RU2606340C2 - Electromagnetic meter of electroconductive fluid flow velocity vector components - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: invention relates to measuring equipment. Feature of the disclosed electromagnetic meter of an electroconductive fluid velocity vector components is that magnets are aligned in such a way, that the magnetic field is directed along the axis of rotation of the magnetic unit, on each of the magnets on its poles there are tips from a magnetic material, free ends of which are located at the minimum possible distance, basing on strength characteristics of the structure, from working surfaces of electrodes, which are located in the middle of the body length in the zone of the magnetic field concentration, herewith the body has an elongated shape with a ratio of the length and the diameter, which provides the body strength during oceanographic measurements.

EFFECT: reduced flow velocity vector components measurement errors caused by the body flow dynamics along with increased sensitivity.

3 cl, 3 dwg

Description

The invention relates to measuring equipment, namely to electromagnetic devices for measuring the parameters of the velocity vector of the flow of conductive fluid, and can be used, for example, when conducting hydrophysical and hydrodynamic studies.

Almost all electromagnetic conductive fluid velocity meters measure the projections (components) of the current velocity vector on the axis between a pair of electrodes in a magnetic field. Speed, as such, is then determined through the components of the current velocity vector. And with the help of liquid flow sensors, the flow rate in any channel is actually determined, and the flow rate is calculated taking into account the channel cross-section.

The most popular in Ukraine and the CIS countries is an autonomous device for long-term studies of the current velocity field in freshwater basins and seas. Given the specifics of long-term measurements of the velocity and direction of currents in the shelf zone and, in particular, in the coastal region of seas and freshwater basins, the device should not have moving elements of the measuring path external to the body, should be resistant to the action of abrasive particles of suspension, which are very many in the surf zone and which are carried out over considerable distances, be corrosion resistant with respect to sea water.

The Faraday effect speedometer [1] is known - a meter of the velocity of an electrically conductive liquid using the Faraday effect, shown in FIG. 1 (item numbers taken from [1]), which includes a set of magnets 18 with alternating north and south poles installed in the housing 12 and adapted for rotation through the shaft 20 by the motor 24 to create an alternating magnetic field. The hull is adjacent to the vessel wall 14 so that the magnetic field propagates in the vessel wall and in the liquid, on the other side of the vessel wall. The electrodes 16a-16c are located in the wall and are in a magnetic field. The sensing coil 30 is isolated from the liquid and is located externally with respect to the housing in such a way that it responds to an alternating magnetic field and controls the signal switching. The fluid flow on the outer wall of the vessel during its movement changes the potential of the electrodes, which provides the corresponding signal. The signals from the sensing coil and electrodes are combined to form a signal corresponding to the speed of the vessel.

Similar to the features of the claimed invention are such features of an analogue: a cylindrical body with a magnetic block of magnets of alternating polarity installed in it and electrodes connected to the electronics block, the working surfaces of which are located in a liquid in the field zone of the magnetic block.

The main disadvantage of this meter is that it is a ship's lag by purpose and cannot, therefore, be used as a separate measuring device. Other disadvantages: bulky design and low intensity of the magnetic field in the working area of the speed measurement due to the applied orientation of the magnets, when the magnetic field is perpendicular to the plane on which the electrodes are located, and its concentrators are absent. As a result of this, the high sensitivity of the meter cannot be ensured.

Known Magnetic flow sensor [2] is a magnetic sensor for measuring the flow rate of a conductive fluid, which, by the totality of the features, is the closest to the proposed invention and is therefore selected as a prototype [2, FIG 57]. The sensor is shown in FIG. 2 (item numbers taken from FIG 57A-57D of the prototype) and includes a housing 3701 located in the fluid stream 3722; at least two pairs of permanent magnets 3703, combined in a magnetic block 3702 located inside the housing to provide a magnetic flux orthogonal to the direction of fluid flow; a drive 3707 for mechanically moving the magnets and alternating the polarity of the magnetic flux to produce an alternating electric voltage in a fluid having a magnitude proportional to the fluid flow rate; at least two electrodes 3711 for contact with the liquid and removal of AC voltage, mounted on the housing and located opposite each other on opposite sides of the flowing part perpendicular to the direction of fluid flow.

The prototype has the following features similar to the essential features of the claimed invention: a cylindrical non-magnetic case in which a magnetic block of at least two pairs of permanent magnets with alternating polarity is mounted rotatably about its axis, several pairs of electrodes are attached to the body of the electronics, whose working surfaces are located in the fluid flow in the field zone of the magnetic block.

The prototype, with all the variety of its versions (58 variants), has a number of significant drawbacks. (Note that the performance according to FIG 57D involves the use of 3703 'electromagnets, therefore, to create a strong magnetic field in order to achieve high sensitivity requires huge energy consumption, which is categorically unacceptable in the operating conditions of the inventive meter.)

The disadvantages of the prototype is the following:

- the installation of electrodes near the flat bottom of the housing is acceptable only when the sensor is located in any channel, when the flow does not run on the housing at an angle significantly different from 90 ° relative to its axis, and the formation of a strongly turbulent region near the electrodes, distorting the flow velocity field, due to the effects of the transition flat bottom - cylindrical surface of the body; but even at 90 ° this transition introduces serious flow distortions;

- the absence of magnetic field concentrators, due to the chosen orientation of the magnets, and, as a consequence, the reduced sensitivity of the meter;

- excess number of electrodes when measuring two components of the current velocity vector - eight electrodes, four are enough;

- the minimum number of magnets for this method of creating an alternating magnetic field is four magnets; a larger number of magnets can reduce the rotation speed of the magnetic system and reduce the energy consumption of the electric motor or, without changing the speed, increase the modulation frequency, which is necessary with a large temporal variability of the studied flow.

The basis of the invention is the task of creating an electromagnetic meter of the components of the velocity vector of an electrically conductive liquid with improved metrological characteristics, the set of essential features of which ensures the achievement of a technical result - reducing the measurement errors of the components of the velocity vector of the flow caused by the dynamics of the flow around the body, and increasing the sensitivity (resolution level). An additional technical result of the invention is to improve the operational properties of the meter - improving weight and size characteristics, ensuring low power consumption and corrosion resistance, increasing the ultimate hydrostatic pressure, ensuring wear resistance in the presence of abrasive particles in the liquid.

The problem is solved in that in an electromagnetic meter, a component of the velocity vector of an electrically conductive liquid containing a cylindrical non-magnetic case, in which a magnetic block of at least two pairs of permanent magnets with alternating polarity is mounted and rotated around the axis and connected to the block electronics several pairs of electrodes, the working surfaces of which are located in a liquid in the field zone of the magnetic unit, it is new that the magnets are oriented t such that the magnetic field is directed along the axis of rotation of the magnetic block, on each of the magnets at its poles are fixed tips of magnetic material, the free ends of which are located at the minimum possible distance, based on the strength characteristics of the structure, from the working surfaces of the electrodes that are located in the middle of the length of the housing in the zone of concentration of the magnetic field, while the hull has an elongated shape with a ratio of length and diameter, ensuring the strength of the hull during oceanographic measurements. In this case, mainly the electrodes are made in the form of collapsible repair-suitable elements, and in the magnetic block an axial hole is provided for laying conductors.

The invention is illustrated with reference to the drawing (Fig. 3), which shows a General view of the meter in section.

показан вектор скорости потока жидкости.The meter contains a cylindrical housing 1, which is made of durable non-magnetic material, for example non-magnetic metal, and has an elongated shape with a given ratio of length and diameter - for example, the length is 4-6 times greater than the diameter. The execution of the hull is robust and ensures reliable operation during oceanographic measurements, while the elongated shape improves the dynamics of the flow around the hull. Arrows in the drawing

shows the fluid velocity vector.

показан вектор индукции магнитного поля.A magnetic unit in the form of a body of revolution made of pairs of constant equally directed magnets of rare-earth metals 2 with alternating polarity is mounted rotatably about its axis in the housing 1 — they are oriented so that the magnetic field is directed along the axis of rotation of the magnetic block. In this case, the magnetic block is made in the form of a ring and contains four pairs of magnets 2 in the form of its sectors, the specified distance between which eliminates their mutual weakening. Arrows in the drawing

The magnetic field induction vector is shown.

On each of the magnets 2 at its poles are fixed pole pieces 3 of magnetic material, for example annealed steel 3, in the form of flat plates of a given thickness, which have ends that are freely protruding relative to the magnets, creating a magnetic field concentration zone. In the drawing, round arrows show the direction of the magnetic field generated by the magnets 2.

On the outer surface of the housing 1 are fixed in its two mutually orthogonal axial planes two pairs of electrodes 4, which in this case are cylindrical in shape and oriented along the housing. The electrodes are installed so that their working surfaces are located in the middle of the length of the housing in the zone of magnetic field concentration and at a predetermined distance from the free ends of the pole pieces 3. In this case, the electrodes are sealed in the passage holes of the metal strong housing and isolated from it. To exclude the bypassing of the useful signal taken from the electrodes, the metal robust housing in the area of the electrodes is electrically insulated (paint or varnish or dielectric film).

Placing the working surfaces of the electrodes in the middle of the elongated housing allows minimizing the distortion of the current velocity field in the near-electrode region and correctly forming the radiation pattern.

Induction of the magnetic field can be increased, for example, by making a groove on the outside of the housing 1, which has a considerable thickness for working at great depths, near the electrodes 4, which makes it possible to provide the required distance from the zone of maximum magnetic field to the moving conductive fluid.

Thus, the magnetic block is placed in the middle of the length of the housing 1 and divides its internal space into two parts, in which other elements of the meter are placed. For example, in one of the parts there is a motor 5, a rotating magnetic unit, for example, an IDR6M micromotor, and a battery 6 for powering the speed regulator of this engine and the electronics unit, and in the other part, the electronics unit 7. The electrical connection between the elements of the two parts of the housing is carried out by conductors. In the case of the requirement for optimal use of the internal space of the housing, according to the claimed invention, an axial hole for the conductor gasket is provided in the magnetic block. This is achieved by using a gear transmission - the magnetic block is mounted on a non-magnetic base 8, mounted through a pair of ball bearings 9 on the hollow shaft 10. The magnetic block is connected through a gear pair of wheels 11 to the engine 5.

During oceanographic studies in the coastal zone, the most vulnerable elements of the meter are electrodes, there is a possibility of their failure. Therefore, the invention proposes the possibility of performing them in the form of collapsible repair-fit elements that are easily dismantled and installed, which improves the performance of the meter.

The device operates as follows.

The micromotor 5 rotates a magnetic block of eight magnets 2 around its axis, as a result of which a magnetic field of alternating magnitude and sign appears in the near-electrode zone of the meter on the outside of the housing 1 in a moving fluid. When each of the four electrodes 4 passes by a region of a different magnetic field concentrated with the help of pole tips 3, potentials of a different sign appear on the electrodes 4.

The difference in the sign of the potentials of each pair of electrodes 4 is fed to the inputs of the elements of the electronics unit 7 (in the drawing, these elements of the block are not shown and are not indicated by positions) - a differential instrumental amplifier, and then to a bandpass filter and a synchronous detector.

The synchronous detector is controlled by a Hall sensor 12, which determines at each moment in time the direction of the magnetic field, and hence the phase of the alternating voltage, which is supplied after amplification and filtering to the synchronous detector.

To eliminate phase distortion of the filtered signals, the rotation speed of the engine 5 is maintained constant using an electronic stabilizer (not shown and not indicated in the drawing).

The applicant made an experimental sample of the proposed meter, which in the tests showed itself well and confirmed the achievement of the technical result of the invention.

Information sources

1. US patent No. 3777561, IPC G01P 5/08, publ. 12/11/1973.

2. US patent No. 6085599, IPC G01F 1/58, publ. 07/11/2000 - a prototype.

Claims (3)

1. An electromagnetic meter of a component of a velocity vector of an electrically conductive liquid, comprising a cylindrical non-magnetic body, in which a magnetic unit of at least two pairs of permanent magnets with alternating polarity is mounted rotationally relative to its axis, and several pairs of electrodes attached to the electronics unit are mounted, the working surfaces of which are located in the liquid in the field zone of the magnetic unit, characterized in that the magnets are oriented so that the magnetic field is directed in the length the axis of rotation of the magnetic block, on each of the magnets at its poles fixed tips of magnetic material, the free ends of which are located at the minimum possible distance, based on the strength characteristics of the structure, from the working surfaces of the electrodes, which are located in the middle of the body length in the magnetic field concentration zone, at this hull has an elongated shape with a ratio of length and diameter, ensuring the strength of the hull during oceanographic measurements. 2. The electromagnetic meter according to claim 1, characterized in that the electrodes are made in the form of collapsible repair-suitable elements. 3. The electromagnetic meter according to claim 1, characterized in that an axial hole for the conductors is made in the magnetic block.

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