Non-full pipe culvert flow measurement method, system and device

Abstract

The present application relates to a kind of non-full pipe culvert flow measurement method, system and equipment, it is related to fluid flow measurement technology technical field.The present application adopts insertable ultrasonic Doppler detection mode, integration liquid level probe synchronously acquires flow velocity and liquid surface height, according to the different liquid level working condition of circular culvert calculation overflow section area, and then obtain real-time flow.The present application installation does not need to break pipe, does not affect normal operation on site, strong anti-interference ability, can adapt to high turbidity, complex water body environment with impurities, equipment has no mechanical wear, operation and maintenance are convenient, effectively solve the accurate measurement problem of power plant non-full pipe culvert flow, applicable to the flow online detection of power plant warm discharge culvert and the like scene.

Description

Technical Field

[0001] This invention relates to the field of fluid flow measurement technology, and particularly to a method, system, and device for measuring the flow rate of a non-full-pipe culvert. Background Technology

[0002] Flow measurement in culverts is a crucial technical area for hydraulic monitoring and water environment protection in power systems. It primarily involves the online metering and control of parameters such as velocity and flow rate during the discharge of circulating cooling wastewater from power plants through concrete culverts. Accurate and stable flow detection is a prerequisite for efficient operation and maintenance of culvert drainage and precise assessment of its water environment impact. Current mainstream measurement methods mainly rely on traditional full-pipe measurement equipment such as clamp-on ultrasonic sensors, Parshall flumes, orifice plates, and nozzles, combined with fixed cross-sectional parameters to calculate flow data. This approach has the following drawbacks: 1. Limitations in adaptability to operating conditions and insufficient accuracy: Traditional measuring equipment is only suitable for full-flow conditions in pipelines. Power plant culverts are mostly in a semi-full or variable-level non-full-pipe state. Various conventional instruments are easily affected by liquid level fluctuations, resulting in large measurement errors and data distortion, and cannot achieve accurate measurement.

[0003] 2. Weak environmental resistance and limited applicable scenarios: Existing solutions are susceptible to interference from fluid conductivity and viscosity. When faced with the high turbidity and impurities in the water environment of power plant wastewater, signal anomalies and data drift are likely to occur, resulting in poor overall environmental adaptability.

[0004] 3. Complex construction and operation and maintenance and significant impact on production: Traditional equipment installation requires cutting off pipelines and shutting down production for construction, resulting in high modification costs; the equipment suffers from mechanical wear and blockage, and daily maintenance also requires water outages, which is not conducive to the continuous and stable operation of the power plant. Summary of the Invention

[0005] This application proposes a method, system, and equipment for measuring the flow rate of a non-full-pipe culvert. The aim is to provide a method for measuring the flow rate of a non-full-pipe culvert, addressing the shortcomings of existing technologies such as poor adaptability to operating conditions, low measurement accuracy, weak environmental interference resistance, cumbersome construction and maintenance, and disruption to normal production. The goal is to construct a precise, stable, and easily deployable online monitoring system.

[0006] To achieve the above objectives, the present invention provides a method for measuring the flow rate of a non-full-pipe culvert, comprising the following steps: S1: Measure the liquid level height inside the culvert pipe using an integrated liquid level measurement probe; S2: Based on the correspondence between the liquid level height and the radius of the culvert pipe, classify the corresponding liquid level conditions; S3: Based on the liquid level conditions, a fixed frequency ultrasonic wave is emitted into the fluid in the culvert using an insertion ultrasonic Doppler sensor. The sound velocity of the fluid in the culvert and the angle between the direction of sound wave propagation and the direction of fluid flow are measured. The fluid flow velocity is calculated based on the Doppler frequency shift generated by the reflection of particles in the fluid in the culvert. S4: Based on the current liquid level conditions, calculate the real-time flow cross-sectional area of ​​the culvert using a matching calculation method, and calculate the real-time flow rate in the culvert by multiplying the fluid velocity by the real-time flow cross-sectional area.

[0007] Furthermore, the fluid velocity is calculated using the Doppler frequency shift generated by the reflection of particles in the fluid within the culvert: The insertion-type ultrasonic Doppler sensor emits ultrasonic waves of a fixed frequency into the fluid. The ultrasonic waves are reflected by solid particles or bubbles in the fluid, resulting in a frequency shift. The frequency shift is proportional to the fluid flow rate. The fluid velocity is calculated by combining the ultrasonic emission frequency, the angle between the sound wave propagation direction and the fluid flow direction, and the sound velocity in the fluid.

[0008] Furthermore, the corresponding liquid level conditions are divided as follows: When the liquid level is less than or equal to the cross-sectional radius of the culvert, it is set as the first liquid level condition. When the liquid level is greater than the radius of the culvert cross-section but less than the diameter of the culvert cross-section, it is set as the second liquid level condition. When the liquid level is equal to the cross-sectional diameter of the culvert, the culvert is in a fully full state, which is set as the third liquid level condition.

[0009] Furthermore, the calculation of the real-time flow cross-sectional area of ​​the culvert pipe using a matching calculation method based on the current operating conditions is as follows: When the current operating condition is the first liquid level condition, the flow cross-sectional area is calculated using the arc area formula; When the current operating condition is the second liquid level condition, the flow cross-sectional area is obtained by subtracting the arc-shaped area of ​​the unfilled area above from the complete circular area of ​​the culvert pipe. When the current operating condition is the third liquid level condition, the cross-sectional area of ​​the flow is taken as the area of ​​the complete circle of the culvert pipe.

[0010] Furthermore, the arc-shaped flow area under all liquid level conditions adopts the same trigonometric function calculation basis, and the inverse cosine function is uniformly calculated in radians. At the boundary where the liquid level is equal to the radius of the culvert, the calculated cross-sectional area values ​​for the two working conditions—half full and below, and above half full—are continuous without abrupt changes, thereby eliminating the calculation deviation caused by the switching of working conditions.

[0011] Furthermore, the installation location of the insertion-type ultrasonic Doppler sensor is selected in the straight pipe area of ​​the culvert, satisfying that the length of the upstream straight pipe section is not less than ten times the inner diameter of the culvert, and the length of the downstream straight pipe section is not less than five times the inner diameter of the culvert. Furthermore, the measurement results of the non-full pipe culvert flow measurement method are not affected by the fluid conductivity and fluid viscosity, and can be applied to harsh fluid environments with high turbidity and containing various impurities.

[0012] Furthermore, the non-full-pipe culvert flow measurement method is applicable to flow measurement scenarios for large-diameter pipes or concrete culverts under low pressure and normal temperature environments.

[0013] Furthermore, the calculation of the arc area under all operating conditions adopts a unified trigonometric function calculation benchmark, and the inverse cosine function calculation uses radians to ensure that the flow cross-sectional area calculation results are continuous and without jumps at the boundary position where the liquid level is equal to the radius of the culvert pipe for operating conditions of half full and below and above half full, thus eliminating the calculation error caused by the switching of operating conditions.

[0014] The present invention also provides a flow measurement system for non-full pipe culverts, comprising: Liquid level acquisition module: used to acquire liquid level height data in the culvert pipe through an integrated liquid level measurement probe; Operating condition judgment module: used to classify different liquid level operating conditions based on the correspondence between the liquid level height and the radius of the culvert pipe; Flow velocity calculation module: Based on the liquid level conditions, it emits ultrasonic waves of a fixed frequency into the fluid in the culvert pipe through an insertion ultrasonic Doppler sensor, measures the sound velocity of the fluid in the culvert pipe and the angle between the sound wave propagation direction and the fluid flow direction, and calculates the fluid flow velocity based on the Doppler frequency shift generated by the reflection of particles in the fluid in the culvert pipe. The calculation output module is used to calculate the real-time flow cross-sectional area of ​​the culvert pipe according to the current liquid level conditions and the matching calculation method. It also calculates the real-time flow rate in the culvert pipe by multiplying the fluid velocity by the real-time flow cross-sectional area.

[0015] The present invention also proposes a flow measurement device for a non-full-pipe culvert, the device being capable of implementing the method described in any of the above-mentioned embodiments, comprising: An insertion-type ultrasonic Doppler sensor is used to emit ultrasonic waves into a fluid and receive the reflected echoes to obtain Doppler frequency shift signals. A liquid level measuring probe, integrated at the end of the device, is used to collect liquid level height data in the culvert pipe; The signal processing unit is electrically connected to the insertion-type ultrasonic Doppler sensor and the liquid level measuring probe, respectively, and is used to process the acquired signals and calculate real-time flow data.

[0016] The present invention provides a method, system, and device for measuring the flow rate of a non-full-pipe culvert, which has the following beneficial effects: 1. Strong adaptability to all liquid level conditions and excellent measurement accuracy: Based on the liquid level height, multiple liquid level conditions are divided and the corresponding flow cross-sectional area calculation logic is matched. It can adapt to non-full pipe states such as half-full and variable liquid level, solve the problem of non-full flow measurement distortion of traditional equipment, and ensure the measurement accuracy of all conditions.

[0017] 2. Good adaptability to complex water bodies and stable and reliable operation: Adopting the insertion ultrasonic Doppler velocity measurement principle, it is not limited by the conductivity and viscosity properties of the fluid, and can be adapted to water environments with high turbidity and silt impurities, effectively avoiding signal failure and data drift problems.

[0018] 3. Low deployment and maintenance costs, suitable for continuous production: The top-mounted installation structure eliminates the need to cut off pipelines or stop production for construction, reducing engineering modification costs; the equipment has no mechanical rotating parts, resulting in less wear and tear and less sludge buildup, allowing for long-term stable online operation. Attached Figure Description

[0019] Figure 1 This is a flowchart of a non-full pipe culvert flow measurement method according to the present invention.

[0020] Figure 2 This is a structural block diagram of a non-full pipe culvert flow measurement system according to the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0022] Reference Figure 1 The diagram below illustrates a flow chart of a non-full pipe culvert flow measurement method proposed in this invention, comprising the following steps: S1, measures the liquid level height inside the culvert pipe using an integrated liquid level measurement probe; S2, Based on the correspondence between the liquid level height and the radius of the culvert pipe, different liquid level conditions are classified; S3, based on the liquid level conditions, a fixed frequency ultrasonic wave is emitted into the fluid in the culvert pipe through an insertion ultrasonic Doppler sensor, the sound velocity of the fluid in the culvert pipe and the angle between the sound wave propagation direction and the fluid flow direction are measured, and the fluid flow velocity is calculated based on the Doppler frequency shift generated by the reflection of particles in the fluid in the culvert pipe. S4. Based on the current liquid level conditions, the real-time flow cross-sectional area of ​​the culvert is calculated using a matching calculation method. The real-time flow rate inside the culvert is then calculated by multiplying the fluid velocity by the real-time flow cross-sectional area.

[0023] As described in step S1 above, an integrated liquid level measurement scheme is used to achieve real-time acquisition of the liquid level height in the culvert. The acquired liquid level height data is fed back to the system in real time, and the system uses the liquid level height data to prepare for the division of working conditions in the next step. The liquid level probe and the ultrasonic Doppler sensor are integrated and installed in one piece, eliminating the need for a separate liquid level detection device, simplifying the on-site installation process, and ensuring that the liquid level data and flow velocity data are on the same spatial reference, eliminating the spatial matching error caused by separate installation.

[0024] As described in step S2 above, multiple liquid level conditions are classified based on the correspondence between liquid level height and pipe radius. Different flow cross-sectional area calculation methods are matched for different filling degrees to solve the problems of measurement distortion and excessive error of traditional full-pipe flowmeters in non-full-pipe conditions. At the same time, a unified trigonometric function calculation benchmark is adopted to ensure that the calculation results at the boundary of the operating condition are continuous without jumps, eliminate the calculation abrupt error caused by the switching of operating conditions, and improve the measurement stability across the entire range.

[0025] As described in step S3 above, fluid velocity detection is achieved using the insertion-type ultrasonic Doppler velocimetry principle. Suspended solid particles and bubbles in the fluid are used as reflection media, and the cross-sectional average velocity is calculated through the proportional relationship between frequency shift and flow velocity. This velocity measurement method is not limited by the conductivity and viscosity properties of the fluid, and can be adapted to complex water environments with high turbidity and many impurities, such as power plant thermal wastewater. It solves the problem of electromagnetic flowmeters and time-difference ultrasonic flowmeters failing in highly turbid wastewater. At the same time, the insertion-type installation structure does not require pipe disconnection and production shutdown, resulting in low construction costs and convenient operation and maintenance.

[0026] As described in step S4 above, by combining the real-time liquid level condition with the corresponding flow cross-sectional area calculation method, the flow velocity detection result and the cross-sectional area calculation result are coupled to obtain the instantaneous flow rate, thereby achieving accurate flow measurement in non-full pipe conditions. The cross-sectional area calculation is based entirely on the geometric principle of circular pipes, without the need for additional weirs or throttling devices, and will not increase pipe pressure loss. It is suitable for low-head drainage scenarios of large-diameter concrete culverts, taking into account both measurement accuracy and on-site adaptability.

[0027] In one embodiment, step S1, measuring the liquid level height inside the culvert pipe using an integrated liquid level measuring probe, includes: The liquid level measurement unit integrated into the sensor terminal emits ultrasonic detection signals vertically downwards; Receive the echo signal reflected from the liquid surface and calculate the sound wave propagation time difference; By combining the sound velocity in the water after correction for ambient temperature, the vertical distance from the probe to the liquid surface is calculated. Based on the preset installation reference height, the liquid level in the culvert pipe is calculated.

[0028] In specific implementation, the liquid level measuring probe and the plug-in ultrasonic Doppler sensor are integrated into an integrated detection rod, which is coaxially installed at the预留 installation position on the top of the culvert pipeline; the acoustic center of the liquid level probe and the acoustic center of the Doppler sensor are both arranged on the same vertical axis, so that the liquid level detection position and the flow velocity detection position are kept consistent, and the spatial detection deviation is eliminated. The liquid level measuring unit adopts the high-frequency ultrasonic reflection detection principle, and emits 200kHz narrow-pulse ultrasonic signals. This frequency takes into account both the water penetration capability and the ranging resolution, and can stably complete the signal reflection detection in the turbid water environment containing sediment.

[0029] During the detection process, the liquid level measuring unit vertically transmits ultrasonic pulse signals downward at a sampling frequency of 5Hz. The signals pass through the water body and are reflected when reaching the gas-liquid interface, and the echo signals are received by the probe; the system records the time difference between the transmission and reception of the ultrasonic signals , combined with the real-time corrected sound velocity of water body , the vertical distance from the end face of the probe to the liquid surface is calculated by the formula . Wherein, the sound velocity of the water body is corrected in real time according to the water temperature collected by the built-in temperature sensor. The correction formula follows the quadratic function relationship between the sound velocity of pure water and temperature, and at the same time, the sound velocity is compensated for the sediment-containing water body to ensure the accuracy of distance calculation.

[0030] The system stores the installation reference height parameter in advance, which is the vertical distance from the end face of the probe to the inner bottom of the culvert pipeline, and is written into the device memory through on-site calibration after the device installation is completed. By subtracting the distance from the probe to the liquid surface from the installation reference height, the liquid level height h in the culvert pipeline can be converted and obtained, wherein is the installation reference height.

[0031] If echo signal jitter occurs due to liquid level fluctuation, the system adopts a moving average filtering algorithm to smooth the liquid level height data of 10 consecutive sampling periods, eliminate abnormal jump values, and output a stable liquid level height result; if the liquid level is detected to exceed the measuring range of the sensor, the system automatically outputs a measuring range over-limit alarm, and keeps the previous frame of valid data to avoid invalid data from interfering with subsequent flow calculation.

[0032] In one embodiment, for step S2, the step of dividing corresponding liquid level working conditions according to the corresponding relationship between the liquid level height and the radius of the culvert pipeline includes: acquiring the radius r and diameter D=2r of the culvert pipeline; comparing the real-time liquid level height h with the radius r and the diameter D respectively; when h≤r, it is determined as the first liquid level working condition (half full and below); when r<h<2r, it is determined as the second liquid level working condition (above half full and below full); When h=2r, it is determined to be the third liquid level condition.

[0033] In practical implementation, the radius r of the culvert The system inputs inherent pipeline parameters before equipment installation, supporting various circular cross-section pipelines such as circular concrete culverts and circular steel pipes. Parameters can be obtained through on-site calibration or by directly inputting the nominal pipeline dimensions. The operating condition division logic adopts a hysteresis comparison mechanism, setting a ±5mm hysteresis interval at the boundary positions of h=r and h=2r to avoid frequent switching of operating conditions caused by small fluctuations in the liquid level, thereby improving system stability.

[0034] The calculation of the arc area under all liquid level conditions adopts a unified trigonometric function calculation benchmark in radians. The inverse cosine function calculation is also output in radians to ensure that the calculated cross-sectional area is completely consistent and continuous without jumps between conditions of half-full or less and above half-full, at the boundary position where the liquid level is equal to the radius of the culvert. Specific verification is as follows: When h=r, substituting h=r into the formula for the first liquid level condition yields the central angle π radians corresponding to the arc area, and the cross-sectional area is... The second liquid level condition involves subtracting the area of ​​the upper arc from the area of ​​the circle, where the height of the upper arc is also r. The calculated area of ​​the arc is also r. Therefore, the cross-sectional area of ​​the flow is The calculation results for the two boundaries are completely equal, with no numerical jumps.

[0035] For the third liquid level condition, when the liquid level continuously exceeds the pipe diameter and the stabilization time exceeds 3 seconds, the system determines it to be a stable full-pipe state and directly uses the area of ​​a complete circle as the flow cross-sectional area. If the liquid level drops back after a short period of exceeding the range, the calculation logic for the high liquid level condition is maintained to avoid misjudgment. Under the third liquid level condition, the system automatically switches to the full-pipe Doppler flowmeter measurement mode to further optimize the flow velocity calculation accuracy and achieve a smooth transition from a non-full pipe to a full pipe.

[0036] In one embodiment, step S3, the step of calculating the fluid velocity using an insertion ultrasonic Doppler sensor, includes: Control the ultrasonic transducer to emit ultrasonic signals of a fixed frequency into the fluid; Receive the echo signal reflected by suspended particles in the fluid and extract the frequency of the echo signal; Calculate the difference between the transmitted frequency and the echo frequency to obtain the Doppler frequency shift; Measure the real-time speed of sound in the fluid to obtain the angle between the direction of sound wave propagation and the direction of fluid flow; The axial velocity of the fluid was calculated based on the derivation of the Doppler frequency shift formula.

[0037] In practical implementation, the insertion-type ultrasonic Doppler sensor uses a piezoelectric ceramic transducer with a transmission frequency of... The frequency is 2MHz, which offers both good penetration and frequency shift detection sensitivity within the turbidity range of power plant wastewater, making it suitable for water environments with sediment content ranging from 0.5g / L to 50g / L. The transducer is installed at a fixed angle on the end of the detection rod. The angle θ between the sound wave emission direction and the pipe axis (fluid flow direction) is preset to 60°. This angle has been optimized through acoustic simulation to balance flow velocity detection sensitivity and signal strength. Installation angle errors are compensated for through factory calibration.

[0038] During velocity measurement, the transducer continuously emits ultrasonic waves at a fixed frequency. As the ultrasonic waves propagate in the water, they are scattered upon encountering suspended solid particles and tiny bubbles moving synchronously with the fluid. The backscattered echoes returning along the emission path are received by the transducer. Because the reflecting particles move with the fluid, the echo signal experiences a Doppler frequency shift, resulting in an increased echo frequency. With transmission frequency There is a difference, and this difference is the Doppler frequency shift. The system performs spectral analysis on the echo signal using Fast Fourier Transform (FFT) to extract the dominant frequency and calculate the precise Doppler frequency shift. This is combined with the Doppler velocity measurement principle formula: Where c is the real-time sound velocity in the fluid, and v is the fluid velocity along the axial direction of the pipe. By transforming and deriving the formula, we obtain the formula for calculating fluid velocity: The real-time sound velocity *c* is corrected using water temperature data collected by a built-in temperature sensor, following an empirical formula relating sound velocity to temperature in water. Compensation is also provided for sound velocity deviations in high-turbidity water to ensure accurate flow velocity calculations. To improve flow velocity representativeness, the system employs a multi-point flow velocity sampling and cross-sectional flow velocity distribution correction scheme: the sensor performs multi-layer flow velocity detection along the water depth direction, acquiring point flow velocities at different depths; combined with the cross-sectional flow velocity distribution model corresponding to the current liquid level, the point flow velocities are weighted and corrected to calculate the average flow velocity of the pipe cross-section. A parabolic flow velocity distribution model is used for low liquid level conditions, while a logarithmic flow velocity distribution model is used for high liquid level and full-pipe conditions, further improving the accuracy of flow velocity detection and reducing the cross-sectional representativeness error caused by single-point velocity measurement.

[0039] In one embodiment, step S4, which involves calculating the real-time flow cross-sectional area and obtaining the real-time flow rate based on the liquid level conditions, includes: Call the corresponding cross-sectional area calculation formula based on the current liquid level conditions; Substituting the pipe radius r and the real-time liquid level h, the current flow cross-sectional area A is calculated. Multiply the average flow velocity v of the cross-section by the flow cross-sectional area A to obtain the instantaneous flow rate Q; the cumulative flow rate is obtained by time-integrating and accumulating the instantaneous flow rate.

[0040] In specific implementation, corresponding cross-sectional area calculation logics are matched for three types of liquid level working conditions respectively, and all calculations are based on the geometric principle of circular cross-section, as detailed below: 1. First liquid level working condition (h≤r): the flow cross-section is a standard circular segment, which is calculated by the circular segment area formula, and the formula is: wherein is an arccosine function, and the operation result adopts the radian system. This formula is derived by subtracting the triangle area from the sector area, and accurately corresponds to the shape of the flow cross-section when the liquid level is lower than the semicircle.

[0041] 2. Second liquid level working condition (r<h<2r): the flow cross-section is obtained by subtracting the unfilled circular segment at the upper part from the complete circle, and is calculated by subtracting the area of the upper small circular segment from the area of the circle. The formula is: wherein the height of the unfilled circular segment at the upper part is h-r. After calculating by the unified circular segment area formula, the area of the circle is used for subtraction, which ensures a consistent calculation benchmark and continuous and no jump at the boundary.

[0042] 3. Third working condition (h>2r): the flow cross-section is a complete circle, and the cross-sectional area is directly calculated by the circle area formula: After the flow cross-sectional area is calculated, multiply the average flow velocity v of the cross-section obtained in step S3 by the cross-sectional area A to obtain the instantaneous flow rate Q=v∙A, and the flow unit can be configured as m 3 / s, m 3 / h, L / s, etc. as required.

[0043] The system has a built-in flow integrating unit, which performs equal time interval integration and accumulation on the instantaneous flow rate, calculates and obtains statistical data such as daily cumulative flow rate, monthly cumulative flow rate and total cumulative flow rate, supports power-off storage, and meets the requirements of thermal discharge metering and environmental protection statistics in power plants.

[0044] To ensure the measurement accuracy, the system is calibrated in full range by a standard flow calibration device before leaving the factory. The measurement error does not exceed ±2% within the 10%~90% range, and the measurement error does not exceed ±1.5% under full pipe working conditions, which meets the accuracy requirements of industrial metering.

[0045] Referring to Figure 2 , it is a structural block diagram of a non-full pipe hidden culvert flow measurement system in an embodiment of the present invention, comprising: The liquid level acquisition module is used to acquire liquid level height data in the culvert pipe through an integrated liquid level measurement probe; The operating condition judgment module is used to classify different liquid level operating conditions based on the correspondence between the liquid level height and the radius of the culvert pipe; The flow velocity calculation module is used to emit ultrasonic waves of a fixed frequency into the fluid in the culvert pipe through an insertion ultrasonic Doppler sensor according to the liquid level conditions, measure the sound velocity of the fluid in the culvert pipe and the angle between the sound wave propagation direction and the fluid flow direction, and calculate the fluid flow velocity based on the Doppler frequency shift generated by the reflection of particles in the fluid in the culvert pipe. The calculation output module is used to calculate the real-time flow cross-sectional area of ​​the culvert pipe according to the current liquid level conditions and the matching calculation method. It also calculates the real-time flow rate in the culvert pipe by multiplying the fluid velocity by the real-time flow cross-sectional area.

[0046] In practical implementation, the liquid level acquisition module interfaces with the hardware driver of the liquid level measurement probe, and is responsible for ultrasonic transmission, echo reception, time difference calculation and liquid level height conversion. At the same time, the built-in filtering algorithm smooths the fluctuating data and outputs stable liquid level data to the working condition judgment module and the calculation output module.

[0047] The operating condition judgment module has a built-in pipeline parameter storage unit and hysteresis comparison logic. It pre-stores inherent parameters such as pipeline radius and diameter. After receiving real-time liquid level data, it divides the liquid level operating conditions through numerical comparison. At the same time, it performs hysteresis anti-shaking processing at the boundary and synchronously sends the operating condition judgment results to the flow velocity calculation module and the calculation output module.

[0048] The flow velocity calculation module is responsible for driving the ultrasonic Doppler transducer to complete ultrasonic emission, echo acquisition, spectrum analysis and frequency shift extraction. It calculates the point flow velocity by combining real-time sound velocity and installation angle parameters, and then matches the corresponding flow velocity distribution correction model according to the current working conditions to calculate the cross-sectional average flow velocity, which is then sent to the calculation output module.

[0049] The calculation output module has a built-in formula library for cross-sectional area calculation under three types of working conditions. It calls the corresponding formula according to the current working condition, substitutes the liquid level and pipeline parameters to calculate the flow cross-sectional area, and then couples the average flow velocity of the cross-section to obtain the instantaneous flow rate. At the same time, the built-in integration unit completes the cumulative flow statistics and supports multiple communication methods such as 485, Ethernet, and 4-20mA to output the flow data to the external monitoring platform.

[0050] For the specific implementation of each module in the above system embodiment, please refer to the above method embodiment, and it will not be repeated here.

[0051] In practical implementation, the insertion-type ultrasonic Doppler sensor and the liquid level measurement probe are integrated into an integrated detection rod. The detection rod is made of 316 stainless steel with anti-corrosion and wear-resistant treatment on the surface, making it suitable for corrosive environments such as sewage and warm drainage. The end of the detection rod is encapsulated with a piezoelectric transducer and a liquid level probe, which are arranged coaxially to ensure consistent detection standards.

[0052] The equipment installation location should be selected in the straight pipe section of the culvert, meeting the requirement that the upstream straight pipe section length is not less than 10 times the inner diameter of the culvert pipe and the downstream straight pipe section is not less than 5 times the inner diameter of the culvert pipe. Avoid areas with turbulent flow such as bends, valves, and diameter changes to ensure uniform distribution of fluid velocity in the pipe and improve measurement accuracy.

[0053] The signal processing unit uses a low-power ARM processor and has built-in signal conditioning circuit, AD sampling circuit, temperature acquisition circuit and storage unit. It is responsible for completing the entire process of ultrasonic signal transmission drive, echo signal amplification and sampling, spectrum analysis, liquid level calculation, working condition judgment, flow totalization and other calculations. At the same time, it has a built-in power management module to support 24V DC power supply and adapt to the power supply environment of industrial sites.

[0054] The equipment has no mechanical rotating parts, no wear or blockage issues, and daily maintenance only requires periodic cleaning of the accumulated debris on the probe surface. It has low maintenance costs, long service life, and is suitable for the long-term continuous operation needs of power plants.

[0055] In summary, this invention measures the liquid level in a culvert using an integrated liquid level probe. Different liquid level conditions are defined based on the relationship between the liquid level and the pipe radius. The fluid velocity is calculated using an insertion-type ultrasonic Doppler sensor based on the Doppler frequency shift effect. Then, a corresponding flow cross-sectional area calculation method is matched according to the liquid level condition to obtain the real-time flow rate. This invention eliminates the need for pipe disconnection during installation, is not limited by fluid conductivity and viscosity, and is suitable for high-turbidity water bodies with many impurities. It can accurately achieve online flow measurement in non-full-pipe culverts, effectively solving the problem of flow measurement in power plant thermal drainage culverts.

[0056] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for measuring the flow rate of a non-full-pipe culvert, characterized in that... This includes the following steps: S1: Measure the liquid level height inside the culvert pipe using an integrated liquid level measurement probe; S2: Based on the correspondence between the liquid level height and the radius of the culvert pipe, classify the corresponding liquid level conditions; S3: Based on the liquid level conditions, a fixed frequency ultrasonic wave is emitted into the fluid in the culvert using an insertion ultrasonic Doppler sensor. The sound velocity of the fluid in the culvert and the angle between the direction of sound wave propagation and the direction of fluid flow are measured. The fluid flow velocity is calculated based on the Doppler frequency shift generated by the reflection of particles in the fluid in the culvert. S4: Based on the current liquid level conditions, calculate the real-time flow cross-sectional area of ​​the culvert using a matching calculation method, and calculate the real-time flow rate in the culvert by multiplying the fluid velocity by the real-time flow cross-sectional area.

2. The method for measuring the flow rate of a non-full-pipe culvert according to claim 1, characterized in that, In step S3, the fluid velocity is calculated using the Doppler frequency shift generated by the reflection of particles in the fluid within the culvert: The insertion-type ultrasonic Doppler sensor emits ultrasonic waves of a fixed frequency into the fluid. The ultrasonic waves are reflected by solid particles or bubbles in the fluid, resulting in a frequency shift. The frequency shift is proportional to the fluid flow rate. The fluid velocity is calculated by combining the ultrasonic emission frequency, the angle between the sound wave propagation direction and the fluid flow direction, and the sound velocity in the fluid.

3. The method for measuring the flow rate of a non-full-pipe culvert according to claim 1, characterized in that, In step S2, the corresponding liquid level conditions are defined as follows: When the liquid level is less than or equal to the cross-sectional radius of the culvert, it is set as the third liquid level condition. When the liquid level is greater than the radius of the culvert cross-section but less than the diameter of the culvert cross-section, it is set as the second liquid level condition. When the liquid level is equal to the cross-sectional diameter of the culvert, the culvert is in a fully full state, which is set as the third liquid level condition.

4. The method for measuring the flow rate of a non-full-pipe culvert according to claim 1, characterized in that, The calculation of the real-time flow cross-sectional area of ​​the culvert pipe using a matching calculation method based on the current operating conditions is as follows: When the current operating condition is the first liquid level condition, the flow cross-sectional area is calculated using the arc area formula; When the current operating condition is the second liquid level condition, the flow cross-sectional area is obtained by subtracting the arc-shaped area of ​​the unfilled area above from the complete circular area of ​​the culvert pipe. When the current operating condition is the third liquid level condition, the cross-sectional area of ​​the flow is taken as the area of ​​the complete circle of the culvert pipe.

5. A method for measuring the flow rate of a non-full-pipe culvert according to claim 3 or 4, characterized in that, The arc-shaped flow area under all liquid level conditions uses the same trigonometric function calculation basis, and the inverse cosine function is uniformly calculated in radians. At the boundary where the liquid level is equal to the radius of the culvert, the calculated cross-sectional area values ​​for the two working conditions—half full and below, and above half full—are continuous without abrupt changes, thereby eliminating the calculation deviation caused by the switching of working conditions.

6. The method for measuring the flow rate of a non-full-pipe culvert according to claim 1, characterized in that, The installation location of the insertion-type ultrasonic Doppler sensor is selected in the area of ​​the straight pipe of the culvert, and the upstream straight pipe section length is not less than ten times the inner diameter of the culvert, and the downstream straight pipe section is not less than five times the inner diameter of the culvert.

7. The method for measuring the flow rate of a non-full-pipe culvert according to claim 1, characterized in that, The measurement results of the non-full pipe culvert flow measurement method are not affected by the fluid conductivity and viscosity, and can be applied to harsh fluid environments with high turbidity and multiple impurities.

8. The method for measuring the flow rate of a non-full-pipe culvert according to claim 1, characterized in that, The non-full-pipe culvert flow measurement method is applicable to flow measurement scenarios for large-diameter pipes or concrete culverts under low pressure and normal temperature environments.

9. A flow measurement system for a non-full-pipe culvert, characterized in that, include: Liquid level acquisition module: used to acquire liquid level height data in the culvert pipe through an integrated liquid level measurement probe; Operating condition judgment module: used to classify different liquid level operating conditions based on the correspondence between the liquid level height and the radius of the culvert pipe; Flow velocity calculation module: Based on the liquid level conditions, it emits ultrasonic waves of a fixed frequency into the fluid in the culvert pipe through an insertion ultrasonic Doppler sensor, measures the sound velocity of the fluid in the culvert pipe and the angle between the sound wave propagation direction and the fluid flow direction, and calculates the fluid flow velocity based on the Doppler frequency shift generated by the reflection of particles in the fluid in the culvert pipe. The calculation output module is used to calculate the real-time flow cross-sectional area of ​​the culvert pipe according to the current liquid level conditions and the matching calculation method. It also calculates the real-time flow rate in the culvert pipe by multiplying the fluid velocity by the real-time flow cross-sectional area.

10. A flow measurement device for a non-full-pipe culvert, characterized in that, The method that can be used to implement any one of claims 1-8 includes: An insertion-type ultrasonic Doppler sensor is used to emit ultrasonic waves into a fluid and receive the reflected echoes to obtain Doppler frequency shift signals. A liquid level measuring probe, integrated at the end of the device, is used to collect liquid level height data in the culvert pipe; The signal processing and computing unit is electrically connected to the insertable ultrasonic Doppler sensor and the liquid level measuring probe, respectively, and is used to process the acquired signals and calculate the real-time flow data.

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