Measuring device and method for low-temperature high-pressure small pressure difference between two sides of screen

Abstract

The application provides a kind of low temperature high pressure under screen both sides gas-liquid small pressure difference measuring device and method, comprising: differential pressure gauge, first pressure pipe, second pressure pipe, screen and gas inlet pipe;One end of first pressure pipe is communicated with the first pressure port of differential pressure gauge, and the other end of first pressure pipe is communicated with the gas cavity of the measured cavity in vacuum interlayer;One end of second pressure pipe is communicated with the second pressure port of differential pressure gauge, and the other end of second pressure pipe is located in screen, and screen is located in the liquid phase of measured cavity;One end of gas inlet pipe is provided with control valve, and the other end of gas inlet pipe is communicated with second pressure pipe, and gas inlet pipe is located outside vacuum interlayer.The application is suitable for low temperature gas-liquid small pressure difference measurement, especially low temperature bubble break point measurement.

Description

Technical Field

[0001] This invention relates to the field of measuring instrument technology, specifically to a measuring device and method for measuring small gas-liquid pressure difference on both sides of a screen under low temperature and high pressure, and more particularly to a method for measuring small pressure difference on both sides of a screen in a low temperature and high pressure environment. Background Technology

[0002] A differential pressure gauge is used to measure the pressure difference between two points. When the two pressure measuring points are far from the receiving device, a pressure tapping tube is required to connect the pressure measuring points and the sensor. When measuring gas phase pressure, the pressure tapping tube should be filled with gas to ensure that the pressure at both ends of the pressure tapping tube is the same as the pressure at the receiving point of the differential pressure gauge diaphragm. When measuring liquid phase pressure, the pressure tapping tube should be filled with liquid, and the pressure tapping tube should ideally be at the same horizontal level as the measuring point to eliminate static pressure error. Generally, when measuring condensable / evaporable media, when using a pressure tapping tube to measure gas phase pressure, the differential pressure gauge should be positioned higher than the measuring point to facilitate the reflux of condensed liquid phase and ensure that there is no static liquid column in the pressure tapping tube causing measurement error; when using a pressure tapping tube to measure liquid phase pressure, the differential pressure gauge should be positioned lower than the measuring point to facilitate the reflux of evaporated vapor.

[0003] Cryogenic double-layer Dewars typically integrate internal flow channels or containers onto the top flange end cap for easy disassembly and assembly of the internal structure. Therefore, the pressure tapping tube needs to run through the top flange. When the pressure tapping tube measures the differential pressure of the cryogenic liquid phase, the differential pressure gauge must not be lower than the pressure measurement point so that the diaphragm of the differential pressure gauge comes into contact with the cryogenic liquid. If the differential pressure gauge is placed outside the Dewar and above the pressure measurement point, liquid phase may enter the pressure tapping tube, leading to inaccurate static pressure measurement. Accurate measurement requires eliminating the error of static pressure inside the pressure tapping tube.

[0004] Screens are one of the main means of achieving gas-liquid separation in microgravity, acceleration-free environments. In spacecraft, they are used for propellant gas-liquid separation. During the design phase, the gas-liquid separation performance of the screen must be measured. The pressure difference across the screen at the point of bubble burst is a crucial parameter of the separation performance, with a magnitude on the order of kilopascals. Measuring the bubble burst point at low temperatures requires a vacuum environment to ensure the propellant is in a supercooled state; the operating environment is 2 MPa. During the bubble burst point test, one side of the screen is filled with gas, and the other with liquid; the pressure difference between the gas and liquid sides of the screen needs to be measured. During measurement, the liquid level is higher than the screen, ensuring the screen wires are fully wetted; therefore, the screen is in a state of liquid above and gas below during measurement.

[0005] There are currently two methods to solve the static pressure difference problem inside the pressure tapping tube: active drainage and heating the pressure tapping tube. However, both methods may encounter other problems when used to measure the liquid level above the screen. Because the liquid phase depth above the screen is relatively shallow, placing the pressure tapping tube above the screen may result in inaccurate assembly; setting it too far apart will lead to inaccurate measurements; placing it too close may puncture the screen; drainage may blow open the liquid film; and heating may also affect the liquid film coverage.

[0006] Patent document CN204679201U discloses a low-temperature differential pressure tester for filters, including a controller housed within the instrument casing. The input terminal of the controller is connected to a differential pressure sensor, the input terminal of which is connected to the filter. The output terminal of the controller is connected to a digital display. However, this patent document does not address the measurement of small gas-liquid pressure differences across a screen at low temperatures. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the purpose of this invention is to provide a measuring device and method for measuring small gas-liquid pressure differences on both sides of a screen under low temperature and high pressure.

[0008] This invention provides a measuring device for a small gas-liquid pressure difference on both sides of a screen under low temperature and high pressure, comprising: a differential pressure gauge, a first pressure inlet tube, a second pressure inlet tube, a screen, and an air inlet tube;

[0009] One end of the first pressure tap is connected to the first pressure measuring port of the differential pressure gauge, and the other end of the first pressure tap is connected to the gas cavity of the measured cavity in the vacuum jacket; one end of the second pressure tap is connected to the second pressure measuring port of the differential pressure gauge, and the other end of the second pressure tap is located inside the sieve, and the sieve is located in the liquid phase of the measured cavity;

[0010] One end of the air intake pipe is equipped with a control valve, and the other end of the air intake pipe is connected to the second pressure pipe. The air intake pipe is located outside the vacuum jacket.

[0011] Preferably, it also includes a height calibration component, which is disposed on the inner wall of the cavity being measured;

[0012] The height calibration component is used to measure the height of the liquid above the screen.

[0013] Preferably, the height calibration component is a multi-point temperature sensor.

[0014] Preferably, the multi-point temperature sensor is a calibrated thermometer.

[0015] Preferably, the multi-point temperature sensor is fixedly mounted on the inner wall of the cavity being measured by a mounting bracket.

[0016] Preferably, the height calibration component is a level gauge.

[0017] This invention also provides a method for measuring the small gas-liquid pressure difference across a screen under low temperature and high pressure, based on the aforementioned device for measuring the small gas-liquid pressure difference across a screen under low temperature and high pressure, comprising the following steps:

[0018] Step 1: Pre-cool the cryogenic container holding the sieve cup until the temperature drops to the saturation temperature of the cryogenic liquid, at which point liquid begins to accumulate in the container;

[0019] Step 2: Introduce helium into the space inside the cup on the lower side of the screen to displace and expel the air in the pipeline and the space on the lower side, so as to keep the pressure difference measurement point on the lower side of the screen positive relative to the upper side;

[0020] Step 3: As the liquid level gradually rises, observe the liquid level position measured by the temperature measuring point or the liquid level gauge. When the liquid level just covers the screen and forms a uniform liquid film, start the measurement and record the liquid level gauge reading at this time, or determine the liquid level position by the temperature reading, calculate the liquid level height, and convert it into the static pressure difference of the low-temperature fluid.

[0021] Step 4: Continuously introduce helium gas at a small flow rate, causing bubbles to bulge out of the screen. Observe the reading of the differential pressure gauge. Reduce the flow rate of helium gas introduced from the lower side until no visible bubbles are visible on the screen surface. Observe the reading of the differential pressure gauge. At this time, the space under the screen will be briefly trapped by air, and the pressure difference will increase until the liquid film ruptures, causing bubbling. Record the data of the maximum pressure difference of the differential pressure gauge and subtract the static pressure difference of the liquid above the screen to obtain the final screen bubble rupture pressure difference.

[0022] Preferably, at least one of the differential pressure measuring points is located inside the liquid phase, and the differential pressure gauge is positioned above the liquid phase.

[0023] Preferably, the liquid phase is measured below the liquid surface, and there is a static pressure difference in the liquid phase in the vertical direction.

[0024] Preferably, the pressure difference between the lower side of the screen and the air cavity above the liquid surface on the upper side of the screen is measured through the second pressure measuring port and the first pressure measuring port, respectively, and the height of the liquid surface above the liquid surface of the screen is measured using a thermometer or a level gauge.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. This invention is applicable to the measurement of small pressure differences between low-temperature gas and liquid, especially the measurement of low-temperature bubble burst point;

[0027] 2. This invention uses a liquid level height-assisted calibration device, which can accurately measure the pressure difference between cryogenic fluids, gas, liquid, or liquid-liquid when the differential pressure gauge is placed above the liquid phase measuring point;

[0028] 3. The measurement method of the present invention can be used for small differential pressure measurements at the kilopascal level;

[0029] 4. The temperature sensor of the present invention is a calibrated thermometer applicable to different low-temperature fluids, and can sensitively distinguish the temperature of gases and liquids;

[0030] 5. For the measurement of pressure difference on both sides of a screen in a cryogenic fluid, where one end of the differential pressure gauge is inside the cryogenic liquid and the other end is in the gas phase, and the differential pressure gauge needs to be placed above the liquid phase measuring point, this invention proposes to use a thermometer or level gauge as an auxiliary means to measure the static pressure height above the screen, converting the liquid / gas pressure difference measurement into a combination of gas / gas pressure difference measurement and liquid level height measurement, which can avoid the problem of fluctuation in cryogenic liquid phase measurement. Attached Figure Description

[0031] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0032] Figure 1 This is a flowchart illustrating the method for measuring the small gas-liquid pressure difference across a screen under low temperature and high pressure according to the present invention.

[0033] Figure 2 This is a schematic diagram of the overall structure of the measuring device for small gas-liquid pressure difference on both sides of the screen under low temperature and high pressure according to the present invention.

[0034] The diagram shows:

[0035] Differential pressure gauge 1, intake pipe 5

[0036] First pressure tap 2, control valve 6

[0037] Second pressure tap 3 Height calibration assembly 7

[0038] Screen 4, Vacuum interlayer 8 Detailed Implementation

[0039] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0040] Example 1:

[0041] like Figure 1 and Figure 2As shown, this embodiment provides a measuring device for a small gas-liquid pressure difference across a screen under low temperature and high pressure, including: a differential pressure gauge 1, a first pressure-sensing tube 2, a second pressure-sensing tube 3, a screen 4, and an inlet pipe 5. One end of the first pressure-sensing tube 2 is connected to the first pressure measuring port of the differential pressure gauge 1, and the other end of the first pressure-sensing tube 2 is connected to the gas chamber of the measured cavity within the vacuum jacket 8. One end of the second pressure-sensing tube 3 is connected to the second pressure measuring port of the differential pressure gauge 1, and the other end of the second pressure-sensing tube 3 is located inside the screen 4, which is located within the liquid phase of the measured cavity. One end of the inlet pipe 5 is equipped with a control valve 6, and the other end of the inlet pipe 5 is connected to the second pressure-sensing tube 3. The inlet pipe 5 is located outside the vacuum jacket 8. The screen is a dense Dutch twill woven screen, which can be considered as a gas-liquid separation device under microgravity.

[0042] The low-temperature, high-pressure, small-differential-pressure measuring device provided in this embodiment also includes a height calibration component 7. The height calibration component 7 is disposed on the inner wall of the measured cavity and is used to measure the height of the liquid above the screen 4. The height calibration component 7 is a multi-point temperature sensor, which is a calibration thermometer. The multi-point temperature sensor is fixedly disposed on the inner wall of the measured cavity by a mounting bracket.

[0043] This embodiment also provides a method for measuring the small gas-liquid pressure difference across a screen under low temperature and high pressure. The method measures the small pressure difference across a screen in a low-temperature, high-pressure environment. Based on the aforementioned measuring device for the small gas-liquid pressure difference across a screen under low temperature and high pressure, the method specifically includes the following steps:

[0044] Step 1: Pre-cool the cryogenic container holding the sieve cup until the temperature drops to the saturation temperature of the cryogenic liquid, at which point liquid begins to accumulate in the container;

[0045] Step 2: Introduce helium into the space inside the cup on the lower side of the screen to displace and expel the air in the pipeline and the space on the lower side, so as to keep the pressure difference measurement point on the lower side of the screen positive relative to the upper side;

[0046] Step 3: As the liquid level gradually rises, observe the liquid level position measured by the temperature measuring point or the liquid level gauge. When the liquid level just covers the screen and forms a uniform liquid film, start the measurement and record the liquid level gauge reading at this time, or determine the liquid level position by the temperature reading, calculate the liquid level height, and convert it into the static pressure difference of the low-temperature fluid.

[0047] Step 4: Continuously introduce helium at a small flow rate, causing bubbles to bulge out of the screen. Observe the reading of the differential pressure gauge. Reduce the flow rate of helium introduced to the lower side until no visible bubbles are visible on the screen surface. Observe the reading of the differential pressure gauge. At this time, the space under the screen will be briefly trapped by air, and the pressure difference will increase until the liquid film ruptures, causing bubbling. Record the data of the maximum instantaneous pressure difference of the differential pressure gauge and subtract the static pressure difference of the liquid above the screen to obtain the final screen bubble rupture pressure difference.

[0048] At least one of the differential pressure measuring points is located inside the liquid phase, and differential pressure gauge 1 is positioned above the liquid phase. The measured location in the liquid phase is below the liquid surface, and a static pressure difference exists in the vertical direction of the liquid phase. The pressure difference between the lower side of the screen 4 and the upper side of the screen 4 above the liquid surface is measured through the second and first pressure measuring ports, respectively. The height of the liquid surface above the screen 4 is measured using a thermometer or a level gauge.

[0049] Example 2:

[0050] The difference from Example 1 is that the height calibration component 7 is a level gauge.

[0051] Example 3:

[0052] Those skilled in the art can understand this embodiment as a more specific description of Embodiment 1.

[0053] This invention provides a differential pressure measurement method combining a differential pressure gauge and a liquid level height auxiliary calibration device. The method includes measuring the pressure difference between the two pressure measuring ports of the differential pressure gauge and the air cavity above the liquid surface on the lower side of the screen and the upper side of the screen, respectively, and obtaining the height of the liquid surface above the screen using a thermometer or a liquid level gauge.

[0054] The liquid phase is measured below the liquid surface, and there is a static pressure difference in the vertical direction. A thermometer or level gauge can measure the height of the liquid above the screen, convert it into a static pressure difference, and then eliminate this error.

[0055] The liquid level height auxiliary calibration device uses a thermometer. This embodiment also provides a differential pressure measuring device that combines a differential pressure gauge and a thermometer, including a differential pressure sensor, a pressure tapping tube, and a temperature sensor.

[0056] The temperature sensor is a calibrated thermometer suitable for different low-temperature fluids, and can sensitively distinguish the temperature of gases and liquids.

[0057] The differential pressure transmitter's pressure taps are connected to the steam chamber above the gas chamber and the liquid chamber, respectively.

[0058] The number of thermometers is set according to the required static pressure accuracy; the higher the accuracy requirement, the denser the arrangement.

[0059] The thermometers are fixed inside the container using a material with low thermal conductivity, so that they do not interfere with each other in temperature measurement.

[0060] This embodiment employs a liquid level height-assisted calibration device, which can accurately measure the pressure difference between cryogenic fluids (gas, liquid, or liquid-liquid) when the differential pressure gauge is placed above the liquid phase measuring point. In other embodiments, the liquid level height-assisted calibration device can be a level gauge that meets the required accuracy, or a multi-point temperature sensor capable of identifying the gas-liquid interface.

[0061] At least one of the differential pressure measuring points is located inside the liquid, and the differential pressure gauge is placed above the liquid phase.

[0062] Cryogenic fluids cannot directly contact the differential pressure gauge; a pressure tapping tube must be used, which is inserted into the gas or liquid chamber. This measurement method can be used for small differential pressure measurements in the kilopascal range.

[0063] The method in this embodiment solves the problem of measurement accuracy. The differential pressure measurement method and device provided in this embodiment, which combines a differential pressure gauge and a liquid level auxiliary calibration device, is suitable for measuring small differential pressures between low-temperature gas and liquid, especially for measuring the low-temperature bubble burst point.

[0064] Example 4:

[0065] The difference between this embodiment and embodiment 3 is that the liquid level height auxiliary calibration device uses a liquid level gauge. This embodiment provides a differential pressure measuring device that combines a differential pressure gauge and a liquid level gauge, including a differential pressure sensor, a pressure tapping tube, and a liquid level gauge.

[0066] The level gauge can sensitively distinguish liquid height within one centimeter and accurately convert it into static pressure difference.

[0067] This invention is applicable to the measurement of small pressure differences between low-temperature gas and liquid, especially the measurement of low-temperature bubble burst point.

[0068] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "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 this application 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 this application.

[0069] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A measuring device for small gas-liquid pressure difference on both sides of a screen under low temperature and high pressure, characterized in that, include: Differential pressure gauge (1), first pressure tap (2), second pressure tap (3), screen (4), and air inlet pipe (5); One end of the first pressure tap (2) is connected to the first pressure measuring port of the differential pressure gauge (1), and the other end of the first pressure tap (2) is connected to the gas cavity of the measured cavity in the vacuum jacket (8); one end of the second pressure tap (3) is connected to the second pressure measuring port of the differential pressure gauge (1), and the other end of the second pressure tap (3) is located inside the screen (4), and the screen (4) is located in the liquid phase of the measured cavity; One end of the air inlet pipe (5) is provided with a control valve (6), and the other end of the air inlet pipe (5) is connected to the second pressure pipe (3). The air inlet pipe (5) is located outside the vacuum jacket (8). The measuring device also includes a height calibration component (7), which is disposed on the inner wall of the cavity being measured; the height calibration component (7) is used to measure the height of the liquid above the screen (4); the height calibration component (7) is a multi-point temperature sensor or a level gauge; The measurement method of the measuring device includes the following steps: Step 1: Pre-cool the cryogenic container holding the sieve cup until the temperature drops to the saturation temperature of the cryogenic liquid, at which point liquid begins to accumulate in the container; Step 2: Introduce helium into the space inside the cup on the lower side of the screen to displace and expel the air in the pipeline and the space on the lower side, so as to keep the pressure difference measurement point on the lower side of the screen positive relative to the upper side; Step 3: As the liquid level gradually rises, observe the liquid level position measured by the temperature measuring point or the liquid level gauge. When the liquid level just covers the screen and forms a uniform liquid film, start the measurement and record the liquid level gauge reading at this time, or determine the liquid level position by the temperature reading, calculate the liquid level height, and convert it into the static pressure difference of the low-temperature fluid. Step 4: Continuously introduce helium gas at a small flow rate, causing bubbles to bulge out of the screen. Observe the reading of the differential pressure gauge. Reduce the flow rate of helium gas introduced from the lower side until no visible bubbles are visible on the screen surface. Observe the reading of the differential pressure gauge. At this time, the space under the screen will be briefly trapped by air, and the pressure difference will increase until the liquid film ruptures, causing bubbling. Record the data of the maximum pressure difference of the differential pressure gauge and subtract the static pressure difference of the liquid above the screen to obtain the final screen bubble rupture pressure difference.

2. The measuring device for small gas-liquid pressure difference on both sides of a screen under low temperature and high pressure according to claim 1, characterized in that, The multi-point temperature sensor uses a calibrated thermometer.

3. The measuring device for small gas-liquid pressure difference on both sides of a screen under low temperature and high pressure according to claim 1, characterized in that, The multi-point temperature sensor is fixedly mounted on the inner wall of the cavity being measured by a mounting bracket.

4. The measuring device for small gas-liquid pressure difference on both sides of a screen under low temperature and high pressure according to claim 1, characterized in that, At least one of the differential pressure measuring points is located inside the liquid phase, and the differential pressure gauge (1) is positioned above the liquid phase.

5. The measuring device for small gas-liquid pressure difference on both sides of a screen under low temperature and high pressure according to claim 1, characterized in that, The liquid phase is measured below the liquid surface, and there is a static pressure difference in the vertical direction.

6. The measuring device for small gas-liquid pressure difference on both sides of a screen under low temperature and high pressure according to claim 1, characterized in that, The pressure difference between the lower side of the screen (4) and the upper side of the screen (4) above the liquid surface is measured by the second pressure measuring port and the first pressure measuring port respectively. The height of the liquid surface above the liquid surface of the screen (4) is measured by a thermometer or a liquid level gauge.

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