Array type blade tip timing sensor based on optical fiber illumination

Abstract

The invention discloses an array type blade tip timing sensor based on optical fiber illumination. The array type blade tip timing sensor comprises a transmitting end coupler, a receiving end coupler, a transmitting cable, a receiving cable, a beam combiner, an optical fiber transceiving cable and a probe, the other end of the transmitting end coupler is connected with a transmitting cable; the plurality of receiving couplers are respectively connected with a receiving cable, the transmitting cable and the receiving cable are both connected with one end of a beam combiner, and the other end of the beam combiner is connected with a probe through an optical fiber transceiving cable; a beam splitter, a collimating lens and a self-focusing lens are arranged in the probe, and a blade to be detected is arranged in front of the probe; the beam splitter divides the optical fiber transceiving cable into a transmitting optical fiber and a receiving optical fiber, the front end of the transmitting optical fiber is provided with a collimating lens, the front end of the receiving optical fiber is provided with a plurality of sensor measuring points arranged in an array form, and the front ends of the sensor measuring points are provided with self-focusing lenses; and the front end surfaces of the transmitting optical fiber and the receiving optical fiber are vertical.

Description

Technical Field

[0001] The present invention belongs to the field of sensors, and particularly relates to an array-type blade tip timing sensor based on optical fiber illumination. Background Art

[0002] Blades in large rotating machinery, such as aircraft engines, gas turbines, flue gas turbines, and steam turbines, are core working components. Non-contact online monitoring of their state parameters, particularly vibration parameters, is crucial for ensuring engine operating quality and the safe operation of critical equipment. With the development of new-generation aircraft engines, rotor blades, demanding high performance and highly optimized structures, are exposed to increasingly complex flow environments. Fluid-structure interaction between the blades and the airflow generates various forms of coupled vibration, including low-order bending vibration, high-order vibration, and combined bending-torsion vibration. Failure modes such as flutter and cracking are directly reflected in transient and subtle changes in the blade's high-order vibration amplitude. The amplitude of these high-order vibration modes and transient vibrations is only tens of microns, and the events occur very quickly. Therefore, the blade tip vibration displacement must be measured with an accuracy better than 10 μm. Furthermore, to accurately measure these high-order and transient vibration parameters, it is necessary to deploy as many sensors as possible around the rotating blade's circumference.

[0003] Blade tip timing measurement technology is a standard technology for non-contact blade vibration measurement. Among them, fiber-optic blade tip timing sensors have the advantages of fast response speed and high measurement accuracy, making them the first choice for non-contact blade vibration sensors. However, due to the limited number of openings in aircraft engine casings, the number of measurement points using traditional fiber-optic timing sensors is very limited, and the distance between measurement points is relatively far, so only low-order vibration measurements can be achieved. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide an array-type blade tip timing sensor based on fiber optic illumination. The sensor includes a group of illumination optical fibers and N groups of freely arranged measurement optical fibers. Through an APD array composed of N APDs, a single sensor can measure the blade tip timing of N measuring points, thereby increasing the number of measuring points without increasing the number of casing openings, thereby achieving accurate measurement of high-order vibration and transient vibration parameters of rotating blades, and can be used to improve the ability to identify high-order and transient vibrations of blades.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] An array-type blade tip timing sensor based on optical fiber illumination, comprising:

[0007] 1 transmitting end coupler, N receiving end couplers, transmitting cable, receiving cable, beam combiner, optical fiber transceiver cable, array sensor probe, N ≥ 4;

[0008] One end of the transmitting end coupler is connected to the laser, and the other end is connected to the transmitting cable;

[0009] N receiving couplers are connected to N receiving cables respectively. The transmitting cable and the receiving cable are both connected to one end of the beam combiner. The other end of the beam combiner is connected to the array sensor probe through an optical fiber transceiver cable.

[0010] The array sensor probe is provided with a beam splitter, a collimating lens and a self-focusing lens array, and a blade to be measured is provided in front of the array sensor probe;

[0011] The beam splitter divides the optical fiber transceiver cable into a transmitting optical fiber and a receiving optical fiber. A collimating lens is provided at the front end of the transmitting optical fiber, and a plurality of sensor measuring points arranged in an array are provided at the front end of the receiving optical fiber. The self-focusing lens array is provided at the front end of the sensor measuring points. The front end faces of the transmitting optical fiber and the receiving optical fiber are in a vertical relationship.

[0012] Furthermore, the transmitting cable, receiving cable and optical fiber transceiver cable are all covered with tensile and compressive resistant cable materials to ensure the ability to resist stretching and trampling.

[0013] Furthermore, the optical fiber transceiver cable contains one transmitting optical fiber for transmitting the transmitting optical signal and N groups of multimode receiving optical fibers for transmitting the receiving optical signal.

[0014] Furthermore, a right-angle bracket is provided in the array sensor probe for fixing the position and angle of the front end of the transmitting optical fiber and the receiving optical fiber. The collimating lens is used to shape the transmitting light beam to form an illumination area on the blade to be measured. Each sensor measuring point is fixed at an angle by a glass tube, and the self-focusing lens array is used to focus the detection light when it is received. During the measurement process, the illumination light is emitted from the transmitting end and irradiated onto the blade to be measured. After that, the reflected light from the end face of the blade passes through the self-focusing lens array and is incident on the receiving end, i.e., the receiving optical fiber.

[0015] Furthermore, the protective structure of the transmitting cable, receiving cable and optical fiber transceiver cable is selected to be a metal armored sheath or a non-metallic sheath.

[0016] Furthermore, by arranging the sensor measuring points in different ways, it is possible to obtain timed signals from several points on the blade to be measured in order to measure vibration parameters.

[0017] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0018] 1. Existing fiber-optic tip timing sensors have a very limited number of measurement points and are widely spaced, making them incapable of measuring high-order and transient vibrations of aircraft engine blades. The sensor of the present invention comprises a set of illumination fibers and N sets of freely arranged measurement fibers. Through an APD array consisting of N APDs, a single sensor can measure the tip timing of N measurement points. This increases the number of measurement points without increasing the number of casing openings, thereby enabling accurate measurement of high-order and transient vibration parameters of rotating blades.

[0019] 2. The sensor's array sensor probe features an optical fiber emitter and a receiving fiber input end mounted at a 90-degree angle. The receiving fiber input end is fused to a self-focusing lens 17 to improve the signal-to-noise ratio. By arranging measurement points along the circumference and axial directions of the blade under test, the sensor simultaneously captures both bending and torsional vibration signals. Compared to traditional fiber-optic blade tip timing sensors, this sensor effectively captures more measurement points and improves timing resolution.

[0020] 3. The outermost layer of all cables installed with optical fibers in the present invention is wrapped with tensile and compressive resistant materials to ensure that the optical fibers are not affected by stepping, pulling, etc., thereby improving reliability.

[0021] 4. The present invention uses a single set of optical fibers at the transmitting end to illuminate the blade area and multiple sets of optical fibers to receive the blade reflection signal. It has a simple structure and high reliability, which is conducive to working on harsh rotor systems such as aircraft engines, steam turbines and gas turbines. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A schematic structural diagram of the array blade tip timing sensor of the present invention is shown.

[0023] Figure 2 A schematic structural diagram of the probe of the present invention is shown.

[0024] Figure 3 A schematic diagram showing the measurement principle of the probe in the present invention is shown.

[0025] Figure 4 A schematic diagram showing the optical fiber array blade tip timing sensor of the present invention measuring blade vibration.

[0026] Figure numerals: 1-transmitting end coupler, 2-transmitting cable, 3-beam combiner, 4-receiving end coupler, 5-receiving cable, 6-optical fiber transceiver cable, 7-array sensor probe, 8-blade to be measured, 9-single-mode optical fiber, 10-multi-mode optical fiber, 11-housing, 12-beam splitter, 13-receiving optical fiber, 14-transmitting optical fiber, 15-collimating lens, 16-sensor measuring point, 17-self-focusing lens array, 18-light spot, 19-laser, 20-laser receiver, 21-blade tip timing processing module. DETAILED DESCRIPTION

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and 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.

[0028] This embodiment provides an array-type blade tip timing sensor based on fiber optic illumination, which mainly solves the technical problem of overcoming the shortcomings of the existing fiber optic blade tip timing test system, which requires multiple holes to be opened on the casing, a single sensor cannot simultaneously measure the bending vibration and torsional vibration of the blade, has fewer measuring points, and has low timing resolution, and cannot meet the high-precision measurement of vibration parameters of modern high-speed aircraft engines. By designing an array-type blade tip timing sensor based on fiber optic illumination, a collimating lens is used to collimate the emitted fiber optic light to achieve local illumination of the blade to form a light spot 18, and the blade reflected light is monitored by multiple optical fibers to achieve multi-point vibration monitoring of the blade. Through different optical fiber arrangements, the axial and circumferential vibration displacement of the rotor blade can be monitored, thereby achieving blade bending vibration and torsional vibration measurement.

[0029] The array-type blade tip timing sensor based on optical fiber illumination provided in this embodiment is as follows: Figure 1 As shown, it includes a transmitting end coupler 1, 8 receiving end couplers 4, a transmitting cable 2, a receiving cable 5, a combiner 3, an optical fiber transceiver cable 6, and an array sensor probe 7. A beam splitter and a glass tube are used inside the probe to arrange the receiving optical fibers in a 4x2 rectangular array, and a right-angle bracket is used to ensure that the output end of the transmitting optical fiber 14 and the incident end of the receiving optical fiber 13 are installed at 90 degrees; a self-focusing lens array 17 is fused at the front end of the receiving optical fiber to improve the signal-to-noise ratio; and the measurement points are arranged in the circumferential and axial directions of the blade to be measured to achieve the simultaneous acquisition of bending vibration and torsional vibration signals. Compared with the traditional optical fiber blade tip timing sensor, more measurement points are effectively acquired, and the timing resolution is improved. The invention is further described below with reference to the accompanying drawings and embodiments.

[0030] Preferably, the transmitting end coupler 1 can use an ST connector. The transmitting end coupler 1 contains a single-mode optical fiber 9 for transmitting optical signals. The single-mode optical fiber is located inside the transmitting cable 2 to ensure that the optical fiber is not affected by stepping on, pulling, etc., thereby improving reliability. The dimensional parameters of the single-mode optical fiber are (core diameter / cladding / coating, μm) 9 / 125 / 150, and the numerical aperture NA is 0.11. The 8 receiving end couplers 4 also use ST connectors. Each receiving cable 5 contains 7 multimode optical fibers 10. The dimensional parameters of the multimode optical fiber are (core diameter / cladding / coating, μm) 50 / 125 / 150, and the numerical aperture NA is 0.22.

[0031] Preferably, the receiving optical fiber 13 is connected to one end of the sensor measuring point 16 via a receiving-end combiner. The receiving optical fiber 13 internally contains eight groups of multimode optical fiber cables, each group containing seven multimode optical fibers. The multimode optical fibers have dimensions of (core diameter / cladding / coating, μm) 50 / 125 / 150, and a numerical aperture (NA) of 0.22. The single-mode optical fiber within the transmitting optical fiber 14 has dimensions of (core diameter / cladding / coating, μm) 9 / 125 / 150, and a numerical aperture (NA) of 0.11. The outermost layers of the transmitting and receiving optical fibers 14 and 13 are wrapped in tensile and compressive resistant materials to protect the optical fibers from being affected by pressure, pulling, etc., thereby improving reliability.

[0032] The array sensor probe 7 adopts Figure 2 The structure shown implements array detection based on fiber optic illumination imaging; it includes a housing 11, a fiber optic transceiver cable 6 connected to a beam splitter 12 and divided into a transmitting fiber 14 and a receiving fiber 13. The transmitting fiber 14 contains a single-mode transmitting fiber, and a collimating lens 15 is fused to the front end of the single-mode transmitting fiber to collimate the output light of the single-mode fiber. At the receiving end of the detection light, the receiving fiber 13 is divided into 8 sensor measuring points 16 by a beam splitter and fixed into a 4x2 array arrangement by a glass tube. A self-focusing lens array 17 is fused to the front end of the sensor measuring points 16 arranged in the 4x2 array to achieve focusing when receiving the detection light. Similarly, the front end (light receiving end) of the receiving fiber is located at the lens focus, wherein each self-focusing lens arranged in an array in the self-focusing lens array 17 corresponds one-to-one to each sensor measuring point 16. A right-angle bracket is provided in the array sensor probe, and the front ends of the transmitting fiber 14 and the receiving fiber 13 are fixed by the right-angle bracket to ensure that the front ends of the transmitting fiber 14 and the receiving fiber 13 are perpendicular to each other. The above single-mode fiber parameters are (core diameter / cladding / coating, μm) 9 / 125 / 150, and the numerical aperture is 0.11; the multi-mode fiber parameters are (core diameter / cladding / coating, μm) 50 / 125 / 150, and the numerical aperture NA is 0.22.

[0033] Preferably, see Figure 3 During the measurement process, the laser is emitted from the transmitting end and irradiated onto the blade 8 to be measured through the collimating lens 15. Then, the reflected light from the end face of the blade 8 to be measured passes through the self-focusing lens array 17 and is incident on the sensor measuring point.

[0034] Preferably, see Figure 4 The transmitting end coupler 1 is externally connected to a laser 19, and the receiving end couplers 5 are in turn externally connected to a laser receiver 20 and a blade tip timing processing module 21. By arranging light spots 18 measuring points in the circumferential and axial directions of the blade to be measured, the bending vibration and torsional vibration signals are obtained by the difference in timing pulses of different light spots 18 measuring points, thereby achieving simultaneous measurement;

[0035] Preferably, the sensor cable protective cover can be made of stainless steel hose, metal hose, plastic-coated armored tube, plastic protective tube, etc.; the inner diameter of the sensor cable protective cover should be larger than the outer diameter of the 8-fiber assembly. For example, for a transmitting cable composed of 4 optical fibers, a plastic-coated armored cable with an outer diameter of 2mm can be selected. For a receiving cable composed of 4 optical fibers, a plastic-coated armored cable with an outer diameter of 6mm can be selected. The lengths of the transmitting cable, receiving cable and optical fiber transceiver cable should meet the actual use requirements, such as selecting a transmitting length of 0.5m, a receiving cable length of 0.5m, and an optical fiber transceiver cable length of 3m.

[0036] Preferably, the single-mode transmitting optical fiber 14, the multi-mode receiving optical fiber 13, the optical fiber in the single-mode transmitting optical fiber cable and the optical fiber in the multi-mode receiving optical fiber cable in the present invention can all adopt an optical fiber structure with a thinner cladding, such as an all-quartz optical fiber.

[0037] The present invention is not limited to the embodiments described above. The above description of the specific embodiments is intended to describe and illustrate the technical solutions of the present invention. The above specific embodiments are merely illustrative and not restrictive. Without departing from the scope of the present invention and the scope of protection of the claims, those skilled in the art may make various specific modifications based on the teachings of the present invention, all of which fall within the scope of protection of the present invention.

Claims

1. An array-type blade tip timing sensor based on fiber optic illumination, characterized in that: include: 1 transmitting end coupler (1), N receiving end couplers (4), a transmitting cable (2), a receiving cable (5), a beam combiner (3), an optical fiber transmitting and receiving cable (6) and an array sensor probe (7), N ≥ 4; One end of the transmitting end coupler (1) is connected to the laser, and the other end is connected to the transmitting cable (2); N receiving couplers (4) are respectively connected to N receiving cables (5), the transmitting cable (2) and the receiving cable (5) are both connected to one end of the beam combiner (3), and the other end of the beam combiner (3) is connected to the array sensor probe (7) via an optical fiber transceiver cable (6); The array sensor probe (7) is provided with a beam splitter (12), a collimating lens (15) and a self-focusing lens array (17), and a blade to be measured is provided in front of the array sensor probe (7); The beam splitter (12) divides the optical fiber transceiver cable (6) into a transmitting optical fiber (14) and a receiving optical fiber (13); a collimating lens (15) is provided at the front end of the transmitting optical fiber (14); a plurality of sensor measuring points (16) arranged in an array form are provided at the front end of the receiving optical fiber (13); and the self-focusing lens array (17) is provided at the front end of the sensor measuring points; and the front end surfaces of the transmitting optical fiber (14) and the receiving optical fiber (13) are in a perpendicular relationship.

2. The array-type blade tip timing sensor based on optical fiber illumination according to claim 1, characterized in that: The transmitting cable (2), the receiving cable (5) and the optical fiber transmitting and receiving cable (6) are all covered with tensile and compressive cable materials to ensure the ability to resist stretching and trampling.

3. The array-type blade tip timing sensor based on optical fiber illumination according to claim 1, characterized in that: The optical fiber transceiver cable (6) contains one transmitting optical fiber for transmitting a transmitting optical signal and N groups of multimode receiving optical fibers for transmitting a receiving optical signal.

4. The array-type blade tip timing sensor based on optical fiber illumination according to claim 1, characterized in that: A right-angle bracket is provided in the array sensor probe (7) for fixing the position and angle of the front ends of the transmitting optical fiber (14) and the receiving optical fiber (13); a collimating lens (15) is used to shape the transmitting light beam to form an illumination area on the blade to be measured; each sensor measuring point (16) is fixed at an angle by a glass tube; a self-focusing lens array (17) is used to focus the detection light when receiving it; during the measurement process, the illumination light is emitted from the transmitting end and irradiated onto the blade to be measured, and then the reflected light from the blade end face is incident on the receiving end, i.e., the receiving optical fiber (13), through the self-focusing lens array (17).

5. The array-type blade tip timing sensor based on optical fiber illumination according to claim 1, characterized in that: The protective structure of the transmitting cable (2), the receiving cable (5) and the optical fiber transmitting and receiving cable (6) is selected to be a metal armored sheath or a non-metallic sheath.

6. The array-type blade tip timing sensor based on optical fiber illumination according to claim 1, characterized in that: Through different arrangements of sensor measuring points, it is possible to obtain timed signals from several points on the blade to be measured in order to measure vibration parameters.

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