Non-full pipe electromagnetic flowmeter

Abstract

This invention discloses a non-full-pipe electromagnetic flowmeter, belonging to the field of flow measurement technology. It includes: a measuring tube for fluid flow; a pair of electrodes symmetrically arranged on the inner wall of the measuring tube for measuring the fluid's conductivity and induced electromotive force; and at least one arc-shaped conductive electrode plate fitted to the inner wall of the measuring tube. This design achieves deep structural integration of electromagnetic induction measurement and arc-shaped capacitive level sensing, enabling simultaneous and accurate acquisition of flow field information and geometric parameters. The optimized electrode and capacitor layout, along with the special material coating, ensures a clear and stable signal source. Simultaneous calculation of the flow area and induced electromotive force enables continuous and accurate metering across all operating conditions, from full-pipe to non-full-pipe.

Description

Technical Field

[0001] This invention relates to the field of flow measurement technology, and more specifically, to a non-full-pipe electromagnetic flow meter. Background Technology

[0002] Existing electromagnetic flowmeters for non-full pipes generally use the differential pressure principle for measurement. In non-full pipe conditions, the liquid level inside the pipe is easily affected by the fluid velocity and pipe slope, resulting in random fluctuations. Furthermore, fluid distribution is prone to phenomena such as flow deviation and eddies, which significantly reduces the accuracy of differential pressure signal acquisition, ultimately leading to high measurement errors and making them unsuitable for high-precision measurement scenarios. Another method uses mechanical structures such as floats and flaps to indirectly calculate fluid flow by detecting liquid level height. These devices are simple in structure and low in cost, but they have poor anti-interference capabilities. Impurities and suspended solids often contained in industrial fluids can easily entangle and wear down mechanical parts, causing parts to jam and sensitivity to decrease. This not only affects the stability of measurement results but also shortens the service life of the equipment, increases subsequent maintenance costs, and makes it difficult to operate reliably for a long time under harsh conditions. Summary of the Invention

[0003] To address the problems existing in the prior art, the present invention aims to provide a non-full-pipe electromagnetic flowmeter that can achieve deep structural integration of electromagnetic induction measurement and arc-shaped capacitive liquid level sensing, realizing the synchronous and accurate acquisition of flow field information and geometric parameters. The optimized layout of electrodes and capacitors and the special material coating ensure the clarity and stability of the signal source. The flow area and induced electromotive force are calculated simultaneously, realizing continuous and accurate measurement under all working conditions from full-pipe to non-full-pipe.

[0004] To solve the above problems, the present invention adopts the following technical solution:

[0005] A non-full-pipe electromagnetic flowmeter, comprising:

[0006] Measuring tube, used for the passage of fluid;

[0007] A pair of electrodes are symmetrically arranged on the inner wall of the measuring tube for measuring the conductivity and induced electromotive force of the fluid.

[0008] At least one arc-shaped conductive electrode plate is provided, which is attached to the inner wall of the measuring tube. The height direction of the arc-shaped conductive electrode plate is parallel to the axis of the measuring tube, and its length direction extends circumferentially along the inner wall of the measuring tube. It is used to measure the capacitance value related to the liquid level height.

[0009] The signal processing and computing unit is electrically connected to the electrodes and the arc-shaped conductive electrode plate;

[0010] The signal processing and computing unit includes:

[0011] An anti-interference module is used to apply dual-frequency excitation signals to the arc-shaped conductive electrode plate and compensate for capacitance measurement deviations caused by fluid flow based on the dual-frequency measurement results; at the same time, it performs time series analysis and prediction on the acquired capacitance value sequence to correct the liquid level signal.

[0012] The liquid level calculation module is used to obtain the current liquid level height h based on the capacitance value corrected by the arc-shaped conductive electrode plate and the pre-stored capacitance-liquid level height relationship curve.

[0013] The flow calculation module is used to calculate the instantaneous flow rate Q by combining the induced electromotive force E obtained by electrode measurement, the fluid conductivity σ, and the current liquid level height h, according to the non-full pipe flow calculation formula.

[0014] Furthermore, the anti-interference module performs compensation for the dual-frequency measurement results, including:

[0015] The first frequency is alternately applied to the arc-shaped conductive electrode plate Second frequency The excitation signal was obtained, and the corresponding capacitive reactance value was measured. and ;

[0016] The difference in capacitive reactance between the two frequencies is calculated as follows: ;

[0017] Based on the pre-calibrated relationship model between flow velocity and capacitance difference, calculate the disturbance intensity caused by the current fluid flow velocity;

[0018] The capacitance value measured at the time of the interference is dynamically compensated based on the intensity of the interference.

[0019] Furthermore, based on the pre-calibrated model of the relationship between flow velocity and capacitive reactance difference, including:

[0020] When the measuring tube is in a stable, non-full-flow state, multiple flow velocity points are simultaneously acquired using a calibration device. Record the actual flow velocity value at each flow velocity point and the dual-frequency capacitive reactance difference measured by the anti-interference module. ;

[0021] Based on the aforementioned multiple data pairs The relationship model was obtained by fitting the data using linear regression. calibration coefficients in and ;

[0022] calibration coefficients , The relational model is stored in the memory of the signal processing and computing unit.

[0023] Furthermore, the intensity of the disturbance caused by the current fluid velocity is calculated, including:

[0024] In the current measurement, the anti-interference module acquires the dual-frequency capacitive reactance difference value in real time. ;

[0025] Call the stored calibration coefficients , The current estimated flow rate is calculated based on the relational model. ;

[0026] Based on the current estimated flow velocity The intensity of the disturbance caused by the current fluid velocity is determined by applying the disturbance calculation formula.

[0027] Furthermore, the control measuring tube is at full volume or a constant known liquid level. Under these conditions, the fluid is made to flow at a series of calibrated velocities. Stable flow;

[0028] At each of the calibrated flow rates Below, record the static capacitance reference value of the arc-shaped conductive electrode plate when there is no flow. And the capacitance value measured during actual flow. ;

[0029] Calculate the capacitance disturbance at each flow velocity point. A set of calibration data was obtained. ;

[0030] Based on calibration data pairs, the formula for calculating interference was determined using curve fitting. Specific form and parameters;

[0031] In actual measurements, the current estimated flow velocity is used as a basis. ,Will Substitute into the calibrated interference calculation formula The capacitance interference intensity caused by the current flow velocity can be directly calculated. .

[0032] Furthermore, dynamic compensation is performed on the currently measured capacitance value based on the interference intensity, achieved through the following formula:

[0033] ;

[0034] This is represented as the original capacitance value measured at the current moment by the arc-shaped conductive electrode plate;

[0035] To estimate the flow rate based on the current data The determined intensity of capacitive interference caused by the current fluid velocity;

[0036] The compensation coefficient is a dimensionless factor related to the liquid level height, with a value ranging from 0.8 to 1.2.

[0037] This is the effective capacitance value output after dynamic compensation, used to calculate the liquid level height.

[0038] Furthermore, time series analysis and prediction are performed on the collected capacitance value sequence to correct the liquid level signal, including:

[0039] The capacitance values ​​of the arc-shaped conductive electrode plate are obtained at a fixed sampling period to form a time series. };

[0040] Establish and train a time series prediction model to predict the static reference capacitance value at the current moment based on the historical capacitance value sequence;

[0041] The actual measured capacitance value is compared with the predicted static reference capacitance value to obtain the prediction deviation;

[0042] The prediction bias is fused with the compensation amount obtained from dual-frequency measurement compensation to generate the final capacitance value.

[0043] Furthermore, the relationship curve between the pre-stored capacitance value and the liquid level height in the liquid level calculation module is obtained by calibrating multiple known liquid level heights under static conditions and fitting them using cubic spline interpolation.

[0044] Furthermore, the formula for calculating the non-full pipe flow rate of the flow calculation module is as follows:

[0045] Where k is the comprehensive instrument coefficient, E is the electrode induced electromotive force, σ is the fluid conductivity, and A(h) is the fluid flow cross-sectional area calculated based on the current liquid level height h.

[0046] Furthermore, the fluid flow cross-sectional area A(h) is calculated based on the current liquid level height h and the inner radius R of the measuring tube, using the following formula:

[0047] when hour, ;

[0048] when hour, .

[0049] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0050] This solution deeply integrates electromagnetic induction measurement with arc-shaped capacitive liquid level sensing in its structure, enabling the synchronous and accurate acquisition of flow field information and geometric parameters. The optimized layout of electrodes and capacitors and the special material coating ensure the clarity and stability of the signal source. Based on this, the non-full pipe flow formula is derived, and the flow area and induced electromotive force are calculated simultaneously, realizing continuous and accurate measurement under all working conditions from full pipe to non-full pipe.

[0051] This solution integrates dual-frequency dynamic measurement and time series prediction algorithms to construct a dual anti-interference mechanism. Dual-frequency measurement effectively eliminates the system interference of steady-state flow velocity on the capacitive field, while the ARIMA model filters out random disturbances such as bubbles and turbulence in real time, so that the liquid level signal remains stable under complex flow conditions. The two work together to improve the dynamic accuracy of liquid level height measurement to a whole new level. Attached Figure Description

[0052] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0053] Figure 1 This is a schematic diagram of the installation of the arc-shaped conductive electrode plate and the electrode inside the measuring tube according to the present invention;

[0054] Figure 2 This is a flowchart illustrating the composition and signal flow of the non-full-pipe electromagnetic flowmeter system of the present invention;

[0055] Figure 3 This is a flowchart illustrating the calculation process from liquid level to flow rate in this invention.

[0056] Explanation of the labels in the diagram:

[0057] 1. Measuring tube; 2. Electrode; 3. Arc-shaped conductive electrode plate; 4. Signal processing and calculation unit; 41. Anti-interference module; 42. Liquid level calculation module; 43. Flow rate calculation module. Detailed Implementation

[0058] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0059] Please see Figures 1 to 3A non-full-pipe electromagnetic flowmeter includes: a measuring tube 1 for fluid to pass through; a pair of electrodes 2 symmetrically arranged on the inner wall of the measuring tube 1 for measuring the conductivity and induced electromotive force of the fluid; and at least one arc-shaped conductive electrode plate 3, which is disposed in contact with the inner wall of the measuring tube 1, with its height direction parallel to the axis of the measuring tube 1 and its length direction extending circumferentially along the inner wall of the measuring tube 1 for measuring the capacitance value related to the liquid level height.

[0060] It should be noted that: a pair of electrodes 2 are located at 10% of the height of the measuring tube 1, and the extended axis of electrode 2 coincides with the center of the measuring tube 1. Electrode 3 is made of highly corrosion-resistant titanium alloy and coated with a layer of nanoscale graphene coating. This coating not only further enhances the conductivity of electrode 3, but also improves the anti-fouling ability of electrode 3 and reduces the impact of impurities in the fluid on the acquisition of electrical signals. This electrode 3 setting can effectively acquire the conductivity signal of the fluid in a non-full tube state, providing accurate basic data for subsequent flow calculation.

[0061] In addition, there are two arc-shaped conductive electrode plates 3, located on both sides of the central axis of the measuring tube 1. The starting ends of the two arc-shaped conductive electrode plates 3 are aligned with the installation position of the electrode 2 in the axial direction of the measuring tube 1. The arc-shaped conductive electrode plates 3 are made of copper sheets with anti-oxidation treatment. The copper oxide protective film on the surface can prevent the copper sheets from oxidizing in a humid fluid environment, which would affect the performance of the capacitor. The layout of the arc-shaped capacitor can fully cover the range of liquid level changes and accurately sense changes in liquid level height.

[0062] In some embodiments of the present invention, a signal processing and computing unit 4 is included, wherein the signal processing and computing unit 4 is also electrically connected to the electrode 2 and the arc-shaped conductive electrode plate 3;

[0063] The signal processing and calculation unit 4 also includes an anti-interference module 41, which is used to apply a dual-frequency excitation signal to the arc-shaped conductive electrode plate 3 and compensate for the capacitance measurement deviation caused by fluid flow based on the dual-frequency measurement results.

[0064] The specific steps are as follows:

[0065] 1. Measurement of Dual-Frequency Excitation and Capacitive Reactance Difference

[0066] The anti-interference module 41 first applies an excitation signal to the arc-shaped conductive electrode plate 3 used for measuring the liquid level: two AC signals of different frequencies are applied alternately, such as the first frequency being... The second frequency is And satisfy The dielectric properties and flow state of fluids have different effects on the disturbance of electric fields at different frequencies, especially for water-based fluids. The anti-interference module 41 simultaneously measures and records the capacitive reactance values ​​at these two frequencies. and Calculate the difference between these two capacitive reactance values ​​to obtain the dual-frequency capacitive reactance difference value:

[0067] ;

[0068] this The value is an intermediate variable in static fluid. It is mainly related to the dielectric constant of the fluid, which remains basically constant; however, when the fluid flows, the distortion and disturbance of the electric field around the electrode plate by the water flow will cause... and Different degrees of change occurred, resulting in It has become a sensitive indicator reflecting the magnitude of fluid flow velocity.

[0069] 2. Establishment and application of a flow velocity estimation model based on capacitive reactance difference

[0070] In order to establish The quantitative relationship between the flow rate and the flow velocity v needs to be calibrated before the flow meter leaves the factory. Under stable, non-full-pipe flow conditions in the measuring tube 1, multiple flow velocity points are simultaneously collected using a high-precision calibration device. The actual flow rate value is obtained by using a high-precision calibration device, which includes: a high-precision standard electromagnetic flowmeter or standard volume tube system as the flow reference, an adjustable overflow device and laser level gauge for precise control and measurement of liquid level, and a data synchronous acquisition and processing unit. This device can reproduce various stable operating conditions under non-full pipe conditions in the laboratory, and synchronously acquire the precise correspondence between flow rate, liquid level and the original signal of the sensor under test, thereby completing the parameter calibration of the mathematical model.

[0071] Next, the dual-frequency capacitive reactance difference value measured by the anti-interference module 41 at the corresponding point is recorded. In order to obtain a series of data for By fitting these data using linear regression, a linear relationship model can be obtained:

[0072] ;

[0073] in, It is the slope of the straight line, which in a physical sense represents the difference in capacitive reactance. The change in flow velocity corresponding to each unit change; It is the intercept of the straight line, representing the theoretical velocity offset when the capacitance difference is zero, that is to say and In order to calibrate the constants, the model and its coefficients are stored in the memory of the signal processing and computing unit 4.

[0074] In one embodiment, for a DN80 pipe and a flow meter used to measure tap water, the following is selected: , The linear regression coefficients obtained through calibration are approximately , This value is for illustrative purposes only; the actual coefficients need to be determined through individual calibration.

[0075] In addition, during actual operation, the anti-interference module 41 obtains the current dual-frequency capacitance difference value in real time. By calling the stored coefficients and The current fluid velocity can then be estimated in real time using the above model:

[0076] ;

[0077] This step transforms the intensity of water flow disturbance, which is difficult to measure directly, into a physical quantity that can be quantitatively estimated: flow velocity. .

[0078] 3. Calibration and calculation of the flow velocity and capacitance interference model

[0079] Estimate the flow rate The next step is to determine the extent to which the flow rate interferes with the capacitance measurement. This requires another calibration model, during which the measuring tube 1 is controlled to be at full capacity or at a constant, known liquid level. The state is adjusted to eliminate the influence of liquid level changes, allowing the fluid to flow at a series of precisely controlled calibrated velocities. (j=1,2,...,m) steady flow.

[0080] At each flow rate Below, the system records two key values: one is the static reference value of the arc capacitance when there is no fluid flow. Secondly, the fluid is... capacitance measured during flow The difference between the two is the capacitance interference caused by pure flow at that flow velocity:

[0081] ;

[0082] This yields another set of calibration data. By performing curve fitting on these data, the formula for calculating the interference can be determined. The specific form and parameters are given by a common empirical formula:

[0083] ;

[0084] in, and The constant obtained through experimental calibration will be used in actual measurements to estimate the flow velocity in real time. By substituting into this calibrated formula, the intensity of capacitive interference caused by the current flow velocity can be directly calculated. .

[0085] 4. Dynamic capacitance compensation and effective liquid level signal output

[0086] Obtain precise interference intensity Then, the original measured value can be compensated, and the anti-interference module 41 reads the original capacitance value measured by the arc-shaped conductive electrode plate 3 at the current moment. Dynamic compensation is achieved through the following formula:

[0087] ;

[0088] In this compensation formula:

[0089] The original measurements include flow disturbances;

[0090] The capacitance interference intensity is calculated from the above steps;

[0091] This is a compensation coefficient, a dimensionless factor related to the liquid level height h. It typically ranges from 0.8 to 1.2 and is used to correct for nonlinear variations in interference effects that may occur with different liquid levels. It can be obtained through pre-calibration. Correspondence;

[0092] This refers to the pure capacitance value that is finally output after dynamic compensation and effectively reflects the true liquid level height.

[0093] In some embodiments of the present invention, the anti-interference module 41 of the non-full-pipe electromagnetic flowmeter, while applying dual-frequency measurement compensation, also runs a dynamic prediction and correction algorithm based on time series analysis in parallel. The purpose of this algorithm is to further address dynamic disturbances such as rapid fluctuations, turbulent vortices, or instantaneous bubbles in fluid flow. These disturbances may not be fully captured by the dual-frequency compensation method based on the steady-state model. The idea is to utilize the continuity and trend of the liquid level signal itself in a short period of time, predict the current static capacitance value through historical data, and compare it with the measured value, thereby achieving higher frequency and more adaptive real-time correction.

[0094] 1. Data sequence construction and model preparation

[0095] With a fixed high sampling period, such as The capacitance measurements from the arc-shaped conductive electrode plate 3 are continuously collected. These values, after preliminary dual-frequency compensation, are stored in chronological order to form a continuous time series. Where the subscript t represents a discrete time index, a time series prediction model is built and trained based on this. Commonly used models include:

[0096] ARIMA (Autoregressive Integral Moving Average) model: suitable for stationary time series with trend or periodic characteristics.

[0097] LSTM (Long Short-Term Memory) Neural Network: A type of recurrent neural network that excels at learning and predicting complex dependencies in long-term sequences. It can effectively remember historical states and has better adaptability to non-stationary sequences.

[0098] The predictive model is trained offline using historical normal operation data, ideally collected under relatively stable flow conditions. Its learning objective is to learn from a past window period, such as a sequence of capacitance values ​​from the past 10 sampling points. Predict the capacitance value at the current time t under the condition of no sudden dynamic disturbance. This predicted value It is considered the best estimate of the static reference capacitance value at the current moment.

[0099] 2. Online prediction, deviation calculation and signal fusion

[0100] In actual online operation, the algorithm works in real time according to the following steps:

[0101] Step 1: At each new sampling time t, the algorithm inputs the latest historical sequence into the trained time series prediction model and calculates the predicted static capacitance value at the current time in real time. .

[0102] Step 2: Calculate the capacitance value at the current moment after dual-frequency compensation. Compared with the predicted value By comparison, the prediction bias at the time series analysis level is obtained:

[0103] ;

[0104] This deviation It mainly includes information on sudden disturbances not included in historical trends, such as instantaneous measurement jumps caused by a rapidly passing bubble or a strong turbulent vortex.

[0105] Step 3: Analyze the biases obtained from time series analysis. Compensation amount for steady-state flow velocity disturbances output by the dual-frequency measurement compensation module. For fusion, a robust fusion strategy is to use a weighted or selection logic:

[0106] ;

[0107] in, It is a dynamically adaptive weighting coefficient, and When the flow is judged to be very stable, The value approaches 1, indicating a strong reliance on the dual-frequency steady-state model; however, when high-frequency, drastic fluctuations are detected in the signal... By reducing and making greater use of the instantaneous biases captured by the time series model, a double-corrected effective capacitance value is ultimately generated for calculating the liquid level height.

[0108] ;

[0109] In some embodiments of the present invention, a liquid level calculation module 42 is also included. The liquid level calculation module 42 is used to obtain the current liquid level height h based on the capacitance value corrected by the arc-shaped conductive electrode plate 3 and through a pre-stored capacitance-liquid level height relationship curve.

[0110] The specific steps are as follows:

[0111] 1. Static calibration and data acquisition

[0112] To obtain a reliable calibration basis, the calibration must be performed under conditions where fluid flow interference is absolutely eliminated. The flowmeter measuring tube 1 is placed on a static calibration platform, and the fluid inside the tube is gradually increased from an empty tube to a full tube using a precision liquid level control system, at each set, known liquid level height. With i=1,2,...,n, after the liquid surface is completely still, record the stable capacitance value output by the arc-shaped conductive electrode plate 3 at this time. Thus, a set of discrete basic data points constituting the calibration curve is obtained: These data points clearly reveal the characteristic that the capacitance value changes monotonically as the liquid level rises.

[0113] 2. Cubic spline interpolation fitting and construction of continuity relationships

[0114] Due to the edge effect of the capacitance field distribution, the capacitance value C and the liquid level height h typically exhibit a non-linear relationship throughout the entire measurement range. , To achieve high-precision interpolation of the pipe radius, the calibration system employs cubic spline interpolation to construct a continuous Ch function relationship h=S(C). This method involves interpolating between two adjacent calibration data points. and Between them, use a cubic polynomial To fit the data, for an interval with n data points, we will obtain n-1 segments of cubic polynomials. These polynomials need to satisfy strict connection conditions:

[0115] (1) Continuity: The function values ​​are equal at the connection points, that is ;

[0116] (2) Continuity of first and second derivatives: first derivative at the connection point and second derivative They are also equal, thus ensuring that the entire curve is perfectly smooth;

[0117] (3) Boundary conditions: Natural boundary conditions are usually used, that is, the second derivative of the curve at both endpoints is zero. .

[0118] By solving the system of linear equations formed by these conditions, all piecewise polynomials can be uniquely determined. The coefficients, ultimately, these piecewise polynomials collectively define a polynomial from... arrive The globally smooth calibration curve h=S(C), the complete functional relationship S(C) and all its polynomial coefficients are solidified and stored in the non-volatile memory of the liquid level calculation module 42.

[0119] 3. Real-time online liquid level calculation

[0120] During actual operation of the flow meter, the liquid level calculation module 42 receives the real-time effective capacitance value from the anti-interference module 41 after dynamic compensation. The module's solution process is essentially a fast table lookup and interpolation calculation:

[0121] First, determine Which calibration range does it fall into? Then, call the stored cubic polynomial corresponding to that interval. Finally, Substituting into the polynomial, the current liquid level can be calculated directly:

[0122] ;

[0123] in, These are the coefficients of the pre-stored interval spline polynomial.

[0124] In some embodiments of the present invention, a flow calculation module 43 is also included. The flow calculation module 43 is used to calculate the instantaneous flow rate Q by combining the induced electromotive force E, fluid conductivity σ and current liquid level height h measured by electrode 2 according to the non-full pipe flow calculation formula.

[0125] The specific steps are as follows:

[0126] 1. Derivation of formulas from full pipe to non-full pipe

[0127] For electromagnetic flowmeters operating in a full-pipe state, the theoretical basis is Faraday's law of electromagnetic induction. When a conductive fluid flows through a set magnetic field at an average velocity v perpendicular to the magnetic field lines, a potential difference E will be induced on a pair of electrodes perpendicular to both the fluid flow direction and the magnetic field direction. For a circular full-pipe, the basic relationship is:

[0128] ;

[0129] Where B is the magnetic flux density, D is the inner diameter of the pipe, and D = 2R. The average flow velocity and volumetric flow rate of the fluid are given. Equals average flow velocity multiplied by pipe cross-sectional area ,Right now Combining the above formula, the formula for full-pipe flow rate can be derived:

[0130] ;

[0131] In actual instruments, coefficients Typically related to fluid conductivity The calibration factors are combined and calibrated as a whole into the instrument coefficient K, hence the full-pipe formula is often written as... .

[0132] In the non-full pipe state, the fluid flow cross-sectional area A is smaller than the full pipe cross-sectional area and is a function of the liquid level height h, denoted as A(h). At this time, the induced electromotive force E is still related to the average fluid velocity. Proportional, but the flow rate should be Therefore, the full-pipe formula needs to be modified by introducing the flow cross-sectional area ratio. Meanwhile, to maintain calibration consistency, the original full-pipe instrument coefficient K is expanded to a comprehensive instrument coefficient k. This coefficient k is determined during factory calibration and covers magnetic field strength, electrode structure, and flow field distribution compensation under non-full-pipe conditions. This leads to a general formula for calculating non-full-pipe flow rate:

[0133] ;

[0134] Among them, conductivity The introduction of allows the formula to adapt to fluids with different electrical conductivities, and the coefficient k implicitly contains the relationship with physical constants such as 1 / B.

[0135] 2. Calculation of fluid flow cross-sectional area A (h)

[0136] The key geometric parameter in the non-full pipe flow formula is the flow cross-sectional area A(h). For a horizontal circular pipe with radius R, when the liquid level is h, that is, measured from the bottom of the pipe, its flow cross-sectional area is the area of ​​the arc-shaped region below the liquid surface. This area needs to be calculated in two cases:

[0137] Scenario 1: Liquid level is lower than or equal to the centerline of the pipeline ;

[0138] At this point, the flow cross-section is a relatively small arc, the area of ​​which can be obtained by subtracting the area of ​​the triangle from the area of ​​the sector. Let the angle corresponding to half of the central angle be... The corresponding sector area is The area of ​​the triangle is Therefore, the cross-sectional area of ​​the flow path is:

[0139] ;

[0140] Scenario 2: The liquid level is higher than the center line of the pipeline ( );

[0141] At this point, the flow cross-section is a large arc shape, exceeding a semicircle. A more convenient method to calculate its area is: subtract the arc-shaped area of ​​the blank area above the liquid surface from the full pipe cross-sectional area. The liquid height in the blank area is 2R-h. Calculate the area of ​​this blank area using the formula in Case 1. The cross-sectional area for circulation is:

[0142] ;

[0143] 3. Real-time calculation process

[0144] During flow meter operation, the flow calculation module 43 executes a coherent real-time calculation chain:

[0145] (1) Receive the real-time liquid level height h from the liquid level calculation module 42, and the induced electromotive force E and fluid conductivity obtained from the electrode 2 measurement and processing circuit. .

[0146] (2) Based on the current h value, determine which of the above situations it belongs to, call the corresponding formula, and calculate the accurate flow cross-sectional area A(h) by combining the inner radius R of the pipe stored in the system.

[0147] (3) E, Substituting A(h) and the pre-calibrated and stored comprehensive instrument coefficient k into the core formula Finally, the instantaneous volumetric flow rate Q is calculated.

[0148] The flow calculation module solves the problem of measuring flow in non-full pipes by combining the law of electromagnetic induction with pipe geometry. Its formula... While inheriting the advantages of traditional electromagnetic flowmeters, this paper introduces a dynamically calculated flow cross-sectional area A(h) driven by precise liquid level measurement, which enables adaptive correction of the measurement formula to the fluid filling rate, thereby ensuring the continuity and accuracy of flow measurement from full pipe to various non-full pipe states.

[0149] The above are merely preferred embodiments of the present invention; however, the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and its improved concept, should be covered within the scope of protection of the present invention.

Claims

1. A non-full-pipe electromagnetic flowmeter, characterized in that, include: Measuring tube (1), used for fluid to pass through; A pair of electrodes (2) are symmetrically arranged on the inner wall of the measuring tube (1) for measuring the conductivity and induced electromotive force of the fluid; At least one arc-shaped conductive electrode plate (3) is provided in contact with the inner wall of the measuring tube (1). The height direction of the arc-shaped conductive electrode plate (3) is parallel to the axis of the measuring tube (1), and its length direction extends circumferentially along the inner wall of the measuring tube (1). It is used to measure the capacitance value related to the liquid level height. The signal processing and computing unit (4) is electrically connected to the electrode (2) and the arc-shaped conductive electrode plate (3); The signal processing and computing unit (4) includes: The anti-interference module (41) is used to apply a dual-frequency excitation signal to the arc-shaped conductive electrode plate (3) and compensate for the capacitance measurement deviation caused by fluid flow based on the dual-frequency measurement results; at the same time, it performs time series analysis and prediction on the collected capacitance value sequence to correct the liquid level signal. The liquid level calculation module (42) is used to obtain the current liquid level height h based on the capacitance value corrected by the arc-shaped conductive electrode plate (3) and the pre-stored capacitance and liquid level height relationship curve. The flow calculation module (43) is used to calculate the instantaneous flow rate Q by combining the induced electromotive force E, fluid conductivity σ and the current liquid level height h obtained by the electrode (2) according to the non-full pipe flow calculation formula.

2. The non-full-pipe electromagnetic flowmeter according to claim 1, characterized in that, The anti-interference module (41) performs compensation for the dual-frequency measurement results, including: The first frequency is alternately applied to the arc-shaped conductive electrode plate (3). Second frequency The excitation signal was obtained, and the corresponding capacitive reactance value was measured. and ; The difference in capacitive reactance between the two frequencies is calculated as follows: ; Based on the pre-calibrated relationship model between flow velocity and capacitance difference, calculate the disturbance intensity caused by the current fluid flow velocity; The capacitance value measured at the time of the interference is dynamically compensated based on the intensity of the interference.

3. The non-full-pipe electromagnetic flowmeter according to claim 2, characterized in that, Based on the pre-calibrated model of the relationship between flow velocity and capacitive reactance, including: When the measuring tube (1) is in a stable non-full-pipe flow state, multiple flow velocity points are simultaneously acquired through a calibration device. The actual flow velocity value is recorded, and the dual-frequency capacitive reactance difference value measured by the anti-interference module (41) at each flow velocity point is recorded. ; Based on multiple data pairs The relationship model was obtained by fitting the data using linear regression. calibration coefficients in and ; calibration coefficients , The relational model is stored in the memory of the signal processing and computation unit (4).

4. A non-full-pipe electromagnetic flowmeter according to claim 3, characterized in that, Calculate the intensity of the disturbance caused by the current fluid velocity, including: In the current measurement, the anti-interference module (41) acquires the dual-frequency capacitance difference value in real time. ; Call the stored calibration coefficients , The current estimated flow rate is calculated based on the relational model. ; Based on the current estimated flow velocity The intensity of the disturbance caused by the current fluid velocity is determined by applying the disturbance calculation formula.

5. A non-full-pipe electromagnetic flowmeter according to claim 4, characterized in that: Control measuring tube (1) at full or constant known liquid level Under these conditions, the fluid is made to flow at a series of calibrated velocities. (j=1,2,...,m) steady flow; At each of the calibrated flow rates Below, record the static capacitance reference value of the arc-shaped conductive electrode plate (3) when there is no flow. And the capacitance value measured during actual flow. ; Calculate the capacitance disturbance at each flow velocity point. A set of calibration data was obtained. ; Based on calibration data pairs, the formula for calculating interference was determined using curve fitting. Specific form and parameters; In actual measurements, the current estimated flow velocity is used as a basis. ,Will Substitute into the calibrated interference calculation formula The capacitance interference intensity caused by the current flow velocity can be directly calculated. .

6. A non-full-pipe electromagnetic flowmeter according to claim 5, characterized in that... Dynamic compensation is performed on the currently measured capacitance value based on the interference intensity, which is achieved by the following formula: ； This is represented as the original capacitance value measured at the current moment by the arc-shaped conductive electrode plate (3); To estimate the flow rate based on the current data The determined intensity of capacitive interference caused by the current fluid velocity; The compensation coefficient is a dimensionless factor related to the liquid level height, with a value ranging from 0.8 to 1.

2. This is the effective capacitance value output after dynamic compensation, used to calculate the liquid level height.

7. A non-full-pipe electromagnetic flowmeter according to claim 1 or 6, characterized in that... Time series analysis and prediction are performed on the collected capacitance value sequence to correct the liquid level signal, including: The capacitance value of the arc-shaped conductive electrode plate (3) is obtained at a fixed sampling period to form a time series { }; Establish and train a time series prediction model to predict the static reference capacitance value at the current moment based on the historical capacitance value sequence; The actual measured capacitance value is compared with the predicted static reference capacitance value to obtain the prediction deviation; The prediction bias is fused with the compensation amount obtained from dual-frequency measurement compensation to generate the final capacitance value.

8. A non-full-pipe electromagnetic flowmeter according to claim 7, characterized in that: The relationship curve between the capacitance value and the liquid level height in the liquid level calculation module (42) is obtained by calibrating multiple known liquid level heights under static conditions and fitting them using cubic spline interpolation.

9. A non-full-pipe electromagnetic flowmeter according to claim 8, characterized in that: The formula for calculating the non-full pipe flow rate of the flow calculation module (43) is as follows: Where k is the comprehensive instrument coefficient determined by factory calibration. This coefficient k is determined during factory calibration and covers magnetic field strength, electrode structure, and flow field distribution compensation under non-full pipe conditions. E is the electrode induced electromotive force, σ is the fluid conductivity, and A(h) is the fluid flow cross-sectional area calculated based on the current liquid level height h.

10. A non-full-pipe electromagnetic flowmeter according to claim 8, characterized in that, The fluid flow cross-sectional area A(h) is calculated based on the current liquid level height h and the inner radius R of the measuring tube (1), and the calculation formula is: when hour, ; when hour, .

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