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    • 专利摘要:
    A device for measuring a flow rate of a gas comprises a probe (S), a voltage source (5) and a pulse count detection circuit (7). The probe has an axial electrode (1) with an exposed end (1P) having a small radius of curvature, and a peripheral electrode (2). The power source applies an alternating voltage between the two electrodes, and electrical discharges that occur through the gas between the two electrodes are detected and counted by the detection circuit. Such a speed measuring device is particularly reliable, and adapted to be used on board an aircraft (AV) to measure its speed relative to the surrounding air.
    公开号:FR3060125A1
    申请号:FR1662169
    申请日:2016-12-08
    公开日:2018-06-15
    发明作者:Paul-Quentin ELIAS
    申请人:Office National dEtudes et de Recherches Aerospatiales ONERA；
    IPC主号:
    专利说明:

    ® FRENCH REPUBLIC
    NATIONAL INSTITUTE OF INDUSTRIAL PROPERTY © Publication number:
    (to be used only for reproduction orders)
    ©) National registration number
    060 125
    62169
    COURBEVOIE © IntCI 8 : G 01 P 5/00 (2017.01)
    PATENT INVENTION APPLICATION
    A1
    ©) Date of filing: 08.12.16. © Applicant (s): NATIONAL STUDIES OFFICE AND OF AEROSPATIAL RESEARCH Establishment (3U) Priority: public - FR. @ Inventor (s): ELIAS PAUL-QUENTIN. ©) Date of public availability of the request: 15.06.18 Bulletin 18/24. ©) List of documents cited in the report preliminary research: Refer to end of present booklet (© References to other national documents ® Holder (s): NATIONAL OFFICE FOR STUDIES AND related: AEROSPATIAL RESEARCH Establishment public. ©) Extension request (s): © Agent (s): CABINET PLASSERAUD.
    DEVICE AND METHOD FOR MEASURING A GAS FLOW SPEED.
    FR 3 060 125 - A1
    A device for measuring a flow rate of a gas comprises a probe (S), a supply source (5) of electric voltage and a detection circuit (7) with pulse counting. The probe comprises an axial electrode (1), one exposed end (1 P) of which has a small radius of curvature, and a peripheral electrode (2). The power source applies an alternating voltage between the two electrodes, and electrical discharges which occur through the gas, between the two electrodes, are detected and counted by the detection circuit. Such a speed measuring device is particularly reliable, and suitable for use on board an aircraft (AV) to measure its speed with respect to the surrounding air.
    DEVICE AND METHOD FOR MEASURING A FLOW SPEED
    GAS
    The present invention relates to a device and method for measuring a gas flow speed, in particular for aeronautical applications.
    Many methods already exist for measuring the speed of a gas flow. In particular, it is known to measure the speed of a gas flow using a Pitot probe. Such a probe comprises a stop pressure tap which is oriented facing the flow, and a static pressure tap which is arranged on a wall tangent to the flow. The difference between the shutdown pressure and the static pressure is then proportional to the square of the gas speed. However, the shut-off pressure tap is constituted by a capillary tube which is likely to be obstructed by frost or dust, or by a fault in maintenance operation, because of which the reliability of the Pitot probes may be insufficient.
    It is also known to measure the speed of a gas flow using an ultrasonic pulse emission probe. The measurement principle is based on a determination of a transit time of the ultrasonic pulses. However, such probes are limited to speeds to be measured which are less than 100 m / s (meter per second).
    It is also known to use a laser beam which crosses the gas flow. A Doppler shift of the backscattered light, or a wavelength shift of an absorption line of a gas component, makes it possible to evaluate the speed of the flow. But such methods require a laser source, at least one optical window to exit the beam to the flow and collect light back. In addition, these optical methods are imprecise when the flow velocity is low.
    Furthermore, ionic probes are also known for measuring the speed of a gas flow. In a first category of such probes, ions are generated in the flow, then collected downstream of
    -2the place of their generation. The speed of the flow can then be deduced from the time between the emission and the collection of the ions, called time of flight of the ions, in the case of a generation of ions by pulses, or deduced from the value of an electric current which collected, in the case of a continuous or quasi-continuous generation of ions. But the probes of this first category require having a source of ions in the gas flow, which can disturb this flow whose speed we want to measure.
    Finally, ion probes of a second category use fine tips which are polarized by a direct electric voltage, positive or negative, to generate ions in the gas flow. For some of these probes, a measuring electrode is placed downstream in the flow to collect electrical charges corresponding to the ions generated. The value of the electric current in the measuring electrode can then be related to the speed of the flow. For other probes, the tip is polarized by a direct voltage which is negative, to produce a negative corona discharge. In this case, a corona discharge pulse current value, or a corona discharge pulse frequency value, provides a measure of the velocity of the flow. Such ionic probes are described in the work “Applications of the corona discharge for measurements of density and velocity transients in air flow,” by FD Werner and RL Geronime, 1953, pp. 53-142, and in US patent 3,945,251 entitled “Trichel Puise Corona gas velocity instrument,” by ET Pierce. However, such ionic probes with continuous electrical polarization have a significant hysteresis, such that successive measurements are affected by a drift in the results, and that it is then difficult to obtain a reliable value for the speed of the gas flow.
    From this situation, an object of the present invention is to propose a new probe for measuring the speed of a gas flow, which does not have the drawbacks of the previous probes mentioned above. In particular, the following qualities are sought:
    -3- a measurement range, also called measurement dynamic, which is extended, possibly controllable, making it possible to measure flows at low speed and at high speed;
    - avoid the use of a capillary which is likely to be blocked;
    - avoid the use of optical windows, which are likely to be soiled or made opaque or diffusing;
    - absence of hysteresis during measurements which are carried out successively;
    - operation compatible with an anti-icing or de-icing system of a probe which is used for measurements; and
    - a structure which electrically isolates a part of a high voltage circuit from a part of a low voltage circuit.
    To achieve at least one of these aims or others, a first aspect of the invention proposes a device for measuring a speed of a gas flow, which comprises:
    a rigid probe intended to be placed in the gas flow, the probe comprising an axial electrode which has an uncovered end intended to be in contact with the gas, this uncovered end having a radius of curvature adapted to produce a reinforcement of field electric by peak effect, and comprising a peripheral electrode which is electrically isolated from the axial electrode, and which has an exposed part also intended to be in contact with the gas, situated at a distance from the axial electrode; and
    - a source of electric voltage supply, having two output terminals which are electrically connected, one to the axial electrode and the other to the peripheral electrode.
    In the context of the present invention, the term “electrode end” having a radius of curvature which is adapted to produce a reinforcement of the electric field by peak effect, an electrode end which has a radius of curvature less than 5 mm (millimeter), preferably less than 2 mm. The electrical effect called peak effect is very well known
    -4 of the skilled person, so there is no need to describe it here. This effect is all the more important as the radius of curvature of the tip of the electrode which forms the point, is small. When this radius of curvature is sufficiently small, less than 5 mm, preferably less than 2 mm, a local electric field is sufficiently increased by the peak geometry to reach a gas ionization threshold.
    According to the invention, the power source produces an electrical voltage which is alternating, that is to say with periods of negative voltage values and periods of positive voltage values which are alternated, and the device comprises in outraged :
    - a detection circuit, comprising at least one conductive turn arranged around an electrical connection which connects one of the electrodes of the probe to one of the terminals of the power source, or arranged around the axial electrode , and comprising a counter arranged to count electrical pulses which are generated in the coil by induction, selectively during at least one window of time during which an electrical potential of the axial electrode is less than an electrical potential of the peripheral electrode.
    Thus, when the probe is supplied with the alternating electrical voltage by the power source, a number of electrical pulses which are counted by the detection circuit, corresponding to a number of electrical discharges which have appeared between the axial electrode and the peripheral electrode through the gas constitutes a measure of the speed of the gas flow.
    Such a device has the following advantages:
    - the use of an alternating voltage between the electrodes of the probe eliminates any behavior at hysteresis;
    - the counting of corona discharge pulses during the periods when the axial electrode, which has the tip, is negatively polarized with respect to the peripheral electrode, limits the measurement operation to a negative corona discharge regime, which generates regular current pulses
    -5contrary to a positive corona discharge regime for which the axial electrode which includes the tip would be positively polarized with respect to the peripheral electrode;
    - the measurement range is very wide. In particular, it is compatible with uses on board aircraft; and
    - the detection of electrical discharge pulses by induction electrically isolates a supply circuit which produces the voltage to be applied between the two electrodes of the probe, and the detection circuit. Operational safety results for the gas flow velocity measurement device, and also for external electrical circuits.
    In various embodiments of a device according to the invention, the following configurations or improvements can be used, separately or in combination of several of them:
    - The uncovered part of the peripheral electrode may have an annular shape around an axis of symmetry of the uncovered end of the axial electrode;
    - The uncovered part of the peripheral electrode can be set back with respect to the uncovered end of the axial electrode, with a direction of withdrawal which is opposite to the uncovered end of the axial electrode; and
    - The device can further comprise a ballast resistor which is connected in series between one of the electrodes of the probe and the terminal of the power source which is connected to this electrode. Such a ballast resistor can advantageously be arranged in the probe. In particular, the ballast resistor can be placed in the probe around a rear end of the axial electrode, opposite its uncovered end, and be in electrical contact with a peripheral surface of this rear end of the axial electrode. Such an arrangement can be used to form an anti-icing or de-icing system for the probe. For example, when the ballast resistor is formed by a cylinder of electrically conductive material, the probe may further comprise a tube
    -6 electrically conductive which is arranged and electrically connected to form a capacitor with the cylinder of the ballast resistor. Thus, an electric current which circulates in the capacitor when the probe is supplied by the power source, generates by Joule effect in the cylinder of the ballast resistor, heat capable of heating the axial electrode. For such a structure of the probe, the conductive turn can also be arranged in the probe around a part of the axial electrode which is not covered by the ballast resistor cylinder, while being insulated therefrom. Optionally, electrical pulse signals which originate from this turn can be amplified or transformed before being transmitted to the outside of the probe, to ensure reliability of this transmission.
    A second aspect of the invention proposes a method for measuring a speed of a gas flow, which comprises the following steps:
    / 1 / providing a rigid probe, comprising an axial electrode which has an uncovered end with a radius of curvature adapted to produce a reinforcement of the electric field by peak effect, and comprising a peripheral electrode which is electrically isolated from the axial electrode, and which has an exposed part located at a distance from the axial electrode;
    / 2 / place the probe in the gas flow, so that the exposed end of the axial electrode and the exposed part of the peripheral electrode are simultaneously in contact with the gas; and / 3 / applying an electric voltage between the axial electrode and the peripheral electrode, so as to produce electric discharges between the two electrodes through the gas.
    According to the invention, the electrical voltage which is applied is an alternating electrical voltage, and the method further comprises the following steps:
    / 4 / detecting and counting electrical pulses which are generated by induction in at least one conductive turn arranged around an electrical connection used to apply the alternating voltage to the electrodes, or arranged around the axial electrode, and which
    -7 correspond to electrical discharges through the gas, selectively during at least one window of time during which an electrical potential of the axial electrode is less than an electrical potential of the peripheral electrode; and / 5 / deduce a value for the speed of the gas flow from a result of counting the electrical pulses.
    Preferably, the gas of the flow comprises at least one compound which has a significant electronegativity, such as air for example, to obtain a negative corona discharge which is more stable from the axial electrode during negative alternations of the supply voltage.
    Preferably, the probe can be oriented relative to the gas flow so that the exposed end of the axial electrode is turned towards a direction upstream of the flow, and that an axis of symmetry of this exposed end of the axial electrode is parallel to the gas flow.
    Preferably also, the counting of the electrical pulses can be continued for several successive time windows, each time window being contained in a negative alternation of the electric potential of the axial electrode relative to the electric potential of the peripheral electrode, separately from every other time window.
    More preferably, an average duration between two successive electrical pulses within the same time window, or an average frequency of the electrical pulses within the same time window, can be calculated. Then the value of the gas flow velocity can be deduced from the average duration or the average frequency.
    Possibly, the calculation of the gas flow speed can result from a calibration phase and a measurement phase, called useful measurement. In this case, the gas flow velocity can be calculated using the formula U = Ui (N 0 - N) / (N 0 - NJ, where N o is a first number of electrical pulses which are counted for a first calibration measurement which is carried out when the speed of the gas flow is zero, N! is a
    -8second number of electrical pulses which are counted for a second calibration measurement carried out when the speed of the gas flow is non-zero and equal to Ui, N is a third number of electrical pulses which are counted for the useful measurement, and U is the value of the gas flow velocity during the useful measurement. For this, the AC voltage which is applied between the two electrodes of the probe is identical for the two calibration measurements and for the useful measurement.
    A method according to the second aspect of the invention can be implemented using a device which is in accordance with the first aspect. In particular, when this device comprises a ballast resistor in the probe, and a tube for forming a capacitor with the ballast resistor, a heating power which is dissipated in the ballast resistor can be adjusted by modifying a frequency or a shape of the alternating voltage which is produced by the power source. Thus, the power source has the two functions of producing negative corona discharge on the one hand, and anti-icing or de-icing of the probe on the other hand, to prevent an electrically insulating layer of ice covering the uncovered end of the axial electrode.
    Finally, a method in accordance with the invention can be implemented on board an aircraft which is adapted to move relative to the air outside this aircraft, forming the flowing gas mentioned above. For this, the probe is rigidly fixed to the aircraft so as to be maintained in the air flow outside the aircraft. In such an application, the peripheral electrode of the probe can advantageously be electrically connected to a ground of the aircraft, so that an electrical potential of this peripheral electrode is constantly equal to an electrical potential of the ground of the aircraft .
    Other particularities and advantages of the present invention will appear in the following description of nonlimiting exemplary embodiments, with reference to the appended drawings, in which:
    - Figure 1 is a block diagram of a measuring device according to the present invention;
    FIG. 1a is an enlargement of part of FIG. 1;
    - Figures 2a-2d are a series of time diagrams to be read in combination, which illustrate an operation of a measuring device according to the invention; and
    - Figure 3 is a sectional view of a probe which is in accordance with a preferred embodiment of the present invention.
    For clarity, the dimensions of the elements which are represented in these figures do not correspond either to actual dimensions or to ratios of actual dimensions. In addition, identical references which are indicated in FIGS. 1 and 3 designate identical elements or which have identical functions.
    In the present description, the expression “negative corona discharge” is understood to mean an ionization of a gas in the vicinity of an electrode end with a small radius of curvature, when a negative voltage is applied to this electrode relative to a peripheral electrode. The pulses of electric current which result from such a negative corona discharge, when the gas is electronegative, such as air for example, are called Trichel pulses. Each pulse lasts a few tens of nanoseconds, with an amplitude of a few milliamps, and a pulse repetition frequency of a few tens of kilohertz. When a positive voltage is applied to the electrode with a small radius of curvature compared to the peripheral electrode, a positive corona discharge is obtained, the characteristics of which are different.
    In accordance with FIG. 1, a probe S comprises an axial electrode 1 and a peripheral electrode 2. The axial electrode 1 has an axis of symmetry A-A, and is housed in a casing 3 which is electrically insulating. An end 1P of the axial electrode 1 is discovered outside the envelope 3, in order to be in contact with a gas external to the probe S. FIG. 1a shows a magnification of the discovered end 1P of the axial electrode 1 This exposed end 1P has a point shape parallel to the axis AA, with a radius of curvature R1 which is less than 5 mm (millimeter), preferably less than 2 mm. The axial electrode 1 is in
    -10 electrically conductive material, preferably an alloy which is resistant to abrasion and atomic spraying when exposed to a plasma.
    The peripheral electrode 2 can have an annular shape also having the axis A-A as the axis of symmetry. It is arranged at a distance from the axial electrode 1, in particular radially with respect to the axis A-A. The peripheral electrode 2 is also made of a material which is electrically conductive, and has an exposed part 2P which is intended to be in contact with the gas external to the probe S at the same time as the axial electrode 1. For the configuration of the probe S which is shown in FIG. 1, the peripheral electrode 2 can be held in a fixed position relative to the axial electrode 1 by at least one arm 3 ′, which is designed to slightly disturb, or disturb the less possible a flow EC of the external gas around the probe S, possibly by allowing a passage of the gas between the envelope 3 and the peripheral electrode 2. The arm 3 'is also designed to electrically isolate the peripheral electrode 2 with respect to to the axial electrode 1, while making it possible to electrically connect the peripheral electrode 2 to an electrical supply terminal of the probe S, as explained below.
    For example, the axial electrode 1 can be made of tungsten (W), molybdenum (Mo) or stainless steel, and the peripheral electrode can be made of stainless steel or aluminum alloy (Al).
    An electrical supply circuit 4 makes it possible to apply an electrical voltage between the axial electrode 1 and the peripheral electrode 2. The supply circuit 4 comprises a voltage supply source 5, and optionally a ballast resistor 6 A first output terminal of the power source 5, denoted HT for high voltage, is connected to the axial electrode 1, and a second output terminal of the power source 5, denoted G, is connected to the peripheral electrode 2. Preferably, the terminal G can be connected to a ground of an AV support of the probe S. In this case, the probe S can be rigidly fixed to the AV support by means of a mast M, and the AV support can contain the electrical supply circuit 4. For such a configuration, an electrical connection 10 connects the axial electrode 1 to the HV terminal of the power source
    -11 electrical 5 through the mast M, and the peripheral electrode 2 is connected to the terminal G through the arm 3 ', the insulating jacket 3 and the mast M. For an aeronautical application, the AV support of the probe S can be an aircraft, for example an airplane, and the gas of flow EC is the surrounding air around the airplane. The purpose of the probe S is then to measure the speed of the air flow EC with respect to the support AV. Preferably, the probe S is oriented with respect to the flow EC so that the axis AA is parallel to the flow, with the exposed end 1P of the axial electrode 1 which is oriented upstream of the flow.
    For example, the ballast resistance 6 can be between 1 megohm (ΜΩ) and 100 ΜΩ, for example a few tens of megohms.
    In such a two-electrode system where the radius of curvature of one of the electrodes is smaller than that of the other electrode, the application of a difference in electrical potential between the two electrodes causes an electric field concentration at proximity to that of the electrodes which has the smallest radius of curvature. By increasing the absolute difference in electric potential between the two electrodes, the electric field which is concentrated in front of the electrode with the smallest radius of curvature can exceed the breakdown threshold of the gas. An electric discharge then occurs through the gas, during which an electronic avalanche will ionize atoms and / or molecules of the gas, and thus form a plasma of positive charges, ie cations, and of negative charges, ie especially electrons. . The properties of this electrical discharge are determined by the nature of the gas, including its density, temperature, chemical composition, and the polarity of the electrical voltage that is applied between the two electrodes.
    When the gas is air, the topology and the behavior of the electric discharge are very different according to the polarity of the electric voltage which is applied. When the electrode with the smallest radius of curvature is positively polarized, a positive corona discharge occurs, in the form of plasma filaments which propagate from this electrode which has the smallest radius of curvature. These plasma filaments, which have distributions
    -12 random spatial and temporal, produce electrical pulses in the closed supply circuit of the electrodes.
    But when the electrode with the smallest radius of curvature is negatively polarized with respect to the other electrode, a negative corona discharge is obtained, in the form of a regular or almost regular series of electrical impulses from Trichel. Each pulse corresponds to the formation of ionic species in the vicinity of the electrode with a small radius of curvature. The time distribution of these pulses is narrow and limited by a maximum frequency. When the electrical voltage that is applied between the two electrodes is below a lower threshold, the pulses are irregular. When the applied voltage exceeds a higher threshold, a quasi-continuous electric discharge regime appears. But between these two lower and upper thresholds, the frequency of the electric discharge pulses through the gas depends on the value of the electric voltage which is applied between the two electrodes, of the gas, including its electronegativity value and its rate d humidity, the velocity of flow EC of gas, the material of the electrode with the smallest radius of curvature, its geometry, including its radius of curvature and its surface roughness, and the ambient electric field.
    The formation of each electrical discharge pulse through the gas proceeds by electronic avalanche, initiated in the area where the electric field is maximum, that is to say near the electrode which has the smallest radius of curvature . Such an avalanche begins with the formation of seed electrons at the tip of the electrode, by field effect emission or by secondary emission which is caused by the impact of a cation on the electrode. In a negative corona discharge, these electrons are repelled from the tip electrode by the electric field which emanates from them. At the same time, they are accelerated and will collide with atoms or molecules of the gas. Some of these electrons which have enough energy will produce ionizing collisions which will each create an additional electron and an additional cation. An exponential multiplication of the number of electrons, called an avalanche, is thus produced, as the electrons move away from the electrode with small radius of curvature. This avalanche will then stop because of two
    -13 phenomena. As the electron cloud moves away from the electrode with small radius of curvature, the electric field which is created by this electrode decreases, consequently reducing the energy of the electrons at the time of new collisions. In addition, the formation of free electric charges in the gas produces an electrostatic screen which attenuates the electric field created by the electrode with small radius of curvature. The electric field to which the electrons are subjected will thus become too weak, and the electrons will bind to atoms or molecules of the gas, in particular molecules of dioxygen (O 2 ) in the case of air, to form anions. Then, the formation of a new avalanche, and therefore of a new electric discharge pulse, is again possible only after the cations and anions produced by the preceding electric discharge have been collected by the two electrodes, thanks to a residual part of the electric field. It is then known, in particular from the document “Numerical studies of Trichel puises in airflows”, by FC Deng, LY Ye and KC Song, J. Phys. D. Apt. Phys., Vol. 46, no. 42, p. 425202, Oct. 2013, that the flow EC of the gas modifies the time which is necessary for such a collection of ions, and therefore modifies consequently the frequency of repetition of the avalanches, i.e. the frequency of the electrical discharges which appear between the two electrodes.
    In addition, it is also known that variations in the instantaneous electric voltage which exists between the two electrodes, variations in the electric current induced in the electrodes and variations in the speed of the EC flow can cause hysteresis on the average current. electric shock.
    Given these observations, the present invention proposes to use:
    - an alternating electrical voltage to polarize the two electrodes relative to one another, in order to remove any hysteresis which could disturb the measurements, thanks to the regular reversal of the sign of this electrical voltage; and
    -14- limit the measurements within periods when the electrode with the smallest radius of curvature is negatively polarized with respect to the other electrode, in order to benefit from the higher regularity of a negative corona discharge compared to a positive corona discharge .
    Under these conditions, pulses of electric current appear in the electrical supply circuit 4, and therefore in the axial electrode 1 and the electrical connection 10, with a pulse frequency, or an average duration between two successive pulses, which depends on the speed of the EC flow. More precisely, the duration between two successive pulses increases when the speed of the EC flow becomes greater, if the exposed tip 1P of the axial electrode 1 is oriented upstream of the EC flow.
    According to an additional characteristic of the invention, such pulses are detected by induction, making it possible to prevent an electrical path continuity connecting the electrical supply circuit 4 to a circuit which is used to detect the negative crown discharge current. . Such a detection circuit 7 comprises at least one conductive turn 8, or possibly several turns in the form of a detection coil, which surrounds (s) the electrical connection 10 and is (are) connected (s) to a counter d impulses 9, denoted COMPT. It is thus possible to count the electrical pulses which are induced in the coil 8 by induction by the electrical discharge pulses which circulate in the electrical connection 10. For example, the coil 8 can be produced in the form of a Rogowski coil known to the skilled person.
    In order to benefit from the advantages which have been mentioned previously for an electric voltage for biasing the electrodes which is alternative, and those of the negative corona discharge, the detection and counting of the pulses is limited according to the invention inside the windows of FN times during which the electrical potential of the axial electrode 1 is lower than that of the peripheral electrode 2. For this, the FN time windows are contained in time periods where the voltage which is delivered by the
    -15source 5 is negative. In the jargon of a person skilled in the art, these periods of time are called negative alternations of the alternating electric voltage.
    FIG. 2a shows the variations in the electric voltage, denoted V H t, which is delivered by the source 5 as a function of time, denoted t. Preferably, these variations can be periodic, but can have any form. A peak value of the voltage V H t may be between 1 kV (kilovolt) and 20 kV, and its frequency may be of the order of a few hundred hertz when the gas of the flow EC is air. AN designates the negative alternations of the voltage V H t Figure 2b shows a possible signal for activating the counting of the pulses which are detected by circuit 7. This activation signal, denoted ARM, authorizes the counting of the pulses at inside time windows FN, which are themselves contained in the negative half-waves AN of the voltage V H t- T F n denotes the duration of each time window FN.
    During each positive alternation of the voltage V H t, the residual negative and positive charges which are present in front of the end 1P of the axial electrode 1 are neutralized. This starts a new window FN for pulse counting without initial parasitic load.
    FIG. 2c is an example of the temporal distribution of the electrical pulses which are detected by the circuit 7, denoted I. These pulses I occur as well during the positive alternations as the negative alternations of the voltage V H t, but only those of the alternations negatives have sufficient regularity to provide a reliable measure of the velocity of the EC flow. FIG. 2c represents for example the absolute value of the voltage which exists between the ends of the conducting coil 8, and which is denoted VdetectionFinally, FIG. 2d shows the evolution of a result of counting of the pulses I, when the counting is carried out continuously for two successive negative half-waves of the electric voltage V H t- The counting result is read after the end of the last time window FN of the counting duration, then a counting reset, denoted RESET, is carried out
    -16 before the start of a new FN time window for a new pulse count.
    Phenomenologically, the average duration T between two successive pulses which are detected is an increasing function of the speed U of the flow EC, when the probe S is oriented upstream of the flow EC as represented in FIG. 1 , according to the following relation: T = α / (β · ν Η τ- U) = T F n / N, where a and β are two positive constants which depend on the geometry of electrodes 1 and 2, gas and the possible inclination of the probe S with respect to the flow EC, and where T F n is still the duration of a time window FN and N is the number of pulses I which are counted during 1 time window FN . To obtain more precise results, it is possible to count the pulses I continuously for several successive time windows FN, as shown in FIG. 2d, then to divide the counting result by the number of time windows FN of the total counting.
    Generally for the invention, when such a phenomenological relationship is used, the constants a and β can be determined using a calibration sequence with the same gas as that of the useful measurements, for the same orientation of the probe S with respect to the flow EC during the calibration sequence as during each useful measurement, and for the same alternating voltage V HT which is produced by the source 5. Such a calibration sequence can comprise the following two measurements:
    - during a first calibration measurement, the speed of the EC flow is zero (U = 0), and the number of pulses counted is N o . Then: α / (β · ν ΗΤ ) = T fn / N 0 , then
    - during a second calibration measurement, the speed of the flow EC is non-zero, known and equal to Ui, and the number of pulses counted is N-ι. Then: α / (β · ν ΗΤ - U-ι) = T fn / N- |.
    Consequently, for a useful measurement, the speed U of the flow EC is given by the relation: U = Ui (N 0 - N) / (N 0 - N-ι), where N is the number of pulses I which are counted for the useful measure. The sequence
    -17 calibration can be performed once initially, or be repeated several times between successive useful measurements when the speed U can be known using other methods. Such other methods can use for example GPS measurements, or an on-board sensor which is of a different type when the AV support is an airplane, in particular a Pitot type probe.
    The dynamic measurement of a device according to the invention can be controlled by the amplitude of the alternating voltage V H t which is applied between the electrodes 1 and 2. In fact, this dynamic is controlled by the average number of pulses I in each time window FN, itself being an increasing function of the alternating voltage V H t- It is thus possible to obtain a good sensitivity for low values of the speed U of the flow EC, for example of of the order of ten meters-per-second, as well as for high values of the speed U, for example of the order of several hundred meters-per-second.
    An additional advantage of the invention results from the digital nature of the measurement signal which is acquired, as opposed to an analog measurement which can be sensitive to electromagnetic disturbances.
    Figure 3 shows an alternative embodiment of a speed measuring device according to the invention. In this embodiment, the peripheral electrode 2 is arranged on the external surface of the insulating envelope 3, set back downstream of the gas flow EC with respect to the end 1P of the axial electrode 1.
    The ballast resistor 6 can be housed in the probe S, and be formed by a cylinder of material with low electrical conduction, which surrounds a rear part of the axial electrode 1, opposite its uncovered end 1P. This cylinder can be in electrical contact with the rear part of the axial electrode 1, and can itself be connected from its rear end, to the electrical connection 10 which comes from the source 5. Advantageously, a tube 11 of electrically conductive material can be arranged around the cylinder of the ballast resistor 6, with a layer 12 of electrically insulating material which is intermediate between the cylinder of the
    -18 ballast resistor 6 and the tube 11. The tube 11 is then electrically connected to ground G. In this way, the cylinder of the ballast resistor 6 and the tube 11 form a cylindrical capacitor. The electric current which circulates in the cylinder of the ballast resistor 6 and in this capacitor when the probe S is supplied with alternating voltage by the source 5, produces heat by Joule effect inside the cylinder of the ballast resistor 6. If the electrically insulating material of the casing 3 is also thermally insulating, the configuration of the probe S concentrates on the axial electrode 1 the heat which is produced in the cylinder of the ballast resistor 6. Such heating can be used to ensure that frost does not form on the exposed end 1P of the axial electrode 1, or to melt it. The heating power of the axial electrode 1 can then be adjusted by modifying the frequency or the shape of the temporal variations of the alternating voltage V H t, in particular by modifying the slope of the rising edges of this alternating voltage without modifying the duration of the windows. of time FN which are dedicated to counting pulses I. In fact, the current which flows through the capacitor formed by the cylinder of the ballast resistor 6 and by the tube 11, can be modified in this way to vary the heating power of the axial electrode 1. Such a method of heating the axial electrode 1 is independent of the existence and the average intensity of the electric discharge current which flows in the electrode 1, through the gas, and in the electrode 2. For example, the material of the cylinder of the ballast resistor 6 can be a conductive resin or carbon graphite (C), and the tube 11 can be made of an aluminum alloy (Al) or a metal tal conductor. The intermediate layer 12 can consist of a polymer material, such as polytetrafluoroethylene (PTFE), Mylar®, Kapton®, or consist of an insulating ceramic whose breakdown voltage is greater than the maximum absolute value of the voltage V H t, and the casing 3 can be made of polymeric material or ceramic.
    The coil 8 of the detection circuit 7 can be arranged around the axial electrode 1, inside the casing 3 between the exposed end 1P of the axial electrode 1 and the anterior end of the resistance cylinder of ballast 6. Thanks to such an arrangement, the detection of pulses of
    -19electric discharge through the gas is not disturbed by the current which is used to possibly heat the axial electrode 1.
    An advantage of such an embodiment is its compactness. In fact, the S probe can have the shape of a cylinder of about one centimeter in diameter, and a few centimeters in length.
    It is understood that the invention can be reproduced by modifying secondary aspects thereof compared to the embodiments which have been described in detail above. In particular, the pulse counter of the detection circuit can be produced in many ways, whether or not incorporating an integrator. In addition, it is recalled that the alternating electrical voltage which is applied between the two electrodes is not necessarily sinusoidal.
    权利要求:
    Claims (6)
    [1" id="c-fr-0001]
    REVEN DICATIONS
    1. Device for measuring a speed of a gas flow, comprising:
    - a rigid probe (S) intended to be placed in the gas flow (EC), the probe comprising an axial electrode (1) which has an uncovered end (1P) intended to be in contact with the gas, said uncovered end having a radius of curvature (R1) adapted to produce an electrical field reinforcement by peak effect, and comprising a peripheral electrode (2) which is electrically isolated from the axial electrode, and which has an exposed part (2P) also intended to be in contact with the gas, located at a distance from the axial electrode; and
    - a power source (5) in electrical voltage, having two output terminals (HT, G) which are electrically connected one to the axial electrode (1) and the other to the peripheral electrode (2) ;
    characterized in that the power source (5) produces an alternating electrical voltage (AC), and in that the device further comprises:
    - a detection circuit (7), comprising at least one conductive turn (8) arranged around an electrical connection (10) which connects one of the electrodes (1, 2) of the probe (S) to one terminals of the power source (5), or disposed around the axial electrode (1), and comprising a counter (9) arranged to count electrical pulses (I) which are generated in the conductive coil by induction, selectively during at least one time window (FN) during which an electrical potential of the axial electrode (1) is less than an electrical potential of the peripheral electrode (2), so that when the probe (S) is supplied with the alternating electrical voltage (AC) by the power source (5), a number of electrical pulses (I) which are counted by the detection circuit (7), corresponding to a number of electrical discharges which have appeared between the axial electrode
    -21 (1) and the peripheral electrode (2) through the gas, is a measure of the speed of flow (EC) of the gas.
    [2" id="c-fr-0002]
    2. Device according to claim 1, wherein the exposed part (2P) of the peripheral electrode (2) has an annular shape around a
    5 axis of symmetry (A-A) of the exposed end (1 P) of the axial electrode (1).
    [3" id="c-fr-0003]
    3. Device according to claim 1 or 2, wherein the uncovered part (2P) of the peripheral electrode (2) is set back relative to the uncovered end (1P) of the axial electrode (1), with a direction of withdrawal which is opposite to said exposed end of the axial electrode.
    10
    [4" id="c-fr-0004]
    4. Device according to any one of the preceding claims, further comprising a ballast resistor (6) connected in series between one of the electrodes (1, 2) of the probe (S) and the terminal of the source of power supply (5) which is connected to said electrode, and the ballast resistor is arranged in the probe.
    5. Device according to claim 4, in which the ballast resistor (6) is arranged in the probe (S) around a rear end of the axial electrode (1), opposite the uncovered end (1P) of said axial electrode, and is in electrical contact with a peripheral surface of said rear end of the axial electrode.
    The device according to claim 5, wherein the ballast resistor (6) is formed by a cylinder of electrically conductive material, and the probe (S) further comprises an electrically conductive tube (11) which is disposed and electrically connected. to form a capacitor with the ballast resistor cylinder, so that an electric current that flows
    25 in the capacitor when the probe is supplied by the power source (5), generates by Joule effect in the cylinder of the ballast resistor, heat capable of heating the axial electrode (1).
    7. Device according to claim 6, in which the conductive turn (8) is arranged in the probe (S) around a part of the axial electrode (1)
    -22 which is not covered by the cylinder of the ballast resistor (6), being electrically isolated from said axial electrode.
    8. Method for measuring a velocity of a gas flow (EC), comprising:
    / 1 / provide a rigid probe (S), comprising an axial electrode (1) which has an uncovered end (1P) with a radius of curvature (R1) adapted to produce an electrical field reinforcement by peak effect, and comprising a peripheral electrode (2) which is electrically isolated from the axial electrode, and which has an exposed part (2P) located at a distance from the axial electrode;
    / 2 / place the probe (S) in the gas flow (EC), so that the exposed end (1P) of the axial electrode (1) and the exposed part (2P) of the peripheral electrode ( 2) are simultaneously in contact with the gas; and / 3 / applying an electric voltage between the axial electrode (1) and the peripheral electrode (2), so as to produce electric discharges between said electrodes through the gas;
    characterized in that the electric voltage which is applied is an alternating electric voltage (AC), and in that the method further comprises the following steps:
    / 4 / detecting and counting electrical pulses (I) which are generated by induction in at least one conductive turn (8) arranged around an electrical connection (10) used to apply the alternating voltage (AC) to the electrodes (1, 2), or arranged around the axial electrode (1), and which correspond to electrical discharges through the gas, selectively during at least one time window (FN) during which an electrical potential of the axial electrode (1 ) is below an electrical potential of the peripheral electrode (2); and / 5 / deduce a value for the speed of flow (EC) of the gas from a result of counting electrical pulses (I).
    -239. Method according to Claim 8, in which the probe (S) is oriented relative to the gas flow (EC) so that the exposed end (1P) of the axial electrode (1) is turned towards an upstream direction of the flow, and that an axis of symmetry (AA) of said exposed end (1P) of the axial electrode (1) is parallel to said gas flow.
    10. The method of claim 8 or 9, wherein the counting of electrical pulses (I) is continued for several successive time windows (FN), each time window being contained in a negative alternation (AN) of the electric potential of l 'axial electrode (1) relative to the electrical potential of the peripheral electrode (2), separately from each other time window.
    11. Method according to any one of claims 8 to 10, according to which an average duration between two electrical pulses (I) which are successive within a time window (FN), or an average frequency of the electrical pulses within a time window, is calculated, and the value of the gas flow velocity (EC) is deduced from the average duration or the average frequency.
    12. Method according to any one of claims 8 to 11, according to which the gas flow speed (EC) is calculated using the formula U = Ui (N 0 - N) / (N 0 - N-ι ), where N o is a first number of electrical pulses (I) counted for a first calibration measurement carried out when the speed of the gas flow is zero, N-ι is a second number of electrical pulses counted for a second calibration measurement carried out when the speed of the gas flow is non-zero and equal to Ui, N is a third number of electrical pulses counted for a useful measurement, and U is a value of the speed of l gas flow during the useful measurement, the alternating electric voltage (AC) applied between the two electrodes (1, 2) of the probe (S) being identical for the first and second calibration measurements and for the useful measurement.
    13. Method according to any one of claims 8 to 12, implemented using a device according to claim 6 or 7, and following
    -24which a heating power which is dissipated in the ballast resistor (6) is adjusted by modifying a frequency or a form of the alternating electric voltage (AC) which is produced by the power source (5).
    14. Method according to any one of claims 8 to 13, implemented
    [5" id="c-fr-0005]
    5 works on board an aircraft (AV) adapted to move relative to air outside said aircraft, the probe (S) being rigidly fixed to the aircraft so as to be maintained in the flow (EC) air outside of said aircraft.
    15. The method of claim 14, wherein the peripheral electrode (2) of the probe (S) is electrically connected to a ground (G)
    [6" id="c-fr-0006]
    10 of the aircraft (AV), so that an electrical potential of said peripheral electrode is constantly equal to an electrical potential of said mass of the aircraft.
    1/2
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    同族专利:
    公开号 | 公开日
    CN110062888B|2021-09-24|
    FR3060125B1|2018-12-07|
    CA3045570A1|2018-06-14|
    ES2865852T3|2021-10-18|
    EP3552026A1|2019-10-16|
    WO2018104627A1|2018-06-14|
    CN110062888A|2019-07-26|
    EP3552026B1|2021-01-27|
    US11035705B2|2021-06-15|
    US20190346298A1|2019-11-14|
    JP6942802B2|2021-09-29|
    JP2020513559A|2020-05-14|
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    US3945251A|1974-10-11|1976-03-23|Stanford Research Institute|Trichel pulse corona gas velocity instrument|
    US4127029A|1977-04-25|1978-11-28|La General De Fluides Geflu|Ionic measuring device|
    FR2491618B1|1980-10-07|1985-06-07|Renault|DIFFERENTIAL TYPE TRANSIT TIME IONIC SENSOR|
    AT501993B1|2006-02-20|2007-06-15|Guenter Dipl Ing Fh Weilguny|Fluid e.g. gas, flow velocity measuring device for aircraft, has sensor electrode whose projection surface is smaller in adjacent cross section surface of fluid flow so that flow is measured over electrode, and velocity value is calculated|
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    US9433071B2|2014-06-13|2016-08-30|Plasma Innovations, LLC|Dielectric barrier discharge plasma generator|
    CN105716788B|2015-11-02|2019-02-22|北京航空航天大学|Three hole transonic speed pressure probes|CN110221094B|2019-07-16|2021-05-04|深圳市锐进微电子有限公司|Airflow detection circuit and device|
    CN111308122B|2019-12-06|2022-02-25|云南师范大学|Gas flow velocity detector and system based on boron-doped silicon quantum dots|
    CN111812354B|2020-06-16|2021-12-03|天津大学|Flow field velocity measurement system based on high-voltage discharge|
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    法律状态:
    2017-11-20| PLFP| Fee payment|Year of fee payment: 2 |
    2018-06-15| PLSC| Publication of the preliminary search report|Effective date: 20180615 |
    2018-11-27| PLFP| Fee payment|Year of fee payment: 3 |
    2020-01-21| PLFP| Fee payment|Year of fee payment: 4 |
    2020-11-20| PLFP| Fee payment|Year of fee payment: 5 |
    2021-11-18| PLFP| Fee payment|Year of fee payment: 6 |
    优先权:
    申请号 | 申请日 | 专利标题
    FR1662169|2016-12-08|
    FR1662169A|FR3060125B1|2016-12-08|2016-12-08|DEVICE AND METHOD FOR MEASURING A SPEED OF GAS FLOW|FR1662169A| FR3060125B1|2016-12-08|2016-12-08|DEVICE AND METHOD FOR MEASURING A SPEED OF GAS FLOW|
    JP2019531049A| JP6942802B2|2016-12-08|2017-12-01|Equipment and methods for measuring gas flow velocity|
    PCT/FR2017/053343| WO2018104627A1|2016-12-08|2017-12-01|Device and method for measuring a gas flow rate|
    ES17821676T| ES2865852T3|2016-12-08|2017-12-01|Device and procedure for measuring a gas flow rate|
    CN201780075863.7A| CN110062888B|2016-12-08|2017-12-01|Device and method for measuring air flow velocity|
    EP17821676.8A| EP3552026B1|2016-12-08|2017-12-01|Device and method for measuring a gas flow rate|
    US16/467,938| US11035705B2|2016-12-08|2017-12-01|Device and method for measuring a gas flow speed|
    CA3045570A| CA3045570A1|2016-12-08|2017-12-01|Device and method for measuring a gas flow rate|
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