Impulse water turbine and bucket

Abstract

The application relates to the technical field of hydroelectric power generation, in particular to an impulse water turbine and a water bucket. The application comprises: a water-facing layer made of metal material; a backwater layer made of carbon fiber composite material; wherein the water-facing layer and the backwater layer are connected to form a double-bowl-shaped water bucket structure symmetrical along a water distribution blade. By combining the high wear resistance of the metal material with the high specific strength and high specific stiffness of the carbon fiber composite material, a runner water bucket blade with higher strength, higher anti-abrasion performance and lighter weight is formed. In the condition of high water head and much silt, the damage of water bucket deformation cracking and even broken bucket is avoided, and the service life of the water bucket is improved.

Description

Technical Field

[0001] This application relates to the field of hydropower technology, specifically to an impulse turbine and a water bucket. Background Technology

[0002] Impulse turbines are key machines for converting water resources into energy, especially at heads above 700 meters. As hydropower development moves towards higher heads and larger capacities, the hydraulic loads and operating conditions borne by turbine runners and their buckets are becoming increasingly demanding.

[0003] Currently, impulse turbine buckets are generally made of high-strength stainless steel through integral forging or casting. In rivers with high sediment content, especially those containing hard sediment, the high-speed jet carrying sediment particles causes severe impact and erosion on the bucket's upstream surface, easily leading to wear, deformation, or even failure of the cup-shaped curved surface. Simultaneously, to increase single-unit capacity, the runner diameter and bucket size are continuously increasing, with correspondingly higher rotational speeds. This means that the buckets bear not only extremely strong impact loads but also enormous centrifugal loads during operation. Under these extreme combined load conditions, traditional single-metal buckets face severe challenges: their excessive mass leads to a geometric increase in centrifugal stress, restricting further expansion of the runner size; their insufficient rigidity margin easily causes excessive deformation or high-frequency vibration of the bucket, affecting not only the accuracy of the flow channel profile and hydraulic efficiency but also posing a risk of fatigue cracking and even bucket breakage. Existing technologies that simply increase metal thickness to improve rigidity and erosion resistance are approaching the limits of material performance and will viciously exacerbate the centrifugal load problem.

[0004] Therefore, a brand-new water bucket structure design is urgently needed, which can significantly improve rigidity, reduce its own weight, and improve dynamic response characteristics while ensuring excellent anti-abrasion performance. This would break through the existing technical bottlenecks and meet the requirements for safe, stable, and efficient operation of impulse turbines under ultra-high head, ultra-large capacity, and harsh water quality conditions. Summary of the Invention

[0005] In view of this, the present application provides an impulse turbine and a water bucket to solve the problems of easy wear and breakage of the water bucket and short service life of existing impulse turbines.

[0006] A first aspect of this application provides an impulse turbine bucket, comprising:

[0007] The water-facing surface layer is made of metal.

[0008] The backwater surface layer is made of carbon fiber composite material;

[0009] The water-facing surface layer and the water-repellent surface layer are connected to form a double-bowl-shaped water bucket structure symmetrical along the water-dividing edge.

[0010] In one embodiment, the backwater surface layer is laid with carbon fibers of different lengths and directions in different areas of the water tank.

[0011] In one embodiment, the carbon fibers of different lengths include at least short carbon fibers with a length between several millimeters and 1 centimeter, and long carbon fibers with a length greater than 1 centimeter.

[0012] The short carbon fiber and the long carbon fiber have a tensile strength of not less than 4000 MPa and a tensile elastic modulus of not less than 290 GPa.

[0013] In one embodiment, the backwater surface layer is provided with long carbon fibers woven in the direction of the jet flow in the direction corresponding to the frontwater surface layer;

[0014] The region along the jet direction of the water-facing surface layer is the central region of the bowl-shaped concave surface on both sides of the water-dividing blade of the water bucket.

[0015] In one embodiment, the backwater surface layer is covered with short carbon fibers woven along the oblique force direction in the oblique jet region corresponding to the frontwater surface layer;

[0016] The oblique jet region of the water-facing surface layer is the outer edge region of the concave surface of the water bucket and the inner edge region adjacent to the water-dividing blade. The oblique force direction is the force direction when the water-facing surface layer of the water bucket intersects the jet obliquely.

[0017] In one embodiment, the backwater surface layer is covered with short carbon fibers woven circumferentially along the water bucket in the outlet centrifugal region and the root region of the water bucket corresponding to the frontwater surface layer.

[0018] The outlet centrifugal region of the water-facing surface layer is the area where the jet flows out of the water bucket under the action of centrifugal force.

[0019] In one embodiment, the water-dividing blade of the water bucket is integrally formed from carbon fiber composite material onto the back water surface layer. The back water surface layer has edge grooves extending inward on both sides, and the water-dividing blade has water-dividing blade grooves on both sides. The water-facing surface layer is snapped and fixed between the edge grooves and the water-dividing blade grooves.

[0020] In one embodiment, the water-facing surface layer and the back-facing surface layer are connected by an anchoring bolt. The anchoring bolt passes through the back-facing surface layer and is connected to the water-facing surface layer. The head of the anchoring bolt is equipped with a curved washer that fits the curved surface of the back-facing surface layer. The anchoring bolt is located in the back-facing groove of the water-dividing blade and / or the thick wall of the water bucket.

[0021] In one embodiment, the thicknesses of the upstream and downstream surfaces are determined based on the first-order natural frequency of the hydraulic characteristics, the jet pulsation impact damping ratio, the bucket-profile displacement / force transmission rate, the impeller pitch circle radius, and the circumferential thrust at the bucket root.

[0022] A second aspect of this application provides an impulse turbine, comprising: a hub, nozzles, and a plurality of water buckets, as provided in the first aspect of this application, evenly distributed on the hub.

[0023] The first aspect of this application provides an impulse turbine bucket, comprising a frontal surface layer made of metal and a backal surface layer made of carbon fiber composite material; wherein the frontal surface layer and the backal surface layer are connected to form a double-bowl-shaped bucket structure symmetrical along the water-dividing edge. By combining the high wear resistance of the metal material with the high specific strength and high specific stiffness of the carbon fiber composite material, a runner bucket blade with higher strength, higher wear resistance, and lighter weight is formed. Under high head and high sediment conditions, bucket deformation and cracking, or even bucket breakage, are avoided, thus improving the bucket's service life. Utilizing the high strength and load reduction of carbon fiber, the first-order natural frequency of the bucket is significantly increased, and the jet pulsation impact damping ratio is improved. This effectively solves the problems of insufficient rigidity and strength of large impulse turbine runner buckets under high head, high speed, and large size conditions, as well as easy wear and failure under high sediment conditions. It not only enables the design and manufacture of impulse turbines with larger outer diameters and higher rigidity, but also makes it possible to design and manufacture large buckets with larger size, greater thickness, larger outer diameter, and higher reliability.

[0024] It is understandable that the beneficial effects of the second aspect mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a three-dimensional structural schematic diagram of the water bucket of an impulse turbine provided in an embodiment of this application;

[0027] Figure 2 This is a diagram showing the correspondence between the distribution of carbon fibers in different regions of the water-facing layer and the backwater layer, provided in an embodiment of this application.

[0028] Figure 3 This is a schematic diagram of the motion trajectory of the impact jet relative to the water bucket provided in one embodiment of this application;

[0029] Figure 4 This is a schematic diagram of the cross-section of the bucket of an impulse turbine provided in an embodiment of this application;

[0030] Figure 5 This is a schematic diagram showing the connection between the water-facing surface layer and the water-returning surface layer through anchoring and limiting bolts according to an embodiment of this application;

[0031] Figure 6 This is a schematic flowchart of a method for determining the thickness of the water-facing and back-facing layers according to an embodiment of this application;

[0032] Figure 7 This is a schematic diagram of the structure of the impulse turbine provided in the embodiments of this application. Detailed Implementation

[0033] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0034] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0035] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0036] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0037] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0038] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0039] like Figure 1 As shown in the embodiment of this application, an impulse turbine bucket includes:

[0040] The water-facing surface layer 11 is made of metal.

[0041] The backwater layer 12 is made of carbon fiber composite material;

[0042] Among them, the water-facing surface layer 11 and the water-returning surface layer 12 are connected to form a double-bowl-shaped water bucket 1 structure symmetrical along the water-dividing blade 123.

[0043] In application, the water bucket 1 is a key component used to withstand the impact of water flow and convert water flow energy into mechanical energy. It is evenly distributed around the circumference of the hub of the impulse turbine. In this embodiment, the bucket blade is double-bowl shaped with a certain curvature and shape to adapt to the impact of water flow and energy conversion. The water-dividing blade 123 is located at the center of the water bucket 1, dividing the jet into two parts, which enter the two half-bowl structures of the water bucket 1 respectively.

[0044] In application, the metal material of the water-facing layer 11 can be high-strength stainless steel or forged steel, while the carbon fiber composite material of the backwater layer 12 can be an ultra-high-strength carbon fiber layer wound with fibers according to the hydraulic load characteristics of the water-facing impact jet. The thickness distribution of the two layers can be determined by the impact pressure of the jet, which is determined by the head Hw and flow rate Q, and the sediment gradation index, to ensure that the carbon fiber + metal double-layer composite water bucket 1 has both sufficient rigidity and strength, as well as good wear resistance and elastic plasticity, and a jet pulsation impact damping ratio. At the same time, the reasonable matching of the thicknesses δ1 of the carbon fiber layer and δ2 of the high-strength metal layer can improve the impact hydraulic performance of the water bucket 1 and the impeller as a whole, while ensuring high reliability and wear resistance, thus guaranteeing the hydraulic efficiency and operational safety of the water bucket 1 under ultra-high head and ultra-large capacity conditions.

[0045] This application combines the high wear resistance of metallic materials with the high specific strength and high specific stiffness of carbon fiber composites to form turbine runner blades 1 with higher strength, higher abrasion resistance, and lighter weight. Under high head and high sediment conditions, this avoids deformation, cracking, and even breakage of the turbine runner 1, thus improving its service life. By utilizing the high strength and load reduction of carbon fiber, the first-order natural frequency of the turbine runner 1 is significantly increased, and the jet pulsation impact damping ratio is improved. This effectively solves the problems of insufficient rigidity and strength of large impulse turbine runners 1 under high head, high speed, and large size conditions, as well as easy wear and failure under high sediment conditions. This not only enables the design and manufacture of impulse turbines with larger outer diameters and higher rigidity, but also makes it possible to design and manufacture large turbine runners 1 with larger size, greater thickness, larger outer diameter, and higher reliability.

[0046] In one embodiment, such as Figure 2 As shown, the backwater surface layer 12 has carbon fibers of different lengths and directions laid in different areas of the water tank 1.

[0047] In applications, the winding method and direction of carbon fiber are determined based on the jet impact load transfer on the upstream side and the flow impact load distribution on the downstream side. Specifically, the laying direction of the carbon fiber can be determined according to the force direction in different areas of the upstream side of water tank 1. The length, tensile strength, and tensile modulus of the carbon fiber are determined according to the magnitude of the force in different areas of the upstream side of water tank 1.

[0048] In application, the carbon fiber modulus, weaving direction and combination of long and short fibers on the back side of the water bucket 1 can be determined by the following four factors: (1) the hydraulic force characteristics of the jet on the front side of the water bucket 1, (2) the hydraulic force characteristics and centrifugal force of the flow around the back side, (3) the lightweight index of the water bucket 1, and (4) the requirements for the outer diameter and height expansion space under the condition of improved load on the outer edge of the hub.

[0049] This application embodiment achieves precise and customized design of material properties by directionally laying carbon fibers of different lengths and directions in different areas of the water tank 1. This design method can be specifically enhanced according to the differences in the actual jet impact force, centrifugal force, and complex hydrodynamic loads borne by each area, so that the main load-bearing direction of the material matches the main stress direction, thereby optimally utilizing the anisotropic potential of carbon fiber composite materials and maximizing the mechanical efficiency of the structure while reducing weight.

[0050] In one embodiment, the impact force Ft on the water-facing surface, the surface stress σ of the water bucket, and the centrifugal force Fc can be calculated. The length and direction of the limit switch can be determined by the direction and magnitude of the impact force Ft and the centrifugal force Fc.

[0051] In applications, the impact of water on the water-facing surface... ;

[0052] Where Ft represents the impact force of the water on the upstream side. For jet velocity, β is the velocity of the water flow when it leaves the bucket, and β is the deflection angle of the bucket. For traffic, The density is the water flow density.

[0053] In application, the surface stress of the water bucket σ=(Ft / A)≤σ 允许 ;

[0054] Where A is the effective force-bearing area of ​​the water bucket facing the impact.

[0055] In application, centrifugal force Fc = mω 2 r;

[0056] Where m is the mass of the water bucket, ω is the angular velocity of the impeller, and r is the radius of rotation or the pitch circle radius of the impeller.

[0057] In one embodiment, the carbon fibers of different lengths include at least short carbon fibers 121 with a length between several millimeters and 1 centimeter, and long carbon fibers 122 with a length greater than 1 centimeter.

[0058] The tensile strength of short carbon fiber 121 and long carbon fiber 122 is not less than 4000 MPa, and the tensile elastic modulus is not less than 290 GPa.

[0059] This application's embodiments, through the combined application of short and long fibers, ensure that the material can achieve both high macroscopic stiffness and large load transfer through long fibers, while utilizing short fibers to better fill complex curved surfaces and withstand localized complex stresses. The aforementioned tensile strength and elastic modulus guarantee, at the material level, that the water bucket structure can withstand ultra-high water head impact loads and high-speed rotating centrifugal loads, further improving the strength of the water bucket.

[0060] In one embodiment, the back surface layer 12 is provided with long carbon fibers 122 woven in the direction of the jet flow in the direction of the back water flow in the jet flow region 111 corresponding to the front surface layer 11.

[0061] Among them, the region 111 along the jet direction of the water-facing surface layer 11 is the central region of the bowl-shaped concave surface on both sides of the water-dividing blade 123 of the water bucket 1.

[0062] In application, one end of the water bucket 1 is the root for connecting the hub, and the other end is the top. The water-facing and water-repelling surfaces of the two semi-bowl structures of the water bucket 1 are both curved surfaces. The direction from the root to the top and following the curvature of the curved surface is defined as the direction of water flow in this embodiment. The direction perpendicular to the direction of water flow along the curved surface and around the water-dividing blade 123 is defined as the circumferential direction. The water flow direction in the central region of the bowl-shaped concave surface is the direction extending from one end of the water bucket 1 to the other along the curved surface of the center of the bowl-shaped concave surface.

[0063] This application embodiment greatly enhances the ability of the water bucket to resist impact deformation and fatigue failure by laying long carbon fibers along the water flow direction in the core area where the water bucket is subjected to the most severe impact from the positive jet.

[0064] In one embodiment, the backwater surface layer 12 is covered with short carbon fibers 121 woven along the oblique force direction in the oblique jet region 112 corresponding to the frontwater surface layer 11.

[0065] Among them, such as Figure 3 As shown, the oblique jet region 112 of the water-facing surface layer 11 is the outer edge region of the bowl-shaped concave surface of the water bucket 1 and the inner edge region adjacent to the water-dividing blade 123. The oblique force direction is the force direction when the water-facing surface layer 11 of the water bucket 1 intersects the impact jet 4 obliquely.

[0066] In application, the force direction of the outer edge region of the bowl-shaped concave surface of the water bucket 1 and the inner edge region of the adjacent water-dividing blade 123 is consistent with the circumferential direction of the water bucket 1. Here, the short carbon fibers 121 of the oblique jet region 112 can be laid in the circumferential direction to enhance the water bucket 1's resistance to oblique impact force.

[0067] This application embodiment reinforces the complex stress area where the jet collides obliquely with the water bucket using obliquely laid short fibers or woven fabrics. This effectively withstands the shear stress and multi-directional stress generated by fluid-structure interaction in this area, avoiding the mechanical weaknesses that occur with fibers in a single direction, thereby significantly improving the torsional resistance and overall durability of the water bucket's flank region.

[0068] In one embodiment, the back surface layer 12 is covered with short carbon fibers 121 circumferentially woven along the water bucket 1 in the outlet centrifugal region 113 and the water bucket root region 114 corresponding to the front surface layer 11.

[0069] The outlet centrifugal region 113 of the water-facing surface layer 11 is the area where the jet flows out of the water bucket 1 under the action of centrifugal force.

[0070] In application, short carbon fibers 121 in the outlet centrifugal region 113 and the root region 114 of the water bucket are woven circumferentially along the water bucket 1 to improve the water bucket 1's resistance to circumferential stress and prevent the water bucket 1 from breaking due to centrifugal force during high-speed rotation. These short fibers have relatively low strength and stiffness, but better molding properties, allowing them to be more evenly distributed in the complex circumferentially shaped matrix of the water bucket 1, filling complex shapes and corners, achieving uniform coverage and good adhesion.

[0071] This embodiment of the application lays fibers circumferentially at the water bucket outlet and root, two key locations subjected to enormous centrifugal tensile stress, aligning the fiber direction with the main direction of the centrifugal tensile stress. This effectively constrains radial deformation and directly bears circumferential tensile force, effectively preventing structural cracking or excessive deformation of the water bucket due to centrifugal force under high-speed rotation.

[0072] In one embodiment, such as Figure 4 As shown, the water-dividing blade 123 of the water tank 1 is integrally formed from carbon fiber composite material on the back water surface layer 12. The back water surface layer 12 has edge grooves 124 extending inward on both sides. The water-dividing blade 123 has water-dividing blade grooves 125 on both sides. The water-facing surface layer 11 is snapped and fixed between the edge grooves 124 and the water-dividing blade grooves 125.

[0073] In application, by setting special stops and grooves on the inner sides of the upper and lower water outlet edges of the carbon fiber layer on the back surface of the water bucket, the metal front surface layer is directly assembled and fixed in the water bucket 1 by means of stops and grooves using the elastic prestress of the carbon fiber layer.

[0074] In this embodiment, the water-dividing blade 123 is integrally formed and mates with the edge groove 124 to achieve a secure installation of the metal water-facing surface. The elasticity of carbon fiber material is utilized to achieve a tight connection, resulting in a simple and reliable structure.

[0075] In one embodiment, such as Figure 5 As shown, the water-facing surface layer 11 and the back-facing surface layer 12 are connected by an anchoring limit bolt 126. The anchoring limit bolt 126 passes through the back-facing surface layer 12 and is connected to the water-facing surface layer 11. The head of the anchoring limit bolt 126 is equipped with a curved gasket 127 that fits the curved surface of the back-facing surface layer 12. The anchoring limit bolt 126 is located in the back-facing groove of the water-dividing blade 123 and / or the thick wall of the water bucket 1.

[0076] In application, the anchoring limit bolt 126 is made of high-strength stainless steel, the same material as the water-facing surface of the bucket, and is connected to the internal thread of the carbon fiber integrated perforated riser. Considering the influence of the protrusions on the back surface of the bucket on the jet and the hydraulic performance of the subsequent bucket, the limit bolt is set at locations such as the groove on the back surface of the water-dividing blade 123 and the upper and lower thick walls, and is symmetrically arranged in the upper and lower buckets. The curved gasket 127 is formed according to the curved surface of the distribution position of the anchoring point on the back of the bucket, that is, it maintains the same curved surface shape as the bucket shape at that location, so as to fit the back surface of the bucket without gaps.

[0077] This embodiment employs anchor bolts with curved gaskets 127 for fastening in specific thick-walled areas. This provides a strong normal preload, ensuring that the metal and composite material layers remain tightly bonded and deform collaboratively under complex loads. Placing the bolts in concealed locations such as the grooves of the water divider 123 minimizes their interference with the flowing water, demonstrating a deep integration of structural design and hydraulic performance requirements.

[0078] In one embodiment, the thicknesses of the upstream surface layer 11 and the downstream surface layer 12 are determined based on the first-order natural frequency of the hydraulic characteristics, the jet pulsation impact damping ratio, the bucket-profile displacement / force transmission rate, the impeller pitch circle radius, and the circumferential thrust at the bucket root.

[0079] In application, the water-facing layer 11 can be configured to occupy approximately 1 / 3 of the half-bowl-shaped thickness of the entire water tank 1, and the water-repelling layer 12 can occupy approximately 2 / 3 of the half-bowl-shaped thickness of the entire water tank 1. This proportion can also be optimized based on the thickness determination method of this application embodiment to achieve higher strength in the water tank 1.

[0080] In applications, such as Figure 6 As shown, the initial thickness of the carbon fiber on the back side is set to δ1, and the thickness of the high-strength steel on the front side is set to δ2. Then, the mass m of the carbon fiber layer is calculated. δ1 The high-strength steel on the water-facing surface has a mass of m. δ2 And calculate the total mass of the water bucket m1=m δ1 +m δ2 The water bucket's lightweight load reduction factor a = m0 - m1 / m0 needs to reach a set value, such as 30%. Then, assuming the water bucket's static stiffness K remains constant, the natural frequency f = (K / m) is calculated. 1 / 2 / 2π. After obtaining the natural frequency f, the first-order natural frequency of the water bucket is further calculated as f1 = f0 / (1-a). 1 / 2 Damping ratio of bucket blades ζ=C / Ce, bucket-hub displacement / force transmission coefficient T d T f Based on Td, Tf can calculate the bucket-profile displacement / force transmissivity, runner pitch circle radius, and bucket root circumferential thrust (i.e., hub circumferential thrust). By setting constraints such as increasing the bucket's first-order natural frequency f1 by a certain percentage (e.g., 20%), achieving a certain bucket blade damping ratio ζ (e.g., 300%), and decreasing the bucket-profile displacement / force transmissivity within a certain range (e.g., 1%-6%), the initial thickness of the carbon fiber on the back surface (δ1) and the thickness of the high-strength steel on the front surface (δ2) are iteratively optimized until a better value is reached. This results in an increase in the runner pitch circle radius and a decrease in the bucket root circumferential thrust.

[0081] Where Z represents the number of nozzles, and Hw represents the head of the impulse turbine. T The circumferential torque generated by the water thrust is given by m0, where m0 is the original weight of the all-metal water bucket, C is the viscous damping coefficient of the system, and Ce is the critical damping.

[0082] This application embodiment correlates the thickness parameters of the upstream surface layer 11 and the downstream surface layer 12 with the first-order natural frequency of the hydraulic characteristics, the jet pulsation impact damping ratio, the water bucket-profile displacement / force transmission rate, the impeller pitch circle radius, and the circumferential thrust at the root of the water bucket. This ensures that the final determined water bucket thickness is not only safe in terms of static strength, but also optimal in terms of dynamic response, thereby fundamentally guaranteeing the water bucket's operating efficiency, stability, and ultra-long service life under extreme working conditions.

[0083] Example 1

[0084] This application's embodiment uses a water head of 800m, a capacity of 800MW, and high sediment content (5~8kg / m³). 3 Under conditions where the silt hardness is 7-8 (Mohs scale), the impact turbine bucket adopts a double-layer composite structure of "high-strength stainless steel water-facing surface + carbon fiber back-facing surface" as described in this application embodiment. The optimal performance is achieved through material matching design and mechanical calculations. The specific implementation design method and performance parameters are as follows:

[0085] I. Core Operating Parameters and Design Constraints

[0086] 1. Hydraulic parameters

[0087] Jet velocity: ;

[0088] Single-nozzle jet power: approximately 200MW (4-nozzle configuration), jet diameter ≈ 0.6m;

[0089] Impact pressure: Peak pressure at the center = 250MPa (including dynamic pressure superposition), exhibiting a Gaussian distribution attenuation;

[0090] Centrifugal force: with a rotor diameter of 7.5m and a rotation speed of 300r / min, the centrifugal force of a single water bucket is approximately 1.8MN;

[0091] 2. Performance Objectives

[0092] Strength safety factor ≥ 1.3 (resistance to combined impact and centrifugal loads);

[0093] Maximum deformation ≤ 0.1mm (to avoid distortion of the flow channel profile);

[0094] Wear resistance life ≥ 6 years (annual wear amount ≤ 1mm);

[0095] II. Structural Parameter Design and Calculation

[0096] 1. High-strength stainless steel layer (17-4PH) on the water-facing side;

[0097] Material properties: Yield strength 1100MPa, elastic modulus 210GPa, hardness HB350, abrasion resistance coefficient (relative value) 1.0;

[0098] Thickness calculation basis:

[0099] Wear resistance constraint: Under conditions with a lot of mud and sand, the annual wear of stainless steel is about 1.2mm (with a sand content of 5kg / m). 3 The design wear allowance is 6mm (6-year lifespan), and the base thickness must be ≥ 8mm (including machining allowance).

[0100] Impact strength constraint: jet center pressure 250MPa, according to the bending strength formula (Support span 50mm, allowable stress 450MPa), the calculated thickness is ≥ 7.2mm;

[0101] Interface protection: The carbon fiber layer must be kept out of the way, with a minimum thickness of ≥ 8mm;

[0102] Recommended thickness: t metal = 10mm (balancing wear resistance, lifespan, and strength safety).

[0103] 2. Backwater surface carbon fiber layer (T800 grade carbon fiber / epoxy resin)

[0104] Material properties: tensile strength 5490 MPa, elastic modulus 294 GPa, density 1.6 g / cm³ 3 The fiber volume fraction can be designed to be 60% - 70%.

[0105] Thickness calculation basis:

[0106] Centrifugal force load: The centrifugal force of a single water bucket is 1.8MN, and the carbon fiber bears 70% of the load (1.26MN), according to the tensile strength formula. (Allowable stress 3000MPa), required cross-sectional area ≈ 420mm² 2 The corresponding thickness is ≥8.4mm (500mm in the width direction of the water bucket).

[0107] Stiffness coordination: The equivalent elastic modulus of the composite structure needs to be ≥260GPa (to avoid overall deformation exceeding 0.1mm). According to the theoretical calculation of the laminate, the thickness of the carbon fiber layer needs to be ≥10mm.

[0108] Recommended parameters:

[0109] Thickness: t carbon fiber = 12mm;

[0110] Fiber volume fraction: 65% (balancing strength and process feasibility);

[0111] Fiber orientation: Radial (0°) accounts for 70% (responding to centrifugal stretching) + Circumferential (90°) accounts for 30% (inhibiting radial fiber buckling).

[0112] III. Performance Improvement Calculation Results

[0113] (a) Improvements in mechanical properties are shown in Table 1:

[0114] Table 1

[0115]

[0116] Calculation basis: ANSYS laminated plate element simulation was used, with loading conditions of 250MPa impact compressive stress + 180MPa centrifugal tensile stress.

[0117] (ii) Improvement of hydraulic performance

[0118] Efficiency improvement: Due to the reduction of deformation from 0.18mm to 0.07mm, the accuracy of the flow channel profile is improved, the jet deflection angle error is reduced to ≤ 0.5°, and the hydraulic efficiency is improved by about 1.2% - 1.5%.

[0119] (Annual increase in power generation of 800MW unit ≈ )

[0120] Reduced pressure pulsation: The high damping characteristics of carbon fiber (loss factor 0.02) reduce the vibration amplitude of the water bucket from 0.15mm to 0.05mm and the pressure pulsation coefficient from 3.5% to 1.8%, thereby reducing unit vibration and noise.

[0121] (III) Improved resistance to silt and sand abrasion

[0122] Metal layer reinforcement effect: The wear resistance coefficient of the 10mm stainless steel layer (surface laser cladding WC-Co coating, HRC65) is increased to 3.5 (relative to the benchmark stainless steel), the annual wear amount is reduced from 1.2mm to 0.34mm, and the wear resistance life is extended from 5 years to 17 years (based on a safe wear amount of 6mm).

[0123] Advantages of the composite structure: The carbon fiber layer does not come into contact with water flow, avoiding direct wear, and the metal layer has a redundant thickness (10mm) to withstand long-term abrasion, eliminating the need for frequent downtime maintenance.

[0124] IV. Key Process Safeguards

[0125] Interface bonding: The stainless steel backing is sandblasted (Ra = 8μm) and treated with silane coupling agent. After the carbon fiber prepreg is laid, it is cured at 120℃ and 0.8MPa pressure to ensure that the interface shear strength is ≥80MPa.

[0126] Edge transition: The carbon fiber layer gradually thins from the center to the edge (12mm - 5mm), reducing the stress concentration factor to below 1.3.

[0127] Quality inspection: Ultrasonic C-scan is used to detect internal defects (porosity ≤1%) in the carbon fiber layer to ensure stable fatigue performance.

[0128] Implementation results and performance indicators (expected) of this example.

[0129] This double-layer composite structure (10mm high-strength stainless steel + 12mm T800 carbon fiber) achieves a 191% increase in strength, a 31% increase in stiffness, a 240% extension in wear resistance life, and a more than 1.2% increase in hydraulic efficiency under conditions of 800m head, 800MW capacity, and high sediment load, fully meeting the safety and economic requirements under extreme conditions. Its core advantage lies in balancing wear resistance and lightweight requirements through the functional division of materials (metal wear resistance + carbon fiber load-bearing capacity), providing a feasible structural upgrade solution for large-capacity impulse turbines.

[0130] This application also provides an impulse turbine, such as... Figure 7 As shown, it includes a hub 2, a nozzle 3, and a plurality of water buckets 1 as described in any of the above embodiments of this application, evenly distributed on the hub 2.

[0131] In application, the hub 2 is an intermediate component connecting the water buckets of an impulse turbine runner and the main shaft, serving to transmit torque and support the water buckets. It has a disc-shaped or hub-shaped structure with a certain thickness and diameter to meet strength and rigidity requirements. It has a central hole for mounting with the main shaft and is fixed to the water buckets in this embodiment along its circumference using welding, bolts, tenons, or other methods. The hub needs to withstand the enormous impact force and torque transmitted from the water buckets and is generally forged from high-strength alloy steel.

[0132] In application, the main function of nozzle 3 is to convert the pressure energy of water into kinetic energy, forming an impact jet with a certain pressure and velocity, which impacts the turbine runner, causing the runner to rotate, thereby converting water energy into mechanical energy. The water distribution coil 5 is a ring-shaped high-pressure water pipe from the water pressure steel pipe of the impulse turbine to the center line elevation of the impulse turbine runner, and leads out the above-mentioned 4 or 6 nozzles evenly distributed, providing strong water pressure to form an impact jet 4 after passing through the nozzles (with internal nozzle needle adjustment), driving the water bucket to drive the hub to rotate at high speed.

[0133] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A water bucket for an impulse turbine, characterized in that, include: The water-facing surface layer (11) is made of metal. The backwater surface layer (12) is made of carbon fiber composite material; The water-facing surface layer (11) and the water-repellent surface layer (12) are connected to form a double-bowl-shaped water bucket structure symmetrical along the water-dividing blade (123); The backwater surface layer (12) has carbon fibers of different lengths and directions laid in different areas of the water tank (1); The backwater surface layer (12) is covered with long carbon fibers (122) woven in the direction of the jet flow in the region (111) corresponding to the frontwater surface layer (11). Among them, the region (111) in the direction of the jet of the water-facing surface layer (11) is the central region of the bowl-shaped concave surface on both sides of the water-dividing blade (123) of the water bucket (1).

2. The impulse turbine bucket as described in claim 1, characterized in that, The short carbon fiber (121) and the long carbon fiber (122) have a tensile strength of not less than 4000 MPa and a tensile elastic modulus of not less than 290 GPa.

3. The impulse turbine bucket as described in claim 1, characterized in that, The backwater surface layer (12) is covered with short carbon fibers (121) woven along the oblique force direction in the oblique jet region (112) corresponding to the frontwater surface layer (11). The oblique jet region (112) of the water-facing surface layer (11) is the outer edge region of the bowl-shaped concave surface of the water bucket (1) and the inner edge region of the adjacent water-dividing blade (123). The oblique force direction is the force direction when the water-facing surface layer (11) of the water bucket (1) intersects with the jet obliquely.

4. The impulse turbine bucket as described in claim 1, characterized in that, The backwater surface layer (12) is covered with short carbon fibers (121) circumferentially woven along the water bucket (1) in the outlet centrifugal region (113) and the root region (114) of the water bucket, which correspond to the frontwater surface layer (11). The outlet centrifugal region (113) of the water-facing surface layer (11) is the area where the jet flows out of the water bucket (1) under the action of centrifugal force.

5. The impulse turbine bucket as described in claim 1, characterized in that, The water-dividing blade (123) of the water bucket (1) is integrally formed from carbon fiber composite material on the back water surface layer (12). The back water surface layer (12) has edge grooves (124) extending inward on both sides. The water-dividing blade (123) has water-dividing blade grooves (125) on both sides. The water-facing surface layer (11) is snapped and fixed between the edge grooves (124) and the water-dividing blade grooves (125).

6. The impulse turbine bucket as described in claim 1, characterized in that, The water-facing surface layer (11) and the back-facing surface layer (12) are connected by an anchoring limit bolt (126). The anchoring limit bolt (126) penetrates the back-facing surface layer (12) and is connected to the water-facing surface layer (11). The head of the anchoring limit bolt (126) is equipped with a curved gasket (127) that fits the curved surface of the back-facing surface layer (12). The anchoring limit bolt (126) is located in the back-facing groove of the water-dividing blade (123) and / or in the thick wall of the water bucket (1).

7. The impact turbine bucket according to claim 1, characterized in that, The thicknesses of the water-facing surface layer (11) and the water-returning surface layer (12) are determined based on the first-order natural frequency of the hydraulic characteristics, the jet pulsation impact damping ratio, the water bucket-profile displacement / force transmission rate, the impeller pitch circle radius, and the circumferential thrust at the root of the water bucket.

8. An impulse turbine, characterized in that, It includes a hub (2), a nozzle (3), and a plurality of impact turbine buckets as described in any one of claims 1 to 7, evenly distributed on the hub (2).

Images