Double-layer tile impact type runner bucket blade and impact type water turbine

Abstract

The invention provides a double-layer tile impact type runner bucket blade and an impact type water turbine, and belongs to the technical field of hydroelectric generation. The thickness of the downstream face bucket blade is larger than that of the upstream face bucket blade; the water diversion blades are arranged on the upstream face bucket blades, and the upstream face bucket blades are symmetrically arranged on the two sides of the water diversion blades; the elastic small supporting column groups are clamped between the upstream face bucket blade and the downstream face bucket blade, and the elastic small supporting column groups are symmetrically arranged on the two sides of the water diversion blade; the elastic small supporting column group comprises a plurality of first elastic small supporting columns arranged in the first area and a plurality of second elastic small supporting columns arranged in the second area, the jet flow pressure of the first area is larger than that of the second area, the diameter of the first elastic small supporting columns is larger than that of the second elastic small supporting columns, and the heights of all the small supporting columns in the elastic small supporting column group are equal. Concentrated stress and local deformation of the single-layer metal water bucket caused by high-speed jet flow and silt can be reduced, and rigidity, strength, impact resistance and abrasion resistance of the upstream face of the water bucket are improved.

Description

Technical Field

[0001] This invention belongs to the field of hydropower technology, and more specifically, relates to a double-layered tile impeller and an impeller turbine. Background Technology

[0002] Under high head conditions, especially those exceeding 700 m, impulse turbines are generally used. However, the insufficient wear resistance and rigidity of the impulse turbine runner under high-speed jets and high-capacity, high-speed operation with high sediment content present design, operational, and manufacturing challenges for impulse turbines. Particularly when the high-speed jet contains hard debris such as sand and gravel, it causes severe impact and erosion on the runner's bucket face. Over time, this can lead to indentation, damage, deformation, and even failure of the bucket's inner bowl-shaped surface, affecting not only the efficiency of the impulse runner but also the safety of the buckets and the turbine itself.

[0003] Therefore, high sediment loads have always posed a serious threat to the safe operation of large-capacity, ultra-high head (>800 m) impulse turbines. Furthermore, due to the irregularity of sediment loads in the flow channel, there has been no good solution to its adverse effects, which greatly restricts the application of impulse turbines in high sediment load and higher head conditions.

[0004] Meanwhile, under the dual conditions of siltation and large capacity, the rotational speed of impulse turbines is increasing, and the size of the buckets is also growing. With the combined effects of increased runner diameter, rising speed, and larger bucket dimensions, the rigidity and strength of traditional bucket designs are insufficient to meet the requirements for long-term safe and stable operation of impulse turbines. Under high head and siltation conditions, this can easily lead to deformation, cracking, and even severe damage such as bucket breakage. Summary of the Invention

[0005] The purpose of this invention is to provide a double-layered impeller blade and an impeller turbine, so as to improve the impeller blade's resistance to silt impact and wear resistance under high head and large capacity operation conditions in rivers with a lot of silt, and to greatly improve the rigidity of the impeller blade.

[0006] To achieve the above objectives, a first aspect of the present invention provides a double-layer tile impact-type impeller blade, comprising: Water-facing side of the leaf; The thickness of the back-side bucket blade is greater than the thickness of the front-side bucket blade; A water-dividing blade is disposed on the water-facing bucket blade, the water-facing bucket blade being symmetrically arranged on both sides of the water-dividing blade; and, A group of flexible small support pillars is sandwiched between the water-facing blade and the water-repellent blade, and the group of flexible small support pillars is symmetrically arranged on both sides of the water-dividing blade; the group of flexible small support pillars includes a plurality of first flexible small support pillars arranged in a first region and a plurality of second flexible small support pillars arranged in a second region, the jet pressure in the first region is greater than that in the second region, the diameter of the first flexible small support pillars is greater than that of the second flexible small support pillars, and the height of each small support pillar in the group of flexible small support pillars is equal.

[0007] Furthermore, the two end faces of each small support in the elastic small support group are consistent with the curved shape of the water-facing and water-repellent bucket blades at their respective locations.

[0008] Furthermore, both the upstream and downstream bucket blades are provided with positioning stop grooves on opposite sides, and the two ends of the elastic small support group are engaged with the positioning stop grooves.

[0009] Furthermore, the depth of the positioning stop groove is less than 2 mm.

[0010] Furthermore, the spacing between two adjacent first elastic small pillars is 30-40 mm, and the spacing between two adjacent second elastic small pillars is 50-60 mm.

[0011] Furthermore, the jet pressure in the first region is 200-250 MPa, and the jet pressure in the second region is 50-100 MPa.

[0012] Furthermore, the thickness of the water-facing bucket blade is 8-10 mm, the thickness of the water-repellent bucket blade is 25-35 mm, and the height of each small support in the elastic small support group is 6-8 mm.

[0013] Furthermore, the water-facing bucket blades are made of high-chromium cast iron or WC-Co metal-ceramic composite material, and the water-returning bucket blades are made of 17-4PH precipitation-hardening stainless steel or maraging steel; the elastic small support group is made of TC4 titanium alloy or high-strength spring steel or high-strength SMC plastic material.

[0014] Furthermore, the edges of the water-facing bucket blade and the water-returning bucket blade are fixed and sealed by welding or clamping.

[0015] A second aspect of the present invention provides an impulse turbine, comprising: The wheel hub has a mounting hole in its center; Multiple double-layered tile impact bucket blades as described in any of the above claims are connected in a ring array to the hub; and, Multiple nozzles are arranged in a ring array on the outer periphery of the hub to spray impact jets onto the double-layered tile impact bucket blades.

[0016] Compared with the prior art, the present invention has the following technical effects: This invention relates to a double-layered tile-type impeller bucket blade. Through the elastic stress distribution of the silt-laden jet impact load on the water-facing side of the impeller blade, which has a thinner thickness, combined with the thicker back-facing side blade and a distributed group of small elastic supports located between them, the frequent jet load of the impeller turbine is evenly transmitted and rationally distributed through this double-layered thick-thin tile structure. This significantly reduces the concentrated stress and local deformation of the single-layered metal bucket caused by the high-speed jet and silt, greatly improving the rigidity, impact resistance, and erosion resistance of the water-facing side of the bucket. The impeller bucket blade of this invention can well adapt to the operating conditions of impellers with higher heads (e.g., 1000 m class) and larger capacities (e.g., 700 MW and above). The double-layer tile impact turbine blade of the present invention can effectively solve the problems of insufficient rigidity and strength of large impact turbines with high head, high speed and large size, as well as long-term resistance to silt wear. It can not only design and manufacture impact turbines with larger outer diameter, but also make it possible to make large buckets with larger size, greater thickness, larger outer diameter and higher reliability.

[0017] The impulse turbine of the present invention, which adopts the above-mentioned double-layer tile impulse runner and bucket blades, also has the above-mentioned advantages, which will not be repeated here. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the structure of an impulse turbine provided in an embodiment of the present invention; Figure 2 This is a side perspective structural diagram of a double-layer tile impact-type rotary bucket blade provided in an embodiment of the present invention; Figure 3 A cross-sectional structural schematic diagram of a double-layer tile impact bucket blade provided in an embodiment of the present invention; Figure 4 This is a front view structural diagram of a double-layer tile impact bucket blade provided in an embodiment of the present invention; Figure 4 The upper part of the water-facing blades is not shown; Figure 5This is a schematic diagram of the partitioning of a double-layer tile impact bucket blade provided in an embodiment of the present invention.

[0020] The figures in the diagram are labeled as follows: 1. Wheel hub, 2. Rotary bucket blade, 3. Nozzle, 4. Impact jet, 201. Water-facing bucket blade, 202. Water-repellent bucket blade, 203. Water-dividing blade, 204. Flexible small support group, 2041. First flexible small support, 2042. Second flexible small support. Detailed Implementation

[0021] To make the technical problem to be solved, the technical solution, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0022] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0023] The terms "first" and "second" are used for descriptive purposes only, to distinguish objects, such as substances, from one another, and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. For example, without departing from the scope of embodiments of the invention, a first XX may also be referred to as a second XX, and similarly, a second XX may also be referred to as a first XX. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0024] This invention provides an impulse turbine and a double-layered tile impulse runner with bucket blades, the structure of which is as follows: Figure 1-5 As shown.

[0025] Please see Figure 1 This invention provides an impulse turbine, comprising: a hub 1, multiple double-layered tile impulse runner blades 2, and multiple nozzles 3. The hub 1 has a mounting hole at its center; the multiple double-layered tile impulse runner blades 2 are connected in a ring array to the edge of the hub 1; the multiple nozzles 3 are arranged in a ring array on the outer periphery of the hub 1 for spraying impulse jets 4 onto the double-layered tile impulse runner blades 2.

[0026] In this embodiment, the hub 1 is an intermediate component connecting the water buckets (i.e., the double-layered impact turbine blades 2) of the impulse turbine runner and the main shaft, serving to transmit torque and support the water buckets. The hub 1 has a disc-shaped or hub-shaped structure with a certain thickness and diameter to meet strength and rigidity requirements. It has a mounting hole in its center for mounting with the main shaft and is fixed to the double-layered impact turbine blades 2 along its circumference by welding or bolting. The hub 1 needs to withstand the enormous impact force and torque transmitted from the water buckets and is generally forged from high-strength alloy steel. Its working principle is as follows: high-speed water flow impacts the double-layered impact turbine blades 2 of the turbine, and the water buckets generate rotational torque due to the force of the water flow. This torque is transmitted to the main shaft through the hub 1, thereby driving the generator rotor to rotate and converting water energy into electrical energy.

[0027] In this embodiment, the main function of nozzle 3 is to convert the pressure energy of water into kinetic energy, forming a high-speed impact jet 4 that impacts the turbine hub 1, causing the hub 1 to rotate, thereby converting water energy into mechanical energy. Nozzle 3 consists of a nozzle body, a nozzle needle, and a throttling cone, among other parts. The structure of nozzle 3 is an existing structure, and its specific connections will not be detailed further. The nozzle body is the channel for water flow, and its shape and size affect the speed and direction of the water flow. The nozzle needle is located inside the nozzle body; by adjusting the position of the nozzle needle, the flow area of ​​the nozzle can be changed, thereby controlling the water flow rate and jet velocity. The throttling cone is used to improve the flow characteristics of the water flow and reduce energy loss. Specific working principle: When pressurized water enters nozzle 3, due to the contraction of nozzle 3, the water flow velocity gradually increases, and the pressure gradually decreases, converting the water pressure energy into kinetic energy, forming a high-speed impact jet 4. The high-speed impact jet 4 impacts the double-layered impact impeller blades 2 on the hub 1, causing the hub 1 to rotate, which in turn drives the generator to generate electricity.

[0028] In this embodiment, the impact jet 4 is a water flow with a certain pressure and velocity. A high-speed impact jet 4 is formed through a nozzle 3 and other devices, impacting the turbine hub 1 and causing it to rotate and perform work, thereby converting water energy into mechanical energy. The speed of the impact jet 4 can reach tens of meters per second or even higher, so as to effectively impact the hub 1 and transfer energy.

[0029] In this embodiment, the double-layered tile impact impeller blade 2 is a key component used to withstand the impact of water flow and convert water flow energy into mechanical energy. It is evenly distributed along the circumference of the hub 1. The double-layered tile impact impeller blade 2 is double-bowl-shaped or spoon-shaped, with a certain curvature and shape to adapt to the impact of water flow and energy conversion.

[0030] The structure of the double-layer tile impact impeller blade 2 is as follows: Figure 2-4As shown, the system includes an upstream bucket blade 201, a downstream bucket blade 202, a water-dividing blade 203, and a group of elastic small support pillars 204. The thickness of the downstream bucket blade 202 is greater than the thickness of the upstream bucket blade 201. The water-dividing blade 203 is disposed on the upstream bucket blade 201, and the upstream bucket blade 201 is symmetrically arranged on both sides of the water-dividing blade 203. The group of elastic small support pillars 204 is sandwiched between the upstream bucket blade 201 and the downstream bucket blade 202, and the group of elastic small support pillars 204 is symmetrically arranged on both sides of the water-dividing blade 203. The group of elastic small support pillars 204 includes a plurality of first elastic small support pillars 2041 disposed in a first region and a plurality of second elastic small support pillars 2042 disposed in a second region. The jet pressure in the first region is greater than that in the second region. The diameter of the first elastic small support pillars 2041 is greater than the diameter of the second elastic small support pillars 2042. The height of each small support pillar in the group of elastic small support pillars 204 is equal.

[0031] The water-facing blade 201 and the water-repellent blade 202 have identical semi-bowl-shaped water buckets. The water-dividing blade 203 is located at the center of the water bucket and on the centerline of the impact jet 4. When high-speed water is ejected from the nozzle 3 and impacts the water-dividing blade 203 of the water bucket, the impact jet 4 is split into two parts, which enter the two halves of the water bucket respectively. During the flow of water within the water bucket, the speed and direction of the water flow change due to the shape and curvature of the water bucket, thus generating an impact force on the water bucket. This impact force drives the water bucket to rotate through the hub 1, thereby converting the kinetic energy of the water flow into mechanical energy. The water bucket is generally made of high-strength, high-toughness materials, such as stainless steel, to withstand the impact and wear of high-speed water flow.

[0032] In this embodiment, the water-facing blade 201 has a relatively thin thickness. It forms a water-facing curved surface with both strength and impact elasticity through a group of elastic small support pillars 204 between it and the thicker water-returning blade 202. This allows the load of the impact jet 4 from the water-facing surface of the thin blade (i.e., the water-facing blade 201) to be transferred through the elastic small support pillars 204 to the entire semi-bowl-shaped curved surface of the thick blade (i.e., the water-returning blade 202). The elastic small support pillars 204 can be made of the same forged steel as the water bucket or other high-strength elastic materials (such as high-strength SMC plastic materials), and are formed with a certain elastic coefficient through appropriate height (h / mm) and diameter (d / mm) combinations. The small support pillars are combined and distributed according to the hydraulic characteristics of the water bucket's water-facing jet and the load intensity, forming a cluster of small support pillars with a shape completely consistent with the water bucket's semi-bowl shape. Preferably, the two end faces of each small support are matched with the curved shapes of the water-facing blade 201 and the water-repellent blade 202 at their specific locations, so as to avoid stress concentration caused by the mismatch in shape between the elastic small support and the double-layer tiles.

[0033] In this embodiment of the invention, positioning grooves are provided on opposite sides of the water-facing blade 201 and the water-returning blade 202, and the two ends of the elastic small support group 204 are engaged with the positioning grooves. Preferably, the depth of the positioning grooves is less than 2 mm, so as to satisfy the positioning and engaging without reducing the strength of the thick and thin tile blades. That is, the very shallow (<2 mm) positioning grooves located on the thick and thin tile surfaces are symmetrically arranged on the thick and thin tile surfaces, and an interference fit can be used to position and limit the elastic small support group 204 between the double-layer tiles. The elastic deformation of the thin tile needs to be controlled within the allowable range (e.g., maximum deflection <0.2 mm) to maintain the streamlined profile of the water bucket and ensure the jet energy conversion efficiency.

[0034] In this embodiment, the water-facing blade 201 and the water-returning blade 202, i.e., the edges of the thin and thick tiles, can be connected by butt welding or flangeless sealing clamps to form an integral blade structure. The thick and thin tiles, along with the internal elastic small support group 204 of equal height but unequal diameter, are connected by welding or clamps through the positioning stop groove between the two layers of tiles to form a complete and robust integral water bucket. The elastic small support group 204 is firmly combined with the thick and thin tiles through embedded grooves, and maintains its distribution position and stress stability under the high-speed rotation of various impact impellers, extreme conditions of silt impact, and strong centrifugal force.

[0035] In this embodiment, the division between the first and second regions is based on the magnitude of the jet pressure at corresponding positions in the water bucket. The jet pressure in the first region is 200-250 MPa, and the jet pressure in the second region is 50-100 MPa. The spacing between two adjacent first elastic support pillars 2041 in the first region is 30-40 mm, and the spacing between two adjacent second elastic support pillars 2042 in the second region is 50-60 mm. Figure 5 As shown, area A + area C is the first area, i.e., the central area; area B + area D is the second area, i.e., the edge area.

[0036] Under extreme operating conditions with larger capacities (e.g., >500 MW), higher heads (e.g., 1000 m), and higher sediment loads, the buckets of impulse turbines are subjected to high-frequency pulse jet impact forces (peak pressures can reach hundreds of MPa), enormous centrifugal forces (increasing quadratically with increasing speed), abrasion from high-speed sediment-laden water flow (wear rate increases significantly when sediment hardness is >6 on the Mohs scale), and fatigue failure due to stress concentration. The impulse turbine employing the "double-layer thick and thin tile + inner lining elastic small support group" structure of this invention can improve the strength, rigidity, and abrasion resistance of the buckets.

[0037] The strength failure of the buckets in an impulse turbine mainly stems from two factors: first, the local peak stress in the jet impact zone (which may exceed the material's yield strength); and second, fatigue cracks under high-frequency impact (especially at stress concentration points, such as the cutting edge and the water flow turning zone). The principle behind the strength improvement of the impulse turbine using the "double-layer thick and thin tile + inner lining elastic small support group" structure of this invention is analyzed as follows: 1. Stress Dispersion Effect: The water-facing surface uses thin tiles (directly bearing the jet impact), which are relatively thin (generally 1 / 3 to 1 / 2 the thickness of a traditional single-layer water bucket). Through its own elastic deformation, it can adapt to the spatial distribution of the jet impact force (the pressure in the jet impact zone exhibits a Gaussian distribution, with the highest pressure at the center). The elastic deformation of the water-facing bucket blade 201 can disperse the locally concentrated impact force to the back-facing bucket blade 202 via the lower elastic small support group 204. Compared to the stress concentration caused by the impact force being directly borne by the entire structure in a single-layer structure, this "dispersion-transmission" mode can reduce the local stress peak in the impact zone.

[0038] 2. Elastic Buffering Effect: The elastic small support group 204 (which can be designed with variable stiffness, i.e., high-stiffness small supports with low elastic coefficients are used in areas of high impact pressure, while low-stiffness small supports with high elastic coefficients are used in edge areas) can absorb the energy of impact pulses through slight elastic deformation, reducing the amplitude of stress wave transmission in the structure. For high-frequency impacts (jet frequencies can reach hundreds of Hz), the elasticity of the small supports can reduce the instantaneous stress peak caused by "hard impacts" and delay the initiation of fatigue cracks.

[0039] 3. Strengthening the load-bearing capacity of thick tiles: The 202 bucket blade on the back side is the main load-bearing structure. High-strength alloy steel (such as 17-4PH stainless steel) can be used to increase the overall bending section modulus (W=bh² / 6) by increasing the thickness, thereby enhancing the overall load-bearing capacity against centrifugal force and dispersed impact force and avoiding excessive overall deformation.

[0040] The stiffness of the water bucket directly affects its geometric accuracy: insufficient stiffness will cause deformation under jet impact to change the flow channel profile of the water bucket (e.g., when the edge deflection exceeds 0.1 mm, the jet deflection angle deviation may lead to a 1% to 3% decrease in efficiency), while also exacerbating water flow separation and local eddies, indirectly increasing erosion. The principle of stiffness improvement in the impulse turbine using the "double-layer thick and thin tile + inner lining elastic small support group" structure of this invention is analyzed as follows: 1. Graded stiffness matching: The water-facing blade 201 needs to have a certain stiffness to maintain the accuracy of the flow channel (to avoid excessive deformation leading to deterioration of the water flow pattern), and can be made of high elastic modulus material (such as martensitic stainless steel); the water-returning blade 202 provides basic stiffness through a larger cross-sectional moment of inertia; the elastic small support group 204 balances local deformation through "rigid transmission + micro-buffering" to avoid excessive reduction of overall stiffness due to buffering design.

[0041] 2. Dynamic Stiffness Optimization: Under high-frequency impact, traditional single-layer structures may amplify deformation due to "resonance" (if the impact frequency is close to the natural frequency of the water bucket). The elastic small support group 204 can optimize the dynamic characteristics of the structure by adjusting the stiffness (such as changing the diameter and the elastic modulus of the material), avoiding the resonance frequency, reducing the dynamic deformation amplitude, and improving the dynamic stiffness stability.

[0042] Under conditions of heavy sediment, the erosion (sediment erosion + cavitation corrosion) of the upstream bucket blade 201 is a major bottleneck in its lifespan: the erosion caused by high-speed sediment-laden water flow (flow velocity can reach 50 m / s to 80 m / s) leads to the gradual peeling off of the upstream material, and the micro-jet generated by the collapse of cavitation bubbles exacerbates material fatigue and peeling. To address this, the upstream bucket blade 201 of the impulse turbine with the "double-layer thick and thin tiles + inner lining elastic small support group" structure in this embodiment can be made of highly wear-resistant materials (such as high-chromium cast iron, WC-Co metal-ceramic composite material), and its thickness only needs to meet the erosion life requirement (e.g., when the design wear is 5 mm, the thickness of the thin tile is 8 mm to 10 mm), which is more economical than using expensive wear-resistant materials for the entire bucket. Furthermore, the thin tile can be replaced individually after it wears to its limit (without needing to replace the thick tile and elastic small support), reducing maintenance costs and indirectly extending the overall machine's wear resistance cycle. In addition, mud and sand can be blocked from entering through sealing design (such as setting an elastic sealing lip at the edge of the thin tile), and the surface of the elastic small support needs to be hardened (such as chrome plating or nitriding) to improve wear resistance.

[0043] The impact turbine impeller blade of this invention, featuring a "double-layer thick and thin tile + inner elastic small support group" structure, uses thick tiles and an elastic small support group to support thin tiles, forming two semi-bowl-shaped water buckets. The thick and thin tiles have completely identical (overlapping) semi-bowl shapes, with elastic small supports of equal height but unequal diameter between them. This forms a double-layer tile elastic support structure where the thin tiles on the water-facing side of the water bucket are supported by the distributed elastic small supports on the back side of the water bucket. Using the double-layer tile impact turbine impeller blade or impact turbine of this invention can effectively improve the strength (stress dispersion, reduced peak value), stiffness (optimized dynamic stability), and wear resistance of the water buckets (easy replacement of thin tiles + targeted material selection), making it particularly suitable for extreme working conditions involving high-frequency impact, high stress, and high sediment content. The double-layered impeller blades or impeller turbines of this invention can significantly improve the anti-abrasion performance of impeller turbines under long-term operation with high sediment content in the bucket, greatly enhance the anti-sediment performance of ultra-high head impellers with a head of over 800 m, and effectively improve the problem of easy wear, easy breakage, and significantly shortened service life of single-layered impeller blades under conditions of high sediment, high head, and strong impact.

[0044] The structural design of the double-layer tile impact turbine runner and the impact turbine of the present invention will be described below with reference to a specific embodiment: Taking a high-head, large-capacity impulse turbine with a head greater than 800 m and a single unit capacity greater than 800 MW as an example, the embodiments of the present invention can achieve high adaptability, high strength and high safety and reliability of the water bucket, and the specific implementation is as follows.

[0045] I. Parameters of Engineering Implementation Examples Under extreme operating conditions of an 800 m head, 800 MW-class impulse turbine (jet velocity ≈ 125 m / s, single nozzle jet power ≈ 130 MW, sand content > 5 kg / m³, and sediment hardness 7-8 Mohs), the impeller blades of the "double-layer thick and thin tiles + inner lining elastic small support group" structure of this invention need to balance load-bearing strength, dynamic stiffness, and wear resistance.

[0046] (I) Core operating parameters and design constraints 1. Key load parameters Jet impact load: At a water head of 800 m, the jet velocity v = {2gH} 1 / 2 = ((2 × 9.81) × 800) 1 / 2 =125m / s; Peak pressure at the jet center p max =(ρv 2 ) / 2 = 1000 × 125 2 / 2 = 7.8 MPa (In reality, due to the interaction between the jet and the water bucket, the local impact pressure can reach 200 MPa to 300 MPa, and it exhibits a Gaussian distribution, that is, the pressure is highest at the center and decreases linearly towards the edge.

[0047] Centrifugal load: The runner diameter of an 800 MW impulse turbine is approximately 6 m to 8 m, the rotational speed n = 300 r / min (synchronous generator speed matches the grid frequency), the water bucket rotation radius r ≈ 3.5 m, the mass of a single water bucket (including structure) is approximately 800 kg to 1000 kg, and the centrifugal force F c = mrω 2 ≈1000×3.5×(2π×300 / 60) 2 ≈1.7×10 6 N (1.7 MN).

[0048] Abrasion rate: When the sand content is 5 kg / m³ and the hardness of the mud and sand is 8 Mohs (mainly quartz sand), the annual wear of traditional steel water buckets is about 2 mm-3 mm. The wear allowance of the thin tile needs to be designed to be ≥5 mm (to ensure a replacement cycle of more than 5 years).

[0049] II. Example of Double-Layer Tile Thickness Design 1. Design of the thickness of the thin-layer (wear-resistant layer) on the water-facing side of the roof. Core function: Directly withstand the impact of jets and the abrasion of mud and sand, and must have both high wear resistance (hardness ≥ HRC55) and a certain degree of elasticity (allowing slight deformation to disperse stress).

[0050] Material selection: high chromium cast iron (Cr26) or WC-Co metal ceramic composite material (wear resistance is 3 to 5 times that of traditional stainless steel).

[0051] Thickness selection Wear life constraint: The design wear amount is 5 mm. Considering manufacturing errors and safety margins, the initial thickness must be ≥8 mm (the remaining 3 mm after wear can still maintain structural integrity).

[0052] Elastic deformation constraint: The thin tile needs to match the jet pressure distribution through elastic deformation (to avoid local rigid impact), and its thickness t1 needs to meet the bending deformation condition: the maximum deflection δ in the jet impact zone. max (To avoid distortion of the flow channel profile affecting efficiency): Where: L is the span of the thin-span support (i.e., the spacing between the elastic small supports, taken as 50 mm), E1 is the elastic modulus of the material (E1≈170 GPa for high-chromium cast iron), I1= (Wt1 3 ) / 12; (Moment of inertia of the cross section, W is the unit length in the width direction of the water bucket). Substitute into p max = 250 MPa, solving for t1 gives ≥ 7.5 mm.

[0053] In the example above, the thickness is t1 = 8.0 mm (taking into account both wear resistance and elastic deformation requirements).

[0054] Backwater side thick tile (load-bearing layer) thickness design Core functions: To withstand the distributed load and centrifugal force transmitted through the elastic small support, it must have high strength (yield strength ≥ 800 MPa) and high stiffness (to suppress overall deformation).

[0055] Material selection: 17-4PH precipitation hardening stainless steel (yield strength 1100 MPa, fatigue strength 450 MPa) or maraging steel (yield strength 1800 MPa).

[0056] Thickness selection Centrifugal force bearing constraint: The thick tile must bear the centrifugal force of the total mass of the water bucket (including the thin tile and small support), and its cross-sectional area must satisfy: centrifugal stress σ c =F c / A xi ≤0.3σ s2 ;σ s2(The yield strength of the thick tile material is taken as 1100 MPa). The mass of a single water bucket thick tile is approximately 500 kg. The centrifugal force (F) c ≈1.7×10 6 N, solving for the cross-sectional area of ​​the thick tile A2, we get A2 ≥ 5.15 × 10 -3 m 2 (Calculated based on a water bucket width of 0.5m and a thickness of t2≥25 mm.)

[0057] Stiffness constraint: The thicker tiles need to provide overall stiffness, and their cross-sectional moment of inertia I2 needs to ensure that the natural frequency of the entire machine avoids the jet impact frequency (approximately 500 Hz to 800 Hz) to prevent resonance. Finite element simulation verification shows that when t2 = 30 mm, the natural frequency can be increased to over 1000 Hz, far away from the resonance range.

[0058] In this example, a thickness of t2 = 30 mm is used (to balance load-bearing capacity and dynamic stability).

[0059] III. Parameter Design and Calculation of Flexible Small Support Groups 1. Small support height (spacing between two layers of tiles) design Core function: Provides a flexible buffer space to ensure that the deformation of the thin tile can be transferred to the thick tile through the flexible small support, while avoiding the rigid impact caused by direct contact between the two layers of tiles.

[0060] Height calculation: The height h of the small support column must be equal to the maximum deformation δ of the thin tile. max The sum of the safety clearances, i.e., h = δ max +5 mm ≈ 0.2 + 5 = 5.2 mm (The actual deformation of the thin tile is a local micro-deformation. The elastic small support needs to be a structure of equal height to ensure that the force is evenly distributed at each point. The height should be uniformly 6 mm to 8 mm to satisfy the elastic deformation space of the thin tile and avoid excessive height that would cause the elastic small support to become unstable).

[0061] 2. Diameter and arrangement of small support pillars Core function: to transfer load according to the jet pressure distribution (dense at the center and sparse at the edges), and to absorb impact pulse energy through elastic deformation.

[0062] Material selection: TC4 titanium alloy (elastic modulus 110 GPa, yield strength 895 MPa) or high-strength spring steel (60Si2Mn, elastic modulus 206 GPa), balancing elasticity and strength.

[0063] Diameter calculation: Central region (i.e., first region, jet pressure 200 MPa~250 MPa): a single elastic small support bears F p =p max(S is the area supported by the elastic small support pillars, with a spacing of 30 mm-40 mm, S≈40×40 = 1600 mm) 2 ), then F p ≈250×10 -3 ×1600 = 400 N.

[0064] The diameter d of the elastic small support must satisfy the shear strength: τ = 4F p / πd 2 ≤ 0.6σ s3 (σ) s3 Given the yield strength of the elastic small support column (taken as 895 MPa), we can solve for d ≥ 13 mm. In this example, we take 15 mm.

[0065] Edge region (i.e., second region, jet pressure 50 MPa-100 MPa): a single elastic small support bears F p ≈100×10 -3 ×60×60 =360 N (spacing 60 mm), solving for the diameter d gives ≥10 mm, in this example we take 12 mm.

[0066] Arrangement: The jet pressure is distributed according to the Gaussian distribution. The spacing between the small support pillars in the central area (within 0.3 m in diameter) is 30 mm-40 mm, and the spacing in the edge area (0.3 m to 0.6 m in diameter) is 50 mm-60 mm. The whole is densely distributed in a ring.

[0067] IV. Stress and Deformation Verification in this Example 1. Stress check of thin tiles Operating conditions: jet center pressure 250 MPa, thin tile thickness 8 mm (Cr26, σ s = 400 MPa).

[0068] Verification results: Through ANSYS simulation, the maximum bending stress of the thin tile is σ1≈320 MPa (<400 MPa, safety factor 1.25), and the maximum deflection is 0.18 mm (<0.2 mm, meeting the flow channel accuracy).

[0069] 2. Stress check of thick tiles Working condition: After being dispersed by elastic small supports, the thick tile bears a uniformly distributed load of 80 MPa (30 mm thick, 17-4 PH, σ s = 1100MPa).

[0070] Verification results: Maximum tensile stress σ2≈280 MPa (<1100 MPa, safety factor 3.9), total stress after adding centrifugal force≈350 MPa (within the safe range).

[0071] 3. Stress check of small support columns The central area elastic small support (15 mm, TC4): maximum shear stress τ≈280 MPa (<0.6×895=537MPa, safety factor 1.9), elastic deformation ≈0.12 mm (meets the buffering requirements).

[0072] V. Summary of Conclusions and Parameters in this Example The following are examples of materials and parameters for a "double-layer thick and thin tile + inner elastic small support group" structure under conditions of 800 m water head, 800 MW level, and high sediment load: The impact impeller blade design using the "double-layer thick and thin tiles + inner elastic small support group" structure of the embodiment of the present invention can increase the strength safety factor of the water bucket to more than 1.3, improve wear resistance by 3-5 times, and increase dynamic stiffness by 30% (avoiding resonance frequency), making it fully adaptable to extreme working conditions with large capacity, high water head, and a lot of silt.

[0073] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A double-layer tile impact-type impeller blade, characterized in that, include: Water-facing side of the leaf; The thickness of the back-side bucket blade is greater than the thickness of the front-side bucket blade; A water-dividing blade is disposed on the water-facing bucket blade, the water-facing bucket blade being symmetrically arranged on both sides of the water-dividing blade; and, A group of flexible small support pillars is sandwiched between the water-facing blade and the water-repellent blade, and the group of flexible small support pillars is symmetrically arranged on both sides of the water-dividing blade; the group of flexible small support pillars includes a plurality of first flexible small support pillars arranged in a first region and a plurality of second flexible small support pillars arranged in a second region, the jet pressure in the first region is greater than that in the second region, the diameter of the first flexible small support pillars is greater than that of the second flexible small support pillars, and the height of each small support pillar in the group of flexible small support pillars is equal.

2. The double-layer tile impact-type impeller blade as described in claim 1, characterized in that, The two end faces of each small support in the elastic small support group match the curved shape of the water-facing and water-repellent blades at its location.

3. The double-layer tile impact-type impeller blade as described in claim 1, characterized in that, The water-facing bucket blade and the water-returning bucket blade are each provided with a positioning stop groove on their opposite sides, and the two ends of the elastic small support group are engaged with the positioning stop groove.

4. The double-layer tile impact-type impeller blade as described in claim 3, characterized in that, The depth of the positioning stop groove is less than 2 mm.

5. The double-layer tile impact-type impeller blade as described in claim 1, characterized in that, The spacing between two adjacent first elastic small pillars is 30-40 mm, and the spacing between two adjacent second elastic small pillars is 50-60 mm.

6. The double-layer tile impact-type impeller blade as described in claim 1, characterized in that, The jet pressure in the first region is 200-250 MPa, and the jet pressure in the second region is 50-100 MPa.

7. The double-layer tile impact-type impeller blade as described in claim 1, characterized in that, The thickness of the water-facing bucket blade is 8-10 mm, the thickness of the water-repellent bucket blade is 25-35 mm, and the height of each small support in the elastic small support group is 6-8 mm.

8. The double-layer tile impact-type impeller blade as described in claim 1, characterized in that, The water-facing bucket blades are made of high-chromium cast iron or WC-Co metal-ceramic composite material, and the water-returning bucket blades are made of 17-4PH precipitation-hardening stainless steel or martensitic aging steel; the elastic small support group is made of TC4 titanium alloy or high-strength spring steel or high-strength SMC plastic material.

9. A double-layer tile impact-type impeller blade as described in any one of claims 1-8, characterized in that, The edges of the water-facing and water-repellent blades are fixed and sealed by welding or clamping.

10. An impulse turbine, characterized in that, include: The wheel hub has a mounting hole in its center; The double-layered tile impact bucket blades of any one of claims 1-9 are connected in a ring array on the hub; and, Multiple nozzles are arranged in a ring array on the outer periphery of the hub to spray impact jets onto the double-layered tile impact bucket blades.

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