Full three-dimensional ultrasonic Doppler velocity measurement device based on phased array and velocity measurement method thereof

Abstract

The invention provides a full-three-dimensional ultrasonic Doppler velocity measurement device based on a phased array and a velocity measurement method thereof, and belongs to the field of liquid metal flow field measurement. The problems that full-three-dimensional flow field measurement is difficult to complete in an existing liquid metal measurement mode, the device is large in size, and the measurement resolution is limited by the width of a piezoelectric crystal are solved. According to the invention, the host describes a measurement task to be carried out to the control module, and then drives the transceiver module to control the transducer to emit multiple pulse ultrasonic waves. After each time of ultrasonic wave emission, the transducer is switched into a receiving mode and receives an echo signal, the echo signal enters the preprocessing module after being amplified and converted and then is sampled by the acquisition module to obtain a Doppler signal required by an ultrasonic pulse repetition Doppler method, and finally, the Doppler frequency shift and a three-dimensional velocity vector are calculated by the host. The device can complete full three-dimensional measurement of a flow field, and is especially suitable for flow field measurement of liquid metal.

Description

Technical Field

[0001] The present invention relates to a full three-dimensional ultrasonic Doppler velocity measurement technology based on a phased array, which is particularly suitable for the field of liquid metal flow field measurement. The present invention can also be applied to various scenarios such as other industrial fields and medical fields. Background Art

[0002] Liquid metal has excellent thermal conductivity and is widely used in nuclear reactors, heat dissipation of high heat flux devices, aerospace and other fields. It is often used to undertake cooling functions in various systems. In the process of applying liquid metal to practical engineering, it is necessary to solve the design and optimization problems of its flow heat transfer system. Flow and heat transfer are inseparable, and the practical application of liquid metal requires a detailed and sufficient analysis of the flow field. However, due to the characteristics of liquid metal such as opacity, high temperature and corrosiveness, commonly used flow field measurement technologies such as laser Doppler velocimetry, hot wire anemometer and particle imaging velocimeter cannot be used. In view of this feature, an ultrasonic Doppler velocimeter (UDV) can be used to measure its flow field.

[0003] Ultrasonic waves are emitted by ultrasonic units, which can transmit or receive ultrasonic waves. Different forms of ultrasonic units convert ultrasonic signals in different ways. UDV transmits ultrasonic waves into the fluid through the ultrasonic unit on the transducer, and the direction forms an angle θ with the flow direction of the fluid. At the same time, the transducer receives the ultrasonic echo of the tracer particles in the fluid. The transducer probe of UDV is divided into single crystal type and array type. The array transducer forms an array through multiple ultrasonic units, and the ultrasonic emission and reception of a single ultrasonic unit (array element) can be controlled separately. Figure 1 The figure shows the principle diagram of ultrasonic Doppler velocity measurement of a single ultrasonic unit. UDV obtains the velocity component of the fluid in the ultrasonic direction, i.e. v in the figure, by analyzing the Doppler effect of the echo. The detailed principle of UDV can be found in the book "Ultrasonic Doppler Velocity Profiler for Fluid Flow".

[0004] Conventional single crystal transducers can only complete one-dimensional flow field measurement, that is, the measurement position is on a line along the ultrasonic emission direction. Existing UDVs often use multi-transducer or array transducer solutions to complete two-dimensional flow field measurements. The multi-transducer solution transmits and receives ultrasonic waves through multiple transducers at different angles to achieve multi-dimensional velocity field measurement. The array transducer solution transmits and receives ultrasonic waves through different ultrasonic units on the transducer, thereby completing multi-dimensional velocity field measurement. Figure 2The figure shows a schematic diagram of an array transducer for two-dimensional flow field measurement. The ellipsis part omits several ultrasonic units in the middle. By sequentially exciting the ultrasonic units in the array transducer, the velocities in the x and y directions at the ultrasonic intersection grid points are measured, and the velocity field of the fluid on the two-dimensional plane is synthesized.

[0005] It can be seen that the above measurement method is difficult to complete full three-dimensional (the measurement area and velocity vector are both three-dimensional) flow field measurement, and the device volume is very large. This method of measuring the velocity at the ultrasonic intersection grid point will result in the measurement resolution being limited by the width of the ultrasonic unit. Summary of the invention

[0006] In view of this, in order to solve the above problems, the present invention introduces phased array technology into the field of ultrasonic Doppler velocity measurement, and designs a full three-dimensional ultrasonic Doppler velocity measurement device based on phased array and a velocity measurement method thereof.

[0007] To achieve the above-mentioned object, the present invention adopts the following technical scheme: a full three-dimensional ultrasonic Doppler velocity measurement device based on a phased array, comprising a host, a control module, a transceiver module, a preprocessing module, an acquisition module and a two-dimensional array ultrasonic transducer;

[0008] The host is used to send the required measurement tasks to the control module, and is also used to calculate the received Doppler signal to obtain the Doppler frequency shift and the three-dimensional velocity vector;

[0009] The control module is used to control the transceiver module and the two-dimensional array ultrasonic transducer to realize multiple pulse ultrasonic transceiver interactions according to the measurement task;

[0010] The transceiver module is used to send the received echo signal to the pre-processing module;

[0011] The preprocessing module is used to demodulate and filter the received ultrasonic waves and send the preprocessed ultrasonic waves to the acquisition module;

[0012] The acquisition module is used to sample and obtain the Doppler signal required by the ultrasonic pulse repetition Doppler method, and send it to the host.

[0013] Furthermore, before the pre-processing module receives the ultrasonic wave, it is necessary to perform signal amplification and A / D conversion on the ultrasonic wave.

[0014] Furthermore, the control module uses a single chip microcomputer as a controller and is equipped with a stable clock source as a time base of the control module.

[0015] Furthermore, the transceiver module includes a transmit beamformer, a three-level pulse generator, a transmit / receive switch and a receive amplifier stage;

[0016] The transmit beamformer is used to control the phase difference between the array elements of the two-dimensional array ultrasonic transducer, thereby controlling the steering of the generated ultrasonic beam, and is also used to send a signal to the three-level pulse generator to apply voltage excitation to the array elements;

[0017] The transmitting / receiving switch is used to realize the transmission and reception of ultrasonic waves;

[0018] The receiving amplifier stage is used to amplify the received ultrasonic waves.

[0019] Furthermore, after emitting ultrasonic waves, the two-dimensional array ultrasonic transducer switches to a receiving mode to receive echo signals, and then switches to a transmitting mode to continue emitting ultrasonic waves.

[0020] Furthermore, the preprocessing module is used to convert the analog signal amplified by the receiving amplifier stage into a digital signal through an analog-to-digital converter, and is also used to perform orthogonal demodulation and low-pass filtering on the digital signal through FPGA, and send it to the acquisition module.

[0021] Furthermore, three-dimensional velocity vectors at different positions are obtained through sector scanning, and finally a three-dimensional velocity field is formed.

[0022] Furthermore, the two-dimensional array ultrasonic transducer is composed of a plurality of ultrasonic units and forms a plane.

[0023] Furthermore, three square areas are divided on the two-dimensional array ultrasonic transducer for receiving echo signals returned by tracer particles in the fluid, and each area contains a single or multiple ultrasonic units.

[0024] A velocity measurement method using a full three-dimensional ultrasonic Doppler velocity measurement device based on a phased array, for a certain measuring point to be scanned, the specific method of measuring the three-dimensional velocity is as follows:

[0025] Step 1: Establish a rectangular coordinate system with the center of the two-dimensional array ultrasonic transducer as the origin, the x-axis and the y-axis being parallel to the two sides of the two-dimensional array ultrasonic transducer, and the axis being perpendicular to the two-dimensional array ultrasonic transducer;

[0026] Step 2: Determine the center point coordinates and measurement point coordinates of the three echo receiving areas, and calculate the unit vector of the measurement point pointing to the two-dimensional array ultrasonic transducer The unit vector of the measuring point pointing to the receiving area and

[0027] Step 3: Send ultrasonic waves (frequency is f0) to the measuring point and receive echo signals, obtain IQ signals through orthogonal demodulation, and perform low-pass filtering on them to remove the original frequency of the transmitted ultrasonic waves;

[0028] Step 4: Using the ultrasonic pulse repetition Doppler method to sample the signals received multiple times to form a Doppler signal;

[0029] Step 5: Extract Doppler frequency shifts f2, f3 and f4 from the Doppler signal;

[0030] Step 6: Calculate the 3D velocity based on the obtained Doppler shift For a single echo receiving area, the Doppler frequency shift calculation formula in the received Doppler signal is:

[0031]

[0032] in, is the unit vector of the receiving area corresponding to the Doppler frequency shift of the measuring point, and c is the sound speed in the measuring fluid. Therefore, the calculation formula for the three-dimensional velocity can be obtained as follows:

[0033]

[0034] Furthermore, in step 5, the Doppler frequency shifts f2, f3 and f4 in the Doppler signal are extracted by fast Fourier transform.

[0035] Compared with the prior art, the phased array-based full three-dimensional ultrasonic Doppler velocity measurement device and velocity measurement method described in the present invention have the following beneficial effects:

[0036] 1. The advantage of the present invention is that a new ultrasonic Doppler velocimeter is established by combining phased array technology with a two-dimensional array ultrasonic transducer. This device is sufficient to complete full three-dimensional measurement of the flow field and is particularly suitable for flow field measurement of liquid metals.

[0037] 2. The phased array technology of the present invention has the advantage of electronically controlled steering and focusing, so that the resolution of the measuring device is not limited by the width of the ultrasonic unit, and the resolution is greatly improved.

[0038] 3. When the device of the present invention is used for speed measurement, only a single transducer is needed, and the size of the device is relatively small.

[0039] 4. The present invention can also be applied to other industrial fields, medical fields and other scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0041] Figure 1 The ultrasonic Doppler velocity measurement principle diagram described in the background technology;

[0042] Figure 2 A schematic diagram of two-dimensional flow field measurement using an array transducer as described in the background art;

[0043] Figure 3 is a schematic diagram of an ultrasonic phased array;

[0044] Figure 4 It is a schematic diagram of one-dimensional array ultrasonic phased array scanning;

[0045] Figure 5 It is a schematic diagram of the detection area of ​​the two-dimensional array ultrasonic phased array;

[0046] Figure 6 It is a schematic diagram of two-dimensional array ultrasonic phased array scanning;

[0047] Figure 7 It is a schematic diagram of the three-dimensional velocity measurement method;

[0048] Figure 8 This is a schematic diagram of the echo signal receiving area distribution;

[0049] Fig. 9 A schematic diagram of the overall structure of the three-dimensional ultrasonic Doppler velocity measurement system of the present invention;

[0050] In the figure: 1-1-single crystal ultrasonic transducer probe, 1-2-tracer particles in the fluid; 2-1-array transducer, 2-2-tracer particles in the fluid, 3-1-one-dimensional array transducer, 3-2-transducer control device, 5-1-two-dimensional array ultrasonic transducer, 5-2-measured fluid domain, 7-2-array element combination area in the transducer. DETAILED DESCRIPTION

[0051] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely explain the technical solutions in the embodiments of the present invention. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict, and the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0052] See also Figure 3-8 This embodiment is described as a full three-dimensional ultrasonic Doppler velocity measurement device based on a phased array. The present invention uses an ultrasonic phased array of a two-dimensional array transducer to achieve full three-dimensional flow field measurement. It includes a host, a control module, a transceiver module, a preprocessing module, an acquisition module and a two-dimensional array ultrasonic transducer (5-1);

[0053] The host is used to send the required measurement tasks to the control module, and is also used to calculate the received Doppler signal to obtain the Doppler frequency shift and the three-dimensional velocity vector;

[0054] The control module is used to control the transceiver module and the two-dimensional array ultrasonic transducer (5-1) to realize multiple pulse ultrasonic wave transceiver interactions according to the measurement task;

[0055] The transceiver module is used to send the received echo signal to the pre-processing module;

[0056] The preprocessing module is used to demodulate and filter the received ultrasonic waves and send the preprocessed ultrasonic waves to the acquisition module;

[0057] The acquisition module is used to sample and obtain the Doppler signal required by the ultrasonic pulse repetition Doppler method, and send it to the host.

[0058] Before the preprocessing module receives the ultrasonic wave, it is necessary to amplify the ultrasonic wave signal and perform A / D conversion.

[0059] The transceiver module includes a transmit beamformer, a three-level pulse generator, a transmit / receive switch and a receive amplifier stage;

[0060] The transmit beamformer is used to control the phase difference between the array elements of the two-dimensional array ultrasonic transducer, thereby controlling the steering of the generated ultrasonic beam, and is also used to send a signal to the three-level pulse generator to apply voltage excitation to the array elements;

[0061] The transmitting / receiving switch is used to realize the transmission and reception of ultrasonic waves;

[0062] The receiving amplifier stage is used to amplify the received ultrasonic waves.

[0063] After emitting ultrasonic waves, the two-dimensional array ultrasonic transducer (5-1) switches to a receiving mode to receive echo signals, and then switches to a transmitting mode to continue emitting ultrasonic waves.

[0064] The preprocessing module is used to convert the analog signal amplified by the receiving amplifier stage into a digital signal through an analog-to-digital converter, and is also used to perform orthogonal demodulation and low-pass filtering on the digital signal through FPGA, and send it to the acquisition module, obtain the three-dimensional velocity vectors at different positions through sector scanning, and finally form a three-dimensional velocity field.

[0065] The two-dimensional array ultrasonic transducer (5-1) is composed of a plurality of ultrasonic transducers and forms a plane.

[0066] Three square areas are divided on the two-dimensional array ultrasonic transducer (5-1) for receiving echo signals returned by tracer particles in the fluid.

[0067] Ultrasonic phased array introduction:

[0068] like Figure 3The figure is a schematic diagram of an ultrasonic phased array, where 3-1 is a one-dimensional array transducer, 3-2 is a control device for the transducer, and the ellipsis omits several ultrasonic units in the middle. The ultrasonic phased array adjusts the phases of different array elements in the array transducer so that the ultrasonic waves emitted by each array element are coherently superimposed in a specific direction, thereby achieving the purpose of focusing the ultrasonic waves to a certain area or steering the ultrasonic waves to a certain direction.

[0069] like Figure 4 The figure shows a scanning schematic diagram of a one-dimensional array ultrasonic phased array. The scanning process is as follows: ultrasonic waves are emitted in one direction, and data of multiple measuring points in that direction are collected based on the time it takes for the echo to return to the transducer. The data is then turned to the next direction and the above steps are repeated until the sector-shaped detection area is scanned.

[0070] like Figure 5 The figure shows a schematic diagram of a two-dimensional array ultrasonic phased array flow field measurement area, 5-1 is a two-dimensional array ultrasonic transducer, and 5-2 is a fluid domain to be measured. The use of the two-dimensional array ultrasonic transducer (5-1) allows the measurement area to be expanded from a fan shape to a cone shape, thus realizing flow field measurement in a three-dimensional area.

[0071] like Figure 6 The figure shows the scanning schematic diagram of the two-dimensional array ultrasonic phased array. The scanning process is as follows: Figure 4 Scan a sector area in the manner described above, then turn to the next sector area and repeat this step until the conical measurement area is scanned.

[0072] like Figure 7 The figure shows a schematic diagram of a three-dimensional velocity measurement method for a fluid, and 7-2 is an array element combination area in the transducer. Based on the characteristic that the array elements in the array transducer can be combined for transmission or reception, three square areas (S2, S3, S4) are divided from the two-dimensional array ultrasonic transducer 5-1 (S1) to receive the echo signals returned by the tracer particles in the fluid. The distribution of the above areas should not be fixed, but three different areas need to be divided to receive the echo signals, so as to achieve the purpose of calculating the three components of the velocity.

[0073] like Figure 8 Shown is a schematic diagram of the distribution of three echo signal receiving areas.

[0074] The velocity measurement method based on the full three-dimensional ultrasonic Doppler velocity measurement device based on the phased array is used for Figure 6 The specific method for measuring the three-dimensional velocity of a certain measuring point in the scan is as follows:

[0075] 1) Establishing a rectangular coordinate system with the center of the two-dimensional array ultrasonic transducer as the origin, the x-axis and the y-axis being parallel to the two sides of the two-dimensional array ultrasonic transducer, and the axis being perpendicular to the two-dimensional array ultrasonic transducer;

[0076] 2) Determine the center point coordinates and measurement point coordinates of the three echo receiving areas, and calculate the unit vector pointing to the two-dimensional array ultrasonic transducer The unit vector of the measuring point pointing to the receiving area and

[0077] 3) Send ultrasonic waves (frequency is f0) to the measuring point and receive echo signals, obtain IQ signals through orthogonal demodulation, and perform low-pass filtering on them to remove the original frequency of the transmitted ultrasonic waves;

[0078] 4) Using the ultrasonic pulse repetition Doppler method to sample the signals received multiple times to form a Doppler signal;

[0079] 5) extracting Doppler frequency shifts f2, f3 and f4 from the Doppler signal;

[0080] 6) Calculate the three-dimensional velocity based on the obtained Doppler frequency shift For a single echo receiving area, the Doppler frequency shift calculation formula in the received Doppler signal is:

[0081]

[0082] in, is the unit vector of the receiving area corresponding to the Doppler frequency shift of the measuring point, and c is the sound speed in the measuring fluid. Therefore, the calculation formula for the three-dimensional velocity can be obtained as follows:

[0083]

[0084] Ultrasonic control and signal processing:

[0085] like Fig. 9 The figure shows the overall structure of the full three-dimensional ultrasonic Doppler velocity measurement system. The host describes the measurement task to be performed to the control module, and then drives the transceiver module to control the transducer to emit multiple pulsed ultrasonic waves. After each ultrasonic wave is emitted, the transducer switches to the receiving mode to receive the echo signal. After amplification and A / D conversion, the echo signal enters the preprocessing module for demodulation, filtering and other preprocessing, and then is handed over to the acquisition module for sampling to obtain the Doppler signal required by the ultrasonic pulse repetition Doppler method, and finally handed over to the host to calculate the Doppler frequency shift and three-dimensional velocity vector.

[0086] The control module uses a single-chip microcomputer as the controller and is equipped with a stable clock source as the time base of the entire system. The transceiver module includes a transmit beamformer, a three-level pulse generator, a transmit / receive switch, and a receive amplifier stage. The beamformer is used to control the phase difference between the array elements of the array transducer, thereby controlling the steering of the generated ultrasonic beam. It sends a signal to the three-level pulse generator to apply voltage excitation to the array element. After emitting ultrasonic waves, the transducer switches to the receiving mode to receive the echo signal, and then switches to the transmitting mode to continue emitting ultrasonic waves.

[0087] The preprocessing module converts the analog signal amplified by the receiving amplifier stage into a digital signal through an analog-to-digital converter. The signal enters the preprocessing module and is orthogonally demodulated and low-pass filtered through the FPGA. The Doppler signal obtained after sampling will enter the host to complete the extraction of the Doppler frequency shift and the three-dimensional velocity vector obtained through calculation. The three-dimensional velocity vectors at different positions are obtained through sector scanning, and finally a three-dimensional velocity field is formed.

[0088] The embodiments of the present invention disclosed above are only used to help illustrate the present invention. The embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. According to the content of this specification, many modifications and changes can be made. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well.

Claims

1. A full three-dimensional ultrasonic Doppler velocity measurement device based on a phased array, characterized in that: It includes a host, a control module, a transceiver module, a pre-processing module, a collection module and a two-dimensional array ultrasonic transducer (5-1); The host is used to send the required measurement tasks to the control module, and is also used to calculate the received Doppler signal to obtain the Doppler frequency shift and the three-dimensional velocity vector; The control module is used to control the transceiver module and the two-dimensional array ultrasonic transducer (5-1) to realize multiple pulse ultrasonic wave transceiver interactions according to the measurement task; The transceiver module is used to send the received echo signal to the pre-processing module; The preprocessing module is used to demodulate and filter the received ultrasonic waves and send the preprocessed ultrasonic waves to the acquisition module; The acquisition module is used to sample and obtain the Doppler signal required by the ultrasonic pulse repetition Doppler method, and send it to the host.

2. The full three-dimensional ultrasonic Doppler velocity measurement device based on phased array according to claim 1, characterized in that: Before the preprocessing module receives the ultrasonic wave, it is necessary to amplify the ultrasonic wave signal and perform A / D conversion.

3. The full three-dimensional ultrasonic Doppler velocimetry device based on phased array according to claim 1, characterized in that: The transceiver module includes a transmit beamformer, a three-level pulse generator, a transmit / receive switch and a receive amplifier stage; The transmit beamformer is used to control the phase difference between the array elements of the two-dimensional array ultrasonic transducer, thereby controlling the steering of the generated ultrasonic beam, and is also used to send a signal to the three-level pulse generator to apply voltage excitation to the array elements; The transmitting / receiving switch is used to realize the transmission and reception of ultrasonic waves; The receiving amplifier stage is used to amplify the received ultrasonic waves.

4. The full three-dimensional ultrasonic Doppler velocimetry device based on phased array according to claim 1, characterized in that: After emitting ultrasonic waves, the two-dimensional array ultrasonic transducer (5-1) switches to a receiving mode to receive echo signals, and then switches to a transmitting mode to continue emitting ultrasonic waves.

5. The full three-dimensional ultrasonic Doppler velocity measurement device based on phased array according to claim 4, characterized in that: The preprocessing module is used to convert the analog signal amplified by the receiving amplifier stage into a digital signal through an analog-to-digital converter, and is also used to perform orthogonal demodulation and low-pass filtering on the digital signal through FPGA, and send it to the acquisition module.

6. The full three-dimensional ultrasonic Doppler velocimetry device based on phased array according to claim 1, characterized in that: The three-dimensional velocity vectors at different positions are obtained through sector scanning, and finally a three-dimensional velocity field is formed.

7. The full three-dimensional ultrasonic Doppler velocity measurement device based on phased array according to claim 1, characterized in that: The two-dimensional array ultrasonic transducer (5-1) is composed of a plurality of ultrasonic units, and forms a rectangular planar array.

8. The full three-dimensional ultrasonic Doppler velocity measurement device based on phased array according to claim 7, characterized in that: Three square areas are divided on the two-dimensional array ultrasonic transducer (5-1) for receiving echo signals returned by tracer particles in the fluid, and each area contains a single or multiple ultrasonic units.

9. A velocity measurement method using the full three-dimensional ultrasonic Doppler velocity measurement device based on phased array according to claim 8, characterized in that: For a certain measuring point to be scanned, the specific method for measuring the three-dimensional velocity is as follows: Step 1: Establish a rectangular coordinate system with the center of the two-dimensional array ultrasonic transducer (5-1) as the origin, the x-axis and the y-axis being parallel to the two sides of the two-dimensional array ultrasonic transducer (5-1), and the z-axis being perpendicular to the two-dimensional array ultrasonic transducer (5-1); Step 2: Determine the coordinates of the center points and measuring points of the three echo receiving areas, and calculate the unit vector pointing to the center of the two-dimensional array ultrasonic transducer (5-1) The unit vector pointing from the measuring point to the center of the receiving area and Step 3: Send ultrasonic waves (frequency is f0) to the measuring point and receive echo signals, obtain IQ signals through orthogonal demodulation, and perform low-pass filtering on them to remove the original frequency of the transmitted ultrasonic waves; Step 4: Using the ultrasonic pulse repetition Doppler method to sample the signals received multiple times to form a Doppler signal; Step 5: Extract Doppler frequency shifts f2, f3 and f4 from the Doppler signal; Step 6: Calculate the 3D velocity based on the obtained Doppler shift For a single echo receiving area, the Doppler frequency shift calculation formula in the received Doppler signal is: in, is the unit vector of the receiving area corresponding to the Doppler frequency shift of the measuring point, c is the sound speed in the measuring fluid, and the calculation formula of the three-dimensional velocity can be obtained as follows:

10. The velocity measurement method using a full three-dimensional ultrasonic Doppler velocity measurement device based on a phased array according to claim 9, characterized in that: In step 5, the Doppler frequency shifts f2, f3 and f4 in the Doppler signal are extracted by fast Fourier transform.

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