Electromagnetic transducer for measuring three-dimensional velocity of flow of electrically conductive fluid

Abstract

The invention relates to an electromagnetic transducer (10) for measuring the three-dimensional velocity component of an electrically conductive fluid flow, comprising:-a cylindrical metal tube (11) forming a core with a high magnetic permeability, said tube extending along a central axis (Z) and comprising a central portion and two end portions on both sides of said central portion, each end portion comprising three bosses (13.1 to 13.6), the three bosses are arranged around the central axis (Z) at an angle of 120 degrees to each other, and each boss defines a flat surface parallel to the central axis (Z); -an electric coil (12), referred to as a primary coil, wound around a central portion of the tube; -six electrical coils (14.1 to 14.6), referred to as receiver coils, each receiver coil being wound around one of said flat surfaces; or six Hall effect sensors, each Hall effect sensor being arranged on one of the flat surfaces.

Description

Field of the Invention

[0001] The present invention relates to the field of instruments and measurements, and more particularly, to the field of transducers dedicated to local point velocity measurement of conductive fluids, and more specifically to three-dimensional point velocity measurement in these fluids.

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

[0003] The present invention is generally applicable to any conductive fluid. Examples of such fluids are conductive ionic solutions such as brine, and even liquid metals. Typical examples of such metals are sodium, potassium, lead, lithium, aluminum, copper, iron, zinc, titanium, and their alloys.

[0004] More specifically, the present invention is applicable to the measurement of dense liquid-type fluids having a density in the range of about 100 kg·m -3 to greater than 10000 kg·m -3 .

[0005] The present invention is particularly suitable for measuring the velocity of a fluid whose melting temperature range is the melting temperature range of a metal that is processed, shaped, or used in liquid form, typically from about -50°C to above 1500°C.

[0006] One expected advantageous application is the measurement of the velocity of a heat transfer fluid, especially in nuclear fission and fusion reactors. Background Art

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

[0008] This is the case in the metal casting industry, where knowing the velocity field in the casting mold and its power supply circuit can predict the quality of the produced parts and limit any scrap. In fact, knowing the flow velocity can control and optimize the filling of the casting mold.

[0009] In the nuclear industry, the velocity field of the metal heat transfer fluid used in some nuclear reactor circuits is a major factor in terms of the stress on the metal structures in contact. Therefore, knowledge of the velocity field is essential.

[0010] It is also a major factor in terms of heat exchange in heat exchangers and the nuclear fuel of these reactors. Knowledge and analysis of the velocity field in critical areas of the reactor (heat exchangers, core outlet, pumps, etc.) are also indicators of correct operation and thus a means of improving safety (overall, the possibility of monitoring these machines).

[0011] Scientific experiments involving large volumes of liquid metal, as well as tests to understand the flow distribution in heat exchanger headers, also require knowledge of the velocity field of the flows involved.

[0012] In the various flow regions listed, the flow conditions are three-dimensional. Most commonly, these flows are characterized by their temperature levels (most commonly a few hundred degrees Celsius) and the density of the fluid used (which can range from a few hundred kg.m -3 to several thousand kg.m -3 ).

[0013] Various velocity measurement techniques are known and used to measure the velocity components of conductive liquid flows.

[0014] These techniques include electromagnetic techniques, which are particularly relevant and reliable in terms of the resistance of the material to the stresses imposed by the environment in which the measurement is carried out. These techniques are even more interesting in the case of dense chemically reactive fluids such as liquid metals.

[0015] The operating principle of an electromagnetic transducer is illustrated by the expression of Ohm's law in a moving fluid under the action of a magnetic field.

[0016] It shows that under the combined action of the moving velocity u and the external magnetic field B, the electrical conductivity σ of the fluid results in the generation of an electric current (current density J):

[0017] [Equation 1]

[0018]

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

[0020] Current density J u is the source of the magnetic field B u . This magnetic field B u distorts the external field B.

[0021] For simplicity, it should be noted that throughout this application, the vector denoted by the letter B, i.e., the magnetic flux density or magnetic induction intensity, is referred to as the magnetic field. It should also be noted that the various formulas provided below are written in the regime of the quasi-permanent approximation of the regime, allowing certain quantities involved in Maxwell's equations, such as displacement current, to be neglected.

[0022] So far, the measurement of the individual velocity components of a flow has usually been carried out by electromagnetic transducers, commonly known by the abbreviations FDFM ("flux distortion flowmeter"), ECFM ("eddy current flowmeter") or PSFM ("phase shift flowmeter").

[0023] Figure 1 、 Figure 2 and Figure 2AShows a conventional FDFM generally designated by reference numeral 1: It is axially symmetric with respect to the central axis X and typically consists of a core 2, an electrical transmission coil called the primary coil 3, and one or two electrical receiver coils called the secondary coils 4, 5. The core 2 is formed by a solid rod 20 extending along the central axis X and solid disks 21 spaced evenly along the central axis X, where the solid rod connects the solid disks together. The primary coil 3 and the secondary coils 4, 5 are wound around the solid rod 20 between the two solid disks 21.

[0024] A current is applied to the primary coil. According to the Maxwell - Ampère equation, the flow of this current generates an external magnetic field B in the immediate vicinity of the primary coil:

[0025] [Equation 2]

[0026]

[0027] where:

[0028] Differential operator;

[0029] μ: Magnetic permeability, where μ = μ r μ0;

[0030] μ0: Magnetic permeability of vacuum;

[0031] B: Passes through the receiver coil.

[0032] The primary current is an alternating current, so B is also an alternating current. Thus, according to the Maxwell - Faraday equation, B induces a voltage in each receiver coil:

[0033] [Equation 3]

[0034]

[0035] where:

[0036] Electric field.

[0037] In addition, B also causes an induced current density J to be generated in the fluid and in any surrounding electrical conductors (including the metal of the tube) affected by this magnetic field i . Figure 3 and Figure 4 respectively show the current density induced by the action of the external magnetic field in an FDFM with one secondary coil 4 and two secondary coils 4, 5 in the absence of flow velocity.

[0038] Current density J i in turn generates a magnetic field B that distorts the external field B i . Thus, the field B varies depending on whether the FDFM is surrounded by a conducting fluid.

[0039] In the absence of fluid movement, the voltage delivered by one or more receiver coils is a function of the external magnetic field B and the field B i .

[0040] In the presence of fluid movement, a new current density J u appears and is the source of the magnetic field B u . As Figure 5A , Figure 5B and Figure 6 shown, this new field alters B, which can be said to be blown by the conducting fluid flow and distorted in the direction of the fluid flow.

[0041] The magnetic flux passing through one or more receiver coils depends on the flow velocity.

[0042] Therefore, the voltage delivered by one or more receiver coils reflects the influence of the magnetic fields B i and B u that distort the external field B.

[0043] This is illustrated by numerical simulation. Figure 7A and Figure 7B are numerical simulations of the magnetic field around the FDFM in the absence and presence of the flow velocity of the conducting fluid, respectively.

[0044] By analyzing the voltage delivered by the receiver coils, the flow velocity of the moving fluid in the region of action of the magnetic field B can be determined.

[0045] As Figure 8 shown, if a single receiver coil 4 of the FDFM 1 is located upstream with respect to the direction of fluid flow, its magnetic flux experiences a decrease as the velocity increases (and vice versa). The voltage e1 it provides decreases by Δ e1 .

[0046] The voltage e1 provided by the FDFM is an image of the flow velocity (indicating the relative direction by comparing the amplitude of the current signal with the signal without velocity).

[0047] In addition, in the case of an FDFM with two receiver coils, as the fluid velocity increases, the downstream receiver coil experiences an increase in the flux passing through it. Its voltage e2 increases by Δe2.

[0048] Thus |Δe2| = |Δe1|.

[0049] Typically, the two receiver coils 4, 5 of the FDFM are electrically coupled in anti - series, as Figure 9 shown.

[0050] In this way, the signal V provided by the dual - coil FDFM is given by:

[0051] V = |e2| - |e1|.

[0052] Where, |e x | is the 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 rotation of the FDFM.

[0054] In practice, an FDFM with two receiver coils is preferably used because the combined use of the voltages transmitted by the two coils doubles the sensitivity and eliminates the dependence of the FDFM response on irrelevant quantities such as temperature:

[0055] V = (|e2| - |e1|) / (|e2| + |e1|).

[0056] The sign of V provides the direction of the velocity without having to compare it with the signal amplitude in the absence of flow velocity.

[0057] Regarding the arrangement of the FDFM relative to the fluid flow, they can be located inside the flow, i.e., on the axis of the tube in the middle of the flow to be characterized: [1]. Thus, the FDFM is located inside the fluid flow, and the fluid flow is on the periphery of the FDFM.

[0058] In practice, as Figure 10 shown, the internal FDFM 1 is usually placed at the center of the annular space defined by two concentric tubes T1, T2 through which the fluid F whose velocity is to be measured flows.

[0059] Other FDFMs can be located outside the flow. Thus, the coils and cores of the external FDFM are arranged around the fluid flow whose velocity is to be measured.

[0060] In practice, the external FDFM is placed around the tube to measure the velocity of the fluid flow through the tube: [2].

[0061] When using the FDFM to evaluate the velocity of the fluid flowing through the tube, whether they are inside or outside the tube, they can only measure one velocity component, i.e., the component along the axis of the tube and thus along its axis of symmetry X. In fact, the tube guides the fluid flow and provides its main direction.

[0062] Generally speaking, for a conventional FDFM placed in an open medium, i.e., placed in a large volume of moving conductive fluid, i.e., placed in a volume where the boundaries are far enough from the FDFM so that it cannot determine the direction of the velocity vector of the flow near the FDFM, it can be seen that the FDFM can only consider a single velocity component of the flow, i.e., the velocity component projected along the axis of symmetry of the FDFM. This is due to the axisymmetric construction of the FDFM.

[0063] Thus, the use of traditional FDFM in an open environment is inconclusive for characterizing multiple velocity components at the location where the FDFM is located. In particular, measuring the velocity of a dense, electrically conductive fluid in an open environment is itself a problem.

[0064] Modeling and simulation of FDFM in an open environment according to the prior art, subjected to different velocities with three-dimensional components, have demonstrated this.

[0065] The inventors have modeled FDFM according to the prior art and have simulated its operation for different velocity stresses around a flowing liquid metal (sodium) stream. The analysis orthogonal coordinate system representing velocity is x, y, z.

[0066] Figure 11 and 11A Shows the case of magnetic flux density, velocity vector, normal cross-section y, and normal cross-section z for an FDFM according to the prior art subjected to the velocity component x.

[0067] Figure 12 and 12A Shows the case of magnetic flux density, velocity vector, normal cross-section x, and normal cross-section z for the same FDFM according to the prior art subjected to the velocity component y.

[0068] Thus, it can be seen that when subjected to a velocity component field along x, the response signal provided by an FDFM according to the prior art is the same as when it is subjected to a single velocity component field along y.

[0069] In summary, an internal or external FDFM according to the prior art cannot be used to simultaneously measure multiple components of the multidimensional flow velocity of a fluid at a given point location.

[0070] It is not possible to simultaneously use multiple FDFMs positioned and oriented to form a direct orthogonal coordinate system or any other arrangement, such as one FDFM for each velocity component, because the magnetic fields of the individual FDFMs placed close to each other will interact.

[0071] In addition, transducers capable of measuring multiple velocity components of a fluid flow at almost a single point are also known: [3], [4], [5].

[0072] These include wire or hot-film probes for aerodynamic measurements. These probes are fragile and are thus limited to use at speeds of a few millimeters per second at most.

[0073] Potential probes can be used to measure local velocities, which may involve multiple velocity components. However, their operation depends on the electrical contact between their electrodes and the fluid to be characterized. They are also highly sensitive to oxidation, especially that of liquid metals. Electrical insulation is also required between the electrodes of the probes used for liquid metals and the metal structure. This limits their use to lower fluid temperature ranges than non-contact electromagnetic measurement techniques.

[0074] Therefore, there is no measurement transducer capable of evaluating multiple components of the flow velocity of a conductive fluid (which may be dense) in a high velocity range and / or at high temperatures.

[0075] Non-contact inductive tomography methods have been tested to measure multi-dimensional fluid flow velocities.

[0076] The open literature [6] describes such a method, which currently can only measure two velocity components at points in the radial plane of the fluid. The ability to measure three velocity components has not been demonstrated.

[0077] Patent EP 1285277 B1 also describes a non-contact inductive tomography method.

[0078] The main limitation faced by non-contact inductive tomography methods is that the useful magnetic field to be observed is 2 to 5 orders of magnitude lower than the magnetic field that needs to be applied.

[0079] In addition, these methods also need to process a relatively small volume of fluid, typically about 1 m³, so that the external magnetic field can propagate throughout the volume to be characterized.

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

[0081] The external magnetic field must also pass through the material of the wall containing the moving fluid because the device implementing the measurement method is placed outside. Therefore, the performance of the method depends on the nature of the wall material, its thickness, and the overall geometry of the tomography.

[0082] In summary, the existing FDFM of the prior art cannot measure multiple velocity components simultaneously. Due to the interference of their mutual transmissions, they cannot be combined together in close proximity to measure multiple velocity components at a given location.

[0083] Existing measurement transducers cannot evaluate multiple velocity components of a conductive fluid (which may be dense) in a high velocity range and / or at high temperatures.

[0084] Three-dimensional flow measurement methods using non-contact tomography are comprehensive. They use devices set outside the fluid volume to be characterized. Their performance capabilities depend on the structure containing the fluid volume. Their signals are difficult to process. The size of the fluid volume they can characterize must be restricted. Thus, they cannot be implemented in large volumes, such as inside a sodium-cooled nuclear reactor vessel.

[0085] Therefore, a solution is needed for three-dimensional measurement of the flow velocity of a conductive fluid (which may be dense), in a high velocity range and / or at high temperature, even in a large volume.

[0086] The object of the present invention is to satisfy this need at least in part. Summary of the Invention

[0087] To this end, according to a first alternative, the object of the present invention is to provide an electromagnetic transducer for measuring the three-dimensional velocity components of a conductive fluid flow, comprising:

[0088] - a cylindrical metal tube that forms a core with high magnetic permeability, the tube extending along a central axis (Z) and including a central portion and two end portions on both sides of the central portion, each end portion including three bosses arranged at 120° to each other around the central axis (Z), each boss defining a flat surface parallel to the central axis (Z);

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

[0090] - six electric coils called receiver coils, each receiver coil being wound around one of the flat surfaces; or six Hall effect sensors, each Hall effect sensor being arranged on one of the flat surfaces.

[0091] According to a second alternative, the subject of the present invention is an electromagnetic transducer for measuring the three-dimensional velocity components of a conductive fluid flow, comprising:

[0092] - a cylindrical metal tube that forms a core with high magnetic permeability, the tube extending along a central axis (Z) and including a central portion and two end portions on both sides of the central portion, each end portion including three bosses arranged at 120° to each other around the central axis (Z), each boss defining a flat surface parallel to the central axis (Z);

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

[0094] - Six electrical coils, referred to as receiver coils, each receiver coil being wound around one of the flat surfaces; or six Hall effect sensors, each Hall effect sensor being arranged on one of the flat surfaces.

[0095] Preferably, the core has a low electrical conductivity to limit the losses caused by variable magnetic induction, namely Joule losses and hysteresis losses associated with the circulation of induced currents.

[0096] Thus, the present invention mainly relates to an electromagnetic transducer that can be operated with an alternating current (first variant) or a direct current (second variant) for non-contact measurement of three three-dimensional components of a conductive fluid.

[0097] The careful arrangement of the receiver coils or Hall effect sensors at 120° to each other allows the contribution of each component of the local velocity vector to be measured by electromagnetic flux distortion without any interference from other contributions.

[0098] The flux distortion electromagnetic transducer according to the present invention can measure velocities from a few millimeters per second to several meters per second.

[0099] In addition, it is applicable to measuring the velocity of dense conductive liquids with a density typically from about 100 kg.m -3 to greater than 10000 kg.m -3 and / or conductive liquids at high temperatures (usually within the melting temperature range of metals processed, shaped or used in liquid form).

[0100] Finally, the electromagnetic transducer proposed according to the present invention overcomes the limitations identified in prior art devices and has many advantages, including:

[0101] - The possibility of simultaneously measuring the three velocity components of a conductive fluid flow in the fluid volume and its immediate vicinity;

[0102] - Unlike the prior art FDFM, it does not have to be combined with other transducers of the same type, which may risk rendering its measurement inoperative;

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

[0104] - The ability to characterize the velocity components of the flow even in very large fluid volumes;

[0105] - Processing the signals it generates, which is much simpler than the reconstruction algorithms required by tomographic methods.

[0106] Another object of the present invention is the use of the electromagnetic transducer as described above for measuring the three-dimensional velocity components of a conductive fluid flow (such as liquid metal in a nuclear reactor). BRIEF DESCRIPTION OF THE DRAWINGS

[0107] Further advantages and features will become more apparent after reading the following illustrative but non - restrictive detailed description with reference to the accompanying drawings:

[0108] Figure 1 is a schematic side view of a flux - distortion flowmeter (FDFM) with a (secondary) receiver coil according to the prior art;

[0109] Figure 2 is a schematic side view of a prior - art FDFM with two (secondary) receiver coils;

[0110] Figure 2A is Figure 2 a longitudinal sectional view;

[0111] Figure 3 taken from Figure 1 and shows the induced current density generated under the action of an external magnetic field in the absence of flow velocity;

[0112] Figure 4 taken from Figure 2 and shows the induced current density generated under the action of an external magnetic field in the absence of flow velocity;

[0113] Figure 5A and Figure 5B taken from Figure 1 and shows the induced current density generated under the action of an external magnetic field in the presence of flow velocity;

[0114] Figure 6 taken from Figure 2 and shows the induced current density generated under the action of an external magnetic field in the presence of flow velocity;

[0115] Figure 7A and Figure 7B are representations of digital simulations of the magnetic field around an FDFM according to the prior art in the absence and presence of the flow velocity of a conductive fluid, respectively;

[0116] Figure 8 taken from Figure 1 and shows the voltage at the terminals of the receiver coil of an FDFM according to the prior art;

[0117] Figure 9 taken from Figure 2 and shows the preferred electrical coupling of the receiver coils in an anti - series configuration, and the voltage at the terminals of the coils and the final voltage measured at the terminals of an FDFM according to the prior art;

[0118] Figure 10is a replica of the prior art FDFM, which is arranged inside an injection tube for measuring the one-dimensional velocity of the flowing fluid F;

[0119] Figure 11 and Figure 11A are, respectively, for the prior art FDFM subjected to the velocity component X, the digital simulation representations of its magnetic flux density and its velocity vectors as the normal cross-section Y and the normal cross-section Z;

[0120] Figure 12 and Figure 12A are, respectively, for the prior art FDFM subjected to the velocity component Y, the digital simulation representations of its magnetic flux density and its velocity vectors as the normal cross-section Y and the normal cross-section Z;

[0121] Figure 13 is a schematic perspective view of an electromagnetic transducer according to an alternative of the present invention that operates using an alternating current and a receiver coil;

[0122] Figure 14 is a side view along the X-axis of the electromagnetic transducer according to Figure 13 ;

[0123] Figure 15 is a front view along the Z-axis of the electromagnetic transducer according to Figure 13 ;

[0124] Figure 16 is taken from the electromagnetic transducer according to Figure 13 and shows the measurement lines and planes;

[0125] Figure 17 and Figure 17A are digital simulation representations of the electromagnetic transducer according to Figure 13 in the presence of a conductive fluid that is stationary;

[0126] Figure 18 is a digital simulation representation of the electromagnetic transducer according to Figure 13 subjected to the velocity component Z;

[0127] Figure 19 , Figure 19A and Figure 19B are digital simulation representations of the electromagnetic transducer according to Figure 13 subjected to the velocity component X;

[0128] Figure 20 is a digital simulation representation of the electromagnetic transducer according to Figure 13 subjected to the velocity component Y;

[0129] Figure 21 is according to Figure 13Schematic perspective and longitudinal sectional views of an electromagnetic transducer, showing the arrangement of electrical connection lines for connection to a primary coil and a secondary coil;

[0130] Figure 22 is a schematic perspective view of an electromagnetic transducer having a Hall effect sensor according to the present invention;

[0131] Figure 23 is a side view along the X-axis of the electromagnetic transducer according to Figure 22 ;

[0132] Figure 24 is a side view along the Y-axis of the electromagnetic transducer according to Figure 22 ;

[0133] Figure 25 is a front view along the Z-axis of the electromagnetic transducer according to Figure 22 ;

[0134] Figure 26 taken from the electromagnetic transducer according to Figure 22 ; showing measurement lines and planes;

[0135] Figure 27 is a schematic perspective and longitudinal sectional view of an electromagnetic transducer according to Figure 22 ; showing the arrangement of electrical connection lines for connection to a primary coil and a secondary coil;

[0136] Figure 28 is a schematic perspective view of an electromagnetic transducer according to an alternative of the present invention having DC operation, a permanent magnet, and a receiver coil;

[0137] Figure 29 is a schematic perspective and longitudinal sectional view of an electromagnetic transducer according to Figure 28 ; showing the arrangement of electrical connection lines for connection to a primary coil and a secondary coil. DETAILED DESCRIPTION

[0138] Throughout the present application, the terms "upstream" and "downstream" should be understood with reference to the direction of fluid flow around the transducer along the Z-axis.

[0139] Throughout the present application, the electromagnetic transducer according to the present invention is defined in a position with respect to an XYZ orthogonal coordinate system forming a trihedron, the trihedron including three pairwise perpendicular axes, namely:

[0140] - the X-axis, defining the lateral direction;

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

[0142] - The Z-axis defines the longitudinal direction perpendicular to the XY plane and defines the general direction along which the transducer extends and the axis of rotation of the primary coil.

[0143] By convention, for the remainder of the specification, the Y-axis is the axis perpendicular to the upper surfaces of the two bosses on the same measurement line L1. The measurement line is defined as an imaginary straight line parallel to the Z-axis and passing through the centers of the upper surfaces of the two bosses on the same normal.

[0144] The index i used for geometrically defining the transducer bosses and coils is the index for electromagnetic coupling and signal processing, as described below.

[0145] The bosses and coils arranged on the same end portion of the transducer core all have the same odd or even index. In the following simulations, the upstream end portion of the core supports the coils with odd indices.

[0146] The voltages generated by the six receiver coils are respectively denoted as e1, e2, e3, e4, e5, and e6.

[0147] Figures 1 to 12A They have been described in the background art. Therefore, they will not be described in detail hereinafter.

[0148] Figures 13 to 16 An electromagnetic transducer 10 for measuring three velocity components of a conductive fluid flow according to the present invention is shown.

[0149] First, the transducer 10 includes a cylindrical metal tube 11 forming an electromagnetic core, which extends along the central axis Z and includes a central portion 110 and two end portions 111, 112 on both sides of the central portion. Preferably, the length of the central portion 110 is equal to the length of each of the two end portions 111, 112.

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

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

[0152] Preferably, all the bosses have the same size and shape.

[0153] Advantageously, the front view of each boss is T-shaped, orthogonal to the central axis (Z), and the head of the T-shape is the flat surface.

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

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

[0156] The operation of the electromagnetic transducer 10 will now be explained in conjunction with simulations conducted by the inventors.

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

[0158] An alternating current is supplied to the primary coil 12.

[0159] This current generates an external magnetic field B, which has three symmetric planes P1, P2, P3 intersecting on the Z axis. Each of these planes passes through one of the measurement lines L1, L2 and L3. The measurement plane P1 is related to a pair of coils 14.1 and 14.2. The measurement plane P2 is related to a pair of coils 14.3 and 14.4. The measurement plane P3 is related to a pair of coils 14.5 and 14.6.

[0160] For simplicity, consider the magnetic coupling that exists respectively between the primary coil 12 and the pair of coils 14.1, 14.2 of the measurement plane P1, between the primary coil 12 and the pair of coils 14.3, 14.4 of the measurement plane P2, and between the primary coil 12 and the pair of coils 14.5, 14.6 of the measurement plane P3.

[0161] As Figure 17 and Figure 17A can be seen, there is a field B i , which neither changes the symmetry of B nor the coupling between the primary coil 12 and the receiver coil or the secondary coil.

[0162] A three-dimensional flowing fluid surrounding the transducer 10 will change 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 by generating the field B u . This distortion can be measured by the induced voltage present on the receiver coils.

[0163] The movement of the conductive fluid along the Z axis only with a positive velocity component around the transducer 10 similarly changes the coupling of the coil pairs in each of the three measurement planes P1, P2, P3. In other words, the receiver coils 14.1, 14.3, 14.5 have an induced voltage increased by Δe at their terminals, while at the same time the coils 14.2, 14.4, 14.6 have an induced voltage decreased by Δe at their terminals. Figure 18Shows the flux distortion under the action of the velocity flow along the Z-axis.

[0164] As described in the background art, the same type of signal processing applied to the coils of the FDFM according to the prior art is applicable to the pairs of coils 14.1, 14.2, and 14.3, 14.4, and 14.5, 14.6 for measuring the velocity component z. Therefore, the voltage differences between the coils e1 - e2 = e3 - e4 = e5 - e6 are linear functions of z.

[0165] The sum of these voltage differences (e1 - e2)+(e3 - e4)+(e5 - e6) can be determined to improve the sensitivity of the transducer 10 with respect to the measurement of the velocity component along the Z-axis.

[0166] A flow represented by a velocity vector contained in any plane passing through the Z-axis and not just having a single component on that axis will cause coupling distortion between the primary coil 12 and each of the coils in the groups of end portions (i.e., the groups of coils 14.1, 14.2, 14.3 and coils 14.4, 14.5, 14.6).

[0167] Therefore, Figure 19 , Figure 19A , Figure 19B Shows the flux distortion under the action of the velocity flow along the X-axis.

[0168] Figure 20 Shows the flux distortion under the action of the velocity flow along the Y-axis.

[0169] Therefore, the transducer 10 according to the present invention can characterize any flow velocity having three-dimensional components.

[0170] Generally, a matrix relationship can be defined to reflect the voltages e1, e2, e3, e4, e5, e6 generated by the six receiver coils 14.1 to 14.6 as the three-dimensional components (Ux, Uy, Uz) of the local velocity vector U.

[0171] This matrix representation is as follows:

[0172]

[0173] Therefore:

[0174] U x = T 11 .e1 + T 12 .e2 + T 13 .e3 + T 14 .e4 + T 15 .e5 + T 16 .e6

[0175] U y = T21 .e1 + T 22 .e2 + T 23 .e3 + T 24 .e4 + T 25 .e5 + T 26 .e6

[0176] U z = T 31 .e1 + T 32 .e2 + T 33 .e3 + T 34 .e4 + T 35 .e5 + T 36 .e6

[0177] T ij defines the contribution of e in the response of the transducer pair to the flow velocity present in the measurement plane i, and thus also defines the contribution in the expression of the velocity component U j . x .

[0178] T ij depends on the characteristics of the transducer material, firstly, the material forming the core 11, the geometries of the bosses 13.1 to 13.6, and the characteristics of the receiver coils, including the number of turns of each coil.

[0179] T ij also reflects the characteristics of the conductive fluid and the influence of temperature on the materials present.

[0180] Finally, T ij is also a function of the excitation applied to the transducer: the nature and intensity of the magnetic excitation generated by the primary coil.

[0181] It can be expressed as follows: T ij = k t .k e .K ij ,

[0182] where:

[0183] k t : temperature-related influencing factors for the various materials present;

[0184] k e : excitation-related influencing factors;

[0185] K ij : reflects the influence of the transducer construction.

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

[0187]

[0188] Generally, as described in the background art, the characteristics of the prior art FDFM are determined by the results of numerical simulation or experiments.

[0189] Reference can be made to the published document [7], which describes a method for calibrating an external FDFM by applying a known volumetric flow rate Q of liquid metal in the injection tube where the FDFM is located. When the flow rate Q is applied, the voltages S1 and S2 generated by the secondary coils 4 and 5 are measured and utilized such that the response A of the FDFM is defined by the following formula:

[0190] A = A1 / A2,

[0191] where:

[0192] A1 = S1 - S2

[0193] A2 = S1 + S2

[0194] The relationship between the response A and the volumetric flow rate Q is A = T.Q.

[0195] The coefficient T reflects the size and material characteristics of the FDFM, as well as the size and material characteristics of the injection tube and the liquid metal, and the dependence of the response on temperature and electrical excitation. There is a value T for the temperature value related to the electrical excitation, and the value T is defined by the amplitude and frequency of the electrical excitation.

[0196] The velocity field in the injection tube that generates the flow rate Q measured by the FDFM according to the prior art contains a velocity parallel to the central axis of the FDFM. The calibration is one-dimensional. A series of coefficients T are determined by parametric tests at a given temperature and excitation.

[0197] For the above electromagnetic transducer 10, it can be calibrated in the same manner as the calibration in [7] but by applying a three-dimensional velocity field.

[0198] In tests at a fixed temperature and excitation, various velocity field components: Ux, Uy, Uz will be applied sequentially along one or more directions.

[0199] During each test, the voltages e1, e2, e3, e4, e5, e6 of the coils 14.1 to 14.6 can be recorded. As long as there are K ij terms to be determined in the matrix K, as many tests as possible will be carried out. In this way, a system of linear equations can be established and solved to calculate each K ij term of the three-dimensional component matrix (Ux, Uy, Uz).

[0200] The tests will be parameterized according to temperature and excitation so as to be able to determine the influence of the weighting terms k t and k e as well.

[0201] To supply power to the primary coil 12 and restore the current in the receiver coils 14.1 to 14.6, the various connecting wires required can be routed within the cylindrical core 11.

[0202] An example of the integration of these connecting wires is as Figure 21 shown: The wire 15 is connected to the primary coil 12, and the wires 16.1, 16.2, 16.3, 16.4 are respectively connected to the receiver coils 14.1, 14.2, 14.3, 14.4.

[0203] As Figures 22 to 27 shown, 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 also be provided with the same core 11 as described above, so as to also generate the electromagnetic transducer 10 operating with an alternating current. In this embodiment, the Hall effect sensors 17.1 to 17.6 are directly fixed to the flat surface defined by the bosses 13.1 to 13.6. The connecting wires 15, 16.1 to 16.6 can be arranged as in the previous embodiment.

[0204] As Figure 28 and Figure 29 shown, instead of the primary coil 12, a permanent magnet 18 having the same core 11 as described above can be provided, so as to also generate the electromagnetic transducer 10 operating with a direct current.

[0205] Other variations and improvements can be envisaged without departing from the scope of the present invention.

[0206] List of references

[0207] [1]:https: / / www.hzdr.de / db / Cms?pOid=55433&pNid=226

[0208] [2]:https: / / ieeexplore.ieee.org / stamp / stamp.jsp?arnumber=9768530 [3]:

[0210] https: / / www.degruyter.com / document / doi / 10.1515 / HTMP.2000.19.3-4.187 / pdf [4]:

[0212] https: / / esfr-smart.eu / wp-content / uploads / 2021 / 04 / S35_1_Sven_Eckert_ESFR_SMAR T_Measuring_Techniques.pdf [5]:

[0214] https: / / link.springer.com / content / pdf / 10.1007 / 978-1-4020-4833-3_17.pdf?pdf=inline%20link

[0215] [6]:https: / / iopscience.iop.org / article / 10.1088 / 1757-899X / 228 / 1 / 012023 / pdf

[0216] [7]:https: / / iopscience.iop.org / article / 10.1088 / 1757-899X / 208 / 1 / 012031 / pdf

Claims

1. An electromagnetic transducer for measuring three-dimensional velocity components of a conductive fluid flow, comprising: - a cylindrical metal tube forming a core with high magnetic permeability, the tube extending along a central axis (Z) and comprising a central portion and two end portions on either side of the central portion, each end portion comprising three bosses arranged at 120° to each other around the central axis (Z) and each boss delimiting a flat surface parallel to the central axis (Z); - an electrical coil, called the primary coil, which is wound around the central part of the tube; - six electrical coils, called receiver coils, each receiver coil being wound around one of the planar surfaces; or six Hall effect sensors, each Hall effect sensor being arranged on one of the planar surfaces.

2. An electromagnetic transducer for measuring three-dimensional velocity components of a conductive fluid flow, comprising: - a cylindrical metal tube forming a core with high magnetic permeability, the tube extending along a central axis (Z) and comprising a central portion and two end portions on either side of the central portion, each end portion comprising three bosses arranged at 120° to each other around the central axis (Z) and each boss delimiting a flat surface parallel to the central axis (Z); - permanent magnets arranged around a central portion of the tube; - six electrical coils, called receiver coils, each receiver coil being wound around one of the planar surfaces; or six Hall effect sensors, each Hall effect sensor being arranged on one of the planar surfaces.

3. The electromagnetic transducer according to claim 1 or 2, wherein: Each boss is T-shaped in front view, perpendicular to the central axis (Z), and the head of the T is the flat surface.

4. Use of an electromagnetic transducer as claimed in claim 1 or 2 for measuring the three-dimensional velocity components of a flow of an electrically conductive fluid, such as liquid metal of a nuclear reactor.

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