Electromagnetic transducer, intended for the measurement of two-dimensional velocities of an electrically conductive fluid flow.

Abstract

Electromagnetic transducer for measuring two-dimensional speeds of an electrically conductive fluid flow. The invention relates to an electromagnetic transducer (10) for measuring the two-dimensional speed components of an electrically conductive fluid flow, 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 two bosses (13.1 to 13.4), diametrically opposed to each other with respect to the central axis (Z) and each delimiting a flat surface, parallel to the central axis (Z), - an electric coil (12), called the primary coil, wound around the central portion of the tube, - a number of four electric coils (14.1 to 14.6), called receiving coils, each wound around one of the flat surfaces, or four Hall effect sensors, each arranged on one of the flat surfaces. Figure for the abstract: fig.13.

Description

Title of the invention: Electromagnetic transducer, intended for measuring two-dimensional speeds of an electrically conductive fluid flow. Technical field

[0001] The present invention relates to the field of instrumentation and measurement, and more particularly that of transducers dedicated to local, point velocimetry of electrically conductive fluids, in particular in the field of two-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 are, for example, electrically conductive ionic solutions such as salt water and, even more so, liquid metals. Usually, these metals are, for example, sodium, potassium, lead, lithium, aluminum, copper, iron, zinc, titanium and their alloys.

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

[0005] The invention is particularly suitable for measuring the speeds of fluids whose melting temperature range is the melting temperature range of metals treated, shaped or used in liquid form, typically from approximately -50°C to more than 1500°C.

[0006] An advantageous application envisaged is the measurement of speeds of coolants, in particular of nuclear fission and fusion reactors. Prior art

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

[0008] This is the case in the metal foundry industry where knowledge of the velocity field in foundry molds and their feed circuits makes it possible to predict the quality of the parts produced and limit scrap. Knowledge of flow rates makes it possible to control and optimize the filling of foundry molds.

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

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

[0011] Scientific experiments using liquid metals in large volumes, tests with a view to knowing flow distributions in exchanger collectors also require knowing the field of flow speeds 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.m 3 to several thousand kg.m3.

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

[0014] Among these, electromagnetic techniques are particularly relevant and robust, in terms of the resistance of the materials to the stresses applied to them by the environment in which the measurement must be carried out. These techniques are all the more interesting if it is a dense and chemically reactive fluid, 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 causes the development of currents (electric current density J) under the action of the displacement speed 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 J u are the source of a magnetic field B u. This field B u 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 request under the name of magnetic field. It is also specified that the different formulations indicated below are written within the framework of the approximation of quasi-permanent regimes, making it possible to neglect certain quantities involved 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 designated by the acronym DDF for "Flow Distortion Flow Meter", or the English acronym ECFM ("Eddy Current Flow Meter") or PSFM ("Phase Shift Flow Meter").

[0023] A conventional DDF, generally designated by the reference 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 transmitting electric coil, called primary 3, and one or two receiving electric coils, called secondary 4, 5. The core 2 is formed of a solid rod 20 extending along the central axis X and solid discs 21 regularly spaced along the central axis (X), the solid rod connecting the solid discs together. The primary 3 and secondary 4, 5 coils are wound around the solid rod 20 between two of the solid discs 21.

[0024] An electric current is imposed in the primary coil. The circulation of this current creates an external magnetic field B in the environment close to the primary coil, according to the Maxwell - Ampere equation:

[0025] [Equation 2]

[0026]

[0027] with:

[0028] V: differential operator

[0029] ; magnetic permeability with F ~

[0030] : magnetic permeability of vacuum

[0031] B: crosses the receiving coils.

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

[0033] [Equation 3] [°° 34 1 vxZ=-f

[0035] with:

[0036] E: electric field.

[0037] Furthermore, B also causes 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 in some way blown by the flow of conductive fluid and deforms in the direction of its 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 presence of electrically conductive fluid flow velocity.

[0044] The analysis of the electrical voltages delivered by the receiving coils makes it possible to determine the flow speed of the fluid in motion in the zone of action of the magnetic field B.

[0045] As shown in [Fig.8], if the single receiver coil 4 of a DDF 1 is upstream relative to the direction of fluid flow, it sees a drop in magnetic flux when the speed increases (and vice versa). The voltage e 2 that it delivers decreases by Ae y.

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

[0047] In addition to this, in the case of a DDF with two receiver coils, the downstream receiver coil sees an increase in the flow passing through it as the fluid velocity increases. Its voltage e 2 increases by Ae 2.

[0048] We have lAe 21= lAe / 1

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

[0050] In this way, the signal V provided 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 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 speed without the need for comparison with the amplitude of the signal without flow speed.

[0057] As regards the arrangement of the DDFs relative to the fluid flow, they can be internal to the flow, i.e. 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 the fluid F whose speeds are to be measured flows.

[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 the 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 this tube: [2].

[0061] When DDFs are used to evaluate the speed of a fluid circulating in a tube, whether internal or external to the latter, they can only measure a speed 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 main direction.

[0062] Generally speaking, a conventional DDF placed in an open environment, i.e. in a large volume of moving electrically conductive fluid, i.e. in a volume whose boundaries are sufficiently far from the DDF so that they do not orient the velocity vector of the flow at the level of the DDF, it is noted that the DDFs can only account for a single velocity component of the flow which is that projected along the axis of axisymmetry of the DDF. This is due to the axisymmetric constitution of a DDF.

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

[0064] Modeling 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 modeled a DDF according to the state of the art and its operation was simulated for different surrounding speed stresses of the flow of a moving liquid metal (sodium). The orthonormal analysis frame in which the speeds 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 component speed X, the magnetic flux density, the speed vector, the normal cut Y and the normal cut Z.

[0067] Figures 12 and 12A illustrate, for this same DDF according to the state of the art subjected to a Y component speed, the magnetic flux density, the speed vector, the X normal cut and the Z normal cut.

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

[0069] In conclusion, the DDFs according to the state of the art, internal or external, cannot be used to measure at a given point location, simultaneously, 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 reference frame or any other arrangement, is also not possible due to the interaction between them of the magnetic fields of the different DDFs placed close to each other.

[0071] Furthermore, transducers are known which are capable of measuring a fluid flow almost at one point with several speed components: [3], [4], [5],

[0072] Among these, we can cite hot wire or 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 local velocity measurements, potentially on several velocity components. However, their operation relies on electrical contact between their electrodes and the fluid to be characterized. Also, they are highly sensitive to oxidation, particularly in liquid metals. It is also necessary to have electrical insulation between the electrodes and the metallic structure of the probe for use with liquid metals. This restricts their use to lower fluid temperature ranges than non-contact electromagnetic measurement technologies.

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

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

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

[0077] Patent EP1285277B1 also describes a method of contactless induction tomography.

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

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

[0080] In addition, these methods require processing algorithms that are complex.

[0081] The external magnetic field must also pass through the material of the walls containing the moving fluid because the equipment implementing the measurement method is placed 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, the DDFs according to the state of the art are incapable of measuring several speed components simultaneously. They cannot be associated with each other, in proximity to each other, to measure several speed components in a given location due to the disturbances that they transmit to each other.

[0083] Existing measurement transducers are not capable of evaluating multiple 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 use equipment placed outside the fluid volume to be characterized. Their performance depends on the structures containing the fluid volume. The processing of their signals is complex. The size of the fluid volume that they can characterize must be limited. Thus, they cannot be implemented in a large volume, such as the interior of a sodium-cooled nuclear reactor vessel.

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

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

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

[0088] - a metallic cylindrical 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 a number of two bosses, diametrically opposed to each other with respect to the central axis (Z) and each delimiting a flat surface, parallel to the central axis (Z),

[0089] - an electric coil, called the primary coil, wound around the central portion of the tube,

[0090] - a number of four electrical coils, called receiving coils, wound each around one of the flat surfaces or four 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 two-dimensional speed components of a flow of an electrically conductive fluid, comprising:

[0092] - a metallic cylindrical 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 a number of two bosses, diametrically opposed to each other with respect to 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 four electrical coils, called receiving coils, wound each around one of the flat surfaces or four Hall effect sensors, each arranged on one of the flat surfaces.

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

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

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

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

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

[0100] The invention also relates to the use of an electromagnetic transducer as described above for measuring the two-dimensional velocity components of a flow of an electrically conductive fluid, such as a liquid metal from a nuclear reactor.

[0101] Ultimately, an electromagnetic transducer according to the proposed invention makes it possible to overcome the identified limitations of the devices of the prior art and presents numerous advantages, including:

[0102] - the possibility of simultaneous measurement of two speed components of a flow of electrically conductive fluid in the volume of fluid in its immediate vicinity;

[0103] - 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;

[0104] - the possibility of positioning within the flow to be characterized in the area to be studied;

[0105] - the characterization of the flow velocity components, even in very large fluid volumes;

[0106] - a processing of the signals it produces, clearly less complex than the reconstruction algorithms required for tomographic measurement methods.

[0107] Other advantages and characteristics will become more apparent upon reading the detailed description, given for illustrative and non-limiting purposes, with reference to the following figures. Brief description of the drawings

[0108] [Fig.l] [Fig.l] is a schematic side view of a state-of-the-art Flow Distortion Meter (FDM) 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, two receiving (secondary) coils.

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

[0111] [Fig.3] [Fig.3] takes up [Fig.l] 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] takes up [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 repeat the figure 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] takes up [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 measurements of the magnetic field around a DDF according to the state of the art, respectively in the absence and presence of flow velocity of electrically conductive fluid.

[0116] [Fig.8] [Fig.8] takes up [Fig.l] and illustrates the electrical voltage across the terminals of the state-of-the-art DDF receiver coil.

[0117] [Fig.9] [Fig.9] takes up [Fig.2] and illustrates on the one hand an electrical coupling preferential of the receiving coils in anti-series as well as the electrical voltages at the terminals of the coils the final voltage recorded at the terminals of the DDF according to the state of the art.

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

[0119] [Fig. 11], [Fig. 11 A] Figures 11 and 11A are representations of simulations digital, for a DDF according to the state of the art subjected to a component speed X, of its magnetic flux density, of its speed vector, respectively in normal X and normal Z sections.

[0120] [Fig. 12], [Fig.l2A] Figures 12 and 12A are representations of simulations digital, for a DDF according to the state of the art subjected to a Y component speed, of its magnetic flux density, of its speed vector, respectively in X normal and Z normal sections.

[0121] [Fig. 13] [Fig. 13] is a schematic perspective view of a transducer electromagnetic according to an alternative of the invention operating with alternating current 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 Y axis of the electromagnetic transducer according to [Fig. 13].

[0124] [Fig. 16] [Fig. 15] is a front view along the Z axis of the electromagnetic transducer according to [Fig. 13].

[0125] [Fig.17] [Fig.17] shows the electromagnetic transducer according to [Fig.13], showing the measurement lines and plane.

[0126] [Fig. 18] [Fig. 18] is a schematic perspective and longitudinal sectional view of an electromagnetic transducer according to [Fig. 13] showing the arrangement of the electrical connection wires to the primary and secondary coils.

[0127] [Fig. 19] [Fig. 19] 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.

[0128] [Fig.20] [Fig.20] shows the electromagnetic transducer according to [Fig.19], showing the measurement lines and plane.

[0129] [Fig.21] [Fig.21] is a schematic perspective and longitudinal sectional view of an electromagnetic transducer according to [Fig.19] showing the arrangement of the electrical connection wires to the primary and secondary coils. Detailed description

[0130] Throughout the present application, the terms “upstream” and “downstream” are to be understood with reference to the direction of flow of a fluid around the transducer along the Z axis.

[0131] Throughout the application, an electromagnetic transducer according to the invention is defined in a position relative to an orthogonal reference frame XYZ constituting a trihedron, comprising three axes perpendicular two by two, namely:

[0132] - an X axis, defining a transverse direction,

[0133] - a Y axis, defining a transverse direction, which with the X axis defines a plane XY,

[0134] - 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.

[0135] By convention, for the following, the Y axis is that normal to the upper face of two bosses of the same measuring line L1. A measuring line is defined as being the imaginary straight line parallel to the Z axis and passing through the center of the upper faces of two bosses of the same normal.

[0136] 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.

[0137] 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 odd-index coils.

[0138] The voltages produced by the four receiving coils are respectively denoted e1, e2, e3, e4.

[0139] Figures 1 to 12A have already been described in the preamble. They will therefore not be detailed later.

[0140] Figures 13 to 17 show an electromagnetic transducer 10 according to the invention, intended to measure two speed components of a flow of an electrically conductive fluid.

[0141] This transducer 10 firstly comprises a metallic cylindrical 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 each of the two end portions 111, 112.

[0142] The upstream end portion 111 comprises two bosses 13.1, 13.3 diametrically opposite each other with respect to the central axis (Z) and each delimiting a flat surface, parallel to the central axis (Z).

[0143] The downstream end portion 112 comprises two bosses 13.2, 13.4 diametrically opposite each other with respect to the central axis (Z) and each delimiting a flat surface, parallel to the central axis (Z).

[0144] Preferably, all the bosses are of identical dimensions and shapes.

[0145] 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.

[0146] A primary electric coil 12 is wound around the central portion 110 of the tube 11.

[0147] Four receiving electric coils 14.1, 14.2, 14.3, 14.4 are each wound respectively around one of the flat surfaces of the bosses 13.1, 13.2, 13.3, 13.4.

[0148] The operation of the electromagnetic transducer 10 is now explained in relation to the simulations carried out by the inventors.

[0149] As defined previously, the transducer 10 has two measurement lines: L1, L2, L3.

[0150] The primary coil 12 is supplied with alternating current.

[0151] This current causes the creation of an external magnetic field B which has a P measurement plan.

[0152] In a simplified manner, 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 P, the pair of coils 14.3 and 14.4 of the measurement plane P.

[0153] There exists 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.

[0154] A three-dimensional flowing fluid surrounding the transducer 10 will modify the magnetic field coupling between the primary coil 12 and the four secondary coils 14.1, 14.2, 14.3, 14.4 because it causes the creation of a field B u . This distortion is measurable thanks to the induced voltages present on the receiving coils.

[0155] A movement of electrically conductive fluid around the transducer 10 having only a positive velocity component along the Z axis, modifies in the same way the couplings of the pairs of coils in the measurement plane P.

[0156] In other words, the receiving coils 14.1, 14.3 have an induced voltage at their terminals which increases by Ae, while at the same time the coils 14.2, 14.4 have an induced voltage at their terminals which decreases by Ae.

[0157] Signal processing of the same type as that applied to the coils of a DDF according to the state of the art 1, as explained in the preamble, is applicable to the pairs of coils 14.1, 14.2 and 14.3, 14.4 to measure the speed component z. Thus, the voltage differences ei - e2 = e3 - e4 between the coils are linear functions of Z.

[0158] It is possible to add up these voltage differences (ei - e2) + (e3 - e4) to increase the sensitivity of the transducer 10 to the measurement of a speed component along Z.

[0159] A flow represented by a velocity vector contained in any plane passing through the Z axis and not having only one 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 and the group of coils 14.3, 14.4.

[0160] Thus, any flow velocity, with two-dimensional components, can be characterized by a transducer 10 according to the invention.

[0161] Generally speaking, a matrix relationship can be defined to translate the voltages produced by the four receiving coils 14.1 to 14.4, eb e2, e3, e4 into three-dimensional components (Ux, Uy) of the local speed vector U.

[0162] This matrix is ​​expressed as follows:

[0163] [Ux] = H] [t / yj [TH T12 T13 T141 ¢2 LT21 T22 T23 T241' e3 .e4.

[0164] Thus,

[0165] U x = Tn.ei + Ti2.e2 + Tu.ej + Ti4.e4

[0166] U v = T2i.ei + T22.e2 + T23.es + T24.e4

[0167] Ty defines the contribution of ej in the response of the transducer with respect to a flow velocity present in the measurement plane i and therefore in the expression of the velocity component U x.

[0168] Ty depends on the characteristics of the transducer materials, firstly the material constituting the core 11, the geometry of the bosses 13.1 to 13.4 and the characteristics of the receiving coils, including the number of turns of each of them.

[0169] Ty also translates the properties of the electrically conductive fluid and also the influence that the temperature exerts on the materials present.

[0170] Finally, Ty is also a function of the excitation provided to the transducer: nature and intensity of the magnetic excitation produced by the primary coil.

[0171] We can express, Ty = kt. ke.Ky

[0172] with

[0173] kt: influence factor linked to the temperature on the different materials present

[0174] ke: influence factor linked to excitation

[0175] Ky: reflects the influence of the transducer's constitution.

[0176] Thus we can express the matrix of two-dimensional components (Ux, Uy) of the local velocity vector U as follows:

[0177] Z7xl = k L k e . Uy\ Aell Æ21 LÆ31 Æ12 ÂT3 K22 K23 K32 K33 K14' K24 K34. e2 e3 .^4.

[0178] Usually, the characteristics of a DDF according to the state of the art, as described in the preamble, are established by means of results of numerical simulations or by experimentation.

[0179] Reference may be made to publication [7] which sets out a method for calibrating an external DDF, by imposing a known volume 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 S 7 and S 2 produced by the secondary coils 4 and 5 are measured and used in such a way that the response A of the DDF is defined by:

[0180] A=Aj!A2

[0181] With

[0182] A ] = S}-S2

[0183] A2=S1 + S2

[0184] We connect the response A with the volume flow rate Q by A = T. Q

[0185] The coefficient T translates 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.

[0186] 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.

[0187] For the electromagnetic transducer 10 which has just been described, we can proceed in the same way as the calibration of [7] but by imposing a two-dimensional velocity field.

[0188] During tests at fixed temperature and excitation, different velocity fields will be successively imposed with components in one or more directions: Ux, Uy.

[0189] During each test, the voltages eb e2, e3, e4 of the coils 14.1 to 14.4 can be recorded. As many tests are carried out as there are Ky terms of the matrix K to be determined. In this way, a linear system of equations can be established and solved so as to calculate each of the Ky terms of the three-dimensional component matrix (Ux, Uy).

[0190] 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.

[0191] For the electrical supply of the primary coil 12 and the recovery of the currents in the receiving coils 14.1 to 14.4, the various necessary connection wires can be passed inside the cylindrical core 11.

[0192] An example of integration of these wires is shown in [Fig.18]: 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.

[0193] Instead of the coils 14.1, 14.2, 14.3, 14.4, Hall effect sensors can be provided with the same core 11 as described previously to also produce an electromagnetic transducer 10 operating with alternating current. In this mode, a Hall effect sensor is fixed directly to the flat surface delimited by a boss 13.1 to 13.4. The connecting wires 15, 16.1 to 16.4 can be installed as in the previous mode.

[0194] As illustrated in Figures 19 to 21, instead of a primary coil 12, a permanent magnet 17 can be provided with the same core 11 as described previously to also produce an electromagnetic transducer 10 operating with direct current. The connecting wires 16.1 to 16.4 can be installed as in the previous mode.

[0195] Other variants and improvements may be envisaged without departing from the scope of the invention. List of cited references

[0196] [1] : https: / / www.hzdr.de / db / Cms ?pOid=55433&pNid=226

[0197] [2]: https: / / ieeexplore.ieee.org / stamp / stamp.jsp?arnumber=9768530

[0198] [3]: https: / / www.degruyter.com / document / doi / 10.1515 / HTMP.2000.19.3-4.187 / pdf

[0199] [4]:https: / / esfr-smart.eu / wp-content / uploads / 2021 / 04 / S35_l_Sven_Ecke rt_ESFR_SMART_Measuring_Techniques.pdf

[0200] [5] :https: / / link.springer.com / content / pdf / 10.1007 / 978- l-4020-4833-3_17.pdf? pdf=inline%201ink

[0201] [6]: https: / / iopscience.iop.Org / article / 10.1088 / 1757-899X / 228 / l / 012023 / pdf

[0202] [7]: https: / / iopscience.iop.Org / article / 10.1088 / 1757-899X / 208 / l / 012031 / pdf

Claims

Claims

1. Electromagnetic transducer (10), intended to measure the two-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 two bosses (13.1 to 13.4), diametrically opposed to each other with respect to the central axis (Z) and each delimiting a flat surface, parallel to the central axis (Z), - an electric coil (12), called the primary coil, wound around the central portion of the tube, - a number of four electric coils (14.1 to 14.6), called receiver coils, each wound around one of the flat surfaces, or four Hall effect sensors, each arranged on one of the flat surfaces.

2. Electromagnetic transducer (10), intended to measure the two-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 two bosses (13.1 to 13.6), diametrically opposed to each other with respect to 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 four electric coils (14.1 to 14.4), called receiver coils, each wound around one of the flat surfaces, or four 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 planar surface.

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

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