Carbon fiber net, underwater cavitation generation device and application of underwater cavitation generation device in cavitation resistance reduction

Abstract

The invention provides a carbon fiber net, an underwater cavitation generation device and application of the underwater cavitation generation device in cavitation resistance reduction, and belongs to the technical field of underwater resistance reduction. The characteristics of light weight, high strength, corrosion resistance and good conductivity of the carbon fiber net are utilized, the used carbon fiber net is a square carbon fiber grid formed by transversely and longitudinally crossing the carbon fiber bundles, and generated cavitation bubbles can be stably resided on the surface of the carbon fiber net by controlling the diameters of the carbon fibers and the carbon fiber bundles, so that the cavitation bubbles are effectively prevented from falling off. And therefore, the anti-drag device can stably stay on the surface of the underwater navigation body and has a long-time anti-drag effect. The result of the embodiment shows that the carbon fiber net provided by the invention forms a full-covering type stably-escaping electrolytic cavitation air curtain layer within 7s, and under the condition of continuous power supply for 5min, the electrolytic cavitation air curtain is continuous and stable, and the drag reduction rate is 30.27%.

Description

Technical Field

[0001] The invention relates to the technical field of underwater drag reduction, and in particular to a carbon fiber net, an underwater cavitation generating device and applications thereof in cavitation drag reduction. Background Art

[0002] As my country pays more and more attention to marine resources, higher requirements are put forward for the speed and range of underwater vehicles. Reducing drag is the key to improving the speed and range of underwater vehicles. At present, various drag reduction technologies have been developed to reduce drag, including compliant wall drag reduction, surface microstructure drag reduction, hydrophobic surface drag reduction, polymer additive drag reduction, cavitation drag reduction, etc. Among them, cavitation drag reduction technology has great application prospects due to its outstanding drag reduction effect.

[0003] Cavitation drag reduction, also known as air layer, air pocket or air curtain drag reduction, is to create bubbles on the surface of an object to achieve the effect of drag reduction and noise reduction, that is, to release air through small holes in the air pipeline laid around the underwater vehicle to produce a diffuse air curtain, which can not only effectively reduce the friction resistance between the outer shell of the underwater vehicle and the water, but also isolate the radiation of the noise source of the hull of the underwater vehicle into the water, thereby achieving the purpose of drag reduction and noise reduction. Its principle is to use the small friction and easy deformation characteristics of bubbles to adjust the underlying flow structure to reduce resistance.

[0004] However, the current cavitation drag reduction still faces many technical difficulties that are difficult to overcome. For example, the relevant prior art discloses a cavitation formation method for underwater vehicle drag reduction. First, the side surface of the underwater vehicle is subjected to a hole opening treatment to obtain an underwater vehicle with air vents on the side surface; the underwater vehicle with air vents on the side surface is subjected to a superhydrophobic treatment to obtain an underwater vehicle with a superhydrophobic coating on the surface, thus completing the supercavitation formation method for promoting drag reduction of underwater vehicles. However, this method requires processing micro-vents on the surface of the underwater vehicle to generate micro-bubbles, which has the problems of great processing difficulty and high cost; and the principle of this method is to discharge gas to the side surface of the underwater vehicle through the vents, and transform the interface of the underwater vehicle from a solid-liquid interface to a solid-gas-liquid interface. This method makes it difficult to control the size of the bubbles and the stable residence of the bubbles on the side surface of the underwater vehicle, which leads to a reduction in the drag reduction effect. Summary of the invention

[0005] The purpose of the present invention is to provide a carbon fiber net, an underwater cavitation generating device and their application in cavitation drag reduction. The carbon fiber net provided by the present invention can be used for cavitation drag reduction of underwater vehicles, has low cost, low processing difficulty, and can form stable resident cavitation.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a carbon fiber mesh, which is a square carbon fiber grid formed by the cross-section and vertical intersection of carbon fiber bundles;

[0008] The side length of the square carbon fiber grid is 1 to 3 mm;

[0009] The diameter of the carbon fiber bundle is 4 to 8 mm; the diameter of the carbon fibers in the carbon fiber bundle is 5 to 9 μm.

[0010] Preferably, the side length of the square carbon fiber grid is 1.6-2.4 mm.

[0011] Preferably, the diameter of the carbon fiber bundle is 4.8-7.2 mm.

[0012] Preferably, the diameter of the carbon fibers in the carbon fiber bundle is 5.6-8.4 μm.

[0013] The present invention also provides an underwater cavitation generating device, characterized in that it comprises a carbon fiber mesh and a power supply, wherein the negative pole of the power supply is connected to the carbon fiber mesh, and the positive pole of the power supply is connected to a conductive rod; the carbon fiber mesh is the carbon fiber mesh described in the above technical solution.

[0014] The present invention also provides the application of the underwater cavitation generating device described in the above technical solution in cavitation drag reduction.

[0015] Preferably, the method of using the underwater cavitation generating device in cavitation drag reduction comprises: covering the surface of an underwater vehicle with the underwater cavitation generating device, placing the device in water, and then applying electricity to perform electrolysis.

[0016] Preferably, the underwater cavitation generating device covers the head and / or middle part of the underwater vehicle.

[0017] Preferably, the voltage of the electrolysis is 5V to 300V.

[0018] Preferably, the electrolysis time is 30 to 300 seconds.

[0019] The present invention provides a carbon fiber net, which is a square carbon fiber grid formed by the vertical and horizontal intersection of carbon fiber bundles; the side length of the square carbon fiber grid is 1-3 mm; the diameter of the carbon fiber bundle is 4-8 mm; the diameter of the carbon fiber in the carbon fiber bundle is 5-9 μm. The present invention utilizes the characteristics of light weight, high strength, corrosion resistance and good conductivity of the carbon fiber net, and selects a carbon fiber net of suitable size to enable it to generate stable bubbles for water electrolysis when powered on, thereby forming cavitations of uniform size; specifically, the carbon fiber net used in the present invention is a square carbon fiber grid formed by the vertical and horizontal intersection of carbon fiber bundles, and by controlling the diameter of the carbon fiber and the carbon fiber bundle, the generated cavitations can be stably retained on the surface of the carbon fiber net, and then stably retained on the surface of the underwater navigation body, with a long-term drag reduction effect. The results of the embodiment show that the carbon fiber net provided by the present invention forms a fully covered and stably dissipated electrolytic cavitation air curtain layer within 7 seconds. When the power supply is continuously supplied for 5 minutes, the electrolytic cavitation air curtain is continuously stable, and the drag reduction rate is 30.27%. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Physical photos of the carbon fiber mesh provided in Example 1 of the present invention, the pure aluminum test piece provided in Comparative Example 1, the pure aluminum mesh provided in Comparative Example 2, and the pure copper mesh provided in Comparative Example 3;

[0021] Figure 2 A schematic diagram of an underwater cavitation generating device provided in Example 2 of the present invention;

[0022] Figure 3 Electrolytic cavitation air curtain images of the underwater cavitation generating device provided in Example 2 of the present invention when it is powered on for 0.5s, 4.5s, 7s and 5min;

[0023] Figure 4 Schematic diagram and physical diagram of an electrolytic cavitation air curtain flow resistance test platform constructed in a laboratory precision circulating water tunnel by an underwater cavitation generating device provided in Example 2 of the present invention;

[0024] Figure 5 The underwater cavitation generating device provided in Example 2 of the present invention is used to build an electrolytic cavitation air curtain flow resistance test platform in a laboratory precision circulating water tunnel, and the electrolytic cavitation air curtain working condition after power is turned on;

[0025] Figure 6 The underwater cavitation generating device provided in Example 2 of the present invention is used to build an electrolytic cavitation air curtain flow resistance test platform in a laboratory precision circulating water tunnel under the condition of electrolytic cavitation air curtain without power supply;

[0026] Figure 7 The flow resistance test results of the pure aluminum test piece provided in Comparative Example 1 of the present invention;

[0027] Figure 8 The flow resistance test results of the pure aluminum mesh provided in Comparative Example 2 of the present invention;

[0028] Fig. 9 The flow resistance test results of the carbon fiber mesh provided in Example 1 of the present invention;

[0029] Fig.10 These are the drag reduction rate test results of the carbon fiber mesh provided in Example 1 of the present invention, the pure aluminum test piece provided in Comparative Example 1, the pure aluminum mesh provided in Comparative Example 2, and the pure copper mesh provided in Comparative Example 3. DETAILED DESCRIPTION

[0030] The present invention provides a carbon fiber mesh, which is a square carbon fiber grid formed by the cross-section and vertical intersection of carbon fiber bundles;

[0031] The side length of the square carbon fiber grid is 1 to 3 mm;

[0032] The diameter of the carbon fiber bundle is 4 to 8 mm; the diameter of the carbon fibers in the carbon fiber bundle is 5 to 9 μm.

[0033] In the present invention, the carbon fiber net is a square carbon fiber grid formed by the cross-section and vertical cross-section of carbon fiber bundles. The present invention utilizes the characteristics of the carbon fiber net, which is light in weight, high in strength, corrosion-resistant and good in conductivity, and selects a carbon fiber net of suitable size so that it can generate stable bubbles for water electrolysis when powered on, thereby forming cavitation bubbles of uniform size.

[0034] In the present invention, the side length of the square carbon fiber mesh is 1 to 3 mm, preferably 1.6 to 2.4 mm, and more preferably 2 mm. The present invention controls the side length of the square carbon fiber mesh to be within the above range, so that the generated cavitation can be stably retained on the surface of the carbon fiber mesh, and then stably retained on the surface of the underwater vehicle, and has a long-term drag reduction effect.

[0035] In the present invention, the diameter of the carbon fiber bundle is 4 to 8 mm, preferably 4.8 to 7.2 mm, and more preferably 6 mm. The present invention controls the diameter of the carbon fiber bundle within the above range, so that the carbon fiber net has a higher mechanical strength, and the generated cavitation is stably retained on the surface of the carbon fiber net, and then stably retained on the surface of the underwater vehicle, which can have a long-term drag reduction effect.

[0036] In the present invention, the diameter of the carbon fiber in the carbon fiber bundle is 5 to 9 μm, preferably 5.6 to 8.4 μm, and more preferably 7 μm. The present invention controls the diameter of the carbon fiber in the carbon fiber bundle within the above range, which can make the carbon fiber net have higher mechanical strength and better flexibility, thereby making the carbon fiber net more conducive to more complete contact with the surface of the underwater navigation body when used.

[0037] The present invention has no particular limitation on the number of carbon fibers in the carbon fiber bundle, as long as the diameter of the carbon fiber bundle reaches a desired range.

[0038] The present invention has no special limitation on the preparation method of the carbon fiber mesh, and any method that can obtain a carbon fiber mesh that meets the above requirements is acceptable.

[0039] The present invention also provides an underwater cavitation generating device, comprising a carbon fiber mesh and a power supply, wherein the negative electrode of the power supply is connected to the carbon fiber mesh, and the positive electrode of the power supply is connected to a conductive rod; the carbon fiber mesh is the carbon fiber mesh described in the above technical solution.

[0040] The present invention has no special limitation on the type of the power source, and any conventional power source may be used.

[0041] In the present invention, the negative electrode of the power source is connected to the carbon fiber net, and the positive electrode of the power source is connected to the conductive rod. In an embodiment of the present invention, the underwater cavitation generating device is placed in water, the negative electrode of the power source is preferably connected to the carbon fiber net, and the positive electrode of the power source is preferably connected to a conductive carbon rod, and the conductive carbon rod is placed in water and can electrolyze water to form bubbles when powered. In an embodiment of the present invention, water is used as a conductive medium, and the carbon fiber net can be used to electrolyze water when powered.

[0042] The present invention also provides the application of the underwater cavitation generating device described in the above technical solution in cavitation drag reduction.

[0043] In the present invention, the method for applying the underwater cavitation generating device in cavitation drag reduction preferably comprises: after covering the surface of an underwater vehicle with the underwater cavitation generating device, placing the device in water, and then applying electricity for electrolysis.

[0044] In the present invention, the underwater cavitation generating device is preferably covered on the surface of the head and / or middle part of the underwater vehicle. In the present invention, the flow resistance of the head and / or middle part of the underwater vehicle is relatively large. By covering the underwater cavitation generating device on the surface of the head and / or middle part of the underwater vehicle, the cavitation air curtain generated by the underwater cavitation generating device can reduce the drag of the underwater vehicle, thereby improving the drag reduction effect.

[0045] In the present invention, the voltage of the electrolysis is preferably 5 V to 300 V, more preferably 120 V to 300 V. In an embodiment of the present invention, the power source is preferably direct current.

[0046] In the present invention, the electrolysis time is preferably 30 to 300 seconds, more preferably 300 seconds. The present invention controls the electrolysis time within the above range to form a stable cavitation gas curtain.

[0047] Since the carbon fiber net used in the present invention is a square carbon fiber grid formed by the vertical and horizontal intersection of carbon fiber bundles, by controlling the diameters of the carbon fibers and carbon fiber bundles, the generated cavitation can be stably retained on the surface of the carbon fiber net, and then stably retained on the surface of the underwater vehicle, and can have a long-term drag reduction effect. Therefore, the cavitation generating device is covered on the surface of the underwater vehicle, and electrolysis is performed after power is applied, so that a stable cavitation air curtain can be formed on the surface of the underwater vehicle.

[0048] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] Example 1

[0050] A carbon fiber net is a square carbon fiber grid formed by vertically and horizontally crossing carbon fiber bundles; the side length of the square carbon fiber grid is 2 mm; the diameter of the carbon fiber bundle is 6 mm; the diameter of the carbon fiber in the carbon fiber bundle is 7 μm.

[0051] The photo of the carbon fiber mesh provided in this example is as follows Figure 1 (a) shown.

[0052] Comparative Example 1

[0053] A pure aluminum test piece with a thickness of 2 mm.

[0054] The photo of the pure aluminum test piece provided in this comparative example is as follows Figure 1 (b) as shown.

[0055] Comparative Example 2

[0056] A pure aluminum mesh is a square aluminum wire grid formed by pure aluminum wires crossing each other horizontally and vertically; the side length of the square aluminum wire grid is 2 mm; and the diameter of the aluminum wire is 0.12 mm.

[0057] The photo of the pure aluminum mesh provided in this comparative example is as follows Figure 1 (c) as shown.

[0058] Comparative Example 3

[0059] A pure copper mesh is a square copper wire grid formed by pure copper wires crossing horizontally, vertically and vertically; the side length of the square copper wire grid is 2mm; and the diameter of the copper wire is 0.12mm.

[0060] The photo of the pure copper mesh provided in this comparative example is as follows Figure 1 (d) as shown.

[0061] Example 2

[0062] The carbon fiber mesh provided in Example 1 is assembled into an underwater cavitation generating device, as shown in the schematic diagram. Figure 2 shown.

[0063] Test Example 1

[0064] The underwater cavitation generating device assembled in Example 2 was powered by a high-voltage DC power supply (120V), and the carbon fiber mesh generated an electrolytic cavitation gas curtain. An electronic digital optical microscope was used to observe and record the high-definition instantaneous image set of the electrolytic cavitation gas curtain generation to stable dissipation behavior process in real time. The electrolytic cavitation gas curtain images at 0.5s, 4.5s, 7s and 5min of power on were obtained as follows: Figure 3 As shown. Figure 3 In the figure, (b), (c), (d) and (e) are the images of the electrolytic cavitation curtain after 0.5s, 4.5s, 7s and 5min of power supply, respectively. Figure 3 It can be seen that electrolytic cavitation is generated immediately when the carbon fiber mesh is energized, and a fully covered stable electrolytic cavitation gas curtain layer is formed within only 7 seconds. The electrolytic cavitation gas curtain remains stable under continuous power supply. During the test, the electrolytic cavitation gas curtain layer remains stable within 5 minutes of continuous power supply.

[0065] Application Example 1

[0066] The underwater cavitation generating device assembled in Example 2 is covered on the surface of an underwater vehicle, placed in water, and then powered on for electrolysis;

[0067] The method for covering the surface of an underwater vehicle with an underwater cavitation generating device is as follows: a test piece made of a non-conductive material is prepared (3D printing), and the underwater cavitation generating device assembled in Example 2 is laid on the surface of the test piece, and is attached to the test piece made of a non-conductive material (simulating an underwater vehicle).

[0068] Test Example 2

[0069] The underwater cavitation generating device assembled in Example 2 of Application Example 1 was used to build an electrolytic cavitation air curtain flow resistance test platform in a laboratory precision circulating water tunnel. Figure 4 As shown. Figure 4 The left picture is a schematic diagram of the electrolytic cavitation air curtain flow resistance test platform, and the right picture is a physical picture of the electrolytic cavitation air curtain flow resistance test platform. It consists of a test piece support plate (i.e. a test piece made of non-conductive material), a support rod, a pressure sensor, an underwater power supply line and a high-voltage DC power supply. After the electrolytic cavitation air curtain flow resistance test platform is powered on, the electrolytic cavitation air curtain working condition is as follows Figure 5 The cavitation air curtain working condition under no power supply is as follows. Figure 6 shown.

[0070] It is proposed to use a test piece support plate with a leading edge airfoil design that is beneficial to reducing flow separation. The carbon fiber mesh or conventional smooth surface metal test piece provided in Example 1 is installed thereon (the carbon fiber mesh or pure metal test piece is connected to the negative electrode of the power supply, and the external carbon rod in the water is connected to the positive electrode of the power supply). The flow resistance of the test piece support plate under different electrolytic cavitation air curtain conditions (electrolysis is powered by a high-voltage DC power supply, voltage: 50V~300V) and conventional surface conditions at the same flow rate is measured respectively.

[0071] like Figure 4 As shown on the left, the specimen support plate and the support rod are respectively subjected to the incoming flow resistance F0 and F1, and the overall force F2 is obtained through force conduction. Since the torque effect in the force transmission process only measures its rotation effect, the pressure sensor can directly measure the flow resistance F3 (= F2). When measuring the flow resistance, under the typical incoming flow velocity condition of the water tunnel test section (0.5m / s~1.5m / s), the flow resistance F1 of the support rod is measured when the specimen support plate is not installed. Secondly, the flow resistance F2 of the specimen support plate and the support rod is measured under the incoming flow velocity condition. Then, the flow resistance of the specimen support plate is F0=F2-F1. Assuming that the combined flow resistance of the specimen support plate and the support rod measured under the electrolytic cavitation gas curtain condition is F2b, and the combined flow resistance of the specimen support plate and the support rod measured under the conventional surface condition is F2s, the flow resistance of the specimen support plate when the electrolytic cavitation gas curtain occurs on the carbon fiber mesh is Fb=F2b-F1; similarly, the flow resistance of the conventional smooth surface specimen support plate is Fs=F2s-F1, so the flow drag reduction rate is η=(Fs-Fb) / Fs.

[0072] The flow resistance test of the surface test pieces of electrode meshes of different conductive materials (i.e., the carbon fiber mesh provided in Example 1, the pure aluminum test piece provided in Comparative Example 1, the pure aluminum mesh provided in Comparative Example 2, and the pure copper mesh provided in Comparative Example 3) was carried out in the laboratory precision circulating water tunnel. The flow velocity (0.4m / s to 1.0m / s) was changed, and the flow resistance of the pure aluminum mesh, pure copper mesh, carbon fiber mesh and pure aluminum test piece was tested under the electrolytic cavitation air curtain working condition (250V / 2A) and the no-power working condition, and then the electrolytic cavitation air curtain flow resistance reduction rate of the surface of the electrode mesh of each conductive material was obtained. The test results are shown in Tables 1 and Figures 7-10 shown. Figure 7 The flow resistance test results of the pure aluminum test piece provided for Comparative Example 1; Figure 8 The flow resistance test results of the pure aluminum mesh provided for Comparative Example 2; Fig. 9 The flow resistance test results of the carbon fiber mesh provided in Example 1; Fig.10 These are the drag reduction rate test results of the carbon fiber mesh provided in Example 1, the pure aluminum test piece provided in Comparative Example 1, the pure aluminum mesh provided in Comparative Example 2, and the pure copper mesh provided in Comparative Example 3.

[0073] Table 1 Flow resistance data of electrode grid surface test pieces with different conductive materials

[0074]

[0075] From the above results, it can be seen that the drag reduction effect of the electrolytic cavitation air curtain of the carbon fiber mesh is outstanding, with an average drag reduction rate of 30.27%, which is much higher than the drag reduction effect of other conductive materials. In addition, carbon fiber has the advantages of light weight, good conductivity, high strength and corrosion resistance. The surface of the electrolytic cavitation air curtain with full coverage of the carbon fiber mesh is stably dissipated, breaking through the shape of the test piece, and the wading surface without the need to modify or add the existing test piece structure. It can be used for cavitation drag reduction and solve the problems of high processing cost and difficulty in drag reduction of underwater navigation bodies and the inability to form stable resident cavitation.

[0076] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A carbon fiber mesh, wherein the carbon fiber mesh is a square carbon fiber grid formed by the cross-section of carbon fiber bundles; The side length of the square carbon fiber grid is 1 to 3 mm; The diameter of the carbon fiber bundle is 4 to 8 mm; the diameter of the carbon fibers in the carbon fiber bundle is 5 to 9 μm.

2. The carbon fiber mesh according to claim 1, characterized in that: The side length of the square carbon fiber grid is 1.6-2.4 mm.

3. The carbon fiber mesh according to claim 1, characterized in that: The diameter of the carbon fiber bundle is 4.8-7.2 mm.

4. The carbon fiber mesh according to claim 1, characterized in that: The diameter of the carbon fibers in the carbon fiber bundle is 5.6 to 8.4 μm.

5. An underwater cavitation generating device, characterized in that: It comprises a carbon fiber mesh and a power source, wherein the negative electrode of the power source is connected to the carbon fiber mesh, and the positive electrode of the power source is connected to a conductive rod; the carbon fiber mesh is the carbon fiber mesh according to any one of claims 1 to 4.

6. Application of the underwater cavitation generating device according to claim 5 in cavitation drag reduction.

7. The use according to claim 6, characterized in that: The method for applying the underwater cavitation generating device in cavitation drag reduction comprises: covering the surface of an underwater vehicle with the underwater cavitation generating device, placing the device in water, and then applying electricity for electrolysis.

8. The use according to claim 7, characterized in that: The underwater cavitation generating device covers the surface of the head and / or middle part of the underwater vehicle.

9. The use according to claim 7, characterized in that: The voltage of the electrolysis is 5V to 300V.

10. The use according to claim 7, characterized in that: The electrolysis time is 30 to 300 seconds.

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