Detector for detecting change in speed of flow of conductive fluid including electromagnetic transducer

Abstract

To provide a detector for detecting a change in the speed of flow of a conductive fluid, which includes an electromagnetic transducer.SOLUTION: A detector for detecting a change in the speed of flow of a conductive fluid comprises: an electromagnetic transducer 10 including a metal cylindrical tube 2 forming a core having high magnetic permeability, an electric coil 3 wound around the tube and intended to be powered with direct current or a permanent magnet arranged around the tube, and at least one electric coil 4 called a receiving coil and wound around the tube while being adjacent to a primary coil or the permanent magnet; and at least one envelope detection circuit connected to the receiving coil and including at least one diode and one load in electrical series with the diode, the load being made up of a capacitor and an electrical resistor.SELECTED DRAWING: Figure 11

Description

Technical Field

[0001] The present invention relates to the field of instrumentation and measurement, and more particularly to the field of transducers dedicated to the measurement of the specific local velocity of a conductive fluid.

[0002] The present invention relates to a detector for detecting a change in the velocity of a conductive fluid, comprising an electromagnetic transducer.

[0003] The present invention is generally applicable to any conductive fluid. Such fluids include, for example, conductive ionic solutions such as salt water, and furthermore liquid metals. Usually, such metals are, for example, sodium, potassium, lead, lithium, aluminum, copper, iron, zinc, titanium, and their alloys.

[0004] More particularly, the present invention is applicable to measurements in fluids of the type of high-density liquids having a density in the range from 100 kg·m -3 to 10,000 kg·m -3 and above.

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

[0006] One advantageous application envisaged is, in particular, to measure the velocity of the heat transfer fluid in fission and fusion reactors.

Background Art

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

[0008] This applies in the metal casting industry, where the recognition of the velocity field in the mold and the power supply circuit of the mold makes it possible to predict the quality of the parts to be manufactured and to suppress defective parts. In fact, recognizing the flow velocity makes it possible to control and optimize the filling of the mold.

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

[0010] The velocity field is also a major factor in heat exchangers and in the heat transfer that occurs in the nuclear fuel regions of these reactors.

[0011] Recognizing and analyzing the velocity field in important areas of the reactor (heat exchangers, reactor core outlet, pumps, etc.) is also an indicator of proper functioning and, by extension, a means of enhancing the safety of these machines and generally a means of enhancing the ability to monitor these machines.

[0012] Scientific experiments using large volumes of liquid metal and tests carried out for the purpose of recognizing the flow distribution in exchanger assemblies also require the recognition of the velocity field of the flow involved.

[0013] In the various flow regions mentioned, the flow conditions are three-dimensional. What often characterizes these flows is the high temperature of those flows, which is often several hundred degrees, and the density of the fluid used, which can range from several hundred kg·m -3 to several thousand kg·m -3 and up to several thousand kg·m.

[0014] Various velocity measurement techniques are known and are used to measure the velocity components of the flow of conductive liquids.

[0015] Among them, electromagnetic technology is particularly relevant and robust in terms of material resistance with respect to the stress applied by the environment in which the measurement needs to be carried out. All of these technologies are even more beneficial when a highly dense and chemically reactive fluid such as liquid metal is involved.

[0016] The operating principle of an electromagnetic transducer is shown by the mathematical formula of Ohm's law in a moving fluid exposed to a magnetic field.

[0017] This mathematical formula shows that the conductivity σ of the fluid results in the development of an electric current (current density J) under the action of the velocity of the movement u combined with the external magnetic field B.

[0018]

Equation

[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 field B u deforms the external magnetic field B.

[0021] Here, for the sake of simplicity, it is stipulated that the vector symbolized by the letter B, which is the magnetic flux density or magnetic induction, is referred to as the magnetic field throughout this application. It is also stipulated that the various equations indicated below are written for the purpose of approximating a semi-permanent system that allows for ignoring certain values that intervene in Maxwell's equations, such as a moving current.

[0022] So far, the measurement of a single velocity component of the flow has generally been carried out by an electromagnetic transducer commonly denoted by the acronyms ECFM ("Eddy Current Flow Meter") or PSFM ("Phase Shift Flow Meter").

[0023] The conventional ECFM generally designated using symbol 1 is shown in FIGS. 1, 2, and 2A. The ECFM is axisymmetric about the central axis Z and typically consists of a core 2, an electric emitter coil called a primary coil 3, and one or two electric receiver coils called secondary coils 4, 5. The core 2 is formed by a solid rod 20 extending along the central axis Z and solid disks 21 regularly spaced along the central axis X, and the solid rod connects the solid disks to each other. The primary coil 3 and the secondary coils 4, 5 are wound around the solid rod 20 between two of the solid disks 21.

[0024] An alternating current is applied to the primary coil. The flow of this current creates an external magnetic field B in the environment near the primary coil according to Maxwell - Ampere's equation.

[0025]

Number

[0026] Here,

[0027]

Number

[0028] The primary current is alternating, so B is also alternating. In this way, B induces a voltage in each of the receiver coils according to Maxwell - Faraday's equation.

[0029]

Number

[0030] Here,

[0031]

Number

[0032] Furthermore, B results in the development of an induced current density J not only in the fluid but also in any surrounding conductors exposed to this magnetic field, including the metal of the pipe. Figures 3 and 4 show the development of the current density induced under the action of an external magnetic field in a situation without flow velocity for one secondary coil 4 and for two secondary coils 4, 5 respectively, with respect to ECFM. i The current density J

[0033] creates a further magnetic field B that deforms the external magnetic field B. i Therefore, the field B is not the same, depending on whether the ECFM is surrounded by a conductive fluid or not. i In the absence of fluid movement, one or more receiving coils deliver a voltage that is a function of the external magnetic field B and the field B.

[0034] i In the presence of fluid movement, a new current density J

[0035] appears and becomes the source of the magnetic field B. This new field changes B, which is so to speak blown by the flow of the conductive fluid and deforms in the direction of the flow of the conductive fluid as shown in Figures 5A, 5B, and 6. u u i u

[0036] The magnetic flux passing through one or more receiving coils depends on the flow velocity.

[0037]

[0038] i u u Therefore, one or more receiving coils deliver a voltage that converts the influence of the magnetic fields B that deform the external magnetic field B.

[0038] Digital simulation shows this. FIGS. 7A and 7B are digital simulations of the magnetic field around the ECFM, with and without the flow velocity of the conductive fluid, respectively.

[0039] By analyzing the voltage sent out by the receiving coil, it is possible to determine the flow velocity of the fluid moving in the region of the action of the magnetic field B.

[0040] As shown in FIG. 8, the single receiving coil 4 of the ECFM1 shows a decrease in magnetic flux when the speed increases (and experiences an increase in magnetic flux when the speed decreases), even though it is upstream with respect to the direction of the fluid flow. The alternating voltage e1 sent out by the receiving coil 4 decreases by Δe1.

[0041] The alternating voltage e1 provided by the ECFM is indicative of the flow velocity (by indication of the relative direction by comparing the amplitude of the current signal with the amplitude of the signal without velocity).

[0042] In addition to this, in the case of the ECFM with two receiving coils, the downstream receiving coil experiences an increase in the magnetic flux passing through that receiving coil as the fluid velocity increases. Its voltage e2 increases by Δe2. Therefore, |Δe2| = |Δe1|.

[0043] Generally, the two receiving coils 4, 5 of the ECFM are electrically connected in reverse series, as shown in FIG. 9.

[0044] In this way, the signal V provided by the ECFM with two coils is V = |e2| - |e1| is provided, where |e x | is the absolute value or amplitude of the voltage e x .

[0045] The signal V is proportional to the velocity component of the flow projected onto the axis of rotation of the ECFM.

[0046] In practice, priority is given to FDFM with two receiving coils 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 ECFM response on irrelevant values such as temperature. V = (|e2| - |e1|) / (|e2| + |e1|) The sign of V provides the direction of the velocity without the need to compare the amplitude of the signal without flow velocity.

[0047] When the ECFM is arranged with respect to the fluid flow, the ECFM can be inside the flow, i.e., positioned on the axis of the tube within the characterized flow (Non-Patent Document 1). Thus, the ECFM is in the fluid flow surrounding the ECFM.

[0048] In practice, as shown in FIG. 10, the internal ECFM1 is generally arranged 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.

[0049] Other ECFMs can be outside the flow. Thus, the coils and cores of the external ECFM are arranged around the fluid flow for which it is desired to measure the velocity.

[0050] In practice, the external ECFM is arranged around the tube to measure the velocity of the fluid flowing through this tube (Non-Patent Document 2).

[0051] When the ECFM is used to evaluate the velocity of the fluid flowing through the tube, the ECFM can only measure one velocity component, which is the component along the axis of the tube, and thus along the axis X of axial symmetry, whether it is inside or outside the tube. Specifically, the tube guides the fluid flow and provides its main direction to the fluid.

[0052] Generally, the signal processing of conventional ECFMs or currently available flow meters can be complex to implement.

[0053] Therefore, there is a need for a simplified solution for measuring the velocity of a flow of a conductive fluid that can be dense in the high velocity range and / or at high temperatures, and for processing the associated signals of such a flow, and a need to do so even for large volumes. SUMMARY OF THE INVENTION PROBLEM TO BE SOLVED BY THE INVENTION

[0054] An object of the present invention is to at least partially satisfy this need. MEANS FOR SOLVING THE PROBLEM

[0055] To that end, an object of the present invention is a detector for detecting a change in the velocity of a flow of a conductive fluid, comprising: a metal cylindrical tube forming a core having a high magnetic permeability, an electric coil called a primary coil, wound around the tube and intended to be powered by direct current, or a permanent magnet disposed around the tube, and at least one electric coil called a receiving coil, wound around the tube while being adjacent to the primary coil or the permanent magnet an electromagnetic transducer comprising: at least one envelope detection circuit connected to the receiving coil and comprising at least one diode and one load electrically in series with the diode, the load being made of a capacitor and an electrical resistor, and a detector comprising:

[0056] According to a first embodiment, the detector comprises a single envelope detection circuit.

[0057] Instead, according to the second embodiment, the detector comprises two envelope detection circuits in parallel with the receiving coil, and the diodes of one of the two circuits are mounted in the opposite direction to the diodes of the other of the two circuits. The detector according to this embodiment makes it possible to detect both an increase and a decrease in the velocity of the fluid flow.

[0058] Advantageously, the detector comprises an electronic device connected to the envelope detection circuit so as to detect a voltage threshold at the output of the capacitor. The electronic device is preferably a Schmitt trigger.

[0059] Preferably, the core is of low conductivity so as to limit the losses induced by variable magnetic induction, namely the Joule losses associated with the flow of the induced current, and the losses due to hysteresis.

[0060] Thus, the invention essentially lies in a detector for detecting a change in the velocity of a conductive fluid in one direction, comprising an electromagnetic transducer operating with either a primary coil powered by direct current or a permanent magnet.

[0061] The envelope detection circuit is very simple as a device for processing the signal received by the receiving coil.

[0062] The detector according to the invention makes it possible to measure a change in the velocity of the fluid, the nominal velocity of the fluid being able to be from a few millimeters per second to a few meters per second.

[0063] Furthermore, the detector according to the invention is suitable for measuring the change in velocity of a conductive liquid which has a high density, typically in the range from 100 kg·m -3 to 10,000 kg·m -3 and / or a high temperature in the range of the melting temperature of the metal which is typically processed, formed or used in liquid form.

[0064] Finally, the proposed detector according to the invention makes it possible to overcome the identified limitations of the prior art devices, - the processing of the signals generated by the detector, in a very simple way compared to existing flow meters and in a way much less complex than the reconstruction algorithms required by prior art ECFM and tomographic measurement methods, and - the possibility of being positioned within the flow characterized in the area under investigation including many advantages.

[0065] Other advantages and features will become more clearly apparent by reading the detailed description provided using non-limiting illustrations with reference to the following figures.

Brief Description of the Drawings

[0066]

Figure 1

Figure 2

Figure 2A

Figure 3

Figure 4

Figure 5A

Figure 5B

Figure 6

Figure 7A

Figure 7B

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

DETAILED DESCRIPTION OF THE INVENTION

[0067] Throughout this application, the terms "upstream" and "downstream" are to be understood as referring to the direction of fluid flow along the axis Z around the transducer.

[0068] Figures 1 to 10 have already been described in the premise part. Therefore, they will not be discussed in detail below.

[0069] Figure 11 shows the electromagnetic transducer 10 of the detector according to the present invention, which is intended to measure the change in the velocity of the flow of the conductive fluid.

[0070] The transducer 10 is axially symmetric about the central axis X and is typically made from a core 2 having a high magnetic permeability, an electrical emitter coil called a primary coil 3, and an electrical receiving coil called a secondary coil 4.

[0071] The core 2 is formed from a tube extending along the central axis X.

[0072] The primary coil 3 and the secondary coil 4 are wound around the tube 2.

[0073] An alternative to the transducer of Figure 11 is shown in Figure 12, where instead of a primary coil supplied with direct current, a permanent magnet 6 may be arranged around the core 2 adjacent to the secondary coil 4.

[0074] An envelope detection circuit 7 is connected to the terminals of the secondary coil 4. As shown in Figure 13, such a circuit 7 is made from a diode 8 connected in series with a load 9 made from a resistor 90 in parallel with a capacitor 91.

[0075] The envelope detection circuit 7 is connected to an electronic device (not shown) having threshold crossing detection. This electronic device may be a Schmitt trigger.

[0076] Here, the operation of the detector having the electromagnetic transducer 10 and the envelope detection circuit 7 will be described.

[0077] When there is a change in the velocity of the fluid surrounding the transducer 10, the receiving coil 4 is the location of an induced electromotive force caused by a change in the magnetic flux coming from either the primary coil 3 supplied with current or the permanent magnet 6.

[0078] The amplitude of the voltage signal e1 sent out by the receiving coil 4 depends on the amplitude of the change in speed. The speed component that the detector can sense is the speed component parallel to the central axis (Z).

[0079] The sign of the detector's signal provides information about whether the change in speed is positive or negative (whether the speed is increasing or decreasing).

[0080] Therefore, the coil 4 sends out a voltage e1 that is rectified by the diode 8 and charges the capacitor 91. The resistor 90 gradually discharges the capacitor so as to limit the period during which the voltage e’1, which is indicative of the envelope of the signal resulting from the value of e1 over time, exists. These values e’1 are detected by a Schmitt trigger.

[0081] Therefore, the presence of the voltage e1 is detected in a very simple way and can be temporarily stored over a period that is a function of the capacitance of the capacitor 91 and the ohmic resistance of the resistor 90.

[0082] In the case of the single envelope circuit 7 according to FIG. 13, only an increase or decrease in the speed of the fluid flowing around the transducer can be obtained.

[0083] Two modifications of the envelope circuit 7 are shown in FIG. 14, where two envelope detection circuits 7 are here connected electrically in parallel with the receiving coil 4. Each of the two circuits is made up of diodes 8.1; 8.2 connected in series with loads 9.1; 9.2 made up of resistors 90.1; 90.2 in parallel with capacitors 91.1; 91.2.

[0084] One of the diodes 8.1 of the two circuits is mounted in the opposite direction to the other diode 8.2 of the two circuits.

[0085] With these two circuits 7, both an increase and a decrease in speed can be detected. The voltages e'1 and e''1 provide information about the presence of a positive change given, for example, by e'1, and the presence of a negative change given, for example, by e''1. These output voltage values e'1, e''1 are each detected by a Schmitt trigger.

[0086] Other modifications and improvements can be envisaged without departing from the scope of the present invention.

[0087] (References) [1]: https: / / www.hzdr.de / db / Cms?pOid=55433&pNid=226 [2]: https: / / ieeexplore.ieee.org / stamp / stamp.jsp?arnumber=9768530

Explanation of Signs

[0088] 2 Core, tube 3 Primary coil, electrical emitter coil 4 Secondary coil, electrical receiver coil 6 Permanent magnet 8, 8.1, 8.2 Diode 9, 9.1, 9.2 Load 90, 90.1, 90.2 Resistor 91, 91.1, 91.2 Capacitor 10 Electromagnetic converter e1, e'1, e''1 Voltage

Claims

1. 1. A detector for detecting a change in velocity of a flow of a conductive fluid, comprising: A metallic cylindrical tube (2) forming a core having high magnetic permeability; an electric coil (3), called a primary coil, wound around the tube and intended to be powered by direct current, or a permanent magnet arranged around the tube; and At least one electric coil (4), called a receiving coil, is wound around the tube adjacent to the primary coil or the permanent magnet. an electromagnetic transducer (10) comprising: At least one envelope detection circuit (7) connected to the receiving coil and comprising at least one diode (8; 8.1, 8.2) and a load (9; 9.1, 9.2) in electrical series with the diode, the load being made up of a capacitor (91; 91.1, 91.2) and an electrical resistor (90; 90.1, 90.2); The detector comprises:

2. 10. The detector of claim 1 comprising a single envelope detection circuit.

3. 2. A detector as claimed in claim 1, comprising two envelope detection circuits in parallel with the receiving coil, the diodes of one of the two circuits being mounted in an opposite orientation to the diodes of the other of the two circuits.

4. At the output of the capacitor there is a voltage threshold (e' １ , e'' １ 4. A detector as claimed in claim 1, further comprising an electronic device connected to the envelope detection circuit to detect an envelope of the signal.

5. 5. The detector of claim 4, wherein the electronic device is a Schmitt trigger.

6. 6. Use of a detector according to any one of claims 1 to 5 for measuring changes in the velocity of a flow of a conductive fluid, such as the liquid metal of a nuclear reactor.

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