Hole-containing C-shaped pier column capable of increasing size of scouring funnel and design method of hole-containing C-shaped pier column

Abstract

The invention belongs to the technical field of engineering sediment, and relates to a device for enlarging the geometric size of a scouring funnel in front of a bottom hole of a hydropower station, in particular to a perforated C-shaped pier column for enlarging the size of a scouring funnel and a design method. And the size and the installation position of the C-shaped pier stud with the hole are calculated according to the size of the bottom hole of the reservoir. According to the invention, the geometric dimension of the scouring funnel can be increased to a greater extent, so that the water taking port can take low-sand-content water, namely, 'gate-front cleaning 'is realized, the abrasion of sand-containing water flow to a flow passage component of a water turbine is reduced, the bottom hole design of a dam can be improved, and the stress distribution of the dam can be optimized.

Description

Technical Field

[0001] The present invention belongs to the technical field of engineering sediment, and relates to a device for expanding the scour funnel in front of the bottom outlet of a hydropower station, specifically referring to a perforated "C"-shaped pier for increasing the size of the scour funnel and its design method. Background Technique

[0002] With China's strong promotion of sustainable economy, energy transformation, and the proposal of the dual-carbon goal, hydropower, as a clean and renewable energy source, has become increasingly important. By the end of 2021, the total installed power generation capacity in the country was approximately 2.38 billion kilowatts, of which the installed hydropower capacity was 391 million kilowatts, accounting for 16.44%. The development of China's water resources only accounts for half of the total, and there is broad space for the development of hydropower. In hydropower generation, the water turbine is the core component. The water turbine in power generation has extremely high speed and mass, so there are relatively high requirements for the sediment content of the water body passing through the water turbine during operation. The damage caused by sediment abrasion to the water turbine is very serious. After sediment particles are carried into the water inlet by high-speed water flow, they will cause abrasion of the flow-through components of the water turbine, affecting the normal operation of the hydropower station and increasing maintenance costs. The problem of sediment abrasion is particularly prominent for high-head power stations (such as the pumped-storage power stations that China is currently vigorously developing, whose water heads can usually reach 400 - 500m). Currently, more than 60,000 dams over 15m high globally were mostly built from the 1930s to the 1970s, and many of these reservoirs have serious siltation. If the normal power generation duration is to be extended, it is necessary to ensure that the sediment content in the water intake of the power station is small. If certain engineering measures can be taken economically to minimize the sediment content passing through the turbine as much as possible, it will undoubtedly be of great help to the normal water intake of existing, under-construction, or planned power stations.

[0003] To reduce sediment passing through the turbine, the measures commonly used in engineering mainly include: (1) adding sediment discharge bottom outlets to reduce the sediment deposition elevation at the front edge of the water intake; (2) using the characteristics of water-sediment movement in bend circulation to take water laterally and discharge sediment forward; (3) using devices such as sediment discharge galleries to discharge sediment. Among them, the bottom outlet is a common method for multi-sand rivers to solve the problem of "clean front" at the water intake. The function of the bottom outlet is to form a local high-speed water flow after it is opened, pull away the sediment deposited in front of the dam, and form a funnel-shaped scour pit, that is, a scour funnel, thereby reducing the bed elevation at the front edge of the water intake of the hydropower station, reducing the sediment content and sediment particle size passing through the turbine, slowing down the abrasion of the flow-through components of the water turbine, and increasing the power generation utilization duration. If certain engineering measures can be taken to increase the geometric size of the scour funnel in front of the hole, it will undoubtedly be of great significance for achieving "clean front" at the water intake of the power station, extending the power generation life of the power station, and reducing maintenance costs. Summary of the Invention

[0004] In view of the problems existing in the prior art, the present invention provides a perforated "C"-shaped pier that can be arranged in front of the bottom hole and a design method. The "C"-shaped pier can effectively increase the geometric size of the scour funnel in front of the bottom hole, help to achieve the intake of water with low sediment content at the water intake, that is, achieve "clean in front of the door", thereby reducing the wear of the flow components of the water turbine by the sediment-laden water flow, and can optimize the stress distribution of the dam while improving the bottom hole design of the dam.

[0005] To achieve the above objectives, the present invention is realized through the following technical solutions:

[0006] In the first aspect, the present invention provides a perforated "C"-shaped pier for increasing the size of the bottom hole scour funnel. The pier includes a square column main body facing the bottom hole and flow-around columns connected to both sides of the square column main body. The height of the square column main body is not less than the vertical distance from the bottom of the bottom hole to the riverbed in front of the dam; the top of the square column main body is flush with the top of the flow-around columns; the bottom edge of the flow-around columns is set higher than the bottom of the square column main body to form a flow-around hole at the bottom of the flow-around columns, thereby forming a perforated "C"-shaped pier in front of the bottom hole; the area enclosed by the projections of the outer edges of the two flow-around columns on the dam surface is not less than the size of the bottom hole orifice.

[0007] The device of the present invention is mainly composed of a square column main body and a flow-around device on the back water surface of the square column to jointly form a perforated "C"-shaped pier in cross-section. During use, the bottom of the square column main body is buried under the sediment, the top is basically flush with the top of the bottom hole, and the two flow-around columns are installed on the back water surface of the square column main body. The square column main body is embedded in the riverbed to stabilize the overall structure and form a large-scale horseshoe vortex system when the water flow passes around the square column main body; the flow-around device on the back water surface of the square column main body is used to control the large-scale turbulent vortices formed between the square column main body and the bottom hole near the bottom hole, so that a large amount of sediment near the bottom hole is continuously suspended and carried out of the bottom hole by the high-speed water flow in the orifice area. It has been proved by experiments that the present invention can effectively increase the geometric size of the scour funnel in front of the bottom hole. This device is easy to install, requires no maintenance, has a low price, remarkable effects, and at the same time has extremely high universality, and is very suitable for popularization and application in large, medium and small hydropower hubs to exert huge economic and safety benefits.

[0008] Further, the flow-around columns are symmetrically arranged on both sides of the square column main body, and the included angle between the flow-around columns and the square column main body is 90°±45°.

[0009] Preferably, both the square column main body and the flow-around columns are square structures.

[0010] Preferably, the width of the upstream-facing surface of the square column main body is 0.8 to 1.2 times the side length or diameter of the bottom hole orifice; the length (along the water flow direction) of the flow-around columns is 0.25 to 0.75 times the side length or diameter of the bottom hole orifice; the height of the flow-around columns is 2.8 to 3.5 times the side length or diameter of the bottom hole orifice.

[0011] Preferably, the thickness of the square column body (along the water flow direction) is 0.125 - 0.375 times the side length or diameter of the bottom hole orifice; the thickness of the flow-around column is 0.125 - 0.250 times the side length or diameter of the bottom hole orifice.

[0012] Preferably, the top of the square column body is higher than or flush with the top end of the bottom hole orifice. Further preferably, the top of the pier column is flush with the top of the bottom hole, so as to avoid the difficulty of opening and closing the intake gate due to the excessive height of the square column body.

[0013] Preferably, an installation seat is provided at the bottom of the square column body, and fastening holes for locking the installation seat are provided on the installation seat.

[0014] Preferably, the square column body and the flow-around column are of an integrally formed structure.

[0015] In a second aspect, the present invention provides a design method for a perforated "C"-shaped pier column for increasing the size of the scour funnel at the bottom hole, comprising the following steps:

[0016] Step 1. Install a perforated "C"-shaped pier column upstream of the bottom hole. The pier column includes a square column body and two flow-around columns. The bottom of the square column body is buried under the sediment, the top is flush with the top of the bottom hole, and the two flow-around columns on both sides are installed on the back water surface of the square column body;

[0017] Step 2. Calculate the geometric dimensions of the square column body according to the size of the bottom hole orifice, including that the thickness of the square column body is equal to 0.125 - 0.375 times the side length or diameter of the orifice, and the width of the upstream face of the square column body is 0.8 - 1.2 times the side length or diameter of the orifice.

[0018] Step 3. The widths of the two flow-around columns on both sides are 0.25 - 0.75 times the side length or diameter of the orifice, and the thicknesses are 0.125 - 0.250 times the side length or diameter of the orifice; the tops of the two flow-around columns on both sides are flush with the top of the square column body, and the height is taken as 2.8 - 3.5 times the side length or diameter of the orifice; the included angle between the two flow-around columns on both sides and the square column body is 90° ± 45°;

[0019] Step 4. The square column body is placed parallel and directly in front of the orifice. The vertical distance between the square column body and the bottom hole is 0.7 - 1.2 times the side length or diameter of the bottom hole, and the top height of the pier column is flush with the top end of the bottom hole.

[0020] After the device is arranged, the size of the scour funnel in front of the orifice is significantly increased, which can effectively reduce the sediment entering the intake and alleviate the abrasion of the water turbine by the sediment-laden water flow. The perforated "C"-shaped pier column is preferably made of concrete (other materials can also be used), which has good corrosion resistance and low cost.

[0021] Thirdly, the present invention also provides a method for increasing the size of the scour funnel at the bottom hole, comprising the steps of: installing the above-mentioned perforated "C"-shaped pier in front of the bottom hole, with the square column body parallel and all placed directly in front of the hole opening, the top of the square column body being flush with the top end of the bottom hole, the flow-around column being located on the back water surface of the square column body, and the vertical distance between the square column body and the bottom hole orifice being greater than the vertical distance from the center of the square column body to the outer edge of the flow-around column.

[0022] Compared with the prior art, the advantages of the present invention are as follows:

[0023] (1) The pier of the present invention is jointly composed of a square column body and a flow-around column on the back water surface of the square column, forming a perforated "C"-shaped pier in cross-section. During use, the bottom of the square column body is buried under the sediment, the top is basically flush with the top of the bottom hole, and the two side flow-around columns are installed on the back water surface of the square column body. The size of the scour funnel formed by using the pier of the present invention is significantly increased, which can effectively reduce the sediment entering the water intake and reduce the wear of the water turbine by the sediment-laden water flow.

[0024] (2) By increasing the size of the scour funnel, the time required for the sediment to fill the scour funnel increases, thereby reducing the opening frequency of the bottom hole, reducing the operation and maintenance cost, and at the same time, the number of bottom hole arrangements can be reduced, thus optimizing the stress distribution of the dam body.

[0025] (3) The pier of the present invention is easy to install, requires no maintenance, has a low price, has a remarkable effect, and at the same time has extremely high universality, and is very suitable for popularization and application in large, medium and small hydropower hubs to exert great economic and safety benefits. Description of the Drawings

[0026] Figure 1 is a physical model diagram of the perforated "C"-shaped pier;

[0027] Figure 2 is a three-dimensional model diagram of the perforated "C"-shaped pier;

[0028] Figure 3 is a three-dimensional model diagram of the perforated "C"-shaped pier with a mounting seat;

[0029] Figure 4 is the relative size and three views (front view, side view, top view) of the model physical object, and the dimensions shown in the figure only correspond to a certain size of the perforated "C"-shaped pier;

[0030] Figure 5 is the top view of the scour funnel at the end of the three working conditions experiments under a water head of 0.65m. From top to bottom, they are no pier, square column body, and perforated "C"-shaped pier. The outer edge line of the scour funnel is shown by the black dotted line;

[0031] Figure 6For the scouring funnels of the pierless column (○), only the square column body (□), and the perforated "C"-shaped pier column (△), the longitudinal section topography ((a), (c)) along the center line of the orifice and the cross-section topography in front of the dam ((b), (d)); Figures (a) and (b) are the test results under a water head of 0.45 m, and Figures (c) and (d) are the test results under a water head of 0.65 m.

[0032] In the figures, 1, bottom hole; 2, square column main body; 3, flow-around column; 4, flow-around hole; 5, mounting seat; 6, fastening hole. Specific implementation manner

[0033] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0034] In order to increase the size of the scouring funnel in front of the bottom hole 1 and help achieve "clean water in front of the door" for power station water intake, the present invention proposes a perforated "C"-shaped pier column that can be arranged in front of the bottom hole 1, as shown in Figure 1 and Figure 2 or Figure 3 .

[0035] In the test, the perforated "C"-shaped pier column was made of acrylic board. In actual engineering, it can be made of concrete pouring to reduce costs, and it can be durable and does not require maintenance.

[0036] The perforated "C"-shaped pier column of the present invention for increasing the size of the scouring funnel of the bottom hole 1 includes a square column main body 2 facing the bottom hole 1 and flow-around columns 3 connected to both sides of the square column main body 2. The height of the square column main body 2 is not less than the vertical distance from the bottom of the bottom hole 1 to the riverbed in front of the dam; the top of the square column main body 2 is flush with the top of the flow-around columns 3; the bottom edge of the flow-around columns 3 is set higher than the bottom of the square column main body 2 to form a flow-around hole 4 at the bottom of the flow-around columns, so as to form a perforated "C"-shaped pier column in front of the bottom hole 1; the area enclosed by the projections of the outer edges of the two flow-around columns 3 on the dam surface (bottom hole surface) is not less than the orifice size of the bottom hole 1.

[0037] The device of the present invention mainly consists of a square column main body 2 and a flow-around device (flow-around columns 3) on the back water surface of the square column, jointly forming a pier column with a perforated "C" cross-section. During use, the bottom of the square column main body 2 is buried under the sediment, the top is basically flush with the top of the bottom hole 1, and the two flow-around columns 3 are installed on the back water surface of the square column main body 2. The square column main body 2 is embedded in the riverbed to stabilize the overall structure and form a large-scale horseshoe vortex system when the water flow passes around the square column main body 2; the flow-around device (flow-around columns 3) on the back water surface of the square column main body 2 is used to control the large-scale turbulent vortices formed between the square column main body 2 and the bottom hole 1 near the bottom hole 1, so that a large amount of sediment near the bottom hole 1 is continuously suspended and carried out of the bottom hole 1 by the high-speed water flow in the orifice area.

[0038] In some examples, an installation seat 5 is provided at the bottom of the square column main body 2, and a fastening hole 6 for locking the installation seat 5 is provided on the installation seat 5.

[0039] In some examples, the square column main body 2 and the flow-around columns 3 are of an integrally formed structure.

[0040] The design method of the perforated "C" type pier column for increasing the size of the scour funnel of the bottom hole 1 in the present invention is as follows: Install a perforated "C" type pier column for increasing the size of the scour funnel upstream of the bottom hole 1, including a square column main body 2 and two flow-around columns 3; the bottom of the square column main body 2 is buried under the sediment, the top is basically flush with the top of the bottom hole 1, and the two flow-around columns 3 are installed on the back water surface of the square column main body 2. Calculate the size of the square column main body 2 according to the orifice size. It is calculated that the thickness of the square column main body 2 (along the water flow direction) is equal to 0.125 - 0.375 times the side length or diameter of the orifice, and the width of the upstream surface of the square column main body 2 is 0.8 - 1.2 times the side length or diameter of the orifice. The width of the two flow-around columns 3 (along the water flow direction) is 0.25 - 0.75 times the side length or diameter of the orifice, and the thickness is 0.125 - 0.250 times the side length or diameter of the orifice. The tops of the two flow-around columns 3 are flush with the top of the square column main body 2, and the height is taken as 2.8 - 3.5 times the side length or diameter of the orifice. The included angle between the two flow-around columns 3 and the square column main body 2 is 90° ± 45°. The square column main body is parallel and placed directly in front of the orifice, and the vertical distance between the square column main body 2 and the bottom hole 1 is 0.7 - 1.2 times the side length or diameter of the bottom hole 1. The top height of this pier column is flush with the top of the bottom hole 1. After arranging this device, the size of the scour funnel formed in front of the orifice is significantly increased, which can effectively reduce the sediment entering the water intake and reduce the wear of the water turbine by the sediment-laden water flow; the top of the device is flush with the top of the bottom hole 1, and it will not cause difficulties in opening and closing the intake gate due to the excessive height of the square column. The perforated "C" type pier column is recommended to be made of concrete (other materials can also be used), which has good corrosion resistance and low cost.

[0041] To verify that the present invention can increase the geometric size of the scour funnel in front of the dam, multiple groups of tests were carried out. The following details the comparative test results of no pier column, only square columns, and perforated "C"-shaped pier columns at water heads of 0.45 m and 0.65 m carried out in an experimental flume.

[0042] This test was carried out in an experimental flume with a length of 7 m, a width of 1 m, and a depth of 1 m. A square hole with a side length D = 0.08 m was opened at the center of the dam surface and 0.2 m above the riverbed. In the test, the horizontal distance of the centerlines of only the square column body 2 and the perforated "C"-shaped pier column from the dam surface (bottom hole 1) was D. The top heights of all pier columns were flush with the top of the orifice. The length of the square column body 2 in the water flow direction was 1 / 8D. The width of the upstream face of all square column bodies 2 was the same as the side length of the orifice. The square column bodies 2 were placed in parallel directly in front of the orifice. One size of the perforated "C"-shaped pier column is shown in Figure 4 the three-view drawings. The characteristic geometric sizes of the scour funnels formed after scouring for 4 hours under the conditions of no pier column, only square columns, and perforated "C"-shaped pier columns at 0.45 m and 0.65 m were measured, including the length in the flume length direction, the width in the flume width direction, and the scour depth directly below the bottom hole 1.

[0043] Table 1 gives the characteristic geometric sizes of the scour funnels formed after scouring for 4 hours under the conditions of no pier column, only the square column body, and the perforated "C"-shaped pier column at 0.45 m and 0.65 m. It can be seen from the table that compared with the case of no pier column, after placing the square column, the length, width, and depth of the funnel increased significantly by 1.0 - 1.6 times (i.e., increased to 2.0 - 2.6 times that of no pier column) under the same water head. After placing the perforated "C"-shaped pier column, the length, width, and depth of the funnel increased significantly by 1.3 - 2.3 times (i.e., increased to 2.3 - 3.6 times that of no pier column) under the same water head, and a larger scour funnel can also be obtained at a low water head of 0.45 m.

[0044] Table 1 Test condition parameters and characteristic geometric sizes of the scour funnel after scouring for 4 hours:

[0045]

[0046] Figure 5 、 Figure 6 Top-view pictures of the scour funnels under the three conditions of no pier column, only square columns, and perforated "C"-shaped pier columns taken at the end of the experiment are given respectively, as well as the longitudinal profile topography of the scour funnel along the centerline of the orifice and the cross-sectional topography in front of the dam. From Figure 5 and Figure 6 it can be clearly seen that the sizes of the scour funnel in all directions under the perforated "C"-shaped pier column are significantly larger than those in the cases of only square columns and no pier column.

[0047] Application of the present invention in specific hydropower stations:

[0048] Sediment abrasion of hydraulic turbines is one of the important factors restricting the output of hydropower plants at present. Structures such as turbine blades, guide vanes, and runner bodies in hydraulic turbines are often subject to sediment abrasion and erosion, which form tiny cracks on the surface of carbon steel molecules or cause metal loss on the surface of flow-through components, seriously affecting the performance of hydraulic turbines, resulting in reduced operating efficiency of hydropower station equipment, increased maintenance costs, and shortened service life, endangering the stable and safe operation of hydropower units. When the sediment content in the river is relatively high during the flood season, if the sediment discharge of the hydropower station is not in place, it may lead to the phenomenon that the sediment passing through the machine damages the hydraulic turbine. The problem of sediment abrasion of hydraulic turbines still plagues multi-sand rivers, especially high-head power stations such as pumped-storage power stations on multi-sand rivers. Therefore, the problem of water intake safety must be considered in the design of hydropower stations. The present invention provides a new idea for solving the "clean front" of the water intake, and proposes a device with a much larger and cheaper size than the traditional one that simply relies on orifice outflow to form a scour funnel, which can effectively reduce the sediment entering the water intake and reduce the abrasion of the sediment-laden water flow on the hydraulic turbine, and has extremely high practical value. By increasing the size of the scour funnel, the time required for the sediment to fill the scour funnel increases, thereby reducing the opening frequency of the bottom holes, reducing the operation and maintenance costs, and at the same time, the number of bottom holes arranged can be reduced, thereby optimizing the stress distribution of the dam body.

[0049] The pier columns of the present invention are easy to install, do not require maintenance, are inexpensive, have remarkable effects, and at the same time have extremely high universality, and are very suitable for popularization and application in large, medium and small hydropower hubs to exert huge economic and safety benefits.

[0050] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A "C"-shaped pier with holes to increase the size of the bottom hole scouring funnel, characterized in that: The pier column comprises a square column body facing the bottom hole and flow columns connected on both sides of the square column body, the height of the square column body is not less than the vertical distance from the bottom of the bottom hole to the riverbed in front of the dam; the top of the square column body is flush with the top of the flow column; the bottom edge of the flow column is higher than the bottom of the square column body, and is used to form a flow hole at the bottom of the flow column, thereby forming a "C"-shaped pier column with a hole in front of the bottom hole; the area enclosed by the outer edges of the two flow columns projected on the dam surface is not less than the size of the bottom hole orifice.

2. A C-shaped pier with holes for increasing the size of the bottom hole scouring funnel according to claim 1, characterized in that: The flow columns are symmetrically arranged on both sides of the square column body, and the angle between the flow columns and the square column body is 90°±45°.

3. A "C"-shaped pier with holes for increasing the size of the bottom hole scouring funnel according to claim 1, characterized in that: The square column body and the flow-around column are both square structures.

4. A "C"-shaped pier with holes for increasing the size of the bottom hole scouring funnel according to claim 3, characterized in that: The width of the flow-facing surface of the square column body is 0.8 to 1.2 times the side length or diameter of the bottom hole; the width of the flow-around column is 0.25 to 0.75 times the side length or diameter of the bottom hole; and the height of the flow-around column is 2.8 to 3.5 times the side length or diameter of the bottom hole.

5. A "C"-shaped pier with holes for increasing the size of the bottom hole scouring funnel according to claim 4, characterized in that: The thickness of the square column body is 0.125 to 0.375 times the side length or diameter of the bottom hole; the thickness of the flow column is 0.125 to 0.250 times the side length or diameter of the bottom hole.

6. A "C"-shaped pier with holes for increasing the size of the bottom hole scouring funnel according to claim 1, characterized in that: The top of the square column body is higher than or flush with the top of the bottom hole opening.

7. A "C"-shaped pier with holes for increasing the size of the bottom hole scouring funnel according to claim 1, characterized in that: A mounting seat is provided at the bottom of the square column body, and a fastening hole for locking the mounting seat is provided on the mounting seat.

8. A "C"-shaped pier with holes for increasing the size of the bottom hole scouring funnel according to claim 1, characterized in that: The square column main body and the flow-around column are an integrally formed structure.

9. A design method for a perforated "C"-shaped pier column with increased bottom hole scouring funnel size, characterized in that: The following steps are involved: A "C"-shaped pier with a hole is installed upstream of the bottom hole. The pier includes a square column body and two flow-around columns. The bottom of the square column body is buried under the mud and the top is flush with the top of the bottom hole. The flow-around columns on both sides are installed on the back water surface of the square column body; The geometric dimensions of the square column body are calculated according to the size of the bottom hole, including the thickness of the square column body is equal to 0.125~0.375 times the side length or diameter of the hole, and the width of the flow surface of the square column body is 0.8~1.2 times the side length or diameter of the hole; The width of the vortex columns on both sides is 0.25~0.75 times the side length or diameter of the orifice, and the thickness is 0.125~0.250 times the side length or diameter of the orifice; the top of the vortex columns on both sides is flush with the top of the square column body, and the height is 2.8~3.5 times the side length or diameter of the orifice; the angle between the vortex columns on both sides and the square column body is 90°±45°; The square column bodies are parallel and placed directly in front of the hole openings. The vertical distance between the square column bodies and the bottom hole is 0.7 to 1.2 times the side length or diameter of the bottom hole. The top height of the pier column is flush with the top of the bottom hole.

10. A method for increasing the size of a bottom hole flushing funnel, characterized in that: The "C"-shaped pier with holes as described in any one of claims 1-8 is installed in front of the bottom hole, the square column bodies are parallel and placed directly in front of the hole opening, the top of the square column body is flush with the top of the bottom hole, the flow column is located on the back water side of the square column body, and the vertical distance between the square column body and the bottom hole opening is greater than the vertical distance from the center of the square column body to the outer edge of the flow column.

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