Magnetic-inductive flow meter and method for designing magnetic-inductive flow meter

Abstract

The invention relates to a magnetic-inductive flow meter (1), comprising: a measuring tube (2) for a conducting medium, the measuring tube (2) being divided into a first side and a second side by a longitudinal plane (LE) and having an outer side surface; -a magnetic field generating device (3), the magnetic field generating device (3) comprising: at least one saddle coil (4) arranged on the outer side surface, the coil wires of the saddle coil (4) defining a saddle coil interior (5), and a saddle coil core assembly (6) having at least one saddle coil core (7), the saddle coil core assembly (6) being arranged in the saddle coil interior (5), a minimum circular sector in which the saddle-shaped coil core assembly (6) is arranged is spanned through a central angle in a cross-section of the magnetic inductive flowmeter (1), the following being adapted for the central angle; and-at least four measuring electrodes (11, 12, 13, 14), at least two measuring electrodes (11, 13) of the at least four measuring electrodes (11, 12, 13, 14) being arranged on a first side and likewise at least two measuring electrodes (12, 14) of the at least four measuring electrodes (11, 12, 13, 14) being arranged on a second side, the central angle spans the smallest circular sector in the cross-section of the at least two measuring electrodes (12, 14) in which the first side is arranged, wherein the following are adapted for the central angle.

Description

Technical Field

[0001] The present invention relates to a magnetic induction flowmeter for determining the velocity-related measurement variables of a flowable medium, and a method for designing a magnetic induction flowmeter according to the present invention. Background Technology

[0002] Magnetic induction flowmeters are used to determine the flow rate and / or volumetric flow rate of a medium in a measuring tube. A magnetic induction flowmeter includes a magnetic field generating device that generates a magnetic field perpendicular to the transverse axis of the measuring tube. One or more coils are typically used for this purpose. To generate a uniformly dominant magnetic field, pole pieces are additionally shaped and attached such that the magnetic field lines extend across the entire cross-section of the tube substantially perpendicular to the transverse axis. A pair of measuring electrodes mounted on the side surface of the measuring tube taps an induced electrical measuring voltage, which is generated when the magnetic field is applied if the conductive medium flows in the direction of the longitudinal axis. Since the tapped measuring voltage depends on the velocity of the flowing medium according to Faraday's law of induction, it is possible to determine the flow rate; and by means of a known tube cross-section, the volumetric flow rate of the medium can be determined from the measuring voltage.

[0003] Magnetic induction flow meters are sensitive to the flow profile of the medium. Depending on the pipe system and the measuring device, measurement errors of a few percent can occur. Therefore, a straight pipe, at least 5 to 10 times the nominal diameter of the measuring tube, is typically installed on the inlet-side end face. However, there are known applications where this minimum distance—the so-called inlet distance—cannot be maintained. This is, for example, when the pipe system is located in a very narrow space. The invention disclosed in DE 102014113408 A1 provides a solution in which the narrowing of the pipe diameter causes flow regulation, thereby minimizing the influence of the flow profile, enabling the use of a 0-DN inlet section, i.e., the magnetic induction flow meter can be placed directly after the interference source without necessarily first arranging a straight pipe between the interference source and the end face of the magnetic induction flow meter. However, a drawback of this design is that while it allows for lower sensitivity to rotating asymmetric flow profiles, it must also accept pressure losses. Furthermore, this design is limited by… The piping system.

[0004] The sensitivity of flow measurement to rotating asymmetric flow profiles depends on the geometry of the measuring tube and the measuring electrodes. Therefore, the influence of the measuring tube and electrode geometry must be considered to correctly describe the velocity-dependent induced voltage. These two influences are mathematically determined by a weighting function. express.

[0005] The effect of geometry on flow can be best represented by the following relationship:

[0006] In order to determine the voltage It can measure the flow rate within the volume of the measuring tube. and weight function Integrate. Utilize Using magnetic fields and the Greenian function defined by the electric boundary conditions To describe the weight function The goal of the optimization method is to... The geometry of the structure can be optimized in a way that applies to the entire flow profile. However, this is not possible for a measuring tube with a single point electrode pair. One possible approach is to provide an adaptation of the electrode shape. However, this is impractical and introduces new difficulties. Another approach is to use multiple pairs of measuring electrodes.

[0007] One solution is provided by a magnetic induction flowmeter known in CN 101294832 A, which has two pairs of measuring electrodes arranged axially symmetrically in the cross-section of the measuring tube to minimize the influence of the flow profile on the determination of the volumetric flow rate. The axes of the two measuring electrodes, defined by the pairs of measuring electrodes, each span a central angle of approximately 40° in the cross-section of the measuring tube.

[0008] Another embodiment is disclosed in DE 10 2015 113 390 A1, wherein the second and third pairs of measuring electrodes are arranged on a defined electrode axis, the defined electrode axis being arranged at an angle of less than or equal to ±45° relative to the first measuring electrode axis perpendicular to the magnetic field orientation.

[0009] EP 0878694 A1 also discloses a magnetic induction flowmeter that, starting from the prior art, improves measurement accuracy within a measurement error range of less than 1% by using two additional pairs of measuring electrodes, the axes of which each span an angle of approximately 45° with the axes of the measuring electrodes in a conventional pair of measuring electrodes and the axis of the measuring tube. This is achieved, in particular, by applying a potential difference to the individually detected and weighted measuring electrodes.

[0010] DE 10 2018 108 197 A1 discloses a magnetic induction flow meter that is robust when used with rotationally asymmetric flow profiles. For this purpose, the magnetic induction flow meter has two or more pairs of measuring electrodes disposed on a measuring tube, and cylindrical coils, each connected to an electrode shoe. The geometry of the electrode shoe is adapted to the central angle of the circular sector containing the measuring electrodes on one side of the measuring tube.

[0011] The disadvantage of this solution is that the cylindrical coil has a higher inductance, resulting in slower switching between preferred magnetic field directions. Furthermore, the cylindrical coil has a larger outer diameter than a comparable saddle coil. The advantage of saddle coils compared to cylindrical coils is that they require less copper wire to achieve a comparable magnetic field strength. This allows for more compact magnetic induction flow meters. Summary of the Invention

[0012] Based on the above-mentioned prior art, the purpose of this invention is to provide an alternative magnetic induction flow meter that minimizes the influence of the rotational asymmetric flow curve on the determination of flow rate and volumetric flow rate.

[0013] This objective is achieved by the magnetic induction flow measurement device according to claim 1 and the method for designing a magnetic induction flow meter according to claim 16.

[0014] The magnetic induction flowmeter according to the present invention for determining the velocity-related measurement variables of a flowable medium includes: - A measuring tube for conducting media. The longitudinal plane divides the measuring tube into a first side and a second side. The measuring tube has an outer surface. - Magnetic field generating equipment, including: --At least one saddle-shaped coil is disposed on the outer surface of the housing. The coil lines of the saddle-shaped coil define the interior of the saddle-shaped coil. --A saddle-shaped coil core assembly having at least one saddle-shaped coil core, the saddle-shaped coil core assembly being disposed inside the saddle-shaped coil. Among them, the central angle It is installed in the cross-section passing through the magnetic induction flow meter. Among them, for the central corner The following applies: Especially And preferably ;as well as -At least two of the at least four measuring electrodes are disposed on the first side, and similarly, at least two of the at least four measuring electrodes are disposed on the second side. Among them, the central angle The smallest circular sector spanning the cross-section in which at least two measuring electrodes on the first side are disposed. Among them, for the central corner The following applies: Especially And preferably .

[0015] Advantageous embodiments of the present invention are the subject of the dependent claims.

[0016] One embodiment specifies that the central angle and central angle The mutual compatibility makes the magnetic induction flow meter insensitive to deviations caused by rotationally symmetric flow to the extent that the magnetic induction flow meter does not produce measurement errors for flow velocity-related measurement variables, especially measurement errors of the flow rate during the test measurement. And / or has a measurement error of less than 1.0%, particularly less than 0.5%, and preferably less than 0.2% of the volumetric flow rate. , Among them, flow rate and / or volumetric flow rate To establish reference values, Among these, the flow rate for rotationally asymmetric flow is determined. and / or volumetric flow rate , In the test measurement, a rotational asymmetric flow is generated by interference located on the inlet side end face of the measuring tube and including at least one interference source.

[0017] One embodiment specifies that the interference source includes a baffle and / or a 90° bend in the tube. The baffle covers at least 10% of the cross-section of the measuring tube. The baffle has a chord that defines the direction of the baffle toward the measuring tube. The baffles can be oriented in either a first baffle orientation or a second baffle orientation. In the first baffle orientation, the string is oriented perpendicular to the main magnetic field axis, and in the second baffle orientation, the string is oriented parallel to the main magnetic field axis. The 90° pipe bend exhibits either a first pipe bend orientation or a second pipe bend orientation. The first tube bending orientation is characterized by its tube axis extending perpendicularly to the main magnetic field axis and the longitudinal axis of the measuring tube, while the second tube bending orientation is characterized by its tube axis extending parallel to the main magnetic field axis and perpendicular to the longitudinal axis of the measuring tube.

[0018] One embodiment specifies that the interference source is located at a distance of 0-DN from the inlet-side end face.

[0019] One embodiment specifies that the saddle-shaped coil inside the cross-section is centered at an angle Surrounding the measuring tube.

[0020] Among them, for the central corner The following applies: Especially And preferably .

[0021] One embodiment specifies that the saddle-shaped coil inside the cross-section is centered at an angle Surrounding the measuring tube, The measuring tube has a nominal diameter DN. in, Applicable, among which Especially as well as Especially .

[0022] One embodiment further includes: -At least three of the at least six measuring electrodes are disposed on the first side, and similarly, at least three of the at least six measuring electrodes are disposed on the second side. Among them, at least three measuring electrodes on the first side are set in the smallest circular sector.

[0023] One embodiment specifies that the saddle-shaped coil core assembly includes two saddle-shaped coil cores that are spaced apart from each other and do not directly contact each other.

[0024] One embodiment specifies the separation distance between the two saddle-shaped coil cores. , Among them, regarding distance The following applies: Especially And preferably .

[0025] One embodiment further includes: --Two saddle-shaped coils, positioned opposite each other on the measuring tube, each have their own saddle-shaped coil interior. Each of the two saddle-shaped coils contains a saddle-shaped coil core assembly.

[0026] One embodiment specifies that each of the two saddle-shaped coil core assemblies includes two saddle-shaped coil cores.

[0027] One embodiment specifies that the saddle-shaped coil core of the first saddle-shaped coil core assembly is connected to the saddle-shaped coil core of the second saddle-shaped coil core assembly.

[0028] One embodiment specifies that the first saddle-shaped coil core of the first saddle-shaped coil core assembly is connected to the first saddle-shaped coil core of the second saddle-shaped coil core assembly via a first field guiding element. The second saddle-shaped coil core of the first saddle-shaped coil core assembly is connected to the second saddle-shaped coil core of the second saddle-shaped coil core assembly via a second field guiding element.

[0029] One embodiment specifies that all measuring electrodes on one side are electrically connected to each other via conductive connecting elements.

[0030] One embodiment specifies that the cross-section inside the saddle-shaped coil has an effective cross-sectional area. .

[0031] Among them, the cross-section of the saddle-shaped coil core assembly has an effective cross-sectional area. , in Applicable, among which In particular And preferably .

[0032] The method according to the present invention for designing a magnetic induction flowmeter according to any one of the preceding claims comprises the following method steps: - Make the central angle and and optional The magnetic induction flowmeter is so well-matched that it is insensitive to deviations in rotationally symmetric flow to the extent that there are no measurement errors of flow velocity-related variables, particularly flow rate measurement errors, during the test measurement. and / or volumetric flow rate The measurement error is less than 1.0%, particularly less than 0.5%, and preferably less than 0.2%. Among them, make the central angle and The adaptation involves performing test measurements using the following methods and steps: - Determine the flow rate for a flow with a fully exhibited flow profile. and / or volumetric flow rate ;as well as - Determine the flow rate for rotationally asymmetric flow. and / or volumetric flow rate , The rotationally asymmetric flow is generated by interference located on the inlet-side end face and including at least one interference source. Attached Figure Description

[0033] The invention will be explained in more detail with reference to the following figures, in which: Figure 1 A perspective view of a magnetic induction flow meter according to the prior art is shown; Figure 2 The image shows a cross-section of a magnetic induction flowmeter according to the prior art. Figure 3 A perspective view of a first embodiment of a magnetic induction flowmeter according to the present invention is shown. Figure 4 The image shows a cross-section through a first embodiment of the magnetic induction flowmeter according to the invention; Figure 5 A perspective view of a second embodiment of the magnetic induction flowmeter according to the present invention is shown; Figure 6 A block diagram illustrating the method steps of a method for designing a magnetic induction flowmeter according to the present invention is shown. Figure 7 An embodiment of a conductive connection element is shown; and Figure 8 Multiple sources of interference. Detailed Implementation

[0034] Figure 1 A perspective view of a magnetic induction flowmeter 1 with an open sensor system is shown. Figure 2 The cross-section through the magnetic induction flowmeter 1 is shown, which is in contrast to... Figure 1 The only difference of the magnetic induction flowmeter 1 is that the field guiding elements 60 and 61 are not shown.

[0035] The magnetic induction flowmeter 1 includes a measuring tube 2 for conducting a flowable and conductive medium. Figure 1 The measuring tube 2 shown is cylindrical. However, it may also have at least one or more sections in which its shape deviates from a cylindrical shape. Alternatively, the measuring tube 2 can also be completely non-cylindrical (e.g., as a square or rectangular tube). The measuring tube 2 can have a metal support tube with an electrically insulating liner disposed on the inner surface of the metal support tube. The electrically insulating liner can be made of plastic, ceramic, and / or glass. The electrically insulating liner is drawn into the carrier tube or applied to the inner surface of the carrier tube in the form of a generally flowable coating medium. Alternatively, the measuring tube 2 can have a support tube made of an electrically insulating material. Therefore, the support tube can be made of plastic, ceramic, or glass. In this case, the additional liner is usually omitted.

[0036] A magnetic field generating device 3 is disposed on the outer surface of the measuring tube, specifically the supporting tube. The magnetic field generating device 3 is designed to generate a magnetic field penetrating the measuring tube 2 and is positioned and oriented on the measuring tube 2 such that the main magnetic field axis of the generated magnetic field intersects perpendicularly with the longitudinal axis of the measuring tube 2. The magnetic field generating device 3 has at least one saddle coil 4, which plays an active role in generating the magnetic field. In the illustrated embodiment, the magnetic field generating device 3 has two saddle coils 4, 9 disposed opposite to each other. The shape of each saddle coil 4, 9 is adapted to the shape of the outer surface of the measuring tube 2. The saddle coils 4, 9 include wound coil wires defining the interior 5 of the saddle coil for receiving saddle coil cores 6, 18. A saddle coil core 6 is disposed within at least one saddle coil 4. In the illustrated embodiment, saddle coil cores 6, 18 are disposed in each of the two saddle coils 4, 9. The saddle coil cores 6, 18 are typically made of a soft magnetic material and have the function of increasing the inductance of the overall saddle coil system. The saddle-shaped coil cores 6 and 18 are designed to fill the interior of the corresponding saddle-shaped coil 5 as completely as possible. However, narrow gaps may also exist between the saddle-shaped coils 4 and 9 and the saddle-shaped coil cores 6 and 18. This results in an approximately Gaussian distribution of the magnetic field strength in the cross-section of the measuring tube and along the axis of the imaginary measuring electrode. The apex of the Gaussian distribution intersects the axis of the main magnetic field. The maximum value of the magnetic field strength is significantly higher than that of the solution without saddle-shaped coil cores, and decreases more radially and gently compared to the case of a magnetic system without saddle-shaped coil cores.

[0037] Two saddle-shaped coil cores 6, 18 are connected to each other via two field guiding elements 60, 61. Two field guiding elements 60, 61 are shown, but alternatively, the magnetic coupling of the two saddle-shaped coil cores 6, 18 can also be achieved using exactly one field guiding element 60. The illustrated field guiding elements 60, 61 are made of a material suitable for guiding magnetic field lines from the saddle-shaped coil core 6 to the saddle-shaped coil core 18 to achieve the magnetic coupling of the two saddle-shaped coil cores 6, 18. Soft magnetic materials are suitable for this purpose. The field guiding elements 60, 61 can be formed from stamped electrical steel sheet.

[0038] Alternatively, the saddle coils 5 and 10 may be without a saddle coil core (not shown). In this case, saddle coils 4 and 9 are air coils. Furthermore, the magnetic field generating device 3 does not have cylindrical coils and pole shoes, as taught, for example, in DE 10 2018108 197 A1.

[0039] Saddle coils 4 and 9 are electrically connected to operating electronics (not shown) designed to operate saddle coils 4 and 9 with an operating signal. The operating signal can be a time-varying voltage or current. Saddle coils 4 and 9 can be connected in series or in parallel with each other.

[0040] The illustrated magnetic induction flowmeter 1 further comprises two measuring electrodes 11, 12, positioned relative to each other, particularly radially, and each of the two measuring electrodes 11, 12 is disposed in an opening in the measuring tube 2. Each measuring electrode 11, 12 is equipped with operating electronics (not shown), configured to measure the measuring voltage applied to the measuring electrode 11, 12 and / or the potential present at the measuring electrode 11, 12. The measuring voltage is proportional to the flow rate of the conductive medium flowing through the measuring tube. The measuring electrodes 11, 12 can take any form known in the prior art (e.g., DE10 2012 109 308 A1). The illustrated magnetic induction flowmeter 1 also comprises a fill level monitoring electrode 30, which is disposed opposite to a reference electrode 31 on the measuring tube. Both electrodes are located inside a saddle-shaped coil 5. The fill level monitoring electrode 30 is designed to monitor whether the fill level is at its maximum value. The reference electrode 31 is connected to an electrical reference potential and is often used in fully electrically insulated measuring tubes 2. However, filling the level monitoring electrode 30 and the reference electrode 31 is not necessary for the present invention.

[0041] Figure 3 A first embodiment of the magnetic induction flowmeter 1 according to the present invention is shown, which is used to determine the velocity-related measurement variables of a flowable medium. Figure 4 It shows crossing Figure 3 The cross-section of the magnetic induction flowmeter 1, wherein, for clarity, the field guiding elements 60 and 61 are not shown.

[0042] The magnetic induction flowmeter 1 has a measuring tube 2 for conducting the medium, which is divided into a first side I and a second side II by a longitudinal plane LE. The longitudinal axis of the measuring tube and the main magnetic field axis of the magnetic field generated by the magnetic field generating device 3 are located in the longitudinal plane LE.

[0043] The magnetic field generating device 3 includes at least one saddle-shaped coil 4, or, in the illustrated case, two saddle-shaped coils 4, 9 arranged opposite to each other. In particular, within the saddle-shaped coils 4, 9, saddle-shaped coil core assemblies 6, 17 having at least one saddle-shaped coil core 7, 18 are provided inside the saddle-shaped coils 5, 10. In the illustrated embodiment, each of the saddle-shaped coil core assemblies 6, 17 includes exactly one saddle-shaped coil core 7, 18. Figure 3 The embodiments shown are based on the present invention and Figure 1 and Figure 2 The difference from the prior art shown is that the central angle in the cross-section of the measuring section of the magnetic induction flowmeter 1, specifically through the measuring section of the magnetic induction flowmeter 1 in which the magnetic field generating device and the measuring electrode are disposed, is... This spans the smallest circular sector (see dashed circular sector) within which saddle-shaped coil core assemblies 6 and 17 are located. This means the center angle Limit and / or restrict the dimensions of saddle-shaped coil core assemblies 6 and 17. Regarding the center angle... The following applies: Especially And preferably .horn The specified limitations are given in degrees. The saddle coil core 7 of the first saddle coil core assembly 6 is specifically and exclusively connected to the saddle coil core 18 of the second saddle coil core assembly via field guiding elements 60, 61.

[0044] The saddle-shaped coil core assemblies 5, 10 and / or the saddle-shaped coil cores only fill a small proportion of the saddle-shaped coil interiors 5, 10. The cross-section of the saddle-shaped coil interiors 5, 10 has an effective cross-sectional area. Furthermore, the cross-sections of the saddle-shaped coil core assemblies 6 and 17 have an effective cross-sectional area. Here, the following applies: ,in, In particular And preferably .

[0045] Furthermore, the magnetic field generating device 3 according to the invention does not have a cylindrical coil and does not have pole shoes, as taught, for example, in DE 10 2018 108 197 A1, CN 204 694 303 U or EP 0 418 033 A1.

[0046] Inside the saddle-shaped coil, 5 and 10 are positioned at a central angle within the cross-section of the magnetic induction flowmeter 1. Enclosing, specifically its boundary, around measuring tube 2 (see dotted-line circular sector). Central angle This involves measuring the lengths of saddle-shaped coils 4 and 9, and indirectly, the proportion of the outer surface area of ​​the measuring tube covered by saddle-shaped coils 4 and 9. (Regarding the center angle...) The following applies: Especially And preferably .horn The specified limits are given in degrees. The area inside the saddle coil 5, 10 is significantly larger than that of the saddle coil core assemblies 6, 17 in the circumferential direction surrounding the outer surface of the measuring tube 2.

[0047] Alternatively, a favorable central angle Able to be derived from equations Description. (Among them) This indicates the nominal diameter of measuring tube 2, and it is explicitly stated that... Especially as well as Especially .

[0048] The magnetic induction flowmeter 1 according to the present invention has at least four measuring electrodes 11, 12, 13, 14, wherein at least two of the at least four measuring electrodes 11, 12, 13, 14 are disposed on a first side I, and at least two of the at least four measuring electrodes 11, 12, 13, 14 (made by...) Figure 3 The measuring tube cover (in the middle) is set on the second side. Central angle The smallest circular sector (see dashed circular sector) in the cross-section of the magnetic induction flowmeter 1, spanning at least two measuring electrodes 11, 13 on the first side I. (Regarding the central angle) The following applies: Especially And preferably .horn The specified limitations are given in degrees. The minimum circular sector is limited by the opening of the measuring electrode in the measuring tube or by the axis of the corresponding external measuring electrode and / or the longitudinal and / or symmetry axis of the external measuring electrode. Therefore, the measuring electrode head may be at least partially located outside the defined minimum circular sector.

[0049] In the illustrated embodiment, the magnetic induction flowmeter 1 has six measuring electrodes 11, 12, 13, 14, 15, and 16. Three measuring electrodes 11, 13, and 15 are disposed on a first side (I) of the measuring tube 2, and three measuring electrodes 12, 14, and 16 are disposed on a second side (II) of the measuring tube 2. All measuring electrodes on one side are arranged within a minimum circular sector. The positioning of the measuring electrodes on each side is determined by a central angle. The circular sector being crossed is determined.

[0050] Central angle and It was not chosen arbitrarily. The central angle. and central angle The mutual adaptation makes the magnetic induction flowmeter 1 insensitive to deviations caused by rotationally symmetric flow to the extent that the magnetic induction flowmeter 1 does not exhibit measurement errors of flow velocity-related measurement variables, especially measurement errors of flow rate during the test measurement. And / or measurement error of volumetric flow rate Less than 1.0%, particularly less than 0.5%, and preferably less than 0.2%. Flow rate. and / or volumetric flow rate Establish reference values ​​and determine the flow rates for rotationally asymmetric flow. and / or volumetric flow rate Rotational asymmetric flow is generated in the test measurement by interference located on the inlet-side end face of the measuring tube 2 and including at least one interference source.

[0051] Central angle It wasn't chosen arbitrarily, but rather adapted / optimized to the center corner. and The free parameters of the magnetic induction flowmeter 1 make it insensitive to deviations caused by rotationally symmetric flow to the extent that the magnetic induction flowmeter 1 does not exhibit measurement errors of velocity-related measurement variables, especially flow rate measurement errors. and / or measurement error of volumetric flow rate Less than 1.0%, particularly less than 0.5%, and preferably less than 0.2%.

[0052] Figure 5 A second embodiment of the magnetic induction flowmeter 1 according to the present invention is shown, which is used to determine the flow velocity-related measurement variables of a flowable medium. Figure 5 Design and Figure 3 The difference lies in that each of the saddle-shaped coil core assemblies 6 and 17 includes two saddle-shaped coil cores 7, 8, 18, and 19 that are spaced apart from each other and do not directly contact each other, and not just one saddle-shaped coil core 7 or 18 for each saddle-shaped coil. The corresponding saddle-shaped coil cores 7, 8, 18, and 19 forming the saddle-shaped coil core pair are spaced apart by a distance... , Especially And preferably .distance It should be kept as low as possible. By splitting the saddle coil core into two separate, spaced-apart saddle coil cores, free space is created in which a horizontal monitoring electrode or reference electrode (not shown) can be arranged. The first saddle coil core 7 of the first saddle coil core assembly 6 is connected to the first saddle coil core 18 of the second saddle coil core assembly 17 via a first field guide element 60, and the second saddle coil core 8 of the first saddle coil core assembly 6 is connected to the second saddle coil core 19 of the second saddle coil core assembly 17 via a second field guide element 61.

[0053] Figure 6 A block diagram illustrating the method steps of a method for designing a magnetic induction flowmeter according to the present invention is shown (see [link]). Figures 3 to 5 ).

[0054] Method step I includes: - Make the central angle and and optional The magnetic induction flowmeter is so well-matched that it is insensitive to deviations in rotationally symmetric flow to the extent that there are no measurement errors of flow velocity-related variables, particularly flow rate measurement errors, during the test measurement. and / or volumetric flow rate The measurement error is less than 1.0%, particularly less than 0.5%, and preferably less than 0.2%.

[0055] Make the central angle and and optional Adaptation is accomplished by performing test measurements. This includes performing steps II and III of the method.

[0056] Method step II includes: - Determine the flow rate for the flow with a fully revealed flow profile in the measuring tube. and / or volumetric flow rate .

[0057] Depending on the distance and type of the interference source, measurement errors occur in magnetic induction flowmeters due to the non-ideal flow profile following the interference, as it typically presents, and has been optimized to, a fully exhibited rotationally symmetric flow profile. A fully exhibited rotationally symmetric flow profile is understood as a flow profile that no longer changes in the flow direction. For example, such a flow profile is formed in a measuring tube with an inlet section corresponding to an inlet section 30 times the nominal width of the measuring tube and a moderate velocity of 2 m / s.

[0058] Method step III includes: - Determine the flow rate in the measuring tube for rotational asymmetric flow. and / or volumetric flow rate .

[0059] The rotational asymmetric flow is generated by interference located on the inlet-side end face and including at least one interference source. The interference source is located at a distance of 0-DN from the inlet-side end face 22. Figure 8 Potential sources of interference are shown. However, different sources of interference may also be suitable. It is reasonable, however, to point out that by optimizing a magnetic induction flowmeter with a baffle or a 90° pipe bend or a combination of two sources of interference (with appropriate orientation), it is possible to create a magnetic induction flowmeter that meets the requirements (measurement error less than 1%, particularly less than 0.5% and preferably less than 0.2%), even for other types of interference sources.

[0060] Steps II and III of the method do not necessarily have to be performed sequentially. Furthermore, steps II and III of the method can be performed using computer simulation programs (e.g., finite element method (FEM) or computational fluid dynamics (CFD) simulations using ANSYS, Comsol, and / or Starccm+) or experimentally.

[0061] Perform steps II and III for multiple center angle pairs or triples.

[0062] In the final step IV of the method, select the center angle pair or triplet that satisfies the measurement error condition.

[0063] Figure 7 An embodiment of the conductive connecting element 40 is shown, which is designed as a bent metal sheet component. Full reference is made to DE10 2018 116 400 A1, which discloses several variations for suitable bent metal sheet components. The bent metal sheet component has three openings that simplify its arrangement and attachment to the measuring electrodes 11, 13, 15. Alternatively, the connecting element 40 can also be one or more cables that electrically connect or short-circuit the measuring electrodes.

[0064] Figure 8 Two interference sources 50 are shown, each capable of having a different orientation relative to the magnetic induction flowmeter. The interference source 50 for test measurements includes a baffle B and / or a 90° tube bend 90°R. The baffle B covers at least 10% or, for example, exactly 12.5% ​​of the cross-section of the measuring tube 2, specifically the measuring channel defined by a liner or support tube. During test measurements, the baffle B can present either a first baffle orientation B1 or a second baffle orientation B2. In the first baffle orientation B1, the chord is oriented perpendicular to the main magnetic field axis, and in the second baffle orientation B2, the chord is oriented parallel to the main magnetic field axis. The 90° tube bend 90°R can also present either a first tube bend orientation R1 or a second tube bend orientation R2 for test measurements. The first tube bending orientation R1 is characterized in that the longitudinal axis of the tube bending 90°R is oriented perpendicular to the main magnetic field axis MA (displaced in the figure) and perpendicular to the longitudinal axis LA of the measuring tube 2, and the second tube bending orientation R2 is characterized in that the longitudinal axis of the tube bending 90°R is oriented parallel to the main magnetic field axis MA and perpendicular to the longitudinal axis LA of the measuring tube 2.

Claims

1. A magnetic induction flowmeter (1) for determining the velocity-related measurement variables of a flowable medium, the magnetic induction flowmeter (1) comprising: - Measuring tube (2) for conducting the medium; The longitudinal plane (LE) divides the measuring tube (2) into a first side (I) and a second side (II). The measuring tube (2) has an outer surface. - Magnetic field generating device (3), the magnetic field generating device (3) includes: --At least one saddle-shaped coil (4); The saddle-shaped coil (4) is disposed on the outer surface. The coil line of the saddle-shaped coil (4) defines the interior (5) of the saddle-shaped coil. --Saddle-shaped coil core assembly (6), the saddle-shaped coil core assembly (6) includes at least one saddle-shaped coil core (7). The saddle-shaped coil core assembly (6) is disposed inside the saddle-shaped coil (5). In the cross-section of the measuring section passing through the magnetic induction flowmeter (1), and particularly through the magnetic induction flowmeter (1), the central angle is... The smallest circular sector spanning the saddle-shaped coil core assembly (6) is configured therein. Among them, for the central angle The following applies: Especially And preferably ;as well as - At least four measuring electrodes (11, 12, 13, 14). Of the at least four measuring electrodes (11, 12, 13, 14), at least two measuring electrodes (11, 13) are disposed on the first side (I), and similarly, at least two measuring electrodes (12, 14) are disposed on the second side (II). Among them, the central angle The smallest circular sector spanning the cross-section in which the first side (I) is disposed, comprising the at least two measuring electrodes (11, 13). Among them, for the central corner The following applies: Especially And preferably .

2. The magnetic induction flowmeter (1) according to claim 1. in, Make the central angle and the central angle The magnetic induction flowmeter (1) is adapted to each other to the extent that it is insensitive to deviations caused by rotationally symmetric flow: the magnetic induction flowmeter (1) does not exhibit measurement errors of flow velocity-related measurement variables, particularly measurement errors of flow rate during the test measurement. And / or has a measurement error of less than 1.0%, particularly less than 0.5%, and preferably less than 0.2% of the volumetric flow rate. , Among them, flow rate and / or volumetric flow rate To establish reference values, Among these, the flow rate for rotationally asymmetric flow is determined. and / or volumetric flow rate , In the test measurement, a rotational asymmetric flow is generated by interference that is disposed on the inlet side end face (22) of the measurement tube (2) and includes at least one interference source (50).

3. The magnetic induction flowmeter (1) according to claim 2. in, The interference source (50) includes a baffle (B) and / or a 90° pipe bend (90°R). Wherein, the baffle (B) covers at least 10% of the cross-section of the measuring tube (2). The baffle (B) has a chord forming a boundary defining the orientation of the baffle (B) toward the measuring tube (2). The baffle (B) is either in a first baffle orientation (B1) or a second baffle orientation (B2). In the first baffle orientation (B1), the string is oriented perpendicular to the main magnetic field axis, and in the second baffle orientation (B2), the string is oriented parallel to the main magnetic field axis. The 90° tube bend (90°R) presents either a first tube bend orientation (R1) or a second tube bend orientation (R2). The first tube bending orientation (R1) is characterized in that the tube axis (101) extends perpendicularly to the main magnetic field axis and the longitudinal axis (LA) of the measuring tube (2), and the second tube bending orientation (R2) is characterized in that the tube axis (101) extends parallel to the main magnetic field axis and perpendicular to the longitudinal axis (LA) of the measuring tube (2).

4. The magnetic induction flowmeter (1) according to claim 2 or 3. in, The interference source (50) is positioned at a distance of 0-DN from the entrance side end face (22).

5. The magnetic induction flowmeter (1) according to any one of the preceding claims. in, The interior (5) of the saddle-shaped coil in the cross-section is at the central angle Surrounding the measuring tube (2). Among them, for the central angle The following applies: Especially And preferably .

6. The magnetic induction flowmeter (1) according to any one of claims 1 to 4. in, The interior (5) of the saddle-shaped coil in the cross-section is at the central angle Surrounding the measuring tube (2). The measuring tube (2) has a nominal diameter. in, Applicable, among which Especially as well as Especially .

7. The magnetic induction flowmeter (1) according to any one of the preceding claims, comprising: - At least six measuring electrodes (11, 12, 13, 14, 15, 16). Of the at least six measuring electrodes (11, 12, 13, 14, 15, 16), at least three measuring electrodes (11, 13, 15) are disposed on the first side (I), and similarly, at least three measuring electrodes (12, 14, 16) are disposed on the second side (II). The at least three measuring electrodes (11, 13, 15) of the first side (I) are disposed in the smallest circular sector.

8. The magnetic induction flowmeter (1) according to any one of the preceding claims. in, The saddle-shaped coil core assembly (6) includes two saddle-shaped coil cores (7, 8) that are spaced apart from each other and do not directly contact each other.

9. The magnetic induction flowmeter (1) according to claim 8, wherein, in, The two saddle-shaped coil cores (7, 8) are spaced apart by a distance , Among them, regarding the distance The following applies: Especially And preferably .

10. The magnetic induction flowmeter (1) according to any one of the preceding claims. in, The magnetic field generating device (3) includes: --Two saddle-shaped coils (4, 9) are arranged opposite to each other on the measuring tube (2). Each of the two saddle-shaped coils (4, 9) has an interior (5, 10) of the saddle-shaped coil. One of the saddle-shaped coil core assemblies (6, 17) is disposed in each of the two saddle-shaped coils inside (5).

11. The magnetic induction flowmeter (1) according to claim 10. in, The two saddle-shaped coil core assemblies (6, 17) each include two saddle-shaped coil cores (4, 9, 18, 19).

12. The magnetic induction flowmeter (1) according to claim 11. in, The saddle coil cores (7, 8) of the first saddle coil core assembly (6) are specifically and exclusively connected to the saddle coil cores (18, 19) of the second saddle coil core assembly (17) via field guiding elements (60, 61).

13. The magnetic induction flowmeter (1) according to claim 11 or 12. in, The first saddle coil core (7) of the first saddle coil core assembly (6) is connected to the first saddle coil core (18) of the second saddle coil core assembly (17) via a first field guiding element (60). The second saddle coil core (8) of the first saddle coil core assembly (6) is connected to the second saddle coil core (19) of the second saddle coil core assembly (17) via the second field guide element (19).

14. The magnetic induction flowmeter (1) according to any one of the preceding claims. in, All measuring electrodes (11, 13, 15 or 12, 14, 16) on one side (I or II) are electrically connected to each other via conductive connecting element (40).

15. The magnetic induction flowmeter (1) according to any one of the preceding claims. in, The interior of the saddle-shaped coil (5, 10) has an effective cross-sectional area in the cross-section. , The saddle-shaped coil core assembly (6, 17) has an effective cross-sectional area in its cross-section. , in Applicable, among which In particular And preferably .

16. A method for designing a magnetic induction flowmeter (1) according to any one of the preceding claims, comprising the method steps of: - Make the central angle and and optional The magnetic induction flowmeter (1) is adapted to each other to the extent that it is insensitive to deviations in rotationally symmetric flow to the degree that there are no measurement errors of flow velocity-related measurement variables, especially flow rate measurement errors, during the test measurement. and / or volumetric flow rate The measurement error is less than 1.0%, particularly less than 0.5%, and preferably less than 0.2%. in, Make the central angle and The adaptation involves performing the test measurements using the following method steps: - Determine the flow rate for a flow with a fully exhibited flow profile. and / or the volumetric flow rate ; as well as - Determine the flow rate for rotationally asymmetric flow. and / or the volumetric flow rate , The rotational asymmetric flow is generated by interference located on the inlet-side end face and including at least one interference source (50).

Images