Mass flow meter

Abstract

The utility model provides a mass flow meter which comprises two or more flow pipes, any flow pipe is in axial symmetry about an imaginary symmetry axis, and each flow pipe comprises a middle pipe section; the inner bent pipe sections are positioned at two ends of the middle pipe section; one end of the transition straight pipe section is smoothly connected with the inner bent pipe section; the middle pipe section of the flow pipe is a straight pipe, a first straight line is defined, and the first straight line coincides with the axis of the middle pipe section; the mass flowmeter further comprises coupling pieces, the two flow pipes are coupled through the coupling pieces, the first coupling piece is fixedly connected with the transition straight pipe section, a first intersection point is defined, the first intersection point is the intersection point of the extension direction of the imaginary axis of the transition straight pipe section and the extension direction of the first coupling piece, the distance between the first intersection point and a first straight line is defined as a first distance, and the distance between the first intersection point and a second straight line is defined as a second distance. The ratio of the first distance to the outer pipe diameter of the middle pipe section is larger than or equal to 4 and smaller than or equal to 12. According to the mass flow meter, the vibration frequency of the flow pipe can be controlled within a reasonable range, and phase difference detection on the two sides of the flow pipe is facilitated.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flow metering, in particular to a mass flow meter. BACKGROUND

[0002] In industrial measurement technology, in order to determine a characteristic measurement variable of a flowing medium, such as a liquid and / or a gas, in a process line, such as a pipe, a measurement system is often used which, by means of a vibrating measurement transducer and a connected measurement device electronics with a driver and evaluation circuit, induces counter forces, such as Coriolis forces, in the flowing medium and generates measurement signals which correspondingly represent at least one measurement variable, such as a mass flow rate, a density, a viscosity or other process parameters, derived from these forces.

[0003] Such measurement systems, often formed by means of an online measurement device with a compact design with an integral measurement transducer, such as a Coriolis mass flow meter, have been known for a long time and are proven in industrial applications. However, Coriolis mass flow meters have requirements with regard to the pipe design, in particular in compact Coriolis mass flow meters, which can influence the pressure sensitivity of the Coriolis mass flow meter and thus the detection accuracy of the mass flow meter. SUMMARY

[0004] The purpose of the present application is to provide a technical solution to solve the problem of the mass flow meter being sensitive to pressure and easily affecting the detection accuracy in the related art.

[0005] In order to achieve the above purpose, the present application provides a mass flow meter, comprising:

[0006] Two or more flow tubes, any flow tube is axisymmetric about an imaginary symmetry axis, the flow tube comprises a middle tube section passing through the imaginary symmetry axis; an inner elbow section located at both ends of the middle tube section, the middle tube section and the inner elbow section are smoothly connected; a transition straight tube section smoothly connected with one end of the inner elbow section, and a transition elbow section smoothly connected with the other end of the transition straight tube section;

[0007] The middle tube section of the flow tube is a straight tube, a first straight line is defined, the first straight line coincides with the axis of the middle tube section;

[0008] The mass flow meter further comprises a coupling sheet, the two or more flow tubes are coupled through the coupling sheet, wherein a first coupling sheet is fixedly connected with the transition straight tube section, a first intersection point is defined, the first intersection point is the intersection point of the extension direction of the imaginary axis of the transition straight tube section and the extension direction of the first coupling sheet, the distance from the first intersection point to the first straight line is defined as a first distance, the ratio of the first distance to the outer tube diameter of the middle tube section is greater than or equal to 4 and less than or equal to 12.

[0009] Further, the imaginary axis of the transition straight pipe section has a directional vector pointing to the coupled inner elbow pipe section; the imaginary axis of the intermediate pipe section has a directional vector pointing to the coupled inner elbow pipe section; the included angle between the directional vector of the intermediate pipe section and the directional vector of the transition straight pipe section is defined as a first included angle, and the angle of the first included angle satisfies: the angle is greater than or equal to 95° and less than or equal to 105°.

[0010] Further, the included angle between the extension direction of the first coupling sheet and the imaginary symmetry axis of the flow pipe is defined as a second included angle, and the angle of the second included angle satisfies: the angle is greater than or equal to 75° and less than or equal to 85°.

[0011] Further, the mass flow meter further comprises a second coupling sheet, and the second coupling sheet is fixedly connected with the transition elbow pipe section.

[0012] The included angle between the extension direction of the second coupling sheet and the imaginary symmetry axis of the flow pipe is defined as a third included angle, and the angle of the third included angle satisfies: the angle is greater than or equal to 25° and less than or equal to 35°.

[0013] Further, the ratio of the length of the intermediate pipe section to the outer pipe diameter of the intermediate pipe section is greater than 0 and less than or equal to 3.

[0014] Further, the ratio of the length of the intermediate pipe section to the outer pipe diameter of the intermediate pipe section is greater than or equal to 1.5.

[0015] Further, the ratio of the curvature radius of the inner elbow pipe section to the curvature radius of the transition elbow pipe section is greater than or equal to 1.25.

[0016] Further, the opening direction of the transition elbow pipe section is parallel to the axial direction of the intermediate pipe section.

[0017] A first straight line is defined, the first straight line coincides with the axis of the intermediate pipe section, a second straight line is defined, the second straight line is parallel to the first straight line, and the second straight line passes through the center of the opening end of the transition elbow pipe section.

[0018] The ratio of the distance between the first straight line and the second straight line to the outer pipe diameter of the flow pipe is less than or equal to 12.

[0019] Further, the bending angle of the inner elbow pipe section is equal to the bending angle of the transition elbow pipe section.

[0020] Further, the mass flow meter comprises two or more flow pipes, the inlet ends of all the flow pipes are used to be connected with the inlet flow divider, the outlet ends of all the flow pipes are used to be connected with the outlet flow divider, the measured fluid flows into each flow pipe equally through the inlet flow divider and flows out through the outlet flow divider, the structural types of all the flow pipes are basically consistent, and the flow pipes are formed by bending metal round pipes.

[0021] Based on the above description, this application provides a mass flow meter. By designing the position of the first coupling plate of the mass flow meter, the ratio of the vertical distance from the first coupling plate to the middle pipe section to the outer diameter of the middle pipe section is designed to be greater than or equal to 4 and less than or equal to 12. This allows the vibration frequency of the flow tube to be controlled within a reasonable range, which is beneficial for the detection of the phase difference between the two sides of the flow tube. Attached Figure Description

[0022] Figure 1 A schematic diagram of a mass flow meter provided in an embodiment of this application;

[0023] Figure 2 This is a schematic diagram of a U-shaped tube in related technologies;

[0024] Figure 3 This is a schematic diagram of a flow tube provided in an embodiment of this application;

[0025] Figure 4 for Figure 3 A schematic diagram showing the radius of curvature of a flow tube;

[0026] Figure 5 for Figure 3 A schematic diagram showing the first included angle marked on the flow pipe;

[0027] Figure 6 A schematic diagram of a flag-style installation scenario provided in an embodiment of this application;

[0028] Figure 7 A schematic diagram of the height of the flow tube provided in an embodiment of this application;

[0029] Figure 8 A schematic diagram of a mass flow meter provided in one embodiment of this application;

[0030] Figure 9 for Figure 8 Schematic diagram of the installation of the first coupling piece;

[0031] Figure 10 for Figure 8 Schematic diagram of the installation of the second coupling plate.

[0032] Reference numerals: intermediate pipe section 11, inner bend pipe section 12, excitation unit 13, vibration sensing unit 14, first pickup sensor 141, second pickup sensor 142, transition straight pipe section 15, transition bend pipe section 16, first coupling plate 17, second coupling plate 18, imaginary axis of symmetry 101. Detailed Implementation

[0033] The present application will be described in detail below with reference to the specific embodiments shown in the accompanying drawings. However, these embodiments do not limit the present application. Any structural, methodological, or functional modifications made by those skilled in the art based on these embodiments are included within the protection scope of the present application.

[0034] The purpose of this application is to provide a high-precision, compact mass flow meter that can meet the needs of fluid medium flow measurement under limited space conditions.

[0035] For the purposes mentioned above, such as Figure 1 As shown in the figure, this application provides a mass flow meter, which includes at least one flow tube, an excitation unit 13 and a vibration sensing unit 14.

[0036] In this embodiment, for two or more flow tubes, the inlet end of each flow tube is connected to an inlet distributor, and the outlet end is connected to an outlet distributor. The flow tubes are used to transport the flowing medium, which is split at the inlet distributor and flows equally into two or more flow tubes, converging at the outlet distributor before flowing out. All flow tubes have a basically consistent structural design. Taking one flow tube as an example, this flow tube is axially symmetrical about an imaginary axis of symmetry. The flow tube includes a middle section 11 passing through the imaginary axis of symmetry and inner bend sections 12 located at both ends of the middle section 11. The middle section 11 and the inner bend sections 12 are smoothly connected. For ease of explanation, in this embodiment, the flow tube is defined as including a first inner bend section and a second inner bend section, wherein the first inner bend section is the inner bend section 12 near the inlet end of the flow tube, and the second inner bend section is the inner bend section 12 near the outlet end of the flow tube.

[0037] The excitation unit 13 is disposed in the intermediate pipe section 11 and is used to drive the flow tube to vibrate. Furthermore, the excitation unit 13 is disposed close to the imaginary axis of symmetry of the flow tube. Preferably, the excitation unit 13 is centrally disposed in the intermediate pipe section 11, and the imaginary axis of symmetry of the flow tube passes through the excitation unit 13. In this way, the vibration of the flow tube can be ensured to be uniform.

[0038] The vibration sensing unit 14 includes pickup sensors symmetrically arranged on both sides of the excitation unit 13. The pickup sensors are used to acquire the vibration status of the flow tube.

[0039] Specifically, the vibration sensing unit 14 includes a first pickup sensor 141 and a second pickup sensor 142. The first pickup sensor 141 is used to acquire the vibration status of the flow tube near the first inner bend section, and the second pickup sensor 142 is used to acquire the vibration status of the flow tube near the second inner bend section. The first pickup sensor 141 and the second pickup sensor 142 are axisymmetric about the imaginary axis of symmetry of the flow tube.

[0040] It should be noted that when the flow tubes vibrate, the voltage waveforms generated by the first pick-off sensor 141 and the second pick-off sensor 142 are sinusoidal waveforms, and the generated sinusoidal waves indicate the movement of one flow tube relative to the other flow tube. In the case where there is no fluid medium flowing in the flow tubes (i.e., no fluid passing through the flow tubes), the sinusoidal waves measured by the two pick-off sensors are in phase, meaning that the two flow tubes move synchronously. When the fluid medium flows through the pipes, the flow tubes will generate a Coriolis force, which will cause the two flow tubes to twist towards each other, thereby causing the sinusoidal waveforms measured by the two pick-off sensors to be relatively phase-shifted. By analyzing the waveforms measured by the pick-off sensors, the flow rate, density, viscosity, and other measurement variables of the fluid medium can be obtained. It is easy to understand that the fluid medium can be a liquid or a gas.

[0041] As an optional implementation, in the mass flow meter provided by the embodiment of the application, the middle pipe section 11 of the flow tube is a straight pipe, and the inner curved pipe section 12 of the flow tube is a curved pipe. The ratio of the length of the middle pipe section 11 to the outer pipe diameter of the middle pipe section 11 is greater than 0 and less than or equal to 3.

[0042] Specifically, in the embodiment of the application, the flow tube is formed by bending a circular pipe. The circular pipe can be made of metal or other materials. In the embodiment of the application, the middle straight pipe section of the flow tube is retained, and the circular pipe is bent at both ends of the middle pipe section 11 to form the first inner curved pipe section and the second inner curved pipe section. By this design of retaining the middle straight pipe section, the inner curved pipe section 12 can be processed in two parts, thereby reducing the stroke length of the single inner curved pipe section 12, reducing the overall processing difficulty, ensuring the consistency of the sizes of the two inner curved pipe sections 12, ensuring the symmetry of the flow tube, and further ensuring the accuracy of the mass flow meter detection.

[0043] It should be noted that the purpose of the application is to provide a high-precision and compact mass flow meter. It is easy to understand that when designing the pipe type of the flow tube, the overall length of the flow tube of the mass flow meter cannot be too long based on the design requirement of compactness.

[0044] In the embodiment of the application, the ratio of the length of the middle pipe section 11 to the outer pipe diameter of the middle pipe section 11 satisfies the following condition: the ratio of the length of the middle pipe section 11 to the outer pipe diameter of the middle pipe section 11 is greater than 0 and less than or equal to 3.

[0045] The flow tube designed in the embodiments of the present application has a middle straight pipe section, which can divide the inner elbow pipe section 12 into two parts for processing, so as to reduce the processing difficulty and ensure the symmetry of the flow tube. In addition, in the embodiments of the present application, the ratio of the length of the middle pipe section 11 to the outer pipe diameter of the middle pipe section 11 is less than or equal to 3. Through this design, sufficient design space can be reserved for the inner elbow pipe section 12, so that the curvature radius of the inner elbow pipe section 12 can be as large as possible under the premise of meeting the compactness requirement, which helps to reduce the turbulence intensity that may occur when the fluid flows through the flow tube, thereby reducing the flow field noise and making the detection of the mass flow meter more accurate. In addition, the curvature radius of the inner elbow pipe section 12 can be as large as possible, which can avoid the deformation of the circular pipe into an elliptical shape during bending, thereby avoiding the increase of the pressure sensitivity of the inner elbow pipe section 12 due to the elliptical deformation and avoiding the occurrence of zero drift.

[0046] In order to further illustrate the mass flow meter provided by the embodiments of the present application, the flow tube with a middle straight pipe section provided by the embodiments of the present application is subjected to vibration stress analysis, and the vibration stress analysis results of the U-shaped flow tube without a middle straight pipe section in related designs are compared. Specifically as follows:

[0047] As shown in Figure 2 , a U-shaped flow tube design schematic without a middle straight pipe section in the related art is shown.

[0048] In the embodiments of the present application, a 32*1.5mm U-shaped pipe is taken as the object of vibration stress analysis. The U-shaped flow tube is axisymmetric about an imaginary symmetry axis, and the U-shaped pipe includes a central elbow pipe portion (S1, S2) and straight pipe portions located on both sides of the elbow pipe portion. It is easy to understand that the central elbow pipe portion (S1, S2) of the U-shaped flow tube is a sensitive part for density and flow rate measurement. Taking the U-shaped pipe imaginary symmetry axis as a boundary, the elbow pipe portion of the U-shaped flow tube can be divided into two inner elbow pipe sections. The present application carries out vibration stress analysis on the U-shaped flow tube, and selects four measurement points as shown in Figure 2 in one of the inner elbow pipe sections. Assuming that the vibration amplitude at the exciter is 100 microns, the amplitudes and stresses of each measurement point on the U-shaped flow tube are shown in Table 1.

[0049] 1 2 3 4 Amplitude [um] 100.00 96.74 89.77 80.00 Stress [Pa] 2.58E+06 2.32E+06 1.72E+06 1.11E+06

[0050] Table 1

[0051] According to Table 1, the maximum amplitude and high level of stress exist near the excitation unit 13. According to the flow tube with a reserved middle straight pipe section designed in the embodiments of the present application, the deformation of the measurement pipe into an elliptical shape near the excitation unit 13 due to the bending of the measurement pipe can be avoided, and thus the increase of the pressure sensitivity of the flow pipe due to the irregular deformation during the processing process can be avoided, and the zero drift can be avoided.

[0052] As shown in Figure 3As shown in FIG. 1, which shows a schematic diagram of a flow tube design provided by an embodiment of the present application, which retains an intermediate straight pipe section. Based on the flow tube design, the flow tube is subjected to vibration stress analysis, and numerical simulation is used to calculate the pressure sensitivity, to obtain the sensitivity of the vibration frequency of the flow meter to pressure, as shown in Table 2. Figure 3 As shown in the flow tube, an embodiment of the present application is subjected to vibration stress analysis, and numerical simulation is used to calculate the pressure sensitivity, to obtain the sensitivity of the vibration frequency of the flow meter to pressure, as shown in Table 2.

[0053]

[0054]

[0055] Table 2

[0056] It should be noted that in the embodiments of the present application, the flow tube provided by the embodiments of the present application and the U-shaped flow tube for comparison have the same size of the inner elbow pipe section 12 and maintain the same height and overall length of the flow meter, so as to exclude the interference of other factors. According to Table 2, it can be known that the flow tube design provided by the embodiments of the present application is obviously lower than the U-shaped pipe design in the related art in terms of pressure sensitivity.

[0057] According to the above description, it can be known that the mass flow meter adopting the flow tube design provided by the embodiments of the present application can effectively reduce the sensitivity of the vibration frequency of the mass flow meter to pressure, and avoid the occurrence of zero drift. In addition, since the density measurement of the mass flow meter is an important process measurement parameter, and the density measurement is calculated based on the vibration frequency of the flow meter, the flow tube design provided by the embodiments of the present application can reduce the sensitivity of the vibration frequency of the flow meter to pressure, and thus has obvious advantages in the density measurement of the fluid.

[0058] Preferably, as an optional implementation manner, in the embodiments of the present application, the ratio of the length of the intermediate pipe section 11 to the outer pipe diameter of the intermediate pipe section 11 satisfies the following condition: the ratio of the length of the intermediate pipe section 11 to the outer pipe diameter of the intermediate pipe section 11 is greater than 1.5 and less than or equal to 3. Through this design, the intermediate pipe section 11 has sufficient length to facilitate the clamping of the intermediate pipe section 11 during the bending processing of the inner elbow pipe section 12, and the processing difficulty of the flow tube is reduced.

[0059] As an optional implementation manner, in the mass flow meter provided by the embodiments of the present application, the flow tube further comprises a transition straight pipe section 15 and a transition elbow pipe section 16, one end of the transition straight pipe section 15 is smoothly connected with the inner elbow pipe section 12, the other end of the transition straight pipe section 15 is smoothly connected with one end of the transition elbow pipe section 16, and the other end of the transition elbow pipe section 16 is used as an outlet end or an inlet end of the flow tube. The ratio of the curvature radius of the inner elbow pipe section 12 to the curvature radius of the transition elbow pipe section 16 is greater than or equal to 1.25.

[0060] Specifically, as shown in FIG. 2, the flow tube provided by the embodiments of the present application comprises an inner elbow pipe section 12, an intermediate pipe section 11, a transition straight pipe section 15 and a transition elbow pipe section 16. Figure 4As shown, the curvature radius R1 of the inner bend section 12 and the curvature radius R2 of the transition bend section 16 are illustrated. The ratio of the curvature radius R1 of the inner bend section 12 to the curvature radius R2 of the transition bend section 16 is greater than or equal to 1.25. This design ensures that, within the overall flow tube, the inner bend section 12, which is the sensitive part for measurement, has a larger curvature radius, while the transition bend section 16, which is the non-sensitive part, has a smaller curvature radius. This allows the mass flow meter to meet the requirements of a compact design while facilitating measurement.

[0061] Furthermore, in this embodiment, the ratio of the radius of curvature of the inner bend section 12 to the radius of curvature of the transition bend section is greater than or equal to 1.25. This design requirement ensures that the radius of curvature of the inner bend section 12, which is a sensitive part for measurement, is as large as possible. This reduces the excessive turbulence intensity caused by an excessively small radius of curvature at the inner bend section 12, or reduces the flow field noise in turbulent conditions, resulting in more accurate measurement results from the mass flow meter. Moreover, it is easy to understand that ensuring a sufficiently large radius of curvature for the inner bend section 12 results in a smaller degree of bending, thereby reducing the ellipticity of the deformation after bending, lowering the pressure sensitivity of the flow tube, and preventing zero-point drift.

[0062] like Figure 5 As shown, as an optional implementation, in this embodiment of the application, the transition straight pipe section and the intermediate pipe section are coupled through an inner bend pipe section. Each transition straight pipe section has an imaginary axis, and the imaginary axis of the transition straight pipe section has a direction vector pointing to the coupled inner bend pipe section. The intermediate pipe section has an imaginary axis, and the imaginary axis of the intermediate pipe section has a direction vector pointing to the coupled inner bend pipe section. The angle between the direction vector of the intermediate pipe section and the direction vector of the transition straight pipe section is defined as the first angle, and the angle of the first angle satisfies the following condition: the angle is greater than or equal to 90° and less than or equal to 105°.

[0063] like Figure 5 As shown, for the transition straight pipe section 15 near the inlet end of the flow tube, the angle between the direction vector of the intermediate pipe section and the direction vector of the transition straight pipe section is denoted as β. For the transition straight pipe section 15 near the outlet end of the flow tube, the angle between the direction vector of the intermediate pipe section and the direction vector of the transition straight pipe section is denoted as α. The angles β and α are equal, satisfying the design requirement of axisymmetry for the flow tube.

[0064] Taking the first included angle β near the inlet end of the flow tube as an example, the first included angle β satisfies an angle greater than or equal to 90° and less than or equal to 105°. Through this design, such as... Figure 5 As shown, when the axial direction of the middle pipe section 11 of the flow tube tends to be horizontal, the axial direction of the transition straight pipe section 15 can be kept in a state that tends to be vertical, so that the flow tube can achieve self-drainage.

[0065] Furthermore, as an optional implementation, the angle of the first included angle satisfies the following conditions: the angle is greater than or equal to 95° and less than or equal to 105°.

[0066] like Figure 6 As shown, this diagram illustrates the mass flow meter provided in this application embodiment in a flag-mounted installation application. In the flag-mounted installation scenario, the axial direction of the intermediate straight pipe section tends to be vertical. At this time, based on the design requirement that the first included angle is greater than or equal to 95°, the transition straight pipe section 15 can still maintain a certain included angle with the horizontal direction, thereby meeting the self-draining requirements.

[0067] Based on the above description, the angle of the first included angle in this application satisfies the following conditions: the angle is greater than or equal to 95°, and less than or equal to 105°. Through this design, the mass flow meter can adapt to the self-draining requirements of both horizontal and flag-mounted installation scenarios, thus broadening the application scenarios of the mass flow meter.

[0068] For ease of explanation, in this embodiment, a first straight line is defined, which coincides with the axis of the intermediate pipe section 11. A second straight line is defined, which is parallel to the first straight line and passes through the center of the opening end of the transition bend pipe section 16.

[0069] like Figure 7 As shown, as an optional implementation, the opening direction of the transition bend section 16 is parallel to the axis of the intermediate section 11. The distance between the first straight line and the second straight line (i.e., Figure 7 The ratio of the CC distance shown to the outer diameter of the flow tube is less than or equal to 12. This design allows for a smaller overall height of the mass flow meter, meeting the requirements for a compact design.

[0070] As an optional implementation, the bending angle of the inner bend section 12 is equal to the bending angle of the transition bend section 16. The bending angle of the bend refers to the minimum positive angle formed by the intersection of the two ends of the bend. The equal bending angles of the inner bend section 12 and the transition bend section 16 ensure that the transition straight section 15 is tangent to both the inner bend section 12 and the transition bend section 16 simultaneously, guaranteeing the stability of fluid flow.

[0071] As an optional implementation, the mass flow meter provided in this application embodiment also includes a processing module (not shown). The processing module is used to send an excitation signal to the excitation unit 13 to cause the flow tube to vibrate at the resonant frequency, and to receive and process the vibration signal transmitted by the vibration sensing unit 14. The vibration signal is used to characterize the vibration of the flow tube.

[0072] The processing module generates at least one mass flow rate measurement value based on the vibration signal. The mass flow rate measurement value represents the instantaneous mass flow rate of the fluid being measured flowing through the mass flow meter.

[0073] As an optional implementation, the processing module further generates a density measurement value based on the vibration signal, the density measurement value representing an instantaneous density of the measured fluid flowing through the mass flow meter.

[0074] According to the above description, the embodiment of the present application provides a compact mass flow meter, the vibration frequency of which is less sensitive to pressure and more accurate in detection.

[0075] As shown in Figure 8 The present application provides a mass flow meter, which includes two or more flow tubes, the structure of the flow tubes is the same as the flow tube structure described above, any flow tube is axisymmetric about an imaginary symmetry axis 101, and includes a middle tube segment passing through the imaginary symmetry axis 101, an inner elbow tube segment located at both ends of the middle tube segment, the middle tube segment and the inner elbow tube segment being smoothly connected, a transition straight tube segment being smoothly connected with one end of the inner elbow tube segment, and a transition elbow tube segment being smoothly connected with the other end of the transition straight tube segment. Among them, the middle tube segment of the flow tube is a straight tube, according to the foregoing, a first straight line is defined, and the first straight line coincides with the axis of the middle tube segment.

[0076] As shown in Figure 8 The mass flow meter further includes a coupling sheet, and the two flow tubes are coupled through the coupling sheet. Specifically, a first coupling sheet 17 is fixedly connected with the transition straight tube segment, a first intersection point is defined, the first intersection point is the intersection of the extension direction of the imaginary axis of the transition straight tube segment and the extension direction of the first coupling sheet 17, the distance from the first intersection point to the first straight line is defined as a first distance, and the ratio of the first distance to the outer tube diameter of the middle tube segment is greater than or equal to 4 and less than or equal to 12.

[0077] Specifically, the coupling sheet can be fixedly connected with the transition straight tube segment of the flow tube in a welding manner. As shown in Figure 8 The extension direction of the coupling sheet and the extension direction of the imaginary axis of the transition straight tube segment are shown. The intersection of the extension direction of the imaginary axis of the transition straight tube segment and the extension direction of the first coupling sheet 17 is defined as a first intersection point, and as shown in Figure 8 The distance from the first intersection point to the first straight line is a first distance, and the first distance is denoted as H1. In the embodiment of the present application, the ratio of the first distance H1 to the outer tube diameter of the middle tube segment is greater than or equal to 4 and less than or equal to 12, so as to control the vibration frequency of the flow tube within a reasonable range.

[0078] It should be noted that if the ratio between the first distance H1 and the outer tube diameter of the middle tube segment is too high, the vibration frequency of the flow tube is too small and is easily disturbed by other frequencies; if the ratio is too small, the vibration frequency of the flow tube is too large and is not conducive to accurately detecting the phase difference on both sides of the flow tube. The present application configures the ratio of the first distance to the outer tube diameter of the middle tube segment to be greater than or equal to 4 and less than or equal to 12, so as to control the vibration frequency of the flow tube within a reasonable range.

[0079] Further, as shown in Figure 8 , as an optional implementation, the opening direction of the transition elbow section is parallel to the axial direction of the intermediate pipe section 11. The distance between the first straight line (coinciding with the axis of the intermediate pipe section) and the second straight line (parallel to the first straight line, and the second straight line passes through the center of the opening end of the transition elbow section) (i.e. the H0 distance shown in Figure 8 ) is less than or equal to 12 times the outer diameter of the flow tube. Through this design, the overall height of the mass flow meter can be made smaller, meeting the design requirements of compactness.

[0080] As shown in Figure 9 , as an optional implementation, the angle between the extension direction of the first coupling sheet 17 and the imaginary symmetry axis 101 of the flow tube is defined as a second angle, denoted as ∠B, and the angle of the second angle ∠B satisfies: the angle is greater than or equal to 75° and less than or equal to 85°. Through the design of the installation angle of the first coupling sheet 17, the vibration frequency of the flow tube can be controlled within a reasonable range.

[0081] As shown in Figure 10 , the mass flow meter further comprises a second coupling sheet 18, and the second coupling sheet 18 is fixedly connected with the transition elbow section;

[0082] The angle between the extension direction of the second coupling sheet 18 and the imaginary symmetry axis 101 of the flow tube is defined as a third angle, denoted as ∠C, and the angle of the third angle ∠C satisfies: the angle is greater than or equal to 25° and less than or equal to 35°. Through the design of the installation angle of the second coupling sheet 18, the vibration energy of the flow tube can be reduced to be transmitted to the base shell, the energy loss can be reduced, and the external vibration can be reduced to be transmitted from the base shell to the flow tube, reducing the interference of the outside to the measuring tube.

[0083] According to Figure 10 , the mass flow meter provided by the present application is provided with at least two coupling sheets on one side of the imaginary symmetry axis 101 of the flow tube, and the number of coupling sheets on both sides of the imaginary symmetry axis 101 of the flow tube is the same and is substantially symmetrically distributed.

[0084] The above disclosure is only the preferred embodiment of the present application, and is not intended to limit the scope of the present application. Those skilled in the art can understand that changes, modifications, substitutions, combinations and simplifications without departing from the spirit and scope of the present application and the appended claims, are equivalent replacement methods still within the scope of the present application.

Claims

1. A mass flow meter comprising: two or more flow tubes, any of which is axisymmetric about an imaginary axis of symmetry, the flow tube comprising a middle tube section passing through the imaginary axis of symmetry; an inner elbow section located at both ends of the middle tube section, the middle tube section being smoothly connected with the inner elbow section; a transition straight tube section being smoothly connected with one end of the inner elbow section; and a transition elbow section being smoothly connected with the other end of the transition straight tube section; characterized in that the middle tube section of the flow tube is a straight tube, defining a first straight line, the first straight line coinciding with the axis of the middle tube section; the mass flow meter further comprises a coupling sheet, the two or more flow tubes being coupled by the coupling sheet, wherein a first coupling sheet is fixedly connected with the transition straight tube section, defining a first intersection point, the first intersection point being the intersection of the extension direction of the imaginary axis of the transition straight tube section and the extension direction of the first coupling sheet, defining a first distance from the first intersection point to the first straight line, the ratio of the first distance to the outer tube diameter of the middle tube section being greater than or equal to 4 and less than or equal to 12. 2.The mass flow meter according to claim 1, characterized in that the imaginary axis of the transition straight tube section has a direction vector pointing to the coupled inner elbow section; the middle tube section has an imaginary axis, the imaginary axis of the middle tube section having a direction vector pointing to the coupled inner elbow section; the included angle between the direction vector of the middle tube section and the direction vector of the transition straight tube section is defined as a first included angle, the angle of the first included angle satisfying: the angle is greater than or equal to 95° and less than or equal to 105°. 3.The mass flow meter according to claim 1, characterized in that an included angle between the extension direction of the first coupling sheet and the imaginary axis of symmetry of the flow tube is defined as a second included angle, the angle of the second included angle satisfying: the angle is greater than or equal to 75° and less than or equal to 85°. 4.The mass flow meter according to claim 1, characterized in that the mass flow meter further comprises a second coupling sheet, the second coupling sheet being fixedly connected with the transition elbow section; an included angle between the extension direction of the second coupling sheet and the imaginary axis of symmetry of the flow tube is defined as a third included angle, the angle of the third included angle satisfying: the angle is greater than or equal to 25° and less than or equal to 35°. 5.The mass flow meter according to claim 1, characterized in that the ratio of the length of the middle tube section to the outer tube diameter of the middle tube section is greater than 0 and less than or equal to 3. 6.The mass flow meter according to claim 1, characterized in that the ratio of the length of the middle tube section to the outer tube diameter of the middle tube section is greater than or equal to 1.

5. 7.The mass flow meter according to claim 1, characterized in that the ratio of the curvature radius of the inner elbow section to the curvature radius of the transition elbow section is greater than or equal to 1.

25. 8.The mass flow meter according to claim 1, characterized in that the opening direction of the transition elbow section is parallel to the axial direction of the middle tube section. a first straight line is defined, which is coincident with the axis of the intermediate pipe section, and a second straight line is defined, which is parallel to the first straight line and passes through the center of the open end of the transition elbow section; the ratio of the distance between the first straight line and the second straight line to the outer pipe diameter of the flow pipe is less than or equal to 12.

9. The mass flow meter of claim 1, wherein the bend angle of the inner elbow section is equal to the bend angle of the transition elbow section.

10. The mass flow meter of claim 1, wherein the mass flow meter includes two or more flow pipes, the inlet ends of all the flow pipes are connected to an inlet flow divider, the outlet ends of all the flow pipes are connected to an outlet flow divider, the measured fluid is equally flowed into each of the flow pipes through the inlet flow divider and flowed out through the outlet flow divider, the flow pipes are substantially identical in structure, and the flow pipes are formed by bending metal round pipes.

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