Calibration system for gas flow measurement

Abstract

The utility model discloses a calibration system for gas flow measurement. The calibration system comprises a gas source part, an experimental pipe section, a sonic nozzle group and a control machine, when the gas flow meter is used for calibration and calibration of gas flow metering, the mass flow of gas is only related to upstream pressure and temperature and is irrelevant to downstream environment, so that the influence caused by downstream measurement errors is avoided, the measurement precision is high, and the gas flow meter is simple in structure, not easy to be influenced by the environment and convenient to maintain. According to the utility model, measurement requirements under different working conditions can be met, and the application range is wide. Moreover, the device can get rid of the limitation of the volume scale and the performance of a measuring device, and the sonic nozzle is directly applied to the calibration work of the hydrogen field real flow.

Description

Technical Field

[0001] This utility model relates to the field of metrology instrument testing technology, specifically to a calibration system for gas flow measurement. Background Technology

[0002] Flow measurement plays a vital role in industry. In the hydrogen energy industry, accurate measurement of hydrogen flow is indispensable for processes such as hydrogen production, storage, transportation, refueling, and utilization. However, due to the complex characteristics of hydrogen, such as its flammability and explosiveness, higher requirements are placed on the design and construction of hydrogen flow measurement standard systems.

[0003] In the hydrogen energy industry, accurate measurement of hydrogen flow rate is crucial. However, a sound standard for accurate hydrogen flow rate measurement is currently lacking, and related management standards and systems are relatively lagging. The establishment of a traceability system for hydrogen flow rate measurement values ​​is still in the exploratory stage. Countries such as Japan, the United States, and Switzerland have begun developing hydrogen flow rate standard systems, mainly including the standard meter method, the pVTt method, and the gravimetric method (also known as the Mt method). Hydrogen flow rate measurement is characterized by high pressure, large flow rate, and complex physical properties. Due to limitations in the size and performance of measuring devices, sonic nozzle calibration technology, which is limited to well-maintained laboratory conditions, cannot be directly applied to the calibration and verification of actual hydrogen flow in the field. Utility Model Content

[0004] In view of the shortcomings of the existing technology, the present invention aims to provide a calibration system for gas flow measurement.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A calibration system for gas flow measurement includes a gas source section, an experimental pipe section, a sonic nozzle assembly, and a control unit;

[0007] The gas source section includes a gas storage tank and an automatic pressure controller, which are connected by a flange and a connecting pipe section.

[0008] The test pipeline section includes a flow meter under test pipeline one, a flow meter under test pipeline two, a test gauge, an upstream pressure gauge, an upstream thermo-hygrometer, a downstream pressure gauge, and a downstream thermo-hygrometer; the inlet end of the test gauge is connected to the automatic pressure controller through the flow meter under test pipeline one, and the outlet end of the test gauge is connected to one end of the flow meter under test pipeline two; the upstream pressure gauge and the upstream thermo-hygrometer are both connected to the flow meter under test pipeline one, and the downstream pressure gauge and the downstream thermo-hygrometer are both connected to the flow meter under test pipeline two;

[0009] The sonic nozzle assembly includes a calibrated sonic nozzle, an upstream pressure gauge, a downstream pressure gauge, a thermometer / hygrometer, an upstream electric valve, and a downstream electric valve. The upstream electric valve and the inlet of the sonic nozzle are connected via an upstream pipeline, and the outlet of the sonic nozzle and the downstream electric valve are connected via a downstream pipeline. The upstream and downstream pressure gauges are connected to the upstream and downstream pipelines, respectively. The thermometer / hygrometer is connected to the upstream pipeline, and the upstream electric valve is connected to the pipeline of the flow meter under test. The controller is connected to each upstream and downstream electric valve. Multiple sonic nozzle assemblies are connected in parallel. The upstream electric valve of each sonic nozzle assembly is connected to the inlet confluence pipeline, and the downstream electric valve of each assembly is connected to the outlet confluence pipeline. The inlet confluence pipeline is connected to a confluence electric valve, which is connected to the other end of the pipeline of the flow meter under test. The controller is connected to the confluence electric valve.

[0010] The automatic pressure controller, the gauge under test, the upstream pressure gauge, the upstream thermo-hygrometer, the downstream pressure gauge, the downstream thermo-hygrometer, the upstream pressure gauge of the sonic nozzle group, the downstream pressure gauge of the sonic nozzle group, the thermo-hygrometer of the sonic nozzle group, the upstream electric valve, and the downstream electric valve are all connected to the controller for communication.

[0011] Furthermore, the gas storage tank is made of 316L stainless steel, and the inner wall of the gas storage tank is covered with an anti-corrosion coating.

[0012] Furthermore, the upstream thermo-hygrometer and the upstream pressure gauge, as well as the downstream pressure gauge and the downstream thermo-hygrometer, are not on the same horizontal plane, and the angle between their surfaces is 90°.

[0013] Furthermore, the outlet manifold is connected to a silencer or a gas recovery device.

[0014] Furthermore, the upstream pressure gauge of the sonic nozzle assembly is installed at a distance of 0.9D-1.1D from the inlet plane of the sonic nozzle, and the temperature and humidity meter of the sonic nozzle assembly is installed at a distance of 1.8D-2.2D from the inlet plane of the sonic nozzle, where 1.0D is 50mm.

[0015] Furthermore, the temperature and humidity meter of the sonic nozzle assembly and the pressure gauge upstream of the sonic nozzle assembly are not on the same horizontal plane, and the angle between their surfaces is 90°.

[0016] Furthermore, the connecting pipe section, the first line of the flow meter under test, the second line of the flow meter under test, the upstream line, the downstream line, the inlet collection line, and the outlet collection line are all made of DN50 316L stainless steel pipe. The inner diameter of the 316L stainless steel pipe is D=50mm, the wall thickness is 105mm, and the inner wall of the 316L stainless steel pipe is covered with an anti-corrosion coating.

[0017] The beneficial effects of this invention are as follows: By setting multiple parallel calibrated sonic nozzles, the flow range of the calibration system can be expanded, thus removing limitations on the size and performance of the sonic nozzle calibration system and meeting the requirements for on-site calibration and verification of hydrogen flow. Furthermore, the use of 316L stainless steel for the gas storage tank and piping materials prevents hydrogen embrittlement during the calibration of the system for hydrogen flow measurement. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the gas flow metering calibration system in an embodiment of this utility model. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings. It should be noted that this embodiment is based on the present technical solution and provides detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to this embodiment.

[0020] This embodiment provides a calibration system for gas flow measurement, such as... Figure 1 As shown, it includes a gas source section, an experimental pipe section, a sonic nozzle group and a control unit. Using the sonic nozzle as the standard meter, it can meet the following conditions for gas flow measurement: (1) Measurement pressure range: 0-35MPa; (2) Measurement temperature range: -20℃ to 60℃; (3) Measurement humidity range: 0-90%; (4) Measurement flow range: 0-67g / s.

[0021] The gas source section includes a gas storage tank 1 and an automatic pressure controller 2, which are connected by a flange 3 and a connecting pipe section 4.

[0022] The automatic pressure controller 2 controls the pipeline pressure according to the target pressure value issued by the controller 17, simulating different working conditions. In this embodiment, the gas storage tank 1 is made of 316L stainless steel, a lower grade, because when the detected gas is hydrogen, hydrogen has strong corrosiveness and will cause hydrogen embrittlement when in contact with metal. 316L stainless steel, due to the addition of molybdenum, has excellent corrosion resistance. Therefore, 316L stainless steel is selected for the gas storage tank to ensure the safety performance of the calibration system. Furthermore, to ensure the safe use of the calibration system and extend its service life, the inner wall of the gas storage tank 1 is covered with an anti-corrosion coating (such as a polymer coating), which can isolate corrosive gases from direct contact with the gas storage tank 1, providing a double protection effect.

[0023] The test pipeline section includes a flow meter under test pipeline 5, a flow meter under test pipeline 18, a gauge under test 6 (i.e., the flow meter under test), an upstream pressure gauge 7, an upstream thermo-hygrometer 8, a downstream pressure gauge 9, and a downstream thermo-hygrometer 10. The inlet end of the gauge under test 6 is connected to the automatic pressure controller 2 through the flow meter under test pipeline 5 (model D50), and the outlet end of the gauge under test 6 is connected to one end of the flow meter under test pipeline 18. The upstream pressure gauge 7 and the upstream thermo-hygrometer 8 are both connected to the flow meter under test pipeline 5, and the downstream pressure gauge 9 and the downstream thermo-hygrometer 10 are both connected to the flow meter under test pipeline 18.

[0024] In this embodiment, both the upstream pressure gauge 7 and the downstream pressure gauge 9 are hydrogen pressure gauges manufactured by Wuxi Huihua Special Instrument Co., Ltd., with a measurement accuracy class of 2.5. They can measure pressures in the range of 0-40 MPa, with an experimental temperature range of -40℃ to 70℃ and a maximum experimental humidity of 90%. The upstream thermo-hygrometer 8 and the downstream thermo-hygrometer 10 are thermo-hygrometers manufactured by Jian Da Ren Ke Co., Ltd., capable of measuring temperatures in the range of -20℃ to 60℃ and humidity in the range of 0-100%, with measurement accuracies of ±0.5℃ and ±3%RH, respectively. The gauge under test 6 is a Coriolis mass flow meter, which better meets the requirements of the complex physical properties of hydrogen compared to other flow meters. To ensure measurement accuracy, the upstream thermo-hygrometer 8 and the upstream pressure gauge 7, as well as the downstream pressure gauge 9 and the downstream thermo-hygrometer 10, are not on the same horizontal plane, but are installed crosswise with an angle of 90° between their surfaces.

[0025] The sonic nozzle assembly includes a calibrated sonic nozzle 14, an upstream pressure gauge 13, a downstream pressure gauge 15, a thermo-hygrometer 12, an upstream electric valve 19, and a downstream electric valve 20. The upstream electric valve 19 and the inlet of the sonic nozzle 14 are connected through an upstream pipeline, and the outlet of the sonic nozzle 14 and the downstream electric valve 20 are connected through a downstream pipeline. The upstream pressure gauge 13 and the downstream pressure gauge 15 are respectively connected to the upstream and downstream pipelines, and the thermo-hygrometer 12 is connected to the upstream pipeline. Multiple sonic nozzle groups are connected in parallel (eight groups in this embodiment). The upstream electric valve 19 of each sonic nozzle group is connected to the inlet manifold 21, and the downstream electric valve 20 of each sonic nozzle group is connected to the outlet manifold 22. The inlet manifold 21 is connected to the manifold electric valve 11, and the outlet manifold 22 is connected to the silencer 16 or the gas recovery device. The manifold electric valve 11 is connected to the other end of the flow meter under test pipeline 18. The controller 17 controls the manifold electric valve 11 and each upstream electric valve 19 and downstream electric valve 20 to control their on / off states.

[0026] According to the requirements of the "Verification Procedure for Critical Flow Venturi Nozzles", in the installation of the sonic nozzle assembly, the upstream pressure gauge 13 can be installed at a distance of 0.9D-1.1D from the inlet plane of the sonic nozzle 14. Selecting 1.0D (50mm), the upstream pressure gauge 13 is set at a distance of 50mm from the inlet plane of the sonic nozzle 14. In the downstream pipeline, the downstream pressure gauge 15 of the sonic nozzle assembly, as long as it does not obstruct the sonic nozzle 14 from reaching critical flow, can be installed at a distance of 70mm from the outlet plane of the sonic nozzle 14. In the installation of the upstream pipeline, the temperature and humidity meter 12 of the sonic nozzle assembly can be installed at a distance of 1.8D-2.2D from the inlet plane of the sonic nozzle 14.

[0027] Similarly, to ensure measurement accuracy, the sonic nozzle assembly thermo-hygrometer 12 and the upstream pressure gauge 13 of the sonic nozzle assembly are not on the same horizontal plane, but are installed crosswise, with the angle between their surfaces being 90°.

[0028] There will be some noise during the experiment. If the gas being tested can be released into the atmosphere, it can be released into the atmosphere after passing through silencer 16. When the gas being tested is hydrogen, due to the complex characteristics of hydrogen's flammability and explosiveness, in order to ensure the safety of the experiment and to conserve resources, the outlet manifold 22 is connected to a gas recovery device. The same applies to other similar gases that need to be recovered and reused.

[0029] Referring to the requirements of the international standard "Verification Procedure for Critical Flow Venturi Nozzles", and through calculation formulas and standard requirements, it is determined that the connecting pipe section 4, the tested flow meter line 1 5, the tested flow meter line 2 18, the upstream line, the downstream line, the inlet confluence line 21, and the outlet confluence line 22 are all made of DN50 316L stainless steel pipe. The inner diameter of the 316L stainless steel pipe is D = 50mm, the wall thickness is 105mm, and the inner wall of the 316L stainless steel pipe is covered with an anti-corrosion coating.

[0030] The model and parameters of flange 3 are determined according to international standards, as shown in Table 1.

[0031] Table 1

[0032]

[0033] The geometry and specific parameters of the sonic nozzle were designed in accordance with the ISO 9300 international standard and the JJG 620 national standard, as shown in Table 2.

[0034] Table 2

[0035]

[0036] In this embodiment of the system, the automatic pressure controller, the gauge under test, the upstream pressure gauge, the upstream thermo-hygrometer, the downstream pressure gauge, the downstream thermo-hygrometer, the upstream pressure gauge of the sonic nozzle assembly, the downstream pressure gauge of the sonic nozzle assembly, the thermo-hygrometer of the sonic nozzle assembly, the upstream electric valve, and the downstream electric valve are all communicatively connected to the control unit. The experimenter can use the control unit 17 to set a pressure, temperature, humidity, etc., for the calibration system to simulate different operating conditions. The control unit 17 can also perform data acquisition and processing.

[0037] The working principle of the calibration system in this embodiment is as follows: the gas to be tested in the gas storage tank flows into the connecting pipe section. After the gas pressure is controlled by the automatic pressure controller, the gas to be tested flows into the test pipe section under the action of pressure difference. After flowing through the gauge under test, the summing electric valve, the upstream electric valve of the sonic nozzle group, the sonic nozzle, the downstream electric valve of the sonic nozzle group, and the silencer or gas recovery device, it finally flows into the atmosphere. Under the control of the automatic pressure controller, the gas pressure flowing through the gauge under test is made equal to the test pressure set by the controller.

[0038] The calibration system of this embodiment will be theoretically verified below.

[0039] Using hydrogen as the tested gas, the critical flow function C of a real gas is calculated. * At standard atmospheric pressure (0.101325 × 10⁻⁶), 6 Pa) is used as the stagnation pressure p0, and the absolute temperature 293.15 K (i.e., 0 °C) is used as the stagnation temperature T0. The critical pressure p is set.c The pressure is 2 MPa, and the critical temperature is T. c The value is 200K. This can be determined by consulting the "Verification Procedure for Critical Flow Venturi Nozzles". i b i c i Substituting the numerical values ​​into the following formula yields the critical flow function C for the actual gas. * The value is 3.582855009.

[0040]

[0041] In the formula,

[0042] (2) The molar mass M of hydrogen is 2 × 10⁻⁶. -3 Given a flow rate of kg / mol and a universal gas constant R of 8.314472 J / (mol·K), the ideal flow rate q can be calculated using the following formula. mi It is 8.4224 g / s.

[0043]

[0044] In the formula, A* represents the throat area of ​​the sonic nozzle.

[0045] (3) The dynamic viscosity μ0 of hydrogen is 0.000008915. Given a 6mm throat diameter d of the sonic nozzle, a dynamic viscosity μ0 = 0.000008915, and an ideal flow rate q... mi Substituting 8.4224 g / s into the following formula, we can obtain the Reynolds number Re at the throat of the sonic nozzle as 2005827.

[0046]

[0047] (4) The discharge coefficient of the sonic nozzle can be calculated using the following formula:

[0048]

[0049] The coefficients a, b, and n in the formula can be obtained from the "Verification Procedure for Critical Flow Venturi Nozzles", and the outflow coefficient of the sonic nozzle is 0.993979.

[0050] (5) Multiply the ideal flow rate and the discharge coefficient of the sonic nozzle to obtain the actual flow rate q of hydrogen. m It is 8.37169283 g / s.

[0051] The national standard requires a flow rate of (0.1-10.01) kg / min for a low-flow sonic nozzle flow rate standard device, which translates to (1.66667-166.83333) g / s. The actual hydrogen flow rate q can then be calculated.m It can be seen that the design of the calibration system in this embodiment meets the requirements of national standards, and the calibration system in this embodiment can be applied to the calibration and calibration of hydrogen in actual field flow.

[0052] For those skilled in the art, various corresponding changes and modifications can be made based on the above technical solutions and concepts, and all such changes and modifications should be included within the protection scope of the claims of this utility model.

Claims

1. A calibration system for gas flow measurement, characterized in that, This includes the gas source section, experimental pipe section, sonic nozzle assembly, and control unit; The gas source section includes a gas storage tank and an automatic pressure controller, which are connected by a flange and a connecting pipe section. The test pipeline section includes a flow meter under test pipeline one, a flow meter under test pipeline two, a test gauge, an upstream pressure gauge, an upstream thermo-hygrometer, a downstream pressure gauge, and a downstream thermo-hygrometer; the inlet end of the test gauge is connected to the automatic pressure controller through the flow meter under test pipeline one, and the outlet end of the test gauge is connected to one end of the flow meter under test pipeline two; the upstream pressure gauge and the upstream thermo-hygrometer are both connected to the flow meter under test pipeline one, and the downstream pressure gauge and the downstream thermo-hygrometer are both connected to the flow meter under test pipeline two; The sonic nozzle assembly includes a calibrated sonic nozzle, an upstream pressure gauge, a downstream pressure gauge, a thermometer / hygrometer, an upstream electric valve, and a downstream electric valve. The upstream electric valve and the inlet of the sonic nozzle are connected via an upstream pipeline, and the outlet of the sonic nozzle and the downstream electric valve are connected via a downstream pipeline. The upstream and downstream pressure gauges are connected to the upstream and downstream pipelines, respectively. The thermometer / hygrometer is connected to the upstream pipeline, and the upstream electric valve is connected to the pipeline of the flow meter under test. The controller is connected to each upstream and downstream electric valve. Multiple sonic nozzle assemblies are connected in parallel. The upstream electric valve of each sonic nozzle assembly is connected to the inlet confluence pipeline, and the downstream electric valve of each assembly is connected to the outlet confluence pipeline. The inlet confluence pipeline is connected to a confluence electric valve, which is connected to the other end of the pipeline of the flow meter under test. The controller is connected to the confluence electric valve. The automatic pressure controller, the gauge under test, the upstream pressure gauge, the upstream thermo-hygrometer, the downstream pressure gauge, the downstream thermo-hygrometer, the upstream pressure gauge of the sonic nozzle group, the downstream pressure gauge of the sonic nozzle group, the thermo-hygrometer of the sonic nozzle group, the upstream electric valve, and the downstream electric valve are all connected to the controller for communication.

2. The calibration system according to claim 1, characterized in that, The gas storage tank is made of 316L stainless steel, and the inner wall of the gas storage tank is covered with an anti-corrosion coating.

3. The calibration system according to claim 1, characterized in that, The upstream thermometer and hygrometer and the upstream pressure gauge, as well as the downstream pressure gauge and the downstream thermometer and hygrometer, are not on the same horizontal plane, and the angle between their surfaces is 90°.

4. The calibration system according to claim 1, characterized in that, The outlet pipeline is connected to a silencer or a gas recovery device.

5. The calibration system according to claim 1, characterized in that, The upstream pressure gauge of the sonic nozzle assembly is installed at a distance of 0.9D-1.1D from the inlet plane of the sonic nozzle, and the temperature and humidity meter of the sonic nozzle assembly is installed at a distance of 1.8D-2.2D from the inlet plane of the sonic nozzle. 1.0D is 50mm.

6. The calibration system according to claim 1, characterized in that, The temperature and humidity meter of the sonic nozzle assembly and the pressure gauge upstream of the sonic nozzle assembly are not on the same horizontal plane, and the angle between their surfaces is 90°.

7. The calibration system according to claim 1, characterized in that, The connecting pipe section, the flow meter under test pipeline one, the flow meter under test pipeline two, the upstream pipeline, the downstream pipeline, the inlet collection pipeline and the outlet collection pipeline are all made of DN50 316L stainless steel pipe. The inner diameter of the 316L stainless steel pipe is D=50mm, the wall thickness is 105mm, and the inner wall of the 316L stainless steel pipe is covered with an anti-corrosion coating.

Images