Ultrasonic guided wave probe applicable to high-temperature liquid metal and acoustic parameter measurement method

Abstract

The present invention provides an ultrasonic waveguide probe and acoustic parameter measurement method suitable for high-temperature liquid metal, comprising: a PZT piezoelectric ceramic, which is physically connected to a waveguide rod via a gel-type coupling agent to achieve acoustic coupling; a waveguide rod, the bottom surface of which is coated with a DLC coating, the DLC coating being deposited by vacuum evaporation coating technology, and the surface roughness meeting the requirement of minimizing acoustic signal attenuation; a heat dissipation device provided on the outer wall of the waveguide rod, for controlling the temperature of the piezoelectric ceramic; the length of the waveguide rod is an integer multiple of the wavelength of the acoustic wave and is optimized and determined in combination with the heat dissipation requirements. The present invention uses conventional piezoelectric ceramics and only requires a coupling agent, a coated stainless steel tube, and supporting air cooling to be used for ultrasonic measurement of high-temperature liquid metal. At the same time, based on the probe design and considering the acoustic coupling effect between the waveguide rod and the liquid metal to be measured, a modified attenuation coefficient measurement method is proposed to make the results more accurate.

Description

Technical Field

[0001] The present invention relates to the technical field of ultrasonic guided wave probes, and in particular to an ultrasonic guided wave probe suitable for high-temperature liquid metal and an acoustic parameter measurement method. Background Art

[0002] In liquid metal reactors (LIMRs) within fourth-generation advanced nuclear energy systems, the coolant's state (e.g., flow rate, solidification, etc.) is crucial to reactor operation and safety. Due to the opaque nature of liquid metal, conventional optical methods are unsuitable for observing its internal behavior. In recent years, ultrasonic methods have begun to be applied to measure flow rates and two-phase behavior (bubbles, solidification, etc.) within liquid metals. Application of ultrasonic methods primarily requires suitable ultrasonic probes.

[0003] However, existing conventional ultrasonic probes typically only withstand temperatures around 60°C-70°C for extended periods, while reactor coolant temperatures range from 400°C-500°C. To improve probe temperature resistance, a common approach is to use guided wave technology. This involves adding a waveguide rod in front of the piezoelectric ceramic to ensure acoustic signal transmission while keeping the piezoelectric ceramic's temperature below its rated operating temperature. However, there are still relatively few ultrasonic probe models suitable for high-temperature liquid metals.

[0004] Furthermore, 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 requires an accurate attenuation coefficient. Conventional attenuation coefficient measurement schemes fail to account for interfacial coupling effects. Liquid metal has a high surface tension, resulting in poor acoustic coupling between the waveguide rod and liquid metal, and between the liquid metal and the wall, making this effect essential.

[0005] Therefore, it is necessary to develop high-temperature ultrasonic waveguide probes suitable for liquid metal reactors and provide more accurate measurement methods of acoustic parameters as the basis for the application of ultrasonic technology in lead-based reactors.

[0006] Objective shortcomings of existing technologies:

[0007] (1) Conventional probes have low temperature resistance, and there are few ultrasonic probe designs suitable for high-temperature environments of 400°C.

[0008] (2) The surface tension of liquid metals used in reactors (such as lead and lead-bismuth alloys) is significantly greater than that of water, and their wettability with conventional probes used in water-based environments is very poor, which seriously affects the propagation of acoustic signals.

[0009] (3) The acoustic 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 effect 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 effect of the two interfaces. Especially in liquid metal environments with high surface tension, there is often some air between the two interfaces, resulting in poor acoustic coupling and a reduction in the sound pressure amplitude. Traditional solutions do not take this effect into account, and the measured attenuation coefficient of liquid metal will be too high.

[0010] Patent application document CN117783273A discloses an ultrasonic imaging system suitable for high-temperature liquid metal, comprising N ultrasonic detection devices, where N is a positive integer and is greater than or equal to 2; the ultrasonic detection devices comprise a probe (1), a waveguide rod (2), and a connecting line (3); the probe (1) is disposed at one end of the waveguide rod (2), and the other end of the waveguide rod (2) is mounted on a pipeline. However, this patent cannot completely solve the existing technical problems, nor can it meet the requirements of the present invention. Summary of the Invention

[0011] In view of 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 suitable for high-temperature liquid metal.

[0012] The ultrasonic guided wave probe suitable for high-temperature liquid metal provided by the present invention comprises:

[0013] PZT piezoelectric ceramics are physically connected to the waveguide rod through a gel-type coupling agent to achieve acoustic coupling;

[0014] The bottom surface of the waveguide rod is coated with a DLC coating, wherein the DLC coating is deposited by vacuum evaporation coating technology and has a surface roughness that meets the requirement of minimizing acoustic signal attenuation;

[0015] A heat sink provided on the outer wall of the waveguide rod is used to control the temperature of the piezoelectric ceramics;

[0016] The length of the waveguide rod is an integer multiple of the wavelength of the sound wave and is optimized and determined in combination with heat dissipation requirements.

[0017] More specifically, a Ni coating is used instead of a DLC coating.

[0018] More specifically, the waveguide rod is made of 316L stainless steel or Ti rod.

[0019] Preferably, the external cooling form of the waveguide rod adopts top-blown air cooling or wall-surface water cooling.

[0020] Preferably, the heat dissipation device is a fan, and its arrangement ensures that the temperature rise gradient of the waveguide rod meets the operating temperature requirement of the piezoelectric ceramic.

[0021] Preferably, the roughness of the DLC coating is quantitatively controlled by a surface morphology analyzer to ensure that the attenuation of the acoustic signal by the gaps between the particles is lower than a preset threshold.

[0022] Preferably, the heat dissipation device controls the temperature of the piezoelectric ceramic to be lower than 60°C.

[0023] According to the acoustic parameter measurement method of the ultrasonic guided wave probe applicable to high-temperature liquid metal provided by the present invention, the attenuation coefficient of the liquid metal to be measured is determined as follows:

[0024] When sound waves propagate to the interface between two different media, they are reflected, transmitted, or diffracted. The strength of the reflection and transmission effects on the interface is determined by the acoustic impedance:

[0025]

[0026] in, is the medium density, is the speed of sound in the medium, Z is the acoustic impedance;

[0027] Using the reflection coefficient and transmission coefficient It represents 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 the stainless steel to the liquid metal to be tested and no diffraction occurs, it is expressed as:

[0028]

[0029]

[0030] in, and are the acoustic impedances of stainless steel and the liquid metal to be tested;

[0031] When the ultrasonic wave propagates in the waveguide rod and reaches the bottom of the waveguide rod, the attenuated sound pressure amplitude It can be calculated using the following formula:

[0032]

[0033] in, is the exciting sound pressure of the piezoelectric ceramic; is the attenuation coefficient of the waveguide rod; is the waveguide rod length.

[0034] Assume that the attenuation coefficient of the liquid metal to be measured is When measuring When the acoustic attenuation is affected by the huge surface tension of the liquid metal, the acoustic coupling effect (wetting effect) between the coating surface and the liquid metal must be considered. The wetting coefficient of the coating and the liquid metal is , the transmission coefficient at the waveguide rod-liquid metal interface considering the wetting effect is defined as:

[0035]

[0036] when When it is 1, it means good wetting; when When it is 0, it means that the wetting is very poor;

[0037] The wetting coefficient between the uncoated stainless steel waveguide rod and the liquid metal is .

[0038] Then the primary echo sound pressure at the waveguide rod-liquid metal interface is:

[0039]

[0040] The primary echo sound pressure at the bottom of the molten metal pool is:

[0041]

[0042] Where h is the thickness of liquid metal;

[0043] Then the sound pressure ratio is:

[0044]

[0045] The attenuation coefficient of the liquid metal to be measured is for:

[0046] .

[0047] Preferably, the wettability of the coating to the liquid metal is The calibration process is as follows:

[0048] Place the probe with waveguide in the air and obtain the primary echo sound pressure amplitude at the waveguide rod-air interface:

[0049]

[0050] Place the probe in the liquid metal to be tested and obtain the primary echo sound pressure amplitude at the waveguide rod-liquid metal interface:

[0051]

[0052] The combined solution is:

[0053]

[0054] The wetting coefficient for:

[0055] .

[0056] Similarly, the wetting coefficient between the uncoated stainless steel waveguide rod and the liquid metal is for:

[0057]

[0058] in, is the primary echo sound pressure amplitude of the uncoated stainless steel waveguide rod-liquid metal interface, is the primary echo sound pressure amplitude at the uncoated stainless steel waveguide rod-air interface, and The measurement method is the same as the above measurement and The method is the same.

[0059] Compared with the prior art, the present invention has the following beneficial effects:

[0060] (1) The present invention proposes an ultrasonic guided wave technology suitable for high-temperature liquid metals. It uses conventional piezoelectric ceramics and only requires a coupling agent, a coated stainless steel tube, and supporting air cooling to be used for ultrasonic measurement of high-temperature liquid metals.

[0061] (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 result more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0063] Figure 1 Schematic diagram of acoustic signal propagation;

[0064] Figure 2 The process for determining the wetting coefficient. DETAILED DESCRIPTION

[0065] The present invention will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several changes and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0066] Example

[0067] This invention proposes a design scheme for ultrasonic waveguide probes suitable for high-temperature liquid metals. In this scheme, conventional PZT piezoelectric ceramics are used, and a gel-type coupling agent is applied and pressed to solidify the waveguide rod to achieve physical connection and acoustic coupling. At the same time, 316L stainless steel is used as the waveguide rod material and a coating is applied to the bottom. A DLC coating (Diamond-Like Carbon) is deposited on the stainless steel surface through vacuum evaporation coating technology. The DLC coating has good wettability with liquid metal and the roughness is kept as small as possible (can be used). quantification) to minimize acoustic signal attenuation caused by gaps between coating particles. A fan dissipates heat from the outer surface of the stainless steel waveguide rod. The waveguide rod length is an integer multiple of the acoustic wavelength, and the optimal length is selected based on heat dissipation requirements (keeping the temperature at the piezoelectric ceramic below 60°C).

[0068] More specifically, the coating type can be changed, such as using Ni coating.

[0069] More specifically, the waveguide rod can also be replaced with a Ti rod or the like.

[0070] Preferably, the external cooling of the waveguide rod is in various forms, and can adopt top-blown air cooling as shown in the schematic diagram, or wall-surface water cooling and the like.

[0071] like Figure 2 The present invention proposes a method for determining the attenuation coefficient of the liquid metal to be measured taking into account the interface acoustic coupling effect, comprising:

[0072] When sound waves propagate to the interface between two different media, reflection, transmission or diffraction of the sound waves will occur due to the difference in acoustic properties. Figure 1 , is a schematic diagram of acoustic signal propagation. is the sound pressure before it first propagates to the coating, is the sound pressure after the first rebound of the coating, is the sound pressure after passing through the coating for the first time, It is the sound pressure before it reaches the stainless steel wall for the first time. It is the sound pressure after rebounding from the stainless steel wall for the first time. It is the sound pressure that bounces off the stainless steel wall and propagates to the coating for the first time. is the sound pressure after passing through the coating for the second time.

[0073] The strength of the reflection and transmission effects at the interface is determined by the acoustic impedance:

[0074]

[0075] in, is the medium density, is the speed of sound in the medium, and Z is the acoustic impedance.

[0076] Common reflection coefficients and transmission coefficient It represents 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 the stainless steel to the liquid metal to be tested and no diffraction occurs, they can be expressed as:

[0077]

[0078]

[0079] in, and are the acoustic impedances of stainless steel and the liquid metal to be measured respectively.

[0080] When the ultrasonic wave propagates in the waveguide rod and reaches the bottom of the waveguide rod, the attenuated sound pressure amplitude It can be calculated using the following formula:

[0081]

[0082] in, is the exciting sound pressure of the piezoelectric ceramic; is the attenuation coefficient of the waveguide rod; is the waveguide rod length.

[0083] Assume that the attenuation coefficient of the liquid metal to be measured is When measuring When applying the coating, due to the huge surface tension of the liquid metal, the effect of the acoustic coupling effect (wetting effect) between the coating surface and the liquid metal on the sound attenuation must be considered.

[0084] The wetting coefficient between the coating and the liquid metal is , then the transmission coefficient at the waveguide rod-liquid metal interface considering the wetting effect is defined as:

[0085]

[0086] This definition means that when When 1 is taken, the wetting is good; when When it is 0, it means that the wetting is very poor.

[0087] Similarly, the wetting coefficient between the uncoated stainless steel waveguide rod and the liquid metal is .

[0088] Then the primary echo sound pressure at the waveguide rod-liquid metal interface is:

[0089]

[0090] The primary echo sound pressure at the bottom of the molten metal pool is:

[0091]

[0092] Where h is the thickness of liquid metal;

[0093] Therefore, the sound pressure ratio is:

[0094]

[0095] Therefore, the attenuation coefficient of the liquid metal to be measured is for:

[0096] .

[0097] about The calibration process is as follows:

[0098] Place the probe with waveguide in the air and obtain the primary echo sound pressure amplitude at the waveguide rod-air interface:

[0099]

[0100] Place the probe in the liquid metal to be tested and obtain the primary echo sound pressure amplitude at the waveguide rod-liquid metal interface:

[0101]

[0102] The combined solution is:

[0103]

[0104] So the wetting coefficient for:

[0105]

[0106] in, and These are all values measured in experiments.

[0107] Similarly, the wetting coefficient between the uncoated stainless steel waveguide rod and the liquid metal is for:

[0108]

[0109] in, is the primary echo sound pressure amplitude of the uncoated stainless steel waveguide rod-liquid metal interface, is the primary echo sound pressure amplitude at the uncoated stainless steel waveguide rod-air interface, and The measurement method is the same as the above measurement and The method is the same.

[0110] In the description of this application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application.

[0111] Those skilled in the art will appreciate that, in addition to implementing the system, device, and various modules provided by the present invention in purely computer-readable program code, it is entirely possible to implement the same program in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, embedded microcontrollers, and the like by logically programming the method steps. Therefore, the system, device, and various modules provided by the present invention can be considered a hardware component, and the modules included therein for implementing various programs can also be considered structures within the hardware component; the modules for implementing various functions can also be considered both software programs for implementing the method and structures within the hardware component.

[0112] The above describes specific embodiments of the present invention. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. The embodiments of this application and the features in the embodiments may be combined with each other in any manner unless there is a conflict.

Claims

1. A method for measuring acoustic parameters of an ultrasonic guided wave probe suitable for high-temperature liquid metal, characterized in that: Use ultrasonic guided wave probes suitable for high-temperature liquid metals, including: PZT piezoelectric ceramics are physically connected to the waveguide rod through a gel-type coupling agent to achieve acoustic coupling; The bottom surface of the waveguide rod is coated with a DLC coating or a Ni coating, wherein the DLC coating is deposited by vacuum evaporation coating technology and the surface roughness meets the requirement of minimizing acoustic signal attenuation; A heat sink provided on the outer wall of the waveguide rod is used to control the temperature of the piezoelectric ceramics; The length of the waveguide rod is an integral multiple of the wavelength of the sound wave; The waveguide rod is made of 316L stainless steel or Ti rod; The external cooling form of the waveguide rod adopts top-blown air cooling or wall-surface water cooling; The roughness of the DLC coating is quantitatively controlled by a surface topography analyzer to ensure that the attenuation of the acoustic signal by the gaps between the particles is lower than a preset threshold; The heat dissipation device controls the temperature of the piezoelectric ceramic to be lower than 60°C; The process of determining the attenuation coefficient of the liquid metal to be measured is: When sound waves propagate to the interface between two different media, they are reflected, transmitted, or diffracted. The strength of the reflection and transmission effects on the interface is determined by the acoustic impedance: in, is the medium density, is the speed of sound in the medium; Z is the acoustic impedance; Using the reflection coefficient and transmission coefficient It represents 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 the stainless steel to the liquid metal to be tested and no diffraction occurs, it is expressed as: in, and are the acoustic impedances of stainless steel and the liquid metal to be tested; When the ultrasonic wave propagates in the waveguide rod and reaches the bottom of the waveguide rod, the attenuated sound pressure amplitude for: in, is the exciting sound pressure of the piezoelectric ceramic; is the attenuation coefficient of the waveguide rod; is the distance traveled in the medium; The attenuation coefficient of the liquid metal to be measured is , the wetting coefficient between the coating and the liquid metal is , then the transmission coefficient at the waveguide rod-liquid metal interface considering the wetting effect is defined as: when When it is 1, it means good wetting; when When it is 0, it means that the wetting is very poor; The wetting coefficient between the uncoated stainless steel waveguide rod and the liquid metal is ; Then the primary echo sound pressure at the waveguide rod-liquid metal interface is: The primary echo sound pressure at the bottom of the molten metal pool is: Where h is the thickness of liquid metal; Then the sound pressure ratio is: The attenuation coefficient of the liquid metal to be measured is for: ； Wetting coefficient of coating and liquid metal and the wetting coefficient between the uncoated stainless steel waveguide rod and the liquid metal The calibration process is as follows: Place the probe with waveguide in the air and obtain the primary echo sound pressure amplitude at the waveguide rod-air interface: Place the probe in the liquid metal to be tested and obtain the primary echo sound pressure amplitude at the waveguide rod-liquid metal interface: The combined solution is: The wetting coefficient for: Wetting coefficient between uncoated stainless steel waveguide rod and liquid metal for: in, is the primary echo sound pressure amplitude of the uncoated stainless steel waveguide rod-liquid metal interface, is the primary echo sound pressure amplitude at the uncoated stainless steel waveguide rod-air interface, and The measurement method is the same as the above measurement and The method is the same.

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