A double orifice balance type flowmeter with corner-tapping

Abstract

The application relates to a double-orifice-plate balanced flowmeter of corner joint pressure taking, which comprises an upstream part, a separation ring and a downstream part; the upstream part is connected with the downstream part through the separation ring; the separation ring comprises a middle outer separation ring and a middle inner separation ring; the upstream part and the downstream part have a symmetrical relationship; the upstream part comprises an upstream sealing cavity, an upstream connecting pipeline, an upstream orifice plate, a high-pressure pressure-taking pipe, an upstream sealing flange and an upstream cavity; and the downstream part comprises a downstream sealing cavity, a downstream connecting pipeline, a downstream orifice plate, a low-pressure pressure-taking pipe, a downstream sealing flange and a downstream cavity, which are symmetrical with the structures in the upstream part. The application has the beneficial effects that: the application is provided with double-orifice plates, the high-pressure pressure-taking port is located on the upstream side of the upstream orifice plate, the low-pressure pressure-taking port is located on the downstream side of the downstream orifice plate, the pressure difference is large, the relative error is small, the measurement precision is high, and the flow range is wider.

Description

Technical Field

[0001] This invention relates to the field of flow measurement devices, and more specifically, to a double-orifice plate balanced flow meter with corner-connected pressure tapping. Background Technology

[0002] Flow measurement is fundamental to ensuring the safe and efficient operation of fluid processes such as cryogenic air separation. Single-orifice differential pressure flowmeters and balanced flowmeters, with their simple structure and measurement principle, are among the most widely used cryogenic flowmeters. Compared to single-orifice differential pressure flowmeters, balanced flowmeters offer higher accuracy (0.3%-0.5%), a wider flow range (10:1), and lower pressure drop, and have gradually replaced single-orifice flowmeters in recent years. Currently used balanced flowmeters use a single multi-orifice plate as the throttling element, which still suffers from the problem of the flow coefficient changing slowly with flow rate (Reynolds number), meaning it cannot remain constant, leading to decreased measurement accuracy. The rapid development of space technology has significantly increased the demand for cryogenic propellants such as liquid oxygen and liquid hydrogen, as well as corresponding flow measurement technologies. Therefore, it is necessary to improve the structure of existing balanced flowmeters to achieve higher measurement accuracy.

[0003] In existing technologies, 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 computationalfluid mechanics, 2020, 14(1), 1095-1105) proved, based on computational fluid dynamics, that multiple perforated plates can suppress the influence of cavitation on measurement accuracy compared to a single perforated plate. However, the paper did not propose a flow meter structure that implements multiple perforated plates.

[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) calculates the pressure drop characteristics of a dual-orifice plate based on computational fluid dynamics methods and experimental measurement data, confirming the existence of a critical plate spacing where the pressure drop has a maximum value. The calculated pressure drop, with the low-pressure tap downstream of the second orifice plate, does not propose a structure for implementing this dual-orifice plate flowmeter, and the pressure drop loss is significantly improved compared to a single orifice plate within the selected plate spacing range.

[0005] A Chinese invention patent application, titled "A Method for Manufacturing a Dual-Orifice Plate Balanced Flowmeter," discloses a dual-orifice plate balanced flowmeter structure. This structure uses flange pressure taps, with the upstream pressure tap located 25.4 mm upstream of the first orifice plate and the downstream pressure tap located between the two orifice plates. The pressure tapping pipe must radially pass through the flange. This invention patent application presents a corner-connected pressure tapping structure for dual-orifice plates, which is completely different in structure.

[0006] Chinese utility model patent 201920160245.9 discloses a three-orifice plate balanced flow meter. In addition to the upstream high-pressure tap, low-pressure taps are provided between each pair of orifice plates to improve measurement accuracy and reduce the flow meter's impact on water flow. This patent does not provide the specific structure of the flow meter, nor does it specify the distance between the orifice plates, thus failing to explain the influence of the orifice plate spacing. It specifies three taps.

[0007] Chinese utility model patent 201921822170.2 discloses a honeycomb rectifier for a double-layer flow meter. This structure includes two perforated plates, a first stage and a second stage, both of which function as rectifiers to achieve better flow rectification before the fluid enters the flow meter. This patent is not a throttling device for the flow meter.

[0008] Chinese invention patent CN110793579 discloses a balanced flow meter. This balanced flow meter, through the combination of a filter plate, a square plate, and a horizontal plate, allows it to operate in harsh environments. Through the combination of a pipe groove, a heating wire, and an inlet valve, the internal temperature of the balanced flow meter can be adjusted, enabling it to operate normally in temperatures below 0 degrees Celsius in winter and above 45 degrees Celsius in summer. This prevents the balanced flow meter from operating outside its temperature range, which could lead to inaccurate flow rate calculations. This invention patent primarily improves dust and temperature resistance, but is essentially still a single-piece perforated plate structure.

[0009] Chinese invention patent CN111678560 discloses a centrally located three-hole balanced flow meter. The flow meter has three central through-holes arranged in an equilateral triangle around the center of the throttling element. Surrounding these three central through-holes are one or two layers of annular through-holes, the area of ​​which is twice the area of ​​the central through-holes. This invention uses a three-hole layout to adjust the flow field, dispersing the impact force on the center and ensuring uniform force distribution. The surrounding annular holes are designed to adjust the flow field, increase measurement accuracy, reduce noise generation, and decrease the requirement for straight pipe sections. Essentially, this invention is a single-piece multi-hole plate structure. Summary of the Invention

[0010] The purpose of this invention is to overcome the shortcomings of the prior art and provide a double multi-hole plate balanced flow meter with corner pressure tapping.

[0011] In a first aspect, a dual-orifice plate balanced flow meter with corner-connected pressure tapping is provided, comprising: an upstream portion, an isolation ring, and a downstream portion; wherein the upstream portion is connected to the downstream portion via the isolation ring.

[0012] The isolation ring includes an outer intermediate isolation ring and an inner intermediate isolation ring; the upstream portion and the downstream portion are symmetrically related, the upstream portion includes an upstream sealing cavity, an upstream connecting pipe, an upstream perforated plate, a high-pressure tapping pipe, an upstream sealing flange, and an upstream cavity, and the downstream portion includes a downstream sealing cavity, a downstream connecting pipe, a downstream perforated plate, a low-pressure tapping pipe, a downstream sealing flange, and a downstream cavity, which are symmetrical to the structures in the upstream portion.

[0013] Preferably, the upstream sealing cavity and the downstream sealing cavity are located on the upstream connecting pipe and the downstream connecting pipe, respectively; the intermediate outer isolation ring and the intermediate inner isolation ring are disposed between the upstream perforated plate and the downstream perforated plate; the high-pressure tapping pipe is connected to the circumferential surface of the upstream sealing cavity, and the low-pressure tapping pipe is connected to the circumferential surface of the downstream sealing cavity.

[0014] Preferably, the upstream sealing cavity, downstream sealing cavity, upstream perforated plate, downstream perforated plate, and intermediate outer isolation ring have the same outer diameter; the outer surfaces of the upstream sealing cavity, upstream perforated plate, intermediate outer isolation ring, downstream perforated plate, and downstream sealing cavity are flush and welded together in sequence.

[0015] Preferably, the upstream sealing cavity, the downstream sealing cavity, the intermediate inner isolation ring, the upstream connecting pipe, and the downstream connecting pipe have the same inner diameter.

[0016] Preferably, the upstream sealing cavity and the downstream sealing cavity have the same hollow structure, each comprising an upstream cavity and a downstream cavity; the open side of the upstream sealing cavity faces the upstream side of the upstream perforated plate; the open side of the downstream sealing cavity faces the downstream side of the downstream perforated plate; the width of the wall surface of the upstream sealing cavity flush with the inner surface of the upstream connecting pipe is less than the width of the outer wall surface of the upstream sealing cavity, and the upstream cavity communicates with the upstream connecting pipe; the width of the wall surface of the downstream sealing cavity flush with the inner surface of the downstream connecting pipe is less than the width of the outer wall surface of the downstream sealing cavity, and the downstream cavity communicates with the downstream connecting pipe.

[0017] Preferably, the high-pressure tapping tube and the low-pressure tapping tube are on the same plane in the axial direction.

[0018] Preferably, both the upstream and downstream perforated plates are disc structures with openings, including a central hole and equidistant holes. The central hole is located at the center of the disc structure, and 4 to 8 equidistant holes are arranged around it. The openings are located within the flow channels of the upstream and downstream connecting pipes. The openings of the upstream and downstream perforated plates are axially aligned, and the axial distance between the upstream and downstream perforated plates is 6 to 12 mm.

[0019] Preferably, the upstream connecting pipe, the upstream sealing cavity, the upstream perforated plate, the intermediate outer isolation ring, the intermediate inner isolation ring, the downstream perforated plate, the downstream sealing cavity, and the downstream connecting pipe are arranged coaxially.

[0020] Preferably, the high-pressure tapping pipe and the low-pressure tapping pipe are connected to the pipeline system under test through the upstream sealing cavity and the downstream sealing cavity, respectively.

[0021] Secondly, a method for installing a dual-orifice plate balanced flow meter with angle tapping as described in the first aspect is provided, comprising:

[0022] S1. Weld the high-pressure tapping pipe and the low-pressure tapping pipe to the outer wall of the upstream sealing cavity and the downstream sealing cavity, respectively.

[0023] S2. Weld the upstream perforated plate and the downstream perforated plate to the open side of the upstream sealing cavity and the downstream sealing cavity, respectively.

[0024] S3. Weld the middle inner isolation ring to the downstream side of the upstream perforated plate;

[0025] S4. Weld the middle outer isolation ring to the sides of the upstream perforated plate and the downstream perforated plate respectively;

[0026] S5. Weld the upstream connecting pipe to the upstream side wall of the upstream sealing cavity; weld the downstream connecting pipe to the downstream side wall of the downstream sealing cavity.

[0027] The beneficial effects of this invention are:

[0028] (1) The angle-connected pressure tapping double perforated plate balanced flowmeter provided by the present invention is equipped with double perforated plates and adopts angle-connected pressure tapping, that is, the high pressure tapping port is on the upstream side of the upstream perforated plate and the low pressure tapping port is on the downstream side of the downstream perforated plate. The pressure difference is large, the relative error is small, the measurement accuracy is high, and the flow range is wider. Furthermore, keeping the distance between the two perforated plates within 6-12mm can effectively reduce pressure loss.

[0029] (2) The upstream sealing cavity of the angle-connected pressure tapping double perforated plate balanced flow meter provided by the present invention is sequentially welded to the upstream perforated plate, the middle outer isolation ring, the downstream sealing cavity, and the downstream perforated plate to form a sealing structure, which greatly reduces the possibility of fluid leakage and is suitable for a wide range from room temperature to low temperature (liquid hydrogen temperature range), ensuring the sealing performance at different temperatures.

[0030] (3) The angle-connected pressure tapping double multi-hole plate balanced flow meter of the present invention has a simple structure, small size, and has the advantages of robust structure, fewer parts, simple assembly and low production cost. Attached Figure Description

[0031] Figure 1 A schematic diagram of a double-orifice plate balanced flow meter with corner tapping provided in this application;

[0032] Figure 2 This is a partially enlarged schematic diagram of the structure of the dual-orifice plate balanced flowmeter provided in this application;

[0033] Figure 3 This is a schematic diagram of the porous plate structure provided in this application;

[0034] Figure 4 This is a schematic diagram of the sealing cavity structure provided in this application;

[0035] Figure 5 A comparison chart of the discharge coefficients of single-orifice plate and double-orifice plate flowmeters provided in this application as a function of Reynolds number;

[0036] Figure 6 A comparison chart of the pressure loss coefficient of single-orifice plate and double-orifice plate flowmeters as a function of Reynolds number provided in this application;

[0037] Explanation of reference numerals in the attached diagram: 1. Upstream sealing cavity; 2. Downstream sealing cavity; 3. Upstream connecting pipe; 4. Downstream connecting pipe; 5. Upstream perforated plate; 6. Downstream perforated plate; 7. Intermediate outer isolation ring; 8. Intermediate inner isolation ring; 9. High-pressure tapping pipe; 10. Low-pressure tapping pipe; 11. Upstream sealing flange; 12. Downstream sealing flange; 13. Upstream cavity; 14. Downstream cavity. Detailed Implementation

[0038] The present invention will be further described below with reference to embodiments. The description of the embodiments below is only for the purpose of helping to understand the present invention. It should be noted that those skilled in the art can make several modifications to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0039] Example 1:

[0040] A type of angle-connected pressure tapping dual-orifice plate balanced flow meter, such as Figure 1 and Figure 2 As shown, it includes: an upstream section, an isolation ring, and a downstream section; the upstream section is connected to the downstream section through the isolation ring;

[0041] The isolation ring includes an outer intermediate isolation ring 7 and an inner intermediate isolation ring 8. The upstream and downstream parts are symmetrical. The upstream part includes an upstream sealing cavity 1, an upstream connecting pipe 3, an upstream perforated plate 5, a high-pressure tapping pipe 9, an upstream sealing flange 11, and an upstream cavity 13. The downstream part includes a downstream sealing cavity 2, a downstream connecting pipe 4, a downstream perforated plate 6, a low-pressure tapping pipe 10, a downstream sealing flange 12, and a downstream cavity 14, which are symmetrical to the structures in the upstream part.

[0042] like Figure 1 and Figure 4 As shown, the upstream sealing cavity 1 and the downstream sealing cavity 2 are located on the upstream connecting pipe 3 and the downstream connecting pipe 4, respectively; the intermediate outer isolation ring 7 and the intermediate inner isolation ring 8 are located between the upstream perforated plate 5 and the downstream perforated plate 6; a high-pressure tapping pipe 9 is connected to the circumferential surface of the upstream sealing cavity 1, and a low-pressure tapping pipe 10 is connected to the circumferential surface of the downstream sealing cavity 2.

[0043] The upstream sealing cavity 1, downstream sealing cavity 2, upstream perforated plate 5, downstream perforated plate 6 and intermediate outer isolation ring 7 have the same outer diameter; the outer surfaces of the upstream sealing cavity 1, upstream perforated plate 5, intermediate outer isolation ring 7, downstream perforated plate 6 and downstream sealing cavity 2 are flush and welded together in sequence.

[0044] The upstream sealing cavity 1, the downstream sealing cavity 2, the intermediate inner isolation ring 8, the upstream connecting pipe 3, and the downstream connecting pipe 4 have the same inner diameter.

[0045] The upstream sealing cavity 1 and the downstream sealing cavity 2 have the same hollow structure, and respectively contain an upstream cavity 13 and a downstream cavity 14; the open side of the upstream sealing cavity 1 faces the upstream side of the perforated plate 5; the open side of the downstream sealing cavity 2 faces the downstream side of the perforated plate 6; the width of the wall surface of the upstream sealing cavity 1 flush with the inner surface of the upstream connecting pipe 3 is less than the width of the outer wall surface of the upstream sealing cavity 1, and the upstream cavity 13 is connected to the upstream connecting pipe 3; the width of the wall surface of the downstream sealing cavity 2 flush with the inner surface of the downstream connecting pipe 4 is less than the width of the outer wall surface of the downstream sealing cavity 2, and the downstream cavity 14 is connected to the downstream connecting pipe 4.

[0046] The high-pressure tapping pipe 9 and the low-pressure tapping pipe 10 are on the same plane in the axial direction.

[0047] like Figure 1 and Figure 3 As shown, both the upstream perforated plate 5 and the downstream perforated plate 6 are disc structures with openings, including a central hole and equidistant small holes. The central hole is located at the center of the disc structure, and 4 to 8 equidistant small holes are arranged around the central hole. The openings are located in the flow channels of the upstream connecting pipe 3 and the downstream connecting pipe 4. The openings of the upstream perforated plate 5 and the downstream perforated plate 6 are axially aligned, and the axial distance between the upstream perforated plate 5 and the downstream perforated plate 6 is 6 to 12 mm.

[0048] The upstream connecting pipe 3, the upstream sealing cavity 1, the upstream perforated plate 5, the intermediate outer isolation ring 7, the intermediate inner isolation ring 8, the downstream perforated plate 6, the downstream sealing cavity 2, and the downstream connecting pipe 4 are arranged coaxially.

[0049] The high-pressure tapping pipe 9 and the low-pressure tapping pipe 10 are connected to the pipeline system under test through the upstream sealing cavity 1 and the downstream sealing cavity 2, respectively.

[0050] For example, this invention uses two perforated plate throttling elements (such as an upstream perforated plate 5 and a downstream perforated plate 6), maintaining a plate spacing of 6–12 mm. Calculations show that the pressure drop from two perforated plates, compared to a single perforated plate of the same thickness (e.g., 3 mm), does not increase; in fact, it may even decrease. More importantly, within the Reynolds number range where cavitation does not occur, the flow coefficient remains almost constant, a key factor in ensuring the accuracy of the flow meter. This invention uses two perforated plates with angled pressure taps, effectively reducing the impact of downstream eddies from the upstream perforated plate on the downstream flow, thereby improving pressure stability in the low-pressure zone after the upstream perforated plate and achieving a stable discharge coefficient.

[0051] Example 2:

[0052] This application provides an installation method for a corner-connected pressure tap dual-orifice plate balanced flow meter, used for installing the corner-connected pressure tap dual-orifice plate balanced flow meter in Embodiment 1, comprising:

[0053] S1. Weld the high-pressure tapping pipe 9 and the low-pressure tapping pipe 10 to the outer wall surfaces of the upstream sealing cavity 1 and the downstream sealing cavity 2, respectively.

[0054] S2. Weld the upstream perforated plate 5 and the downstream perforated plate 6 to the open sides of the upstream sealing cavity 1 and the downstream sealing cavity 2, respectively.

[0055] S3. Weld the middle inner isolation ring 8 to the downstream side of the upstream perforated plate 5;

[0056] S4. Weld the middle outer isolation ring 7 to the sides of the upstream perforated plate 5 and the downstream perforated plate 6 respectively;

[0057] S5. Weld the upstream connecting pipe 3 to the upstream side wall of the upstream sealing cavity 1; weld the downstream connecting pipe 4 to the downstream side wall of the downstream sealing cavity 2.

[0058] Example 3:

[0059] The pressure tapping coefficient of the traditional single-perforated plate flange method is compared with that of the double-perforated plate corner tapping method of this invention. In this embodiment, the perforated plate is characterized by a central hole and four evenly distributed peripheral holes, each with an opening diameter of 4.5 mm; the outer diameter of the perforated plate is 25 mm; the equivalent diameter ratio is 0.4; the thickness of both perforated plates is 3 mm; the spacing between the two perforated plates is 3 mm; the openings on the two perforated plates are aligned; the upstream straight pipe section length is 400 mm, and the downstream straight pipe section length is 500 mm. Supercooled liquid nitrogen is used as the working fluid, the pipe temperature is 77 K, the pipe wall is kept insulated, and the average Reynolds number at the pipe inlet is 2.0e+5 to 5.0e+5.

[0060] In this embodiment, the average Reynolds number at the pipe inlet is adjusted by regulating the liquid nitrogen velocity in the inlet pipe. Traditionally, pressure tapping is done at a point 25.4 mm from the upstream end face of the orifice plate as the high-pressure tapping position, and at a point 25.4 mm from the downstream end face of the orifice plate as the low-pressure tapping position. In this embodiment, the dual-orifice plate balanced flowmeter uses pressure tapping at the upstream wall of the upstream orifice plate (distance 0), i.e., at the upstream cavity immediately adjacent to the upstream orifice plate as the high-pressure tapping position, and pressure tapping at the downstream wall of the downstream orifice plate (distance 0), i.e., at the downstream cavity immediately adjacent to the downstream end of the downstream orifice plate as the low-pressure tapping position. The discharge coefficient of the angle-tap dual-orifice plate balanced flowmeter of this invention is numerically calculated.

[0061] The calculation results comparing the stability of the discharge coefficient under different pressure tapping methods are as follows: Figure 5As shown in the figure, the horizontal axis represents the Reynolds number, and the vertical axis represents the discharge coefficient. Compared with the traditional single-orifice plate flange pressure tapping method, the angle-connected pressure tapping dual-orifice plate balanced flowmeter of the present invention significantly improves the stability of the discharge coefficient. Within the Reynolds number range of 2.0e+5 to 5.0e+5, the fluctuation is reduced from 6% to 0.55%. It is evident that the balanced flowmeter of the present invention exhibits more significant structural advantages, higher discharge coefficient stability, and higher measurement accuracy.

[0062] Example 4:

[0063] The pressure loss performance of the traditional single-orifice plate flange pressure tapping method and the double-orifice plate corner connection pressure tapping method of this invention is compared. Both flowmeters have the same orifice plate characteristics, consisting of a central hole and four evenly distributed peripheral holes, with an opening diameter of 4.5 mm; the outer diameter of the orifice plate is 25 mm; the thickness of the two orifice plates in this invention is 3 mm; the spacing between the two orifice plates is 3 mm; the openings on the two orifice plates of the double-orifice plate balanced flowmeter are aligned; the upstream straight pipe section length is 400 mm, and the downstream straight pipe section length is 500 mm. Subcooled liquid nitrogen is used as the working fluid, the pipe temperature is 77 K, the pipe wall is kept insulated, and the average Reynolds number at the pipe inlet is 2.0e+5 to 5.0e+5.

[0064] Traditional flange pressure tapping uses a 25.4mm distance from the upstream end face of the orifice plate as the high-pressure tapping position and a 25.4mm distance from the downstream end face as the low-pressure tapping position. This embodiment of the dual-orifice plate balanced flowmeter uses a pressure tapping position on the upstream wall of the upstream orifice plate (distance 0), meaning the high-pressure tapping position is located in the upstream cavity immediately adjacent to the upstream orifice plate. Similarly, a pressure tapping position is located on the downstream wall of the downstream orifice plate (distance 0), meaning the low-pressure tapping position is located in the downstream cavity immediately adjacent to the downstream end of the downstream orifice plate. The pressure loss coefficient of the angle-tap dual-orifice plate balanced flowmeter of this invention is numerically calculated.

[0065] The calculation results comparing the pressure loss of the two flow meters are as follows: Figure 6 As shown in the figure, the horizontal axis represents the Reynolds number, and the vertical axis represents the permanent pressure loss coefficient. Compared to the traditional single-orifice plate balanced flowmeter, the permanent pressure loss coefficient of the dual-orifice plate balanced flowmeter of this invention is significantly reduced, with the average permanent pressure loss coefficient decreasing from 68.94 to 59.91. Within the Reynolds number range of 2.0e+5 to 5.0e+5, compared to the traditional single-orifice plate balanced flowmeter, the pressure loss coefficient of the dual-orifice plate balanced flowmeter of this invention changes steadily and shows a decreasing trend.

[0066] In summary, the angle-connected pressure tapping dual-orifice plate balanced flowmeter provided by this invention accelerates the contraction and pressure recovery performance of the fluid through the use of two orifice plates. This ensures that the dramatic pressure drop and recovery occur between the two orifice plates. Simultaneously, the downstream orifice plate improves the vortex region downstream of the upstream orifice plate, reducing the permanent pressure loss of the fluid. The angle-connected pressure tapping method of the dual-orifice plate balanced flowmeter designed in this invention, which taps pressure on the walls of both the upstream and downstream orifice plates, maintains an almost constant discharge coefficient within the Reynolds number range of 2.0e+5 to 5.0e+5, and its pressure loss coefficient is significantly lower than that of traditional single-orifice plate flowmeters, significantly improving the overall performance of the flowmeter.

Claims

1. A double-orifice plate balanced flow meter with angle-connected pressure tapping, characterized in that, include: An upstream portion, an isolation ring, and a downstream portion; the upstream portion is connected to the downstream portion via the isolation ring. The isolation ring includes an outer intermediate isolation ring (7) and an inner intermediate isolation ring (8); the upstream portion and the downstream portion are symmetrical, the upstream portion includes an upstream sealing cavity (1), an upstream connecting pipe (3), an upstream perforated plate (5), a high-pressure tapping pipe (9), an upstream sealing flange (11), and an upstream cavity (13), the downstream portion includes a downstream sealing cavity (2), a downstream connecting pipe (4), a downstream perforated plate (6), a low-pressure tapping pipe (10), a downstream sealing flange (12), and a downstream cavity (14), which are symmetrical to the structures in the upstream portion; the upstream sealing cavity (1) and the downstream sealing cavity (2) are the same hollow structure, each containing an upstream cavity (11) and a downstream cavity (13). 3) and downstream cavity (14); the open side of the upstream sealing cavity (1) faces the upstream side of the upstream perforated plate (5); the open side of the downstream sealing cavity (2) faces the downstream side of the downstream perforated plate (6); the width of the wall surface of the upstream sealing cavity (1) flush with the inner surface of the upstream connecting pipe (3) is less than the width of the outer wall surface of the upstream sealing cavity (1), and the upstream cavity (13) is connected to the upstream connecting pipe (3); the width of the wall surface of the downstream sealing cavity (2) flush with the inner surface of the downstream connecting pipe (4) is less than the width of the outer wall surface of the downstream sealing cavity (2), and the downstream cavity (14) is connected to the downstream connecting pipe (4); the installation method of the angle-connected pressure tapping double perforated plate balanced flow meter includes: S1. Weld the high-pressure tapping pipe (9) and the low-pressure tapping pipe (10) to the outer wall surfaces of the upstream sealing cavity (1) and the downstream sealing cavity (2), respectively. S2. Weld the upstream perforated plate (5) and the downstream perforated plate (6) to the open sides of the upstream sealing cavity (1) and the downstream sealing cavity (2), respectively. S3. Weld the middle inner isolation ring (8) to the downstream side of the upstream perforated plate (5); S4. Weld the middle outer isolation ring (7) to the sides of the upstream perforated plate (5) and the downstream perforated plate (6) respectively; S5. Weld the upstream connecting pipe (3) to the upstream side wall of the upstream sealing cavity (1); weld the downstream connecting pipe (4) to the downstream side wall of the downstream sealing cavity (2).

2. The angle-connected pressure tapping dual-orifice plate balanced flowmeter according to claim 1, characterized in that, The upstream sealing cavity (1) and the downstream sealing cavity (2) are located on the upstream connecting pipe (3) and the downstream connecting pipe (4), respectively; the intermediate outer isolation ring (7) and the intermediate inner isolation ring (8) are located between the upstream perforated plate (5) and the downstream perforated plate (6); the high pressure tapping pipe (9) is connected to the circumferential surface of the upstream sealing cavity (1), and the low pressure tapping pipe (10) is connected to the circumferential surface of the downstream sealing cavity (2).

3. The angle-connected pressure tapping dual-orifice plate balanced flowmeter according to claim 2, characterized in that, The upstream sealing cavity (1), downstream sealing cavity (2), upstream perforated plate (5), downstream perforated plate (6) and intermediate outer isolation ring (7) have the same outer diameter; the outer surfaces of the upstream sealing cavity (1), upstream perforated plate (5), intermediate outer isolation ring (7), downstream perforated plate (6) and downstream sealing cavity (2) are flush and welded together in sequence.

4. The angle-connected pressure tapping dual-orifice plate balanced flowmeter according to claim 3, characterized in that, The upstream sealing cavity (1), the downstream sealing cavity (2), the intermediate inner isolation ring (8), the upstream connecting pipe (3), and the downstream connecting pipe (4) have the same inner diameter.

5. The angle-connected pressure tapping dual-orifice plate balanced flowmeter according to claim 1, characterized in that, The high-pressure tapping tube (9) and the low-pressure tapping tube (10) are on the same plane in the axial direction.

6. The angle-connected pressure tapping dual-orifice plate balanced flowmeter according to claim 1, characterized in that, Both the upstream perforated plate (5) and the downstream perforated plate (6) are disc structures. The disc structure has openings, including a central hole and equally spaced holes. The central hole is located at the center of the disc structure. There are 4 to 8 equally spaced holes around the central hole. The openings are located in the flow channels of the upstream connecting pipe (3) and the downstream connecting pipe (4). The openings of the upstream perforated plate (5) and the downstream perforated plate (6) are axially aligned. The axial distance between the upstream perforated plate (5) and the downstream perforated plate (6) is 6 to 12 mm.

7. The angle-connected pressure tapping dual-orifice plate balanced flowmeter according to claim 1, characterized in that, The upstream connecting pipe (3), upstream sealing cavity (1), upstream perforated plate (5), intermediate outer isolation ring (7), intermediate inner isolation ring (8), downstream perforated plate (6), downstream sealing cavity (2) and downstream connecting pipe (4) are arranged coaxially.

8. The angle-connected pressure tapping dual-orifice plate balanced flowmeter according to claim 1, characterized in that, The high-pressure tapping pipe (9) and the low-pressure tapping pipe (10) are connected to the pipeline system under test through the upstream sealing cavity (1) and the downstream sealing cavity (2), respectively.

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