A ducted propeller with cavitation delay based on superhydrophobic slip effect and a manufacturing method thereof

Abstract

The present invention relates to a ducted propeller for delaying cavitation based on a super-hydrophobic slip effect and a manufacturing method thereof, comprising: a duct; a stator fixedly disposed in the duct; and a rotor, wherein the rotor comprises a rotating shaft rotatably connected to the stator and a plurality of blades fixedly connected to the rotating shaft, the tip of each blade being provided with a first super-hydrophobic layer; wherein a tip gap is formed between the first super-hydrophobic layer and the inner wall of the duct, and the surface of the first super-hydrophobic layer has a gas-liquid interface slip effect, thereby delaying tip gap vortex cavitation, reducing noise, and weakening cavitation risk without changing the duct wall and rotor blade tip structure of the ducted propeller.

Description

Technical Field

[0001] The present invention relates to the technical field of underwater propellers, in particular to a ducted propeller based on super-hydrophobic slip effect cavitation delay and a manufacturing method thereof. Background Art

[0002] Ducted propellers are currently the most common type of propulsion system used on ships and other vessels, particularly those operating at high speeds, due to their advantages such as high critical speed, low radiated noise, and high propulsion efficiency. However, the presence of the duct also introduces new flow phenomena and technical challenges. Among these, tip gap flow is a characteristic feature of ducted propellers, significantly different from that of traditional propeller propulsion. Tip gap dimensions vary slightly depending on the duct profile (converging or diverging), but are generally on the order of millimeters. Inside the tip gap, as the rotor blades rotate, the water flows from the rotor pressure side (upstream surface) to the rotor suction side (backstream surface), causing significant flow separation at the rotor blade tip, forming a tip separation vortex, which interacts with the turbulent boundary layer flow on the inner wall of the duct, forming a tip separation vortex, a tip leakage vortex and its induced vortex in the tip gap and entangles with each other, forming a spiral vortex system that blocks the flow channel and reduces propulsion efficiency; as the rotor speed increases, the strength of the tip gap vortex structure increases, the pressure in the vortex core area is lower than the saturated vapor pressure of the water body, combined with the gas core originally existing in the water body, the water body in the vortex core area undergoes a phase change, that is, the tip gap vortex cavitation begins; as the rotor speed further increases, the tip gap vortex cavitation area further expands to the back of the rotor blade (suction surface), and at the same time, cavitation noise, cavitation erosion and shaft vibration noise are generated, forming significant radiation noise, which seriously affects the acoustic performance of the vehicle.

[0003] At present, the common practice to improve the noise and cavitation of ducted propellers is to cut grooves on the duct wall or set up a turbulent flow structure at the rotor blade tip to change the tip gap flow mode. By changing the tip gap vortex ring volume, the tip gap vortex structure strength is reduced and the formation of tip gap vortex is suppressed. However, it is difficult to avoid the formation of flow separation vortex, which has an adverse effect on the propulsion efficiency and noise of the ducted propeller. Summary of the Invention

[0004] In response to the shortcomings of the above-mentioned existing production technology, the applicant provides a ducted propeller with cavitation delay based on super-hydrophobic slip effect and a manufacturing method thereof, thereby delaying tip gap vortex cavitation, reducing noise and weakening cavitation risk without changing the duct wall and rotor blade tip structure of the ducted propeller.

[0005] The technical solutions adopted in the present invention are as follows:

[0006] A ducted propeller based on super-hydrophobic slip effect cavitation delay, comprising:

[0007] catheter;

[0008] a stator, fixedly disposed in the guide tube;

[0009] a rotor comprising a rotating shaft rotatably connected to the stator, and a plurality of blades fixedly connected to the rotating shaft, wherein a tip of each blade is provided with a first super-hydrophobic layer;

[0010] A tip gap is formed between the first super-hydrophobic layer and the inner wall of the conduit, and the surface of the first super-hydrophobic layer has a gas-liquid interface slip effect.

[0011] The inner wall is provided with a second super-hydrophobic layer, the surface of the second super-hydrophobic layer has a gas-liquid interface slip effect, and the tip gap is the gap between the first super-hydrophobic coating and the second super-hydrophobic coating.

[0012] As a further improvement of the above technical solution:

[0013] The first super-hydrophobic layer and the second super-hydrophobic layer both satisfy: a hydrophobic angle greater than or equal to 150°, and an oleophobic angle greater than or equal to 150°.

[0014] The thickness of the first super-hydrophobic layer and the second super-hydrophobic layer are both 20 μm to 50 μm.

[0015] The first super-hydrophobic layer and the second super-hydrophobic layer are both made of flexible materials.

[0016] The flexibility of the flexible material is greater than or equal to 1 mm.

[0017] The first super-hydrophobic layer and the second super-hydrophobic layer are both formed by spraying, the adhesion of the first super-hydrophobic layer is level 0 or level 1, the adhesion of the second super-hydrophobic layer is level 0 or level 1, and the impact resistance of the first super-hydrophobic layer and the second super-hydrophobic layer is greater than or equal to 25 kg·cm.

[0018] The size of the tip gap is 1 mm to 100 mm.

[0019] A method for manufacturing a ducted propeller based on super-hydrophobic slip effect cavitation delay comprises the following steps:

[0020] Surface treatment: performing surface treatment on the blade tips of the rotor blades of the ducted propeller and the inner wall of the duct;

[0021] Spraying: Liquid material is evenly sprayed on the blade tip and the inner wall of the duct. After the liquid material dries and solidifies, a first super-hydrophobic layer is formed on the blade tip and a second super-hydrophobic layer is formed on the inner wall of the duct. The surfaces of the first super-hydrophobic layer and the second super-hydrophobic layer both have a gas-liquid interface slip effect;

[0022] Assembly: The rotating shaft of the assembled rotor is rotated and installed in the conduit through a stator arranged in the conduit, and a tip gap is formed between the first super-hydrophobic coating and the second super-hydrophobic coating.

[0023] As a further improvement of the above technical solution:

[0024] The liquid material includes a first liquid material and a second liquid material,

[0025] The process of uniformly spraying liquid material on the blade tip and the inner wall of the duct includes the following steps:

[0026] Evenly spraying the first liquid material on the blade tip and the inner wall of the conduit, and forming a primer coating when the first liquid material dries and solidifies;

[0027] The second liquid material is evenly sprayed on the surface of the primer coating. When the second liquid material is dried and solidified, a surface coating is formed. The surface of the surface coating has a gas-liquid interface slip effect.

[0028] The beneficial effects of the present invention are as follows:

[0029] The present invention has a compact and reasonable structure and is easy to operate. By arranging a first super-hydrophobic layer at the blade tip and utilizing the gas-liquid interface slip effect on the surface of the first super-hydrophobic layer, the blade gap vortex separation length is increased, thereby delaying the tip gap vortex cavitation, reducing noise and weakening the cavitation risk without changing the inner wall of the duct and the blade tip structure (i.e., the vortex circulation amount).

[0030] At the same time, the present invention also has the following advantages:

[0031] A super-hydrophobic layer is provided on both the blade tip and the inner wall of the duct. The slip effect of the gas-liquid interface on the super-hydrophobic surface is utilized to increase the tip gap vortex separation length, delay the onset of tip gap vortex cavitation, reduce wall shear, delay the onset of shear cavitation on the inner wall of the duct, reduce noise and cavitation risks, and comprehensively improve the acoustic performance of the ducted propeller. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a structural schematic diagram of the ducted propeller of the present invention.

[0033] Figure 2 It is a three-dimensional diagram of the duct propeller of the present invention.

[0034] Figure 3 This is the super-hydrophobic microstructure morphology on the surface of the super-hydrophobic layer of the present invention.

[0035] Figure 4 This is a schematic diagram of increasing the tip gap vortex separation length of the present invention.

[0036] Figure 5 This is the dimensionless mean streamwise velocity profile of the Newtonian fluid near the wall.

[0037] Figure 6 : is a comparison diagram of the radiation noise of the ducted propeller of Example 2 and the conventional ducted propeller under the working condition of the critical cavitation number of the conventional ducted propeller.

[0038] Figure 7This is a comparison chart of the cavitation starting speeds of the ducted propeller of Example 2 and the conventional ducted propeller under their respective critical cavitation number conditions.

[0039] Figure 8 Schematic diagram of the process for manufacturing a ducted propeller and the implementation scheme for achieving cavitation delay performance.

[0040] Among them: 2. stator; 3. duct; 4. rotor; 5. rotating shaft; 6. pressure side; 7. suction side; 8. blade tip; 9. inner wall; 10. hub; 11. axis. DETAILED DESCRIPTION

[0041] The specific embodiments of the present invention will be described below with reference to the accompanying drawings.

[0042] Example 1:

[0043] like Figure 1 、 Figure 2 As shown, the ducted propeller based on super-hydrophobic slip effect cavitation delay of this embodiment includes a duct 3, a stator 2 and a rotor 4.

[0044] The stator 2 is fixed in the guide tube 3;

[0045] The rotor 4 includes a rotating shaft 5 rotatably connected to the stator 2, and also includes a plurality of blades fixedly connected to the rotating shaft 5, and a blade tip 8 of each blade is provided with a first super-hydrophobic layer;

[0046] A gap is formed between the first super-hydrophobic layer and the inner wall 9 of the conduit 3 , and the surface of the first super-hydrophobic layer has a gas-liquid interface slip effect.

[0047] The specific structure of the ducted propeller is as follows Figure 1 、 Figure 2 As shown, the stator 2 is a streamlined bracket structure. The stator 2 includes a connecting seat located at the center of the conduit 3. A rotating shaft 5 is rotatably mounted on the connecting seat. The rotating shaft 5 is transmission-connected to a driving mechanism, which is usually a motor.

[0048] When the ducted propeller is in operation, the rotor shaft 5 rotates relative to the stator 2, forming a tip-gap vortex within the tip gap. The pressure surface 6 of the rotor 4 faces the stator 2, while the suction surface 7 faces away from the stator. A hub 10 is mounted on the end of the rotor shaft 5 facing away from the stator 2. The hub 10, the rotor shaft 5, and the axis 11 of the duct 3 coincide. The ducted propeller can be installed at the stern of a ship.

[0049] The surface of a super-hydrophobic layer usually has a micro-nano rough structure. When water contacts this surface, air will be trapped in the grooves of the surface microstructure. The liquid does not directly contact most of the solid substrate area. Only the raised top of the microstructure is in contact with the liquid. Figure 3As shown in the figure, a gas-liquid interface is formed between the liquid and the solid substrate. Because of the large gas-liquid interface area below the liquid, the superhydrophobic gas-liquid interface slip effect significantly reduces the wall friction resistance encountered by Newtonian fluids (such as water and seawater) when flowing over the superhydrophobic surface, resulting in a slip length and slip speed on the superhydrophobic surface.

[0050] The tip gap vortex is located in the separation boundary layer at the blade tip 8. Due to the slip effect of the gas-liquid interface on the surface of the first super-hydrophobic layer, the ducted propeller of this embodiment has a longer tip gap vortex separation length compared to ducted propellers with the same duct 3 and stator 2 dimensions. The size of the tip gap vortex is determined by and is directly proportional to the tip gap vortex separation length. When the vortex circulation volume remains unchanged, increasing the tip gap vortex separation length and the tip gap vortex size increases the vortex structure strength, restoring the low-pressure area at the vortex center, delaying tip gap vortex cavitation, and increasing the critical cavitation number, making cavitation initiation more difficult. Cavitation does not occur at the original cavitation number, thus reducing the overall noise reduction performance of the ducted propeller.

[0051] like Figure 4 As shown, since the structures of the rotor 4 and the inner wall 9 of the duct 3 remain unchanged, the starting position of the tip gap vortex remains unchanged, and the tip gap vortex separation length extends toward the suction surface 7 in accordance with the three-dimensional twisting direction of the blade tip 8. After the tip gap vortex separation length of the blade tip 8 becomes larger, the tip gap vortex scale increases, the tip gap vortex moves away from the tip, and the cavitation bubble collapses far away from the wall, which can reduce the cavitation erosion of the rotor surface caused by the collapse of the cavitation bubble. The red color indicates the increase in the tip gap vortex separation length.

[0052] Compared with the ducted propeller with the duct 3 and stator 2 of the same specifications and dimensions, the ducted propeller of this embodiment does not undergo cavitation at the original cavitation number, and the onset of cavitation is delayed, thereby reducing the overall noise level of the ducted propeller. Due to the slip effect of the gas-liquid interface of the super-hydrophobic layer, the tip vortex cavitation position is moved away from the solid surface, and both cavitation and noise are significantly reduced. As a result, under the critical state, the cavitation noise is significantly reduced, the cavitation onset speed is increased, and the acoustic performance of the ducted propeller is significantly improved.

[0053] The ducted propeller of this embodiment is provided with a first super-hydrophobic layer on the blade tip 8. The gas-liquid interface slip effect on the surface of the first super-hydrophobic layer is utilized to increase the blade gap vortex separation length. Thus, without changing the structure of the inner wall 9 of the duct 3 and the blade tip 8 (i.e., the vortex circulation amount), the tip gap vortex cavitation is delayed, noise is reduced, and the cavitation risk is weakened.

[0054] Example 2:

[0055] The present embodiment is a ducted propeller with cavitation delay based on super-hydrophobic slip effect. On the basis of the first embodiment, the inner wall 9 is provided with a second super-hydrophobic layer, the surface of the second super-hydrophobic layer has a gas-liquid interface slip effect, and the tip gap is the gap between the first super-hydrophobic coating and the second super-hydrophobic coating.

[0056] Since shear cavitation occurs in the attachment boundary layer near the inner wall 9 of the conduit 3, the surface of the second superhydrophobic layer located on the inner wall 9 has a gas-liquid interface slip effect. By reducing the shear stress on the fluid, the onset of shear cavitation can be delayed, so that cavitation will only form at a higher rotation speed, thereby reducing radiation noise.

[0057] Figure 5 Middle U + is the dimensionless mean streamwise velocity in the near-wall region, y + represents the dimensionless normal height of the near-wall region, the straight line is the dimensionless average flow velocity profile of the Newtonian fluid near the wall region, and is a linear distribution function with a fixed slope. Figure 5 The black straight line in the middle represents the ordinary hydraulic smooth surface (solid surface), whose average velocity on the wall is zero, and the red straight line represents the slip velocity and slip length on the wall of the superhydrophobic surface, as shown in Figure 5 The dimensionless slip velocity U at the mesoscale + There is a downward height at the normal height, which is the dimensionless slip length L of the inner scale + .U + and y + The expression is as follows:

[0058] U + =U(y) / u * , where U(y) is the average velocity along the normal y height, u * is the wall friction velocity, , where τ is the wall shear stress, U ∞ is the free stream velocity;

[0059] y + =y×u * / ν, where y is the normal height, u * is the wall friction velocity, and ν is the fluid kinematic viscosity coefficient.

[0060] Since the surface of the second super-hydrophobic layer has a gas-liquid interface slip effect with a slip velocity and a slip length, the shear stress of the fluid on the wall is reduced, the shear strength is lowered, and the onset of shear cavitation can be delayed, so that cavitation will only form at a higher rotation speed, thereby reducing radiation noise.

[0061] The present embodiment is a ducted propeller that delays cavitation based on the superhydrophobic slip effect. Superhydrophobic layers are provided on both the blade tip 8 and the inner wall 9 of the duct 3. The superhydrophobic surface gas-liquid interface slip effect is utilized to increase the tip gap vortex separation length, delay the onset of tip gap vortex cavitation, reduce wall shear, delay the onset of shear cavitation on the inner wall 9 of the duct 3, reduce noise and cavitation risks, and comprehensively improve the acoustic performance of the ducted propeller.

[0062] The ducted propeller of this embodiment is suitable for various types of ducted propellers and water pump impeller machinery, and is particularly suitable for rotors 4 and ducts 3 with high requirements for radiated noise and large blade tip loads. It can effectively suppress tip gap vortex cavitation at the blade tip 8 of the rotor 4 and shear cavitation on the inner wall 9 of the duct 3, reduce radiated noise and structural vibration noise, weaken the risk of cavitation, reduce the harm of noise pollution generated by ship navigation to marine life, especially large marine life that relies on hearing or sonar systems to hunt, and develop a green marine economy.

[0063] For example, both the first super-hydrophobic layer and the second super-hydrophobic layer satisfy the following conditions: a hydrophobic angle greater than or equal to 150°, and an oleophobic angle greater than or equal to 150°, thereby ensuring superior super-hydrophobic performance parameters of the super-hydrophobic layer and ensuring effective slip length and slip speed.

[0064] For example, the thickness of the first super-hydrophobic layer and the second super-hydrophobic layer is 20 μm to 50 μm. The hydrophobic layer is provided with a certain thickness to ensure the structural strength and stability of the material without affecting the value of the vortex ring.

[0065] Exemplarily, the first super-hydrophobic layer and the second super-hydrophobic layer are both made of flexible materials, thereby increasing a buffer between the fluid and the solid and reducing the shear stress of the fluid on the solid surface.

[0066] Furthermore, the flexibility of the flexible material is greater than or equal to 1 mm. The flexibility testing standard is based on GB / T 1731-93, and the excellent cushioning effect of the material is utilized to improve the sliding effect.

[0067] Exemplarily, the first super-hydrophobic layer and the second super-hydrophobic layer are both formed by spraying, the adhesion of the first super-hydrophobic layer is level 0 or level 1, the adhesion of the second super-hydrophobic layer is level 0 or level 1, and the impact strength of the first super-hydrophobic layer and the second super-hydrophobic layer is greater than or equal to 25 kg·cm.

[0068] Adhesion level 0 is the best, indicating no square peeling and good coating adhesion. Level 1 means that there is a little coating peeling at the intersection of the cuts, but the peeling area does not exceed 5%. The adhesion test standard is GB 9286-1998.

[0069] The impact resistance of both the first and second super-hydrophobic layers is greater than or equal to 25 kg·cm. The impact resistance test standard is GB / T 1732–93, ensuring the super-hydrophobic layers' ability to resist erosion and meet the operating conditions of the ducted propeller.

[0070] The surfaces of the blade tip 8 and the inner wall 9 of the duct 3 may specifically be copper surfaces.

[0071] The tip gap size of this embodiment is 1 mm to 100 mm, and the cavitation delay performance within this size range is significant.

[0072] Figure 6 、 Figure 7 The acoustic performance test of the conventional ducted propeller of the same specification and the ducted propeller of this embodiment is compared. The diameter of the two ducted propellers is 0.24 meters. The blade tip 8 of the conventional ducted propeller and the inner wall 9 of the duct 3 are not provided with a super-hydrophobic layer.

[0073] like Figure 6 The radiation noise generated by the conventional ducted propeller when cavitation occurs at the critical cavitation number (i.e., at the onset of cavitation) is at least 15 dB higher than the radiation noise generated by the ducted propeller of this embodiment under the same operating conditions as the conventional ducted propeller, that is, the ducted propeller of this embodiment has cavitation delay.

[0074] like Figure 7 The cavitation starting speed of the ducted propeller of this embodiment under the condition of its own critical cavitation number is increased by at least 7% compared with the cavitation starting speed of the conventional ducted propeller under the condition of its own critical cavitation number, that is, the cavitation starting speed is increased.

[0075] like Figure 6 、 Figure 7 As shown, the experiment proves that the ducted propeller of this embodiment has delayed cavitation onset in the critical state of the conventional ducted propeller, significantly reduces the radiation noise, increases the cavitation onset speed, and significantly improves the acoustic performance of the ducted propeller.

[0076] Example 3:

[0077] The manufacturing method of the ducted propeller based on the super-hydrophobic slip effect cavitation delay of the second embodiment includes the following steps:

[0078] Surface treatment: Surface treatment is performed on the blade tips 8 of the rotor 4 of the ducted propeller and the inner wall 9 of the duct 3 to remove the residual paint film, rust, oil stains, oxide scale and other debris on the surface to achieve a rust-free, oil-free, dust-free and water-free surface.

[0079] Protective treatment: Protectively cover the position other than the inner wall 9 of the duct 3, and protect the position other than the blade tip 8 of the blade. Seamless tape can be used for covering;

[0080] Spraying: The liquid material is evenly sprayed on the blade tip 8 and the inner wall 9 of the conduit 3. After the liquid material dries and solidifies, a first super-hydrophobic layer is formed on the blade tip 8, and a second super-hydrophobic layer is formed on the inner wall 9 of the conduit 3. The surfaces of the first super-hydrophobic layer and the second super-hydrophobic layer both have a gas-liquid interface slip effect;

[0081] Assembly: The rotating shaft 5 of the assembled rotor 4 is rotated and installed in the conduit 3 through the stator 2 arranged in the conduit 3, and a tip gap is formed between the first super-hydrophobic coating and the second super-hydrophobic coating.

[0082] Example 4:

[0083] The manufacturing method of the ducted propeller of this embodiment is further optimized based on the third embodiment and includes the following steps:

[0084] Surface treatment: Surface treatment is performed on the blade tips 8 of the rotor 4 of the ducted propeller and the inner wall 9 of the duct 3 to remove the residual paint film, rust, oil stains, oxide scale and debris on the surface to achieve a rust-free, oil-free, dust-free and water-free surface.

[0085] Protective treatment: Protectively cover the position other than the inner wall 9 on the duct 3, and protect the position other than the blade tip 8 on the blade. Seamless tape can be used for covering.

[0086] Spraying: The liquid material is evenly sprayed on the blade tip 8 and the inner wall 9 of the conduit 3. After the liquid material dries and solidifies, a first super-hydrophobic layer is formed on the blade tip 8, and a second super-hydrophobic layer is formed on the inner wall 9 of the conduit 3. The surfaces of the first super-hydrophobic layer and the second super-hydrophobic layer both have a gas-liquid interface slip effect;

[0087] When spraying, it is necessary to be in a dust-free environment with an exhaust device or corresponding air dust collection equipment. In addition, spraying to form a super-hydrophobic layer is mainly divided into two steps: first, forming a base coating, and second, forming a surface coating. Using spraying to form a super-hydrophobic layer is convenient for operation, and using a double-layer spraying method to improve the stability of the super-hydrophobic layer;

[0088] The liquid material includes a first liquid material and a second liquid material.

[0089] The process of uniformly spraying the liquid material on the blade tip 8 and the inner wall 9 of the conduit 3 includes the following steps:

[0090] The first liquid material is evenly sprayed on the blade tip 8 and the inner wall 9 of the conduit 3, and a primer coating is formed when the first liquid material dries and solidifies;

[0091] Evenly spraying a second liquid material on the surface of the primer coating, and forming a surface coating when the second liquid material is dried and solidified, wherein the surface of the surface coating has a gas-liquid interface slip effect;

[0092] Finally, the primer coating and the surface coating on the blade tip 8 are superimposed and combined to form a first super-hydrophobic layer, and the primer coating and the surface coating on the inner wall 9 of the conduit 3 are superimposed and combined to form a second super-hydrophobic layer.

[0093] Both the primer coating and the surface coating meet the following requirements: flexibility is greater than or equal to 1mm, adhesion is level 0 or level 1, and impact resistance is greater than or equal to 25kg·cm.

[0094] Assembly: The shaft 5 of the assembled rotor 4 is rotated and installed in the conduit 3 through the stator 2 set in the conduit 3, and a tip gap is formed between the first super-hydrophobic coating and the second super-hydrophobic coating. The hub 10, the shaft 5, and the axis 11 of the conduit 3 coincide with each other, and the size of the tip gap is adjusted to be uniform. The assembly is completed and can be used normally.

[0095] Finally, the motor of the ducted propeller is started, and the rotor 4 rotates, generating thrust to propel the vehicle. Water flows through the ducted propeller and between the first super-hydrophobic layer on the blade tip 8 and the second super-hydrophobic layer on the inner wall 9. The super-hydrophobic surfaces of the first and second super-hydrophobic layers produce a gas-liquid interface slip effect, which is mainly manifested in the following two aspects:

[0096] On the one hand, Newtonian fluid (such as water, seawater) forms a slip length L on the super hydrophobic surface of the inner wall 9 of the conduit 3 + and slip speed U s + , reducing the wall friction resistance, causing the dimensionless average flow velocity profile in the near-wall region to shift downward, indicating that the superhydrophobic gas-liquid interface slip effect reduces the wall shear and delays the onset of shear cavitation on the inner wall 9 of the conduit 3, as shown in Figure 5 As shown;

[0097] On the other hand, Newtonian fluid (such as water, seawater) forms a slip length L on the super hydrophobic surface of the blade tip 8 + and slip speed U s + , which increases the tip gap vortex separation length and increases the size of the tip gap vortex structure. Without changing the vortex ring volume, the tip gap vortex intensity is weakened, the low pressure area of ​​the tip gap vortex center is restored, and the onset of tip gap vortex cavitation is delayed. This shows that the superhydrophobic gas-liquid interface slip effect increases the tip gap vortex separation length and delays the onset of tip gap vortex cavitation. Figure 4 shown.

[0098] Therefore, the cavitation start of the ducted propeller in this embodiment is delayed, which significantly reduces the radiation noise, increases the cavitation start speed of the ducted propeller, and improves the acoustic performance of the ducted propeller. Figure 6 、 Figure 7 shown.

[0099] The process of manufacturing the ducted propeller and the schematic diagram of the implementation scheme for achieving cavitation delay performance in this embodiment are shown in FIG. Figure 8 shown.

[0100] A specific implementation of the spraying process in the manufacturing method of the ducted propeller of this embodiment is as follows:

[0101] Forming primer coating:

[0102] Stir the first liquid material (primer) thoroughly and evenly. It can be applied by air spraying. An HVLP gun (high flow, low pressure, such as the German SCHUTZE S941 model) can be used to spray multiple times in a thin and even manner. The model of the first liquid material can be JN-SS002.

[0103] After spraying, wait for 20-30 minutes for the first liquid material (primer) to dry to form a primer coating with a coating thickness of 10μm to 25μm. During this period, a hot air gun and a hair dryer can be used to accelerate the drying of the primer.

[0104] For the finished surface coating, thoroughly stir the second liquid material (topcoat). Do not use the same spray gun as the base coat. Select a new spray gun, but also use an HVLP gun (high volume low pressure, such as the German SCHUTZE S941). Apply the second liquid material multiple times in thin, even layers. After drying, the coating thickness should be 10 to 25 μm. Therefore, the total thickness of the super-hydrophobic layer should be 20 to 50 μm. The model number for the second liquid material is JN-SS003.

[0105] Specifically, the spray gun pressure of the HVLP gun used for spraying is: 0.138Mpa to 0.241Mpa, the nozzle diameter is: 0.5mm to 1.27mm, and the spraying distance is: 15cm to 25cm; the construction environment temperature for spraying is: 10℃ to 30℃, and the relative humidity is: 45% to 75%; the rotor 4 can be assembled as a whole and then sprayed, or the blade tips 8 can be sprayed before being assembled into the rotor 4.

[0106] After spraying, the coating is allowed to stand and cure for approximately 5-10 minutes. The surface of the coating will exhibit super-hydrophobic properties 30 minutes after spraying, with optimal super-hydrophobic properties achieved after 2 hours. The hydrophobic angle is no less than 150°, the oleophobic angle is no less than 150°, the first and second super-hydrophobic layers are UV-resistant for at least one year, and the operating temperature is between -31°C and 150°C. The adhesion of the super-hydrophobic coating is no greater than level 1 (i.e., the coating peeling area is less than or equal to 5%), the flexibility of the super-hydrophobic coating is greater than or equal to 1mm, and the impact strength is no less than 25kg·cm, forming super-hydrophobic blade tips 8 and super-hydrophobic inner walls 9.

[0107] The above description is an explanation of the present invention, not a limitation of the present invention. The scope of the present invention is defined in the claims. Any modifications may be made within the scope of protection of the present invention.

Claims

1. A ducted propeller based on super-hydrophobic slip effect cavitation delay, characterized by: include: catheter (3); A stator (2) is fixedly mounted in the guide tube (3); A rotor (4), the rotor (4) comprising a rotating shaft (5) rotatably connected to the stator (2), and comprising a plurality of blades fixedly connected to the rotating shaft (5), wherein a blade tip (8) of each blade is provided with a first super-hydrophobic layer; A tip gap is formed between the first super-hydrophobic layer and the inner wall (9) of the conduit (3), and the surface of the first super-hydrophobic layer has a gas-liquid interface slip effect, which increases the vortex size of the tip gap; The inner wall (9) is provided with a second super-hydrophobic layer, the surface of the second super-hydrophobic layer has a gas-liquid interface slip effect, reducing the shear stress on the fluid, and the tip gap is the gap between the first super-hydrophobic layer and the second super-hydrophobic layer; The first super-hydrophobic layer and the second super-hydrophobic layer both satisfy: a hydrophobic angle greater than or equal to 150°, and an oleophobic angle greater than or equal to 150°; The thickness of the first super-hydrophobic layer and the second super-hydrophobic layer are both 20 μm to 50 μm; The first super-hydrophobic layer and the second super-hydrophobic layer are both made of flexible materials, and the flexibility of the flexible materials is greater than or equal to 1 mm.

2. The ducted propeller based on super-hydrophobic slip effect cavitation delay according to claim 1, characterized in that: The first super-hydrophobic layer and the second super-hydrophobic layer are both formed by spraying, the adhesion of the first super-hydrophobic layer is level 0 or level 1, the adhesion of the second super-hydrophobic layer is level 0 or level 1, and the impact resistance of the first super-hydrophobic layer and the second super-hydrophobic layer is greater than or equal to 25 kg·cm.

3. The ducted propeller based on super-hydrophobic slip effect cavitation delay according to claim 1, characterized in that: The size of the tip gap is 1 mm to 100 mm.

4. A method for manufacturing a ducted propeller based on super-hydrophobic slip effect cavitation delay according to claim 1, characterized in that: The following steps are involved: Surface treatment: performing surface treatment on the blade tips (8) of the rotor (4) of the ducted impeller and the inner wall (9) of the duct (3); Spraying: evenly spraying the liquid material on the blade tip (8) and the inner wall (9) of the conduit (3); after the liquid material dries and solidifies, a first super-hydrophobic layer is formed on the blade tip (8); and a second super-hydrophobic layer is formed on the inner wall (9) of the conduit (3); the surfaces of the first super-hydrophobic layer and the second super-hydrophobic layer both have a gas-liquid interface slip effect; Assembly: The rotating shaft (5) of the assembled rotor (4) is rotated and installed in the conduit (3) through the stator (2) arranged in the conduit (3), and a tip gap is formed between the first super-hydrophobic coating and the second super-hydrophobic coating.

5. The manufacturing method according to claim 4, wherein: The liquid material includes a first liquid material and a second liquid material, The process of uniformly spraying the liquid material on the blade tip (8) and the inner wall (9) of the guide tube (3) comprises the following steps: Evenly spraying a first liquid material on the blade tip (8) and the inner wall (9) of the guide tube (3), and forming a primer coating when the first liquid material dries and solidifies; The second liquid material is evenly sprayed on the surface of the primer coating. When the second liquid material is dried and solidified, a surface coating is formed. The surface of the surface coating has a gas-liquid interface slip effect.

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