Turbine blade non-contact strain measuring device and measuring method based on optical fiber bundle

Abstract

The invention provides a turbine blade non-contact strain measurement device and method based on an optical fiber bundle, and the device comprises a probe assembly which is provided with an observation window at the inner side end and a first interface and a second interface at the outer side end, and the included angle between the first interface and the second interface is a right angle; one end of the first optical fiber image transmission bundle is connected with the first interface, and one end of the second optical fiber image transmission bundle is connected with the second interface; one end of the first rear group lens is connected with the other end of the first optical fiber image transmitting bundle, and the other end of the first rear group lens is connected with a first high-speed camera; and one end of the second rear group lens is connected with the other end of the second optical fiber image transmitting bundle, and the other end of the second rear group lens is connected with the second high-speed camera. A multi-structure mode is adopted, aberration such as distortion is controlled within a small range, and two-channel visual clear imaging of two wavebands can be achieved.

Description

Technical Field

[0001] The invention relates to the technical field of aero-engine strength test and measurement, and in particular to a non-contact strain measurement device and a measurement method for turbine blades based on an optical fiber bundle. Background Art

[0002] Aircraft engine turbine rotor blades operate in harsh environments. They are prone to fatigue cracks and even damage and fracture under various loads brought by vibration, high temperature, high pressure, and high speed. Therefore, in order to achieve optimal design, vibration feature acquisition, and fault diagnosis and prediction of aircraft engine turbine blades, it is necessary to perform strain measurement on the engine's turbine rotor blades.

[0003] At present, the commonly used and mature turbine rotor strain measurement method at home and abroad is the contact resistance strain test method. This method requires the installation of high-temperature strain gauges on the blade surface, which affects the aerodynamic performance of the blade; the maximum operating temperature is not higher than 1100°C, which cannot meet the use requirements of advanced aircraft engine turbine blades; the signal needs to be connected to the signal acquisition equipment through a high-speed slip ring, the slip ring needs to be cooled, and the engine is greatly modified, which affects the engine's working performance. The non-contact turbine blade strain measurement method has the advantages of not changing the blade surface structure, being able to get rid of the slip ring constraint, and having a high upper temperature limit. The traditional binocular visual strain measurement device is limited by the optical path design, the structure is slender, the space occupied is large, and the installation is difficult. In addition, the traditional non-contact turbine blade strain measurement method usually uses hard connection to realize the optical path design, which is easily affected by the engine's own vibration environment and cannot realize the online measurement of the engine turbine blade. Summary of the invention

[0004] In view of this, the embodiments of the present specification provide a non-contact strain measurement device and method for turbine blades based on an optical fiber bundle, so as to achieve the purpose of non-contact strain measurement of turbine blades.

[0005] The embodiments of this specification provide the following technical solutions: a non-contact strain measurement device for turbine blades based on an optical fiber bundle, comprising: a probe assembly, wherein an observation window is provided at the inner end, and a first interface and a second interface are provided at the outer end, and the angle between the first interface and the second interface is a right angle; a first optical fiber imaging bundle and a second optical fiber imaging bundle, wherein one end of the first optical fiber imaging bundle is connected to the first interface, and one end of the second optical fiber imaging bundle is connected to the second interface; a first rear lens group and a second rear lens group, wherein one end of the first rear lens group is connected to the other end of the first optical fiber imaging bundle, and the other end of the first rear lens group is connected to a first high-speed camera; one end of the second rear lens group is connected to the other end of the second optical fiber imaging bundle, and the other end of the second rear lens group is connected to a second high-speed camera.

[0006] Furthermore, the probe assembly includes: a probe shell having an inner cavity, an outer wall of the probe shell being provided with a first light window and a second light window arranged at intervals along the axial direction, wherein along the axial direction of the probe shell, the first light window is located on the inner side of the second light window, and the observation window covers the outside of the first light window and the second light window; a fully reflective mirror is arranged in the inner cavity and located at the first light window; and a semi-transparent and semi-reflective mirror is arranged in the inner cavity and located at the second light window.

[0007] Furthermore, the probe assembly also includes a probe body, which is connected to the outer end of the probe housing, and the probe body includes: a front group lens, including multiple lens units, which are arranged in sequence along the axial direction of the probe body; a sealing lens, which is arranged on the outside of the front group lens; a beam splitter, which is arranged on the outside of the sealing lens, and the first interface and the second interface are both arranged at the beam splitter.

[0008] Furthermore, optical fiber image transmission bundle connectors are provided at both the first interface and the second interface.

[0009] Furthermore, the probe assembly is also provided with a water cooling pipe for cooling the probe assembly.

[0010] Furthermore, an air-cooling purge pipe is also provided on the probe assembly, the inlet of the air-cooling purge pipe is located at the outer end of the probe assembly, and the outlet of the air-cooling purge pipe is located at the observation window.

[0011] Furthermore, the probe assembly is also provided with a light illumination assembly for illuminating the blade to be measured.

[0012] Furthermore, the light illumination assembly includes: an illumination optical fiber, which is inserted into the probe assembly and one end of which is placed at the observation window; and a high-temperature reflector, which is arranged at the observation window and is used to reflect the stroboscopic light introduced by the illumination optical fiber to the surface of the blade to be measured.

[0013] The present invention also provides a measurement method, which uses the above-mentioned turbine blade non-contact strain measurement device based on optical fiber bundle to perform measurement.

[0014] Furthermore, the measuring method comprises the following steps:

[0015] Step 1: Drill a hole in the engine turbine casing and design a flange, and install it so that the observation window faces the blade to be tested;

[0016] Step 2: Adjust the distance between the observation window and the blade to be measured so that the high-speed camera can clearly image the blade;

[0017] Step 3: Set the shooting speed, frame rate, shutter speed and trigger mode parameters of the high-speed camera, and use the signal generator external trigger to simultaneously control the two high-speed cameras and the light source to achieve synchronous image acquisition;

[0018] Step 4: Turn on the water cooling system and the air cooling system to cool the probe assembly.

[0019] Step 5: running the aircraft engine to enter the working condition to be tested;

[0020] Step 6: operate the signal generator to send trigger signals to the two high-speed cameras and the light source to collect engine blade information;

[0021] Step seven, calculate the strain field of the blade to be tested based on the collected engine blade information and using the DIC algorithm.

[0022] Compared with the prior art, the beneficial effects that can be achieved by at least one of the above-mentioned technical solutions adopted in the embodiments of this specification include at least the following: the embodiments of the present invention adopt a multiple structure approach, and distortion and other aberrations are controlled within a smaller range, which can achieve clear dual-channel visual imaging in two bands. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 It is a schematic diagram of the test installation of the non-contact strain measurement device for turbine blades based on optical fiber bundles of the present invention;

[0025] Figure 2 It is a schematic structural diagram of a non-contact strain measurement device for turbine blades based on an optical fiber bundle of the present invention;

[0026] Figure 3 It is a structural diagram of the optical fiber lighting of the present invention;

[0027] Figure 4 It is a schematic diagram of the structure of the probe assembly of the present invention;

[0028] Explanation of the accompanying reference numerals: 1. Non-contact strain measurement device for turbine blades based on optical fiber bundle; 2. Turbine blade to be measured; 3. Rear lens group; 4. Optical fiber imaging bundle; 5. Optical fiber lighting assembly; 501. Illuminating optical fiber; 502. Flashing light; 503. High-temperature reflector; 6. Water-cooling pipe; 7. Air-cooled purge pipe; 8. Fixed flange; 9. Probe assembly; 901. Optical fiber imaging bundle connector; 902. Beam splitter; 903. Sealing lens; 904. Sealing ring; 905. Front lens group; 906. Probe housing; 907. Semi-transparent and semi-reflective mirror; 908. Fully reflective mirror; 10. Observation window. DETAILED DESCRIPTION

[0029] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0030] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0031] like Figure 1 As shown, the non-contact strain measurement device 1 of turbine blades based on an optical fiber bundle of an embodiment of the present invention is installed on the surface of the turbine casing of an aircraft engine, in front and behind the turbine blade 2 to be measured, and the optical window of the probe is facing the profile of the turbine blade 2 to be measured. The working environment of the probe installation position is harsh. The ambient gas is adiabatically compressed by the engine compressor, and then isobarically heated by the combustion chamber to form high-temperature and high-pressure combustion gas. The high-temperature and high-pressure combustion gas impacts the turbine blades to produce high-speed rotation. Therefore, the thermal protection probe works in the harsh environment of high temperature and high pressure like the turbine blades. In addition, in addition to high temperature and high pressure loads, the turbine blades also bear the loads caused by airflow impact and high-speed rotation. They are very easy to deform and are important monitoring points for the safe and reliable operation of the engine. The non-contact strain measurement device 1 of turbine blades based on an optical fiber bundle can collect clear image information on the surface of the turbine blades in the harsh environment of the engine turbine gap and transmit it to the high-speed camera.

[0032] Specific as Figures 2 to 4 As shown, an embodiment of the present invention provides a non-contact strain measurement device for turbine blades based on an optical fiber bundle, comprising a probe assembly 9, a first optical fiber imaging bundle, a second optical fiber imaging bundle, a first rear lens group, a second rear lens group, a first high-speed camera, and a second high-speed camera. An observation window 10 is provided at the inner end of the probe assembly 9, and a first interface and a second interface are provided at the outer end, and the angle between the first interface and the second interface is a right angle; the first optical fiber imaging bundle and the second optical fiber imaging bundle, one end of the first optical fiber imaging bundle is connected to the first interface, and one end of the second optical fiber imaging bundle is connected to the second interface; the first rear lens group and the second rear lens group, one end of the first rear lens group is connected to the other end of the first optical fiber imaging bundle, and the other end of the first rear lens group is connected to the first high-speed camera; one end of the second rear lens group is connected to the other end of the second optical fiber imaging bundle, and the other end of the second rear lens group is connected to the second high-speed camera.

[0033] The embodiment of the present invention adopts a multiple structure approach, and aberrations such as distortion are controlled within a relatively small range, thereby being able to achieve clear dual-channel visual imaging in two bands.

[0034] It should be noted that the first high-speed camera and the second high-speed camera are used to convert the digital image collected by the probe assembly 9 into an image signal; the first rear lens group and the second rear lens group form the rear lens group 3, the first optical fiber image transmission bundle and the second optical fiber image transmission bundle form the optical fiber image transmission bundle 4, and the rear lens group 3 can project the image transmitted by the optical fiber image transmission bundle 4 to the corresponding photosensitive chip of the high-speed camera after focusing and imaging; the first optical fiber image transmission bundle and the second optical fiber image transmission bundle are both integrated optical devices composed of a large number of optical fibers arranged in a certain rule, which use passive optical fibers as image transmission elements to realize the transmission and transformation of light energy in a two-dimensional spatial distribution, and transmit the image information of the turbine surface to the rear lens group 3. The first optical fiber image transmission bundle and the second optical fiber image transmission bundle can realize the transmission and transformation of light energy in a two-dimensional space, and have the advantages of light weight and good flexibility. The introduction of the first optical fiber image transmission bundle and the second optical fiber image transmission bundle makes the structure of the entire optical system more flexible, and can effectively isolate the vibration hazards caused by the engine to the image acquisition; in addition, the use of the first optical fiber image transmission bundle and the second optical fiber image transmission bundle is conducive to the arrangement of non-contact strain measurement devices in the limited working space of the engine.

[0035] like Figure 4 As shown, the probe assembly 9 includes: a probe housing 906, a full reflector 908 and a semi-transparent semi-reflector 907. The probe housing 906 has an inner cavity, and the outer wall of the probe housing 906 is provided with a first light window and a second light window arranged at intervals along the axial direction. Along the axial direction of the probe housing 906, the first light window is located on the inner side of the second light window, and the observation window 10 covers the outside of the first light window and the second light window. The observation window 10 can block the external high-temperature engine combustion gas and transmit the reflected light of the measured blade.

[0036] See attached Figure 4 To explain, the outer side of the present invention refers to Figure 4 The upper side in the vertical direction, the inner side refers to Figure 4 Below in the vertical direction.

[0037] The total reflective mirror 908 is arranged in the inner cavity and located at the first light window; the semi-transparent and semi-reflective mirror 907 is arranged in the inner cavity and located at the second light window. The semi-transparent and semi-reflective mirror 907 is used to reflect a partial band (such as a blue band) of the light reflected from the surface of the turbine blades penetrating the second light window to the front lens group 905, and at the same time transmit a partial band (such as a green band) of the light reflected from the surface of the turbine blades penetrating the first light window and reflected by the total reflective mirror 908 to the front lens group 905; the total reflective mirror 908 is used to reflect the entire band of the light reflected from the surface of the turbine blades penetrating the first light window to the semi-transparent and semi-reflective mirror 907.

[0038] In the embodiment of the present invention, the probe assembly 9 further includes a probe body, which is connected to the outer end of the probe housing 906. The probe body includes a front lens group 905, a sealing lens 903 and a beam splitter 902. The front lens group 905 includes a plurality of lens units, which are sequentially arranged along the axial direction of the probe body; the sealing lens 903 is arranged outside the front lens group 905; the beam splitter 902 is arranged outside the sealing lens 903, and the first interface and the second interface are both arranged at the beam splitter 902.

[0039] The beam splitter 902 in the embodiment of the present invention is used to split the two beams of light from the binocular probe, one of which is along Figure 4 One beam goes vertically upward into the first high-speed camera, and the other beam goes horizontally into the second high-speed camera. A sealing ring 904 is also provided at the sealing lens 903. The sealing lens 903 and the sealing ring 904 cooperate to seal the front end of the assembly to reduce the deformation of the lens group caused by uneven heating. The front lens group 905 is used to control the image magnification ratio and imaging position, and transmit a clear image to the optical fiber image transmission bundle 4. The number and specifications of the lens units of the front lens group 905 can be adjusted or selected according to different needs.

[0040] Preferably, both the first interface and the second interface are provided with an optical fiber image transmission bundle connector 901. The optical fiber image transmission bundle connector 901 is used to fix the corresponding first optical fiber image transmission bundle and the second optical fiber image transmission bundle.

[0041] like Figure 2 As shown, the probe assembly 9 in the embodiment of the present invention is also provided with a water cooling pipe 6 for cooling the probe assembly 9. The probe housing 906 can be used to fix the optical component and can also cooperate with the water cooling pipe 6 to play a role in thermal protection.

[0042] Preferably, the probe assembly 9 is further provided with an air-cooling purge pipe 7, the inlet of which is located at the outer end of the probe assembly 9, and the outlet of which is located at the observation window 10. The air-cooling purge pipe 7 is used to lead cold air to the outer wall of the observation window 10, purge the outer surface of the glass of the observation window 10, form a wind knife in front of the observation window 10, isolate the carbon smoke inside the engine, and cool the outer surface of the glass of the observation window 10 at the same time.

[0043] The probe assembly 9 is also provided with a light illumination assembly 5 for illuminating the blade to be measured. The light illumination 5 is mainly used to transmit the light emitted by the stroboscopic light source to the surface of the blade to be measured.

[0044] like Figure 3 As shown, the light illumination assembly 5 includes an illumination fiber 501 and a high temperature reflector 503. The illumination fiber 501 is inserted into the probe assembly 9, and one end of the illumination fiber 501 is placed at the observation window 10; the high temperature reflector 503 is arranged at the observation window 10 and is used to reflect the stroboscopic light 502 introduced by the illumination fiber 501 to the surface of the blade to be measured.

[0045] The illumination optical fiber 501 is used to introduce the stroboscopic light 502 of the external light source into the engine casing; the stroboscopic light 502 is the illumination light transmitted by the illumination optical fiber 501; the high-temperature reflector 503 is a reflective mirror formed by electrical machining and grinding on the surface of the probe made of high-temperature alloy, and is used to reflect the stroboscopic light 502 introduced by the illumination optical fiber 501 to the surface of the blade to be measured.

[0046] The stroboscopic light source 502 is a pulse light source, which is used to provide a high-intensity light source for image acquisition. At the same time, the pulse light source is used to reduce the exposure time of the high-speed camera and eliminate image smear.

[0047] The embodiment of the present invention further comprises a fixing flange 8, which is arranged outside the probe assembly 9 and is used for fixing connection with the engine turbine casing.

[0048] It should be noted that the shell of the probe assembly 9 is manufactured in an integrated manner using a 3D printing method, and contains a high-efficiency water-cooling pipe 6 inside, which can cool the internal temperature of the probe and reduce the thermal changes of the optical components inside the probe; in addition, it contains an air-cooled purge pipe 7, which can effectively isolate the high-temperature fuel gas in the engine, blow away the carbon smoke in the fuel gas, and keep the light window clean.

[0049] The specific working process of the embodiment of the present invention is as follows:

[0050] The reflected light from the blade test area enters the probe assembly 9 through the observation window 10. One beam of light passes through the total reflection mirror 908, and the semi-transparent and semi-reflective mirror 907 allows the blue light to pass through and enter the front lens group 905, and then enters the beam splitter 902 through the sealing lens 903, and enters the first optical fiber image transmission bundle after being split by the beam splitter 902, and enters the first high-speed camera through the first rear lens group. The other beam of light passes through the semi-transparent and semi-reflective mirror 907 to reflect the green light through the front lens group 905 and the sealing lens 903, enters the beam splitter 902, and then enters the second optical fiber image transmission bundle, and enters the second high-speed camera through the second rear lens group.

[0051] The present invention also provides a measurement method, which uses a non-contact strain measurement device for turbine blades based on an optical fiber bundle for measurement. The specific measurement method includes the following steps:

[0052] Step 1: Drill a hole in the engine turbine casing and design a flange, and install it so that the observation window 10 faces the blade to be tested;

[0053] Step 2: Adjust the distance between the observation window 10 and the blade to be measured so that the high-speed camera can clearly image;

[0054] Step 3: Set the shooting speed, frame rate, shutter speed and trigger mode parameters of the high-speed camera, and use the signal generator external trigger to simultaneously control the two high-speed cameras and the light source to achieve synchronous image acquisition;

[0055] Step 4: Turn on the water cooling system and the air cooling system to cool the probe assembly 9.

[0056] Step 5: running the aircraft engine to enter the working condition to be tested;

[0057] Step 6: operate the signal generator to send trigger signals to the two high-speed cameras and the light source to collect engine blade information;

[0058] Step seven, calculate the strain field of the blade to be tested based on the collected engine blade information and using the DIC algorithm.

[0059] The present invention is different from the traditional binocular visual strain measurement device. The turbine blade strain measurement method based on the optical fiber bundle transmits the image collected by the small high-temperature resistant probe to the high-speed camera through the optical fiber bundle. Since the optical fiber bundle itself is resistant to high temperature and can be bent arbitrarily, it can effectively isolate the engine vibration environment and is suitable for the narrow and harsh working environment of aircraft engine turbine blades.

[0060] The above is only a specific embodiment of the present invention, and cannot be used to limit the scope of the invention. Therefore, the replacement of equivalent components, or equivalent changes and modifications made according to the scope of protection of the patent of the present invention, should still fall within the scope of this patent. In addition, the technical features of the present invention can be freely combined with each other, with each other, and with each other.

Claims

1. A non-contact strain measurement device for turbine blades based on an optical fiber bundle, characterized in that: include: A probe assembly (9), wherein an observation window (10) is provided at an inner end thereof, and a first interface and a second interface are provided at an outer end thereof, wherein the angle between the first interface and the second interface is a right angle; a first optical fiber imaging bundle and a second optical fiber imaging bundle, wherein one end of the first optical fiber imaging bundle is connected to the first interface, and one end of the second optical fiber imaging bundle is connected to the second interface; A first rear lens group and a second rear lens group, wherein one end of the first rear lens group is connected to the other end of the first optical fiber imaging bundle, and the other end of the first rear lens group is connected to a first high-speed camera; one end of the second rear lens group is connected to the other end of the second optical fiber imaging bundle, and the other end of the second rear lens group is connected to a second high-speed camera.

2. The non-contact strain measurement device for turbine blades based on optical fiber bundle according to claim 1, characterized in that: The probe assembly (9) comprises: A probe housing (906) has an inner cavity, and an outer wall of the probe housing (906) is provided with a first light window and a second light window spaced apart in the axial direction, and along the axial direction of the probe housing (906), the first light window is located on the inner side of the second light window, and the observation window (10) covers the outside of the first light window and the second light window; A total reflective mirror (908), arranged in the inner cavity and located at the first light window; A semi-transparent and semi-reflective mirror (907) is arranged in the inner cavity and located at the second light window.

3. The non-contact strain measurement device for turbine blades based on optical fiber bundle according to claim 2, characterized in that: The probe assembly (9) further comprises a probe body connected to the outer end of the probe housing (906), wherein the probe body comprises: A front lens group (905) comprises a plurality of lens units, which are arranged in sequence along the axial direction of the probe body; A sealing lens (903) is arranged outside the front lens group (905); The beam splitter (902) is arranged outside the sealing lens (903), and the first interface and the second interface are both arranged at the beam splitter (902).

4. The non-contact strain measurement device for turbine blades based on optical fiber bundle according to claim 3, characterized in that: The first interface and the second interface are both provided with optical fiber image transmission bundle connectors (901).

5. The non-contact strain measurement device for turbine blades based on optical fiber bundle according to claim 1, characterized in that: The probe assembly (9) is also provided with a water cooling pipe (6) for cooling the probe assembly (9).

6. The non-contact strain measurement device for turbine blades based on optical fiber bundle according to claim 1, characterized in that: An air-cooling purge pipe (7) is also provided on the probe assembly (9), the inlet of the air-cooling purge pipe (7) is located at the outer end of the probe assembly (9), and the outlet of the air-cooling purge pipe (7) is located at the observation window (10).

7. The non-contact strain measurement device for turbine blades based on optical fiber bundle according to claim 1, characterized in that: The probe assembly (9) is also provided with a light illumination assembly (5) for illuminating the blade to be measured.

8. The non-contact strain measurement device for turbine blades based on optical fiber bundle according to claim 7, characterized in that: The light illumination assembly (5) comprises: An illumination optical fiber (501) is inserted into the probe assembly (9), and one end of the illumination optical fiber (501) is placed at the observation window (10); The high temperature reflector (503) is arranged at the observation window (10) and is used to reflect the stroboscopic light (502) introduced by the illumination optical fiber (501) to the surface of the blade to be measured.

9. A measurement method, using a non-contact strain measurement device for turbine blades based on an optical fiber bundle, characterized in that: The non-contact strain measurement device for turbine blades based on an optical fiber bundle is the non-contact strain measurement device for turbine blades based on an optical fiber bundle as claimed in any one of claims 1 to 8.

10. The measuring method according to claim 9, characterized in that: The measuring method comprises the following steps: Step 1: Drill a hole in the engine turbine casing and design a flange, and install it so that the observation window (10) is directly opposite to the blade to be tested; Step 2, adjusting the distance between the observation window (10) and the blade to be measured so that the high-speed camera can clearly image; Step 3: Set the shooting speed, frame rate, shutter speed and trigger mode parameters of the high-speed camera, and use the signal generator external trigger to simultaneously control the two high-speed cameras and the light source to achieve synchronous image acquisition; Step 4: Turn on the water cooling system and the air cooling system to cool the probe assembly (9). Step 5: running the aircraft engine to enter the working condition to be tested; Step 6: operate the signal generator to send trigger signals to the two high-speed cameras and the light source to collect engine blade information; Step seven, calculate the strain field of the blade to be tested based on the collected engine blade information and using the DIC algorithm.

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