Sewage flow limiting well with automatic silt removal at corner of sewage pipe network and automatic silt removal method thereof

Abstract

The present invention discloses a sewage flow limiting well for automatic silting at the corners of a sewage pipe network and an automatic silting method thereof. The sewage flow limiting well includes a well body and a sewage inlet pipe, a sewage outlet pipe and an overflow pipe connected thereto; a silting module, a flow limiting module and an overflow module are arranged in the well body; the silting module is used to transport sediment brought in from upstream to the downstream to prevent siltation in the well body; the flow limiting module is arranged in the sewage outlet pipe to intercept sewage and initial rainwater in the dry season to prevent water volume shock to the sewage treatment plant caused by excessive rainwater entering the sewage pipe network in the rainy season; the overflow module is arranged in the overflow pipe to discharge surface water with less pollution in the rainy season. This method utilizes the lateral circulation generated at the corners of the sewage pipe network and simultaneously installs a swirl flow limiting valve to transform the inspection well at the corner of the sewage pipe network. The present invention solves the problems of sediment accumulation in traditional sewage pipe networks and the large water inflow to sewage treatment plants in the rainy season.

Description

Technical Field

[0001] The invention relates to a sewage flow limiting well for automatic silting at a corner of a sewage pipe network and an automatic silting method thereof, belonging to the technical field of sewage pipe networks. Background Art

[0002] As a vital urban infrastructure, drainage systems have always played a vital role in collecting and transporting rainwater, urban sewage, and industrial wastewater. They also shoulder crucial responsibilities such as preventing and controlling water pollution and flood control. The proper functioning of drainage systems is directly linked to a city's economic development, ecological environment, and the well-being of its people. Over the long term, various problems have emerged within sewage pipe networks due to inadequate design and poor operational management. These problems primarily manifest in the precipitation and accumulation of suspended solids (SS) within drainage pipes. This is particularly true at corners, where the flow balance in straight pipes is disrupted, leading to intense mixing and significant energy loss. This in turn significantly impedes the transport of solids within the pipes, leading to further siltation. As one of the major drainage pipe problems, siltation significantly impacts the proper functioning of urban drainage systems. Surveys show that sedimentation is present in most drainage pipes. This sedimentation not only impairs the flow of sewage, but also contributes to microbial activity, which is believed to be a major cause of corrosion, odor, and greenhouse gas emissions. Before the rainy season arrives, sedimentation depths in some urban sewage pipes can reach 50%. During this sedimentation process, large amounts of domestic pollutants undergo anaerobic hydrolysis or microaerobic reactions, resulting in low influent concentrations in sewage treatment plants. Therefore, the sedimentation and attenuation of pollutants in pipe networks is also a major factor contributing to insufficient carbon sources in sewage treatment plant influents.

[0003] To prevent siltation in drainage pipes and avoid disrupting normal drainage during the rainy season, most cities desilt their pipes twice or more annually. Large pipes are typically desilted approximately every three years, while some small and medium-sized pipes require desilting once or twice a month. This is particularly true in cities with flat terrain, where the terrain is less advantageous and pipe slopes are generally more gradual, resulting in low flow rates and a high risk of siltation. Furthermore, studies have shown that up to 80% of the pollutant load in combined sewer systems during rainy season overflows can be attributed to sediment erosion. Harmful substances in these sediments, such as viruses, bacteria, and heavy metals, can be directly discharged into natural water bodies, causing severe water pollution and harming the aquatic ecosystem and human health. Furthermore, during heavy rains, large amounts of rainwater flowing into sewage pipes not only significantly reduce the COD content of the influent to sewage treatment plants but also significantly impact their daily operations.

[0004] To control or reduce the pollution and safety risks caused by sediment accumulation in drainage pipes, developed countries like the United States and Europe began to focus on and research methods for controlling sediment accumulation in pipes in the 1960s. These methods primarily involve removing sediment through offline and online hydraulic flushing or mechanical desilting, or by regularly dredging silted pipe sections. Table 1 lists commonly used sediment control or desilting methods in both China and abroad.

[0005] Table 1 Pipeline sediment control measures at home and abroad

[0006]

[0007] Commonly used pipeline sediment control and dredging measures at home and abroad can be roughly divided into two categories:

[0008] 1) Online automatic flushing mode that does not affect the normal operation of the drainage pipe. The hydraulic balancing valve plate and hydraulic self-purification system belong to this category, which can control the accumulation of sediment in the drainage pipe in real time. This method often leads to problems such as equipment being entangled with garbage due to poor source control, resulting in poor drainage and loss of its original function.

[0009] 2) Offline active cleaning methods using external equipment, such as winch desilting and high-pressure water jetting, fall into this category. However, these methods consume large amounts of energy and water, are costly, and are not suitable for desilting small-diameter branch lines. Furthermore, current hydraulic and mechanical methods for controlling sediment in pipelines require the installation of mechanical devices within the pipeline or on the roadside, requiring long-term operation and maintenance, and potentially leading to flood control safety issues in the drainage system. Therefore, a combination of these two types of measures should be utilized based on the actual construction and operation of drainage pipelines.

[0010] Sediment in existing sewage pipe networks is generally viscous and difficult to remove, requiring significant human, material, and financial resources. Desilting requires the use of centralized desilting vehicles or manual desilting machinery, which carries significant operating, personnel, and maintenance costs, significantly increasing the economic burden of desilting. Furthermore, desilting costs are significantly increased for smaller pipe branches and inaccessible areas. Furthermore, due to the lack of systematic monitoring of sediment in pipe networks, superficial inspections alone cannot fully assess the appropriate desilting methods and timing. Further, the use of more advanced technologies and regular, comprehensive inspections of the pipe network are necessary to accurately determine the appropriate desilting timing. Therefore, desilting sediment from sewage pipe networks is a complex task. However, desilting sediment from pipe networks is crucial for maintaining urban environmental quality and protecting public health. Therefore, achieving more scientific management and desilting of sediment in sewage pipe networks is crucial for building a healthy and stable urban water environment. Summary of the Invention

[0011] To address the high cost and difficulty of sediment desilting in traditional sewage pipe networks, as well as the difficulty in determining the timing of desilting due to a lack of supervision, the present invention discloses a sewage flow limiting well for automatic desilting at the corners of sewage pipe networks and an automatic desilting method. The sewage flow limiting well has the advantages of automatic desilting and intercepting dry season sewage and early rainwater in the rainy season. It can reduce the accumulation of sediment in the pipe network, and at the same time, it can alleviate the water inlet pressure of sewage treatment plants in the rainy season, further reducing the overall cost. The specific technical solution is as follows:

[0012] A sewage flow limiting well with automatic desilting at the corner of a sewage pipe network, comprising a well body with a tee at the bottom, wherein the tee pipes connected to the well body are a sewage inlet pipe, a sewage outlet pipe and an overflow pipe; a desilting module, a flow limiting module and an overflow module are arranged in the well body;

[0013] The desilting module extends from the sewage inlet pipe to between the sewage outlet pipe and the overflow pipe, and is used to transport sediment brought in from the upstream to the downstream to prevent siltation in the well body;

[0014] The flow limiting module is arranged at the outlet of the sewage pipe, and the well water flows out through the flow limiting module, which is used to intercept the sewage in the dry season and the initial rainwater, and prevent the water volume impact of the sewage treatment plant caused by excessive rainwater entering the sewage pipe network in the rainy season;

[0015] The overflow module is arranged in the overflow pipe and is used to discharge surface water with less pollution in the rainy season.

[0016] Furthermore, the desilting module includes a diversion slope, a guide plate, and a low weir. The guide plate extends from the sewage inlet pipe to a position between the sewage outlet pipe and the overflow pipe in the well body. The guide plate divides the desilting module into an inner bend flow area and an outer bend flow area. The side connected to the sewage outlet pipe is the inner bend flow area, and the other side is the outer bend flow area.

[0017] The drainage slope is arranged in the longitudinal section of the sewage inlet pipe, sloping from bottom to top toward the downstream of the water flow, and is arranged from the upstream end of the guide plate to the side wall of the sewage inlet pipe, that is, the entrance position of the outer flow field of the bend; the drainage slope is used to guide the sewage in the pipe network into the outer flow field;

[0018] The low weir is lower than the height of the guide plate, connected to the guide plate at the sewage inlet in the well body, and extends to the well wall next to the sewage outlet; the longitudinal cross-section of the low weir is triangular in shape, with inclined and curved walls on both sides, which is used to change the intensity and path of the horizontal circulation in the original pipeline.

[0019] Furthermore, the flow limiting module includes a swirl flow limiting valve arranged at the pipe mouth of the sewage outlet pipe, the swirl flow limiting valve is composed of an inlet pipe, a water outlet and a conical volute cavity, and according to the flow limiting needs, the central axis of the volute cavity is installed with an upward tilt. The function of the swirl flow limiting valve is to intercept dry season rainwater and initial rainwater, and limit the amount of sewage entering the sewage pipe; the sewage outlet pipe is used to transport the sewage intercepted by the swirl flow limiting valve to the sewage treatment plant.

[0020] Furthermore, the overflow module includes a filter screen arranged in the overflow pipe, which is installed at the inlet of the overflow pipe and is used to separate suspended particulate matter on the surface of the sewage network when overflow occurs in the rainy season; the overflow pipe is used to transport the later rainwater separated by the filter screen to the urban water body.

[0021] Furthermore, the cross-section of the flow basin inside the bend is smaller than the flow basin outside the bend, and the bottom slope height is lower than the flow basin outside the bend. When the water consumption is low in a day, most of the sewage will flow along the flow basin inside the bend through the corner in the well body and enter the swirl flow limiting valve; when the water consumption is peak in a day, most of the sewage will flow along the flow basin outside the bend through the corner in the well body, and then pass through the throwing effect of the low weir, and finally enter the swirl flow limiting valve.

[0022] Furthermore, the sewage inlet pipe and the sewage outlet pipe are at the same height and are located at the bottom of the well body, and the overflow pipe is higher than the sewage inlet pipe and the sewage outlet pipe.

[0023] Furthermore, when sewage flows from the sewage inlet pipe into the basin within the bend and enters the sewage outlet pipe at the downstream corner of the bend, a transverse circulation is formed. The transverse circulation is mainly generated by the combined action of lateral pressure and centrifugal force. The centrifugal force is generated when the sewage passes through the corner of the pipe network. The expression of the centrifugal force F exerted on the unit volume of sewage in the pipe is F = ρv 2 / r, where ρ is the density of the sewage, v is the longitudinal flow velocity of the sewage, and r is the radius of curvature corresponding to the position of the sewage; the lateral pressure is because when the water flows through the bend, due to the existence of centrifugal force, the equilibrium state of the water surface is destroyed, causing the water surface outside the bend to rise and the water surface inside the bend to fall, resulting in a horizontal gradient of the water surface J r As a result, the expression of the lateral pressure P is P = ρg J r The lateral pressure P is evenly distributed longitudinally and points outward. Since the sewage pipe network wall has no sliding conditions and is mainly affected by viscous shear stress, the flow velocity gradient on the sewage pipe wall is very large, and the tangential flow velocity will increase rapidly from 0 to a finite value, causing the centrifugal force F to gradually increase from the bottom layer to the surface in the longitudinal direction and point inward. The lateral pressure P and the centrifugal force F act together on the cross section of the pipe network to form a resultant torque. Under the action of the resultant torque, the sewage flows forward while accompanied by a lateral circulation.

[0024] Water surface horizontal gradient J r It is the main factor that produces lateral pressure. Considering two-dimensional steady flow, take a small water column with unit bottom area and height h at the curvature radius r, and analyze its lateral force to obtain J r The expression is as follows, where a0 is the velocity distribution unevenness coefficient, v0 is the longitudinal average velocity, τ r0 is the bottom lateral resistance,

[0025]

[0026] The expression of velocity distribution unevenness coefficient a0 is as follows:

[0027]

[0028] Wherein, H is the water level height in the longitudinal direction of the bend;

[0029] The low weir changes the intensity and path of the lateral circulation. Changing the path of the lateral circulation means that the existence of the low weir causes the bottom sediments to be thrown out in the process of moving from the outside to the inside; changing the intensity of the lateral circulation means that the existence of the low weir provides another lateral channel for the water flow that is about to be narrowed, effectively avoiding the waterlogging caused by the conversion of kinetic energy of water into potential energy, and increasing the lateral flow velocity component accordingly. Since the water flows towards the low weir at a greater speed, this provides favorable conditions for the transport of sediments.

[0030] Furthermore, the design flow rate of the swirl flow limiting valve should be able to meet the needs of intercepting both initial rainwater and dry season sewage;

[0031] The inlet of the overflow pipe is located on the wall of the well body and faces the direction of surface flow. There is a height difference with the bottom of the inspection well. The sewage water level does not reach the height of the overflow pipe mouth during the dry season and the early rainy season. Only when the water volume is large in the middle and late rainy season, the water level in the sewage flow limiting well will reach the overflow pipe mouth.

[0032] A method for automatically desilting sewage pipe network corners, the method being based on a sewage flow limiting well for automatically desilting sewage pipe network corners. The method includes three operating conditions: the first being a low water level in the dry season, the second being a high water level in the dry season, and the third being a water level in the rainy season.

[0033] (1) Low water level in dry season:

[0034] When the water level is low in the dry season, since the bottom slope of the basin in the bend is lower, most of the sewage will enter the silt removal and flow limiting well from the basin in the bend after being transported through the sewage inlet pipe. At this time, the sewage flow is small and basically has no ability to carry sediments. The curvature radius of the inner side of the bend is smaller than the curvature radius of the outer side of the bend, so the lateral circulation intensity generated on the inner side of the bend is relatively small. Therefore, even if some sediments are carried in the sewage at low flow, it is not easy to accumulate in the silt removal and flow limiting well. Then the sewage cuts into the cavity of the swirl flow limiting valve at a tangent angle and finally enters the downstream of the sewage network or the sewage treatment plant through the sewage outlet pipe. Since the amount of sewage is small, the liquid level difference before and after the swirl flow limiting valve is small, the water head is low, and the water flows through the swirl cavity by gravity. The swirl flow limiting valve does not swirl and is only hindered by a smooth angle, so the head loss is very small and has almost no effect on the pipeline flow.

[0035] (2) High water level in dry season:

[0036] When the water level is high in the dry season, the flow rate becomes larger, so the sewage has a stronger ability to carry sediments, and under the action of gravity, the surface sewage contains less sediment, and the bottom sewage contains more sediment. Since the width of the outer basin of the bend is wider, due to the diversion effect of the guide plate, most of the sewage with more sediments in the bottom enters the outer basin of the bend under the drainage effect of the diversion slope, and the remaining bottom sewage enters the inner basin along the inside of the bend. Among them, the guide plate mainly plays the role of diverting the more turbid sewage in the bottom, so the height of the guide plate is not high. The surface sewage in the inner basin of the bend and the outer basin of the bend are connected. After the sewage is transported through the sewage inlet pipe, most of the bottom sewage with more sediments will enter the outer basin along the outside of the bend. When the sewage enters the sewage flow limiting well, the centrifugal force will be generated due to the sewage flowing around the bend corner, thereby forming a horizontal gradient of the water surface, further forming a pressure difference, and finally, under the action of the pressure difference and centrifugal force, a horizontal circulation will be formed here, superimposed on the mainstream Finally, a spiral flow is formed. The existence of the spiral flow allows the sewage to move forward while bringing the surface water from the inside of the bend to the outside of the bend, and bringing the deep water from the outside of the bend to the inside of the bend. The existence of the low weir changes the direction of the horizontal circulation. Under the action of the low weir, the sewage with more sediment in the bottom layer is thrown from the bottom to the working direction to form a longitudinal ring. Due to the no-slip condition of the boundary, the flow velocity gradient in the longitudinal direction is very large, and because the amount of sediment carried is proportional to the high power of the velocity, the position after being thrown has greater potential for transporting sediment, effectively avoiding the accumulation of organic matter on the inside of the bend. At the same time, the existence of the low weir increases the component of the horizontal flow velocity, further improving the automatic silt removal ability of the system. Subsequently, the sewage cuts into the cavity of the swirl flow limiting valve at a tangent angle, and finally enters the downstream of the sewage network or the sewage treatment plant through the sewage outlet pipe. When the water level is high in the dry season, the sewage still flows through the swirl cavity by gravity, and the swirl flow limiting valve will not swirl;

[0037] (3) Water level in rainy season:

[0038] When the water level is in the rainy season, the flow in the pipe network is greater, and overflow may even occur. A large amount of rainwater and sewage mixed sewage will enter the dredging and flow limiting well after being transported through the sewage inlet pipe. The initial water absorption capacity of the soil will first intercept the rainfall and gradually become saturated. When the soil is saturated and can no longer absorb rainfall, the rainfall will begin to form runoff. In cities and urbanized areas, due to the hardening of the road surface and the installation of drainage facilities, rainfall will form runoff faster. At the same time, the initial rainwater will carry a large amount of sediment, nutrients and other pollutants, which has a great impact on the water environment. When the initial rainwater and pipe network sewage enter the dredging and flow limiting well at the same time, the water level has not yet reached the highest water level of the rainy season. Most of the rainwater and sewage mixed water still pass through the dredging of the low weir like the high flow in the dry season, and then enter the swirl flow limiting valve under the action of gravity and finally enter the sewage pipe network. Downstream or in the sewage treatment plant, as the rainfall continues, the water level in the sewage flow limiting well will continue to rise. When it reaches the height of the overflow pipe, due to the effect of the lateral circulation of the bend, the clearer surface water will enter the overflow pipe from the inside of the bend along the direction of the overflow pipe mouth through the filter screen, and finally enter the urban water body. As the water level rises, the flow rate continues to increase, and air will enter the valve cavity through the air hole of the swirl flow limiting valve, blocking the water flow to form a swirl and forming a high-speed tangential velocity in the valve cavity. At the same time, the valve cavity is filled with air to form a swirl core, thereby reducing the water cross-section, thereby realizing the function of precise flow control. Due to its unique hydraulic and aerodynamic principles, when the maximum interception volume is reached, the increase in the water level in the well has no obvious effect on the increase in the interception volume, so that it will not cause a large water impact on the daily operation of the sewage treatment plant.

[0039] The beneficial effects of the present invention are:

[0040] This invention leverages hydraulic phenomena at corners to achieve automatic desilting of sewage pipe networks, effectively addressing the difficulties and high costs of desilting urban sewage pipe networks. The low weir design not only changes the direction and intensity of lateral circulation, but also effectively propels sediment to areas with faster flow rates, significantly improving the water's automatic desilting capabilities and significantly reducing sediment accumulation in the pipes. Simultaneously, a large amount of organic matter is carried downstream with the sediment into the pipe network and then to the sewage treatment plant, helping to alleviate carbon source shortages at the sewage treatment plant, reduce the dosage of carbon sources and phosphorus removal agents, and achieve low-carbon operation of the drainage system. The swirl flow limiting valve at the outlet of the sewage pipe effectively intercepts dry season sewage and initial rainwater. Furthermore, due to its unique hydraulic and aerodynamic principles, once the maximum interception rate is reached, rising water levels in the well have no significant effect on the increase in interception rate, allowing the intercepted sewage to be evenly discharged to the sewage treatment plant, thus achieving precise flow control. This not only reduces surface runoff pollution but also minimizes significant water volume impacts on the daily operations of the sewage treatment plant. This reduces the inlet pressure on sewage treatment plants during the rainy season. The design of this sewage flow-limiting well also significantly mitigates the damage caused by combined sewer overflows to urban water bodies during the rainy season. In the early stages of the rainy season, the water level does not reach the height of the overflow pipe. During the rainy season, the sediment content in the inspection wells after daily automatic dredging is very low, and the overflow pipe opening faces the surface flow direction. Therefore, the overflow water contains very few pollutants and is then screened by the filter before entering the overflow pipe and being discharged into the urban water body. The overflow water entering the urban water body through the overflow pipe is basically late rainwater and is relatively clear surface water due to the effect of horizontal circulation, thus greatly alleviating the harm caused by combined sewer overflows. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a plan view of the sewage flow limiting well at the corner of the sewage pipe network;

[0042] Figure 2 This is the AA cross-section of the sewage flow limiting well;

[0043] Figure 3 This is the BB cross-section of the sewage flow limiting well;

[0044] Figure 4 This is a schematic diagram of flow velocity and lateral circulation at the sewage flow limiting well section;

[0045] Figure 5 Schematic diagram of the lateral force acting on water flow. DETAILED DESCRIPTION

[0046] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0047] There are multiple inspection wells in the sewage pipe network. One side of the inspection well is connected to the sewage inlet pipe, and the other side is connected to the sewage outlet pipe. The present invention also has an overflow pipe. A filter is set in the overflow pipe. Figure 2-3 It can be seen that the bottom diameter of the inspection well is relatively large, and a closing section is provided at the upper section. A well wall 10 is provided around the top opening of the inspection well, and a well cover 12 and a support 11 are provided on the well wall 10.

[0048] like Figure 1-3 , which is a plan and cross-sectional view (taking 120° as an example) of an automatic desilting and flow-limiting well suitable for use at the corner of a sewage pipe network according to the present invention, mainly includes a sewage inlet pipe 1, a diversion slope 2, a guide plate 3, a low weir 4, a sewage flow-limiting well 5, an overflow pipe 6, a filter screen 7, a sewage outlet pipe 8, a swirl flow-limiting valve 9, a well wall 10, a support 11, a well cover 12, a swirl flow-limiting valve inlet pipe 13, a swirl flow-limiting valve volute cavity 14, and a swirl flow-limiting valve outlet 15.

[0049] Due to differences in topography, regional population, and industrial distribution, cities may experience differences in slope, water volume, and peak water usage in different sections of the urban sewage network. Figure 2 As can be seen from the AA cross-sectional view of the sewage interception and flow limiting well, the automatic silt removal and flow limiting well suitable for the corners of the sewage pipe network of the present invention includes three operating conditions, the first is the low water level in the dry season, the second is the high water level in the dry season, and the third is the water level in the rainy season.

[0050] (1) Low water level in dry season:

[0051] During the dry season, when the water level is low, most of the sewage will enter the desilting and limiting well 5 from the inner basin of the bend after being transported through the sewage inlet pipe 1. At this time, the sewage flow rate is small and basically has no ability to carry sediments. In addition, the curvature radius of the inner side of the bend is smaller than the curvature radius of the outer side of the bend, so the transverse circulation intensity generated on the inner side of the bend is relatively small. Therefore, even if some sediments are carried in the sewage at low flow, it is not easy to accumulate in the desilting and limiting well 5. The sewage then cuts into the cavity of the swirl limiting valve 9 at a tangent angle and finally enters the downstream of the sewage network or the sewage treatment plant through the sewage outlet pipe 8. Due to the small amount of sewage, the liquid level difference before and after the swirl limiting valve 9 is small, the water head is low, and the water flows through the swirl cavity by gravity. The swirl limiting valve 9 does not swirl and is only hindered by a smooth angle, so the water head loss is very small and has almost no effect on the pipeline flow.

[0052] (2) High water level in dry season:

[0053] When the water level is high in the dry season, the flow rate becomes larger, so the sewage has a stronger ability to carry sediments. And under the action of gravity, the surface sewage contains less sediment, and the bottom sewage contains more sediment. Since the width of the outer basin of the bend is wider, due to the diversion effect of the guide plate 3, most of the sewage with more sediments in the bottom layer enters the outer basin of the bend under the drainage effect of the diversion plate 2, and the remaining bottom sewage enters the inner basin along the inner side of the bend. Among them, the guide plate 3 mainly plays the role of diverting the more turbid sewage in the bottom layer, so the height of the guide plate 3 is not high, and the surface sewage in the inner basin of the bend and the outer basin of the bend are connected. After the sewage is transported through the sewage inlet pipe 1, most of the bottom sewage with more sediments will enter the outer basin along the outside of the bend. After the sewage enters the sewage flow limiting well 5, the centrifugal force generated by the sewage flowing around the bend corner will form a horizontal gradient of the water surface, further forming a pressure difference, and finally, under the action of the pressure difference and centrifugal force, a horizontal circulation will be formed here (such as Figure 4 、 Figure 5 As shown in the figure, the main flow is superimposed to form a spiral flow. The existence of the spiral flow allows the sewage to move forward while bringing the surface water from the inside of the bend to the outside of the bend, and bringing the deep water from the outside of the bend to the inside of the bend. Figure 4 It can be seen that the presence of the low weir 4 changes the direction of the lateral circulation. Under the action of the low weir, the sewage with a lot of sediment in the bottom layer is thrown from the working condition 1' point to the working condition 2' point. Due to the no-slip condition of the boundary, the flow velocity gradient in the longitudinal direction is very large. Because the amount of sand carried is proportional to the high power of the velocity, the working condition 2' point has a greater potential for transporting sediments than the working condition 1' point, which can effectively avoid the accumulation of organic matter on the inside of the bend. At the same time, the presence of the low weir increases the component of the lateral flow velocity, further improving the automatic silt removal capability of the system. The sewage then cuts into the cavity of the swirl flow limiting valve 9 at a tangent angle, and finally enters the downstream of the sewage network or the sewage treatment plant through the sewage outlet pipe 8. When the water level is high in the dry season, the sewage still flows through the swirl cavity by gravity, and the swirl flow limiting valve 9 will not swirl.

[0054] (3) Water level in rainy season:

[0055] When the water level is in the rainy season, the flow in the pipe network is even greater, and even overflow may occur. A large amount of rainwater and sewage mixed sewage will enter the silt removal and flow limiting well 5 after being transported through the sewage inlet pipe 1. The initial water absorption capacity of the soil will first intercept the rainfall and gradually become saturated. When the soil is saturated and can no longer absorb rainfall, the rainfall will begin to form runoff. In cities and urbanized areas, due to the hardening of the road surface and the installation of drainage facilities, rainfall will form runoff more quickly. At the same time, the initial rainwater will carry a large amount of sediment, nutrients and other pollutants, which has a great impact on the water environment. When the initial rainwater and the pipe network sewage enter the silt removal and flow limiting well at the same time, the water level has not yet reached the highest water level of the rainy season. Most of the rainwater and sewage mixed water will still be silted through the low weir like the high flow in the dry season, and then enter the swirl flow limiting valve under the action of gravity and finally enter the downstream sewage pipe network or sewage treatment plant. As rainfall continues, the water level in the sewage flow limiting well will continue to rise. When it reaches the height of the overflow pipe, due to the effect of the lateral circulation of the bend, the relatively clear surface water will enter the overflow pipe from the inside of the bend along the direction opposite the overflow pipe mouth through the filter screen, and finally enter the urban water body. As the water level rises, the flow rate continues to increase, and air will enter the valve cavity through the pores of the swirl flow limiting valve, blocking the water flow to form a swirl and forming a high tangential velocity in the valve cavity. At the same time, the valve cavity is filled with air to form a swirl core, thereby reducing the water flow section and achieving the function of precise flow control. Due to its unique hydraulic and aerodynamic principles, it can be achieved that when the maximum interception volume is reached, the increase in the water level in the well has no significant effect on the increase in the interception volume, so it will not cause a large water impact on the daily operation of the sewage treatment plant.

[0056] The following combination Figure 1-5 Specific introduction to the layout and principle of the present invention:

[0057] This patented method utilizes the lateral circulation generated at the corners of the sewage pipe network and installs a swirl flow limiting valve to transform the inspection well at the corner of the sewage pipe network, thereby solving the problems of sediment accumulation in traditional sewage pipe networks and the large water inflow to sewage treatment plants during the rainy season. The invention consists of three parts: a silt removal module, a flow limiting module, and an overflow module.

[0058] The desilting module is used to transport sediment brought in from upstream to downstream to prevent siltation in the inspection well;

[0059] The flow limiting module is connected to the water outlet of the inspection well to intercept sewage and initial rainwater in the dry season, preventing water volume shock to the sewage treatment plant caused by excessive rainwater entering the sewage pipe network during the rainy season;

[0060] The overflow module is used to discharge surface water with less pollution during the rainy season.

[0061] The dredging module consists of three parts: a drainage slope, a guide plate and a low weir. The guide plate divides the dredging module into two parts: the inner flow basin of the bend and the outer flow basin of the bend; the drainage slope is used to introduce sewage in the pipeline network into the external flow field; the low weir is used to change the intensity and path of the horizontal circulation in the original pipeline. The front end of the low weir is connected to the guide plate, and the rear end is connected to the pipeline network inspection well.

[0062] The flow limiting module includes a swirl flow limiting valve and a sewage pipe. The swirl flow limiting valve is used to intercept dry season rainwater and initial rainwater, limiting the amount of sewage entering the sewage pipe; the sewage pipe is used to transport the sewage intercepted by the swirl flow limiting valve to the sewage treatment plant.

[0063] The overflow module includes a filter screen and an overflow pipe. The filter screen is installed at the entrance of the overflow pipe and is used to separate suspended particulate matter on the surface of the sewage network when overflow occurs in the rainy season; the overflow pipe is used to transport the later rainwater separated by the filter screen to the urban water body.

[0064] The desilting module is divided into two parts: the inner bend basin and the outer bend basin. The inner bend basin has a narrower cross-section and a lower slope. When the sewage network water volume is low, most of the sewage will flow along the inner flow field, through the sewage network corner, and into the swirl flow limiting valve. The outer bend basin has a wider cross-section and a higher bottom slope. When the sewage network water volume is high, most of the sewage will flow along the outer flow field, through the sewage network corner, and then be thrown away by the low weir before entering the swirl flow limiting valve.

[0065] Transverse circulation is mainly caused by the combined action of lateral pressure and centrifugal force. Centrifugal force is generated when sewage passes through the corner of the pipe network. The expression of centrifugal force F on unit volume of sewage in the pipe is F = ρv 2 / r; lateral pressure is caused by the existence of centrifugal force when water flows through a bend, which destroys the equilibrium state of the water surface, causing the water surface on the concave bank to rise and the water surface on the convex bank to fall, resulting in a horizontal gradient of the water surface. r As a result, the expression of the lateral pressure P is P = ρg J r The lateral pressure P is evenly distributed longitudinally and points outward. Since the sewage pipe network wall has no sliding conditions and is mainly affected by viscous shear stress, the flow velocity gradient on the sewage pipe wall is very large, and the tangential flow velocity will increase rapidly from 0 to a finite value, causing the centrifugal force F to gradually increase from the bottom layer to the surface in the longitudinal direction and point inward. The lateral pressure P and the centrifugal force F act together on the cross section of the pipe network to form a resultant torque. Under the action of the resultant torque, the sewage flows forward while accompanied by a lateral circulation.

[0066] Water surface horizontal gradient J r It is the main factor that produces lateral pressure. Considering a two-dimensional steady flow, take a small water column with a unit bottom area and a height of h at a curvature radius r, and analyze its lateral force to obtain J rThe expression is as follows, where a0 is the velocity distribution unevenness coefficient, v0 is the longitudinal average velocity, τ r0 is the bottom lateral resistance.

[0067]

[0068] The expression of the velocity distribution unevenness coefficient a0 is as follows.

[0069]

[0070] Low weirs alter the intensity and path of lateral circulation. Changing the path of lateral circulation means that the presence of low weirs causes bottom sediment to be thrown outward as it moves from the outside to the inside. Changing the intensity of lateral circulation means that the presence of low weirs provides another lateral channel for the water flow that is about to narrow. This effectively avoids the backwater caused by the conversion of kinetic energy into potential energy and instead increases the lateral flow velocity component. Since the water rushes toward the low weir at a greater speed, this creates favorable conditions for sediment transport.

[0071] The design flow of the swirl flow limiting valve must be able to meet the needs of intercepting both initial rainwater and dry season sewage.

[0072] The overflow pipe inlet is located on the outer wall of the inspection well, facing the surface flow direction, and at a certain height difference from the bottom of the inspection well. During the dry season and the early rainy season, the sewage water level does not reach the overflow pipe opening. Only in the middle and late rainy season, when the water volume is high, does the water level in the sewage flow control well reach the overflow pipe opening.

[0073] The technical means disclosed in the solution of the present invention are not limited to the technical means disclosed in the above technical means, but also include technical solutions composed of any combination of the above technical features.

[0074] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A sewage flow limiting well with automatic silt removal at the corner of a sewage pipe network, characterized in that: A well body comprising a tee at the bottom, wherein the tee pipes connected to the well body are a sewage inlet pipe, a sewage outlet pipe and an overflow pipe; a dredging module, a flow limiting module and an overflow module are arranged in the well body; The desilting module extends from the sewage inlet pipe to between the sewage outlet pipe and the overflow pipe, and is used to transport sediment brought in from the upstream to the downstream to prevent siltation in the well body; The flow limiting module is arranged at the outlet of the sewage pipe, and the well water flows out through the flow limiting module, which is used to intercept the sewage in the dry season and the initial rainwater, and prevent the water volume impact of the sewage treatment plant caused by excessive rainwater entering the sewage pipe network in the rainy season; The overflow module is arranged in the overflow pipe and is used to discharge the surface water with less pollution in the rainy season; The desilting module includes a drainage slope, a guide plate, and a low weir. The guide plate extends from the sewage inlet pipe to a position between the sewage outlet pipe and the overflow pipe in the well body. The guide plate divides the desilting module into an inner bend flow area and an outer bend flow area. The inner bend flow area is on the side connected to the sewage outlet pipe, and the outer bend flow area is on the other side. The cross section of the flow area inside the bend is smaller than the cross section of the flow area outside the bend, and the bottom slope height of the flow area inside the bend is lower than the bottom slope height of the flow area outside the bend; The drainage slope is arranged in the longitudinal section of the sewage inlet pipe, sloping from bottom to top toward the downstream of the water flow, and is arranged from the upstream end of the guide plate to the side wall of the sewage inlet pipe, that is, the entrance position of the outer flow field of the bend; the drainage slope is used to guide the sewage in the pipe network into the outer flow field; The low weir is lower than the height of the guide plate, connected to the guide plate at the sewage inlet in the well body, and extends to the well wall next to the sewage outlet; the longitudinal cross-section of the low weir is triangular in shape, with inclined and curved walls on both sides, which is used to change the intensity and path of the horizontal circulation in the original pipeline.

2. The sewage flow limiting well with automatic desilting at the corner of the sewage pipe network according to claim 1 is characterized in that: The flow limiting module includes a swirl flow limiting valve arranged at the pipe mouth of the sewage outlet pipe. The swirl flow limiting valve includes an inlet pipe, an outlet and a conical volute cavity. According to the flow limiting needs, the central axis of the volute cavity is installed with an upward tilt. The function of the swirl flow limiting valve is to intercept dry season rainwater and initial rainwater, and limit the amount of sewage entering the sewage pipe; the sewage outlet pipe is used to transport the sewage intercepted by the swirl flow limiting valve to the sewage treatment plant.

3. The sewage flow limiting well with automatic desilting at the corner of the sewage pipe network according to claim 1 is characterized in that: The overflow module includes a filter screen arranged in the overflow pipe, which is installed at the inlet of the overflow pipe and is used to separate suspended particulate matter on the surface of the sewage pipe network when overflow occurs in the rainy season; the overflow pipe is used to transport the later rainwater separated by the filter screen to the urban water body.

4. The sewage flow limiting well with automatic desilting at the corner of the sewage pipe network according to claim 2 is characterized in that: When the water consumption is at its low point in the day, most of the sewage will flow along the inner basin of the bend through the corner inside the well body and enter the swirl flow limiting valve; when the water consumption is at its peak point in the day, most of the sewage will flow along the outer basin of the bend through the corner inside the well body, and then be thrown away by the low weir, and finally enter the swirl flow limiting valve.

5. The sewage flow limiting well with automatic desilting at the corner of the sewage pipe network according to claim 1 is characterized in that: The sewage inlet pipe and the sewage outlet pipe are at the same height and are located at the bottom of the well body, and the overflow pipe is higher than the sewage inlet pipe and the sewage outlet pipe.

6. The sewage flow limiting well with automatic desilting at the corner of the sewage pipe network according to claim 1 is characterized in that: Sewage flows from the sewage inlet pipe into the basin within the bend, and forms a transverse circulation when it turns downstream into the sewage outlet pipe. The transverse circulation is mainly generated by the combined action of lateral pressure and centrifugal force. The centrifugal force is generated when the sewage passes through the corner of the pipe network. The expression of the centrifugal force F per unit volume of sewage in the pipe is F = ρv 2 / r, where ρ is the density of the sewage, v is the longitudinal flow velocity of the sewage, and r is the radius of curvature corresponding to the position of the sewage; the lateral pressure is because when the water flows through the bend, due to the existence of centrifugal force, the equilibrium state of the water surface is destroyed, causing the water surface outside the bend to rise and the water surface inside the bend to fall, resulting in a horizontal gradient of the water surface J r As a result, the expression of the lateral pressure P is P = ρgJ r The lateral pressure P is evenly distributed longitudinally and points outward. Since the sewage pipe network wall has no sliding conditions and is mainly affected by viscous shear stress, the flow velocity gradient on the sewage pipe wall is very large, and the tangential flow velocity will increase rapidly from 0 to a finite value, causing the centrifugal force F to gradually increase from the bottom layer to the surface in the longitudinal direction and point inward. The lateral pressure P and the centrifugal force F act together on the cross section of the pipe network to form a resultant torque. Under the action of the resultant torque, the sewage flows forward while accompanied by a lateral circulation. Water surface horizontal gradient J r It is the main factor that produces lateral pressure. Considering two-dimensional steady flow, take a small water column with unit bottom area and height h at the curvature radius r, and analyze its lateral force to obtain J r The expression is as follows, where a0 is the velocity distribution unevenness coefficient, v0 is the longitudinal average velocity, τ r0 is the bottom lateral resistance, The expression of velocity distribution unevenness coefficient a0 is as follows: Wherein, H is the water level height in the longitudinal direction of the bend; The low weir changes the intensity and path of the lateral circulation. Changing the path of the lateral circulation means that the existence of the low weir causes the bottom sediments to be thrown out in the process of moving from the outside to the inside; changing the intensity of the lateral circulation means that the existence of the low weir provides another lateral channel for the water flow that is about to be narrowed, effectively avoiding the waterlogging caused by the conversion of kinetic energy of water into potential energy, and increasing the lateral flow velocity component accordingly. Since the water flows towards the low weir at a greater speed, this provides favorable conditions for the transport of sediments.

7. The sewage flow limiting well with automatic desilting at the corner of the sewage pipe network according to claim 2 is characterized in that: The design flow rate of the swirl flow limiting valve should be able to meet the needs of intercepting both initial rainwater and dry season sewage; The inlet of the overflow pipe is located on the wall of the well body and faces the direction of surface flow. There is a height difference with the bottom of the inspection well. The sewage water level does not reach the height of the overflow pipe mouth during the dry season and the early rainy season. Only when the water volume is large in the middle and late rainy season, the water level in the sewage flow limiting well will reach the overflow pipe mouth.

8. The automatic desilting method at the corner of the sewage pipe network is characterized by: The method is implemented based on the sewage flow limiting well for automatic desilting at the corner of the sewage pipe network as described in any one of claims 2 to 7, and the method includes three operating conditions, the first being a low water level in the dry season, the second being a high water level in the dry season, and the third being a water level in the rainy season; (1) Low water level in dry season: When the water level is low in the dry season, since the bottom slope of the basin in the bend is lower, most of the sewage will enter the sewage flow limiting well from the basin in the bend after being transported through the sewage inlet pipe. At this time, the sewage flow is small and basically has no ability to carry sediments. The curvature radius of the inner side of the bend is smaller than the curvature radius of the outer side of the bend, so the lateral circulation intensity generated on the inner side of the bend is relatively small. Therefore, even if some sediments are carried in the sewage at low flow, it is not easy to accumulate in the sewage flow limiting well. Then the sewage cuts into the cavity of the swirl flow limiting valve at a tangent angle, and finally enters the downstream of the sewage network or the sewage treatment plant through the sewage outlet pipe. Since the amount of sewage is small, the liquid level difference before and after the swirl flow limiting valve is small, the water head is low, and the water flows through the cavity by gravity. The swirl flow limiting valve will not swirl and is only hindered by a smooth angle, so the water head loss is very small, and there is almost no effect on the pipeline flow. (2) High water level in dry season: When the water level is high in the dry season, the flow rate becomes larger, so the sewage has a stronger ability to carry sediments, and under the action of gravity, the surface sewage contains less sediment, and the bottom sewage contains more sediment. Since the width of the outer basin of the bend is wider, due to the diversion effect of the guide plate, most of the sewage with more sediments in the bottom layer enters the outer basin of the bend under the diversion effect of the diversion slope, and the remaining bottom sewage enters the inner basin of the bend along the inner side of the bend. Among them, the guide plate mainly plays the role of diverting the more turbid sewage in the bottom layer, so the height of the guide plate is not high. The surface sewage in the inner basin of the bend and the outer basin of the bend are connected. After the sewage is transported through the sewage inlet pipe, most of the bottom sewage with more sediments will enter the outer basin along the outside of the bend. When the sewage enters the sewage flow limiting well, the centrifugal force will be generated due to the sewage flowing around the bend corner, thereby forming a horizontal gradient of the water surface, further forming a pressure difference, and finally, under the action of the pressure difference and centrifugal force, a horizontal circulation will be formed here, superimposed on the main After the flow, a spiral flow is finally formed. The existence of the spiral flow allows the sewage to move forward while bringing the surface water from the inside of the bend to the outside of the bend, and bringing the deep water from the outside of the bend to the inside of the bend. The existence of the low weir changes the direction of the lateral circulation. Under the action of the low weir, the sewage with a lot of sediment in the bottom layer is thrown from the bottom to the working direction to form a longitudinal ring. Due to the no-slip condition of the boundary, the flow velocity gradient in the longitudinal direction is very large, and because the amount of sediment carried is proportional to the high power of the velocity, the position after being thrown has greater potential for transporting sediments, effectively avoiding the accumulation of organic matter on the inside of the bend. At the same time, the existence of the low weir increases the component of the lateral flow velocity, further improving the automatic silt removal ability of the system. Subsequently, the sewage cuts into the cavity of the swirl flow limiting valve at a tangent angle, and finally enters the downstream of the sewage network or the sewage treatment plant through the sewage outlet pipe. When the water level is high in the dry season, the sewage still flows through the cavity by gravity, and the swirl flow limiting valve will not swirl; (3) Water level in rainy season: When the water level is in the rainy season, the flow in the pipe network is greater, and overflow may even occur. A large amount of rainwater and sewage mixed sewage will enter the sewage flow limiting well after being transported through the sewage inlet pipe. The initial water absorption capacity of the soil will first intercept the rainfall and gradually become saturated. When the soil is saturated and can no longer absorb rainfall, the rainfall will begin to form runoff. In cities and urbanized areas, due to the hardening of the road surface and the installation of drainage facilities, rainfall will form runoff faster. At the same time, the initial rainwater will carry a large amount of sediment, nutrients and other pollutants, which has a great impact on the water environment. When the initial rainwater and pipe network sewage enter the sewage flow limiting well at the same time, the water level has not yet reached the highest water level in the rainy season. Most of the rainwater and sewage mixed water still pass through the dredging of low weirs like the high flow in the dry season, and then enter the swirl flow limiting valve under the action of gravity and finally enter the sewage pipe network. Downstream or in the sewage treatment plant, as the rainfall continues, the water level in the sewage flow limiting well will continue to rise. When it reaches the height of the overflow pipe, due to the effect of the lateral circulation of the bend, the clearer surface water will enter the overflow pipe from the inside of the bend along the direction of the overflow pipe mouth through the filter screen, and finally enter the urban water body. As the water level rises, the flow rate continues to increase, and air will enter the cavity through the pores of the swirl flow limiting valve, blocking the water flow to form a swirl and forming a high-speed tangential velocity in the cavity. At the same time, the cavity is filled with air to form a swirl core, thereby reducing the water cross-section and realizing the function of precise flow control. Due to its unique hydraulic and aerodynamic principles, when the maximum interception volume is reached, the increase in the water level in the well has no obvious effect on the increase in the interception volume, so that it will not cause a large water impact on the daily operation of the sewage treatment plant.

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