Measurement correction and optimization arrangement method for external clamping type ultrasonic flowmeter in disturbed flow field

Abstract

The invention provides a measurement correction and optimization arrangement method for an external clamping type ultrasonic flowmeter in a disturbed flow field, which comprises the following steps of: firstly, simulating the disturbed flow field in an actual pipeline in an industrial field by using computational fluid mechanics simulation software to obtain accurate flow field distribution near disturbance; secondly, performing integration on each ultrasonic propagation path grid point in different measurement modes to obtain in-pipe flow velocity simulation values and section average velocity at positions with different lengths away from a disturbance point, multiplying the values by the section area to obtain uncorrected flow and standard reference flow, and comparing the uncorrected flow and the standard reference flow to obtain flow deviation distribution; and then establishing a function relationship between flow deviation distribution and sensor installation arrangement, and obtaining a measurement path combination enabling the flow deviation to be insensitive to a sensor installation angle through data analysis, thereby correcting measurement results at different positions of the downstream of the disturbance pipeline through quantitative correction factors. According to the method, the measurement result with the measurement error lower than 2% can be obtained in the straight pipe section range of ten times of the pipeline diameter at the downstream of the elbow pipe in an industrial field.

Description

Technical Field

[0001] The invention relates to the technical field of flow measurement, and in particular to a measurement correction and optimization arrangement method of an external clamp-on ultrasonic flowmeter under a disturbed flow field. Background Art

[0002] Regular inspection of flow meters to ensure the accuracy of flow measurement is one of the important links to ensure trade fairness. However, the current inspection of gas flow meters is mainly based on laboratory inspection, which has problems such as long inspection cycle and restrictions on normal work needs, and faces the challenge of weak on-site inspection technology.

[0003] With the advancement of science and technology, clamp-on ultrasonic flowmeters have emerged. They are portable, non-invasive, and easy to use, and have good application prospects in online gas flow measurement and on-site flowmeter detection. Ultrasonic flowmeters usually use the time difference method for measurement, and the measurement accuracy is greatly affected by the actual flow field. There are many common typical disturbance structures in industry, such as tapered / expanded pipes, 90° elbows, and double-plane 180° elbows. These structures will cause the downstream flow field to produce lateral flow or vortexes, which greatly interfere with the measurement of ultrasonic flowmeters. The metrological verification regulations for ultrasonic flowmeters JJG1030-2007 clearly state that without installing a flow conditioner, the installation of the clamp-on ultrasonic flowmeter needs to ensure that the upstream and downstream straight pipe sections are 22D (pipeline diameter) in front and 8D in the back, and this is under the condition of smaller disturbances such as tapered pipes. Compared with the contact ultrasonic flowmeter, which can use multi-channel and rectifier to compensate for the error caused by the disturbed flow field (the straight pipe section is required to be 10D in front and 5D in the back), the channel line information obtained by the clamp-on ultrasonic flowmeter is limited, and the use conditions are very harsh. In industrial sites, it is usually difficult to meet such a long front straight pipe section, especially under the condition of a larger pipe diameter. At this time, the underdeveloped flow in the pipe will cause a large error in the measurement of the clamp-on ultrasonic flowmeter, which brings great challenges to the application of the instrument. Correcting the disturbance introduced by the flow field through the correction factor is an effective method, but under the condition of complex flow fields, the installation position and installation angle of the clamp-on ultrasonic flowmeter sensor will affect the measurement results. Each independent operation mode requires a separate correction factor, which not only requires a huge database, but also introduces a lot of uncertainty. Therefore, it is worth studying how to overcome the influence of its installation position and installation angle within a shorter straight pipe section length range through the limited channel line information obtained by the clamp-on ultrasonic flowmeter to obtain more accurate measurement results.

[0004] The real flow experiment is a feasible solution, but the on-site detection conditions are complex and changeable, and it is difficult to cover all working conditions and instrument installation methods through experiments. In addition, the real flow experiment method requires a lot of manpower, material and financial resources. Therefore, from the perspective of the distribution of the disturbed flow field, it is very important to find a suitable method to guide the layout of the external clamp-on ultrasonic flowmeter and the correction of the measurement results through reasonable simulation and result analysis, and to establish a corresponding database to compensate for the measurement errors caused by the disturbed flow field and sensor layout. Summary of the invention

[0005] In view of the existing actual flow experiments for flow measurement of external clamp-on ultrasonic flowmeters, there are complex and changeable on-site detection conditions, and it is difficult to cover all working conditions and instrument installation methods through experiments. In addition, the actual flow experiment method requires a lot of manpower, material and financial resources. The present invention provides a measurement correction and optimization layout method for an external clamp-on ultrasonic flowmeter under a disturbed flow field. The method obtains a disturbance flow field correction factor based on computational fluid dynamics simulation, and obtains the optimized installation layout path of the external clamp-on ultrasonic flowmeter sensor through data fitting. The method can compensate for the flow measurement deviation introduced by disturbance and sensor installation, and realize high-accuracy measurement within a shorter distance from the disturbance in the industrial field.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] The measurement correction and optimization arrangement method of the clamp-on ultrasonic flowmeter under the disturbed flow field comprises the following steps:

[0008] S1. Use computational fluid dynamics simulation software to simulate the disturbed flow field in the actual pipeline at the industrial site. According to the physical object under study, the model is established, meshed, initial and boundary conditions are set, simulation calculations are performed, and results are post-processed. The mesh at the bend of the pipeline inlet section is encrypted to obtain a more accurate flow field distribution near the disturbance.

[0009] S2. Define the actual gas or liquid medium composition and temperature and pressure conditions in the simulation as the initial settings, simulate and obtain the flow velocity and flow field distribution in the pipeline, divide the flow velocity into the radial flow velocity along the mainstream and the longitudinal flow velocity caused by the disturbance, and then obtain the flow velocity distribution in each grid point on the sound path passing through the center of the pipeline;

[0010] S3. According to the time difference method principle of the external clamp-on ultrasonic flowmeter, the ultrasonic propagation paths under different measurement modes of the external clamp-on ultrasonic flowmeter sensor are extracted respectively. According to the velocity distribution obtained in step S2, the ultrasonic propagation forward and reverse flow time in the grid points along different ultrasonic paths is calculated. Then, each ultrasonic propagation path grid point is integrated to calculate the total ultrasonic propagation forward and reverse flow time between the upstream and downstream sensors of the external clamp-on ultrasonic flowmeter. Based on this, the simulated flow velocity values ​​in the pipe at different lengths from the disturbance point are calculated. Then, the uncorrected flow rate under different distance disturbance position conditions is obtained by multiplying the simulated flow velocity value along the ultrasonic propagation path by the cross-sectional area. At the same time, the velocity surface integral is performed on the cross section at the measured position. The calculated average cross-sectional velocity is multiplied by the cross-sectional area to obtain the standard reference flow rate. The uncorrected flow rate is compared with the standard reference flow rate to obtain the flow deviation distribution measured by the flowmeter.

[0011] S4. Establish a functional relationship between the obtained flow deviation distribution and the installation position and installation angle of the clamp-on ultrasonic flowmeter sensor. Through data evaluation and analysis, obtain a measurement path combination that makes the flow deviation insensitive to the installation angle of the clamp-on ultrasonic flowmeter sensor. Measure the flow velocity and flow value according to different sensor combinations, that is, overcome the influence of the sensor installation angle on the flow deviation fluctuation through a multi-channel sensor arrangement path combination, so that the flow deviation at the same distance downstream of the disturbance can be compensated and corrected with a quantitative correction factor. On this basis, establish a database of sensor installation combinations and corresponding quantitative correction factors under different types of disturbance conditions, and achieve accurate measurement within the length range of a straight pipe section less than ten times the pipe diameter downstream of the disturbance flow field in an industrial field.

[0012] Furthermore, in the simulation of step S1, the fully developed flow field calculated separately is mapped to the upstream fluid domain inlet in a user-defined manner, thereby effectively reducing the size of the geometric model and the amount of calculation of this simulation.

[0013] Furthermore, the flow velocity and flow field distribution in step S2 are obtained by setting the length of the upstream inlet section of the disturbance to 7 times the pipe diameter, the length of the downstream pipeline of the disturbance to 100 times the pipe diameter, and setting a total of 35 inlet velocities in the range of 1-35m / s, with each 1m / s as a point, for batch calculation simulation.

[0014] Furthermore, in step S3, the ultrasonic propagation paths under the commonly used industrial sensor diagonal arrangement and reflection arrangement are extracted, and for each sensor arrangement, at 8 positions of 2 times the pipe diameter, 5 times the pipe diameter, 10 times the pipe diameter, 20 times the pipe diameter, 30 times the pipe diameter, 50 times the pipe diameter, 80 times the pipe diameter, and 100 times the pipe diameter downstream of the disturbance, and at 17 angles of 0°, 30°, 45°, 60°, 90°, 120°, 135°, 150°, 180°, 210°, 225°, 240°, 270°, 300°, 315°, 330°, and 360° with the horizontal plane, integral calculation is performed along the grid points of the ultrasonic propagation path to obtain 136 sets of flow velocity simulation values ​​along the ultrasonic propagation path.

[0015] Furthermore, in step S4, it is obtained through data algorithm analysis that when two sets of relatively vertically arranged sensor reflection installation combinations are used downstream of the double-plane elbow, the dependence of the measured flow deviation distribution on the sensor installation angle disappears, and at the same distance position as the disturbance downstream, the deviation fluctuation can be controlled within the range of ±2%, so that the flow deviation fluctuation is independent of the sensor installation angle, and each disturbance distance corresponds to a quantitative correction factor.

[0016] Furthermore, the quantitative correction factor is obtained by taking the average of the correction factors under 17 angle conditions of 0°, 30°, 45°, 60°, 90°, 120°, 135°, 150°, 180°, 210°, 225°, 240°, 270°, 300°, 315°, 330°, and 360° with the horizontal plane at each disturbance distance position.

[0017] Furthermore, for different types of disturbances, the flow field distribution in the inlet velocity range of 1-35m / s, the temperature range of 10-30℃, and the pressure range of 0-10MPa was simulated and calculated; and the 136 flow field distributions at 8 positions with a distance of 2, 5, 10, 20, 30, 50, 80, and 100 times the diameter of the pipe downstream of the disturbance and at 17 angles of 0°, 30°, 45°, 60°, 90°, 120°, 135°, 150°, 180°, 210°, 225°, 240°, 270°, 300°, 315°, 330°, and 360° to the horizontal plane were calculated. The flow deviation along the ultrasonic propagation path is grouped, and the sensor installation combination that makes the flow deviation insensitive to the ultrasonic propagation path is analyzed; then, according to each disturbance distance position, the correction factors under 17 angle conditions of 0°, 30°, 45°, 60°, 90°, 120°, 135°, 150°, 180°, 210°, 225°, 240°, 270°, 300°, 315°, 330°, and 360° with the horizontal plane are taken as the average value to obtain the quantitative correction factor, and a database of sensor installation combinations and quantitative correction factors corresponding to different disturbance types is established, which can be used for use under different flow rates and field conditions.

[0018] Furthermore, the method further comprises the following steps:

[0019] S5. When using an external clamp-on ultrasonic flowmeter at an industrial site, first estimate the measured flow rate and convert it to a flow velocity based on the pipe cross-section parameters; then, based on the database established in step S4, use the interpolation method to estimate the correction factor required for the disturbed flow field, and obtain the actual flow rate under the estimated correction factor condition; then, compare the theoretical correction factor corresponding to the actual flow rate with the estimated correction factor. If the error between the two is less than 1%, the flow value measured by this method is considered valid. Otherwise, continue to iterate the calculation using the theoretical correction factor of the current measured flow rate until the error is less than 1%.

[0020] Compared with the prior art, the measurement correction and optimization layout method of the external clamp-on ultrasonic flowmeter under a disturbed flow field provided by the present invention provides a correction method and sensor layout technical solution for improving the measurement accuracy of the external clamp-on ultrasonic flowmeter downstream of an industrial disturbance. Through the multi-channel sensor layout path installation combination, the influence of the installation angle of the external clamp-on ultrasonic flowmeter sensor on the flow measurement deviation fluctuation can be overcome within a range of ten times the pipe diameter downstream of the disturbance, and quantitative correction can be achieved at a position at the same distance as the disturbance, thereby obtaining an accurate gas flow value, and realizing high-accuracy measurement within a shorter distance from the disturbance at the industrial site. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1It is a schematic diagram of establishing and meshing a double-plane curved pipe model provided by the present invention.

[0022] Figure 2 It is a schematic diagram of batch setting and calculation of entry conditions provided by the present invention.

[0023] Figure 3 It is a schematic diagram of flow velocity and flow field distribution at different distances downstream of the disturbance provided by the present invention.

[0024] Figure 4 It is a schematic diagram of the method for extracting grid velocity along the ultrasonic propagation path provided by the present invention.

[0025] Figure 5 It is a schematic diagram of the relationship between the flow deviation distribution provided by the present invention and the change in the sensor installation arrangement.

[0026] Figure 6 It is a schematic diagram of the measurement deviation distribution provided by the present invention as the sensor installation angle changes.

[0027] Figure 7 It is a schematic diagram of the dual-channel sensor arrangement path installation combination method after calculation and analysis provided by the present invention.

[0028] Figure 8 It is a schematic diagram of the error distribution between the test and the simulation provided by the present invention.

[0029] Fig. 9 It is a schematic diagram of a correction factor distribution database independent of the sensor rotation angle provided by the present invention.

[0030] Fig.10 It is a schematic diagram of the overall calculation iterative judgment process provided by the present invention. DETAILED DESCRIPTION

[0031] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below with reference to specific diagrams.

[0032] In order to better understand the technical solution provided by the present invention, the following embodiments will take the double-plane elbow disturbance as an example. This type of disturbance often occurs in industrial sites, and the flow field downstream of the disturbance is very complex and irregular. The metrological verification procedure for ultrasonic flowmeters JJG1030-2007 stipulates that an external clamp-on ultrasonic flowmeter needs to be used within a range beyond 70D (pipe diameter) downstream of the disturbance. However, it is difficult to have such a long straight pipe section in actual industrial sites.

[0033] Specifically, the present invention provides a method for measuring, correcting and optimizing the arrangement of a clamp-on ultrasonic flowmeter under a disturbed flow field, comprising the following steps:

[0034] S1. Use computational fluid dynamics simulation software such as ANSYS or COMSOL software to simulate the disturbed flow field in the actual pipeline at the industrial site. According to the physical object under study, the model is established, meshed, initial and boundary conditions are set, simulation calculations and result post-processing are carried out in sequence. Specifically, the Design Modeler and Mesh modules in ANSYS software can be used to model and mesh the double-plane elbow under study, and the mesh at the elbow of the pipeline inlet section can be encrypted to obtain a more accurate flow field distribution near the disturbance, such as Figure 1 As shown. As a specific embodiment, the length of the upstream inlet section of the disturbance is set to 7D (7 times the pipe diameter). The fully developed flow field calculated in another separate simulation is mapped to the upstream fluid domain inlet in a user-defined manner, so as to add a fully developed flow field to the inlet surface of the fluid domain, thereby effectively reducing the size of the geometric model and the amount of calculation of this simulation. The inlet condition is set to the velocity inlet. According to the actual situation of the field working conditions, the length of the downstream pipeline of the disturbance is 100D (100 times the pipe diameter), and the outlet condition is set to the pressure outlet. The backflow suppression option is selected, indicating that the fluid will continue to flow after passing through the outlet pipe section. The simulation adopts the method of solving the steady-state Reynolds averaged Navier-Stokes (RANS) equations, and the RNG k-ε model considering turbulent vortices is selected.

[0035] S2. According to the different needs of the actual site, the gas or liquid medium components and temperature and pressure conditions of the actual site are defined as the initial settings in the simulation. By using the custom calculation module in ANSYS FLUENT, the length of the upstream inlet section of the disturbance is set to 7 times the pipe diameter, the length of the downstream pipeline of the disturbance is set to 100 times the pipe diameter, and a total of 35 inlet velocities are set in the range of 1-35m / s, with each 1m / s as a point, for batch calculation. The other conditions remain unchanged, such as Figure 2 As shown in the figure, the flow velocity and flow field distribution in the pipeline under different gas or liquid media (including specific component composition), disturbance type, temperature and pressure, flow rate conditions, etc. are simulated. Figure 3 According to the velocity distribution at each grid point on the sound path passing through the center of the pipeline, the velocity is divided into the radial velocity along the mainstream and the longitudinal velocity caused by the disturbance, and then the velocity distribution u at each grid point on the sound path passing through the center of the pipeline is obtained. i =cosθv i,x -sinθv i,y Among them, θ represents the angle between the ultrasonic propagation direction and the fluid flow direction, v i,x and v i,y are the radial and longitudinal components of the flow velocity in grid i, respectively.

[0036] S3, according to the time difference method principle of the clamp-on ultrasonic flowmeter, the ultrasonic propagation paths under different measurement modes of the clamp-on ultrasonic flowmeter sensor, such as diagonal arrangement (Z method) and reflection arrangement (V method), are extracted respectively, and according to the flow velocity distribution obtained in step S2, the ultrasonic propagation forward and reverse flow times at the grid points along different ultrasonic paths are calculated to be t i,up = l i / (c+u i ) and t i,down = l i / (cu i ). Among them, t i,up and t i,down are the ultrasonic propagation forward and reverse flow times in grid i, l i is the length of the ultrasonic propagation path in the grid i, and c is the sound velocity of ultrasound in the medium. The ultrasonic propagation paths under the commonly used diagonal and reflective sensor arrangements in industry were extracted, and for each sensor arrangement, at 8 positions 2D, 5D, 10D, 20D, 30D, 50D, 80D, and 100D downstream of the disturbance, and at 17 angles of 0°, 30°, 45°, 60°, 90°, 120°, 135°, 150°, 180°, 210°, 225°, 240°, 270°, 300°, 315°, 330°, and 360° with the horizontal plane, the grid points along the ultrasonic propagation path were integrated and calculated to obtain 136 sets of flow velocity simulation values ​​along the ultrasonic propagation path. The specific method is as follows: Figure 4 Then, each ultrasonic propagation path grid point is integrated to calculate the ultrasonic propagation forward and reverse flow times between the upstream and downstream sensors of the external clamp-on ultrasonic flowmeter. and Then, according to the total propagation time of ultrasound in the forward and reverse flow, the simulated value of the flow velocity in the pipe at different distances from the disturbance point is calculated. down -t up ) / 2cosθt up t down , L represents the length of the ultrasonic propagation path between the upstream and downstream sensors, and then the uncorrected flow rate Q = kAv under different distance disturbance conditions is obtained by multiplying the simulated flow velocity value along the ultrasonic propagation path by the cross-sectional area, where A is the cross-sectional area of ​​the pipeline, k is the flow correction coefficient, and k = v sur / v,v sur is the surface average axial velocity. At the same time, the velocity surface integral is performed on the cross section at the measured position, and the calculated average cross section velocity is multiplied by the cross section area to obtain the standard reference flow rate. The uncorrected flow rate is compared with the standard reference flow rate to obtain the flow meter measurement flow deviation distribution Q under specific gas medium, disturbance conditions, sensor layout mode, and layout position. dev =(QQsur ) / Q sur ×100%,Q sur Indicates standard reference flow rate.

[0037] S4. Establish a functional relationship between the obtained flow deviation distribution and the installation position and installation angle of the external clamp-on ultrasonic flowmeter sensor, such as Figure 5 As shown, it can be found that at the position 3D downstream of the disturbance, the flow deviation fluctuates in the range of -3.63% to -12.58% and -5.52% to -9.98% using the measurement methods of diagonal arrangement and reflection arrangement; at the position 5D downstream of the disturbance, the flow deviation fluctuates in the range of -3.59 to -10.42% and -3.93% to -7.85% respectively. Such irregular fluctuations indicate that it is impossible to use quantitative correction factors for the measurement correction of the disturbance flow within the range of 10D downstream of the disturbance. Therefore, it is necessary to further evaluate and analyze the Matlab data to obtain a measurement path combination that makes the flow deviation insensitive to the installation angle of the clamp-on ultrasonic flowmeter sensor. When using dual-path or other multi-path combination measurements, since the ultrasonic propagation path passes through the center line of the pipeline, the weight coefficients of different paths are the same, and the flow velocity and flow values ​​are v i Represents the average flow velocity under each measurement path. According to different sensor combinations, the flow velocity flow value v is measured. In the embodiment, through data algorithm analysis, it is found that when two sets of relatively vertically arranged sensor reflection installation combinations are used downstream of the double-plane elbow, the dependence of the measured flow deviation distribution on the sensor installation angle disappears. At the same distance position as the downstream of the disturbance, the deviation fluctuation can be controlled within the range of ±2%, such as Figure 6 As shown in , the flow deviation fluctuation is independent of the sensor installation angle, and each disturbance distance corresponds to a quantitative correction factor. Figure 7 The multi-channel sensor arrangement path combination shown, combined with a reasonable quantitative compensation correction factor, can overcome the influence of the sensor installation angle on the flow deviation fluctuation, so that the flow deviation at the same distance downstream of the disturbance can be compensated and corrected by the quantitative correction factor, and high-precision measurement within a short distance downstream of the disturbance can be achieved. In order to verify that the simulation method and technical route provided by the present invention are feasible, an experimental verification work was carried out on a pipeline with a high-precision standard table, in which two groups of sensors were arranged perpendicular to each other. During the test, the quantitative correction factor generated by the simulation was used, and the obtained flow deviation can be controlled within ±2%. Figure 8 On this basis, a database of sensor installation combinations and corresponding quantitative correction factors under different types of disturbance conditions is established, such as Fig. 9 As shown, an external clamp-on ultrasonic flowmeter is used to achieve accurate measurement within the length range of a straight pipe section less than ten times the pipe diameter (10D) downstream of the disturbed flow field in the industrial field.

[0038] As a specific embodiment, the quantitative correction factor is obtained by taking the average of the correction factors under 17 angle conditions of 0°, 30°, 45°, 60°, 90°, 120°, 135°, 150°, 180°, 210°, 225°, 240°, 270°, 300°, 315°, 330°, and 360° with the horizontal plane at each disturbance distance position, that is, each disturbance distance corresponds to a quantitative correction factor, and at this time the flow deviation fluctuation is not related to the sensor installation angle.

[0039] As a specific embodiment, for different types of disturbances, the flow field distribution in the inlet flow velocity range of 1-35m / s, the temperature range of 10-30°C, and the pressure range of 0-10MPa is simulated and calculated; and then the flow field distribution in 8 positions at 2 times the pipe diameter, 5 times the pipe diameter, 10 times the pipe diameter, 20 times the pipe diameter, 30 times the pipe diameter, 50 times the pipe diameter, 80 times the pipe diameter, and 100 times the pipe diameter downstream of the disturbance is calculated, and the angles with the horizontal plane are 0°, 30°, 45°, 60°, 90°, 120°, 135°, 150°, 180°, 210°, 225°, 240°, 270°, 300°, 315°, 330°, and 360°, respectively. 36 groups of flow deviations along the ultrasonic propagation path are analyzed to obtain the sensor installation combination that makes the flow deviation insensitive to the ultrasonic propagation path; then, according to each disturbance distance position, the correction factors under 17 angle conditions of 0°, 30°, 45°, 60°, 90°, 120°, 135°, 150°, 180°, 210°, 225°, 240°, 270°, 300°, 315°, 330°, and 360° with the horizontal plane are taken as the average value to obtain the quantitative correction factor, and a database of sensor installation combinations and quantitative correction factors corresponding to different disturbance types is established, which can be used under different flow rates and field conditions.

[0040] As a specific embodiment, the method further comprises the following steps:

[0041] S5. When using an external clamp-on ultrasonic flowmeter at an industrial site, first estimate the measured flow rate and convert it to a flow velocity based on the pipe cross-sectional parameters; then, based on the database established in step S4, use the existing interpolation method to estimate the correction factor required for the disturbed flow field, and obtain the measured flow rate under the estimated correction factor condition; then compare the theoretical correction factor corresponding to the measured flow rate with the estimated correction factor. If the error between the two is less than 1%, the flow value measured by this method is considered valid. Otherwise, continue to iterate the calculation using the theoretical correction factor of the current measured flow rate until the error is less than 1%. Fig.10 shown.

[0042] The aforementioned embodiments of the present invention aim at the disturbance pipeline structure at the industrial site that brings errors to the measurement of the external clamp-on ultrasonic flowmeter and the limitations of the application scenarios. A fluid mechanics simulation method is used to obtain the flow field distribution downstream of the disturbance, and the deviation distribution of the external clamp-on ultrasonic flowmeter under different layout modes and measurement path conditions is calculated. Data evaluation and analysis are performed to obtain a measurement path combination and a corresponding correction factor that makes the flow deviation insensitive to the sensor installation angle, thereby proposing a layout scheme and a correction method for the external clamp-on ultrasonic flowmeter in a specific scenario, so as to achieve accurate measurement results within a shorter straight pipe section length at the industrial site.

[0043] Compared with the prior art, the measurement correction and optimization layout method of the external clamp-on ultrasonic flowmeter under a disturbed flow field provided by the present invention provides a correction method and sensor layout technical solution for improving the measurement accuracy of the external clamp-on ultrasonic flowmeter downstream of an industrial disturbance. Through the multi-channel sensor layout path installation combination, the influence of the installation angle of the external clamp-on ultrasonic flowmeter sensor on the flow measurement deviation fluctuation can be overcome within a range of ten times the pipe diameter downstream of the disturbance, and quantitative correction can be achieved at a position at the same distance as the disturbance, thereby obtaining an accurate gas flow value, and realizing high-accuracy measurement within a shorter distance from the disturbance at the industrial site.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A method for measuring, correcting and optimizing the arrangement of a clamp-on ultrasonic flowmeter under a disturbed flow field, characterized in that: The following steps are involved: S1. Use computational fluid dynamics simulation software to simulate the disturbed flow field in the actual pipeline at the industrial site. According to the physical object under study, the model is established, meshed, initial and boundary conditions are set, simulation calculations are performed, and results are post-processed. The mesh at the bend of the pipeline inlet section is encrypted to obtain a more accurate flow field distribution near the disturbance. S2. Define the actual gas or liquid medium composition and temperature and pressure conditions in the simulation as the initial settings, simulate and obtain the flow velocity and flow field distribution in the pipeline, divide the flow velocity into the radial flow velocity along the mainstream and the longitudinal flow velocity caused by the disturbance, and then obtain the flow velocity distribution in each grid point on the sound path passing through the center of the pipeline; S3. According to the time difference method principle of the external clamp-on ultrasonic flowmeter, the ultrasonic propagation paths under different measurement modes of the external clamp-on ultrasonic flowmeter sensor are extracted respectively. According to the velocity distribution obtained in step S2, the ultrasonic propagation forward and reverse flow time in the grid points along different ultrasonic paths is calculated. Then, each ultrasonic propagation path grid point is integrated to calculate the total ultrasonic propagation forward and reverse flow time between the upstream and downstream sensors of the external clamp-on ultrasonic flowmeter. Based on this, the simulated flow velocity values ​​in the pipe at different lengths from the disturbance point are calculated. Then, the uncorrected flow rate under different distance disturbance position conditions is obtained by multiplying the simulated flow velocity value along the ultrasonic propagation path by the cross-sectional area. At the same time, the velocity surface integral is performed on the cross section at the measured position. The calculated average cross-sectional velocity is multiplied by the cross-sectional area to obtain the standard reference flow rate. The uncorrected flow rate is compared with the standard reference flow rate to obtain the flow deviation distribution measured by the flowmeter. S4. Establish a functional relationship between the obtained flow deviation distribution and the installation position and installation angle of the clamp-on ultrasonic flowmeter sensor. Through data evaluation and analysis, obtain a measurement path combination that makes the flow deviation insensitive to the installation angle of the clamp-on ultrasonic flowmeter sensor. Measure the flow velocity and flow value according to different sensor combinations, that is, overcome the influence of the sensor installation angle on the flow deviation fluctuation through a multi-channel sensor arrangement path combination, so that the flow deviation at the same distance downstream of the disturbance can be compensated and corrected with a quantitative correction factor. On this basis, establish a database of sensor installation combinations and corresponding quantitative correction factors under different types of disturbance conditions, and achieve accurate measurement within the length range of a straight pipe section less than ten times the pipe diameter downstream of the disturbance flow field in an industrial field.

2. The measurement correction and optimization arrangement method of the clamp-on ultrasonic flowmeter under the disturbed flow field according to claim 1 is characterized in that: In the simulation of step S1, the fully developed flow field calculated separately is mapped to the upstream fluid domain inlet in a user-defined manner, thereby effectively reducing the size of the geometric model and the amount of calculation of this simulation.

3. The measurement correction and optimization arrangement method of the clamp-on ultrasonic flowmeter under disturbed flow field according to claim 1 is characterized in that: The flow velocity and flow field distribution in step S2 are obtained by setting the length of the upstream inlet section of the disturbance to 7 times the pipe diameter, the length of the downstream pipeline of the disturbance to 100 times the pipe diameter, and setting a total of 35 inlet velocities in the range of 1-35m / s, with each 1m / s as a point, and performing batch calculation simulation.

4. The measurement correction and optimization arrangement method of the clamp-on ultrasonic flowmeter under the disturbed flow field according to claim 1 is characterized in that: In the step S3, the ultrasonic propagation paths under the commonly used industrial sensor diagonal arrangement and reflection arrangement are extracted, and for each sensor arrangement, at 8 positions 2 times the pipe diameter, 5 times the pipe diameter, 10 times the pipe diameter, 20 times the pipe diameter, 30 times the pipe diameter, 50 times the pipe diameter, 80 times the pipe diameter, and 100 times the pipe diameter downstream of the disturbance, and at 17 angles of 0°, 30°, 45°, 60°, 90°, 120°, 135°, 150°, 180°, 210°, 225°, 240°, 270°, 300°, 315°, 330°, and 360° with the horizontal plane, integral calculation is performed along the grid points of the ultrasonic propagation path to obtain 136 groups of flow velocity simulation values ​​along the ultrasonic propagation path.

5. The measurement correction and optimization arrangement method of the clamp-on ultrasonic flowmeter under the disturbed flow field according to claim 1 is characterized in that: In step S4, it is obtained through data algorithm analysis that when two sets of relatively vertically arranged sensor reflection installation combinations are used downstream of the double-plane elbow, the dependence of the measured flow deviation distribution on the sensor installation angle disappears, and at the same distance position as the disturbance downstream, the deviation fluctuation can be controlled within the range of ±2%, so that the flow deviation fluctuation is independent of the sensor installation angle, and each disturbance distance corresponds to a quantitative correction factor.

6. The measurement correction and optimization arrangement method of the clamp-on ultrasonic flowmeter under the disturbed flow field according to claim 5 is characterized in that: The quantitative correction factor is obtained by taking the average value of the correction factors under 17 angle conditions of 0°, 30°, 45°, 60°, 90°, 120°, 135°, 150°, 180°, 210°, 225°, 240°, 270°, 300°, 315°, 330°, and 360° with the horizontal plane at each disturbance distance position.

7. The measurement correction and optimization arrangement method of the clamp-on ultrasonic flowmeter under disturbed flow field according to claim 1 is characterized in that: For different types of disturbances, the simulation and calculation obtain the flow field distribution in the inlet flow velocity range of 1-35m / s, the temperature range of 10-30℃, and the pressure range of 0-10MPa; then, 136 groups of flow fields at 8 positions with a distance of 2 times the pipe diameter, 5 times the pipe diameter, 10 times the pipe diameter, 20 times the pipe diameter, 30 times the pipe diameter, 50 times the pipe diameter, 80 times the pipe diameter, and 100 times the pipe diameter downstream of the disturbance and with an angle of 0°, 30°, 45°, 60°, 90°, 120°, 135°, 150°, 180°, 210°, 225°, 240°, 270°, 300°, 315°, 330°, and 360° to the horizontal plane are calculated. The flow deviation on the ultrasonic propagation path is analyzed to obtain the sensor installation combination that makes the flow deviation insensitive to the ultrasonic propagation path; then, according to each disturbance distance position, the correction factors under 17 angle conditions of 0°, 30°, 45°, 60°, 90°, 120°, 135°, 150°, 180°, 210°, 225°, 240°, 270°, 300°, 315°, 330°, and 360° with the horizontal plane are taken as the average value to obtain the quantitative correction factor, and the sensor installation combination and quantitative correction factor database corresponding to different disturbance types are established, which can be used for use under different flow rates and field working conditions.

8. The measurement correction and optimization arrangement method of the clamp-on ultrasonic flowmeter under disturbed flow field according to claim 1 is characterized in that: The method further comprises the following steps: S5. When using an external clamp-on ultrasonic flowmeter at an industrial site, first estimate the measured flow rate and convert it to a flow velocity based on the pipe cross-section parameters; then, based on the database established in step S4, use the interpolation method to estimate the correction factor required for the disturbed flow field, and obtain the actual flow rate under the estimated correction factor condition; then, compare the theoretical correction factor corresponding to the actual flow rate with the estimated correction factor. If the error between the two is less than 1%, the flow value measured by this method is considered valid. Otherwise, continue to iterate the calculation using the theoretical correction factor of the current measured flow rate until the error is less than 1%.

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