Wide-range low-temperature flow measurement benchmark device driven by air pressure and variable-lift pump and wide-range low-temperature flow measurement benchmark method

Abstract

The invention relates to the technical field of flow calibration, and provides a wide-range low-temperature flow measurement benchmark device and method with air pressure and variable-lift pump driving, and the device comprises an air pressure driving loop, a variable-lift pump driving loop and a weighing assembly; the variable lift pump driving loop comprises a low-temperature liquid storage tank, a low-temperature pump and a control valve group; the top of the low-temperature liquid storage tank is connected to the pneumatic driving loop; the low-temperature pump is connected to the bottom of the low-temperature liquid storage tank, the control valve group is connected between a low-temperature pump inlet and a low-temperature pump outlet, and the low-temperature pump outlet is connected to the flowmeter to be calibrated; the control valve group is suitable for being switched between a first state and a second state; the weighing assembly is connected to an outlet of the flowmeter to be calibrated; when small-flow calibration is carried out, the control valve group is in a first state, and small-flow output is achieved through air pressure driving; when large-flow calibration is carried out, the control valve set is switched to the second state, the fluid is pressurized through the low-temperature pump, stable output under large flow is ensured, and the small-flow calibration requirement and the large-flow calibration requirement can be met at the same time.

Description

Technical Field

[0001] This invention relates to the field of flow calibration technology, and in particular to a wide-range cryogenic flow measurement reference device and method that combines air pressure and variable head pump drive. Background Technology

[0002] In cutting-edge scientific fields such as superconductivity, quantum computing, aerospace, and large-scale scientific engineering, high-precision, wide-range flow measurement of cryogenic fluids (such as liquid helium, liquid hydrogen, and liquid oxygen) is crucial for ensuring the stable operation and performance verification of related systems. As the pinnacle of the measurement value transfer and traceability system, the metrological performance of cryogenic flow measurement reference devices, especially their range coverage and stability at different flow rates, directly determines the accuracy and reliability of flow measurement. Therefore, developing flow measurement reference devices with wide range and high stability has become an urgent need to drive the development of these technologies.

[0003] In existing technologies, cryogenic flow measurement reference devices generally employ pneumatic drive technology. This technology involves injecting pre-cooled pressurized gas (such as helium) into the gas phase space of a sealed cryogenic storage tank. By utilizing the established stable static pressure difference, the cryogenic liquid is smoothly displaced from the cryogenic storage tank, thereby achieving flow control and measurement.

[0004] However, the driving force of the aforementioned pneumatic drive technology comes from the limited static pressure of the gas, resulting in a relatively low driving head. This makes it difficult to overcome the significantly increased pipeline resistance losses under high flow conditions, thus preventing the stable and rapid delivery of large flow rates. Furthermore, due to the volumetric effect of the gas phase space itself, the system exhibits a sluggish response during pressure build-up and regulation, further weakening the stability of flow control. Summary of the Invention

[0005] This invention provides a wide-range cryogenic flow measurement reference device and method that combines air pressure and variable head pump drive, in order to solve the defects of existing technology that rely on air pressure drive, resulting in slow response and poor flow stability under high flow conditions, and to achieve high-precision and high-stability cryogenic fluid flow measurement over a wide range.

[0006] This invention provides a wide-range cryogenic flow measurement reference device that combines gas pressure and variable head pump drive, comprising: Pneumatic drive circuit; A variable head pump drive circuit includes a cryogenic storage tank, a cryogenic pump, and a control valve assembly. The cryogenic storage tank stores cryogenic fluid, and a gas inlet at the top of the tank is connected to a pneumatic drive circuit. The cryogenic pump is connected to a liquid outlet at the bottom of the tank. The control valve assembly is connected between the inlet and outlet of the cryogenic pump, and the outlet of the pump is connected to the inlet of a flow meter to be calibrated. The control valve assembly is adapted to switch between a first state and a second state. In the first state, the pneumatic drive circuit pressurizes the cryogenic storage tank, and the cryogenic liquid in the tank flows to the flow meter to be calibrated via the control valve assembly. In the second state, the pneumatic drive circuit stops pressurizing the cryogenic storage tank, and the cryogenic liquid in the tank flows to the flow meter to be calibrated after being pressurized by the control valve assembly and the cryogenic pump. A weighing assembly is used to connect to the outlet of the flow meter to be calibrated in order to weigh the cryogenic fluid flowing out of the flow meter.

[0007] According to the present invention, a wide-range cryogenic flow measurement reference device that combines pneumatic pressure and variable head pump drive is provided, wherein the control valve group includes: A pump inlet valve is located between the liquid outlet and the inlet of the cryogenic pump; A bypass valve is provided between the liquid outlet and the outlet of the cryogenic pump; In the first state, the pump inlet valve is closed and the bypass valve is open; in the second state, the pump inlet valve is open and the bypass valve is closed.

[0008] According to the present invention, a wide-range cryogenic flow measurement reference device with both air pressure and variable head pump drive is provided. The variable head pump drive circuit further includes a liquid control valve. One end of the liquid control valve is connected to the outlet of the cryogenic pump and the connection position of the bypass valve, and the other end of the liquid control valve is connected to the inlet of the flow meter to be calibrated.

[0009] According to the present invention, a wide-range cryogenic flow measurement reference device with both gas pressure and variable head pump drive is provided. The gas pressure drive circuit includes an inert gas source, a precooler, a gas flow controller and a gas control valve connected in sequence. The gas control valve is connected to the gas inlet at the top of the cryogenic storage tank. In the first state, the gas control valve is open; in the second state, the gas control valve is closed.

[0010] According to the present invention, a wide-range cryogenic flow measurement reference device is provided that combines air pressure and variable head pump drive, wherein the cryogenic pump is a variable frequency centrifugal pump, a cryogenic piston pump or a gear pump.

[0011] According to the present invention, a wide-range cryogenic flow measurement reference device with both air pressure and variable head pump drive is provided, wherein the weighing component includes: A cryogenic fluid collection tank is connected to the outlet of the flow meter to be calibrated; A weighing device is used to measure the weight of the fluid in the cryogenic fluid collection tank.

[0012] This invention also provides a wide-range cryogenic flow measurement method that combines gas pressure and variable head pump drive, based on the wide-range cryogenic flow measurement reference device that combines gas pressure and variable head pump drive described above, the method comprising: Compare the target traffic value with the preset traffic switching threshold; When the target flow rate is less than the preset flow switching threshold, the control valve group is in the first state, and the air pressure drive circuit is used to pressurize the cryogenic liquid tank so that the cryogenic liquid in the cryogenic liquid tank flows to the flow meter to be calibrated through the control valve group. When the target flow rate is greater than or equal to the preset flow switching threshold, the control valve group is controlled to be in the second state, and the pneumatic drive circuit is controlled to stop pressurizing the cryogenic liquid storage tank. The cryogenic liquid in the cryogenic liquid storage tank flows to the flow meter to be calibrated after being pressurized by the control valve group and the cryogenic pump. The cryogenic fluid flowing out of the flow meter to be calibrated is weighed using a weighing component.

[0013] According to the present invention, a wide-range cryogenic flow measurement method combining pneumatic and variable head pump drive is provided, which pressurizes the cryogenic storage tank using a pneumatic drive circuit, comprising: The target driving gas flow rate corresponding to the target flow rate value is determined based on the preset relationship between the liquid flow rate and the driving gas flow rate. Based on the target driving gas flow rate, the gas flow controller is controlled to inject high-pressure gas into the cryogenic storage tank at the target driving gas flow rate.

[0014] According to the present invention, a wide-range cryogenic flow measurement method that combines pneumatic pressure and variable head pump drive, before controlling the control valve assembly to be in the second state, further includes: The control pump inlet valve, bypass valve, and cryogenic pump are opened, while the liquid control valve is closed, and this continues for a preset duration.

[0015] According to the present invention, a wide-range cryogenic flow measurement method combining gas pressure and variable head pump drive is provided. After the cryogenic liquid in the cryogenic storage tank is pressurized by the control valve group and the cryogenic pump and flows to the flow meter to be calibrated, the method further includes: Obtain the current flow rate value of the flow meter to be calibrated; Based on the difference between the current flow rate and the target flow rate, the speed of the cryogenic pump is adjusted until the difference is less than a preset deviation.

[0016] The present invention provides a wide-range cryogenic flow measurement reference device that combines pneumatic and variable-head pump drives. This device integrates a pneumatic drive circuit with a variable-head pump drive circuit and is equipped with a control valve assembly that can switch between two states. During low-flow calibration, the control valve assembly is in the first state, utilizing pneumatic drive to achieve a low-disturbance, highly stable small flow output. During high-flow calibration, the control valve assembly switches to the second state, using the cryogenic pump to actively pressurize the fluid, providing a sufficiently high drive head to overcome pipeline resistance at high flow rates and ensure stable output at high flow rates. Thus, by coordinating the pneumatic and variable-head pump drive circuits, the device's range coverage is broadened, simultaneously meeting the calibration requirements for both low and high flow rates, and achieving stable flow output throughout the entire wide range, significantly improving the device's applicability. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of the wide-range cryogenic flow measurement reference device provided by the present invention, which combines air pressure and variable head pump drive.

[0019] Figure 2 This is a schematic flowchart of the wide-range cryogenic flow measurement method provided by the present invention, which combines air pressure and variable head pump drive.

[0020] Figure label: 1. Inert gas source; 2. Precooler; 3. Gas flow controller; 4. Gas control valve; 5. Gas inlet; 6. Liquid outlet; 7. Cryogenic storage tank; 8. Bypass valve; 9. Pump inlet valve; 10. Cryogenic pump; 11. Liquid control valve; 12. Flow meter to be calibrated; 13. Cryogenic fluid collection tank; 14. Weighing device. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0022] In the description of the embodiments of the present invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of the present invention. In addition, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0023] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of the present invention based on the specific circumstances.

[0024] In embodiments of the present invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0025] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0026] An embodiment of the first aspect of the present invention provides a wide-range cryogenic flow measurement reference device that combines gas pressure and variable head pump drive, such as... Figure 1 As shown, the calibration device includes a pneumatic drive circuit, a variable head pump drive circuit, and a weighing assembly.

[0027] The variable head pump drive circuit includes a cryogenic storage tank 7, a cryogenic pump 10, and a control valve assembly. The cryogenic storage tank 7 is used to store cryogenic fluid, and the gas inlet 5 at the top of the cryogenic storage tank 7 is connected to the pneumatic drive circuit. The cryogenic pump 10 is connected to the liquid outlet 6 at the bottom of the cryogenic storage tank 7, and the control valve assembly is connected between the inlet and outlet of the cryogenic pump 10. The outlet of the cryogenic pump 10 is used to connect to the inlet of the flow meter 12 to be calibrated. The control valve assembly is adapted to switch between a first state and a second state. In the first state, the pneumatic drive circuit pressurizes the cryogenic storage tank 7, and the cryogenic liquid in the cryogenic storage tank 7 flows to the flow meter 12 to be calibrated through the control valve assembly. In the second state, the pneumatic drive circuit stops pressurizing the cryogenic storage tank 7, and the cryogenic liquid in the cryogenic storage tank 7 flows to the flow meter 12 to be calibrated after being pressurized by the control valve assembly and the cryogenic pump 10.

[0028] The weighing assembly is used to connect to the outlet of the flow meter 12 to be calibrated in order to weigh the cryogenic fluid flowing out of the flow meter 12.

[0029] Understandably, the cryogenic storage tank 7 is used to store cryogenic fluids such as liquid helium. Its top gas inlet 5 is connected to a pneumatic drive circuit to receive pressurized gas. The cryogenic pump 10 is connected to the liquid outlet 6 at the bottom of the storage tank, and its outlet is used to connect to the inlet of the flow meter 12 to be calibrated. A control valve assembly is located between the inlet and outlet of the cryogenic pump 10 and can switch between a first state and a second state. Under low-flow conditions, the device enters the pneumatic drive mode. At this time, in the first state, the control valve assembly operates, and the pneumatic drive circuit is active, injecting pressurized gas into the cryogenic storage tank 7. Using gas phase pressure, the cryogenic liquid in the storage tank 7 is directly pushed to the flow meter 12 to be calibrated via the control valve assembly (bypassing the cryogenic pump 10), achieving stable low-flow output without pump drive. Under high flow rate conditions, the device enters the cryogenic pump drive mode (i.e., variable head pump drive mode). In this mode, the control valve group is in its second state, the pneumatic drive circuit stops supplying pressure, and the cryogenic liquid, guided by the control valve group, enters the cryogenic pump 10. After being pressurized by the cryogenic pump 10, it is then delivered to the flow meter 12 to be calibrated. The active pressurization by the cryogenic pump 10 provides a sufficiently high drive head, thereby overcoming the significantly increased pipeline resistance under high flow rate conditions and ensuring stable and rapid delivery under these conditions. The weighing component measures the cryogenic fluid flowing out of the flow meter 12 in real time, enabling wide-range, high-accuracy, and high-dynamic-response flow calibration. This provides reliable technical support for the metrology and performance verification of cryogenic systems in fields such as superconductivity, quantum computing, and aerospace.

[0030] It should be noted that the flow meter can be a measuring instrument to be calibrated that is installed in the test section.

[0031] It should be noted that pneumatic drive is limited by the finite static pressure head of the gas, making it difficult to overcome pipeline resistance under high flow conditions. Furthermore, its pressure regulation response is sluggish, resulting in a narrow flow range and poor stability. The cryogenic pump 10 directly pressurizes the cryogenic fluid, providing it with strong flow power, enabling stable operation and precise control under high flow conditions. However, under low flow conditions, the pump's hydraulic efficiency and operational stability drop sharply, easily leading to unstable flow phenomena such as cavitation and surge, making precise and stable control of small flow rates difficult. By combining the pneumatic drive circuit with the variable head pump drive circuit, the device's flow range is greatly expanded, achieving precise calibration across the entire flow range from small to large flow rates.

[0032] The wide-range cryogenic flow measurement reference device provided in this invention combines pneumatic and variable-head pump drives, and is equipped with a control valve group that can switch between two states. During low-flow calibration, the control valve group is in the first state, using pneumatic drive to achieve a low-disturbance, high-stability small flow output. During high-flow calibration, the control valve group switches to the second state, using the cryogenic pump 10 to actively pressurize the fluid, providing a sufficiently high drive head to overcome pipeline resistance at high flow rates, ensuring stable output at high flow rates. Thus, by coordinating the pneumatic and variable-head pump drives, the device's range is broadened, simultaneously meeting the calibration requirements for both low and high flow rates, and achieving stable flow output throughout the entire wide range, significantly improving the device's applicability.

[0033] In one embodiment of the present invention, the pneumatic drive circuit is connected to the gas inlet 5 at the top of the cryogenic storage tank 7 for stable drive under low flow conditions. Figure 1 As shown, the pneumatic drive circuit includes an inert gas source 1, a precooler 2, a gas flow controller 3, and a gas control valve 4 connected in sequence. The gas control valve 4 is connected to the gas inlet 5 at the top of the cryogenic storage tank 7.

[0034] In this system, inert gas source 1 provides high-pressure driving gas for the pneumatic drive mode. For example, inert gas source 1 can be any inert gas source 1; it should be noted that inert gas source 1 can also be other inert gases that do not react or undergo phase change with the cryogenic fluid, such as high-purity nitrogen, depending on the specific application scenario and the properties of the working fluid, to ensure the safety and stability of the system operation.

[0035] The precooler 2 is used to cool the driving gas entering the cryogenic storage tank 7, which can significantly reduce the thermal disturbance and evaporation loss of the cryogenic liquid in the tank when it is injected into the cryogenic storage tank 7, and ensure the stability of the liquid phase.

[0036] The gas flow controller 3 is used to precisely control the flow rate of the driving gas injected into the cryogenic storage tank 7, thereby achieving precise and stable control of the displaced micro-liquid flow rate.

[0037] Gas control valve 4 acts as a gas path on / off valve, used to select or isolate the gas pressure drive mode. In the gas pressure drive mode, the control valve assembly is in the first state, and gas control valve 4 is open, allowing precisely controlled drive gas to enter the cryogenic storage tank 7 to achieve a stable, low-flow output. In the isolated gas pressure drive mode, the control valve assembly is in the second state, and gas control valve 4 is closed, stopping the gas pressure drive and switching to cryogenic pump drive mode.

[0038] It should be noted that this embodiment is not only applicable to liquid helium, but can also be widely used in the metering and control of other types of cryogenic fluids such as liquid hydrogen, liquid nitrogen, liquid oxygen, and liquefied natural gas. It is especially suitable for application scenarios that require high-precision flow calibration, filling, transportation and process control over a wide flow range.

[0039] In one embodiment of the present invention, such as Figure 1 As shown, the control valve group includes a pump inlet valve 9 and a bypass valve 8. The pump inlet valve 9 is located between the liquid outlet 6 and the inlet of the cryogenic pump 10; the bypass valve 8 is located between the liquid outlet 6 and the outlet of the cryogenic pump 10. In the first state, the control valve group has the pump inlet valve 9 closed and the bypass valve 8 open, allowing the cryogenic fluid to completely bypass the cryogenic pump 10 and flow directly to the flow meter 12 to be calibrated via the bypass valve 8. This provides a low-resistance flow path for the low-flow-rate pneumatic drive mode and avoids disturbance to the fluid by the pump body. In the second state, the control valve group has the pump inlet valve 9 open and the bypass valve 8 closed, ensuring that the cryogenic fluid must be pressurized by the cryogenic pump 10 to provide delivery power for the cryogenic fluid under high-flow-rate conditions. This enables the switching of the cryogenic pump drive mode. The control valve group has a simple structure, reliable operation, and ensures the accuracy of switching between the two modes.

[0040] In this embodiment, the variable head pump drive circuit includes a cryogenic storage tank 7, a pump drive pipeline, and a bypass pipeline. One end of the bypass pipeline is connected to the liquid outlet 6 at the bottom of the cryogenic storage tank 7, and the other end of the bypass pipeline is connected to the inlet of the flow meter 12 to be calibrated. A pump inlet valve 9 and a cryogenic pump 10 are provided on the bypass pipeline, and the pump inlet valve 9 is arranged close to the cryogenic storage tank 7. One end of the bypass pipeline is connected to the pipeline between the cryogenic storage tank 7 and the pump inlet valve 9, and the other end is connected to the pipeline between the cryogenic pump 10 and the flow meter 12 to be calibrated. A bypass valve 8 is provided on the bypass pipeline.

[0041] Understandably, liquid outlet 6 is located at the cryogenic fluid discharge port at the bottom of cryogenic storage tank 7. Cryogenic storage tank 7 is used to store cryogenic fluid as the measuring working medium. When pneumatically driven, bypass valve 8 connects the fluid in cryogenic storage tank 7 to a flow meter via a bypass pipeline for flow measurement. Pump inlet valve 9 controls the inflow of cryogenic fluid into cryogenic pump 10. Cryogenic pump 10 provides mechanical power for the transport of cryogenic fluid under high flow conditions, and its speed can be controlled by a frequency converter to achieve continuous flow adjustment.

[0042] Furthermore, the variable head pump drive circuit also includes a liquid control valve 11. One end of the liquid control valve 11 is connected to the outlet of the cryogenic pump 10 and the connection position of the bypass valve 8, and the other end of the liquid control valve 11 is connected to the inlet of the flow meter 12 to be calibrated.

[0043] Understandably, a liquid control valve 11 is installed at the inlet of the flow meter 12 to control the inflow of cryogenic fluid into the flow meter. When the cryogenic pump 10 is started, the liquid control valve 11 is closed, while the pump inlet valve 9 and the bypass valve 8 are opened, thus establishing a local internal circulation loop (the fluid path is: pump inlet valve 9 → cryogenic pump 10 → bypass valve 8 → return to pump inlet valve 9). In this state, the cryogenic liquid circulates within this closed loop, precooling the cryogenic pump 10 and achieving a smooth start-up. This precooling process continues for a preset duration until the cryogenic pump 10 is fully cooled and its operating state is stable. Then, the bypass valve 8 is closed, and the liquid control valve 11 is opened, entering the cryogenic pump drive mode.

[0044] In one embodiment of the present invention, the cryogenic pump 10 can be a variable frequency centrifugal pump, which smoothly changes the pump speed by adjusting the drive frequency, thereby achieving continuous and stable regulation of large flow rates. Alternatively, a cryogenic piston pump, gear pump, or other positive displacement pump can be selected to provide higher outlet pressure and more precise flow control capabilities, better meeting the requirements for pressure levels or flow pulsation characteristics under different operating conditions. It should be noted that the pump type can be optimized and configured according to the specific characteristics of the cryogenic fluid medium and the target flow range to ensure good controllability and output stability under high flow rate conditions.

[0045] In one embodiment of the present invention, such as Figure 1 As shown, the weighing assembly includes a cryogenic fluid collection tank 13 and a weighing element 14. The cryogenic fluid collection tank 13 is connected to the outlet of the flow meter 12 to be calibrated and is used to collect all the cryogenic fluid flowing through the flow meter 12 to be calibrated. The weighing element 14 serves as a mass measurement reference and is used to accurately measure the total weight of the cryogenic fluid in the cryogenic fluid collection tank 13.

[0046] It should be noted that the cryogenic fluid collection tank 13 has good thermal insulation performance, which is used to safely and stably collect the outflowing cryogenic fluid, reduce evaporation loss caused by environmental heat exchange, and ensure the accuracy of weighing measurement.

[0047] For example, the cryogenic fluid collection tank 13 is mounted on the weighing component 14. The high-precision weighing sensor measures the change in the mass of the collected fluid over time in real time, which can directly obtain the reference value of the mass flow rate, providing the most reliable quantitative basis for the calibration of the flow meter.

[0048] Based on the wide-range cryogenic flow measurement reference device with both gas pressure and variable head pump drive provided in any of the above embodiments, the second aspect of the present invention proposes a wide-range cryogenic flow measurement method with both gas pressure and variable head pump drive, such as... Figure 2 As shown, the method includes the following steps: Step 10: Compare the target traffic value with the preset traffic switching threshold.

[0049] Among them, the preset flow switching threshold refers to a critical flow value pre-stored in the control system for decision-making on drive mode switching. The setting of this threshold is mainly based on the fact that the stability of the pneumatic drive mode will decrease when it is higher than this value, and the operating efficiency of the cryogenic pump is low or unstable phenomena may occur when it is lower than this value. This threshold can be determined by combining theoretical calculation and experimental calibration, and is usually within the overlapping range between the minimum stable flow rate of the cryogenic pump and the maximum stable flow rate of the pneumatic drive, for example, but not limited to, the range of 10 kg / h to 50 kg / h (kilograms per hour).

[0050] Step 20: When the target flow value is less than the preset flow switching threshold, control the control valve group to be in the first state, and use the pneumatic drive circuit to pressurize the cryogenic liquid storage tank 7, so that the cryogenic liquid in the cryogenic liquid storage tank 7 flows through the control valve group to the flowmeter 12 to be calibrated.

[0051] Step 30: When the target flow value is greater than or equal to the preset flow switching threshold, control the control valve group to be in the second state, and control the pneumatic drive circuit to stop pressurizing the cryogenic liquid storage tank 7. The cryogenic liquid in the cryogenic liquid storage tank 7 flows through the control valve group and is pressurized by the cryogenic pump 10 and then flows to the flowmeter 12 to be calibrated.

[0052] Step 40: Weigh the cryogenic fluid flowing out of the flowmeter 12 to be calibrated based on the weighing component.

[0053] It can be understood that the target flow value Qa is compared with the preset flow switching threshold Qt.

[0054] If Qa < Qt, it is determined as a small flow condition, and the pneumatic drive mode is entered. In the pneumatic drive mode, the control valve group is in the first state, and the pneumatic drive circuit is in the working state to inject pressurized gas into the cryogenic liquid storage tank 7. The gas phase pressure is used to directly push the cryogenic liquid in the cryogenic liquid storage tank 7 through the control valve group (bypassing the cryogenic pump 10) to the flowmeter 12 to be calibrated, realizing stable small flow output without pump drive.

[0055] If Qa ≥ Qt, it is determined as a large flow condition, and the cryogenic pump drive mode is entered. In the cryogenic pump drive mode, the control valve group is in the second state, the pneumatic drive circuit is closed to stop pressurization, so that the cryogenic liquid enters the cryogenic pump 10 under the guidance of the control valve group, and after being pressurized by the cryogenic pump 10, it is then transported to the flowmeter 12 to be calibrated. Through the active pressurization of the cryogenic pump 10, a sufficiently high driving head can be provided to overcome the significantly increased pipeline resistance under large flow rates, ensuring stable and rapid transportation under large flow conditions.

[0056] During the entire calibration process, the mass of the cryogenic fluid flowing out is weighed in real time through the weighing component connected to the outlet of the flowmeter 12 to be calibrated, so as to obtain high-accuracy flow reference data and complete the calibration of the flowmeter.

[0057] Optionally, in step 20, pressurizing the cryogenic storage tank 7 using a pneumatic drive circuit may specifically include the following steps: Step 21: Based on the preset relationship between liquid flow rate and driving gas flow rate, determine the target driving gas flow rate corresponding to the target flow rate value.

[0058] Step 22: Based on the target driving gas flow rate, control the gas flow controller 3 to inject high-pressure gas into the cryogenic storage tank 7 at the target driving gas flow rate.

[0059] Understandably, based on the preset model between the target liquid flow rate and the driving gas flow rate, the gas injection rate (target driving gas flow rate) required to achieve the target flow rate value is calculated, and a control command corresponding to this set value (target driving gas flow rate) is sent to the gas flow controller 3. The gas flow controller 3 accurately injects the high-pressure gas cooled by the precooler 2 into the gas phase space of the cryogenic storage tank 7 at a stable rate (required gas injection rate). The pressure inside the tank rises steadily, displacing the cryogenic liquid from the liquid outlet 6 at the target flow rate. The liquid then flows through the flow meter to be calibrated 12 into the cryogenic fluid collection tank 13, where the mass measurement is completed by the weighing element 14.

[0060] Optionally, in step 30, before the control valve assembly is in the second state, the following steps are also included: The precooling process of cryogenic pump 10.

[0061] Specifically, the control pump inlet valve 9, bypass valve 8 and cryogenic pump 10 are opened, and the liquid control valve 11 is closed for a preset duration to achieve pre-cooling of cryogenic pump 10.

[0062] Understandably, the pre-cooling process of the cryogenic pump 10 involves circulating the cryogenic fluid within the pump without directing it to the flow meter 12 to be calibrated. This allows the pump body and internal components to gradually cool to the operating temperature, effectively preventing cavitation or thermal shock caused by large temperature differences when the cryogenic pump 10 starts up. This ensures that the cryogenic pump 10 can start up smoothly and safely and quickly enter a stable operating state.

[0063] Optionally, in step 30, before the control air pressure drive circuit stops pressurizing the cryogenic storage tank 7, and before the cryogenic liquid in the cryogenic storage tank 7 flows to the flow meter 12 to be calibrated after being pressurized by the control valve group and the cryogenic pump 10, the following steps are also included: Obtain the current flow value of the flow meter 12 to be calibrated.

[0064] Based on the difference between the current flow rate and the target flow rate, adjust the speed of the cryogenic pump 10 until the difference is less than the preset deviation.

[0065] It can be understood that in the cryopump driving mode, after the cryopump 10 is pre-cooled, the bypass valve 8 is closed and the liquid control valve 11 is opened, so that the cryogenic fluid flows to the flowmeter to be calibrated 12 after being pressurized by the cryopump 10. Then, the PID (Proportional-Integral-Differential) closed-loop control algorithm is started, and the current flow value collected in real time from the flowmeter is used as the process feedback variable, compared with the target flow value, and the rotation speed of the cryopump 10 is continuously and dynamically adjusted according to the deviation between the two until the difference between the current flow value and the target flow value is less than the preset deviation, so as to achieve high-precision and stable control of the flow rate and improve the stability and accuracy of the large-flow calibration point. Finally, the outflowing cryogenic fluid enters the cryogenic fluid collection tank 13, and the mass measurement is completed by the weighing component 14, providing accurate reference data for flow calibration.

[0066] In a specific embodiment of the present invention, a wide-range cryogenic flow measurement reference device with both pneumatic and variable head pump drives includes a pneumatic drive circuit, a variable head pump drive circuit, and a weighing component.

[0067] The pneumatic drive circuit includes an inert gas source 1, a pre-cooler 2, a gas flow controller 3, and a gas control valve 4 connected in sequence.

[0068] The variable head pump drive circuit includes a cryogenic liquid storage tank 7, a cryopump 10, a liquid control valve 11, and a control valve group. The control valve group includes a pump inlet valve 9 and a bypass valve 8 connected in parallel; the gas inlet 5 at the top of the cryogenic liquid storage tank 7 is connected to the gas control valve 4, and the liquid outlet 6 at the bottom of the cryogenic liquid storage tank 7 is connected to the liquid control valve 11 through the pump inlet valve 9 and the cryopump 10 arranged in sequence. The bypass valve 8 is connected between the liquid outlet 6 at the bottom of the cryogenic liquid storage tank 7 and the liquid control valve 11, and the liquid control valve 11 is connected to the inlet of the flowmeter to be calibrated 12.

[0069] The weighing component is connected to the outlet of the flowmeter to be calibrated 12.

[0070] The working process of the wide-range cryogenic flow measurement reference device with both pneumatic and variable head pump drives in this embodiment is as follows: S1. Initialization In the initial state, all valves are in a preset safe initial state, that is, the gas control valve 4, the pump inlet valve 9, the liquid control valve 11, and the bypass valve 8 are all in the closed state, and the cryopump 10 is in the stop standby state.

[0071] S2. Select the drive mode Compare the target flow value Qa with the preset flow switching threshold Qt; for example, the preset flow switching threshold Qt is 20 kg / h.

[0072] If Qa < Qt, it is determined as a small flow condition, and enter the pneumatic drive mode; If Qa ≥ Qt, it is determined to be a high-flow-rate operating condition, and the system enters the cryogenic pump drive mode.

[0073] For example, if the target flow rate Qa is 5 kg / h, select and enter the pneumatic drive mode and execute step S3; if the target flow rate Qa is 100 kg / h, select and enter the cryogenic pump drive mode and execute step S4.

[0074] S3, pneumatic drive mode In pneumatic drive mode, gas control valve 4, bypass valve 8, and liquid control valve 11 are opened, while ensuring pump inlet valve 9 is closed, thereby isolating the variable head pump drive. In this way, the cryogenic fluid, under pneumatic pressure, bypasses the cryogenic pump 10 and flows directly to the flow meter 12 to be calibrated via bypass valve 8.

[0075] Subsequently, based on the preset model between the target liquid flow rate and the driving gas flow rate, which stores the preset relationship between the liquid flow rate and the driving gas flow rate, the driving gas flow rate (target driving gas flow rate) of approximately 0.8 slpm (standard liters per minute) is calculated to stably deliver 5 kg / h (target flow rate value) of liquid helium. The controller then sends the control command corresponding to this set value to the gas flow controller 3. The gas flow controller 3 precisely injects the high-pressure helium gas cooled by the precooler 2 into the gas phase space of the cryogenic storage tank 7 at a rate of 0.8 slpm. The pressure inside the tank rises steadily, and the liquid helium is stably delivered at the target rate of 5 kg / h. The cryogenic liquid helium flows through the flow meter to be calibrated 12 and enters the cryogenic fluid collection tank 13. The instantaneous reading of the flow meter and the mass change data of the weighing device 14 are recorded simultaneously, completing the measurement process.

[0076] S4, Cryogenic Pump Drive Mode In cryogenic pump drive mode, gas control valve 4 is kept closed, while pump inlet valve 9 and bypass valve 8 are opened, and liquid control valve 11 is closed, establishing a local internal circulation loop for the start-up and precooling of cryogenic pump 10. Cryogenic pump 10 is started smoothly. The cryogenic liquid is drawn into cryogenic pump 10 and pressurized, then flows back to the inlet pipe of cryogenic pump 10 through bypass valve 8 to form a local internal circulation loop. After the pump body is fully precooled and runs stably (judged by temperature sensor or running time), bypass valve 8 is closed and liquid control valve 11 is opened. At this time, the cryogenic fluid, pressurized by cryogenic pump 10, begins to flow towards the test section where the flowmeter 12 to be calibrated is located. The PID closed-loop control algorithm is then activated, using the current flow rate value collected in real-time from the flowmeter as the process feedback variable, comparing it with 100 kg / h (target flow rate value), and continuously and dynamically adjusting the speed of cryogenic pump 10 according to the deviation between the two until the flow rate collected in real-time by the flowmeter is stabilized at 100 kg / h within the allowable error range.

[0077] After the flow rate stabilizes, the weighing device 14 measures the mass change data inside the cryogenic fluid collection tank 13 to complete the measurement process.

[0078] S5, Reset After the measurement task is completed, close all valves, stop the operation of gas flow controller 3 and cryogenic pump 10, and restore the entire device to a safe initial standby state.

[0079] This embodiment combines a wide-range cryogenic flow rate measurement reference device and method driven by both pneumatic pressure and variable head pumps. By integrating pneumatic pressure drive and variable head pump drive modes, it achieves full-range coverage from extremely small flow rates (e.g., 1 kg / h) to large flow rates (e.g., 500 kg / h), significantly expanding the range ratio. In the small flow rate range, a pulsation-free and smooth-response pneumatic pressure drive mode is used to ensure the stability and high accuracy of the measurement process. In the large flow rate range, relying on the cryogenic pump and PID closed-loop control, a powerful delivery capacity and precise flow rate locking are achieved, thereby ensuring high accuracy and high stability throughout the entire range. In addition, the low-energy pneumatic pressure drive mode is activated under low flow rate conditions, effectively avoiding the high-power cryogenic pump from operating in an inefficient range, effectively optimizing energy utilization efficiency, and further reducing overall operating costs.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A wide-range cryogenic flow measurement reference device that combines pneumatic pressure and variable head pump drive, characterized in that, include: Pneumatic drive circuit; A variable head pump drive circuit includes a cryogenic storage tank, a cryogenic pump, and a control valve assembly. The cryogenic storage tank stores cryogenic fluid, and a gas inlet at the top of the tank is connected to a pneumatic drive circuit. The cryogenic pump is connected to a liquid outlet at the bottom of the tank. The control valve assembly is connected between the inlet and outlet of the cryogenic pump, and the outlet of the pump is connected to the inlet of a flow meter to be calibrated. The control valve assembly is adapted to switch between a first state and a second state. In the first state, the pneumatic drive circuit pressurizes the cryogenic storage tank, and the cryogenic liquid in the tank flows to the flow meter to be calibrated via the control valve assembly. In the second state, the pneumatic drive circuit stops pressurizing the cryogenic storage tank, and the cryogenic liquid in the tank flows to the flow meter to be calibrated after being pressurized by the control valve assembly and the cryogenic pump. A weighing assembly is used to connect to the outlet of the flow meter to be calibrated in order to weigh the cryogenic fluid flowing out of the flow meter.

2. The wide-range cryogenic flow measurement reference device with both air pressure and variable head pump drive as described in claim 1, characterized in that, The control valve assembly includes: A pump inlet valve is located between the liquid outlet and the inlet of the cryogenic pump; A bypass valve is provided between the liquid outlet and the outlet of the cryogenic pump; In the first state, the pump inlet valve is closed and the bypass valve is open; in the second state, the pump inlet valve is open and the bypass valve is closed.

3. The wide-range cryogenic flow measurement reference device with both air pressure and variable head pump drive as described in claim 2, characterized in that, The variable head pump drive circuit also includes a liquid control valve, one end of which is connected to the outlet of the cryogenic pump and the connection position of the bypass valve, and the other end of which is connected to the inlet of the flow meter to be calibrated.

4. The wide-range cryogenic flow measurement reference device with both air pressure and variable head pump drive as described in claim 1, characterized in that, The pneumatic drive circuit includes an inert gas source, a precooler, a gas flow controller, and a gas control valve connected in sequence. The gas control valve is connected to the gas inlet at the top of the cryogenic storage tank. In the first state, the gas control valve is open; in the second state, the gas control valve is closed.

5. The wide-range cryogenic flow measurement reference device with both air pressure and variable head pump drive as described in any one of claims 1 to 4, characterized in that, The cryogenic pump is a variable frequency centrifugal pump, a cryogenic piston pump, or a gear pump.

6. The wide-range cryogenic flow measurement reference device with both air pressure and variable head pump drive as described in any one of claims 1 to 4, characterized in that, The weighing component includes: A cryogenic fluid collection tank is connected to the outlet of the flow meter to be calibrated; A weighing device is used to measure the weight of the fluid in the cryogenic fluid collection tank.

7. A wide-range cryogenic flow measurement method that combines air pressure and variable head pump drive, characterized in that, Based on the wide-range cryogenic flow measurement reference device with both gas pressure and variable head pump drive as described in any one of claims 1 to 6, the method includes: Compare the target traffic value with the preset traffic switching threshold; When the target flow rate is less than the preset flow switching threshold, the control valve group is in the first state, and the air pressure drive circuit is used to pressurize the cryogenic liquid tank so that the cryogenic liquid in the cryogenic liquid tank flows to the flow meter to be calibrated through the control valve group. When the target flow rate is greater than or equal to the preset flow switching threshold, the control valve group is controlled to be in the second state, and the pneumatic drive circuit is controlled to stop pressurizing the cryogenic liquid storage tank. The cryogenic liquid in the cryogenic liquid storage tank flows to the flow meter to be calibrated after being pressurized by the control valve group and the cryogenic pump. The cryogenic fluid flowing out of the flow meter to be calibrated is weighed using a weighing component.

8. The wide-range cryogenic flow measurement method with both air pressure and variable head pump drive as described in claim 7, characterized in that, Pressurizing the cryogenic storage tank using a pneumatic drive circuit includes: The target driving gas flow rate corresponding to the target flow rate value is determined based on the preset relationship between the liquid flow rate and the driving gas flow rate. Based on the target driving gas flow rate, the gas flow controller is controlled to inject high-pressure gas into the cryogenic storage tank at the target driving gas flow rate.

9. The wide-range cryogenic flow measurement method with both air pressure and variable head pump drive as described in claim 7, characterized in that, Before the control valve assembly is in the second state, the following is also included: The control pump inlet valve, bypass valve, and cryogenic pump are opened, while the liquid control valve is closed, and this continues for a preset duration.

10. The wide-range cryogenic flow measurement method with both air pressure and variable head pump drive as described in claim 9, characterized in that, After the cryogenic liquid in the cryogenic storage tank is pressurized by the control valve assembly and the cryogenic pump and flows to the flow meter to be calibrated, the method further includes: Obtain the current flow rate value of the flow meter to be calibrated; Based on the difference between the current flow rate and the target flow rate, the speed of the cryogenic pump is adjusted until the difference is less than a preset deviation.

Images