CN109269625B - Double-optical-fiber-beam leaf-end timing measurement method based on dynamic threshold - Google Patents
Double-optical-fiber-beam leaf-end timing measurement method based on dynamic threshold Download PDFInfo
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- CN109269625B CN109269625B CN201811244318.9A CN201811244318A CN109269625B CN 109269625 B CN109269625 B CN 109269625B CN 201811244318 A CN201811244318 A CN 201811244318A CN 109269625 B CN109269625 B CN 109269625B
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- 238000000691 measurement method Methods 0.000 title claims abstract description 13
- 239000013307 optical fiber Substances 0.000 claims abstract description 60
- 238000000034 method Methods 0.000 claims abstract description 9
- 239000002184 metal Substances 0.000 claims description 7
- 230000003750 conditioning effect Effects 0.000 claims description 4
- 238000001514 detection method Methods 0.000 claims description 4
- 239000003292 glue Substances 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 claims description 3
- 239000000463 material Substances 0.000 claims description 3
- 238000005259 measurement Methods 0.000 claims description 3
- 238000012545 processing Methods 0.000 claims description 3
- 230000009977 dual effect Effects 0.000 claims 4
- 230000007613 environmental effect Effects 0.000 abstract description 2
- 230000010363 phase shift Effects 0.000 abstract description 2
- 230000001960 triggered effect Effects 0.000 abstract description 2
- 238000012360 testing method Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
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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
- G01H9/006—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means using fibre optic sensors the vibrations causing a variation in the relative position of the end of a fibre and another element
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- Length Measuring Devices By Optical Means (AREA)
Abstract
A double-optical-fiber-beam leaf-end timing measurement method based on a dynamic threshold value is provided, a double-optical-fiber-beam leaf-end timing sensor structure is designed, spatial phase shift is carried out between optical fiber beams for a fixed distance, each optical fiber beam can independently sense a light intensity signal, the intersection point of the light intensity signals of the two optical fiber beams is used as the dynamic threshold value, a leaf-end timing signal is triggered, and the arrival time of a blade is judged. Compared with the traditional method of triggering the leaf end timing signal by a fixed threshold, the dynamic threshold dual-optical-fiber-beam leaf end timing measurement method can theoretically eliminate the influence of the leaf end gap change on the leaf end timing signal, inhibit the timing uncertainty caused by environmental noise and the like, and improve the leaf end timing precision. The invention has the advantages of high precision, strong reliability and the like.
Description
Technical Field
The invention belongs to the technical field of blade vibration testing of aero-engines, and particularly relates to a double-optical-fiber-beam blade-end timing measuring method based on a dynamic threshold.
Background
A blade end timing measurement technology is generally adopted in blade vibration testing of an aircraft engine, blade end timing signals are generated through judging of blade reflection light intensity information, and blade vibration information is analyzed through time sequence difference information of blade tips/blade roots. The key technical difficulty of the leaf end timing measurement is the generation of a high-precision and high-reliability leaf end timing signal; timing precision restriction factors such as dynamic clearance change of blade tips, noise and the like cause the technical difficulty. In order to restrain the influence of dynamic tip clearance on timing precision, a double-optical-fiber-beam blade end timing measurement method based on a dynamic threshold value is provided.
Disclosure of Invention
In order to overcome the difficulties in the prior art, the invention aims to provide a dynamic threshold-based double-optical-fiber-beam leaf end timing measurement method which has the advantages of high precision, strong reliability and the like.
In order to achieve the purpose, the invention adopts the technical scheme that:
a double-optical-fiber-beam leaf end timing measurement method based on dynamic threshold comprises the following steps:
1) processing two holes with parallel axes by a cylindrical metal block, wherein the hole center distance is proper, and the hole diameter is based on the optical fiber bundle;
2) respectively placing two same optical fiber bundles A, B into the two holes in the step 1), fixing and finely adjusting the positions by using high-temperature-resistant glue, and finishing the manufacture of a double-optical-fiber-bundle leaf-end timing sensor measuring head, wherein the optical fiber bundles comprise an emitting optical fiber and a receiving optical fiber;
3) fixing the measuring head obtained in the step 2) at a certain position away from the blade, wherein light emitted by the emitting optical fiber in the optical fiber bundle A, B in the measuring head is incident on the blade, is reflected by the blade and then returns to the optical fiber bundle A, B to receive the optical fiber, and after photoelectric detection and circuit conditioning, two paths of voltage analog signals corresponding to the light intensity signals are obtained;
4) and triggering a blade end timing signal by taking the intersection point of the two paths of voltage analog signals as a dynamic threshold value, and judging the arrival time of the blade so as to eliminate the influence of the blade end clearance change on the blade end timing signal.
The metal block in the step 1) is made of common high-temperature-resistant materials, and the section of the metal block is oval.
In the step 1), the distance between the hole centers is 100-500 μm, and in the step 3), the distance between the measuring head and the blade is 1-2 mm.
The measuring head of the leaf end timing sensor in the step 2) is of a double-optical-fiber-bundle structure, wherein the optical fiber bundle is of a structure of 1+6, one optical fiber in the middle is a transmitting optical fiber, and 6 optical fibers surrounding the transmitting optical fiber are receiving optical fibers.
The dynamic threshold value in the step 4) is selected as an intersection point of two changed voltage analog signals, and compared with a traditional fixed threshold value method, the dynamic threshold value method has good self-adaptive capacity for the change of the voltage signals.
Compared with the prior art, the invention has the beneficial effects that:
1) the invention can sense the change of the reflected light intensity signal of the blade through the double optical fiber beams, and triggers the timing signal of the blade end by taking the intersection point of the signals as a dynamic threshold, thereby basically eliminating the influence of the blade tip clearance, and having strong reliability, good stability and high precision.
2) The invention provides a novel method for triggering a leaf end timing signal, which eliminates errors from a hardware level, has higher precision and popularization and application values compared with the traditional fixed threshold value method, and is very suitable for the technical field of blade vibration testing of an aircraft engine.
Drawings
Fig. 1 is a theoretical schematic of the present invention.
FIG. 2 is a schematic diagram of dynamic threshold leaf-end timing signal triggering.
FIG. 3 is a diagram illustrating conventional leaf-end timing signal triggering.
FIG. 1 shows a blade; 2 is a cylindrical metal block; 3 is an optical fiber bundle A; 4 is an optical fiber bundle B; 5 is a measuring head of a timing sensor at the blade end; 6 is leaf end timing signal; 7 is a voltage analog signal corresponding to the light intensity signal sensed by the optical fiber bundle A; and 8 is a voltage analog signal corresponding to the light intensity signal sensed by the optical fiber bundle B.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described below with reference to the accompanying drawings and examples.
A double-optical-fiber-beam leaf end timing measurement method based on dynamic threshold comprises the following steps:
1) processing two holes with parallel axes on a cylindrical metal block 2 with an elliptic section made of common high-temperature resistant material, wherein the distance between the centers of the holes is 100-500 mu m, and the diameter of the holes is based on the placement of an optical fiber bundle;
2) respectively placing two identical optical fiber bundles A3 and B4 into the two holes in the step 1), fixing the optical fiber bundles by using high-temperature-resistant glue and finely adjusting the positions of the optical fiber bundles, and finishing the manufacture of the measuring head 5 of the double-optical-fiber-bundle leaf-end timing sensor; the optical fiber bundle A3 and the optical fiber bundle B4 are in a 1+6 structure, one optical fiber in the middle is a transmitting optical fiber, and six optical fibers surrounding the middle are receiving optical fibers;
3) as shown in fig. 1, a measuring head 5 is fixed at a position 1 mm-2 mm away from a blade 1, light emitted by an optical fiber bundle a3 is emitted to impinge on the blade 1, reflected by the blade 1 and returned to a receiving optical fiber thereof, after photoelectric detection and circuit conditioning, a voltage analog signal 7 corresponding to a light intensity signal sensed by the optical fiber bundle a is obtained, light emitted by an optical fiber bundle B4 impinges on the blade 1, reflected by the blade 1 and returned to the receiving optical fiber thereof, and after photoelectric detection and circuit conditioning, a voltage analog signal 8 corresponding to a light intensity signal sensed by the optical fiber bundle B is obtained;
4) the intersection point of the two voltage analog signals 7 and 8 is used as a dynamic threshold, as shown in fig. 2, a blade end timing signal 6 is triggered, and the blade arrival time is judged.
In summary, the invention discloses a double-optical-fiber-beam leaf end timing measurement method based on a dynamic threshold, and designs a double-optical-fiber-beam leaf end timing sensor structure, wherein spatial phase shift between optical fiber beams is fixed, each optical fiber beam can independently sense a light intensity signal, and the intersection point of the light intensity signals of the two optical fiber beams is used as the dynamic threshold to trigger a leaf end timing signal and judge the arrival time of a leaf. Compared with the traditional method of triggering the leaf end timing signal by a fixed threshold, the dynamic threshold dual-optical-fiber-beam leaf end timing measurement method can theoretically eliminate the influence of the leaf end gap change on the leaf end timing signal, inhibit the timing uncertainty caused by environmental noise and the like, and improve the leaf end timing precision. The invention has the advantages of high precision, strong reliability and the like.
Claims (5)
1. A double-optical-fiber-beam leaf-end timing measurement method based on dynamic threshold is characterized by comprising the following steps:
1) processing two holes with parallel axes by a cylindrical metal block, wherein the hole center distance is proper, and the hole diameter is based on the optical fiber bundle;
2) respectively placing two same optical fiber bundles A, B into the two holes in the step 1), fixing and finely adjusting the positions by using high-temperature-resistant glue, and finishing the manufacture of a double-optical-fiber-bundle leaf-end timing sensor measuring head, wherein the optical fiber bundles comprise an emitting optical fiber and a receiving optical fiber;
3) fixing the measuring head obtained in the step 2) at a certain position away from the blade, wherein light emitted by the emitting optical fiber in the optical fiber bundle A, B in the measuring head is incident on the blade, is reflected by the blade and then returns to the optical fiber bundle A, B to receive the optical fiber, and after photoelectric detection and circuit conditioning, two paths of voltage analog signals corresponding to the light intensity signals are obtained;
4) and triggering a blade end timing signal by taking the intersection point of the two paths of voltage analog signals as a dynamic threshold value, and judging the arrival time of the blade so as to eliminate the influence of the blade end clearance change on the blade end timing signal.
2. A dynamic threshold-based dual-optical-fiber-beam leaf-end timing measurement method according to claim 1, wherein the metal block in step 1) is made of a common high-temperature-resistant material and has an oval cross section.
3. A method for measuring the timing of the end of a dual optical fiber beam blade based on dynamic threshold as claimed in claim 1, wherein the distance between the centers of the holes in step 1) is 100 μm to 500 μm, and the distance between the measuring head and the blade in step 3) is 1mm to 2 mm.
4. A dual optical fiber beam leaf end timing measurement method based on dynamic threshold value as claimed in claim 1, wherein the measuring head of the leaf end timing sensor in step 2) is in dual optical fiber beam structure, wherein the optical fiber beam is in "1 + 6" structure, the middle 1 optical fiber is the transmitting optical fiber, and the surrounding 6 optical fibers are the receiving optical fibers.
5. A method for dual optical fiber bundle leaf-end timing measurement based on dynamic threshold value according to claim 1, wherein the dynamic threshold value is selected in step 4) as the intersection point of two varying voltage analog signals.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201811244318.9A CN109269625B (en) | 2018-10-24 | 2018-10-24 | Double-optical-fiber-beam leaf-end timing measurement method based on dynamic threshold |
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| CN113358205A (en) * | 2021-04-26 | 2021-09-07 | 西安交通大学 | Measuring device and measuring method for synchronously detecting blade vibration and blade tip clearance |
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| JPH02185602A (en) * | 1989-01-11 | 1990-07-20 | Mitsubishi Heavy Ind Ltd | Device of measuring rotor blade-to-casing gap |
| CN103364069B (en) * | 2012-04-05 | 2016-12-07 | 中国航空工业集团公司沈阳发动机设计研究所 | Non-contact type rotating blade vibration testing method based on non-rotating speed positioning |
| CN104501728A (en) * | 2014-12-12 | 2015-04-08 | 天津大学 | Tip clearance measurement method based on all-fiber tip timing |
| CN104515474A (en) * | 2014-12-12 | 2015-04-15 | 天津大学 | Real-time monitoring blade tip clearance measuring method |
| CN107101600B (en) * | 2017-05-04 | 2019-09-10 | 天津大学 | Movable vane piece tip clearance and vibration parameters based on microwave merge measuring device |
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