Kaplan turbine runner and anti-cavitation bionic blade thereof

Abstract

The utility model discloses a Kaplan turbine runner and an anti-cavitation bionic blade thereof, and belongs to the technical field of fluid machinery and engineering equipment, the Kaplan turbine runner comprises a blade body, a strip-shaped flexible part is arranged on the suction surface of the blade body, and the whole flexible part is tightly attached to the upstream of the cavitation position of the blade in the spanwise direction of the blade. One part, in the length direction, of the flexible part is connected with the blade, the other part of the flexible part freely swings under excitation of unsteady incoming flow, and flow separation is controlled by a turbulent flow vortex with a certain frequency generated through self-adaptive flutter. The flexible part capable of swinging freely is arranged on the suction surface of the blade to generate turbulent flow vortex to control flow separation, so that the lowest pressure of the suction surface of the blade is improved, cavitation is improved, and the blade has the advantages of low cost, convenience in arrangement and the like.

Description

Technical Field

[0001] The utility model relates to the field of fluid machinery and engineering equipment, and particularly relates to a runner of a Kaplan turbine and an anti-cavitation bionic blade thereof. Background Technique

[0002] For the runner blades of a conventional Kaplan turbine, when the operating conditions of the turbine deviate from the design point, especially when the inlet attack angle of the blade is relatively large, flow separation will occur on the suction surface, resulting in a very low pressure in some areas on the back of the blade, thereby inducing cavitation.

[0003] In the prior art, a Chinese invention patent with the publication number CN112412869B and the patent name "An anti-cavitation axial flow pump and an impeller with cavitation suppression strips" discloses an anti-cavitation axial flow pump and an impeller with cavitation suppression strips, belonging to the field of pump technology. The impeller of the anti-cavitation axial flow pump includes a hub and blades; along the direction from the leading edge to the trailing edge of the blade, one or more cavitation suppression strips are arranged on the front half of its suction surface, and the cavitation suppression strip is a strip-shaped convex structure with its length direction arranged along the span direction; on the suction surface, two or more cavitation suppression strips are arranged, and along the direction from the leading edge to the trailing edge of the blade, the two or more cavitation suppression strips are arranged at intervals; along the direction from the leading edge to the trailing edge, one or more cavitation suppression strips are fixedly arranged on the rear half of the suction surface adjacent to the trailing edge.

[0004] This patent arranges cavitation suppression strips arranged along the span direction on the front half of the blade suction surface, so as to suppress the occurrence of cavitation at the leading edge of the blade suction surface by increasing the pressure on the blade surface in front of the suppression strip. However, the cavitation suppression strips in this patent are made of hard materials, and they block the fluid through the convex structure to increase the pressure on the blade surface in front of the suppression strip. And this solution proposes a structure that perturbs the downstream flow field by arranging flexible members on the blade to increase the pressure on the blade surface behind the flexible material. Summary of the Utility Model

[0005] The utility model aims to solve the problem that the pressure in some areas on the back of the blade in the prior art is low and prone to induce cavitation, and proposes a runner of a Kaplan turbine and an anti-cavitation bionic blade thereof. This solution realizes increasing the lowest pressure on the blade suction surface by setting flexible members on the blade suction surface to adaptively flutter to generate turbulent vortices with a certain frequency to control flow separation, thereby achieving the purpose of improving cavitation.

[0006] In order to achieve the above utility model purpose, the technical solution of the utility model is as follows:

[0007] An anti-cavitation bionic blade, including a blade body, is characterized in that a strip-shaped flexible member is arranged on the suction surface of the blade body. The flexible member is integrally arranged along the span direction of the blade and closely adheres to the upstream of the cavitation position of the blade. The flexible member includes integrally formed flexible component one and flexible component two. Flexible component one of the flexible member along its length direction is connected to the blade, and flexible component two will swing freely under the excitation of unsteady incoming flow, and generate turbulent flow vortices with a certain frequency through adaptive flutter to control flow separation.

[0008] Further, a part of the flexible member along its length direction is fixedly connected to the blade body by means of pasting or riveting.

[0009] Further, the flexible component two is serrated, including a number of triangular blocks arranged continuously along the length direction of the flexible component one.

[0010] Further, the height of the triangular block is equal to the distance between the tips of two adjacent triangular blocks.

[0011] Further, the height of the triangular block and the distance between the tips of two adjacent triangular blocks are both set to 0.05 times the runner diameter.

[0012] Further, the flexible component one is in a straight line or arc shape and closely adheres to the surface of the blade body.

[0013] Further, the present utility model also proposes a runner of a Kaplan turbine, and the runner of the Kaplan turbine includes the above-mentioned anti-cavitation bionic blade.

[0014] In summary, the present utility model has the following advantages:

[0015] 1. By pasting a flexible member on the suction surface of the blade, under the excitation of unsteady incoming flow, the flexible member generates turbulent flow vortices with a certain frequency through adaptive flutter to control flow separation, so as to improve the lowest pressure on the suction surface of the blade, thereby realizing the function of improving cavitation;

[0016] 2. In the present utility model, the flexible member includes integrally formed flexible component one and flexible component two. Among them, the flexible component two is designed as a serrated structure, which can further break and mix turbulent vortices, making the flow of water on the back of the blade more uniform;

[0017] 3. The present utility model improves cavitation by pasting a flexible member on the suction surface of the blade. The structure is relatively simple to implement, does not damage the blade body, does not affect the strength and service life of the blade, and has low cost and convenient arrangement, which is conducive to popularization. Description of the Drawings

[0018] Figure 1This is a schematic structural diagram of a cavitation-resistant bionic blade for a Kaplan turbine of the present utility model;

[0019] Figure 2 It is the pressure distribution diagram on the back of the blade in the prior art;

[0020] Figure 3 It is a schematic structural diagram of a runner of a Kaplan turbine;

[0021] In the figure:

[0022] 1. Blade body, 2. First flexible component, 3. Second flexible component, 5. Blade front end, 6. Blade rear end. Specific embodiments

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present utility model clearer, the technical solutions in the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model. Apparently, the described embodiments are some but not all of the embodiments of the present utility model. Usually, the components of the embodiments of the present utility model described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0024] Therefore, the following detailed description of the embodiments of the present utility model provided in the accompanying drawings is not intended to limit the scope of the present utility model to be protected, but merely represents the selected embodiments of the present utility model. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present utility model.

[0025] It should be noted that: Similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0026] In the description of the present utility model, it should be noted that the orientation or positional relationship indicated by the terms "upper", "vertical", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the present utility model is usually placed during use, or the orientation or positional relationship commonly understood by those skilled in the art. It is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation of the present utility model. In addition, the terms "first", "second", etc. are only used for descriptive distinction and cannot be understood as indicating or implying relative importance.

[0027] In the description of the present utility model, it should also be noted that unless otherwise clearly specified and defined, the terms "arrangement", "installation", and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.

[0028] The conventional runner structure of a Kaplan turbine is as Figure 3 shown, mainly including a runner body and blades distributed on the runner body. The runner body rotates around the runner shaft, and the blades rotate following the runner body. When the operating condition of the turbine deviates from the design point, especially when the angle of attack at the blade inlet is relatively large, flow separation will occur on the suction surface of the blade, resulting in a very low pressure in some areas on the back of the blade, thereby inducing cavitation. In this solution, the blade inlet is the front end, and the blade outlet is the rear end. Generally, the lowest pressure point is distributed at a position relatively close to the rear in the middle of the blade airfoil, as Figure 2 shown. In the figure, the left end is the front end 5 of the blade, and the right end is the rear end 6 of the blade.

[0029] The present utility model discloses an anti-cavitation bionic blade, including a blade body 1. A strip-shaped flexible member is arranged on the suction surface of the blade body 1. The flexible member is integrally arranged along the spanwise direction of the blade close to the upstream of the cavitation position of the blade. A part of it along the length direction is fixedly connected to the blade, and the other part swings freely under the excitation of unsteady oncoming flow, generating a turbulent vortex with a certain frequency through adaptive flutter to control flow separation. Among them, "upstream" correspondingly refers to the side close to the blade inlet, and "spanwise" refers to the radial direction in which the blade points from the runner to the blade edge. The flexible member arranged upstream of the cavitation position of the blade can improve the downstream flow field.

[0030] Embodiment 1

[0031] This embodiment provides an anti-cavitation bionic blade, including a blade body 1, as Figure 1 shown. In the figure, the lower end of the blade is the front end 5 of the blade, that is, the blade inlet; the upper end of the blade is the rear end 6 of the blade, that is, the blade outlet. A strip-shaped flexible member is arranged on the suction surface of the blade body 1. A part of the flexible member along the length direction is fixedly connected to the blade, and this part is called the first flexible component 2, which mainly plays the role of connecting with the blade body 1; the other part connected to the first flexible component 2 is called the second flexible component 3. The second flexible component 3 swings freely under the excitation of unsteady oncoming flow, generating a turbulent vortex with a certain frequency through adaptive flutter to control flow separation.

[0032] In this embodiment, the first flexible component 2 and the second flexible component 3 are integrally formed.

[0033] Furthermore, the flexible component 1 is strip-shaped and is fixed on the suction surface of the blade body 1 in the form of pasting or riveting, and is arranged closely upstream of the cavitation position of the blade along the blade span direction.

[0034] In this embodiment, the flexible component 1 can be arranged as a straight line consistent with the blade span on the blade surface, or can be arc-shaped.

[0035] Embodiment 2

[0036] On the basis of Embodiment 1, this embodiment proposes an anti-cavitation bionic blade, and further explains the structure of the flexible component 2.

[0037] In this embodiment, the flexible component 2 is designed in a serrated shape and includes a number of triangular blocks arranged continuously along the length direction of the flexible component 1. The serrated structure of the flexible component 2 can further break and mix the turbulent vortices, making the flow of water on the back of the blade more uniform.

[0038] Preferably, as Figure 1 shown, the height s of the triangular block is equal to the distance h between the tips of two adjacent triangular blocks, and the height s of the triangular block and the distance h between the tips of two adjacent triangular blocks are preferably set to 0.05 times the runner diameter.

[0039] In this embodiment, the flexible part needs to have sufficient strength and is not easily damaged, and also needs to have sufficient flexibility to produce a certain amount of deformation. Materials such as polyvinyl chloride (PVC), polyethylene (PE), and polyester (PET) can be used for production.

[0040] The utility model pastes a flexible part on the suction surface of the blade. Under the excitation of unsteady incoming flow, the flexible part generates turbulent vortices with a certain frequency through adaptive flutter to control flow separation. At the same time, the serrated structure further breaks and mixes the turbulent vortices, making the flow of water on the back of the blade more uniform, realizing the function of increasing the lowest pressure on the suction surface of the blade and thus improving cavitation.

[0041] Embodiment 3

[0042] This embodiment proposes a runner of a Kaplan turbine, and the runner of the Kaplan turbine has the anti-cavitation bionic blade described in Embodiment 1 and Embodiment 2.

[0043] The above is only a preferred embodiment of the utility model, and does not impose any form of limitation on the utility model. Any simple modification and equivalent change made to the above embodiments based on the technical essence of the utility model all fall within the protection scope of the utility model.

Claims

1. An anti-cavitation bionic blade, comprising a blade body (1), characterized in that: A long strip of flexible member is arranged on the suction surface of the blade body (1), and the flexible member is arranged as a whole along the span direction of the blade, close to the upstream of the position where cavitation occurs in the blade; the flexible member comprises an integrally formed flexible component one (2) and a flexible component two (3), the flexible component one (2) arranged along the length direction of the flexible member is connected to the blade, and the flexible component two (3) swings freely under the excitation of an unsteady incoming flow, and generates a vortex of a certain frequency through adaptive flutter to control flow separation.

2. The anti-cavitation bionic blade according to claim 1, characterized in that: A portion of the flexible member along its length direction is connected and fixed to the blade body by bonding or riveting.

3. The anti-cavitation bionic blade according to claim 1, characterized in that: The flexible component 2 (3) is sawtooth-shaped and comprises a plurality of triangular blocks arranged continuously along the length direction of the flexible component 1.

4. The anti-cavitation bionic blade according to claim 3, characterized in that: The height of the triangular block is equal to the distance between the tips of two adjacent triangular blocks.

5. The anti-cavitation bionic blade according to claim 4, characterized in that: The height of the triangular block and the distance between the tips of two adjacent triangular blocks are both set to 0.05 times the diameter of the rotating wheel.

6. The anti-cavitation bionic blade according to claim 1, characterized in that: The flexible component 1 (2) is in a straight line or an arc shape and is closely attached to the surface of the blade body (1).

7. The anti-cavitation bionic blade according to claim 1, characterized in that: The flexible member is made of polyvinyl chloride, polyethylene or polyester.

8. A propeller-type water turbine runner, characterized in that: The impeller of the propeller turbine comprises an anti-cavitation bionic blade as described in any one of claims 1 to 7.

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