Differential pressure type flow measuring device and measuring method for low-temperature fluid

Abstract

The invention provides a differential pressure type flow measuring device and method for low-temperature fluid, the differential pressure type flow measuring device comprises a pipeline, flow equalizing parts and a differential pressure transducer, a plurality of porous balance plates are arranged in the pipeline at intervals along the length direction of the pipeline, the flow equalizing parts are arranged between two adjacent porous balance plates, and a plurality of pressure detecting devices are arranged. The pressure detection devices are connected with the pipeline and used for measuring the pressure values of the low-temperature fluid on the two sides of each porous balance plate. Through the porous balance plates connected in series in the pipeline and the flow equalizing pieces between the porous balance plates, gas-liquid two-phase low-temperature fluid flowing through the pipeline is mixed more uniformly, when the low-temperature fluid in the pipeline flows through the porous balance plates and the flow equalizing pieces, the pressure difference can be uniformly reduced for multiple times, the pressure drop generated by each stage is not enough to cause cavitation, and the low-temperature fluid in the pipeline flows through the porous balance plates and the flow equalizing pieces. The cavitation effect is effectively avoided, and the accuracy of the flow measurement result of the low-temperature fluid at the downstream of the pipeline is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of cryogenic fluid measurement, and particularly relates to a differential pressure type flow measurement device and a measurement method for cryogenic fluids. Background Art

[0002] Currently, the rapid development of technologies such as aerospace and liquid air energy storage has greatly increased the demand for cryogenic fluids, and thus there is a further need for cryogenic fluid flow measurement technology.

[0003] The physical properties such as density, viscosity, and thermal conductivity of cryogenic fluids are quite different from those of normal temperature fluids. In particular, the low boiling point makes cryogenic fluids very easy to vaporize, and cavitation effects may occur due to excessive pressure drop when passing through throttling elements. Therefore, the presence of gas phase is the main reason affecting the accuracy and reliability of flow measurement. In actual measurement, the small amount of vaporization of cryogenic fluids is inevitable.

[0004] Currently, the flow meters used for cryogenic fluids mainly include turbine flow meters, vortex street flow meters, Coriolis flow meters, orifice plate flow meters, etc. However, the above flow meters have moving parts, complex installation, and mostly adopt the method of separate metering, dividing the entire measurement process into several independent metering processes. The required equipment is complex and costly, and it is easily interfered by factors such as fluid physical properties, pressure fluctuations, and flow field changes during the measurement process, affecting its measurement accuracy and stability. Summary of the Invention

[0005] The present invention provides a differential pressure type flow measurement device and a measurement method for cryogenic fluids to solve the defect that the flow measurement results of cryogenic fluids with gas-liquid two-phase in the prior art are inaccurate.

[0006] In a first aspect, the present invention provides a differential pressure type flow measurement device for cryogenic fluids, comprising:

[0007] A pipeline, in which a plurality of porous balance plates are arranged at intervals along its length direction;

[0008] A flow equalizing member, arranged between two adjacent porous balance plates;

[0009] A plurality of pressure detection devices, all of which are connected to the pipeline and are used to measure the pressure values of the cryogenic fluids on both sides of each porous balance plate respectively.

[0010] According to the differential pressure type flow measurement device for cryogenic fluids provided by the present invention, the outer edge of the porous balance plate is connected to the inner wall of the pipeline, and a plurality of through holes are uniformly arranged on the porous balance plate.

[0011] According to the differential pressure flow measurement device for cryogenic fluid provided by the present invention, the pressure detection device is a differential pressure sensor, the number of the differential pressure sensors is the same as the number of the porous balance plates and the positions correspond one to one, and the differential pressure sensor is provided with a pair of pressure interfaces, and the pair of pressure interfaces are connected to the pipes on both sides of the porous balance plate through pressure pipes respectively.

[0012] According to the differential pressure flow measurement device for cryogenic fluid provided by the present invention, pressure ports are respectively arranged on the pipes on both sides of the porous balance plate, and the pressure-leading pipes are connected to the pressure ports.

[0013] According to the differential pressure flow measurement device for cryogenic fluid provided by the present invention, the axial direction of the pressure-inducing tube is perpendicular to the axial direction of the pipeline.

[0014] According to the differential pressure flow measurement device for cryogenic fluid provided by the present invention, the pressure-inducing tube is provided with a bending portion, and the axial direction of the pressure-inducing tube at both ends of the bending portion is perpendicular to the axial direction of the pipeline.

[0015] The pressure differential flow measurement device for cryogenic fluid provided by the present invention further comprises a switching assembly, one end of which is connected to the pressure port, and the other end of which is detachably connected to the pressure-leading pipe.

[0016] According to the pressure differential flow measurement device for cryogenic fluid provided by the present invention, a plurality of flow equalizing components are provided, and the flow equalizing components are wire meshes or flow equalizers.

[0017] According to the pressure differential flow measurement device for cryogenic fluid provided by the present invention, a heat insulation layer is provided on the outside of the pipeline.

[0018] In a second aspect, the present invention further provides a method for measuring the flow rate of a cryogenic fluid by a differential pressure method, using the device for measuring the flow rate of a cryogenic fluid by a differential pressure method as described in the first aspect, comprising:

[0019] A low-temperature fluid with a density of ρ is introduced into the pipeline;

[0020] The cryogenic liquid flows through a plurality of porous balancing plates and flow equalizing parts in the pipeline in sequence, and generates a pressure difference on both sides of each porous balancing plate;

[0021] The pressure value of the cryogenic fluid on both sides of each porous balancing plate is measured by a pressure detection device, and the pressure difference ΔP of the cryogenic fluid on both sides of each porous balancing plate is calculated;

[0022] Calculating an equivalent diameter ratio β of each porous balance plate, wherein the equivalent diameter ratio β is a ratio of the sum of the areas of all through holes on each of the porous balance plates to the cross-sectional area A of the pipeline;

[0023] The flow rate q corresponding to each porous balance plate is calculated based on the pressure difference ΔP between the low-temperature fluids on both sides of each porous balance plate and the discharge coefficient C v , and the calculation formula is:

[0024]

[0025] A differential pressure type flow measurement device and method for low-temperature fluids provided by the present invention include a pipeline, a flow equalizing member and a differential pressure sensor. By arranging a plurality of porous balance plates at intervals along the length direction in the pipeline, the flow equalizing member is arranged between two adjacent porous balance plates, and a plurality of pressure detection devices are provided. The pressure detection devices are connected to the pipeline for measuring the pressure values of the low-temperature fluids on both sides of each porous balance plate, and calculating the pressure difference between the low-temperature fluids on both sides of each porous balance plate according to the pressure values; with such a setting, through a plurality of porous balance plates connected in series in the pipeline and the flow equalizing members between the porous balance plates, the mixing of the gas-liquid two-phase low-temperature fluid flowing through is made more uniform. When the low-temperature fluid in the pipeline flows through each porous balance plate and the flow equalizing member, the pressure difference can be evenly reduced multiple times, and the pressure drop generated at each stage is not sufficient to cause cavitation, effectively avoiding the cavitation effect, improving the accuracy of the flow measurement result of the low-temperature fluid downstream of the pipeline, and the flow measurement value of the last-stage porous balance plate can be selected as the flow measurement result of the low-temperature fluid in the pipeline.

[0026] In addition, the present invention has no moving parts, is simple to install, has a wide application range, low cost, can directly obtain measurement data, avoids the complex equipment and high cost required by the method of separate measurement, and can effectively detect the presence of gas phase in the liquid by comparing the flow measurement results at each porous balance plate. Description of the Drawings

[0027] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0028] Figure 1 is a schematic structural diagram of a pipeline provided by an embodiment of the present invention;

[0029] Figure 2 is a schematic structural diagram of a differential pressure type flow measurement device for low-temperature fluids provided by an embodiment of the present invention;

[0030] Figure 3 is a flow block diagram of a differential pressure type flow measurement method for low-temperature fluids provided by an embodiment of the present invention.

[0031] Reference Signs:

[0032] 1. Pipeline; 2. Porous balance plate; 3. Flow equalizing component; 4. Differential pressure sensor; 5. Pressure guiding pipe; 6. Pressure tapping; 7. Adapter assembly; 8. Connecting flange. Detailed implementation manners

[0033] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below with reference to the accompanying drawings in the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without any creative efforts shall fall within the protection scope of the present invention.

[0034] The following Figures 1 to 2 describes a differential pressure type flow measurement device and a measurement method for cryogenic fluids provided in the embodiments of the present invention.

[0035] A differential pressure type flow measurement device for cryogenic fluids provided in this embodiment includes: a pipeline 1, a flow equalizing component 3, and a pressure detection device.

[0036] Among them, a plurality of porous balance plates 2 are arranged at intervals along the length direction inside the pipeline 1, the flow equalizing component 3 is arranged between two adjacent porous balance plates 2, and a plurality of pressure detection devices are provided. The pressure detection devices are all connected to the pipeline 1 and are used to measure the pressure values of the cryogenic fluids on both sides of each porous balance plate 2 respectively.

[0037] It can be seen from the above solution that when the present invention is in use, cryogenic fluids are introduced into the pipeline 1. Through a plurality of porous balance plates 2 connected in series in the pipeline 1 and the flow equalizing component 3 between the porous balance plates 2, the mixture of the flowing gas-liquid two-phase cryogenic fluids becomes more uniform. Due to the symmetric porous structure characteristics of the porous balance plates 2, the resistance to the fluid is small, and the flow field can be balanced to effectively balance the fluid distribution, reduce eddy currents, vibrations and signal noises. When the cryogenic fluids in the pipeline 1 flow through each porous balance plate 2 and the flow equalizing component 3, the differential pressure can be evenly reduced multiple times, and the pressure drop generated at each stage is not enough to cause cavitation, effectively avoiding the cavitation effect and improving the accuracy of the flow measurement result of the cryogenic fluids downstream of the pipeline 1. The flow measurement value of the last-stage porous balance plate 2 can be selected as the flow measurement result of the cryogenic fluids in the pipeline 1. This device has no moving parts, is simple to install, and has a low cost, avoiding the complex equipment and high costs required by the method of separate measurement. By comparing the flow measurement results at each porous balance plate 2, the presence of gas phase in the liquid can also be effectively detected.

[0038] The above-mentioned cryogenic fluids can be liquids with low boiling points and easy to vaporize such as liquid nitrogen and liquid hydrogen, or liquids containing gas phase itself, making this flow measurement device have a wide range of applications.

[0039] Optionally, the pressure detection device can measure the pressure of the cryogenic fluid on both sides of the porous balance plate 2 in the pipeline 1 by means of flange pressure tapping, corner pressure tapping, diameter-distance pressure tapping, etc. These methods are all existing technologies and can be selected according to the actual required accuracy and installation requirements. For example, for flange pressure tapping, the pressure tapping element (such as a pressure gauge or a pressure sensor) is installed on the flange, and then the flange is connected to the pipeline 1, usually using bolts or welding, and the pressure in the pipeline 1 is measured through the pressure tapping element; or for diameter-distance pressure tapping, the distance between the center line of the pressure tapping port 6 and a certain specified end face of the pipeline 1, that is, the distance between the pressure tapping ports 6, is used to measure the pressure in the pipeline 1. A suitable pressure tapping position is selected on the pipeline 1 to install the pressure tapping port 6, the distance between the pressure tapping ports 6 is measured, and the measured distance value is substituted into the relevant formula or calculation model to calculate the pressure value in the pipeline 1.

[0040] In this embodiment, the outer edge of the porous balance plate 2 is connected to the inner wall of the pipeline 1. For example, both the pipeline 1 and the porous balance plate 2 are set to be circular, the outer diameter of the porous balance plate 2 is adapted to the inner diameter of the pipeline 1, so that the outer peripheral surface of the porous balance plate 2 is connected to the inner wall of the pipeline 1, and a number of through holes are uniformly arranged on the porous balance plate 2 for the cryogenic fluid to pass through.

[0041] In some embodiments, two porous balance plates 2 are provided, and the two porous balance plates 2 are respectively arranged at positions close to both ends of the pipeline 1. Of course, three or more porous balance plates 2 can also be provided, so that the upstream porous balance plate 2 among the series-connected porous balance plates 2 and the flow equalizing parts 3 between the porous balance plates 2 can make the mixture of the gas-liquid two-phase cryogenic fluid more uniform and improve the accuracy of the measurement results of the downstream flowmeter.

[0042] In this embodiment, a number of flow equalizing parts 3 are provided. The flow equalizing parts 3 can be wire meshes or flow equalizers. The flow equalizing parts 3 are used to improve the flow state of the fluid in the pipeline 1, so that the fluid can be evenly dispersed on the cross-section of the pipeline 1 after passing through the flow equalizing parts 3, reduce the problem of uneven flow velocity distribution, and is also beneficial to reducing the noise and vibration in the pipeline 1 and improving the safety and stability of the pipeline 1 transportation.

[0043] In this embodiment, the pressure detection device is a differential pressure sensor 4. The differential pressure sensor 4 has the same number as the porous balance plate 2 and is in one-to-one correspondence in position. The differential pressure sensor 4 is provided with a pair of pressure interfaces, and the pair of pressure interfaces are respectively communicated with the pipeline 1 on both sides of the porous balance plate 2 through the pressure guiding pipes 5, and the axial direction of the pressure guiding pipes 5 is perpendicular to the axial direction of the pipeline 1 to avoid the influence of the fluid flow on the measurement results and avoid the non-perpendicularity of the flow direction of the cryogenic fluid in the pipeline 1 and the flow direction of the cryogenic fluid in the pressure tapping pipe, so that the fluid flow generates a certain impact force or vibration on the pressure tapping pipe, thereby ensuring the accuracy of the measurement results.

[0044] In some embodiments, pressure ports 6 are respectively provided on the pipelines 1 on both sides of the porous balance plate 2, and the pressure lead pipe 5 is connected to the pressure port 6 so as to pass the low-temperature fluid in the pipeline 1 into the pressure differential sensor 4 through the pressure lead pipe 5, so as to measure the pressure difference of the low-temperature fluid on both sides of each porous balance plate 2.

[0045] Preferably, the pressure-guiding pipe 5 is provided with a bending portion, and the axial direction of the pressure-guiding pipe 5 at both ends of the bending portion is perpendicular to the axial direction of the pipeline 1 .

[0046] With such arrangement, the bent portion can be used to buffer the instantaneous impact of the measured medium on the spring tube in the differential pressure sensor 4, which can well protect the mechanical structure of the digital display meter or the differential pressure sensor 4 from damage and extend the service life.

[0047] Furthermore, in order to facilitate the connection between the pressure-leading pipe 5 and the pipeline 1, an adapter assembly 7 is also included, one end of the adapter assembly 7 is connected to the pressure taking port 6, and the other end is detachably connected to the pressure-leading pipe 5; in some embodiments, the adapter assembly 7 can be an adapter tube and a locking nut connected to the pipeline 1, one end of the adapter tube is sealed and connected to the pressure taking port 6 of the pipeline 1, for example, by welding, to ensure the air tightness at the pressure taking port 6; the other end of the adapter tube is detachably connected to the pressure-leading pipe 5, for example, by a threaded connection, an external thread is provided at one end of the pressure-leading pipe 5 close to the pipeline 1, and a locking nut is sleeved on the adapter tube, the internal thread of the locking nut is adapted to the external thread of the pressure-leading pipe 5, and the pressure-leading pipe 5 is docked with the adapter tube during connection, and then the pressure-leading pipe 5 is connected to the adapter tube by screwing the locking nut.

[0048] With such arrangement, by providing the adapter assembly 7, when connecting the differential pressure sensor 4 to the pipeline 1, it is only necessary to connect the pressure-leading pipe 5 to the adapter assembly 7, and the differential pressure sensor 4 is easy to assemble and disassemble, thereby improving the convenience of use and the measurement efficiency.

[0049] In this embodiment, connecting flanges 8 are provided at both ends of the pipeline 1, which can facilitate the connection of the differential pressure flow measuring device to the pipeline 1 of the low-temperature fluid. An insulation layer is provided on the outside of the pipeline 1. The insulation layer can be an insulating material of a certain thickness wrapped around the outside of the pipeline 1, such as glass fiber, asbestos, aerogel felt, etc., which is used to reduce heat exchange with the external environment and prevent the low-temperature fluid from generating gas during the flow process of the pipeline 1.

[0050] The present invention also provides a pressure differential flow measurement method for cryogenic fluids. The pressure differential flow measurement device for cryogenic fluids described above can be used to measure the flow values ​​at each porous balance plate 2 in the pipeline 1.

[0051] Specifically, the measurement steps include:

[0052] S1: A cryogenic fluid with a density of ρ is introduced into pipe 1;

[0053] S2: The cryogenic liquid flows through a plurality of porous balance plates 2 and flow equalizing members 3 in the pipeline 1 in sequence, and pressure differences are generated on both sides of each porous balance plate 2.

[0054] S3: Measure the pressure values of the cryogenic fluid on both sides of each porous balance plate 2 through a pressure detection device, and calculate the pressure difference ΔP of the cryogenic fluid on both sides of each porous balance plate 2.

[0055] S4: Calculate the equivalent diameter ratio β of each porous balance plate 2. The equivalent diameter ratio β is the square root of the ratio of the sum of the areas of all through holes on each porous balance plate 2 to the cross-sectional area A of the pipeline 1.

[0056] S5: Calculate the flow rate q corresponding to each porous balance plate 2 according to the pressure difference ΔP of the cryogenic fluid on both sides of each porous balance plate 2 and the discharge coefficient C v , where the discharge coefficient C of each porous balance plate 2 is a known technical parameter of the porous balance plate 2, and the calculation formula is:

[0057]

[0058] In some embodiments, a porous balance plate 2 is provided at each of the positions near both ends in the pipeline 1, a wire mesh is provided in the middle of the pipeline 1, the pressure on both sides of each porous balance plate 2 is measured by a differential pressure sensor 4, and a porous balance plate 2 and the corresponding differential pressure sensor 4 can form a flowmeter for fluid measurement. Along the flow direction of the cryogenic fluid, by comparing the flow rate values corresponding to the two porous balance plates 2 before and after, the presence of gas phase in the liquid can be effectively detected: if the two flow rate values are basically equal, it indicates that the fluid does not contain gas; if the two flow rate values differ greatly, it indicates that the fluid contains gas. The reason is that the gas-liquid mixing uniformity of the cryogenic fluid when flowing through each porous balance plate 2 is different, resulting in different flow rate measurement values. Since the porous balance plate 2 upstream of the pipeline 1 improves the mixing uniformity of the gas-liquid two-phase cryogenic fluid, the flow rate measurement result at the downstream porous balance plate 2 is more accurate. Therefore, the flow rate measurement value of the last-stage porous balance plate 2 can be selected as the flow rate measurement result of the cryogenic fluid in the pipeline 1.

[0059] The invention is simply installed, can directly obtain measurement data, avoids the complex equipment and high costs required by the separation measurement method, and can effectively detect the presence of gas phase in the liquid by comparing the flow rate measurement results at each porous balance plate 2.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A differential pressure type flow measurement device for cryogenic fluids, characterized in that, Comprising: A pipe (1), in which a plurality of porous balance plates (2) are arranged at intervals along its length direction; A flow equalizing member (3), arranged between two adjacent porous balance plates (2); A plurality of pressure detection devices, all of which are connected to the pipe (1) and are used to measure the pressure values of the cryogenic fluid on both sides of each porous balance plate (2) respectively.

2. The differential pressure type flow measurement device for cryogenic fluid according to claim 1, wherein The outer edge of the porous balance plate (2) is connected to the inner wall of the pipe (1), and a plurality of through holes are arranged on the porous balance plate (2).

3. The differential pressure type flow measurement device for cryogenic fluid according to claim 1, characterized in that, The pressure detection device is a differential pressure sensor (4), the number of differential pressure sensors (4) is the same as that of the porous balance plates (2) and their positions correspond one by one. The differential pressure sensor (4) is provided with a pair of pressure interfaces, and a pair of the pressure interfaces are respectively communicated with the pipe (1) on both sides of the porous balance plate (2) through pressure guiding pipes (5).

4. The differential pressure type flow measurement device for cryogenic fluid according to claim 3, characterized in that, Pressure tapping ports (6) are respectively arranged on the pipes (1) on both sides of the porous balance plate (2), and the pressure guiding pipes (5) are connected to the pressure tapping ports (6).

5. The differential pressure type flow measurement device for cryogenic fluid according to claim 3, characterized in that, The axial direction of the pressure guiding pipe (5) is perpendicular to the axial direction of the pipe (1).

6. The differential pressure type flow measurement device for cryogenic fluid according to claim 5, wherein The pressure guiding pipe (5) is provided with a bending part, and the axial directions of the pressure guiding pipes (5) at both ends of the bending part are perpendicular to the axial direction of the pipe (1).

7. The differential pressure type flow measurement device for cryogenic fluid according to claim 4, characterized in that, It further comprises an adapter assembly (7), one end of the adapter assembly (7) is connected to the pressure tapping port (6), and the other end is detachably connected to the pressure guiding pipe (5).

8. The differential pressure type flow measurement device for cryogenic fluid according to claim 1, characterized in that, A plurality of the flow equalizing members (3) are arranged, and the flow equalizing members (3) are wire meshes or flow equalizers.

9. The differential pressure type flow measurement device for cryogenic fluid according to claim 1, characterized in that, A heat insulation layer is arranged outside the pipe (1).

10. A differential pressure type flow measurement method for cryogenic fluids, which uses the differential pressure type flow measurement device for cryogenic fluids according to any one of claims 1-9, characterized in that, Comprising: Introducing a cryogenic fluid with a density of ρ into the pipe; The cryogenic liquid flows through a plurality of porous balance plates and flow equalizing members in sequence in the pipe, and pressure differences are generated on both sides of each porous balance plate; Measuring the pressure values of the cryogenic fluid on both sides of each porous balance plate through the pressure detection device, and calculating the pressure difference ΔP of the cryogenic fluid on both sides of each porous balance plate; Calculating the equivalent diameter ratio β of each porous balance plate, and the equivalent diameter ratio β is the ratio of the sum of the areas of all the through holes on each porous balance plate to the cross-sectional area A of the pipe. Calculate the flow rate q corresponding to each porous equilibrium plate based on the pressure difference ΔP of the low-temperature fluid on both sides of each porous equilibrium plate and the discharge coefficient C v , and the calculation formula is:

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