A double orifice plate balanced flowmeter with flange pressure tapping and method

Abstract

A double orifice plate balanced flowmeter and method with flange pressure tapping, comprising an upstream sealing flange, a downstream sealing flange, two sealing washers, a double orifice plate assembly, a low-pressure pressure tapping pipe, a high-pressure pressure tapping pipe, a plurality of fastening bolts and a plurality of nuts; the upstream sealing flange and the downstream sealing flange are clamped by the respective fastening bolts and nuts, and the double orifice plate assembly is hermetically arranged between the upstream sealing flange and the downstream sealing flange under the action of the two sealing washers, and a high-pressure pressure tapping pipe and a low-pressure pressure tapping pipe are respectively arranged on the outer peripheral walls of the upstream sealing flange and the downstream sealing flange to take pressure on the fluid in the fluid channels of the upstream sealing flange and the downstream sealing flange. The beneficial effects of the present invention are: the balanced flowmeter is applicable to the temperature range from room temperature to liquid hydrogen temperature range, has high sealing performance, eliminates the possibility of leakage of cryogenic fluids such as liquid hydrogen and liquid nitrogen, and has strong detachable structure. During specific implementation, the maintenance and replacement of the double orifice plate assembly and the sealing washers are relatively convenient.

Description

Technical Field

[0001] The present invention relates to the technical field of flow measurement, and more specifically, to a double orifice plate balanced flowmeter with flange pressure tapping. Background Art

[0002] The rapid development of the aerospace field has greatly increased the demand for cryogenic fluids such as liquid hydrogen and liquid nitrogen. Flow measurement is a basic requirement for cryogenic fluids during transportation, and its accuracy and efficiency are of utmost importance. As a type of differential pressure flowmeter, the orifice flowmeter has the advantages of simple structure, high reliability, and no moving parts, so it is often used for the flow measurement of cryogenic fluids. However, in actual measurement, when cryogenic fluids flow through the orifice plate, a large eddy current area will form downstream, and the existence of the eddy current area seriously affects the accuracy and efficiency of its flow measurement.

[0003] In the existing technology, in the paper "3D numerical investigation of energy transfer and loss of cavitation flow in perforated plates" (Xiaogang Xu, Liang Fang, Anjun Li, Zhenbo Wang and Shuxun Li. Engineering applications of computational fluid mechanics, 2020, 14(1), 1095-1105), taking normal temperature water as the medium, the cavitation flow losses of multi-stage orifice plates are compared and analyzed by using the method of computational fluid mechanics, which proves that compared with a single orifice plate, the multi-stage orifice plate effectively weakens the degree of cavitation. However, the paper does not mention the influence of pressure loss and measurement accuracy, nor does it propose whether it can be used for flow measurement.

[0004] The paper "Aerodynamics analysis of superheated steam flow through multi-stage perforated plates" (Jin-yuan Qian, Cong-wei Hou, Jia-yi Wu, Zhi-xin Gao, Zhi-jiang Jin, International Journal of Heat and Mass Transfer, 2019, 141: 48-57) uses superheated steam as the medium and adopts the method of computational fluid dynamics to compare and analyze the pressure drop performance of double-stage perforated plates, proving that there is a critical spacing between the two perforated plates, and the pressure loss reaches the maximum value. Under the double-stage perforated plate structure proposed in the paper, the permanent pressure loss reaches the maximum, which is significantly increased compared with the single-plate perforated plate, which is extremely unfavorable for flow measurement, and the paper does not propose whether this structure of double-stage perforated plates can be used for flow measurement.

[0005] Chinese invention patent 201920160245.9 discloses an orifice plate balanced flowmeter, the main components of which are three porous plates, with three pressure-inducing pipes, which measure the pressure between the three porous plates and behind the third porous plate, respectively, improving the accuracy of flow measurement and reducing the impact of the flowmeter on water flow. The invention patent does not mention the distance arrangement between the plates, nor the size of the permanent pressure loss, and cannot explain the impact of the distance between the plates on the flow measurement.

[0006] Chinese invention patent 201921822170.2 discloses a double-layer flow meter honeycomb rectifier, the main components of which are a primary rectifier plate and a secondary rectifier plate. After the gas flows through the two rectifier plates, the air intake is uniform, with obvious noise reduction and rectification effects, and the requirements for the front and rear straight pipe sections are small. In this invention patent, the rectifier is the main component, while in the flow meter, the main component is the throttling device.

[0007] Chinese invention patent CN110793579 discloses a new type of balanced flow meter, which is mainly composed of a filter plate, a square plate and a horizontal plate. When used together, the balanced flow meter can be used in places with poor environments. In addition, the pipe body groove, heating wire and water inlet valve in the device can adjust the internal temperature of the balanced flow meter, so that it can work normally under the temperature conditions below 0 degrees in winter and above 45 degrees in summer, preventing the balanced flow meter from working outside the working temperature range and causing inaccurate flow measurement. In this invention, the main component of the balanced flow meter, the porous plate, has not been improved, and the throttling component is still a single porous plate. The main purpose is to improve the working ability of the balanced flow meter to adapt to the environment.

[0008] Chinese invention patent CN105973320 discloses a high-precision balanced flowmeter. The structure includes a connecting pipe, a straight pipe section, a sensor, two sealing rings, and two pressure guiding pipes. Air channels are provided on the upstream and downstream end faces of the perforated plate, and buffer grooves communicating with the inside of the connecting pipe are opened. In this invention, after the gas flows through the perforated plate with a tapered section, a straight section, and a divergent section, it is buffered again in the buffer grooves, improving the service life of the connecting pipe in connection measurement with different types of sensors and facilitating the quick installation and disassembly by the staff. In this invention, the component for generating a pressure difference in the balanced flowmeter is still a single perforated plate.

[0009] In recent years, the balanced flowmeter has been developed on the basis of the orifice flowmeter. It not only inherits the measurement advantages of the orifice flowmeter, but also has higher measurement accuracy, lower permanent pressure loss, and higher balanced flow field ability compared with the traditional orifice flowmeter. Currently used balanced flowmeters all use a single perforated plate as the main component for flow measurement, which results in a relatively large eddy current area and pressure loss downstream of the perforated plate and low measurement accuracy. Therefore, there is an urgent need for improvement. Summary of the Invention

[0010] The purpose of the present invention is to overcome the above deficiencies and provide a balanced flowmeter with double perforated plates for flange tapping, aiming to further reduce the pressure loss to improve the accuracy and efficiency of flow measurement.

[0011] A double-porous plate balanced flowmeter with flange pressure tapping, comprising an upstream sealing flange, a downstream sealing flange, two sealing gaskets, a double-porous plate assembly, a low-pressure pressure tapping pipe, a high-pressure pressure tapping pipe, a plurality of fastening bolts and a plurality of nuts; wherein, both the upstream sealing flange and the downstream sealing flange have fluid channels and a plurality of through holes, and the plurality of through holes are arranged at intervals along the circumferential direction of the upstream sealing flange or the downstream sealing flange. The end faces of the upstream sealing flange and the downstream sealing flange are also respectively concavely provided with a throttle part groove and a sealing groove located in the throttle part groove. The two sealing gaskets are respectively installed in the corresponding sealing grooves. The ends of the upstream sealing flange and the downstream sealing flange provided with the throttle part grooves face each other. The double-porous plate assembly is concavely provided with a plurality of through holes. The double-porous plate assembly is arranged in the two throttle part grooves and is located between the two sealing gaskets. Each through hole is located inside the sealing gasket and is communicated with the two fluid channels. The plurality of fastening bolts respectively pass through the corresponding through holes of the upstream sealing flange and the downstream sealing flange and are threadedly connected with the corresponding nuts, so that the bottom of the sealing groove of the upstream sealing flange and the bottom of the sealing groove of the downstream sealing flange jointly press the corresponding sealing gaskets with the two end faces in the thickness direction of the double-porous plate assembly; a high-pressure pressure tapping hole communicated with the fluid channel of the upstream sealing flange is opened on the outer peripheral wall of the upstream sealing flange, and a low-pressure pressure tapping hole communicated with the fluid channel of the downstream sealing flange is opened on the outer peripheral wall of the downstream sealing flange. The axis of the high-pressure pressure tapping hole is arranged in parallel with the axis of the low-pressure pressure tapping hole 4. One end of the high-pressure pressure tapping pipe extends into the high-pressure pressure tapping hole, and one end of the low-pressure pressure tapping pipe extends into the low-pressure pressure tapping hole. The other ends of the high-pressure pressure tapping pipe and the low-pressure pressure tapping pipe are respectively connected with a pressure acquisition system.

[0012] Preferably: The double-porous plate assembly is arranged in a circular sheet shape and is formed by welding two porous plates and a single-hole plate. A plurality of the through holes penetrate through the two porous plates, and each of the through holes on the two porous plates is arranged in one-to-one correspondence. The single-hole plate is penetrated with a communication port, and the communication port is communicated with at least two through holes on the porous plate.

[0013] Preferably: One of the plurality of through holes is located at the center of the double-porous plate assembly, and the other through holes among the plurality of through holes are arranged at intervals along the circumferential direction of the double-porous plate assembly.

[0014] Preferably: The depth of the sealing gasket groove is less than the thickness of the sealing gasket, and the thickness of the sealing gasket is not greater than the sum of the depths of the sealing gasket groove and the throttle part groove.

[0015] Preferably: The aperture of the high-pressure pressure tapping hole is equal to the aperture of the low-pressure pressure tapping hole.

[0016] Preferably, the double orifice plate balanced flowmeter with flange pressure tapping further includes an upstream connecting pipe, a downstream connecting pipe, an upstream connecting flange, and a downstream connecting flange. The upstream connecting flange and the downstream connecting flange both include air conveying holes located at the central position and a plurality of mounting holes. The mounting holes are arranged at intervals along the circumferential direction of the upstream connecting flange or the downstream connecting flange. One end of the upstream connecting pipe is communicated with and hermetically connected to the fluid passage of the upstream sealing flange, and the other end of the upstream connecting pipe is communicated with and hermetically connected to the air conveying hole of the upstream connecting flange. One end of the downstream connecting pipe is communicated with and hermetically connected to the fluid passage of the downstream sealing flange, and the other end of the downstream connecting pipe is communicated with and hermetically connected to the air conveying hole of the downstream connecting flange.

[0017] The operation method of the double orifice plate balanced flowmeter with flange pressure tapping includes the following steps:

[0018] S1. Weld the high-pressure pressure guiding pipe and the low-pressure pressure guiding pipe into the high-pressure pressure tapping hole and the low-pressure pressure tapping hole opened on the upstream sealing flange and the downstream sealing flange respectively;

[0019] S2. Weld two orifice plates with the same opening method and the same opening size to the two end faces of a single orifice plate respectively;

[0020] S3. Weld one side of the upstream connecting pipe and the downstream connecting pipe to the connecting pipe end faces of the upstream sealing flange and the downstream sealing flange respectively;

[0021] S4. Weld the other sides of the upstream connecting pipe and the downstream connecting pipe to the end faces of the upstream connecting flange and the downstream connecting flange respectively;

[0022] S5. Install the double orifice plate assembly and the sealing gasket in the throttle part groove and the sealing gasket groove respectively, and connect them with the corresponding nuts through each fastening bolt to obtain better sealing performance.

[0023] S6. During measurement, connect the flowmeter to the measurement pipeline through the upstream connecting flange and the downstream connecting flange, and connect the high-pressure pressure guiding pipe 7 and the low-pressure pressure guiding pipe to the external pressure acquisition system, and read the flow data from the pressure acquisition system.

[0024] Adopting the above scheme, the beneficial effects of the present invention are as follows:

[0025] 1. By arranging a double orifice plate assembly between the upstream sealing flange and the downstream sealing flange and taking pressure on the outer peripheral surfaces of the upstream sealing flange and the downstream sealing flange respectively, the pressure difference at this position is large and relatively stable, and the relative error is small, so that the double orifice plate balanced flowmeter with flange pressure tapping has a high measurement accuracy.

[0026] 2. The two perforated plates of the double perforated plate assembly are separated by a single perforated plate, which can effectively reduce the permanent pressure loss and improve the accuracy of differential pressure measurement.

[0027] 3. The cooperation of the upstream sealing flange, the downstream sealing flange and the two sealing gaskets forms a sealing structure, which can obtain high sealing performance and is applicable to occasions under different temperature conditions.

[0028] 4. The double perforated plate balanced flowmeter with flange tapping in the present invention has a simple and compact structure, few components, light weight, is easy to process, install and disassemble, has low production cost, high reliability and practicability, is applicable to the temperature range from room temperature to liquid hydrogen temperature range (20K @ 1 bar), has high sealing performance, and excludes the possibility of leakage of low-temperature fluids such as liquid hydrogen and liquid nitrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a structural cross-sectional view of an embodiment of a double perforated plate balanced flowmeter with flange tapping in the present invention;

[0030] Figure 2 is a partially enlarged schematic view of a double perforated plate balanced flowmeter with flange tapping in the present invention;

[0031] Figure 3 is a schematic structural view of the double perforated plate assembly in the present invention;

[0032] Figure 4 is a schematic structural view of the upstream sealing flange in the present invention;

[0033] Figure 5 is a graph showing the variation of the discharge coefficient with the Reynolds number of a traditional single perforated plate balanced flowmeter and the present invention;

[0034] Figure 6 is a graph showing the variation of the permanent pressure loss coefficient with the Reynolds number of a traditional single perforated plate balanced flowmeter and the present invention.

[0035] DESCRIPTION OF THE REFERENCE NUMERALS: 1. Downstream sealing flange; 2. Sealing gasket; 3. Double perforated plate assembly; 4. Low-pressure tapping hole; 5. Low-pressure pressure guiding pipe; 6. High-pressure tapping hole; 7. High-pressure pressure guiding pipe; 8. Upstream sealing flange; 9. Throttle part groove; 10. Sealing gasket groove; 11. Fastening bolt; 12. Upstream connecting pipe; 13. Downstream connecting pipe; 14. Upstream connecting flange; 15. Downstream connecting flange; 16. Nut; 17. Fluid channel; 18. Through hole; 19. Through hole; 20. Communication port; 21. Air injection hole; 22. Mounting hole. DETAILED DESCRIPTION OF THE INVENTION

[0036] The present invention is further described below in conjunction with embodiments. The description of the following embodiments is only used to help understand the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principles of the present invention, several improvements and modifications may be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0037] like Figures 1 to 4 As shown, as an embodiment, a double porous plate balanced flowmeter with flange pressure taking includes an upstream sealing flange 8, a downstream sealing flange 1, two sealing gaskets 2, a double porous plate assembly 3, a low-pressure pressure pipe 5, a high-pressure pressure pipe 7, a plurality of fastening bolts 11 and a plurality of nuts 16; wherein, the upstream sealing flange 8 and the downstream sealing flange 1 both have a fluid channel 17 and a plurality of through holes 18, the fluid channel 17 is used for the circulation of low-temperature fluids such as liquid hydrogen and liquid nitrogen, and the plurality of through holes 18 are used for the corresponding fastening bolts 11 to pass through, in order to make the upstream sealing flange 8 and the downstream sealing flange 1 evenly stressed after being connected by the fastening bolts 11, the plurality of through holes 18 are arranged at intervals along the circumference of the upstream sealing flange 8 or the downstream sealing flange 1.

[0038] Furthermore, the end faces of the upstream sealing flange 8 and the downstream sealing flange 1 are both recessed with a throttling groove 9 and a sealing groove within the throttling groove 9. The two sealing gaskets 2 are respectively installed in the corresponding sealing grooves. It should be noted that in order to ensure that the sealing characteristics of the sealing gasket 2 do not change under low temperature conditions, the material of the sealing gasket 2 is preferably polytetrafluoroethylene or a metal gasket, especially when the sealing gasket 2 is an oxygen-free copper gasket, which is softer in material and has better low-temperature resistance, and can have excellent sealing performance when used for a long time at low temperatures.

[0039] The upstream sealing flange 8 and the downstream sealing flange 1 are provided with one end of the throttling groove 9 and are arranged facing each other. The double porous plate assembly 3 is recessed with multiple through holes 19. The double porous plate assembly 3 is arranged in the two throttling grooves 9 and is located between the two sealing gaskets 2. Each through hole 19 is located on the inner side of the sealing gasket 2 and is connected to the two fluid channels 17. In this way, when the double porous plate assembly 3 is arranged between the upstream sealing flange 8 and the downstream sealing flange 1, the fluid can flow from the fluid channel 17 of the upstream sealing flange 8 to the fluid channel 17 of the downstream sealing flange 1 through the through holes 19 on the double porous plate assembly 3.

[0040] To ensure the sealing performance at the connection between the upstream sealing flange 8 and the downstream sealing flange 1, multiple fastening bolts 11 respectively pass through the corresponding through holes 18 of the upstream sealing flange 8 and the downstream sealing flange 1 and are threadedly connected to the corresponding nuts 16, so that the bottom surfaces of the sealing grooves of the upstream sealing flange 8 and the bottom surfaces of the sealing grooves of the downstream sealing flange 1 jointly press the corresponding sealing washers 2 with the two end faces in the thickness direction of the double perforated plate assembly 3, thereby realizing the sealing performance of the connection between the upstream sealing flange 8 and the downstream sealing flange 1.

[0041] It should be noted that the upstream sealing flange 8 and the downstream sealing flange 1 are made of stainless steel, with a relatively hard material, while the double perforated plate assembly 3 is made of a relatively soft material. Such a combination forms a composite seal of hard and soft materials, enabling this sealing method to be preferably used under low-temperature conditions.

[0042] To measure the flow rate of the fluid, a high-pressure pressure tapping hole 6 communicating with the fluid passage 17 of the upstream sealing flange 8 is provided on the outer peripheral wall of the upstream sealing flange 8 in this embodiment, and a low-pressure pressure tapping hole 4 communicating with the fluid passage 17 of the downstream sealing flange 1 is provided on the outer peripheral wall of the downstream sealing flange 1. The axis of the high-pressure pressure tapping hole 6 is arranged in parallel with the axis of the low-pressure pressure tapping hole 4. One end of the high-pressure pressure guiding pipe 7 extends into the high-pressure pressure tapping hole 6, and one end of the low-pressure pressure guiding pipe 5 extends into the low-pressure pressure tapping hole 4. The other ends of the high-pressure pressure guiding pipe 7 and the low-pressure pressure guiding pipe 5 are respectively connected to the pressure acquisition system.

[0043] To facilitate the formation of the double perforated plate assembly 3 and ensure its sealing performance, in this embodiment, the double perforated plate assembly 3 is arranged in a circular sheet shape and is formed by welding two perforated plates and a single-hole plate. The double perforated plate assembly 3 is coaxially arranged with both the upstream sealing flange 8 and the downstream sealing flange 1. A plurality of through holes 19 penetrate through the two perforated plates. The through holes 19 on the two perforated plates are arranged in one-to-one correspondence, and the sizes of the through holes 19 on the two perforated plates are equal, and the through holes 19 on the two perforated plates are aligned without deviation in the axial direction. In addition, a communication port 20 penetrates through the single-hole plate, and the communication port 20 is communicated with at least two through holes 19 on the perforated plate.

[0044] Furthermore, one of the plurality of through holes 19 is located at the center of the double perforated plate assembly 3, and the other through holes 19 among the plurality of through holes 19 are arranged at intervals along the circumferential direction of the double perforated plate assembly 3. And the inner diameter of the single-hole plate between the two perforated plates is the same as the inner diameter of the connecting pipe. The thicknesses of the two perforated plates and the single-hole plate are all 3 to 10 mm, and they are respectively welded to the upstream and downstream perforated plates, thus forming a double perforated plate assembly 3.

[0045] As an embodiment, the hole-opening method for both of the two perforated plates is to open a central through hole 19 at the center and 4 to 8 through holes 19 with equal center distances around it.

[0046] In addition, the depth of the groove of the sealing gasket 2 is less than the thickness of the sealing gasket 2, and the thickness of the sealing gasket 2 is not greater than the sum of the depths of the groove of the sealing gasket 2 and the groove of the throttle member 9. This ensures that only the outer peripheral wall of the sealing gasket 2 contacts the groove wall of the groove of the sealing gasket 2 and does not contact the inner peripheral wall of the groove of the throttle member 9, reducing the contact area and improving the sealing performance at the same time.

[0047] It should be noted that in order to ensure accurate pressure extraction, the aperture of the high-pressure pressure extraction hole 6 in this embodiment is equal to the aperture of the low-pressure pressure extraction hole 4. In this way, the inner diameters and lengths of the high-pressure pressure guiding pipe 7 and the low-pressure pressure guiding pipe 5 can be set to be equal, and the horizontal cross-sections of the high-pressure pressure guiding pipe 7 and the low-pressure pressure guiding pipe 5 are in the same plane. In this way, the requirements of flange pressure extraction can be met and the pressure extraction can be ensured to be relatively accurate.

[0048] As an embodiment, the distances from the centers of the high-pressure pressure extraction hole 6 and the low-pressure pressure extraction hole 4 to the upstream end face and the downstream end face of the double perforated plate assembly 3 are kept consistent, both being 25.4 mm, meeting the requirements of flange pressure extraction.

[0049] In addition, the double perforated plate balanced flowmeter with flange pressure extraction further includes an upstream connecting pipe 12, a downstream connecting pipe 13, an upstream connecting flange 14, and a downstream connecting flange 15. The upstream connecting flange 14 and the downstream connecting flange 15 both include an air delivery hole 21 located at the central position and a plurality of mounting holes 22. The mounting holes 22 are arranged at intervals along the circumferential direction of the upstream connecting flange 14 or the downstream connecting flange 15; one end of the upstream connecting pipe 12 is communicated with and hermetically connected to the fluid passage 17 of the upstream sealing flange 8, and the other end of the upstream connecting pipe 12 is communicated with and hermetically connected to the air delivery hole 21 of the upstream connecting flange 14; one end of the downstream connecting pipe 13 is communicated with and hermetically connected to the fluid passage 17 of the downstream sealing flange 1, and the other end of the downstream connecting pipe 13 is communicated with and hermetically connected to the air delivery hole 21 of the downstream connecting flange 15.

[0050] It should be noted that in order to ensure the sealing performance of the connection between the upstream connecting pipe and the upstream connecting flange 14 and the upstream sealing flange 8, the two ends of the upstream connecting pipe are connected to the upstream connecting flange 14 and the upstream sealing flange 8 by welding. Similarly, in order to ensure the sealing performance of the connection between the downstream connecting pipe and the downstream connecting flange 15 and the downstream sealing flange 1, the two ends of the downstream connecting pipe are also connected to the downstream connecting flange 15 and the downstream sealing flange 1 by welding.

[0051] The installation, measurement, and disassembly steps of the double perforated plate balanced flowmeter with flange pressure extraction are as follows:

[0052] S1. Weld the high-pressure pressure guiding pipe 7 and the low-pressure pressure guiding pipe 5 into the high-pressure pressure extraction hole 6 and the low-pressure pressure extraction hole 4 opened in the upstream sealing flange 8 and the downstream sealing flange 1 respectively;

[0053] S2. Weld two perforated plates with the same perforation method and size on both end faces of a single perforated plate respectively.

[0054] S3. Weld one side of the upstream connecting pipe 12 and the downstream connecting pipe 13 on the connecting pipe end faces of the upstream sealing flange 8 and the downstream sealing flange 1 respectively.

[0055] S4. Weld the other sides of the upstream connecting pipe 12 and the downstream connecting pipe 13 on the end faces of the upstream connecting flange 14 and the downstream connecting flange 15 respectively.

[0056] S5. Install the double-perforated plate assembly 3 and the sealing gasket 2 in the throttling part groove 9 and the sealing gasket 2 groove respectively, and connect them with the corresponding nuts 16 through each fastening bolt 11 to obtain better sealing performance.

[0057] S6. During measurement, connect the entire flowmeter to the measurement pipeline through the upstream connecting flange 14 and the downstream connecting flange 15, and connect the high-pressure pressure guiding pipe 7 and the low-pressure pressure guiding pipe 5 to the external pressure acquisition system, then the flow data can be read from the pressure acquisition system.

[0058] During disassembly, separate each fastening bolt 11 from the corresponding nut 16, then the upstream sealing flange 8 and the downstream sealing flange 1 can be separated, so that the sealing gasket 2 or the double-perforated plate assembly 3 can be replaced.

[0059] The present invention will be further described below in combination with test comparison embodiments.

[0060] Test comparison embodiment 1:

[0061] In test comparison embodiment 1, the magnitude and stability of the outflow coefficients of a traditional single-perforated plate balanced flowmeter and the double-perforated plate balanced flowmeter of the present invention are compared. In this embodiment, the perforated plate characteristics of the two flowmeters are the same. The double-perforated plate assembly 3 is composed of two perforated plates and a single perforated plate; the perforation methods and sizes of the two perforated plates are the same, and it is composed of a central hole and four equally spaced surrounding holes. The diameters of the central hole and the surrounding holes are both 4.5 mm, the outer diameters are both 72 mm, the equivalent diameter ratio is 0.4, the opening diameter of the surrounding holes on the perforated plate is 16 mm, and the thicknesses of the two perforated plates are both 3 mm; the opening diameter of the single perforated plate is the same as the inner diameter of the pipeline, which is 25 mm, and the thickness is 3 mm, that is, the thickness of the double-perforated plate assembly 3 is 9 mm; the openings of the two perforated plates of the double-perforated plate assembly 3 are flush and have no deviation axially; the length of the upstream straight pipe section of the double-perforated plate assembly 3 is 250 mm, and the length of the downstream straight pipe section is 375 mm. Supercooled liquid nitrogen is used as the measurement working medium, the pipeline inlet temperature is 77 K, and the pipeline wall surface is kept adiabatic. The average Reynolds number at the pipeline inlet is from 2.0e+5 to 5.5e+5.

[0062] In this embodiment, by adjusting the velocity of subcooled liquid nitrogen at the pipeline inlet, the average Reynolds number at the pipeline inlet is adjusted. The double orifice plate balanced flowmeter of this embodiment uses flange pressure tapping, that is, the position 25.4 mm upstream of the upstream end face of the double orifice plate assembly 3 is used as the high-pressure pressure tapping point, and the position 25.4 mm downstream of the downstream end face of the double orifice plate is used as the low-pressure pressure tapping point. Theoretical calculations were carried out on the discharge coefficient of a double orifice plate balanced flowmeter with flange pressure tapping of the present invention at different inlet average Reynolds numbers.

[0063] The calculation results of the stability comparison of the discharge coefficients under different throttling components are as Figure 5 shown. Compared with the traditional single orifice plate balanced flowmeter, the double orifice plate balanced flowmeter with flange pressure tapping of the present invention has significantly improved both the magnitude and stability of the discharge coefficient. The average discharge coefficient has increased from 0.665 to 0.731, and the fluctuation change of the discharge coefficient has decreased from 7.2% to 0.55%. Therefore, the throttling component structure of the present invention has obvious advantages, with a higher and more stable discharge coefficient and more accurate measurement.

[0064] In Test Comparison Example 2, the permanent pressure loss performance of the traditional single orifice plate balanced flowmeter and the double orifice plate balanced flowmeter of the present invention was compared. In this embodiment, the orifice plate characteristics of the two flowmeters are the same. The characteristics of the double orifice plate assembly 3 are composed of two orifice plates and a single orifice plate; the opening methods and opening sizes of the two orifice plates are the same, and its characteristics are composed of a central hole and four equally spaced peripheral holes. The diameters of the central hole and the peripheral holes are both 4.5 mm, the outer diameters are both 72 mm, the equivalent diameter ratio is 0.4, the opening diameter of the peripheral holes on the orifice plate is 16 mm, and the thicknesses of the two orifice plates are both 3 mm; the opening diameter of the single orifice plate is the same as the inner diameter of the pipeline, which is 25 mm, and the thickness is 3 mm, that is, the thickness of the double orifice plate assembly 3 is 9 mm; the openings of the two orifice plates of the double orifice plate assembly 3 are axially flush; the length of the upstream straight pipe section of the double orifice plate assembly 3 is 250 mm, and the length of the downstream straight pipe section is 375 mm. Subcooled liquid nitrogen is used as the measurement working medium, the pipeline inlet temperature is 77 K, and the pipeline wall surface is kept adiabatic. The average Reynolds number at the pipeline inlet is from 2.0e+5 to 5.5e+5.

[0065] In this embodiment, by adjusting the velocity of subcooled liquid nitrogen at the pipeline inlet, the average Reynolds number at the pipeline inlet is adjusted. The positions 25 mm upstream of the upstream end face and 150 mm downstream of the downstream end face of the throttling components of the two flowmeters are respectively used as the high-pressure and low-pressure pressure tapping points for permanent pressure loss calculation, and theoretical calculations and comparisons are carried out.

[0066] The calculation results of the comparison of the permanent pressure loss characteristics of the two flowmeters are as Figure 6As shown. Compared with the traditional single-piece porous plate balanced flowmeter, the pressure loss of a double-porous plate balanced flowmeter with flange tapping in the present invention has been significantly reduced, and the average permanent pressure loss coefficient has decreased from 68.9 to 59.9.

[0067] In summary, a double-porous plate balanced flowmeter with flange tapping designed in the present invention accelerates the contraction of the fluid and the recovery of pressure through the double-porous plate throttle component, causing the intense pressure reduction and recovery to occur within the double-porous plate component 3. The double-porous plate component 3 improves the downstream eddy current zone condition, significantly improves the magnitude and stability of the discharge coefficient, reduces the permanent pressure loss of the fluid, and significantly improves the overall performance of the flowmeter.

Claims

1. A double orifice plate balanced flowmeter with flange pressure tapping, characterized in that: The double orifice plate balanced flowmeter with flange tapping includes an upstream sealing flange (8), a downstream sealing flange (1), two sealing gaskets (2), a double orifice plate assembly (3), a low-pressure pressure tapping pipe (5), a high-pressure pressure tapping pipe (7), a plurality of fastening bolts (11) and a plurality of nuts (16); wherein, Both the upstream sealing flange (8) and the downstream sealing flange (1) have fluid channels (17) and a plurality of through holes (18). The plurality of through holes (18) are arranged at intervals along the circumferential direction of the upstream sealing flange (8) or the downstream sealing flange (1). The end faces of the upstream sealing flange (8) and the downstream sealing flange (1) are both recessed with a throttle element groove (9) and a sealing groove located in the throttle element groove (9). The two sealing gaskets (2) are respectively installed in the corresponding sealing grooves. The ends of the upstream sealing flange (8) and the downstream sealing flange (1) provided with the throttle element grooves (9) face each other. The double orifice plate assembly (3) is recessed with a plurality of through holes (19). The double orifice plate assembly (3) is arranged in the two throttle element grooves (9) and located between the two sealing gaskets (2). Each through hole (19) is located inside the sealing gasket (2) and is communicated with the two fluid channels (17). The plurality of fastening bolts (11) respectively pass through the corresponding through holes (18) of the upstream sealing flange (8) and the downstream sealing flange (1) and are threadedly connected with the corresponding nuts (16), so that the bottom of the sealing groove of the upstream sealing flange (8) and the bottom of the sealing groove of the downstream sealing flange (1) jointly press the corresponding sealing gaskets (2) with the two end faces in the thickness direction of the double orifice plate assembly (3); A high-pressure pressure tapping hole communicated with the fluid channel (17) of the upstream sealing flange (8) is formed on the outer peripheral wall of the upstream sealing flange (8). A low-pressure pressure tapping hole (4) communicated with the fluid channel (17) of the downstream sealing flange (1) is formed on the outer peripheral wall of the downstream sealing flange (1). The axis of the high-pressure pressure tapping hole (6) is parallel to the axis of the low-pressure pressure tapping hole (4). One end of the high-pressure pressure tapping pipe (7) extends into the high-pressure pressure tapping hole (6). One end of the low-pressure pressure tapping pipe (5) extends into the low-pressure pressure tapping hole (4). The other ends of the high-pressure pressure tapping pipe (7) and the low-pressure pressure tapping pipe (5) are respectively connected with a pressure acquisition system; The double orifice plate assembly (3) is arranged in a circular sheet shape and is welded by two orifice plates and a single orifice plate. A plurality of through holes (19) penetrate through the two orifice plates. Each through hole (19) on the two orifice plates is arranged in one-to-one correspondence. The single orifice plate is penetrated with a communication port (20). The communication port (20) is communicated with at least two through holes (19) on the orifice plate; One of the plurality of through holes (19) is located at the center of the double orifice plate assembly (3), and the other through holes (19) among the plurality of through holes (19) are arranged at intervals along the circumferential direction of the double orifice plate assembly (3).

2. The double-porous-plate balanced flowmeter with flange pressure tapping according to claim 1, wherein: The depth of the groove of the sealing washer (2) is less than the thickness of the sealing washer (2), and the thickness of the sealing washer (2) is not greater than the sum of the depths of the groove of the sealing washer (2) and the groove of the throttling member (9).

3. The double orifice plate balanced flowmeter with flange pressure tapping according to claim 1, characterized in that: The aperture of the high-pressure pressure tapping hole (6) is equal to the aperture of the low-pressure pressure tapping hole (4).

4. The double-porous plate balanced flowmeter with flange pressure tapping according to claim 1, wherein: The double orifice plate balanced flowmeter with flange pressure tapping further includes an upstream connecting pipe (12), a downstream connecting pipe (13), an upstream connecting flange (14) and a downstream connecting flange (15). The upstream connecting flange (14) and the downstream connecting flange (15) both include air delivery holes (21) located at the central position and a plurality of mounting holes (22). Each of the mounting holes (22) is arranged at intervals along the circumferential direction of the upstream connecting flange (14) or the downstream connecting flange (15); one end of the upstream connecting pipe (12) is communicated with and hermetically connected to the fluid passage (17) of the upstream sealing flange (8), and the other end of the upstream connecting pipe (12) is communicated with and hermetically connected to the air delivery hole (21) of the upstream connecting flange (14); one end of the downstream connecting pipe (13) is communicated with and hermetically connected to the fluid passage (17) of the downstream sealing flange (1), and the other end of the downstream connecting pipe (13) is communicated with and hermetically connected to the air delivery hole (21) of the downstream connecting flange (15).

5. The operating method of the double orifice plate balanced flowmeter with flange pressure tapping according to claim 1, characterized in that, It includes the following steps: S1. Weld the high-pressure pressure guiding pipe (7) and the low-pressure pressure guiding pipe (5) into the high-pressure pressure tapping hole (6) and the low-pressure pressure tapping hole (4) opened on the upstream sealing flange (8) and the downstream sealing flange (1) respectively; S2. Weld two orifice plates with the same opening method and the same opening size to both end faces of a single orifice plate respectively; S3. Weld one sides of the upstream connecting pipe (12) and the downstream connecting pipe (13) to the connecting pipe end faces of the upstream sealing flange (8) and the downstream sealing flange (1) respectively; S4. Weld the other sides of the upstream connecting pipe (12) and the downstream connecting pipe (13) to the end faces of the upstream connecting flange (14) and the downstream connecting flange (15) respectively; S5. Install the double orifice plate assembly (3) and the sealing washer (2) into the groove of the throttling member (9) and the groove of the sealing washer (2) respectively, and connect them with the corresponding nuts (16) through each fastening bolt (11) to obtain better sealing performance; S6. During measurement, connect the flowmeter to the measurement pipeline through the upstream connecting flange (14) and the downstream connecting flange (15), and communicate the high-pressure pressure guiding pipe (7) and the low-pressure pressure guiding pipe (5) with an external pressure acquisition system, and read the flow data from the pressure acquisition system.

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