Industrial pump impeller and design method thereof

Abstract

The present invention relates to the technical field of non-variable displacement pumps, and specifically provides an industrial pump impeller and a design method thereof, with the purpose of resolving the technical problems of existing impellers, such as flow separation and efficiency limitations, surface friction and cavitation, and insufficient noise and vibration control. The impeller comprises a hub and a plurality of blades arranged circumferentially along the hub, wherein the blades comprise: an airfoil-shaped structure radially distributed along the hub, wherein the chord length decreases linearly from the root to the tip, and the mounting angle decreases from the root to the tip; an array of micro-grooves is provided on the pressure surface of the blade, wherein the orientation of the micro-grooves forms an angle with the main flow direction of the pressure surface of the blade; spiral grooves and pits are arranged on the suction surface of the blade, wherein the spiral direction of the spiral grooves is consistent with the rotation direction of the impeller; and the trailing edge of the blade is provided with serrations. By performing a special structural design on the surface of the impeller blades, surface friction is reduced, axial thrust is enhanced, boundary layer separation is delayed, noise and vibration are reduced, and cavitation is suppressed.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid variable displacement machinery, in particular to an industrial pump impeller and a design method thereof. Background Art

[0002] Axial-flow impellers, as core components of fluid machinery, are widely used in aeroengines, water pumps, wind turbines, and other fields. Their performance directly affects equipment efficiency, energy consumption, and lifespan. Traditional axial-flow impeller designs are often based on empirical formulas and standard airfoils (such as the NACA series). While these designs can meet basic requirements, they still face the following bottlenecks in complex scenarios such as high loads and variable operating conditions:

[0003] Flow separation and efficiency limitation: The pressure surface of traditional blades is prone to boundary layer separation, resulting in energy loss, especially under non-design conditions, where efficiency drops significantly; tip leakage flow causes energy loss of up to 20%-30%. Traditional methods improve this by reducing the tip clearance, but are limited by processing accuracy and vibration risks.

[0004] Surface friction and cavitation problems: The friction resistance between high-speed fluid and the blade surface accounts for 15%-25% of the total energy consumption; cavitation in the low-pressure area seriously reduces the life of the impeller. Traditional coating technology is difficult to balance wear resistance and drag reduction effects.

[0005] Insufficient noise and vibration control: Broadband noise and resonance problems caused by trailing edge vortex shedding have long plagued high-speed impeller design. Summary of the Invention

[0006] In response to the technical problems of flow separation and efficiency limitation, surface friction and cavitation, and insufficient noise and vibration control in existing impellers, the present invention provides an industrial pump impeller and a design method thereof. By performing special structural design on the surface of the impeller blades, micro-grooves are used to guide boundary layer flow and reduce surface friction; spiral grooves are used to suppress tip leakage and enhance axial thrust; pits are used to excite controllable micro-vortices and delay boundary layer separation; sawtooth cutting is used to cut the trailing vortex structure to reduce noise and vibration; and a super-hydrophobic coating is used to reduce fluid adhesion and suppress cavitation.

[0007] The technical solution of the present invention is:

[0008] An industrial pump impeller comprises a hub and a plurality of blades arranged circumferentially of the hub, wherein the blades comprise:

[0009] The wing-shaped structure distributed radially along the hub has a chord length that decreases linearly from the root to the tip, and an installation angle that decreases from the root to the tip;

[0010] The pressure surface of the blade is provided with an array of micro grooves, and the direction of the micro grooves forms an angle with the main flow direction of the pressure surface of the blade;

[0011] The suction surface of the blade is provided with spiral grooves and pits, and the spiral direction of the spiral grooves is consistent with the rotation direction of the impeller;

[0012] The trailing edge of the blade is provided with serrations.

[0013] Optionally, along the chord length direction of the blade, the micro groove is located in the front 30% area of the pressure surface of the blade.

[0014] Optionally, the grain direction of the micro grooves forms an angle of 15° to 25° with the axis of the hub.

[0015] Optionally, along the chord length direction of the blade, the spiral groove is located in the rear 20% area of the suction surface of the blade.

[0016] Optionally, along the chord length direction of the blade, the pit is located in the middle 30% area of the suction surface.

[0017] Optionally, the pit is hemispherical, and the pit coverage is 20% to 40%.

[0018] Optionally, the entire surface of the blade is covered with a super-hydrophobic coating.

[0019] A method for designing an industrial pump impeller comprises the following steps:

[0020] S10. Basic geometric parameter design:

[0021] Based on the flow rate Q, pressure rise ΔP and speed N, calculate the impeller outer diameter D and hub diameter d;

[0022] Set the blade chord length distribution;

[0023] Set the installation angle distribution;

[0024] S20, pressure surface micro groove design:

[0025] Design a micro-groove array in the 30% chord length area on the blade pressure surface;

[0026] Micro-groove parameters: wavelength 0.2mm~0.5mm, depth 0.05mm~0.1mm;

[0027] S30, suction surface spiral groove and pit design:

[0028] In the 20% chord length area behind the suction surface, a spiral groove is designed that is consistent with the impeller's rotation direction;

[0029] In the middle 30% chord length area of the suction surface, a hemispherical dimple array is arranged;

[0030] S40, trailing edge serration design:

[0031] Processing periodic triangular serrations on the trailing edge of the blade;

[0032] S50, super hydrophobic coating process:

[0033] Sandblasting pretreatment is performed on the entire surface of the blade;

[0034] applying a superhydrophobic coating via plasma-enhanced chemical vapor deposition;

[0035] S60, performance verification and optimization:

[0036] Verify the flow field characteristics through CFD simulation. If the tip leakage is greater than 5% of the design flow rate Q, increase the spiral groove depth to 2mm~3mm.

[0037] If the flow at the front edge of the pressure surface separates, increase the density of microgrooves;

[0038] The experimental test of pressure rise ΔP and efficiency η requires η ≥ 85% and ΔP error ≤ 5%.

[0039] Optionally, in step S10:

[0040] Satisfy the hub ratio d / D=0.3~0.5;

[0041] Set the blade chord length distribution: it decreases linearly from the hub to the blade tip, with the root chord length Croot = 0.15D and the tip chord length Ctip = 0.08D;

[0042] Set the installation angle distribution: root installation angle βroot = 40°±2°, tip installation angle βtip = 20°±2°, and transition according to a linear rule;

[0043] In step S50:

[0044] The thickness of the super-hydrophobic coating is 5 μm~20 μm, the contact angle is ≥150°, and the process gas is a mixture of hexamethyldisiloxane and oxygen.

[0045] Optionally, in step S20, the direction of the micro-grooves is optimized by particle image velocimetry experiments so that the grooves match the direction of the local streamlines;

[0046] In step S30, the pitch P of the spiral groove and the rotation speed N satisfy the relationship: .

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] By designing the surface structure of the impeller blades in a special way, micro grooves are used to guide the boundary layer flow and reduce surface friction; spiral grooves are used to suppress tip leakage and enhance axial thrust; pits are used to stimulate controllable micro vortices and delay boundary layer separation; saw teeth are used to cut the trailing vortex structure to reduce noise and vibration; and a super hydrophobic coating is used to reduce fluid adhesion and inhibit cavitation. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0050] Figure 1 Schematic diagram of the three-dimensional structure of the industrial pump impeller in the present invention;

[0051] Figure 2 It is a structural diagram of the blade pressure surface;

[0052] Figure 3 It is a structural diagram of the suction surface of the blade;

[0053] Figure 4 Schematic diagram of the structure of micro grooves;

[0054] Figure 5 This is a step diagram of the impeller design method of the present invention.

[0055] Reference numerals:

[0056] 10. Wheel hub.

[0057] 20. Blade; 21. Micro groove; 22. Spiral groove; 23. Pits; 24. Serrations; 25. Pressure surface; 26. Suction surface; 27. Superhydrophobic coating; 28. Blade tip. DETAILED DESCRIPTION

[0058] Hereinafter, only certain exemplary embodiments are briefly described. As will be appreciated by those skilled in the art, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and description are to be considered as illustrative in nature and not restrictive.

[0059] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the products of the present invention are conventionally placed when in use, or are the orientations or positional relationships conventionally understood by those skilled in the art. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be understood as limiting the present invention.

[0060] The disclosure below provides many different embodiments or examples for realizing different structures of the present invention. In order to simplify the disclosure of the present invention, the components and settings of specific examples are described below. Of course, they are merely examples and are not intended to limit the present invention. In addition, the present invention may repeat reference numbers and / or reference letters in different examples. Such repetition is for the purpose of simplicity and clarity and does not in itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides examples of various specific processes and materials, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0061] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0062] Example 1:

[0063] See also Figure 1 This embodiment discloses an industrial pump impeller, including a hub 10 and blades 20, wherein the hub 10 is a cylindrical structure, and multiple blades 20 (generally 4-6 blades) are evenly arranged in the circumferential direction of the hub 10, and the extension direction of the blades 20 is the same as the radial direction of the hub 10.

[0064] See also Figure 2 and Figure 3 The impeller's blades 20 comprise airfoil-shaped structures distributed radially along the hub 10. The chord length of the blades 20 decreases linearly from the root to the tip 28, and the installation angle of the blades 20 decreases from the root to the tip 28. The root herein refers to the end of the blade 20 connected to the hub 10, and the tip 28 refers to the end of the blade 20 away from the hub 10. The chord length of the blade 20 refers to the length of the chord line on the cross-section of the blade 20. The installation angle is the angle between the chord line of the blade 20 and the impeller's rotation plane, which directly affects the angle of attack of the fluid relative to the blade 20.

[0065] The angle of attack of the leading edge region of the blade 20 is set to 15° to 25°, and the angle of attack of the trailing edge region of the blade 20 is set to -5° to 5°.

[0066] The blade 20 also includes an array structure of micro grooves 21 arranged on the pressure surface 25. All the micro grooves 21 have a certain angle with the main flow direction of the pressure surface 25 of the blade 20 in the circumferential direction. The angle is between 10° and 30°, and the micro grooves 21 are inclined toward the tip 28 of the blade 20 along the main flow direction.

[0067] The blade 20 further includes a spiral groove 22 and a pit 23 provided on the suction surface 26 , wherein the spiral direction of the spiral groove 22 is consistent with the rotation direction of the blade 20 . The spiral groove 22 and the pit 23 are distributed in two areas of the suction surface 26 .

[0068] Finally, a serration 24 is provided on the trailing edge of the blade 20, which cuts the wake vortex and reduces the noise by 3-5 dB. The entire surface of the blade 20 is covered with a super-hydrophobic coating 27, which reduces the fluid adhesion resistance and resists cavitation.

[0069] In this embodiment, by making a special structural design on the surface of the impeller blade 20, micro grooves 21 are used to guide the boundary layer flow and reduce surface friction; spiral grooves 22 are used to suppress leakage from the blade tip 28 and enhance axial thrust; pits 23 are used to excite controllable micro vortices and delay boundary layer separation; serrations 24 are used to cut the wake vortex structure and reduce noise and vibration; and a super hydrophobic coating 27 is used to reduce fluid adhesion and suppress cavitation.

[0070] Preferably, the hub ratio is determined according to d / D=0.3-0.5, wherein D is the circumferential diameter formed by the rotation trajectory of the tip of the blade 20 , and d is the diameter of the hub 10 .

[0071] Impeller efficiency is typically highest (approximately 85% to 90%) when the hub / hub ratio is d / D = 0.3 to 0.5, due to the optimal match between the flow path cross-sectional area and the flow velocity. Test data shows that a water pump impeller has an efficiency of 88% when d / D = 0.35, while the efficiency drops to 82% when d / D = 0.5.

[0072] The smaller the hub ratio, the greater the gap between the blade tip 28 and the blade 20 height, and the more significant the leakage loss. For example, when d / D = 0.3, the leakage loss of the blade tip 28 may account for 15% of the total, while when d / D = 0.5, it can be reduced to 8%.

[0073] An excessively small hub-to-hub ratio results in excessively high velocity at the blade tip 28, exacerbating cavitation in the low-pressure zone. For example, when d / D = 0.3, the cavitation rate at the blade tip 28 may be twice that of when d / D = 0.5. This results in insufficient support for the hub 10, stress concentration at the blade root 20, and increased fatigue risk.

[0074] A hub ratio that is too large (e.g. >0.5) may cause the hub 10 to be bulky, increase the impeller's rotational inertia, and affect the start-stop response.

[0075] By calculating the hub ratio, the flow channel cross-sectional area can be controlled to balance the flow rate and structural strength.

[0076] The chord length of the blade 20 is from the hub 10 to the blade tip 28. Decreasing (C h is the chord length of the blade 20 connected to the hub 10, R is the impeller radius, that is, the radial distance from the surface of the hub 10 to the surface of the blade tip 20, Chord length reduction coefficient, r is the radial position, that is, the distance between any point on the blade and the hub 10 bias surface, 0≤r≤R). Therefore, the chord length C of the blade 20 root root =0.15D, blade 20, tip 28, chord length C tip =0.08D. The chord length at the root of the blade 20 is 15% of the outer diameter, and decreases to 8% at the tip 28 to adapt to the radial velocity distribution and reduce the load on the blade tip 28.

[0077] The blade 20's installation angle decreases linearly from 40°±2° to 20°±2° from the root to the tip 28. The distribution of blade 20 installation angles is a comprehensive result of velocity triangle theory, radial equilibrium equations, and engineering experience. This pattern matches the fluid's angle of attack and prevents flow separation.

[0078] The specific structure of the micro groove 21 is as follows Figure 4 As shown, the microgrooves 21 have a sharkskin-like structure, reducing frictional resistance by approximately 15% through boundary layer control. Specifically, the microgrooves 21 comprise tiny depressions with a length between 50 μm and 200 μm and a depth between 10 μm and 50 μm. The spacing between adjacent microgrooves 21 is 1 mm to 3 mm. Based on the chord length of the blade 20, all microgrooves 21 are distributed within the front 30% of the pressure surface 25 of the blade 20.

[0079] The spiral grooves 22 have a semicircular cross-section, and each spiral groove 22 has a gradually expanding structure, so that the width of the spiral groove 22 at the outlet is three times the width of the inlet. (In this embodiment, the inlet width of the spiral groove 22 is 1 mm, the outlet width is 3 mm, and the pitch of the spiral groove 22 is 20 mm to 50 mm.) This structure guides secondary flow, reduces the risk of flow separation, enhances axial flow, and suppresses leakage from the blade tip 28 (reducing losses by 18% to 25%).

[0080] The dimples 23 are hemispherical (for uniform flow disturbance) or trapezoidal (for enhanced vortex intensity), selected based on the local flow velocity gradient. All dimples 23 are staggered in a hexagonal or rectangular grid to avoid the formation of continuous grooves in the flow direction and reduce flow resistance. The center-to-center distance between adjacent dimples 23 is 1.5 to 2 times the diameter (e.g., for a 0.5 mm diameter, the spacing is 0.75 mm to 1.0 mm).

[0081] The dimples 23 form a structure on the surface of the blade 20 that is similar to the surface of a golf ball. The drag reduction effect of the dimples 23 on the surface of a golf ball (with a diameter of 2 mm to 4 mm) has been widely verified. However, the impeller operating conditions are more complex (higher flow velocity and more unstable flow state). Reducing the diameter of the dimples 23 can meet more sophisticated flow control requirements.

[0082] The dimples 23 optimize fluid dynamics by changing the local flow field characteristics. Their effects include:

[0083] Reducing surface friction resistance: The dimples 23 generate micro-eddies, which destroy the laminar flow state of the boundary layer, delay flow separation, and reduce energy loss.

[0084] Suppressing cavitation and noise: The pits 23 can disperse the cavitation collapse energy generated by high-speed fluid, reduce the risk of cavitation damage, and reduce the noise caused by wake vortex shedding.

[0085] Enhanced turbulent mixing: By promoting micro-scale turbulence of the fluid, the energy transfer efficiency is improved, especially under high speed or variable working conditions.

[0086] The parameters of the pit 23 are a diameter of 0.3 mm to 0.8 mm and a coverage of 20% to 40%.

[0087] The boundary layer thickness on the surface of blade 20 is typically in the millimeter range (e.g., 1mm to 5mm). The diameter of dimple 23 needs to be smaller than this thickness to effectively disturb the flow field. A diameter of 0.3mm to 0.8mm allows it to penetrate the high-shear zone at the bottom of the boundary layer, stimulating stable micro-eddies while avoiding excessive disturbances that could waste energy.

[0088] CFD simulation numerical results show that when the diameter of the pit 23 is less than 1 mm, it has the best effect on suppressing the leakage flow and separation flow of the blade tip 28 (efficiency improvement of 5% to 8%). If the diameter of the pit 23 is too large, it will increase the flow resistance.

[0089] Low coverage (20%-30%) dimples 23: Sparsely distributed, mainly used for local flow modification (such as suppressing blade root separation), suitable for low Reynolds numbers (Re<105) or laminar flow-dominated areas. High coverage (30%-40%) dimples 23: Densely distributed, enhance global turbulent mixing, suitable for high Reynolds numbers (Re>106) or areas with significant turbulence (such as blade tips 28).

[0090] Wind tunnel tests show that when the coverage of dimples 23 reaches 30%, the impeller pressure-lift efficiency increases by 12%. Increasing it to 40% only increases it by an additional 2%, but frictional resistance increases by 15%. Therefore, 20%–40% is the Pareto optimal range for efficiency-drag.

[0091] The tooth height of the trailing edge serrations 24 is 1 mm to 3 mm, and the tooth pitch is 5 mm to 15 mm.

[0092] The tooth height refers to the vertical height of a serration 24 from the base to the tip of the trailing edge of the blade 20. This parameter directly affects the intensity of the disturbance caused by the fluid flowing through the serration 24. A higher tooth height can enhance the vortex shearing effect, but this must be balanced against increased drag and structural strength. The tooth pitch refers to the center-to-center distance between two adjacent serrations 24.

[0093] The tooth pitch determines the density of the serrations 24 . A smaller tooth pitch can improve the precision of flow control, but may increase manufacturing difficulty and flow resistance.

[0094] According to the principles of fluid mechanics, the trailing edge serrations 24 cut large-scale vortices into smaller turbulent structures, reducing vortex shedding energy and thus reducing broadband noise (can reduce noise by 3dB~8dB). (St is the Strouhal number, U is the flow velocity, and d is the characteristic size). The serrations 24 reduce the sound pressure level by destroying the periodicity of the vortex.

[0095] The serrations 24 delay boundary layer separation, particularly at the high-load region of the blade tip 28, improving efficiency by approximately 2%–5%. Experiments have shown that a 2mm tooth height reduces the separation zone length by 30%.

[0096] A maximum tooth width of 3mm prevents flow separation or additional resistance caused by excessive tooth height (the resistance increase must be controlled within 5%). A minimum tooth width of 1mm ensures effective perturbation of the boundary layer and avoids weak noise reduction due to insufficient height.

[0097] Small pitch (5mm-8mm) is suitable for high speed (>3000RPM) or high turbulence intensity conditions, enhancing the vortex cutting effect. Large pitch (10mm-15mm) is used for medium and low speed impellers, balancing noise reduction requirements and manufacturing complexity.

[0098] The super-hydrophobic coating 27 has a thickness of 5 μm to 20 μm and a contact angle of ≥150°. Through microscopic nanostructures and low-surface-energy chemical modification, the super-hydrophobic coating 27 achieves the following functions:

[0099] Drag reduction: Reduce the viscous resistance between the fluid and the blades 20, and reduce energy consumption (friction resistance can be reduced by 15% to 25%).

[0100] Anti-cavitation: inhibit the impact of cavitation collapse on the material and extend the life of the impeller (cavitation rate is reduced by 50%~70%).

[0101] Anti-fouling and anti-corrosion: Prevent the adhesion of microorganisms, salt spray or particulate matter, reducing corrosion and maintenance costs.

[0102] The thickness of the coating is designed based on the balance between durability and functionality and process adaptability:

[0103] 1. Balance between durability and functionality:

[0104] Lower limit (5μm): Ensures complete surface coverage of the nanostructure to avoid local defects that could degrade performance. If the thickness is less than 5μm, the coating is susceptible to localized flaking due to fluid shear or particle erosion.

[0105] Upper limit (20μm): Too thick a coating may cause cracking due to internal stress and significantly affect the aerodynamic shape of the impeller (for every 10μm increase in thickness, the tip 28 clearance loss increases by 0.2%~0.5%).

[0106] Experimental data: When the coating thickness is 10μm, the wear-resistant life can reach 5000 hours, while the life of 5μm is 3000 hours, and 20μm is reduced to 4000 hours due to brittleness.

[0107] 2. Process adaptability:

[0108] Plasma-enhanced chemical vapor deposition (PECVD): The typical deposition rate is 1μm / h~3μm / h, and the process time for 5μm~20μm thickness is 1~20 hours, which is suitable for industrial production.

[0109] Spraying process: Thickness uniformity is ±2μm, multiple spraying and curing are required, the cost is low but the adhesion is weak.

[0110] The physical meaning and implementation method of contact angle ≥150°:

[0111] The contact angle is the angle formed by a liquid droplet on a solid surface, reflecting the surface hydrophobicity.

[0112] Superhydrophobic surface standard: CA ≥ 150°, rolling angle (the tilt angle at which the droplet starts to roll) < 10°.

[0113] Mechanism of action: Surface micro-nanostructures (such as nanopillars and micropores) work synergistically with low surface energy substances (such as fluorosilane) to form a Cassie-Baxter state, allowing the droplets to suspend on the air layer.

[0114] Implementation technology:

[0115] Nanostructure design: micron-scale substrate + nanoscale protrusions, for example, carbon nanotubes (diameter 50nm~100nm) are grown on micron-scale pits 23 (diameter 1μm~5μm) to form a hierarchical structure.

[0116] Parameter optimization: When the structure height / spacing ratio (H / S) is ≥1.5, the contact angle can reach above 160°.

[0117] Chemical modification:

[0118] Fluorosilane (such as FAS-17): Surface energy is as low as 10mN / m~15mN / m (the surface energy of pure water is 72mN / m), and durability is enhanced through chemical bonding.

[0119] Silica nanoparticle doping: Improves mechanical strength and hardness up to 5GPa~8GPa.

[0120] In one specific embodiment:

[0121] The concentration of microgrooves 21 in the front 30% of the pressure surface 25 is a comprehensive decision based on maximizing boundary layer control efficiency, intervening in the energy-loss-dominant zone, biomimetic insights, and manufacturing feasibility. This design achieves an optimal balance between reducing friction (15%-20%), delaying flow separation (5%-8%), and extending impeller life (reducing wear by 30%).

[0122] Boundary layer control based on fluid mechanics: After the fluid contacts the leading edge of the blade 20, the boundary layer gradually thickens from zero. In the first 30% of the pressure surface 25, the boundary layer is in a laminar state and is relatively thin (approximately 0.1mm to 0.5mm). At this time, the introduction of micro-grooves 21 can effectively intervene in the flow and avoid subsequent turbulent separation. The micro-grooves 21 suppress the critical Reynolds number Re that transitions to turbulent flow by disturbing the laminar boundary layer. crit , extending the laminar flow region (efficiency improvement of 3% to 5%). Experiments have shown that providing micro-grooves 21 in the front 30% of the region can shift the transition point back by 20% to 30% of the chord length.

[0123] Minimize energy loss: The front section has a high fluid velocity (usually 70% to 90% of the peak velocity) and is the dominant area of friction resistance. The surface shear stress is large, and friction resistance accounts for 60% to 80% of the total resistance. The micro grooves 21 can significantly reduce energy consumption by reducing drag. The front section grooves make the friction resistance coefficient The drag reduction is reduced by 15%~20%, while the drag reduction effect in the middle and rear sections is only 5%−8% (due to turbulence dominance).

[0124] The shark's epidermal scutes have 21 microgrooves (approximately 0.1 mm deep) concentrated on the head and front of the torso (corresponding to the initial flow contact zone), reducing drag through a similar mechanism. Studies have shown that these biomimetic grooves in the front section can reduce swimming drag by 10% to 15%.

[0125] Processing feasibility: The curvature of the front section is gentle, and laser engraving or precision molds can ensure the groove dimensional accuracy (±0.02mm). The curvature of the back section varies greatly, which increases the processing difficulty and easily leads to groove deformation or fracture.

[0126] Anti-wear design: The front grooves are subject to high-speed fluid impact and require material reinforcement (such as tungsten carbide coating) to improve wear resistance. If the grooves extend to the rear end, turbulent erosion may cause structural failure after long-term operation.

[0127] In another specific embodiment:

[0128] The spiral grooves 22 are located within the trailing 20% of the suction surface 26 of the blade 20. This design is based on the following core principles: efficient flow control, parameter adaptability, and manufacturing feasibility. This impeller design improves efficiency by 5% to 8% (delayed separation and reduced leakage), reduces noise by 5dB to 8dB (vortex breaking effect), and extends life by 20% to 30% (vibration and cavitation suppression) across a wide range of operating conditions.

[0129] Highly Efficient Flow Control: Longitudinal vortex generation and leakage diversion significantly improve efficiency and stability against adverse pressure gradients and leakage flows. The spiral structure of the spiral grooves 22 induces longitudinal vortices (streamwise vortices) in the fluid, which rotate in the same direction as the impeller. This enhances momentum exchange near the wall and counteracts adverse pressure gradients. The spiral direction of the spiral grooves 22 is aligned with the leakage flow at the blade tip 28, forming a "spiral barrier" that reduces mixing losses between the leakage flow and the main flow. Experimental results show that leakage flow can be reduced by 15% to 20%. The spiral grooves 22 break up large-scale wake vortices into small-scale turbulence, reducing noise levels (approximately 5dB to 8dB) and reducing vibration by dissipating turbulent kinetic energy.

[0130] Parameter Adaptability: The dimensions of the spiral grooves 22 are precisely matched to the local boundary layer thickness and flow velocity, maximizing energy yield. The boundary layer thickness δ in the last 20% of the flow is approximately 1mm to 3mm, indicating turbulent flow (Reynolds number Reθ > 2000). The depth of the spiral grooves 22 (1mm to 3mm) is comparable to δ, directly intervening in the core of the boundary layer and improving control efficiency. The pitch P is 20mm to 50mm, matching the local mainstream velocity, ensuring that the vortex size is adapted to the boundary layer thickness.

[0131] Manufacturing feasibility: The gentle curvature and lower flow rate in the rear section ensure machining accuracy and coating durability. The curvature of the rear 20% area changes gently, making it suitable for five-axis milling or additive manufacturing (such as SLM). The forming accuracy of the spiral groove 22 can reach ±0.05mm. If the spiral groove 22 extends to the front section (high curvature area), machining becomes more difficult and can easily lead to geometric distortion. The surface of the spiral groove 22 needs to be sprayed with tungsten carbide or diamond-like carbon coating (thickness 5μm-10μm) with a hardness of ≥1200HV to resist high shear wear. The lower flow rate in the rear section (compared to the front section) can control the risk of coating spalling.

[0132] Disadvantages compared to other locations: The front section is primarily laminar flow, and the spiral grooves 22 disrupt laminar flow stability and increase frictional resistance (10%-15%). The mainstream velocity in the front section is high, and the spiral grooves 22 can easily induce cavitation (cavitation rate increased by 30%). The pressure gradient in the middle section is small, so the spiral grooves 22 have limited effect (efficiency improvement is only 2%-3%), potentially disrupting the mainstream flow and causing flow distortion.

[0133] In another specific embodiment:

[0134] The dimple 23 is located within the middle 30% of the suction surface 26, achieving the optimal solution for fluid dynamics, geometric compatibility, and engineering feasibility. Flow control: Stabilizes the boundary layer and inhibits separation during the critical transition and initial stages of the adverse pressure gradient. Parameter adaptation: The dimple 23 dimensions are precisely matched to the local flow velocity and boundary layer thickness, maximizing energy yield. Manufacturing advantages: Gentle curvature and mainstream velocity conditions ensure machining accuracy and coating durability.

[0135] Fluid Mechanics: The horseshoe vortices and recirculation vortices induced by the dimples 23 enhance near-wall turbulent pulsations, improve boundary layer momentum exchange, and resist adverse pressure gradients. Experimental data show that when the dimples 23 coverage is 30%, the separation onset can be delayed by 20% of the chord length, improving efficiency by 5% to 8%. The dimples 23 promote bypass transitions through localized perturbations, avoiding the instability of natural transitions and making turbulence development more uniform. When the dimples 23 have a diameter of 0.5 mm, the transition zone length is shortened by 40% and frictional resistance is reduced by 12%. The transverse vortices generated by the dimples 23 reversely couple with the secondary flow, weakening the channel vortex intensity and reducing mixing losses. The dimple 23 array reduces the kinetic energy of the leakage vortex at the blade tip 28 by 25% and reduces pressure rise fluctuations by 15%.

[0136] Geometric Adaptability: The middle region, where the flow velocity reaches its peak (approximately 1.5 to 2 times the inlet velocity), but the pressure gradient begins to shift from favorable to adverse pressure, represents a critical window for flow control. The diameter of the dimple 23 (0.3 to 0.8 mm) matches the local boundary layer thickness (0.5 to 1.5 mm), penetrating the viscous sublayer for effective perturbation. Turbulent kinetic energy begins to rise rapidly in this region. By introducing controlled perturbations, the dimple 23 shifts the peak turbulent kinetic energy from the free shear layer to the near-wall region, reducing mainstream energy dissipation. The blade 20 has a gentle curvature in the middle region, making it suitable for stamping or laser ablation of the dimple 23 with an accuracy of ±0.02 mm.

[0137] Engineering feasibility: The large curvature of the front section may easily cause the pit 23 to deform, and the excessive adverse pressure gradient in the back section may weaken the effect of the pit 23.

[0138] Example 2:

[0139] See also Figure 5 This embodiment discloses a method for designing an industrial pump impeller as described in the first embodiment, comprising the following steps:

[0140] S10. Basic geometric parameter design:

[0141] Based on the flow rate Q, pressure rise ΔP and speed N, the impeller outer diameter D and the hub 10 diameter d are calculated;

[0142] Setting the chord length distribution of blade 20;

[0143] Set the installation angle distribution;

[0144] S20, pressure surface 25 micro groove 21 design:

[0145] An array of micro grooves 21 is designed in the front 30% chord length area of the pressure surface 25 of the blade 20;

[0146] Micro-groove 21 parameters: wavelength λ = 0.2 mm ~ 0.5 mm, depth δ = 0.05 mm ~ 0.1 mm;

[0147] S30, Design of spiral groove 22 and pit 23 on suction surface 26:

[0148] In the 20% chord length area behind the suction surface 26, a spiral groove 22 is designed in the same direction as the impeller rotation;

[0149] An array of hemispherical dimples 23 is arranged in the middle 30% chord length region of the suction surface 26 .

[0150] S40, trailing edge serration 24 notch design:

[0151] Periodic triangular serrations 24 are machined on the trailing edge of the blade 20;

[0152] S50, super hydrophobic coating 27 process:

[0153] Performing sandblasting pretreatment on the entire surface of the blade 20;

[0154] The superhydrophobic coating was applied by plasma enhanced chemical vapor deposition (PECVD) 27 .

[0155] S60, performance verification and optimization:

[0156] Verify the flow field characteristics through CFD simulation. If the leakage of the blade tip 28 is greater than 5%Q, increase the depth of the spiral groove 22 to 2 mm to 3 mm.

[0157] If the flow at the leading edge of the pressure surface 25 separates, the density of the micro-grooves 21 is increased;

[0158] The experimental test of pressure rise ΔP and efficiency η requires η ≥ 85% and ΔP error ≤ 5%.

[0159] In step S10:

[0160] Satisfy the hub ratio d / D=0.3~0.5;

[0161] The chord length distribution of the blade 20 is set as follows: the chord length at the root decreases linearly from the hub 10 to the blade tip 28, and the chord length at the blade tip 28 decreases linearly;

[0162] Set the installation angle distribution: root installation angle β root =40°±2°, blade tip 28 installation angle β tip =20°±2°, transition according to linear law;

[0163] In step S50:

[0164] The thickness of the super-hydrophobic coating 27 is 5 μm~20 μm, the contact angle is ≥150°, and the process gas is a mixture of hexamethyldisiloxane and oxygen.

[0165] In step S20 , the direction of the micro-grooves 21 is optimized by particle image velocimetry (PIV) experiments to match the direction of the grooves with the local streamlines;

[0166] In step S30, the pitch P of the spiral groove 22 and the rotation speed N satisfy the relationship:

[0167] (N unit is r / min, P unit is mm).

[0168] In one specific embodiment:

[0169] Design selection of hub ratio: The initial hub ratio can be estimated by flow rate Q and pressure rise ΔP: This formula is applicable to medium and low specific speed (Ns =100~500) axial flow impeller.

[0170] The Pareto optimal solution of efficiency-pressure rise-noise is selected through parametric scanning (such as d / D = 0.3, 0.35, 0.4, 0.45, 0.5) combined with flow field simulation.

[0171] For additively manufactured impellers, d / D ≥ 0.35 is usually selected to ensure the printability of the support structure in the hub 10 area.

[0172] Design of mounting angle:

[0173] Wind tunnel tests on the NACA65 series airfoils have shown that a 28° decrease in mounting angle from root to tip optimizes lift-to-drag ratio, with a typical range of: , .

[0174] CFD simulation and experimental verification: In the case of an axial flow pump impeller, when the installation angle is linearly reduced from 40° to 20°, the efficiency η increases from 78% to 86%; the leakage loss at the tip 28 is reduced from 18% to 9%; and the stall angle of attack is delayed from 8° to 12°.

[0175] Manufacturing process and quality control of pit 23:

[0176] Precision machining technology:

[0177] Laser ablation: Suitable for high-hardness materials (such as titanium alloys), with an accuracy of ±0.02mm and a processing efficiency of 50-100 pits per second.

[0178] Chemical etching: used for stainless steel or aluminum alloys. The distribution of pits 23 is controlled by a mask. It has low cost but slightly lower accuracy (±0.05mm).

[0179] Coverage Control: Use CAD / CAM software to program the machining path, with a coverage error of ≤3%. For example, at a coverage of 30%, 150 to 200 dimples 23 (0.5 mm diameter) must be machined per square centimeter.

[0180] Manufacturing process and quality control of sawtooth 24:

[0181] Precision machining methods:

[0182] Electric discharge machining (EDM): Accuracy of ±0.02mm, suitable for high hardness alloys, but the cost is higher.

[0183] Laser cutting: high efficiency, suitable for stainless steel or titanium alloy, tooth pitch error ≤ 0.1mm.

[0184] Additive manufacturing: Complex serrations 24 can be formed in one piece, but post-processing and polishing are required (Ra ≤ 6.3 μm).

[0185] Tooth root reinforcement design: Tooth root fillet radius R = 0.1mm~0.3mm, to avoid stress concentration and improve fatigue life (can be extended by 20%~30%).

[0186] Performance verification and experimental data:

[0187] Wind tunnel test case:

[0188] Parameters: tooth height 2mm, tooth pitch 10mm, impeller speed 2500RPM.

[0189] Results: Noise dropped from 90dB to 83dB, a 7.8% decrease; efficiency increased by 3.5% (from 84% to 87%); and tip leakage was reduced by 12%.

[0190] CFD simulation conclusion: When the tooth height / tooth pitch ratio hp=0.2~0.3, the eddy kinetic energy attenuation rate is the largest and the noise reduction effect is the best.

[0191] The manufacturing process of the superhydrophobic coating 27 is as follows: additive manufacturing (SLM) post-processing, after impeller printing, sandblasting (Ra = 3-5 μm) → chemical activation (H2SO4 / H2O2 treatment) → PECVD coating deposition, with a total time of <24 hours.

[0192] According to the second embodiment, an impeller that meets the conditions of the first embodiment can be designed. This design method deeply integrates bionics, fluid mechanics and manufacturing technology through parameterized formulas and multi-physical field verification, thereby achieving a comprehensive improvement in the efficiency, life and stability of the impeller.

[0193] The above-described embodiments merely represent specific implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, and all such variations and improvements fall within the scope of protection of the present invention.

Claims

1. An industrial pump impeller comprising a hub and a plurality of blades arranged circumferentially of the hub, characterized in that: The blade comprises: The wing-shaped structure distributed radially along the hub has a chord length that decreases linearly from the root to the tip, and an installation angle that decreases from the root to the tip; The pressure surface of the blade is provided with an array of micro grooves, the direction of the micro grooves is at an angle to the main flow direction of the blade pressure surface, the micro grooves are located in the front 30% area of the blade pressure surface, and the direction of the micro grooves is at an angle of 15° to 25° to the axis of the hub; The suction surface of the blade is provided with a spiral groove and a pit. The spiral direction of the spiral groove is consistent with the rotation direction of the impeller. Along the chord length direction of the blade, the spiral groove is located in the last 20% area of the suction surface of the blade. The cross section of the spiral groove is semicircular. Each of the spiral grooves has a gradually expanding structure, so that the width of the outlet end of the spiral groove is three times the width of the inlet end. The pit is located in the middle 30% area of the suction surface. The pit is hemispherical and the pit coverage rate is 20% to 40%; The trailing edge of the blade is provided with serrations.

2. The industrial pump impeller according to claim 1, characterized in that The entire surface of the blade is covered with a super-hydrophobic coating.

3. A design method for an industrial pump impeller according to claim 1 or 2, characterized in that: The following steps are involved: S10. Basic geometric parameter design: Based on the flow rate Q, pressure rise ΔP and speed N, calculate the impeller outer diameter D and hub diameter d; Set the blade chord length distribution; Set the installation angle distribution; S20, pressure surface micro groove design: Design a micro-groove array in the 30% chord length area on the blade pressure surface; Micro-groove parameters: wavelength 0.2mm~0.5mm, depth 0.05mm~0.1mm; S30, suction surface spiral groove and pit design: In the 20% chord length area behind the suction surface, a spiral groove is designed that is consistent with the impeller's rotation direction; In the middle 30% chord length area of the suction surface, a hemispherical dimple array is arranged; S40, trailing edge serration design: Processing periodic triangular serrations on the trailing edge of the blade; S50, super hydrophobic coating process: Sandblasting pretreatment is performed on the entire surface of the blade; applying a superhydrophobic coating via plasma-enhanced chemical vapor deposition; S60, performance verification and optimization: Verify the flow field characteristics through CFD simulation. If the tip leakage is greater than 5% of the design flow rate Q, increase the spiral groove depth to 2mm~3mm. If the flow at the front edge of the pressure surface separates, increase the density of microgrooves; The experimental test of pressure rise ΔP and efficiency η requires η ≥ 85% and ΔP error ≤ 5%.

4. The design method of an industrial pump impeller according to claim 3, characterized in that: In the step S10: Satisfy the hub ratio d / D=0.3~0.5; Set the blade chord length distribution: from the hub to the blade tip in a linear proportion, the root chord length C root =0.15D, blade tip chord length C tip =0.08D; Set the installation angle distribution: root installation angle β root =40°±2°, blade tip installation angle β tip =20°±2°, transition according to linear law; In step S50: The thickness of the super-hydrophobic coating is 5 μm~20 μm, the contact angle is ≥150°, and the process gas is a mixture of hexamethyldisiloxane and oxygen.

5. The design method of an industrial pump impeller according to claim 4, characterized in that: In step S20, the direction of the micro-grooves is optimized by particle image velocimetry experiments so that the grooves match the direction of the local streamlines; In step S30, the pitch P of the spiral groove and the rotation speed N satisfy the relationship: 。

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