Runner mechanism and Francis turbine unit

Abstract

The application discloses a runner mechanism and a Francis turbine unit. The runner mechanism comprises an upper crown, a lower ring and blades. The inlet edge of the blade comprises a local reinforced thickened zone and a main body connected through a continuous transition structure. The continuous transition structure extends along the water flow direction of the blade. The continuous transition structure and the main body of the blade form a bidirectional gradual three-dimensional streamline curved surface along the water flow direction of the blade. The thickness of the continuous transition structure gradually and smoothly transitions from the inlet edge to the main body in a curvature decreasing trend. The curvature decreasing direction is from the inlet edge to the middle part of the main body along the water flow direction of the blade. The outlet edge comprises a vortex-reducing trailing edge structure which is a spatial curved surface structure twisted and extended from the pressure surface side to the suction surface side. In this way, the runner mechanism is not prone to stress concentration in the inlet edge and outlet edge areas under the action of long-term periodic water flow load, and fatigue cracks in the runner mechanism are not gradually expanded or even broken, thereby prolonging the service life of the runner mechanism.

Description

Technical Field

[0001] This invention belongs to the field of mechanical and hydroelectric equipment technology, specifically relating to a runner mechanism and a mixed-flow turbine unit. Background Technology

[0002] Pumped storage power stations, including their mixed-flow turbine units, typically operate in environments with high sediment content and high corrosion. This causes suspended sediment in the water to erode the turbine blades, leading to gradual wear and reduced turbine efficiency.

[0003] Currently, to solve the above-mentioned technical problems, existing technologies mainly use blade welding, spraying wear-resistant materials, or improving blade materials to alleviate them. However, these methods often only slow down the erosion rate and cannot solve the problem from the perspective of overall structural optimization. Moreover, they may still fail under high erosion or long-term operating environments. Because the inlet side of the impeller mechanism is subjected to high-speed water flow impact and sediment impact, and the outlet side is subject to eddies, cavitation collapse, and backflow disturbances, both of which are subjected to the coupled effects of erosion, cavitation erosion, and media corrosion for a long time, wear corrosion is likely to occur. Under the long-term periodic water flow load, the impeller mechanism is prone to stress concentration in the inlet and outlet areas, which leads to the gradual expansion of fatigue cracks or even fracture of the impeller mechanism, thereby affecting the service life of the impeller mechanism. Summary of the Invention

[0004] This application discloses a runner mechanism and a mixed-flow turbine unit, aiming to solve the problem that under long-term periodic water flow load, stress concentration is easily generated in the inlet and outlet areas of the runner mechanism, which leads to the gradual propagation of fatigue cracks or even fracture of the runner mechanism, thereby affecting the service life of the runner mechanism.

[0005] Firstly, to address the aforementioned problems, embodiments of this application provide a runner mechanism for a mixed-flow turbine unit, the runner mechanism comprising: An upper crown and a lower ring are spaced apart, and multiple blades are arranged between the upper crown and the lower ring; The blade includes a main body, an inlet edge, an outlet edge, a pressure surface, and a suction surface. The inlet edge is located at one edge of the main body, and the outlet edge is located at the other edge of the main body. The direction of the inlet edge pointing to the outlet edge is consistent with the direction of water flow into the blade. The pressure surface is located outside the direction of water flow in the blade, and the suction surface is located inside the direction of water flow in the blade. The inlet edge includes a locally reinforced thickened strip and a continuous transition structure. The locally reinforced thickened strip and the main body are connected by the continuous transition structure. The continuous transition structure extends along the water flow direction of the blade, and the continuous transition structure and the blade main body form a bidirectional gradually changing three-dimensional streamlined surface along the water flow direction of the blade. The thickness of the continuous transition structure smoothly transitions from the inlet edge to the main body with a decreasing curvature trend, and the decreasing curvature direction is from the inlet edge along the water flow direction of the blade to the middle of the main body. The thickness of the locally reinforced thickened strip is greater than the thickness of the main body. The water outlet edge includes a vortex-reducing edge structure, which is located at the edge where the water outlet edge and the lower ring are connected. The vortex-reducing edge structure is a spatial curved surface structure that extends to the pressure surface side to the suction surface side.

[0006] In some embodiments, the continuous transition structure includes multiple continuous smooth transition surfaces along the direction from the upper crown to the lower ring, and the continuous smooth transition surface is a cross-sectional airfoil curve surface structure. The cross-sectional airfoil curve includes a pressure surface curve and a suction surface curve. The pressure surface curve and the suction surface curve are both fitted with high-order spline curves between the locally reinforced thickened strip and the main body, and satisfy the continuity of the first and second derivatives.

[0007] In some embodiments, the thickness of the locally reinforced thickened strip increases non-linearly along the direction from the upper crown to the lower ring, and the thickness change curve of the locally reinforced thickened strip is parabolic or exponential.

[0008] In some embodiments, the pressure surface includes a plurality of first curved surface structures, and the radii of curvature of the plurality of first curved surface structures gradually change along the water flow direction of the blade along a first gradient. The suction surface includes a plurality of second curved surface structures, and the radii of curvature of the plurality of second curved surface structures gradually change along the water flow direction of the blade along a second gradient. The first gradient is greater than the second gradient. The radius of curvature of the multiple first curved surface structures included in the pressure surface varies continuously along the direction from the upper crown to the lower ring and along the water flow direction of the blade.

[0009] In some embodiments, the radius of curvature of the plurality of first surface structures included in the pressure surface increases non-linearly along the direction from the upper crown to the lower ring; Along the water flow direction of the blade, the radius of curvature of the plurality of first curved surface structures included in the pressure surface in the first region of the blade gradually increases, and the radius of curvature of the plurality of first curved surface structures included in the pressure surface in the second region of the blade gradually decreases. The first region of the blade is the region between the water inlet edge and the middle of the main body, and the second region of the blade is the region between the middle of the main body and the water outlet edge.

[0010] In some embodiments, the radius of curvature of each of the first surface structures is greater than the radius of curvature of the second surface structure.

[0011] In some embodiments, the profile of the vortex tail reduction structure is distributed with a sweep angle along the direction from the upper crown to the lower ring, and the angle of the sweep angle increases non-linearly along the direction from the upper crown to the lower ring. The pressure side and the suction side are connected by a transitional circular arc spatial curved surface structure, and the radius of the transitional circular arc spatial curved surface structure is 0.5 to 2 times the thickness of other areas of the water outlet side; The radius of curvature of the spatial curved surface structure gradually decreases along the direction from the upper crown to the lower ring. The radius of curvature of the spatial curved surface structure on the pressure side is greater than the radius of curvature on the suction side. The gradient of the radius of curvature change of the spatial curved surface structure near the lower ring region is greater than the gradient of the radius of curvature change of the spatial curved surface structure near the upper crown region.

[0012] In some embodiments, the blade further includes a first connecting root and a second connecting root, the first connecting root connecting the body and the upper crown, and the second connecting root connecting the body and the lower ring; The first connecting root is provided with a first reinforced transition zone, and the second connecting root is provided with a second reinforced transition zone. Both the first and second reinforced transition zones include a thickness gradient section and a curvature gradient section. The thickness gradient section changes gradually along the direction from the main body to the upper crown or from the main body to the lower ring, and the curvature gradient section changes gradually along the direction from the main body to the upper crown or from the main body to the lower ring. The inlet side, the outlet side, the first connecting root, the second connecting root, and the pressure surface are configured with partitioned materials.

[0013] In some embodiments, a flow channel is formed between two adjacent blades, and the flow area of ​​the flow channel gradually increases from the middle of the flow channel in the direction from the inlet side to the outlet side or from the outlet side to the inlet side towards both sides.

[0014] In some embodiments, the pressure surface has a first reinforcing coating configured as an anti-erosion and abrasion coating, and the suction surface has a second reinforcing coating configured as an anti-cavitation damage coating.

[0015] In some embodiments, the plurality of blades include a first blade and a second blade, wherein the first blade is larger in size in the direction along the upper crown pointing to the lower ring than the second blade is larger in the direction along the upper crown pointing to the lower ring, and the first blade and the second blade are arranged alternately.

[0016] Secondly, embodiments of this application also provide a mixed-flow turbine unit, the mixed-flow turbine unit including a volute, movable guide vanes, a bottom ring, a draft tube, a top cover, and the runner mechanism described in any of the first aspects; the volute is connected to the bottom ring, the movable guide vanes are disposed between the bottom ring and the runner mechanism, the runner mechanism is disposed between the top cover and the bottom ring, and the draft tube is disposed on the side of the runner mechanism away from the top cover.

[0017] According to the embodiments of this application, since the inlet edge includes a locally reinforced thickened zone and a continuous transition structure, the locally reinforced thickened zone and the main body are connected by the continuous transition structure. The thickness of the locally reinforced thickened zone is greater than the thickness of the main body. Therefore, when water flows through the inlet edge, the locally reinforced thickened zone enhances the strength of the leading edge region of the inlet edge, forming a leading edge reinforced region with impact resistance. This enhances the blade's erosion resistance under high-speed, sediment-laden water flow and slows down the material wear development in the leading edge region of the impeller mechanism. Subsequently, based on the continuous transition structure extending along the water flow direction of the blade, the continuous transition structure and the blade main body form a bidirectionally gradually changing three-dimensional streamlined surface. The thickness of the continuous transition structure smoothly transitions from the inlet edge to the main body with a decreasing curvature trend, and the decreasing curvature direction is from the inlet edge towards the center of the main body along the water flow direction of the blade. Under the action of the continuous transition structure, geometric abrupt changes are eliminated and local stress concentration is avoided, ensuring that the load on the inlet edge can be continuously transmitted during water flow, allowing the water flow to be transmitted uniformly and smoothly along the continuous transition structure. Furthermore, since the outlet edge includes a vortex-reducing trailing edge structure, located at the edge connecting the outlet edge and the lower ring, and this structure is a spatial curved surface extending to the suction side from the pressure side, the spatial curved surface formed by the vortex-reducing trailing edge structure allows for the adjustment and smoothing of the trailing edge geometry of the outlet edge, reducing the flow separation intensity in the trailing edge region and thus weakening the unsteady excitation effect of the vortex in the trailing edge region on the blades. In summary, in the impeller mechanism provided in this application embodiment, the improvement of the inlet edge structure not only creates a leading-edge reinforcement region with impact resistance to enhance the blades' erosion resistance under high-speed, sediment-laden water flow and slow down material wear development in the leading-edge region of the impeller mechanism, but also, under the action of the continuous transition structure, eliminates geometric abrupt changes and avoids local stress concentration, ensuring that the load on the inlet edge can be continuously transmitted during water flow, allowing the water flow to be transmitted uniformly and smoothly along the continuous transition structure. By improving the exit edge structure, the spatial curved surface structure formed by the reduced vortex trailing edge structure can be used to adjust and smooth the transition of the exit edge geometry, thereby reducing the flow separation intensity in the exit edge region and weakening the unsteady excitation effect of the vortex in the exit edge region on the blades. In this way, the runner mechanism is less prone to stress concentration in the inlet and outlet regions under long-term periodic water flow loads, preventing fatigue cracks from gradually propagating or even fracturing, thus extending the service life of the runner mechanism. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a partial structural schematic diagram of a runner mechanism for a mixed-flow turbine unit provided in an embodiment of this application; Figure 2 This is a schematic diagram of the blades included in the runner mechanism of a mixed-flow turbine unit provided in an embodiment of this application; Figure 3 This is a schematic diagram of a water turbine pump unit provided in an embodiment of this application.

[0020] Explanation of reference numerals in the attached figures: 1: Runner mechanism; 11: Upper crown; 12: Lower ring; 13: Blade; 131: Main body; 132: Inlet edge; 1321: Locally reinforced thickened zone; 1322: Continuous transition structure; 133: Outlet edge; 1331: Vortex tail reduction structure; 134: Pressure surface; 135: First connecting root; 136: Second connecting root; 14: Flow channel; 2: volute; 3: movable guide vane; 4: bottom ring; 5: tailrace pipe; 6: top cover. Detailed Implementation

[0021] The terms "first" and "second" in the specification and claims of this application may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise stated, "multiple" means two or more. Furthermore, "and / or" in the specification and claims indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0022] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, 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, and therefore should not be construed as a limitation of this application.

[0023] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0024] Firstly, to solve the above problems, such as Figure 1 and Figure 2 As shown in the figure, this application provides a runner mechanism for a mixed-flow turbine unit, the runner mechanism comprising: An upper crown 11 and a lower ring 12 are spaced apart, and multiple blades 13 are arranged between the upper crown 11 and the lower ring 12.

[0025] The blade 13 includes a main body 131, an inlet edge 132, an outlet edge 133, a pressure surface 134, and a suction surface. Figure 1 and Figure 2 (Not shown in the image) The inlet edge 132 is located at one edge of the main body 131, and the outlet edge 133 is located at the other edge of the main body 131. The direction of the inlet edge 132 pointing to the outlet edge 133 is consistent with the direction of water flow into the blade 13. The pressure surface 134 is located outside the direction of water flow in the blade 13, and the suction surface is located inside the direction of water flow in the blade 13.

[0026] The inlet edge 132 includes a locally reinforced thickened strip 1321 and a continuous transition structure 1322. The locally reinforced thickened strip 1321 and the main body 131 are connected by the continuous transition structure 1322. The continuous transition structure 1322 extends along the water flow direction of the blade 13, and the continuous transition structure 1322 and the main body 131 of the blade 13 form a bidirectional gradually changing three-dimensional streamlined surface along the water flow direction of the blade 13. The thickness of the continuous transition structure 1322 smoothly transitions from the inlet edge 132 to the main body 131 with a decreasing curvature trend, and the decreasing curvature direction is from the inlet edge 132 along the water flow direction of the blade 13 to the middle of the main body 131. The thickness of the locally reinforced thickened strip 1321 is greater than the thickness of the main body 131.

[0027] The water outlet edge 133 includes a vortex-reducing edge structure 1331, which is located at the edge where the water outlet edge 133 and the lower ring 12 are connected. The vortex-reducing edge structure 1331 is a spatial curved surface structure that extends to the side of the pressure surface 134 to the side of the suction surface.

[0028] As can be seen from the above embodiments, in this application embodiment, since the water inlet edge 132 includes a locally reinforced thickened strip 1321 and a continuous transition structure 1322, the locally reinforced thickened strip 1321 and the main body 131 are connected by the continuous transition structure 1322. The thickness of the locally reinforced thickened strip 1321 is greater than the thickness of the main body 131. Therefore, when water flows through the water inlet edge 132, the strength of the leading edge region of the water inlet edge 132 is enhanced by the locally reinforced thickened strip 1321, so that the water inlet edge 132 forms a leading edge reinforced region with impact resistance, which is used to enhance the erosion resistance of the blade 13 under the action of high-speed sand-laden water flow and slow down the material wear development of the leading edge region of the impeller mechanism. Subsequently, based on the continuous transition structure 1322 extending along the water flow direction of the blade 13, the continuous transition structure 1322 and the main body 131 of the blade 13 form a bidirectional gradually changing three-dimensional streamlined surface. The thickness of the continuous transition structure 1322 smoothly transitions from the water inlet edge 132 to the main body 131 with a decreasing curvature trend, and the direction of the decreasing curvature is from the water inlet edge 132 along the water flow direction of the blade 13 to the middle of the main body 131. Under the action of the continuous transition structure 1322, geometric abrupt changes are eliminated and local stress concentration is avoided, so as to ensure that the load on the water inlet edge 132 can be continuously transmitted during water flow transmission, so that the water flow is transmitted evenly and smoothly along the continuous transition structure 1322. Furthermore, since the water outlet edge 133 includes a vortex-reducing trailing edge structure 1331, which is located at the edge where the water outlet edge 133 and the lower ring 12 connect, the vortex-reducing trailing edge structure 1331 is a spatial curved surface structure that extends to the suction surface from the pressure surface 134 side. Therefore, the spatial curved surface structure formed by the vortex-reducing trailing edge structure 1331 can be used to adjust the sweepback geometry of the trailing edge of the water outlet edge 133 and smooth the transition, thereby reducing the flow separation intensity in the trailing edge region of the water outlet edge 133 and weakening the unsteady excitation effect of the vortex in the trailing edge region of the water outlet edge 133 on the blade 13. In summary, in the impeller mechanism provided in this application embodiment, the improvement of the inlet edge 132 structure not only enables the inlet edge 132 to form a leading edge reinforcement region with impact resistance, thereby enhancing the erosion resistance of the blade 13 under the action of high-speed sediment-laden water flow and slowing down the material wear development in the leading edge region of the impeller mechanism, but also, under the action of the continuous transition structure 1322, eliminates geometric abrupt changes and avoids local stress concentration, ensuring that the load on the inlet edge 132 can be continuously transmitted during water flow transmission, so that the water flow is transmitted uniformly and smoothly along the continuous transition structure 1322. Through the improvement of the outlet edge 133 structure, the spatial curved surface structure formed by the vortex trailing edge structure 1331 can be used to adjust the sweepback geometry of the trailing edge of the outlet edge 133 and smooth the transition, reducing the flow separation intensity in the trailing edge region of the outlet edge 133, thereby weakening the unsteady excitation effect of the vortex in the trailing edge region of the outlet edge 133 on the blade 13.In this way, the runner mechanism is less likely to generate stress concentration in the inlet side 132 and outlet side 133 areas under long-term periodic water flow load, which will prevent fatigue cracks in the runner mechanism from gradually expanding or even breaking, thereby extending the service life of the runner mechanism.

[0029] In the above embodiment, the upper crown 11 is located at the top of the impeller mechanism and is directly connected to the main shaft via a flange structure, serving to transmit torque. It also provides support for the upper end of the blades 13, together forming the top boundary of the flow channel. The upper crown 11 typically has pressure-reducing holes or pressure-reducing devices (such as rotating pressure-reducing plates) to significantly reduce the load on the thrust bearing from the axial water thrust by balancing the water pressure above and below the impeller. The lower ring 12 is located at the lower end of the blades 13, connecting them into an integral ring structure, greatly improving the rigidity and deformation resistance of the impeller mechanism, making it particularly suitable for high-speed operation. The lower ring 12 and the upper crown 11 work together to form a complete flow channel profile, ensuring stable water flow. The lower leak-proof ring is fixed to the lower ring 12 to reduce downward leakage. Some designs include cooling water holes in the middle of the leak-proof ring to assist in heat dissipation.

[0030] Furthermore, the inlet edge 132 is the spatial curved edge on which the water flow first enters the flow channel 14 of the blade 13 of the runner mechanism. It is the contour edge of the high-pressure inlet side of the blade 13. In a mixed-flow turbine unit, the inlet edge 132 is located on the outer edge (large diameter side) of the runner mechanism. One side of the inlet edge 132 is connected to the upper crown 11, and the other side is connected to the lower ring 12. The water flow comes from the guide mechanism, enters the flow channel 14 of the blade 13 radially from the outside along the inlet edge 132, and then flows inward and axially towards the outlet edge 133 (inner small diameter). The outlet edge 133 is the spatial edge on which the water flow leaves the flow channel 14 of the blade 13. It is the outflow side edge of the flow channel 14 of the blade 13. In a mixed-flow turbine unit, the outlet edge 133 is located on the inner side (small diameter side) of the runner mechanism, between the upper crown 11 and the lower ring 12. The main body 131 of blade 13 is the large, solid, airfoil-shaped section in the middle of blade 13 after removing the two edges 132 (inlet edge) and 133 (outlet edge). This is the core pressure-bearing and energy-converting area of ​​blade 13. It should be noted that the pressure surface 134 is the curved surface of blade 13 that experiences higher pressure from the water flow. The water flow acts directly on this surface, resulting in high static pressure. The surface of blade 13 facing the direction of rotation is the pressure surface 134, located on the outer side of blade 13 in the direction of water flow. The suction surface is the surface of blade 13 on the side with higher flow velocity, located on the inner side of blade 13 in the direction of water flow.

[0031] It should also be noted that the "bidirectional" in the bidirectional gradient three-dimensional streamlined surface can be understood as the continuous transition structure 1322 pointing from the inlet edge 132 to the outlet edge 133 and from the upper crown 11 to the lower ring 12. The "gradual" in the bidirectional gradient three-dimensional streamlined surface can be understood as the continuous and smooth change in thickness, curvature, and placement angle of the continuous transition structure 1322, without abrupt steps or sharp corners. The "three-dimensional streamlined" in the bidirectional gradient three-dimensional streamlined surface can be understood as a spatially twisted surface, where the airfoil cross-sections at each location are different, conforming to the streamlines of the water flow.

[0032] In some embodiments, the continuous transition structure 1322 includes multiple continuous smooth transition surfaces along the direction from the upper crown 11 to the lower ring 12, and the continuous smooth transition surface is a cross-sectional airfoil curve surface structure. The cross-sectional airfoil curve includes a pressure surface curve and a suction surface curve. The pressure surface curve and the suction surface curve are fitted with high-order spline curves between the locally reinforced thickened strip 1321 and the main body 131, and satisfy the continuity of the first derivative and the second derivative.

[0033] In this embodiment, both the pressure surface curve and the suction surface curve are fitted with high-order spline curves between the locally reinforced thickened strip 1321 and the main body 131. This can be understood as using third-order or higher B-splines / NURBS splines. By using multiple control points, the boundary contours of the locally reinforced thickened strip 1321 and the main body 131 of the blade 13 are transitionally interpolated. The position, tangent, and curvature of the curves can be independently constrained, achieving smooth splicing of complex spatial contours and avoiding abrupt curvature changes caused by arc or straight line splicing. In other words, the endpoint of the locally reinforced thickened strip 1321 and the starting point of the main body 131 of the blade 13 are used as the boundary constraints of the spline. Then, control points are set to generate a transition spline curve, achieving a smooth transition of the pressure surface curve and the suction surface curve in terms of position, tangent, and curvature. The continuity of the first derivative can be understood as the tangent direction of the curve / surface at the junction of the pressure surface curve and the suction surface curve being consistent, without sharp corners or bends. The continuity of the second derivative can be understood as the continuity of the curvature magnitude and curvature change at the junction of the pressure surface curve and the suction surface curve, without abrupt curvature inflection points. In this way, the curvature of the surface between the locally reinforced thickened zone 1321 and the main body 131 can be smoothly changed, allowing water to flow along the surface without disturbance, without generating local eddies or flow separation, avoiding additional low-pressure peaks, reducing the risk of cavitation in the inlet edge 132 region, and at the same time, the curvature stress transitions smoothly without local stress peaks, avoiding the formation of stress concentration points and reducing the risk of cracks.

[0034] In some embodiments, the thickness of the locally reinforced thickened strip 1321 increases non-linearly along the direction from the upper crown 11 to the lower ring 12, and the thickness change curve of the locally reinforced thickened strip 1321 is parabolic or exponential.

[0035] In this embodiment, the nonlinear increase can be understood as the thickness of the locally reinforced thickening band 1321 not increasing uniformly (not linearly) along the direction from the upper crown 11 to the lower ring 12. Parabolic or exponential curves represent two forms of the thickness variation curve of the locally reinforced thickening band 1321. The parabolic type, i.e., the quadratic function type, shows a quadratic parabolic change in the thickness variation curve of the locally reinforced thickening band 1321, with a gradually changing thickness growth rate, a smooth transition, and a relatively mild curvature change. The exponential type can be understood as the thickness variation curve of the locally reinforced thickening band 1321 changing according to an exponential function, causing the thickness of the locally reinforced thickening band 1321 to increase faster closer to the lower ring 12; the thickness amplification effect is more pronounced on the lower ring 12 side. This maximizes the thickening amplitude in the blade root region and minimizes the thickening amplitude in the middle region of the inlet edge 132 of the blade 13, thus matching the differences in hydrodynamic load and sediment scouring intensity at different blade heights of the blade 13.

[0036] In some embodiments, the pressure surface 134 includes a plurality of first curved surface structures, and the radius of curvature of the plurality of first curved surface structures gradually changes along the water flow direction of the blade 13 along a first gradient. The suction surface includes a plurality of second curved surface structures, and the radius of curvature of the plurality of second curved surface structures gradually changes along the water flow direction of the blade 13 along a second gradient. The first gradient is greater than the second gradient.

[0037] In this embodiment, the pressure surface 134 is the curved surface of the blade 13 that bears the impact of water flow and has higher pressure. The water flow directly acts on this curved surface, resulting in high static pressure. The surface of the blade 13 facing the direction of rotation is the pressure surface 134, which is located on the outer side of the blade 13 in the direction of water flow. The suction surface is the surface of the blade 13 on the side with higher flow velocity, which is located on the inner side of the blade 13 in the direction of water flow. Therefore, when the pressure surface 134 includes multiple first curved surface structures, and the radii of curvature of the multiple first curved surface structures gradually change along the direction of water flow of the blade 13 along a first gradient, and the suction surface includes multiple second curved surface structures, and the radii of curvature of the multiple second curved surface structures gradually change along the direction of water flow of the blade 13 along a second gradient, the first gradient is greater than the second gradient, making the curvature gradient of the pressure surface 134 side greater than the curvature gradient of the suction surface side, thereby maintaining the water flow adhesion performance of the suction surface side.

[0038] In some embodiments, the radius of curvature of the plurality of first curved surface structures included in the pressure surface 134 varies continuously along the direction from the upper crown 11 to the lower ring 12 and along the water flow direction of the blade 13.

[0039] In this embodiment, in the pressure surface 134 region of the blade 13, the pressure surface is reconstructed into a spatial curved surface, so that the pressure surface 134 is changed from a single smooth curved surface to a load-bearing curved surface structure with continuously changing characteristics. When the curvature radius of the multiple first curved surface structures included in the pressure surface 134 continuously changes along the direction from the upper crown 11 to the lower ring 12, the stress distribution of the blade 13 is more uniform, thereby reducing the stress concentration and periodic deformation formed in the local high pressure area. It should be noted that the radius of curvature of the multiple first curved surface structures included in the pressure surface 134 changes continuously along the direction from the upper crown 11 to the lower ring 12. This can be understood as the multiple first curved surface structures included in the pressure surface 134 satisfying positional continuity, tangential continuity, and curvature continuity between any adjacent first curved surface structures. That is, the first and second partial derivatives of the multiple first curved surface structures included in the pressure surface 134 along the chord direction (direction from the inlet edge 132 to the outlet edge 133) and the spanwise direction (direction from the upper crown 11 to the lower ring 12) of the blade 13 are continuous, and there is no step abrupt change in curvature or reversal of curvature direction, so as to ensure the continuity and uniformity of load transmission on the surface of the blade 13. Among them, the multiple first curved surface structures included in the pressure surface 134 are mainly varied along the chord direction of the blade 13 (the direction from the inlet edge 132 to the outlet edge 133), and the multiple first curved surface structures included in the pressure surface 134 are secondary varied along the chord direction of the blade 13 (the direction from the inlet edge 132 to the outlet edge 133). The curvature radius changes of the multiple first curved surface structures included in the pressure surface 134 in the two directions are superimposed on each other, and together constitute the continuous curvature distribution field of the pressure surface 134 in three-dimensional space.

[0040] In some embodiments, the radius of curvature of the plurality of first curved surface structures included in the pressure surface 134 increases nonlinearly in the direction from the upper crown 11 to the lower ring 12. This makes the curvature of the lower ring 12 region greater than that of the upper crown 11 region, which can match the higher flow velocity and larger hydrodynamic load in the lower ring 12 region, while compensating for the uneven stress caused by the wall effect in the lower ring 12 region.

[0041] In some embodiments, along the water flow direction of the blade 13, the radius of curvature of the plurality of first curved surface structures included in the pressure surface 134 in the first region of the blade 13 gradually increases, and the radius of curvature of the plurality of first curved surface structures included in the pressure surface 134 in the second region of the blade 13 gradually decreases. The first region of the blade 13 is the region between the inlet edge 132 and the middle of the body 131, and the second region of the blade 13 is the region between the middle of the body 131 and the outlet edge 133.

[0042] In this embodiment, along the water flow direction of blade 13, the radius of curvature of the multiple first curved surface structures included in the pressure surface 134 within the first region of blade 13 gradually increases, which can enhance the load-bearing capacity of the central region of blade 13 and match the peak hydrodynamic load on the first region of blade 13. The gradual increase in the radius of curvature of the multiple first curved surface structures included in the pressure surface 134 within the first region of blade 13 along the water flow direction smoothly guides the water flow and reduces the flow separation intensity in the outlet edge 133 region. It should be noted that the change in the radius of curvature of the multiple first curved surface structures included in the pressure surface 134 within the first region of blade 13 along the water flow direction satisfies the continuity of the first and second derivatives to ensure that there are no local abrupt changes in curvature.

[0043] In some embodiments, the radius of curvature of each first surface structure is greater than the radius of curvature of the second surface structure. This results in the pressure surface 134 having stronger load-bearing capacity and resistance to deformation, while maintaining the water flow adhesion performance and flow stability of the suction surface.

[0044] Furthermore, it should be noted that the cross-sectional profiles of the multiple first curved surface structures are higher-order spline curves along the water flow direction of the blade 13. These higher-order spline curves satisfy the continuity of the first and second derivatives between the inlet edge 132 and the outlet edge 133, and the curvature of the higher-order spline curves exhibits a monotonically changing trend along the chord direction. The chord length ratios between the control points of the higher-order spline curves are arranged in a geometric or arithmetic sequence along the direction from the inlet edge 132 to the outlet edge 133 to precisely control the curvature distribution and geometric shape of the multiple first curved surface structures along the chord direction. The cross-sectional profiles of multiple first curved surface structures are distributed differently at different heights along the direction from the upper crown 11 to the lower ring 12. That is, the curvature distribution of the cross-sectional profiles near the upper crown 11 is different from that near the lower ring 12. Furthermore, the cross-sectional profiles at each height are connected by a continuous and smooth transition surface to adapt to the differences in water flow velocity and pressure distribution at different radii inside the impeller mechanism, thereby achieving a uniform distribution of the surface load of the blade 13 along the spanwise direction.

[0045] In some embodiments, the profile of the vortex tail edge structure 1331 is distributed with a sweep angle along the direction from the upper crown 11 to the lower ring 12, and the angle of the sweep angle increases non-linearly along the direction from the upper crown 11 to the lower ring 12.

[0046] In this embodiment, the sweep angle is the relative offset angle between different sections of the profile of the vortex tail structure 1331 in the direction from the upper crown 11 to the lower ring 12. In other words, it is the angle at which the profile at the upper crown 11, the profile at the middle section, and the profile at the lower ring 12 are staggered along the circumferential direction. That is, the blade 13 is cut into layers of airfoil sections along the direction from the upper crown 11 to the lower ring 12, and the airfoils at different heights are not aligned on the same ray. They are offset and rotated along the direction from the inlet edge 132 to the outlet edge 133. The angle corresponding to this offset is the sweep angle. The profile is arranged according to the sweep angle pattern, which is called a sweep angle distribution of the profile. In this way, the sweep angle increases non-linearly along the direction from the upper crown 11 to the lower ring 12, so that the outlet edge 133 has a differentiated water flow output direction at different heights along the direction from the upper crown 11 to the lower ring 12, in order to match the difference in the outlet velocity distribution at different blade heights of the blade 13. The sweep angle is between 10° and 37°. In some embodiments, the pressure surface 134 side and the suction surface side are connected by a transition arc spatial curved surface structure, the radius of which is 0.5 to 2 times the thickness of other areas of the water outlet edge 133.

[0047] In this embodiment, since the pressure surface 134 and the suction surface are connected by a transitional arc spatial curved surface structure, and the radius of the arc of the transitional arc spatial curved surface structure is 0.5 to 2 times the thickness of other areas of the water outlet edge 133, the transitional arc spatial curved surface structure is constructed in the cross section of the blade 13 in the direction of water flow. From the upstream profile of the water outlet edge 133 to the end of the water outlet edge 133, the curvature transitions smoothly. That is, the absolute value of the curvature change rate of the surface of the water outlet edge 133 along the flow direction is less than 20% of the absolute value of the curvature change rate of the upstream blade 13 body 131, so as to achieve a smooth convergence of the geometric surface of the water outlet edge 133 region.

[0048] In some embodiments, the radius of curvature of the spatial curved surface structure gradually decreases along the direction from the upper crown 11 to the lower ring 12, and the radius of curvature of the spatial curved surface structure on the pressure surface 134 side is greater than that on the suction surface side. This results in a greater curvature of the outlet edge 133 in the lower ring 12 region compared to the upper crown 11 region, thereby enhancing the water flow discharge capacity on the lower ring 12 region side. Simultaneously, the curvature of the outlet edge 133 surface on the pressure surface 134 side is greater than that on the suction surface side, making the curvature of the outlet edge 133 on the pressure surface 134 side more pronounced, thereby enhancing the discharge capacity of high-energy water flow on the pressure surface 134 side and suppressing flow separation at the outlet edge 133.

[0049] In some embodiments, the curvature radius variation gradient of the spatial curved surface structure near the lower ring 12 region is greater than that near the upper crown 11 region. This means that the geometric adjustment amplitude of the outlet edge 133 in the lower ring 12 region is greater than that in the upper crown 11 region, compensating for the non-uniform velocity distribution in the lower ring 12 region caused by the wall effect and reducing the intensity and frequency of the wake vortex in the lower ring 12 region.

[0050] It should be noted that the cross-sectional profile of the outlet edge 133 surface along the water flow direction of the blade 13 is a higher-order spline curve. This higher-order spline curve satisfies the continuity of the first and second derivatives from the upstream region of the outlet edge 133 to the end of the outlet edge 133, and the curvature of the higher-order spline curve shows a monotonically changing trend along the flow direction. The chord length ratios between the control points of the higher-order spline curve are arranged in a geometric series from the upstream of the outlet edge 133 to the end of the outlet edge 133 to precisely control the geometric configuration and curvature distribution of the outlet edge 133 surface.

[0051] In some embodiments, the blade 13 further includes a first connecting root 135 and a second connecting root 136. The first connecting root 135 connects the body 131 and the upper crown 11, and the second connecting root 136 connects the body 131 and the lower ring 12. The first connecting root 135 is provided with a first reinforced transition zone, and the second connecting root 136 is provided with a second reinforced transition zone. Both the first and second reinforced transition zones include a thickness gradient section and a curvature gradient section. The thickness gradient section changes gradually along the direction from the body 131 to the upper crown 11 or from the body 131 to the lower ring 12, and the curvature gradient section changes gradually along the direction from the body 131 to the upper crown 11 or from the body 131 to the lower ring 12.

[0052] In this embodiment, the first connecting root 135 is provided with a first reinforced transition zone, and the second connecting root 136 is provided with a second reinforced transition zone. Both the first and second reinforced transition zones include a thickness gradient section and a curvature gradient section. The thickness change direction of the thickness gradient section gradually changes along the direction from the main body 131 to the upper crown 11 or from the main body 131 to the lower ring 12. Therefore, a continuous load transfer path is formed between the first connecting root 135 and the upper crown 11, and between the second connecting root 136 and the lower ring 12. This makes the geometry of the blade root continuously and smoothly transition from the blade body 131 towards the upper crown 11 or the lower ring 12, thereby eliminating the geometric discontinuity between the first connecting root 135 and the upper crown 11, and between the second connecting root 136 and the lower ring 12. Meanwhile, by improving the degree of geometric abrupt change in the first connecting root 135 and the second connecting root 136, the stress peak values ​​of the first connecting root 135 and the second connecting root 136 are reduced, thereby enhancing the blade 13's ability to resist fatigue crack initiation under cyclic loading.

[0053] It should be noted that the thickness of the thickness gradient section gradually decreases from the body 131 along the spanwise direction (the direction from the upper crown 11 to the lower ring 12 and from the lower ring 12 to the upper crown 11) towards the upper crown 11 and lower ring 12. Simultaneously, it gradually decreases from the middle of the blade 13 along the chordwise direction (water flow direction) towards the inlet and outlet sides. In the spanwise gradient direction, the thickness of the thickness gradient section decreases progressively; that is, from the body 131 towards the upper crown 11 or lower ring 12 it connects with, the thickness at the root of the blade 13 gradually decreases, eventually smoothly connecting with the surface thickness of the upper crown 11 or lower ring 12. In the chordwise gradient direction, the thickness of the thickness gradient section decreases asymmetrically from the middle of the blade 13 towards the inlet and outlet sides, with a greater rate of decrease near the outlet side than near the inlet side. This is to accommodate the higher stress concentration in the connection area between the blade 13's outlet side and the upper crown 11 and lower ring 12.

[0054] In some embodiments, the inlet edge 132, outlet edge 133, first connecting root 135, second connecting root 136, and pressure surface 134 are configured with partitioned materials. This allows for targeted reinforcement of areas subject to high scouring, high stress, and high fatigue, further enhancing the overall strength of the impeller mechanism.

[0055] For example, the inlet edge 132 is provided with a first wear-resistant reinforcing layer, which is configured as high-hardness martensitic stainless steel or tungsten carbide reinforced composite material; the outlet edge 133 is provided with a second wear-resistant reinforcing layer, which is configured as cobalt-based or nickel-based anti-cavitation material; the first connecting root 135 and the second connecting root 136 are provided with fatigue-resistant reinforcing layers, which are configured as high-toughness fatigue-resistant martensitic stainless steel; and the pressure surface 134 has a strength-reinforcing layer in the middle, which is configured as a high-strength martensitic stainless steel matrix.

[0056] In some embodiments, a flow channel 14 is formed between two adjacent blades 13, and the flow area of ​​the flow channel 14 gradually increases from the middle of the flow channel 14 in the direction from the inlet edge 132 to the outlet edge 133 or from the outlet edge 133 to the inlet edge 132 to both sides.

[0057] In this embodiment, since a flow channel 14 is formed between two adjacent blades 13, the flow area of ​​the flow channel 14 gradually increases from the middle of the flow channel 14 in the direction from the inlet edge 132 to the outlet edge 133 or from the outlet edge 133 to the inlet edge 132. Therefore, the effective flow area of ​​the flow channel 14 exhibits a pattern of first converging and then expanding along the water flow direction. Starting from the inlet edge 132 region, the flow channel 14 extends towards the central region of the impeller mechanism. Due to the combined effect of the gradual narrowing of the axial gap between the upper crown 11 and the lower ring 12 and the gradual reduction of the circumferential distance between adjacent blades 13, the effective flow area of ​​the flow channel 14 shows a decreasing trend, which accelerates the water flow and realizes the conversion of pressure energy into kinetic energy. When the water flow passes through the minimum flow section in the middle of the flow channel 14, the flow channel 14 continues to extend towards the outlet of the lower ring 12, and the flow area shows an increasing trend, causing the water flow velocity to gradually decrease, and some kinetic energy is converted back into pressure energy.

[0058] It should be noted that the flow area of ​​the flow channel 14 gradually increases from the middle of the flow channel 14 along the direction from the inlet side 132 to the outlet side 133, or from the outlet side 133 to the inlet side 132, towards both sides. This change is not constant. From the impeller inlet to the minimum flow cross-section section, the rate of change increases, meaning the rate of decrease in flow area gradually accelerates. From the minimum flow cross-section to the impeller outlet section, the rate of change decreases, meaning the rate of increase in flow area gradually slows down. The minimum flow cross-section is located at 40%–60% of the total length of the flow channel 14 along the flow direction. The flow area at this minimum cross-section is 50%–80% of the flow area at the impeller inlet and 60%–85% of the flow area at the impeller outlet. Furthermore, the wall of the flow channel 14 is defined by the inner profile of the upper crown 11, the inner profile of the lower ring 12, and the pressure surface 134 and suction surface of each of the two adjacent blades 13. The cross-sectional profiles of the four walls along the water flow direction are all constructed using high-order spline curves. The continuity conditions of the first and second derivatives are satisfied throughout the entire flow channel 14 from the inlet to the outlet. The wall curvature changes continuously along the flow direction, and there are no local abrupt changes in concavity or convexity or reversals in the curvature direction. The chord length ratio between the control points of the cross-sectional profile is arranged in a geometric or arithmetic sequence from the inlet to the outlet of the flow channel 14.

[0059] Furthermore, the cross-sectional configuration of the flow channel 14 varies at different blade heights. Specifically, the cross-sectional shape of the flow channel 14 near the upper crown 11 region differs from that near the lower ring 12 region. The cross-sections of the flow channel 14 at each blade height are connected by continuous, smooth transition surfaces to accommodate the differences in water velocity and pressure distribution at different radii within the impeller mechanism. Moreover, the water velocity within the flow channel 14 between the blades 13 exhibits a continuous trend of first increasing and then decreasing along the flow direction, while the pressure exhibits a continuous trend of first decreasing and then increasing along the flow direction. Both velocity and pressure reach their extreme values ​​at the minimum flow cross-section of the flow channel 14, and the rates of change of velocity and pressure are continuous along the flow direction, without any abrupt changes or drastic gradients.

[0060] In some embodiments, the pressure surface 134 has a first reinforcing coating configured as an anti-erosion and abrasion coating, and the suction surface has a second reinforcing coating configured as an anti-cavitation damage coating.

[0061] In this embodiment, since the pressure surface 134 is the working surface dominated by water flow impact and high pressure load, the first reinforcing coating may include a hard alloy coating, a nickel-based tungsten carbide coating, etc. Therefore, when the pressure surface 134 has a first reinforcing coating, and the first coating is configured as an anti-erosion and wear coating, it can absorb the impact energy of cavitation collapse, inhibit the erosion, pitting, and porosity of the base metal, delay the expansion of cavitation pits, and prevent the base metal from being rapidly eroded. As sand-laden water flows at high speed across the pressure surface 134, the second reinforcing coating can resist the cutting and chiseling wear of sand and gravel particles, reduce the material removal rate, and alleviate the ploughing and fish-scale wear on the surface of the blade 13. Since the suction surface is the surface of the blade 13 with a higher flow velocity, it can resist the impact erosion caused by cavitation collapse, inhibit cavitation damage, and protect the base metal of the rotor suction surface.

[0062] In some embodiments, the plurality of blades 13 include a first blade 13 and a second blade 13. The first blade 13 has a larger dimension in the direction from the upper crown 11 to the lower ring 12 than the second blade 13 in the same direction. The first blade 13 and the second blade 13 are arranged alternately. This arrangement, with the larger first blade 13 and the smaller second blade 13 alternating circumferentially, improves the flow field distribution inside the impeller mechanism, suppresses eddies and pressure pulsations within the flow channel 14, enhances hydraulic stability, and reduces the risk of cavitation. It should be noted that within the radial section of the impeller, the leading edge of the first blade 13 is located on the first circumference near the outer periphery of the lower ring 12, and the leading edge of the second blade 13 is located on the second circumference near the center of the impeller. The diameter of the first circumference is larger than the diameter of the second circumference. The trailing edges of both the first and second blades 13 are located on the same circumference near the center of the impeller. In other words, the extension length of the second blade 13 towards the outer periphery of the lower ring 12 is less than that of the first blade 13, resulting in a shorter circumferential unfolded length for the second blade 13 compared to the first blade 13. The first and second blades 13 have the same height dimension between the upper crown 11 and the lower ring 12, meaning both extend from the upper crown 11 to the lower ring 12, and their spans in the axial direction of the impeller are consistent. The unfolded length of the second blade 13 is 50% to 85% of the unfolded length of the first blade 13. The first and second blades 13 are distributed alternately along the circumferential direction of the impeller, and the number of first and second blades 13 is equal.

[0063] In addition, such as Figure 3 As shown in the illustration, this application also provides a mixed-flow turbine unit, which includes a volute 2, movable guide vanes 3, a bottom ring 4, a draft tube 5, a top cover 6, and a runner mechanism 1 as described in any of the above embodiments. The volute 2 is connected to the bottom ring 4, the movable guide vanes 3 are disposed between the bottom ring 4 and the runner mechanism 1, the runner mechanism 1 is disposed between the top cover 6 and the bottom ring 4, and the draft tube 5 is disposed on the side of the runner mechanism 1 away from the top cover 6. The beneficial effects of this mixed-flow turbine unit are the same as those of the aforementioned runner mechanism 1, and will not be elaborated further in this application.

[0064] The various embodiments in the specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0065] Although preferred embodiments of the present application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present application.

[0066] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes said element.

[0067] The present application has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of the present application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present application. Therefore, the content of this specification should not be construed as a limitation of the present application.

Claims

1. A runner mechanism for a mixed-flow turbine unit, characterized in that, The rotating wheel mechanism includes: An upper crown (11) and a lower ring (12) are spaced apart, and multiple blades (13) are provided between the upper crown (11) and the lower ring (12). The blade (13) includes a main body (131), an inlet edge (132), an outlet edge (133), a pressure surface (134), and a suction surface. The inlet edge (132) is located at one edge of the main body (131), and the outlet edge (133) is located at the other edge of the main body (131). The direction in which the inlet edge (132) points to the outlet edge (133) is consistent with the direction of water flow into the blade (13). The pressure surface (134) is located outside the direction of water flow of the blade (13), and the suction surface is located inside the direction of water flow of the blade (13). The inlet edge (132) includes a locally reinforced thickened strip (1321) and a continuous transition structure (1322). The locally reinforced thickened strip (1321) and the main body (131) are connected by the continuous transition structure (1322). The continuous transition structure (1322) extends along the water flow direction of the blade (13), and the continuous transition structure (1322) and the main body (131) of the blade (13) form a bidirectionally gradually changing three-dimensional streamlined surface along the water flow direction of the blade (13). The thickness of the continuous transition structure (1322) smoothly transitions from the inlet edge (132) to the main body (131) with a decreasing curvature trend. The decreasing curvature direction is from the inlet edge (132) along the water flow direction of the blade (13) to the middle of the main body (131). The thickness of the locally reinforced thickened strip (1321) is greater than the thickness of the main body (131). The water outlet edge (133) includes a vortex-reducing edge structure (1331), which is located at the edge where the water outlet edge (133) and the lower ring (12) are connected. The vortex-reducing edge structure (1331) is a spatial curved surface structure that extends to the side of the pressure surface (134) to the side of the suction surface.

2. The runner mechanism for a mixed-flow turbine unit according to claim 1, characterized in that, The continuous transition structure (1322) along the direction from the upper crown (11) to the lower ring (12) includes multiple continuous smooth transition surfaces, and the continuous smooth transition surface is a cross-sectional airfoil curve surface structure. The cross-sectional airfoil curve includes a pressure surface curve and a suction surface curve. The pressure surface curve and the suction surface curve are fitted with high-order spline curves between the local reinforcement thickening strip (1321) and the main body (131), and satisfy the continuity of the first derivative and the second derivative.

3. The runner mechanism for a mixed-flow turbine unit according to claim 1, characterized in that, Along the direction from the upper crown (11) to the lower ring (12), the thickness of the locally reinforced thickened strip (1321) increases non-linearly, and the thickness change curve of the locally reinforced thickened strip (1321) is parabolic or exponential.

4. The runner mechanism for a mixed-flow turbine unit according to claim 1, characterized in that, The pressure surface (134) includes a plurality of first curved surface structures, and the radius of curvature of the plurality of first curved surface structures gradually changes along the water flow direction of the blade (13) along a first gradient. The suction surface includes a plurality of second curved surface structures, and the radius of curvature of the plurality of second curved surface structures gradually changes along the water flow direction of the blade (13) along a second gradient. The first gradient is greater than the second gradient. The radius of curvature of the plurality of first surface structures included in the pressure surface (134) varies continuously along the direction from the upper crown (11) to the lower ring (12) and along the water flow direction of the blade (13).

5. The runner mechanism for a mixed-flow turbine unit according to claim 4, characterized in that, The radius of curvature of the plurality of first surface structures included in the pressure surface (134) increases nonlinearly along the direction from the upper crown (11) to the lower ring (12); Along the water flow direction of the blade (13), the radius of curvature of the plurality of first curved surface structures included in the pressure surface (134) in the first region of the blade (13) gradually increases, and the radius of curvature of the plurality of first curved surface structures included in the pressure surface (134) in the second region of the blade (13) gradually decreases. The first region of the blade (13) is the region between the water inlet edge (132) and the middle part of the main body (131), and the second region of the blade (13) is the region between the middle part of the main body (131) and the water outlet edge (133).

6. The runner mechanism for a mixed-flow turbine unit according to claim 4, characterized in that, The radius of curvature of each of the first surface structures is greater than the radius of curvature of the second surface structure.

7. The runner mechanism for a mixed-flow turbine unit according to claim 4, characterized in that, The profile of the vortex tail edge structure (1331) is distributed with a sweep angle along the direction from the upper crown (11) to the lower ring (12), and the angle of the sweep angle increases non-linearly along the direction from the upper crown (11) to the lower ring (12). The pressure surface (134) side and the suction surface side are connected by a transition arc spatial curved surface structure, and the arc radius of the transition arc spatial curved surface structure is 0.5 to 2 times the thickness of other areas of the water outlet edge (133); The radius of curvature of the spatial curved surface structure gradually decreases along the direction from the upper crown (11) to the lower ring (12). The radius of curvature of the spatial curved surface structure on the pressure surface (134) side is greater than the radius of curvature on the suction surface side. The radius of curvature of the spatial curved surface structure near the lower ring (12) is greater than the radius of curvature near the upper crown (11) region.

8. The runner mechanism for a mixed-flow turbine unit according to claim 1, characterized in that, The blade (13) further includes a first connecting root (135) and a second connecting root (136), the first connecting root (135) connecting the body (131) and the upper crown (11), and the second connecting root (136) connecting the body (131) and the lower ring (12). The first connecting root (135) is provided with a first reinforced transition zone, and the second connecting root (136) is provided with a second reinforced transition zone. Both the first reinforced transition zone and the second reinforced transition zone include a thickness gradient section and a curvature gradient section. The thickness change direction of the thickness gradient segment is gradually along the direction from the main body (131) to the upper crown (11) or from the main body (131) to the lower ring (12), and the radius of curvature of the curvature gradient segment is gradually along the direction from the main body (131) to the upper crown (11) or from the main body (131) to the lower ring (12). The inlet edge (132), the outlet edge (133), the first connecting root (135), the second connecting root (136), and the pressure surface (134) are configured with partitioned materials.

9. The runner mechanism for a mixed-flow turbine unit according to claim 1, characterized in that, A flow channel (14) is formed between two adjacent blades (13). The flow area of ​​the flow channel (14) gradually increases from the middle of the flow channel (14) in the direction from the water inlet side (132) to the water outlet side (133) or from the water outlet side (133) to the water inlet side (132) to both sides.

10. The runner mechanism for a mixed-flow turbine unit according to claim 1, characterized in that, The pressure surface (134) has a first reinforcing coating configured as an anti-erosion and wear coating, and the suction surface has a second reinforcing coating configured as an anti-cavitation damage coating.

11. The runner mechanism for a mixed-flow turbine unit according to claim 1, characterized in that, The plurality of blades (13) include a first blade (13) and a second blade (13), wherein the first blade (13) is larger in size in the direction along the upper crown (11) pointing to the lower ring (12) than the second blade (13) in the direction along the upper crown (11) pointing to the lower ring (12), and the first blade (13) and the second blade (13) are arranged alternately.

12. A mixed-flow turbine generator unit, characterized in that, The mixed-flow turbine unit includes a spiral casing (2), movable guide vanes (3), bottom ring (4), tailrace pipe (5), top cover (6), and a runner mechanism (1) as described in any one of claims 1 to 11. The volute (2) is connected to the bottom ring (4), the movable guide vane (3) is disposed between the bottom ring (4) and the impeller mechanism (1), the impeller mechanism (1) is disposed between the top cover (6) and the bottom ring (4), and the tailwater pipe (5) is disposed on the side of the impeller mechanism (1) away from the top cover (6).

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