Temperature measurement method of ceramic matrix composite material structure based on optical fiber sensor

Abstract

The present invention relates to a method for testing the temperature of a ceramic-based composite material structure based on an optical fiber sensor, and belongs to the technical field of aeroengine testing. The method is to prepare a high-temperature-resistant ceramic composite coating on the surface of a curved part of a ceramic-based composite material substrate to install and fix a flexible optical fiber sensor, and to achieve a structural temperature test of a composite material substrate part by pre-calibrating the temperature fitting curve obtained by calibrating the test data of the optical fiber sensor. The method can be used for structural temperature testing of ceramic-based composite curved surface parts for next-generation aeroengines under high-temperature working environments, and provide effective data support for the development, verification and improvement of related materials and components.

Description

Technical Field

[0001] The invention relates to a ceramic-based composite material structure temperature testing method based on an optical fiber sensor, which can realize the structural temperature testing of composite material substrate parts in a high-temperature working environment of an aero-engine, and belongs to the technical field of aero-engine testing. Background Art

[0002] In the current development of aero-engines, silicon carbide ceramic matrix composites (CMC-SiC) are being developed as materials for medium-load stationary parts of engines such as combustion chambers, guide vanes, turbine outer rings and tail nozzles to meet the research and development needs of the aviation field for engines with higher thrust-to-weight ratios, lower fuel consumption rates and higher stability. As the material used in the latest generation of engines, silicon carbide ceramic matrix composites have excellent mechanical properties such as high specific strength, high specific modulus, high hardness, wear resistance and corrosion resistance, as well as excellent high-temperature stability properties such as high-temperature oxidation resistance, ablation resistance, good high-temperature thermal stability and low thermal stress between fibers and matrix. However, there are also many problems in use, such as the hot end components based on silicon carbide ceramic matrix composites work in a high-temperature oxidation environment for a long time, are subjected to strong thermal stress, and are eroded by various environments, resulting in large changes in fiber performance; lack of test data under specific application conditions as design input; structural changes are very random, and when used as hot end components of engines, the conventional deterministic design method cannot be used. Reliability analysis must be based on actual test data to provide support for the development, verification and improvement of related materials and components.

[0003] In order to accurately obtain the life of the hot end components, it is necessary to obtain the temperature distribution of the hot end components, but the current high-temperature temperature test of the hot end components is difficult. The temperature-indicating paint commonly used in the contact method is generally a qualitative measurement with low temperature measurement accuracy, and can only obtain the highest temperature; the temperature measurement method based on resistance, etc., has the problem of being seriously affected by the electromagnetic interference of the three high environments of the engine. Optical fiber sensors have significant advantages such as high temperature resistance, small size, and anti-electromagnetic interference. They can be effectively used for structural temperature testing of hot end components based on silicon carbide ceramic-based composite materials. Its flexible flexible sensor structure design and installation method are more suitable for the surface shapes of various curved parts such as turbine blades. The flexible optical fiber sensor is installed and fixed by preparing a high-temperature resistant ceramic composite coating with good thermal expansion coefficient matching through plasma spraying process. The prepared high-temperature resistant ceramic composite coating has good thermal expansion coefficient matching and bonding strength with the substrate, which improves the high-reliability installation and accurate testing of optical fiber sensors on the surface of ceramic-based composite curved parts. Summary of the invention

[0004] The purpose of the present invention is to provide a method for testing the temperature of a ceramic-based composite material structure based on an optical fiber sensor; the method is to prepare a high-temperature resistant ceramic composite coating on the surface of a curved part of a ceramic-based composite material substrate to install and fix a flexible optical fiber sensor, and to achieve a structural temperature test of the composite material substrate part by pre-calibrating the temperature fitting curve obtained by calibrating the optical fiber sensor test data.

[0005] The temperature testing method of ceramic matrix composite material structure based on optical fiber sensor includes the following steps:

[0006] Step 1: temperature calibrate the optical fiber sensor to be installed to obtain a calibration curve;

[0007] 1) Place the standard temperature sensor and the optical fiber sensor in a high-temperature furnace to ensure that they are on the same isotherm. The optical fiber sensor is connected to the demodulator and the host computer, and the standard temperature sensor is connected to the thermometer.

[0008] 2) Set multiple calibration temperature points; at each calibration temperature point, record the temperature indication of the standard temperature sensor and the optical quantity output value of the optical fiber sensor; cool down naturally to room temperature; repeat the test for more than one time;

[0009] 3) Perform quadratic fitting on the multiple sets of standard thermocouple indications obtained in step 1 (2) and the output optical quantity values ​​of the optical fiber sensor to obtain the temperature-optical quantity function relationship:

[0010] λ n =a n T 2 +b n T+c n

[0011] Where: n is the output optical quantity value of the fiber optic sensor, T is the standard thermocouple indication, and n is the number of calibration test cycles; a n 、b n 、c n is the coefficient;

[0012] The calibration temperature point is respectively introduced into the temperature-output optical quantity function relationship of each test to obtain the output optical quantity value of the optical fiber sensor at the calibration point, and the output optical quantity value of the optical fiber sensor is averaged. The calibration temperature point is fitted with the average value of the output optical quantity value of the optical fiber sensor at the corresponding temperature point by quadratic terms to obtain the calibration curve of the optical fiber sensor:

[0013] t=Aλ 2 +Bλ+C;

[0014] Where λ is the output optical quantity value of the fiber optic sensor; A, B, and C are the sensor calibration curve function coefficients.

[0015] Step 2: The flexible optical fiber sensor is fixedly mounted on the surface of the part through a plasma-based thermal spraying installation process;

[0016] Pretreatment: Clean the parts, use alcohol to scrub the area where the parts are to be installed, and then blow dry with clean compressed air.

[0017] Preparation of transition layer: Use metal shielding tooling to shield and protect the non-installation area of ​​the part, and install it on the part turntable or rotating axis in the vacuum chamber of the low-pressure plasma spraying system through the connecting tooling. Use pure Si powder with a slightly larger thermal expansion coefficient than the substrate and good high-temperature oxidation resistance and anti-penetration performance. Use a low-pressure plasma spray gun clamped by a manipulator to spray the Si transition layer on the area to be installed on the surface of the part, and spray it to the set coating thickness.

[0018] Transition layer heat treatment: After the transition layer of the part is sprayed, remove the protective tooling and put it into a vacuum heat treatment furnace for vacuum diffusion treatment.

[0019] Preparation of intermediate layer: The intermediate layer is prepared according to the design requirements (it is also possible to have no intermediate layer). The intermediate layer is sprayed on the area to be installed on the surface of the part by an atmospheric plasma spray gun clamped by a multi-axis manipulator. The coating material uses 3Al2O3-2SiO2 powder with a higher thermal expansion coefficient than the Si transition layer and higher thermal stability. During the spraying process, compressed air is used to cool the other parts of the part, and the coating is sprayed to the set coating thickness.

[0020] Protection and fixation of optical fiber sensors: Use asbestos tape without residual glue to fix the optical fiber installation part on both sides of the installation area to keep the optical fiber flat as a whole, and then use thermal spray high-temperature tape and protective tooling to cover the asbestos tape surface and other parts of the optical fiber.

[0021] Preparation of installation surface layer: The optical fiber installation surface layer is sprayed on the area to be installed on the surface of the part by an atmospheric plasma spray gun clamped by a multi-axis manipulator. The coating material uses silicate ceramic powder with a higher thermal expansion coefficient than the Si transition layer and the 3Al2O3-2SiO2 intermediate layer, and good thermal insulation and CMAS corrosion resistance. During the spraying process, compressed air is used to cool the other parts of the part, and the coating is sprayed to the set coating thickness.

[0022] Post-processing: remove all spray protection, check the fiber optic installation location and area, use alcohol to wipe the tape residue, blow dry with compressed air and package to complete the fiber optic sensor installation.

[0023] Step 3: Use a high temperature furnace to perform temperature loading and testing on the parts equipped with the optical fiber sensor;

[0024] Place the parts in a high-temperature furnace, apply temperature loading, and record the optical quantity values ​​output by the sensor at each temperature point.

[0025] Step 4: Data processing, calculate the component structure temperature.

[0026] Substitute the optical quantity value obtained in step three into the calibration curve obtained in step one to obtain the temperature value corresponding to the output optical quantity value, that is, the temperature of the component structure.

[0027] A standard thermocouple can also be installed on the back of the part in step three. The temperature collected by the standard thermocouple is used to compare with the temperature calculated by the optical fiber sensor in step four to verify the accuracy of the optical fiber sensor test and calculation results.

[0028] Beneficial Effects

[0029] 1. The present invention relates to a method for testing the temperature of a ceramic-based composite material structure based on an optical fiber sensor, and belongs to the technical field of aeroengine testing. The method is to install and fix a flexible optical fiber sensor on the surface of a curved part of a ceramic-based composite material substrate by using a plasma spraying process to prepare a high-temperature resistant ceramic composite coating, and to calibrate the test data of the optical fiber sensor to provide a temperature fitting curve at different temperature points, thereby realizing the structural temperature test of the composite material substrate part.

[0030] 2. The high temperature resistant ceramic composite installation coating prepared by the method of the present invention has good thermal expansion coefficient matching and bonding strength with the substrate, and has excellent high temperature oxidation resistance and molten salt corrosion resistance, realizing high reliability installation of flexible optical fiber sensors on the surface of ceramic matrix composite curved surface parts. This method can be used for structural temperature testing of ceramic matrix composite curved surface parts for next generation aero-engines under high temperature working environment, providing effective data support for the development, verification and improvement of related materials and components. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is the temperature calibration curve of the optical fiber sensor of the present invention;

[0032] Figure 2 It is the process route diagram of the installation method of the present invention;

[0033] Figure 3 This is a schematic diagram of the installation structure of the optical fiber sensor of the present invention.

[0034] Among them, 1-parts, 2-transition layer, 3-middle layer, 4-optical fiber sensor, 5-surface layer. DETAILED DESCRIPTION

[0035] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of the present invention.

[0036] Embodiment 1:

[0037] The temperature testing method of ceramic matrix composite material structure based on optical fiber sensor includes the following steps:

[0038] Step 1: temperature calibrate the optical fiber sensor to be installed to obtain a calibration curve;

[0039] 1) Place the standard temperature sensor and the fiber grating sensor in a high temperature furnace to ensure that they are on the same isotherm. Connect the fiber grating sensor to the demodulator and the host computer, and connect the standard temperature sensor to the thermometer.

[0040] 2) Set multiple calibration temperature points such as 650℃, 750℃, 900℃, 1000℃, 1050℃, 1100℃, etc., and keep each calibration temperature point for 30 minutes after reaching it; at each calibration temperature point, record the temperature indication of the first-level standard thermocouple and the output wavelength of the fiber grating sensor; cool down naturally to room temperature; repeat the test 5 times.

[0041] Table 1 Fiber Bragg Grating Sensor Test Data

[0042]

[0043]

[0044] 3) Perform quadratic fitting on the 5 sets of standard thermocouple indications obtained in step 1 (2) and the wavelength values ​​of the fiber grating sensor to obtain 5 temperature-wavelength function relationship equations:

[0045] λ1=0.00000462T 2 +0.0114T+1,553.733;

[0046] λ2=0.00000474T 2 +0.0114T+1,553.724;

[0047] λ3=0.00000478T 2 +0.0114T+1,553427.727;

[0048] λ4=0.00000483T 2 +0.0114T+1,553.726;

[0049] λ5=0.00000481T 2 +0.0114T+1,553.724.

[0050] Substituting the calibration point 650℃, we get: 1，650℃ =1553.493nm,λ 2，650℃ =1553.545nm,λ 3，650℃ =1553.487nm,λ 4，650℃ =1553.602nm,λ 5，650℃ =1553.567nm.

[0051] Take the average value of the 5 wavelength values ​​in step 3), that is: Repeat the above steps to obtain the average wavelength values ​​at each calibration temperature, as shown in Table 2.

[0052] Table 2 Average wavelength values ​​at various calibration temperatures

[0053] Calibration temperature point (℃) Sensor wavelength value (nm) 650 1553.539 750 1555.167 900 1557.490 1000 1559.261 1050 1560.495 1100 1561.659

[0054] The calibration curve of the fiber Bragg grating sensor is obtained by fitting the quadratic term of the average wavelength value of the fiber Bragg grating sensor at the calibration temperature point and the corresponding temperature point, t = -1.998λ 2 +6279.206λ-4932684.841, such as Figure 3 shown.

[0055] Step 2: Install and fix the flexible optical fiber sensor;

[0056] Pretreatment: Three-dimensional (3D) woven silicon carbide fiber reinforced silicon carbide composites (SiC f / SiC) part 1 is cleaned, the area to be installed of part 1 is scrubbed with alcohol, and then blown dry with clean compressed air;

[0057] Preparation of transition layer: Use metal shielding tooling to shield and protect the non-installation area of ​​part 1, and install it on the part turntable in the vacuum chamber of the low-pressure plasma spraying system through the connecting tooling. Use pure Si powder and spray the Si transition layer on the area to be installed on the surface of the part through a low-pressure plasma spray gun clamped by a manipulator. The current is 1500A, the power is 85kW, the argon (Ar) flow rate is 100L / min, the hydrogen (H2) flow rate is 8L / min, the powder feeding amount is 20g / min, the vacuum degree is 30mbar, the spraying distance is 350mm, and the coating thickness is sprayed to 0.15mm;

[0058] Transition layer heat treatment: After the transition layer of the parts is sprayed, remove the protective tooling and put them into a vacuum heat treatment furnace for vacuum diffusion treatment. The heat treatment temperature is 1300℃, the vacuum degree is 30mbar, the insulation time is 60min, and the parts are cooled with the furnace.

[0059] Preparation of intermediate layer: The intermediate layer is prepared according to the design requirements. The intermediate layer is sprayed on the surface of the part in the area to be installed by an atmospheric plasma spray gun clamped by a multi-axis manipulator. The coating material uses 3Al2O3-2SiO2 powder with a higher thermal expansion coefficient than the Si transition layer and higher thermal stability. The spraying power is 35kw, the argon (Ar) flow rate is 45l / min, the hydrogen (H2) flow rate is 7l / min, the powder feeding amount is 35g / min, and the spraying distance is 150mm. During the spraying process, compressed air is used to cool the other parts of the part. The substrate temperature is controlled at (150℃±20℃) and the coating is sprayed to a thickness of 0.2mm.

[0060] Protection and fixation of fiber grating sensors: Use asbestos tape without residual glue to fix the fiber grating installation part on both sides of the installation area to keep the fiber flat as a whole, and then use thermal spray high-temperature tape and protective tooling to cover the asbestos tape surface and other parts of the fiber;

[0061] Preparation of installation surface layer: The optical fiber installation surface layer is sprayed on the area to be installed on the surface of the part by an atmospheric plasma spray gun clamped by a multi-axis manipulator. The coating material uses a silicate ceramic powder with a higher thermal expansion coefficient than the Si transition layer and the 3Al2O3-2SiO2 intermediate layer, and good heat insulation and CMAS corrosion resistance. The spraying power is 40kw, the argon (Ar) flow rate is 35l / min, the hydrogen (H2) flow rate is 6l / min, the powder feeding amount is 40g / min, the spraying distance is 120mm, and compressed air is used to cool the other parts of the part during the spraying process. The substrate temperature is controlled at (150℃±20℃), and the coating is sprayed to a thickness of 0.6mm;

[0062] Post-processing: remove all spray protection, check the fiber optic installation location and area, use alcohol to wipe the tape residue, blow dry with compressed air and package to complete the fiber optic sensor installation.

[0063] (3) Using a high temperature furnace to perform temperature loading and testing on parts equipped with fiber grating sensors;

[0064] A primary platinum resistor was installed on the back of the part with the fiber Bragg grating sensor installed. The installed part was placed in a high-temperature furnace and tested at 650℃, 750℃, 900℃, 1000℃, 1050℃, and 1100℃. The wavelength value of the sensor at each temperature point was recorded, see Table 3.

[0065] Table 3 Wavelength values ​​at each test point

[0066]

[0067]

[0068] (4) Data processing: calculating the temperature of the part structure.

[0069] Substituting the output wavelength value of the fiber Bragg grating sensor installed on the part structure into the calibration curve of the fiber Bragg grating sensor, the temperature value corresponding to the wavelength value can be obtained, that is, the temperature of the part structure. Compared with the thermocouple temperature value, the maximum deviation is -8.13℃, as shown in Table 4.

[0070] Table 4 Sensor Calculation Temperature

[0071] Wavelength(nm) Calculated temperature value (℃) Standard thermocouple (℃) Deviation(℃) 1553.492 645.37 649.3 -3.93 1555.097 755.90 749.4 6.50 1557.462 900.01 898.4 1.61 1559.194 991.37 999.5 -8.13 1560.427 1049.11 1047 2.11 1561.596 1098.24 1096.4 1.84

[0072] The specific description above further illustrates the purpose, technical solutions and beneficial effects of the invention in detail. It should be understood that the above is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A temperature test method for ceramic matrix composite material structure based on optical fiber sensor, characterized in that: The steps include: Step 1: temperature calibrate the optical fiber sensor to be installed to obtain a calibration curve; 1) Place the standard temperature sensor and the optical fiber sensor in a high-temperature furnace to ensure that they are on the same isotherm. The optical fiber sensor is connected to the demodulator and the host computer, and the standard temperature sensor is connected to the thermometer. 2) Set multiple calibration temperature points; at each calibration temperature point, record the temperature indication of the standard temperature sensor and the optical quantity output value of the optical fiber sensor; cool down naturally to room temperature; repeat the test for more than one time; 3) Perform quadratic fitting on the multiple sets of standard thermocouple indications obtained in step 1 and the output optical quantity values ​​of the optical fiber sensor to obtain the temperature-optical quantity function relationship: λ n =a n T 2 +b n T+c n Where: n is the output of the optical fiber sensor; T is the standard thermocouple indication; n is the number of calibration test cycles; a n 、b n 、c n is the coefficient; The calibration temperature point is respectively introduced into the temperature-output optical quantity function relationship of each test to obtain the output optical quantity value of the optical fiber sensor at the calibration point, and the output optical quantity value of the optical fiber sensor is averaged. The calibration temperature point is fitted with the average value of the output optical quantity value of the optical fiber sensor at the corresponding temperature point by quadratic terms to obtain the calibration curve of the optical fiber sensor: t=Aλ 2 +Bλ+C Where: λ is the optical quantity output by the optical fiber temperature sensor; A, B, C are the sensor calibration curve function coefficients, Step 2: The flexible optical fiber sensor is fixedly mounted on the surface of the part through a plasma-based thermal spraying installation process; The specific implementation of step 2 is as follows: Pretreatment: Clean the parts, use alcohol to scrub the area where the parts are to be installed, and then blow dry with clean compressed air; Preparation of transition layer: Use metal shielding tooling to shield and protect the non-installation area of ​​the part, and install it on the part turntable or rotating axis in the vacuum chamber of the low-pressure plasma spraying system through the connecting tooling. Use pure Si powder with a slightly larger thermal expansion coefficient than the substrate and good high-temperature oxidation resistance and anti-penetration performance. Use a low-pressure plasma spray gun clamped by a manipulator to spray the Si transition layer on the surface of the part to be installed, and spray to the set coating thickness; Transition layer heat treatment: After the transition layer of the parts is sprayed, remove the protective tooling and put them into a vacuum heat treatment furnace for vacuum diffusion treatment; Preparation of intermediate layer: The intermediate layer is prepared according to the design requirements. The intermediate layer is sprayed on the area to be installed on the surface of the part by an atmospheric plasma spray gun clamped by a multi-axis manipulator. The coating material uses 3Al2O3-2SiO2 powder with a higher thermal expansion coefficient than the Si transition layer and higher thermal stability. Compressed air is used to cool the other parts of the part during the spraying process, and the coating is sprayed to the set coating thickness; Protection and fixation of optical fiber sensors: Use asbestos tape without residual glue to fix the optical fiber installation part on both sides of the area to be installed to keep the optical fiber flat as a whole, and then use thermal spray high-temperature tape and protective tooling to cover the asbestos tape surface and other parts of the optical fiber; Preparation of installation surface layer: The optical fiber installation surface layer is sprayed on the area to be installed on the surface of the part by an atmospheric plasma spray gun held by a multi-axis manipulator. The coating material is a silicate ceramic powder with a higher thermal expansion coefficient than the Si transition layer and the 3Al2O3-2SiO2 intermediate layer and good heat insulation and CMAS corrosion resistance. During the spraying process, compressed air is used to cool the other parts of the part, and the coating is sprayed to the set coating thickness; Post-processing: remove all spray protection materials, check the fiber installation location and area, use alcohol to wipe the tape residue, blow dry with compressed air and package to complete the fiber optic sensor installation; Step 3: Use a high temperature furnace to perform temperature loading and testing on the parts equipped with the optical fiber sensor; Place the parts in a high-temperature furnace, apply temperature loading, and record the optical quantity values ​​output by the sensor at each temperature point; Step 4: Data processing, calculating the temperature of the component structure; Substitute the optical quantity value obtained in step three into the calibration curve obtained in step one to obtain the temperature value corresponding to the output optical quantity value, that is, the temperature of the component structure.

2. The method for testing temperature of a ceramic matrix composite material structure based on an optical fiber sensor as claimed in claim 1, characterized in that: A standard thermocouple is installed on the back of the part in step three. The temperature collected by the standard thermocouple is used to compare with the temperature calculated by the optical fiber sensor in step four to verify the accuracy of the optical fiber sensor test and calculation results.

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