Acoustic emission probe for gas turbine blade crack detection

Abstract

This utility model discloses an acoustic emission probe for detecting cracks in gas turbine blades, relating to the field of acoustic emission probe technology. It includes an electromagnetic shielding shell, with a layered sensing unit disposed on the top of the inner wall of the shell. The layered sensing unit comprises a lithium niobate piezoelectric single crystal wafer, a porous zirconia buffer layer, and an aluminum nitride coupling layer. The lithium niobate piezoelectric single crystal wafer, the porous zirconia buffer layer, and the aluminum nitride coupling layer are connected by vacuum diffusion welding. The polarization direction of the lithium niobate piezoelectric single crystal wafer is perpendicular to the blade surface. A curved adaptive substrate is disposed at the bottom of the aluminum nitride coupling layer. The lithium niobate piezoelectric single crystal wafer can still function normally at high temperatures. Vacuum diffusion welding prevents adhesive layer failure. The curved adaptive substrate perfectly fits the blade surface with different curvatures, ensuring the long-term stability and reliability of the probe.

Description

Technical Field

[0001] This utility model relates to the field of acoustic emission probe technology, specifically to an acoustic emission probe for detecting cracks in gas turbine blades. Background Technology

[0002] Currently, gas turbine blade crack detection primarily employs acoustic emission technology, capturing the elastic waves released during crack propagation by mounting a piezoelectric acoustic emission probe on the blade surface. Traditional probes use a single piezoelectric ceramic element (such as PZT) as the sensing core, directly bonded to the blade surface with a high-temperature adhesive. To withstand high-temperature environments, an alumina ceramic heat insulation layer is typically wrapped around the outer shell, and a nickel-based alloy casing provides basic protection. Signal transmission uses a high-temperature coaxial cable connected to the acquisition system via an external amplifier. However, in high-temperature environments (>500℃), the piezoelectric material undergoes thermal depolarization, causing a sharp drop in sensitivity, making it difficult to accurately capture crack signals. Furthermore, the adhesive ages and easily detaches, affecting detection stability. Therefore, we propose an acoustic emission probe for gas turbine blade crack detection. Summary of the Invention

[0003] The purpose of this invention is to address the problems of traditional probes that use a single piezoelectric ceramic sheet (such as PZT) as the sensing core, directly bonded to the blade surface with high-temperature adhesive. To withstand high-temperature environments, an alumina ceramic heat insulation layer is typically wrapped around the outer shell, and a nickel-based alloy shell provides basic protection. Signal transmission uses a high-temperature coaxial cable connected to the acquisition system via an external amplifier. However, in high-temperature environments (>500℃), the piezoelectric material undergoes thermal depolarization, resulting in a sharp drop in sensitivity, making it difficult to accurately capture crack signals. Furthermore, the adhesive ages and easily detaches, affecting detection stability. This invention provides an acoustic emission probe for detecting cracks in gas turbine blades.

[0004] To achieve the above objectives, this utility model specifically adopts the following technical solution:

[0005] An acoustic emission probe for detecting cracks in gas turbine blades includes an electromagnetic shielding shell. A layered sensing unit is disposed on the top of the inner wall of the electromagnetic shielding shell. The layered sensing unit includes a lithium niobate piezoelectric single crystal, a porous zirconia buffer layer, and an aluminum nitride coupling layer. The lithium niobate piezoelectric single crystal, the porous zirconia buffer layer, and the aluminum nitride coupling layer are connected by vacuum diffusion welding. The polarization direction of the lithium niobate piezoelectric single crystal is perpendicular to the blade surface. A curved adaptive substrate is disposed at the bottom of the aluminum nitride coupling layer.

[0006] Furthermore, the porous zirconia buffer layer has a porosity of 40%-60%, a pore size gradient distribution from 50μm on the surface to 200μm on the bottom layer, and is embedded with serpentine microchannels in which liquid gallium-indium alloy circulates.

[0007] Furthermore, the aluminum nitride coupling layer has a pyramid-shaped micro-bump array processed on its surface, and the top of the aluminum nitride coupling layer is plated with a gold film, and the gaps between the micro-bumps on the surface of the aluminum nitride coupling layer are filled with liquid gallium indium tin alloy.

[0008] Furthermore, the curved adaptive substrate is a nickel-titanium shape memory alloy sheet, and a honeycomb microstructure is formed on the nickel-titanium shape memory alloy sheet by laser etching, and the microstructure is filled with high-temperature silicone oil gel.

[0009] Furthermore, the electromagnetic shielding shell comprises an inner Invar alloy layer, a middle alumina insulating layer, and an outer Hastelloy alloy layer, wherein the Invar alloy, the alumina insulating layer, and the Hastelloy alloy are fixed by a hot isostatic pressing composite connection.

[0010] Furthermore, the outer wall of the electromagnetic shielding shell is fitted with a mechanical protective sleeve, and the outer wall of the mechanical protective sleeve is evenly distributed with multiple turns of silicon carbide ceramic anti-collision rings.

[0011] Furthermore, the bottom of the electromagnetic shielding shell is threaded with a compression thread plug, and the upper end of the compression thread plug abuts against the bottom of the curved adaptive base. A conduit is provided at the bottom of the compression thread plug, and the signal transmission line of the layered sensing unit passes through the conduit.

[0012] The beneficial effects of this utility model are as follows:

[0013] 1. The acoustic emission signal generated by the gas turbine blades of this invention is transmitted to an aluminum nitride coupling layer via a curved adaptive substrate. Due to its excellent acoustic impedance matching characteristics, the aluminum nitride coupling layer effectively reduces energy loss during sound wave transmission. Next, the sound wave enters a porous zirconia buffer layer, designed to further smooth the sound wave signal and reduce noise interference. Finally, the sound wave signal is received by a lithium niobate piezoelectric single crystal wafer. Due to its excellent piezoelectric effect, the sound wave signal is converted into an electrical signal. This electrical signal is then processed and analyzed to accurately determine whether a crack exists in the gas turbine blade and its specific location. Throughout the process, the electromagnetic shielding shell effectively shields against external electromagnetic interference, ensuring the accuracy and stability of the detection results. This acoustic emission probe design not only improves the accuracy of crack detection but also greatly enhances its applicability in complex industrial environments.

[0014] 2. This invention, through its serpentine microchannels and circulating liquid gallium-indium alloy, effectively dissipates heat, further ensuring the performance stability of the lithium niobate piezoelectric single crystal wafer under high-temperature environments and improving detection accuracy. The liquid gallium-indium alloy, as a heat transfer medium, possesses excellent fluidity and thermal conductivity, allowing heat to be rapidly dissipated, preventing performance degradation caused by excessively high probe internal temperatures.

[0015] 3. This invention, through its pyramidal micro-protrusion array, increases the contact area between the aluminum nitride coupling layer and the blade surface, improving the coupling efficiency of acoustic waves and thus enhancing the receiving sensitivity of the acoustic emission signal. Simultaneously, the gold film plated on top possesses excellent conductivity and stability, further ensuring the transmission quality of the acoustic emission signal. Liquid gallium indium tin alloy, filling the gaps between the micro-protrusions, not only acts as a lubricant, reducing friction between the coupling layer and the blade surface, but also serves as a heat conduction medium, assisting in heat dissipation and ensuring the probe's long-term stable operation in high-temperature environments. Attached Figure Description

[0016] Fig. 1 This is a perspective view of the present invention;

[0017] Fig. 2 This is a front sectional view of the present invention;

[0018] Fig. 3 This is a partial cross-sectional view of the electromagnetic shielding shell in this utility model.

[0019] Reference numerals: 1. Electromagnetic shielding shell; 2. Lithium niobate piezoelectric single crystal wafer; 3. Porous zirconium oxide buffer layer; 4. Aluminum nitride coupling layer; 5. Curved adaptive substrate; 6. Invar alloy; 7. Alumina insulating layer; 8. Hastelloy alloy; 9. Press-fit threaded plug; 10. Conduit; 11. Mechanical protective sleeve. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings.

[0021] Please see Figs. 1-3 This utility model provides an acoustic emission probe for detecting cracks in gas turbine blades, including an electromagnetic shielding shell 1. A layered sensing unit is provided on the top of the inner wall of the electromagnetic shielding shell 1. The layered sensing unit includes a lithium niobate piezoelectric single crystal 2, a porous zirconia buffer layer 3, and an aluminum nitride coupling layer 4. The lithium niobate piezoelectric single crystal 2, the porous zirconia buffer layer 3, and the aluminum nitride coupling layer 4 are connected by vacuum diffusion welding, and the polarization direction of the lithium niobate piezoelectric single crystal 2 is perpendicular to the blade surface. A curved adaptive substrate 5 is provided at the bottom of the aluminum nitride coupling layer 4.

[0022] The working principle and usage process of this invention are as follows: During use, the acoustic emission signal generated by the gas turbine blade is transmitted to the aluminum nitride coupling layer 4 through the curved adaptive substrate 5. Due to its excellent acoustic impedance matching characteristics, the aluminum nitride coupling layer 4 effectively reduces energy loss during sound wave transmission. Next, the sound wave enters the porous zirconia buffer layer 3, which is designed to further smooth the sound wave signal and reduce noise interference. Finally, the sound wave signal is received by the lithium niobate piezoelectric single crystal 2. Due to its excellent piezoelectric effect, the sound wave signal is converted into an electrical signal. This electrical signal is then processed and analyzed to accurately determine whether there is a crack in the gas turbine blade and its specific location. Throughout the process, the electromagnetic shielding shell 1 effectively shields against external electromagnetic interference, ensuring the accuracy and stability of the detection results. This acoustic emission probe design not only improves the accuracy of crack detection but also greatly enhances its applicability in complex industrial environments.

[0023] The piezoelectric constant d of lithium niobate piezoelectric single crystal 2 at 800℃ 33 Maintaining a temperature >15 pC / N, and avoiding adhesive layer failure through vacuum diffusion welding, the curved adaptive substrate 5 exhibits 8% deformation at a phase transition temperature of 150℃, perfectly fitting blade surfaces with varying curvatures, thus ensuring the long-term stability and reliability of the probe. The design of this acoustic emission probe fully considers the practical needs of gas turbine blade crack detection.

[0024] In this embodiment, preferably, the porous zirconia buffer layer 3 has a porosity of 40%-60%, with a pore size gradient distribution from 50μm at the surface to 200μm at the bottom. It contains embedded serpentine microchannels within which liquid gallium-indium alloy circulates. The serpentine microchannels and the circulating liquid gallium-indium alloy effectively dissipate heat, further ensuring the stable performance of the lithium niobate piezoelectric single crystal wafer 2 under high-temperature conditions and improving detection accuracy. As a heat transfer medium, the liquid gallium-indium alloy's excellent fluidity and thermal conductivity allow heat to be rapidly dissipated, preventing performance degradation caused by excessively high probe internal temperatures.

[0025] In this embodiment, preferably, the aluminum nitride coupling layer 4 has a pyramidal array of micro-bumps on its surface, and a gold film is deposited on the top of the aluminum nitride coupling layer 4. The gaps between the micro-bumps on the surface of the aluminum nitride coupling layer 4 are filled with liquid gallium indium tin alloy. The pyramidal array of micro-bumps increases the contact area between the aluminum nitride coupling layer 4 and the blade surface, improving the coupling efficiency of the acoustic waves and thus enhancing the receiving sensitivity of the acoustic emission signal. Simultaneously, the gold film deposited on the top has good conductivity and stability, further ensuring the transmission quality of the acoustic emission signal. The liquid gallium indium tin alloy filling the gaps between the micro-bumps not only acts as a lubricant, reducing friction between the coupling layer and the blade surface, but also serves as a heat conduction medium, assisting in heat dissipation and ensuring the long-term stable operation of the probe in high-temperature environments.

[0026] In this embodiment, preferably, the curved adaptive substrate 5 is a nickel-titanium shape memory alloy sheet, and a honeycomb microstructure is formed on the nickel-titanium shape memory alloy sheet by laser etching. The microstructure is filled with high-temperature silicone oil gel. The nickel-titanium shape memory alloy sheet has good shape memory effect and superelasticity, and can deform and return to its original shape at different temperatures, thereby adapting to the slight changes on the blade surface. The honeycomb microstructure formed by laser etching increases the contact points between the substrate and the blade surface, improving the fit. The high-temperature silicone oil gel, as a filler, not only enhances the sealing of the substrate, but also absorbs some vibration energy, further reducing noise interference. This design allows the probe to fit tightly on the blade surface with various curvatures, maintaining stable detection performance even under harsh conditions such as high temperature and high pressure.

[0027] In this embodiment, preferably, the electromagnetic shielding shell 1 comprises an inner Invar alloy 6, a middle alumina insulating layer 7, and an outer Hastelloy alloy 8. The Invar alloy 6, alumina insulating layer 7, and Hastelloy alloy 8 are fixed by thermostatic pressing (HIP) composite connection. The electromagnetic shielding shell 1 effectively shields against external electromagnetic interference, ensuring accurate transmission of acoustic emission signals. The inner Invar alloy 6 has a good low coefficient of thermal expansion and high permeability, effectively reducing the impact of thermal expansion on probe performance and improving the electromagnetic shielding effect. The middle alumina insulating layer 7 provides excellent electrical insulation and high-temperature resistance, ensuring stable operation of the probe in high-temperature environments. The outer Hastelloy alloy 8 not only has high strength and corrosion resistance but also further enhances the electromagnetic shielding effect. Fixed by HIP composite connection, these three layers are tightly bonded, forming a robust and efficient electromagnetic shielding structure.

[0028] In this embodiment, preferably, the outer wall of the electromagnetic shielding shell 1 is fitted with a mechanical protective sleeve 11, and the outer wall of the mechanical protective sleeve 11 has multiple uniformly distributed silicon carbide ceramic anti-collision rings. The mechanical protective sleeve 11 and the silicon carbide ceramic anti-collision rings effectively enhance the probe's impact resistance, preventing damage caused by accidental collisions in complex industrial environments. Silicon carbide ceramic, with its high hardness and good wear resistance, provides an additional protective layer for the probe, ensuring its stability and durability during long-term use. This design not only improves the probe's safety but also extends its service life.

[0029] In this embodiment, preferably, the bottom of the electromagnetic shielding shell 1 is threadedly connected to a clamping threaded plug 9, and the upper end of the clamping threaded plug 9 abuts against the bottom of the curved adaptive base 5. A conduit 10 is provided at the bottom of the clamping threaded plug 9, and the signal transmission line of the layered sensing unit passes through the conduit 10. Through the clamping threaded plug 9 and the conduit 10, effective fixation and protection of the signal transmission line of the layered sensing unit are achieved. The clamping threaded plug 9 is tightly connected to the electromagnetic shielding shell 1 via a threaded connection, ensuring stable contact between the signal transmission line and the curved adaptive base 5, avoiding signal transmission problems caused by loosening. Simultaneously, the conduit 10 provides a safe passage for the signal transmission line, preventing damage from external factors in complex industrial environments, further ensuring the reliability and stability of signal transmission. This design not only simplifies the probe structure but also improves its overall performance and reliability.

[0030] The above description of the disclosed embodiments enables those skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An acoustic emission probe for detecting cracks in gas turbine blades, characterized in that: The device includes an electromagnetic shielding shell (1), and a layered sensing unit is provided on the top of the inner wall of the electromagnetic shielding shell (1). The layered sensing unit includes a lithium niobate piezoelectric single crystal (2), a porous zirconia buffer layer (3), and an aluminum nitride coupling layer (4). The lithium niobate piezoelectric single crystal (2), the porous zirconia buffer layer (3), and the aluminum nitride coupling layer (4) are connected by vacuum diffusion welding. The polarization direction of the lithium niobate piezoelectric single crystal (2) is perpendicular to the blade surface. A curved adaptive substrate (5) is provided at the bottom of the aluminum nitride coupling layer (4).

2. The acoustic emission probe for detecting cracks in gas turbine blades according to claim 1, characterized in that: The porous zirconia buffer layer (3) has a porosity of 40%-60%, and the pore size gradient distribution is from 50μm on the surface to 200μm on the bottom layer. It is embedded with serpentine microchannels, and liquid gallium indium alloy circulates in the microchannels.

3. The acoustic emission probe for detecting cracks in gas turbine blades according to claim 1, characterized in that: The aluminum nitride coupling layer (4) has a pyramid-shaped micro-bump array on its surface, and a gold film is plated on the top of the aluminum nitride coupling layer (4). The gaps between the micro-bumps on the surface of the aluminum nitride coupling layer (4) are filled with liquid gallium indium tin alloy.

4. The acoustic emission probe for detecting cracks in gas turbine blades according to claim 1, characterized in that: The curved adaptive substrate (5) is a nickel-titanium shape memory alloy sheet, and a honeycomb microstructure is formed on the nickel-titanium shape memory alloy sheet by laser etching, and the microstructure is filled with high-temperature silicone oil gel.

5. The acoustic emission probe for detecting cracks in gas turbine blades according to claim 1, characterized in that: The electromagnetic shielding shell (1) includes an inner layer of Invar alloy (6), a middle layer of alumina insulation layer (7) and an outer layer of Hastelloy alloy (8), wherein the Invar alloy (6), the alumina insulation layer (7) and the Hastelloy alloy (8) are fixed by thermo-isostatic composite connection.

6. The acoustic emission probe for detecting cracks in gas turbine blades according to claim 1, characterized in that: The outer wall of the electromagnetic shielding shell (1) is fitted with a mechanical protective sleeve (11), and multiple silicon carbide ceramic anti-collision rings are evenly distributed on the outer wall of the mechanical protective sleeve (11).

7. The acoustic emission probe for detecting cracks in gas turbine blades according to claim 1, characterized in that: The bottom of the electromagnetic shielding shell (1) is threaded with a compression thread plug (9), and the upper end of the compression thread plug (9) abuts against the bottom of the curved adaptive base (5). The bottom of the compression thread plug (9) is provided with a conduit (10), and the signal transmission line of the layered sensing unit passes through the conduit (10).

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