Laminar flow meter

Abstract

The application discloses a laminar flow meter, which comprises a Venturi structure and a laminar flow element in sequence, and further comprises a differential pressure sensor provided with an upstream pressure tapping and a downstream pressure tapping at two ends respectively, wherein the upstream pressure tapping is connected with a throat of the Venturi structure, and the downstream pressure tapping is connected with an outlet of the laminar flow element; when fluid flows through the Venturi structure, the negative pressure generated by the throat is used to compensate for the quadratic linear pressure loss of the laminar flow element, so that the pressure loss and the flow of the laminar flow element are in an approximate linear relationship; under the limitation that the range of the differential pressure sensor is unchanged, the range of the laminar flow element can be increased only by relying on the pressure compensation of the Venturi structure, without the need of increasing the size of the laminar flow element, so that the profile size of the laminar flow meter can be reduced to a certain extent.

Description

Technical Field

[0001] This invention relates to the field of flow measurement technology, and in particular to a laminar flow meter. Background Technology

[0002] Laminar flow meters offer advantages such as no moving parts, wide rangeability, accurate measurement, and fast response, making them widely used in industries such as semiconductor manufacturing, automotive electronics, food processing, chemical and pharmaceutical manufacturing, and medical applications. Based on the Hagen-Poiseuille law, laminar flow meters consist of a laminar flow element and a differential pressure sensor. When fluid passes through the laminar flow element, the flow rate is calculated by establishing a linear relationship between the pressure drop of the laminar flow element and the flow rate, i.e., ΔP = K1 * Q. Here, ΔP is the pressure drop of the laminar flow element (i.e., the pressure difference across the flow element), K1 is the linear pressure drop coefficient, and Q is the flow rate of the laminar flow element.

[0003] In reality, due to manufacturing and assembly deviations, there are significant differences between individual laminar flow elements, making the coefficient K1 uncertain. Taking a laminar flow element formed by bundled capillary tubes as an example, within a specific flow range, the linear relationship between pressure loss and flow rate of the laminar flow element only holds true in a fully developed laminar flow stage. Furthermore, the kinetic energy loss of the fluid at the inlet and outlet of the laminar flow element and the flow resistance loss at the capillary inlet section are approximately quadratic linear. That is, the actual formula for the pressure loss and flow rate of the laminar flow element is ΔP = K1*Q + K2*Q. 2 Where ΔP is the pressure loss of the laminar flow element, K1 is the linear pressure loss coefficient, Q is the flow rate of the laminar flow element, and K2 is the quadratic linear pressure loss coefficient. The actual relationship between the pressure loss and flow rate of a laminar flow element is a superposition of linear and quadratic linear relationships. When the range of the differential pressure sensor is fixed, the existence of quadratic linear pressure loss will lead to a reduction in the flow measurement range and a decrease in accuracy at low flow rates.

[0004] To reduce the proportion of secondary linear pressure loss in laminar flow meters, existing methods include increasing the length and number of capillary tubes. However, this increases the size of the laminar flow elements, resulting in a larger overall size of the laminar flow meter. Therefore, how to reduce the secondary linear pressure loss of laminar flow meters while minimizing their overall size is a technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a laminar flow meter that uses the Venturi effect to compensate for the quadratic linear pressure loss of the laminar flow element so that its pressure loss and flow rate have an approximately linear relationship, thereby reducing the profile size of the laminar flow meter without increasing the size of the laminar flow element.

[0006] To achieve the above objectives, the present invention provides a laminar flow meter, comprising a Venturi structure and a laminar flow element connected in sequence, and a differential pressure sensor with an upstream pressure sampling port and a downstream pressure sampling port at both ends respectively. The upstream pressure sampling port is connected to the throat of the Venturi structure, and the downstream pressure sampling port is connected to the outlet of the laminar flow element. When the fluid flows through the Venturi structure, the negative pressure generated at the throat is used to compensate for the secondary linear pressure loss of the laminar flow element.

[0007] Preferably, the cross-sectional area of ​​the throat is smaller than the outlet cross-sectional area of ​​the laminar flow element.

[0008] Preferably, it further includes a first outer shell, which is a cylindrical shell. The center of the cylindrical shell is provided with a first venturi orifice and a first flow channel orifice that are coaxially connected. The inlet section, constriction section, throat and diffuser section of the first venturi orifice are coaxially connected in sequence to form a venturi structure, and the throat is the throat. The laminar flow element is specifically a capillary bundle, which is distributed in a concentric circle and fixed in the first flow channel orifice. The upstream pressure port and the downstream pressure port are both provided on the side wall of the cylindrical shell and both extend radially. The upstream pressure port is perpendicularly connected to the throat, and the downstream pressure port is perpendicularly connected to the end of the first flow channel orifice away from the first venturi orifice.

[0009] Preferably, it further includes a second outer shell, which is a rectangular shell. The rectangular shell includes an upper cover and a lower cover that interlock with each other. The upstream pressure port and the downstream pressure port are both disposed through the upper cover. A second Venturi groove and a second flow channel groove are formed in the lower cover along the flow direction. The upstream pressure port is perpendicularly connected to the second Venturi groove, and the downstream pressure port is perpendicularly connected to the second flow channel groove. The second Venturi groove and the lower side of the upper cover form a Venturi structure. Laminar flow elements are filled in the second flow channel groove. The laminar flow elements include several sets of laminar flow baffles stacked together. A rectangular flow channel is formed between any two adjacent laminar flow baffles. Each set of laminar flow baffles includes a laminar flow plate and two laminar flow blocks fixed on the same side of the laminar flow plate and located at both ends of the laminar flow plate.

[0010] Preferably, it further includes a third outer shell, which includes an upper shell and a lower shell that are interlocked and detachably connected. The upper shell is provided with a positioning groove, and the lower shell is provided with a positioning protrusion that cooperates with the positioning groove. The upstream pressure port and the downstream pressure port are both disposed through the upper shell. The laminar flow element is sleeved on the positioning protrusion. The laminar flow element includes several sets of stacked gasket assemblies, and an annular flow channel is formed between any two adjacent sets of gasket assemblies. Each set of gasket assemblies includes stacked layered gaskets and spacer gaskets, and the outer diameter of the spacer gasket is smaller than the outer diameter of the layered gaskets. The bottom of the lower shell has an air inlet and an air outlet. The lower shell has a third venturi groove and a third flow channel groove. The third venturi groove and the lower side of the upper shell surround to form a venturi structure. The inlet of the third venturi groove is connected to the air inlet, and the outlet of the third flow channel groove is connected to the air outlet. The third venturi groove is vertically connected to the upstream pressure port, and the third flow channel groove is vertically connected to the downstream pressure port.

[0011] Preferably, a sealing element is provided at the connection between the upper shell and the lower shell.

[0012] Preferably, it further includes a fourth outer shell, which is a plate shell. The plate shell includes a cap and a bottom cover that interlock with each other. The upstream pressure port and the downstream pressure port are both disposed through the cap. A fourth Venturi groove and a fourth flow channel groove are formed inside the bottom cover, which are connected along the length direction of the plate shell. The fourth Venturi groove and the lower side of the cap form a Venturi structure. The laminar flow element is linearly fixed in the fourth flow channel groove.

[0013] Preferably, the laminar flow element includes several parallel laminar flow combs integrally fixed in the fourth flow channel groove, and a laminar flow channel is formed between any two adjacent laminar flow combs; or, the laminar flow element includes several capillaries uniformly distributed linearly in the fourth flow channel groove.

[0014] Preferably, it further includes a fifth outer shell, within which a fifth venturi cavity is formed. At least one of the upper and lower sides of the fifth venturi cavity is provided with a trapezoidal protrusion, which extends along the width direction of the fifth outer shell to make the fifth venturi cavity a venturi structure. The fifth outer shell is also provided with a plurality of fifth laminar flow cavities, and thin-walled grids divide the fifth laminar flow cavities to form a laminar flow element. The fifth laminar flow cavities are connected to the fifth venturi cavity along the length direction of the fifth outer shell. The top of the fifth outer shell is provided with an upstream pressure port and a downstream pressure port, the upstream pressure port being located at the throat of the venturi structure and the downstream pressure port being located at the rear end of the laminar flow element.

[0015] Compared with the prior art, the laminar flow meter provided by the present invention includes a Venturi structure, a laminar flow element and a differential pressure sensor. The Venturi riser and the laminar flow element are connected in sequence. The throat of the Venturi structure is provided with an upstream pressure sampling port, and the outlet of the laminar flow element is provided with a downstream pressure sampling port. The two ends of the differential pressure sensor are respectively connected to the upstream pressure sampling port and the downstream pressure sampling port.

[0016] When fluid flows through the Venturi structure, the throat of the Venturi structure generates negative pressure according to the Venturi effect, reducing the static pressure value collected by the upstream pressure sampling port. This compensates for the secondary linear pressure loss of the laminar flow element, reduces the proportion of secondary linear pressure loss in the laminar flow meter, and makes the pressure loss and flow rate of the laminar flow element approximately linear. Under the limitation of the constant range of the differential pressure sensor, the range of the laminar flow element can be increased by relying solely on the pressure compensation of the Venturi structure, without increasing the size of the laminar flow element. This can reduce the profile size of the laminar flow meter to a certain extent. Attached Figure Description

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

[0018] Figure 1 This is a schematic diagram of the working principle of a laminar flow meter provided in a specific embodiment of the present invention;

[0019] Figure 2 This is a cross-sectional view of a laminar flow meter provided in the first specific embodiment of the present invention;

[0020] Figure 3 for Figure 1 Side view;

[0021] Figure 4 This is a top view of a laminar flow meter provided in a second specific embodiment of the present invention;

[0022] Figure 5 for Figure 4 Sectional view along line AA;

[0023] Figure 6 for Figure 4 Sectional view along the BB direction;

[0024] Figure 7 This is a top view of a laminar flow meter provided in a third specific embodiment of the present invention;

[0025] Figure 8 for Figure 7 C-axis sectional view;

[0026] Figure 9 A top view of the bottom cover of the laminar flow meter provided in the fourth specific embodiment of the present invention;

[0027] Figure 10 for Figure 9 Side view;

[0028] Figure 11 for Figure 9 Another view;

[0029] Figure 12 A top view of the bottom cover of the laminar flow meter provided in the fifth specific embodiment of the present invention;

[0030] Figure 13 for Figure 12 Sectional view along the DD direction;

[0031] Figure 14 for Figure 12Sectional view along the EE direction.

[0032] The attached figures are labeled as follows:

[0033] Venturi structure 1, first Venturi orifice 11, second Venturi groove 12, third Venturi groove 13, fourth Venturi groove 14, fifth Venturi cavity 15, laminar flow element 2, capillary bundle 21, laminar flow baffle 22, gasket assembly 23, layered gasket 231, spacer gasket 232, laminar flow comb 241, capillary 242, fifth laminar flow cavity 25, differential pressure sensor 3, upstream pressure sampling port 31, downstream pressure sampling port 32 First outer shell 41, first flow channel hole 411, second outer shell 42, upper cover 421, lower cover 422, second flow channel groove 423, third outer shell 43, upper shell 431, positioning groove 4311, lower shell 432, positioning protrusion 4321, air inlet 4322, air outlet 4323, third flow channel groove 433, seal 434, fourth outer shell 44, bottom cover 441, fourth flow channel groove 4411, and fifth outer shell 45. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] This invention discloses a laminar flow meter, as shown in the attached figure. Figure 1 As shown, the device includes a Venturi structure 1, a laminar flow element 2, and a differential pressure sensor 3. The Venturi structure 1 and the laminar flow element 2 are connected sequentially. Fluid flows into the laminar flow element 2 through the Venturi structure 1, resulting in laminar flow within the laminar flow element 2. The differential pressure sensor 3 has an upstream pressure sampling port 31 and a downstream pressure sampling port 32 at its two ends. The upstream pressure sampling port 31 is connected to the throat of the Venturi structure 1, and the downstream pressure sampling port 32 is connected to the outlet of the laminar flow element 2. The structure and working principle of the differential pressure sensor 3 can be found in existing technologies and will not be described in detail here.

[0037] When fluid flows through the Venturi structure 1, the throat of the Venturi structure 1 generates negative pressure according to the Venturi effect, providing negative feedback to the upstream pressure sampling port 31, reducing the static pressure value collected by the upstream pressure sampling port 31, thereby compensating for the secondary linear pressure loss of the laminar flow element 2, reducing the proportion of the secondary linear pressure loss of the laminar flow meter, and making the pressure loss and flow rate of the laminar flow element 2 approximately linear. Furthermore, reducing the cross-sectional area of ​​the throat of the Venturi structure 1 to increase the negative pressure generated by the Venturi effect can make the pressure difference and flow rate of the laminar flow element 2 exhibit the characteristics of large pressure difference with flow rate in the small flow range and small pressure difference with flow rate in the large flow range. Under the limitation of the unchanged range of the differential pressure sensor 3, pressure compensation only needs to rely on the Venturi structure 1 to improve the measurement accuracy in the small flow range and increase the range of the laminar flow element 2 without increasing the size of the laminar flow element 2, which can reduce the profile size of the laminar flow meter to a certain extent.

[0038] The cross-sectional area of ​​the throat is smaller than the cross-sectional area of ​​the outlet of the laminar flow element 2. After adding the Venturi structure 1, the pressure loss and flow rate of the laminar flow element 2 can be linearly related, which can improve the range of the laminar flow meter.

[0039] In the first specific embodiment, as shown in the appendix Figure 2 and 3 As shown, the laminar flow meter also includes a first outer shell 41, which is a cylindrical shell. A first Venturi orifice 11 and a first flow channel orifice 411 are coaxially connected at the center of the cylindrical shell, meaning their central axes coincide. The first Venturi orifice 11 is a stepped orifice. The inlet section, constriction section, throat, and diffuser section of the first Venturi orifice 11 are coaxially connected to form a Venturi structure 1, with the throat being the throat portion. The inlet section and throat are both cylindrical orifices, while the constriction section and diffuser section are both conical orifices. The first flow channel orifice 411 is a cylindrical orifice. The laminar flow element 2 is specifically a capillary bundle 21, which is concentrically distributed and fixed within the first flow channel orifice 411. Of course, the capillary bundle 21 can also be replaced by a grid, hexagonal honeycomb core, pore array, sintered powder filter element, etc., and is not specifically limited here.

[0040] Both the upstream pressure-collecting port 31 and the downstream pressure-collecting port 32 are located on the sidewall of the cylindrical shell, and both extend radially. The upstream pressure-collecting port 31 is perpendicularly connected to the throat, and the downstream pressure-collecting port 32 is perpendicularly connected to the end of the first flow channel orifice 411 away from the first venturi orifice 11. It should be noted that the downstream pressure-collecting port 32 is located downstream of the outlet of the laminar flow element 2. The upstream pressure-collecting port 31 and the downstream pressure-collecting port 32 are linearly distributed along the axial direction of the cylindrical shell.

[0041] Compared to the first embodiment, the second embodiment changes the structure of the outer shell, while the rest of the technical solutions are the same as the first embodiment.

[0042] In the second specific embodiment, as shown in the appendix Figures 4 to 6 As shown, the laminar flow meter also includes a second housing 42, which is a rectangular shell. The rectangular shell includes an upper cover 421 and a lower cover 422 that are interlocked. The upstream pressure port 31 and the downstream pressure port 32 are both provided through the upper cover 421.

[0043] A second Venturi channel 12 and a second flow channel 423 are formed within the lower cover 422, and the two are connected along the flow direction. The second Venturi channel 12 and the lower side of the upper cover 421 form a Venturi structure 1. The second Venturi channel 12 consists of an inlet section, a contraction section, a throat, and a diffuser section, with the throat being the throat portion. The inlet section and throat are both rectangular channels with a constant width, while the contraction section and diffuser section are both trapezoidal channels with gradually changing widths. The second flow channel 423 is a rectangular channel, and its width is equal to the width of the larger end of the diffuser section of the second Venturi channel 12. The second Venturi channel 12 is perpendicularly connected to the upstream pressure port 31, and the second flow channel 423 is perpendicularly connected to the downstream pressure port 32.

[0044] The laminar flow element 2 fills the second flow channel groove 423. The width of the laminar flow element 2 is equal to the width of the second flow channel groove 423, and the length of the laminar flow element 2 is less than the length of the second flow channel groove 423. The laminar flow element 2 includes several sets of stacked laminar flow baffles 22. A rectangular flow channel is formed between any two adjacent laminar flow baffles 22, so that the fluid is in a laminar flow state within the entire rectangular flow channel. Each set of laminar flow baffles 22 includes a laminar flow plate and two laminar flow blocks fixed on the same side of the laminar flow plate and located at both ends of the laminar flow plate. The laminar flow plate and the two laminar flow baffles form a U-shaped groove. Of course, the structure of each set of laminar flow baffles 22 is not limited to this.

[0045] Compared to the first embodiment, the third embodiment changes the structure of the outer shell, while the rest of the technical solutions are the same as the first embodiment.

[0046] In the third specific embodiment, as shown in the appendix Figure 7 and 8 As shown, the laminar flow meter also includes a third housing 43, which is a split design. The third housing 43 includes an upper housing 431 and a lower housing 432 that are interlocked and detachably connected. The upper housing 431 has a positioning groove 4311, and the lower housing 432 has a positioning protrusion 4321 that mates with the positioning groove 4311, facilitating quick installation of the upper and lower housings 431 and 432. A connecting bolt for connecting the upper housing 431 and the lower housing 432 passes between the positioning groove 4311 and the positioning protrusion 4321. The connecting bolt is equipped with a lock nut, enabling a detachable connection between the upper housing 431 and the lower housing 432 for easy assembly and disassembly. Of course, the connection method between the upper housing 431 and the lower housing 432 is not limited to this.

[0047] The laminar flow element 2 is sleeved on the positioning protrusion 4321. The laminar flow element 2 includes several sets of stacked gasket assemblies 23. An annular flow channel is formed between any two adjacent sets of gasket assemblies 23, so that the fluid is in a laminar flow state within the entire annular flow channel. Each set of gasket assemblies 23 includes stacked layered gaskets 231 and spacer gaskets 232. Both the layered gaskets 231 and the spacer gaskets 232 are annular, and the outer diameter of the spacer gasket 232 is smaller than the outer diameter of the layered gaskets 231. Of course, the layered gaskets 231 and the spacer gaskets 232 are not limited to annular shapes, but can be rectangular, etc., and are not specifically limited here.

[0048] The bottom of the lower shell 432 has an air inlet 4322 and an air outlet 4323. The lower shell 432 has a third venturi groove 13 and a third flow channel groove 433. The third venturi groove 13 and the lower side of the upper shell 431 form a venturi structure 1. The inlet of the third venturi groove 13 is connected to the air inlet 4322, and the outlet of the third flow channel groove 433 is connected to the air outlet 4323.

[0049] Both the upstream pressure port 31 and the downstream pressure port 32 are installed through the upper shell 431. The upstream pressure port 31 is vertically connected to the third venturi groove 13, and the downstream pressure port 32 is vertically connected to the third flow channel groove 433.

[0050] A sealing element 434 is provided at the connection between the upper shell 431 and the lower shell 432 to seal the gap between the upper shell 431 and the lower shell 432, so that the third shell 43 has good sealing performance. Specifically, the upper shell 431 is provided with an annular groove, and the sealing element 434 is specifically a rubber sealing ring installed in the annular groove, but is not limited to this.

[0051] Compared to the first embodiment, the fourth embodiment changes the structure of the outer shell, while the rest of the technical solutions are the same as the first embodiment.

[0052] In the fourth specific embodiment, as shown in the appendix Figures 9 to 11 As shown, the laminar flow meter also includes a fourth housing 44, which is a plate shell with a relatively thin thickness and an overall plate shape. The plate shell includes a cap and a bottom cover 441 that interlock. The bottom cover 441 has a fourth Venturi groove 14 and a fourth flow channel groove 4411 that are connected along the length of the plate shell. The fourth Venturi groove 14 and the lower side of the cap form a Venturi structure 1. The laminar flow element 2 is linearly fixed in the fourth flow channel groove 4411. The upstream pressure port 31 and the downstream pressure port 32 are both provided through the cap. The upstream pressure port 31 is perpendicularly connected to the throat of the fourth Venturi groove 14, and the downstream pressure port 32 is perpendicularly connected to the fourth flow channel groove 4411. In the fourth specific embodiment, it is preferable that the fourth housing 44 has only one layer of laminar flow element 2.

[0053] The laminar flow element 2 includes several parallel laminar flow combs 241, all of which are integrally fixed in the fourth flow channel 4411. A laminar flow channel is formed between any two adjacent laminar flow combs 241, so that the fluid is in a laminar flow state within the laminar flow channel. Of course, the structure of the laminar flow element 2 is not limited to this. The laminar flow element 2 can also achieve the purpose of the present invention by including several capillary tubes 242 that are linearly and uniformly distributed in the fourth flow channel 4411.

[0054] Compared to the first embodiment, the fifth embodiment changes the structure of the outer shell, while the rest of the technical solutions are the same as the first embodiment.

[0055] In the fifth specific embodiment, as shown in the appendix Figures 12 to 14 As shown, the laminar flow meter further includes a fifth housing 45, within which a plate-shaped cavity is formed. A fifth Venturi cavity 15 is provided within the plate-shaped cavity. At least one of the upper and lower sides of the fifth Venturi cavity 15 has a trapezoidal protrusion extending along the width direction of the fifth housing 45, thus making the fifth Venturi cavity 15 a Venturi structure 1. Preferably, the trapezoidal protrusion is integrally formed at the bottom of the fifth Venturi cavity 15.

[0056] The fifth outer shell 45 is also provided with several fifth laminar flow cavities 25. The thin-walled grid divides the fifth laminar flow cavities 25 to form the laminar flow element 2. The fifth laminar flow cavities 25 are connected to the fifth venturi cavity 15 along the length of the fifth outer shell 45. The top of the fifth outer shell 45 is provided with an upstream pressure port 31 and a downstream pressure port 32. The upstream pressure port 31 is located at the throat of the venturi structure 1, and the downstream pressure port 32 is located at the rear end of the laminar flow element 2.

[0057] Of course, the structure of the laminar flow meter is not limited to the five specific embodiments mentioned above, and can be replaced by other similar structures, which are not specifically limited here.

[0058] It should be noted that in this specification, relational terms such as first and second are used only to distinguish one entity from several other entities, and do not necessarily require or imply any such actual relationship or order between these entities.

[0059] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A laminar flow meter, characterized in that, It includes a Venturi structure (1) and a laminar flow element (2) connected in sequence, and also includes a differential pressure sensor (3) with an upstream pressure sampling port (31) and a downstream pressure sampling port (32) at both ends respectively. The upstream pressure sampling port (31) is connected to the throat of the Venturi structure (1), and the downstream pressure sampling port (32) is connected to the outlet of the laminar flow element (2). When the fluid flows through the Venturi structure (1), the negative pressure generated at the throat is used to compensate for the quadratic linear pressure loss of the laminar flow element (2).

2. The laminar flow meter according to claim 1, characterized in that, The cross-sectional area of ​​the throat is smaller than the outlet cross-sectional area of ​​the laminar flow element (2).

3. The laminar flow meter according to claim 1, characterized in that, It also includes a first outer shell (41), which is a cylindrical shell. The center of the cylindrical shell is provided with a first Venturi hole (11) and a first flow channel hole (411) that are coaxially connected. The inlet section, constriction section, throat and diffusion section of the first Venturi hole (11) are coaxially connected in sequence to form the Venturi structure (1). The throat is the throat. The laminar flow element (2) is specifically a capillary bundle (21). The capillary bundle (21) is distributed in a concentric circle. The capillary bundle (21) is fixed in the first flow channel hole (411). The upstream pressure port (31) and the downstream pressure port (32) are both provided on the side wall of the cylindrical shell and both extend radially. The upstream pressure port (31) is perpendicularly connected to the throat. The downstream pressure port (32) is perpendicularly connected to the end of the first flow channel hole (411) away from the first Venturi hole (11).

4. The laminar flow meter according to claim 1, characterized in that, It also includes a second outer shell (42), which is a rectangular shell. The rectangular shell includes an upper cover (421) and a lower cover (422) that interlock with each other. The upstream pressure port (31) and the downstream pressure port (32) are both disposed through the upper cover (421). The lower cover (422) forms a second Venturi groove (12) and a second flow channel groove (423) along the flow direction. The upstream pressure port (31) is perpendicularly connected to the second Venturi groove (12), and the downstream pressure port (32) is connected to the second flow channel groove. (423) is vertically connected; the second Venturi groove (12) and the lower side of the upper cover (421) form the Venturi structure (1); the laminar flow element (2) is filled in the second flow channel groove (423), the laminar flow element (2) includes several sets of stacked laminar flow baffles (22), and a rectangular flow channel is formed between any two adjacent laminar flow baffles (22); each set of laminar flow baffles (22) includes a laminar flow plate and two laminar flow blocks fixed on the same side of the laminar flow plate and located at both ends of the laminar flow plate respectively.

5. The laminar flow meter according to claim 1, characterized in that, It also includes a third outer shell (43), which includes an upper shell (431) and a lower shell (432) that are interlocked and detachably connected. The upper shell (431) is provided with a positioning groove (4311), and the lower shell (432) is provided with a positioning protrusion (4321) that cooperates with the positioning groove (4311). The upstream pressure port (31) and the downstream pressure port (32) are both provided through the upper shell (431). The laminar flow element (2) is sleeved on the positioning protrusion (4321). The laminar flow element (2) includes several sets of stacked gasket assemblies (23), and an annular flow channel is formed between any two adjacent sets of gasket assemblies (23). Each set of gasket assemblies (23) includes stacked layered gaskets (231) and spacer gaskets (231). 232), the outer diameter of the spacer (232) is smaller than the outer diameter of the layered spacer (231); the bottom of the lower shell (432) is formed with an air inlet (4322) and an air outlet (4323), the lower shell (432) is formed with a third Venturi groove (13) and a third flow channel groove (433), the third Venturi groove (13) and the lower side of the upper shell (431) surround to form the Venturi structure (1), the inlet of the third Venturi groove (13) is connected to the air inlet (4322), the outlet of the third flow channel groove (433) is connected to the air outlet (4323); the third Venturi groove (13) is vertically connected to the upstream pressure port (31), and the third flow channel groove (433) is vertically connected to the downstream pressure port (32).

6. The laminar flow meter according to claim 5, characterized in that, A sealing element (434) is provided at the connection between the upper shell (431) and the lower shell (432).

7. The laminar flow meter according to claim 1, characterized in that, It also includes a fourth outer shell (44), which is a plate shell. The plate shell includes a cap and a bottom cover (441) that are interlocked. The upstream pressure port (31) and the downstream pressure port (32) are both disposed through the cap. A fourth Venturi groove (14) and a fourth flow channel groove (4411) that are connected along the length direction of the plate shell are formed in the bottom cover (441). The fourth Venturi groove (14) and the lower side of the cap form the Venturi structure (1). The laminar flow element (2) is linearly fixed in the fourth flow channel groove (4411).

8. The laminar flow meter according to claim 7, characterized in that, The laminar flow element (2) includes several parallel laminar flow combs (241) integrally fixed in the fourth flow channel groove (4411), and a laminar flow channel is formed between any two adjacent laminar flow combs (241); or, the laminar flow element (2) includes several capillaries (242) uniformly distributed linearly in the fourth flow channel groove (4411).

9. The laminar flow meter according to claim 1, characterized in that, It also includes a fifth outer shell (45), in which a fifth venturi cavity (15) is formed. At least one of the upper and lower sides of the fifth venturi cavity (15) is provided with a trapezoidal protrusion. The trapezoidal protrusion extends along the width direction of the fifth outer shell (45) so that the fifth venturi cavity (15) becomes the venturi structure (1). The fifth outer shell (45) is also provided with a plurality of fifth laminar flow cavities (25). The thin-walled grid divides the fifth laminar flow cavities (25) to form the laminar flow element (2). The fifth laminar flow cavities (25) are connected to the fifth venturi cavity (15) along the length direction of the fifth outer shell (45). The top of the fifth outer shell (45) is provided with the upstream pressure port (31) and the downstream pressure port (32). The upstream pressure port (31) is located at the throat of the venturi structure (1), and the downstream pressure port (32) is located at the rear end of the laminar flow element (2).

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