Pelton turbine and its nozzle

Abstract

The application relates to the technical field of hydraulic power generation, in particular to an impulse water turbine and a nozzle thereof. The inner wall of the nozzle is provided with spiral rifling; the spiral rifling is used for rotating the high-speed water flow passing through the nozzle to realize the separation of the silt in the water flow through centrifugal force. The method of embedding bolt rifling in the nozzle at the end of the flow channel of the distribution disc pipe of the impulse water turbine realizes the separation and stratification of high-density silt in the high-speed fluid, changes the silt mixed water flow without distribution rules into stratified separated water flow with regular distribution of silt outer edge, and thus provides a basis for the precise anti-wear and anti-impact material setting and shape and thickness compensation design of the inner layer of the water bucket. The silt resistance of the impulse water turbine can be greatly improved, and the service life of the impulse water turbine runner under the conditions of much silt, high water head and large capacity can be greatly prolonged.

Description

Technical Field

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

[0002] In high-head (greater than 700m) hydropower, impulse turbines have become the preferred choice for this operating condition due to their unique design principles and energy conversion characteristics. However, large-capacity, high-speed impulse turbines operating in silty rivers face severe challenges related to runner wear. The high-speed jet carries hard particles such as silt and gravel, which continuously impact and erode the runner's buckets, causing gradual dents and deformation on the bucket's cup-shaped working surface, and in severe cases, even structural failure. This wear not only reduces the turbine's energy conversion efficiency but also poses a direct threat to the structural integrity of the runner and the safe and stable operation of the unit.

[0003] Currently, no systematic and effective solution has been developed to address the erosion problem of impulse turbines under high sediment load conditions. Due to the significant irregularities and randomness in the sediment content, particle size distribution, and inflow conditions in rivers, traditional protective measures are insufficient to achieve the desired results. Existing technologies mostly focus on surface hardening of materials or local optimization of structural forms, but none have fundamentally solved the problem of sediment particle separation in the jet. This technological bottleneck severely restricts the widespread application of impulse turbines under high sediment load conditions, and breakthroughs through innovative technological means are urgently needed. Summary of the Invention

[0004] In view of this, the present application provides an impact turbine and its nozzle, which can transform irregularly distributed mud and sand mixed water flow into a layered separated water flow with regular mud and sand distribution on the outer edge. This provides a basis for the precise setting of wear-resistant and impact-resistant materials in the inner layer of the water bucket and the design of its shape and thickness compensation, thereby improving the wear resistance of the water bucket.

[0005] A first aspect of this application provides a nozzle for an impulse turbine, wherein the inner wall of the nozzle is provided with helical rifling.

[0006] The spiral rifling is used to rotate the high-speed water flow passing through the nozzle, thereby separating the sediment in the water flow through centrifugal force.

[0007] In one embodiment, the helical rifling includes alternating positive and negative riflings that extend helically along the axial direction of the nozzle.

[0008] In one embodiment, the inner wall of the nozzle is provided with helical ridges, the helical ridges forming the male line, and the inner wall surfaces between adjacent helical ridges forming the female line; or

[0009] 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.

[0010] In one embodiment, the width of the positive line is less than or equal to the width of the negative line.

[0011] 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.

[0012] In one embodiment, the direction of the spiral rifling is consistent with the rotation direction of the water turbine.

[0013] In one embodiment, the number of spiral rifling grooves is an integer multiple of 12.

[0014] In one embodiment, the parameters of the helical rifling are determined by the following method:

[0015] 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.

[0016] Establish a model relating the geometric parameters of the helical rifling to the flow field characteristics;

[0017] The parameters of the helical rifling are determined based on the aforementioned relational model, including pitch, bore width, and depth of the helical rifling.

[0018] 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.

[0019] 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.

[0020] 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 wear-resistant and impact-resistant materials and the design of their shape and thickness compensation in the inner layer of the water bucket. 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.

[0021] It is understandable that the beneficial effects of the second aspect mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here. Attached Figure Description

[0022] 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.

[0023] Figure 1 This is a schematic diagram of the nozzle structure of an impulse turbine provided in an embodiment of this application;

[0024] Figure 2 This is a schematic diagram of the nozzle structure of an impulse turbine provided in another embodiment of this application;

[0025] Figure 3 This is a schematic diagram of the nozzle structure of an impulse turbine provided in another embodiment of this application;

[0026] Figure 4 This is a schematic diagram of another angle structure of the nozzle provided in one embodiment of this application;

[0027] Figure 5 This is a schematic diagram of the pitch provided in one embodiment of this application;

[0028] Figure 6 This is a schematic flowchart of a method for determining helical rifling parameters provided in an embodiment of this application;

[0029] Figure 7 This is a schematic diagram of the structure of an impulse turbine provided in one embodiment of this application;

[0030] Figure 8 This is a schematic diagram of the partitioned additive layer of an impulse turbine provided in one embodiment of this application. Detailed Implementation

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] like Figure 1 As shown in the embodiment of this application, a nozzle for an impulse turbine is provided, wherein the inner wall of the nozzle 3 is provided with helical rifling 31;

[0039] The spiral rifling 31 is used to generate rotation in the high-speed water flow passing through the nozzle 3, so as to separate the mud and sand in the water flow through centrifugal force.

[0040] In application, nozzle 3 is located at the end of the water distribution coil 5 of the impulse turbine. 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, thereby converting water energy into mechanical energy. Figure 2 As shown, nozzle 3 is equipped with a nozzle needle 32. By adjusting the position of the nozzle needle 32, the flow area of ​​nozzle 3 can be changed, thereby controlling the water flow rate and jet velocity. When pressurized water enters the nozzle, due to the contraction of the nozzle, the water velocity gradually increases and the pressure gradually decreases. Through the action of the helical rifling 31, the jet flows out from the nozzle orifice 33 of nozzle 3 with a rotating water flow characteristic. The pressure energy of the water is converted into kinetic energy, forming a high-speed impact jet 4 acting on the water-facing surface 11 of water tank 1 (water tank 1 includes a water-facing surface 11 and a back surface 12). The impact jet 4 impacts the water tank blades on the impeller, causing the impeller to rotate, which in turn drives the generator to generate electricity.

[0041] In one embodiment, such as Figure 3 As shown, the spiral rifling 31 includes alternating male and female riflings 311 and 312, which extend spirally along the axial direction of the nozzle 3.

[0042] In application, each helical rifling 31 consists of a male groove (width a / mm) and a female groove (width b / mm), and has a specific depth h (mm) and pitch P (length of one revolution of a water particle / m). When the male groove is formed by the inner wall of the nozzle, the depth h is the concave depth of the female groove. When the female groove is formed by the inner wall of the nozzle, the depth h is the convex height of the male groove.

[0043] The embodiments of this application feature a spiral channel composed of alternating positive and negative lines. The positive lines provide the main guiding surface and directly interact with the water flow to transfer momentum, while the negative lines accommodate secondary flow of the fluid and stabilize the flow field. This alternating structure ensures that the water flow obtains a uniform and continuous tangential velocity component, avoiding the generation of unstable vortices or separation zones, thereby forming a stable and symmetrical rotating flow field. This is a key structural guarantee for achieving efficient and uniform centrifugal separation.

[0044] In one embodiment, such as Figure 4 As shown, the inner wall of nozzle 3 is provided with spiral ridges, which form a positive line 311, and the inner wall surface between adjacent spiral ridges forms a negative line 312; or

[0045] The inner wall of nozzle 3 is provided with spiral grooves, which form negative lines 312, and the inner wall surface between adjacent spiral grooves forms positive lines 311.

[0046] This application's embodiments cover two different manufacturing process paths: additive manufacturing and subtractive manufacturing. The first method, which forms a positive line by constructing convex ridges, is more suitable for welding or additive manufacturing. The second method, which forms a negative line by cutting grooves, is suitable for traditional machining. Both methods can achieve the same function of guiding water flow rotation. The specific method can be adapted to different production conditions and technical backgrounds, reducing the threshold and cost of process implementation and enhancing the practicality and promotional value of this invention.

[0047] In one embodiment, the width of the positive line 311 is less than or equal to the width of the negative line 312.

[0048] This embodiment of the application, by designing the width of the male line to be less than or equal to that of the female line, can minimize the flow resistance of the spiral protrusions to the main body while ensuring sufficient contact area to transmit rotational torque. The narrower male line reduces abrupt changes in the flow cross-section and streamline interference, while the wider female line channel provides smoother flow space for the fluid, helping to maintain a higher axial flow velocity and reduce turbulence intensity and hydraulic losses, thereby optimizing the overall flow efficiency of the nozzle while achieving sediment separation.

[0049] In one embodiment, the helical rifling 31 is a gradually decreasing rifling, and the pitch of the helical rifling 31 gradually decreases along the direction of water flow.

[0050] In applications, such as Figure 5 As shown, the pitch P refers to the axial distance between corresponding points of two adjacent threads on the helix.

[0051] In this embodiment, the helical rifling is specifically designed as a gradually decreasing pitch rifling, meaning the pitch gradually decreases along the flow direction. This achieves precise control over the water flow's rotational acceleration process. The larger pitch at the inlet section makes the initial rotation of the water flow relatively gentle, which is conducive to the stable development of the flow and avoids a sudden drop in pressure. Subsequently, the pitch gradually decreases, which is equivalent to gradually increasing the rotational curvature of the guide surface, thereby continuously increasing the rotational angular velocity of the water flow and steadily enhancing the centrifugal force. This allows sediment particles to undergo a gradually accelerated migration process, avoiding particle collision rebound or flow field instability that may be caused by a sudden increase in centrifugal force, thus improving the reliability and efficiency of the separation process.

[0052] In one embodiment, the spiral rifling 31 has the same rotation direction as the turbine.

[0053] This embodiment avoids interference between the rotating jet and the turbine's motion, conforming to the system's dynamic coordination. When the direction of the rotating jet is the same as the direction of the water bucket's motion, the relative velocity when the water impacts the water bucket can be reduced, thereby reducing hydrodynamic noise and vibration caused by the impact. It also facilitates the smooth entry of the jet into the water bucket and efficient energy transfer, improving the stability and energy conversion efficiency of the turbine operation, and optimizing the overall performance at the system level.

[0054] In one embodiment, the number of helical rifling grooves 31 is an integer multiple of 12.

[0055] 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.

[0056] In one embodiment, such as Figure 6 As shown, the parameters of the helical rifling 31 are determined by the following method:

[0057] 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.

[0058] Establish a model relating the geometric parameters of the helical rifling 31 to the flow field characteristics;

[0059] 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.

[0060] 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, ks This is a correction coefficient; 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 rifling are determined by reverse engineering, including pitch P, bore width a, groove width b, and rifling depth h.

[0061] This application starts with the goal of sediment separation (migrating to the outer edge), reverse-engineers the required flow field characteristics (such as minimum tangential velocity), and then solves for specific structural dimensions by establishing a physical model between the rifling geometry parameters and the flow field characteristics. This ensures that the designed rifling parameters meet functional requirements while also considering operational efficiency and reliability, greatly improving the success rate and optimization level of the design.

[0062] This application provides an embodiment of an impulse turbine, such as... Figure 6 As shown, it includes a rotor, a water distribution coil, and a nozzle 3 as described in any one of claims 1 to 8, wherein the nozzle 3 is connected to the water distribution coil.

[0063] In one embodiment, the impeller includes a hub 2 and water buckets 1 evenly distributed on the hub 2. A partitioned additive layer 118 is provided on the working surface of the water bucket 1. The position of the partitioned additive layer 118 corresponds to the mud and sand impact area on the outer edge of the jet after being treated by the helical rifling 31.

[0064] In applications, the partitioned additive layer 118 can be a wear-resistant coating. The wear-resistant coating in the outer region withstands the impact of mud and sand, while the central region forms a protective area that only withstands the impact of clean water. The thickness and range of the additive need to be determined based on the distribution of mud and sand and the impact energy.

[0065] Among them, nozzle 3 is installed on water distribution coil 5, which 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 evenly distributed nozzles, providing strong water pressure to form an impact jet 4 after passing through the nozzles (with internal spray needle adjustment), driving the water bucket to drive the hub to rotate at high speed. Figure 8 As shown, the hub 2 and the water bucket 1 mounted on the hub 2 together form the runner of the impulse turbine, which is driven to rotate by the impulse jet 4.

[0066] 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.

[0067] This application proposes an adaptive design for the water bucket based on the characteristics of the jet after helical rifling, namely, the setting of a zoned additive layer. This achieves targeted protection, eliminating the need for uniform reinforcement of the entire working surface of the water bucket. Instead, high-hardness wear-resistant material is applied to the outer edge track based on the concentrated impact area of ​​sediment determined by the rotating jet. This functionally driven gradient material design can significantly improve the protection level and lifespan of critical wear-resistant areas while minimizing the use of expensive wear-resistant materials and controlling manufacturing costs.

[0068] Example 1

[0069] Taking a high-head, large-capacity impulse turbine with a head greater than 800m and a single-unit capacity greater than 700MW as an example, the embodiments of this application can achieve high adaptability, high strength, and high safety and reliability of the water bucket and the hub. The process for determining the relevant parameters of the nozzle is as follows:

[0070] I. Scheme for Separating Sediment with Spiral Rifling Inside the Nozzle

[0071] 1. Basic parameter settings

[0072] Turbine model: XLD-100 impulse turbine;

[0073] Design flow: Q =10m 3 / s;

[0074] Flow channel diameter: D =0.5m, radius R =0.25m;

[0075] Axial flow velocity: v a = Q / (πR 2 ） =50.93m / s;

[0076] Rifling parameters: pitch P =1.5m, length L=2m;

[0077] Sediment parameters: density ρ s =2650kg / m 3 Inlet concentration C 0 = 50 kg / m 3 ;

[0078] Water parameters: density ρ w =1000kg / m 3 The dynamic viscosity of clear water is calculated based on a water temperature of 20°C.

[0079] 2. Calculation of the rotational characteristics of helical rifling

[0080] helix angle α :tan α =2 πR / P =2 π ×0.25 / 1.5=1.047⇒ α =46.3°;

[0081] Tangential velocity v t : v t = v a ⋅tan α =50.93×1.047=53.3m / s;

[0082] Rotational angular velocity ω : ω = v t / R =53.3 / 0.25=213.2rad / s;

[0083] 3. Calculation of Sediment Separation Effect

[0084] Critical separation particle size r p,c (Pick r = R , v r =0.1; v z =5.093m / s):

[0085] r p,c =2( ρs - ρw ) rω 2 9 μVR =2×(2650−1000)×0.25×(213.2)2 ×9×1.0×10 −3 ×5.093=1.12×10 −5 m=11.2 μ m, meaning a particle size greater than 11.2 mm. μ Mud and sand particles of m size can be effectively separated.

[0086] Radial migration distance Δ r :

[0087] Δ r =21× Rω 2 ( L / vz ) 2 =21×0.25×(213.2) 2 ×(50.932) 2 =0.226m;

[0088] Flow channel radius R =0.25m, therefore almost all particles migrate to the outer edge of the jet (Δ r ≈ R ).

[0089] 4. Sediment concentration distribution at the jet cross section

[0090] Ignoring thermal motion terms, at the jet exit (radius) r 0= R The sediment concentration distribution at 0.25m is as follows:

[0091] C (r) =50⋅exp(−2×1000× vz 2 (2650−1000)×(213.2)2( r 2 -0.25 2 ));

[0092] when r When the radius is 0.2m (central area):

[0093] C (0.2) =50⋅exp(−2×1000×50.9321650×213.22×(0.2 2 -0.25 2 ))≈0.12kg / m3;

[0094] when r When =0.25m (outer edge): C (0.25) =50kg / m 3 ;

[0095] It can be seen that the sediment concentration in the central area drops to 0.24% of the inlet concentration, achieving efficient separation.

[0096] 5. Water tank zone protection design

[0097] Based on the jet cross-section analysis, the working surface of the water bucket can be divided into:

[0098] Central clear water area: radius r <0.2m, no additional wear-resistant treatment required;

[0099] 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%.

[0100] 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.

[0101] II. Specific Implementation Methods for Helical Rifling on the Inner Wall of the Nozzle

[0102] (I) Scheme for helical rifling inside the nozzle of an impulse turbine

[0103] The sediment separation within the nozzle of an impulse turbine is achieved by using helical rifling on the inner wall to generate rotation in the high-speed water flow, utilizing centrifugal force to separate the denser sediment (ρ≈2650kg / m³). 3 It is pushed towards the outer edge of the jet. Specific parameter calculations and examples are as follows.

[0104] 1. Principles and Parameters

[0105] (1) Core conditions for centrifugal separation

[0106] For sediment particles to move outwards in a rotating water flow, the centrifugal force they experience must be greater than the viscous resistance of the flow. Key parameters include:

[0107] nozzle inner diameter D =0.5m, radius R =0.25m;

[0108] Axial flow velocity v z =50.93m / s;

[0109] Sediment particle radius r s ≈0.1mm=10 −4 m (typical sediment size);

[0110] The dynamic viscosity of water, η = 1.002 × 10⁻⁶ -3 Pa·s, density ρ w =1000kg / m 3 .

[0111] (2) Rotational speed and radial migration conditions

[0112] Radial velocity of sediment particles v r Must meet: within the nozzle length L Inside, migrating from the axis to the outer edge (distance) R =0.25m), that is v r ≥ R ⋅ v z / L (Axial flow time) t = L / vz ,need v r ⋅ t ≥ R ).

[0113] Based on the balance between centrifugal force and viscous resistance, we get: v r ≈0.0146⋅ v θ 2 ; ( v θ (This refers to the linear velocity of the water flow in the circumferential direction).

[0114] (3) Relationship between pitch and circumferential speed

[0115] Rifling pitch P For axial movement P The water flow rotates once at a distance (circumference length 2). πR Therefore v θ =(2 πR ⋅ v z ) / P Substitute R =0.25m v z =50.93m / s, therefore: v θ≈80 / P (approximation).

[0116] 2. Parameters in this example

[0117] Assuming nozzle length L =4m (approximately 8 times the nozzle inner diameter, consistent with common proportions of impulse turbine nozzles):

[0118] (1) Radial velocity requirement: v r ≥40.25×50.93≈3.18m / s;

[0119] (2) Circumferential speed requirement: from v r =0.0146 v θ 2 ≥3.18, therefore v θ ≥14.8m / s;

[0120] (3) Pitch calculation: from v θ =80 / P ≥14.8, that is P ≤5.4m (take) P =5m is used as the outlet screw pitch).

[0121] 3. Determination of rifling parameters

[0122] (1) Pitch: Gradient rifling is used (to avoid excessive initial turbulence), inlet pitch P 入 =8m (slower water flow rotation), outlet screw pitch P 出 =5m (rotation speeds up), with a linear transition within the intermediate axial length L (4m) to ensure smooth and enhanced rotation.

[0123] (2) Number of rifling lines: inner diameter 0.5m (large diameter), which needs to ensure uniform water flow rotation and low resistance. In this example, 96 lines are selected (multiples of 12, which is convenient for processing and reduces water flow disturbance).

[0124] (3) Rotation direction: right-handed (consistent with the mechanical rotation direction of the impulse turbine, which is beneficial to the stability of the water flow).

[0125] (4) Rifling type: Gradual rifling (pitch gradually changes from large to small) to avoid energy loss and turbulence caused by excessive rotation at the inlet, so that the sediment gradually migrates to the outside.

[0126] This method generates sufficient centrifugal force through progressively increasing rotation, allowing sediment to migrate smoothly to the outer edge of the nozzle while reducing water flow energy loss.

[0127] (II) Examples of specific parameters for single-strand spiral rifling

[0128] The design of the width (positive / negative groove width) and depth of a single rifling groove needs to balance three core objectives: ① effectively transmitting rotational torque to ensure the water flow rotates as expected; ② minimizing water flow resistance and energy loss; ③ ensuring the structural strength of the nozzle (avoiding material weakening due to excessive rifling depth). Considering the operating conditions of an impulse turbine nozzle (high flow velocity, sediment-laden water) and the parameters in the example above (0.5m inner diameter, 96 rifling grooves), the specific parameters are determined as follows:

[0129] 1. Design Basis and Constraints

[0130] (1) Water flow disturbance control: If the spiral rifling is too wide or too deep, the water flow will form vortices in the groove, increasing resistance and energy loss (impulse turbines have high efficiency requirements, and the energy loss increased by the spiral rifling should be controlled within 0.5%).

[0131] (2) Rotational torque transmission: The spiral rifling on the inner wall of the nozzle needs to effectively contact the high-speed water flow of the impact turbine and drive the water flow to rotate through friction. The width and depth of the spiral rifling need to be sufficient to generate "guiding force" while avoiding excessive interference with the smoothness of the water flow.

[0132] (3) Structural strength: The nozzle material is mostly high-strength steel (such as Q345). If the rifling depth is too deep, it will weaken the inner wall thickness and reduce the pressure resistance (the working pressure of the nozzle is usually 1MPa~5MPa).

[0133] 2. Width Calculation (positive and negative lines)

[0134] Rifling consists of alternating "raised" (convex) and "recessed" sections in the circumferential direction, with the total width required to cover the entire inner circumference.

[0135] Inner circumference length of nozzle: C = πD = π ×0.5≈1.571m=1571mm;

[0136] Number of rifling grooves: 96 (each rifling groove corresponds to 1 bullish groove + 1 bearish groove), therefore, the width of a single group (bullish groove + bearish groove): a + b = C / 96 ≈1571 / 96≈16.4mm

[0137] Referencing the proportions of fluid machinery (such as water pump impellers) (the width of the positive line should be slightly less than or equal to the width of the negative line to reduce resistance), take:

[0138] The width of the raised section (a) is 6.8mm (the raised part contacts the water flow and transmits the rotational torque; the width should not be too wide to avoid increasing resistance).

[0139] Width of the negative line (b): 9.6mm (the concave part is designed to accommodate water flow disturbances; the width is slightly larger to reduce eddies).

[0140] 3. Calculation of rifling depth (h)

[0141] The rifling depth (i.e., the radial distance between the bottom of the grommets and the top of the grommets) must satisfy the following condition: it should be sufficient to rotate the water flow without generating significant resistance. For turbine nozzles with higher flow velocities (50.93 m / s), the depth needs to be slightly increased to enhance rotation guidance, but resistance must be controlled; a depth of 1.0% of the nozzle diameter is recommended.

[0142] h =1%× D =0.01×500mm=5mm;

[0143] (1) Verification of the effect of resistance: The depth of 5mm is only 1% of the inner diameter. When the water flows axially, the vortex intensity in the groove is relatively weak (Reynolds number). Re ≈2.5×10 7 Although it is turbulent, the groove size is much smaller than the velocity gradient scale, and the energy loss can be controlled within 0.5%, which meets the efficiency requirements of impulse turbines.

[0144] (2) Structural strength verification: The nozzle wall thickness is typically ≥15mm, and can be thickened at the end. A depth of 5mm has no significant impact on the pressure resistance of working pressures from 1MPa to 5MPa (strength check: the remaining wall thickness can withstand pressures ≥8MPa, with sufficient redundancy). The parameters of the rifling width (a, b) and depth (h) are shown in Table 1:

[0145] Table 1

[0146]

[0147] The above parameter combination can effectively drive the water flow to rotate while minimizing energy loss. Combined with the previously designed pitch and number of jets, it can achieve the separation of sediment towards the outer edge of the jet.

[0148] 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 nozzle for an impulse turbine, characterized in that, The inner wall of the nozzle (3) is provided with helical rifling (31). The spiral rifling (31) is used to rotate the high-speed water flow passing through the nozzle (3) so as to separate the mud and sand in the water flow by centrifugal force. 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).

2. The nozzle of the impulse turbine as described in claim 1, characterized in that, The spiral rifling (31) includes alternating positive rifling (311) and negative rifling (312), which extend spirally along the axial direction of the nozzle (3).

3. The nozzle of the impulse turbine as described in claim 2, characterized in that, The inner wall of the nozzle (3) is provided with spiral ridges, which form the male line (311), and the inner wall surfaces between adjacent spiral ridges form the female line (312); or The inner wall of the nozzle (3) is provided with a spiral groove, which forms the negative line (312), and the inner wall surface between adjacent spiral grooves forms the positive line (311).

4. The nozzle of the impulse turbine as described in claim 2, characterized in that, The width of the positive line (311) is less than or equal to the width of the negative line (312).

5. The nozzle of the impulse turbine as described in claim 1, characterized in that, The spiral rifling (31) is a gradually decreasing rifling, and the pitch of the spiral rifling (31) gradually decreases along the direction of water flow.

6. The nozzle of the impulse turbine as described in claim 1, characterized in that, The spiral rifling (31) has the same rotation direction as the turbine.

7. The nozzle of the impulse turbine as described in claim 1, characterized in that, The number of the spiral rifling (31) is an integer multiple of 12.

8. An impulse turbine, characterized in that, It includes a rotor, a water distribution coil (5), and a nozzle (3) as described in any one of claims 1 to 7, wherein the nozzle (3) is connected to the water distribution coil (5).

9. The impulse turbine as described in claim 8, characterized in that, The impeller includes a hub (2) and water buckets (1) evenly distributed on the hub (2). A partitioned additive layer (118) is provided on the working surface of the water bucket (1). The position of the partitioned additive layer (118) corresponds to the mud and sand impact area on the outer edge of the jet after being treated by the spiral rifling (31).

Images