Piezoelectric ultrasonic transducer of gas flowmeter

Abstract

The utility model relates to piezoelectric devices with mechanical input and electrical output, and more particularly to piezoelectric transducers [H10N 30 / 00, H10N 30 / 30, H02N 2 / 18, H04R 17 / 00]. A piezoelectric ultrasonic transducer of a gas flowmeter comprises an ultrasonic piezoelement, a metal ring having an outer surface and an inner surface, a thermal sensor in contact with the inner surface of the metal ring, and output terminals of the transducer which are configured to allow connection of the transducer to a gas flowmeter, wherein the outer surface of the metal ring has radial protuberances and the output terminals of the transducer include an output terminal of the thermal sensor, connected to the thermal sensor. Rapid and efficient measurement of the temperature of a gas is achieved in that the piezoelectric transducer, incorporated into an ultrasonic gas flowmeter, measures an acoustic signal propagating in the gas.

Description

[0001] Piezoelectric Ultrasonic Gas Flowmeter Transducer Description

[0002] The field of technology to which the utility model belongs

[0003] The utility model relates to piezoelectric devices with a mechanical input and an electrical output, in particular to piezoelectric transducers [H10N 30 / 00, H10N 30 / 30, H02N 2 / 18, H04R 17 / 00].

[0004] State of the art

[0005] The prior art discloses an ULTRASONIC PIEZOELECTRIC TRANSDUCER [RU2739150C1, published 21.12.2020], comprising an ultrasonic piezoelectric element, a metal ring having an outer and inner surface, and output contacts of the transducer, wherein the outer surface of the metal ring is made with radial protrusions.

[0006] The disadvantage of this analogue is the impossibility of obtaining data on the temperature of the working environment of the piezoelectric transducer due to the lack of a temperature sensor. Consequently, the transducer cannot be used to correctly measure the parameters of sound wave propagation in gas, its frequency and speed, since this transducer does not take into account the temperature and density of the gas, which affect the speed of propagation of the sound wave in the gas.

[0007] Also known from the prior art is a prototype PIEZOELECTRIC TRANSDUCER FOR ULTRASONIC GAS FLOWMETERS [RU2715084C1, published 02 / 25 / 2020], comprising an ultrasonic piezoelectric element, a metal ring having an outer and inner surface, and output contacts of the transducer, wherein the outer surface of the metal ring is made with radial protrusions.

[0008] A drawback of the prototype is the inability to obtain gas temperature data from the piezoelectric transducer of the gas flow meter due to the lack of a temperature sensor. This reduces the reliability of gas mass flow determination, as it does not take into account the dependence of gas density on temperature. The transducer is used as part of an ultrasonic gas flow meter with excess pressure. Since gas density changes with temperature, accurate mass flow measurement requires measuring both gas density and temperature. Furthermore, gas density and temperature affect the speed of sound wave propagation; measuring gas density and temperature is necessary for accurate measurement of sound wave parameters.

[0009] Disclosure of the essence of the utility model.

[0010] The purpose of a utility model is to eliminate the shortcomings of the prototype.

[0011] The technical result consists in the possibility of quickly measuring the temperature of a gas in which an acoustic signal is propagated, measured by a piezoelectric transducer as part of an ultrasonic gas flow meter.

[0012] The specified technical result is achieved due to the fact that the piezoelectric ultrasonic transducer of the gas flow meter contains an ultrasonic piezoelectric element, a metal ring having an outer and inner surface, a thermal sensor in contact with the inner surface of the metal ring, and output contacts of the transducer, configured to connect the transducer to the gas flow meter, wherein the outer surface of the metal ring is made with radial protrusions, and the output contacts of the transducer include an output contact of the thermal sensor, connected to the thermal sensor.

[0013] In particular, the output contacts of the transducer contain polar output contacts of the transducer connected to an ultrasonic piezoelectric element.

[0014] In particular, the output contacts of the converter are made in the form of a coaxial connector.

[0015] Brief description of the drawings.

[0016] Fig. 1 shows the first example of the implementation of the claimed piezoelectric ultrasonic transducer of a gas flow meter, longitudinal section.

[0017] Fig. 2 shows a front view of the piezoelectric ultrasonic transducer of the gas flow meter from Fig. 1.

[0018] Fig. 3 shows a side view of the piezoelectric ultrasonic transducer of the gas flow meter from Fig. 1.

[0019] Fig. 4 shows a second example of the embodiment of the claimed piezoelectric ultrasonic transducer of the gas flow meter, a front view. Fig. 5 shows the piezoelectric ultrasonic transducer of the gas flow meter from Fig. 4, a side view.

[0020] The figures show: 1 - piezoelectric element housing; 2 - ultrasonic piezoelectric element; 3 - membrane; 4 - protector; 5 - plug; 6 - metal ring; 7 - damper; 8 - internal cavity; 9 - internal channel of the plug; 10 - branch; 11 - connecting wire; 12 - internal channel of the metal ring; 13 - temperature sensor; 14 - connecting wire unit; 15 - damper cavity; 16 - internal channel of the damper; 17 - signal wire; 18 - tail; 19 - output contact; 20 - internal sealed channel; 21 - external sealed channel; 22 - separating channel; 23 - contact insulator; 24 - connector; 25 - heat-shrinkable tube; 26 - contact board; 27 - positive signal wire; 28 - negative signal wire; 29 - thermometer wire; 30 - coaxial connector; 31 - coaxial connector terminal.

[0021] Implementation of a utility model

[0022] A piezoelectric ultrasonic transducer of a gas flow meter (hereinafter referred to as the transducer) comprises a piezoelectric element unit capable of converting acoustic signals into electrical signals and, preferably, vice versa, an acoustic decoupling unit capable of isolating oscillations in the acoustic decoupling unit, and an output unit capable of connecting the transducer to the gas flow meter, wherein said units are connected to each other (Fig. 2, Fig. 4). The connection of the units is ensured by welding, preferably arc welding in a protective gas environment.

[0023] 1.1 PIEZOELECTRIC ELEMENT UNIT

[0024] The piezoelectric element block (Fig. 1) contains a housing 1 of the piezoelectric element block, an ultrasonic piezoelectric element 2, a membrane 3 and a protector 4.

[0025] The ultrasonic piezoelectric element 2 is capable of converting the acoustic vibrations of the membrane 3 into an electrical signal and vice versa. The ultrasonic piezoelectric element 2 operates at a radial deformation frequency determined by the diameter of the ultrasonic piezoelectric element 2. The membrane 3 is formed in the end portion of the housing 1 of the piezoelectric element unit and may be formed as a single piece with the housing 1 or connected to it by welding or soldering. The membrane 3 is made of low-density and high-rigidity materials, such as metals and alloys, in particular titanium, aluminum or magnesium alloys, of small thickness and such an effective area that the resonant frequency of the membrane 3 vibrations is greater than the resonant frequency of the ultrasonic piezoelectric element 2 vibrations. The membrane 3 is capable of performing oscillatory movements and converting its own vibrations into an acoustic signal propagated in the gas with which the transducer is in contact.

[0026] Protector 4 is rigidly connected to the side of ultrasonic piezoelectric element 2 facing the closing side of membrane 3 and to membrane 3 by soldering or gluing. Protector 4 is designed to convert radial oscillations of ultrasonic piezoelectric element 2 into axial oscillations of membrane 3 and to protect ultrasonic piezoelectric element 2 from mechanical damage during axial oscillations of membrane 3.

[0027] 1.2. ACOUSTIC DECOUPLING UNIT

[0028] The acoustic isolation unit (Fig. 1) contains a plug 5 connected to the ultrasonic piezoelectric element 2, a metal ring 6 connected to the housing 1 of the piezoelectric element unit, and a damper 7 connected to the metal ring 6.

[0029] 1.2.1. Cork

[0030] Plug 5 is configured to secure ultrasonic piezoelectric element 2 at locations of minimal deformation during vibration. Plug 5 extends along the surface of membrane 3 of the piezoelectric element block, forming a hollow internal cavity 8, an internal channel 9 of the plug, and a branch 10. Internal channel 9 of the plug and internal cavity 8 are connected via branch 10, allowing for the placement of connecting wire 11.

[0031] The internal cavity 8, formed along the surface of the membrane 3 of the piezoelectric element block, separates the ultrasonic piezoelectric element 2 with the protector 4 attached to it from the membrane 3 with the possibility of protecting the ends of the ultrasonic piezoelectric element 2 from mechanical damage during the oscillation of the membrane 3 and ensuring the oscillation of the ultrasonic piezoelectric element 2. The internal channel 9 of the plug is formed along the axial line of the transducer in the center of the plug 5 in the form of a hollow body of revolution with the possibility of ensuring the isolation of the oscillations of the ultrasonic piezoelectric element 2.

[0032] 1.2.2. Metal ring

[0033] In particular, metal ring 6 can be made of aluminum, copper, or steel. Metals have a lower heat capacity coefficient than polymeric materials. Therefore, when the ring is made of metal, the temperature change of metal ring 6 increases for the same amount of heat transferred, thereby increasing the rate of heat exchange between metal ring 6 and the gas. Therefore, compared to a polymeric ring, making the ring metal increases the rate of temperature change of metal ring 6, thereby increasing the rate at which metal ring 6 reaches the gas temperature.

[0034] The metal ring 6 is formed along the body 1 of the piezoelectric element block, wherein the metal ring 6 has an internal and external surface.

[0035] The outer surface of the metal ring 6 is designed to be in contact with the environment, in particular, with the gas when installed in a gas flow meter. The outer surface of the metal ring 6 is provided with radial projections to increase the area of ​​the outer surface of the metal ring 6. The radial projections represent sections of increased diameter of the ring, preferably increasing the diameter by 20-40%. According to the Newton-Richam law (1), providing the outer surface of the metal ring 6 with radial projections increases the amount of heat transferred to the metal ring 6 from the gas per unit of time, i.e., increases the rate of heat exchange between the gas and the metal ring 6. Consequently, the time during which the temperature of the metal ring 6 becomes equal to the temperature of the gas, in particular, the gas whose flow rate is measured by the gas flow meter with the installed transducer, is reduced.

[0036] A hollow internal channel 12 of the metal ring is formed in the metal ring 6, which is a continuation of the internal channel 9 of the plug. The internal surface of the metal ring 6 is formed by the internal channel 12 of the metal ring.

[0037] The internal channel 12 of the metal ring is made along the axial line of the converter in the center of the plug 5 with a cavity near the place of connection of the plug 5 with the metal ring 6 with a temperature sensor 13 placed in it for determining the temperature of the metal ring 6. A connecting wire 11 is connected to the temperature sensor 13.

[0038] The temperature sensor 13 is located in the cavity of the internal channel 12 of the metal ring in such a way that the surface of the temperature-sensitive element of the temperature sensor 13 has contact with the internal surface of the metal ring 6. The contact can be provided by a permanent connection of the temperature sensor, for example, by soldering, welding, a fastening element, or a detachable connection, for example, by means of a threaded connection or a tight contact provided by fixing the temperature sensor 13 in the position of contact with the internal surface of the metal ring 6 by a mechanical clamp.

[0039] Contact between the temperature-sensitive element of temperature sensor 13 and the inner surface of metal ring 6 enables heat exchange. Temperature sensor 13 is designed as a resistance thermometer with the ability to change the resistance of the conductive portion depending on changes in gas temperature, the acoustic vibrations of which are measured by the transducer - as the gas temperature increases, the temperature of metal ring 6 increases due to heat exchange; through heat exchange through the permanent contact between the inner surface of metal ring 6 and the temperature-sensitive element of temperature sensor 13, the temperature of the temperature-sensitive element increases and the resistance of the conductive element of temperature sensor 13 increases according to dependence (2), as a result of which the overall resistance of the electrical circuit of temperature sensor 13 increases.

[0040] According to the heat transfer formula (3), at the same time, with a higher heat exchange rate, that is, with a greater amount of heat transferred per unit of time, the difference in the change in temperature of the metal ring 6 and the gas temperature will be smaller, as well as the difference between the temperature of the metal ring 6 and the temperature of the temperature-sensitive element of the temperature sensor 13. Therefore, for the prompt determination of the gas temperature by the gas flow meter converter, that is, obtaining a temperature value close to the actual temperature value at the time of measurement, a high rate of heat exchange is required between the temperature-sensitive element of the temperature sensor 13 and the metal ring 6 and between the metal ring 6 and the gas.

[0041] Along the inner channel 9 of the plug and the inner channel 12 of the metal ring, a connecting wire assembly 14 is located, connected to connecting wire 11 on one side and signal wires 17 on the other side. The connecting wire assembly 14 is configured to transmit a signal from the ultrasonic piezoelectric element 2 to the output unit and to isolate the vibrations of the ultrasonic piezoelectric element 2.

[0042] 1.2.3. Damper

[0043] The damper 7 is designed with the possibility of acoustically separating the output unit and the metal ring 6 using the cavities 15 of the damper and additionally damping the vibrations of the membrane 3. The damper 7 is designed in such a way that an internal channel 16 of the damper is formed in it along the axial line of the converter in the center of the damper 7 with the possibility of acoustically separating the output unit and the metal ring 6 and placing signal wires 17 in it for connecting the output unit to the node 14 of the connecting wires.

[0044] 1.3. OUTPUT BLOCK

[0045] The output unit comprises a tail 18 (Fig. 1) and output contacts 19 (Fig. 3) extending therefrom, configured to connect a transducer in a gas flow meter. The output contacts 19 comprise an output contact of a temperature sensor 13 for transmitting data on the gas temperature to the gas flow meter. In particular, the output contacts 19 may be implemented in the form of a coaxial connector 30 (Fig. 4, Fig. 5). The output unit is configured to connect a transducer in a gas flow meter; for this purpose, the output contacts 19 are configured to correspond to the contacts of the gas flow meter to which the transducer is connected, and, preferably, the outer surface of the tail 18 comprises a thread configured to screw the transducer tail into the gas flow meter.

[0046] 1.3.1. Shank

[0047] The tail 18 is separated from the damper 7 by the damper's cavities 15 and is connected to the damper 7 only at the ends. The tail 18 is formed coaxially along the transducer in such a way that, along the transducer's centerline at the center of the tail 18, a compound-filled internal sealed channel 20, a compound-filled external sealed channel 21, and a hollow separating channel 22 between them are formed with the ability to accommodate signal wires 17. In the second embodiment of the search object, the separating channel 22 is also filled with compound.

[0048] 1.3.1.1. Internal sealed channel Internal sealed channel 20 contains (Fig. 1) contact insulators 23 and connector 24.

[0049] Insulators 23 contacts are made at both ends of the internal sealed channel 20 with the ability to provide isolation of the signal circuit and electrical safety of the converter.

[0050] The connector 24 is made on the side of the dividing channel 22 with the possibility of connecting the signal wires 17 of the internal sealed channel 20 with the signal wires 17 of the dividing channel 22.

[0051] The connection points of the signal wires 17 of the internal sealed channel 20 with the signal wires 17 of the damper 7 are made with the help of an insulator 23 of contacts connected to the unit of connecting wires 14 by soldering in the cavity 15 of the damper.

[0052] The internal sealed channel 20 is filled with an epoxy compound with the ability to seal the conductive elements, signal wires 17, the connection points of the signal wires 17 with the insulators 23 of the contacts and connector 24 and to protect the components of the circuit from the effects of temperature, mechanical damage, moisture and vibration.

[0053] 1.3.1.2. Separation channel

[0054] The dividing channel 22 is designed with the possibility of dividing the internal sealed channel 20 and the external sealed channel 21 and placing signal wires 17 between them.

[0055] The signal wires 17 of the separating channel 22 at the connection points with the connectors 24 are made with heat-shrinkable tubes 25 for electrical insulation of the connections and increasing the tightness of the connection.

[0056] 1.3.1.3. External sealed channel

[0057] The outer sealed channel 21 (Fig. 1) contains contact insulators 23 and connector 24.

[0058] Insulators 23 contacts are made at both ends of the outer sealed channel 21 with the ability to ensure insulation and tightness of the signal circuit of the ultrasonic piezoelectric element 2 and the thermal sensor 13 and electrical safety of the converter.

[0059] The connector 24 is made on the side of the separating channel 22 with the possibility of connecting the signal wires 17 of the external sealed channel 21 with the signal wires 17 of the separating channel 22. The connection points of the signal wires 17 of the external sealed channel 21 with the output contacts 19 are made using an insulator 23 of the contacts and a soldered board 26 of the contacts with the possibility of connecting the converter to external devices.

[0060] The outer sealed channel 21 is filled with epoxy compound for sealing the conductive elements, signal wires 17, the connection points of the signal wires 17 with the insulators 23 of the contacts and connector 24 and for protecting the circuit components from the effects of temperature, mechanical damage, moisture and vibration.

[0061] 1.3.2. Output contacts

[0062] Output contacts 19 are formed (Fig. 3) by a positive signal wire 27, located to the left of the center of the contact board 26, a negative signal wire 28, located to the right of the center of the contact board 26, and a thermometer wire 29, located above the center of the contact board 26.

[0063] The second embodiment example of the utility model, shown in Fig. 4 and Fig. 5, differs from the first embodiment example in that the output contacts 19 are made in the form of a coaxial connector 30, containing a terminal 31 of the coaxial connector, connected to the positive signal wire 27 of the piezoelectric element and the wire 29 of the thermometer by means of a soldered connection and located in the center of the coaxial connector 30 (Fig. 5), the negative terminal of the ultrasonic piezoelectric element 2 is connected to the housing 1 of the piezoelectric element block.

[0064] The piezoelectric transducer is used as follows.

[0065] The transducer, part of the gas flow meter, is positioned to measure the flow of gas through which an acoustic signal propagates, connecting the transducer's output contacts 19 to the gas flow meter. When an acoustic wave impacts transducer membrane 3, it oscillates. These oscillations are transmitted through the plug's internal cavity 8 to ultrasonic piezoelectric element 2. Protector 4 converts the axial oscillations of membrane 3 into radial oscillations of ultrasonic piezoelectric element 2, which causes mechanical deformation of ultrasonic piezoelectric element 2. When ultrasonic piezoelectric element 2 is mechanically deformed, an electric charge is generated in its material, the transducer's electrical circuit is closed, and electric current flows through the transducer's electrical circuit. Electric current is transmitted from ultrasonic piezoelectric element 2 to the piezoelectric element's output contacts 19 through connecting wire assembly 14.The electrical circuit of the temperature sensor 13 is closed through the connecting wires 11, and an electric current flows through the temperature sensor 13.

[0066] In this case, the metal ring 6 of the converter is heated or cooled to the gas temperature by heat exchange. The temperature-sensitive element of the temperature sensor 13 is heated or cooled to the gas temperature by heat exchange through contact with the metal ring 6. As the temperature of the temperature-sensitive element increases, the resistance of the conductive element of the temperature sensor 13 increases according to dependence (2), resulting in an increase in the overall resistance of the electrical circuit of the temperature sensor 13. When an electrical signal is removed from the output contact 19 of the temperature sensor, the overall voltage and current of the electrical circuit of the temperature sensor 13 are determined and, using Ohm's law, the overall resistance of the electrical circuit of the temperature sensor is determined, according to dependence (2), the gas temperature is determined.

[0067] Q = aATF, (1) where a is the heat transfer coefficient; ΔT is the temperature difference, [°C]; F is the surface area, [m 2 ].

[0068] R = Ro(l + aAT), (2) where R o - the resistance of a given conductor at 0 °C, [Ohm]; a - the temperature coefficient of resistance of the conductor material, [1 / K]; DT - the change in body temperature, [°C].

[0069] Q = stDT, (3) where Q is the amount of heat, [J]; c is the specific heat capacity, [J / (kg* °C)]; m is the body mass, [kg]; DT is the change in body temperature, [°C].

[0070] The practical use of the claimed device will provide the ability to quickly measure the temperature of the gas in which the acoustic signal is propagated, measured by a piezoelectric transducer as part of an ultrasonic gas flow meter.

Claims

FORMULA 1. A piezoelectric ultrasonic transducer for a gas flow meter, comprising an ultrasonic piezoelectric element, a metal ring having an outer and inner surface, a temperature sensor in contact with the inner surface of the metal ring, and output contacts of the transducer, configured to connect the transducer to the gas flow meter, wherein the outer surface of the metal ring is made with radial protrusions, and the output contacts of the transducer include an output contact of the temperature sensor, connected to the temperature sensor.

2. The converter according to claim 1, in which the output contacts of the converter contain polar output contacts of the converter connected to the ultrasonic piezoelectric element.

3. The converter according to item 1, in which the output contacts of the converter are made in the form of a coaxial connector.

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