CN114199331A - Flow calculation method suitable for multi-channel ultrasonic flowmeter - Google Patents

Flow calculation method suitable for multi-channel ultrasonic flowmeter Download PDF

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CN114199331A
CN114199331A CN202111393497.4A CN202111393497A CN114199331A CN 114199331 A CN114199331 A CN 114199331A CN 202111393497 A CN202111393497 A CN 202111393497A CN 114199331 A CN114199331 A CN 114199331A
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张鼎
杨杰
邓德兵
赵清森
王加勇
陈伟
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China General Nuclear Power Corp
CGN Power Co Ltd
Suzhou Nuclear Power Research Institute Co Ltd
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CGN Power Co Ltd
Suzhou Nuclear Power Research Institute Co Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/66—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by measuring frequency, phase shift or propagation time of electromagnetic or other waves, e.g. using ultrasonic flowmeters
    • G01F1/667—Arrangements of transducers for ultrasonic flowmeters; Circuits for operating ultrasonic flowmeters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/66—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by measuring frequency, phase shift or propagation time of electromagnetic or other waves, e.g. using ultrasonic flowmeters
    • G01F1/667—Arrangements of transducers for ultrasonic flowmeters; Circuits for operating ultrasonic flowmeters
    • G01F1/668—Compensating or correcting for variations in velocity of sound
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Abstract

The invention discloses a flow calculation method suitable for a multi-channel ultrasonic flowmeter, which comprises the following steps: calculating Reynolds number R of flow fieldeThe span interval of (1); r is to beeThe span interval of (2) is equally divided on a logarithmic coordinate axis; building a system model measured by the ultrasonic flowmeter, and setting boundary conditions of numerical simulation calculation; carrying out numerical calculation on each working condition point, and acquiring flow field data after calculation convergence; determining a sound channel position and a weighted value of the multi-channel ultrasonic flowmeter, and calculating an axial average flow speed; calculating the average sound velocity along the sound channel line; calculating the average sound velocity of the multi-channel ultrasonic flowmeter on each channel line; and obtaining the average flow velocity in the axial direction under each working condition; obtaining the actual axial average flow velocity of each working condition; calculating the deviation between the measured average axial flow velocity and the actual average axial flow velocity under each working condition, and averaging to obtain the average measured deviation; measuring value of multichannel ultrasonic flowmeterCorrecting a line speed profile; the resulting average axial flow velocity.

Description

Flow calculation method suitable for multi-channel ultrasonic flowmeter
Technical Field
The invention belongs to the technical field of flow measurement, and particularly relates to a flow calculation method suitable for a multi-channel ultrasonic flowmeter.
Background
The ultrasonic flowmeter based on time difference method is a kind of flow measuring device which is a mainstream in the market at present, and calculates the flow speed of the fluid by measuring the time difference of the ultrasonic wave in the forward and backward flow propagation process. As shown in fig. 1, the average flow velocity in the pipe is V, the diameter in the pipe is D, the angle between the central connecting line of the two transducers and the flow direction is phi, and the length of the sound channel is L (the sound channel refers to the actual path of the ultrasonic signal propagating between the paired ultrasonic transducers).
The actual propagation speed of the sound wave in the fluid is determined by the propagation speed c of the sound wave in the static state of the mediumfAnd the component of the fluid axial average flow velocity V in the direction of propagation of the acoustic wave. The forward and reverse travel times of the acoustic wave can be expressed as:
Figure BDA0003369146580000011
Figure BDA0003369146580000012
in the formula, tdThe time of the ultrasonic wave propagating in the downstream of the fluid; t is tuThe time of ultrasonic wave propagation in the counter-current flow of the fluid.
Solving the two equations simultaneously to obtain an expression of the axial average flow velocity of the fluid in the pipe:
Figure BDA0003369146580000013
the relationship between the average axial flow velocity of fluid in the pipe and the average axial flow velocity of the measured sound channel is established through ideal flow field conditions, and then the relationship is multiplied by the cross-sectional area of the fluid, so that the volume flow of the fluid can be obtained, as shown in the following formula:
qv＝VA
in the formula, qvIs the volume flow rate; a is the cross-sectional area of the fluid.
The principle is the measuring principle of the single-channel ultrasonic flowmeter. The single-channel flowmeter only has 1 sound channel flow velocity and is sensitive to the change of the flow state. In order to improve the measurement accuracy of the ultrasonic flowmeter, a plurality of sound channels are arranged in parallel on the section to be measured, and the obtained sound channel speed can represent the average speed in the corresponding parallel strips on the section to be measured. For the circular pipe section, the flow in the circular pipe is calculated by adopting a Gauss-Legendre integral method, and as shown in FIG. 2, the following formula is a volume flow calculation formula.
Figure BDA0003369146580000021
In the formula, n is the number of channels; wiIs the weighting coefficient on the i channel; x is the number ofiIs ri/R；ViIs the axial average flow velocity on the i channel.
When the number of channels n is determined, there is an optimal set of Wi、xiValue of qvThe calculation accuracy of (2) is the highest.
The measurement principle of the current mainstream multi-channel time difference method ultrasonic flowmeter is obtained.
For multi-channel ultrasonic flow meters, numerical integration methods are used in solving the flow, and volumetric flow is solved by using a finite number of channels to weight and sum. The method is a universal calculation method, and the influence of the change of the fluid velocity profile in the pipe on the calculation result is not considered. As shown in fig. 3, when the flow field conditions (such as reynolds number) vary in a large range, the velocity profile of the fluid in the pipe may be deformed, or the conditions of the pipe section upstream of the measurement position are poor, the conditions of the straight pipe section are insufficient, and the velocity profile is asymmetrically arranged, which may affect the measurement accuracy.
Disclosure of Invention
In view of the above, to overcome the defects of the prior art, the present invention aims to provide a flow calculation method suitable for a multi-channel ultrasonic flowmeter.
In order to achieve the purpose, the invention adopts the following technical scheme:
a flow calculation method suitable for a multi-channel ultrasonic flowmeter comprises the following steps:
1) according to the use requirements and equipment parameters of the multi-channel ultrasonic flowmeter, confirming the arrangement forms of upstream and downstream pipe sections at the measuring position, including the length of a straight pipe, the number of elbows, the structure of the elbows, whether a valve exists, whether reducing exists and the like; confirming the diameter and the wall surface roughness of the pipeline between the ultrasonic transducers; confirming the variation range of fluid parameters in the pipeline;
2) calculating the Reynolds number R of the flow field according to the variation range of the fluid parameters in the pipelineeSpan interval of [ R ]e min，Re max]；
3) R is to beeThe span interval of (2) is equally divided on a logarithmic coordinate axis to obtain n Reynolds number nodes, wherein n is more than or equal to 7, m flow field working condition points are designed for each Reynolds number through different flow, temperature and pressure combinations, and m is more than or equal to 3;
4) building a system model measured by the ultrasonic flowmeter in numerical simulation software, and setting boundary conditions of numerical simulation calculation;
5) based on the system model in the step 4), carrying out numerical calculation on each working condition point, and acquiring flow field data after calculation convergence;
6) determining the sound channel position and the weighted value of the multi-channel ultrasonic flowmeter by adopting a Gauss-Legendre numerical integration method, and calculating the axial average flow speed;
7) deriving coordinate parameters and speed coordinate parameters of each sound channel line in a coordinate axis, and calculating the average sound velocity along the sound channel line;
8) repeating the step 7) on other sound channel parameters to obtain the average sound velocity of the multi-channel ultrasonic flowmeter on each sound channel line; and repeating the step 6) to obtain the measured axial average flow velocity V under each working conditionmeasure；
9) The axial average flow speed on the middle section of the energy converter is used as a theoretical true value, and the actual axial average flow speed V of each working condition is obtained by an integral methodacutal；
10) Calculating the deviation between the measured average axial flow velocity and the actual average axial flow velocity under each working condition;
11) averaging the measurement deviation under each Reynolds number condition to obtain an average measurement deviation;
12) performing polynomial fitting on the average measurement deviation and the Reynolds number to obtain a fitting formula; and carrying out velocity profile correction on the measured value in the multi-channel ultrasonic flowmeter, wherein the correction coefficient is as follows:
Figure BDA0003369146580000031
in the formula, Kσσ' is the average measurement deviation for the correction coefficient;
13) and correcting the measured average axial flow speed according to the correction coefficient.
According to some preferred aspects of the invention, the fluid parameters in step 1) include flow rate, pressure, temperature.
According to some preferred aspects of the invention, the Reynolds number R of the flow field in step 2)eCalculated by the following formula:
Figure BDA0003369146580000032
where ρ is the fluid density; v is the average axial flow velocity in the pipe; d is the diameter of the pipeline; μ is the fluid kinematic viscosity.
According to some preferred implementation aspects of the invention, the modeling range of the system model in step 4) is at least 50D for the upstream pipeline and at least 20D for the downstream pipeline with reference to the ultrasonic flow meter measurement point.
According to some preferred implementation aspects of the invention, the boundary conditions in step 4) are numerically calculated using the volume flow, the fluid temperature, and the fluid pressure at each operating condition in step 3).
According to some preferred aspects of the invention, the axial average flow velocity in step 6) is calculated by the following formula:
Figure BDA0003369146580000033
in the formula, VmeasureIs the axial average flow velocity, ViIs the average speed of sound, x, on the vocal tract lineiFor the channel position, w, of a multi-channel ultrasonic flowmeteriThe weighted value of the position of the sound channel of the multi-channel ultrasonic flowmeter.
According to some preferred aspects of the invention, the average speed of sound along the channel line in step 7) is calculated by:
1) the position coordinate of a certain point R on the AB sound channel in the x and y coordinate system is set as (L)Rx，LRy) Velocity coordinate is (V)Rx，VRy)；
2) With A (L)Ax，LAy) Establishing a uniaxial coordinate system in the AB direction for the origin, wherein the position coordinate of the R point is the distance relative to the A point
Figure BDA0003369146580000041
Speed value of
Figure BDA0003369146580000042
The position and velocity coordinates of R are
Figure BDA0003369146580000043
Figure BDA0003369146580000044
3) The average speed of sound along the channel line is calculated by the following formula:
Figure BDA0003369146580000045
in the formula, VABIs the average speed of sound along the line of the channel, LAIs the position coordinate of point A, LBIs the position coordinate of point B.
According to some preferred aspects of the invention, the measurement deviation σ in step 10) is calculated by the following formula:
Figure BDA0003369146580000046
wherein σ is a measurement deviation; vmeasureIs the axial average flow velocity; vacutalIs the actual axial average flow velocity.
According to some preferred aspects of the invention, the measured average axial flow velocity corrected according to the correction factor is:
Figure BDA0003369146580000047
where V is the corrected average axial flow velocity.
Due to the adoption of the technical scheme, compared with the prior art, the invention has the beneficial effects that: according to the flow calculation method suitable for the multi-channel ultrasonic flowmeter, the correction coefficient of the velocity profile is introduced, so that the measurement error caused by the non-uniform flow field of the pipeline and the deformation of the velocity profile along with the Reynolds number can be eliminated; the method is used for compensating the influence of the change of the velocity profile along with the Reynolds number on the measurement precision, and ensures that the ultrasonic flowmeter has stable measurement precision under the conditions of large-range change of the Reynolds number in specific application scenes (arrangement of an upstream pipe section and a downstream pipe section, pipe section roughness and the like).
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In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a schematic diagram of a prior art transit time ultrasonic flow meter measurement;
FIG. 2 is a schematic diagram of a measurement principle of a multi-channel ultrasonic flowmeter in the prior art;
FIG. 3 is a velocity profile at different Reynolds numbers;
fig. 4 is a schematic diagram of measurement of 4 channels in the embodiment of the present invention.
Detailed Description
In order to make those skilled in the art better understand the technical solution of the present invention, the technical solution in the embodiment of the present invention will be clearly and completely described below with reference to the drawings in the embodiment of the present invention, and it is obvious that the described embodiment is only a part of the embodiment of the present invention, and not a whole embodiment. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 4, the process of generating the velocity profile correction factor for a certain ultrasonic flowmeter having 4 channels in the present embodiment under a specific application scenario includes the following steps, where the specific application scenario refers to a certain fixed position where the flowmeter is installed on a pipeline, and the upstream and downstream pipeline layouts are fixed.
1. According to the use requirements and equipment parameters of the multi-channel ultrasonic flowmeter, confirming the arrangement forms of upstream and downstream pipe sections at the measuring position, including the length of a straight pipe, the number of elbows, the structure of the elbows, whether a valve exists, whether reducing exists and the like; confirming the diameter and the wall surface roughness of the pipeline between the ultrasonic transducers; and confirming the variation range of the fluid parameters in the pipeline, including flow, pressure and temperature.
2. Calculating the Reynolds number R of the flow field according to the variation range of the fluid parameters in the pipelineeSpan interval of [ R ]e min，Re max]. Reynolds number R of flow fieldeCalculated according to the following formula:
Figure BDA0003369146580000051
where ρ is the fluid density; v is the average axial flow velocity in the tube; d-pipe diameter; μ -fluid kinematic viscosity.
3. R is to beeSpan interval of [ R ]e max，Re max]Equally dividing on a logarithmic coordinate axis with the base 10 as a base to obtain n Reynolds number nodes, wherein n is more than or equal to 7. Through different flow, temperature and pressure combinations, m flow field working points are designed for each Reynolds number, and m is more than or equal to 3. Each reynolds number node and corresponding flow field condition as shown in table 1 were obtained.
TABLE 1 Reynolds number nodes and corresponding flow field conditions
Re min Re 2 Re 3 … Re max
Working condition 1 qv11 t11 p11 qv21 t21 p21 qv31 t31 p31 qvn1 tn1 pn1
Working condition 2 qv12 t12 p12 qv22 t22 p22 qv32 t32 p32 qvn2 tn2 pn2
…
Operating mode m qv1m t1m p1m qv2m t2m p2m qv3m t3m p3m qvn m tnm pnm
4. And (3) building a system model measured by the ultrasonic flowmeter in numerical simulation software according to all parameters in the step 1, wherein the modeling range is at least 50D away from the upstream pipeline and at least 20D away from the downstream pipeline by taking the measuring point of the ultrasonic flowmeter as a reference. If the valve and other equipment exist in the range, the valve can be simplified into reducing treatment, and the diameter of the reducing aperture is calculated according to the size of the valve.
5. Setting a numerical simulation calculation boundary condition. Taking the volume flow, the fluid temperature and the fluid pressure under each working condition in the table 1 as boundary conditions for numerical calculation; and performing numerical calculation on each working condition point, and acquiring flow field data after calculation convergence, wherein the flow field data comprises position parameters, speed parameters, pressure, temperature, kinematic viscosity, dynamic viscosity, density and the like of each point.
6. Method for determining sound channel position x of multi-channel ultrasonic flowmeter by Gauss-Legendre numerical integrationiSum weight wiAnd the axial average flow velocity is calculated by the following formula.
Figure BDA0003369146580000061
In the formula, VmeasureIs the axial average flow velocity, ViIs the average speed of sound, x, on the vocal tract lineiFor the channel position, w, of a multi-channel ultrasonic flowmeteriThe weighted value of the position of the sound channel of the multi-channel ultrasonic flowmeter.
7. And deriving coordinate parameters and speed coordinate parameters of each sound channel line in x and y coordinate axes.
As shown in FIG. 4, the position coordinate of a certain point R on the AB channel in the x and y coordinate system is (L)Rx，LRy) Velocity coordinate is (V)Rx，VRy). A uniaxial coordinate system in the AB direction is established by taking A as an origin, and the position coordinate of the R point is
Figure BDA0003369146580000062
The velocity coordinate is
Figure BDA0003369146580000063
In summary, the position and velocity coordinates of R are
Figure BDA0003369146580000064
Figure BDA0003369146580000065
The average sound velocity V along the vocal tract line is calculated by an integration method using the following formulaAB。
Figure BDA0003369146580000071
In the formula, VABIs the average speed of sound along the channel line.
8. Repeating the step 7 for the other sound channel parameters to obtain the average sound velocity V of the multi-channel ultrasonic flowmeter on each sound channel line1、V2、V3……Va. And step 6 is executed to obtain the axial average flow velocity V measured under each working conditionmeasureAs shown in table 2.
TABLE 2 measurement of average axial flow Rate under various operating conditions
Re min Re 2 Re 3 … Re max
Working condition 1 V11 measure V21 measure V31 measure V41 measure
Working condition 2 V12 measure V22 measure V32 measure V42 measure
…
Operating mode m V13 measure V23 measure V33 measure V43 measure
9. Because numerical simulation calculation has calculation errors, the axial average flow velocity on the middle section of the transducer is used as a theoretical true value; obtaining the actual axial average flow velocity V of each working condition by carrying out double integral on the circular sectionacutalAs shown in table 3.
Figure BDA0003369146580000072
Wherein VrθR is the circular cross-sectional radius for the axial velocity at each integration point.
TABLE 3 actual average axial flow Rate under various operating conditions
Re min Re 2 Re 3 … Re max
Working condition 1 V11 acutal V21 acutal V31 acutal V41 acutal
Working condition 2 V12 acutal V22 acutal V32 acutal V42 acutal
…
Operating mode m V13 acutal V23 acutal V33 acutal V43 acutal
10. And calculating the deviation sigma of the measured average axial flow speed and the actual average axial flow speed under each working condition.
Figure BDA0003369146580000073
Wherein σ is a measurement deviation; vmeasureIs the axial average flow velocity; vacutalIs the actual axial average flow velocity.
11. The measurement deviations σ for each Reynolds number condition were averaged to obtain an average measurement deviation σ' as shown in Table 4.
TABLE 4 average axial flow Rate measurement bias at Reynolds numbers
Re min Re 2 Re 3 … Re max
Mean deviation of measurement σ′1 σ′2 σ′3 σ′n
12. Polynomial averaging of measured deviation and Reynolds number in Table 4 dataFitting to obtain a fitting formula sigma-f (R)e). And carrying out velocity profile correction on the measured value in the multi-channel ultrasonic flowmeter, wherein the correction coefficient is as follows:
Figure BDA0003369146580000081
in the formula, KσTo correct the coefficients, σ' is the average measurement deviation.
13. And correcting the measured average axial flow speed according to the correction coefficient to be:
Figure BDA0003369146580000082
where V is the corrected average axial flow velocity.
The method aims at the situation that the multi-channel ultrasonic flowmeter is applied in a specific scene, a numerical simulation technology is utilized to carry out simulation calculation on a plurality of characteristic working conditions, and flow field data under each characteristic working condition are obtained. The specific application scenario refers to that the flowmeter is installed at a certain fixed position, and the upstream pipeline and the downstream pipeline are clearly arranged. Characteristic working condition is Reynolds number R of flow fieldeAs a key reference value, the Reynolds number is a main factor influencing the flow field velocity profile on the premise of no change of an application scene. Taking the average axial flow velocity obtained by integral calculation on the section of the middle position of the multi-channel flowmeter as the actual average axial flow velocity Vactual. The speed along the sound channel direction calculated on each sound channel by a linear integration method is the sound channel average sound velocity, and the measured average axial flow velocity V of the ultrasonic flowmeter can be obtained by using a Gauss-Legendre numerical integration methodmeasure. Calculating the measurement deviation sigma of the ultrasonic flowmeter under each characteristic working condition, and fitting ReCurve with σ. In a multi-channel ultrasonic flowmeter, a velocity profile correction coefficient K is introducedσAnd further correcting the measurement result of the flow rate.
In the prior art, when the flow field conditions (such as Reynolds number) are changed in a large range, the fluid velocity profile in the pipe is deformed, or the pipe section strip at the upstream of the measuring positionThe method has the advantages that the measurement precision is affected due to poor components, insufficient conditions of the straight pipe section and asymmetrical arrangement of the speed profile, so that the influence of the change on the measurement precision is eliminated by introducing the speed profile correction coefficient. After the velocity profile correction coefficient is introduced, the measurement error caused by the non-uniformity of the pipeline flow field and the deformation of the velocity profile along with the Reynolds number can be eliminated. Multi-channel flow meter in order to verify the measurement with a certain accuracy, the minimum flow q must be reachedminTo maximum flow q of the labelmaxCan ensure a certain precision qminAt least 0.3 m/s. If the flowmeter requires a high accuracy and a flow range (q)min，qmax) With a large span, the measurement errors introduced by the velocity profile will cause the meter to fail certification. The method disclosed by the patent is used for correcting the flow calculation, so that the stability of the measurement accuracy of the multi-channel flowmeter in the verification process can be improved.
The numerical simulation calculation is carried out on a certain multi-channel ultrasonic flowmeter, the pipe diameter is 250mm, the water temperature is 20 ℃, and the pressure is 0.3 MPa. Under the working condition that the flow velocity is 0.3m/s, the measurement deviation is 0.58%, and when the flow velocity reaches more than 6m/s, the measurement deviations are all about 0.05%. If the flow meter requires a measurement accuracy of 0.3%, the measurement accuracy cannot be guaranteed due to the influence of the simple velocity profile change on the measurement accuracy. By introducing a correction factor KσThe method can eliminate the measurement error caused by the velocity profile and improve the calibration precision of the flowmeter.
The invention provides a velocity profile correction calculation method which is used for compensating the influence of the velocity profile along with the change of Reynolds number on the measurement accuracy and ensuring that an ultrasonic flowmeter has stable measurement accuracy under the conditions of specific application scenes (arrangement of upstream and downstream pipe sections, pipe section roughness and the like) and large-range change of the Reynolds number. The method comprises the steps of calculating the average speed of the ultrasonic flowmeter along the sound channel direction by a linear integration method, taking the average speed as the measuring speed of the ultrasonic transducer, and acquiring the measured value of the ultrasonic flowmeter by using numerical simulation data; and designing a characteristic working condition boundary condition for numerical calculation by taking Re as a key value, obtaining the measurement deviation sigma under each Reynolds number Re, and obtaining a fitting relational expression.
The above embodiments are merely illustrative of the technical concept and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the content of the present invention and implement the invention, and not to limit the scope of the invention, and all equivalent changes or modifications made according to the spirit of the present invention should be covered by the scope of the present invention.

Claims (9)

1. A flow calculation method suitable for a multi-channel ultrasonic flowmeter is characterized by comprising the following steps:
1) according to the use requirements and equipment parameters of the multi-channel ultrasonic flowmeter, confirming the arrangement forms of an upstream pipe section and a downstream pipe section of a measuring position, confirming the diameter and the wall surface roughness of a pipeline between ultrasonic transducers and confirming the variation range of fluid parameters in the pipeline;
2) calculating the Reynolds number R of the flow field according to the variation range of the fluid parameters in the pipelineeThe span interval of (1);
3) r is to beeThe span interval of (2) is equally divided on a logarithmic coordinate axis to obtain n Reynolds number nodes, wherein n is more than or equal to 7, m flow field working condition points are designed for each Reynolds number through different flow, temperature and pressure combinations, and m is more than or equal to 3;
4) building a system model measured by the ultrasonic flowmeter in numerical simulation software, and setting boundary conditions of numerical simulation calculation;
5) based on the system model in the step 4), carrying out numerical calculation on each working condition point, and acquiring flow field data after calculation convergence;
6) determining the sound channel position and the weighted value of the multi-channel ultrasonic flowmeter by adopting a Gauss-Legendre numerical integration method, and calculating the axial average flow speed;
7) deriving coordinate parameters and speed coordinate parameters of each sound channel line in a coordinate axis, and calculating the average sound velocity along the sound channel line;
8) repeating the step 7) on other sound channel parameters to obtain the average sound velocity of the multi-channel ultrasonic flowmeter on each sound channel line; and repeating the step 6) to obtain the measured axial average flow velocity V under each working conditionmeasure；
9) Using axial flats on the transducer mid-sectionThe average flow velocity is taken as a theoretical true value, and the actual axial average flow velocity V of each working condition is obtained by an integral methodacutal；
10) Calculating the deviation between the measured average axial flow velocity and the actual average axial flow velocity under each working condition;
11) averaging the measurement deviation under each Reynolds number condition to obtain an average measurement deviation;
12) performing polynomial fitting on the average measurement deviation and the Reynolds number to obtain a fitting formula; and carrying out velocity profile correction on the measured value in the multi-channel ultrasonic flowmeter, wherein the correction coefficient is as follows:
Figure FDA0003369146570000011
in the formula, Kσσ' is the average measurement deviation for the correction coefficient;
13) and correcting the measured average axial flow speed according to the correction coefficient.
2. The calculation method according to claim 1, wherein the fluid parameters in step 1) include flow rate, pressure, temperature.
3. The calculation method according to claim 1, wherein the Reynolds number R of the flow field in the step 2)eCalculated by the following formula:
Figure FDA0003369146570000021
where ρ is the fluid density; v is the average axial flow velocity in the pipe; d is the diameter of the pipeline; μ is the fluid kinematic viscosity.
4. The calculation method according to claim 1, wherein the modeling range of the system model in step 4) is at least 50D for the upstream pipeline and at least 20D for the downstream pipeline with reference to the ultrasonic flow meter measurement point.
5. The calculation method according to claim 1, wherein the boundary conditions in step 4) are calculated by taking the volume flow, the fluid temperature and the fluid pressure under each working condition in step 3) as numerical boundary conditions.
6. The method of claim 1, wherein the average axial flow velocity in step 6) is calculated by the following formula:
Figure FDA0003369146570000022
in the formula, VmeasureIs the axial average flow velocity, ViIs the average speed of sound, x, on the vocal tract lineiFor the channel position, w, of a multi-channel ultrasonic flowmeteriThe weighted value of the position of the sound channel of the multi-channel ultrasonic flowmeter.
7. The calculation method according to claim 4, wherein the average speed of sound along the channel line in step 7) is calculated by:
1) the position coordinate of a certain point R on the AB sound channel in the x and y coordinate system is set as (L)Rx，LRy) Velocity coordinate is (V)Rx，VRy)；
2) With A (L)Ax，LAy) Establishing a uniaxial coordinate system in the AB direction for the origin, wherein the position coordinate of the R point is a distance relative to the A point
Figure FDA0003369146570000023
Speed value of
Figure FDA0003369146570000024
The position and velocity coordinates of R are
Figure FDA0003369146570000025
Figure FDA0003369146570000026
3) The average speed of sound along the channel line is calculated by the following formula:
Figure FDA0003369146570000027
in the formula, VABIs the average speed of sound along the line of the channel, LAIs the position coordinate of point A, LBIs the position coordinate of point B.
8. Calculation method according to claim 1, characterized in that the measurement deviation σ in step 10) is calculated by the following formula:
Figure FDA0003369146570000031
wherein σ is a measurement deviation; vmeasureIs the axial average flow velocity; vacutalIs the actual axial average flow velocity.
9. The method of claim 8, wherein the measured average axial flow velocity is corrected based on a correction factor of
Figure FDA0003369146570000032
Where V is the corrected average axial flow velocity.
CN202111393497.4A 2021-11-23 2021-11-23 Flow calculation method suitable for multi-channel ultrasonic flowmeter Pending CN114199331A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116698141A (en) * 2023-07-28 2023-09-05 山东大学 Speed measurement error correction method and system for ultrasonic flowmeter under different working conditions
CN116754029A (en) * 2023-08-17 2023-09-15 北京嘉洁能科技股份有限公司 Pipeline flow measurement method and calorimeter integrator system

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116698141A (en) * 2023-07-28 2023-09-05 山东大学 Speed measurement error correction method and system for ultrasonic flowmeter under different working conditions
CN116698141B (en) * 2023-07-28 2023-10-27 山东大学 Speed measurement error correction method and system for ultrasonic flowmeter under different working conditions
CN116754029A (en) * 2023-08-17 2023-09-15 北京嘉洁能科技股份有限公司 Pipeline flow measurement method and calorimeter integrator system
CN116754029B (en) * 2023-08-17 2023-11-17 北京嘉洁能科技股份有限公司 Pipeline flow measurement method and calorimeter integrator system

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