Three-dimensional flowmeter probe and flow measurement method

Abstract

This invention relates to a three-dimensional flow meter probe and a flow velocity measurement method, belonging to the field of ultrasonic fluid measurement technology. The three-dimensional flow meter probe includes a transmitting unit and three receiving units. The transmitting unit is located at the center of the probe, and the receiving units are distributed circumferentially around the transmitting unit. Both the transmitting and receiving units include a piezoelectric micromechanical ultrasonic transducer array. This three-dimensional flow meter probe, using a piezoelectric micromechanical ultrasonic transducer array to construct the transmitting and receiving units, and through a central transmitting and circumferential receiving layout, can achieve probe miniaturization while receiving Doppler echo signals from multiple directions, thereby realizing spatial multidimensional flow velocity measurement and meeting the needs of three-dimensional flow field analysis.

Description

Technical Field

[0001] This invention belongs to the field of ultrasonic fluid measurement technology, and particularly relates to a three-dimensional flow meter probe and a flow velocity measurement method. Background Technology

[0002] Ultrasonic Doppler current meters measure water flow velocity using the Doppler effect and are widely used in fields such as hydrological monitoring and marine exploration.

[0003] In existing technologies, current meter probes are typically assembled from traditional piezoelectric ceramic transducers, with a central transmitting transducer surrounded by multiple receiving transducers to achieve multidimensional flow velocity measurement. However, piezoelectric ceramic transducers are relatively large, making it difficult to miniaturize and integrate them into an array. Such probes, assembled from multiple independent transducers, are not only structurally bulky and difficult to install in confined spaces or portable devices, but their large size also significantly interferes with the water flow field when used underwater, affecting measurement accuracy.

[0004] To address the aforementioned shortcomings, this invention provides a three-dimensional flow meter probe based on a piezoelectric micromechanical ultrasonic transducer, thereby reducing the probe size and minimizing interference with the water flow field. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a three-dimensional flow meter probe and a flow velocity measurement method. By employing a piezoelectric micromechanical ultrasonic transducer array to construct a transmitting unit and three receiving units, and arranging the three receiving units in a 120° equidistant circular distribution around the transmitting unit, the overall volume of the probe can be effectively reduced, making the probe structure more compact.

[0006] The present invention provides a three-dimensional flow meter probe, including a transmitting unit and three receiving units. The transmitting unit is located at the center of the probe and is used to transmit signals. The three receiving units are distributed in a 120° equidistant circle around the transmitting unit and are used to receive signals. Both the transmitting unit and the receiving unit include a piezoelectric micromechanical ultrasonic transducer array.

[0007] Compared to the shortcomings of traditional piezoelectric ceramic transducers, such as large size and difficulty in array integration, this solution uses a piezoelectric micromechanical ultrasonic transducer array to form the transmitting and receiving units. Through the layout of central transmission and circumferential reception, it can achieve probe miniaturization while receiving Doppler echo signals from multiple directions, thereby realizing spatial multidimensional flow velocity measurement and meeting the needs of three-dimensional flow field analysis.

[0008] In some embodiments, each piezoelectric micromechanical ultrasonic transducer in the piezoelectric micromechanical ultrasonic transducer array is monolithically integrated onto the same transducer chip using MEMS technology.

[0009] Compared to the shortcomings of traditional piezoelectric ceramic transducers, such as poor frequency consistency and reliance on mechanical cutting and assembly, this solution integrates each piezoelectric micromechanical ultrasonic transducer onto the same transducer chip using MEMS technology. This eliminates the need for a backing layer and complex acoustic matching structure, enabling mass production and reducing manufacturing costs and process difficulty. Furthermore, the precision of photolithography ensures excellent frequency and sensitivity consistency among the transducers.

[0010] In some embodiments, the piezoelectric micromechanical ultrasonic transducer includes: The substrate has a cavity formed from the front side inwards; A support layer is formed above the substrate and covers the cavity; The bottom electrode layer is formed above or below the support layer; A piezoelectric layer is formed above the bottom electrode layer when the bottom electrode layer is located above the support layer; and above the support layer when the bottom electrode layer is located below the support layer. The top electrode layer is formed above the piezoelectric layer; When the bottom electrode layer is located above the support layer, the support layer, bottom electrode layer, piezoelectric layer and top electrode layer together form a multi-layer composite vibrating membrane suspended above the cavity; when the bottom electrode layer is located below the support layer, the support layer, piezoelectric layer and top electrode layer together form a multi-layer composite vibrating membrane suspended above the cavity, and the transmission and reception of ultrasonic waves are realized through the bending vibration mode of the vibrating membrane.

[0011] This technical solution enables the piezoelectric micromechanical ultrasonic transducer to efficiently transmit and receive ultrasonic waves through bending vibration mode at a microscale by setting a multi-layer composite vibration membrane structure suspended above the cavity. This solves the problem of large size and difficulty in miniaturization of traditional bulk piezoelectric ceramic transducers, and provides a basic unit for constructing miniaturized, high-performance flow meter probes.

[0012] In some embodiments, the three-dimensional flow meter probe also includes a probe housing, with the transmitting unit and the receiving unit installed inside the probe housing, and the acoustic surfaces of the transmitting unit and the receiving unit facing the same side of the probe housing.

[0013] This technical solution integrates multiple micro transducer modules into a single probe structure by setting up a probe housing and installing the transmitting and receiving units in the same housing with their acoustic surfaces facing the same side. This facilitates underwater deployment and multidimensional flow velocity measurement in narrow areas (such as drainage networks and open channels).

[0014] In some embodiments, the probe housing is provided with an acoustic window, and the transmitting unit and the receiving unit are assembled in the acoustic window inside the probe housing. The normal direction of the acoustic window of the receiving unit intersects the normal direction of the acoustic window of the transmitting unit at a predetermined distance above the probe.

[0015] This technical solution assembles the transmitting and receiving units at the acoustic window and limits the intersection of the normal directions of the receiving and transmitting units at a predetermined distance above the probe, so that multiple receiving beams are focused in space on the same measurement area, thereby effectively improving the echo signal strength and measurement signal-to-noise ratio in complex environments such as sandy water bodies.

[0016] In some embodiments, the piezoelectric micromechanical ultrasonic transducer array operates at a frequency of 10 kHz to 20 MHz.

[0017] This technical solution limits the operating frequency to 10kHz to 20MHz, allowing the probe to select the appropriate frequency to operate according to actual measurement needs (such as open channels, pipes, or narrow areas), thus taking into account both penetration depth and measurement resolution in different scenarios.

[0018] In some embodiments, the transmitting unit further includes a driving circuit co-packaged with the piezoelectric micromechanical ultrasonic transducer array, and the receiving unit further includes a preamplifier circuit co-packaged with the piezoelectric micromechanical ultrasonic transducer array, the input of which is connected to the electrodes of the piezoelectric micromechanical ultrasonic transducer array.

[0019] This technical solution shortens the electrical connection path between the transducer and the signal processing circuit by encapsulating the transmitting unit and the driving circuit together, and the receiving unit and the preamplifier circuit together, thereby reducing the influence of parasitic parameters and external interference, which is beneficial to the accurate extraction of Doppler ultrasound frequency shift signals.

[0020] Based on the aforementioned three-dimensional flow meter probe, the present invention also provides a flow velocity measurement method, which is applied to the aforementioned three-dimensional flow meter probe and includes the following steps: Frequency difference acquisition: At the sampling point location, acquire the frequency difference between the received signals of the three receiving units and the transmitted signals of the transmitting unit; Calculate the flow velocity: with the center point of the transmitting unit as the origin. With the normal direction of the transmitting unit as axis, The direction away from the three receiving units is the positive direction. axis and center point of the first receiving unit form flat, The shaft is located at In the plane, and shaft and The included angle of the shaft is 90 degrees. The axes are uniquely determined by the rules of a right-handed rectangular coordinate system, establishing... The three-dimensional flow velocity of the water at the sampling point is calculated according to equation (1). , , The expression for equation (1) is: (1); In equation (1), The speed of sound waves in water flow. The frequency of the transmitting signal of the transmitting unit. The frequency difference between the signal received by the first receiving unit and the signal transmitted by the transmitting unit. The frequency difference between the signal received by the second receiving unit and the signal transmitted by the transmitting unit. The frequency difference between the signal received by the third receiving unit and the signal transmitted by the transmitting unit; The elevation angle of the first receiving unit relative to the transmitting unit is, specifically... The acute angle between the negative axis direction and the normal direction of the first receiving unit; For the water flow along The component of velocity in the axial direction, For the water flow along The component of velocity in the axial direction, For the water flow along The component of velocity in the axial direction.

[0021] This technical solution enables synchronous and unambiguous measurement of the three-dimensional velocity vector of water flow.

[0022] In some embodiments, the velocity calculation step further includes: calculating the velocity and direction of the water flow at the sampling point according to equation (2), which is expressed as: (2); In equation (2), The magnitude of the three-dimensional flow velocity; for The magnitude of the two-dimensional flow velocity in the plane; for Two-dimensional flow velocity in a plane and The included angle of the axes represents the two-dimensional flow velocity in the plane. The direction of flow.

[0023] This technical solution integrates the component information of three orthogonal directions into an intuitive total velocity scalar value and a single flow direction angle, which facilitates the direct output of the overall speed and planar flow direction of the water flow.

[0024] In some embodiments, a step of determining sampling points is included before the step of obtaining the frequency difference. The step of determining sampling points includes: changing the pitch angle. and / or the distance between the transmitting unit and the receiving unit Determine the sampling point at Position in the negative direction of the axis.

[0025] This technical solution determines the position of the sampling point in the negative Z-axis direction by changing the elevation angle and / or the distance between the transmitting unit and the receiving unit before acquiring the frequency difference, thus making the sampling depth adjustable.

[0026] Based on the above scheme, the three-dimensional flow meter probe in this embodiment of the invention uses a piezoelectric micromechanical ultrasonic transducer array instead of a traditional piezoelectric ceramic transducer. Since the piezoelectric micromechanical ultrasonic transducer itself has the characteristic of small size, the volume of the transducer part in the probe can be reduced. By setting up one transmitting unit and three receiving units, and the receiving units are distributed in a circle around the transmitting unit, the probe can receive Doppler echo signals from multiple different directions, thereby obtaining the velocity components of the fluid in different directions and realizing multidimensional flow velocity measurement. Attached Figure Description

[0027] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the piezoelectric micromechanical ultrasonic transducer in an embodiment of the present invention; Figure 2 This is a schematic diagram of the transducer chip in an embodiment of the present invention; Figure 3 This is a schematic diagram of the ultrasonic transducer module in an embodiment of the present invention; Figure 4 This is a schematic diagram of the structure of the three-dimensional flow meter probe in an embodiment of the present invention; Figure 5 This is a schematic diagram of the spatial rectangular coordinate system in the velocity calculation step of the velocity measurement method in this embodiment of the invention; Figure 6 The pitch angle in the flow velocity measurement method of this invention embodiment A schematic diagram.

[0028] In the picture: 1. Piezoelectric micromechanical ultrasonic transducer; 2. Transducer chip; 3. Ultrasonic transducer module; 4. Probe; 11. Substrate; 12. Cavity; 13. Support layer; 14. Bottom electrode layer; 15. Piezoelectric layer; 16. Top electrode layer; 21. Bottom electrode pad; 22. Top electrode pad; 31. Signal processing circuit; 32. Lead wire; 33. Housing; 34. Encapsulation material; 41. Transmitting unit; 42. First receiving unit; 43. Second receiving unit; 44. Third receiving unit; 45. Probe housing. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0030] In the description of this invention, it should be understood that the terms "center", "lateral", "longitudinal", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0031] The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first," "second," or "third" may explicitly or implicitly include one or more of that feature.

[0032] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0033] The terms “system,” “unit,” and “module” used in this article are methods for distinguishing different components, elements, parts, sections, or assemblies at different levels. These terms may be replaced by other expressions that achieve the same purpose.

[0034] like Figures 1-4 As shown, in one embodiment of the three-dimensional flow meter probe and flow velocity measurement method of the present invention, the three-dimensional flow meter probe includes a transmitting unit 41 and a first receiving unit 42, a second receiving unit 43, and a third receiving unit 44. The transmitting unit 41 is located at the center of the probe and is used to transmit signals. The three receiving units are distributed in a 120° equidistant circle around the transmitting unit 41 and are used to receive signals. Both the transmitting unit 41 and the receiving units include an array of piezoelectric micromechanical ultrasonic transducers 1.

[0035] In the above illustrative embodiment, the three-dimensional flow meter probe is constructed by using an array of piezoelectric micromechanical ultrasonic transducers 1 to form a transmitting unit 41 and three receiving units. The three receiving units are arranged in a circumferential distribution at 120° intervals around the transmitting unit 41. Compared with probes assembled using traditional piezoelectric ceramic transducers, this effectively reduces the overall volume of the probe 4, making the structure of the probe 4 more compact. The smaller size of the probe 4 reduces physical interference to the surrounding water flow field when used underwater, thereby reducing the measurement error introduced by the presence of the probe 4 itself. At the same time, based on the array characteristics of the piezoelectric micromechanical ultrasonic transducers 1, the probe 4 can still achieve a uniform angular layout of the three receiving channels while maintaining a small volume, providing the necessary geometric configuration basis for three-dimensional flow velocity measurement.

[0036] In some embodiments, such as Figure 2 As shown, each piezoelectric micromechanical ultrasonic transducer 1 in the array of piezoelectric micromechanical ultrasonic transducers 1 is monolithically integrated onto the same transducer chip 2 using MEMS technology. In this embodiment, the array size is six by six.

[0037] Furthermore, such as Figure 1 As shown, the specific structure of the piezoelectric micromechanical ultrasonic transducer 1 is as follows: The substrate 11 is made of silicon, and a cavity 12 is formed by etching from its front side inwards. A support layer 13 is formed above the substrate 11 and covers the cavity 12. The support layer 13 can have various structural shapes such as square, hexagonal, or circular. A bottom electrode layer 14 is formed above the support layer 13, and the bottom electrode material is molybdenum. A piezoelectric layer 15 is formed above the bottom electrode layer 14, and the piezoelectric material is a thin film material with piezoelectric effect, such as aluminum nitride or lead zirconate titanate. A top electrode layer 16 is formed above the piezoelectric layer 15, and the top electrode material is gold. The support layer 13, bottom electrode layer 14, piezoelectric layer 15, and top electrode layer 16 together constitute a multilayer composite vibrating membrane suspended above the cavity 12. Ultrasonic waves are transmitted and received through the bending vibration mode of the vibrating membrane. In this embodiment, the operating frequency of the piezoelectric micromechanical ultrasonic transducer array 1 is 5MHz.

[0038] In some embodiments, when the piezoelectric micromechanical ultrasonic transducer 1 is configured in the transmitting unit 41, alternating current is applied to the bottom electrode layer 14 and the top electrode layer 16, respectively. Vibration is generated by the inverse piezoelectric effect of the piezoelectric layer 15, thereby emitting sound waves. When the piezoelectric micromechanical ultrasonic transducer 1 is configured in the receiving unit, the sound signal causes the piezoelectric layer 15 to vibrate. The generated electrical signal is transmitted through the bottom electrode layer 14 and the top electrode layer 16 by utilizing the piezoelectric effect of the piezoelectric layer 15.

[0039] In some embodiments, such as Figure 2As shown, the transducer chip 2 is an array structure composed of multiple piezoelectric micromechanical ultrasonic transducers 1. In this array, the electrical connection leads of all bottom electrode layers 14 together form the bottom electrode pad 21, and the electrical connection leads of all top electrode layers 16 together form the top electrode pad 22. Figure 3 As shown, the bottom electrode pad 21 and the top electrode pad 22 are bonded to the signal processing circuit 31 via lead wire 32 to achieve the conversion of acoustic and electrical signals. The signal processing circuit 31 includes a driving circuit in the transmitting unit 41 and a preamplifier circuit in the receiving unit.

[0040] In some embodiments, the transmitting unit 41 further includes a driving circuit co-packaged with the piezoelectric micromechanical ultrasonic transducer 1 array, and the receiving unit further includes a preamplifier circuit co-packaged with the piezoelectric micromechanical ultrasonic transducer 1 array. The input terminal of the preamplifier circuit is connected to the electrodes of the piezoelectric micromechanical ultrasonic transducer 1 array and is used to amplify the received weak echo signal with low noise.

[0041] In some embodiments, such as Figure 3 As shown, the transducer chip 2 is connected to the driving circuit or preamplifier circuit via lead wire 32 and then assembled inside the housing 33. The lead wire 32 of the driving circuit or preamplifier circuit extends from the opening at the bottom of the housing 33. At the opening and above the transducer chip 2, an encapsulation material 34 matching the acoustic impedance of the water environment is used for encapsulation. This encapsulation material 34 ensures the module's airtightness, and its impedance matches the water environment, effectively reducing the loss of acoustic signals during propagation. In this embodiment, the acoustic impedance of the encapsulation material 34 is 1.05 × 10⁻⁶. 6 Pa·s / m.

[0042] In some embodiments, such as Figure 4 As shown, the probe also includes a probe housing 45. The transmitting unit 41 and the receiving unit are installed inside the probe housing 45, with their acoustic surfaces facing the same side of the probe housing 45. An acoustic window is provided on the probe housing 45, and the transmitting unit 41 and the receiving unit are assembled at the acoustic window inside the probe housing 45. The ultrasonic transducer module 3, as the transmitting unit 41, is assembled at the center of the probe housing 45, emitting ultrasonic waves into the water through the acoustic window of the probe housing 45. The ultrasonic transducer module 3, as the receiving unit, is assembled inside the probe housing 45, arranged in a circle with the transmitting unit 41 as the center, receiving the echoes reflected from the water through the acoustic window of the probe housing 45. The normal directions of the acoustic windows of the three receiving units intersect the normal direction of the acoustic window of the transmitting unit 41 at a predetermined distance above the probe 4.

[0043] Based on the aforementioned three-dimensional flow meter probe 4, the present invention also provides a flow velocity measurement method, which is applied to the aforementioned three-dimensional flow meter probe 4 or a three-dimensional flow meter including the aforementioned three-dimensional flow meter probe, and includes the following steps: Frequency difference acquisition: At the sampling point location, acquire the frequency difference between the signals received by the three receiving units and the signals transmitted by the transmitting unit 41; Calculate the flow rate: such as Figure 5 As shown, the origin is taken from the center point of the transmitting unit 41. With the normal direction of the transmitting unit 41 as axis, The direction away from the three receiving units is the positive direction. The axis and the center point of the first receiving unit 42 form flat, The shaft is located at In the plane, and shaft and The included angle of the shaft is 90 degrees. The axes are uniquely determined by the rules of a right-handed rectangular coordinate system, establishing... The three-dimensional flow velocity of the water at the sampling point is calculated according to equation (1). , , The expression for equation (1) is: (1); In equation (1), The speed of sound waves in water flow. The transmission signal frequency of the transmitting unit 41 The frequency difference between the signal received by the first receiving unit 42 and the signal transmitted by the transmitting unit 41. The frequency difference between the signal received by the second receiving unit 43 and the signal transmitted by the transmitting unit 41. The frequency difference between the signal received by the third receiving unit 44 and the signal transmitted by the transmitting unit 41; for example Figure 6 As shown, The elevation angle of the first receiving unit 42 relative to the transmitting unit 41 is specifically... The acute angle between the negative axis direction and the normal direction of the first receiving unit 42; For the water flow along The component of velocity in the axial direction, When it is positive, it represents the water flowing along Flow in the positive direction of the axis, When negative, it represents the water flowing along... Negative axial flow; For the water flow along The component of velocity in the axial direction, When it is positive, it represents the water flowing along Flow in the positive direction of the axis, When negative, it represents the water flowing along... Negative axial flow; For the water flow along The component of velocity in the axial direction, When it is positive, it represents the water flowing along Flow in the positive direction of the axis, When negative, it represents the water flowing along... Negative flow along the axis. In the above illustrative embodiment, the flow velocity measurement method of the present invention can calculate the mutually decoupled three-dimensional flow velocities by simultaneously acquiring the Doppler frequency difference of three receiving units and establishing a spatial rectangular coordinate system with the transmitting unit 41 as the origin. The sign of each component velocity directly corresponds to the positive or negative flow of water along the corresponding coordinate axis, thereby realizing the synchronous and unambiguous measurement of the three-dimensional flow velocity vector (including magnitude and direction).

[0044] In some embodiments, the velocity calculation step further includes: calculating the velocity and direction of the water flow at the sampling point according to equation (2), where equation (2) is expressed as: (2); In equation (2), The magnitude of the three-dimensional flow velocity; for The magnitude of the two-dimensional flow velocity in the plane; for Two-dimensional flow velocity in a plane and The included angle of the axes represents the two-dimensional flow velocity in the plane. The direction of flow.

[0045] It should be noted that three-dimensional velocity measurement typically approximates the motion of water flow as a two-dimensional flow within a fixed plane. The angle of deviation along the Z-axis is generally negligible due to its small value. Under this simplification, the magnitude of the three-dimensional velocity is obtained through synthetic calculation, but its flow direction is still characterized using the flow direction of the two-dimensional velocity, i.e., it is assumed that the water flow only occurs on the horizontal plane (in this embodiment). The flow is within a plane and does not reflect deflection in the Z-axis direction.

[0046] This embodiment integrates the component information of three orthogonal directions into an intuitive total velocity scalar value and a single flow direction angle, which facilitates the direct output of the overall speed and planar flow direction of the water flow.

[0047] In some embodiments, a step of determining sampling points is included before the step of obtaining the frequency difference. The step of determining sampling points includes: changing the pitch angle. and / or the distance between the transmitting unit 41 and the receiving unit Determine the sampling point at Position in the negative Z-axis direction. The sampling depth is adjustable by changing the pitch angle and / or the distance between the transmitting unit 41 and the receiving unit before acquiring the frequency difference.

[0048] Furthermore, the distance between the sampling point and the transmitting unit 41 is used to characterize the sampling point's position. The position in the negative axis direction, the distance between the sampling point and the transmitting unit 41, is determined by equation (3), which is expressed as: (3); In equation (3), The distance between the sampling point and the transmitting unit 41 is denoted as .

[0049] In some embodiments, in the step of obtaining the frequency difference, the frequency difference between the signals received by the three receiving units and the signals transmitted by the transmitting unit 41 is calculated according to equation (4), and the expression of equation (4) is: (4); In equation (4), The frequency of the signal received by the first receiving unit 42. The frequency of the signal received by the second receiving unit 43. The frequency of the signal received by the third receiving unit 44.

[0050] In some embodiments, in addition to the three-dimensional flow meter probe 4 described above, the three-dimensional flow meter also has a built-in temperature sensor for measuring the water environment temperature, and in the flow velocity calculation step, the sound wave velocity in the water flow is also included. The result is obtained by calculation using equation (5), and the expression for equation (5) is: (5); In equation (5), The temperature of the aquatic environment.

[0051] Through the description of several embodiments of the three-dimensional flow meter probe and flow velocity measurement method of the present invention, it can be seen that the embodiments of the three-dimensional flow meter probe and flow velocity measurement method of the present invention have at least one or more of the following advantages: 1. The three-dimensional flow meter probe provided by the present invention replaces the traditional piezoelectric ceramic transducer with an array of piezoelectric micromechanical ultrasonic transducers 1. Since the piezoelectric micromechanical ultrasonic transducer 1 itself has the characteristic of small size, the volume of the transducer part in the probe can be reduced.

[0052] 2. The three-dimensional flow meter probe provided by the present invention, by setting up a transmitting unit 41 and three receiving units, and the receiving units are distributed in a circle around the transmitting unit 41, can enable the probe to receive Doppler echo signals from multiple different directions, thereby obtaining the velocity components of the fluid in different directions and realizing multi-dimensional flow velocity measurement.

[0053] 3. The flow velocity measurement method provided by this invention realizes synchronous and unambiguous measurement of the three-dimensional flow velocity vector (including magnitude and direction) of water flow.

[0054] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0055] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A three-dimensional flowmeter probe, characterized in that, It includes one transmitting unit and three receiving units. The transmitting unit is located at the center of the probe and is used to transmit signals. The three receiving units are distributed in a 120° equidistant circle around the transmitting unit and are used to receive signals. Both the transmitting unit and the receiving unit include a piezoelectric micromechanical ultrasonic transducer array.

2. The three-dimensional flowmeter probe according to claim 1, characterized in that, Each piezoelectric micromechanical ultrasonic transducer in the piezoelectric micromechanical ultrasonic transducer array is monolithically integrated onto the same transducer chip using MEMS technology.

3. The three-dimensional flowmeter probe according to claim 2, characterized in that, Piezoelectric micromechanical ultrasonic transducers include: The substrate has a cavity formed from the front side inwards; A support layer is formed above the substrate and covers the cavity; The bottom electrode layer is formed above or below the support layer; A piezoelectric layer is formed above the bottom electrode layer when the bottom electrode layer is located above the support layer; and above the support layer when the bottom electrode layer is located below the support layer. The top electrode layer is formed above the piezoelectric layer; When the bottom electrode layer is located above the support layer, the support layer, bottom electrode layer, piezoelectric layer and top electrode layer together form a multi-layer composite vibrating membrane suspended above the cavity; when the bottom electrode layer is located below the support layer, the support layer, piezoelectric layer and top electrode layer together form a multi-layer composite vibrating membrane suspended above the cavity, and the transmission and reception of ultrasonic waves are realized through the bending vibration mode of the vibrating membrane.

4. The three-dimensional flowmeter probe according to claim 2, characterized in that, It also includes a probe housing, with the transmitting unit and the receiving unit installed inside the probe housing, and the acoustic surfaces of the transmitting unit and the receiving unit facing the same side of the probe housing.

5. The three-dimensional flowmeter probe according to claim 4, characterized in that, An acoustic window is provided on the probe housing. The transmitting unit and the receiving unit are assembled in the acoustic window inside the probe housing. The normal direction of the acoustic window of the receiving unit intersects the normal direction of the acoustic window of the transmitting unit at a predetermined distance above the probe.

6. The three-dimensional flowmeter probe according to claim 2, characterized in that, The piezoelectric micromechanical ultrasonic transducer array operates at frequencies from 10 kHz to 20 MHz.

7. The three-dimensional flowmeter probe according to claim 2, characterized in that, The transmitting unit also includes a driving circuit co-packaged with the piezoelectric micromechanical ultrasonic transducer array, and the receiving unit also includes a preamplifier circuit co-packaged with the piezoelectric micromechanical ultrasonic transducer array. The input terminal of the preamplifier circuit is connected to the electrodes of the piezoelectric micromechanical ultrasonic transducer array.

8. A method for measuring flow velocity, characterized in that, The method of applying the three-dimensional flowmeter probe as described in any one of claims 1-7 includes the following steps: Frequency difference acquisition: At the sampling point location, acquire the frequency difference between the received signals of the three receiving units and the transmitted signals of the transmitting unit; Calculate the flow velocity: with the center point of the transmitting unit as the origin. With the normal direction of the transmitting unit as axis, The direction away from the three receiving units is the positive direction. axis and center point of the first receiving unit form flat, The shaft is located at In the plane, and shaft and The included angle of the shaft is 90 degrees. The axes are uniquely determined by the rules of a right-handed rectangular coordinate system, establishing... The three-dimensional flow velocity of the water at the sampling point is calculated according to equation (1). , , The expression for equation (1) is: （1）； In equation (1), The speed of sound waves in water flow. The frequency of the transmitting signal of the transmitting unit. The frequency difference between the signal received by the first receiving unit and the signal transmitted by the transmitting unit. The frequency difference between the signal received by the second receiving unit and the signal transmitted by the transmitting unit. The frequency difference between the signal received by the third receiving unit and the signal transmitted by the transmitting unit; The elevation angle of the first receiving unit relative to the transmitting unit is, specifically... The acute angle between the negative axis direction and the normal direction of the first receiving unit; For the water flow along The component of velocity in the axial direction, For the water flow along The component of velocity in the axial direction, For the water flow along The component of velocity in the axial direction.

9. The flow velocity measurement method according to claim 8, characterized in that, The velocity calculation step also includes: calculating the velocity and direction of the water flow at the sampling point according to equation (2), which is expressed as: （2）； In equation (2), The magnitude of the three-dimensional flow velocity; for The magnitude of the two-dimensional flow velocity in the plane; for Two-dimensional flow velocity in a plane and The included angle of the axes represents the two-dimensional flow velocity in the plane. The direction of flow.

10. The flow velocity measurement method according to claim 8, characterized in that, The step of obtaining the frequency difference also includes a step of determining the sampling point, which includes: changing the pitch angle and / or the distance between the transmitting unit and the receiving unit Determine the sampling point at Position in the negative direction of the axis.

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