Magnetic-inductive flowmeter, bluff body insert for a magnetic-inductive flowmeter, and method for operating a magnetic-inductive flowmeter

Abstract

The invention relates to a magnetic-inductive flowmeter (1) for determining the flow rate of a medium, comprising: a measuring tube (2) for carrying the medium; a magnetic field generating device (3) for generating a magnetic field which penetrates at least part of the medium perpendicularly to the flow direction of the medium; at least two electrodes (4) for tapping a measurement current induced in the medium; and a control and evaluation unit (5). The magnetic-inductive flowmeter is characterised in that the measuring tube (2) comprises a bluff body insert (6) which is arranged upstream of the electrodes (4) as viewed in the flow direction and has a bluff body (7) for generating vortices in the medium. The invention also relates to a corresponding bluff body insert (6) and to a method (100) for operating a magnetic-inductive flowmeter (1) according to the invention.

Description

[0001] Magnetic-inductive flowmeter, interfering body insert for a magnetic-inductive flowmeter and method for operating a magnetic-inductive flowmeter

[0002] The invention relates to a magnetic-inductive flowmeter for determining the flow of a medium, comprising a measuring tube for guiding the medium, a magnetic field generating device for generating a magnetic field that penetrates the medium at least partially perpendicular to the flow direction of the medium, at least two electrodes for tapping a measuring voltage induced in the medium, and a control and evaluation unit. Furthermore, the invention relates to an obstruction body insert and a method for operating a magnetic-inductive flowmeter.

[0003] The measuring principle of magnetic-inductive flow measurement has been known in the state of the art for many decades. In magnetic-inductive flow measurement, the medium flowing in the measuring tube is subjected to a magnetic field, with the magnetic field having at least one magnetic field component perpendicular to the direction of flow of the medium. The Lorentz force acts on the charged particles in the medium, causing them to deflect perpendicular to the direction of flow and perpendicular to the direction of the magnetic field. This induces a measuring voltage in the medium that is proportional to the flow and is tapped using a pair of electrodes.

[0004] A prerequisite for reliable magnetic-inductive flow measurement is that the medium has a minimum conductivity. If the conductivity of the medium is below the required minimum conductivity, the accuracy of the magnetic-inductive flow measurement cannot be guaranteed, making the measuring principle unsuitable for such media.

[0005] It is quite common to use a magnetic-inductive flowmeter for measuring several different media. In particular, a user may purchase a magnetic-inductive flowmeter with the intention of measuring a specific medium, but then want to use the magnetic-inductive flowmeter for a different medium, or only for a different medium. In particular, the conductivity of a medium may not be sufficient for reliable magnetic-inductive flow measurement. Nevertheless, from a user perspective, it is economically preferable to be able to use an existing system for measurement.

[0006] The invention is therefore based on the object of providing a magnetic-inductive flowmeter that can also be used for measuring media with low conductivity. Furthermore, the invention is based on the object of providing a method for determining the flow of a medium using a magnetic-inductive flowmeter that can also be used to measure media with low conductivity.

[0007] The object is achieved in the magnetic-inductive flowmeter according to the invention firstly and essentially in that the measuring tube has a disruptive body insert arranged in front of the electrodes as seen in the direction of flow, with a disruptive body for generating vortices in the medium.

[0008] The invention is based on the finding that vortices generated by a disruptive body lead to periodic pressure fluctuations in the medium. These pressure fluctuations cause a change in the electrochemical potential at the measuring electrodes. Due to the periodic pressure fluctuations, the change in the electrochemical potential is also periodic and leads to a measuring voltage that varies with the periodicity of the vortices and can be tapped between the electrodes.

[0009] The shedding of the vortices on the disruptive body is independent of the conductivity of the medium. Furthermore, the shedding frequency is proportional to the volume flow of the medium. The magnetic-inductive flowmeter according to the invention thus enables the determination of the volume flow of media with an electrical conductivity that is insufficient for conventional magnetic-inductive flow measurement. This allows users to perform two different measurement modes with the magnetic-inductive flowmeter. On the one hand, "classic" magnetic-inductive flow measurements can be performed on sufficiently electrically conductive media.On the other hand, in media with a very low electrical conductivity, voltage measurement signals, which arise essentially due to the changing electrochemical potential at the electrodes - caused by the vortex in the medium generated by the disturbing body - can be measured and evaluated in order to carry out a flow measurement.

[0010] The magnetic-inductive flowmeter according to the invention thus makes it possible to significantly increase the range of measurable media, since the minimum conductivity of the medium no longer represents an exclusionary criterion.

[0011] The periodically shedding vortices and the resulting periodic pressure fluctuations lead to a periodic change in the electrochemical potential at the measuring electrodes and thus to a periodic change in the measuring voltage that can be tapped between the electrodes. Accordingly, the voltage measurement signal tapped at the electrodes has a periodic signal component. A particularly preferred embodiment of the magnetic-inductive flowmeter is characterized in that the control and evaluation unit is designed such that it taps a voltage measurement signal between the electrodes, examines the voltage measurement signal for periodicity, and calculates a volume flow from a determined frequency.In particular, the control and evaluation unit is designed to carry out the method described below for operating a magnetic-inductive flowmeter and carries it out during operation of the magnetic-inductive flowmeter.

[0012] As known from the theory of vortex flow measurement technology, the frequency of the shedding vortex eddies is proportional to the flow velocity of the medium and thus also to the volume flow. Accordingly, the frequency occurring in the voltage measurement signal is also proportional to the flow velocity and thus to the volume flow.

[0013] The measurement signal caused by the shift in the electrochemical potential at the measuring electrodes is not very large. To ensure good resolution and evaluation, in a particularly preferred embodiment, the control and evaluation unit is designed to subject the voltage measurement signal to a frequency analysis. Accordingly, in this embodiment, the measurement signal is evaluated not in the time domain, but in the frequency domain. Preferably, the control and evaluation unit is designed to subject the signal to an FFT analysis (fast Fourier transformation). This has the advantage that an evaluation can be performed with significantly less computing power.

[0014] The bluff body insert can be designed differently in various variants of the magnetic-inductive flowmeter according to the invention. In a particularly preferred embodiment, the bluff body insert comprises a tube section. The bluff body is arranged at or in a first end of the tube section, and a fastening section is arranged at a second end of the tube section.

[0015] The bluff insert is then inserted with its tube section into the measuring tube of the magnetic-inductive flowmeter. For this purpose, the outer diameter of the tube section of the bluff insert is particularly advantageous if it is minimally smaller than the inner diameter of the measuring tube of the magnetic-inductive flowmeter. Furthermore, the length of the tube section of the bluff insert is preferably selected such that the bluff is positioned sufficiently close to the electrodes so that the pressure fluctuations of the vortices in the area of ​​the electrodes are sufficiently large. The distance of the bluff from the electrodes depends on the diameter of the measuring tube as well as the size and geometry of the bluff insert.

[0016] The mounting section secures the bluff body insert in or to the measuring tube. The mounting can be either direct or indirect. In this context, an indirect mounting is, for example, a clamp connection, in which the mounting section is clamped and thus secured.

[0017] In practice, it is common for the measuring tube of the magnetic-inductive flowmeter to be installed in a pipeline by inserting it between a first and a second pipe. For this purpose, flange sections are usually formed at the ends of the measuring tube. The pipes in the pipeline also have corresponding flange sections, so that the connections between the measuring tube and the pipes are realized as flange connections.

[0018] In a particularly preferred embodiment of the magnetic-inductive flowmeter according to the invention, the fastening section is designed as a flange section or as an orifice plate. When the measuring tube is installed in the pipeline, the fastening section is arranged between the first pipe of the pipeline and the measuring tube—i.e., in the area of ​​the flange connection.

[0019] In a preferred embodiment, in which the fastening section is designed as a flange section, the flange section has through-holes for the passage of fastening screws. The measuring tube also has through-holes. The arrangement of the through-holes and corresponding through-holes on the measuring tube flange are identical.

[0020] An alternative variant of the magnetic-inductive flowmeter is characterized by the mounting section being designed as an orifice plate. This design allows the bluff body insert to be indirectly attached to the measuring tube by clamping it in the area of ​​the pipe connection between the measuring tube and the pipeline. This design offers the advantage that the orifice plate can be designed with thin walls. This saves material and also allows for a shorter design compared to a flange section.

[0021] In a particularly preferred embodiment, the bluff insert is detachably connected to the measuring tube. This means, in particular, that the measuring tube and the bluff insert can be separated again without causing significant damage to either component. In another variant, the bluff insert is permanently connected to the measuring tube. Depending on the material, this permanent variant can be implemented in different ways.

[0022] In a particularly preferred embodiment, both the bluff body insert and the measuring tube are made of steel, preferably stainless steel. A permanent connection is then achieved in one variant by welding. Manufacturing from stainless steel also offers the advantage that the bluff body insert is resistant to aggressive media as well as high or low temperatures.

[0023] In another variant, both the measuring tube and the bluff insert are made of a plastic. Preferably, at least one of the elements is manufactured using a generative manufacturing process, for example, 3D printing. A permanent connection can then be achieved, for example, by fusing or gluing the two components. Alternatively, the measuring tube and the bluff insert can be manufactured as a single component directly during production, for example, using 3D printing. The bluff insert is particularly preferably made of polyetheretherketone (PEEK).

[0024] If the measuring tube and the bluff body insert are detachably connected to each other, care must be taken to ensure that sufficient sealing is achieved at the connection points.

[0025] In a particularly preferred embodiment, when the bluff body insert is connected to the measuring tube, a sealing element is arranged between the fastening section and the measuring tube. The sealing element is particularly preferably designed as a sealing ring. A groove for inserting the sealing element is particularly preferably formed in the fastening section of the bluff body insert on the side facing the tube section—and thus the measuring tube. In the assembled state, a sealing element is inserted into the groove, thus sealing the connection.

[0026] In a particularly preferred embodiment, the side of the fastening section facing the pipe section—and thus the measuring tube—is roughened. This means that the surface has a greater roughness than usual. This can be achieved, for example, by introducing grooves or by forming small burrs. This simplifies sealing between the fastening section and the measuring tube.

[0027] In another variant, the side of the mounting cut facing the measuring tube is mirrored to the side of the measuring tube facing the deflector insert. When the deflector insert is inserted into the measuring tube, the two surfaces fit together precisely. This significantly simplifies sealing the connection point.

[0028] It was explained above that the outer diameter of the tube section of the bluff body insert is slightly smaller than the inner diameter of the measuring tube. Nevertheless, there is a gap between the tube section and the measuring tube in which medium can accumulate. This can be particularly problematic if the medium hardens or has a finite shelf life, in particular if it is of organic origin. In order to prevent deposits of the medium in the gap between the measuring tube and the bluff body insert, a particularly preferred embodiment of the magnetic-inductive flowmeter provides for a sealing element to be arranged between the bluff body insert and the measuring tube. The sealing element is particularly preferably implemented as a sealing ring. More preferably, the tube section of the bluff body insert has a recess at its first end for inserting a sealing element.This is a simple way to seal the space between the bluff insert and the measuring tube.

[0029] The disruptive body of the disruptive body insert creates vortices in the medium, which are evaluated to determine the flow rate. The disruptive body insert, however, is an additional component that is arranged in the measuring tube and influences the flow profile of the medium not only due to the disruptive body. In order to keep the fluidic influence on the medium, apart from the disruptive body, as low as possible, a preferred embodiment is characterized in that the disruptive body insert is conically tapered at both ends, thus creating a smooth transition between the disruptive body and the measuring tube. The disruptive body insert is designed in such a way that there are no abrupt jumps at the transitions to the measuring tube, which could cause the medium to become turbulent.

[0030] The disruptive body itself is particularly preferably manufactured according to the geometries known to be advantageous from the state of the art in vortex flow measurement technology.

[0031] According to the invention, it has been recognized that the effect of changing the measuring voltage by shifting the electrochemical potential is greatest when the longitudinal axis of the perturbation body is arranged orthogonally to the connecting line of the electrodes. A particularly preferred embodiment of the magnetic-inductive flowmeter according to the invention is accordingly characterized in that the longitudinal axis of the perturbation body is perpendicular to the connecting line of the measuring electrodes.

[0032] To ensure reproducible orientation of the bluff insert in the measuring tube and to align the bluff insert, one variant features a marking for positioning the bluff insert in the measuring tube of the magnetic-inductive flowmeter. In particular, the measuring tube also features a corresponding marking.

[0033] In addition to the magnetic-inductive flowmeter, the invention also relates to a bluff body insert for insertion into a measuring tube of a magnetic-inductive flowmeter. This object is achieved by the bluff body insert in that the bluff body insert has a bluff body for generating vortices in the medium flowing in the measuring tube.

[0034] In further embodiments of the bluff body insert according to the invention, the bluff body insert is designed according to the variants described in connection with the magnetic-inductive flowmeter according to the invention. All embodiments of the various embodiments, with their respective advantages, also apply analogously to the bluff body insert according to the invention.

[0035] In addition to the magnetic-inductive flowmeter and the disruptive body insert according to the invention, the invention also relates to a method for operating a magnetic-inductive flowmeter, with a measuring tube for guiding a medium, with a magnetic field generating device for generating a magnetic field that passes through the medium perpendicular to the flow direction, with at least two electrodes for tapping a measuring voltage induced in the medium, with a control and evaluation unit and with a disruptive body arranged in the measuring tube in front of the electrodes as seen in the flow direction.

[0036] In the method, the object is achieved in that in a vortex generation step, vortices are generated in the flowing medium by the disruptive body, wherein the vortices lead to pressure fluctuations in the medium and wherein the vortices have a vortex frequency which is proportional to the volume flow of the medium, that in a voltage tapping step, a measuring voltage is tapped as a voltage measurement signal between the electrodes, wherein the measurement voltage is generated at least partially by a change in the electrochemical potential at the electrodes due to the pressure fluctuations caused by the vortices, that in an analysis step, the voltage measurement signal is examined for a periodic signal component, that in a frequency determination step, the frequency of the periodic signal component is determined and that in a flow determination step, a value for the flow of the medium is determined using the determined frequency.

[0037] The flow value determined in this way is further referred to as vortex-based flow value.

[0038] The method according to the invention enables the flow rate of a medium to be determined even when the medium's conductivity is low. However, the method is also suitable when the medium has a sufficient minimum conductivity to perform conventional magnetic-inductive flow measurements.

[0039] Since the voltage measurement signal generated due to the shift in the electrochemical potential is small, one embodiment of the method is characterized in that, in the analysis step for determining the periodicity of the voltage measurement signal, a frequency analysis of the recorded voltage measurement signal is performed and an amplitude spectrum of the voltage measurement signal is generated. In the frequency determination step, a frequency of a maximum occurring in the amplitude spectrum is then determined. Using the thus determined frequency, a value for the flow rate of the medium is determined.

[0040] An FFT analysis (fast Fourier analysis) is particularly preferred.

[0041] In a preferred variant of the method according to the invention, the method is carried out without applying a magnetic field. In another variant, the vortex-based flow rate is determined with a magnetic field applied.

[0042] A preferred development of the method provides that, in addition to the vortex-based flow value, a conventional magnetic-inductive flow measurement is also implemented. Accordingly, in one variant of the method according to the invention, a magnetic field permeating the medium is generated in a magnetic field generation step. In an MID analysis and determination step, the voltage measurement signal tapped in the voltage tapping step is then analyzed according to methods known from the prior art for determining the flow using magnetic-inductive flow measurement technology, and a value for the flow of the medium is determined. This flow value is referred to as the MID-based flow value.

[0043] If both the vortex-based flow rate and the MID-based flow rate are determined, the value for the medium flow rate determined in the flow rate determination step (vortex-based flow rate) and the value determined in the MID analysis and determination step (MID-based flow rate) can be compared in a comparison step. A variant of the method according to the invention is therefore characterized in that, in a comparison step, the value for the medium flow rate determined in the flow rate determination step (vortex-based flow rate) is compared with the value determined in the MID analysis and determination step (MID-based flow rate).

[0044] According to the invention, it has been recognized that by comparing the two flow values, conclusions can be drawn about certain properties of the medium.

[0045] It has been recognized that, for example, conclusions can be drawn as to whether a single-phase or a two-phase medium is present.

[0046] In a large proportion of classic applications for magnetic-inductive flowmeters or classic vortex flowmeters, the flow of single-phase liquid media is determined. However, if a medium is in two-phase flow, meaning the flowing medium consists of a gaseous phase and a liquid phase, determining the flow becomes more difficult. In particular, it is difficult to determine the individual phase components of the medium.

[0047] In a conventional magnetic-inductive flow measurement, the presence of a two-phase flow leads to the magnetic-inductive flowmeter indicating, to a first approximation, the flow rate of the entire flow. However, as the gas content increases, this value becomes less accurate, making reliable statements impossible. Even with a conventional vortex flowmeter, the flow rate of the entire flow is measured to a first approximation.

[0048] However, before the individual flow components of the two phases can be determined in the presence of a two-phase medium, it must first be recognized that a two-phase flow exists at all.

[0049] According to the invention, it has been recognized that when a single-phase medium is present, the vortex-based flow value and the MID-based flow value essentially agree. If, on the other hand, a two-phase medium is present, the vortex-based flow value and the MID-based flow value differ from one another. A particularly preferred embodiment of the method according to the invention is accordingly characterized in that when the two flow values ​​- vortex-based flow value and MID-based flow value - deviate from one another by more than a predetermined tolerance value, a two-phase flow of the medium is signaled in a signaling step. This embodiment is based in particular on the recognition that the MID-based flow value increases with increasing gas volume fraction, whereas the vortex-based flow value decreases with increasing gas volume fraction.

[0050] Preferably, the tolerance value is set to a value of at least one percent of the MID-based flow rate or to a value of at least one percent of the vortex-based flow rate. The tolerance value can also be set to a higher value. When selecting a suitable tolerance value, the prevailing flow conditions can be taken into account in particular to avoid false signaling under unfavorable flow conditions.

[0051] To determine the flow rate for the liquid phase of the medium, in a further development of the method, an average value is calculated from the vortex-based flow rate and the MID-based flow rate in a liquid phase determination step. This average value is assumed to be the flow rate for the liquid phase of the medium and is output preferentially.

[0052] In order to determine an approximate value for the flow of the gaseous phase, in a further development, the previously determined mean value is subtracted from the MID-based flow value in a gas phase determination step.

[0053] The larger the gas volume fraction in the medium, the more difficult it is to determine the vortex-based flow value, as the periodic signal component of the voltage measurement signal becomes weaker. In order to still be able to reliably determine the vortex-based flow value, a variant of the method for determining the vortex-based flow value records several voltage measurement signal data sets. Each of these voltage measurement signal data sets is subjected to frequency analysis, and an amplitude spectrum is generated for each one. Subsequently, either i. the amplitude spectra of the several voltage measurement signal data sets are averaged and the vortex frequency is determined from the averaged amplitude spectrum, whereby a value for the flow of the medium is then determined using the vortex frequency, or ii.A vortex frequency is determined from each of the amplitude spectra, the vortex frequencies are averaged, and a value for the flow rate of the medium is determined using the averaged vortex frequency.

[0054] To ensure the determination of the vortex-based flow rate with sufficient reliability, yet without unnecessarily demanding computational resources, the number of averages can be adjusted variably. The higher the gas content in the medium, the greater the number of averages should be.

[0055] Which averages are involved depends on the previously described variant selected for determining the vortex-based flow value.

[0056] In a particularly preferred variant, in which, according to i., the amplitude spectra of the multiple voltage measurement signal data sets are averaged and the vortex frequency is determined from the averaged amplitude spectrum, the entire method is carried out several times in succession, resulting in multiple averaged amplitude spectra and multiple vortex frequencies determined from the averaged amplitude spectra. A variant according to the invention now provides for a standard deviation of the vortex frequencies to be determined. In addition, a limit value for the standard deviation is specified. If the standard deviation of the vortex frequencies is above the limit value, the number of amplitude spectra from which the averaged amplitude spectrum is generated is increased, so that the number of averagings is increased to generate the averaged amplitude spectrum.

[0057] In another variant, in which the vortex frequencies are averaged to a mean vortex frequency according to ii., which is used to determine the vortex-based flow value, the standard deviation of the vortex frequencies is calculated and compared against a limit value. If the standard deviation is greater than the limit value, further averaging must be performed, i.e., further amplitude spectra must be recorded, from each of which a vortex frequency is determined, so that the number of vortex frequencies averaged to determine the mean vortex frequency is increased. Overall, the number of vortex frequencies averaged is increased until the determined standard deviation of the vortex frequencies falls below a specified limit value.

[0058] In a particularly preferred embodiment, the limit value in both variants is set to 2% of the current flow value.

[0059] In detail, there are now numerous possibilities for designing and developing the magnetic-inductive flowmeter according to the invention, the disruptive body insert according to the invention, and the method according to the invention. Reference is made to the claims subordinate to the independent claims and to the description of preferred embodiments in conjunction with the drawing. The drawing shows:

[0060] Fig. 1 is a schematic representation of a magnetic-inductive flowmeter with a bluff body insert in a first embodiment,

[0061] Fig. 2 is a representation of a disruptive body insert in a first embodiment,

[0062] Fig. 3 is a representation of a disruptive body insert in a second embodiment,

[0063] Fig. 4 is a schematic representation of a magnetic-inductive flowmeter with a bluff body insert in a second embodiment,

[0064] Fig. 5 is a block diagram of a first variant of a method for operating a magnetic-inductive flowmeter,

[0065] Fig. 6 is a block diagram of a second variant of a method for operating a magnetic-inductive flowmeter,

[0066] Fig. 7 is a block diagram of a first partial sequence of a method and

[0067] Fig. 8 is a block diagram of a second subsequence of a method.

[0068] Fig. 1 shows a magnetic-inductive flowmeter 1 for determining the flow of a medium. The magnetic-inductive flowmeter 1 comprises a measuring tube 2 for guiding the medium, a magnetic field generating device 3 for generating a magnetic field that penetrates the medium at least partially perpendicular to the flow direction of the medium, two electrodes 4 for tapping a measuring voltage induced in the medium, and a control and evaluation unit 5. Fig. 1 shows a sectional view, so only one of the electrodes 4 is visible.

[0069] In the measuring tube 2, a bluff insert 6 with a bluff body 7 for generating vortices in the medium is arranged upstream of the electrodes 4 in the direction of flow - represented by the arrow. The vortices generate periodic pressure fluctuations in the medium, which cause a shift in the electrochemical potential at the electrodes 4, which is noticeable in a periodic signal component in the voltage measurement signal tapped at the electrodes 4. The control and evaluation unit 5 of the magnetic-inductive flowmeter is designed such that it taps a voltage measurement signal between the electrodes, examines the voltage measurement signal for periodicity, and calculates a volume flow from the frequency. In particular, it is designed to carry out the method described in connection with Figures 5 and 6.

[0070] Fig. 2 shows a baffle insert 6. The baffle insert 6 has a tubular section 8. The baffle 7 is arranged at a first end 9 of the tubular section 8. A fastening section 11 is arranged at a second end 10 of the tubular section 8. In the illustrated embodiment, the fastening section 11 is designed as a flange section 12.

[0071] Another embodiment of the disruptive body insert 6 is shown in Fig. 3. Here, the disruptive body insert 6 also has a tube section 8. The disruptive body 7 is arranged at a first end 9 of the tube section 8. A fastening section 11 is arranged at a second end 10 of the tube section 8. In contrast to the embodiment shown in Fig. 2, the fastening section 11 is designed as a cover 13.

[0072] Fig. 1 shows an embodiment in which the disruptive body insert 6 has a flange section 12 and is detachably connected to the measuring tube 2. Fig. 1 also shows that the measuring tube 2 of the magnetic-inductive flowmeter 1 is inserted between a first tube 15 and a second tube 16 of a pipeline by means of flange connections 14. The fastening section 11 of the disruptive body insert 6 is arranged between the first tube 15 and the measuring tube 2. The measuring tube 2 also has a flange section 17. Both the flange section 17 of the measuring tube 2 and the fastening section 11 and the flange section 18 of the first tube 15 have screw recesses 19 through which connecting screws 20 are guided and thus fasten the measuring tube 2 in the pipeline and the disruptive body insert 6 to the measuring tube 2.

[0073] To seal the measuring tube 2 and the bluff body insert 6, a sealing element 21 is arranged between the fastening section 11 and the measuring tube 2. As can be seen particularly in Fig. 2, the fastening section 11 has a circumferential groove 22 into which the sealing element 21 is inserted.

[0074] As can be seen in Fig. 1, there is a gap 23 between the measuring tube 2 and the bluff body insert 6, in which medium could accumulate. To prevent such accumulation, an additional sealing element 24 is arranged between the tube section 8 and the measuring tube 2. This sealing element 24 is inserted into a groove 25 formed at the first end 9 of the tube section 9.

[0075] Fig. 4 shows a further embodiment of a magnetic-inductive flowmeter 1. Both the measuring tube 2 of the magnetic-inductive flowmeter 1 and the bluff insert 6 are made of a plastic material. In this variant, the bluff insert 6 is permanently connected to the measuring tube 2. This is achieved by an adhesive connection 26 between the flange section 17 of the measuring tube 2 and the fastening section 11 of the bluff insert 6, designed as an orifice plate 13.

[0076] In both the embodiment shown in Fig. 1 and the embodiment shown in Fig. 4, the obstruction body 7 of the obstruction body insert 6 is arranged perpendicular to a connecting line of the electrodes 4. This achieves the greatest possible measuring effect. To simplify the positioning of the obstruction body insert 6 in the measuring tube 2, the obstruction body insert 6 preferably has a marking 27. This can be seen, for example, in Fig. 2. The measuring tube 2 can also have a corresponding marking.

[0077] As can be seen in the illustrations of the magnetic-inductive flowmeters 1, the bluff body 7 is arranged upstream of the electrodes 4, as seen in the direction of flow of the medium. The distance to the electrodes 4 is dimensioned such that the vortices generated by the bluff body 7 generate a sufficiently large pressure fluctuation in the region of the electrodes 4. Furthermore, it can be seen that the bluff body insert 6 is designed to be fluidically advantageous. For this purpose, it has conical tapers 28 at its ends 9, 10. These ensure that no additional turbulence is generated at edges in the medium, which would merely cause a disruptive effect.

[0078] Fig. 5 shows a method 100 for operating a magnetic-inductive flowmeter, comprising a measuring tube for conducting a medium, a magnetic field generating device for generating a magnetic field perpendicular to the flow direction through the medium, at least two electrodes for tapping a measuring voltage induced in the medium, a control and evaluation unit, and a disruptive body arranged in the measuring tube upstream of the electrodes as seen in the flow direction. The method 100 is characterized in that, in a vortex generation step 101, vortices are generated in the flowing medium by the disruptive body. The vortexes lead to pressure fluctuations in the medium and have a vortex frequency that is proportional to the volume flow of the medium. In a voltage tapping step 102, a measuring voltage is tapped as a voltage measurement signal between the electrodes.In an analysis step 103, the voltage measurement signal is examined for a periodic signal component. To determine the periodicity of the voltage measurement signal, a frequency analysis of the recorded voltage measurement signal is performed and an amplitude spectrum of the voltage measurement signal is generated. In a frequency determination step 104, the frequency of the periodic signal component is determined. This frequency is the vortex shedding frequency of the vortices on the disruptive body. Finally, in a flow determination step 105, a value for the flow of the medium, namely the vortex-based flow value, is determined using the determined frequency. In the variant shown, the method is carried out without an applied magnetic field.In the illustrated variant, in analysis step 103, a frequency analysis of the recorded voltage measurement signal is performed to determine the periodicity of the voltage measurement signal, and an amplitude spectrum of the voltage measurement signal is generated. In frequency determination step 104, a frequency of a maximum occurring in the amplitude spectrum is determined.

[0079] Fig. 6 shows a further method for operating the magnetic-inductive flowmeter according to the invention. In the method presented here, a magnetic field that permeates the medium during the method is first generated in a magnetic field generation step 106. This is done in a manner known from the prior art. After the voltage tapping step 102 has been carried out, the method performs two different analyses of the measurement signal. The first analysis corresponds to the procedure described in connection with Fig. 5. In a second analysis, in an MID analysis and determination step 107, the voltage measurement signal tapped in the voltage tapping step 102 is analyzed according to methods known from the prior art for determining the flow using magnetic-inductive flow measurement technology, and a value for the flow of the medium is determined - MID-based flow value.Since the described method uses a magnetic field for measurement, the magnetic-inductive effects are superimposed on the electrochemical effects. The control and evaluation unit accordingly performs two different analyses of the voltage measurement signal. In a comparison step 108, the medium flow value determined in the flow determination step 105 is compared with the value determined in the MID analysis and determination step 107. If it is determined in the comparison step 108 that the vortex-based flow value and the MID-based flow value deviate from each other by more than a predetermined tolerance value, a two-phase flow of the medium is signaled in a signaling step 109. In this case, the tolerance value is set to one percent of the MID-based flow value.

[0080] To determine the flow rate for the liquid phase of the medium, an average value is calculated from the vortex-based flow rate and the MID-based flow rate in a liquid phase determination step 110, and this average value is set and output as the flow rate for the liquid phase of the medium. In a gas phase determination step 111, the previously determined average value is then subtracted from the MID-based flow rate to determine a value for the flow rate of the gaseous phase.

[0081] Fig. 7 shows a block diagram of a partial sequence of a method according to the invention. To determine the vortex-based flow value, in the illustrated partial sequence, several voltage measurement signal data sets are recorded in the voltage tapping step 102'. For each of the voltage measurement signal data sets, a frequency analysis is carried out in the analysis step 103', and an amplitude spectrum is generated. Furthermore, in the illustrated method, the amplitude spectra of the several voltage measurement signal data sets are averaged. In the frequency determination step 104', the vortex frequency is determined from the averaged amplitude spectrum. Using this vortex frequency, a value for the flow of the medium is then determined in the flow determination step 105'. The number of amplitude spectra over which the average is calculated in the analysis step 103' is selected variably.To determine the number of averagings, the illustrated subsequence of the method is executed several times in succession; exemplary runs are shown in Fig. 3. In this way, several averaged amplitude spectra are generated, and a vortex frequency is determined from each of the averaged amplitude spectra, so that several vortex frequencies are determined. Subsequently, in method step 112, a standard deviation of the vortex frequencies is determined and compared with a predetermined limit value. The number of amplitude spectra over which the average is calculated, i.e. from which the averaged amplitude spectrum is generated, is increased until the standard deviation falls below the predetermined limit value. In this case, the limit value is set to a value of 2% of the current flow value.

[0082] Fig. 8 shows a particularly alternative subsequence of the method. To determine the vortex-based flow value, several voltage measurement signal data sets are recorded in the voltage sampling step 102. In the analysis step 103, a frequency analysis is performed for each of the voltage measurement signal data sets, and an amplitude spectrum is generated. In the frequency determination step 104, a vortex frequency is determined from each of the amplitude spectra, and the vortex frequencies are averaged. The number of vortex frequencies over which the average is calculated is variably selected. In this case, a standard deviation of the vortex frequencies is determined, and the number of vortex frequencies over which the average is calculated is increased until the determined standard deviation of the vortex frequencies falls below a predetermined limit. In the flow determination step 105, a value for the flow of the medium is then determined using the averaged vortex frequency. Reference numeral

[0083] 1 Magnetic-inductive flowmeter

[0084] 2 measuring tube

[0085] 3 Magnetic field generating device

[0086] 4 electrodes

[0087] 5 Control and evaluation unit

[0088] 6 Destruction body deployment

[0089] 7 disruptive bodies

[0090] 8 Pipe section

[0091] 9 First end of the pipe section

[0092] 10 Second end of the pipe section

[0093] 11 Fastening section

[0094] 12 Flange section

[0095] 13 aperture

[0096] 14 Flange connection

[0097] 15 First pipe of a pipeline

[0098] 16 Second pipe of a pipeline

[0099] 17 Flange section of the measuring tube

[0100] 18 Flange section of the first pipe

[0101] 19 screw recesses

[0102] 20 connecting screws

[0103] 21 Sealing element

[0104] 22 grooves

[0105] 23 space

[0106] 24 Sealing element

[0107] 25 grooves

[0108] 26 Adhesive bond

[0109] 27 Conical tapers 100 procedures

[0110] 101 Vortex generation step

[0111] 102 Voltage tapping step

[0112] 103 Analysis step 104 Frequency tuning step

[0113] 105 Through flow sb e mood ss step

[0114] 106 Magnetic field generation step

[0115] 107 MID analysis and determination step

[0116] 108 Comparison step 109 Signaling step

[0117] 110 Liquid phase determination step

[0118] 111 Gas phase determination step

[0119] 112 Procedure step

Claims

Patent claims 1. Magnetic-inductive flow meter (1) for determining the flow of a medium, with a measuring tube (2) for guiding the medium, with a magnetic field generating device (3) for generating a magnetic field that passes through the medium at least partially perpendicular to the flow direction of the medium, with at least two electrodes (4) for tapping a measuring voltage induced in the medium and with a control and evaluation unit (5), characterized in that the measuring tube (2) has a disruptive body insert (6) arranged in front of the electrodes (4) as seen in the flow direction, said disruptive body having a disruptive body (7) for generating vortices in the medium.

2. Magnetic-inductive flowmeter (1) according to claim 1, characterized in that the control and evaluation unit (5) is designed such that it taps a voltage measurement signal between the electrodes (4), searches the voltage measurement signal for a periodic signal component, determines a frequency and determines a volume flow from the frequency, in particular that the control and evaluation unit (5) is designed such that it carries out the method according to patent claim 13 - in particular according to patent claims 13 to 15 - during operation of the magnetic-inductive flowmeter (1).

3. Magnetic-inductive flowmeter (1) according to claim 2, characterized in that the control and evaluation unit (5) subjects the voltage measurement signal to a frequency analysis.

4. Magnetic-inductive flowmeter (1) according to one of claims 1 to 3, characterized in that the disruptive body insert (6) has a pipe section (8), that the disruptive body (7) is arranged on or in a first end (9) of the pipe section (8) and that a fastening section (11) is arranged on a second end (10) of the pipe section (8).

5. Magnetic-inductive flowmeter (1) according to claim 4, characterized in that the fastening section (11) is designed as a flange section (12) or that the fastening section (11) is designed as a diaphragm (13), that the measuring tube (2) of the magnetic-inductive flowmeter, when installed in a pipeline, is inserted with flange connections (14) between a first pipe (15) of the pipeline and a second pipe (16) of the pipeline and that the fastening section (11) is arranged between the first pipe (15) and the measuring tube (2).

6. Magnetic-inductive flowmeter (1) according to one of claims 1 to 5, characterized in that the disruptive body insert (6) is detachably connected to the measuring tube (2) - in particular via a screw connection to the measuring tube (2) - or that the disruptive body insert (6) is non-detachably connected to the measuring tube (2) - in particular is welded or glued to the measuring tube (2).

7. Magnetic-inductive flowmeter (1) according to one of claims 1 to 6, characterized in that in the state of the disruptive body insert (6) connected to the measuring tube (2), a sealing element (21) is arranged between the fastening section (11) and the measuring tube (2), in particular that the fastening section (11) of the disruptive body insert (6) has a groove (22) for receiving a sealing element (21) on its side facing the tube section (8).

8. Magnetic-inductive flowmeter (1) according to one of claims 1 to 7, characterized in that a sealing element (24) for sealing an intermediate space (23) between the disruptive body insert (6) and the measuring tube (2) is arranged between the tube section (8) of the disruptive body insert (6) and the measuring tube (2), in particular that the tube section (8) of the disruptive body insert (6) has a groove (25) at its first end (9) for receiving the sealing element (24).

9. Magnetic-inductive flowmeter (1) according to one of claims 1 to 8, characterized in that the disruptive body insert (6) is designed at its ends in such a way that a substantially continuous transition between the disruptive body insert (6) and the measuring tube (2) is realized.

10. Magnetic-inductive flowmeter (1) according to one of claims 1 to 9, characterized in that the longitudinal axis (1) of the disruptive body (7) is perpendicular to a connecting line of the electrodes (4), in particular that the disruptive body insert (6) has a marking (27) for positioning the disruptive body insert (6) in the measuring tube (2) of the magnetic-inductive flowmeter (1), further in particular that the measuring tube (2) also has a corresponding marking.

11. Disturbance body insert (6) for insertion into a measuring tube (2) of a magnetic-inductive flowmeter (1), characterized in that the disturbance body insert (6) has a disturbance body (7) for generating vortices in the medium flowing in the measuring tube.

12. Disturbance body insert (6) according to claim 11, characterized in that the disturbance body insert (6) is designed according to the features characterizing the disturbance body insert (6) of at least one of claims 2 to 10.

13. A method (100) for operating a magnetic-inductive flowmeter, comprising a measuring tube for guiding a medium, a magnetic field generating device for generating a magnetic field permeating the medium perpendicular to the flow direction, at least two electrodes for tapping a measuring voltage induced in the medium, a control and evaluation unit, and a disruptive body arranged in the measuring tube in front of the electrodes as seen in the flow direction, characterized in that in a vortex generating step (101), vortices are generated in the flowing medium by the disruptive body, wherein the vortices lead to pressure fluctuations in the medium and wherein the vortices have a vortex frequency that is proportional to the volume flow of the medium, that in a voltage tapping step (102), a measuring voltage is tapped as a voltage measurement signal between the electrodes,wherein the measuring voltage is generated at least partially by a change in the electrochemical potential at the electrodes due to the pressure fluctuations caused by the vortices, that in an analysis step (103) the voltage measurement signal is examined for a periodic signal component, that in a frequency determination step (104) the frequency of the periodic signal component is determined, and that in a flow determination step (105) a value for the flow of the medium - vortex-based flow value - is determined using the determined frequency.

14. The method (100) according to claim 13, characterized in that in the analysis step (103) for determining the periodicity of the voltage measurement signal, a frequency analysis of the recorded voltage measurement signal is carried out and an amplitude spectrum of the voltage measurement signal is generated, and in the frequency determination step (104) a frequency of a maximum occurring in the amplitude spectrum is determined.

15. Method (100) according to claim 13 or 14, characterized in that in a magnetic field generation step (106) a magnetic field penetrating the medium is generated, and that in an MID analysis and determination step (107) the voltage measurement signal tapped in the voltage tapping step (102) is analyzed according to methods known from the prior art for determining the flow by means of magnetic-inductive flow measurement technology and a value for the flow of the medium - MID-based flow value - is determined.

16. The method according to claim 15, characterized in that in a comparison step (108) the value for the flow of the medium determined in the flow determination step (105) - vortex-based flow value - and the value determined in the MID analysis and determination step (107) - MID-based flow value - are compared with each other 17. The method according to claim 16, characterized in that if the two flow values ​​- vortex-based flow value and MID-based flow value - deviate from each other beyond a predetermined tolerance value, a two-phase flow of the medium is signaled in a signaling step (109), in particular that the tolerance value is set to a value of at least one percent of the MID-based flow value or the vortex-based flow value.

18. Method according to one of claims 15 to 17, characterized in that in a liquid phase determination step (110) an average value is formed from the vortex-based flow value and the MID-based flow value and that the average value is assumed and preferably output as the flow value for the liquid phase of the medium, in particular that further in a gas phase determination step (111) to determine a value for the flow of the gaseous phase the previously determined average value is subtracted from the MID-based flow value.

19. Method according to one of claims 13 to 18, characterized in that to determine the vortex-based flow value, a plurality of voltage measurement signal data sets are recorded, that a frequency analysis is carried out for each of the voltage measurement signal data sets and an amplitude spectrum is generated and that either i. the amplitude spectra of the plurality of voltage measurement signal data sets are averaged and that the vortex frequency is determined from the averaged amplitude spectrum and a value for the flow of the medium is determined using the vortex frequency or that ii. a vortex frequency is determined from each of the amplitude spectra, that the vortex frequencies are averaged and that a value for the flow of the medium is determined using the averaged vortex frequency.

20. Method according to claim 19, characterized in that in i. the number of amplitude spectra over which averaging is carried out is selected variably, in particular that the method is carried out several times in succession so that several averaged amplitude spectra and several vortex frequencies determined from the averaged amplitude spectra are present, that a standard deviation of the vortex frequencies is determined and that the number of amplitude spectra from which the averaged amplitude spectrum is generated is increased until the standard deviation falls below a predetermined limit value (112), and that in ii. the number of vortex frequencies over which averaging is carried out is selected variably, in particular that a standard deviation of the vortex frequencies is determined and that the number of vortex frequencies over which averaging is carried out is increased until the determined standard deviation of the vortex frequencies falls below a predetermined limit value.

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