Mass flow meter

Abstract

The present application provides a mass flow meter comprising: at least one flow tube, any one of which is axially symmetric about an imaginary axis of symmetry; the shock excitation unit is arranged on the middle pipe section and used for driving the flow pipe to vibrate; the vibration sensing unit comprises pickup sensors symmetrically arranged on the two sides of the excitation unit, and the pickup sensors are used for acquiring vibration signals of the flow pipe; furthermore, the flow pipe comprises a middle pipe section passing through the imaginary symmetry axis and inner bent pipe sections located at the two ends of the middle pipe section, the middle pipe section is in smooth connection with the inner bent pipe sections, the middle pipe section of the flow pipe is a straight pipe, the inner bent pipe section of the flow pipe is a bent pipe, and the ratio of the length of the middle pipe section to the outer pipe diameter of the middle pipe section is larger than 0 and smaller than or equal to 3. According to the mass flow meter, the sensitivity of the vibration frequency of the mass flow meter affected by pressure is low, and detection is more accurate.

Description

Technical Field

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

[0002] In industrial measurement technology, in order to determine the characteristic measurement variables of a flowing medium (e.g., liquid and / or gas) in a process pipeline (e.g., pipe), a measurement system is often used, which, by means of a vibration-type measurement transducer and connected measurement device electronics with a driver and evaluation circuitry, induces reaction forces (e.g., Coriolis forces) in the flowing medium and generates measurement signals derived from these forces that correspondingly represent at least one measurement variable (e.g., mass flow rate, density, viscosity, or other process parameters).

[0003] This type of measurement system (often formed by an in-line measurement device with a compact design incorporating an integrated measurement transducer such as a Coriolis mass flow meter) has been known for a long time and proven in industrial applications. However, Coriolis mass flow meters have requirements for tube design, especially in compact Coriolis mass flow meters, where the tube design affects the pressure sensitivity of the Coriolis mass flow meter and thus its detection accuracy. Summary of the Invention

[0004] The purpose of this application is to provide a technical solution to address the problem in related technologies that mass flow meters are sensitive to pressure, which can easily affect detection accuracy.

[0005] For the purposes described above, this application provides a mass flow meter, comprising:

[0006] At least one flow tube, any flow tube is axisymmetric about an imaginary axis of symmetry, the flow tube includes an intermediate tube segment passing through the imaginary axis of symmetry and inner bend tube segments located at both ends of the intermediate tube segment, the intermediate tube segment and the inner bend tube segments are smoothly connected;

[0007] The excitation unit is located in the middle pipe section and is used to drive the flow tube to vibrate.

[0008] The vibration sensing unit includes pickup sensors symmetrically arranged on both sides of the excitation unit. The pickup sensors are used to acquire the vibration of the flow tube.

[0009] The middle section of the flow tube is a straight pipe, and the inner curved section of the flow tube is a curved pipe. The ratio of the length of the middle section to the outer diameter of the middle section is greater than 0 and less than or equal to 3.

[0010] Furthermore, the ratio of the length of the intermediate pipe section to the outer diameter of the intermediate pipe section is greater than or equal to 1.5.

[0011] Furthermore, the flow tube also includes a transition straight pipe section and a transition bend pipe section. One end of the transition straight pipe section is smoothly connected to the inner bend pipe section, and the other end of the transition straight pipe section is smoothly connected to one end of the transition bend pipe section. The other end of the transition bend pipe section serves as the outlet or inlet end of the flow tube.

[0012] The ratio of the radius of curvature of the inner bend to that of the transition bend is greater than or equal to 1.25.

[0013] Furthermore, 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 also 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, which satisfies the following conditions: the angle is greater than or equal to 90° and less than or equal to 105°.

[0014] Furthermore, the angle of the first included angle is greater than or equal to 95°.

[0015] Furthermore, the opening direction of the transition bend is parallel to the axial direction of the intermediate pipe section;

[0016] Define a first straight line that coincides with the axis of the intermediate pipe section. Define a second straight line that is parallel to the first straight line and passes through the center of the open end of the transition bend pipe section.

[0017] The ratio of the distance between the first and second straight lines to the outer diameter of the flow tube is less than or equal to 12.

[0018] Furthermore, the bending angle of the inner bend section is equal to that of the transition bend section.

[0019] Furthermore, the mass flow meter also includes a processing module, which is used to send an excitation signal to the excitation unit to make the flow tube vibrate at the resonant frequency, and to receive and process the vibration signal transmitted by the vibration sensing unit. The vibration signal is used to characterize the vibration of the flow tube.

[0020] 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.

[0021] Furthermore, the processing module also generates density measurement values ​​based on the vibration signal, which represent the instantaneous density of the fluid being measured flowing through the mass flow meter.

[0022] Furthermore, the mass flow meter includes two or more flow tubes. The inlet end of all flow tubes is used to connect to the inlet splitter, and the outlet end of all flow tubes is used to connect to the outlet splitter. The measured fluid flows into each flow tube equally through the inlet splitter and flows out through the outlet splitter. The structure of all flow tubes is basically the same, and the flow tubes are formed by bending metal round tubes.

[0023] Based on the above description, this application provides a mass flow meter that reduces the sensitivity of the mass flow meter's vibration frequency to pressure by designing the flow tube shape, thereby making the detection more accurate. Attached Figure Description

[0024] Figure 1 A schematic diagram of a mass flow meter provided in an embodiment of this application;

[0025] Figure 2 This is a schematic diagram of a U-shaped tube in related technologies;

[0026] Figure 3 This is a schematic diagram of a flow tube provided in an embodiment of this application;

[0027] Figure 4 for Figure 3 A schematic diagram showing the radius of curvature of a flow tube;

[0028] Figure 5 for Figure 3 A schematic diagram showing the first included angle marked on the flow pipe;

[0029] Figure 6 A schematic diagram of a flag-style installation scenario provided in an embodiment of this application;

[0030] Figure 7 A schematic diagram of the height of the flow tube provided in an embodiment of this application.

[0031] 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. Detailed Implementation

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] It should be noted that when the flow tubes vibrate, the voltage waveforms generated by the first pickup sensor 141 and the second pickup sensor 142 are sinusoidal waveforms. These sinusoidal waves indicate the movement of one flow tube relative to the other. When there is no flowing fluid medium in the flow tubes (i.e., no fluid flows through them), the sinusoidal waves measured by the two pickup sensors are in phase, meaning the two flow tubes move synchronously. However, when a fluid medium flows through the pipes, a Coriolis force is induced, causing the two flow tubes to twist in opposite directions. This results in a phase shift in the sinusoidal waveforms measured by the two pickup sensors. By analyzing the waveforms measured by the pickup 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.

[0040] As an optional implementation, in the mass flow meter provided in this application embodiment, the middle pipe section 11 of the flow tube is a straight pipe, the inner bend section 12 of the flow tube is a bend, and the ratio of the length of the middle pipe section 11 to the outer diameter of the middle pipe section 11 is greater than 0 and less than or equal to 3.

[0041] Specifically, in this embodiment, the flow tube is formed by bending a circular tube, which can be metal or other materials. In this embodiment, the flow tube retains a straight section in the middle, and the circular tube is bent at both ends of the middle section 11 to form a first inner bend section and a second inner bend section. By retaining the straight section in the middle, the inner bend section 12 can be processed in two parts, thereby reducing the stroke length of a single inner bend section 12, reducing the overall processing difficulty, ensuring that the dimensions of the inner bend sections 12 on both sides are consistent, ensuring the symmetry of the flow tube, and thus ensuring the accuracy of the mass flow meter detection.

[0042] It should be noted that the purpose of this application is to provide a high-precision, compact mass flow meter. It is easy to understand that, based on the compact design requirements, the overall length of the mass flow meter's flow tube cannot be too long when designing the flow tube configuration.

[0043] In this embodiment of the application, the ratio of the length of the intermediate pipe section 11 to the outer 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 diameter of the intermediate pipe section 11 is greater than 0 and less than or equal to 3.

[0044] The flow tube designed in this embodiment has a straight middle section, which allows the inner bend section 12 to be processed in two parts, reducing processing difficulty and ensuring the symmetry of the flow tube. Furthermore, in this embodiment, the ratio of the length of the middle section 11 to its outer diameter is less than or equal to 3. This design provides sufficient design space for the inner bend section 12, maximizing its radius of curvature while meeting compact requirements. This helps reduce the turbulence intensity that may occur when fluid flows through the flow tube, thereby reducing flow field noise and making the mass flow meter's detection more accurate. Additionally, maximizing the radius of curvature of the inner bend section 12 avoids elliptical deformation of the circular tube during bending, thus preventing an increase in the pressure sensitivity of the inner bend section 12 due to elliptical deformation and avoiding zero-point drift.

[0045] To further illustrate the mass flow meter provided in the embodiments of this application, this application also performs vibration stress analysis on the flow tube with an intermediate straight pipe section provided in the embodiments of this application, and compares the vibration stress analysis results with those of a U-shaped flow tube without an intermediate straight pipe section in related designs. Specifically, as follows:

[0046] like Figure 2 As shown, it illustrates a schematic diagram of a U-shaped flow tube design without an intermediate straight pipe section in the related art.

[0047] In this embodiment, a 32*1.5mm U-shaped tube is used as the object of vibration stress analysis. This U-shaped tube is axisymmetric about an imaginary axis of symmetry. The U-shaped tube includes a central bend (S1, S2) and straight sections on either side of the bend. It is easy to understand that the central bend (S1, S2) is the sensitive part for density and flow rate measurement. Using the imaginary axis of symmetry as a boundary, the bend of the U-shaped tube can be divided into two inner bend sections. This application performs vibration stress analysis on the U-shaped tube, selecting a section from one of the inner bend sections... Figure 2 The four measurement points are shown in Table 1. Assuming the vibration amplitude at the exciter is 100 micrometers, the amplitude and stress at each measurement point on the U-shaped flow tube are shown in Table 1.

[0048] 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

[0049] Table 1

[0050] As shown in Table 1, the maximum amplitude and high level of stress exist near the excitation unit 13. The flow tube design with a retained intermediate straight section, as provided in this embodiment, avoids the deformation into an elliptical shape near the excitation unit 13 due to the bending of the measuring tube. This prevents the flow tube from experiencing increased pressure sensitivity due to irregular deformation caused by ellipticity during processing, thus avoiding zero-point drift.

[0051] like Figure 3As shown, it illustrates a flow pipe design schematic diagram with a retained intermediate straight pipe section provided in an embodiment of this application. Based on Figure 3 The flow tube shown in this application is subjected to vibration stress analysis, and pressure sensitivity is calculated by numerical simulation to obtain the sensitivity of the flow meter vibration frequency to pressure, as shown in Table 2.

[0052] U-shaped tube Trapezoidal tube (in this design) Frequency @ 1 bar [Hz] 174.82 164.41 Frequency @2 bar [Hz] 174.83 164.42 df / bar[Hz] 0.0066 0.0046 Sensitivity [ppm / bar] 37.76 27.75

[0053] Table 2

[0054] It should be noted that in the embodiments of this application, the flow tube provided in this application and the U-shaped flow tube for comparison both have the same inner bend section 12 and maintain the same height and overall length of the flow meter to eliminate interference from other factors. As shown in Table 2, the flow tube design provided in this application is significantly less sensitive to pressure than the U-shaped tube design in related technologies.

[0055] As can be seen from the above description, the mass flow meter using the flow tube design provided in this application embodiment can effectively reduce the sensitivity of the mass flow meter's vibration frequency to pressure, thus avoiding zero-point drift. Furthermore, since density measurement is an important process measurement parameter for mass flow meters, and density measurement is calculated based on the flow meter's vibration frequency, the tube design provided in this application embodiment can reduce the sensitivity of the flow meter's vibration frequency to pressure, thus offering significant advantages in fluid density measurement.

[0056] Preferably, as an optional implementation, in this embodiment, the ratio of the length of the intermediate pipe segment 11 to the outer diameter of the intermediate pipe segment 11 satisfies the following condition: the ratio of the length of the intermediate pipe segment 11 to the outer diameter of the intermediate pipe segment 11 is greater than 1.5 and less than or equal to 3. With this design, the intermediate pipe segment 11 retains sufficient length to facilitate clamping of the intermediate pipe segment 11 during the bending process of the inner bend pipe segment 12, thus reducing the processing difficulty of the flow pipe.

[0057] As an optional implementation, the mass flow meter provided in this application embodiment further includes a transition straight pipe section 15 and a transition bend pipe section 16 in the flow tube. One end of the transition straight pipe section 15 is smoothly connected to the inner bend pipe section 12, and the other end of the transition straight pipe section 15 is smoothly connected to one end of the transition bend pipe section 16. The other end of the transition bend pipe section 16 serves as the outlet or inlet end of the flow tube. The ratio of the radius of curvature of the inner bend pipe section 12 to the radius of curvature of the transition bend pipe section 16 is greater than or equal to 1.25.

[0058] Specifically, such as 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.

[0059] 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.

[0060] 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°.

[0061] 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.

[0062] 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.

[0063] 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°.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] As an optional implementation, the processing module also generates density measurements based on vibration signals, which represent the instantaneous density of the fluid being measured flowing through the mass flow meter.

[0072] Based on the above description, this application provides a compact mass flow meter with low sensitivity to pressure affecting its vibration frequency, resulting in more accurate detection.

[0073] The above-disclosed embodiments are merely preferred embodiments of this application, but are not intended to limit the scope of this application. Those skilled in the art will understand that any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and scope of this application and the appended claims are equivalent substitutions and still fall within the scope of the invention.

Claims

1. A mass flow meter, comprising: At least one flow tube, any one of the flow tubes being axisymmetric about an imaginary axis of symmetry, the flow tube including an intermediate tube segment passing through the imaginary axis of symmetry and inner bend tube segments located at both ends of the intermediate tube segment, the intermediate tube segment and the inner bend tube segments being smoothly connected; A vibration unit is disposed in the intermediate pipe section and is used to drive the flow pipe to vibrate; The vibration sensing unit includes pickup sensors symmetrically arranged on both sides of the excitation unit, the pickup sensors being used to acquire the vibration of the flow tube; Its features are, The intermediate pipe section of the flow pipe is a straight pipe, the inner bend section of the flow pipe is a bend, and the ratio of the length of the intermediate pipe section to the outer diameter of the intermediate pipe section is greater than 0 and less than or equal to 3.

2. The mass flow meter according to claim 1, characterized in that, The ratio of the length of the intermediate pipe section to the outer diameter of the intermediate pipe section is greater than or equal to 1.

5.

3. The mass flow meter according to claim 1, characterized in that, The flow tube further includes a transition straight pipe section and a transition bend pipe section. One end of the transition straight pipe section is smoothly connected to the inner bend pipe section, and the other end of the transition straight pipe section is smoothly connected to one end of the transition bend pipe section. The other end of the transition bend pipe section serves as the outlet end or inlet end of the flow tube. The ratio of the radius of curvature of the inner bend to the radius of curvature of the transition bend is greater than or equal to 1.

25.

4. The mass flow meter according to claim 3, characterized in that, The transition straight pipe section and the intermediate pipe section are coupled together via the inner bend pipe section. Each of the transition straight pipe sections has an imaginary axis, and the imaginary axis of the transition straight pipe section has a direction vector pointing towards the coupled inner bend pipe section. The intermediate pipe section also has an imaginary axis, and the imaginary axis of the intermediate pipe section has a direction vector pointing towards 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 a first angle, which satisfies the following conditions: the angle is greater than or equal to 90° and less than or equal to 105°.

5. The mass flow meter according to claim 4, characterized in that, The angle of the first included angle is greater than or equal to 95°.

6. The mass flow meter according to claim 3, characterized in that, The opening direction of the transition bend is parallel to the axial direction of the intermediate pipe section. Define a first straight line that coincides with the axis of the intermediate pipe section; define a second straight line that is parallel to the first straight line and passes through the center of the open end of the transition bend pipe section. The ratio of the distance between the first straight line and the second straight line to the outer diameter of the flow tube is less than or equal to 12.

7. The mass flow meter according to claim 3, characterized in that, The bending angle of the inner bend is equal to the bending angle of the transition bend.

8. The mass flow meter according to claim 1, characterized in that, The mass flow meter also includes a processing module, which is used to send an excitation signal to the excitation unit 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, the vibration signal being used to characterize the vibration of the flow tube. The processing module generates at least a mass flow rate measurement value based on the vibration signal, the mass flow rate measurement value representing the instantaneous mass flow rate of the measured fluid flowing through the mass flow meter.

9. The mass flow meter according to claim 8, characterized in that, The processing module also generates a density measurement value based on the vibration signal, which represents the instantaneous density of the fluid being measured flowing through the mass flow meter.

10. The mass flow meter according to claim 1, characterized in that, The mass flow meter includes two or more flow tubes. The inlet end of all the flow tubes is connected to an inlet distributor, and the outlet end of all the flow tubes is connected to an outlet distributor. The fluid to be measured flows into each flow tube equally through the inlet distributor and flows out through the outlet distributor. All the flow tubes have a basically the same structure and are formed by bending a metal round tube.

Images