CN110702208A - Optical fiber bundle type blade tip timing sensor based on self-focusing lens - Google Patents
Optical fiber bundle type blade tip timing sensor based on self-focusing lens Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
- G01H9/004—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means using fibre optic sensors
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/32—Optical coupling means having lens focusing means positioned between opposed fibre ends
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/42—Coupling light guides with opto-electronic elements
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Abstract
The invention belongs to the field of sensors, and aims to effectively reduce the diameter of a light spot and improve the timing resolution of an optical fiber type tip timing sensor. The technical scheme includes that a plurality of multimode optical fibers tightly surround a single mode optical fiber to form an optical fiber bundle, the self-focusing lens is assembled at the front end of the optical fiber bundle, the single mode optical fiber is connected with a laser and a photoelectric receiver through a circulator, the multimode optical fiber is only connected with the photoelectric receiver, laser emitted by the laser is projected to the end face of a blade through the single mode optical fiber and the self-focusing lens, and laser reflected by the end face of the blade passes through the self-focusing lens and then is projected to the photoelectric receiver through the single mode optical fiber and the multimode optical fiber respectively. The invention is mainly applied to the design and manufacture occasions of the optical fiber sensor.
Description
Technical Field
The invention belongs to the field of sensors. The invention particularly relates to an optical fiber type tip timing sensor, in particular to an optical fiber bundle type tip timing sensor based on a self-focusing lens, which improves timing resolution by reducing the diameter of a light spot.
Background
Blades of large-scale rotating machinery such as an aircraft engine, a gas turbine, a flue gas turbine, a steam turbine and the like are used as core acting elements, and online monitoring of state parameters, particularly vibration parameters, of the blades is vital to guarantee the operation quality of the engine and the operation safety of major equipment. Particularly, since the development of modern aeroengines, rotor blades with high performance requirements and high optimization structures are in a more complex flow field environment, the fluid-solid coupling action of the blades and a streaming can generate coupling vibration in various forms including low-order bending vibration, high-order vibration, bending-torsion composite vibration and the like, the failure forms such as flutter, crack and the like are directly reflected on the tiny change of the high-order vibration amplitude of the blades, the vibration amplitude of the high-order vibration mode of the blades is only dozens of micrometers, and the measurement precision of vibration displacement is required to be better than 10 micrometers so as to realize the accurate measurement of the tiny amplitude.
The tip timing measurement technology is a standard configuration technology for non-contact blade vibration measurement, wherein the optical fiber type tip timing sensor has the advantages of high response speed, high measurement precision and the like, and is the first choice of the non-contact blade vibration measurement sensor. The traditional optical fiber type tip timing sensor adopts a structure that six multimode receiving optical fibers tightly surround one multimode transmitting optical fiber, the transmitting optical fiber and the receiving optical fiber are mutually independent, a high signal-to-noise ratio can be obtained, but the divergence angle of the transmitting optical fiber is large, and the diameter of a light spot is large. When the rotating linear speed of a moving blade of a compressor of an aero-engine can reach 700m/s, the vibration displacement measurement precision is 10 microns, the timing resolution of a blade tip timing measurement system is required to reach 3ns, and the diameter of a light spot is required to be smaller than 63 microns, while when the numerical aperture of a transmitting optical fiber of a traditional optical fiber type blade tip timing sensor is 0.22, the diameter of the light spot at the position of 0.5mm of the minimum blade tip clearance is still 220 microns, and the requirements of modern aero-engines are difficult to meet.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide the optical fiber bundle type blade tip timing sensor based on the self-focusing lens with high timing resolution, so that the diameter of a light spot is effectively reduced, and the timing resolution of the optical fiber type blade tip timing sensor is improved. The invention adopts the technical scheme that an optical fiber bundle type blade tip timing sensor based on a self-focusing lens, a plurality of multimode optical fibers tightly surround a single mode optical fiber to form an optical fiber bundle, the self-focusing lens is assembled at the front end of the optical fiber bundle, the single mode optical fiber is connected with a laser and a photoelectric receiver through a circulator, the multimode optical fiber is only connected with the photoelectric receiver, laser emitted by the laser is projected to the end face of a blade through the single mode optical fiber and the self-focusing lens, laser reflected by the end face of the blade passes through the self-focusing lens and then is respectively projected to the photoelectric receiver through the single mode optical fiber and,
the laser outputs laser through a transmitting end coupler, the transmitting end coupler internally comprises a single-mode transmitting optical fiber for transmitting optical signals, and the optical fiber is positioned in the tensile and compression resistant transmitting cable;
the photoelectric receiver receives laser signals through a receiving end coupler, the receiving end coupler comprises a single-mode receiving optical fiber and six multi-mode receiving optical fibers for transmitting blade reflected light signals, and the optical fibers are located inside the tensile and compression-resistant receiving cable;
the optical fiber transceiving cable comprises a single-mode transceiving optical fiber for simultaneously transmitting optical signals and transmitting blade reflected optical signals and six multimode receiving optical fibers for transmitting the blade reflected optical signals, and the outside of the optical fiber transceiving cable is wrapped by the optical fiber transceiving cable;
one single-mode transceiving optical fiber and six multi-mode receiving optical fibers simultaneously receive reflected optical signals of the end faces of the blades;
the optical fiber receiving and transmitting cable is characterized by also comprising a core inserting sleeve, wherein a single-mode receiving and transmitting optical fiber and six multi-mode receiving optical fibers in the optical fiber receiving and transmitting cable are inserted into the core inserting sleeve, the front end of the core inserting sleeve is provided with a self-focusing lens, and light emitted by the single-mode receiving and transmitting optical fiber can effectively reduce the diameter of a light spot irradiated to the end face of the blade after being focused by the self-focusing lens;
ferrule sleeveThe length of the inner coreless fiber, namely the distance between the single-mode transceiving fiber and the end face of the self-focusing lens is L1The length of the self-focusing lens is Z, and the distance from the end surface of the self-focusing lens to the end surface of the blade is L2The gradient index of the self-focusing lens is alpha, and the axial refractive index of the self-focusing lens is n1The object-side top focal length of the self-focusing lens is LFL 'is the image-side back focal length of the self-focusing lens'FLength L of coreless fiber in ferrule sleeve1The determination method comprises the following steps: expression of object space top focal length and image space top focal lengthAccording to the actual working condition environment, the distance L from the image side end face of the self-focusing lens, namely the actual sensor end face to the blade end face2Controlling the length Z of the cut autofocus lens such that L1＝-LF＝L′F＝L2At this time, the spot diameter irradiated to the blade end surface 14 is the smallest.
The single-mode transmitting optical fiber, the single-mode receiving optical fiber and the single-mode transceiving optical fiber are correspondingly connected with three ports of the circulator respectively, so that an optical signal transmitted by the single-mode transmitting optical fiber can only be received by the single-mode transceiving optical fiber, and a blade reflected optical signal transmitted by the single-mode transceiving optical fiber can only be received by the single-mode receiving optical fiber.
The invention has the characteristics and beneficial effects that:
the defects that the existing optical fiber type tip timing sensor has large spot diameter, low timing resolution and poor timing precision, and cannot meet the requirements of the modern aero-engine compressor moving blade rotating linear speed of 700m/s and vibration displacement measurement precision of 10 mu m on the timing resolution of 3ns are overcome. The optical fiber bundle tip timing sensor based on the self-focusing lens is designed, six multimode optical fibers are utilized to tightly surround a single mode optical fiber to form an optical fiber bundle, the self-focusing lens is assembled at the front end of the optical fiber bundle, the single mode optical fiber is connected with a laser and a photoelectric receiver through a circulator, and the multimode optical fiber is only connected with the photoelectric receiver, so that the light spot diameter is reduced, the intensity of a return light signal is effectively improved, and the timing resolution of the optical fiber type tip timing sensor is improved.
Description of the drawings:
FIG. 1 shows a schematic diagram of a self-focusing lens based fiber optic bundle tip timing sensor of the present invention.
Fig. 2 is a schematic diagram showing the relative positional relationship between the optical fiber in the ferrule sleeve 11 of the present invention, the self-focusing lens 13, and the blade end face 14.
In fig. 1: the optical fiber transmitting and receiving device comprises a transmitting end coupler 1, a receiving end coupler 2, a tensile and compression resistant transmitting cable 3, a tensile and compression resistant receiving cable 4, a single-mode transmitting optical fiber 5, a multi-mode receiving optical fiber 6, a circulator 7, a single-mode transmitting and receiving optical fiber 8, a single-mode receiving optical fiber 9, an optical fiber transmitting and receiving cable 10, a ferrule sleeve 11, a coreless optical fiber 12, a self-focusing lens 13 and a blade end face 14.
Detailed Description
The sensor adopts a structure that six multimode fibers tightly surround a single mode fiber to form a fiber bundle, a self-focusing lens is assembled at the front end of the fiber bundle, the single mode fiber is connected with a laser and a photoelectric receiver through a circulator, and the multimode fibers are only connected with the photoelectric receiver; the invention can effectively improve the intensity of the return light signal while reducing the diameter of the light spot, and is beneficial to improving the timing resolution of the optical fiber type blade tip timing sensor.
In order to overcome the defects in the prior art, the invention designs an optical fiber bundle type blade tip timing sensor based on a self-focusing lens with high timing resolution, which mainly solves the technical problems that:
the timing sensor overcomes the defects that the existing optical fiber type tip timing sensor has low timing resolution and poor timing precision and cannot meet the requirements of the modern aero-engine compressor moving blade rotating linear speed of 700m/s and the vibration displacement measurement precision of 10 mu m on the timing resolution of 3 ns. The optical fiber bundle type blade tip timing sensor based on the self-focusing lens is designed, six multimode optical fibers are utilized to tightly surround a single mode optical fiber to form an optical fiber bundle, the self-focusing lens is assembled at the front end of the optical fiber bundle, the single mode optical fiber is connected with a laser and a photoelectric receiver through a circulator, and the multimode optical fiber is only connected with the photoelectric receiver, so that the light spot diameter is reduced, the intensity of a return light signal is effectively improved, and the timing resolution of the optical fiber type blade tip timing sensor is improved.
In order to achieve the above object, the present invention adopts a technical solution of designing a self-focusing lens-based fiber-optic bundle type tip timing sensor, as shown in fig. 1, including: the device comprises a transmitting end coupler 1, a receiving end coupler 2, a tensile and compressive transmitting cable 3, a compressive and tensile receiving cable 4, a single-mode transmitting optical fiber 5, a multi-mode receiving optical fiber 6, a circulator 7, a single-mode receiving optical fiber 8, a single-mode receiving optical fiber 9, an optical fiber receiving and transmitting cable 10, a ferrule sleeve 11, a coreless optical fiber 12, a self-focusing lens 13 and a blade end face 14;
furthermore, in the invention, the transmitting end coupler 1 contains a single-mode transmitting optical fiber 5 for transmitting optical signals, and the optical fiber is positioned in the tensile and compressive transmitting cable 3, so that the optical fiber is not influenced by treading, pulling and the like, and the reliability is improved;
further, in the invention, the receiving end coupler 2 comprises a single-mode receiving optical fiber 9 and six multi-mode receiving optical fibers 6 for transmitting blade reflected light signals, and the optical fibers are positioned in the tensile and compression-resistant receiving cable 4, so that the optical fibers are not influenced by treading, pulling and the like, and the reliability is improved;
furthermore, in the invention, the optical fiber transceiving cable 10 contains a single-mode transceiving optical fiber 8 for simultaneously transmitting optical signals and transmitting blade reflected optical signals and six multimode receiving optical fibers 6 for transmitting blade reflected optical signals, and the outside of the optical fiber transceiving cable is wrapped by a tensile and compression resistant cable, so that the optical fibers are not influenced by treading, pulling and the like, and the reliability is improved; the invention adopts a single-mode transceiving optical fiber 8 and six multimode receiving optical fibers 6 to simultaneously receive the reflected light signals of the blade end surface 14, can make up the defects of small incident angle range and low receiving optical power of the single-mode optical fiber receiving optical signals, and improves the signal-to-noise ratio of the received signals;
further, in the invention, a single-mode transceiving optical fiber 8 and six multimode receiving optical fibers 6 in the optical fiber transceiving cable 10 are inserted into the ferrule sleeve 11, the self-focusing lens 13 is assembled at the front end of the ferrule sleeve 11, and light emitted by the single-mode transceiving optical fiber 8 can effectively reduce the diameter of a light spot irradiated to the end face 14 of the blade after being focused by the self-focusing lens 13;
further, in the present invention, as shown in fig. 2, the length of the coreless fiber 12 in the ferrule sleeve 11 (i.e., the distance from the single-mode transmitting/receiving fiber 8 to the end face of the self-focusing lens) is set to L1The length of the self-focusing lens 13 is Z, and the distance from the end face of the self-focusing lens to the end face 14 of the blade is L2The gradient index of the self-focusing lens 13 is alpha, and the axial refractive index of the self-focusing lens 13 is n1The object-side top focal length of the self-focusing lens 13 is LFThe image-side back focal length of the self-focusing lens 13 is L'FThe length L of the coreless fiber 12 in the ferrule sleeve 111The determination method comprises the following steps: expression of object space top focal length and image space top focal length
According to the actual working condition, the distance L from the image side end face of the self-focusing lens (i.e. the actual sensor end face) to the end face 14 of the blade2Controlling the length Z of the cut autofocus lens such that L1＝-LF＝L′F＝L2The spot diameter irradiated to the end face 14 of the blade is the smallest at this time;
further, in the present invention, the single-mode transmitting fiber 5, the single-mode receiving fiber 9, and the single-mode transceiving fiber 8 are respectively connected to three ports of the circulator 7, so that the optical signal transmitted by the single-mode transmitting fiber 5 can only be received by the single-mode transceiving fiber 8 with a small insertion loss, and a large isolation exists between the optical signal and the single-mode receiving fiber 9, the blade reflected optical signal transmitted by the single-mode transceiving fiber 8 can only be received by the single-mode receiving fiber 9 with a small insertion loss, and a large isolation exists between the optical signal and the single-mode transmitting fiber 5;
further, in the invention, the transmitting end coupler 1 can adopt a commonly used optical fiber coupler such as an ST joint, an FC joint and the like, and the receiving end coupler 2 can adopt a commonly used optical fiber coupler such as an ST joint, an FC joint and the like;
further, in the invention, the tensile and compressive transmitting cable 3, the tensile and compressive receiving cable 4 and the optical fiber transceiving cable 10 can be stainless steel hoses, metal hoses, plastic-coated armored pipes, plastic protection pipes and the like; the inner diameter of the tensile and compression resistant transmitting cable 3 is larger than the outer diameter of the single-mode transmitting optical fiber 5, the inner diameters of the compression resistant tensile receiving cable 4 and the optical fiber transceiving cable 10 are larger than the outer diameters of the circumscribed circles of all the optical fibers in the compression resistant tensile receiving cable and the optical fiber transceiving cable after being reasonably arranged, and the length of the compression resistant tensile receiving cable and the optical fiber transceiving cable meets the actual use.
Furthermore, in the invention, the single-mode transmitting optical fiber 5, the multimode receiving optical fiber 6, the single-mode transceiving optical fiber 8 and the single-mode receiving optical fiber 9 can adopt optical fiber structures with thinner claddings, so that the distance between the single-mode transceiving optical fiber 8 and the multimode receiving optical fiber 6 in the optical fiber transceiving cable 10 is shorter, and the signal-to-noise ratio of the received signal of the sensor is higher; the inner diameter of the coreless fiber 12 is larger than the outer diameter of the circumscribed circle after the six multimode receiving fibers 6 and the single-mode transceiving fiber 8 are reasonably arranged.
In order to overcome the defects in the prior art, the invention designs an optical fiber bundle type blade tip timing sensor based on a self-focusing lens with high timing resolution, which mainly solves the technical problems that:
the timing sensor overcomes the defects that the existing optical fiber type tip timing sensor has low timing resolution and poor timing precision and cannot meet the requirements of the modern aero-engine compressor moving blade rotating linear speed of 700m/s and the vibration displacement measurement precision of 10 mu m on the timing resolution of 3 ns. An optical fiber bundle type blade tip timing sensor based on a self-focusing lens is designed, six multimode optical fibers are utilized to tightly surround a single mode optical fiber to form an optical fiber bundle, the self-focusing lens is assembled at the front end of the optical fiber bundle, the single mode receiving and transmitting optical fiber is connected with a laser and a photoelectric receiver through a circulator, and the multimode receiving optical fiber is only connected with the photoelectric receiver, so that the diameter of a light spot is reduced, the intensity of a return light signal is effectively improved, and the timing resolution of the optical fiber type blade tip timing sensor is improved.
The invention is realized by the following steps:
the invention designs a fiber bundle type blade tip timing sensor based on a self-focusing lens, as shown in figure 1, comprising: the device comprises a transmitting end coupler 1, a receiving end coupler 2, a tensile and compressive transmitting cable 3, a compressive and tensile receiving cable 4, a single-mode transmitting optical fiber 5, a multi-mode receiving optical fiber 6, a circulator 7, a single-mode receiving optical fiber 8, a single-mode receiving optical fiber 9, an optical fiber receiving and transmitting cable 10, a ferrule sleeve 11, a coreless optical fiber 12, a self-focusing lens 13 and a blade end face 14. Compared with the traditional optical fiber type blade tip timing sensor, the single-mode optical fiber and self-focusing lens have the advantages of small beam waist radius and small numerical aperture, the diameter of a light spot irradiated to the end face of the blade is reduced, and the timing resolution of the sensor is improved.
The invention is further described with reference to the following figures and examples.
Further, in the present invention, the transmitting-side coupler 1 may employ an ST tap. The transmitting end coupler 1 is internally provided with a single-mode transmitting optical fiber 5 for transmitting optical signals, and the optical fiber is positioned in the tensile and compression resistant transmitting cable 3 so as to ensure that the optical fiber is not influenced by treading, pulling and the like and improve the reliability; the outer diameter of the single-mode emission fiber 5 for emitting optical signals can be selected as (core diameter/cladding/coating layer, μm)9/125/150, and the numerical aperture NA is 0.11;
further, in the present invention, the receiving-end coupler 2 may employ an ST tap. The receiving end coupler 2 is internally provided with a single-mode receiving optical fiber 9 and six multi-mode receiving optical fibers 6 for transmitting blade reflected light signals, and the optical fibers are positioned in the tensile and compressive receiving cable 4 so as to ensure that the optical fibers are not influenced by treading, pulling and the like and improve the reliability; the outer diameter parameter of the single-mode receiving optical fiber 9 for transmitting the light signal of the blade can be selected as (core diameter/cladding/coating layer, mum) 9/125/150, and the numerical aperture NA is 0.11; the outer diameter of the multimode receiving fiber 6 can be chosen as (core diameter/cladding/coating layer, mum) 50/125/150, the numerical aperture NA is 0.22;
furthermore, in the invention, the optical fiber transceiving cable 10 contains a single-mode transceiving optical fiber 8 for simultaneously transmitting optical signals and transmitting blade reflected optical signals and six multimode receiving optical fibers 6 for transmitting blade reflected optical signals, and the outside of the optical fiber transceiving cable is wrapped by a tensile and compression resistant cable, so that the optical fibers are not influenced by treading, pulling and the like, and the reliability is improved; the outer diameter parameter of the single mode transceiving optical fiber 8 for simultaneously transmitting the optical signal and transmitting the vane reflected optical signal can be selected as (core diameter/cladding/coating layer, mum) 9/125/150, and the numerical aperture NA is 0.11; the outer diameter of the multimode receiving fiber 6 can be chosen as (core diameter/cladding/coating layer, mum) 50/125/150, the numerical aperture NA is 0.22;
furthermore, in the invention, a single-mode transceiving optical fiber 8 and six multimode receiving optical fibers 6 in the optical fiber transceiving cable 10 are inserted into the ferrule sleeve 11, the self-focusing lens 13 is assembled at the front end of the ferrule sleeve 11, and the diameter of a light spot irradiated to the end face of the blade can be effectively reduced after light emitted by the single-mode transceiving optical fiber 8 is focused by the self-focusing lens 13;
further, in the present invention, if the distance from the actual sensor end face, i.e., the image-side end face of the self-focusing lens, to the blade end face 14 is 15mm, the length of the coreless fiber 12 in the ferrule sleeve 11, i.e., the distance from the single-mode transmitting/receiving fiber 8 to the object-side end face of the self-focusing lens, is also 15mm, and the axial refractive index n is calculated based on the gradient index α of the self-focusing lens 131Cutting the length Z of the self-focusing lens so that
At this time, the blade end face 14 is located at the image focus position of the self-focusing lens 13, and the diameter of a light spot irradiated on the blade end face 14 is the minimum;
further, in the present invention, the circulator 7 may adopt a polarization maintaining optical circulator to ensure the coupling efficiency of the single mode fiber and the circulator, the single mode transmitting fiber 5, the single mode receiving fiber 9 and the single mode transceiving fiber 8 are respectively connected to three ports of the circulator 7, so that the optical signal transmitted by the single mode transmitting fiber 5 can only be received by the single mode transceiving fiber 8 with a small insertion loss, and has a large isolation from the single mode receiving fiber 9, the blade reflected optical signal transmitted by the single mode transceiving fiber 8 can only be received by the single mode receiving fiber 9 with a small insertion loss, and has a large isolation from the single mode transmitting fiber 5;
further, in the invention, the tensile and compressive transmitting cable 3, the tensile and compressive receiving cable 4 and the optical fiber transceiving cable 10 can be stainless steel hoses, metal hoses, plastic-coated armored pipes, plastic protection pipes and the like; the inner diameter of the tensile and compression resistant transmitting cable 3 is larger than the outer diameter of the single-mode transmitting optical fiber 5, and if a plastic-coated armored cable with the outer diameter of 3.9mm is selected; the inner diameters of the compression-resistant tensile receiving cable 4 and the optical fiber transceiving cable 10 are larger than the outer diameter of a circumscribed circle after all optical fibers in the optical fiber transceiving cable are reasonably arranged, for example, a plastic-coated armored cable with the outer diameter of 5.5mm is selected; the lengths of the tensile and compressive transmitting cable 3, the tensile and compressive receiving cable 4 and the optical fiber transceiving cable 10 are required to meet the actual use requirement, and if the length of the tensile and compressive transmitting cable 3 is selected to be 0.5m, the length of the tensile and compressive receiving cable 4 is selected to be 0.5m, and the length of the optical fiber transceiving cable 10 is selected to be 3 m;
furthermore, in the invention, the single-mode transmitting optical fiber 5, the multi-mode receiving optical fiber 6, the single-mode transceiving optical fiber 8 and the single-mode receiving optical fiber 9 can adopt optical fiber structures with thinner claddings, such as all-quartz optical fibers, so that the distances between the single-mode transceiving optical fiber 8 and the multi-mode receiving optical fiber 6 in the optical fiber transceiving cable 10 are closer; the inner diameter of the coreless fiber 12 is larger than the outer diameter of the circumscribed circle after the six multimode receiving fibers 6 and the single-mode transceiving fiber 8 are reasonably arranged.
Claims (4)
1. An optical fiber bundle type blade tip timing sensor based on a self-focusing lens is characterized in that a plurality of multimode optical fibers tightly surround a single mode optical fiber to form an optical fiber bundle, the self-focusing lens is assembled at the front end of the optical fiber bundle, the single mode optical fiber is connected with a laser and a photoelectric receiver through a circulator, the multimode optical fiber is only connected with the photoelectric receiver, laser emitted by the laser is projected to the end face of a blade through the single mode optical fiber and the self-focusing lens, and reflected laser on the end face of the blade passes through the self-focusing lens and then is projected to the photoelectric receiver through the single mode optical.
2. The self-focusing lens based fiber optic bundle tip timing sensor as claimed in claim 1, wherein the laser outputs laser light through a launch end coupler, the launch end coupler containing a single-mode launch fiber for launching optical signals, the fiber being located inside the tension and compression resistant launch cable;
the photoelectric receiver receives laser signals through a receiving end coupler, the receiving end coupler comprises a single-mode receiving optical fiber and six multi-mode receiving optical fibers for transmitting blade reflected light signals, and the optical fibers are located inside the tensile and compression-resistant receiving cable;
the optical fiber transceiving cable comprises a single-mode transceiving optical fiber for simultaneously transmitting optical signals and transmitting blade reflected optical signals and six multimode receiving optical fibers for transmitting the blade reflected optical signals, and the outside of the optical fiber transceiving cable is wrapped by the optical fiber transceiving cable;
one single-mode transceiving optical fiber and six multi-mode receiving optical fibers simultaneously receive reflected optical signals of the end faces of the blades;
the optical fiber receiving and transmitting cable is characterized by further comprising a core inserting sleeve, a single-mode receiving and transmitting optical fiber and six multi-mode receiving optical fibers in the optical fiber receiving and transmitting cable are inserted into the core inserting sleeve, a self-focusing lens is assembled at the front end of the core inserting sleeve, and light emitted by the single-mode receiving and transmitting optical fiber can effectively reduce the diameter of a light spot irradiated to the end face of the blade after being focused by the self-focusing lens.
3. The self-focusing lens-based fiber optic bundle tip timing sensor of claim 2, wherein the length of the coreless fiber in the core-insertion sleeve, i.e., the distance from the single-mode transceiver fiber to the end face of the self-focusing lens, is L1The length of the self-focusing lens is Z, and the distance from the end surface of the self-focusing lens to the end surface of the blade is L2The gradient index of the self-focusing lens is alpha, and the axial refractive index of the self-focusing lens is n1The object-side top focal length of the self-focusing lens is LFL 'is the image-side back focal length of the self-focusing lens'FLength L of coreless fiber in ferrule sleeve1The determination method comprises the following steps: expression of object space top focal length and image space top focal lengthAccording to the actual working condition environment, the distance L from the image side end face of the self-focusing lens, namely the actual sensor end face to the blade end face2Controlling the length Z of the cut autofocus lens such that L1＝-LF＝L'F＝L2At this time, the spot diameter irradiated to the blade end surface 14 is the smallest.
4. The self-focusing lens-based fiber optic bundle tip timing sensor according to claim 1, wherein a single-mode transmitting fiber, a single-mode receiving fiber and a single-mode transceiving fiber are respectively and correspondingly connected to three ports of the circulator, so that the optical signal transmitted by the single-mode transmitting fiber can only be received by the single-mode transceiving fiber, and the blade reflected optical signal transmitted by the single-mode transceiving fiber can only be received by the single-mode receiving fiber.
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| CN112902859A (en) * | 2021-02-02 | 2021-06-04 | 上海交通大学 | Blade tip timing technology-based blade tip clearance online measurement method and device |
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