Leaky wave transducer and leaky wave flow sensing system

Abstract

The present invention provides a leaky wave transducer and a leaky wave flow sensing system, wherein the leaky wave transducer is arranged inside or outside a fluid pipeline for sending or receiving a leaky wave signal, and comprises a substrate and an electrode array arranged on the substrate, the propagation speed of the surface wave of the substrate is greater than the body sound speed of the fluid in the fluid pipeline, and the frequency of the leaky wave signal is changed by changing the positive and negative polarity of each electrode in the electrode array. By changing the frequency of the leaky wave signal, the present invention reduces the attenuation degree of the leaky wave signal in the propagation process, maintains the signal strength stable, and improves the measurement stability and accuracy of the sensing system.

Description

Technical Field

[0001] The present invention relates to the technical field of flow measurement, and in particular to a leaky wave transducer and a leaky wave flow sensor system. Background Art

[0002] The ultrasonic flow sensing system uses the piezoelectric effect of piezoelectric materials and adopts appropriate transmitting circuits to add alternating electric energy to the piezoelectric elements of the transmitter. These piezoelectric elements are usually rectangular or circular thin sheets, whose length, width or diameter is much greater than their thickness. Under the excitation of external alternating electric energy, these piezoelectric elements usually resonate in the thickness direction and emit ultrasonic signals of a certain frequency. The resonant frequency is determined by the material properties and geometric dimensions (mainly thickness) of the piezoelectric element and cannot be changed once it is made. The ultrasonic signal is emitted into the fluid pipeline from a certain direction and propagates, and then received by the receiver, which converts the ultrasonic signal into an electrical signal for detection. According to the principle of signal detection, the ultrasonic flow sensing system currently mainly adopts two types: time difference method and Doppler method. The Doppler method uses the acoustic Doppler principle to determine the fluid flow rate by measuring the ultrasonic Doppler frequency shift scattered by the reflector in the inhomogeneous fluid. It is suitable for measuring the flow rate of fluids containing suspended particles, bubbles, etc. The time difference method reflects the flow velocity of the fluid by measuring the difference in the time of ultrasonic signal propagation downstream and upstream. The propagation direction of the ultrasonic wave can have a certain angle with the pipeline or be completely coaxial.

[0003] In the process of fluid transportation such as sewage treatment, chemical production, oil transportation, and mud injection on drilling platforms, the type and physical properties of the fluid in the pipeline, such as density, viscosity, and the number of solid particles or bubbles contained, often change. These changes will affect the absorption and scattering degree of the ultrasonic signal during the propagation process, and thus change the intensity, frequency components, and signal-to-noise ratio of the received ultrasonic signal. For example, when the viscosity of the fluid increases, the degree of absorption of the ultrasonic signal by the fluid will increase, causing the signal amplitude to gradually weaken during the propagation process. When the number of solid particles or bubbles in the fluid increases, the scattering degree of the ultrasonic signal will increase, causing the ultrasonic signal to weaken or deform.

[0004] According to the acoustic principle, when the attenuation of ultrasonic signals increases due to the increase of viscosity or impurities in the fluid, the attenuation of low-frequency ultrasonic signals is relatively slow and the signal amplitude is more stable, while the attenuation of high-frequency ultrasonic signals is relatively fast and the amplitude decreases greatly. When the fluid itself is relatively clean and the viscosity is low, the signal amplitude of high-frequency and low-frequency ultrasonic signals is relatively stable during propagation, but high-frequency ultrasonic signals can bring higher accuracy and resolution to the flow rate measurement of liquids. The resonant frequency of the existing ultrasonic flow sensor systems on the market cannot be changed, and the selection of their operating frequency is usually a result of a compromise between the system's measurement stability and resolution when the type and physical properties of the fluid remain unchanged. If the type and physical properties of the fluid in the fluid pipeline change frequently, the ultrasonic flow sensor system emits a single-frequency ultrasonic signal, and the attenuation degree will vary greatly during propagation, which will lead to unstable received signal strength and waveform, resulting in poor system measurement stability and accuracy, and even failure of the ultrasonic flow sensor system in severe cases. Summary of the invention

[0005] The object of the present invention is to provide a leaky wave transducer and a leaky wave flow sensing system, which can reduce the attenuation of the leaky wave signal during propagation by changing the frequency of the leaky wave signal, maintain the stability of the signal strength, and improve the measurement stability and accuracy of the sensing system.

[0006] In order to achieve the above-mentioned purpose, the present invention provides a leaky wave transducer, which is arranged inside or outside a fluid pipeline for sending or receiving leaky wave signals, including a substrate and an electrode array arranged on the substrate, the propagation speed of the surface wave of the substrate is greater than the body sound speed of the fluid in the fluid pipeline, and the frequency of the leaky wave signal is changed by changing the positive and negative polarity of each electrode in the electrode array.

[0007] Optionally, each of the electrodes is in a strip shape, and adjacent electrodes are arranged at equal intervals on a surface of the substrate.

[0008] Optionally, each of the electrodes is ring-shaped, and adjacent electrodes are equally spaced around the substrate.

[0009] Optionally, the material of the substrate includes one of piezoelectric crystal, piezoelectric ceramic or piezoelectric polymer; and / or the material of the electrode includes one or more of gold, silver, copper, aluminum, nickel or tungsten.

[0010] The present invention also provides a leakage wave flow sensing system, comprising:

[0011] Two leaky wave transducers as described above, either one of the two leaky wave transducers serving as a transmitting end for transmitting a leaky wave signal under the excitation of an excitation electrical signal, and the other serving as a receiving end for receiving the leaky wave signal;

[0012] A switching module, electrically connected to each of the leaky wave transducers, for changing the frequency of the leaky wave signal and controlling the two leaky wave transducers to act as the transmitting end and the receiving end in turn;

[0013] A control module is electrically connected to the switching module, and is used to send the excitation electrical signal to the transmitting end and receive the leakage wave signal from the receiving end through the switching module, and obtain the flow rate of the fluid in the fluid pipeline according to the time difference or phase difference between two adjacent leakage wave signals received, and determine whether to change the frequency of the leakage wave signal according to the signal characteristics of two adjacent leakage wave signals received.

[0014] Optionally, the switching module includes a first switching unit and a second switching unit, and the control module includes a signal transmitting unit and a signal receiving unit. The first switching unit is electrically connected to the signal transmitting unit and the signal receiving unit, and is used to control the two leakage wave transducers to be electrically connected to the signal transmitting unit and the signal receiving unit in turn through the first switching unit. The second switching unit is electrically connected to the signal transmitting unit and the signal receiving unit, and is used to change the positive and negative polarity of each electrode in the electrode array of the two leakage wave transducers through the second switching unit. When the polarity of the electrode is positive, the electrode is electrically connected to the signal transmitting unit or the signal receiving unit; when the polarity of the electrode is negative, the electrode is grounded.

[0015] Optionally, when it is determined that the frequency of the leaky wave signal needs to be changed, an adjustment frequency is obtained according to the center distance between two adjacent positive electrodes in the electrode array, the propagation speed of the surface wave of the substrate, and the body sound speed of the fluid in the fluid pipeline;

[0016] The frequency of the leaky wave signal is changed to the adjustment frequency.

[0017] Optionally, the two leaky wave transducers are both arranged on the inner side or the outer side of the fluid pipeline, and the two leaky wave transducers are at different positions in the axial direction of the fluid pipeline.

[0018] Optionally, the two leaky wave transducers are both arranged on the inner side of the fluid pipeline, a through hole is opened on the fluid pipeline, and the leads of the leaky wave transducers are led out through the through hole and electrically connected to the switching module.

[0019] Optionally, the two leaky wave transducers include a first sealing layer outside; and / or a second sealing layer is provided between the lead and the inner wall of the through hole.

[0020] In the leakage wave transducer and leakage wave flow sensing system provided by the present invention, the leakage wave transducer includes a substrate and an electrode array arranged on the substrate, the propagation speed of the surface wave of the substrate is greater than the body sound speed of the fluid in the fluid pipeline, and the frequency of the leakage wave signal is changed by changing the positive and negative polarity of each electrode in the electrode array; either one of the two leakage wave transducers in the system serves as a transmitting end that sends the leakage wave signal under the excitation of the excitation electrical signal, and the other serves as a receiving end that receives the leakage wave signal; the switching module is electrically connected to each leakage wave transducer, and is used to change the frequency of the leakage wave signal and control the two leakage wave transducers to take turns as the transmitting end and the receiving end; the control module is electrically connected to the switching module, and is used to send the excitation electrical signal to the transmitting end and receive the leakage wave signal from the receiving end through the switching module, and obtain the flow rate of the fluid in the fluid pipeline according to the time difference or phase difference between the leakage wave signals received twice adjacently, and judge whether to change the frequency of the leakage wave signal according to the signal characteristics of the leakage wave signals received twice adjacently. When the type and physical properties of the fluid in the fluid pipeline change, the positive and negative polarity of each electrode in the switching electrode array is selected by judging the results, which can change the frequency of the leakage wave signal, reduce the attenuation of the leakage wave signal during the propagation process, maintain signal strength stability, and improve the measurement stability and accuracy of the sensing system. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 to Figure 4 A schematic diagram of the structure of a leaky wave transducer provided in Embodiment 1 of the present invention;

[0022] Figure 5 and Figure 6 A schematic diagram of the structure of a leakage wave flow sensor system provided in Embodiment 1 of the present invention;

[0023] Figure 7 A measurement flow chart of a leaky wave flow sensor system provided in Embodiment 1 of the present invention;

[0024] Figure 8 A schematic diagram of the structure of a leaky wave transducer provided in Embodiment 2 of the present invention;

[0025] Fig. 9 and Fig.10 A schematic diagram of the structure of a leakage wave flow sensor system provided in Embodiment 3 of the present invention;

[0026] Wherein, the accompanying drawings are marked as follows:

[0027] 10, 100 - leaky wave transducer; 11, 110 - substrate; 12, 120 - electrode; 20, 200 - fluid pipeline; 30 - switching module; 31 - first switching unit; 32 - second switching unit; 40 - control module; 41 - signal transmitting unit; 42 - signal receiving unit; 43 - computing unit. DETAILED DESCRIPTION

[0028] The specific implementation of the present invention will be described in more detail below in conjunction with the schematic diagram. The advantages and features of the present invention will become clearer based on the following description. It should be noted that the drawings are all in a very simplified form and are not in exact proportions, and are only used to facilitate and clearly assist in explaining the purpose of the embodiments of the present invention.

[0029] Embodiment 1

[0030] Figure 1 to Figure 4 A schematic diagram of the structure of a leaky wave transducer provided in this embodiment; Figure 5 and Figure 6 A schematic diagram of the structure of the leakage wave flow sensor system provided in this embodiment; Figure 7 This is a measurement flow chart of the leaky wave flow sensor system provided in this embodiment.

[0031] Please refer to Figure 1 , this embodiment provides a leaky wave transducer, the leaky wave transducer 10 is arranged inside or outside a fluid pipeline for sending or receiving leaky wave signals. The leaky wave transducer 10 includes a substrate 11 and an electrode array arranged on the substrate 11, wherein the electrode array includes a plurality of electrodes 12, and the number of electrodes 12 is not limited in this embodiment. Each electrode 12 in the electrode array is in a strip shape, and every two adjacent electrodes 12 are arranged at equal intervals. In this embodiment, the material of the substrate 11 includes one of piezoelectric crystals, piezoelectric ceramics or piezoelectric polymers, such as quartz, barium titanate BT, lead zirconate titanate PZT, PVDF, but not limited to the above materials; and / or, the material of the electrode array includes one or more of gold, silver, copper, aluminum, nickel or tungsten, but not limited to the above materials; the electrode array can be formed on the substrate 11 by sputtering, evaporation, and etching processes, but not limited to the above processes. In the present embodiment, the leaky wave transducer 10 is relatively small and flat, so that when the leaky wave transducer 10 is located inside the fluid pipeline, it will not hinder the flow of the fluid or cause turbulence in the flow field.

[0032] Please refer to Figure 2 In this embodiment, the propagation speed of the surface wave of the substrate 11 is required to be greater than the body sound speed of the fluid in the fluid pipeline. In this way, when the surface wave propagates in the substrate 11, part of the energy of the surface wave will be converted into a leaky wave signal, and the leaky wave signal is emitted into the fluid at an angle θ with the surface of the leaky wave signal transmitting end ( Figure 2 The arrow in the middle shows the emission direction of the leaky wave signal), and the frequency of the leaky wave signal is changed by changing the positive and negative polarity of each electrode 12 in the electrode array. In this embodiment, the propagation speed of the surface wave of the substrate 11 is determined by the physical properties of the substrate 11, such as the density and elastic modulus of the substrate 11.

[0033] Please refer to Figure 5, this embodiment also provides a leakage wave flow sensing system for measuring the flow rate of the fluid in the fluid pipeline 20. The leakage wave flow sensing system includes two leakage wave transducers 10 as described above, a switching module 30 and a control module 40, wherein either of the two leakage wave transducers 10 serves as a transmitting end for transmitting leakage wave signals under the excitation of an excitation electrical signal, and the other serves as a receiving end for receiving leakage wave signals; the switching module 30 is electrically connected to each leakage wave transducer 10, and is used to change the frequency of the leakage wave signal and control the two leakage wave transducers 10 to serve as the transmitting end and the receiving end in turn; the control module 40 is electrically connected to the switching module 30, and is used to send an excitation electrical signal to the transmitting end and receive the leakage wave signal from the receiving end through the switching module 30, and obtain the flow rate of the fluid in the fluid pipeline 20 according to the time difference or phase difference between two adjacent leakage wave signals received, and determine whether to change the frequency of the leakage wave signal according to the signal characteristics of the two adjacent leakage wave signals received.

[0034] In this embodiment, the two leaky wave transducers 10 are at different axial positions in the fluid pipeline 20, that is, the two leaky wave transducers 10 are spaced apart in the axial direction of the fluid pipeline 20, so that the leaky wave signal emitted by one leaky wave transducer 10 can be received by the other leaky wave transducer 10 after moving a certain distance with the fluid. Furthermore, the two leakage wave transducers 10 are both arranged on the inner side of the fluid pipeline 20. When the two leakage wave transducers 10 are both arranged on the inner side of the fluid pipeline 20, a through hole (not shown in the figure) is opened on the fluid pipeline 20, and the lead of the leakage wave transducer 10 is led out through the through hole and electrically connected to the switching module 30; and when the leakage wave transducer 10 is arranged on the inner side of the fluid pipeline 20, a first sealing layer (not shown in the figure) is arranged on the outside of the two leakage wave transducers 10, and / or a second sealing layer (not shown in the figure) is arranged between the lead and the inner wall of the through hole, wherein the first sealing layer and the second sealing layer can be plastic, epoxy resin or silicone material, but are not limited to the above materials. The first sealing layer and the second sealing layer prevent the leakage wave transducer 10 from direct contact with air or fluid, thereby avoiding corrosion, oxidation, short circuit and mechanical wear.

[0035] Please refer to Figure 6 The switching module includes a first switching unit 31 and a second switching unit 32, and the control module includes a signal transmitting unit 41 and a signal receiving unit 42. The first switching unit 31 is electrically connected to the signal transmitting unit 41 and the signal receiving unit 42, and the first switching unit 31 is electrically connected to the two leaky wave transducers 10. The first switching unit 31 controls the two leaky wave transducers 10 to be electrically connected to the signal transmitting unit 41 and the signal receiving unit 42 in turn; Figure 6In the figure, the first switching unit 31 is simply illustrated by two single-pole double-throw switches, and the two single-pole double-throw switches respectively connect the signal transmitting unit 41 with one leakage wave transducer 10 and the signal receiving unit 42 with another leakage wave transducer 10. By switching the two single-pole double-throw switches, the two leakage wave transducers 10 can be electrically connected to the signal transmitting unit 41 and the signal receiving unit 42 in turn, but the first switching unit 31 is not limited to being two single-pole double-throw switches. The first switching unit 31 can also be a switching circuit composed of a MOS tube, etc.

[0036] The second switching unit 32 is electrically connected to the signal transmitting unit 41 and the signal receiving unit 42, and the second switching unit 32 is electrically connected to the two leakage wave transducers 10. Specifically, the second switching unit 32 is electrically connected to each electrode 12 in the electrode array of the leakage wave transducer 10, and the positive and negative polarities of each electrode 12 in the electrode array of the two leakage wave transducers 10 are changed by the second switching unit 32. Figure 6 The T in the figure is a schematic diagram of a partial connection between a leakage wave transducer 10 and the second switching unit 32. At T, only a single-pole double-throw switch is simply illustrated in the second switching unit 32. This single-pole double-throw switch is used to connect an electrode 12 in the electrode array of a leakage wave transducer 10 with the signal transmitting unit 41, the signal receiving unit 42 or the ground. In fact, the second switching unit 32 includes several single-pole double-throw switches. Each electrode 12 in the two leakage wave transducers 10 needs to be connected to a single-pole double-throw switch to electrically connect each electrode 12 to the signal transmitting unit 41, the signal receiving unit 42 or the ground. However, the second switching unit 32 is not limited to only including a single-pole double-throw switch, and it can also be a multi-channel switching circuit composed of MOS tubes. In this embodiment, when the polarity of the electrode 12 is positive, the positive electrode is electrically connected to the signal transmitting unit 41 or the signal receiving unit 42 according to whether the leakage wave transducer 10 is used as a transmitting end or a receiving end. When the leakage wave transducer 10 is used as a transmitting end, the positive electrode is electrically connected to the signal transmitting unit 41, and when the leakage wave transducer 10 is used as a receiving end, the positive electrode is electrically connected to the signal receiving unit 42; when the polarity of the electrode 12 is negative, the negative electrode is grounded. In the second switching unit 32 at T, "+" indicates that the polarity of the electrode 12 corresponding to the port is positive, and "-" indicates that the polarity of the electrode 12 corresponding to the port is negative. Figure 6 It is not directly indicated that the second switching unit 32 is electrically connected to the signal transmitting unit 41 and the signal receiving unit 42, and the connection relationship can be known from "+" or "-".

[0037] In this embodiment, the control module also includes a calculation unit 43, which obtains the flow rate of the fluid based on the time difference or phase difference between the leakage wave signals received twice adjacently by the signal receiving unit 42, and determines whether to change the frequency of the leakage wave signal based on the signal characteristics of the leakage wave signals received twice adjacently.

[0038] In this embodiment, a default frequency is selected for the leakage wave flow sensor system, and the transmitting end transmits a leakage wave signal of the default frequency, such as the default frequency is the highest resonance frequency, and monitors in real time whether the signal characteristics of the received leakage wave signal meet the preset requirements. For example, if the amplitude of the received leakage wave signal is greater than the preset threshold, or the fluctuation range of the amplitude exceeds the preset range, it can be determined that the type or physical properties of the fluid have changed relative to the default fluid, so that the attenuation capacity of the leakage wave signal is increased. At this time, the second switching unit 32 changes the positive and negative polarity of each electrode 12 in the electrode array to switch the frequency of the leakage wave signal emitted by the transmitting end to a lower frequency, and monitors again whether the signal characteristics of the received leakage wave signal meet the preset requirements. If so, the frequency is maintained, otherwise it continues to switch to a lower frequency.

[0039] When the first leakage wave transducer 10 is used as a transmitting end, all electrodes 12 assigned as positive electrodes are electrically connected to the signal transmitting unit 41, and the signal transmitting unit 41 applies a continuous or pulsed excitation electrical signal to excite the transmitting end, while all electrodes 12 assigned as negative electrodes are grounded, and the transmitting end generates a leakage wave signal and transmits it in the direction of the receiving end. At the same time, the second leakage wave transducer 10 is used as a receiving end, and all electrodes 12 assigned as positive electrodes are electrically connected to the signal receiving unit 42, while all electrodes 12 assigned as negative electrodes are grounded. After all electrodes 12 assigned as positive electrodes convert the received leakage wave signal into an electrical signal, it is recorded and converted into a digital signal by the ADC sampling circuit of the signal receiving unit 42, and can also be recorded by the analog circuit of the signal receiving unit 42, and the flow rate of the fluid is calculated by the calculation unit 43. In the next period, the two leakage wave transducers 10 are exchanged through the first switching unit 31, the first leakage wave transducer 10 is used as a receiving end, and the second leakage wave transducer 10 is used as a leakage wave signal transmitting end, and the leakage wave signal is transmitted in the opposite direction.

[0040] Please continue to refer to Figure 2 When a leaky wave transducer 10 is used as a transmitting end, the positive and negative polarities of the adjacent electrodes 12 in the electrode array of the transmitting end are reversed through the second switching unit. At this time, the negative electrode is grounded, and the positive electrode is electrically connected to the signal transmitting unit. The signal transmitting unit generates a continuous or pulsed excitation electrical signal to stimulate the transmitting end to generate mechanical vibration, thereby forming a surface wave in the substrate 11 of the transmitting end for propagation. It is important to require that the propagation speed V of the surface wave of the substrate 11 is s Greater than the fluid's body sound velocity V b , when the surface wave propagates in the substrate 11, part of the energy of the surface wave will be converted into a leaky wave signal, and the leaky wave signal is emitted into the fluid at an angle θ with the surface of the leaky wave signal transmitting end. In this embodiment, the calculation formula of the angle θ is as follows:

[0041]

[0042] For example, when the material of the substrate 11 is PZT material, the corresponding surface wave propagation velocity V of the substrate 11 is s About 2366m / s. If the fluid is water, the body sound velocity of water at room temperature is V b is about 1485 m / s, which satisfies the propagation velocity V of the surface wave of the substrate 11. s Greater than the fluid's body sound velocity V b According to the calculation formula, the angle θ is 51.1°.

[0043] When the center distance between two adjacent electrodes 12 in the electrode array of the transmitting end is d, the center distance between two adjacent positive electrodes 12 is D1, D1 = 2d, the calculation formula of the wavelength λ1 of the leakage wave signal emitted by the transmitting end is as follows:

[0044] λ1=D1sinθ

[0045] For example, when d = 0.48 mm, D1 = 0.96 mm, θ = 51.1°, that is, the wavelength λ1 of the leaky wave signal emitted by the transmitter is 0.75 mm, the calculation formula of the corresponding leaky wave signal frequency f1 is as follows:

[0046]

[0047] According to the wavelength λ1 of the leakage wave signal emitted by the leakage wave signal transmitting end as 0.75mm, it can be known that the frequency f1 of the corresponding leakage wave signal is 2MHz, and f1 is the highest resonance frequency of the leakage wave flow sensing system, that is, when the positive and negative polarities of adjacent electrodes in the electrode array of the transmitting end are opposite, the frequency of the leakage wave signal emitted by the transmitting end is the highest resonance frequency of the leakage wave flow sensing system.

[0048] Please refer to Figure 3 For the same transmitting end, every two adjacent electrodes 12 in the electrode array can be combined into a group as an equivalent electrode ( Figure 3 The dotted box in the middle is an equivalent electrode), and then the second switching unit is used to alternately assign positive and negative electrodes to each equivalent electrode. When the above conditions remain unchanged, the material of the substrate 11 is still PZT material, and the corresponding surface wave propagation speed V of the substrate 11 is s About 2366m / s, the fluid is still water, and the body sound velocity of water at room temperature is V b is about 1485m / s, θ=51.1°, d=0.48mm, at this time, the center distance between two adjacent equivalent positive electrodes D2=1.92mm, the wavelength λ2 of the leakage wave signal emitted by the transmitter is 1.5mm, it can be seen that the frequency f2 of the corresponding leakage wave signal becomes f2=1MHz.

[0049] Please refer to Figure 4For the same transmitting end, every three adjacent electrodes 12 in the electrode array can be combined into a group as an equivalent electrode ( Figure 4 The dotted box in the middle is an equivalent electrode), and then the second switching unit is used to alternately assign positive and negative electrodes to each equivalent electrode. When the above conditions remain unchanged, the material of the substrate 11 is still PZT material, and the corresponding surface wave propagation speed V of the substrate 11 is s About 2366m / s, the fluid is still water, and the body sound velocity of water at room temperature is V b is about 1485m / s, θ=51.1°, d=0.48mm, at this time, the center distance between two adjacent equivalent positive electrodes D3=2.88mm, the wavelength λ3 of the leakage wave signal emitted by the transmitter is 2.25mm, it can be seen that the frequency f3 of the corresponding leakage wave signal becomes f3=0.67MHz.

[0050] By analogy, when the center distance between two adjacent equivalent positive electrodes is continuously increased, a leakage wave signal with a lower frequency can be obtained. If the number of electrodes in the electrode array is n, we can finally get The leakage wave signals of different frequencies are generated, thereby realizing a variable frequency leakage wave flow sensing system. The highest resonance frequency of the leakage wave flow sensing system is determined by the center distance between two adjacent electrodes in the electrode array. When the positive and negative polarities of each electrode in the electrode array are changed according to the above method by the second switching unit, the frequency of the leakage wave signal emitted by the transmitting end is changed. In this embodiment, when the frequency of the leakage wave signal at the transmitting end is switched, the signal transmitting unit generates a continuous or pulsed excitation electrical signal of the same frequency to stimulate the transmitting end to generate a stronger leakage wave signal.

[0051] At this time, another leakage wave transducer serves as the receiving end. When the frequency of the leakage wave signal emitted by the transmitting end is selected, the receiving frequency of the receiving end is preferably set to the same frequency as that of the transmitting end, that is, the center distance between the two adjacent equivalent positive electrodes in the transmitting end and the receiving end is the same. In this way, the strength of the received signal can be increased. Similarly, when the positive and negative polarity of each electrode in the electrode array is changed by the second switching unit according to the above method, the receiving frequency of the receiving end is changed.

[0052] Please refer to Figure 7, the leakage wave flow sensor system starts self-checking, the leakage wave flow sensor system selects the highest resonance frequency as the current working frequency, and after obtaining the received leakage wave signal in the downstream and upstream directions of the fluid, calculates the flow velocity of the fluid, and judges whether the signal characteristics of the received leakage wave signal meet the preset requirements, such as amplitude, spectrum and noise, etc. If satisfied, continue to use the current working frequency, obtain the received leakage wave signal in the downstream and upstream directions of the fluid, calculate the flow velocity of the fluid and judge the signal characteristics; if not satisfied, it is determined that the frequency of the leakage wave signal needs to be changed, and an adjustment frequency is obtained according to the center distance between two adjacent equivalent positive electrodes in the electrode array, the propagation speed of the surface wave of the substrate and the body sound speed of the fluid in the fluid pipeline, and the frequency of the leakage wave signal is changed to the adjustment frequency, and after continuing to obtain the received leakage wave signal in the downstream and upstream directions of the fluid, the flow velocity is calculated and the signal characteristics are judged until it is determined that the signal characteristics of the received leakage wave signal meet the preset requirements. At this time, the working frequency is the optimal resonance frequency, so that the flow velocity measurement result is more stable and accurate. In this embodiment, after the frequency of the leaky wave signal is changed, it can be set to periodically return to check whether the signal characteristics at the highest resonance frequency meet the preset requirements.

[0053] Embodiment 2

[0054] Figure 8 This is a schematic diagram of the structure of the leaky wave transducer provided in this embodiment. Figure 8 The difference between this embodiment and the first embodiment is that each electrode 120 in the electrode array is ring-shaped, and adjacent electrodes 120 are equally spaced around the substrate 110, which facilitates the leakage wave transducer 100 to be directly welded and fixed to the inner or outer side of the fluid pipeline with a circuit board with corresponding pads.

[0055] Embodiment 3

[0056] Fig. 9 and Fig.10 This is a schematic diagram of the structure of the variable frequency leakage wave flow sensor system provided in this embodiment. Fig. 9 and Fig.10The difference between this embodiment and the first embodiment is that the two leaky wave transducers 100 are both arranged on the outside of the fluid pipeline 200, and are respectively arranged on both sides of the fluid pipeline 200 or both are arranged on the same side of the fluid pipeline 200, and the two leaky wave transducers 100 are at different positions in the axial direction of the fluid pipeline 200. When the two leaky wave transducers 100 are respectively arranged on both sides of the fluid pipeline 200, the leaky wave signal emitted by one of the leaky wave transducers 100 passes through the fluid pipeline 200 and is received by the other leaky wave transducer 100; when the two leaky wave transducers 100 are both arranged on the same side of the fluid pipeline 200, the leaky wave signal emitted by one of the leaky wave transducers 100 is reflected by the bottom of the fluid pipeline 200 and is received by the other leaky wave transducer 100. After multiple reflections, the signal strength will weaken, but the measurement accuracy may not necessarily deteriorate, because the longer propagation time of the sound wave makes the time difference between the upstream and downstream larger and easier to distinguish.

[0057] In summary, in the leakage wave transducer and leakage wave flow sensing system provided by the present invention, the leakage wave transducer includes a substrate and an electrode array arranged on the substrate, the propagation speed of the surface wave of the substrate is greater than the body sound speed of the fluid in the fluid pipeline, and the frequency of the leakage wave signal is changed by changing the positive and negative polarity of each electrode in the electrode array; either one of the two leakage wave transducers in the system serves as a transmitting end that sends a leakage wave signal under the excitation of an excitation electrical signal, and the other serves as a receiving end that receives the leakage wave signal; the switching module is electrically connected to each leakage wave transducer, and is used to change the frequency of the leakage wave signal and control the two leakage wave transducers to take turns as a transmitting end and a receiving end; the control module is electrically connected to the switching module, and is used to send an excitation electrical signal to the transmitting end and receive the leakage wave signal from the receiving end through the switching module, and obtain the flow rate of the fluid in the fluid pipeline according to the time difference or phase difference between two adjacent received leakage wave signals, and determine whether to change the frequency of the leakage wave signal according to the signal characteristics of the two adjacent received leakage wave signals. When the type and physical properties of the fluid in the fluid pipeline change, the positive and negative polarity of each electrode in the switching electrode array is selected by judging the results, which can change the frequency of the leakage wave signal, reduce the attenuation of the leakage wave signal during the propagation process, maintain signal strength stability, and improve the measurement stability and accuracy of the sensing system.

[0058] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any technician in the relevant technical field, without departing from the scope of the technical solution of the present invention, makes any form of equivalent replacement or modification to the technical solution and technical content disclosed in the present invention, which does not depart from the content of the technical solution of the present invention and still falls within the protection scope of the present invention.

Claims

1. A leaky wave flow sensing system, characterized in that: include: Two leaky wave transducers, the leaky wave transducers are arranged inside or outside a fluid pipeline for sending or receiving leaky wave signals, the leaky wave transducers include a substrate and an electrode array arranged on the substrate, the propagation speed of the surface wave of the substrate is greater than the body sound speed of the fluid in the fluid pipeline, the frequency of the leaky wave signal is changed by changing the positive and negative polarity of each electrode in the electrode array, any one of the two leaky wave transducers serves as a transmitting end for sending the leaky wave signal under the excitation of an excitation electrical signal, and the other serves as a receiving end for receiving the leaky wave signal; A switching module, electrically connected to each of the leaky wave transducers, for changing the frequency of the leaky wave signal and controlling the two leaky wave transducers to act as the transmitting end and the receiving end in turn; A control module is electrically connected to the switching module, and is used to send the excitation electrical signal to the transmitting end and receive the leakage wave signal from the receiving end through the switching module, and obtain the flow rate of the fluid in the fluid pipeline according to the time difference or phase difference between two adjacent leakage wave signals received, and determine whether to change the frequency of the leakage wave signal according to the signal characteristics of two adjacent leakage wave signals received.

2. The leaky wave flow sensor system according to claim 1, characterized in that: The switching module includes a first switching unit and a second switching unit, and the control module includes a signal transmitting unit and a signal receiving unit. The first switching unit is electrically connected to the signal transmitting unit and the signal receiving unit, and is used to control the two leakage wave transducers to be electrically connected to the signal transmitting unit and the signal receiving unit in turn through the first switching unit. The second switching unit is electrically connected to the signal transmitting unit and the signal receiving unit, and is used to change the positive and negative polarity of each electrode in the electrode array of the two leakage wave transducers through the second switching unit. When the polarity of the electrode is positive, the electrode is electrically connected to the signal transmitting unit or the signal receiving unit; when the polarity of the electrode is negative, the electrode is grounded.

3. The leaky wave flow sensor system according to claim 1, characterized in that: When it is determined that the frequency of the leaky wave signal needs to be changed, an adjustment frequency is obtained according to the center distance between two adjacent positive electrodes in the electrode array, the propagation speed of the surface wave of the substrate, and the body sound speed of the fluid in the fluid pipeline; The frequency of the leaky wave signal is changed to the adjustment frequency.

4. The leaky wave flow sensor system according to claim 1, characterized in that: The two leaky wave transducers are both arranged on the inner side or the outer side of the fluid pipeline, and the two leaky wave transducers are at different positions in the axial direction of the fluid pipeline.

5. The leaky wave flow sensor system according to claim 4, characterized in that: The two leaky wave transducers are both arranged on the inner side of the fluid pipeline. A through hole is opened on the fluid pipeline. Leads of the leaky wave transducers are led out through the through hole and are electrically connected to the switching module.

6. The leaky wave flow sensor system according to claim 5, characterized in that: The two leaky wave transducers include a first sealing layer outside; and / or a second sealing layer is arranged between the lead wire and the inner wall of the through hole.

Images