A method for detecting failure of thermal insulation coating

Abstract

The present invention relates to the field of aerospace technology, and in particular to a method for detecting the failure of a thermal insulation coating. A thermal insulation plate is vertically arranged on the surface of a plate to be detected that is coated with a thermal insulation coating, so as to separate the plate to be detected into a first part with a larger area and a second part with a smaller area; a heat dissipation base plate is fixedly connected to the edge of the second part away from the thermal insulation plate; wherein the heat dissipation base plate is provided with a groove; the piezoelectric ceramic is fixed in the groove; a high-temperature flame is sprayed out by a spray gun to heat the plate to be detected; a low-temperature fluid is used to cool the plate to be detected; a signal receiving and processing device is used to receive the electrical signal emitted by the piezoelectric ceramic; and the signal receiving and processing device is used to process the electrical signal. An embodiment of the present invention provides a method for detecting the failure of a thermal insulation coating, which can detect the failure process of a thermal insulation coating.

Description

Technical Field

[0001] The present invention relates to the field of aerospace technology, and in particular to a method for detecting failure of a thermal insulation coating. Background Art

[0002] Aircraft engines operate in high-temperature environments. To protect the engine materials, they require thermal insulation coatings. However, thermal insulation coatings are prone to damage in high-temperature environments, compromising their thermal insulation properties. Therefore, failure detection of thermal insulation coatings is crucial. Summary of the Invention

[0003] An embodiment of the present invention provides a thermal insulation coating failure detection method capable of detecting the failure process of the thermal insulation coating.

[0004] An embodiment of the present invention provides a thermal insulation coating failure detection method, comprising:

[0005] The heat insulation plate is vertically arranged on the surface of the plate to be tested coated with the heat insulation coating, so as to separate the plate to be tested into a first part with a larger area and a second part with a smaller area;

[0006] A heat dissipation base plate is fixedly connected to the edge of the second portion away from the heat insulation plate; wherein the heat dissipation base plate is provided with a groove;

[0007] fixing the piezoelectric ceramic in the groove;

[0008] Using a spray gun to spray high-temperature flame to heat the plate to be tested;

[0009] Using low-temperature fluid to cool the plate to be tested;

[0010] Using a signal receiving and processing device to receive the electrical signal emitted by the piezoelectric ceramic;

[0011] The signal receiving and processing device is used to process the electrical signal.

[0012] In one possible design, processing the electrical signal by the signal receiving and processing device includes:

[0013] performing a first signal amplification, filtering process, and a second signal amplification process on the electrical signal;

[0014] The characteristics of the electrical signal are analyzed.

[0015] In one possible design, analyzing the characteristics of the electrical signal includes:

[0016] Acquiring acoustic emission signals of failure types through experiments; wherein the failure types include interlaminar fracture and cracks;

[0017] Performing Fourier transform and wavelet packet transform decomposition on the acoustic emission signal of the failure type to obtain a first frequency feature;

[0018] Processing the electrical signal using continuous wavelet transform to obtain a second frequency feature;

[0019] By comparing the second frequency characteristic with the first frequency characteristic, the failure type of the thermal insulation coating that generates the electrical signal is obtained.

[0020] In a possible design, after fixing the piezoelectric ceramic in the groove and before using a spray gun to spray a high-temperature flame to heat the plate to be tested, the method further includes:

[0021] A heat dissipation cover is provided on the top of the heat dissipation base plate; wherein, the heat dissipation cover and the heat dissipation base plate are both hollow shell structures, the heat dissipation base plate is filled with water, and the heat dissipation cover and the heat dissipation base plate are connected through evaporation holes.

[0022] In one possible design, it also includes:

[0023] The heat-absorbing and evaporated gas is discharged through the exhaust channel preset on the heat dissipation cover;

[0024] The gas discharged from the exhaust channel drives the preset first fan blade to rotate;

[0025] After the first fan blade rotates, it drives the second fan blade coaxially connected to it to rotate; wherein, the heat dissipation base is connected to a liquid replenishing device through a liquid inlet pipe, and the second fan blade is used to provide power for the liquid inlet pipe connected to the bottom of the heat dissipation base.

[0026] In one possible design, it also includes:

[0027] Output the corrosive medium to the plate to be tested;

[0028] The concentration of the corrosive medium in the gas above the plate to be tested is collected using a collection pipe; wherein the collection pipe passes through the heat insulation plate and the heat dissipation base plate, one end of the collection pipe passes through the heat insulation plate and is located above the first part, and the other end of the collection pipe is connected to a gas concentration analysis device for detecting the concentration of the corrosive medium.

[0029] In a possible design, the method of collecting the concentration of the corrosive medium in the gas above the plate to be tested by using a collection pipe includes:

[0030] The flow rate of the gas collected by the collection pipeline is adjusted according to the temperature sensor preset on the heat dissipation base plate, and the temperature collected by the temperature sensor is inversely proportional to the gas flow rate of the collection pipeline;

[0031] The collected gas is passed into the gas analysis chamber through the collection pipeline to analyze the concentration of the corrosive medium in the gas.

[0032] In a possible design, a sealing plate is provided on the upper portion of the groove to make the groove a sealed space, and a vacuum channel is provided on the inner wall of the groove, and the vacuum channel is used to make the groove a vacuum environment.

[0033] In a possible design, the piezoelectric ceramic is fixed to the heat dissipation base plate via at least one connecting column.

[0034] In a possible design, the distance between the end of the heat dissipation base plate close to the heat insulation plate and the groove is 8 to 15 cm.

[0035] Compared with the prior art, the present invention has at least the following beneficial effects:

[0036] In this embodiment, flames and low-temperature fluids can be sprayed through a spray gun, and a heat shield separates the plate to be tested into a first part and a second part. The first part, which has a larger area, is used to receive the flame sprayed by the spray gun, simulating the high temperature environment of the engine when it is working and the low temperature environment when it is not working, so as to test the service life of the thermal insulation coating; the second part, which has a smaller area, is used to place the piezoelectric ceramic used to collect the acoustic wave signal generated by the damage of the thermal insulation coating. Because the test environment temperature is high and the operating temperature of the piezoelectric ceramic does not exceed 200°C, it is impossible to place the piezoelectric ceramic directly on the thermal insulation coating. If other high-temperature resistant waveguide devices are used to guide the acoustic wave signal to a lower temperature area, and then the piezoelectric ceramic is connected to the waveguide device in the lower temperature area, the waveguide device has a long waveguide path and many components, which can easily cause a certain degree of damage to the acoustic wave, resulting in distortion of the collected acoustic wave. Therefore, the present application directly places the piezoelectric ceramic on the thermal insulation coating. To avoid the high temperature problem, the heat shield is used to separate the second part where the piezoelectric ceramic is placed from the first part heated by the spray gun, which greatly prevents heat from being transferred from the upper part of the thermal insulation coating to the piezoelectric ceramic. Furthermore, a small amount of high temperature will still be transferred to the second part through the thermal insulation coating. Although the amount of heat transferred is far less than the heat output by the spray gun, the extremely high temperature output by the spray gun can still damage the piezoelectric ceramic. Therefore, a heat sink is installed on the second part, and the piezoelectric ceramic is placed in the groove of the heat sink. After the piezoelectric ceramic collects the acoustic wave signal, it is transmitted as an electric current to the signal receiving and processing device for analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0038] Figure 1 This is a flow chart of a thermal insulation coating failure detection method provided by an embodiment of the present invention;

[0039] Figure 2 It is a structural schematic diagram of a thermal insulation coating failure detection device provided by an embodiment of the present invention.

[0040] In the picture:

[0041] 100-plate to be tested;

[0042] 1-Spray gun;

[0043] 2- thermal insulation board;

[0044] 3- heat dissipation base plate;

[0045] 4-heat dissipation cover;

[0046] 5-groove;

[0047] 6- piezoelectric ceramics;

[0048] 7-evaporation hole;

[0049] 8-Exhaust channel;

[0050] 9-liquid inlet pipe;

[0051] 10-Fluid replenishment device;

[0052] 11-first fan blade;

[0053] 12- second fan blade;

[0054] 13- Collection pipeline;

[0055] 14-connecting column;

[0056] 15-Gas analysis chamber;

[0057] 16-exhaust plate;

[0058] 17-collection port;

[0059] 18-first exhaust port;

[0060] 19- second exhaust port;

[0061] 20-Gas concentration analysis device. DETAILED DESCRIPTION

[0062] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0063] In the description of the embodiments of the present invention, unless otherwise expressly specified or limited, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance; unless otherwise specified or explained, the term "plurality" refers to two or more; the terms "connected" and "fixed" should be understood in a broad sense. For example, "connected" can mean a fixed connection, a detachable connection, an integral connection, or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0064] In the description of this specification, it should be understood that the directional terms such as "upper" and "lower" described in the embodiments of the present invention are described from the perspectives shown in the accompanying drawings and should not be understood as limiting the embodiments of the present invention. In addition, in the context, it should be understood that when it is mentioned that an element is connected "upper" or "lower" of another element, it can not only be directly connected "upper" or "lower" of the other element, but also indirectly connected "upper" or "lower" of the other element through an intermediate element.

[0065] Please refer to Figure 1 and Figure 2 , an embodiment of the present invention provides a thermal insulation coating failure detection method, comprising:

[0066] The heat insulation board 2 is vertically arranged on the surface of the plate body 100 to be tested that is coated with the heat insulation coating, so as to separate the plate body 100 to be tested into a first part with a larger area and a second part with a smaller area;

[0067] The heat dissipation base plate 3 is fixedly connected to the edge of the second portion away from the heat insulation plate 2; wherein the heat dissipation base plate 3 is provided with a groove 5;

[0068] Fixing the piezoelectric ceramic 6 in the groove 5;

[0069] Use the spray gun 1 to spray high-temperature flames to heat the plate 100 to be tested;

[0070] Using low-temperature fluid to cool the plate 100 to be tested;

[0071] Using a signal receiving and processing device to receive the electrical signal emitted by the piezoelectric ceramic 6;

[0072] The signal receiving and processing device is used to process the electrical signal.

[0073] In this embodiment, flames and low-temperature fluids can be sprayed out through a spray gun 1, and the thermal insulation plate 2 separates the plate body 100 to be tested into a first part and a second part. The first part with a larger area is used to receive the flame sprayed from the spray gun 1, simulating the high temperature environment of the engine when it is working and the low temperature environment when it is not working, so as to test the service life of the thermal insulation coating; the second part with a smaller area is used to place the piezoelectric ceramic 6 for collecting the sound wave signal generated by the damage of the thermal insulation coating. Since the test environment temperature is high and the operating temperature of the piezoelectric ceramic 6 does not exceed 200°C, the piezoelectric ceramic 6 cannot be placed directly on the thermal insulation coating. If other high-temperature resistant waveguide devices are used to guide the sound wave signal to a lower temperature area, and then the piezoelectric ceramic 6 is set in the lower temperature area to connect with the waveguide device, then since the waveguide path of the waveguide device is longer and there are more components, it is easy to cause a certain degree of damage to the sound wave, resulting in distortion of the collected sound wave. Therefore, the present application directly places the piezoelectric ceramic 6 on the thermal insulation coating. In order to circumvent the high temperature problem, the thermal insulation plate 2 is used to separate the second part where the piezoelectric ceramic 6 is placed and the first part heated by the spray gun 1, which largely prevents heat from being transferred from the upper part of the thermal insulation coating to the piezoelectric ceramic 6. Furthermore, a small part of the high temperature will still be transferred to the second part through the thermal insulation coating. Although the transferred heat is much less than the heat output by the spray gun 1, the temperature output by the spray gun 1 is extremely high, and a small part of the heat may still damage the piezoelectric ceramic 6. Therefore, a heat dissipation base plate 3 is provided on the second part, and the piezoelectric ceramic 6 is provided in the groove 5 of the heat dissipation base plate 3. After the piezoelectric ceramic 6 collects the acoustic wave signal, it is transmitted to the signal receiving and processing device in the form of an electric current for analysis.

[0074] In some embodiments of the present invention, processing an electrical signal using a signal receiving and processing device includes:

[0075] Performing initial signal amplification, filtering, and re-signal amplification on the electrical signal;

[0076] Analyze the characteristics of electrical signals.

[0077] In this embodiment, the electrical signal is first amplified, then filtered using a filter to eliminate clutter, and finally processed again to obtain an electrical signal with a high signal-to-noise ratio for analysis.

[0078] In some embodiments of the present invention, analyzing the characteristics of the electrical signal includes:

[0079] Acquiring acoustic emission signals of failure types through experiments; failure types include interlaminar fracture and cracks;

[0080] Perform Fourier transform and wavelet packet transform on the acoustic emission signal of the failure type to obtain the first frequency feature;

[0081] Processing the electrical signal using continuous wavelet transform to obtain a second frequency feature;

[0082] By comparing the second frequency characteristic with the first frequency characteristic, the failure type of the thermal insulation coating that generates the electrical signal is obtained.

[0083] In this embodiment, the first frequency feature represents the signal feature of the failure type and has a characteristic frequency range. The frequency of the second frequency feature falls within the range defined by the first frequency feature corresponding to which failure type, and the actual failure type is determined.

[0084] In some embodiments of the present invention, after the piezoelectric ceramic 6 is fixed in the groove 5 and before the high-temperature flame is sprayed by the spray gun 1 to heat the plate 100 to be tested, the following steps are further included:

[0085] A heat dissipation cover plate 4 is provided on the top of the heat dissipation base plate 3; wherein, the heat dissipation cover plate 4 and the heat dissipation base plate 3 are both hollow shell structures, the heat dissipation base plate 3 is filled with water, and the heat dissipation cover plate 4 and the heat dissipation base plate 3 are connected through the evaporation hole 7.

[0086] In this embodiment, heat dissipation baseplate 3 is filled with water, and its bottom is directly connected to the heat source insulation coating. Heat is conducted to the water within baseplate 3, causing it to heat up and vaporize. This vaporization absorbs a large amount of heat, maintaining the piezoelectric ceramic 6 within groove 5 at a suitable temperature. Heat dissipation cover plate 4 on top of baseplate 3 receives the high-temperature vapor that expands during vaporization and dissipates it, achieving efficient heat dissipation.

[0087] In some embodiments of the present invention, the method further comprises:

[0088] The heat-absorbing and evaporated gas is discharged through the exhaust channel 8 preset on the heat dissipation cover plate 4;

[0089] The gas discharged from the exhaust channel 8 drives the preset first fan blade 11 to rotate;

[0090] After the first fan blade 11 rotates, it drives the second fan blade 12 coaxially connected to it to rotate; wherein, the heat dissipation base plate 3 is connected to the liquid replenishing device 10 through the liquid inlet pipe 9, and the second fan blade 12 is used to provide power for the liquid inlet pipe 9 connected to the bottom of the heat dissipation base plate 3.

[0091] In this embodiment, the vaporized gas is discharged through the exhaust channel 8. The gas expands rapidly at high temperature and forms a higher air pressure under the restriction of the exhaust channel 8. The high pressure provides a stronger power for the gas circulation, and then when it passes through the first fan blade 11, it drives it to rotate. The first fan blade 11 and the second fan blade 12 are axially connected, which drives the second fan blade 12 to rotate. The second fan blade 12 replenishes the low-temperature water in the liquid replenishing device 10 to the heat dissipation base plate 3 through the liquid inlet pipe 9, thereby achieving continuous and efficient heat dissipation.

[0092] It should be noted that the first blade 11 and the second blade 12 on different axes can be linked together by means of a gear set.

[0093] In some embodiments of the present invention, the method further comprises:

[0094] Outputting the corrosive medium to the plate 100 to be tested;

[0095] The concentration of the corrosive medium in the gas above the plate body 100 to be tested is collected by using a collection pipe 13; wherein the collection pipe 13 passes through the heat insulation board 2 and the heat dissipation base plate 3, one end of the collection pipe 13 passes through the heat insulation board 2 and is located above the first part, and the other end of the collection pipe 13 is connected to a gas concentration analysis device for detecting the concentration of the corrosive medium.

[0096] In the real working environment of an aircraft, in addition to being exposed to high temperatures, it will also be corroded by volcanic ash, PM2.5 and gaseous corrosive media. The combination of corrosive media and high temperature is an important factor causing the failure of the thermal insulation coating. Therefore, in order to more realistically reflect the service life of the thermal insulation coating, in addition to creating a high-temperature environment, a corrosive medium environment must also be created. Therefore, in addition to spraying a high-temperature flame, the spray gun 1 also sprays a corrosive medium with an adjustable concentration. However, the concentration of the corrosive medium in the spray gun 1 is different from the concentration on the surface of the thermal insulation coating. Therefore, the concentration of the corrosive medium must be collected. Specifically, the gas above the thermal insulation coating is collected through the collection pipe 13. Similarly, the gas detection device cannot perform detection at high temperatures. Therefore, the collection pipe 13 passes through the heat dissipation base plate 3. After the collected gas passes through the heat dissipation base plate 3, the heat is dissipated through the heat dissipation base plate 3, and the temperature drops rapidly. Finally, it is received and tested by the gas concentration analysis device 20 to obtain the concentration of the corrosive medium.

[0097] The gas concentration analysis device 20 can be installed in the gas analysis chamber 15. The gas analysis chamber 15 includes a collection port 17 connected to the collection pipe 13, a first exhaust port 18, and a second exhaust port 19. The gas analysis chamber 15 includes a reciprocating exhaust plate 16, which divides the gas analysis chamber 15 into two parts. The collection port 17 and the first exhaust port 18 are located on opposite sides of the chamber wall, while the second exhaust port 19 is located on the same side of the chamber wall as the collection port 17. During gas collection, the exhaust plate 16 moves from the chamber wall where the collection port 17 is located to the side of the first exhaust port 18, allowing the gas to fill the gas analysis chamber 15 for concentration testing. After the test is completed, the collection port 17 is closed, the first exhaust port 18 and the second exhaust port 19 are opened, and the exhaust plate 16 is controlled to move to the chamber wall where the collection port 17 is located, allowing the internal gas to be discharged through the second exhaust port 19. The second exhaust port 19 is then closed, and the collection port 17 is opened to continue gas collection.

[0098] In some embodiments of the present invention, the concentration of the corrosive medium in the gas above the plate 100 to be tested is collected by using the collection pipe 13, including:

[0099] The flow rate of the gas collected by the collection pipe 13 is adjusted according to the temperature sensor preset on the heat dissipation base plate 3. The temperature collected by the temperature sensor is inversely proportional to the gas flow rate of the collection pipe 13.

[0100] The collected gas is passed through the collection pipe 13 into the gas analysis chamber 15 to analyze the concentration of the corrosive medium in the gas.

[0101] If the temperature of the heat dissipation base plate 3 is too high, it will affect the performance of the concentration sensor and the piezoelectric ceramic 6. Therefore, the collected gas flow is adjusted according to the collected temperature. If the temperature is too high, the collected gas volume is reduced to reduce the heat dissipation pressure.

[0102] In some embodiments of the present invention, a sealing plate is provided on the upper portion of the groove 5 to make the groove 5 a sealed space, and a vacuum channel is provided on the inner wall of the groove 5 to make the groove 5 a vacuum environment.

[0103] In this embodiment, vacuum can provide heat insulation and create a suitable working environment for the piezoelectric ceramic 6 .

[0104] The inner wall of the groove 5 is provided with a line pipe for connecting the lines, and the port of the line pipe is provided with a sealing ring to keep the groove 5 sealed.

[0105] In some embodiments of the present invention, the piezoelectric ceramic 6 is fixed on the heat dissipation base plate 3 via at least one connecting column 14 .

[0106] In this embodiment, the contact area between the piezoelectric ceramic 6 and the heat dissipation base plate 3 is reduced by the connecting pillars 14, which is beneficial to reducing heat transfer.

[0107] In some embodiments of the present invention, the distance between the end of the heat dissipation base plate 3 close to the heat insulation plate 2 and the groove 5 is 8 to 15 cm.

[0108] In this embodiment, a distance of 8 to 15 cm can dissipate most of the heat in time, thereby protecting the piezoelectric ceramic 6 in the rear position.

[0109] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A thermal insulation coating failure detection method, characterized in that: include: The heat insulation plate is vertically arranged on the surface of the plate to be tested coated with the heat insulation coating, so as to separate the plate to be tested into a first part with a larger area and a second part with a smaller area; A heat dissipation base plate is fixedly connected to the edge of the second portion away from the heat insulation plate; wherein the heat dissipation base plate is provided with a groove; fixing the piezoelectric ceramic in the groove; Using a spray gun to spray high-temperature flame to heat the plate to be tested; Using low-temperature fluid to cool the plate to be tested; Using a signal receiving and processing device to receive the electrical signal emitted by the piezoelectric ceramic; Processing the electrical signal using the signal receiving and processing device; After fixing the piezoelectric ceramic in the groove and before using a spray gun to spray a high-temperature flame to heat the plate to be tested, the method further includes: A heat dissipation cover is provided on the top of the heat dissipation base plate; wherein, the heat dissipation cover and the heat dissipation base plate are both hollow shell structures, the heat dissipation base plate is filled with water, and the heat dissipation cover and the heat dissipation base plate are connected through evaporation holes.

2. The method according to claim 1, characterized in that The processing of the electrical signal by the signal receiving and processing device includes: performing a first signal amplification, filtering process, and a second signal amplification process on the electrical signal; The characteristics of the electrical signal are analyzed.

3. The method according to claim 2, characterized in that The analyzing the characteristics of the electrical signal includes: Acquiring acoustic emission signals of failure types through experiments; wherein the failure types include interlaminar fractures and cracks; Performing Fourier transform and wavelet packet transform decomposition on the acoustic emission signal of the failure type to obtain a first frequency feature; Processing the electrical signal using continuous wavelet transform to obtain a second frequency feature; By comparing the second frequency characteristic with the first frequency characteristic, the failure type of the thermal insulation coating that generates the electrical signal is obtained.

4. The method according to claim 1, wherein Also includes: The heat-absorbing and evaporated gas is discharged through the exhaust channel preset on the heat dissipation cover; The gas discharged from the exhaust channel drives the preset first fan blade to rotate; After the first fan blade rotates, it drives the second fan blade coaxially connected to it to rotate; wherein, the heat dissipation base is connected to a liquid replenishing device through a liquid inlet pipe, and the second fan blade is used to provide power for the liquid inlet pipe connected to the bottom of the heat dissipation base.

5. The method according to claim 1, wherein Also includes: Output the corrosive medium to the plate to be tested; The concentration of the corrosive medium in the gas above the plate to be tested is collected using a collection pipe; wherein the collection pipe passes through the heat insulation plate and the heat dissipation base plate, one end of the collection pipe passes through the heat insulation plate and is located above the first part, and the other end of the collection pipe is connected to a gas concentration analysis device for detecting the concentration of the corrosive medium.

6. The method according to claim 5, characterized in that The method of collecting the concentration of the corrosive medium in the gas above the plate to be tested by using a collection pipeline includes: The flow rate of the gas collected by the collection pipeline is adjusted according to the temperature sensor preset on the heat dissipation base plate, and the temperature collected by the temperature sensor is inversely proportional to the gas flow rate of the collection pipeline; The collected gas is passed into a gas analysis chamber through the collection pipeline to analyze the concentration of the corrosive medium in the gas.

7. The method according to claim 1, characterized in that A sealing plate is provided on the upper portion of the groove to make the groove a sealed space, and a vacuum channel is provided on the inner wall of the groove to make the groove a vacuum environment.

8. The method according to claim 1, characterized in that The piezoelectric ceramic is fixed on the heat dissipation base plate through at least one connecting column.

9. The method according to claim 1, characterized in that The distance between the end of the heat dissipation base plate close to the heat insulation plate and the groove is 8 to 15 cm.

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