Methods for suppressing vortices in the draft tube of a water turbine

Abstract

This invention discloses a method for suppressing vortices in the draft tube of a hydroelectric turbine, comprising the following steps: a. The draft tube of the hydroelectric turbine is constructed by connecting and installing a conical section and an elbow section; b. To suppress vortices in the draft tube, several vortex-suppressing grids are installed circumferentially on the draft tube wall in the middle part of the conical section, depending on different operating conditions; c. The vortex-suppressing grids consist of a frame and several parallel grating bars within the frame; d. The draft water from the turbine generator runner passes through the upper part of the draft tube conical section to the vortex-suppressing grids in the middle part. The vortex-suppressing grids gradually reduce the vortex intensity of the water flow reaching the tube wall surface, thereby eliminating the draft tube vortex through multiple vortex-suppressing grids. When the draft water from the turbine runner enters the conical section of the draft tube, the vortex-laden water flow passes through the tube wall and first passes through the vortex-suppressing grids. Under the interception effect of the vortex-suppressing grids, the vortex of the water flow is destroyed, thus achieving the purpose of suppressing vortices.

Description

Technical Field

[0001] This invention belongs to the field of water conservancy engineering technology, specifically relating to a method for suppressing and eliminating vortices in the tailrace pipe of a water turbine, which is applicable to improving the internal modification of the tailrace pipe of a water turbine. Background Technology

[0002] The hydraulic stability of the draft tube of a turbine is a crucial standard for evaluating the unit's performance and energy indicators. Therefore, studying the flow performance and vortex formation mechanism of the draft tube under partial load conditions is extremely important. For many years, numerous scholars both domestically and internationally have conducted extensive research on the flow characteristics of the draft tube of mixed-flow turbines. Low-frequency pressure pulsations within the draft tube are related to the head, and these pressure pulsations are caused by vortices within the draft tube. Currently, methods to improve the partially unstable flow state within the draft tube mainly include optimizing the shape of the runner's discharge cone, optimizing the runner's flow path, optimizing the draft tube cone and bend sections, adding air to the draft tube center, and altering the turbine's cavitation coefficient. Currently, a common method is to optimize the draft tube cone section by installing guide grids or damping grids. These guide grids or damping grids are generally located in the center of the draft tube. They only affect the vortex zones in the center of the draft tube, while the vortices formed by the water flow on the draft tube wall are not effectively suppressed, resulting in poor vortex suppression. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for suppressing vortices in the draft tube of a hydraulic turbine. This method can be used to modify the conical section of the existing draft tube and can also be combined with existing vortex suppression structures in the center of the draft tube. Depending on the operating conditions, the method of this invention can be used alone or in combination with existing vortex suppression methods in the center of the draft tube. Its vortex suppression effect is significant.

[0004] To achieve the above objectives, the turbine tailrace vortex suppression method of the present invention adopts the following technical solution:

[0005] A method for suppressing vortices in the draft tube of a water turbine includes the following steps:

[0006] a. The turbine tailrace pipe is constructed by connecting and installing conical sections and elbow sections;

[0007] b. To suppress vortices in the tailrace pipe, several vortex-suppressing grids are installed circumferentially on the tailrace pipe wall in the middle part of the conical section, depending on different operating conditions.

[0008] c. The vortex-eliminating grid consists of a frame and several parallel gratings within the frame;

[0009] d. The tailrace water from the turbine generator runner passes through the upper part of the tailrace cone section to the middle part of the vortex-eliminating grid. The vortex-eliminating grid gradually reduces the vortex intensity of the water flow at the pipe wall surface of the tailrace pipe. By passing through multiple vortex-eliminating grids, the purpose of eliminating tailrace vortices is achieved.

[0010] In the above-mentioned turbine tailrace vortex suppression method, the frame of the vortex suppressor grid in step c is a parallelogram, with the side of the parallelogram parallel to the conical section pipe wall. The upper and lower points of the side of the vortex suppressor grid facing the conical section are respectively connected by an upper connecting ring and a lower connecting ring.

[0011] The above-mentioned vortex suppression method for the turbine tailrace tube involves installing two U-shaped grooves on the tube wall near the conical section of the tailrace tube. The bottoms of the two U-shaped grooves are connected by a base plate. A U-shaped retaining strip is provided on one side of the corresponding vortex suppressor grid. The U-shaped strip is inserted downward into the two U-shaped grooves until it is stopped by the base plate at the bottom plate.

[0012] By adopting the above technical solution, the present invention has the following beneficial effects:

[0013] The turbine draft tube vortex suppression method described in this invention involves welding two U-shaped grooves inside the draft tube and inserting and fixing the vortex-suppressing grid of this invention into the two U-shaped grooves. Draft water from the turbine runner enters the conical section of the draft tube. When the vortex-laden water flows through the draft tube wall, it first passes through the vortex-suppressing grid. Under the interception effect of the grid, the vortex in the water flow is disrupted, achieving the purpose of vortex suppression. Simultaneously, as the diameter of the conical section gradually increases downwards, the flow velocity of the vortex-laden water gradually decreases due to the interception effect of the vortex-suppressing grid and the gradually expanding draft tube, resulting in a gradual decrease in pressure. This improves the operational reliability of the turbine and effectively expands the safe operating range and operational regulation capability of the turbine. Depending on different operating conditions, this invention can be used alone or in combination with existing vortex-suppressing structures in the center of the draft tube. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of the present invention;

[0015] Figure 2 This is a view of the vortex-reducing grid along direction A in Figure 1;

[0016] Figure 3 This is a schematic diagram of the vortex-eliminating grid structure;

[0017] Figure 4 yes Figure 1 Partial B-direction view of the vortex-eliminating grid and tailrace pipe;

[0018] Figure 5 yes Figure 4 Top magnified view of the connection between the U-shaped groove and the anti-vortex grid

[0019] Figure 6 yes Figure 4 A magnified bottom view of the connection between the U-shaped groove and the anti-vortex grid. Detailed Implementation

[0020] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0021] A method for suppressing vortices in the draft tube of a water turbine includes the following steps: Figures 1-6 As shown, a. The turbine draft tube is constructed by connecting and installing a conical section 1 and an elbow section 3; b. To suppress draft tube vortices, several vortex-eliminating grids 2 are installed circumferentially on the draft tube wall in the middle part of the conical section, depending on different operating conditions; c. The vortex-eliminating grid consists of a frame 4 and several parallel gratings 5 ​​within the frame; d. The draft water from the turbine generator runner passes through the upper part of the draft tube conical section to the vortex-eliminating grid in the middle part. The vortex-eliminating grid gradually reduces the vortex intensity of the water flow reaching the draft tube wall, thereby eliminating the draft water vortex through multiple vortex-eliminating grids.

[0022] The turbine draft tube vortex suppression method of this invention, in step c, uses a parallelogram-shaped frame for the vortex suppressor grid. The sides of the parallelogram are parallel to the conical section pipe wall. Upper connecting ring 6 and lower connecting ring 7 connect the upper and lower points of the side of the vortex suppressor grid facing the conical section, respectively. After all the vortex suppressors are installed, near the center of the draft tube, the apex corners of all the vortex suppressors are welded to the annular upper connecting ring, and the bottom corners of all the vortex suppressors are welded to the annular lower connecting ring. Thus, one side of all the vortex suppressors is connected by the upper and lower connecting rings, and the other side of all the vortex suppressors is fixed to the draft tube wall. The inner and outer sides of all the vortex suppressors are fixed as a single unit, improving the overall performance of the vortex suppressor grid.

[0023] The vortex suppression method for the draft tube of a turbine as described in this invention involves installing two U-shaped grooves 8 on the tube wall near the conical section of the draft tube. The bottoms of the two U-shaped grooves are connected by a base plate 10. A U-shaped retaining strip 9 is provided on one side of the corresponding vortex suppressor. The U-shaped strip is inserted downwards into the two U-shaped grooves until it is stopped by the base plate. Two U-shaped grooves are welded to the tube wall in the middle section of the conical section of the draft tube, and the bottoms of the two U-shaped grooves are fixedly welded together by the base plate, thus fixing the two U-shaped grooves together at the bottom. Several mounting slots for installing vortex suppressors are circumferentially arranged in the middle section of the conical section inside the draft tube. The vortex suppressors are then inserted one by one into the U-shaped grooves until they reach the base plate.

[0024] The working process of this invention is as follows:

[0025] First, two U-shaped grooves are welded to the wall of the conical section in the middle of the draft tube. The bottoms of the two U-shaped grooves are then fixedly welded together with a base plate, thus securing the two U-shaped grooves at the bottom. At this point, several mounting slots for installing vortex suppressors are already circumferentially arranged in the middle of the conical section inside the draft tube. The vortex suppressors are then inserted one by one into the U-shaped grooves up to the base plate. After all the vortex suppressors are installed, near the center of the draft tube, the apex corners of all the vortex suppressors are welded to the upper connecting ring, and the bottom corners are welded to the lower connecting ring. This connects one side of all the vortex suppressors through the upper and lower connecting rings, and the other side of all the vortex suppressors is fixed to the draft tube wall. The inner and outer sides of all the vortex suppressors are fixed as a single unit, improving the overall performance of the vortex suppressors.

[0026] The water flow carrying vortices flows towards the wall of the draft tube, passing sequentially through vortex-suppressing grids. Since these grids are circumferentially installed, the vortices are significantly disrupted after the water flows through all of them, thus eliminating vortices in the draft tube. Through this invention, when water carrying vortices flows through the draft tube wall, it first passes through the vortex-suppressing grids. The vortices are disrupted by the interception effect of the grids, thus suppressing vortices. Simultaneously, as the diameter of the conical section gradually increases downwards, the flow velocity of the water carrying vortices gradually decreases due to the interception effect of the vortex-suppressing grids and the gradually widening draft tube, resulting in a gradual decrease in pressure. This improves the operational reliability of the turbine and effectively expands its safe operating range and operational regulation capabilities.

[0027] This invention can be used to modify the conical section of an existing tailrace pipe, and can also be used in conjunction with the existing tailrace pipe center part suppression vortex structure. Depending on different working conditions, this invention can be used alone, or it can be used in conjunction with the existing tailrace pipe center part anti-vortex structure.

[0028] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for suppressing vortices in the draft tube of a water turbine, characterized in that, Includes the following steps: a. The turbine tailrace pipe is constructed by connecting and installing a conical section (1) and an elbow section (3); b. To suppress tailrace vortices, several anti-vortex grids are installed circumferentially on the tailrace wall in the middle part of the conical section, depending on the different working conditions (2). c. The vortex-eliminating grid is composed of a frame (4) and several parallel grate bars (5) within the frame; the frame of the vortex-eliminating grid is a parallelogram, the side of the parallelogram is parallel to the conical section pipe wall, and the upper and lower points of the side of the vortex-eliminating grid facing the conical section are respectively connected by an upper connecting ring (6) and a lower connecting ring (7). d. The tailwater from the turbine generator runner passes through the upper part of the tailwater conical section to the middle part of the vortex-eliminating grid. The vortex-eliminating grid gradually reduces the vortex intensity of the water flow at the pipe wall surface of the tailwater pipe. By passing through multiple vortex-eliminating grids, the purpose of eliminating tailwater vortices is achieved. Two U-shaped grooves (8) are installed on the pipe wall near the tailwater pipe of the conical section. The bottom of the two U-shaped grooves are connected by a base plate (10). A U-shaped clip (9) is provided on one side of the corresponding anti-vortex grid. The U-shaped clip is inserted downward into the two U-shaped grooves until it is stopped by the base plate at the bottom plate.

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