A fish gathering system based on fish weir

Abstract

The application discloses a fish collecting system based on a fish weir, wherein a tail water channel is divided into a thin-wall weir water channel and a fish collecting water channel; on one hand, the thin-wall weir has a certain height, which prevents fish from swimming into the thin-wall weir water channel from the thin-wall weir, so that the fish swim into the fish collecting tank in the fish collecting water channel only; on the other hand, the application designs a suitable height of the thin-wall weir, so that the water flow speed flowing out of the fish collecting tank is not greater than the swimming ability of the fish, so that most of the fish can swim into the fish collecting tank without any obstacle. The simple structure of the application is suitable for developing water conservancy and generating electricity in a river with small runoff, and the cost investment is low, and a complicated fish collecting and attracting system does not need to be redesigned.

Description

Technical Field

[0001] This invention relates to the fields of water conservancy engineering and environmental protection engineering, specifically to a fish collection system based on a fish weir. Background Technology

[0002] Hydropower stations disrupt fish migration along rivers, affecting their migratory behavior and gene flow. Therefore, hydropower stations often incorporate fish collection and transport systems and fish lifts to manually transfer fish upstream and downstream of the dam, promoting fish population exchange and maintaining aquatic ecological balance. Both fish collection and transport systems and fish lifts include fish-attracting devices, which are crucial components determining the overall effectiveness of the system. Only when the fish-attracting devices capture a sufficient number of fish can the lifting and transport systems function effectively. Various methods of attracting fish exist, such as light, food, and water flow conditions. In engineering projects, fish-attracting devices typically use water flow to lure fish in, such as... Figure 5 Fish attracting devices are often placed in the tailrace channel of hydropower stations. The tailrace channel of micro hydropower stations is narrowed, and the outlet of the fish attracting device 5 is constructed as a funnel-shaped fish inlet. The fish inlet is the same width as the tailrace channel. The tailwater from the power generation in the tailrace channel forms a fish attracting water flow in the fish attracting device 5 and near the fish inlet, which induces fish to swim into the fish attracting device 5 along the fish inlet.

[0003] Due to the large flow rate, some micro hydropower stations have a high tailrace water level after the tailrace channel is narrowed, resulting in a high head difference between the upstream and downstream of the tailrace channel. This causes the water flow to be too fast, preventing fish from swimming into the fish attraction device. Summary of the Invention

[0004] This invention addresses the problem that in current micro-hydropower tailrace discharge channels, the flow velocity in fish collection systems and other discharge channels often exceeds the swimming capacity of fish, and fish tend to swim into channels with higher flow velocities. When the flow velocity in other discharge channels exceeds that of the fish collection system, fish cannot be induced into the fish collection channel. This invention provides a fish collection system based on a fish weir.

[0005] The technical solution of this invention is: a fish collection system based on a fish weir, including a tailrace channel of a hydroelectric power station, wherein a diversion retaining wall is installed in the tailrace channel to divide the tailrace channel into sections with widths B respectively along the water flow direction. J and B Y Fish collection channels and thin-walled weir channels are constructed. In the thin-walled weir channel, a thin-walled weir is set up perpendicular to the direction of water flow to prevent fish from swimming back against the current. Fish collection boxes are arranged in the fish collection channel along the direction of water flow.

[0006] The height of the thin-walled weir is designed according to the following steps:

[0007] Step 1: First, assume the weir height a = H0, where H0 is the upstream water level of the tailrace channel, i.e., assume the head of water above the thin-walled weir is H. YThe flow rate is 0, the thin-walled weir channel is completely blocked, and water flows downstream only from the fish collection channel. The flow rate Q of the tailrace channel is equal to the flow rate Q of the fish collection channel. J Fish collection channel flow rate Q J Calculated using the broad-crested weir flow rate formula:

[0008]

[0009] The value of m is obtained by consulting the flow coefficient table of the broad-crested weir with an inclined upstream face or the flow coefficient table of the broad-crested weir without a sill. The upstream head H of the fish collection channel is calculated according to equation (1). J Based on the assumed upstream water head H of the fish-collecting canal J Given a height *a* equal to that of the thin-walled weir, obtain the value of H0 and calculate the flow velocity V in the fish-collecting channel. J =Q J / (B J *H J );

[0010] Step 2, if V J If the speed exceeds the swimming speed of fish, then the value of the thin-walled weir height 'a' should be reduced, and the head H above the thin-walled weir should be increased. Y =H0-a;

[0011] Based on the flow rate Q of the thin-walled weir canal Y Calculation formula for the flow velocity V in a thin-walled weir channel. Y =Q Y / (H Y *B Y ):

[0012]

[0013]

[0014] Q Y Where m is the flow rate, m0 is the flow coefficient, and H is the flow rate. Y For the water head above the weir;

[0015] Fish collection channel flow rate Q J =QQ Y Then calculate H according to equation (1) J Calculate the flow velocity V in the fish collection channel. J =Q J / (B J *H J );

[0016] Step 3, compare Qρ(H) according to the principle of energy conservation. Y +a)+QρV 2 / 2g and Q Y (H Y +a)+Q Y VY 2 / 2g+Q J H J +Q J V J 2 If the difference of / 2g is positive and lower than the empirical value, it conforms to the law of conservation of energy.

[0017] Step 4, if the flow velocity V of the fish collection channel J If the flow rate exceeds the swimming speed of the fish, reduce the value of the thin-walled weir height 'a' and repeat steps 2-3 until the flow velocity V in the fish collection channel is reached. J The upper limit of the height of a thin-walled weir is obtained by considering that the speed is less than the swimming speed of fish and conforms to the law of conservation of energy.

[0018] Step 5: Continue to reduce the height of the thin-walled weir, repeating steps 2-3 until the flow velocity V in the fish collection channel is reached. J The speed is less than the swimming speed of fish, conforms to the law of conservation of energy, and the water head H upstream of the fish collection channel is... J By approximating the lower limit of the designed fish collection channel water level, the lower limit of the thin-walled weir height can be obtained.

[0019] If the height of the thin-walled weir obtained in step 5 is lower than the lower limit value, then the lower limit value shall be used as the lower limit value of the thin-walled weir height.

[0020] Furthermore, the fish collection channel is equipped with a submerged fish collection box, a secondary fish inlet gate and a primary fish inlet gate, fixed piers on both sides and a fixed base at the bottom. Both the primary and secondary fish inlets are designed with a V-shaped mesh structure that allows water flow. The fish collection box outlet is designed with an inverted funnel opening. The upper part of the fish collection box is a water-permeable mesh structure, and the lower part is a water-impermeable box body. The water-impermeable box body is embedded in the bottom plate of the fish collection channel. The two sides of the fish collection box body are fixed to the foundation structure wall by support rods, allowing water flow to pass through. m = 0.385.

[0021] Furthermore, the tailrace flow rate Q = 31.4 m³ / s. 3 / s, B J =4m and B Y =16m, a =1.36~1.38m.

[0022] The beneficial effects of this invention are:

[0023] According to the present invention, a fish collection system based on a fish weir is provided. After the tailrace channel is divided into a thin-walled weir channel and a fish collection channel, on the one hand, the thin-walled weir has a certain height, preventing fish from swimming into the thin-walled weir channel; therefore, the fish only swim into the fish collection box in the fish collection channel. On the other hand, the present invention, by designing a suitable thin-walled weir height, ensures that the flow velocity of the water flowing out of the fish collection box does not exceed the swimming ability of the fish, allowing most fish to swim in without obstacles. The simple structure of the present invention is suitable for hydropower development in rivers with small runoff, has low construction costs, and does not require the redesign of a complex fish collection and attraction system. Attached Figure Description

[0024] Figure 1 This is a schematic diagram showing the plan layout of the thin-walled weir channel and fish collection channel within the tailrace channel;

[0025] Figure 2 This is a schematic diagram of the vertical cross-section of the thin-walled weir channel within the tailrace channel;

[0026] Figure 3 This is a schematic diagram of the vertical cross-section of the fish collection channel within the tailrace channel;

[0027] Figure 4 This is a schematic diagram of the plan structure of the fish collection box inside the fish collection channel;

[0028] Figure 5 This is a schematic diagram of the fish collection tank installation. Detailed Implementation

[0029] To enable those skilled in the art to better understand the technical solutions of the present invention, preferred embodiments of the present invention are described below in conjunction with specific examples. However, it should be understood that the accompanying drawings are for illustrative purposes only and should not be construed as limiting the present invention. For better illustration of this embodiment, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable that some well-known structures and their descriptions may be omitted in the drawings for those skilled in the art. The positional relationships described in the drawings are for illustrative purposes only and should not be construed as limiting the present invention.

[0030] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present invention.

[0031] like Figures 1-3 A diversion wall is installed in the tailrace channel 4 to divide the tailrace channel into a fish collection channel 1 and a thin-walled weir channel 3, with widths of B respectively. J and B Y A thin-walled weir 2 is installed in the thin-walled weir channel 3 to prevent fish from migrating upstream. Figures 4-5 Fish collection boxes 5 are placed in the fish collection channel 1 to collect the fish that swim in.

[0032] Along the water flow direction, the fish collection channel consists of a submerged fish collection box 5, a secondary fish inlet gate and a primary fish inlet gate 6, two side fixed supports 7, and a bottom fixed base. Both the primary and secondary fish inlet gates 6 are designed with a V-shaped mesh structure in the horizontal direction, gradually narrowing. The secondary fish inlet gate is also narrowed in the vertical direction. Behind the secondary fish inlet gate is the fish collection box 5 with an inverted funnel-shaped opening to collect fish and prevent them from escaping. The upper part of the fish collection box 5 is a mesh structure, and the lower part is a waterproof box body, which is embedded in the bottom plate of the fish collection channel 1. The box body is also equipped with a fish release gate and an escape-proof mesh opening. After fish swim upstream through the escape-proof opening into the fish collection box, if the flow velocity in the upper mesh box is too high, the fish can rest in the lower part embedded in the ground to avoid the continuous impact of the excessively high flow velocity. During the lifting process of the fish collection box, water overflows through the mesh in the upper part, while the fish concentrate in the solid wall structure in the lower part, which also reduces the weight of the fish and water during the lifting process.

[0033] The fish collection channel 1 maintains a 5m wide water passage in the middle. Both the primary and secondary fish passage gates 6 are permeable grates. The primary fish passage gate is an inverted V-shaped mesh gate, 4.5m high, consistent with the height of the overflow weir. The secondary fish passage gate is an inverted V-shaped gate in the horizontal direction, narrowing downwards to 1.5m and horizontally to 1m. To facilitate lifting, the width of the fish collection tank 5 can be reduced to 1m, but structural stability must be ensured. The two sides of the tank must be firmly fixed to the foundation wall using support rods 7. The support rods 7 structure cannot be a solid wall to maintain the 5m wide water passage cross-section.

[0034] The flow velocity V of the fish-collecting channel J It should not exceed the swimming speed of fish, i.e., V. J <1m / s.

[0035] According to the basic formula for weir flow, when the weir is a rectangular thin-walled weir 2, the flow rate Q of the thin-walled weir channel 3 is... Y According to the calculation of thin-walled weirs, the weir flow formula is Equation (2);

[0036] The flow rate Q of fish collection channel 1 J Based on the calculation of the broad-crested weir, in this embodiment, the fish collection box 5, the secondary fish inlet gate and the primary fish inlet gate 6, and the fixed piers on both sides 7 in the fish collection channel are all permeable structures. Therefore, the fish collection channel is equivalent to the case of free outflow of the broad-crested weir without lateral contraction. The weir flow formula is Equation (1), m = 0.385.

[0037] The total discharge flow of the hydroelectric generator unit is Q = 31.4 m³. 3 / s, B J =4m and B Y =16m. These three quantities are known.

[0038] Step 1: First, assume the weir height a >= H0, where H0 is the upstream water level of the tailrace channel, i.e., assume the head H above the thin-walled weir. Y =<0, the thin-walled weir is completely blocked, and water flows downstream only from the fish collection channel. Q = 31.4m 3 / s=Q J Fish collection channel flow rate Q J Calculation formula:

[0039]

[0040] Q J B is the flow rate of the fish collection channel. J The width of the fish collection system is given, and the value of m for the broad-crested weir varies between 0.32 and 0.385. The value of m is obtained from the flow coefficient tables of sloping broad-crested weirs on the upstream face or broad-crested weirs without sills. Since the fish collection box has a mesh structure and does not obstruct water flow, the width of the fish collection channel is not reduced. When When the weir height a* of the broad-crested weir is 0 and B / B0* = 1 (representing free outflow and no lateral contraction of the broad-crested weir), the value of m is 0.385, which is the maximum value of m for the broad-crested weir.

[0041] H is calculated according to equation (1) J Upstream head H of the fish-collecting canal J Equal height H with thin-walled weir J =H0=2.385m. The flow velocity V in the fish-collecting channel at this time is... J =Q J / (B J *H J The flow rate is 2.633 m / s, which exceeds the swimming speed of fish. Therefore, it is necessary to reduce the height 'a' of the thin-walled weir and divert the flow through the thin-walled weir channel to reduce the flow rate and velocity of the fish collection channel.

[0042] Step 2, assuming the thin-walled weir height drop is a = 1.8m, and the head of water above the thin-walled weir is H Y =H0-a=0.485m,

[0043] Thin-walled weir canal flow rate Q Y Calculation formula:

[0044]

[0045]

[0046] Q Y Where m is the flow rate, m0 is the flow coefficient, and B is the flow rate. Y For the width of the weir, H Y Let 'a' be the head above the weir and 'a' be the height of the thin-walled weir. Calculate the flow velocity V in the channel above the thin-walled weir. Y =Q Y / (HY *B Y = 1.433 m / s.

[0047] Fish collection channel flow rate Q J =QQ Y =18.83m 3 / s, calculate H according to equation (1) J =1.695m, calculate the flow velocity V of the fish collection channel. J =Q J / (B J *H J =2.22 m / s, which exceeds the swimming speed of fish.

[0048] Calculate the total flow velocity in the tailrace channel V = Q / [(H Y B Y +(H Y +a)B J = 1.82 m / s.

[0049] Compared to the initial assumption, the fish-gathering channel is diverted due to the flow rate being split, so the upstream head H... J The flow rate decreases, the flow velocity decreases, and the flow rate and volume increase in thin-walled weirs and canals.

[0050] Step 3: Verify the energy conservation principle according to equation (4).

[0051] Qρ(H Y +a)+QρV 2 / 2g=80.182;

[0052] Q Y (H Y +a)+Q Y V Y 2 / 2g+ Q J H J +Q J V J 2 / 2g=77.842 Equation (4)

[0053] The difference between 77.842 and 80.182 is due to drag loss. The drag loss is not greater than the threshold and the change is within the allowable range, which is in line with the law of conservation of energy.

[0054] Step 4: Reduce the height of the thin-walled weir, and repeat steps 2 and 3 until the flow velocity V in the fish collection channel is reached. J The upper limit of the height of a thin-walled weir is obtained by considering that the speed is less than the swimming speed of fish and that the law of conservation of energy applies.

[0055] If the weir height obtained in step 5 is lower than the lower limit, then the lower limit is used as the lower limit value for the thin-walled weir height. This is used to prevent the weir height from being less than the downstream water level.

[0056] Step 5: Continue to reduce the height of the thin-walled weir, repeating steps 2 and 3 until the flow velocity V in the fish collection channel is reached. J The speed is less than the swimming speed of fish, conforms to the law of conservation of energy, and the water head H upstream of the fish collection channel is... J The lower limit of the thin-walled weir height is obtained by converging to the lower limit of the designed fish collection channel water level.

[0057] The iterative process in this embodiment is shown in Table 1, until the height a of the thin-walled weir is reduced to 1.38m, and the flow velocity V in the fish collection channel... J =0.946m / s, and if we continue to lower a to 1.36 meters, the water head upstream of the fish collection channel will decrease to 0.141m, which is greater than the lower limit water level of the fish collection channel of 1.4 meters, and the difference is within 0.1 meters. If the weir height is further reduced, the water level passing through the fish collection channel may be too low, which is not suitable for attracting fish.

[0058] Therefore, the height of the thin-walled weir is designed to be 1.36–1.38 m.

[0059] Table 1

[0060]

[0061] By changing the width of the fish collection channel and the width of the thin-walled weir channel in this embodiment, a more ideal design height for the thin-walled weir can be obtained, which can meet the flow velocity and water level requirements of the fish collection channel, and can also prevent fish from migrating back through the thin-walled weir, so that the fish only swim towards the fish collection channel.

Claims

1. A fish collection system based on a fish weir, comprising a tailrace channel of a hydroelectric power station, wherein a diversion retaining wall is installed in the tailrace channel to divide the tailrace channel into sections of width B along the water flow direction. J and B Y Fish collection channels and thin-walled weir channels are constructed. In the thin-walled weir channel, a thin-walled weir is set up perpendicular to the direction of water flow to prevent fish from swimming back against the current. Fish collection boxes are arranged in the fish collection channel along the direction of water flow. Its features are, The height of the thin-walled weir is designed according to the following steps: Step 1, first assume the height of the thin-walled weir is a = H0 H0 is the water level upstream of the tailrace channel, i.e., the head of water above the thin-walled weir. HY The flow rate is 0, the thin-walled weir channel is completely blocked, and water flows downstream only from the fish collection channel. The flow rate Q of the tailrace channel is equal to the flow rate Q of the fish collection channel. J Fish collection channel flow rate Q J Calculated using the broad-crested weir flow rate formula: （1） The value of m is obtained by consulting the flow coefficient table of the broad-crested weir with an inclined upstream face or the flow coefficient table of the broad-crested weir without a sill. The upstream head H of the fish collection channel is calculated according to equation (1). J Based on the assumed upstream water head H of the fish-collecting canal J Given a height *a* equal to that of the thin-walled weir, obtain the value of H0 and calculate the flow velocity V in the fish-collecting channel. J =Q J / (B J *H J ); Step 2, if V J If the speed exceeds the swimming speed of fish, then the value of the thin-walled weir height 'a' should be reduced, and the head H above the thin-walled weir should be increased. Y =H0-a; Based on the flow rate Q of the thin-walled weir canal Y Calculation formula for the flow velocity V in a thin-walled weir channel. Y =Q Y / (H Y *B Y ): （2） （3） For overcurrent flow, For flow coefficient, HY For the water head above the weir; Fish collection channel flow rate Q J =QQ Y Then calculate H according to equation (1) J Calculate the flow velocity V in the fish collection channel. J =Q J / (B J *H J ); Step 3, compare Q(H) according to the principle of energy conservation. Y +a)+ QV 2 / 2g and Q Y (H Y +a)+Q Y V Y 2 / 2g+ Q J H J +Q J V J 2 If the difference of / 2g is positive and lower than the empirical value, it conforms to the law of conservation of energy. Step 4, if the flow velocity V of the fish collection channel J If the flow rate exceeds the swimming speed of the fish, reduce the value of the thin-walled weir height 'a' and repeat steps 2-3 until the flow velocity V in the fish collection channel is reached. J The upper limit of the height of a thin-walled weir is obtained by considering that the speed is less than the swimming speed of fish and conforms to the law of conservation of energy. Step 5: Continue to reduce the height of the thin-walled weir, repeating steps 2 and 3 until the flow velocity V in the fish collection channel is reached. J The speed is less than the swimming speed of fish, conforms to the law of conservation of energy, and the water head H upstream of the fish collection channel is... J By approximating the lower limit of the designed fish collection channel water level, the lower limit of the thin-walled weir height can be obtained.

2. The fish collection system based on a fish-blocking weir according to claim 1, characterized in that, If the height of the thin-walled weir obtained in step 5 is lower than the lower limit value, then the lower limit value shall be used as the lower limit value of the thin-walled weir height.

3. A fish collection system based on a fish-blocking weir according to claim 1, characterized in that, The fish collection channel is equipped with a submerged fish collection box, a secondary fish inlet gate and a primary fish inlet gate, fixed piers on both sides and a fixed base at the bottom. Both the primary and secondary fish inlets are designed with a V-shaped mesh structure that allows water flow. The fish collection box outlet is designed with an inverted funnel opening. The upper part of the fish collection box is a water-permeable mesh structure, and the lower part is a water-impermeable box body. The water-impermeable box body is embedded in the bottom plate of the fish collection channel. The two sides of the fish collection box body are fixed to the foundation structure wall by fixed piers, allowing water flow to pass through. m=0.385.

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