CN111426366A - Calibration device and method for gas mass flowmeter in special working state - Google Patents
Calibration device and method for gas mass flowmeter in special working state Download PDFInfo
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Abstract
The invention belongs to the technical field of flowmeter calibration, and discloses a calibration device for a gas mass flowmeter in a special working state, which comprises a gas generator, wherein the gas generator is communicated with a pressure reducing valve, a tested flowmeter and a standard device in a serial mode or communicated with the tested flowmeter and the standard device in a parallel mode, so that the calibration of the tested flowmeter in the working state of required pressure, different component gases or polluted gases is completed. A calibration method for the gas mass flowmeter in a special working state is also disclosed.
Description
Technical Field
The invention belongs to the technical field of flowmeter calibration, and particularly relates to a calibration device and method for a gas mass flowmeter in a special working state.
Background
At present, the thermal gas mass flowmeter is widely applied to various industrial fields, such as measurement of gas consumption of a pneumatic control device when a nuclear power unit is in operation, flow measurement of branch pipes in a smelting field of a steel enterprise, measurement of combustion air distribution in the energy industry, measurement of oxygen and anesthetic flow in the medical and health industry, measurement of chlorine, ozone and other flows in the public and public industries, measurement of gas flows of natural gas, coal gas, air, torch gas and the like, flow measurement of automobile exhaust, flow measurement of a CEMS (continuous emission monitoring system) and the like. Calibration of thermal gas mass flowmeters is therefore of particular importance.
In a laboratory, a thermal gas mass flowmeter uses high-purity nitrogen as a gas medium at normal temperature and normal pressure, a detected meter and a standard are connected in series for calibration, and in an industrial field, the types of actually used gas media are many, some gas media are even mixed gas, and the thermal gas mass flowmeter can also work under high pressure. For example, steel enterprises often use argon or a mixed gas of argon and carbon dioxide as a medium, and the inlet pressure of a gas mass flowmeter for a nuclear power plant is higher than normal pressure. Moreover, most industrial flow meters are heavily contaminated and, if connected in series with a standard, can damage the standard. At this time, the existing calibration method of the thermal gas mass flowmeter has limitation.
Therefore, metering of thermal gas mass flowmeters for special operating conditions is a major concern in these emerging industries.
Disclosure of Invention
The invention provides a calibration device and a calibration method for a gas mass flowmeter in a special working state, which solve the problem that the calibration of the existing thermal gas mass flowmeter cannot adapt to the calibration of high pressure, mixed gas and other states.
The invention can be realized by the following technical scheme:
a calibration device for a gas mass flowmeter in a special working state comprises a gas generator, wherein the gas generator is communicated with a pressure reducing valve, a to-be-tested flowmeter and a standard device in a series mode or communicated with the to-be-tested flowmeter and the standard device in a parallel mode, and calibration of the to-be-tested flowmeter in a working state of required pressure, different component gases or polluted gases is completed.
Further, the gas generator is sequentially communicated with the pressure reducing valve, the pressure gauge, the detected flowmeter, the flow regulating valve and the standard device, and the calibration of the detected flowmeter in a pressure state required by work is completed by regulating the pressure reducing valve and the flow regulating valve.
Further, the gas generator is sequentially communicated with the pressure stabilizing valve, the flow regulating valve, the commutator and the standard device, and the commutator is also communicated with the detected flowmeter to finish the calibration of the detected flowmeter in a polluted gas state.
Further, the gas generator is used to generate a single component gas or a multi-component gas.
Further, when the gas generator generates multi-component gas, the conversion coefficient is calculated by using the following equation, the reading of the detected flowmeter is corrected,
where ρ is1...ρnDenotes the density, C, of the respective gas in the multicomponent gas in the standard stateP1...CPnDenotes the specific heat at constant pressure, omega, of the respective gases in the multi-component gas1...ωnRepresenting the flow of the respective gas in the multi-component gas, omegaTRepresenting the flow of a multi-component gas, N1...NnRepresenting the molecular composition coefficient of the corresponding gas in the multi-component gas.
A calibration method based on the calibration device for a gas mass flowmeter in a special operating state, characterized in that: for the series connection mode, firstly, the inlet pressure of the detected flowmeter reaches the pressure required by work by adjusting a pressure reducing valve; and adjusting the flow regulating valve, simultaneously observing the readings of the standard device, enabling the readings of the standard device to sequentially reach the flow points of the full range of 100%, 50%, 20% and 10% of the detected flow meter, sequentially reading the readings of the detected flow meter and the standard device after the flow is stable, repeating the flow points for three times, calculating corresponding indicating value errors and repeatability, and completing the calibration of the detected flow meter.
For the parallel connection mode, firstly, the commutator is switched to the end of the standard device, the flow regulating valve is regulated, the reading of the standard device is observed at the same time, the reading of the standard device sequentially reaches the flow points of the full range of 100%, 50%, 20% and 10% of the detected flowmeter, after the flow is stable, the reading of the standard device is read, then, the commutator is switched to the end of the detected flowmeter, the reading of the detected flowmeter is read, each flow point is repeated for three times, the corresponding indicating value error and repeatability are calculated, and the calibration of the detected flowmeter is completed.
Further, when the gas generator generates multi-component gas, the conversion coefficient is calculated by using the following equation, the reading of the detected flowmeter is corrected,
where ρ is1...ρnDenotes the density, C, of the respective gas in the multicomponent gas in the standard stateP1...CPnDenotes the specific heat at constant pressure, omega, of the respective gases in the multi-component gas1...ωnRepresenting the flow of the respective gas in the multi-component gas, omegaTRepresenting the flow of a multi-component gas, N1...NnRepresenting the molecular composition coefficient of the corresponding gas in the multi-component gas.
The beneficial technical effects of the invention are as follows:
the calibration device is formed by sequentially connecting a gas generator, a pressure reducing valve, a pressure gauge, a detected flowmeter, a flow regulating valve and a standard device in series, the detected flowmeter in a pressure state required by work is calibrated, the calibration requirement of the detected flowmeter working in a high-pressure state is met, meanwhile, a calculation method of a conversion coefficient of the reading of the detected flowmeter in a multi-component gas working state is provided, and a mixed gas correction coefficient table with different proportions of single-component oxygen, single-component argon, carbon dioxide and argon is provided through experiments. In addition, the device for calibrating the thermal gas mass flow meter working in the state of the polluted gas is formed in a parallel connection mode by means of the commutator, and the calibration requirement of the thermal gas mass flow meter working in the state of the polluted gas is met.
Drawings
FIG. 1 is a schematic diagram of a prior art calibration device;
FIG. 2 is a schematic view of the structural connection of the in-line calibration device of the present invention;
FIG. 3 is a schematic diagram of the calibration error of the thermal gas mass flowmeter of manufacturer A at different inlet pressures for each flow point according to the present invention;
FIG. 4 is a schematic diagram of the calibration error of the thermal gas mass flowmeter of manufacturer B at different inlet pressures for each flow point according to the present invention;
FIG. 5 is a schematic diagram of the structural connection of the parallel calibration device of the present invention;
the device comprises a gas generator 1, a pressure stabilizing valve 2, a flow regulating valve 3, a detected flowmeter 4, a standard device 5, a pressure reducing valve 6, a pressure gauge 7 and a commutator 8.
Detailed Description
The following detailed description of the preferred embodiments will be made with reference to the accompanying drawings.
The prior thermal gas mass flowmeter calibrating device is shown in figure 1, a calibrating system of the prior thermal gas mass flowmeter calibrating device mainly comprises a gas generator 1 taking high-purity nitrogen as a gas source, a pressure stabilizing valve 2, a flow regulating valve 3, a detected flowmeter 4, a standard device 5 and the like, which are connected in series in sequence, and the inlet pressure of the thermal gas mass flowmeter is basically normal pressure because the pressure stabilizing valve and the flow regulating valve are added at the front end of the thermal gas mass flowmeter. In an industrial site, the actually used gas media are various, some gas media are even mixed gas, and the thermal gas mass flow meter can also work under high pressure, for example, steel enterprises often use argon or argon and carbon dioxide mixed gas as a gas medium, and the inlet pressure of the thermal gas mass flow meter for a nuclear power station is generally higher than normal pressure. In order to ensure the accuracy and reliability of the thermal gas mass flow metering value under the special working states, the invention provides a calibration device and a calibration method under the high-pressure working state, researches a correction method under the special gas working state, and provides a correction coefficient table of mixed gas of single-component oxygen, single-component argon, carbon dioxide and argon in different proportions.
The invention provides a calibration device for a gas mass flowmeter in a special working state, which comprises a gas generator, wherein the gas generator 1 is communicated with a pressure reducing valve 6, a to-be-detected flowmeter 7 and a standard device 5 in a serial mode or communicated with the to-be-detected flowmeter 4 and the standard device 5 in a parallel mode, so that the calibration of the to-be-detected flowmeter 4 in a state of pressure required by working, different component gases or polluted gases is completed.
In order to calibrate the high-pressure thermal gas mass flowmeter, assuming that the inlet pressure of the high-pressure thermal gas mass flowmeter reaches 1.0MPa, the front end pressure of the detected flowmeter 4 needs to be increased, the flow regulating valve 3 is arranged at the rear end of the detected flowmeter 4 to avoid the influence of the flow regulating valve 3 on the front end pressure of the detected flowmeter 4, namely, the pressure meter 7 is arranged at the outlet of a gas source, then the detected flowmeter 4 is connected, the flow regulating valve 3 is connected, and finally the standard device 5 is connected. Specifically, the gas generator 1 is sequentially communicated with a pressure reducing valve 6, a pressure gauge 7, a flow meter 4 to be tested, a flow regulating valve 3, and a standard 5, as shown in fig. 2, the inlet pressure of the thermal gas mass flowmeter is made to reach a desired target value by adjusting the pressure reducing valve 6 and observing the reading of the pressure gauge 7, and the calibration of different flow points of the flow meter 4 to be tested in a pressure state required for operation is completed by adjusting the flow regulating valve 3.
The standard 5 adopts a piston type gas small-flow standard device, such as an S L-800 type dry flow calibrator, when gas flows through, a piston moves in a cylinder, and the volume flow of the gas passing through the standard can be measured according to the time and the known volume value of the piston moving between two photoelectric emitters, a pressure sensor and a temperature sensor are arranged on a base, so that the mass flow of the gas can be calculated, the flow range of the standard is (5-50000) m L/min, the expansion uncertainty is 0.2% (k is 2), and a common 1.0-level thermal gas mass flow meter can be calibrated.
To investigate the effect of the magnitude of the inlet pressure on the calibration results of the thermal gas mass flow meter, the following experiment was performed. The accuracy grade of two thermal gas mass flowmeters with the working state inlet pressure of 1.0MPa, which are respectively produced by A manufacturer and B manufacturer, is 1.0 grade, the working medium is nitrogen, and the thermal gas mass flowmeters pass factory inspection and are not put into use for testing. The inlet pressure is reduced to 1.0MPa, 0.5MPa, 0.2MPa and 0.1MPa in sequence by adjusting the pressure reducing valve, namely, the pressure is reduced from high pressure to normal pressure. The test is carried out according to JJG 1132 and 2017 thermal gas mass flowmeter verification regulations, and four flow points are calibrated to be 100%, 50%, 20% and 10% of a full range respectively. To analyze the difference in the calibration results, calibration error curves were plotted for each flow point at different inlet pressures, as shown in fig. 3 and 4.
As can be seen from fig. 3 and 4, when the inlet pressure of the thermal gas mass flowmeter in the working state is 1.0MPa, the indicating error of the flowmeter is minimum and meets the requirement of the accuracy level of 1.0 when the inlet applies 1.0 MPa. If the inlet pressure is not enough, the calibration result of the thermal gas mass flow meter is influenced, and the smaller the inlet pressure is, the larger the influence on the calibration result is. Therefore, the high-pressure thermal gas mass flowmeter must ensure that the inlet pressure is consistent with the using state during calibration, and can be calibrated by adopting a calibration device shown in fig. 2.
The thermal gas mass flowmeter is generally calibrated by nitrogen when leaving a factory, and if other gases are used in actual use, the readings can be corrected, namely multiplied by a flow conversion coefficient. In the case of a single-component gas, the conversion factor can be found in the product specification, and in the case of a multi-component gas, the conversion factor C is calculated according to the following formula:
C＝0.3106N/ρ(CP) (1)
in the formula: ρ represents the density of the gas in a standard state;
CPrepresents the specific heat at constant pressure of the gas;
n represents a gas molecular composition coefficient, i.e., a factor related to the composition of the gas molecular composition, as shown in table 1 below.
TABLE 1 gas molecule composition coefficient Table
| Molecular constitution of gas | Examples of such applications are | Value of N |
| Monoatomic molecule | Ar He | 1.01 |
| Diatomic molecules | CO N2 | 1.00 |
| Triatomic molecule | CO2 NO2 | 0.94 |
| Polyatomic molecules | NH3 C4H8 | 0.88 |
For a multi-component gas, there is the following formula:
N＝N1(ω1/ωT)+N2(ω2/ωT)+...+Nn(ωn/ωT) (2)
in the formula: omega1...ωnIndicating the flow of the respective gases；
ωTRepresents the flow rate of the multi-component gas;
N1...Nnrepresenting the molecular composition coefficient of the respective gas.
Substituting (2) into (1) to obtain:
in the formula: rho1...ρnRepresents the density of the corresponding gas in a standard state;
CP1...CPnindicating the specific heat at constant pressure of the respective gases.
In order to verify whether the actual condition is consistent with the theoretical conversion result, comparative tests of different gas sources are carried out, wherein the gas sources respectively adopt single-component nitrogen, single-component oxygen, single-component argon, carbon dioxide and argon of 0.5: 0.5 mixed gas, carbon dioxide and argon 0.2: 0.8 mixed gas, A, B two-manufacturer flow meters were used in the test, the inlet pressure of these flow meters was atmospheric, the accuracy rating was 1.0, the mixed gas passed factory inspection and was not put into use. The actual conversion factors obtained by the test and the theoretical conversion factors obtained by calculation are shown in table 2 below.
TABLE 2 conversion factor tables for different gas media
As can be seen from table 2, the actual conversion coefficient is substantially the same as the theoretical conversion coefficient, and some differences still exist in some cases. For the same gas medium, the actual conversion coefficients of the thermal gas mass flowmeters of manufacturers A and B are different, which shows that the conversion coefficients are related to the internal manufacturing structure of the flowmeter. For a single component gaseous medium, the conversion factor obtained from the test was found to be consistent with the factor provided in the manufacturer's product specification.
In laboratory calibration, when the gaseous medium is a single-component gas, the conversion factor can be used directly in the product technical specification. When the gas medium is multi-component gas, if the precision requirement of a user on the thermal gas mass flowmeter is general, the coefficient obtained by theory can be directly used for conversion, and if the precision requirement of the user on the flowmeter is higher, the user is advised to consult a manufacturer to correct the actual conversion coefficient provided by the manufacturer, or the correction coefficient is obtained by testing according to the method provided by the invention. For common mixed gas media, the user can refer to the actual conversion coefficient provided by the invention for correction.
For a thermal gas mass flowmeter with a clean working environment, a serial connection mode is generally used in a laboratory for calibration, that is, a detected flowmeter and a standard device are connected in series, as shown in fig. 1, but for a thermal gas mass flowmeter with an unclean working environment and used media, the standard device is damaged by adopting the calibration mode, a parallel connection mode can be considered, as shown in fig. 5, specifically, the gas generator 1 is sequentially communicated with a pressure stabilizing valve 2, a flow regulating valve 3, a commutator 8 and a standard device 5, the commutator 8 is also communicated with a detected flowmeter 4, so that polluted gas is prevented from flowing into the standard device 5, and the calibration of the detected flowmeter 4 in a polluted gas state is completed. Although the parallel connection mode can well protect the standard, whether the parallel connection condition has influence on the calibration result of the thermal type gas mass flowmeter is researched. The same thermal gas mass flowmeter to be calibrated is connected with the standard device according to the modes of fig. 1 and fig. 5 respectively, so that calibration results in the two modes of series connection and parallel connection are obtained, as shown in table 3, the indication errors in the two modes are similar, the parallel connection mode has little influence on the calibration results, and the polluted flowmeter can be calibrated in the parallel connection mode.
TABLE 3 calibration results of series and parallel connection
| Flow point (L/min) | Indicating value error (series connection mode) | Indicating value error (parallel connection mode) |
| 30 | 0.23％ | 0.25％ |
| 15 | 0.25％ | 0.26％ |
| 6 | 0.19％ | 0.22％ |
| 3 | 0.21％ | 0.23％ |
Also in this parallel connection, for the calibration of the thermal gas mass flow meter operating in a mixed gas state, the conversion coefficient can still be calculated using the following equation, the reading of the flow meter under test is corrected,
where ρ is1...ρnDenotes the density, C, of the respective gas in the multicomponent gas in the standard stateP1...CPnDenotes the specific heat at constant pressure, omega, of the respective gases in the multi-component gas1...ωnRepresenting the flow of the respective gas in the multi-component gas, omegaTRepresenting the flow of a multi-component gas, N1...NnRepresenting the molecular composition coefficient of the corresponding gas in the multi-component gas.
The invention also provides a calibration method of the calibration device for the gas mass flowmeter under the special working state, which is based on the calibration method, and for the series connection mode, the inlet pressure of the detected flowmeter is enabled to reach the pressure required by the working by adjusting the pressure reducing valve; and adjusting the flow regulating valve, simultaneously observing the readings of the standard instrument to enable the readings of the standard instrument to sequentially reach the flow points of the full range of 100%, 50%, 20% and 10% of the detected flow meter, after the flow is stable, sequentially reading the readings of the detected flow meter and the standard instrument, repeating the flow points for three times, calculating corresponding indicating value errors and repeatability, and completing the calibration of the detected flow meter.
For the parallel connection mode, firstly, the commutator is switched to the end of the standard device, the flow regulating valve is regulated, the reading of the standard device is observed at the same time, the reading of the standard device sequentially reaches the flow points of the full range of 100%, 50%, 20% and 10% of the detected flowmeter, after the flow is stable, the reading of the standard device is read, then, the commutator is switched to the end of the detected flowmeter, the reading of the detected flowmeter is read, each flow point is repeated for three times, the corresponding indicating value error and repeatability are calculated, and the calibration of the detected flowmeter is completed.
In summary, the present invention provides a serial flow meter calibration device and method in a high pressure operating state and a parallel flow meter calibration device and method in a contaminated gas operating state for a thermal gas mass flow meter in a special operating state, compares actual conversion coefficients and theoretical conversion coefficients in different gas media, and gives a single-component oxygen, a single-component argon, carbon dioxide, and argon of 0.5: 0.5 mixed gas, carbon dioxide and argon 0.2: the actual conversion coefficient of the mixed gas is 0.8, and the method provides a proposal for the calibration of the thermal gas mass flow meter under a special gas state.
Although specific embodiments of the present invention have been described above, it will be appreciated by those skilled in the art that these are merely examples and that many variations or modifications may be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is therefore defined by the appended claims.
Claims (7)
1. A calibrating device that is used for gas quality flowmeter under special operating condition which characterized in that: the gas generator is communicated with the pressure reducing valve, the detected flowmeter and the standard in a serial mode or communicated with the detected flowmeter and the standard in a parallel mode, and calibration of the detected flowmeter under the conditions of pressure required by work, different component gases or polluted gases is completed.
2. The calibrating device for a gas mass flowmeter under special operating conditions according to claim 1, characterized in that: the gas generator is sequentially communicated with the pressure reducing valve, the pressure gauge, the detected flowmeter, the flow regulating valve and the standard device, and the calibration of the detected flowmeter in a pressure state required by work is completed by regulating the pressure reducing valve and the flow regulating valve.
3. The calibrating device for a gas mass flowmeter under special operating conditions according to claim 1, characterized in that: the gas generator is sequentially communicated with the pressure stabilizing valve, the flow regulating valve, the commutator and the standard device, and the commutator is also communicated with the detected flowmeter to finish the calibration of the detected flowmeter in a polluted gas state.
4. Calibration device for a gas mass flowmeter under special operating conditions, according to claim 2 or 3, characterized in that: the gas generator is used for generating single-component gas or multi-component gas.
5. The calibrating device for a gas mass flowmeter under special operating conditions according to claim 4, characterized in that: when the gas generator generates multi-component gas, the conversion coefficient is calculated by using the following equation, the reading of the detected flowmeter is corrected,
where ρ is1...ρnDenotes the density, C, of the respective gas in the multicomponent gas in the standard stateP1...CPnRepresenting the specific heat at constant pressure, omega, of the respective gas in a multi-component gas1...ωnRepresenting the flow of the respective gas in the multi-component gas, omegaTRepresenting the flow of a multi-component gas, N1...NnRepresenting the molecular composition coefficients of the respective gases in the multi-component gas.
6. A calibration method for a gas mass flowmeter under a special operating condition, according to claim 1, wherein: for the series connection mode, firstly, the inlet pressure of the detected flowmeter reaches the pressure required by work by adjusting a pressure reducing valve; and adjusting the flow regulating valve, simultaneously observing the readings of the standard instrument to enable the readings of the standard instrument to sequentially reach the flow points of the full range of 100%, 50%, 20% and 10% of the detected flow meter, after the flow is stable, sequentially reading the readings of the detected flow meter and the standard instrument, repeating the flow points for three times, calculating corresponding indicating value errors and repeatability, and completing the calibration of the detected flow meter.
For the parallel connection mode, firstly, the commutator is switched to the end of the standard device, the flow regulating valve is regulated, the reading of the standard device is observed at the same time, the reading of the standard device sequentially reaches the flow points of the full range of 100%, 50%, 20% and 10% of the detected flowmeter, after the flow is stable, the reading of the standard device is read, then, the commutator is switched to the end of the detected flowmeter, the reading of the detected flowmeter is read, each flow point is repeated for three times, the corresponding indicating value error and the repeatability are calculated, and the calibration of the detected flowmeter is completed.
7. A calibration method for a gas mass flow meter according to claim 6, characterized in that: when the gas generator generates multi-component gas, the conversion coefficient is calculated by using the following equation, the reading of the detected flowmeter is corrected,
where ρ is1...ρnDenotes the density, C, of the respective gas in the multicomponent gas in the standard stateP1...CPnRepresenting the specific heat at constant pressure, omega, of the respective gas in a multi-component gas1...ωnRepresenting the flow of the respective gas in the multi-component gas, omegaTRepresenting the flow of a multi-component gas, N1...NnRepresenting the molecular composition coefficients of the respective gases in the multi-component gas.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111780835A (en) * | 2020-07-24 | 2020-10-16 | 安东仪器仪表检测有限公司 | Calibration method for high-efficiency liquid phase transfer liquid flowmeter |
| CN112555140A (en) * | 2020-10-30 | 2021-03-26 | 中国航发西安动力控制科技有限公司 | Calibration equipment and calibration method for gas-liquid ratio tester |
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2020
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111780835A (en) * | 2020-07-24 | 2020-10-16 | 安东仪器仪表检测有限公司 | Calibration method for high-efficiency liquid phase transfer liquid flowmeter |
| CN112555140A (en) * | 2020-10-30 | 2021-03-26 | 中国航发西安动力控制科技有限公司 | Calibration equipment and calibration method for gas-liquid ratio tester |
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