Method for determining parameters of impulse water turbine, bucket and pin column

Abstract

The application relates to the technical field of hydroelectric power generation, in particular to an impulse water turbine, a water bucket and a pin column distribution parameter determination method. The water bucket is a double-bowl structure symmetrical along a water distribution blade, the water bucket has a water-facing surface for bearing water flow impact and a backwater surface opposite to the water-facing surface, a plurality of pin columns are embedded along the normal direction of the backwater surface, the end of the pin column is matched with the surface of the water-facing surface to form a continuous smooth curved surface of the water-facing surface. 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 prolonged.

Description

Technical Field

[0001] This application relates to the field of hydropower technology, specifically to a method for determining the distribution parameters of an impulse turbine, water buckets, and pins. 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 a method for determining the distribution parameters of an impulse turbine, a water bucket, and a pin column, in order to solve the problems of easy wear and breakage of the water bucket and short service life of existing impulse turbines.

[0006] The first aspect of this application provides an impact turbine bucket, the bucket being a double-bowl-shaped structure symmetrical along the water-dividing edge. The bucket has a water-facing surface for bearing the impact of water flow and a backwater surface opposite to the water-facing surface. The backwater surface is provided with a plurality of pins embedded in its normal direction, the ends of the pins being adapted to the surface of the water-facing surface to form a continuous smooth curved surface of the water-facing surface.

[0007] In one embodiment, the water-facing side has multiple zones, and the pins on the back side corresponding to different zones have different distribution parameters, including the pin outer diameter and / or pin density.

[0008] In one embodiment, the partitioning of the water-facing surface is determined based on three-dimensional pressure distribution data of the water-facing surface, and different partitions correspond to different preset pressure ranges;

[0009] The distribution parameters of the pin are positively correlated with the pressure magnitude of the corresponding water-facing zone.

[0010] In one embodiment, the partition includes an impact center zone, a transition zone, and an exit zone;

[0011] The impact center zone, transition flow zone, and outlet zone are divided based on the three-dimensional pressure distribution data of the upstream surface. The impact center zone is the area of ​​maximum pressure distribution on the upstream surface, the outlet zone is the area of ​​minimum pressure distribution on the upstream surface, and the transition flow zone is the intermediate pressure distribution area between the maximum and minimum pressure.

[0012] The pin distribution parameters corresponding to the impact center region are greater than those corresponding to the transition flow region, which in turn are greater than those corresponding to the exit region.

[0013] In one embodiment, the outer diameter of the pin corresponding to the impact center area is 20mm~25mm, and the spacing between adjacent pins is 30mm~40mm;

[0014] The outer diameter of the pin corresponding to the transition flow zone is 16mm~20mm, and the spacing between adjacent pins is 40mm~50mm.

[0015] The outer diameter of the pin corresponding to the outlet area is 12mm~16mm, and the spacing between adjacent pins is 50mm~60mm.

[0016] In one embodiment, the pin is fixed to the water hopper by a threaded connection, and the material of the pin is the same as that of the water hopper.

[0017] A second aspect of this application provides a method for determining pin distribution parameters, including:

[0018] Obtain the three-dimensional pressure distribution data of the water bucket's upstream surface under jet impact;

[0019] Based on the three-dimensional pressure distribution data, the water-facing side partitions are determined, and the water-facing side partitions are mapped to the back water side to obtain the pin reinforcement areas corresponding to each water-facing side partition.

[0020] The reinforcement level of each pin reinforcement area is determined based on the three-dimensional pressure distribution data.

[0021] Based on the reinforcement level, pin layout parameters are determined for each of the pin reinforcement areas.

[0022] In one embodiment, determining the reinforcement level of each pin reinforcement region based on the three-dimensional pressure distribution data includes:

[0023] Based on the pressure magnitude range in the three-dimensional pressure distribution data, the upstream surface is divided into the impact center zone, the transition flow zone, and the outlet zone;

[0024] The reinforcement level of the pin reinforcement area corresponding to the impact center zone is level one, the reinforcement level of the pin reinforcement area corresponding to the transition flow zone is level two, and the reinforcement level of the pin reinforcement area corresponding to the exit zone is level three.

[0025] The impact center region is the area of ​​maximum pressure distribution on the upstream side, the outlet region is the area of ​​minimum pressure distribution on the upstream side, and the transition flow region is the intermediate pressure distribution region where the pressure is between the maximum and minimum pressure.

[0026] In one embodiment, determining the pin layout parameters for each pin reinforcement region according to the reinforcement level includes:

[0027] For the pin reinforcement area with a reinforcement level of one, a first pin with a first distribution density and a first outer diameter is configured;

[0028] For the pin reinforcement area with a reinforcement level of two, a second pin with a second distribution density and a second outer diameter is configured, wherein the second distribution density is less than the first distribution density and the second outer diameter is less than the first outer diameter;

[0029] For a pin reinforcement area with a reinforcement level of three, a third pin with a third distribution density and a third outer diameter is configured, wherein the third distribution density is less than the second distribution density and the third outer diameter is less than the second outer diameter.

[0030] A third aspect of the present application provides an impulse turbine, comprising: a hub, nozzles, and a plurality of water buckets, as provided in the first aspect of the present application, evenly distributed on the hub.

[0031] The impulse turbine bucket provided in the first aspect of this application achieves a balance between structural reinforcement and hydraulic performance by embedding pins in the normal direction of the bucket's back surface and keeping the front surface smooth. This design allows the internal stress of the bucket to be effectively dispersed to a wider area through the pins when subjected to high-energy jet impact, thereby significantly improving fatigue resistance and deformation resistance. At the same time, since the front surface maintains its original continuous smooth curved surface, hydraulic loss or efficiency reduction caused by structural reinforcement is avoided, providing a basic guarantee for the safe and stable operation of high-head, large-capacity impulse turbines.

[0032] It is understandable that the beneficial effects of the second and third aspects mentioned above can be found in the relevant descriptions in the first aspect above, and will not be repeated here. Attached Figure Description

[0033] 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.

[0034] 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;

[0035] Figure 2 This is a schematic diagram of the water-facing surface area provided in an embodiment of this application;

[0036] Figure 3 This is a schematic diagram of the pin distribution provided in an embodiment of this application;

[0037] Figure 4 This is a schematic diagram of the structure of the impulse turbine provided in the embodiments of this application;

[0038] Figure 5 This is a schematic flowchart of a method for determining pin distribution parameters provided in an embodiment of this application. Detailed Implementation

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] Furthermore, in the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0045] 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.

[0046] like Figure 1As shown in the embodiment of this application, an impact turbine water bucket is provided. The water bucket 1 is a double bowl-shaped structure symmetrical along the water-dividing blade 123. The water bucket 1 has a water-facing surface 11 for bearing the impact of water flow and a back water surface 12 opposite to the water-facing surface 11. A plurality of pins 13 are embedded in the back water surface 12 along its normal direction. The ends of the pins 13 are adapted to the surface of the water-facing surface 11 to form a continuous smooth curved surface of the water-facing surface 11.

[0047] In application, the water-facing surface 11 and the water-repellent surface 12 of this embodiment are two surfaces of an integrally formed water bucket, which is made of high-strength stainless steel or forged steel.

[0048] In applications, the water jet is a key component used to withstand the impact of water flow and convert water flow energy into mechanical energy. It typically consists of jet blades, a jet back, and a water-dividing blade, evenly distributed around the hub. In this embodiment, the jet blades are double-bowl shaped to accommodate the impact of the water flow and the energy conversion. The water-dividing blade is located at the center of the water jet, dividing the jet into two parts, which enter the two halves of the water jet respectively. When high-speed water is ejected from the nozzle and impacts the water-dividing blade, the water flow is divided into two parts, which enter the two halves of the water jet respectively. During the flow of water within the water jet, the speed and direction of the water flow change due to the shape and curvature of the water jet, thus generating an impact force on the water jet. This impact force drives the water jet to rotate through the hub, driving the impeller and main shaft to rotate, converting the kinetic energy of the water flow into mechanical energy. The water jet is made of high-strength, high-toughness materials, such as stainless steel, to withstand the impact and wear of high-speed water flow.

[0049] In application, the pins are made of the same material as the water bucket and are arranged according to the hydraulic characteristics of the jet flow and the load intensity distribution on the water bucket's upstream side. The height (length) and outer diameter of the pins are also set according to the bowl shape and thickness of the water bucket's upstream side, forming a family of pins on the downstream side of the water bucket based on the bowl shape and load distribution. This ensures uniform and effective reinforcement from the non-upstream and downstream sides by utilizing the impact water force. The pin family is made of high-strength steel with varying heights and diameters, and can be fixed by threaded holes. The shape and thickness of the inner and upstream outer surfaces remain consistent, ensuring that the surface of the water bucket on the inner upstream side remains a continuous and smooth curved surface.

[0050] This embodiment of the application achieves a balance between structural reinforcement and hydraulic performance by embedding pins in the normal direction of the back surface of the water bucket while keeping the front surface smooth. This design allows the internal stress of the water bucket to be effectively dispersed to a wider area through the pins when subjected to high-energy jet impact, thereby significantly improving fatigue resistance and deformation resistance. At the same time, since the front surface maintains its original continuous smooth curved surface, hydraulic loss or efficiency reduction caused by structural reinforcement is avoided, providing a basic guarantee for the safe and stable operation of high-head, large-capacity impulse turbines.

[0051] In one embodiment, the water-facing side 11 has multiple partitions, and the pins 13 corresponding to different partitions on the back side 12 have different distribution parameters, including the outer diameter of the pin 13 and / or the density of the pin 13.

[0052] This application embodiment achieves precise reinforcement design based on actual load by dynamically linking the distribution parameters of the upstream side partitioning with the pins on the downstream side. This method breaks through the limitations of traditional uniform reinforcement methods, making the material distribution highly matched with mechanical requirements. It avoids the risk of insufficient reinforcement in high-strength areas and prevents material waste in low-stress areas, thereby optimizing the overall stiffness-to-weight ratio of the bucket and improving the product's economy and reliability. According to the jet hydraulic characteristics and load distribution on the upstream side of the bucket, high-strength pins with unequal height and diameter are distributed using a threaded perforation method. The pins (threaded perforation type) remain a continuous and smooth curved surface on the inner surface and the bowl-shaped surface of the bucket, thus forming a bucket reinforced by a family of pins built into the downstream side. This effectively solves the problems of insufficient stiffness and strength and long-term resistance to silt wear in large impulse turbines with high head, high speed, and large runners. It not only enables the design and manufacture of impulse turbines with larger outer diameters, but also makes it possible to design and manufacture large buckets with larger size, greater thickness, larger outer diameter, and higher reliability.

[0053] In one embodiment, the partitioning of the water-facing surface 11 is determined based on the three-dimensional pressure distribution data of the water-facing surface 11, and different partitions correspond to different preset pressure ranges;

[0054] Among them, the distribution parameters of pin 13 are positively correlated with the pressure magnitude of the corresponding water-facing surface 11 zone.

[0055] In the application, in order to accurately determine the partitioning of the water-facing surface 11, the core calculation principle of the water bucket force and the principle of the back pin to improve the rigidity were analyzed.

[0056] The core calculation principle of the water bucket force is analyzed as follows:

[0057] The water buckets of an impulse turbine primarily bear the impact force of the jet, which is the core load causing bucket deformation and fatigue failure. Its magnitude can be calculated using the momentum theorem.

[0058] Let the jet density be ρ (the density of water ρ = 1000 kg / m³). 3 Given a flow rate of Q, a jet velocity of v1, a water velocity v2 leaving the bucket, and a bucket deflection angle of θ (typically θ = 160°~170°), the impact force is:

[0059] F = ρQ (v1 - v2 cosθ)

[0060] The impact force will cause the water bucket to generate a bending moment M = F·L (where F is the cantilever length of the water bucket), which in turn generates bending stress and deformation, and is the main cause of fatigue failure.

[0061] The principle by which the back pin enhances rigidity is analyzed as follows:

[0062] The core function of installing high-strength pins (similar to reinforcing ribs) on the back is to increase the moment of inertia I of the water tank section, thereby reducing bending stress and deflection. This is specifically based on the formulas of mechanics of materials.

[0063] Bending stress: σ = (M·y) / I, where y is the distance from the farthest point of the cross section to the neutral axis, and I is the moment of inertia of the cross section.

[0064] Deflection: δ = (M·L) 3 ) / (3E·I), where E is the elastic modulus of the material and L is the cantilever length.

[0065] The larger I is, the smaller the bending stress σ and deflection δ, that is, the higher the stiffness (resistance to deformation) and strength (resistance to damage).

[0066] After the following analysis, based on the hydraulic characteristics of the jet impact on the water-facing surface of the water turbine, the three-dimensional pressure field distribution can be obtained by simulating the impact motion of the jet on the water turbine using computational fluid dynamics (CFD). In a fluid analysis program similar to ANSYS Fluent, the SST k-ω turbulence model and the VOF multiphase flow model are used to simulate the pressure distribution of the impulse turbine under different operating conditions, and partitions are obtained based on the pressure range. The pressure distribution partitions on the water-facing surface are mapped to the backwater surface through structural mechanics to obtain the corresponding pin-reinforced areas. High-strength pins are then used to strengthen the impact resistance of the water-facing surface of the water turbine.

[0067] With a water head of 1000m and a jet diameter DJ =0.5 m Taking the impact turbine bucket as an example, three-dimensional pressure field distribution data were obtained. Among them, the apex region of the bowl-shaped curved surface directly impacted by the jet (approximately 1.2 mm in diameter) was analyzed. DJ The pressure is at its maximum, reaching [amount missing]. P max =15 MPa ~20 MPa (with jet pressure) ρv 2 / 2 is equivalent. ρ (where the density is water), dividing it into impact center zones (for Figure 2 Area A). Stress distribution and pressure distribution are strongly correlated, but are more significantly affected by the uneven thickness and geometric curvature of the water bucket: the impact center area, which directly bears the jet impact and has a large curvature and thin thickness (usually 20mm to 30mm) of the bowl-shaped surface, has the largest equivalent stress, reaching up to σmax =250 MPa ~300 MPa (Approximately 80% of the material's yield strength).

[0068] In the region extending from the impact center towards hub 2 (i.e., the root region of the water bucket), the water flow deflects along the curved surface, and the pressure decreases exponentially with increasing flow distance, with a pressure range of 5. MPa ~15 MPa It is divided into a transition flow region (corresponding to) Figure 2 Area B).

[0069] Water-dividing blade 123 on both sides (within ±10° range), corresponding to Figure 2 In zone C, the water flow splits into two streams, resulting in large pressure fluctuations and localized negative pressure (−0.5MPa~5MPa), which easily leads to cavitation vibrations. However, the water-splitting blade has high strength and high surface curvature, so there is no need to install pins for reinforcement.

[0070] As the water flows away from the edge of the water tank, the pressure drops to 1. MPa ~3 MPa It is designated as an export zone (for Figure 2 (Area D).

[0071] This application embodiment defines the zoning criteria as three-dimensional pressure distribution data and pressure range, and positively correlates the pin parameters with the pressure magnitude. This transforms the design scheme from experience-oriented to data-driven. By introducing quantifiable pressure parameters as design input, the objectivity and reliability of the design are greatly improved, further ensuring the strength of the water bucket.

[0072] In one embodiment, the partition includes an impact center zone 115, a transition flow zone 116, and an exit zone 117.

[0073] The impact center zone 115, the transition flow zone 116, and the outlet zone 117 are divided based on the three-dimensional pressure distribution data of the upstream surface 11. The impact center zone 115 is the area of ​​maximum pressure distribution on the upstream surface 11, the outlet zone 117 is the area of ​​minimum pressure distribution on the upstream surface 11, and the transition flow zone 116 is the intermediate pressure distribution area between the maximum and minimum pressure.

[0074] The pin 13 distribution parameter corresponding to the impact center region 115 > the pin 13 distribution parameter corresponding to the transition flow region 116 > the pin 13 distribution parameter corresponding to the exit region 117.

[0075] This application embodiment defines three typical zones—the impact center zone, the transition flow zone, and the outlet zone—and their pressure characteristics, and establishes the relationship between pin parameters and the zones, simplifying the complex pressure distribution into clear engineering design rules. This division method conforms to the actual attenuation law of the impact jet on the water bucket surface, greatly simplifying the design process and ensuring the effectiveness of the strengthening effect.

[0076] In one embodiment, the outer diameter of the pin 13 corresponding to the impact center area 115 is 20mm~25mm, and the spacing between adjacent pins 13 is 30mm~40mm.

[0077] The outer diameter of the pin 13 corresponding to the transition flow zone 116 is 16mm~20mm, and the spacing between adjacent pins 13 is 40mm~50mm;

[0078] The outer diameter of the pin 13 corresponding to the exit area 117 is 12mm~16mm, and the distance between adjacent pins 13 is 50mm~60mm.

[0079] In application, the spacing between adjacent pins 13 refers to the spacing between adjacent pins 13 in the same ring when the pins 13 are arranged in a circumferential direction. In the embodiments of this application, the circumferential direction refers to the direction in which the water bucket surface surrounds the central axis where the water-dividing blade is located.

[0080] In application, based on the above distribution parameters, a topology optimization method (such as the variable density method) is used to determine the optimal layout of the pins. The objective function is to minimize the equivalent elastic strain energy on the backwater surface, with the constraint that the pin volume percentage is ≤15%. A pin distribution density cloud map is generated through iterative calculation. For regions with large pressure gradients (such as the bowl-shaped curved surface transition zone), the pin density is increased by 30%–50%.

[0081] In application, in the impact center zone 115, within a thickness ≥15mm at the bottom of the bowl-shaped curved surface, pins of equal thickness to the bowl shape are arranged to achieve a fit between the top surface of the pins and the backwater surface. Similarly, in the transition flow zone 116, within a thickness 8mm to 15mm at the bottom of the bowl-shaped curved surface, pins of equal thickness to the bowl shape are arranged to achieve a fit between the top surface of the pins and the backwater surface. In the outlet zone 117, within a thickness ≤8mm at the bottom of the bowl-shaped curved surface, pins of equal thickness to the bowl shape are arranged to achieve a fit between the top surface of the pins and the backwater surface.

[0082] Furthermore, the pin diameter d is specifically determined based on the local stress σ, and the calculation formula is as follows:

[0083] d =(4 F / π [ σ ]) 1 / 2 ·γ ;

[0084] Where: F is the axial force (N) borne by a single pin, obtained by finite element analysis; [σ] is the allowable stress of the pin material (MPa), which is 200MPa for 316L stainless steel; γ is the safety factor, which is 1.2 to 1.5.

[0085] The embodiments of this application specify the numerical range of the outer diameter and spacing of the pins. These parameters are based on typical load calculations and engineering verification under high water head conditions. This ensures that the pins themselves have sufficient shear and bending strength under extreme working conditions. At the same time, the reasonable spacing setting avoids excessive stress concentration, ensures the integrity of the reinforcing layer, and provides quantitative assurance for the long-term durability of the product in harsh silt environments.

[0086] In one embodiment, the pin 13 is fixed to the water tank 1 by a threaded connection, and the material of the pin 13 is the same as that of the water tank 1.

[0087] The pin in this embodiment is threaded and made of the same material as the water hopper. The threaded connection ensures accurate positioning and high bonding strength of the pin installation, avoiding material deterioration or deformation in the heat-affected zone that may be caused by welding. The material consistency fundamentally eliminates the risk of connection failure caused by the difference in thermal expansion coefficient or electrochemical potential between dissimilar materials, and improves the long-term stability and maintenance convenience of the structure.

[0088] This application also provides an impulse turbine, such as... Figure 4 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.

[0089] 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 along its circumference by welding or bolting. 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. Its working principle is as follows: high-speed water flow impacts the water buckets of the turbine, generating a rotational torque in the buckets due to the force of the water flow. This torque is transmitted to the main shaft through the hub, thereby driving the generator rotor to rotate and converting water energy into electrical energy.

[0090] In application, the main function of nozzle 3 is to convert the pressure energy of water into kinetic energy, forming a high-speed jet that impacts the turbine runner, causing it to rotate and thus converting water energy into mechanical energy. It consists of a nozzle body, a nozzle needle, and a throttling cone. The nozzle body is the water flow channel; its shape and size affect the speed and direction of the water flow. The nozzle needle is located inside the nozzle body; by adjusting its position, the nozzle's flow area 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 and reduce energy loss. Specifically, when pressurized water enters the nozzle, due to the nozzle's contraction, the water flow velocity gradually increases, and the pressure gradually decreases, converting the water's pressure energy into kinetic energy, forming a high-speed jet. This high-speed jet impacts the blades on the turbine runner, causing the runner to rotate, which in turn drives the generator to produce electricity. The water distribution coil 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 spray needle adjustment), which drives the water bucket to drive the hub to rotate at high speed.

[0091] This application provides a method for determining pin distribution parameters, such as... Figure 5 As shown, it includes the following steps S101~S104:

[0092] Step S101: Obtain the three-dimensional pressure distribution data of the water-facing surface 11 of the water bucket 1 under the impact of the jet;

[0093] Step S102: Based on the three-dimensional pressure distribution data, determine the 11 sections of the water-facing surface and map the 11 sections of the water-facing surface to the 12 sections of the backwater surface to obtain the pin reinforcement areas corresponding to each 11 sections of the water-facing surface.

[0094] Step S103: Determine the reinforcement level of each pin reinforcement area based on three-dimensional pressure distribution data;

[0095] Step S104: Determine the pin layout parameters for each pin reinforcement area according to the reinforcement level.

[0096] This application embodiment organically combines fluid load and structural response by acquiring pressure data, mapping zones, and determining parameters, achieving a closed-loop design from performance requirements to structural realization. This not only ensures the scientific nature of the design scheme but also makes the design process traceable and optimizable, providing methodological support for the continuous improvement of product performance.

[0097] In one embodiment, determining the reinforcement level of each pin reinforcement region based on three-dimensional pressure distribution data includes:

[0098] Based on the pressure magnitude range in the three-dimensional pressure distribution data, the upstream surface 11 is divided into the impact center zone 115, the transition flow zone 116, and the outlet zone 117.

[0099] Among them, the reinforcement level of the pin reinforcement area corresponding to the impact center zone 115 is level one, the reinforcement level of the pin reinforcement area corresponding to the transition flow zone 116 is level two, and the reinforcement level of the pin reinforcement area corresponding to the exit zone 117 is level three.

[0100] The impact center zone 115 is the area of ​​maximum pressure distribution on the upstream surface 11, the outlet zone 117 is the area of ​​minimum pressure distribution on the upstream surface 11, and the transition flow zone 116 is the intermediate pressure distribution area between the maximum and minimum pressure.

[0101] This application embodiment directly associates the reinforcement level with the specific zone and defines the zone characteristics as the pressure magnitude range, thereby realizing the correlation between pressure distribution and reinforcement degree and ensuring the accuracy of distribution parameters.

[0102] In one embodiment, pin layout parameters are determined for each pin reinforcement area according to the reinforcement level, including:

[0103] For the pin reinforcement area with a reinforcement level of one, a first pin 131 with a first distribution density and a first outer diameter is configured;

[0104] For the pin reinforcement area with a reinforcement level of level 2, a second pin 132 with a second distribution density and a second outer diameter is configured, wherein the second distribution density is less than the first distribution density and the second outer diameter is less than the first outer diameter;

[0105] For the pin reinforcement area with a reinforcement level of three, a third pin 133 with a third distribution density and a third outer diameter is configured, wherein the third distribution density is less than the second distribution density and the third outer diameter is less than the second outer diameter.

[0106] The embodiments of this application configure the pin layout parameters in a stepped manner based on the reinforcement level. This progressive design ensures that the structural reinforcement strength and load attenuation are synchronized, ensuring the smooth transmission of stress inside the water bucket and avoiding local stress concentration caused by sudden changes in stiffness. This optimizes the stress state of the structure as a whole and extends its fatigue life.

[0107] Example 1

[0108] This application uses a high-head, large-capacity impulse turbine with a head greater than 800m and a single-unit capacity greater than 700MW as an example to illustrate the method as follows:

[0109] I. Parameters of Engineering Implementation Examples

[0110] 1. Water bucket parameters (1000m water head)

[0111] Model: HES-500MW impulse turbine bucket

[0112] Design head: H=1000m

[0113] Jet diameter: d_j = 0.4m

[0114] Radius of curvature of the bowl-shaped surface: R = 1.2m

[0115] Material: ZG06Cr13Ni4Mo (yield strength σ) s =400MPa), bowl-shaped curved surface thickness: A area 25mm, B area 20mm~25mm, D area 15mm~20mm.

[0116] Key value of load contour map: σ max =280MPa (Area A), σ B =150MPa (B zone), σ D =80MPa (D zone).

[0117] 2. Pin Layout and Diameter Selection (Based on Stress-Pin Bearing Capacity Matching)

[0118] Area A corresponds to the backwater side:

[0119] The equivalent load that the pin needs to bear F A = σ A ⋅ A unit / n ( A The unit is the area of ​​region A. n (Number of pins).

[0120] Take the area of ​​region A as 0.2 m 2 20 pins are installed, and the bearing capacity of a single pin needs to be... F A ≥280 MPa ×0.2 m 2 / 20=2800 N .

[0121] From the pin strength formula F = σ s ⋅( πd 2 / 4) (safety factor 1.5), resulting in d ≥4×2800×1.5 / ( π (×400×106)≈0.020 m Therefore, choose d =20 mm The spacing is 35mm (arranged in a plum blossom pattern).

[0122] Area B corresponds to the backwater side:

[0123] stress σ B =150 MPa Area 0.3 m 2 Arrange 15 pins, with a single pin load. F B =150 MPa ×0.3 m 2 / 15=3000 N Calculated d =16 mm , spaced 45mm apart (circular arrangement).

[0124] Area D corresponds to the backwater side:

[0125] stress σ D =80 MPa Area 0.25 m 2 Ten pins are installed, with a single pin load. F D =80 MPa ×0.25 m 2 / 10=2000 N ,choose d =14 mm The spacing is 55mm.

[0126] 3. Pin Layout Scheme

[0127] Core area: 20 pins with d=20mm are arranged in a quincunx pattern at a spacing of 35mm in the φ800mm area at the bottom of the bowl shape;

[0128] Transition zone: Arrange 15 pins with a diameter of d=16mm in a ring with a spacing of 45mm in a radius of 800-1200mm.

[0129] Edge area: Arrange 15 pins with d=12mm in a radius of 1200-1500mm, evenly distributed in the circumference, with a spacing of 55mm.

[0130] Pin outer diameter selection

[0131] (1) Load distribution calculation

[0132] Assume the water bucket's upstream surface bears a maximum impact pressure P_max = 15 MPa, and the effective area A = 0.1 m². 2 The total load F_total = P_max × A = 1.5 × 10 6N. The number of pins is determined to be n=50 through topology optimization. Therefore, the load borne by a single pin is F = F_total / n = 3 × 10⁻⁶. 4 N.

[0133] (2) Diameter calculation

[0134] Substitute into the formula:

[0135] ;

[0136] d = π ×200×1064×3×104×1.3=0.0178 m =17.8 mm

[0137] Take the standard diameter d = 20mm.

[0138] (3) Verification of resistance to silt and sand abrasion

[0139] According to Archimedes' law of wear, the wear rate ε of the pin is proportional to the cube of the flow velocity v. Assuming a maximum flow velocity v = 80 m / s, the wear coefficient of the pin material k = 5 × 10⁻⁶. -14 m 3 If the annual wear rate is / (N・m), then the annual wear rate Δh is: Δ h = k ⋅ v 3⋅ t =5×10−14×803×8760×3600=0.092 mm. It meets the design requirement of ≤1mm wear over 10 years.

[0140] 5. Performance Verification

[0141] Static analysis was performed using ANSYS Workbench, and the results show:

[0142] The maximum equivalent stress decreased from 280 MPa before optimization to 195 MPa, a reduction of 30.4%.

[0143] The natural frequency was increased from 480Hz to 620Hz to avoid the resonance zone;

[0144] The sediment abrasion test showed that the wear on the back surface was reduced by 65% ​​compared with the traditional design, and the service life was extended to more than 12 years.

[0145] 6. Manufacturing process in this example

[0146] The pin hole is machined using a five-axis linkage machining center with a positioning accuracy of ±0.02mm;

[0147] The pin is connected to the base material by vacuum diffusion welding, with a bonding strength ≥350MPa;

[0148] The surface treatment uses high-velocity oxygen fuel (HVOF) spraying, and the coating bonding strength is ≥70MPa.

[0149] 7. Continuous surface construction techniques in this example

[0150] The mounting holes for the pins are machined using wire electrical discharge machining (EDM), with an inner wall roughness Ra ≤ 0.8 μm. The pins are connected to the water tank base using tapered threads (2 mm pitch, 1:10 taper), with a thread depth of 2 / 3 of the pin height. After installation, the exposed portion of the pins is coated using laser cladding technology to form a 0.3 mm to 0.5 mm thick WC-Co cemented carbide layer with a surface hardness exceeding HV1200.

[0151] The embodiments of this application achieve dynamic matching between pin layout and load distribution through topology optimization, which improves stiffness by 40% compared with the traditional uniform layout scheme; the use of threaded perforation and cladding coating technology enhances the structure while maintaining a hydraulic surface roughness Ra≤1.6μm; the pin material is selected as 316L stainless steel + WC-Co coating, which achieves the optimal combination of corrosion resistance and wear resistance.

[0152] The method of this invention has been validated in engineering projects, such as the Zhala 500MW impulse turbine bucket, a similar high-head, large-capacity impulse turbine project. Model test results show that the optimal efficiency reaches 92.3%, and the weighted average efficiency is 90.7%, both setting world records for similar units. Actual operating data shows that the wear on the back surface of the bucket is reduced by 68% compared to traditional designs, and the maintenance cycle is extended to 8 years, significantly improving the reliability and economy of the unit.

[0153] 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, The water bucket (1) is a double-bowl-shaped structure symmetrical along the water-dividing blade (123). The water bucket (1) has a water-facing surface (11) for bearing the impact of water flow and a back water surface (12) opposite to the water-facing surface (11). The back water surface (12) is provided with a plurality of pins (13) along its normal direction. The ends of the pins (13) are adapted to the surface of the water-facing surface (11) to form a continuous smooth curved surface of the water-facing surface (11). The water-facing surface (11) has multiple partitions, and the pins (13) corresponding to different partitions on the backwater surface (12) have different distribution parameters, including the outer diameter of the pins (13) and / or the density of the pins (13).

2. The impulse turbine bucket as described in claim 1, characterized in that, The partitioning of the water-facing surface (11) is determined based on the three-dimensional pressure distribution data of the water-facing surface (11), and different partitions correspond to different preset pressure ranges; The distribution parameters of the pin (13) are positively correlated with the pressure magnitude of the corresponding water-facing surface (11) partition.

3. The impulse turbine bucket as described in claim 1, characterized in that, The zone includes the impact center zone (115), the transition zone (116), and the exit zone (117). The impact center region (115), transition flow region (116) and outlet region (117) are divided based on the three-dimensional pressure distribution data of the upstream surface (11). The impact center region (115) is the maximum pressure distribution area of ​​the upstream surface (11), the outlet region (117) is the minimum pressure distribution area of ​​the upstream surface (11), and the transition flow region (116) is an intermediate pressure distribution area with pressure between the maximum and minimum pressure. The pin (13) distribution parameters corresponding to the impact center region (115) are greater than the pin (13) distribution parameters corresponding to the transition flow region (116) and the pin (13) distribution parameters corresponding to the outlet region (117).

4. The impulse turbine bucket as described in claim 3, characterized in that, The outer diameter of the pin (13) corresponding to the impact center area (115) is 20mm~25mm, and the distance between adjacent pins (13) is 30mm~40mm; The outer diameter of the pin (13) corresponding to the transition flow zone (116) is 16mm~20mm, and the spacing between adjacent pins (13) is 40mm~50mm; The outer diameter of the pin (13) corresponding to the outlet area (117) is 12mm~16mm, and the distance between adjacent pins (13) is 50mm~60mm.

5. The impulse turbine bucket as described in claim 1, characterized in that, The pin (13) is fixed to the water bucket (1) by a threaded connection, and the material of the pin (13) is the same as that of the water bucket (1).

6. A method for determining the pin distribution parameters of an impulse turbine bucket as described in any one of claims 1-5, characterized in that, include: Obtain the three-dimensional pressure distribution data of the water bucket (1) facing the water (11) under the impact of the jet; Based on the three-dimensional pressure distribution data, the water-facing surface (11) partition is determined, and the water-facing surface (11) partition is mapped to the back surface (12) to obtain the pin reinforcement area corresponding to each water-facing surface (11) partition; The reinforcement level of each pin reinforcement area is determined based on the aforementioned three-dimensional pressure distribution data; Based on the reinforcement level, pin layout parameters are determined for each of the pin reinforcement areas.

7. The method for determining pin distribution parameters as described in claim 6, characterized in that, The determination of the reinforcement level of each pin reinforcement area based on the three-dimensional pressure distribution data includes: Based on the pressure range in the three-dimensional pressure distribution data, the water-facing surface (11) is divided into the impact center zone (115), the transition flow zone (116), and the outlet zone (117). Among them, the reinforcement level of the pin reinforcement area corresponding to the impact center area (115) is level one, the reinforcement level of the pin reinforcement area corresponding to the transition flow area (116) is level two, and the reinforcement level of the pin reinforcement area corresponding to the outlet area (117) is level three. The impact center region (115) is the region of maximum pressure distribution on the water-facing surface (11), the outlet region (117) is the region of minimum pressure distribution on the water-facing surface (11), and the transition flow region (116) is the region of intermediate pressure distribution between the maximum and minimum pressure.

8. The method for determining pin distribution parameters as described in claim 7, characterized in that, The step of determining pin layout parameters for each pin reinforcement region according to the reinforcement level includes: For the pin reinforcement area with a reinforcement level of one, a first pin (131) with a first distribution density and a first outer diameter is configured. For the pin reinforcement area with a reinforcement level of level 2, a second pin (132) with a second distribution density and a second outer diameter is configured, wherein the second distribution density is less than the first distribution density and the second outer diameter is less than the first outer diameter; For a pin reinforcement area with a reinforcement level of three, a third pin (133) with a third distribution density and a third outer diameter is configured, wherein the third distribution density is less than the second distribution density and the third outer diameter is less than the second outer diameter.

9. 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 5, evenly distributed on the hub (2).

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