A detector equipped with an electromagnetic transducer for detecting changes in the flow velocity of a conductive fluid.

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 specifically to the field of transducers dedicated to measuring specific local velocity of conductive fluids.

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

[0003] The present invention is generally applicable to all conductive fluids. Such fluids include, for example, conductive ionic solutions such as brine, and even liquid metals. Typically, such metals are, for example, sodium, potassium, lead, lithium, aluminum, copper, iron, zinc, titanium, and their alloys.

[0004] More specifically, the present invention relates to 100 kg·m -3 From 10,000 kg·m -3 This applies to measurements in fluids of the high-density liquid type, which have densities in the ultra-high degree range.

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

[0006] One promising application that is envisioned is measuring the velocity of heat transfer fluids, particularly in nuclear fission and fusion reactors. [Background technology]

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

[0008] This is also true in the metal casting industry, where recognizing the velocity field in the mold and its power supply circuit makes it possible to predict the quality of the manufactured parts and reduce defects. 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 specific reactor circuits is a major factor in the stress on the metal structures it contacts. Therefore, understanding the velocity field is essential.

[0010] The velocity field is also a major factor in heat exchange present in heat exchangers and in the region of nuclear fuel in these reactors.

[0011] Recognizing and analyzing the velocity field in critical areas of the reactor (such as heat exchangers, core outlets, and pumps) is an indicator of proper functioning, and consequently, a means of improving the safety of these machines, and generally a means of improving the ability to monitor them.

[0012] Scientific experiments using large volumes of liquid metal, as well as tests conducted to recognize flow distribution in exchanger manifolds, also require recognition of the velocity field of the flow involved.

[0013] In various flow domains mentioned, the flow conditions are three-dimensional. Characterizing these flows in most cases are their high temperature, often several hundred degrees, and several hundred kg·m³. -3 From several thousand kg·m -3 This is the density of the fluid used, which can extend to a certain range.

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

[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 high-density and chemically reactive fluids such as liquid metals are 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 when there is no electric field E.

[0020] Current density J u is the source of the magnetic field B u This field B u modifies 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 ignoring specific values intervening in the Maxwell equations, such as moving currents.

[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 axially symmetric 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. This current flow 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 current, so B is also alternating current. 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 an additional magnetic field B i that modifies 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.

[0034] 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 i .

[0035] In the presence of fluid movement, a new current density J u appears and becomes the source of the magnetic field B u . This new field changes B, and B is, so to speak, blown by the flow of the conductive fluid and deformed in the direction of the flow of the conductive fluid as shown in Figures 5A, 5B, and 6.

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

[0037] Therefore, one or more receiving coils deliver a voltage that converts the influence of the magnetic fields B i and B u that deform the external magnetic field B.

[0038] Digital simulations demonstrate this. Figures 7A and 7B show 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 emitted by the receiving coil, it becomes possible to determine the flow velocity of the fluid moving within the region of effect of magnetic field B.

[0040] As shown in Figure 8, the single receiving coil 4 of the ECFM1, despite being upstream of the fluid flow direction, exhibits a decrease in magnetic flux as the velocity increases (and an increase in magnetic flux as the velocity decreases). The AC voltage e1 delivered by the receiving coil 4 decreases by Δe1.

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

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

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

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

[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, the combined use of the voltages delivered by these two coils is given priority to the FDFM with two receiving coils because it doubles the sensitivity and eliminates the dependence of the ECFM's response on irrelevant values ​​such as temperature. V = (|e2| - |e1|) / (|e2| + |e1|) The symbol V indicates the direction of velocity without the need to compare it to the amplitude of the signal without considering the flow velocity.

[0047] When an ECFM is positioned relative to a fluid flow, the ECFM can be within the flow, that is, it can be positioned along the axis of the pipe within the characterized flow (Non-Patent Literature 1). Thus, the ECFM is within the fluid flow surrounding it.

[0048] In practice, as shown in Figure 10, the internal ECFM1 is generally located in the center of an annular space defined by two concentric tubes T1, T2 through which the fluid F whose velocity is to be measured flows.

[0049] Other ECFMs may be outside the flow. Therefore, the coils and cores of the external ECFMs are positioned around the flow of the fluid whose velocity is to be measured.

[0050] In practice, an external ECFM is positioned around the tube to measure the velocity of the fluid flowing through it (Non-Patent Literature 2).

[0051] When ECFM is used to evaluate the velocity of a fluid flowing through a pipe, it can only measure one velocity component, which is the component along the pipe's axis, and therefore along the axis of axial symmetry X, whether it is inside or outside the pipe. Clearly, the pipe guides the fluid flow and provides the fluid with its primary direction.

[0052] In general, processing signals from conventional ECFM or currently available flowmeters can be complex to implement.

[0053] Therefore, there is a need to propose a simplified solution for measuring the velocity of conductive fluid flows, which may be dense, over a high velocity range and / or at high temperatures, and for processing the associated signals of such flows, even in large volumes. [Overview of the project] [Problems that the invention aims to solve]

[0054] The objective of this invention is to satisfy this need at least partially. [Means for solving the problem]

[0055] Therefore, the object of the present invention is a detector for detecting changes in the flow velocity of a conductive fluid, A metal cylindrical tube that forms a core with high magnetic permeability, An electrical coil, also called a primary coil, which is wound around the tube and intended to supply power with direct current, or a permanent magnet placed around the tube, and A receiving coil, which is at least one electrical coil wound around the tube, adjacent to the primary coil or permanent magnet. An electromagnetic converter equipped with, - An envelope detection circuit comprising at least one diode and one load electrically in series with the diode, connected to a receiving coil, wherein the load is made of a capacitor and an electric resistor. It is a detector equipped with [a certain feature].

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

[0057] Alternatively, according to the second embodiment, the detector comprises two envelope detection circuits in parallel with a receiving coil, with a diode in one of the two circuits mounted in the opposite direction to the diode in the other circuit. The detector according to this embodiment is capable of detecting both an increase and a decrease in the velocity of the fluid flow.

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

[0059] Preferably, the core has low conductivity to limit losses induced by variable magnetic induction, i.e., Joule losses associated with the induced current flow and losses due to hysteresis.

[0060] Therefore, the present invention essentially relates to a detector for detecting a change in the velocity of a conductive fluid in one direction, comprising an electromagnetic transducer that operates with either a primary coil powered by DC or a permanent magnet.

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

[0062] The detector according to the present invention makes it possible to measure changes in fluid velocity, and the nominal fluid velocity can range from a few millimeters per second to a few meters per second.

[0063] Furthermore, the detector according to the present invention typically has a capacity of 100 kg·m -3 From 10,000 kg·m -3 It is suitable for measuring the rate change of conductive liquids that are dense, have a density up to an ultra-high degree, and / or have a high temperature that is typically within the melting temperature range of the metal being processed, formed, or used in liquid form.

[0064] Finally, the detector according to the proposed invention will enable overcoming the identified limitations of prior art devices. - Processing of the detector-generated signal using a method that is significantly simpler than existing flowmeters, and far less complex than the reconstruction algorithms required for prior art ECFM and tomography-based measurement methods, and - Potential to be positioned within the characteristic flow of the area being investigated It has many advantages, including [mention specific advantages here].

[0065] Other advantages and features become clearer by referring to the following diagram and reading the detailed description provided with non-limiting illustrations. [Brief explanation of the drawing]

[0066] [Figure 1] This is a schematic side view of a prior art eddy current flowmeter (ECFM) having one receiving (secondary) coil. [Figure 2] This is a schematic side view of an ECFM according to prior art, which has two receiving (secondary) coils. [Figure 2A] Figure 2 is a longitudinal side view. [Figure 3] Figure 1 is shown again, illustrating the development of the current density induced under the action of an external magnetic field when there is no flow velocity. [Figure 4] Figure 2 is shown again, illustrating the development of the current density induced under the action of an external magnetic field when there is no flow velocity. [Figure 5A] Figure 1 is shown again, illustrating the expansion of the current density induced under the action of an external magnetic field when there is a flow velocity. [Figure 5B] Figure 1 is shown again, illustrating the expansion of the current density induced under the action of an external magnetic field when there is a flow velocity. [Figure 6] Figure 2 is shown again, illustrating the development of the current density induced under the action of an external magnetic field when there is a flow velocity. [Figure 7A]This is a diagram of a digital simulation of the magnetic field around an ECFM using prior art, in the absence of a conductive fluid flow velocity. [Figure 7B] This is a diagram of a digital simulation of the magnetic field around an ECFM using prior art, given the flow velocity of a conductive fluid. [Figure 8] Figure 1 is shown again, illustrating the voltages before and after the terminals of the receiving coil of an ECFM according to prior art. [Figure 9] Figure 2 is shown again, illustrating, on the one hand, the preferred electrical connection of the receiving coil in reverse series, the voltage across the terminals of the coil, and the final voltage measured across the terminals of the ECFM according to the prior art. [Figure 10] This is a diagram of a reproduction of an ECFM using prior art, such as being placed inside an embedded tube for measuring the one-dimensional velocity of a flowing fluid F. [Figure 11] This is a schematic side view of an electromagnetic transducer for a detector that detects changes in speed, according to the present invention, which has a primary coil powered by a DC current and a receiving (secondary) coil. [Figure 12] This is a schematic side view of an electromagnetic transducer for a detector to detect changes in speed according to the present invention, which has a permanent magnet and a receiving (secondary) coil. [Figure 13] This is a schematic diagram of an envelope detection circuit for a detector according to the present invention. [Figure 14] This is a schematic diagram of two envelope detection circuits for a detector according to the present invention. [Modes for carrying out the invention]

[0067] Throughout this application, the terms “upstream” and “downstream” are understood to refer to the direction of fluid flow along axis Z around the transducer.

[0068] Figures 1 to 10 have already been explained in the prerequisites section. Therefore, they will not be examined in detail below.

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

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

[0071] Core 2 is formed from tubes that extend along the central axis X.

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

[0073] An alternative to the converter in Figure 11 is shown in Figure 12, in which, instead of a primary coil powered by a DC current, a permanent magnet 6 may be arranged around the core 2 adjacent to the secondary coil 4.

[0074] The 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 up of 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 having threshold overshoot detection, which is not shown. This electronic device may be a Schmitt trigger.

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

[0077] When there is a change in the velocity of the fluid surrounding the transducer 10, the receiving coil 4 is the location of the induced motor force caused by the change in magnetic flux coming from either the primary coil 3, which is 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 velocity. The velocity component that the detector can sense is the velocity component parallel to the central axis (Z).

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

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

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

[0082] In the case of the single envelope circuit 7 shown in Figure 13, only an increase or decrease in the velocity of the fluid flowing around the transducer is obtained.

[0083] Two variations of the envelope circuit 7 are shown in Figure 14, where the two envelope detection circuits 7 are electrically connected in parallel with the receiving coil 4. Each of the two circuits is made from a load 9.1;9.2 made from resistors 90.1;90.2 in parallel with capacitors 91.1;91.2 and diodes 8.1;8.2 connected in series with a load 9.1;9.2 made from resistors 90.1;90.2 in parallel with capacitors 91.1;91.2.

[0084] Diode 8.1 in one of the two circuits is mounted in the opposite direction to diode 8.2 in the other circuit.

[0085] These two circuits 7 allow for the detection of both increases and decreases in speed. Voltages e'1 and e''1 provide information about the presence of a positive change, for example, given by e'1, and the presence of a negative change, for example, given by e''1. These output voltage values ​​e'1 and e''1 are detected by a Schmitt trigger, respectively.

[0086] Other modifications and improvements can be envisioned 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 Symbols]

[0088] 2 cores, tubes 3. Primary coil, electric emitter coil 4. Secondary coil, electric receiving coil 6 Permanent Magnets 8, 8.1, 8.2 Diodes 9, 9.1, 9.2 Load 90, 90.1, 90.2 resistor 91, 91.1, 91.2 Capacitors 10 Electromagnetic Converters e1, e'1, e''1 voltages

Claims

1. A detector for detecting changes in the flow velocity of a conductive fluid, A metal cylindrical tube (2) that forms a core having high magnetic permeability, An electric coil (3) called a primary coil, which is wound around the tube and intended to be powered by direct current, or a permanent magnet placed around the tube, and A receiving coil, and at least one electric coil (4) that is wound around the tube, adjacent to the primary coil or the permanent magnet. An electromagnetic converter (10) is provided, Connected to the receiving coil, at least one envelope detection circuit (7) comprising at least one diode (8; 8.1, 8.2) and one load (9; 9.1, 9.2) electrically in series with the diode, wherein the load is made of a capacitor (91; 91.1, 91.2) and an electrical resistor (90; 90.1, 90.2), and A detector equipped with the following features.

2. The detector according to claim 1, comprising a single envelope detection circuit.

3. The detector according to claim 1, comprising two envelope detection circuits in parallel with the receiving coil, wherein the diode in one of the two circuits is mounted in the opposite direction to the diode in the other of the two circuits.

4. At the output of the capacitor, the voltage threshold (e' １ , e'' １ The detector according to claim 1, comprising an electronic device connected to the envelope detection circuit to detect the envelope.

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

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

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