CN114459554A - Method for improving instantaneous flow metering precision of ultrasonic gas meter based on pressure data - Google Patents
Method for improving instantaneous flow metering precision of ultrasonic gas meter based on pressure data Download PDFInfo
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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
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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
- G01F1/05—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 using mechanical effects
- G01F1/34—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 using mechanical effects by measuring pressure or differential pressure
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F15/00—Details of, or accessories for, apparatus of groups G01F1/00 - G01F13/00 insofar as such details or appliances are not adapted to particular types of such apparatus
- G01F15/02—Compensating or correcting for variations in pressure, density or temperature
- G01F15/04—Compensating or correcting for variations in pressure, density or temperature of gases to be measured
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Abstract
The invention relates to a method for improving the instantaneous flow metering precision of an ultrasonic gas meter based on pressure data. The method is characterized in that: installing a differential pressure sensor in the ultrasonic gas meter, wherein two gas pressure acquisition ports of the differential pressure sensor are respectively installed in a flow channel and outside the flow channel, so that the pressure difference between the inside and outside of the flow channel of the ultrasonic gas meter is detected, the downstream propagation time and the upstream propagation time of the ultrasonic wave in the gas at the current moment are measured by adopting a time difference method, and the instantaneous flow is calculated by utilizing the downstream propagation time and the upstream propagation time of the ultrasonic wave in a gas medium; and judging whether the wave jump problem exists or not according to the measured pressure difference and the instantaneous flow, and correcting the downstream propagation time and the upstream propagation time at the current moment by using pressure difference data when the wave jump phenomenon occurs, so that the accurate instantaneous flow at the current moment is obtained, and the metering precision of the instantaneous flow of the ultrasonic gas meter is improved.
Description
Technical Field
The invention relates to a method for improving the instantaneous flow metering precision of an ultrasonic gas meter based on pressure data.
Background
The ultrasonic gas meter has the advantages of non-contact measurement, no movable part, no pressure loss, extremely high measurement precision and the like, and is a research hotspot in the field of gas measurement. The ultrasonic gas meter widely used in the market is generally based on a time difference method, and instantaneous flow is estimated by measuring forward flow propagation time and backward flow propagation time of ultrasonic waves in a gas medium, so that the forward flow propagation time and the backward flow propagation time of the ultrasonic waves in the gas medium are key measurement values of instantaneous flow measurement of the ultrasonic gas meter, and the measurement precision is directly influenced. In the existing scheme, a threshold value method is adopted to detect the propagation time of an ultrasonic signal in a gas medium, but the amplitude change or deformation of the received ultrasonic signal can be caused by the change of the working temperature of an ultrasonic gas meter, the instability of a gas flow field or the change of gas components, so that the threshold value is easily triggered on different rising edges of the ultrasonic signal instead of being always triggered on the same rising edge, and the measured downstream propagation time and the measured upstream propagation time generate time errors of one or more ultrasonic transducer excitation signal periods, namely, a wave jumping phenomenon, thereby causing the calculation of instantaneous flow and larger deviation of an actual value. In the prior art, a plurality of groups of data are collected, and the problem of wave hopping is processed by using a software averaging algorithm, but the method can influence the timeliness and accuracy of metering readings.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to provide a technical scheme of a method for improving the instantaneous flow metering precision of an ultrasonic gas meter based on pressure data.
The method for improving the instantaneous flow metering precision of the ultrasonic gas meter based on the pressure data is characterized by comprising the following steps of: installing a differential pressure sensor in the ultrasonic gas meter, wherein two gas pressure acquisition ports of the differential pressure sensor are respectively installed in a flow channel and outside the flow channel, so that the pressure difference between the inside and outside of the flow channel of the ultrasonic gas meter is detected, the downstream propagation time and the upstream propagation time of the ultrasonic wave in the gas at the current moment are measured by adopting a time difference method, and the instantaneous flow is calculated by utilizing the downstream propagation time and the upstream propagation time of the ultrasonic wave in a gas medium; and judging whether the wave jump problem exists according to the measured pressure difference and the instantaneous flow, and correcting the downstream propagation time and the upstream propagation time at the current moment by using pressure difference data when the wave jump phenomenon occurs, so as to obtain the accurate instantaneous flow at the current moment.
The method for improving the instantaneous flow metering precision of the ultrasonic gas meter based on the pressure data is characterized in that the instantaneous flow calculation comprises the following steps:
(1) measuring the relation between the pressure difference and the instantaneous flow, (2) measuring the instantaneous flow by using a time difference method, and (3) judging whether the wave is jumped or not, and adjusting the forward flow propagation time and the reverse flow propagation time of the ultrasonic wave in the gas medium.
The method for improving the instantaneous flow metering precision of the ultrasonic gas meter based on the pressure data is characterized in that the method for measuring the relation between the pressure difference and the instantaneous flow in the step (1) is as follows:
installing a differential pressure sensor in the flow channel of the ultrasonic gas meter, and detecting the pressure difference inside and outside the flow channel of the ultrasonic gas meter through the differential pressure sensor; according to the Bernoulli equation, the pressure inside and outside the flow channel of the ultrasonic gas meter meets the following formula:
wherein the content of the first and second substances,
is the pressure in the cavity of the ultrasonic gas meter,
is the pressure in the flow channel of the ultrasonic gas meter,
is the average flow velocity of the gas medium in the cavity of the ultrasonic gas meter,
is the average flow velocity of the gas medium in the flow passage of the ultrasonic gas meter,
is the gas density;
from conservation of mass, we obtain:
wherein the content of the first and second substances,
is the sectional area in the cavity of the ultrasonic gas meter,
the cross section area in the flow channel of the ultrasonic gas meter;
the pressure difference between the inside and the outside of the flow passage of the ultrasonic gas meter is obtained by the formulas (1) and (2)
：
According to the formula (3), the pressure difference between the inside and the outside of the flow channel of the ultrasonic gas meter measured by the differential pressure sensor is related to the average flow velocity of the gas medium in the flow channel, and the instantaneous flow is the product of the average flow velocity of the gas medium in the flow channel and the cross section area of the flow channel, so that the pressure difference between the inside and the outside of the flow channel of the ultrasonic gas meter is related to the instantaneous flow of the ultrasonic gas meter;
and (3) sequentially introducing flow to obtain pressure difference data under different instantaneous flows, and performing data fitting on the pressure difference data and the instantaneous flows by using a function model:
wherein, in the step (A),
which is indicative of a pressure difference,
which is indicative of the instantaneous flow rate of the fluid,
is a functional model fitted to the pressure difference and instantaneous flow.
The method for improving the instantaneous flow metering precision of the ultrasonic gas meter based on the pressure data is characterized in that the step (2) of measuring the instantaneous flow by using a time difference method comprises the following steps:
in the above formulas (4) and (5),
is the cross section area of the flow passage of the ultrasonic gas meter,
is the gas in the flow passage of the ultrasonic gas meterThe average velocity of the bulk medium is,
is the length of the sound path,
is the angle of the sound track,
is the downstream propagation time of the ultrasonic wave in the gas medium,
is the countercurrent propagation time of ultrasonic waves in a gas medium; wherein, the cross section area of the flow passage
Length of sound path
Angle of sound channel
Is a constant value, and the instantaneous flow can be calculated according to the downstream propagation time and the upstream propagation time of the ultrasonic wave in the gas medium
。
The method for improving the instantaneous flow metering precision of the ultrasonic gas meter based on the pressure data is characterized in that the step (3) is used for judging whether the wave is jumped or not, and the steps of adjusting the forward flow propagation time and the reverse flow propagation time of the ultrasonic wave in the gas medium are as follows:
calculating the instantaneous flow at the current moment according to the time difference method measuring principle in the step (2)
And (2) the function relation between the pressure difference and the instantaneous flow obtained in the step (1) can be used for deducing the theoretical pressure difference at the current moment
(ii) a Differential pressure sensor for detecting pressure difference inside and outside flow channel of ultrasonic gas meter in real time
When the difference between the measured pressure difference and the theoretical pressure difference
，
The maximum range of the allowable difference between the actually measured pressure difference and the theoretical pressure difference indicates that no wave jump phenomenon exists at the moment; when the difference between the measured pressure difference and the theoretical pressure difference
When the instantaneous flow is calculated incorrectly, the ultrasonic waves have the existence of bouncing waves in the time measurement of the downstream propagation time and the upstream propagation time in the gas medium, so that the downstream propagation time and the upstream propagation time of the ultrasonic waves in the gas medium need to be adjusted;
from measured pressure differences
And the functional relation between the pressure difference and the instantaneous flow rate to deduce the theoretical instantaneous flow rate
，
The theoretical forward flow propagation time and the theoretical reverse flow propagation time of the ultrasonic wave in the gas medium approximately satisfy the following relations:
in the formulae (6) and (7),
is the theoretical downstream propagation time of the ultrasonic wave in the gas medium,
is the theoretical countercurrent propagation time of ultrasonic waves in a gas medium,
is the propagation velocity of sound waves in a gaseous medium; in addition, when the wave jumping phenomenon occurs, the forward flow propagation time of the ultrasonic wave in the gas medium is actually measured
And the theoretical downstream propagation time of ultrasonic waves in a gas medium
Approximately differing by an integer number of ultrasonic transducer excitation signal periods, and actually measuring the counter-current propagation time of ultrasonic waves in a gas medium
Theoretical counter-current propagation time with ultrasonic wave in gas medium
Approximately differing by an integer number of ultrasonic transducer excitation signal periods, the approximate relationship is as follows:
in the formulas (8) and (9),
is the period of the excitation signal of the ultrasonic transducer,
、
represents the wave number; the passing formula (6) -9 can adjust the actual measurement forward flow propagation time and the actual measurement reverse flow propagation time of the ultrasonic wave in the gas medium, thereby obtaining the instantaneous flow at the current moment
The following formula:
the invention installs a differential pressure sensor in the ultrasonic gas meter, the differential pressure sensor detects the pressure difference inside and outside the flow channel of the ultrasonic gas meter, obtains the data corresponding to the pressure difference and the instantaneous flow, and fits the data, and establishes the functional relation between the pressure difference and the instantaneous flow; when the ultrasonic gas meter is used, the theoretical pressure difference at the current moment is obtained according to the current moment instantaneous flow and the function relation between the pressure difference and the instantaneous flow, and the theoretical pressure difference is compared with the pressure difference actually measured by the differential pressure sensor, so that whether the wave jumping phenomenon exists or not is judged; when the wave hopping phenomenon occurs, the actually measured downstream propagation time and the actually measured upstream propagation time of the ultrasonic wave in the gas medium are corrected by using the pressure difference data, so that the accurate instantaneous flow is obtained, and the measurement precision of the instantaneous flow of the ultrasonic gas meter is improved.
Detailed Description
The invention relates to a method for improving the instantaneous flow metering precision of an ultrasonic gas meter based on pressure data, wherein a differential pressure sensor is arranged in a flow passage of the ultrasonic gas meter, the differential pressure sensor is used for detecting the pressure difference between the inside and the outside of the flow passage of the ultrasonic gas meter, obtaining the data corresponding to the pressure difference and the instantaneous flow, and fitting the data to establish the functional relation between the pressure difference and the instantaneous flow; when the ultrasonic gas meter is used, the theoretical pressure difference at the current moment is obtained according to the current moment instantaneous flow and the function relation between the pressure difference and the instantaneous flow, and the theoretical pressure difference is compared with the pressure difference actually measured by the differential pressure sensor, so that whether the wave jumping phenomenon exists or not is judged; when the wave jump phenomenon occurs, the pressure difference is used for correcting the measured forward flow propagation time and the measured backward flow propagation time of the ultrasonic wave in the gas medium.
The calculation of the instantaneous flow rate comprises the following steps:
(1) measuring pressure differential versus instantaneous flow
A differential pressure sensor is arranged in a flow channel of the ultrasonic gas meter, and two gas pressure acquisition ports of the differential pressure sensor are respectively arranged in the flow channel and outside the flow channel, so that the pressure difference between the inside and the outside of the flow channel of the ultrasonic gas meter is detected. According to the Bernoulli equation, the pressure inside and outside the flow channel of the ultrasonic gas meter meets the following formula:
wherein the content of the first and second substances,
is the pressure in the cavity of the ultrasonic gas meter,
is the pressure in the flow channel of the ultrasonic gas meter,
is the average flow velocity of the gas medium in the cavity of the ultrasonic gas meter,
is the average flow velocity of the gas medium in the flow passage of the ultrasonic gas meter,
is the gas density;
from conservation of mass, we obtain:
wherein the content of the first and second substances,
is the sectional area in the cavity of the ultrasonic gas meter,
the cross section area in the flow channel of the ultrasonic gas meter;
the pressure difference between the inside and the outside of the flow passage of the ultrasonic gas meter is obtained by the formulas (1) and (2)
：
According to the formula (3), the pressure difference between the inside and the outside of the flow channel of the ultrasonic gas meter measured by the differential pressure sensor has a certain relation with the average flow velocity of the gas medium in the flow channel, and the instantaneous flow is the product of the average flow velocity of the gas medium in the flow channel and the cross section area of the flow channel, so that the pressure difference between the inside and the outside of the flow channel of the ultrasonic gas meter has a certain relation with the instantaneous flow of the ultrasonic gas meter. And (3) sequentially introducing flow to obtain pressure difference data under different instantaneous flows, and performing data fitting on the pressure difference data and the instantaneous flows by using a function model:
wherein, in the step (A),
which is indicative of a pressure difference,
which is indicative of the instantaneous flow rate of the fluid,
is a functional model fitted to the pressure difference and instantaneous flow. With reference to equation (3), function
Can be
，
、
、
Is the pressure difference data and instantaneous flow rate according to
And (5) carrying out coefficient obtained by data fitting. Therefore, according to the functional relation between the pressure difference and the instantaneous flow, the theoretical pressure difference at the current moment can be deduced from the instantaneous flow at the current moment; the theoretical instantaneous flow at the current moment can be deduced from the actually measured pressure difference at the current moment.
In practical application, the structures of the flow channel and the cavity of the ultrasonic gas meters in different types can be different, so that the relation between the pressure difference and the flow needs to be measured through the device firstly. In this embodiment, a G6 ultrasonic gas meter is selected, a critical flow venturi nozzle method gas flow standard device is adopted, two gas pressure acquisition ports of a differential pressure sensor are respectively installed inside and outside a flow channel, a gas medium is air, and a relationship between a pressure difference and a flow rate is shown in the following table under the temperature of 20 ℃ in the experimental environment.
As can be seen from the above table, when the flow rate is 2.5m3The pressure difference is 21.29Pa, and the flow range is (4-5) m3At the time of/h, the pressure difference is (40-60) Pa. In this embodiment, the selection is made
The function model performs data fitting on the pressure difference data and the instantaneous flow. Wherein the density of the gas
1.208kg/m are taken3(temperature 20 ℃ C., pressure 101.6 kPa),
、
、
is a fitting coefficient to be solved, and obtains the following functional relation:
the density of the gas is affected by the temperature, known as the absolute temperature
Lower gas density
(the present embodiment)
Is a light-emitting diode of 293.15K,
is 1.208 kg/L) at absolute temperature by the ideal gas equation
Lower density
：
That is, the pressure difference versus flow becomes:
(2) calculating instantaneous flow by using time difference method measurement principle
In the above formulas (4) and (5),
is the cross section area of the flow passage of the ultrasonic gas meter,
is the average velocity of the gas medium in the flow passage of the ultrasonic gas meter,
is the length of the sound path,
is the angle of the sound track,
is the downstream propagation time of the ultrasonic wave in the gas medium,
is the countercurrent propagation time of ultrasonic waves in a gas medium; wherein, the cross-sectional area of the flow passage
Length of sound path
Angle of sound channel
Is a constant value, and the instantaneous flow can be calculated according to the downstream propagation time and the upstream propagation time of the ultrasonic wave in the gas medium
. It can be seen that the forward flow propagation time and the backward flow propagation time of the ultrasonic wave in the gas medium are key measurement values of the instantaneous flow measurement of the ultrasonic gas meter, and the measurement precision is affected.
(3) Judging whether the wave is jumped or not, and adjusting the downstream propagation time and the upstream propagation time of the ultrasonic waves in the gas medium
Calculating the instantaneous flow at the current moment according to the time difference method measuring principle in the step (2)
And (2) the function relation between the pressure difference and the instantaneous flow obtained in the step (1) can be used for deducing the theoretical pressure difference at the current moment
：
Differential pressure sensor for detecting pressure difference inside and outside flow channel of ultrasonic gas meter in real time
When the difference between the measured pressure difference and the theoretical pressure difference
，
The maximum range of the allowable difference between the actually measured pressure difference and the theoretical pressure difference indicates that no wave jump phenomenon exists at the moment; when the difference between the measured pressure difference and the theoretical pressure difference
It is explained that the instantaneous flow rate is calculated with an error, and the forward propagation time and the backward propagation time of the ultrasonic wave in the gas medium need to be adjusted because a beat wave exists in the time measurement of the forward propagation time and the backward propagation time of the ultrasonic wave in the gas medium. According to the curve fitted in the present embodiment,
is 3.2Pa, so the maximum range of the allowable difference between the measured pressure difference and the theoretical pressure difference at the current moment
5Pa may be taken.
From measured pressure differences
And the functional relation between the pressure difference and the instantaneous flow rate to deduce the theoretical instantaneous flow rate
：
Theoretical instantaneous flow
The theoretical forward flow propagation time and the theoretical reverse flow propagation time of the ultrasonic wave in the gas medium approximately satisfy the following relations:
in the formulae (6) and (7),
is the theoretical downstream propagation time of the ultrasonic wave in the gas medium,
is the theoretical countercurrent propagation time of ultrasonic waves in a gas medium,
is the propagation velocity of sound waves in a gaseous medium.
Speed of sound in air at 293.15K
Taking the value of 343.64m/s, the speed of sound is affected by temperature, at absolute temperature
Speed of sound of lower
：
Speed of sound in equation (16) when temperature changes
And (6) carrying out calculation by the formulas (6) and (7) to obtain the theoretical forward flow propagation time and the theoretical reverse flow propagation time of the ultrasonic wave in the gas medium.
In addition, when the wave jumping phenomenon occurs, the forward flow propagation time of the ultrasonic wave in the gas medium is actually measured
And the theoretical downstream propagation time of ultrasonic waves in a gas medium
Approximately differing by an integer number of ultrasonic transducer excitation signal periods, and actually measuring the counter-current propagation time of ultrasonic waves in a gas medium
Theoretical counter-current propagation time with ultrasonic wave in gas medium
Approximately differing by an integer number of ultrasonic transducer excitation signal periods, the approximate relationship is as follows:
in the formulas (8) and (9),
is the period of the excitation signal of the ultrasonic transducer,
、
representing the wave number. The passing formula (6) -9 can adjust the actual measurement forward flow propagation time and the actual measurement reverse flow propagation time of the ultrasonic wave in the gas medium, thereby obtaining the instantaneous flow at the current moment
The following formula:
sound path length of ultrasonic gas meter in this embodiment
Is 0.0725m, vocal tract angle
Is 45 ℃ and the cross-sectional area of the flow passage
Is 0.0004m2Period of excitation signal of ultrasonic transducer
Is 5 us. A set of experimental data was selected to further illustrate that when the instantaneous flow rate was 4.89m3H, function of pressure difference and instantaneous flowThe difference value between the theoretical pressure difference and the actually measured pressure difference at the current moment is 1.69Pa due to the number relation, and the difference value between the theoretical pressure difference and the actually measured pressure difference is less than 5Pa, so that the phenomenon of wave jumping is avoided. It can now be further verified that the theoretical instantaneous flow rate is 4.79m from the measured pressure difference of 56.07Pa and the instantaneous flow rate as a function of the pressure difference3Therefore, the wave number is 212.59us by the formulas (8) and (9) when the theoretical forward propagation time of the ultrasonic wave in the gas medium is 209.36us and the theoretical reverse propagation time of the ultrasonic wave in the gas medium is 212.62us, the actual forward propagation time of the ultrasonic wave in the gas medium is 210.3us, and the theoretical reverse propagation time of the ultrasonic wave in the gas medium is 212.59us
、
Is 0.
In summary, the invention installs the differential pressure sensor in the ultrasonic gas meter, detects the pressure difference inside and outside the flow channel of the ultrasonic gas meter through the differential pressure sensor, establishes the functional relationship between the pressure difference and the flow, and judges whether the wave jump problem exists in the downstream propagation time and the upstream propagation time of the ultrasonic wave in the gas medium measured in the time difference method, thereby preventing the occurrence of wrong measurement data. When the wave jumping phenomenon occurs, the pressure difference is used for correcting the forward flow propagation time and the reverse flow propagation time of the ultrasonic wave in the gas medium at the current moment, so that the instantaneous flow is adjusted, and the reliability and the accuracy of gas metering are improved.
Claims (5)
1. The method for improving the instantaneous flow metering precision of the ultrasonic gas meter based on the pressure data is characterized by comprising the following steps of: installing a differential pressure sensor in the ultrasonic gas meter, wherein two gas pressure acquisition ports of the differential pressure sensor are respectively installed in a flow channel and outside the flow channel, so that the pressure difference between the inside and outside of the flow channel of the ultrasonic gas meter is detected, the downstream propagation time and the upstream propagation time of the ultrasonic wave in the gas at the current moment are measured by adopting a time difference method, and the instantaneous flow is calculated by utilizing the downstream propagation time and the upstream propagation time of the ultrasonic wave in a gas medium; and judging whether the wave jump problem exists according to the measured pressure difference and the instantaneous flow, and correcting the downstream propagation time and the upstream propagation time at the current moment by using pressure difference data when the wave jump phenomenon occurs, so as to obtain the accurate instantaneous flow at the current moment.
2. The method for improving the instantaneous flow metering accuracy of the ultrasonic gas meter based on the pressure data as claimed in claim 1, wherein the calculation of the instantaneous flow comprises the following steps:
(1) measuring the relation between the pressure difference and the instantaneous flow, (2) measuring the instantaneous flow by using a time difference method, and (3) judging whether the wave is jumped or not, and adjusting the forward flow propagation time and the reverse flow propagation time of the ultrasonic wave in the gas medium.
3. The method for improving the instantaneous flow metering accuracy of the ultrasonic gas meter based on the pressure data as claimed in claim 2, wherein the method for measuring the relation between the pressure difference and the instantaneous flow in the step (1) is as follows:
installing a differential pressure sensor in the flow channel of the ultrasonic gas meter, and detecting the pressure difference inside and outside the flow channel of the ultrasonic gas meter through the differential pressure sensor; according to the Bernoulli equation, the pressure inside and outside the flow channel of the ultrasonic gas meter meets the following formula:
wherein the content of the first and second substances,
is the pressure in the cavity of the ultrasonic gas meter,
is the pressure in the flow channel of the ultrasonic gas meter,
is average flow of gas medium in the cavity of the ultrasonic gas meterAt the speed of the operation of the device,
is the average flow velocity of the gas medium in the flow passage of the ultrasonic gas meter,
is the gas density;
from conservation of mass, we obtain:
wherein, the first and the second end of the pipe are connected with each other,
is the sectional area in the cavity of the ultrasonic gas meter,
the cross section area in the flow channel of the ultrasonic gas meter;
the pressure difference between the inside and the outside of the flow passage of the ultrasonic gas meter is obtained by the formulas (1) and (2)
：
According to the formula (3), the pressure difference between the inside and the outside of the flow channel of the ultrasonic gas meter measured by the differential pressure sensor is related to the average flow velocity of the gas medium in the flow channel, and the instantaneous flow is the product of the average flow velocity of the gas medium in the flow channel and the cross section area of the flow channel, so that the pressure difference between the inside and the outside of the flow channel of the ultrasonic gas meter is related to the instantaneous flow of the ultrasonic gas meter;
sequentially introducing flow to obtain pressure difference data under different instantaneous flows, and performing data processing on the pressure difference data and the instantaneous flows by using a function modelFitting:
wherein, in the step (A),
which is indicative of a pressure difference,
which is indicative of the instantaneous flow rate of the fluid,
is a functional model fitted to the pressure difference and instantaneous flow.
4. The method for improving the instantaneous flow metering accuracy of the ultrasonic gas meter based on the pressure data as claimed in claim 3, wherein the step (2) of measuring the instantaneous flow by using the time difference method comprises the following steps:
in the above formulas (4) and (5),
is the cross section area of the flow passage of the ultrasonic gas meter,
is the average velocity of the gas medium in the flow passage of the ultrasonic gas meter,
is the length of the sound path,
is the angle of the sound track,
is the downstream propagation time of the ultrasonic wave in the gas medium,
is the countercurrent propagation time of ultrasonic waves in a gas medium; wherein, the cross-sectional area of the flow passage
Length of sound path
Angle of sound channel
Is a constant value, and the instantaneous flow can be calculated according to the downstream propagation time and the upstream propagation time of the ultrasonic wave in the gas medium
。
5. The method for improving the instantaneous flow metering accuracy of the ultrasonic gas meter based on the pressure data as claimed in claim 4, wherein the step (3) is to judge whether the wave is jumped or not, and the steps of adjusting the forward flow propagation time and the backward flow propagation time of the ultrasonic wave in the gas medium are as follows:
calculating the instantaneous flow at the current moment according to the time difference method measuring principle in the step (2)
And (2) the function relation between the pressure difference and the instantaneous flow obtained in the step (1) can be used for deducing the theoretical pressure difference at the current moment
(ii) a Differential pressure sensor for detecting pressure difference inside and outside flow channel of ultrasonic gas meter in real time
When the difference between the measured pressure difference and the theoretical pressure difference
，
The maximum range of the allowable difference between the actually measured pressure difference and the theoretical pressure difference indicates that no wave jump phenomenon exists at the moment; when the difference between the measured pressure difference and the theoretical pressure difference
When the instantaneous flow is calculated incorrectly, the ultrasonic waves have the existence of bouncing waves in the time measurement of the downstream propagation time and the upstream propagation time in the gas medium, so that the downstream propagation time and the upstream propagation time of the ultrasonic waves in the gas medium need to be adjusted;
from measured pressure differences
And the functional relation between the pressure difference and the instantaneous flow rate to deduce the theoretical instantaneous flow rate
，
The theoretical forward flow propagation time and the theoretical reverse flow propagation time of the ultrasonic wave in the gas medium approximately satisfy the following relations:
in the formulae (6) and (7),
is the theoretical downstream propagation time of the ultrasonic wave in the gas medium,
is the theoretical countercurrent propagation time of ultrasonic waves in a gas medium,
is the propagation velocity of sound waves in a gaseous medium; in addition, when the wave jumping phenomenon occurs, the forward flow propagation time of the ultrasonic wave in the gas medium is actually measured
And the theoretical downstream propagation time of ultrasonic waves in a gas medium
Approximately differing by an integer number of ultrasonic transducer excitation signal periods, and actually measuring the counter-current propagation time of ultrasonic waves in a gas medium
Theoretical counter-current propagation time with ultrasonic wave in gas medium
Approximately differing by an integer number of ultrasonic transducer excitation signal periods, the approximate relationship is as follows:
in the formulas (8) and (9),
is the period of the excitation signal of the ultrasonic transducer,
、
represents the wave number; the passing formula (6) -9 can adjust the actual measurement forward flow propagation time and the actual measurement reverse flow propagation time of the ultrasonic wave in the gas medium, thereby obtaining the instantaneous flow at the current moment
The following formula:
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Cited By (2)
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| CN117782271A (en) * | 2024-02-26 | 2024-03-29 | 山东新一代标准化研究院有限公司 | Wave jump phenomenon correction method, system, equipment and medium for gas ultrasonic flowmeter |
| CN117782271B (en) * | 2024-02-26 | 2024-05-10 | 山东新一代标准化研究院有限公司 | Wave jump phenomenon correction method, system, equipment and medium for gas ultrasonic flowmeter |
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| CN114459554B (en) | 2022-07-15 |
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