A calibration device for a single-phase cryogenic fluid flowmeter

Abstract

The present invention discloses a calibration device for a single-phase cryogenic fluid flowmeter, which includes a cryogenic fluid Dewar filling tank, a standard cryogenic flowmeter, an upstream vacuum cavity, a downstream vacuum cavity, a calibrated cryogenic flowmeter, a vacuum cavity outer tube bellows, a cryogenic solenoid valve, and a cryogenic fluid Dewar collection tank that are coaxially arranged in the vertical direction. Based on the standard flowmeter method, the cryogenic fluid flows from bottom to top in the vertical direction, filling the pipeline with a single-phase cryogenic fluid, ensuring the measurement accuracy of the standard cryogenic flowmeter. Compared with the calibration device based on the traditional weighing method, the calibration device of the present invention has higher measurement accuracy, simpler device structure, lower cost, more convenient operation, and more reliable calibration. In addition, under the structural design of the present invention, the sealing performance is better, the heat leakage loss is smaller, and each system component is convenient to disassemble, simplifying the steps of the operator, and can be used for the calibration of single-phase cryogenic fluid flowmeters.

Description

Technical Field

[0001] The present invention relates to a flowmeter calibration device, and more particularly to a calibration device for a single-phase cryogenic fluid flowmeter. Background Art

[0002] Cryogenic fluids generally refer to fluids with a temperature below their standard boiling point of 120K. The measurement of cryogenic fluid flow is crucial for the rapid development of the cryogenic field. Its main applications include the storage, transportation, and filling processes of cryogenic fluids such as liquid hydrogen and liquid nitrogen. Its accuracy and efficiency are of utmost importance. For the measurement of cryogenic fluid flow, a cryogenic fluid flowmeter is indispensable. In other words, the high-precision calibration of a cryogenic fluid flowmeter is of great significance. Commonly used calibration devices are mainly based on three calibration methods, namely the weighing method, the volumetric method, and the standard flowmeter method.

[0003] The principle of the weighing method is achieved through the ratio of mass and time, and it is further divided into the static method and the dynamic method. The static method means that during the measurement process, when all the fluid flows into the weighing container, the time taken for the process is recorded, and the total mass of the fluid flowing into the weighing container is measured. The average mass flow rate is obtained through the weighed fluid mass and the time interval, and then the calibrated flow rate is calculated based on the density of the measured fluid. The dynamic method means that under the condition of constant pressure and temperature, when the fluid is in a steady-state flow, the calibrated flow rate is calculated through the mass increase per unit time of the weighing container and the density of the measured fluid.

[0004] The volumetric method is similar to the weighing method, and its principle is achieved through the ratio of the volume and time of the measured fluid in the collection container, and the volume flow rate can be directly calculated.

[0005] The principle of the standard flowmeter method is to use a flowmeter that has been calibrated efficiently and accurately as a standard flowmeter. It is connected in series with the calibration flowmeter in the same pipeline. Within a certain time interval, the average measured value of the standard flowmeter is used as the standard flow rate value to evaluate the indication of the calibration flowmeter. The standard meter method is the most commonly used calibration method at present, and it has the advantages of simplicity, reliability, and high efficiency, which simplifies the steps of the operator.

[0006] In the existing technology, the paper "Calibration of a Cryogenic Turbine-Based Volumetric Flow Meter (CTVFM) Using Sub-Cooled Liquid Nitrogen and Solution for Its Practical Issues" (De Souza I, Sarkar A, Anand A, Sarkar, M, Kumar J S, Gour A S, Rao V V, IEEE Sensors Journal, 2021, 21(10): 12077-12083) introduced a method for calibrating a cryogenic turbine flow meter with sub-cooled liquid nitrogen as the medium, built a calibration experimental platform for the sub-cooled liquid nitrogen cryogenic turbine flow meter, and carried out calibration. However, the calibration method in the paper actually adopted the volumetric method and was quite different from the structure of the calibration device of the present invention.

[0007] In the paper "Design of an On-line Verification Device for a Volumetric Flow Meter by the Standard Meter Method" (Wang Zengxin, Li Jianping, China New Telecommunications, 2019, 21(01): 225-226), with aviation kerosene as the medium, the design of an on-line verification device for a calibrated volumetric flow meter was carried out by the standard meter method. High-tech industrial control technologies such as PID regulation and double-pulse synchronous counting were adopted to achieve automatic verification during the verification process. In the flow meter calibration device proposed in this paper, the design of the acquisition part of the commonly used calibration device was mainly carried out to achieve automatic verification during the verification process, rather than optimizing and improving the basic structure of the calibration device.

[0008] In the paper "A Method for Improving the Measurement Accuracy of a Low-Temperature Liquid Flow Standard Device by the Mass Method" (Chen Fenghua, Qi Jiningwu, Gao Biao, Wang Shuo, Pan Qin, Measurement Technique, 2017(05): 28-30), with liquefied natural gas as the medium, a method for improving the measurement of a low-temperature liquid flow standard device by the weighing method was proposed, which solved the problem of the start-stop synchronization of the measurement of the flow meter to be inspected and the filling action of the gas storage container. In this paper, the weighing method was used for the calibration of the low-temperature liquid flow standard device, and the standard meter method was not mentioned.

[0009] Chinese invention patent CN113588047.A discloses a flow meter calibration system and method for a cryogenic propellant rocket engine, mainly including a container filling unit, a container, a supply pipeline, a weighing unit, a quick recovery container, a weighing filling and recovery unit, and a recovery unit connected in sequence. The calibration system of this invention solves the problem of low accuracy when using a flow meter to measure in an existing cryogenic propellant rocket engine, but the calibration device adopted in this invention is based on the weighing method.

[0010] The Chinese utility model patent CN215984776.U discloses a low-temperature fluid flow measurement and calibration device, which includes two subcoolers to ensure the subcooling of low-temperature liquids. The operating conditions of the system can be adjusted according to the operating conditions of the low-temperature flowmeter. The flowmeter and the low-temperature pump can be tested and calibrated simultaneously, with high efficiency and low cost. In this invention, the calibration device is still based on the weighing method and uses a low-temperature pump, which is quite different from the structure and system components designed in the present invention. Summary of the Invention

[0011] The present invention provides a calibration device for a single-phase low-temperature fluid flowmeter. Compared with the calibration device based on the traditional weighing method, it has higher measurement accuracy, simpler device structure, lower cost, more convenient operation, more reliable calibration, better sealing performance, smaller heat leakage loss under the structural design of the present invention, and convenient disassembly of each system component, which simplifies the steps of the operator and can be used for the calibration of a single-phase low-temperature fluid flowmeter.

[0012] For this reason, the present invention adopts the following technical solutions:

[0013] On the one hand, the present invention provides a calibration device for a single-phase low-temperature fluid flowmeter, which includes: a low-temperature fluid Dewar filling tank, a standard low-temperature flowmeter, an upstream vacuum chamber, a downstream vacuum chamber, a calibrated low-temperature flowmeter, a vacuum chamber outer tube bellows, a low-temperature solenoid valve, and a low-temperature fluid Dewar collection tank; the low-temperature fluid Dewar filling tank, the standard low-temperature flowmeter, the upstream vacuum chamber, the downstream vacuum chamber, the calibrated low-temperature flowmeter, and the vacuum chamber outer tube bellows are coaxially arranged in the vertical direction;

[0014] Among them, the low-temperature fluid Dewar filling tank is used for the storage and supply of low-temperature liquids and provides heat insulation for the internal standard low-temperature flowmeter and the upstream low-temperature pipeline. The standard low-temperature flowmeter is arranged in the low-temperature fluid Dewar filling tank and immersed in the low-temperature fluid. The standard low-temperature flowmeter is used to provide a standard flow; the standard low-temperature flowmeter is connected to the calibrated low-temperature flowmeter located above the outside of the low-temperature fluid Dewar filling tank through a section of detachable upstream low-temperature pipeline, and the upstream low-temperature pipeline is separated from the outlet flange on the upper end face of the low-temperature fluid Dewar filling tank by the upstream vacuum chamber to avoid heat leakage; the calibrated low-temperature flowmeter is located in the downstream vacuum chamber; the upstream vacuum chamber is closely connected to the downstream vacuum chamber, and the upstream low-temperature pipeline is not exposed to the environment and enters the downstream vacuum chamber immediately after passing through the upstream vacuum chamber;

[0015] The downstream vacuum chamber is hermetically welded to the vacuum chamber outer tube bellows, and the outlet of the calibrated low-temperature flowmeter is connected to the horizontal end face of the vacuum chamber outer tube bellows through a section of downstream vacuum pipeline for the disassembly and installation of the calibrated low-temperature flowmeter;

[0016] The outlet of the bellows of the outer tube of the vacuum chamber is connected to the cryogenic fluid Dewar collection tank through a section of downstream pipeline; a cryogenic solenoid valve is provided on the downstream pipeline;

[0017] Both the cryogenic fluid Dewar filling tank and the cryogenic fluid Dewar collection tank are equipped with gas filling and deflation valves, and the cryogenic fluid Dewar filling tank is also provided with a filling valve.

[0018] As a preferred solution of the present invention, the outer diameter of the upstream vacuum chamber is the same as the inner diameter of the outlet flange. The outlet flange is welded to the side surface of the upstream vacuum chamber, and the materials are all stainless steel. The outlet flange and the upper end surface of the cryogenic fluid Dewar filling tank are sealed by a metal gasket.

[0019] As a preferred solution of the present invention, the side surface of the upstream vacuum pipeline is welded and sealed to the horizontal end surface of the upstream vacuum chamber. The standard cryogenic flowmeter is connected to the upstream cryogenic pipeline through a flange, and the upstream cryogenic pipeline located in the cryogenic fluid Dewar filling tank is immersed in the cryogenic fluid; the data signal line of the standard cryogenic flowmeter is led out to the normal temperature environment through the standard cryogenic flowmeter data acquisition port.

[0020] As a preferred solution of the present invention, the gas filling and deflation valve on the cryogenic fluid Dewar filling tank can be used as both the deflation valve of the cryogenic fluid Dewar filling tank and the gas filling valve of the high-pressure gas source. The cryogenic fluid is pressed out from bottom to top in the vertical direction under the high-pressure gas source, so that the pipeline is filled with a single-phase cryogenic fluid to ensure the measurement accuracy of the standard cryogenic flowmeter.

[0021] As a preferred solution of the present invention, the downstream vacuum chamber is welded and sealed to the bellows of the outer tube of the vacuum chamber and the horizontal end surface of the upstream vacuum chamber respectively; the downstream vacuum chamber is internally connected to the upstream vacuum chamber, and a vacuum interface is provided on the wall surface of the downstream vacuum chamber to connect an external vacuum pumping device; the downstream vacuum chamber and the upstream vacuum chamber are evacuated to ensure that the cryogenic fluid in the pipeline is single-phase.

[0022] As a preferred solution of the present invention, the upstream and downstream end faces of the calibrated cryogenic flowmeter are respectively connected to the horizontal end faces of the upstream vacuum pipeline and the downstream vacuum pipeline by sealed flanges; the data signal line of the calibrated cryogenic flowmeter is led out to the normal temperature environment through the calibrated cryogenic flowmeter data acquisition port opened on the upstream vacuum chamber.

[0023] As a preferred solution of the present invention, the downstream pipeline is wrapped with heat insulation material, and the cryogenic solenoid valve is provided on the downstream pipeline to adjust the flow rate.

[0024] As a preferred solution of the present invention, the cryogenic fluid Dewar collection tank is used to collect the cryogenic fluid, and the gas filling and deflation valve provided thereon is used to ensure the safety of the calibration device.

[0025] On the other hand, the present invention provides a calibration method for the above-mentioned calibration device, which includes the following steps:

[0026] S1. The upstream vacuum chamber and the downstream vacuum chamber are connected to a vacuum pump to evacuate. When the vacuum degree is maintained below 10 -1 Pa, it is considered that the vacuum condition of the calibration device is satisfied, and the vacuum pump always remains working during the calibration process;

[0027] S2. The external low-temperature fluid storage tank is connected to the liquid injection valve of the low-temperature fluid Dewar liquid injection tank through a pipeline. Open the corresponding gas filling and deflation valve, and fill the low-temperature fluid until the low-temperature fluid sprays out of the gas filling and deflation valve, then stop filling;

[0028] S3. Close the liquid injection valve, connect the high-pressure gas source to the gas filling and deflation valve of the low-temperature fluid Dewar liquid injection tank, open the low-temperature solenoid valve and keep it at a small opening, and open the gas filling and deflation valve of the low-temperature fluid Dewar collection tank;

[0029] S4. Adjust the pressure of the high-pressure gas source, and open the gas filling and deflation valve of the low-temperature fluid Dewar liquid injection tank to pre-cool the calibration device. When the temperature of the upstream vacuum pipeline surface collected is close to the temperature of the low-temperature fluid in the pipeline and remains unchanged, the pre-cooling is completed;

[0030] S5. According to the required calibration range, balance the pressure provided by the high-pressure gas source and the opening of the low-temperature solenoid valve; use the data acquisition system to record the data signals of the standard low-temperature flowmeter and the calibrated low-temperature flowmeter in real time, and record the time interval and the change of the flow indication number during steady-state flow;

[0031] S6. Adjust the opening of the low-temperature solenoid valve, repeat step S5, and record the data signals of the standard low-temperature flowmeter and the calibrated low-temperature flowmeter at different openings;

[0032] S7. Adjust the pressure of the high-pressure gas source, repeat step S6, to obtain the data signals of the standard low-temperature flowmeter and the calibrated low-temperature flowmeter under more working conditions;

[0033] S8. Process the data signals to calibrate the calibrated low-temperature flowmeter.

[0034] The beneficial effects of the present invention are:

[0035] 1. For the calibration device of a single-phase low-temperature fluid flowmeter of the present invention, its calibration method is based on the standard flowmeter method. The low-temperature fluid flows from bottom to top in the vertical direction, filling the pipeline with single-phase low-temperature fluid, ensuring the measurement accuracy of the standard low-temperature flowmeter.

[0036] 2. In the present invention, the standard low-temperature flowmeter is immersed in the low-temperature fluid without the need for heat preservation. Its data signal line is led out to the normal temperature environment through the data acquisition port of the standard low-temperature flowmeter for reading the indication number.

[0037] 3. All the flanges in the present invention are knife-edge flanges, and the two end faces of the sealing flange are sealed by metal gaskets to ensure the sealing performance under low-temperature conditions. Especially when the sealing gasket is an oxygen-free copper gasket, the material is relatively soft and has good low-temperature resistance, while the stainless steel material is relatively hard. The combination with the relatively hard flange end face forms a composite seal of soft-hard combination. Therefore, this sealing method can well meet the use under low-temperature conditions.

[0038] 4. The outer tube bellows of the vacuum chamber in the present invention is telescopic. Therefore, the downstream vacuum pipeline has a telescopic margin in the vertical direction to facilitate the disassembly and installation of the calibrated cryogenic flowmeter.

[0039] 5. The vacuum interface in the present invention is used to connect with a vacuum pump to provide vacuum degree for the vacuum chamber, effectively solving the problem of large heat leakage of cryogenic fluid in the pipeline. The pipeline is filled with single-phase cryogenic fluid, ensuring the accuracy of the indication of the calibrated cryogenic flowmeter.

[0040] 6. The downstream pipeline with heat insulation material in the present invention not only reduces the heat leakage of the cryogenic fluid pipeline, but also greatly reduces the cost.

[0041] 7. The cryogenic solenoid valve in the present invention can adjust the opening degree of the valve in real time through a signal switch, thereby adjusting the flow rate and reducing the cumbersome operation brought to the operator by the traditional manual cryogenic valve.

[0042] 8. The cryogenic fluid Dewar collection tank in the present invention can collect the cryogenic fluid in the pipeline, reduce waste, and the provided air release valve also ensures the safety of the calibration device.

[0043] 9. Compared with the calibration device based on the traditional weighing method, the calibration device of the present invention has higher measurement accuracy, simpler device structure, lower cost, more convenient operation, and more reliable calibration.

[0044] 10. Under the structural design of the present invention, the sealing performance is better, the heat leakage loss is smaller, the disassembly of each system component is convenient, simplifying the steps of the operator, and it can be used for the calibration of single-phase cryogenic fluid flowmeters. Description of the Drawings

[0045] Figure 1 is the calibration principle diagram of the standard flowmeter method of the present invention;

[0046] Figure 2 is the structural schematic diagram of a calibration device for a single-phase cryogenic fluid flowmeter of the present invention;

[0047] Figure 3 is the change diagram of the outflow coefficient of the calibrated cryogenic equilibrium flowmeter with the flow rate in the second embodiment of the present invention.

[0048] Description of the drawing reference numerals: 1. Cryogenic fluid Dewar filling tank; 2. Filling pipe; 3. Gas filling and venting pipe; 4. Filling valve; 5. Gas filling and venting valve; 6. Standard cryogenic flowmeter; 7. Upstream cryogenic pipeline; 8. Upstream vacuum pipeline; 9. Outlet flange; 10. Data acquisition port of the standard cryogenic flowmeter; 11. Downstream vacuum cavity; 12. Calibration cryogenic flowmeter; 13. Demountable bracket; 14. Downstream vacuum pipeline; 15. Data acquisition port of the calibration cryogenic flowmeter; 16. Bellows of the outer pipe of the vacuum cavity; 17. Cryogenic solenoid valve; 18. Cryogenic fluid Dewar collection tank; 19. Sealing flange; 20. Vacuum interface; 21. Upstream vacuum cavity; 22. Downstream pipeline. Detailed implementation manners

[0049] The present invention will be further described and explained below in conjunction with the detailed implementation manners. The embodiments are only demonstrations of the present disclosure content and do not delimit the scope of limitation. The technical features of each implementation manner in the present invention can be combined correspondingly without conflict.

[0050] As Figure 1 shown, it is a schematic diagram of the principle of the present invention. The calibration method of the present invention is based on the standard flowmeter method. The cryogenic fluid flows from bottom to top in the vertical direction, filling the pipeline with a single-phase cryogenic fluid, ensuring the measurement accuracy of the standard cryogenic flowmeter. Figure 1 Among them, the high-pressure gas source provides a stable and adjustable pressure for the supply of the cryogenic liquid flow rate; the cryogenic fluid Dewar filling tank is used for the storage and supply of the cryogenic liquid and insulates the internal standard cryogenic flowmeter and the upstream cryogenic pipeline; the standard cryogenic flowmeter is used to provide the standard flow rate; the vacuum cavity is used to provide the measurement conditions of low temperature and full pipe to ensure the accuracy of the cryogenic calibration flowmeter; the cryogenic solenoid valve is used to adjust the flow rate; the cryogenic fluid Dewar collection tank is used to collect the cryogenic liquid during the calibration process and can also adjust the system pressure.

[0051] As Figure 2As shown in the figure, a calibration device for a single-phase cryogenic fluid flowmeter of the present invention includes a cryogenic fluid Dewar filling tank 1, an upstream cryogenic pipeline 7, an upstream vacuum pipeline 8, an upstream vacuum cavity 21, an outlet flange 9, a downstream vacuum pipeline 14, a vacuum cavity outer tube bellows 16, as well as a detachable bracket 13, a cryogenic solenoid valve 17, and a cryogenic fluid Dewar collection tank 18, which are coaxially arranged in the vertical direction; the outlet flange 9 and the upstream vacuum cavity 21 are both made of 304 or 316 stainless steel; the downstream vacuum cavity 11 is made of aluminum alloy, which reduces its own weight while ensuring vacuum; the sealing gaskets between the sealing flanges are all made of oxygen-free copper. The standard cryogenic flowmeter 6 is arranged in the cryogenic fluid Dewar filling tank 1 and immersed in the cryogenic fluid; the standard cryogenic flowmeter 6 is connected to the calibration cryogenic flowmeter 12 located above the outside of the cryogenic fluid Dewar filling tank 1 through a detachable upstream cryogenic pipeline 7, where the upstream cryogenic pipeline 7 is separated from the outlet flange 9 on the upper end face of the cryogenic fluid Dewar filling tank 1 by the upstream vacuum cavity 21 to avoid heat leakage; the calibration cryogenic flowmeter 12 is located in the downstream vacuum cavity 11; the upstream vacuum cavity 21 is closely connected to the downstream vacuum cavity 11, and the upstream cryogenic pipeline 7 is not exposed to the environment and enters the downstream vacuum cavity 11 immediately after passing through the upstream vacuum cavity 21;

[0052] The downstream vacuum cavity 11 and the vacuum cavity outer tube bellows 16 are sealed by welding, and the outlet of the calibration cryogenic flowmeter 12 is connected to the horizontal end face of the vacuum cavity outer tube bellows 16 through a section of downstream vacuum pipeline 14 for the disassembly and installation of the calibration cryogenic flowmeter 12;

[0053] The outlet of the vacuum cavity outer tube bellows 16 is connected to the cryogenic fluid Dewar collection tank 18 through a section of downstream pipeline 22; a cryogenic solenoid valve 17 is arranged on the downstream pipeline 22;

[0054] Both the cryogenic fluid Dewar filling tank 1 and the cryogenic fluid Dewar collection tank 18 are provided with gas filling and deflation valves 5, and the cryogenic fluid Dewar filling tank 1 is also provided with a filling valve 4.

[0055] In a specific embodiment of the present invention, the cryogenic fluid Dewar filling tank 1 and the upstream vacuum cavity 21 of the present invention are bolted through the outlet flange 9, and the downstream vacuum cavity 11 is hermetically connected to the horizontal end faces of the upstream vacuum cavity 21 and the vacuum cavity outer tube bellows 16 by welding, serving as the sealed connection between the liquid supply part and the vacuum part.

[0056] In a specific embodiment of the present invention, the upstream low-temperature pipeline 7 in the invention is fixedly welded to the horizontal end face of the upstream vacuum cavity 21, and the distance from the upstream low-temperature pipeline 7 to the bottom of the inner tank of the cryogenic fluid dewar filling tank 1 is greater than 50 cm to meet the installation requirements of the standard cryogenic flowmeter 6 and its upstream straight pipe section. The downstream vacuum pipeline 14 is fixedly welded to the horizontal end face of the vacuum cavity outer pipe bellows 16, and the expansion allowance of the vacuum cavity outer pipe bellows 16 is greater than 10 mm to facilitate the installation and fixation of the calibration cryogenic flowmeter 12.

[0057] In a specific embodiment of the present invention, the cryogenic fluid dewar filling tank 1, the upstream vacuum cavity 21, the downstream vacuum cavity 11, and the vacuum cavity outer pipe bellows 16 in the invention provide cryogenic vacuum conditions for the standard cryogenic flowmeter 6 and the calibration cryogenic flowmeter 12.

[0058] The inner diameters of the upstream low-temperature pipeline 7, the upstream vacuum pipeline 8, the downstream vacuum pipeline 14, and the downstream pipeline 22 with thermal insulation material in the invention are all kept consistent.

[0059] The material of the downstream pipeline 22 with thermal insulation material in the invention can be a stainless steel hard pipe or a corrugated hose of 304 or 316. If a corrugated hose is used, it should be supported by a bracket, and the cryogenic fluid pressure in the pipeline should be less than the pressure that the pipeline can withstand.

[0060] The cryogenic solenoid valve 17 in the invention can adjust the opening degree through a signal switch to meet the calibration under different flow conditions.

[0061] The volume of the cryogenic fluid dewar collection tank 18 in the invention needs to be not less than the volume of the cryogenic fluid dewar filling tank 1.

[0062] The standard cryogenic flowmeter 6 and the calibration cryogenic flowmeter 12 in the invention are both vertically installed, and the cryogenic fluid flows from bottom to top.

[0063] For the connection between the sealing flanges in the invention, the sealing gaskets are all oxygen-free copper gaskets to form a composite seal of soft and hard matching to ensure the sealing performance under cryogenic conditions.

[0064] The installation steps are as follows:

[0065] S1. The cryogenic fluid dewar filling tank 1 is respectively welded and sealed to the sides of the filling pipe 2 and the gas filling and venting pipe 3. The filling pipe 2 and the gas filling and venting pipe 3 are respectively welded and sealed to the end faces of the filling valve 4 and the gas filling and venting valve 5. The pipeline of the filling pipe 2 extends to the bottom of the cryogenic fluid dewar collection tank 18.

[0066] S2. The side of the upstream vacuum pipeline 8 is welded and sealed to the horizontal end face of the upstream vacuum cavity 21, the outlet flange 9 is welded to the side of the upstream vacuum cavity 21, and the standard cryogenic flowmeter 6 is connected to the upstream cryogenic pipeline 7 by a sealed flange;

[0067] S3. The outlet flange 9 is sealed to the upper end face flange of the cryogenic fluid dewar filling tank 1, so that the standard cryogenic flowmeter 6 extends into the cryogenic fluid dewar filling tank 1;

[0068] S4. The downstream vacuum cavity 11 is respectively welded and sealed to the horizontal end face of the vacuum cavity outer pipe bellows 16 and the upstream vacuum cavity 21, and the detachable bracket 13 is used to support the downstream vacuum cavity 11;

[0069] S5. The downstream vacuum pipeline 14 is welded and sealed to the horizontal end face of the vacuum cavity outer pipe bellows 16, and the upstream and downstream end faces of the calibrated cryogenic flowmeter 12 are respectively connected to the horizontal end faces of the upstream vacuum pipeline 8 and the downstream vacuum pipeline 14 by sealed flanges to meet the use in a cryogenic vacuum environment;

[0070] S6. The downstream vacuum pipeline 14, the downstream pipeline 22 with heat insulation material, the cryogenic solenoid valve 17 and the cryogenic fluid dewar collection tank 18 are sequentially connected by flanges along the fluid flow direction, and the system forms a seal.

[0071] When disassembling, it is the opposite of the above steps.

[0072] The following further describes the present invention with reference to embodiments. The description of the following embodiments is only for helping to understand the present invention. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and modifications can still be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0073] Embodiment 1:

[0074] Embodiment 1 provides a calibration method for a calibration device of a single-phase cryogenic fluid flowmeter, including the following steps:

[0075] S1. The vacuum interface 20 is connected to a vacuum pump to evacuate the vacuum cavity part. When the vacuum degree is maintained below 10 -1 Pa, it is considered that the vacuum condition of the calibration device is met, and the vacuum pump always remains working during the calibration process;

[0076] S2. The cryogenic fluid storage tank is connected to the filling valve 4 of the cryogenic fluid dewar filling tank 1 through a pipeline. Open the corresponding gas filling and deflation valve 5, and stop filling when the cryogenic fluid sprays out from the gas filling and deflation valve 5;

[0077] S3. Close the liquid injection valve 4, connect the high-pressure gas source to the gas filling and deflation valve 5 of the cryogenic fluid Dewar liquid injection tank 1, open the cryogenic solenoid valve 17 and keep it slightly open, and open the gas filling and deflation valve 5 of the cryogenic fluid Dewar collection tank 18;

[0078] S4. Adjust the pressure of the high-pressure gas source, and open the gas filling and deflation valve 5 of the cryogenic fluid Dewar liquid injection tank 1 to pre-cool the calibration device. When the temperature on the surface of the upstream vacuum pipeline 8 collected is close to the temperature of the cryogenic fluid in the pipeline and remains unchanged, the pre-cooling is completed;

[0079] S5. Record the data signals of the standard cryogenic flowmeter 6 and the calibrated cryogenic flowmeter 12 in real time through the data acquisition system, and record the time interval and the change of the flow indication during steady-state flow;

[0080] S6. Adjust the opening degree of the cryogenic solenoid valve 17, repeat step S5, and record the data signals of the standard cryogenic flowmeter 6 and the calibrated cryogenic flowmeter 12 at different opening degrees;

[0081] S7. Adjust the pressure of the high-pressure gas source, repeat step S6, to obtain the data signals of the standard cryogenic flowmeter 6 and the calibrated cryogenic flowmeter 12 under more working conditions;

[0082] S8. Evaluate and calibrate the calibrated cryogenic flowmeter 12.

[0083] Embodiment 2:

[0084] In Embodiment 2, a calibration device for a single-phase cryogenic fluid flowmeter of the present invention is built and tested. In this embodiment, the standard cryogenic flowmeter 6 is a cryogenic turbine flowmeter, and the calibrated cryogenic flowmeter 12 is a cryogenic balanced flowmeter. The specification dimensions match the pipeline dimensions, both are DN40, and the straight pipe lengths before and after the corresponding flowmeters both meet the measurement conditions. The volumes of the cryogenic fluid Dewar liquid injection tank 1 and the cryogenic fluid Dewar collection tank 18 are both 300L, and the height of the detachable bracket 13 is 1700mm. Sub-cooled liquid nitrogen is used as the measurement working medium, the pipeline inlet temperature is 77K, and the pipeline wall surface is kept adiabatic.

[0085] In this embodiment, the gauge pressure of the high-pressure gas source is 0.2MPa. By adjusting the opening degree of the cryogenic solenoid valve 17, the flow rate of sub-cooled liquid nitrogen is adjusted, and the opening degrees are 0.4, 0.5, and 0.6 respectively. Record the flow indication of the cryogenic turbine flowmeter and the indication of the differential pressure of the cryogenic balanced flowmeter at different opening degrees, and calibrate the outflow coefficient C value of the cryogenic balanced flowmeter. Its expression is:

[0086]

[0087] Where β is the equivalent diameter ratio of the orifice plate of the balanced flowmeter, q mThe mass flow rate, D is the inner diameter of the pipeline, ρ is the liquid density, and Δp is the pressure difference of the cryogenic balanced flowmeter. The results are as Figure 3 shown, and the discharge coefficients of the cryogenic balanced flowmeter at different flow rates are obtained, and the calibration is effective.

[0088] In summary, a calibration device for a single-phase cryogenic fluid flowmeter designed by the present invention can be well applied to the calibration of cryogenic fluid flowmeters, has good sealing performance, and excludes the possibility of cryogenic fluid leakage. It ensures that the cryogenic fluid in the flowmeter is all single-phase. Compared with the calibration device based on the traditional weighing method, it has higher measurement accuracy, simpler device structure, lower cost, more convenient operation, and more reliable calibration. In addition, due to the detachable structure of the present invention, during specific implementation, each system component can be easily disassembled, simplifying the steps of the operator, and can be used for the calibration of single-phase cryogenic fluid flowmeters.

[0089] The above embodiments only represent several implementation manners of the present invention, and the description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent of the present invention. For those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A calibration device for a single-phase cryogenic fluid flowmeter, characterized in that it includes: a cryogenic fluid Dewar injection tank (1), a standard cryogenic flowmeter (6), an upstream vacuum cavity (21), a downstream vacuum cavity (11), a calibrated cryogenic flowmeter (12), a vacuum cavity outer tube bellows (16), a cryogenic solenoid valve (17), and a cryogenic fluid Dewar collection tank (18); the cryogenic fluid Dewar injection tank (1), the standard cryogenic flowmeter (6), the upstream vacuum cavity (21), the downstream vacuum cavity (11), the calibrated cryogenic flowmeter (12), and the vacuum cavity outer tube bellows (16) are coaxially arranged in the vertical direction; Among them, the cryogenic fluid Dewar injection tank (1) is used for the storage and supply of cryogenic liquids and insulates the internal standard cryogenic flowmeter and the upstream cryogenic pipeline. The standard cryogenic flowmeter (6) is arranged in the cryogenic fluid Dewar injection tank (1) and is immersed in the cryogenic fluid. The standard cryogenic flowmeter is used to provide a standard flow rate; The standard cryogenic flowmeter (6) is connected to the calibrated cryogenic flowmeter (12) located above the outside of the cryogenic fluid Dewar injection tank (1) through a detachable upstream cryogenic pipeline (7). Among them, the upstream cryogenic pipeline (7) is separated from the outlet flange (9) on the upper end face of the cryogenic fluid Dewar injection tank (1) by the upstream vacuum cavity (21) to avoid heat leakage; the calibrated cryogenic flowmeter (12) is located in the downstream vacuum cavity (11); the upstream vacuum cavity (21) is closely connected to the downstream vacuum cavity (11), and the upstream cryogenic pipeline (7) is not exposed to the environment and enters the downstream vacuum cavity (11) immediately after passing through the upstream vacuum cavity (21); The downstream vacuum cavity (11) is welded and sealed with the vacuum cavity outer tube bellows (16). The outlet of the calibrated cryogenic flowmeter (12) is connected to the horizontal end face of the vacuum cavity outer tube bellows (16) through a downstream vacuum pipeline (14) for the disassembly and installation of the calibrated cryogenic flowmeter (12); The outlet of the vacuum cavity outer tube bellows (16) is connected to the cryogenic fluid Dewar collection tank (18) through a downstream pipeline (22); a cryogenic solenoid valve (17) is arranged on the downstream pipeline (22); Both the cryogenic fluid Dewar injection tank (1) and the cryogenic fluid Dewar collection tank (18) are provided with gas filling and deflation valves (5), and the cryogenic fluid Dewar injection tank (1) is also provided with a liquid injection valve (4).

2. The calibration device for a single-phase cryogenic fluid flowmeter according to claim 1, characterized in that the outer diameter of the upstream vacuum cavity (21) is the same as the inner diameter of the outlet flange (9). The outlet flange (9) is welded to the side of the upstream vacuum cavity (21), and the materials are both stainless steel. The outlet flange (9) is sealed with the upper end face of the cryogenic fluid Dewar injection tank (1) through a metal gasket.

3. The calibration device for a single-phase cryogenic fluid flowmeter according to claim 1, characterized in that The side of the upstream vacuum pipeline (8) is welded and sealed to the horizontal end face of the upstream vacuum cavity (21). The standard cryogenic flowmeter (6) is connected to the upstream cryogenic pipeline (7) through a flange. The upstream cryogenic pipeline (7) located inside the cryogenic fluid Dewar filling tank (1) is immersed in the cryogenic fluid. The data signal line of the standard cryogenic flowmeter (6) is led out to the normal temperature environment through the standard cryogenic flowmeter data acquisition port (10).

4. The calibration device for a single-phase cryogenic fluid flowmeter according to claim 1, characterized in that, the gas filling and deflation valve (5) on the cryogenic fluid Dewar filling tank (1) can be used as both the deflation valve of the cryogenic fluid Dewar filling tank (1) and the gas filling valve of the high-pressure gas source. The cryogenic fluid is pressed out from bottom to top in the vertical direction under the high-pressure gas source, so that the pipeline is filled with single-phase cryogenic fluid to ensure the measurement accuracy of the standard cryogenic flowmeter (6).

5. The calibration device for a single-phase cryogenic fluid flowmeter according to claim 1, characterized in that, The downstream vacuum cavity (11) is respectively welded and sealed to the horizontal end faces of the vacuum cavity outer tube bellows (16) and the upstream vacuum cavity (21). The downstream vacuum cavity (11) is internally connected to the upstream vacuum cavity (21). A vacuum interface (20) is provided on the wall surface of the downstream vacuum cavity (11) to connect to an external vacuum pumping device. The downstream vacuum cavity (11) and the upstream vacuum cavity (21) are evacuated to ensure that the cryogenic fluid in the pipeline is single-phase.

6. The calibration device for a single-phase cryogenic fluid flowmeter according to claim 1, characterized in that, The upstream and downstream end faces of the calibration cryogenic flowmeter (12) are respectively sealed and flange-connected to the horizontal end faces of the upstream vacuum pipeline (8) and the downstream vacuum pipeline (14). The data signal line of the calibration cryogenic flowmeter (12) is led out to the normal temperature environment through the calibration cryogenic flowmeter data acquisition port (15) opened on the upstream vacuum cavity (21).

7. The calibration device for a single-phase cryogenic fluid flowmeter according to claim 1, characterized in that, The downstream pipeline (22) is wrapped with heat insulation material, and the cryogenic solenoid valve (17) is arranged on the downstream pipeline (22) to adjust the flow rate.

8. The calibration device for a single-phase cryogenic fluid flowmeter according to claim 1, characterized in that, The cryogenic fluid Dewar collection tank (18) is used to collect the cryogenic fluid, and the gas filling and deflation valve (5) provided thereon is used to ensure the safety of the calibration device.

9. The calibration method of the calibration device according to any one of claims 1-8, characterized in that, comprises the following steps: S1. The upstream vacuum chamber (21) and the downstream vacuum chamber (11) are connected to a vacuum pump to evacuate the air. When the vacuum degree is maintained below 10 -1 Pa, it is considered that the vacuum condition of the calibration device is satisfied, and the vacuum pump always remains working during the calibration process; S2. The external cryogenic fluid storage tank is connected to the filling valve (4) of the cryogenic fluid Dewar filling tank (1) through a pipeline. Open the corresponding gas filling and deflation valve (5), and stop filling when cryogenic fluid sprays out from the gas filling and deflation valve (5); S3. Close the filling valve (4), connect the high-pressure gas source to the gas filling and deflation valve (5) of the cryogenic fluid Dewar filling tank (1), open the cryogenic solenoid valve (17) and keep it slightly open, and open the gas filling and deflation valve (5) of the cryogenic fluid Dewar collection tank (18); S4. Adjust the pressure of the high-pressure gas source, and open the gas filling and bleeding valve (5) of the cryogenic fluid dewar filling tank (1) to pre-cool the calibration device. The pre-cooling is completed when the temperature on the surface of the upstream vacuum pipeline (8) collected is close to the temperature of the cryogenic fluid in the pipeline and remains unchanged. S5. According to the required calibration range, balance the pressure provided by the high-pressure gas source and the opening degree of the cryogenic solenoid valve; record the data signals of the standard cryogenic flowmeter (6) and the calibrated cryogenic flowmeter (12) in real time through the data acquisition system, and record the time interval and the change of the flow indication number during steady-state flow. S6. Adjust the opening degree of the cryogenic solenoid valve (17), repeat step S5, and record the data signals of the standard cryogenic flowmeter (6) and the calibrated cryogenic flowmeter (12) at different opening degrees. S7. Adjust the pressure of the high-pressure gas source, repeat step S6, to obtain the data signals of the standard cryogenic flowmeter (6) and the calibrated cryogenic flowmeter (12) under more working conditions. S8. Process the data signals to calibrate the calibrated cryogenic flowmeter (12).

Images