Multispectral radiation temperature measuring device based on endoscopic probe

Abstract

The utility model provides a multispectral radiation temperature measuring device based on an endoscopic probe. The multispectral radiation temperature measuring device is particularly suitable for temperature detection of engine turbine blades. The device comprises an endoscopic probe, a cooling protective cover, a fixed flange plate, a multispectral camera and a three-dimensional temperature field analysis module, radiation signals and image information of a blade are effectively obtained through a reflector and a dichroscope which are arranged at the front end of the endoscopic probe, and by combining the advanced cooling protective cover and an active illumination structure design, the blade radiation detection accuracy is improved. A multispectral camera is used for imaging, and in-situ online measurement of the three-dimensional morphology and the temperature field of the turbine blade is achieved. The device is compact in structure, and has the characteristics of small size, high temperature resistance, high definition, full-field measurement and the like.

Description

Technical Field

[0001] The invention relates to the field of in-situ measurement of temperature of a turbine blade of an aero-engine, and in particular to a multi-spectral radiation temperature measurement device based on an endoscopic probe. Background Art

[0002] As one of the core components of the engine, turbine blades work in a complex environment of high temperature, high pressure, high speed and variable working conditions for a long time, and the surface is prone to cracks, falling blocks and other damage. Accurately measuring and describing the three-dimensional temperature field of turbine blades and their changing process can, on the one hand, ensure the service safety of the engine, and on the other hand, provide important data support for the structural design and optimization of high-performance engine turbine blades. Radiation temperature measurement has been widely used in various industrial radiation temperature measurement, medical radiation temperature measurement and important scientific research due to its advantages such as high efficiency, non-contact, wide adaptability and fast response speed. Every object releases heat in the form of infrared radiation, and its radiation intensity is related to the temperature of the object. The radiation temperature measuring instrument receives the infrared radiation emitted by the object, converts it into an electrical signal, and then calculates the temperature of the object through an algorithm.

[0003] Accurate measurement of turbine blade temperature has always been a technical challenge in engineering. The reason is that the operating conditions in the engine combustion chamber are too harsh. The test signals received by the sensor often undergo multiple transmissions and are affected by vibration, aerodynamics, combustion and other factors. The signal-to-noise ratio is low, resulting in a serious decrease in measurement accuracy. Secondly, the internal structure of the combustion chamber is compact and the space is limited, which imposes strict restrictions on the installation position and size of sensors and other accessories, resulting in a limited number of observation points and fixed positions, which affects the acquisition of diagnostic information.

[0004] To solve this problem, the patent (CN 116147780 A) provides a small radiation temperature measurement probe for aircraft engine turbine blades, including a reflector, a probe housing, a light pipe, a mounting seat, a photoelectric detector, a fixing plate, a back cover and other parts. The structural parts are all made of GH3044 high-temperature alloy, which has good high temperature and high pressure resistance. The photoelectric detector uses a mercury cadmium telluride infrared photoelectric detector with cooling, and a micro thermoelectric cooler is used to adjust the temperature difference between the inside of the detector and the environment, so that the photosensitive material can work stably; it has the advantages of small size, light weight, and easy disassembly, and can be flexibly used in the temperature measurement scenarios of turbine blades of various types of aircraft engines.

[0005] There are still some problems that need to be improved in this technology: 1) The front end of the probe needs to be extended into the engine at 1400℃. The optical lens cannot withstand such high temperatures, so a corresponding cooling system must be designed; 2) This technology only considers temperature measurement in optical design, but not imaging, so it can only obtain temperature data and cannot realize blade image visualization; 3) This technology belongs to single-view single-point measurement, which cannot describe the two-dimensional and three-dimensional temperature field distribution of the entire blade surface. The two-dimensional and three-dimensional temperature field is precisely the key to understanding the blade material and damage mechanism. Summary of the invention

[0006] (I) Technical Problems to be Solved by the Present Invention

[0007] In view of the shortcomings of existing detection devices, the present invention proposes a multi-spectral radiation temperature measurement device and method based on an endoscopic probe. Through ingenious optical path design and a dedicated cooling protection cover, the image of the turbine blades and the three-dimensional temperature field under working conditions can be visualized. It has the characteristics of small size, high temperature resistance, high definition, and full-field measurement.

[0008] (II) Technical solution of the present invention

[0009] On the one hand, the present invention provides a multi-spectral radiation temperature measurement device based on an endoscopic probe, which is characterized in that it includes:

[0010] The endoscopic probe adopts a dual-channel coaxial optical path, including a lens barrel, and a reflector, a dichroic mirror and an imaging objective lens sequentially arranged in the lens barrel along the optical axis of the probe, and a first light window and a second light window are arranged side by side at the front end of the lens barrel; the reflector is located at the first light window of the lens barrel, and is used to collect and reflect radiation energy from the surface of the turbine blade to be measured; the dichroic mirror is located at the second light window of the lens barrel, and is used to separate and reflect radiation energy of different wavelengths; the imaging objective lens is used to focus the collected radiation energy onto a multi-spectral camera;

[0011] A cooling protection cover is sleeved outside the lens barrel, and a third light window and a fourth light window for mounting a sapphire lens are arranged side by side at the front end, and the third light window is the same size as the first light window and the center is vertically aligned, and the fourth light window is the same size as the second light window and the center is vertically aligned, and a plurality of water inlets and outlets are distributed at the rear end, and a water vapor pipeline is arranged inside the cooling protection cover, which is connected to an external water cooling box through the water inlet and the water outlet;

[0012] A multispectral camera, connected to the endoscope probe, having multiple channels and a wavelength range of 550-980 nm, for receiving turbine blade radiation signals transmitted by the endoscope probe, extracting blade images at different wavelengths, realizing blade image visualization, and simultaneously reading the grayscale value of the multispectral image, and calculating the true temperature and emissivity of the blade by Planck's law;

[0013] The three-dimensional temperature field analysis module is connected to the multi-spectral camera and reconstructs the three-dimensional temperature field of the blade from the image acquired by the multi-spectral camera based on the algebraic reconstruction principle.

[0014] Furthermore, it also includes a fixing flange for connecting and fixing the lens barrel and the cooling protection cover.

[0015] Furthermore, it also includes an active light source, which is sent to the front end of the endoscopic probe through optical fiber lighting to illuminate the engine blade to be tested so as to enhance the intensity of the light signal captured by the spectral camera; the radiation signal of the blade passes through the reflector and the dichroic mirror in turn, and is finally imaged through the imaging objective lens, received by the multi-spectral camera, and transmitted to the three-dimensional temperature field analysis module.

[0016] Preferably, the angle between the reflector and the probe optical axis is 52°, the angle between the dichroic mirror and the probe optical axis is 52°, and they are fixed in the lens barrel through a limiting slot, and the distance between the two is 18 mm to achieve binocular imaging effect.

[0017] Preferably, the imaging objective lens comprises 12 lenses, of which 10 are standard spherical lenses and 2 are aspherical lenses. The total length of the optical system is 165 mm, the paraxial magnification is 1.5, the overall focal length is 65 mm, and the optical aperture is less than 10 mm.

[0018] On the other hand, the present invention also provides a multi-spectral radiation temperature measurement method based on an endoscopic probe using the above-mentioned temperature measurement device, which is characterized in that it includes the following steps:

[0019] S1. Multispectral image acquisition and calibration:

[0020] The multi-spectral radiation temperature measurement device is calibrated using a standard black body to establish a mapping relationship between the radiation intensity E and the grayscale value of the spectral image;

[0021] Install the multispectral radiation temperature measurement device according to the preset layout, and collect multispectral images of the blades at two different viewing angles through a multispectral camera;

[0022] S2. Two-dimensional temperature field and emissivity calculation:

[0023] Using 25 multispectral images acquired by a multispectral camera, combined with Planck's law, we established the following equations:

[0024]

[0025] In the formula, E m (R λi ) is the radiation intensity of the i-th wavelength, λ i represents the i-th wavelength, where 1≤i≤m; ε is the emissivity of the blade to be measured, C1 and C 2 are the first radiation constant and the second radiation constant respectively, T is the temperature of the blade;

[0026] The least square method is used to solve the equations to obtain the temperature T and emissivity ε of the blade;

[0027] S3. 3D morphology and temperature field reconstruction:

[0028] Accurately calibrate the internal and external parameters of the multi-spectral radiation temperature measurement device;

[0029] Using the calibration parameters, the binocular information of the spectral image is obtained in combination with the first light window and the second light window, and the three-dimensional morphology of the turbine blade is restored using a three-dimensional reconstruction algorithm;

[0030] The three-dimensional temperature field distribution of the turbine blade is obtained by iterative calculation using the algebraic reconstruction technique (ART) algorithm combined with binocular information and multispectral data.

[0031] During the iteration process, the algorithm starts from the given initial value, gradually back-projects the projection residual uniformly along the ray direction, and continuously corrects the image until the preset conditions are met, thereby obtaining an accurate three-dimensional temperature field distribution.

[0032] Preferably, the cooling protection cover and the sapphire lens are fixed by laser welding, which can isolate them from the high temperature environment and reduce the working environment temperature of the optical lens, and prevent pollutants from falling on the mirror surface and affecting the imaging effect.

[0033] Preferably, the inner interlayer of the cooling protective cover is provided with precise water vapor pipes, and the rear end is connected to the endoscope probe barrel through a fixed flange. The protective cover is provided with three air inlets and three air outlets, and the diameters of the air inlets and the air outlets are both 2mm, and are connected to an external water cooling box; the front end of the cooling protective cover is sprayed with a precise zirconium oxide coating to protect the internal optical lens.

[0034] Preferably, a layer is opened on the middle wall of the endoscope probe barrel, and the active light source 18 is sent to the front end of the endoscope probe by means of optical fiber lighting, and illuminates the engine blade to be tested through a dichroic mirror, thereby ensuring the intensity of the light signal captured by the spectral camera.

[0035] Preferably, the multispectral camera has 25 channels and a wavelength range of 550-980nm. The spectral camera can extract images of leaves at different wavelengths and realize leaf image visualization. At the same time, the grayscale value of the multispectral image is read, and the true temperature of the leaf is obtained through Planck's law, and the emissivity of the leaf is obtained.

[0036] ③Technical effects of the present invention

[0037] The present invention proposes a multi-spectral radiation temperature measurement device based on an endoscopic probe, which can be applied to the temperature measurement of engine blades under harsh working conditions of high temperature, high pressure and high speed. Compared with the prior art, the advantages of the present invention are:

[0038] 1) The present invention adopts an advanced coaxial optical path design, which can not only realize the real-time measurement of the temperature of the engine turbine blades, but also can produce clear images, which is beneficial to the engine fault diagnosis.

[0039] 2) The present invention improves the upper temperature limit of the endoscope probe through the precise design of the cooling protection cover, thereby ensuring the normal operation of the imaging objective lens.

[0040] 3) The present invention utilizes the advantage of high spectral resolution of multispectral cameras, and cooperates with specially coated reflectors and dichroic mirrors to extract blade images at different angles, and restores the three-dimensional morphology and three-dimensional temperature field distribution of the blades through a three-dimensional reconstruction algorithm.

[0041] 4) By utilizing the blade images of different wavelengths separated by the multi-spectral camera, the three-dimensional temperature field of the blade can be obtained through the three-dimensional temperature field analysis system, thereby providing important data reference for blade material selection and structural design; the method of the present invention is simple to operate, has strong anti-noise interference ability, and has unique advantages in the field of three-dimensional reconstruction under sparse angles. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a schematic diagram of a multi-spectral radiation temperature measurement device based on an endoscopic probe.

[0043] Figure 2 It is a schematic diagram of the structure of an endoscopic probe with a cooling protective cover.

[0044] Figure 3 It is a schematic diagram of the structure of the cooling protection cover.

[0045] Figure 4 This is a partial area diagram of the water cooling pipe of the cooling protection cover.

[0046] Figure 5 It is the optical system diagram of the imaging objective.

[0047] Figure 6 It is the MTF curve of the imaging objective optical system.

[0048] Figure 7 It is a calculation process diagram of the three-dimensional temperature field algebraic reconstruction algorithm.

[0049] Wherein: 1-turbine blade to be tested, 2-first light window, 3-second light window, 4-engine casing, 5-cooling protection cover, 6-endoscopic probe, 7-multi-spectral camera, 8-data connection line, 9-three-dimensional temperature field analysis system, 10-third light window, 11-fourth light window, 12-fixed flange, 13-air cooling inlet, 14-air cooling outlet, 15-reflector, 16-dichroic mirror, 17-imaging objective lens, 18-active light source. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. The technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the invention and the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0051] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. The experimental methods without specific conditions in the following examples are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. Unless otherwise specified, all percentages, ratios, proportions or parts are by weight.

[0052] Figure 1 It is a schematic diagram of a multi-spectral radiation temperature measurement device based on an endoscope probe, which mainly includes a turbine blade 1 to be measured, an endoscope probe 6, a cooling protection cover 5, a fixed flange 16, a multi-spectral camera 7 and a three-dimensional temperature field analysis system 9. The front end of the endoscope probe 6 is respectively provided with a first light window 2 and a second light window 3, and the diameters of the first light window 2 and the second light window 3 are both 12 mm. A reflector 15 is installed inside the first light window 2, and a dichroic mirror 16 is installed inside the second light window 3. The thicknesses of the reflector 15 and the dichroic mirror 16 are 1.5 mm and 2 mm respectively, and they are fixed to the probe lens barrel through a limit card slot; the angle between the reflector 15 and the optical axis of the endoscope probe is 52°, and the angle between the dichroic mirror 16 and the optical axis of the endoscope probe is 52°. The centers of the reflector 15 and the dichroic mirror 16 both fall on the optical axis, and the distance between the two is 18 mm. The binocular imaging effect of the engine blade is achieved through a special coating process.

[0053] Figure 2 The front end of the endoscopic probe 6 collects radiation energy from the surface of the engine blade 1 through the first light window 2 and the second light window 3 and enters the probe lens barrel, and is received by the multi-spectral camera 7 through the imaging objective lens 17 . Figure 5 and Figure 6They are the optical system diagram and MTF curve diagram of the imaging objective lens. The imaging objective lens 17 includes 12 lenses, including 10 standard spherical lenses and 2 aspherical lenses. The total length of the optical system is 165 mm, the paraxial magnification is 1.5, the overall focal length is 65 mm, the optical aperture is less than 10 mm, and various aberrations are controlled within a relatively small range.

[0054] Considering that the light energy entering the imaging lens group 13 through the reflector 14 is limited, a layer is opened on the middle wall of the endoscope probe 6, and an active light source 18 is added to ensure that the detector captures light energy of sufficient intensity. The active light source 18 is sent to the front end of the endoscope probe by optical fiber lighting, and illuminates the engine blade to be tested through the dichroic mirror 16, ensuring the intensity of the light signal captured by the spectral camera, which is conducive to the reconstruction of the three-dimensional morphology and temperature field of the turbine blade.

[0055] The front end of the endoscopic probe 6 extends into the interior of the cooling protection cover 5, and then the whole extends into the interior of the casing 4. The front end diameter of the cooling protection cover is less than 20mm, and the front end of the protection cover successively opens a third light window 10 and a fourth light window 11, which are also 12mm in diameter; the third light window 10 is the same size as the first light window 2, and the centers of the light windows are vertically aligned; the fourth light window 11 is the same size as the second light window 3, and the centers of the light windows are also vertically aligned. The third light window 10 and the fourth light window 11 are both equipped with sapphire lenses with a thickness of 2.5mm. The light windows and the sapphire lenses are fixed by laser welding. On the one hand, they can be isolated from the high temperature environment and reduce the working environment temperature of the optical lens. On the other hand, they can prevent pollutants from falling on the mirror surface and affecting the imaging effect.

[0056] Figure 3 The cooling protection cover has a structure diagram in which a precise water vapor pipeline is arranged in the inner interlayer, and the rear end is connected to the endoscope probe barrel through a fixed flange 16 . Figure 4 A local area diagram of the water cooling pipeline of the cooling protective cover is given. The protective cover is provided with three air inlets 13 and three air outlets 14. The diameters of the air inlets and the air outlets are both 2 mm and are connected to an external water cooling box. The front end of the cooling protective cover 5 is sprayed with a precise zirconium oxide coating to protect the internal optical lens.

[0057] The other end of the endoscopic probe 6 is connected to a multispectral camera 7, which has 25 channels and a wavelength range of 550-980nm. The spectral camera can extract images of blades at different wavelengths, visualize blade images, and read the grayscale value of the multispectral image at the same time. The true temperature of the blade is obtained by Planck's law, and the emissivity of the blade is obtained at the same time. Further, the binocular information obtained by the first light window 2 and the second light window 3 is used to obtain the two-dimensional and three-dimensional temperature field distribution of the turbine blade to be measured with the help of an algebraic iteration algorithm.

[0058] The steps of calculating the two-dimensional temperature field and emissivity of the blade by multispectral image are as follows: 1) calibrate the multispectral radiation temperature measurement device using a standard black body to establish the relationship between the radiation intensity E and the grayscale value of the spectral image; 2) Figure 1 Install a multi-spectral radiation temperature measurement device, turn on the water-cooling and air-cooling device, and use a multi-spectral camera to collect multi-spectral images of the blade at two viewing angles; 3) Use the 25 multi-spectral images obtained by the spectral camera to establish the following equations using Planck's law, and use the least squares method to solve the blade temperature T and emissivity ε:

[0059]

[0060] In the formula, E m (R λi ) is the radiation intensity of the i-th wavelength, λ i represents the i-th wavelength, where 1≤i≤m; ε is the emissivity of the blade to be measured, C 1 and C 2 are the first radiation constant and the second radiation constant respectively, T is the temperature of the blade;

[0061] Furthermore, the multispectral images obtained by the first light window 2 and the second light window 3 are separated by the spectral curves distinguished by the reflector 15 and the dichroic mirror 16, and the three-dimensional morphology of the blade and its temperature field are reconstructed using the multi-view information contained therein. The specific steps are as follows: 1) Calibrate the internal and external parameters of the multispectral radiation temperature measurement device; 2) Use the parameters obtained by calibration, combine the binocular information of the spectral image obtained by the first light window 2 and the second light window 3, and use the three-dimensional reconstruction algorithm to restore the three-dimensional morphology of the turbine blade; 3) Use the ART algorithm to obtain the three-dimensional temperature field distribution of the turbine blade. Figure 7 This is the calculation process diagram of the three-dimensional temperature field algebraic reconstruction algorithm. The principle is as follows:

[0062]

[0063] Where k is the number of iterations, 1≤i≤N, and λ is the relaxation factor (0<λ<2). The algorithm first gives the reconstruction area an initial value, which is generally zero, and then evenly back-projects the obtained projection residuals along the ray direction one by one, continuously correcting the image until it meets the required requirements, and then ends the iterative process to obtain the three-dimensional temperature field distribution of the turbine blade.

[0064] This embodiment combines the endoscopic probe technology with the multi-spectral radiation temperature measurement technology, and adopts the technical means of the combination of dual-channel coaxial optical path, cooling protection system and three-dimensional temperature field analysis system, which can more accurately measure the temperature of turbine blades in high temperature environments, and provide more comprehensive data support through three-dimensional temperature field analysis. This progress is of great significance in the field of temperature measurement of aircraft engine turbine blades.

Claims

1. A multi-spectral radiation temperature measurement device based on an endoscopic probe, characterized in that: include: The endoscopic probe adopts a dual-channel coaxial optical path, including a lens barrel, and a reflector, a dichroic mirror and an imaging objective lens sequentially arranged in the lens barrel along the optical axis of the probe, and a first light window and a second light window are arranged side by side at the front end of the lens barrel; The reflector is located at the first light window of the lens barrel and is used to collect and reflect radiation energy from the surface of the turbine blade to be measured; The dichroic mirror is located at the second light window of the lens barrel and is used to separate and reflect radiation energy of different wavelengths; The imaging objective lens is used to focus the collected radiation energy onto the multi-spectral camera; A cooling protection cover is sleeved outside the lens barrel, and a third light window and a fourth light window for mounting a sapphire lens are arranged side by side at the front end, and the third light window is the same size as the first light window and the center is vertically aligned, and the fourth light window is the same size as the second light window and the center is vertically aligned, and a plurality of water inlets and water outlets are distributed at the rear end, and a water vapor pipeline is arranged inside the cooling protection cover, which is connected to an external water cooling box through the water inlet and the water outlet; A multispectral camera, connected to the endoscope probe, having multiple channels and a wavelength range of 550-980 nm, for receiving turbine blade radiation signals transmitted by the endoscope probe, extracting blade images at different wavelengths, realizing blade image visualization, and simultaneously reading the grayscale value of the multispectral image, and calculating the true temperature and emissivity of the blade by Planck's law; The three-dimensional temperature field analysis module is connected to the multi-spectral camera and reconstructs the three-dimensional temperature field of the blade from the image acquired by the multi-spectral camera based on the algebraic reconstruction principle.

2. The multi-spectral radiation temperature measurement device based on an endoscopic probe according to claim 1 is characterized in that: It also includes a fixing flange plate, which is used for connecting and fixing the lens barrel and the cooling protection cover.

3. The multi-spectral radiation temperature measurement device based on an endoscopic probe according to claim 1 is characterized in that: It also includes an active light source, which is sent to the front end of the endoscopic probe through optical fiber lighting to illuminate the engine blade to be tested to enhance the intensity of the light signal captured by the spectral camera; the radiation signal of the blade passes through the reflector and the dichroic mirror in turn, and is finally imaged through the imaging objective lens, received by the multi-spectral camera, and transmitted to the three-dimensional temperature field analysis module.

4. The multi-spectral radiation temperature measurement device based on an endoscopic probe according to claim 1 is characterized in that: The angle between the reflector and the probe optical axis is 52°, the angle between the dichroic mirror and the probe optical axis is 52°, and they are fixed in the lens barrel through a limiting slot, and the distance between the two is 18 mm to achieve binocular imaging effect.

5. The multi-spectral radiation temperature measurement device based on an endoscopic probe according to claim 1, characterized in that: The imaging objective lens includes 12 lenses, of which 10 are standard spherical lenses and 2 are aspherical lenses. The total length of the optical system is 165 mm, the paraxial magnification is 1.5, the overall focal length is 65 mm, and the optical aperture is less than 10 mm.

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