Electromagnetic transducer, intended for measuring three-dimensional velocities of an electrically conductive fluid flow.

Abstract

Electromagnetic transducer, intended for measuring three-dimensional velocities of an electrically conductive fluid flow. The invention relates to an electromagnetic transducer (10), intended for measuring the three-dimensional velocity components of an electrically conductive fluid flow, comprising: - a cylindrical metallic tube (11) forming a core with high magnetic permeability, which extends along a central axis (Z), comprising a central portion and two end portions, on either side of the central portion, each comprising three bosses (13.1 to 13.6), arranged at 120° to each other around the central axis (Z) and each delimiting a flat surface, parallel to the central axis (Z), - an electrical coil (12), called the primary coil, wound around the central portion of the tube, - six electrical coils (14.1 to 14.6), called receiving coils, each wound around one of the flat surfaces, or six hall effect sensors, each arranged on one of the flat surfaces. Figure for the abbreviation: fig.13.

Description

Title of the invention: Electromagnetic transducer, intended for the measurement of three-dimensional velocities of an electrically conductive fluid flow. technical field

[0001] The present invention relates to the field of instrumentation and measurement, and more particularly to that of transducers dedicated to local, point velocimetry of electrically conductive fluids, in particular in the field of three-dimensional point velocimetry in these fluids.

[0002] The invention relates to an electromagnetic transducer for measuring the velocity components of an electrically conductive fluid.

[0003] The invention applies generally to any electrically conductive fluid. These fluids include, for example, electrically conductive ionic solutions such as salt water, and even more so, liquid metals. Typically, these metals include, for example, sodium, potassium, lead, lithium, aluminum, copper, iron, zinc, titanium, and their alloys.

[0004] More particularly, the invention applies to measurements in dense liquid-type fluids having a density in a range of 100 kg.m3 to more than 1000 kg.m3.

[0005] The invention is particularly suitable for fluid velocity measurements where the melting temperature range is the melting temperature range of metals treated, shaped or used in liquid form, typically from about -50 °C to over 1500 °C.

[0006] One advantageous application envisaged is the measurement of velocities of heat transfer fluids, in particular of nuclear fission and fusion reactors. Previous technique

[0007] In many applications, it is necessary to know the velocity field of an electrically conductive fluid in motion.

[0008] This is the case in the metal foundry industry, where knowledge of the velocity range in foundry molds and their feeding circuits makes it possible to predict the quality of the parts produced and limit scrap. Knowledge of flow velocities allows for the control and optimization of the filling of foundry molds.

[0009] In the nuclear industry, the velocity field of the metallic heat transfer fluids used in the circuits of certain nuclear reactors is a major factor in the stress on metallic structures in contact. Therefore, knowledge of this is essential.

[0010] This is also a major factor in the heat exchanges occurring in the heat exchangers and at the level of the nuclear fuel in these reactors. Knowledge and analysis of the velocity field in key locations of a reactor (heat exchangers, core outlet, pump, etc.) is also an indicator of proper operation and therefore a means of increasing safety and, overall, the monitoring capabilities of these machines.

[0011] Scientific experiments involving liquid metals in large volumes, tests aimed at understanding flow distributions in heat exchanger manifolds, also require knowledge of the velocity field of the flows involved.

[0012] In the various flow zones mentioned, the flow conditions are three-dimensional. What also most often characterizes these flows is their temperature level, most often several hundred degrees, and the density of the fluids used, the range of which can extend from a few hundred kg.m3 to several thousand kg.m3.

[0013] Various velocimetry techniques are known and used to measure the velocity components of a flow of electrically conductive liquid.

[0014] Among these, electromagnetic techniques are particularly relevant and robust, in terms of the resistance of materials to the stresses applied to them by the environment in which the measurement is to be carried out. These techniques are all the more advantageous when dealing with dense and chemically reactive fluids, such as liquid metals.

[0015] The operating principle of electromagnetic transducers is illustrated by the expression of Ohm's law in the moving fluid subjected to a magnetic field.

[0016] It shows that the conductivity o of the fluid leads to the development of currents (electric current density J) under the action of the displacement velocity u combined with the external magnetic field B:

[0017] [Equation 1]

[0018] J^E+uxB}

[0019] This occurs even in the absence of an electric field E.

[0020] The current densities Ju are the source of a magnetic field Bu. This field Bu distorts the external field B.

[0021] It is specified here that, for simplification, the vector symbolized by the letter B, which is the magnetic flux density or magnetic induction, is designated in the set of the demand under the name of magnetic field. It is also specified that the different formulations indicated later are written within the framework of the quasi-steady regime approximation, allowing us to neglect certain quantities appearing in Maxwell's equations, such as displacement currents.

[0022] To date, measurements of a single velocity component of a flow are commonly carried out by electromagnetic transducers, commonly referred to by the acronym DDF for "Flow Distortion Flow Meter", or the Anglo-Saxon ECFM ("Eddy Current Flow Meter") or PSFM ("Phase Shift Flow Meter").

[0023] A conventional DDF, generally designated by reference numeral 1, is shown in the figures 1, 2, and 2A: It is axisymmetric with a central axis X and typically consists of a core 2, a primary (or transmitting) electrical coil 3, and one or two secondary (or receiving) electrical coils 4, 5. The core 2 is formed of a solid rod 20 extending along the central axis X and solid disks 21 regularly spaced along the central axis (X), with the solid rod connecting the disks. The primary (3) and secondary (4, 5) coils are wound around the solid rod 20 between two of the disks 21.

[0024] An electric current is imposed in the primary coil. The flow of this current creates an external magnetic field B in the immediate vicinity of the primary coil, according to the Maxwell-Ampère equation:

[0025] [Equation 2]

[0026]

[0027] with:

[0028] V: differential operator

[0029] ; magnetic permeability with F ~

[0030] : magnetic permeability of vacuum

[0031] B: passes through the receiving coils.

[0032] The primary current is alternating, so that B is also alternating. In this way, B induces an electrical voltage in each of the receiving coils, according to the Maxwell-Faraday equation:

[0033] [Equation 3] [°°341 vxZ=-f

[0035] with:

[0036] E: electric field.

[0037] Furthermore, B also leads to the development of induced current densities Ji in the fluid, as well as in any surrounding electrical conductor subjected to this magnetic field, including the metal of the tubes. Figures 3 and 4 show the development of induced current densities under the action of the external magnetic field, in the absence of flow velocity, for a DDF, respectively with one secondary coil 4, and with two secondary coils 4, 5.

[0038] The current densities Ji in turn create a magnetic field Bi distorting the external field B. Thus, the field B is not the same depending on whether the DDF is surrounded by an electrically conductive fluid or not.

[0039] In the absence of fluid movement, the receiving coil(s) deliver electrical voltages which are functions of the external magnetic field B and the field Bi.

[0040] In the presence of fluid movement, new current densities Ju appear and are the source of a magnetic field Bu. This new field modifies B, which is somehow blown away by the flow of conducting fluid and deforms in the direction of the flow, as illustrated in Figures 5A, 5B and 6.

[0041] The magnetic flux passing through the receiving coil(s) depends on the flow velocity.

[0042] The receiving coil(s) therefore deliver electrical voltages reflecting the influence of the magnetic fields B and B u which distort the external field B.

[0043] Numerical simulations illustrate this. Figures 7A and 7B are numerical simulations of the magnetic field around a DDF respectively in the absence and in the presence of flow velocity of electrically conductive fluid.

[0044] The analysis of the electrical voltages delivered by the receiving coils makes it possible to determine the flow velocity of the fluid moving in the area of ​​action of the magnetic field B.

[0045] As shown in [Fig. 8], if the single receiving coil 4 of a DDF 1 is upstream with respect to the direction of fluid flow, it experiences a decrease in magnetic flux as the velocity increases (and vice versa). The voltage e2 that it delivers decreases by Ae y.

[0046] The voltage e; supplied by the DDF is the image of the flow velocity (with indication of the direction relative thanks to the comparison of the amplitude of the current signal with the amplitude of the signal without velocity).

[0047] In addition to this, in the case of a DDF with two receiving coils, the downstream receiving coil experiences an increase in the flux passing through it as the fluid velocity increases. Its voltage e2 increases by Ae2.

[0048] We have lAe 21= lAe / 1

[0049] Generally, the two receiving coils 4, 5 of a DDF are electrically coupled in anti-series, as shown in [Fig.9].

[0050] In this way, the signal V supplied by the two-coil DDF is given by:

[0051] V=\e2\-\e}\

[0052] with \e J: modulus or amplitude of the voltage e x.

[0053] The signal V is proportional to the velocity component of the flow projected onto the axis of revolution of the DDF.

[0054] In practice, the DDF with two receiving coils is preferred, because the combined use of the voltages delivered by these two coils makes it possible to double the sensitivity and eliminate the dependence of the DDF's response on irrelevant quantities such as temperature:

[0055] V={\e 2\-\em\e 2\ + \e

[0056] The sign of V gives the direction of the velocity without needing to compare with the amplitude of the signal without flow velocity.

[0057] As regards the arrangement of the DDFs relative to the fluid flow, they can be internal to the flow, that is to say positioned on the axis of a tube in the middle of the flow to be characterized: [1], A DDF is thus within the fluid flow, the latter being peripheral to the DDF.

[0058] In practice, as shown in [Fig. 10], an internal DDF 1 is generally placed in the center of an annular space, delimited by two concentric tubes T1, T2, in which flows the fluid F whose velocities we seek to measure.

[0059] Other DDFs may be external to the flow. The coils and core of the external DDFs are thus arranged around the fluid flow for which velocities are to be measured.

[0060] In practice, an external DDF is placed around a tube to measure the velocity of the fluid flowing in that tube: [2].

[0061] When DDFs are used to evaluate the velocity of a fluid flowing in a tube, whether internal or external to the latter, they can only measure a velocity component which is that along the axis of the tube and therefore along their axis of axisymmetry X. Indeed, the tube guides the flow of the fluid and gives it its principal direction.

[0062] Generally speaking, a conventional flow dynamic system (FDS) placed in an open medium, that is, in a large volume of electrically conductive fluid in motion, i.e., in a volume whose boundaries are sufficiently far from the FDS so that they do not orient the flow velocity vector at the FDS, can only account for a single flow velocity component, which is that projected along the FDS's axis of symmetry. This is due to the axisymmetric structure of a FDS.

[0063] Therefore, it is not conclusive to use conventional DDFs in an open environment to characterize several velocity components at the DDF implantation site. In particular, measuring the velocity of dense, electrically conductive fluids in open media is a problem in itself.

[0064] The modelling and simulations of a DDF according to the state of the art, in an open environment, subjected to different speeds of three-dimensional components, prove this.

[0065] The inventors have modeled a flow dynamics system (FDS) according to the prior art and its operation has been simulated for different ambient velocity loads of the flow of a moving liquid metal (sodium). The orthonormal coordinate system in which the velocities are expressed is x, y, z.

[0066] Figures 11 and 1 IA illustrate, for this DDF according to the state of the art subjected to a velocity of component x, the magnetic flux density, the velocity vector, the normal y cut and the normal cut.

[0067] Figures 12 and 12A illustrate, for this same DDF according to the state of the art subjected to a velocity of component y, the magnetic flux density, the velocity vector, the cut with normal x and the cut with normal z.

[0068] It is therefore observed that, when subjected to a velocity field with component along x, a DDF according to the state of the art provides the same response signal as when it is subjected to a velocity field with a single component y.

[0069] In conclusion, state-of-the-art DDFs, whether internal or external, cannot be used to measure, simultaneously at a given point location, several components of the multidimensional flow velocity of a fluid.

[0070] The simultaneous use of several DDFs, one per velocity component, for example positioned and oriented so as to form a direct orthonormal frame or any other arrangement, is also not possible because of the interaction between them of the magnetic fields of the different DDFs placed close to each other.

[0071] Furthermore, transducers capable of measuring, almost at a single point, several velocity components of a fluid flow are known: [3], [4], [5],

[0072] Among these, we can mention wire or hot-film probes for aerodynamic measurements. These probes are fragile and therefore limited to use for speeds of a few millimeters per second at best.

[0073] Potential probes allow for local velocity measurements, potentially across multiple velocity components. However, their operation relies on electrical contact between their electrodes and the fluid being characterized. Therefore, they are highly susceptible to oxidation, particularly in liquid metals. Electrical insulation between the electrodes and the probe's metallic structure is also necessary for use with liquid metals. This restricts their application to lower fluid temperature ranges than non-contact electromagnetic measurement technologies.

[0074] Thus, there are no measurement transducers capable of evaluating several flow velocity components of electrically conductive fluids, which can be dense, for a range of high velocities and / or at high temperatures.

[0075] Non-contact induction tomography methods have already been tested for measuring multidimensional fluid flow velocities.

[0076] Publication [6] describes such a method: this method is currently only capable of measuring two velocity components at points in a radial plane of the fluid. The ability to measure three velocity components is not demonstrated.

[0077] Patent EP1285277B1 also describes a method of non-contact induction tomography.

[0078] The main constraint faced by non-contact induction tomography methods is that the useful magnetic field to be observed is on the order of 2 to 5 orders of magnitude lower than that of the magnetic field which it is necessary to apply.

[0079] Moreover, these methods also require working on relatively small volumes of fluid, typically on the order of 1 m, so that the external magnetic field can propagate throughout the entire volume to be characterized.

[0080] Moreover, these methods require complex processing algorithms.

[0081] The external magnetic field must also pass through the material of the walls containing the The fluid is in motion because the equipment implementing the measurement method is located outside. The performance of the method therefore depends on the nature of the wall material, its thickness, and also the overall geometry of the tomograph.

[0082] In summary, state-of-the-art DDFs are unsuitable for measuring several velocity components simultaneously. They cannot be combined in close proximity to one another to measure several velocity components at a given location due to the interference they transmit to each other.

[0083] Existing measurement transducers are not capable of evaluating several flow velocity components of electrically conductive fluids, which may be dense, for a range of high velocities and / or at high temperatures.

[0084] Three-dimensional flow measurement methods using non-contact tomography are global. They employ equipment positioned outside the fluid volume to be characterized. Their performance depends on the structures containing the fluid volume. Processing their signals is complex. The size of the fluid volume they can characterize must be limited. Thus, they cannot be implemented in a large volume, such as the inside of a sodium-cooled nuclear reactor vessel.

[0085] There is therefore a need to propose a solution for three-dimensional measurements of flow velocities of electrically conductive fluids, which can be dense, for a range of high velocities and / or at high temperatures, even in large volumes.

[0086] The aim of the invention is to meet at least part of this need. Description of the invention

[0087] To this end, the invention relates, according to a first alternative, to an electromagnetic transducer, intended to measure the three-dimensional velocity components of a flow of an electrically conductive fluid, comprising:

[0088] - a cylindrical metallic tube forming a core with high magnetic permeability, which extends along a central axis (Z), comprising a central portion and two end portions, on either side of the central portion, each comprising three bosses, arranged at 120° to each other around the central axis (Z) and each delimiting a flat surface, parallel to the central axis (Z),

[0089] - an electrical coil, called the primary coil, wound around the central portion from the tube,

[0090] - a number of six electrical coils, called receiving coils, each wound around one of the flat surfaces or six hall effect sensors, each arranged on one of the flat surfaces.

[0091] According to a second alternative, the invention relates to an electromagnetic transducer, intended to measure the three-dimensional velocity components of a flow of an electrically conductive fluid, comprising:

[0092] - a cylindrical metallic tube forming a core with high magnetic permeability, which extends along a central axis (Z), comprising a central portion and two end portions, on either side of the central portion, each comprising three bosses, arranged at 120° to each other around the central axis (Z) and each delimiting a flat surface, parallel to the central axis (Z),

[0093] - a permanent magnet arranged around the central portion of the tube,

[0094] - a number of six electrical coils, called receiving coils, each wound around one of the flat surfaces or six hall effect sensors, each arranged on one of the flat surfaces.

[0095] Preferably, the core has low electrical conductivity to limit the losses induced by the variable magnetic induction, namely the joule losses related to the circulation of the induced current and the hysteresis losses.

[0096] Thus, the invention essentially consists of an electromagnetic transducer that can be operated in alternating current (first variant) or in direct current (second variant) for the non-contact measurement of three three-dimensional components of an electrically conductive fluid.

[0097] The judicious arrangement of the receiving coils or Hall effect sensors at 120° to each other makes it possible to measure, by distortion of electromagnetic flux, the contribution of each of the components of the local velocity vector without perturbation by the other contributions.

[0098] A flux distortion electromagnetic transducer according to the invention makes it possible to measure speeds from a few millimeters per second to several meters per second.

[0099] In addition, it is suitable for measuring the velocities of electrically conductive liquids, which are dense, typically with a density of the order of 100 to more than 10,000 kg.m3, and / or which are at high temperature, typically in the range of the melting temperatures of metals processed, shaped or used in liquid form.

[0100] In conclusion, an electromagnetic transducer according to the proposed invention overcomes the identified limitations of prior art devices and offers numerous advantages, including:

[0101] - the possibility of simultaneous measurement of the three velocity components of a flow of electrically conductive fluid in the volume of fluid that is in its immediate vicinity;

[0102] - no need to associate it with other transducers of the same type at the risk of render its measures inoperative, as is the case with a DDF according to the state of the art;

[0103] - the possibility of positioning within the flow to be characterized in the area to be studied;

[0104] - the characterization of the flow velocity components, even in very large volumes of fluid;

[0105] - a processing of the signals it produces, significantly less complex than the reconstruction algorithms required for tomographic measurement methods.

[0106] The invention also relates to the use of an electromagnetic transducer as described above for measuring the three-dimensional velocity components of a flow of an electrically conductive fluid, such as a liquid metal from a nuclear reactor.

[0107] Other advantages and features will become clearer from the detailed description, given by way of illustration and not limitation, with reference to the following figures. Brief description of the drawings

[0108] [Fig.1] [Fig.1] is a schematic side view of a State of the Art Flow Distortion (FDD) Flowmeter with a receiving (secondary) coil.

[0109] [Fig.2] [Fig.2] is a schematic side view of a DDF according to the state of the art, at two receiving (secondary) coils.

[0110] [Fig.2A] [Fig.2A] is a longitudinal sectional view of [Fig.2].

[0111] [Fig.3] [Fig.3] reproduces [Fig.1] and illustrates the development of densities of currents induced under the action of the external magnetic field in the absence of flow velocity.

[0112] [Fig.4] [Fig.4] reproduces [Fig.2] and illustrates the development of densities of currents induced under the action of the external magnetic field in the absence of flow velocity.

[0113] [Fig.5A], [Fig.5B] Figures 5A and 5B reproduce Figure 5A and illustrate the development of induced current densities under the action of the external magnetic field in the presence of a flow velocity.

[0114] [Fig.6] [Fig.6] reproduces [Fig.2] and illustrates the development of densities of currents induced under the action of the external magnetic field in the presence of a flow velocity.

[0115] [Fig.7A], [Fig.7B] Figures 7A and 7B are representations of simulations numerical values ​​of the magnetic field around a DDF according to the state of the art, respectively in the absence and in the presence of flow velocity of electrically conductive fluid.

[0116] [Fig.8] [Fig.8] reproduces [Fig.1] and illustrates the electrical voltage across the terminals of the DDF receiving coil according to the state of the art.

[0117] [Fig.9] [Fig.9] reproduces [Fig.2] and illustrates a preferential electrical coupling receiving coils in anti-series as well as the electrical voltages across the coil terminals and the final voltage measured across the DDF terminals according to the state of the art.

[0118] [Fig. 10] [Fig. 10] is a reprographic reproduction of a DDF according to the state of art as arranged internally in an implantation tube for the measurement of a one-dimensional velocity of a flowing fluid F.

[0119] [Fig. 11], [Fig. 11A] Figures 11 and 11A are representations of simulations numerical values, for a DDF according to the state of the art subjected to a velocity of component X, of its magnetic flux density, of its velocity vector, respectively in cross-section with normal Y and normal Z.

[0120] [Fig. 12], [Fig. 12A] Figures 12 and 12A are representations of simulations numerical values, for a DDF according to the state of the art subjected to a velocity of component Y, of its magnetic flux density, of its velocity vector, respectively in cross-section with normal X and normal Z.

[0121] [Fig. 13] [Fig. 13] is a schematic perspective view of an electromagnetic transducer according to an alternative of the invention with alternating current operation and receiving coils.

[0122] [Fig. 14] [Fig. 14] is a side view along the X axis of the electromagnetic transducer according to [Fig. 13].

[0123] [Fig. 15] [Fig. 15] is a front view along the Z axis of the electromagnetic transducer according to [Fig. 13].

[0124] [Fig.16] [Fig.16] reproduces the electromagnetic transducer according to [Fig.13], showing the measurement lines and planes.

[0125] [Fig. 17], [Fig.17A] Figures 17 and 17A are representations of numerical simulations of the electromagnetic transducer according to [Fig. 13] in the presence of an electrically conductive fluid without movement.

[0126] [Fig. 18] [Fig. 18] is a numerical simulation representation of an electromagnetic transducer according to [Fig. 13] subjected to a velocity of component Z.

[0127] [Fig.19], [Fig.19A], [Fig.19B] Figures 19, 19A and 19B are representations of numerical simulations of an electromagnetic transducer according to [Fig. 13] subjected to a velocity of component X.

[0128] [Fig.20] [Fig.20] is a numerical simulation representation of an electromagnetic transducer according to [Fig. 13] subjected to a velocity of component Y.

[0129] [Fig.21] [Fig.21] is a schematic perspective and longitudinal section view of an electromagnetic transducer according to [Fig. 13] showing the arrangement of the electrical connecting wires to the primary and secondary coils.

[0130] [Fig.22] [Fig.22] is a schematic perspective view of an electromagnetic transducer according to the invention with Hall effect sensors.

[0131] [Fig.23] [Fig.23] is a side view along the X axis of the electromagnetic transducer according to [Fig.22].

[0132] [Fig.24] [Fig.2] is a side view along the Y axis of the electromagnetic transducer according to [Fig.22].

[0133] [Fig.25] [Fig.25] is a front view along the Z axis of the electromagnetic transducer according to [Fig.22].

[0134] [Fig.26] [Fig.26] reproduces the electromagnetic transducer according to [Fig.22], showing the measurement lines and planes.

[0135] [Fig.27] [Fig.27] is a schematic perspective and longitudinal section view of an electromagnetic transducer according to [Fig.22] showing the arrangement of the electrical connecting wires to the primary and secondary coils.

[0136] [Fig.28] [Fig.28] is a schematic perspective view of an electromagnetic transducer according to an alternative of the invention with direct current operation, permanent magnet and receiving coils.

[0137] [Fig.29] [Fig.29] is a schematic perspective and longitudinal section view of an electromagnetic transducer according to [Fig.28] showing the arrangement of the electrical connecting wires to the primary and secondary coils. Detailed description

[0138] Throughout this application, the terms "upstream" and "downstream" are to be understood by reference to the direction of the flow of a fluid around the transducer along the Z-axis.

[0139] In the application as a whole, an electromagnetic transducer according to the invention is defined in a position relative to an orthogonal XYZ frame constituting a trihedron, comprising three axes perpendicular in pairs, namely:

[0140] - an X-axis, defining a transverse direction,

[0141] - a Y-axis, defining a transverse direction, which together with the X-axis defines a plane XY,

[0142] - a Z-axis, defining a longitudinal direction, perpendicular to the XY plane, and defining the general direction in which the transducer extends and the axis of revolution of the primary coil.

[0143] By convention, for the remainder of this text, the Y axis is the normal axis to the upper face of two bosses of the same measurement line Ll. A measurement line is defined as the imaginary line parallel to the Z axis and passing through the center of the upper faces of two bosses with the same normal.

[0144] The indices i used to geometrically define the bosses and coils of the transducer are those used for electromagnetic couplings and signal processing, as explained below.

[0145] The bosses and coils arranged on the same end portion of the transducer core are all either of the same odd or even index. In the simulations below, the upstream end portion of the core supports the coils of odd index.

[0146] The voltages produced by the six receiving coils are respectively noted e1, e2, e3, e4, e5, e6.

[0147] Figures 1 to 12A have already been described in the preamble. They will therefore not be detailed further.

[0148] Figures 13 to 16 show an electromagnetic transducer 10 according to the invention, intended to measure the three velocity components of a flow of an electrically conductive fluid.

[0149] This transducer 10 first comprises a cylindrical metallic tube 11 forming an electromagnetic core, which extends along a central axis Z, comprising a central portion 110 and two end portions 111, 112, on either side of the central portion. Preferably, the length of the central portion 110 is equal to that of each of the two end portions 111, 112.

[0150] The upstream end portion 111 comprises three bosses 13.1, 13.3, 13.5 arranged at 120° to each other around the central axis (Z) and each delimiting a flat surface, parallel to the central axis (Z).

[0151] The downstream end portion 112 comprises three bosses 13.2, 13.4, 13.6 arranged at 120° to each other around the central axis (Z) and each delimiting a flat surface, parallel to the central axis (Z).

[0152] Preferably, all bosses are of identical dimensions and shapes.

[0153] Advantageously, each boss has a T-shape in front view, orthogonal to the central axis (Z), the head of the T being the flat surface.

[0154] A primary electrical coil 12 is wound around the central portion 110 of the tube 11.

[0155] Six electrical receiving coils 14.1, 14.2, 14.3, 14.4, 14.5, 14.6 are each wound respectively around one of the flat surfaces of the bosses 13.1, 13.2, 13.3, 13.4, 13.5, 13.6.

[0156] The operation of the electromagnetic transducer 10 is now explained in relation to the simulations carried out by the inventors.

[0157] As defined previously, the transducer 10 has three measurement lines: L1, L2, L3.

[0158] The primary coil 12 is supplied with alternating current.

[0159] This current results in the creation of an external magnetic field B which has three The planes of symmetry PI, P2, and P3 intersect on the Z-axis. Each of these planes passes through one of the measurement lines L1, L2, or L3. The measurement plane PI is relative to the pair of coils 14.1 and 14.2. The measurement plane P2 is relative to the pair of coils 14.3 and 14.4. The measurement plane P3 is relative to the pair of coils 14.5 and 14.6.

[0160] In a simplified way, we consider the magnetic couplings which exist between the primary coil 12 and respectively the pair of coils 14.1 and 14.2 of the measurement plane PI, the pair of coils 14.3 and 14.4 of the measurement plane P2 and the pair of coils 14.5 and 14.6 of the measurement plane P3.

[0161] As can be seen in Figures 17 and 17A, there is a field B t which does not modify either the symmetry of B or the coupling between the primary coil 12 and the receiving or secondary coils.

[0162] A three-dimensional flowing fluid surrounding the transducer 10 will modify the magnetic field coupling between the primary coil 12 and the six secondary coils 14.1, 14.2, 14.3, 14.4, 14.5, 14.6, due to the fact that it causes the creation of a field B u. This distortion is measurable by means of the induced voltages present on the receiving coils.

[0163] A movement of electrically conductive fluid around the transducer 10, having only a positive velocity component along the Z-axis, similarly modifies the couplings of the coil pairs in each of the three measurement planes P1, P2, P3. In other words, the receiving coils 14.1, 14.3, 14.5 have an induced voltage across their terminals that increases by Ae, while at the same time the coils 14.2, 14.4, 14.6 have an induced voltage across their terminals that decreases by Ae. This flux distortion under the action of a velocity flow along the Z-axis is shown in [Fig. 18].

[0164] Signal processing of the same type as that applied to the coils of a DDF according to the prior art 1, as explained in the preamble, is applicable to the coil pairs 14.1, 14.2 and 14.3, 14.4 and 14.5, 14.6 for measuring the velocity component z. Thus, the voltage differences ei - e2 = e3 - e4 = e5 - e6 between the coils are linear functions of Z.

[0165] It is possible to sum these voltage differences (ei - e2) + (e3 - e4) + (e5 - e6) to increase the sensitivity of the transducer 10 to the measurement of a velocity component along Z.

[0166] A flow represented by a velocity vector contained in any plane passing through the Z axis and not having only a single component on this axis, will distort the coupling between the primary coil 12 and respectively each of the coils of the groups in the end portions, namely the group of coils 14.1, 14.2, 14.3 and the group of coils 14.4, 14.5, 14.6.

[0167] Figures 19, 19A, 19B thus illustrate a flow distortion under the action of a flow with velocity along the X axis.

[0168] Fig. 20 illustrates the flow distortion under the action of a flow with velocity along the Y axis.

[0169] Thus, any flow velocity, with three-dimensional components, can be characterized by a transducer 10 according to the invention.

[0170] In general, a matrix relationship can be defined to translate the voltages produced by the six receiving coils 14.1 to 14.6, eb e2, e3, e4, e5, e6, into three-dimensional components (Ux, Uy, Uz) of the local velocity vector U.

[0171] This matrix is ​​expressed as follows:

[0172] 'Ux' Uy .UZ; TU 731 .731 7'12 T22 T32 Tl 3 T23 T33 7T4 734 T34 T15 T25 T35 T\6' T26 . 736. 'el' e2 e3 e4 e5 ■ e6.

[0173] Thus

[0174] U x = Tn.ei + Ti2.e2 + T13.e3 + T14.e4 + T15.e5 + T16.e6

[0175] U v = T2i.ei + T22.e2 + T23.e3 + T24.e4 + T25.es + T26.ee

[0176] U z = T3i.ei + T32.e2 + T33.e3 + T34.e4 + T35.e5 + T36.e6

[0177] Ty defines the contribution of ej in the transducer's response to a flow velocity present in the measurement plane i and therefore, in the expression of the velocity component U x.

[0178] Ty depends on the characteristics of the materials of the transducer, to the first order the material constituting the core 11, the geometry of the bosses 13.1 to 13.6 and the characteristics of the receiving coils, including the number of turns of each of them.

[0179] Ty also translates the properties of the electrically conductive fluid and also the influence that temperature exerts on the materials present.

[0180] Finally, Ty is also a function of the excitation supplied to the transducer: nature and intensity of the magnetic excitation produced by the primary coil.

[0181] We can express, Ty = kt. ke.Ky

[0182] with

[0183] kt: temperature-related influencing factor on the different materials present

[0184] ke: excitation-related influencing factor

[0185] Ky: translates the influence of the transducer's construction.

[0186] Thus we can express the matrix of three-dimensional components (Ux, Uy, Uz) of the local velocity vector U as follows:

[0187] 'Ux' = kt. ke. 'eV uy e2 Æll Æ12 Æ13 Æ14 Æ15 KÏ6' n'X UZ Æ21 K22 K23 Æ24 K25 K26 ej oA .Æ31 K32 K33 Æ34 K35 K36. 64-e5,e6,

[0188] Usually, the characteristics of a DDF according to the state of the art, as described in the preamble, are established through the results of numerical simulations or by experimentation.

[0189] Reference can be made to publication [7], which describes a method for calibrating an external DDF by imposing a known volumetric flow rate Q of a liquid metal in the implantation tube around which the DDF is positioned. While the flow rate Q is imposed, the voltages S7 and S2 produced by the secondary coils 4 and 5 are measured and used such that the response A of the DDF is defined by:

[0190] A=A, / A2

[0191] With

[0192] A1 = S1-S2

[0193] A2=Sj + S2

[0194] The response A is related to the volumetric flow rate Q by A = T. Q

[0195] The coefficient T reflects the dimensional and material characteristics of the DDF, as well as the implantation tube, the liquid metal, and the dependence of the response on temperature and electrical excitation. There is a value of T for a temperature value associated with an electrical excitation, which is defined by its amplitude and frequency.

[0196] The velocity field in the implantation tube producing the flow rate Q measured by the DDF according to the state of the art contains velocities parallel to the central axis of the DDF. The calibration is one-dimensional. The series of coefficients T is determined by parametric tests at given temperature and excitation.

[0197] For the electromagnetic transducer 10 which has just been described, one can proceed in the same manner as the calibration of [7] but by imposing a three-dimensional velocity field.

[0198] During tests at fixed temperature and excitation, different velocity fields will be successively imposed with components in one or more directions: Ux, Uy, Uz.

[0199] During each test, the voltages eb e2, e3, e4, e5, e6 of the coils 14.1 to 14.6 can be recorded. As many tests are performed as there are terms Ky of the matrix K to be determined. In this way, a linear system of equations can be established and solved to calculate each of the terms Ky of the matrix of three-dimensional components (Ux, Uy, Uz).

[0200] The tests will be parameterized in temperature and excitation so as to also be able to determine the influence of the weighting terms kt and ke.

[0201] For the power supply of the primary coil 12 and the recovery of currents in the receiving coils 14.1 to 14.6, the various connecting wires required can be passed inside the cylindrical core 11.

[0202] An example of the integration of these wires is shown in [Fig.21]: the electrical wires 15 are connected to the primary coil 12, and the electrical wires 16.1, 16.2, 16.3, 16.4 are connected respectively to the receiving coils 14.1, 14.2, 14.3, 14.4.

[0203] As illustrated in Figures 22 to 27, instead of the coils 14.1, 14.2, 14.3, 14.4, 14.5, 14.6, Hall effect sensors 17.1, 17.2, 17.3, 17.4, 17.5, 17.6 can be provided with the same core 11 as described previously to also create an electromagnetic transducer 10 operating with alternating current. In this configuration, a Hall effect sensor 17.1 to 17.6 is fixed directly onto the flat surface delimited by a boss 13.1 to 13.6. The connecting wires 15, 16.1 to 16.6 can be installed as in the previous configuration.

[0204] As illustrated in figures 28 and 29, instead of a primary coil 12, a permanent magnet 18 with the same core 11 as previously described can also be provided to produce an electromagnetic transducer 10 operating with direct current.

[0205] Other variants and improvements may be envisaged without departing from the scope of the invention. List of cited references

[0206] [1]: https: / / www.hzdr.de / db / Cms?pOid=55433&pNid=226

[0207] [2]: https: / / ieeexplore.ieee.org / stamp / stamp.jsp?arnumber=9768530

[0208] [3]: https: / / www.degruyter.com / document / doi / 10.1515 / HTMP.2000.19.3-4.187 / pdf

[0209] [4]:https: / / esfr-smart.eu / wp-content / uploads / 2021 / 04 / S35_l_Sven_Ecke rt_ESFR_SMART_Measuring_Techniques.pdf

[0210] [5] :https: / / link.springer.com / content / pdf / 10.1007 / 978-l-4020-4833-3_17.pdf? pdf=inline%201ink

[0211] [6]: https: / / iopscience.iop.Org / article / 10.1088 / 1757-899X / 228 / l / 012023 / pdf

[0212] [7]: https: / / iopscience.iop.Org / article / 10.1088 / 1757-899X / 208 / l / 012031 / pdf

Claims

Demands

1. Electromagnetic transducer (10), intended to measure the three-dimensional velocity components of a flow of an electrically conductive fluid, comprising: - a metallic cylindrical tube (11) forming a core with high magnetic permeability, which extends along a central axis (Z), comprising a central portion and two end portions, on either side of the central portion, each comprising a number of three bosses (13.1 to 13.6), arranged at 120° to each other around the central axis (Z) and each delimiting a flat surface, parallel to the central axis (Z), - an electrical coil (12), called the primary coil, wound around the central portion of the tube, - a number of six electrical coils (14.1 to 14.6), called receiving coils, each wound around one of the flat surfaces, or six hall effect sensors, each arranged on one of the flat surfaces.

2. Electromagnetic transducer (10), intended for measuring the three-dimensional velocity components of a flow of an electrically conductive fluid, comprising: - a metallic cylindrical tube (11) forming a core with high magnetic permeability, which extends along a central axis (Z), comprising a central portion and two end portions, on either side of the central portion, each comprising a number of three bosses (13.1 to 13.6), arranged at 120° to each other around the central axis (Z) and each delimiting a flat surface, parallel to the central axis (Z), - a permanent magnet (18) arranged around the central portion of the tube, - a number of six electrical coils (14.1 to 14.6), called receiving coils, each wound around one of the flat surfaces, or six hall effect sensors, each arranged on one of the flat surfaces.

3. Electromagnetic transducer (10), each boss having a T-shape in front view, orthogonal to the central axis (Z), the head of the T being the flat surface.

4. Use of an electromagnetic transducer according to any one of the preceding claims, for measuring the three-dimensional velocity components of a flow of an electrically conductive fluid, such as a liquid metal from a nuclear reactor.

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