A biomimetic self-air-supplying anti-cavitation surface

Abstract

The application discloses a kind of bionic automatic air-supplying anti-cavitation surfaces.The surface includes a substrate, an electrode sheet, and a layer of hydrophobic material disposed on the electrode sheet for anti-cavitation.The electrode sheet is connected to a direct current power source, and when the electrode sheet is in contact with liquid water, an electrolysis reaction occurs, generating gas.The hydrophobic material is gas-philic under water, and the gas generated by the electrode is maintained in the pores of the hydrophobic material without escaping.When surrounding cavitation bubbles collapse, the gas in the pores changes the direction of the jet, protecting important components from the impact of high-speed jets.When the gas in the pores is depleted, an electrolysis reaction replenishes the gas, and the electrolysis reaction automatically ends when the gas replenishment is complete.The application can avoid material suffering from cavitation, and automatically replenish gas through electrolysis, while avoiding energy waste from constant electrolysis in a calm state.It is an intelligent anti-cavitation structure surface.

Description

A biomimetic, automatically gas-replenishing, cavitation-resistant surface Technical Field

[0001] This invention is designed for industrial fields such as shipbuilding, water conservancy, and chemical engineering, specifically relating to a method that uses automatic gas replenishment to generate an air layer to alleviate cavitation erosion and protect the structural surface of important components. Background Technology

[0002] Cavitation is a widespread phenomenon in fluid devices such as underwater propellers, turbines, dam gates, and hydraulic pumps. Cavitation refers to the phenomenon in flowing liquids where, when the pressure in a local area suddenly drops below the corresponding temperature saturation pressure, the liquid vaporizes and forms bubbles. When these cavitation bubbles travel with the liquid flow to a higher-pressure area, they lose their conditions for existence and suddenly collapse, generating high-pressure, high-speed jets directed towards solid walls. Repeated jet impacts cause fatigue damage and even surface erosion of the wall material, a phenomenon known as cavitation erosion. Cavitation erosion of critical components severely impacts mechanical efficiency and service life. While strengthening the target material can mitigate cavitation damage to some extent, it still succumbs to cavitation erosion after prolonged testing. Recent research has found that cavitation bubbles generate reverse jets away from the wall at the boundary of the cavitation layer. These reverse jets reverse the direction of the collapsing cavitation jet impact, effectively mitigating cavitation erosion of the wall material. However, the cavitation layer on the wall is unstable and easily detached from the wall by strong disturbances from fluid flow or shock waves generated by cavitation collapse. This invention designs a biomimetic automatic gas replenishment anti-cavitation surface, which can generate reverse jets from cavitation bubbles and intelligently replenish gas when there is insufficient gas on the surface, thus solving the problem of poor durability of traditional gas layer surfaces. Summary of the Invention

[0003] To mitigate and suppress the damage caused by cavitation to material surfaces, this invention provides a biomimetic automatic gas replenishment anti-cavitation surface, which can effectively reduce the damage caused by cavitation and improve the efficiency and service life of instruments.

[0004] To achieve the above-mentioned effective anti-cavitation protection process, the technical solution adopted by the present invention is as follows:

[0005] The surface of the structure is located in an area prone to cavitation erosion, and includes a substrate, an electrode sheet, and a hydrophobic material layer disposed on the electrode sheet for resisting cavitation erosion.

[0006] The substrate is embedded or adhered to components of underwater rotating machinery or cavitation-prone parts of water conservancy and chemical engineering.

[0007] The electrode is connected to a DC power supply. When the electrode comes into contact with liquid water, an electrolytic reaction occurs, generating gas. The other electrode of the DC power supply is connected to an inert electrode to form a current path.

[0008] The hydrophobic material layer has gas affinity underwater, and the gas generated by the electrode will be maintained in the pores of the hydrophobic material without escaping.

[0009] When the cavitation bubbles around the surface of the structure collapse, the gas in the pores will change the direction of the jet, protecting the surface from the impact of the high-speed jet and thus protecting important components.

[0010] In addition, the electrolysis reaction only occurs when strongly disturbed liquid enters the pores. Under calm conditions, the pores on the surface can maintain gas for a long time without electrolysis reaction, avoiding the energy waste caused by continuous electrolysis reaction.

[0011] The hydrophobic material layer has a through-hole structure arranged in a uniform hexagonal honeycomb pattern, and the through-hole diameter d needs to ensure that gas does not escape, satisfying: d ≤ 1.0 mm.

[0012] Only a gas layer with a certain thickness on the surface can change the jet direction of cavitation bubbles. The gas equivalent thickness D* of the hydrophobic material layer is defined as: where d is the through-hole diameter of the hydrophobic material layer, a is the through-hole spacing, and N is the thickness of the hydrophobic material layer. To change the jet direction of cavitation bubbles, the equivalent thickness D* of the hydrophobic material layer needs to satisfy: D* ≥ 0.05R, where R is the equivalent radius of the cavitation bubble.

[0013] The electrode sheet has a conical structure arranged in a uniform hexagonal honeycomb pattern. To ensure that the hydrophobic material can stably maintain gas, the height h of the cone should satisfy: h < N; the cones on the electrode sheet correspond to the through-holes of the hydrophobic material layer and are used in combination.

[0014] Current research on cavitation erosion believes that the frequent impact of the jet generated when cavitation bubbles collapse near the solid surface is the main cause of material damage. The present invention uses the gas affinity of the hydrophobic material underwater to maintain the gas electrolytically generated by the electrode sheet at the pores of the hydrophobic layer to change the collapse direction of cavitation bubbles, which can effectively inhibit the material damage caused by cavitation. In addition, the electrolysis reaction only occurs when the surrounding cavitation bubbles collapse or other strong disturbances cause the gas to escape and thus the liquid enters the pores. Under calm conditions, the pores on the surface can maintain gas for a long time without electrolysis reaction.

[0015] The beneficial effects of the technical solution of the present invention are:

[0016] The present invention provides a brand-new and efficient anti-cavitation technology. By embedding electrolytic sheets and hydrophobic surface layers at the positions prone to cavitation erosion of mechanical components, the gas layer formed on the hydrophobic surface is used to change the jet direction of cavitation bubbles, thereby alleviating material damage.

[0017] This invention can electrolyze and replenish gas, solving the problem of surface failure caused by gas dissolving in liquid or escaping. At the same time, it avoids energy waste caused by continuous electrolysis in a calm state, making it an intelligent anti-cavitation structural surface layer. Attached Figure Description

[0018] Figure 1 is a schematic diagram of the device of the present invention and its anti-cavitation principle;

[0019] Figure 2 is a schematic diagram of the substrate of the device of the present invention;

[0020] Figure 3 is a schematic diagram of the hexagonal honeycomb conical array structure of the electrode sheet of the device of the present invention;

[0021] Figure 4 is a schematic diagram of the hexagonal honeycomb array structure of the hydrophobic material layer of the device of the present invention.

[0022] Figure 5 is a high-speed camera image of cavitation bubbles collapsing near a smooth surface (the numbers in the image represent time, in milliseconds);

[0023] Figure 6. High-speed camera image of cavitation bubble collapse near the anti-cavitation surface layer (numbers in the figure represent time, unit: milliseconds). Detailed Implementation

[0024] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0025] As shown in Figures 1-4, the surface layer of the present invention includes a substrate, electrode sheets, and a hydrophobic material layer disposed on the electrode sheets for cavitation resistance. The surface layer is disposed on the part or surface subjected to liquid impact. The electrode sheets are connected to a DC power supply. When the electrode sheets come into contact with liquid water, an electrolytic reaction occurs, generating gas. The other electrode of the DC power supply is connected to an inert electrode to form a current path. The hydrophobic material layer has gas affinity underwater, and the gas generated by the electrode is maintained in the pores of the hydrophobic material and does not escape.

[0026] During the manufacturing process, ensure that the diameter d of the through-hole in the hydrophobic material layer is less than or equal to 1 mm, the height h of the cone on the electrode sheet is less than the thickness N of the hydrophobic material layer, and that the through-hole diameter d, the hole spacing a, and the thickness N of the hydrophobic material layer also meet the following requirements: Where R is the equivalent radius of the cavitation bubble.

[0027] During installation or processing, ensure that the cavitation-resistant surface layer is placed in an area prone to cavitation. Avoid installation in areas where cavitation is initially formed.

[0028] Example:

[0029] Since the cavitation process of underwater moving parts is difficult to observe, this example uses spark-induced cavitation for observation, and the relevant references are as follows:

[0030] [1]Wei Z, Zhang C, Shen C, et al. Manipulation of the collapse direction of the cavitation bubbles near the boundary with attached gas plastron[J]. Physics of Fluids, 2023, 35(8).

[0031] [2]Huang G, Zhang M, Ma X, et al. Dynamic behavior of a single bubble between the free surface and rigid wall [J]. Ultrasonics sonochemistry, 2020, 67: 105147.

[0032] In this example, the equivalent radius R of the cavitation induced by the electric spark is 5 mm; the diameter d of the through hole in the hydrophobic material layer of the device is 1 mm, the hole spacing a is 1.6 mm, and the thickness N is 3 mm; the height h of the cone array on the electrode sheet of the device is 2 mm.

[0033] As shown in Figures 5 and 6, the cavitation-resistant structural surface layer and the smooth surface used as a control were placed near the cavitation bubbles. High-speed camera observation revealed the following:

[0034] In contrast, cavitation bubbles near a smooth surface collapse jets towards the surface, forming cavitation erosion.

[0035] Cavitation bubble jets near the anti-cavitation surface layer are directed away from the surface layer to avoid cavitation erosion.

[0036] As can be seen from this example, the present invention changes the jet direction when cavitation bubbles collapse, causing it to move away from the structural surface, thereby effectively mitigating cavitation erosion of the material and efficiently protecting the structural surface.

[0037] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any person skilled in the art can use the above-disclosed technical content as a basis for any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention, all of which shall still fall within the scope of the technical solution of the present invention.

Claims

1. A biomimetic, automatically gas-replenishing, cavitation-resistant surface, characterized in that: Composed of a substrate (1), electrode sheets (2), and a hydrophobic material layer (3), this surface allows cavitation bubbles to generate reverse jets, avoiding jet impact damage to the surface from cavitation bubbles. Furthermore, it can self-regulate and replenish gas when there is insufficient gas on the surface, solving the problem of poor durability of traditional gas layer surfaces. The substrate (1) should be made of insulating material and embedded or adhered to components susceptible to cavitation erosion. The substrate (1) material includes ceramics, glass, rubber, and resin. The cone height h of the array on the electrode sheets (2) is less than the thickness N of the hydrophobic material layer (3). The electrode sheet (2) material includes copper, platinum, titanium, nickel, and graphite. The through-hole diameter d of the array of the hydrophobic material layer (3) is less than or equal to 1 mm, and the through-hole diameter d, hole spacing a, and hydrophobic material layer thickness N should also satisfy: Where R is the equivalent radius of the cavitation bubble, the hydrophobic material layer (3) includes polytetrafluoroethylene (PTFE), polydimethylsiloxane (PDMS), fluorine-containing materials, and micro / nano structure materials; the cone on the electrode sheet (2) corresponds one-to-one with the through hole of the hydrophobic material layer (3) and is used in conjunction; the biomimetic automatic gas replenishment anti-cavitation surface maintains the gas generated by the electrolysis of the electrode sheet (2) in the through hole of the hydrophobic material layer (3) and stops the electrolysis reaction after being filled with gas; the biomimetic automatic gas replenishment anti-cavitation surface changes the direction of the surrounding cavitation bubble collapse jet and protects the surface from damage.

2. The biomimetic automatic gas-replenishing anti-cavitation surface according to claim 1, characterized in that: The cavitation-prone components are parts of hydraulic equipment or parts of water conservancy and hydropower equipment.

Images