Impact water turbine and nozzle thereof

Abstract

The invention relates to the technical field of hydroelectric generation, in particular to an impulse turbine and a nozzle thereof. A spiral rifling is arranged on the inner wall of the nozzle; the spiral rifling is used for enabling high-speed water flow passing through the nozzle to rotate so as to achieve separation of silt in the water flow through centrifugal force. Through the method that bolt rifling is arranged in a spray pipe at the tail end of a flow channel of a water distribution coil of the impulse turbine, separation and layering of high-density silt are achieved in high-speed fluid, and silt mixed water flow without distribution rules is changed into layered separation water flow regularly distributed on the outer edge of the silt. Therefore, a basis is provided for the arrangement and the shape and thickness compensation design of the accurate wear-resistant and impact-resistant material on the inner layer of the water bucket. The anti-sediment performance of the impact type water turbine wheel can be greatly improved, and the service life of the impact type water turbine wheel under the sediment-laden, high-water-head and large-capacity operation conditions is greatly prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydroelectric power generation, in particular to an impulse water turbine and a nozzle thereof. BACKGROUND

[0002] In the field of high water head (greater than 700m) hydroelectric power generation, the impulse water turbine has become the first choice for this working condition due to its unique design principle and energy conversion characteristics. However, large-capacity, high-speed impulse water turbines operating in multi-sediment river conditions face severe runner wear challenges. The hard particles such as sand and gravel carried in the high-speed jet produce continuous impact and erosion on the water bucket, causing the bowl-shaped working surface of the water bucket to gradually appear indentations, deformations and other damages, and even cause structural failure in severe cases. Such wear not only reduces the energy conversion efficiency of the water turbine, but also directly threatens the structural integrity of the runner and the safe and stable operation of the unit.

[0003] At present, there is no systematic and effective solution to the erosion problem of the impulse water turbine under the condition of multi-sediment. Due to the significant irregularity and randomness of the sediment content, particle size distribution and incoming flow conditions in the river, it is difficult for traditional protective measures to achieve the expected effect. The existing technologies mostly focus on the hardening treatment of the material surface or the local optimization of the structure, but none of them can fundamentally solve the problem of separation of sediment particles in the jet. This technical bottleneck seriously restricts the popularization and application of the impulse water turbine under the condition of multi-sediment, and it is urgent to achieve breakthrough through innovative technical means. SUMMARY

[0004] Therefore, the embodiments of the present application provide an impulse water turbine and a nozzle thereof, which can change the sediment mixed water flow without distribution regularity into a layered separated water flow with regular distribution of sediment on the outer edge, thereby providing a basis for the accurate anti-wear and anti-impact material setting and shape, thickness compensation design in the inner layer of the water bucket, and further improving the wear resistance of the water bucket.

[0005] A first aspect of the embodiments of the present application provides a nozzle of an impulse water turbine, an inner wall of the nozzle is provided with a spiral rifling. The spiral rifling is used to make the high-speed water flow passing through the nozzle rotate to separate the sediment in the water flow by centrifugal force.

[0006] In one embodiment, the spiral rifling includes alternately distributed male lines and female lines, the male lines and the female lines extend spirally along the axial direction of the nozzle.

[0007] In one embodiment, the inner wall of the nozzle is provided with spiral ribs, the spiral ribs constitute the male lines, and the inner wall surface between adjacent spiral ribs constitutes the female lines; or The nozzle has a spiral groove on its inner wall, which forms the negative line, and the inner wall surface between adjacent spiral grooves forms the positive line.

[0008] In one embodiment, the width of the positive line is less than or equal to the width of the negative line.

[0009] In one embodiment, the helical rifling is a progressive rifling, and the pitch of the helical rifling gradually decreases along the direction of water flow.

[0010] In one embodiment, the direction of the spiral rifling is consistent with the rotation direction of the water turbine.

[0011] In one embodiment, the number of spiral rifling grooves is an integer multiple of 12.

[0012] In one embodiment, the parameters of the helical rifling are determined by the following method: Based on the physical principles of particle motion in a rotating flow field, the flow field characteristics required to migrate sediment particles to the outer edge of the jet are determined. Establish a model relating the geometric parameters of the helical rifling to the flow field characteristics; The parameters of the helical rifling are determined based on the aforementioned relational model, including pitch, bore width, and depth of the helical rifling.

[0013] A second aspect of this application provides an impulse turbine, comprising: a runner, a distribution coil, and a nozzle as described in the first aspect of this application, wherein the nozzle is connected to the distribution coil.

[0014] In one embodiment, the impeller includes a hub and water buckets evenly distributed on the hub. A partitioned additive layer is provided on the working surface of the water buckets, and the position of the partitioned additive layer corresponds to the mud and sand impact area on the outer edge of the jet after being treated by the helical rifling.

[0015] The first aspect of this application provides a nozzle for an impulse turbine, wherein the inner wall of the nozzle is provided with helical rifling. The helical rifling is used to generate rotation in the high-speed water flow passing through the nozzle, thereby achieving the separation of sediment in the water flow through centrifugal force. By incorporating bolt rifling into the nozzle at the end of the flow channel of the impulse turbine's distribution coil, high-density sediment can be separated and stratified in high-speed fluid, transforming the irregularly distributed sediment-mixed water flow into a stratified water flow with regularly distributed sediment at its outer edge. This provides a basis for the precise setting of anti-wear and anti-impact materials in the inner layer of the water bucket and the design of its shape and thickness compensation. This can greatly improve the sediment resistance of the impulse turbine impeller and significantly extend the service life of the impulse turbine runner under conditions of high sediment, high head, and large capacity operation.

[0016] It can be understood that the beneficial effects of the second aspect described above can be referred to the relevant description in the first aspect described above, which will not be repeated here. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows. Obviously, the drawings in the following description only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0018] Figure 1 is a structural schematic diagram of a nozzle of an impulse water turbine provided by an embodiment of the present application; Figure 2 is a structural schematic diagram of a nozzle of an impulse water turbine provided by another embodiment of the present application; Figure 3 is a structural schematic diagram of a nozzle of an impulse water turbine provided by another embodiment of the present application; Figure 4 is another angle structural schematic diagram of a nozzle provided by an embodiment of the present application; Figure 5 is a pitch schematic diagram provided by an embodiment of the present application; Figure 6 is a flow chart of a helical rifling parameter determination method provided by an embodiment of the present application; Figure 7 is a structural schematic diagram of an impulse water turbine provided by an embodiment of the present application; Figure 8 is a partitioned additive layer schematic diagram of an impulse water turbine provided by an embodiment of the present application. DETAILED DESCRIPTION

[0019] In the following description, specific details are set forth in order to provide a thorough understanding of embodiments of the present application. However, persons of ordinary skill in the art will readily recognize that embodiments of the present application can be practiced without these specific details. In other instances, well-known structures, devices, circuits, and processes have not been described in detail so as not to unnecessarily obscure aspects of the present application.

[0020] It should be noted that when an element is referred to as being "fixed" or "set" on another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or indirectly connected to the other element.

[0021] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like, indicating the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0022] It should be understood that when used in the specification and the appended claims of the present application, the term "comprising" indicates the presence of the described features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0023] It should also be understood that the term "and / or" used in the description of the present application and the appended claims means any combination of one or more of the associated listed items and all possible combinations thereof, and includes these combinations.

[0024] In addition, in the description of the present application and the appended claims, the terms "first", "second", "third" and the like are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0025] In the present application, the reference "one embodiment" or "some embodiments" and the like means that the specific features, structures or characteristics described in connection with the embodiment are included in one or more embodiments of the present application. Therefore, the statements "in one embodiment", "in some embodiments", "in other some embodiments", "in further some embodiments" and the like appearing in different places in the specification are not necessarily all referring to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized. The terms "include", "contain", "have" and their variants mean "include but are not limited to", unless otherwise specifically emphasized.

[0026] As Figure 1 The nozzle of the impulse water turbine provided by the embodiments of the present application is shown in FIG. 1. The inner wall of the nozzle 3 is provided with a spiral rifling 31. The spiral rifling 31 is used to make the high-speed water flow through the nozzle 3 rotate to realize the separation of the silt in the water flow by centrifugal force.

[0027] In application, the nozzle 3 is located at the end of the distribution disc pipe 5 of the impulse water turbine. The main function of the nozzle 3 is to convert the pressure energy of water into kinetic energy to form a high-speed jet flow, which impacts the runner of the water turbine to make the runner rotate, thereby converting the water energy into mechanical energy. As Figure 2As shown, the nozzle 3 is provided with a spray needle 32, by adjusting the position of the spray needle 32, the flow area of the nozzle 3 can be changed, so as to control the flow and jet velocity of water. When the water flow enters the nozzle, due to the contraction effect of the nozzle, the velocity of the water flow gradually increases, and the pressure gradually decreases. Through the action of the spiral rifling 31, the jet flow presents the characteristics of rotating water flow from the nozzle port 33 of the nozzle 3. The pressure of the water can be converted into kinetic energy to form a high-speed impact jet 4 acting on the water surface 11 of the bucket 1 (the bucket 1 includes the water surface 11 and the backwater surface 12). The impact jet 4 impacts the bucket blades on the runner, causing the runner to rotate, and in turn driving the generator to generate electricity.

[0028] In one embodiment, as shown in Figure 3 The spiral rifling 31 includes alternately distributed male lines 311 and female lines 312, and the male lines 311 and the female lines 312 extend spirally along the axial direction of the nozzle 3.

[0029] In application, each spiral rifling 31 is composed of a male line (width a / mm) and a female line (width b / mm), and has a specific depth h (mm) and a pitch P (length / m of one rotation of water flow particles). When the male line is formed by the inner wall of the nozzle, the depth h is the concave depth of the female line. When the female line is formed by the inner wall of the nozzle, the depth h is the convex height of the male line.

[0030] The embodiment of the present application is composed of alternately arranged male lines and female lines, wherein the male lines provide the main guide surface and directly act on the water flow to transfer momentum, and the female lines accommodate the secondary flow of the fluid and stabilize the flow field. This alternating structure can ensure that the water flow obtains uniform and continuous tangential velocity components, avoid the generation of unstable vortex or separation zone, and thus form a stable and symmetrical rotating flow field, which is a key structural guarantee for realizing efficient and uniform centrifugal separation.

[0031] In one embodiment, as shown in Figure 4 The inner wall of the nozzle 3 is provided with spiral ribs, the spiral ribs constitute the male lines 311, and the inner wall surface between adjacent spiral ribs constitutes the female lines 312; or The inner wall of the nozzle 3 is provided with spiral grooves, the spiral grooves constitute the female lines 312, and the inner wall surface between adjacent spiral grooves constitutes the male lines 311.

[0032] The embodiment of the present application covers two different manufacturing process paths of additive and subtractive. The first one is more suitable for surfacing or additive manufacturing by building ribs to form male lines, and the second one is suitable for traditional mechanical machining by cutting grooves to form female lines. Both of the two methods can realize the same function of guiding the rotation of water flow, and can be adaptively selected according to different production conditions and technical backgrounds, which reduces the threshold and cost of process implementation, and enhances the practicality and popularization value of the invention.

[0033] In one embodiment, the width of the male line 311 is less than or equal to the width of the female line 312.

[0034] In one embodiment, the width of the male line 311 is less than or equal to the width of the female line 312.

[0035] In one embodiment, the spiral rifling 31 is a variable pitch rifling, and the pitch of the spiral rifling 31 gradually decreases along the water flow direction.

[0036] In application, as shown in FIG. 2, the pitch P refers to the axial distance between the corresponding points of two adjacent threads on the spiral line. Figure 5

[0037] In one embodiment, the spiral rifling 31 is a variable pitch rifling, and the pitch of the spiral rifling 31 gradually decreases along the water flow direction.

[0038] In one embodiment, the spiral rifling 31 is a variable pitch rifling, and the pitch of the spiral rifling 31 gradually decreases along the water flow direction.

[0039] In one embodiment, the spiral rifling 31 is a variable pitch rifling, and the pitch of the spiral rifling 31 gradually decreases along the water flow direction.

[0040] In one embodiment, the spiral rifling 31 is a variable pitch rifling, and the pitch of the spiral rifling 31 gradually decreases along the water flow direction.

[0041] ​In this embodiment, the number of rifling grooves is specifically limited to an integer multiple of 12, ensuring that the grooves are completely symmetrical and uniformly distributed around the nozzle circumference. This high degree of circumferential symmetry ensures that the guiding force on the water flow is uniform and consistent, thereby generating a stable, symmetrical, and rigid vortex with no central axis drift. This effectively prevents localized wear and vibration caused by flow field asymmetry, providing a stable and predictable sediment distribution pattern for the water bucket.

[0042] In one embodiment, such as Figure 6 As shown, the parameters of the helical rifling 31 are determined by the following method: Based on the physical principles of particle motion in a rotating flow field, the flow field characteristics required to migrate sediment particles to the outer edge of the jet are determined. Establish a model relating the geometric parameters of the helical rifling 31 to the flow field characteristics; The parameters of the helical rifling 31 are determined based on the relational model, including the pitch, the width of the male rifling 311, the width of the female rifling 312, and the depth of the helical rifling 31.

[0043] In the application, input sediment gradation parameters (including particle size d) p and density ρ p The equivalent radius r of the nozzle inner wall and the length L of the nozzle helical rifling segment are first determined based on the radial migration distance Δr and the fluid axial velocity U. x The radial slip velocity w required to calculate sediment particles r req Its value is approximately equal to (Δr·U) x ) / L; then, using this radial slip velocity, combined with the fluid viscosity μ, the density difference between the particles and the fluid (ρ) p Parameters such as -ρ) are used to derive the minimum tangential velocity u through mechanical equilibrium relationships. θmin (d p ),Right now The ratio of minimum tangential velocity to axial velocity is then defined as the minimum rotational intensity S. min (d p ), that is, S min (d p )=u θmin / U x Furthermore, a critical condition for sediment separation is proposed, requiring the actual rotational intensity S to be greater than S0. min (d p ), where S is derived from the empirical formula Calculate, k s The correction coefficient is used; when the separation condition is met, the pitch P corresponding to the target separation gradation must satisfy the constraint inequality. Finally, based on the known nozzle inner diameter D, helical section length L, and the calculated S... min (d p), the key design parameters of the spiral rifling, including the pitch P, the width of the male thread a, the width of the female thread b and the depth of the rifling h, are determined by reverse solving.

[0044] The embodiment of the present application starts from the target of separating sediment (migrating to the outer edge), reverses the required flow field characteristics (such as the minimum tangential velocity), and then solves the specific structure size by establishing a physical model between the geometric parameters of the rifling and the flow field characteristics. It can ensure that the designed rifling parameters not only meet the functional requirements but also take into account the operation efficiency and reliability, greatly improving the success rate and optimization level of the design.

[0045] The embodiment of the present application provides an impulse water turbine, as shown in Figure 6 The embodiment of the present application provides an impulse water turbine, as shown in

[0046] In one embodiment, the runner includes a hub 2 and buckets 1 uniformly distributed on the hub 2, and a partitioned additive layer 118 is arranged on the working surface of the bucket 1. The position of the partitioned additive layer 118 corresponds to the sediment impact area of the outer edge of the jet after being treated by the spiral rifling 31.

[0047] In application, the partitioned additive layer 118 can be a wear-resistant coating. The wear-resistant coating in the outer edge area bears the impact of sediment, and the central area forms a protection area for bearing only the impact of clean water. The thickness and range of the additive need to be determined according to the distribution and impact energy of the sediment.

[0048] The nozzle 3 is arranged on the distributor pipe 5, the distributor pipe 5 is an annular high water pressure pipeline from the penstock of the impulse water turbine to the centerline elevation of the runner of the impulse water turbine, and uniformly arranges the above-mentioned four nozzles or six nozzles, and provides strong water pressure to form an impact jet 4 through the nozzle (with a spray needle adjustment) to drive the bucket to rotate at high speed. As shown in Figure 8 The hub 2 and the bucket 1 assembled on the hub 2 jointly form a runner of the impulse water turbine, and the runner is driven to rotate by the impact jet 4.

[0049] In application, the hub 2 is an intermediate part for connecting the bucket of the runner of the impulse water turbine and the main shaft, and plays a role in transmitting torque and supporting the bucket. It is disc-shaped or hub-shaped structure with a certain thickness and diameter to meet the strength and stiffness requirements. The center has a hole for cooperation and installation with the main shaft, and is fixed with the bucket through welding or bolt connection and the like along the circumferential edge. The hub needs to bear the huge impact force and torque transmitted by the bucket, and generally adopts high-strength alloy steel forging. Its working principle is that the high-speed water flow impacts the bucket of the water turbine, the bucket generates a rotary torque under the action of the water flow, the torque is transmitted to the main shaft through the hub, and then drives the generator rotor to rotate, converting water energy into electric energy.

[0050] The embodiment of the application is directed to the jet characteristics after helical rifling treatment, and proposes a corresponding adaptive design for the water bucket, that is, to set a partition additive layer. Targeted protection is realized, which no longer needs to uniformly reinforce the entire water bucket working surface, but can apply high-hardness wear-resistant materials on the outer edge track according to the concentrated impact area of the sediment determined by the rotating jet. This functional requirement-oriented gradient material design can significantly improve the protection level and life of the key wear-resistant area while maximizing the saving of expensive wear-resistant materials and controlling the manufacturing cost.

[0051] Embodiment one Taking a high-head and large-capacity impulse water turbine with a water head greater than 800m and a single-machine capacity greater than 700MW as an example, the embodiment of the application can realize high adaptation, high strength and high safety and reliable operation of the water bucket and the hub, and the determination process of the related parameters of the nozzle is as follows: I. Implementation scheme of setting helical rifling for sediment separation in the nozzle 1. Basic parameter setting Water turbine type: XLD-100 type impulse water turbine; Design flow: Q = 10m 3 / s; Flow passage diameter: D = 0.5m, radius R = 0.25m; Axial flow velocity: v a = Q / (πR 2 ） = 50.93m / s; Helical rifling parameters: pitch P = 1.5m, length L = 2m; Sediment parameters: density p s = 2650kg / m 3 , inlet concentration C 0= 50kg / m 3 ; Water body parameters: density p w = 1000kg / m 3 , and the dynamic viscosity of clear water is calculated according to the water temperature of 20℃; 2. Calculation of helical rifling rotation characteristics Helix angle α : tan α = 2 πR / P = 2 π × 0.25 / 1.5 = 1.047⇒ α = 46.3°; Tangential velocityv t : v t = v a ⋅tan α =50.93×1.047=53.3m / s; rotational angular velocity w : w = v t / R =53.3 / 0.25=213.2rad / s; 3. Calculation of sediment separation effect Critical separation particle size r p,c (Take r = R , v r =0.1; v z =5.093m / s): r p,c =2( p s − p w ) r w 2 9 μ v r =2×(2650−1000)×0.25×(213.2) 2 ×9×1.0×10 −3 ×5.093=1.12×10 −5 m=11.2 μ m, i.e. sediment particles with a particle size greater than 11.2 μ m can be effectively separated.

[0052] Radial migration distance Δ r : Δ r =21× R w 2 ( L / v z ) 2 =21×0.25×(213.2) 2 ×(50.932) 2 =0.226m; Flow passage radius R =0.25m, so almost all particles migrate to the outer edge of the jet (Δ r ≈ R ).

[0053] 4. Sediment concentration distribution in the cross section of the jet Ignoring the thermal motion term, the sediment concentration distribution at the outlet of the jet (radius r 0=R The sediment concentration distribution at 0.25m is as follows: C (r) =50⋅exp(−2×1000× v z 2 (2650−1000)×(213.2)2( r 2 -0.25 2 )); when r When the radius is 0.2m (central area): C (0.2) =50⋅exp(−2×1000×50.9321650×213.22×(0.2 2 -0.25 2 ))≈0.12kg / m3; when r When =0.25m (outer edge): C (0.25) =50kg / m 3 ; It can be seen that the sediment concentration in the central area drops to 0.24% of the inlet concentration, achieving efficient separation.

[0054] 5. Water tank zone protection design Based on the jet cross-section analysis, the working surface of the water bucket can be divided into: Central clear water area: radius r <0.2m, no additional wear-resistant treatment required; Outer edge sediment zone: radius 0.2m ≤ r For depths ≤0.25m, a 5mm thick tungsten carbide additive layer is installed, which is expected to withstand the impact velocity of mud and sand. v θ =53.3m / s, the wear rate is reduced by more than 90%.

[0055] The above examples demonstrate that helical rifling can induce strong rotation in high-speed water flow, utilizing centrifugal force to achieve efficient separation of sediment from water (critical particle size > 11.2 mm). μ With a particle separation efficiency exceeding 95%, and combined with the bucket zonal additive design, the wear of sediment on the central working surface of the bucket can be significantly reduced, fundamentally solving the wear problem of impact turbines. In practical applications, the helical rifling parameters can be optimized according to the sediment particle size distribution to further improve the separation effect.

[0056] II. Specific Implementation Methods for Helical Rifling on the Inner Wall of the Nozzle (I) Scheme for helical rifling inside the nozzle of an impulse turbine The separation of sediment in the nozzle of the impulse water turbine is achieved by the helical rifling of the inner wall, which causes the high-speed water flow to rotate, and the centrifugal force pushes the sediment with a higher density (p ≈ 2650 kg / m 3 ) to the outer edge of the jet. The specific parameter calculation and examples are as follows.

[0057] 1. Principle and parameters (1) Core condition of centrifugal separation The centrifugal force received by the sediment particles in the rotating water flow must be greater than the viscous resistance of the water flow, so that they can move outward. The key parameters include: Nozzle inner diameter D = 0.5 m, radius R = 0.25 m; Axial flow velocity v z = 50.93 m / s; Sediment particle radius r s ≈ 0.1 mm = 10 −4 m (typical sediment size); Water dynamic viscosity η = 1.002 × 10 -3 Pa·s, density p w = 1000 kg / m 3 .

[0058] (2) Rotational speed and radial migration condition The radial velocity of the sediment particles v r must satisfy: in the nozzle length L , from the center to the outer edge (distance R = 0.25 m), that is v r ≥ R ⋅ v z / L (axial flow time t = L / v z , need v r ⋅ t ≥ R ).

[0059] According to the balance between centrifugal force and viscous resistance, we have: v r ≈ 0.0146 ⋅ v θ 2 ; ( v θ is the linear velocity of water in the circumferential direction).

[0060] (3) Relationship between pitch and peripheral velocity Rifle pitch P For axial advancement P Distance when the water flow rotates one circle (circumferential length 2 πR Therefore v θ = (2 πR ⋅ v z ) / P Substitute R = 0.25 m, v z = 50.93 m / s, we get v θ ≈ 80 / P (approximate value).

[0061] 2. Parameters in this example Assume the length of the nozzle L = 4 m (about 8 times the inner diameter of the nozzle, which conforms to the common proportion of impulse water turbines): (1) Radial velocity requirement: v r ≥ 40.25 × 50.93 ≈ 3.18 m / s; (2) Peripheral velocity requirement: from v r = 0.0146 v θ 2 ≥ 3.18, we get v θ ≥ 14.8 m / s; (3) Pitch calculation: from v θ = 80 / P ≥ 14.8, that is P ≤ 5.4 m (take P = 5 m as the outlet pitch).

[0062] 3. Determination of rifling parameters (1) Pitch: adopt a gradually changing rifling (to avoid excessive initial turbulence), the inlet pitch P 入 = 8 m (the water flow rotates slowly), the outlet pitch P 出 = 5 m (the rotation is accelerated), and the linear transition in the intermediate axial length L (4 m) ensures smooth rotation enhancement.

[0063] (2) Number of rifling lines: the inner diameter is 0.5 m (large diameter), which needs to ensure uniform water flow rotation and small resistance. In this example, 96 lines are taken (a multiple of 12, which facilitates processing and reduces water flow disturbance).

[0064] (3) Rotation direction: Right-handed (consistent with the mechanical rotation direction of the impulse water turbine, which is beneficial to water flow stability).

[0065] (4) Type of rifling: Gradual rifling (pitch gradually decreases from large to small), which avoids excessive rotation at the inlet, resulting in energy loss and turbulence, and makes the sediment gradually migrate to the outside.

[0066] This method can generate sufficient centrifugal force through gradually increasing rotation, allowing the sediment to smoothly migrate to the outer edge in the nozzle while reducing water flow energy loss.

[0067] (II) Specific parameter example of single helical rifling The width (positive line / negative line width) and depth of a single rifling need to balance three core objectives: ① effectively transmit rotational torque to ensure water flow rotates as expected; ② minimize water flow resistance and energy loss; ③ ensure nozzle structural strength (avoid material weakening due to excessive rifling depth). Based on the working conditions of the impulse water turbine nozzle (high flow rate, sediment-laden water flow) and the parameters in the previous example (inner diameter 0.5m, 96 riflings), the specific parameters are determined as follows: 1. Design basis and constraints (1) Water flow disturbance control: Excessive width or depth of the helical rifling can cause vortex formation in the groove, increasing resistance and energy loss (impulse water turbines have high efficiency requirements, and the energy loss caused by the helical rifling should be controlled within 0.5%).

[0068] (2) Rotational torque transmission: The helical rifling on the inner wall of the nozzle needs to effectively contact the high-speed water flow of the impulse water turbine, driving the water flow to rotate through friction. The width and depth of the helical rifling need to be sufficient to generate "guiding force" while avoiding excessive intervention in water flow smoothness.

[0069] (3) Structural strength: The nozzle material is mostly high-strength steel (such as Q345), and excessive rifling depth can weaken the inner wall thickness, leading to a decrease in pressure resistance (the working pressure of the nozzle is usually 1MPa~5MPa).

[0070] 2. Width calculation (positive line and negative line) The rifling is composed of "positive lines" (protruding parts) and "negative lines" (recessed parts) alternating in the circumferential direction, and the total width needs to cover the entire inner circumference.

[0071] Nozzle inner circumference length: C = πD = π ×0.5≈1.571m=1571mm; Number of riflings: 96 (each rifling corresponds to 1 positive line + 1 negative line), so the width of a single group (positive line + negative line) is: a + b = C / 96≈1571 / 96≈16.4mm Reference to the fluid mechanics (such as water pump impeller) ratio (the width of the male line is slightly smaller than or equal to the width of the female line, reducing resistance), take: Male line width (a): 6.8mm (convex part, contact with water flow to transfer rotary torque, width should not be too wide to avoid increasing resistance); Female line width (b): 9.6mm (concave part, accommodate water flow disturbance, width is slightly larger to reduce vortex).

[0072] 3. Spiral rifling depth (h) calculation Rifling depth (i.e. the radial distance between the bottom of the female line and the top of the male line) needs to meet: both drive water rotation and not produce significant resistance. The flow velocity of the turbine nozzle is higher (50.93m / s), and needs to be slightly deeper to enhance rotation guidance, but needs to control resistance, take the depth as 1.0% of the caliber: h =1%× D =0.01×500mm=5mm; (1) Verify the impact of resistance: the depth of 5mm is only 1% of the inner diameter, when the water flow flows along the axial direction, the vortex intensity in the groove is weak (Reynolds number R e ≈2.5×10 7 , belongs to turbulent flow, but the groove size is much smaller than the flow velocity gradient scale), the energy loss can be controlled within 0.5%, which meets the efficiency requirements of the impulse water turbine.

[0073] (2) Structural strength verification: the nozzle wall thickness is usually ≥15mm, and can be thickened at the end section, and the depth of 5mm has no significant effect on the pressure resistance of 1MPa~5MPa working pressure (strength check: the remaining wall thickness can withstand ≥8MPa pressure, with sufficient redundancy). The spiral rifling width (a, b) and depth (h) parameters are as shown in Table 1: Table 1 The above parameter combination can effectively drive water rotation under the premise of minimizing energy loss, and cooperate with the previously designed pitch and number of strips to realize the separation of sediment to the outer edge of the jet.

[0074] The above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. A nozzle for a Pelton turbine, characterized in that The inner wall of the nozzle (3) is provided with a spiral rifling (31); The spiral rifling (31) is used for making the high-speed water flow through the nozzle (3) rotate to realize the separation of the sediment in the water flow by centrifugal force.

2. The nozzle of a Pelton turbine according to claim 1, characterized in that The spiral rifling (31) comprises alternatingly distributed male lines (311) and female lines (312), which extend spirally along the axial direction of the nozzle (3).

3. The nozzle of a Pelton turbine according to claim 2, characterized in that The inner wall of the nozzle (3) is provided with spiral ribs, which constitute the male lines (311), and the inner wall surface between adjacent spiral ribs constitutes the female lines (312); or The inner wall of the nozzle (3) is provided with spiral grooves, which constitute the female lines (312), and the inner wall surface between adjacent spiral grooves constitutes the male lines (311).

4. The nozzle of a Pelton turbine according to claim 2, characterized in that The width of the male line (311) is less than or equal to the width of the female line (312).

5. The nozzle of a Pelton turbine according to claim 1, characterized in that, The spiral rifling (31) is a variable-pitch rifling, and the pitch of the spiral rifling (31) gradually decreases along the water flow direction.

6. The nozzle of a Pelton turbine according to claim 1, characterized in that, The rotation direction of the spiral rifling (31) is consistent with the rotation direction of the water turbine.

7. The nozzle of a Pelton turbine according to claim 1, characterized in that, The number of the spiral rifling (31) is an integer multiple of 12.

8. The nozzle of a Pelton turbine according to claim 1, characterized in that, The parameters of the spiral rifling (31) are determined by the following method: Based on the physical principle of particle motion in a rotating flow field, the flow field characteristics required for sediment particles to migrate to the outer edge of the jet are determined; A relationship model between the geometric parameters of the spiral rifling (31) and the flow field characteristics is established; According to the relationship model, the parameters of the spiral rifling (31) are determined, including the pitch, the width of the male line (311), the width of the female line (312), and the depth of the spiral rifling (31).

9. A Pelton turbine, characterized by The turbine comprises a runner, a water distribution disc pipe (5), and the nozzle (3) according to any one of claims 1-8, and the nozzle (3) is connected with the water distribution disc pipe (5).

10. The Pelton turbine of claim 9, wherein The runner comprises a hub (2) and buckets (1) uniformly distributed on the hub (2), and a partitioned additive layer (118) is arranged on the working surface of the bucket (1), and the position of the partitioned additive layer (118) corresponds to the sediment impact area of the outer edge of the jet after being treated by the spiral rifling (31).

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