A static calibration device and method for thin film strain gauge in-situ deposited on the surface of turbine engine rotor blades

Abstract

The present invention discloses a static calibration device and method for a thin film strain gauge deposited in situ on the surface of an aircraft engine turbine rotor blade. The present invention belongs to the field of high temperature strain testing technology. It is used to calibrate a thin film strain gauge deposited in situ on the surface of a rotating component in a high temperature zone such as an aircraft engine turbine rotor blade. The calibration device consists of a resistance wire heater, a turbine engine rotor, a thin film strain gauge deposited in situ on the surface of a turbine engine rotor blade, a thin film thermocouple, and a capacitive distance sensor. The strain of the thin film strain gauge is introduced by the centrifugal force caused by high-speed rotation, and the strain size is calibrated by a capacitive distance sensor; by calibrating the strain sensitivity coefficient of the thin film strain gauge at different temperatures, the decoupling of temperature and strain is achieved. The present invention provides an effective experimental platform and method for the calibration of thin film strain gauges deposited in situ on the surface of rotating components in a high temperature zone of an aircraft engine.

Description

Technical Field

[0001] The invention belongs to the technical field of high temperature strain testing, and relates to a static calibration device and a calibration method for a thin film strain gauge deposited in situ on the surface of a turbine rotor blade of an aero-engine. Technical Background

[0002] Aircraft engines, gas turbines and other high-temperature rotating parts work in extreme environments for a long time. For example, aircraft engine turbine rotor blades are subjected to high temperature, high pressure, strong vibration and airflow during operation. Long-term operation in extreme environments will cause blade creep or even cracking, leading to flight disasters. Therefore, real-time monitoring of blade strain is of great significance to reducing the accident rate and ensuring flight safety.

[0003] Thin film strain gauges deposited in situ on the surface of turbine rotor blades refer to the process of preparing strain-sensitive materials directly on the surface of blades by physical or chemical coating, which is used to detect the strain of blades. Compared with strain gauges installed by traditional pasting, it avoids signal lag and creep caused by pasting, and has the advantage of high temperature resistance. Different from strain detection at room temperature, strain sensors working under high temperature conditions are very sensitive to temperature changes. It is extremely important to calibrate them and eliminate the interference of temperature on strain detection. However, since the structure of rotating parts in high temperature areas such as turbine blades is often more complex, it is impossible to calibrate the thin film strain gauges prepared on them by traditional tensile testing machines or cantilever beam loading methods, which limits the application prospects of such sensors.

[0004] The Chinese patent number 201610953071.2, "A device for high-temperature strain calibration from room temperature to 1800°C", uses a high-temperature furnace, a force loading device, and a cantilever beam to perform high-temperature strain calibration on a strain sensor attached to the surface of a cantilever beam. This method applies strain to the strain gauge by changing the deflection of the cantilever beam, and the high-temperature furnace is used to provide uniform temperature changes, thereby calibrating the strain sensor. This method requires the strain gauge to be prepared on the above-mentioned cantilever beam, and is not suitable for components with more complex structures such as blades. The Chinese patent number "201721562164.9" "A test device for high-temperature mechanical properties of graphite materials at 1100°C" tests the mechanical properties of the sample based on a tensile testing machine, a high-temperature furnace, and a high-temperature fixture. This method has high requirements for the tensile substrate and is also not suitable for rotating parts with more complex structures such as blades.

[0005] It can be seen that the currently available high-temperature strain calibration devices and methods are unable to perform high-precision calibration on thin-film strain gauges deposited in situ on the surface of rotating parts in high-temperature areas such as turbine engine rotor blades. Summary of the invention

[0006] The purpose of the present invention is to invent a static calibration device and calibration method for thin film strain gauges deposited in situ on the surface of aircraft engine turbine rotor blades in view of the above technical defects. It provides an effective experimental platform for the static calibration of thin film strain gauges deposited in situ on the surface of aircraft engine turbine rotor blades, and provides data support for strain detection of aircraft engine turbine blades in high temperature environments.

[0007] A static calibration device for a thin film strain gauge deposited in situ on the surface of an aircraft engine turbine rotor blade, characterized in that the device comprises a resistance wire heater 8, a turbine engine rotor 6, a thin film strain gauge 3 and a thin film thermocouple 2 deposited in situ on the surface of a rotor blade 1, a capacitive distance sensor 7, a temperature control unit 9, and a data acquisition unit 10;

[0008] The resistance wire heater 8 is placed parallel to the turbine engine rotor 6 at a distance of 0.5-0.7m; the resistance wire is made of nickel-chromium alloy wire, and the maximum heating temperature is 1400°C; the resistance wire heater 8 and the temperature control unit 9 are used to provide a uniform temperature field of 25-1400°C, and the temperature stability is ≤1°C / hour.

[0009] The turbine engine rotor 6 is composed of a turbine disk and a rotor blade 1, with a standard operating speed of 10000rpm and an acceleration operating speed of 10850rpm; a thin film strain gauge 3 for detecting the strain of the rotor blade 1 and a thin film thermocouple 2 for detecting the temperature of the rotor blade 1 are prepared in situ on the back surface of the rotor blade 1 by physical or chemical plating; the symmetry axis of the thin film strain gauge 3 and the thin film thermocouple 2 coincides with the line connecting the capacitive ranging sensor 7 and the center of the turbine engine rotor 6, and is 30-50mm away from the top of the blade; the electrical signals of the thin film strain gauge 3 and the thin film thermocouple 2 are led out from the pad 4 through high-temperature conductive paste and lead 5.

[0010] The thin film strain gauge 3 and the thin film thermocouple 2 are made of high temperature resistant metal or ceramic, including but not limited to NiCr (maximum tolerance of 450°C), PdCr (maximum tolerance of 700°C), Pt (maximum tolerance of 1000°C), ZnO (maximum tolerance of 1000°C), In 2 O 3 (maximum tolerance 1300℃), etc., practitioners can make choices based on actual test conditions.

[0011] The capacitive distance sensor 7 is placed parallel to the turbine engine rotor blade 1 at a distance of 1-3 mm, and the resolution of the capacitive distance sensor 7 is ≤ 0.5 um; the tensile strain of the turbine engine rotor blade 1 is detected by detecting the change in capacitance.

[0012] A static calibration method for thin film strain gauges deposited in situ on the surface of aero-engine turbine rotor blades includes the following two parts:

[0013] Part 1: Establish the corresponding relationship between the resistance change of the thin film strain gauge 3 and the strain and temperature change:

[0014] The first step is to measure the initial resistance R of the thin film strain gauge 3 0 and the initial length L of the rotor blade 1 0 .

[0015] The second step is to calibrate the thin film thermocouple 2: place the rotor blade 1 prepared with the thin film thermocouple 2 in a high-temperature muffle furnace, the controllable temperature range of the high-temperature muffle furnace is 25-1400°C, and the temperature control accuracy is ≤±1°C; place the hot end of the thin film thermocouple 2 in the furnace and the cold end outside the furnace; the standard S-type thermocouple 13 is used to detect the hot end temperature of the thin film thermocouple 2, and the standard K-type thermocouple 12 is used to detect the cold end temperature of the thin film thermocouple 2; the ice point device 14 is used to provide a standard zero point temperature for the standard S-type and K-type thermocouples; the high-temperature furnace is heated from 25°C to the temperature to be calibrated of the thin film thermocouple 2 at a heating rate of 5°C / min, and the data acquisition unit 10 synchronously records the cold end temperature, hot end temperature and voltage output curve of the thin film thermocouple 2, and establishes a corresponding relationship between the output voltage and temperature of the thin film thermocouple 2;

[0016] The third step is to drive the turbine engine rotor 6 at a speed of 10,000 rpm under standard conditions; after the speed stabilizes, the capacitive distance sensor 7 is used to measure the radial extension ΔL of the rotor blade 1; and the strain magnitude ε (ε=ΔL / L) introduced by the centrifugal force is calculated. The resistance wire heater 8 and the temperature control unit 9 apply a uniform temperature field to the turbine engine rotor 6, with a temperature range of 25°C to the temperature to be calibrated of the thin film strain gauge 3, a heating rate of 10°C / min, and a heating of 50°C for 10 minutes. The data acquisition unit 10 synchronously records the resistance change ΔR of the thin film strain gauge 3 and the output voltage of the thin film thermocouple 2 at a sampling interval of 50°C; the blade temperature T is measured based on the calibrated thin film thermocouple 2, and the strain sensitivity coefficient of the thin film strain gauge at different temperatures T is calculated as follows:

[0017]

[0018] Wherein, K is the strain sensitivity coefficient of the thin film strain gauge 3 .

[0019] Part 2: According to the temperature of the rotor blade 1 measured by the thin film thermocouple 2, the strain sensitivity K of the thin film strain gauge 3 is determined, and the strain magnitude is inferred in combination with the resistance change ΔR of the thin film strain gauge 3. The formula is as follows:

[0020] BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of a static room temperature calibration device for thin film strain gauges deposited in situ on the surface of aero-engine turbine rotor blades.

[0022] Figure 2 Schematic diagram of a static high-temperature calibration device for thin-film strain gauges deposited in situ on the surface of aero-engine turbine rotor blades.

[0023] Figure 3 Schematic diagram of the thin film thermocouple calibration device.

[0024] Figure 4 ITO-In 2 O 3 The corresponding relationship between the output voltage and temperature of the thin film thermocouple.

[0025] Figure 5 Corresponding relationship between strain sensitivity K and temperature T of Pd-13%Cr thin film strain gauge

[0026] Among them, 1-rotor blade; 2-thin film thermocouple; 3-thin film strain gauge; 4-soldering pad; 5-lead; 6-turbine engine rotor; 7-capacitive ranging sensor; 8-resistance wire heater; 9-temperature control unit; 10-data acquisition unit; 11-high temperature muffle furnace; 12-K type thermocouple; 13-S type thermocouple; 14-freezing point device.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention provides a high-temperature strain static calibration device and calibration method with a simple structure, convenient operation and high precision for thin film strain gauges deposited in situ on the surface of blades of rotating parts in high-temperature zones such as aircraft engines and gas turbines. The centrifugal force introduced by high-speed rotation applies radial strain to the blades, and the capacitive distance sensor is used to calibrate the strain introduced by the centrifugal force. The in-situ deposited thin film strain gauge and thin film thermocouple are used to detect the strain and temperature of the blades respectively; by calibrating the strain sensitivity coefficient of the thin film strain gauge at different temperatures, the interference of temperature on strain detection is eliminated, thereby improving the detection accuracy of the thin film strain gauge under high-temperature conditions. This calibration method solves the problem that the existing high-temperature strain calibration method cannot calibrate thin film strain gauges deposited in situ on the surface of rotating parts in high-temperature zones with complex structures and harsh working environments, further improving the detection accuracy of such sensors and expanding their application prospects. Specific embodiments

[0028] The specific implementation of the present invention is described in detail below with reference to the accompanying drawings and technical solutions

[0029] The present invention discloses a static calibration device for a thin film strain gauge deposited in situ on the surface of an aeroengine turbine rotor blade. The device comprises a resistance wire heater, a turbine engine rotor, a thin film strain gauge and a thin film thermocouple deposited in situ on the back surface of the rotor blade, a capacitive distance measuring sensor, and a data acquisition unit.

[0030] The resistance wire heater is placed parallel to the turbine engine rotor at a distance of 0.5m; the resistance wire is made of nickel-chromium alloy wire with a maximum tolerance temperature of 1400°C. Based on the temperature control unit, a uniform temperature field of 25-700°C is provided for the turbine engine rotor blades, and the temperature stability is ≤1°C / hour.

[0031] The turbine engine rotor consists of a turbine disk and rotor blades, with a standard operating speed of 10,000 rpm and an acceleration operating speed of 10,850 rpm; the surface of the rotor blade is prepared with a thin film strain gauge for detecting blade strain and a thin film thermocouple for detecting blade temperature based on magnetron sputtering coating; the symmetry axis of the thin film strain gauge 3 and the thin film thermocouple 2 coincides with the line connecting the capacitive ranging sensor 7 and the center of the turbine engine rotor 6, which is 30 mm away from the top of the blade; the electrical signals of the thin film strain gauge and the thin film thermocouple are led out from the welding pad through high-temperature conductive silver paste and platinum wire; the failure temperature of the high-temperature conductive silver paste is 1,100°C.

[0032] The thin film strain gauge material is Pd-13% Cr, which has good linearity and repeatability at 700°C; the thin film thermocouple electrode material is In 2 O 3 and ITO, with good repeatability below 1300°C.

[0033] The capacitive distance measuring sensor 7 is placed parallel to the turbine engine rotor blade 1 at a distance of 2 mm, with a detection resolution of 0.3 um and a maximum detection range of 200 um; it is used to detect the tensile strain of the turbine engine rotor blade caused by centrifugal force.

[0034] A static calibration method for thin film strain gauges deposited in situ on the surface of aero-engine turbine rotor blades includes the following two parts:

[0035] Part 1: Establish the corresponding relationship between the resistance change of the thin film strain gauge 3 and the strain and temperature change:

[0036] The first step is to measure the initial resistance R of the thin film strain gauge. 0 and the initial length L of the rotor blade 1 0 In this embodiment, R 0 The size is 210.2Ω, L 0 The size is 100mm.

[0037] The second step is to calibrate the thin film thermocouple. 2 O 3 The rotor blade of the thin film thermocouple is placed in a high-temperature muffle furnace, the hot junction of the thin film thermocouple is placed in the furnace, and the cold end is placed outside the furnace; the temperature in the furnace is controlled to rise from 25°C to 700°C at a rate of 5°C per minute, and the temperature control accuracy is ≤±1°C; the standard S-type thermocouple is used to detect the hot end temperature of the thin film thermocouple, and the standard K-type thermocouple is used to detect the cold end temperature of the thin film thermocouple; the ice point device is used to provide a standard zero point temperature for the standard S-type and K-type thermocouples; the high-temperature furnace is heated from 25°C to the temperature to be marked of the thin film thermocouple 2 at a heating rate of 5°C / min, and the data acquisition unit 10 synchronously records the cold end temperature, hot end temperature and voltage output curve of the thin film thermocouple 2, and establishes a corresponding relationship between the output voltage and temperature of the thin film thermocouple 2, such as Figure 4 shown.

[0038] The third step is to drive the turbine engine rotor 6 at a speed of 10,000 rpm under standard conditions; after the speed stabilizes, the capacitive distance sensor 7 is used to measure the length extension ΔL of the rotor blade 1; and calculate the strain ε (ε=ΔL / L) introduced by the centrifugal force. In this embodiment, ΔL is 69.3 μm, so the blade tensile strain caused by the centrifugal force can be calculated to be 693 με. The resistance wire heater 8 and the temperature control unit 9 apply a uniform temperature field to the turbine engine rotor 6, with a temperature range of 25°C-700°C, a heating rate of 10°C / min, and a heating of 50°C for 10 minutes. The data acquisition unit 10 synchronously records the resistance change ΔR of the thin film strain gauge 3 and the output voltage of the thin film thermocouple 2 at a sampling interval of 50°C; based on the calibrated thin film thermocouple 2, the blade temperature T is measured, and further, the strain sensitivity coefficient of the thin film strain gauge corresponding to different temperatures T is calculated according to the following formula, such as Figure 5 shown.

[0039]

[0040] Part II: In actual testing, the strain sensitivity K of the thin film strain gauge 3 can be determined based on the temperature T of the rotor blade 1 measured by the thin film thermocouple 2. Furthermore, the strain magnitude can be inferred based on the resistance change ΔR of the thin film strain gauge 3. The formula is as follows:

[0041]

Claims

1. A static calibration device for thin film strain gauges deposited in situ on the surface of turbine rotor blades of aircraft engines, Its characteristics are: The device is composed of a resistance wire heater (8), a turbine engine rotor (6), a thin film strain gauge (3) and a thin film thermocouple (2) deposited in situ on the back surface of a rotor blade (1), a capacitive distance sensor (7), a temperature control unit (9), and a data acquisition unit (10); The resistance wire heater (8) is placed in parallel with the turbine engine rotor (6) at a distance of 0.5-0.7 m; the resistance wire is made of nickel-chromium alloy wire, and the maximum heating temperature is 1400° C.; the resistance wire heater (8) and the temperature control unit (9) are used to provide a uniform temperature field of 25-1400° C., and the temperature stability is ≤1° C. / hour; The turbine engine rotor (6) is composed of a turbine disk and a rotor blade (1), with a standard operating speed of 10,000 rpm and an accelerated operating speed of 10,850 rpm; a thin film strain gauge (3) for detecting the strain of the rotor blade (1) and a thin film thermocouple (2) for detecting the temperature of the rotor blade (1) are prepared in situ on the back surface of the rotor blade (1) by physical or chemical plating; the symmetry axis of the thin film strain gauge (3) and the thin film thermocouple (2) coincides with the line connecting the capacitive distance sensor (7) and the center of the turbine engine rotor (6), and is 30-50 mm away from the top of the blade; the electrical signals of the thin film strain gauge (3) and the thin film thermocouple (2) are led out from the pad (4) through high-temperature conductive paste and leads (5).

2. The static calibration device for the thin film strain gauge deposited in situ on the surface of the turbine rotor blade of an aircraft engine as claimed in claim 1, It is characterized in that The thin film strain gauge (3) and the thin film thermocouple (2) are made of high temperature resistant metal or ceramic.

3. The static calibration device for the thin film strain gauge deposited in situ on the surface of the turbine rotor blade of an aircraft engine as claimed in claim 1, It is characterized in that The capacitive distance sensor (7) is placed parallel to the turbine engine rotor blade (1) at a distance of 1-3 mm, and the resolution of the capacitive distance sensor (7) is ≤0.5 um.

4. A static calibration method implemented by the static calibration device of the thin film strain gauge in-situ deposited on the surface of the turbine rotor blade of an aircraft engine according to claim 1, comprising the following two parts: Part I: Establish the corresponding relationship between the resistance change and strain and temperature change of the thin film strain gauge (3): The first step is to measure the initial resistance R of the thin film strain gauge (3) 0 and the initial length L of the rotor blade (1) 0 ; The second step is to calibrate the thin film thermocouple (2): placing the rotor blade 1 prepared with the thin film thermocouple (2) in a high-temperature muffle furnace, wherein the controllable temperature range of the high-temperature muffle furnace is 25-1400°C, and the temperature control accuracy is ≤±1°C; placing the hot end of the thin film thermocouple (2) in the furnace and the cold end outside the furnace; a standard S-type thermocouple (13) is used to detect the hot end temperature of the thin film thermocouple (2), and a standard K-type thermocouple (12) is used to detect the cold end temperature of the thin film thermocouple (2); an ice point meter (14) is used to provide a standard zero point temperature for the standard S-type and K-type thermocouples; the high-temperature furnace is heated from 25°C to the temperature to be calibrated of the thin film thermocouple (2) at a heating rate of 5°C / min, and the data acquisition unit (10) synchronously records the cold end temperature, hot end temperature and voltage output curve of the thin film thermocouple (2), and establishes a corresponding relationship between the output voltage and temperature of the thin film thermocouple (2); The third step is to drive the turbine engine rotor (6) at a speed of 10,000 rpm under standard conditions; after the speed stabilizes, the capacitive distance sensor 7 is used to measure the radial extension ΔL of the rotor blade (1); and calculate the strain ε introduced by the centrifugal force. in, ε=ΔL / L; the resistance wire heater (8) and the temperature control unit (9) apply a uniform temperature field to the turbine engine rotor (6), the temperature range is from 25°C to the temperature to be calibrated of the thin film strain gauge (3), the heating rate is 10°C / min, the temperature is raised to 50°C and the temperature is kept for 10 minutes; the data acquisition unit (10) synchronously records the resistance change ΔR of the thin film strain gauge (3) and the output voltage of the thin film thermocouple (2) at a sampling interval of 50°C; the blade temperature T is measured based on the calibrated thin film thermocouple (2), and the strain sensitivity coefficient of the thin film strain gauge at different temperatures T is calculated as follows: Wherein, K is the strain sensitivity coefficient of the thin film strain gauge (3); Part II: Based on the temperature of the rotor blade (1) measured by the thin film thermocouple (2), the strain sensitivity K of the thin film strain gauge (3) is determined, and the strain magnitude is inferred in combination with the resistance change ΔR of the thin film strain gauge (3). The formula is as follows:

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