Multi-channel probe for the hot-end component based on fiber optic bundle

Abstract

The present invention discloses a high-performance multi-channel probe for hot-end components based on an optical fiber bundle, which relates to the field of temperature and stress detection of engine hot-end components and is composed of a probe barrel, an optical fiber image bundle, a high-temperature resistant protective cover, a temperature detector and a stress detector. The present invention adopts three optical windows, two of which are used for measuring strain and one for measuring temperature. The structural design of the whole optical system is compact, and it can realize clear binocular vision imaging of the local area of the hot-end component, and has the characteristics of withstanding a high temperature of 1000 °C, high optical fiber coupling efficiency, and less energy loss.

Description

Technical Field

[0001] The present invention relates to the field of stress and temperature detection of engine blades, and provides a multi-channel probe for hot-end components based on an optical fiber bundle, which is a multi-channel integrated optical probe with high stability. Background Art

[0002] Hot-end components are the core of an engine, and the thrust of both the engine and the aircraft comes from the hot-end components. The increase in the temperature before the turbine has made R & D personnel pay more attention to the state of hot-end components, and the hot-end component detection technology has become a technical problem that needs to be overcome urgently at home and abroad. The engine operates in harsh environments such as high temperature, high pressure, and strong magnetic fields. The reason why hot-end components are difficult to detect is that their shapes are complex and their structures are compact, and some common detection methods are no longer applicable in environments of high temperature, high pressure, and strong electromagnetic interference. How to avoid and weaken the influence of these complex environmental factors and complete the high-quality transmission of images is the primary problem to be solved.

[0003] Traditional lens materials cannot withstand high-temperature and high-pressure environments, are prone to deformation, and affect the imaging effect. Therefore, most of the imaging lenses of current engine stress measurement devices and the lens barrels of high-temperature probes choose high-temperature-resistant materials, but this method is costly and limited by the types of existing lens materials, and the highest temperature it can withstand is limited. Secondly, the existing detection devices generally adopt a single-channel measurement method and cannot achieve the simultaneous measurement of temperature fields and stress fields. The current detection devices adopt a single-lens imaging method, and the structure at the rear end of the probe is too large, and the structure is extremely unreasonable, which brings great difficulties to actual assembly and testing. Summary of the Invention

[0004] (1) Technical problems to be solved by the present invention

[0005] Aiming at the deficiencies of current existing detection devices, the present invention proposes a multi-channel probe based on an optical fiber bundle, which can realize the synchronous measurement of the temperature and stress fields of engine blades under harsh working environments and more comprehensively understand the working state of the blades.

[0006] (2) Technical solutions of the present invention

[0007] The probe mainly consists of a probe lens barrel, a reflecting mirror, a beam splitter, a front group of lenses, a temperature detector, an optical fiber image transmission bundle, a stress detector, a high-temperature-resistant protective cover, and a mounting flange, etc. The system uses three optical windows, two of which are used to measure strain and one is used to measure temperature.

[0008] A light passing hole is provided on the barrel wall at one end of the probe barrel. The reflected light from the area to be measured enters the interior of the probe barrel through the light passing hole, and is successively divided into a first reflected light and a first transmitted light by the reflecting mirror, the beam splitter, the front group of lenses, and the first dichroic mirror. The first reflected light enters the third rear group of lenses and is received by the temperature detector to measure the temperature field. The first transmitted light is divided into a second reflected light and a second transmitted light by the second dichroic mirror. The second reflected light and the second transmitted light pass through the first rear group of lenses and the second rear group of lenses respectively, and are finally received by the first stress detector and the second stress detector to complete binocular vision clear imaging and measure the stress field.

[0009] The total length of the front group of lenses in the present invention is 154 mm, including at least 4 spherical lenses, and the object space numerical aperture is 0.05, which can achieve clear imaging of the object to be measured within the working distance range of 20 - 100 mm, and aberration such as distortion is controlled within a very small range.

[0010] The temperature measurement optical window of this device uses a near-infrared quartz fiber with a core diameter of 1 mm, and this fiber can transmit light in the wavelength range of 800 - 2500 nm.

[0011] The fiber optic image bundle is an integrated optical element formed by arranging a large number of optical fibers according to a certain rule and order, which can realize the transmission and transformation of light energy in two-dimensional space, and has advantages such as light weight and good flexibility. Introducing the fiber optic image bundle makes the structure of the entire optical system more flexible, breaks the traditional spatial layout of the optical system that must be straight or folded, makes the probe structure more reasonable, and effectively solves the problems of difficult probe assembly and testing. The performance of the fiber optic image bundle is mainly related to parameters such as numerical aperture and transmission loss. After imaging on one end face of the fiber bundle, the image information will be decomposed into pixel elements equal to the number of single optical fibers, and re-converge into an image at the end of the fiber bundle. The fiber optic image bundle used in this device is a large-section quartz fiber optic image bundle with a core diameter of 8 mm and a numerical aperture of 0.22, with the number of pixel units greater than 50000, good stability, low loss, and at the same time, the 1-meter length also provides more choices for the assembly of the components at the rear end of the probe.

[0012] The first rear group of lenses is composed of at least three spherical lenses, which can collect light wave bands of 1200 - 1500 nm for temperature measurement. The second rear group of lenses is composed of at least three spherical lenses plus one aspherical lens, with an object space numerical aperture of 0.26, which can collect the band of 420 - 480 nm for stress measurement. The third rear group of lenses is composed of at least three spherical lenses plus one aspherical lens, which can collect the band of 520 - 560 nm, with an object space numerical aperture of 0.45, for stress measurement. The numerical apertures of the second rear group of lenses and the third rear group of lenses are both larger than the numerical aperture of the fiber bundle, the system coupling efficiency is high, and the light energy loss is small.

[0013] A high-temperature resistant protective cover is added to the front end of the probe. A plurality of air inlets are evenly distributed on the high-temperature resistant protective cover. Cold air is continuously injected through the air inlets, so that the entire front end of the probe, including the reflecting mirror and the beam splitter mirror, is immersed in a cold air environment, reducing the operating temperature of the front end of the probe. At the same time, continuously injecting cold air can also purge the pollutants remaining on the surface of the reflecting mirror, ensuring the imaging quality. In addition, a mounting flange is provided on the outer side of the barrel wall of the probe barrel for fixing to the casing of the turbine blade of the engine to be measured, preventing the high-temperature gas inside the casing from overflowing.

[0014] (III) Technical effects of the present invention

[0015] 1) The present invention adopts a multi-channel measurement method. Only one small hole needs to be opened in the engine casing to simultaneously measure the temperature and stress field. At the same time, the diameter of the front end of the probe is smaller, reducing the damage to the engine itself.

[0016] 2) The fiber optic image bundle with the characteristics of being non-electrified, small in volume, easy to bend, and good in electromagnetic resistance is introduced into the stress measurement path of the present invention, making the structure at the rear end of the probe more reasonable and facilitating actual assembly and testing.

[0017] 3) The present invention greatly improves the operating temperature of the front end of the probe by adding a high-temperature resistant protective cover, reducing the development cost of the probe; at the same time, it improves the imaging quality without increasing the design difficulty of the optical system.

[0018] 4) The multi-channel probe for hot end components based on fiber optic bundles proposed by the present invention is not only applicable to the temperature and stress measurement of engine blades in high-temperature environments, but also applicable to the temperature and stress measurement of other targets to be measured in similar environments. Description of the drawings

[0019] Figure 1 is a schematic diagram of the working state of a multi-channel integrated probe for hot end components based on fiber optic bundles of the present invention.

[0020] Figure 2 is an optical system diagram of the front group of lenses.

[0021] Figure 3 is a partial schematic diagram of the high-temperature resistant protective cover.

[0022] Figure 4 is a cross-sectional view of the fiber optic image bundle.

[0023] In the figure: 1 - engine blade, 2 - local area of the blade, 3 - mirror, 4 - front lens group, 5 - mounting flange, 6 - probe barrel, 7 - near-infrared quartz optical fiber, 8 - first rear lens group, 9 - temperature detector, 10 - first dichroic mirror, 11 - second dichroic mirror, 12 - first fiber optic image bundle, 13 - second rear lens group, 14 - first stress detector, 15 - third rear lens group, 16 - second stress detector, 17 - air inlet, 18 - fiber cladding, 19 - fiber single filament, 20 - second fiber optic image bundle, 21 - beam splitter. Detailed implementation manners

[0024] In order to more clearly elaborate on the technical solution of the present invention, the following will further describe the present invention with reference to specific embodiments and the accompanying drawings.

[0025] Figure 1 A schematic diagram of the working state of the present invention is shown. A light passing hole is provided on the barrel wall at one end of the probe barrel 6, and a first optical window, a second optical window, and a third optical window are successively provided on the barrel wall at the other end. One end of the near-infrared quartz optical fiber 7 is connected to the first optical window, and the other end of the near-infrared quartz optical fiber 7 is connected to the temperature detector 9 through the first rear lens group 8. One end of the first fiber optic image bundle 12 is connected to the second optical window, and the other end of the first fiber optic image bundle 12 is connected to the first stress detector 14 through the second rear lens group 13. One end of the second fiber optic image bundle 20 is connected to the third optical window, and the other end of the second fiber optic image bundle 20 is connected to the second stress detector 16 through the third rear lens group 15; A mirror 3, a front lens group 4, a first dichroic mirror 10, and a second dichroic mirror 11 are successively placed in the probe barrel 6. The light reflected by the local area 2 of the blade enters the inside of the probe barrel 6 through the light passing hole at the front end of the probe, and is divided into a first reflected light and a first transmitted light through the total reflection mirror 3, the beam splitter 21, the front lens group 4, and the first dichroic mirror 10. The first reflected light is received by the temperature detector 9 after passing through the first optical window, the near-infrared quartz optical fiber 7, and the first rear lens group 8. The first transmitted light is divided into a second reflected light and a second transmitted light by the second dichroic mirror 11. The second reflected light is received by the first stress detector 14 after passing through the second optical window, the fiber optic image bundle 12, and the second rear lens group 13. The second transmitted light is received by the second stress detector 16 after passing through the third optical window, the fiber optic image bundle 12, and the third rear lens group 15.

[0026] Figure 2 It is the optical system diagram of the front lens group 4. The total length is 154 mm, including at least 3 spherical lenses. The object-side numerical aperture is 0.05, which can achieve clear imaging of the object to be measured within the working distance range of 20 - 100 mm. Aberrations such as distortion are controlled within a very small range. The front lens group 4 is fixed inside the probe barrel 6 through a mechanical structure, and the structure is compact.

[0027] The first dichroic mirror of this device has a high reflectivity for the optical wavelength band of 1.0 - 1.4 μm and a high transmittance for the visible light wavelength band of 300 - 780 nm; the second dichroic mirror has a high reflectivity for the light in the 420 - 480 nm band and a high transmittance for the light in the 500 - 560 nm band.

[0028] The first rear lens group of this device is composed of at least three spherical lenses, which can collect the light wave band of 1200 - 1500 nm for temperature measurement. The second rear lens group is composed of at least three spherical lenses and one aspherical lens, with an object-side numerical aperture of 0.26, which can collect the band of 420 - 480 nm for stress measurement. The third rear lens group is composed of at least three spherical lenses and one aspherical lens, which can collect the band of 520 - 560 nm, with an object-side numerical aperture of 0.45, for stress measurement. The numerical apertures of the second rear lens group and the third rear lens group are both larger than that of the fiber bundle, and the system has a high coupling efficiency and less light energy loss.

[0029] The front end of the probe extends into the high-temperature and high-pressure environment through the opening on the casing. In order to avoid the deformation of the lens in the high-temperature environment and affect the imaging quality, a high-temperature resistant protective cover is added to the front end of the probe. Figure 3 The structural schematic diagram of the high-temperature resistant protective cover is given. Its principle is to cool the front end of the probe by continuously blowing in cold air. The cold air is injected through multiple air inlets 17 with a diameter of 1.5 mm, so that the front end of the probe, including the mirror 3, is immersed in the cold air environment, playing a role in reducing the temperature. At the same time, continuously injecting cold air can also purge the pollutants remaining on the mirror surface to ensure the imaging quality. An installation flange 5 is provided on the outer side of the barrel wall of the probe barrel for fixing with the casing of the engine turbine blade to be measured.

[0030] Figure 4 It is a cross-sectional schematic diagram of the fiber optic image transmission bundle. The fiber optic image transmission bundle is an integrated optical element composed of a large number of single fiber filaments 19 arranged according to a certain rule and order, which can realize the transmission and transformation of light energy in two-dimensional space. The image transmission performance of the fiber bundle is mainly related to the numerical aperture and transmission loss, etc. The structure and image transmission performance of the single fiber filaments that make up the fiber optic image transmission number basically determine the performance of the fiber bundle. Therefore, it should have good spectral transmittance to be able to transmit images in a wide spectral band. The large cross-section quartz fiber optic image transmission bundle used in this device has a core diameter of 8 mm, a fiber cladding 18 thickness of 3 mm, and a numerical aperture of 0.22. The number of pixel units is greater than 50000, and the numerical aperture of the fiber bundle is larger than that of the front lens group. Therefore, all the light information passing through the front lens group is received by the fiber optic image transmission bundle, ensuring the image transmission quality. At the same time, the 1-meter length also provides more choices for the spatial assembly of the rear-end components.

[0031] The temperature measurement optical window of this device uses a near-infrared quartz optical fiber 7 with a core diameter of 1 mm and a numerical aperture of 0.22. The length is selected as 1.5 meters, and the light transmission band covers 800 - 2500 nm, which can meet the measurement requirements for the temperature of engine blades. The common SMA905 interface is selected for the connection, which is convenient for connecting with the detector. Considering that the optical fiber can be bent, this also provides more choices for the connection position of the temperature detector at the rear end.

Claims

1. A multi-channel probe for a hot-end component based on an optical fiber bundle, comprising a probe barrel, characterized in that, a light passing hole is provided on the barrel wall at one end of the probe barrel, and a first optical window, a second optical window and a third optical window are sequentially provided on the barrel wall at the other end. One end of the first optical window is connected to one end of a near-infrared quartz optical fiber, and the other end of the near-infrared quartz optical fiber is connected to a temperature detector through a first rear group of lenses. One end of the second optical window is connected to one end of a first fiber optic image bundle, and the other end of the first fiber optic image bundle is connected to a first stress detector through a second rear group of lenses. One end of the third optical window is connected to one end of a second fiber optic image bundle, and the other end of the second fiber optic image bundle is connected to a second stress detector through a third rear group of lenses; A reflecting mirror, a front group of lenses, a first dichroic mirror and a second dichroic mirror are sequentially placed in the probe barrel; the reflected light from the area to be measured enters the interior of the probe barrel through the light passing hole, and is divided into a first reflected light and a first transmitted light through the reflecting mirror, the beam splitter, the front group of lenses and the first dichroic mirror in sequence. The first reflected light is received by the temperature detector after passing through the first optical window, the near-infrared quartz optical fiber and the first rear group of lenses. The first transmitted light is divided into a second reflected light and a second transmitted light by the second dichroic mirror. The second reflected light is received by the first stress detector after passing through the second optical window, the first fiber optic image bundle and the second rear group of lenses. The second transmitted light is received by the second stress detector after passing through the third optical window, the second fiber optic image bundle and the third rear group of lenses; the front group of lenses is composed of at least four spherical lenses, and the object-side numerical aperture is 0.05, which is used to clearly image the object to be measured within a working distance range of 20-100 mm; the first rear group of lenses is composed of at least three spherical lenses, and collects the light wave band of 1200-1500 nm, which is used for temperature measurement; the second rear group of lenses is at least composed of three spherical lenses plus one aspherical lens, the object-side numerical aperture is 0.26, and collects the band of 420-480 nm, which is used for stress measurement; the third rear group of lenses is composed of at least three spherical lenses plus one aspherical lens, collects the band of 520-560 nm, and the object-side numerical aperture is 0.45, which is used for stress measurement; The numerical apertures of the second rear group of lenses and the third rear group of lenses are both larger than the numerical aperture of the fiber optic bundle.

2. The multi-channel probe for a hot-end component based on an optical fiber bundle according to claim 1, characterized in that, an installation flange is provided on the outer side of the barrel wall of the probe barrel for fixing with the casing of the engine turbine blade to be measured.

3. The multi-channel probe for a hot-end component based on an optical fiber bundle according to claim 2, characterized in that, a high-temperature resistant protective cover is further provided at the front end of the outer side of the barrel wall of the probe barrel for reducing the temperature of the probe barrel and ensuring that the front group of lenses can work normally.

4. The multi-channel probe for a hot-end component based on an optical fiber bundle according to claim 1, characterized in that, The first fiber optic image bundle and the second fiber optic image bundle are integrated optical elements formed by arranging a large number of optical fibers according to a certain law and sequence, with a numerical aperture of 0.22 and a core diameter of 8 mm, and can realize the transmission and transformation of light energy in a two-dimensional space.

5. The multi-channel probe for the hot end component based on the fiber optic bundle according to claim 1, characterized in that the core diameter of the near-infrared quartz optical fiber is 1 mm and is used for the transmission of light in the 800 - 2500 nm band.

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