CN114877975A - Ultrasonic water meter flow error correction method based on reynolds number of pipeline inlet - Google Patents
Ultrasonic water meter flow error correction method based on reynolds number of pipeline inlet Download PDFInfo
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- CN114877975A CN114877975A CN202210652059.3A CN202210652059A CN114877975A CN 114877975 A CN114877975 A CN 114877975A CN 202210652059 A CN202210652059 A CN 202210652059A CN 114877975 A CN114877975 A CN 114877975A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F25/00—Testing or calibration of apparatus for measuring volume, volume flow or liquid level or for metering by volume
- G01F25/10—Testing or calibration of apparatus for measuring volume, volume flow or liquid level or for metering by volume of flowmeters
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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
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
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Abstract
The invention discloses an ultrasonic water meter flow error correction method based on a reynolds number of a pipeline inlet. Calculating to obtain a flow correction coefficient through the Reynolds number of the pipeline inlet, the standard instantaneous flow and the instantaneous flow of the ultrasonic water meter to be measured at different flow points, and establishing a nonlinear correction model of the flow correction coefficient and the Reynolds number of the pipeline inlet in different flow intervals, wherein each flow interval comprises 30% of flow points in two adjacent intervals. Calculating a flow correction coefficient by using calibration flow points with large error values at 30% -70% and relatively concentrated in each flow interval to calibrate the flow in the interval; after two corrections, the error of the flow point in the flow interval is greatly reduced. The error correction method of the invention ensures that the correction models of each flow interval are mutually independent, the flow points of different flow intervals are not influenced mutually, the correction difficulty is reduced, and the method is suitable for the ultrasonic water meter with wide range ratio and high accuracy.
Description
Technical Field
The invention belongs to the technical field of flow detection, and relates to an ultrasonic water meter flow error correction method based on a reynolds number of a pipeline inlet.
Background
The error is a key index for evaluating the quality of the ultrasonic water meter, the difference between the measured flow and the standard flow accounts for the percentage of the standard flow, and the smaller the percentage is and the smaller the repeatability is, the better the performance of the ultrasonic water meter is. Before the ultrasonic water meter leaves a factory, an accumulative flow experiment needs to be carried out on a calibrating device, and error correction is carried out according to an experiment result, so that the accuracy grade is met, and whether a product is qualified or not is determined according to a flow correction result.
The ultrasonic water meter mostly adopts a time transmission method measuring principle, the water flow velocity is mainly calculated by calculating the forward and backward flow propagation time difference of ultrasonic waves in water, and finally the forward and backward flow propagation time difference is converted into the flow passing through a water meter pipeline. The speed of ultrasonic propagation measurement is the linear velocity V in the pipeline L And the standard flow rate Q is equal to the cross-sectional area S and the cross-sectional average velocity V F The correction factor is calculated by an empirical calculation formula. However, the empirical formulas are all corrected and compensated under ideal conditions, and in actual conditions, the motion state of fluid in the pipe of the ultrasonic water meter is complex (see the attached figures 1-4 in the specification), and the linear velocity V is caused by the influence of environmental factors such as the temperature and the viscosity coefficient of the fluid L And section mean velocity V F There is a certain difference that the empirical formula is difficult to correctly reflect the actual flow conditions. The flow measurement accuracy is improved by correcting errors through piecewise linear interpolation of standard flow Q and time difference T. However, in the measurement of a small-caliber ultrasonic water meter, in order to improve the sound path, an insert, a column and a bracket are often used to increase the propagation path of ultrasonic waves, so that the deviation of the actual flow field inside the pipeline from an ideal state becomes more disordered, and therefore, the traditional error correction method is not suitable any more. Especially in small-flow measurement, the interval between calibration points is small, the nonlinearity is more obvious, the correction of the flow points can not only influence each other, but also increase the correction difficulty, and the calibration efficiency is low
Disclosure of Invention
The invention provides an ultrasonic water meter flow error correction method based on a reynolds number of a pipeline inlet, aiming at the problems existing in ultrasonic water meter error correction.
The technical scheme adopted by the invention is as follows:
calculating to obtain a flow correction coefficient through the Reynolds number of the pipeline inlet, the standard instantaneous flow and the instantaneous flow of the ultrasonic water meter to be measured at different flow points, and establishing Q Ⅰ ～Q Ⅱ ,Q Ⅱ ～Q Ⅲ ,Q Ⅲ ～Q Ⅳ ,Q Ⅳ ～Q Ⅴ .. nonlinear correction model (Q) of flow correction coefficient and pipeline inlet Reynolds number in equal different flow intervals Ⅰ 、Q Ⅱ 、Q Ⅲ 、Q Ⅳ 、Q Ⅴ Is the flow point in the range of the measured ultrasonic water meter), and each flow interval comprises 30 percent of the flow points in each of two adjacent intervals. Calculating a flow correction coefficient by using calibration flow points with large error values at 30% -70% and relatively concentrated in each flow interval to calibrate the flow in the interval; after two corrections, the error of the flow point in the flow interval is greatly reduced. The error correction method of the invention ensures that the correction models of each flow interval are mutually independent and the flow points of different flow intervals are not influenced mutually.
The invention has the beneficial effects that:
1. the existing ultrasonic water meter error correction method is a linear formula for correcting flow and time difference, and the method introduces the Reynolds number of a pipeline inlet into a correction model. The reynolds number is a dimensionless number that can be used to characterize fluid flow conditions. The fluid condition of the small-caliber ultrasonic water meter is complex and does not accord with the traditional flow coefficient correction formula, the Reynolds number calculation formula comprises variables such as fluid density, flow velocity and viscosity coefficient, the variables are related to the fluid state, and the Reynolds number of the pipeline inlet is introduced into a correction model, so that the correction error is comprehensively corrected from a single time difference to multiple aspects of the fluid state.
2. The correction model of each flow interval is independent, so that the correction of a single flow point does not influence other flow points, and the correction difficulty of operators is reduced. In the process of measuring the small flow of the ultrasonic water meter, the error correction of one calibration flow point can affect the error of the adjacent calibration flow points, the error of the peripheral calibration flow points needs to be verified after correction, when the flow error exceeds the precision requirement, the correction coefficient needs to be repeatedly confirmed, and the experiment is repeated, so that the correction difficulty is increased, and the time for calibrating the ultrasonic water meter is also increased. By adopting the correction method, the independent correction model of each flow interval is established, the error correction of the mutually overlapped intervals is not influenced, the correction and the calibration of the flow point are convenient, and the correction method is more suitable for the ultrasonic water meter with wide range ratio and high accuracy.
Drawings
FIG. 1 is a simulated velocity cloud plot of a vertical cross-section of the flow of an ultrasonic watermeter conduit Q3;
FIG. 2 is a simulated velocity cloud plot of a horizontal cross-section of the flow of an ultrasonic watermeter conduit Q3;
FIG. 3 is a simulated velocity cloud plot of the vertical cross-section of the ultrasonic watermeter conduit Q1 flow;
FIG. 4 is a simulated velocity cloud plot of a horizontal cross-section of the flow of an ultrasonic watermeter conduit Q1;
FIG. 5 is a schematic diagram of flow interval division;
FIG. 6 is a flow chart of the ultrasonic water meter error correction method based on the Reynolds number of the pipeline inlet according to the present invention;
FIG. 7 is a diagram of a flow correction model according to the present invention.
Detailed Description
The present invention is described in further detail below with reference to the attached drawing figures.
The technical scheme adopted by the invention is as follows: reynolds number Re of pipeline inlet and standard instantaneous flow Q at different flow points S And ultrasonic water meter instantaneous flow Q m Establishing Q Ⅰ ～Q Ⅱ ,Q Ⅱ ～Q Ⅲ ,Q Ⅲ ～Q Ⅳ ,Q Ⅳ ～Q Ⅴ .., non-linear correction model in several different flow intervals (where Q Ⅰ 、Q Ⅱ 、Q Ⅲ 、Q Ⅳ 、Q Ⅴ .. flow points within the range of an ultrasonic water meter), wherein the interval division is shown in figure 5. Considering that a flow field in a pipeline is influenced by secondary flow and pulsating flow and system errors of an experimental calibration device, flow points are not stable at a fixed value, each flow interval needs to contain 30% of the flow points of adjacent intervals, and the flow points of a critical interval are contained in 2 correction models at the same time. Then, in each flow interval, calculating a flow correction coefficient by adopting flow points with larger error values and relatively concentrated positions of 30-70% for calibrating the flow in the interval; twice throughAfter correction, the error of the flow point in the flow interval is greatly reduced.
Fig. 6 is a flowchart of an ultrasonic water meter error correction method based on the reynolds number of the inlet of the pipeline, and the method includes the following steps:
the method comprises the following steps: the measured ultrasonic water meter is arranged on the water flow standard calibrating device, and different flow points in the range are set through an upper computer of the water flow standard calibrating device. After the flow is stable, recording the standard instantaneous flow Q of the standard table under each flow point S And the instantaneous flow Q of the ultrasonic water meter to be measured m And the time difference value T measured by the ultrasonic water meter to be measured is acquired in real time.
In order to reduce the influence of random error and obtain an accurate correction model, the flow Q is measured at the same standard instant S And acquiring time difference values T measured by the ultrasonic water meter to be measured for multiple times, and calculating to obtain average time difference values T.
According to the standard instantaneous flow Q S Calculating the average flow velocity V of the inlet section of the pipeline F See formula (1); and calculating the Reynolds number Re of the pipeline inlet by the formula (2).
Wherein rho, v and mu are density, flow velocity and viscosity coefficient of the fluid respectively, d is characteristic length, S is cross-sectional area of fluid domain of the pipeline, and Q is S Is a standard instantaneous flow value.
According to the formula (3), calculating to obtain the linear velocity V measured by the ultrasonic water meter to be measured L And calculating the instantaneous flow Q of the ultrasonic water meter to be measured according to a formula (4) m . And then calculating to obtain a flow correction coefficient Y according to a formula (5) so as to establish a correction model of the Reynolds number of the pipeline inlet and the flow correction coefficient of each flow interval.
Where C is the propagation velocity of the ultrasonic wave in water,
for the average time difference obtained by sampling, K is the ratio of the average speed under ideal state and the linear average speed, Q m The instantaneous flow value of the ultrasonic water meter to be measured is shown, Y is a flow correction coefficient, L is a sound path, and theta is an included angle between an ultrasonic path and a pipeline central axis.
Step two: and establishing a correction model of the flow correction coefficient Y and the Reynolds number Re of the pipeline inlet. Establishing Q based on a large amount of experimental data acquired and calculated in the step one Ⅰ ～Q Ⅱ ,Q Ⅱ ～Q Ⅲ ,Q Ⅲ ～Q Ⅳ ,Q Ⅳ ～Q Ⅴ .., non-linear correction model in several different flow intervals (where Q Ⅰ 、Q Ⅱ 、Q Ⅲ 、Q Ⅳ 、Q Ⅴ .., flow point in the measuring range of the ultrasonic water meter to be measured), and obtaining a flow correction model of each flow interval through matlab by taking the reynolds number Re of the pipeline inlet and the flow correction coefficient Y as independent variables and functions: y is i ＝a i ·Re n +b i ·Re n-1 +····+c i In the formula a i 、b i …c i And the flow intervals can directly overlap each 30% flow point of two adjacent intervals.
In this embodiment, according to a minimum flow point Q1, a demarcation flow point Q2, a common flow point Q3, an overload flow point Q4, 0.33(Q1+ Q3), and 0.67(Q1+ Q3) of a cold water meter in a national metrological verification rule of jjjg-162-2009-cold water meter, five sequentially connected flow intervals are obtained by dividing a measured ultrasonic water meter, wherein the five flow intervals are respectively Q1-Q2, Q2-0.33 (Q1+ Q3), 0.33(Q1+ Q3) -0.67 (Q1+ Q3), 0.67(Q1+ Q3) -Q3, and Q3-Q4, a flow correction model map corresponding to the flow interval is established, and as shown in fig. 7, a broken line in the map is drawn by collected and calculated experimental data; the real curve is a source of a correction model polynomial, and the consistency degree of the trend line and the virtual broken line is improved by adjusting the number of n. Considering the calculation efficiency of the correction model added into the single chip microcomputer and the polynomial coefficient can not be too small, n is generally between 2 and 4.
Step three: after a correction model of each flow interval is established, substituting the Reynolds numbers of the pipeline inlets of all the calibration flow points into the corresponding correction model, and calculating to obtain the flow correction coefficients Y of all the corresponding flow intervals i And calculating the corrected instantaneous flow Q 'of the ultrasonic water meter to be measured according to a formula (6)' m . The correction model can realize the primary correction of the ultrasonic water meter, but the pipeline size, the transducer characteristic, the hardware circuit and the like of each ultrasonic water meter cannot be completely consistent. The protruding structures such as the upright post bracket in the pipeline have great influence on the flow field, and the flow needs to be corrected for the second time in order to improve the measurement precision of the ultrasonic water meter again. The invention corrects the instantaneous flow Q' m And standard instantaneous flow rate Q S Calculating a quadratic correction factor Z i (see equation 7), the measured flow value is further made to approach the true value by applying a quadratic correction method.
Q′ m ＝Y i ×Q m (6)
The calculated quadratic correction coefficient Z i Substituting into formula (8), calculating to obtain secondary corrected instantaneous flow Q ″) m ：
Q″ m ＝Z i ×Q′ m (8)
Finally, the secondary corrected instantaneous flow Q ″, is calculated m And standard instantaneous flow rate Q S To an error value therebetween.
Table 1 shows experimental data obtained by the method of the present invention, and table 2 shows experimental data obtained by the conventional method, and errors of both methods meet the secondary accuracy requirement of the ultrasonic water meter. However, with the conventional method, the error correction of one flow point may affect the error of the adjacent flow point, and after the correction, the error of the surrounding flow point needs to be verified, and when the flow error exceeds the accuracy requirement, the correction coefficient needs to be repeatedly confirmed, and the experiment is repeated. The two methods are compared, the traditional method has poor error repeatability at a small flow, and the minimum flow is 0.01m 3 H is used as the reference value. The instantaneous flow Q' after the secondary correction by using the method of the invention m And standard instantaneous flow rate Q S The difference between the two is greatly reduced, the repeatability of the measurement error of the ultrasonic water meter is better, and the minimum flow is 0.0063m 3 /h。
TABLE 1 experimental data based on the Reynolds number error correction method at the entrance of a pipeline
TABLE 2 Experimental data of conventional error correction method
In the process of calibrating the actual flow, all flow correction coefficients and secondary correction coefficients in the range do not need to be calculated, but a calibration flow point Q with a large error value and relatively concentrated is taken in each flow interval iuse (can be selected between 30% and 70% of the flow interval), and the flow correction coefficient Y is calculated iuse And a secondary flow correction coefficient Z iuse Y of the flow point iuse And Z iuse And substituting the formula (6) and the formula (8) as the unique value of the correction coefficient in the flow interval.
Claims (5)
1. An ultrasonic water meter flow error correction method based on a reynolds number of a pipeline inlet is characterized by comprising the following steps:
the method comprises the following steps: setting the flow point in the range of the ultrasonic water meter to be measured by an upper computer of the water flow standard calibrating device, and collecting the standard instantaneous flow Q of the standard meter under different flow points S And the instantaneous flow Q of the ultrasonic water meter to be measured m Calculating to obtain a reynolds number of a pipeline inlet and a flow correction coefficient according to the time difference value measured by the ultrasonic water meter to be measured;
step two: establishing a plurality of different flow intervals based on the data acquired and calculated in the step one, and fitting to obtain a flow correction coefficient Y of each flow interval i A modified model of the Reynolds number of the pipeline inlet;
step three: substituting the Reynolds number of the pipeline inlet of the calibration flow point in each flow interval into the correction model in the step two to obtain a flow correction coefficient Y corresponding to each flow interval i And calculating the corrected instantaneous flow Q 'of the ultrasonic water meter to be measured according to the formula (6)' m ：
Q′ m ＝Y i ×Q m (6)
Then, a quadratic correction coefficient Z is calculated according to the formula (7) i ：
The calculated quadratic correction coefficient Z i Substituting into formula (8), calculating to obtain secondary corrected instantaneous flow Q ″) m ：
Q″ m ＝Z i ×Q′ m (8)
Step four: calculating the secondary corrected instantaneous flow Q m And standard instantaneous flow rate Q S To an error value therebetween.
2. The ultrasonic water meter flow error correction method based on the reynolds number of the inlet of the pipeline as claimed in claim 1, wherein:
in the second step, each flow interval comprises 30% of flow points of adjacent intervals.
3. The ultrasonic water meter flow error correction method based on the reynolds number of the inlet of the pipeline as claimed in claim 1, wherein:
and in each flow interval in the third step, the flow points with larger error values and relatively concentrated at the positions of 30-70% are used as calibration flow points to calculate a flow correction coefficient for calibrating the flow in the interval.
4. The ultrasonic water meter flow error correction method based on the reynolds number of the inlet of the pipeline as claimed in claim 1, wherein:
in the first step, the time difference value measured by the ultrasonic water meter to be measured is the average time difference value measured by the ultrasonic water meter to be measured for many times.
5. The ultrasonic water meter flow error correction method based on the reynolds number of the inlet of the pipeline as claimed in claim 1, wherein:
in the second step, the flow point Q of the ultrasonic water meter to be measured is set according to the upper computer Ⅰ 、Q Ⅱ 、Q Ⅲ 、Q Ⅳ 、Q Ⅴ .., establishing Q Ⅰ ～Q Ⅱ ,Q Ⅱ ～Q Ⅲ ,Q Ⅲ ～Q Ⅳ ,Q Ⅳ ～Q Ⅴ ... different flow intervals.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116793462A (en) * | 2023-08-21 | 2023-09-22 | 成都千嘉科技股份有限公司 | Calibration method and calibration device based on ultrasonic gas meter |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116793462A (en) * | 2023-08-21 | 2023-09-22 | 成都千嘉科技股份有限公司 | Calibration method and calibration device based on ultrasonic gas meter |
| CN116793462B (en) * | 2023-08-21 | 2023-11-03 | 成都千嘉科技股份有限公司 | Calibration method and calibration device based on ultrasonic gas meter |
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