Non-contact sensor system and method for measuring free surface flow and pressure flow in a conduit

Abstract

The present invention is embodied in a system that employs an online metering station for measuring both pressure flow and free surface flow in an underground conduit without the need for physical contact with the fluid located in the conduit; operating under both laminar and turbulent conditions; providing continuous flow measurement; providing remote data transmission to a central control room or mobile device for real-time access; detecting pipe sediment; making computational adjustments; and alerting for cleaning maintenance. Furthermore, embodiments of the invention are not interrupted by sewer pipe cleaning and are not limited by sewer flow velocity, flow depth, or Froude number. The preferred system includes a pair of standpipes (or "pipes") mounted on top of a buried underground conduit. A sensor for measuring the distance between the sensor and the surface of the fluid flowing below the sensor ("sensor-fluid distance") is located at the top of each standpipe. Using as-built conditions, the sensor-fluid distance can be used to find real-time flow depth and velocity through the underground conduit.

Description

Technical Field

[0001] This invention relates to an apparatus for measuring the flow rate of fluid located within a conduit. More specifically, this invention relates to measuring free surface flow rate and pressure flow rate located within an underground conduit. Background Technology

[0002] A wastewater system comprises three parts: (1) a collection system; (2) a wastewater treatment plant; and (3) an effluent discharge. Owners of wastewater systems typically charge users of the system fees to fund operating costs, maintenance costs, and capital expenditures for improvements. As the population using wastewater systems grows and industrial and commercial water use increases, wastewater flow also increases, necessitating capital improvements to expand wastewater systems. Modern sewer systems are designed not to receive rainwater (surface drainage from rainfall or snowmelt)—these systems are dedicated to wastewater (comprising domestic, commercial, and industrial wastewater). These dedicated sewer systems can inadvertently receive rainwater seeping from pipe joints or access panels due to aging or improper construction. Furthermore, approximately 12% of wastewater systems in the United States are served by combined sewer systems, which use a single pipe to transport wastewater and rainwater to treatment facilities.

[0003] Sewer systems are used to transport domestic, commercial, and industrial wastewater to treatment facilities. When rainwater enters a sewer system, there is a risk that the total flow may exceed the capacity of the sewer or treatment facility. When this occurs, overflows may occur into surface water bodies such as lakes, rivers, estuaries, or coastal waters, contaminating natural water bodies with sewage.

[0004] Wastewater overflows contain contaminants, including pathogens, aerobic pollutants, suspended solids, nutrients, toxic substances, and floating matter. The presence of contaminants in the flow can have various adverse effects on the physical properties of surface water, impair the viability of aquatic habitats, and pose a potential threat to drinking water supplies.

[0005] The EPA defines “wet weather flow” as the combined flow of wastewater and infiltrated rainwater. The EPA requires wastewater operators to maintain sufficient capacity to accommodate wet weather flows. Therefore, wastewater system operators need to know (1) the total volume of water flowing into the plant and (2) the total volume of water flowing into interceptors and collection pipes so that operators can predict and mitigate the risk of overflows.

[0006] Another benefit of understanding flow rates within a system is that it establishes a basis for cost-sharing when multiple entities share wastewater treatment facilities and / or collection systems. Furthermore, long-term, real-time wastewater flow monitoring plays a crucial role in planning the expansion of treatment plants and collection systems.

[0007] Flow rate can be measured instantaneously or continuously. Instantaneous flow rate measurements can be obtained using a primary flow meter. A primary flow meter generates a predictable hydraulic response based on the flow rate through it. Examples of such meters include weirs and flumes that link water depth (head) to flow rate; venturi and orifice plates that link pressure differential to flow rate; and magnetometers that link induced voltage to flow rate. These standard primary flow meters have been proven accurate if installed and constructed according to established standards. Continuous flow measurement systems typically consist of a primary flow meter, flow sensor, transmitter, flow recorder, and accumulator.

[0008] Among existing technologies, the Parshall flume is the most reliable wastewater flow measurement device. The Parshall flume is an open channel flow metering device developed to measure free surface flow. In physics, free surface flow describes the situation where a fluid flows partially within a conduit, with the flowing fluid surface simultaneously subjected to zero vertical normal stress and parallel shear stress. Free surface flow is set up as a fixed hydraulic structure and is used to measure the volumetric flow rate of inflows / outflows in industrial emissions, municipal sewage pipes, and wastewater treatment plants. Parshall flumes accelerate flow by contracting parallel sidewalls and lowering the bottom plate at the flume throat. Under free-flow conditions, the flow velocity can be calculated from the water depth at a designated location upstream of the flume throat. Parshall flumes are not patented. Discharge tables are publicly available information. If the flow rate exceeds the tank's flow capacity, submersion will occur, and the flow rate must be adjusted according to factors provided by the respective manufacturer. If submersion occurs exceeding the manufacturer-specified limits, point measurements must be taken at both the primary and secondary measurement points, and submersion corrections must be applied to the flow equation. It is important to note that the secondary measurement point (Hb) of a Parshall flume is located in the throat. Measuring Hb can be difficult because the flow rate in the flume throat is turbulent and susceptible to water level fluctuations. A 90% adjustment is considered the practical upper limit for correcting for submerged flow. Due to the geometry of the Parshall flume, sediment may accumulate and scavenging is necessary to obtain accurate readings.

[0009] Among existing technologies, the Parshall flume is considered the most reliable system and is widely used in wastewater treatment plants in the United States. For online flow measurement (such as sewer collection systems), the Parshall flume is placed in the basement. This placement is cumbersome because it requires frequent inspection and removal of sediment.

[0010] To replace manual reading of flow depth, flow sensors can be installed to measure the hydraulic response of a primary flow measurement device and transmit these responses to a recording system. Typically, sensors include ultrasonic transmitters, floats, pressure transducers, capacitive probes, differential pressure batteries, and electromagnetic batteries. Sensor signals are generally converted into flow units using mechanical, electromechanical, or electronic systems, either directly recorded on graphs or transmitted to a data system. Systems utilizing recorders are generally equipped with flow accumulators that display the total flow rate in real time.

[0011] Many flow measurement devices are contact-type continuous flow measurement systems, which have sensors immersed in the wastewater flow. These sensors are susceptible to damage and / or reduced reliability and accuracy due to deposits that accumulate on them. Therefore, these sensors require frequent cleaning, maintenance, and even repair and replacement. In addition to traditional Parshall flumes, several non-contact flow meter sensors are available on the market. These sensors operate within access ports and include velocity laser sensors and depth sensors. These sensors derive the flow rate by measuring depth (area) and multiplying it by the measured velocity. Using depth-velocity flow sensors has several disadvantages: (1) The velocity obtained by the depth-velocity flow sensor may be inaccurate and not equivalent to the average velocity of the sewage flow in the duct. (2) The depth-velocity flow sensor is ineffective for inspection ports with increased flow rates. (3) Measurements will be interrupted during maintenance. (4) High maintenance costs, and (5) When the sensor is installed in an open chamber and / or access hole, lens condensation is difficult to reduce. Most importantly, all existing flow meters measure free surface flow, but cannot measure pressure flow. Summary of the Invention

[0012] This invention is embodied as an online metering station for measuring both free surface flow rate and pressure flow rate in underground fluid conduits. Some advantages of this invention include: (a) no physical contact with the fluid in the conduit is required; (b) it operates under both laminar and turbulent conditions; (c) it provides continuous flow measurement; (d) it provides remote data transmission to a central control room or mobile device for real-time access; (e) it detects pipe deposits; (f) it performs calculations and adjustments; and (g) it alerts users to cleaning and maintenance. Furthermore, embodiments of this invention are not interrupted by sewer cleaning and are not limited by sewer flow velocity, depth, or Froude number.

[0013] This preferred system comprises a pair of risers (or “pipes”) mounted on top of a buried underground conduit. A ranging sensor, used to measure the distance between the sensor and the surface of the fluid flowing below the sensor (“sensor-fluid distance”), is located on top of each riser. The sensor-fluid distance can be used to determine the flow depth. In this way, the sensor-fluid distance can indicate that the conduit is in a free surface flow state (the conduit is not full). Alternatively, the sensor-fluid distance can indicate that the conduit is in a pressure flow state (the conduit is full). Knowing the sensor-fluid distance at both locations at the same time point is important because these two data points can be used to determine the free surface flow rate and the pressure flow rate when combined with completion conditions and friction loss equations in the art. The risers are preferably oriented perpendicular to the apex of the underground conduit. It is important to keep the ranging sensor away from the conduit to prevent condensation from forming on the sensor's lens. Therefore, each riser is preferably at least 3 feet long. An optional dehumidifier system can also be used. A preferred dehumidifier system includes a humidity sensor, a dehumidifier, and recirculation piping to prevent condensation from forming on the sensor's lens. Preferably, the two risers are located between two access ports. Each riser should be located close to the access port, but at a distance that prevents flow interruptions and / or backflow from the access port within the duct section measured by the riser. Typically, this distance is at least 100 feet. There should be no lateral inflow, longitudinal pipe slope changes, horizontal changes, and / or pipe size / material changes between the risers. The two risers should be separated from each other to allow for calculation of energy losses between them. Typically, the two risers should be spaced 10 times the inverse of the duct slope or 100 feet apart, whichever is longer. The ranging sensor is preferably housed in an instrument compartment at the top of each riser. This instrument compartment may also include other sensing devices, recording devices, transmission devices, and other auxiliary equipment. Preferably, the system operates as follows: • The data logger records the sensor-fluid distance measurements at each of the two risers, with timestamps. • The transmitter sends recorded data wirelessly or via wired connection to a remotely located data processor.

[0014] • The data processor uses recorded data received from the transmitter to calculate the actual flow rate and velocity of the fluid. This calculation is performed using well-documented and tested friction loss equations. In this way, the preferred system can provide an automated monitoring system for measuring fluid flow rate within a duct without requiring contact with the flow. A key benefit of this invention is the ability to provide continuous flow measurement over long periods in underground conduits, regardless of flow performance, whether on a free surface or fully submerged. Another key benefit is that actual flow data is available to municipalities and sanitation districts (“stakeholders”) to use the EPA’s Storm Flood Management Model (SWMM) to manage their sewer systems. Actual flow data collected from key sewage lines throughout the sewage basin is crucial for calibrating the SWMM and establishing daily flow curves based on population and development type. With better modeling, stakeholders can identify deficient areas and plan for the expansion of sewage lines and wastewater treatment plants. Attached Figure Description

[0015] The key features of the invention summarized above can be clearly understood by referring to the accompanying drawings illustrating the methods and systems of the invention. It should be understood that such drawings depict preferred embodiments of the invention, and therefore should not be considered as limiting the scope of other embodiments conceivable by the invention. Therefore: Figure 1 A preferred embodiment of the present invention is shown, comprising two risers connected to an underground conduit.

[0016] Figure 2 An embodiment of a single riser with an instrumentation chamber accommodating a ranging sensor is shown.

[0017] Figure 3 An embodiment is shown in which a hole is cut through the apex of the conduit and a saddle flange is installed.

[0018] Figure 4 The opening for receiving the riser is shown via a saddle flange.

[0019] Figure 5 The full pipeline riser saddle is shown.

[0020] Figure 6 Part of the pipe saddle is shown.

[0021] Figure 7 An implementation scheme for mounting a sensor on a riser using a flange is shown.

[0022] Figure 8 A side section view of one embodiment of the placement of the ranging sensor in the riser is shown, along with the importance of the riser diameter.

[0023] Figure 9 A cross-sectional view of one embodiment of the placement of a ranging sensor in a riser is shown, along with the importance of the riser diameter.

[0024] Figure 10 A side cross-sectional view of another embodiment of the placement of the ranging sensor in the riser is shown, highlighting the importance of the riser diameter, where moving the sensor further below the riser keeps the emitted beam width at the top of the duct smaller.

[0025] Figure 11 A cross-sectional view of another embodiment of the placement of the ranging sensor in the riser is shown, highlighting the importance of the riser diameter, where moving the sensor further below the riser keeps the emitted beam width at the top of the duct smaller.

[0026] Figure 12 An implementation scheme for a sensor housing a compartment is shown. Figure 13 A side cross-sectional view of an embodiment of a sensor housing a compartment is shown. Figure 14 A cross-sectional view of the sensor housing the compartment is shown. Figure 15 The hydraulic symbols used in the hydraulic flow equation are shown.

[0027] Figure 16 The conditions for an open channel (free surface) are shown.

[0028] Figure 17 The pressure and flow rate (pipe full) conditions are shown.

[0029] Figure 18 The conditions for flow continuity are shown.

[0030] Figure 19 An implementation scheme of a preferred communication flow between devices, computers, and stakeholders in an instrument room located at the first and second risers is shown.

[0031] Figure 20 shows a preferred dehumidifier system.

[0032] Figure 21 shows an example of wastewater flow rate (MGD) versus time (hours).

[0033] Figure 22 illustrates Snell's law.

[0034] Figure 23 illustrates the application of Snell's Law to flight paths. Detailed Implementation

[0035] Figure 1 An embodiment of the preferred system 10 is shown. In a broader sense, the preferred system 10 includes a first riser 20 and a second riser 30. At their bottom (or “far end”), the first riser 20 and the second riser 30 are each connected to an underground conduit 40. At the top (or “proximal end”) of each riser 20, 30 is an instrument compartment (or “housing”) 50. Instrumentation 50 preferably houses sensors and a processor for measuring, verifying, recording, and calculating the flow depth in the underground conduit 40 below each riser 20, 30. As previously mentioned, the distance sensor is crucial to the invention. In short, the distance sensor measures the distance to the liquid level (free flow) in the underground conduit 40 or to the liquid level (pressure flow) in the risers 20, 30. The preferred ranging sensor 60 is an optical measuring device, preferably an ultra-accurate laser or ultrasonic proximity meter. The preferred ranging sensor 60 emits an infrared laser from its emitting sensor, which is reflected from the liquid surface in the conduit 40 and then returns to the sensor's receiving lens. The precise distance is then calculated by comparing the return time (“time offlight”) with the speed constant of light. For example, the optical measuring device sold under the trademark TruSense, model S-300, has been found suitable for this purpose. Those skilled in the art will recognize other suitable measuring devices. The choice between the two is based on the distance that must be measured. The ranging sensor 60 is preferably made of a corrosion-resistant and water-resistant material (such as IP67 protection (prevents water ingress at a depth of 15 cm to 1 meter for 30 minutes)).

[0036] The ranging sensor 60 preferably records timestamps of the travel time (or "time of flight") of the light beam from its emission onto the flow surface, its reflection from the flow, and subsequently received by the sensor. Of particular interest are the following two times of flight: the first time of flight between the ranging sensor 60 and the underlying fluid surface; and the last time of flight between the ranging sensor 60 and the bottom of the conduit 40 or the top of the deposit at the bottom of the conduit 40 (whichever is higher).

[0037] Similarly, the following two distances are of most interest. The first optical distance 62 is the distance from the ranging sensor 60 to the fluid surface below (see...). Figure 15 (H11 in the text). The second optical distance 66 is the distance from the measuring sensor 60 to the bottom of the fluid (see H11 in the text). Figure 15 (H10 in the diagram). If there is no deposit at the bottom of the conduit 40, the second optical distance 66 will be equal to the completion distance. If there is deposit at the bottom of the conduit 40, the second optical distance 66 will be less than the completion distance.

[0038] To obtain the flow depth 64 within conduit 40, the user will subtract the first optical distance 62 from the completed distance. To obtain the depth of sediment, the user will subtract the second optical distance 66 from the completed distance. The presence of sediment may require cleaning the sewer or adjusting the flow depth.

[0039] Preferred steps for determining flow depth and sediment depth: 1. Connect the bottom end of the riser to the underground conduit. 2. Orient the riser so that it is perpendicular to the apex of the conduit. 3. Connect the measurement sensor (e.g., TruSense, model S-300) to the top. 4. Program the sensor's interface software for RS-232 SCII commands used for WIFI transmission and communication, including timestamped readings of the first and last flight times.

[0040] 5. Collect consecutive first and last flight time readings for the first 72 hours after the sewer is cleaned. 6. For a given timestamp, the time of the first flight - the time of the last flight = the flight time spent traveling in the water.

[0041] 7. Taking into account the fatigue reflection angle at a specific time, the speed of Vw in water = water depth / (time spent in water / 2) 8. The first flight time reading is the travel time from reaching below the fluid surface to returning (2*(H11)). Figure 15 Furthermore, the distance can be calculated using the equation D=v*T / 2 based on the first flight time reading. 9. The last flight time reading is the flight time (2*H10) from the bottom of the duct (or the top of the deposit in the duct, if present) to the return.

[0042] 10. If (last flight time reading – first flight time reading) / (2 * Vw) is less than (H10 - H11), then sediment is present. The sediment thickness can be approximated as (H10 - H11) - (last flight time reading – first flight time reading) / (2 * Vw). Wastewater exhibits a seasonal pattern with fixed and known periods. However, 24-hour wastewater flow rates reflect a close similarity between diurnal ratios and time curves. (Figure 21) Periodic patterns exist in wastewater flow rates, with a distinguishable pattern between peak summer water usage and off-peak winter water usage. The first and last time-of-flight readings, taken after cleaning sewer sediment between risers, provide baseline conditions with no sediment.

[0043] The verification and comparison of the last flight time reading is based on Snell's Law (Figures 22 and 23, also known as the Snell-Cartesian Law and the Law of Refraction), which is a formula used to describe the relationship between the angle of incidence and the angle of refraction when referring to light or other waves passing through the boundary of two different isotropic media such as water, glass, or air. Therefore, the last reading time based on Snell's Law includes the beam penetrating the water surface, being deflected at the air / water interface, being reflected from the bottom, being deflected again at the water / air interface, and reaching the sensor receiver. Snell's law states that the ratio of the sines of the angle of incidence to the sines of the angle of refraction is equal to the ratio of the phase velocities in the two media, or equal to the reciprocal of the ratio of their refractive indices. sinθ2 / sinθ1 = v2 / v1 = n1 / n2 Where each θ is the angle measured from the normal to the boundary, v is the speed of light in the corresponding medium (SI units are meters per second or m / s), and n is the refractive index of the corresponding medium (unitless).

[0044] The deposits are generally more viscous, softer, more irregular, and more porous than the bottom of the plastic conduit. The deposits most likely at the bottom absorb the majority of the beam, with almost no reflection. However, using a beam diffuser, the reflections can cover a larger area at the bottom, potentially producing enough reflected beams for a final reading. like Figure 19 As shown, sensor data as small as 10 milliseconds can be collected when necessary. Timestamped data can be transmitted wirelessly or via a physical connection to a control center for processing to generate real-time flow and velocity data. The data and the resulting calculations can be transmitted to mobile devices such as smartphones on-site. In this way, stakeholders can receive this real-time flow data to manage their sewer systems. Figure 3 A preferred method for attaching the riser to the conduit is shown. As shown, the apex 100 of the exposed conduit 40 is marked, and the apex elevation is recorded with reference to the culvert bottom elevation of the adjacent inspection port. Preferably, these measurements are performed by a certified surveyor. Next, a core drill bit size 104 matching the riser mount size 108 is selected. The core drill rig is mounted, centered at apex 100. The culvert is cored, and a section of the culvert is removed. The thickness of the culvert section is measured to determine the thickness of the conduit 40. Next, install the commercially available or custom-made connector saddle 112. This can be a full-pipe riser saddle (see [link]). Figure 5 ) or part of the pipe saddle ( Figure 6Preferably, the saddle is adhered to the culvert bore 110 with a hydrogen sulfide anti-corrosion adhesive (or other suitable waterproof adhesive) to secure the saddle firmly to the conduit. Those skilled in the art will recognize other methods of drilling holes in the conduit and connecting the riser.

[0045] Figure 7 A preferred mounting assembly for the distance sensor 60 is shown. The preferred method for mounting the distance sensor 60 to the top of the riser is with a sealed flange to prevent odor release into the air.

[0046] Return to reference Figure 1 Riser pipes 20 and 30 are oriented perpendicular to the apex of conduit 40, preferably within + / - 3 degrees of the vertical direction. The risers are vertically mounted on conduit 40, such that the beam 80 of the ranging sensor 60 (see...) Figure 15 The slope of the conduit 40 is perpendicular to that of the conduit 40. This setup should optimize the reflection of the light beam from the fluid flow within the conduit 40 to the receiver of the sensor 60 for accurate distance measurement. The diameters of risers 20 and 30 should be sized such that (1) the emitted laser / ultrasonic beam 80 of the ranging sensor does not contact the inner wall of the riser (see...). Figure 8 (2) The first reflected beam (opposite to beam 80) can travel directly back to the sensor's receiver to determine the correct distance between the ranging sensor lens and the fluid surface. Figure 15 ).

[0047] Preferably, each riser 20, 30 is at least 3 feet long. There is no limitation on the possible riser lengths. Sewer pipes are typically buried 4 to 30 feet below the surface. However, this invention can be used to measure other gravity / pressure flows, such as irrigation water, rainwater, and raw water buried at depths ranging from barely covered to 600 feet deep, such as the water pipelines in New York City that transport lake water from hundreds of miles away. The usable length of riser 20 and 30 depends on the accuracy of the sensor installed in the pipe. Some sensors can measure with an accuracy of 0.01 mm at distances up to 12 inches, while others can measure with an accuracy of + / - 0.4 inches at distances up to 600 feet. The available pipe diameter depends on the sensor's radiometric intensity. Figures 8 to 11 As shown, the beam width from the ranging sensor 60 increases as the beam moves away from the beam source (emitter). The diameter of the tube must be large enough so that the beam does not contact the tube wall. For example, compare... Figures 8 to 9 and Figures 10 to 11 The design should set the sensor elevation and riser diameter according to the sensor manufacturer's specifications. Optionally, the ranging sensor 60 may have a diffuse lens. The diffuse lens provides a wider contact area 82, which offers better ground disturbance coverage for the second and third return time measurements. However, as... Figure 8 As shown, a diffuser lens typically increases the beam width by 82. Therefore, in situations where a diffuser lens can be used, it may be necessary to adjust the riser diameter to accommodate the correspondingly wider beam width 82. Alternatively, as... Figures 10 to 11 As shown, the ranging sensor 60 can be located below the ground and closer to the conduit to keep the beam within the inner diameter of the risers 20 and 30.

[0048] It is important to keep the measuring sensor 60 away from the conduit 40 to prevent condensation from forming on the lens of the distance sensor 60. Optionally, a dehumidification system can be used. As shown in Figure 20, a preferred dehumidification system is connected to risers 20 and 30 near the distance sensor 60. Preferably, the dehumidifier system includes two humidity sensors 120 and 124, a dehumidifier 128, and a recirculation pipe 132 to prevent condensation from forming near the lens of the distance sensor. The first humidity sensor 120 should be placed near the distance sensor. The second humidity sensor 124 should be placed at the intake end of the recirculation pipe 132. The recirculation pipe 132 should be positioned such that the intake end is away from the sensor and the exhaust end is close to the bottom of the distance sensor, with wastewater droplets being directed through a drip outlet 136 to a perforated pipe 140 outside the instrument compartment 50. As shown, a carbon filter 142 and pebbles 144 can also be used.

[0049] Instrument Room like Figures 12 to 14 As shown, the instrument room 50 is preferably a watertight utility storage facility that meets the regulatory requirements for installation on HS-20 traffic-loaded pavement. In addition to the distance sensor 60, the instrument room 50 preferably also houses a field processor 90, a memory 92, and a database 94 (see [reference]). Figure 19 The flow rate is calculated using the timestamps from flow depth measurements, known pipe bottom elevation, slope, distance between sensors, and conduit material. Alternatively, the instrument room may house a transmitter to transmit data to a remote processor and database. Preferably, information is transmitted via a wireless network 96, but hardwired transmission is also possible. Optionally, the instrument room 50 may house other auxiliary equipment.

[0050] Preferably, risers 20 and 30 are located between two access ports 22 and 32. Each riser should be located close to the access port but at a distance such that there is no flow interruption and / or no backflow from the access port in the conduit section measured by the riser. Importantly, there should be no lateral inflow, no change in longitudinal pipe slope, and no change in pipe size / material between the two risers. The two risers 20 and 30 should be separated from each other to calculate the energy loss between the two risers. Typically, the two risers should be spaced at least 100 feet apart or 0.1 times the inverse of the conduit slope, whichever is longer. Preferably, the distance between the two risers should not exceed 1000 feet. The distance between risers 20 and 30 is 42 (see...) Figure 1 The distance 44 between risers 20, 30 and adjacent access holes 22, 32 can be accurately determined through ground measurements and / or as-built drawings. Figure 1 The distance must be set large enough that no eddies and / or vortices from the access port can propagate to the riser. Preferably, this distance is at least 5 feet. There should be no lateral pipe changes and / or changes in conduit size between the risers. This is to ensure that longitudinal friction loss is the only form of energy loss between the two risers. Under these conditions, the only energy loss of the fluid between the two risers comes from friction. Therefore, calculating friction yields the energy loss between the two risers. This can be done using the energy equation and the continuity equation. Friction can also be used to calculate flow rate.

[0051] As an example, for a pipeline operating at full capacity (pressure flow), friction losses can be calculated using the Reynolds number of the Darcy friction factor based on turbulent and laminar flow in the Moody diagram or the Hazen-Williams empirical C value. Similarly, for pipes not operating at full capacity (free surface), friction losses can be calculated using the Körbruck formula, another friction factor based on Reynolds for turbulent and laminar flow, or the Manning N value for uniform flow on a free surface.

[0052] Exemplary hydraulic analysis of flow measurement systems Note: Figures 15 to 18 It is an analytical graph depicting the detailed flow rate and velocity described below.

[0053] use Figure 15 The dimensions shown, at the first riser 20, the distance (H10) 66 from the sensor to the inner bottom of the conduit can be obtained by summing the distance from the ranging sensor 60 to the conduit apex (H1a) 68, the conduit thickness (T), and the conduit diameter (D), as shown in the following equation: H10 = H1a + T + D (Equation 1) The flow depth (Y1) 64 at the first riser 20 can be calculated by subtracting the distance from the sensor to the water (H11) from the distance from the sensor to the bottom of the conduit (H10) 66, as shown in the figure. Y1 = H10 - H11 (Equation 2) Similarly, at position 30 of the second riser, H20 = H2a + T + D (Equation 3) Y2 = H20 – H21 (Equation 4) The apex elevation is recorded by a certified surveyor with reference to the bottom elevation of the culvert pipe in adjacent inspection holes (see [reference]). Figure 16 ),from Figure 3 The benchmark is derived from Z1 = Elevation of the top of riser No. 1 - T - D Z2 = Elevation of the top of riser No. 2 - T - D Flow rate is obtained: The flow rate is derived from the energy equation at the two risers (20, 30), which will be balanced by the flow friction loss in the conduit from the first riser 20 to the second riser 30. Frictional loss of free surface flow ( Figure 16 The value can be determined by using the Manning n-value, the Moody diagram of free surface flow, or a friction factor equation based on the Reynolds number (such as the Swamee-Jain equation). Frictional loss in full pipe flow ( Figure 17 Friction factors can be derived from factors such as the Moody diagram, which covers friction factors for both turbulent and laminar flow, the Hayzen-Williams C value, and other established empirical friction factors. The velocity is derived from the continuity equation Q = V * A.

[0054] The computational Bernoulli equation can be used for both steady and unsteady flows. For example, the distance between the first riser 20 and the second riser 30 is less than 600 feet, and most sewer systems are designed for flows between 2.75 fps and 4 fps, corresponding to flow times of less than 3.5 minutes. The flow rates derived from applying the steady-flow and unsteady-flow equations may show slight differences at the recorded timestamps. However, this difference is not significant when plotting hydrographs and / or total flows over a full 24 hours. The following demonstrates that by using the steady-flow equations to derive flow rates, these equations require less processing time when the timestamp interval is as small as 10 milliseconds. Nevertheless, if the unsteady-flow equations provide better user comfort, this invention can also utilize them.

[0055] Free surface flow (open channel) when Y1<D and Y2<D, Figure 16 A. Bernoulli's equation for friction with Manning's n-value (steady laminar flow) (Equation 5) E1 = E2 – HL E1 = energy at standpipe 30 E2 = energy at standpipe 20 HL = head loss from standpipe 20 to standpipe 30 (Equation 6) E1 = datum Z1 + hydraulic depth (Y1 at standpipe 30) + velocity head (V1 at standpipe 30 2 / 2g) E2 = datum Z2 + hydraulic depth (Y2 at standpipe 20) + velocity head (V1 at standpipe 20 2 / 2g) HL = length (from standpipe 20 to standpipe 30) * friction slope The friction slope can be expressed by the Manning's n-value equation.

[0056] The friction slope over the flow length is the average of the friction slopes at standpipe 20 and standpipe 30.

[0057]

[0058] (Equation 7) Equation 6 is simplified by putting the unknown on the left side of the equation for equation solving.

[0059]

[0060] (Equation 8) Equation 7 is simplified by introducing a specific K-number of variable hydraulic parameters (A1, RH1 and RH2) to solve the equation

[0061]

[0062]

[0063]

[0064] Solve for the following:

[0065]

[0066]

[0067] B. Darcy–Weisbach friction factor for frictional losses between risers A free surface exists in the form of the Colbrook-White equation. Such conditions can exist in pipes where the fluid is partially filled. For the free surface flow rate: its estimate of the free surface flow rate... f This parameter is valid for all flow regimes (laminar, transitional, and turbulent), as detailed below: (Equation 9)

[0068] Where a is:

[0069] And b is:

[0070] in Re h Let be the Reynolds number, where h The characteristic hydraulic length (hydraulic radius of 1D flow or water depth of 2D flow), and R h The radius is the hydraulic radius (1D flow) or the water depth (2D flow). The Lambert W function can be calculated as shown below.

[0071] (Equation 10) The Lambert W function in Equation 9 can be calculated as follows:

[0072] C. Swami and Jain developed the following simplified equation for the Darcy friction factor. (Equation 11)

[0073] in ƒ Darcy friction factor e Pipe roughness D Pipe inner diameter Re Reynolds number Pressure and flow rate (pipe full) when Y1>D and Y2>D ( Figure 17 ) A. Darcy-Weisbach equation for friction loss between risers using Moody diagrams The total energy loss (dh) between riser 1 and riser 2 is the total energy at riser 2 (E2) minus the total energy at riser 1 (E1), as shown in the following equation: dh = E2-E1

[0074] Friction gradient is the head loss over the entire length, as shown in the equation below.

[0075] The Darcy-Weisbach equation for friction loss is obtained using the Moody diagram, as shown below. (Equation 12)

[0076] (Equation 13)

[0077] Combine equations (11) and (12) (Equation 14)

[0078] When the pipe material is known, the absolute roughness can be found in the material absolute roughness table published by the manufacturer.

[0079] Relative roughness (k / D) = (Absolute roughness / 1000 / (pipe diameter * 0.3048)) Find the specific density and temperature of the liquid in the conduit from the physical property table. v (Kinematic viscosity) Assume the coefficient of friction is f And the flow rate Q is solved using Equation 14. Find the corresponding Reynolds number from the equation shown below. ReD=VD / v Find the corresponding friction factor from the Moody diagram using the Reynolds number. f。 ( Figure 10 ) Repeat equations c and d until f converges.

[0080] Flow rate (Q) = V (velocity) * pipe area Flow rate = Q / A B. Bernoulli's equation for friction using the Heizen-Williams C-value (steady laminar flow) (Equation 15)

[0081] = Frictional head loss of water from riser 2 to riser 1, in feet. c = Hezen-Williams roughness constant q = Volumetric flow rate (gallons / minute) dh = Hydraulic inner diameter (inches).

[0082] Example 1 — Open Channel Flow

[0083] Open channel - Y < pipe diameter

[0084] Solve Q

[0085] Solve the Q equation

[0086] Example 2 — Pressure Flow Rate

[0087] Through the Hayzen-Williams formula

[0088] via Darcy Weisbach

[0089] While various embodiments have been described above, it should be understood that these embodiments are presented by way of example only and not limitation. Therefore, the breadth and scope of preferred embodiments should not be limited to any of the exemplary embodiments described above, but should be defined only by the following claims and their equivalents.

Claims

1. An online metering station for measuring free surface flow rate or pressure flow rate located in an underground conduit, the online metering station comprising: A first tube located underground, the first tube including a distal end and a proximal end, the distal end of the first tube being connected to the underground conduit, the first tube being oriented perpendicular to a first apex of the underground conduit. A second tube located underground, the second tube including a distal end and a proximal end, the distal end of the second tube being connected to the underground conduit, the second tube being oriented perpendicular to a second apex of the underground conduit. The first and second pipes are each at least three feet long. The first pipe and the second pipe are located between the two access ports of the underground conduit, and at least 5 feet away from each adjacent access port. A first optical measuring device, connected to the proximal end of the first tube, is configured to measure a first distance through the first tube to the first liquid level. A second optical measuring device, connected to the proximal end of the second tube, is configured to measure a second distance through the second tube to the second liquid level, and The first pipe and the second pipe are separated by a third distance, said third distance being at least 100 feet. The first distance, the second distance, and the third distance can be used in conjunction with a set of completion conditions to calculate the free surface flow rate or the pressure flow rate of the fluid flowing in the underground conduit.

2. The online metering station according to claim 1, further comprising an instrument room connected to the proximal end of the first tube, the instrument room accommodating a communication device connected to the first optical measuring device and the second optical measuring device.

3. The online metering station according to claim 1, wherein the online metering station further comprises a dehumidifier system connected to the proximal end of the first pipe or the second pipe.

4. The online metering station according to claim 3, wherein the dehumidifier system further includes a humidity sensor and a recirculation pipeline.

5. The online metering station according to claim 2, wherein the online metering station is accessed from the ground.

6. The online metering station according to claim 1, wherein the first liquid level is located inside the first pipe.

7. The online metering station according to claim 1, wherein the first optical measuring device is further configured to measure the distance between the first optical measuring device located in the underground conduit and the sediment level.

8. The online metering station according to claim 1, wherein the first optical measuring device includes an emitted light beam, the emitted light beam including a width at the top of the underground conduit, the width being smaller than the inner diameter of the first conduit.

9. The online metering station according to claim 1, further comprising an inspection hole, the inspection hole being positioned at a fourth distance from the first pipe, the fourth distance being at least five times the diameter of the underground conduit from the inspection hole.

10. The online metering station according to claim 1, wherein the underground conduit includes a uniform inner diameter located between the first pipe and the second pipe.

11. The online metering station according to claim 1, wherein the underground conduit is not connected between the first pipe and the second pipe.

12. The online metering station according to claim 1, wherein the underground conduit has no slope change between the first pipe and the second pipe.

13. The online metering station according to claim 1, wherein the underground conduit further includes a uniform inner surface roughness located between the first pipe and the second pipe.

14. A method for measuring free surface flow rate or pressure flow rate in an underground conduit, the method comprising, A first distance is measured to reach a first liquid level through a first pipe, the first pipe including a distal end and a proximal end, the distal end of the first pipe being connected to the underground conduit, and the first pipe being oriented perpendicular to a first apex of the underground conduit. A second distance is measured to reach a second liquid level through a second pipe, the second pipe including a distal end and a proximal end, the distal end of the second pipe being connected to the underground conduit, the second pipe being oriented perpendicular to a second apex of the underground conduit, and both the first and second pipes having a length of at least three feet. The completion conditions are determined, including the slope of the underground conduit, the cross-sectional area of ​​the underground conduit, the distance between the first and second conduits being at least 100 feet, and the surface material inside the conduit. Calculate the free surface flow rate or the pressure flow rate of the liquid flowing in the underground conduit.

15. The method of claim 14, further comprising reporting the free surface flow rate or the pressure flow rate to stakeholders.

16. The method of claim 14, further comprising calculating the depth of sediment located in the underground conduit.

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