Device and method for converting flow states of open channel flow and pipeline flow

Abstract

The invention relates to the technical field of water flow conveying between water treatment structures, in particular to a device and method for converting the flow state of open channel flow and the flow state of pipeline flow. The device is arranged at the intersection of the open channel and the vertical pipe. The open channel is located on the upstream of the vertical pipe, and the downstream of the vertical pipe is connected with the transverse pipe. The device comprises a guide rail group and a guide cylinder. The upper part of the guide cylinder is used for blocking water, blocking up the water level in an upstream open channel, stabilizing flow and reducing gas suction at a water flow inlet; a paddle at the lower part of the guide cylinder divides water flow entering the vertical pipe into four parts, so that rotation is eliminated, and gas suction is further prevented. When the water level in the upstream open channel is too high or too low, the guide cylinder moves upwards or downwards along with the guide rail set, and the water level in the open channel is controlled by changing the size of the gap between the guide cylinder and the vertical pipe. The lowest liquid level in an upstream channel can be effectively controlled, spiral flow and gas suction at an inlet of the vertical pipe are prevented, the water conveying capacity is improved, pipeline noise is lowered, and damage to a pipeline system caused by water plug flow in a water conveying pipe is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of water flow transportation between water treatment structures, and in particular to a device and method for converting flow states between open channel flow and pipeline flow. Background Art

[0002] The water flow in the municipal water plant is often accompanied by the flow state conversion between open channel flow and pipeline flow. In the process, the open channel flow changes its flow state to pipeline flow through the inlet of the riser, and the spiral flow at the pipe mouth sucks in a large amount of air. When the liquid level in the open channel is low, the air intake increases accordingly; when the subsequent pipeline is transformed from the riser to the horizontal pipe, the water flow rate slows down, the gas escapes from the water and gathers in the upper part of the pipeline to form air bags and piston flow, resulting in a decrease in the water conveyance capacity of the horizontal pipe; and there are significant impacts, surge sounds, and loud noises at the outlet of the horizontal pipe; especially when the air bag rushes out of the horizontal pipe, it generates high momentum and non-steady-state impact, which has an adverse effect on the flow capacity of the pipeline to transport the fluid and the operation and maintenance of the pipeline.

[0003] Chinese patent CN107803051A discloses an internal flow type gas eliminator, whose structure mainly includes an outer cylinder, a spiral ascending channel, an intermediate cylinder and an inner cylinder, etc., mainly through the gas-containing petroleum between the outer cylinder and the intermediate cylinder, along the spiral ascending channel to form a spiral flow to escape the gas in the water, and the pure liquid phase flows out through the bottom, so as to achieve accurate measurement of the quality of the petroleum. Prior art CN2205850Y is a cyclone noise reducer for a drainage pipe system, whose structure mainly includes a number of guide plates arranged around a specific cross-section of the inner wall of the drainage pipe, and through the formation of a spiral flow to escape the gas in the water, the drainage noise in the indoor drainage riser of the building is eliminated.

[0004] Both of the above-mentioned two existing devices rely on the formation of spiral flow to eliminate air or noise, and have a single function. They are unable to achieve the effect of reducing gas at the source (preventing gas from being inhaled into the water). When applied to municipal water supply scenarios (open channel flow and pipeline flow conversion), when the open channel liquid level is maintained at a low level, the vortex suction effect is intensified, resulting in piston flow and other unfavorable flow states in the subsequent water supply pipes that affect the water supply efficiency and have a destructive effect on the pipeline system. Summary of the invention

[0005] In order to solve the technical problem that the existing technology cannot achieve source gas reduction and is difficult to apply to the municipal water delivery process, the present invention provides a device and method for converting flow states between open channel flow and pipeline flow. The specific technical solution is as follows:

[0006] The present invention provides a device for converting flow states of open channel flow and pipeline flow, which is arranged at the intersection of the open channel and a riser; the open channel is located upstream of the riser, and the downstream of the riser is connected to a cross pipe; the device comprises a guide rail group and a flow guide cylinder, the guide rail group is used on the inner wall of the open channel just above the riser along the axial direction of the riser, the lower part of the flow guide cylinder is located inside the riser and there is a gap between the riser and the riser for water flow to pass through, the outer periphery of the upper part of the flow guide cylinder is provided with a slide bar group slidably matched with the guide rail group, the upper end and the lower end of the flow guide cylinder are sealed, and the outer periphery of the lower part of the flow guide cylinder is provided with a plurality of blades at intervals.

[0007] A further improvement of the present invention is that the guide tube includes an upper cylindrical section and a lower conical section, and the interior of the guide tube is a cavity; a plurality of blades are located on the outer periphery of the conical section. A lid for sealing is provided on the top of the cylindrical section, and a vent valve for sealing is provided at the bottom of the conical section. The lid can be opened and closed for water injection. When the lid and the vent valve are closed, the device is sealed.

[0008] A further improvement of the present invention is that the blade is triangular, and the hypotenuse of the blade is fixed to the conical section. The guide rail group includes multiple guide rails, and the multiple guide rails are arranged at intervals. The number of the slide bar groups is multiple, and the multiple slide bar groups are arranged one-to-one with the multiple guide rails.

[0009] The present invention also provides a method for converting flow states between open channel flow and pipeline flow using the above-mentioned device, comprising the following steps:

[0010] Calculate the lower edge limit height of the guide rail assembly according to the following formula:

[0011]

[0012] Among them, h c is the limit height of the lower edge of the guide rail group, that is, the distance from the lower edge of the guide rail group to the bottom of the open channel, q is the designed water flow rate per unit width of the open channel, g is the gravity acceleration, and α is the flow constant, which is 1. If h is calculated c If it is less than 0.05m, then take h c It is 0.05m.

[0013] According to the lower edge limit height of the guide rail group calculated above, the guide rail group is installed on the inner wall of the open channel directly above the riser along the axial direction of the riser, and the distance between the bottom of the guide rail group and the open channel is fixed to control the minimum flow cross-section when the open channel flows into the riser.

[0014] The water injection quality of the device is calculated according to the following formula:

[0015] M=(h2-h1)·B·L·ρ-M0;

[0016] Where M is the water injection mass, h1 is the rapid water depth corresponding to the design flow rate (at this time, the flow velocity v<α1 / 6 ·q 2 / 3 ), h2 is the slow flow depth corresponding to the design flow rate (at this time, the flow velocity v>α 1 / 6 ·q 2 / 3 ), B is the width of the open channel, L is the length of the open channel, ρ is the water density, and M0 is the mass of the cylindrical section. If M≤0, no water injection is required.

[0017] According to the water injection mass calculated above, if M>0, open the top cover of the guide tube and inject water into the guide tube. After the water injection is completed, close the cover and slide the guide tube onto the guide rail one by one through the slide rod group.

[0018] The low-liquid-level open channel water flow with bubbles flows to the inlet of the riser, encounters the water blocking of the guide tube, the water level in the open channel rises, the bubbles escape from the water surface in front of the guide tube and far away from the inlet of the riser, and the water flows into the riser;

[0019] The water flow entering the riser enters the riser through the gap between the guide tube and the inlet of the riser, and when flowing through the surface of the guide tube, it is divided into multiple sections by multiple blades, and the swirl is destroyed, and the swirl no longer sucks gas into the riser;

[0020] As the water depth in the open channel increases, the buoyancy of the guide tube increases, and the guide tube moves upward along the guide rail. The flow cross section of the open channel flowing into the riser increases, the water flow entering the riser increases, and the water level in the open channel slowly decreases until the guide tube moves down along the guide rail and slides to the bottom plate at the lower edge of the guide rail by the next set of slide rods, and the flow cross section of the open channel flowing into the riser is minimized. This cycle repeats.

[0021] The application of the technical solution of the present invention has the following beneficial effects:

[0022] 1. The present invention limits the limit height of the lower edge of the guide rail and injects a specific mass of water into the guide tube, so that the guide tube can block the water and raise the liquid level when the liquid level in the open channel is low, reduce the water flow rate, and prevent gas from mixing into the water and degassing (gas escaping from the water).

[0023] 2. The present invention provides a slide bar group that can slide up and down in the guide rail. When the liquid level in the open channel rises above a certain height due to the above-mentioned water blocking effect, the guide tube can move vertically upward along the guide rail driven by the slide bar group as the buoyancy changes, thereby realizing adaptive stable liquid level.

[0024] 3. The present invention divides the water flow into several sections at the inlet of the riser (the location where the vortex is generated) by arranging blades, thereby destroying the vortex, preventing the vortex from sucking air into the riser, and reducing the flow rate of water flowing into the riser, thereby achieving inlet de-vortexing to prevent gas from mixing into water and degassing (gas escaping from the water).

[0025] 4. The present invention combines the cylindrical section, conical section, blades, guide rails and slide rod group mentioned above, and each component automatically cooperates with the flow state of the open channel flow, thereby comprehensively realizing the need for no external power, adaptive stabilization of the liquid level, and prevention of gas from entering the pipeline with the water flow, thereby avoiding the occurrence of piston flow in the subsequent water pipe, which affects the water delivery efficiency and has a destructive effect on the pipeline system.

[0026] 5. The present invention can be manufactured using corrosion-resistant materials such as stainless steel, has a simple structure, and basically requires no maintenance or overhaul, thereby reducing the maintenance and management costs of the water plant.

[0027] In addition to the above-described purposes, features and advantages, the present invention has other purposes, features and advantages. The present invention will be further described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0029] Figure 1 It is a perspective view of a flow guide tube provided with triangular blades in Embodiment 1 of the device for converting flow patterns between open channel flow and pipeline flow of the present invention;

[0030] Figure 2 It is a side view of the present invention installed at the intersection of an open channel and a riser.

[0031] Among them, 1. guide tube; 1a. cylindrical section; 1b. conical section; 1c. paddle; 1d. slide rod group; 1e. lifting ring; 1f. cover; 1g. vent valve; 2. guide rail group; 2a. guide rail; 2b. bottom plate; 3. open channel; 4. riser. DETAILED DESCRIPTION

[0032] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0033] See also Figure 1-2 As shown, a device for converting the flow state of open channel flow and pipeline flow. The device is arranged at the intersection of the open channel 3 and the riser 4, and is made of stainless steel. The open channel 3 is located upstream of the riser 4, and the riser 4 is connected to the cross pipe downstream. The device of the present invention includes a guide rail group 2 and a guide tube 1, the guide rail group 2 is used to be installed on the inner wall of the open channel 3 directly above the riser 4 along the axial direction of the riser 4, the guide tube is located inside the riser 4 and there is a gap between the guide tube and the riser 4 for water to flow through, the outer periphery of the cylindrical section 1a of the guide tube is provided with a slide rod group 1d that is slidably matched with the guide rail group 2, the upper end and the lower end of the guide tube are sealed, and the outer periphery of the lower part of the guide tube is provided with a plurality of blades 1c at intervals.

[0034] The present invention limits the limit height of the lower edge of the guide rail and injects a specific mass of water into the guide tube, so that the guide tube 1 can block water and raise the liquid level when the liquid level in the open channel is low, reduce the water flow rate, and prevent gas from mixing into the water and being deflated (gas in the water escaping); by arranging a slide bar group 1d that can slide up and down in the guide rail group 2, when the liquid level in the open channel rises above a certain height due to the above-mentioned water blocking effect, the guide tube 1 can change with the buoyancy it receives and move vertically upward along the direction of the guide rail under the drive of the slide bar group 1d, thereby realizing adaptive stable liquid level and effectively eliminating the adverse factor of strong air suction into the pipeline due to the low liquid level.

[0035] At the same time, the present invention divides the water flow into several sections at the entrance of the riser 4 (the position where the vortex is generated) by setting the blade 1c, destroying the vortex, preventing the vortex from sucking air into the riser, and reducing the flow rate of water flowing into the riser, achieving inlet de-vortexing to prevent gas from mixing into the water and degassing (gas escaping from the water). By combining the above-mentioned cylindrical section 1a, conical section 1b, blade 1c, guide rail group 2 and slide rod group 1d, the various components of the present invention automatically work in coordination with the flow state of the open channel flow, and comprehensively realize the need for no external power, adaptive stabilization of the liquid level, and prevention of gas from entering the pipeline with the water flow, avoiding the occurrence of piston flow in the subsequent water pipe, which affects the water delivery efficiency and has a destructive effect on the pipeline system, and ensuring the smooth flow of water in the subsequent pipeline, providing a solid guarantee for the long-term and stable operation of the pipeline.

[0036] Preferably, Figure 1 As shown, the guide tube includes an upper cylindrical section 1a and a lower conical section 1b, and a plurality of blades 1c are located on the outer periphery of the conical section 1b. Specifically, the total height of the guide tube is 1.5 to 2.5 times the diameter of the riser 4, the height of the upper cylindrical section 1a is 0.8 to 1 times the diameter of the riser 4, and the height of the lower conical section 1b is 0.5 to 1.7 times the diameter of the riser 4; the diameter of the upper cylindrical section 1a is consistent with the bottom diameter of the lower conical section 1b, which is 0.8 to 1.5 times the diameter of the riser 4. The slide rod group 1d is located at the lower part of the cylindrical section 1a.

[0037] Preferably, a cover 1f for sealing is provided at the top of the cylindrical section 1a, and a drain valve 1g for sealing is provided at the bottom of the conical section 1b, so as to facilitate draining the water in the guide tube during maintenance. When the amount of water transported between structures changes dramatically, clean water can be injected through the cover 1f on the top of the device to increase gravity. When the amount of water decreases, part or all of the clean water in the device can be drained through the drain valve 1g at the bottom to reduce gravity. When the cover 1f and the drain valve 1g are closed, the device is sealed.

[0038] Embodiment 1, as Figure 1As shown, the blade 1c is triangular in shape, and the hypotenuse of the blade 1c is fixed to the conical section 1b. In this embodiment, four blades 1c are symmetrically arranged along the axis of the surface of the conical section 1b. Each blade 1c can be in a vertical form, and the maximum outer diameter of the blade 1c is 0.9 to 0.95 times the diameter of the riser 4. The cylindrical section 1a at the upper part of the guide tube is used to block water and increase the water level in the upstream open channel 3 to further eliminate gas; the blade 1c at the lower part of the guide tube divides the water flow entering the riser 4 into four parts, thereby eliminating gas. When the water level in the upstream open channel 3 is too high or too low, the device moves up or down with the guide rail group 2, and controls the water level in the open channel 3 by changing the size of the gap between it and the riser 4.

[0039] Preferably, the guide rail group 2 includes a plurality of guide rails 2a, the plurality of guide rails 2a are arranged at intervals, the number of the slide bar groups 1d is a plurality of groups, and the plurality of slide bar groups 1d are arranged in a one-to-one correspondence with the plurality of guide rails 2a. Figure 2 As shown, the guide rail 2a is installed at the position of the channel wall around the entrance of the riser 4, wherein, as Figure 1 As shown, the bottom of the guide rail 2a is sealed by the bottom plate 2b, which is made of steel. Two sides of the guide rail 2a are sealed to fix the guide tube in the horizontal direction to prevent the guide tube from rotating. The intersection of the other two sides leaves a gap for the slide bar group 1d to slide up and down. The size of the gap is 1.5 to 3 times the diameter of the slide bar group 1d. The diameter of the slide bar group 1d is 5mm to 50mm, and it moves up and down with the guide tube under the action of buoyancy. The bottom plate 2b of the guide rail 2a is 0.05 to 0.2m away from the bottom of the channel. The height of the guide rail 2a is 0.7 to 0.9 times the height of the open channel 3, and the top is 0.3 to 0.5m lower than the top of the channel.

[0040] Preferably, Figure 1 and Figure 2 As shown, the upper end of the guide tube is sealed by closing the cover 1f, and a lifting ring 1e is provided at the top of the cylindrical section 1a and around the cover 1f. By opening the cover 1f, water can be poured into the guide tube 1 from the top of the cylindrical section 1a to appropriately increase the gravity of the device. The lifting ring 1e is used for fixing the hook when the device is lifted out for maintenance.

[0041] like Figure 2 As shown, the present invention also provides a method using the above device for converting flow states between open channel flow and pipeline flow, comprising the following steps:

[0042] Calculate the lower edge limit height of guide rail set 2 according to the following formula:

[0043]

[0044] Among them, h c is the limit height of the lower edge of the guide rail group 2, that is, the distance from the lower edge of the guide rail group 2 to the bottom of the open channel 3, h kis the water depth of the open channel 3 flow falling into the riser 4, q is the water flow rate per single width, g is the gravity acceleration, and α is the flow constant, which is taken as 1. If h c If it is less than 0.05m, then take h c It is 0.05m.

[0045] According to the lower edge limit height of the guide rail group 2 calculated above, the guide rail group 2 is installed on the inner wall of the open channel 3 just above the riser 4 along the axial direction of the riser, and the distance between the bottom of the guide rail and the open channel 3 is fixed to control the minimum flow cross-section when the open channel 3 flows into the riser 4.

[0046] The water injection quality of the device is calculated according to the following formula:

[0047] M=(h2-h1)·B·L·ρ-M0;

[0048] Where M is the water injection mass, h1 is the rapid water depth corresponding to the design flow rate (at this time, the flow velocity v<α 1 / 6 ·q 2 / 3 ), h2 is the slow flow depth corresponding to the design flow rate (at this time, the flow velocity v>α 1 / 6 ·q 2 / 3 ), B is the width of the open channel, L is the length of the open channel, ρ is the water density, and M0 is the mass of the cylindrical segment 1a. If M≤0, no water injection is required.

[0049] According to the water injection mass calculated above, if M>0, open the top cover 1f of the guide tube 1 and inject water into the guide tube 1. After the water injection is completed, close the cover 1f and slide the guide tube 1 onto the guide rail 2a through the slide rod group 1d in a one-to-one correspondence.

[0050] The low-liquid-level open channel water flow with bubbles flows to the inlet of the riser 4, encounters the water blocking of the guide tube 1, and the water level in the open channel rises. The bubbles escape from the water surface in front of the guide tube 1 and far away from the inlet of the riser 4, and the water flows into the riser 4.

[0051] The water flow entering the riser 4 enters the riser 4 through the gap between the guide tube 1 and the inlet of the riser 4. When flowing through the surface of the guide tube 1, it is divided into multiple sections by multiple blades 1c, and the swirl is destroyed, and the swirl no longer sucks gas into the riser.

[0052] As the water depth in the open channel 3 increases, the buoyancy of the guide tube 1 increases, and the guide tube 1 moves upward along the guide rail 2a. The flow cross section of the open channel flowing into the riser 4 increases, and the water flow entering the riser 4 increases. The water level in the open channel 3 slowly decreases until the guide tube 1 moves down along the guide rail 2a and slides to the bottom plate 2b of the guide rail 2a by the next set of slide rods 1d, and the flow cross section of the open channel flowing into the riser 4 is minimized. This process repeats.

[0053] During operation, the low-liquid-level open channel water flow with air bubbles flows to the inlet of the riser 4, encounters the water blocking of the guide tube 1, and the water level in the open channel rises, so that: (1) the air bubbles entrained in the open channel flow escape from the water surface in front of the guide tube 1 and away from the inlet of the riser 4; (2) the suction enhancement effect caused by the low liquid level when the water flows into the riser 4 is eliminated; at the same time, the water flows into the riser 4 through the gap between the guide tube 1 and the inlet of the riser 4, and the vortex that should have been formed is divided into multiple sections by the multiple blades 1c, the vortex is destroyed, and the vortex suction effect is eliminated. Therefore, no gas is sucked into the riser 4 with the vortex.

[0054] During the operation, the water depth in the open channel 3 increases continuously from the initial low liquid level state, the buoyancy of the guide tube 1 increases, the guide tube 1 moves upward along the guide rail 2a, the flow cross section of the open channel flowing into the riser 4 increases, the water flow entering the riser 4 increases, and the water level in the open channel 3 slowly decreases until the guide tube 1 moves down along the guide rail 2a and slides to the guide rail bottom plate 2b by the next set of slide rods, and the flow cross section of the open channel flowing into the riser 4 is minimized. This cycle repeats.

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A device for converting flow patterns between open channel flow and pipeline flow, arranged at the intersection of an open channel (3) and a riser (4); the open channel (3) is located upstream of the riser (4), and the riser (3) is connected to a cross pipe downstream; characterized in that: The liquid level stabilizing and anti-racemic gas inhalation device comprises a guide rail group (2) and a guide tube (1), wherein the guide rail group (2) is used to be installed on the inner wall of an open channel (3) directly above the standpipe (4) along the axial direction of the standpipe (4), the lower part of the guide tube is located inside the standpipe (4) and there is a gap between the guide tube and the standpipe (4) for water to flow through, the outer periphery of the guide tube is provided with a slide bar group (1d) that is slidably matched with the guide rail group (2), the upper end and the lower end of the guide tube are sealed, and the outer periphery of the lower part of the guide tube is provided with a plurality of blades (1c) at intervals.

2. The device for converting flow states between open channel flow and pipeline flow according to claim 1, characterized in that: The guide tube comprises an upper cylindrical section (1a) and a lower conical section (1b); the interior of the guide tube is a cavity, and a plurality of blades (1c) are located on the outer periphery of the conical section (1b).

3. The device for converting flow states between open channel flow and pipeline flow according to claim 2, characterized in that: The top of the cylindrical section (1a) is provided with a cover (1f) for sealing, and the bottom end of the conical section (1b) is provided with a vent valve (1g) for sealing.

4. The device for converting flow states between open channel flow and pipeline flow according to claim 2, characterized in that: The blade (1c) is triangular in shape, and the hypotenuse of the blade (1c) is fixed to the conical section (1b).

5. The device for converting flow states between open channel flow and pipeline flow according to claim 1, characterized in that: The guide rail group (2) comprises a plurality of guide rails (2a), the plurality of guide rails (2a) are arranged at intervals, the number of the slide bar groups (1d) is a plurality of groups, and the plurality of slide bar groups (1d) are arranged in a one-to-one correspondence with the plurality of guide rails (2a).

6. A method for converting flow regimes using the device for converting flow regimes between open channel flow and pipeline flow as claimed in claim 3, characterized in that: The steps include: Calculate the lower edge limit height of the guide rail assembly (2) according to the following formula: Among them, h c is the limit height of the lower edge of the guide rail group (2), that is, the distance between the lower edge of the guide rail group (2) and the bottom of the open channel (3); q is the designed water flow rate per unit width of the open channel (3); g is the gravity acceleration; α is the flow constant, which is 1; if h is calculated c If it is less than 0.05m, then take h c 0.05m; According to the above calculated lower edge limit height of the guide rail assembly (2), the guide rail assembly (2) is installed on the inner wall of the open channel (3) directly above the riser (4) along the axial direction of the riser (4), and the distance between the bottom of the guide rail assembly (2) and the open channel (3) is fixed to control the minimum flow cross section when the open channel (3) flows into the riser (4); The water injection quality of the device is calculated according to the following formula: M=(h2-h1)·B·L·ρ-M0; Where M is the water injection mass; h1 is the rapid water depth corresponding to the design flow rate (at this time, the flow velocity v<α 1 / 6 ·q 2 / 3 ), h2 is the slow flow depth corresponding to the design flow rate (at this time, the flow velocity v>α 1 / 6 ·q 2 / 3 ); B is the width of the open channel; L is the length of the open channel; ρ is the water density; M0 is the mass of the cylindrical section (1a); if M≤0, no water injection is required; According to the water injection mass calculated above, if M>0, open the top cover (1f) of the guide tube (1) and inject water into the guide tube (1). After the water injection is completed, close the cover (1f) and slide the guide tube (1) onto the guide rail (2a) in a one-to-one correspondence through the slide rod group (1d); The low-liquid-level open channel water flow carrying air bubbles flows to the inlet of the riser (4), encounters the water blocking of the guide tube (1), the water level in the open channel rises, the air bubbles escape from the water surface in front of the guide tube (1) and away from the inlet of the riser (4), and the water flow enters the riser (4); The water flow entering the riser (4) enters the riser (4) through the gap between the guide tube (1) and the entrance of the riser (4), and when flowing through the surface of the guide tube (1), it is divided into a plurality of sections by a plurality of blades (1c), and the swirl flow is destroyed, so that the swirl flow no longer sucks gas into the riser (4); As the water depth in the open channel (3) increases, the buoyancy of the guide tube (1) increases, and the guide tube (1) moves upward along the guide rail (2a). The flow cross section when the open channel flows into the riser (4) increases, and the water flow entering the riser (4) increases. The water level in the open channel slowly decreases until the guide tube (1) moves downward along the guide rail (2a) and slides to the bottom plate (2b) at the lower edge of the guide rail (2a) by the next set of slide rods (1d). The flow cross section when the open channel flows into the riser (4) is reduced to a minimum, and this cycle repeats.

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