, a porous wetting anisotropic electrode, and an adjustable DC power supply; the water tank contains an electrolyte; the porous wetting anisotropic electrode is installed on the water tank, and its surface and interior on the electrolyte side are superhydrophilic, while its surface and interior on the working fluid side are superhydrophobic. The porous wetting anisotropic electrode is powered by an adjustable DC power supply; The specific steps for preparing the porous wetting anisotropic electrode are as follows: Step 1: A porous titanium plate prepared by powder metallurgy is used as the anode, and a graphite plate with the same area and facing the porous titanium plate is used as the cathode. Sodium chloride solution is used as the reaction solution to generate a micro-nano composite structure on the surface of the porous titanium plate. Step 2: After thoroughly cleaning and drying the corroded porous titanium plate with deionized water, partially immerse it in a fluorosilane ethanol solution and heat it to react so that fluorosilane molecules are grafted onto the porous titanium surface to obtain a locally superhydrophobic porous titanium electrode. Step 3: Wrap an inert mask layer around the superhydrophobic part of the porous titanium electrode, and treat the porous titanium electrode with an oxygen plasma cleaner to remove excess organic impurities from the surface, so that the static contact angle of the droplets in the superhydrophilic part is less than 10 degrees and penetrates into the interior of the porous structure. After removing the mask, a porous wetting anisotropic electrode with local superhydrophobicity and local superhydrophilicity is obtained.

2. The gas film drag reduction device based on a porous wetting anisotropic electrode according to claim 1, characterized in that: In step 2, the depth to which the dried porous titanium plate is immersed in the fluorosilane ethanol solution is controlled between 1 / 2 and 2 / 3 of its overall thickness.

3. The gas film drag reduction device based on a porous wetting anisotropic electrode according to claim 1, characterized in that: In step 2, the solution concentration and reaction time ensure that the static contact angle of the superhydrophobic part after treatment is greater than 150 degrees and the roll-off angle is less than 10 degrees.

4. The gas film drag reduction device based on a porous wetting anisotropic electrode according to any one of claims 1-3, characterized in that: The porous wetting anisotropic electrode is composed of one or more sets forming a circuit, with the electrodes separated by an insulating partition; the upper surface of the insulating partition is superhydrophobic, and the upper surface is flush with the upper surface of the superhydrophobic portion of the porous wetting anisotropic electrode.

5. The gas film drag reduction device based on a porous wetting anisotropic electrode according to claim 4, characterized in that: The water tank includes a circulating water pump, a circulating pipe, an electrolytic water tank, and a circulating water tank. Both the electrolytic water tank and the circulating water tank contain electrolyte and are connected by the circulating water pump and the circulating pipe. The electrolyte enters the electrolytic water tank from the circulating water tank through the circulating water pump. The porous wetting anisotropic electrode is installed on the water electrolysis tank to ensure that the superhydrophilic part of the porous wetting anisotropic electrode is completely wetted by the electrolyte, while the superhydrophobic part is not wetted.

6. A method for controlling a drag-reducing gas film layer using the gas film layer drag reduction device based on a porous wetting anisotropic electrode as described in claim 1, characterized in that... The specific steps are as follows: Step 1: Connect the DC power supply to produce hydrogen and oxygen through water electrolysis. The gas is generated in the form of bubbles inside the superhydrophilic part of the porous wetting anisotropic electrode and spontaneously transfers and converges from the superhydrophilic part to the superhydrophobic part inside the porous wetting anisotropic electrode, thereby increasing the thickness of the gas film layer sealed in the superhydrophobic porous structure on the surface of the porous wetting anisotropic electrode. Step 2: Under the shearing action of water flow in the external flow field, the superhydrophobic coating sprayed on the rear surface of the porous wetting anisotropic electrode will automatically adsorb the gas discharged from the porous wetting anisotropic electrode and spread into a uniform gas film, thereby realizing the generation and stable maintenance of a large-area drag-reducing gas film layer.

7. The method for controlling a drag-reducing gas film layer using a gas film layer drag-reducing device based on a porous wetting anisotropic electrode according to claim 6, characterized in that: In step one, the gas production and the thickness of the drag-reducing gas film layer are precisely controlled by controlling the output current of the DC power supply. The relationship between the volume of the generated gas and the electric current satisfies the following formula: V=(3×I×t×R×T) / (2×F×P) Where I represents the current magnitude, t represents the energizing time, and R, T, F, and P are the gas constant, ambient temperature, Faraday constant, and ambient water pressure, respectively. The gas generation rate of the porous wetting anisotropic electrode is expressed as Q = (3 × I × R × T) / (2 × F × P). The thickness of the drag-reducing gas film layer is expressed as H=Q / (L×v); Where L is the spanwise width of the superhydrophobic surface, and v is the characteristic velocity of water flow in the external environment; The above formulas allow for precise calculation and control of gas production and gas film thickness under different environmental conditions.

8. An application of a gas film drag reduction device based on the porous wetting anisotropic electrode as described in claim 1, characterized in that... The specific steps are as follows: Step a: Fabricate a porous, wettable, anisotropic electrode; Step b: Construct the electrolysis tank; Step c: Install the electrolytic water tank and the circulating water tank; install the electrolytic water tank in an embedded manner on the bottom of the hull or the surface of a rectangular pipe, ensuring that the upper surface of the superhydrophobic part of the porous wetting anisotropic electrode is flush with the inner wall of the ship hull / pipe, and use sealing silicone rubber to seal and insulate the circuit and electrode edges; connect the electrolytic water tank and the circulating water tank through a circulation pipeline and a water pump, and use water or other alkaline electrolyte; Step d: Spray a superhydrophobic coating; remove rust from the hull or pipe wall behind the electrolytic water tank and the porous wetting anisotropic electrode, and then clean the surface with acetone, anhydrous ethanol and pure water in sequence; spray a superhydrophobic coating with a static contact angle greater than 150 degrees on the cleaned surface and above the insulating partition between the electrodes, and it can be used after the coating has solidified and dried.

9. The application of the gas film drag reduction device based on a porous wetting anisotropic electrode according to claim 8, characterized in that: The method for fabricating the electrolytic water tank in step b is as follows: a square electrolytic water tank is made using organic glass or PVC material with insulating and corrosion-resistant properties. Electrode slots and perforation positions are reserved at the top of the electrolytic water tank for installing porous wetting anisotropic electrodes and arranging circuitry. The porous wetting anisotropic electrodes are installed in the reserved slots inside the electrolytic water tank, forming multiple sets of porous wetting anisotropic electrodes arranged in an array. The superhydrophobic portion of the porous wetting anisotropic electrodes contacts the working fluid, while the superhydrophilic portion contacts the interior of the electrolytic water tank. Each set of porous wetting anisotropic electrodes consists of a cathode and an anode, separated by an insulating plate. The upper surface of the insulating plate is coated with a superhydrophobic coating, ensuring it is flush with the surface of the superhydrophobic portion of the porous wetting anisotropic electrodes. The sets of porous wetting anisotropic electrodes are connected in parallel circuits, and the circuitry is connected to the positive and negative terminals of a DC power supply to form a loop.

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