Ultrasonic guided wave probe suitable for high-temperature liquid metal and acoustic parameter measuring method

Abstract

The invention provides an ultrasonic guided wave probe suitable for high-temperature liquid metal and an acoustic parameter measurement method, and the ultrasonic guided wave probe comprises PZT piezoelectric ceramic which is physically connected with a waveguide rod through a gel type coupling agent and achieves acoustic coupling; the surface of the bottom of the waveguide rod is coated with a DLC coating, the DLC coating is deposited through a vacuum evaporation coating technology, and the surface roughness meets the requirement of sound signal attenuation minimization; the heat dissipation device is arranged on the outer wall surface of the waveguide rod and used for controlling the temperature of the piezoelectric ceramics; the length of the waveguide rod is integer multiples of the wavelength of the sound wave and is optimized and determined by combining the heat dissipation requirement. According to the invention, conventional piezoelectric ceramic is used, and only a coupling agent, a section of stainless steel tube with a coating and matched air cooling heat dissipation are needed, so that ultrasonic measurement of high-temperature liquid metal can be realized; meanwhile, based on the probe design, the acoustic coupling effect of the waveguide rod and the liquid metal to be measured is considered, and a corrected attenuation coefficient measurement method is provided, so that the result is more accurate.

Description

Technical Field

[0001] The present invention relates to the technical field of ultrasonic guided wave probes, and specifically, to an ultrasonic guided wave probe applicable to high-temperature liquid metal and a method for measuring acoustic parameters. Background Art

[0002] In a liquid metal reactor in the fourth-generation advanced nuclear energy system, the state of the coolant (such as flow rate, whether it solidifies, etc.) is closely related to the normal operation state and safety issues of the reactor. Due to the opaque nature of liquid metal, common optical methods are not applicable to the observation of the internal behavior of liquid metal. In recent years, ultrasonic methods have begun to be applied to measure the flow rate and two-phase behavior (bubbles, solidification, etc.) in liquid metal. The application of ultrasonic methods first requires a suitable ultrasonic probe.

[0003] However, existing conventional ultrasonic probes often can only withstand temperatures of about 60°C - 70°C for a long time, while the coolant temperature in the reactor ranges from 400°C - 500°C. To improve the temperature resistance performance of the probe, a common method is to adopt guided wave technology. That is, a waveguide rod is added in front of the piezoelectric ceramic to ensure the transmission of acoustic signals while keeping the temperature of the piezoelectric sheet not exceeding the tolerance temperature. There are still relatively few types of ultrasonic probes applicable to high-temperature liquid metal.

[0004] At the same time, in ultrasonic measurement methods involving amplitude signals, such as transmission tomography, the attenuation coefficient is one of the most critical acoustic parameters. Accurate signal analysis is inseparable from accurate attenuation coefficients. Conventional attenuation coefficient measurement schemes do not consider the interface coupling effect. The surface tension of liquid metal is very large, and the acoustic coupling effect at the waveguide rod-liquid metal interface and the liquid metal-wall interface is not good, and this effect must be considered.

[0005] Therefore, it is necessary to develop a high-temperature ultrasonic guided probe applicable to liquid metal reactors and provide a more accurate method for measuring acoustic parameters as the basis for the application of ultrasonic technology in lead-based reactors.

[0006] Objective disadvantages of the prior art: (1) Conventional probes have low temperature resistance, and there are few design schemes for ultrasonic probes applicable to high-temperature environments of 400°C.

[0007] (2) The surface tension of liquid metals (such as lead, lead-bismuth alloy) used in reactors is significantly greater than that of water, and the wettability with conventional probes used in water-based environments is very poor, seriously affecting the propagation of acoustic signals.

[0008] (3) The sound wave propagation path of the ultrasonic guided wave probe passes through the waveguide rod-liquid metal interface and the liquid metal-wall interface. The acoustic coupling effects of these two interfaces will affect the acoustic signal. Existing solutions for measuring the attenuation coefficient of metals based on ultrasonic guided wave technology do not consider the coupling effects of the two interfaces. Especially in the environment of liquid metal with a large surface tension, there is often some air between the two interfaces, resulting in poor acoustic coupling effect and thus reducing the acoustic pressure amplitude. The traditional solutions do not consider this effect, and the measured attenuation coefficient of the liquid metal will be on the high side.

[0009] Patent application document CN117783273A discloses an ultrasonic imaging system applicable to high-temperature liquid metal, which includes N ultrasonic detection devices, where N≥2 and is a positive integer; the ultrasonic detection device includes a probe (1), a waveguide rod (2) and a connecting wire (3). The probe (1) is arranged at one end of the waveguide rod (2), and the other end of the waveguide rod (2) is installed on the pipeline. However, this patent cannot completely solve the existing technical problems and cannot meet the requirements of the present invention. Summary of the Invention

[0010] Aiming at the defects in the prior art, the purpose of the present invention is to provide an ultrasonic guided wave probe and an acoustic parameter measurement method applicable to high-temperature liquid metal.

[0011] The ultrasonic guided wave probe applicable to high-temperature liquid metal provided by the present invention includes: PZT piezoelectric ceramics, physically connected to the waveguide rod through a gel-type coupling agent to achieve acoustic coupling; The waveguide rod, whose bottom surface is coated with a DLC coating. The DLC coating is deposited by vacuum evaporation coating technology, and the surface roughness meets the requirement of minimizing the attenuation of the acoustic signal; A heat dissipation device arranged on the outer wall surface of the waveguide rod, used to control the temperature at the piezoelectric ceramics; The length of the waveguide rod is an integer multiple of the acoustic wavelength and is optimized and determined in combination with the heat dissipation requirements.

[0012] More specifically, an Ni coating is used instead of the DLC coating.

[0013] More specifically, the waveguide rod is made of 316L stainless steel or a Ti rod.

[0014] Preferably, the external cooling form of the waveguide rod adopts the top blowing air cooling or the wall surface water cooling method.

[0015] Preferably, the heat dissipation device is a fan, and its arrangement ensures that the temperature rise gradient of the waveguide rod meets the working temperature requirements of the piezoelectric ceramics.

[0016] Preferably, the roughness of the DLC coating is quantitatively controlled by a surface profiler to ensure that the attenuation of the acoustic signal caused by the voids between particles is lower than a preset threshold.

[0017] Preferably, the temperature at the piezoelectric ceramic is controlled by the heat dissipation device to be lower than 60 °C.

[0018] According to the method for measuring acoustic parameters of an ultrasonic guided wave probe applicable to high-temperature liquid metal provided by the present invention, the determination process of the attenuation coefficient of the liquid metal to be measured is as follows: When sound waves propagate to the interface between two different media, reflection, transmission, or diffraction of the sound waves occurs. The strength of the reflection and transmission effects on the interface is determined by the acoustic impedance:

[0019] Among them, is the density of the medium, is the speed of sound in the medium, and Z is the acoustic impedance; Using the reflection coefficient and the transmission coefficient to represent the ratios of the sound pressures of the reflected sound wave and the transmitted sound wave to the original sound pressure. When the sound wave propagates from stainless steel to the liquid metal to be measured and no diffraction occurs, it is expressed as:

[0020]

[0021] Among them, and are the acoustic impedances of stainless steel and the liquid metal to be measured, respectively; When the ultrasonic wave propagates to the bottom of the waveguide rod in the waveguide rod, the amplitude of the sound pressure after attenuation can be calculated by the following formula:

[0022] Among them, is the excitation sound pressure of the piezoelectric ceramic; is the attenuation coefficient of the waveguide rod; is the length of the waveguide rod.

[0023] Assume that the attenuation coefficient of the liquid metal to be measured is . When measuring , due to the huge surface tension of the liquid metal, the influence of the acoustic coupling effect (wetting effect) between the coating surface and the liquid metal on the acoustic attenuation must be considered. Take the wetting coefficient of the coating and the liquid metal as , and define the transmission coefficient at the waveguide rod-liquid metal interface considering the wetting effect as:

[0024] When takes 1, it indicates good wetting; when is 0, it indicates extremely poor wetting; Take the wetting coefficient between the uncoated stainless steel waveguide rod and the liquid metal as .

[0025] Then the sound pressure of the first echo at the waveguide rod-liquid metal interface is:[[]]

[0026] The sound pressure of the first echo at the bottom of the metal molten pool is:[[]]

[0027] Where h is the thickness of the liquid metal; Then the sound pressure ratio is:[[]]

[0028] Then the attenuation coefficient of the liquid metal to be measured is:[[]] .

[0029] Preferably, the calibration process of the wetting coefficient between the coating and the liquid metal is as follows:[[]] Place the probe with guided waves in the air to obtain the amplitude of the sound pressure of the first echo at the waveguide rod-air interface:[[]]

[0030] Place the probe in the liquid metal to be measured to obtain the amplitude of the sound pressure of the first echo at the waveguide rod-liquid metal interface:[[]]

[0031] Solve simultaneously to obtain:[[]]

[0032] Then the wetting coefficient is:[[]] .

[0033] Similarly, the wetting coefficient between the uncoated stainless steel waveguide rod and the liquid metal is:[[]]

[0034] Where is the amplitude of the sound pressure of the first echo at the uncoated stainless steel waveguide rod-liquid metal interface, is the amplitude of the sound pressure of the first echo at the uncoated stainless steel waveguide rod-air interface, and The measurement methods of and are the same as the above measurement

[0035] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention proposes an ultrasonic guided wave technology applicable to high-temperature liquid metals. Using conventional piezoelectric ceramics, only a coupling agent, a section of stainless steel pipe with a coating, and supporting air-cooled heat dissipation are required to be used for ultrasonic measurement of high-temperature liquid metals; (2) The present invention takes into account the acoustic coupling effect (wettability) between the waveguide rod and the liquid metal to be measured, and proposes a modified attenuation coefficient measurement method to make the results more accurate. Description of the Drawings

[0036] By reading the following detailed description of non-limiting embodiments with reference to the accompanying drawings, other features, objects, and advantages of the present invention will become more apparent: Figure 1 It is a schematic diagram of sound signal propagation; Figure 2 It is a determination process of the wetting coefficient. Detailed Embodiments

[0037] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several changes and improvements can still be made. These all belong to the protection scope of the present invention.

[0038] Embodiment The present invention proposes a design scheme for an ultrasonic guided wave probe applicable to high-temperature liquid metals. In this scheme, conventional PZT piezoelectric ceramics are used, and physical connection and acoustic coupling are achieved by applying a gel-type coupling agent between the waveguide rod and pressing and curing. At the same time, 316L stainless steel is used as the waveguide rod material and a coating is applied at the bottom. A DLC coating (Diamond-Like Carbon coating) is deposited on the stainless steel surface through vacuum evaporation coating technology. The DLC coating has good wettability with liquid metals, and the roughness is controlled as small as possible (quantifiable) to minimize the attenuation of sound signals due to the existence of voids between coating particles. The outer wall surface of the stainless steel waveguide rod is cooled by a fan. The length of the waveguide rod is taken as an integer multiple of the acoustic wavelength, and the optimal length is selected in combination with the heat dissipation situation (so that the temperature at the piezoelectric ceramic is lower than 60 °C). More specifically, the type of coating can be replaced, such as using a Ni coating, etc.

[0039] More specifically, the waveguide rod can also be replaced with a Ti rod, etc.

[0040]

[0041] ​Preferably, the external cooling of the waveguide rod has various forms. Top blowing air cooling in the schematic diagram can be adopted, or wall surface water cooling and other methods can be used.

[0042] As Figure 2 , the present invention proposes a method for determining the attenuation coefficient of a liquid metal to be measured considering the interface acoustic coupling effect, including: When sound waves propagate to the interface of two different media, due to the difference in acoustic properties, reflection, transmission, or diffraction of sound waves will occur. As Figure 1 , it is a schematic diagram of sound signal propagation. Among them, is the sound pressure before the first propagation to the coating, is the sound pressure after the first rebound through the coating, is the sound pressure after the first penetration through the coating, is the sound pressure before the first propagation to the stainless steel wall surface, is the sound pressure after the first rebound through the stainless steel wall surface, is the sound pressure before the first propagation to the coating after the first rebound through the stainless steel wall surface, is the sound pressure after the second penetration through the coating.

[0043] The strength of the reflection and transmission effects on the interface is determined by the acoustic impedance:

[0044] Among them, is the medium density, is the sound speed in this medium, and Z is the acoustic impedance.

[0045] The commonly used reflection coefficient and transmission coefficient represent the ratio of the sound pressure of the reflected sound wave and the transmitted sound wave to the original sound pressure. When the sound wave propagates from stainless steel to the liquid metal to be measured and there is no diffraction, they can be expressed as:

[0046]

[0047] Among them, and are the acoustic impedances of stainless steel and the liquid metal to be measured respectively.

[0048] When the ultrasonic wave propagates to the bottom of the waveguide rod in the waveguide rod, the amplitude of the attenuated sound pressure can be calculated by the following formula:

[0049] Among them, is the excitation sound pressure of the piezoelectric ceramic; is the attenuation coefficient of the waveguide rod; is the length of the waveguide rod.

[0050] Assume that the attenuation coefficient of the liquid metal to be measured is . During the measurement , due to the huge surface tension of the liquid metal, the influence of the acoustic coupling effect (wetting effect) between the coating surface and the liquid metal on the acoustic attenuation must be considered.

[0051] Take the wetting coefficient of the coating and the liquid metal as , then the transmission coefficient at the waveguide rod-liquid metal interface considering the wetting effect is defined as:

[0052] The meaning of this definition is that when takes 1, the wetting is good; when is 0, it means the wetting is extremely poor.

[0053] Similarly, take the wetting coefficient between the stainless steel waveguide rod without coating and the liquid metal as .

[0054] Then the acoustic pressure of the first echo at the waveguide rod-liquid metal interface is:

[0055] The acoustic pressure of the first echo at the bottom of the metal molten pool is:

[0056] where h is the thickness of the liquid metal; Therefore, the acoustic pressure ratio is:

[0057] So the attenuation coefficient of the liquid metal to be measured is: .

[0058] Regarding the calibration process is as follows: Place the probe with guided waves in the air to obtain the amplitude of the acoustic pressure of the first echo at the waveguide rod-air interface:

[0059] Place the probe in the liquid metal to be measured to obtain the amplitude of the acoustic pressure of the first echo at the waveguide rod-liquid metal interface:

[0060] Solve simultaneously to get:

[0061] So the wetting coefficient is:

[0062] Among them, and are all values measured in the experiment.

[0063] Similarly, the wetting coefficient between the stainless steel waveguide rod without coating and the liquid metal is:

[0064] Among them, is the amplitude of the first echo sound pressure at the stainless steel waveguide rod - liquid metal interface without coating, is the amplitude of the first echo sound pressure at the stainless steel waveguide rod - air interface without coating, and The measurement methods of and are the same as the above-mentioned measurement

[0065] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application.

[0066] Those skilled in the art know that in addition to implementing the systems, devices and their respective modules provided by the present invention in the form of pure computer-readable program code, the method steps can be logically programmed to enable the systems, devices and their respective modules provided by the present invention to be implemented in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, embedded microcontrollers, etc. to achieve the same program. Therefore, the systems, devices and their respective modules provided by the present invention can be regarded as a kind of hardware component, and the modules included therein for implementing various programs can also be regarded as the structure within the hardware component; the modules for implementing various functions can also be regarded as either software programs for implementing the method or the structure within the hardware component.

[0067] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Without conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. An ultrasonic guided wave probe applicable to high-temperature liquid metal, characterized in that, Including: A PZT piezoelectric ceramic, physically connected to a waveguide rod through a gel-type couplant to achieve acoustic coupling; The waveguide rod, whose bottom surface is coated with a DLC coating, the DLC coating is deposited by vacuum evaporation coating technology, and the surface roughness meets the requirement of minimizing the attenuation of acoustic signals; A heat dissipation device provided on the outer wall surface of the waveguide rod for controlling the temperature at the piezoelectric ceramic; The length of the waveguide rod is an integer multiple of the acoustic wavelength and is optimized and determined in combination with the heat dissipation requirements.

2. The ultrasonic guided wave probe applicable to high-temperature liquid metal according to claim 1, characterized in that Use a Ni coating instead of a DLC coating.

3. The ultrasonic guided wave probe applicable to high-temperature liquid metal according to claim 1, characterized in that, The waveguide rod is made of 316L stainless steel or a Ti rod.

4. The ultrasonic guided wave probe applicable to high-temperature liquid metal according to claim 1, wherein The external cooling form of the waveguide rod adopts top blowing air cooling or wall surface water cooling.

5. The ultrasonic guided wave probe applicable to high-temperature liquid metal according to claim 1, wherein The heat dissipation device is a fan, and its arrangement ensures that the temperature rise gradient of the waveguide rod meets the working temperature requirements of the piezoelectric ceramic.

6. The ultrasonic guided wave probe applicable to high-temperature liquid metal according to claim 1, wherein The roughness of the DLC coating is quantitatively controlled by a surface profiler to ensure that the attenuation of the acoustic signal by the voids between particles is lower than a preset threshold.

7. The ultrasonic guided wave probe applicable to high-temperature liquid metal according to claim 1, characterized in that, The heat dissipation device controls the temperature at the piezoelectric ceramic to be lower than 60 °C.

8. A method for measuring acoustic parameters of an ultrasonic guided wave probe applicable to high-temperature liquid metal according to any one of claims 1 to 7, characterized in that, The determination process of the attenuation coefficient of the liquid metal to be measured is as follows: When the acoustic wave propagates to the interface of two different media, the reflection, transmission or diffraction of the acoustic wave occurs, and the strength of the reflection and transmission effects on the interface is determined by the acoustic impedance: wherein, is the medium density, is the speed of sound in the medium; Z is the acoustic impedance; Using the reflection coefficient and the transmission coefficient to represent the ratios of the sound pressures of the reflected and transmitted sound waves to the original sound pressure. When the sound wave propagates from stainless steel to the liquid metal to be measured without diffraction, it is expressed as: Among them, and are the acoustic impedances of the stainless steel and the liquid metal to be measured, respectively. When the ultrasonic wave propagates in the waveguide rod to the bottom of the waveguide rod, the amplitude of the sound pressure after attenuation is as follows: Among them, is the excitation sound pressure of the piezoelectric ceramic; is the attenuation coefficient of the waveguide rod; is the propagation distance in the medium; Denote the attenuation coefficient of the liquid metal to be measured as , and take the wetting coefficient of the coating and the liquid metal as . Then the transmission coefficient at the waveguide rod-liquid metal interface considering the wetting effect is defined as: When taking 1, it indicates good wetting; when is 0, it indicates extremely poor wetting; Take the wetting coefficient between the stainless steel waveguide rod without coating and the liquid metal as ; Then the sound pressure of the first echo at the waveguide rod-liquid metal interface is: The sound pressure of the first echo at the bottom of the metal molten pool is: Where h is the thickness of the liquid metal; Then the sound pressure ratio is: The attenuation coefficient of the liquid metal to be measured is as follows: 。 9. The method for measuring acoustic parameters of an ultrasonic guided wave probe applicable to high-temperature liquid metal according to claim 8, characterized in that, Wetting coefficient between the coating and the liquid metal and the wetting coefficient between the stainless steel waveguide rod without coating and the liquid metal are calibrated as follows: Place the probe with guided waves in the air to obtain the amplitude of the sound pressure of the first echo at the waveguide rod-air interface: Place the probe in the liquid metal to be measured to obtain the amplitude of the sound pressure of the first echo at the waveguide rod-liquid metal interface: Solve simultaneously to obtain: The wetting coefficient is as follows: Similarly, the wetting coefficient between the stainless steel waveguide rod without coating and the liquid metal is as follows: Among them, is the sound pressure amplitude of the first echo at the stainless steel waveguide rod-liquid metal interface without coating, is the sound pressure amplitude of the first echo at the stainless steel waveguide rod-air interface without coating, and The measurement methods of and are the same as the above measurement

Images