Thermal Mass Flow Meter

Abstract

The present disclosure provides a thermal mass flowmeter, which relates to the field of flow measurement technology. The thermal mass flowmeter includes: a plug rod, the first end of the plug rod is arranged in the target tube body; a protective flow channel, which is arranged in the first end of the plug rod; wherein the protective flow channel includes a main flow channel and a bypass flow channel, the bypass flow channel is arranged on the side of the main flow channel close to the first end of the plug rod, and the bypass flow channel includes a measuring device, and the measuring device is used to measure the fluid flow of the target tube body. Its structure is simple, and the protective flow channel can penetrate into the interior of the target tube body through the plug rod and directly contact the mainstream fluid, so that the physical properties of the fluid in the protective flow channel are consistent with those of the fluid in the pipeline; at the same time, the measuring device is arranged in the bypass flow channel, and the flow field in the bypass flow channel is evenly distributed, so that the measurement stability is improved, and at the same time, it is ensured that the measuring device is not easily contaminated or damaged by the impurities in the mainstream fluid.

Description

Technical Field

[0001] The present disclosure relates to the technical field of flow measurement, and in particular to a thermal mass flowmeter. Background Art

[0002] A thermal mass flow meter is a flow meter that can measure the mass flow rate of a fluid, and generally includes two types: a capillary thermal mass flow meter and a full-bore thermal mass flow meter.

[0003] Capillary thermal mass flowmeter is a bypass flowmeter. It measures the flow of the bypass channel through the detection element, and then obtains the fluid flow of the entire flow section according to the flow splitting relationship between the main channel and the bypass channel. However, capillary thermal mass flowmeter has many structural parts, complex design, difficult on-site installation and maintenance, and high cost.

[0004] Full-bore thermal mass flowmeters are usually insertion flowmeters, whose detection elements are directly mounted on the insertion rod, one end of which is inserted into the target pipe body through the pipe wall to directly detect the flow rate or flow of the fluid therein. However, the detection element of the full-bore thermal mass flowmeter is directly in contact with the mainstream fluid in the target pipe body, and is easily contaminated or damaged by dust particles, oil mist, etc. in the mainstream fluid. Summary of the invention

[0005] In view of this, an embodiment of the present disclosure provides a thermal mass flowmeter to solve the problems in the related art that the detection element of the thermal mass flowmeter is easily contaminated, the measurement stability is poor, and the main and bypass fluid medium characteristics are inconsistent.

[0006] In a first aspect, an embodiment of the present disclosure provides a thermal mass flowmeter, comprising: an insertion rod, the first end of the insertion rod is arranged in a target tube body; a protective flow channel, arranged at the first end of the insertion rod; wherein the protective flow channel comprises a main flow channel and a bypass flow channel, the bypass flow channel is arranged on a side of the main flow channel close to the first end of the insertion rod, and the bypass flow channel comprises a measuring device, and the measuring device is used to measure the fluid flow of the target tube body.

[0007] In combination with the first aspect, in certain implementations of the first aspect, the side wall of the main channel includes a first opening and a second opening, and the first opening and the second opening are arranged in sequence along the flow direction of the fluid in the target tube body; the protective channel also includes a bypass channel inlet channel and a bypass channel outlet channel; wherein the first opening is connected to the first end of the bypass channel inlet channel, the second end of the bypass channel inlet channel is connected to the first end of the bypass channel, the second end of the bypass channel is connected to the first end of the bypass channel outlet channel, and the second end of the bypass channel outlet channel is connected to the second opening.

[0008] In combination with the first aspect, in certain implementations of the first aspect, a sealing ring is provided at the connection between the second end of the bypass flow channel inlet flow channel and the first end of the bypass flow channel, and a sealing ring is provided at the connection between the second end of the bypass flow channel and the bypass flow channel outlet flow channel.

[0009] In combination with the first aspect, in some implementations of the first aspect, the shapes of the first opening and the second opening include a circle or a rectangle.

[0010] In combination with the first aspect, in certain implementations of the first aspect, the protective flow channel also includes a substrate and a bypass flow channel packaging structure, and the first surface of the substrate and the first surface of the bypass flow channel packaging structure are arranged opposite to each other and constitute a bypass flow channel; wherein the measuring device is arranged on the first surface of the substrate, and the center of the first surface of the bypass flow channel packaging structure protrudes upward to form a Venturi-type flow channel.

[0011] In combination with the first aspect, in certain implementations of the first aspect, the angle of the contraction section of the Venturi-type flow channel is not higher than 30 degrees, and the angle of the diffusion section of the Venturi-type flow channel is not higher than 30 degrees.

[0012] In combination with the first aspect, in certain implementations of the first aspect, the contraction section angle of the Venturi-type flow channel is not higher than 14 degrees, and the diffusion section angle of the Venturi-type flow channel is not higher than 14 degrees.

[0013] In combination with the first aspect, in certain implementations of the first aspect, the main flow channel includes one of a straight-through flow channel, a Venturi flow channel, and an orifice flow channel.

[0014] In combination with the first aspect, in certain implementations of the first aspect, the equivalent diameter of the bypass flow channel is determined based on a maximum measured flow rate of the measuring device and physical properties of the fluid inside the target pipe body.

[0015] In combination with the first aspect, in certain implementations of the first aspect, the equivalent length of the bypass flow channel is 2 / 5 to 4 / 5 of the diameter of the protection flow channel.

[0016] In combination with the first aspect, in certain implementations of the first aspect, a length of the protective flow channel in the axial direction is not greater than a diameter length of the insertion rod.

[0017] In the thermal mass flowmeter provided in the present invention, its protective flow channel can penetrate deep into the target pipe body through an insertion rod and directly contact the mainstream fluid, so that the physical properties of the fluid in the protective flow channel are consistent with the fluid in the pipeline; at the same time, the measuring device is arranged inside the bypass flow channel of the protective flow channel, and the flow field in the bypass flow channel is evenly distributed, so that the measurement stability is improved, and at the same time it is ensured that the measuring device is not easily contaminated by impurities in the mainstream fluid or damaged by impact. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1Shown is a schematic diagram of an application scenario of a thermal mass flow meter provided by an exemplary embodiment of the present disclosure.

[0019] Figure 2 Shown is a schematic structural diagram of a thermal mass flowmeter provided by an exemplary embodiment of the present disclosure.

[0020] Figure 3 Shown is a schematic structural diagram of a protection flow channel provided by an exemplary embodiment of the present disclosure.

[0021] Figure 4a Shown is a schematic structural diagram of a bypass flow channel provided by an exemplary embodiment of the present disclosure.

[0022] Figure 4b Shown is a schematic structural diagram of a bypass flow channel provided by yet another exemplary embodiment of the present disclosure.

[0023] Figure 5a to Figure 5d Shown are schematic structural diagrams of a main flow channel provided by an exemplary embodiment of the present disclosure.

[0024] Reference numerals:

[0025] 110-thermal mass flowmeter; 120-target tube body; 310-main channel; 311-first opening; 312-second opening; 320-bypass channel; 321-measuring device; 322-substrate; 323-bypass channel packaging structure; 330-bypass channel inlet channel; 340-bypass channel outlet channel; 350-sealing ring. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0027] Thermal mass flow meters can be used in a variety of scenarios. For example, in industrial production processes, thermal mass flow meters can be used to measure the flow of reactants, catalysts, raw materials and other substances to ensure the stability and efficiency of the production process; or thermal mass flow meters can be used in natural gas pipelines to measure the flow of natural gas in natural gas pipelines.

[0028] As described above, common thermal mass flow meters generally include capillary thermal mass flow meters and full-bore thermal mass flow meters.

[0029] As a bypass flowmeter, the capillary thermal mass flowmeter is mainly composed of a meter body as the main flow channel, a bypass flow channel for installing the detection element, and a throttling component. Since the detection element is installed in a relatively ideal bypass environment, the sensor is not easily contaminated and is protected from damage by the impact of particles. The flow field distribution in the flow channel is controllable, and the measurement stability is relatively high. However, due to the large number of structural parts and the complex design, on-site installation and maintenance are difficult and the cost is high. In addition, since the bypass flow channel is installed close to the pipe wall, the fluid flowing inside it is mainly the fluid adjacent to the inner wall of the pipe. The medium temperature and physical properties are easily affected by the external ambient temperature, which makes the fluid temperature and physical properties different from the mainstream fluid, thereby causing additional measurement deviations.

[0030] As an insertion flowmeter, the full-bore thermal mass flowmeter is mainly composed of a detection rod inserted into the pipe. The detection element is usually installed at the end of the rod, which can directly sense the fluid temperature and physical properties of the mainstream fluid in the pipe. It has a simple structure, is easy to install and maintain, and has a low cost. However, since the detection element is in direct contact with the mainstream fluid in the pipe, it is easily contaminated or damaged by dust particles, oil mist, etc. in the mainstream fluid, which can cause irreversible measurement deviations; and because the detection elements are in the mainstream flow channel, the fluctuations and turbulence of the fluid have a great impact on the detection elements, and the measurement stability is relatively poor. It can usually only be used in applications where the measurement accuracy requirements are not high.

[0031] In view of the above technical problems, the present disclosure provides a thermal mass flowmeter. The thermal mass flowmeter disclosed in the present disclosure includes an insertion rod and a protective flow channel. Among them, the protective flow channel can penetrate into the interior of the target pipe body through the insertion rod and directly contact the mainstream fluid, so that the physical properties of the fluid in the protective flow channel are consistent with the fluid in the pipeline. The measuring device is arranged inside the bypass flow channel of the protective flow channel, and the flow field in the bypass flow channel is evenly distributed, so that the measurement stability is improved, and at the same time, it is ensured that the measuring device is not easily contaminated or damaged by impurities in the mainstream fluid.

[0032] Figure 1 FIG. 1 is a schematic diagram of an application scenario of a thermal mass flow meter provided by an exemplary embodiment of the present disclosure. Figure 1 As shown, the implementation environment includes a thermal mass flow meter 110 and a target tube 120 .

[0033] The thermal mass flowmeter 110 can be inserted into the target tube 120 to measure the flow rate of the fluid inside the target tube 120. The target tube 120 can be a pipeline, a flow meter tube, or any container containing the fluid to be measured. The arrow direction in the figure indicates the flow direction of the mainstream fluid in the target tube 120.

[0034] When it is necessary to measure the fluid flow rate inside the target tube body 120, the thermal mass flowmeter 110 can be directly installed on the target tube body 120 through the cutout on the tube wall of the target tube body 120 to complete the measurement; after the measurement is completed, the thermal mass flowmeter 110 can also be easily disassembled. Therefore, the thermal mass flowmeter in the embodiment of the present disclosure is relatively easy to install and maintain and easy to use.

[0035] Furthermore, the thermal mass flowmeter 110 can be inserted into the interior of the target tube body 120 through the hole-shaped cutout on the tube wall of the target tube body 120, so that the measuring device in the thermal mass flowmeter 110 is located in the middle of the target tube body 120. The fluid in the target tube body 120 flows from the upstream direction of the measuring device to the downstream direction of the measuring device, and in this process the measuring device can measure the flow rate of the fluid in the middle of the target tube body 120. Therefore, the result measured by the thermal mass flowmeter in the embodiment of the present disclosure is consistent with the mainstream fluid in the target tube body, thereby improving the accuracy of the measurement result.

[0036] The thermal mass flowmeter provided by the embodiments of the present disclosure is described below with reference to the accompanying drawings.

[0037] Figure 2 FIG. 1 is a schematic diagram of the structure of a thermal mass flow meter provided by an exemplary embodiment of the present disclosure. Figure 2 As shown, the thermal mass flow meter includes an insertion rod 210 , a protection channel 220 and a meter head 230 . The protection channel 220 is disposed at a first end of the insertion rod 210 , and the meter head 230 is disposed at a second end of the protection channel 220 .

[0038] During the actual measurement process, the protective channel 220 and part of the insertion rod 210 are inserted into the target tube body, and the measuring device arranged in the protective channel 220 can measure the fluid flow of the target tube body; the header 230 is located outside the target tube body, and the header 230 includes an output device, which can present the measurement result of the fluid flow in the target tube body.

[0039] Reference below Figure 3 The specific structure of the protection flow channel provided in this embodiment is introduced in detail.

[0040] Figure 3 FIG. 1 is a schematic diagram of the structure of a protective flow channel provided by an exemplary embodiment of the present disclosure. Figure 3 As shown, the protection channel includes a main channel 310 and a bypass channel 320. The bypass channel 320 is arranged in parallel with the main channel 310. More specifically, the bypass channel 320 is arranged on one side of the main channel 310 close to the first end of the insertion rod.

[0041] The side wall of the main channel 310 includes a first opening and a second opening arranged in sequence along the fluid flow direction. The fluid in the target tube body flows from the first end of the main channel 310 to the second end; in this process, the fluid enters the first end of the bypass channel 320 through the first opening on the wall of the main channel 310, flows out from the second end of the bypass channel 320, and enters the main channel 310 again through the second opening.

[0042] A measuring device 321 is provided inside the bypass channel 320. The measuring device 321 may be a device capable of measuring fluid flow, such as a MEMS (Micro-Electro-Mechanical System) flow sensor. Since impurities such as particles carried by the fluid in the target tube body are not easy to enter the bypass channel 320, the measuring device 321 installed in the bypass channel 320 is not easy to be contaminated and is not easy to be damaged by the impact of impurities.

[0043] The bypass channel 320 may be in a regular shape, such as a cuboid, a cylinder, etc. The flow channel structure with a consistent structure can provide sufficient flow field development space for the upstream flow channel of the measuring device 321. When the fluid flows through the measuring device 321, the fluid is fully developed and the flow field is uniform, which is conducive to improving the measurement stability of the measuring device 321.

[0044] In some embodiments, the protection channel further includes a bypass channel inlet channel and a bypass channel outlet channel. Figure 3 The first end of the bypass channel inlet channel 330 is connected to the first opening of the main channel 310, and the second end of the bypass channel inlet channel 330 is connected to the first end of the bypass channel 320; the first end of the bypass channel outlet channel 340 is connected to the second end of the bypass channel 320, and the second end of the bypass channel outlet channel 340 is connected to the second opening of the main channel 310.

[0045] The fluid upstream of the main channel 310 enters the bypass channel inlet channel 330 from the first opening, flows through the bypass channel inlet channel 330, and enters the bypass channel 320 through the second end of the bypass channel inlet channel 330; the fluid flows through the bypass channel 320, and enters the bypass channel outlet channel 340 through the second end of the bypass channel 320. During this process, the measuring device 321 in the bypass channel 320 can detect the flow rate of the fluid flowing through the bypass channel 320. Based on the diversion relationship between the main channel 310 and the bypass channel 320, the fluid flow rate in the target pipe body can be further calculated; then, the fluid flows through the bypass channel outlet channel 340, and enters the main channel 310 again through the second end of the bypass channel outlet channel 340.

[0046] In the embodiment of the present disclosure, the bypass flow channel inlet flow channel and the bypass flow channel outlet flow channel can realize the diversion and confluence of the fluid in the main channel. At the same time, due to the effect of the bypass flow channel inlet flow channel, impurities and other pollutants carried by the fluid in the main channel can be further reduced from entering the bypass flow channel, thereby preventing them from causing pollution or damage to the measuring device.

[0047] In some embodiments, continue to refer to Figure 3 A sealing ring 350 is provided at the connection between the second end of the bypass flow channel inlet flow channel 330 and the first end of the bypass flow channel 320 , and a sealing ring 350 is provided at the connection between the second end of the bypass flow channel 320 and the bypass flow channel outlet flow channel 340 .

[0048] In the disclosed embodiment, the sealing ring can ensure the fluid sealing in the bypass flow channel, thereby effectively preventing the fluid from leaking from the interface into the interior of the plug rod and causing contamination or corrosion to the drive circuit of the measuring device. At the same time, the sealing ring is elastic and soft, which can alleviate the vibration and impact of the fluid on the bypass flow channel, thereby improving the stability of the connection.

[0049] Exemplarily, the sealing ring is an O-ring. The O-ring can achieve the effect of radial sealing at the connection: the O-ring can slide up and down, making the installation of the bypass channel 320 more flexible, reducing the machining accuracy requirements for the mechanical structure of the bypass channel 320 and the bypass channel inlet channel 330 and the bypass channel outlet channel 340, and avoiding stress deformation or damage to the microchannel structure due to the mutual extrusion of structural parts.

[0050] In some embodiments, the bypass channel is composed of a substrate and a bypass channel packaging structure. Figure 3 The substrate 322 includes a first surface and a second surface, the first surface of the substrate 322 faces the main flow channel 310, and the second surface of the substrate 322 faces the first end of the plug. Similarly, the bypass flow channel packaging structure 323 includes a first surface and a second surface, the first surface of the bypass flow channel packaging structure 323 faces the first end of the plug and is arranged opposite to the first surface of the substrate 322, and the second surface of the bypass flow channel packaging structure 323 faces the main flow channel 310.

[0051] Thus, the first surface of the substrate 322 and the first surface of the bypass channel packaging structure 323 together form the bypass channel 320 . The measuring device 321 is disposed on the first surface of the substrate 322 to measure the fluid flow in the bypass channel 320 .

[0052] Figure 4a FIG. 1 is a schematic diagram of the structure of a bypass flow channel provided by an exemplary embodiment of the present disclosure. Figure 4aAs shown, the first surface of the substrate 322 and the first surface of the bypass channel packaging structure 323 can be a flat regular plane. In this way, a bypass channel of a regular shape, such as a cuboid, a cylinder, etc., can be formed. The arrow direction in the figure indicates the flow direction of the fluid.

[0053] Figure 4b FIG. 2 is a schematic diagram of the structure of a bypass flow channel provided by another exemplary embodiment of the present disclosure. Figure 4b As shown, the center of the first surface of the bypass channel encapsulation structure 323 is convex upward, so that the structure of the bypass channel 320 is a Venturi structure. Exemplarily, the contraction section angle of the formed Venturi channel is not higher than 30 degrees, and the diffusion section angle of the Venturi channel is not higher than 30 degrees.

[0054] In the disclosed embodiment, the fluid can be gradually accelerated and regulated in the bypass flow path to form a high-speed fluid zone with a uniform and stable flow field at the location of the measuring device, thereby greatly improving the response speed and sensitivity of the measuring device and improving the measurement accuracy and stability.

[0055] Specifically, the design of the contraction angle of the Venturi flow channel can help reduce the impact and vibration of the fluid. The size of the contraction angle will affect the flow characteristics of the fluid and the pressure distribution in the flow channel. If the contraction angle is too large, the fluid flow may be unstable and vortex may be generated; if the contraction angle is too small, the fluid flow may be too smooth, which is not conducive to the generation of the Venturi effect.

[0056] The design of the diffuser angle can help reduce the turbulence of the fluid and reduce the wear and erosion of the fluid on the flow channel. The size of the diffuser angle will also affect the flow characteristics of the fluid and the pressure distribution in the flow channel. If the diffuser angle is too small, the fluid flow may be too concentrated, increasing the turbulence of the fluid and the erosion of the fluid on the flow channel; if the diffuser angle is too large, the fluid flow may be too dispersed, reducing the flow efficiency of the fluid.

[0057] In some embodiments, the angle of the contraction section of the Venturi-type flow channel is not higher than 14 degrees, and the angle of the diffusion section is not higher than 14 degrees. At this time, the flow field of the measured fluid in the contraction section changes smoothly, the existence of eddies can be avoided, and the disturbance of the flow field by eddies can be reduced. In this way, the performance of the Venturi-type flow channel can be further optimized, the efficiency and stability of the fluid flow can be improved, the erosion and wear of the flow channel and the measuring device by the fluid can be reduced, and the measurement stability can be improved.

[0058] The above describes the structure of the bypass channel in detail. Figure 3 , Figure 5a to Figure 5d The specific structure of the main channel is further introduced.

[0059] In some embodiments, the main flow channel may be a straight-through flow channel, a Venturi flow channel, or an orifice flow channel. Figure 5a FIG. 1 is a schematic diagram of the structure of a main flow channel provided by an exemplary embodiment of the present disclosure. Figure 5a As shown, the main channel is a straight-through channel; the fluid in the main channel flows from left to right. The first opening 311 of the main channel is located in the upstream direction of the main channel, and the second opening 312 is located in the downstream direction of the main channel. Since there is a certain pressure difference when the fluid passes through the main channel, part of the fluid enters the bypass channel from the upstream first opening 311, passes through the measuring device, and returns to the main channel from the second opening 312. Figure 5b , Figure 5c The main flow channels shown are respectively a Venturi type flow channel and an orifice type flow channel.

[0060] It is understandable that the structure of the main channel may include other structural forms, as long as it is ensured that the fluid in the main channel can form throttling or pressure difference, and the present disclosure does not make any specific restrictions on this.

[0061] In some embodiments, the shapes of the first opening and the second opening on the main channel wall can be circular or rectangular, so as to better adapt to the shapes of the bypass channel inlet channel and / or the bypass channel outlet channel, and improve the stability and sealing of the connection. It can be understood that in addition to circular or rectangular, the shapes of the first opening and the second opening can also be set to other shapes, and the shapes of the first opening and the second opening can be the same or different, and the present disclosure does not make specific restrictions on this.

[0062] like Figure 5a to Figure 5c As shown, the first opening and the second opening are circular in shape; Figure 5d As shown, the first opening and the second opening are in a rectangular shape. It is understandable that the flow path form of the main channel and the opening forms of the first opening and the second opening can be combined arbitrarily and are not limited to the above-listed forms.

[0063] The above introduces in detail the specific structures of the bypass flow channel and the main flow channel. The following will specifically introduce the design parameters of the bypass flow channel and the main flow channel, such as the length and diameter.

[0064] Specifically, according to the fluid mechanics Hagen-Poiseuille equation and Fanning formula, there are the following relationships between the main design parameters:

[0065]

[0066] Wherein, μ represents the viscosity of the fluid medium; U max represents the maximum measured flow rate of the measuring device; l represents the equivalent length of the bypass flow channel; d represents the equivalent diameter of the bypass flow channel; ∑ξ represents the local resistance coefficient of the main flow channel of the protection flow channel; ρ represents the fluid density; U main Indicates the fluid flow rate in the main channel.

[0067] In some embodiments, the equivalent diameter of the bypass flow channel is determined based on the maximum measured flow rate of the measuring device and the physical properties of the fluid inside the target tube body to ensure that the fluid in the bypass flow channel is in a laminar flow state.

[0068] Exemplarily, for a circular bypass channel structure, the Reynolds number, a dimensionless parameter of fluid mechanics, can be determined first. The dimensionless parameter of fluid mechanics, Reynolds Number (Re), can distinguish whether the flow state of the fluid is laminar or turbulent. Specifically, the Reynolds number can be expressed as the following formula Re=ρvd / μ, where v represents the flow velocity of the fluid, ρ represents the density of the fluid, μ represents the viscosity of the fluid medium, and d represents the characteristic length, which can be taken as the equivalent diameter of the bypass channel. The specific value of the Reynolds number can be determined based on experience or actual conditions. Exemplarily, the Reynolds number is less than 2300. For a circular channel, when the Reynolds number is less than 2300, the flow state of the fluid in the channel can be considered to be laminar.

[0069] It can be seen that when the maximum measured flow rate of the measuring device and the physical properties of the fluid are known, the equivalent diameter d of the bypass flow channel can be determined.

[0070] In some embodiments, the equivalent length of the bypass flow channel is 2 / 5 to 4 / 5 of the diameter of the protection flow channel.

[0071] Specifically, the equivalent length l of the bypass flow channel is k*d, where k is an empirical constant, which depends on factors such as the shape, size and fluid properties of the flow channel, and illustratively, k is greater than 10. Therefore, after determining the equivalent diameter d of the bypass flow channel, the equivalent length l of the bypass flow channel can be further calculated.

[0072] At the same time, the equivalent length of the bypass flow channel should be 2 / 5 to 4 / 5 of the diameter D of the protection flow channel, that is, 0.4D≤l≤0.8D. According to the above value relationship, the diameter D of the protection flow channel can be determined according to the equivalent length l of the bypass flow channel. In this way, the equivalent length of the bypass flow channel, the diameter length of the protection flow channel, the value range of the diameter of the main flow channel, and the spacing between the first opening and the second opening and other parameters can be determined, so that the structural design of the thermal mass flowmeter in the present disclosure can be completed.

[0073] In some embodiments, the length of the protective channel in the axial direction is not greater than the diameter of the plug rod, thereby ensuring that the protective channel and part of the plug rod are smoothly installed in the target tube body. More specifically, the length of the protective channel in the axial direction is equal to the diameter of the plug rod, thereby ensuring that the connection between the plug rod and the protective channel is smooth. At the same time, a sufficiently long protective channel can better meet the diameter and length design of the bypass channel.

[0074] The thermal mass flowmeter provided by the embodiment of the present disclosure has a simple structural design, while taking into account the advantages of existing insertion flowmeters and bypass flowmeters. On the one hand, the thermal mass flowmeter disclosed in the present disclosure adopts a convenient insertion installation type, and the measuring device is located in the middle of the target pipe body, which can directly sense the changes in the mainstream fluid and greatly reduce the influence of environmental factors; on the other hand, the measuring device is set in the bypass flow channel of the protective flow channel, which can greatly reduce the risk of pollution and particle impact damage, and the flow field is uniform and controllable, and the measurement stability is greatly improved.

[0075] It should be understood that the term "including" and its variations used in the present disclosure are open inclusions, that is, "including but not limited to". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one other embodiment". In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0076] The above description is only a preferred embodiment of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent substitutions, etc. made within the spirit and principles of the present disclosure should be included in the protection scope of the present disclosure.

Claims

1. A thermal mass flowmeter, characterized in that: include: An insertion rod, a first end of which is disposed in the target tube body; A protective flow channel, disposed at the first end of the insertion rod; Wherein, the protection flow channel includes a main flow channel and a bypass flow channel, the bypass flow channel is arranged on a side of the main flow channel close to the first end of the insertion rod, and the bypass flow channel includes a measuring device, and the measuring device is used to measure the fluid flow of the target tube body; The protective flow channel also includes a substrate and a bypass flow channel packaging structure, the first surface of the substrate and the first surface of the bypass flow channel packaging structure are arranged opposite to each other and constitute the bypass flow channel; wherein the measuring device is arranged on the first surface of the substrate, and the center of the first surface of the bypass flow channel packaging structure protrudes upward to form a Venturi-type flow channel.

2. The thermal mass flowmeter according to claim 1, characterized in that: The side wall of the main flow channel includes a first opening and a second opening, and the first opening and the second opening are sequentially arranged along the flow direction of the fluid in the target tube body; The protection flow channel also includes a bypass flow channel inlet flow channel and a bypass flow channel outlet flow channel; Wherein, the first opening is connected to the first end of the bypass flow channel inlet flow channel, the second end of the bypass flow channel inlet flow channel is connected to the first end of the bypass flow channel, the second end of the bypass flow channel is connected to the first end of the bypass flow channel outlet flow channel, and the second end of the bypass flow channel outlet flow channel is connected to the second opening.

3. The thermal mass flowmeter according to claim 2, characterized in that: A sealing ring is provided at the connection between the second end of the bypass flow channel inlet flow channel and the first end of the bypass flow channel, and a sealing ring is provided at the connection between the second end of the bypass flow channel and the bypass flow channel outlet flow channel.

4. The thermal mass flowmeter according to claim 2, characterized in that: The shapes of the first opening and the second opening include a circle or a rectangle.

5. The thermal mass flowmeter according to claim 1, characterized in that: The contraction section angle of the Venturi-type flow channel is not higher than 14 degrees, and the diffusion section angle of the Venturi-type flow channel is not higher than 14 degrees.

6. The thermal mass flowmeter according to claim 1, characterized in that: The main flow channel includes one of a straight-through flow channel, a Venturi flow channel and an orifice flow channel.

7. The thermal mass flowmeter according to claim 1, characterized in that: The equivalent diameter of the bypass flow channel is determined based on the maximum measured flow rate of the measuring device and the physical properties of the fluid inside the target pipe body.

8. The thermal mass flowmeter according to claim 1, characterized in that: The equivalent length of the bypass flow channel is 2 / 5 to 4 / 5 of the diameter of the protection flow channel.

9. The thermal mass flowmeter according to claim 1, characterized in that: The length of the protective flow channel in the axial direction is not greater than the diameter length of the insertion rod.

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