A non-contact measurement system and method for the diameter of film holes in turbine blades

Abstract

The present invention relates to the field of blade film hole measurement technology, and in particular to a non-contact measurement system and method for the aperture of a turbine blade film hole. Its technical solution includes a tunable laser, a polarization controller, an optical fiber circulator, a vertically coupled whispering gallery microcavity, a photodetector, a three-dimensional displacement device, a turbine blade, and a dual-axis turntable. The output end of the tunable laser is connected to the input end of the polarization controller. The present invention realizes nanometer-level precision non-contact measurement of the aperture of the turbine blade film hole through the evanescent field sensitivity characteristics of the sub-wavelength-scale whispering gallery microcavity probe, and breaks through the industry measurement difficulties caused by contact damage, optical diffraction limitations and insufficient industrial CT accuracy of large aspect ratio microholes. The detection accuracy is improved to the nanometer level under the premise of zero damage. At the same time, with the miniaturized optical fiber system and the dual-axis dynamic calibration structure, the cost of complex deep hole detection is significantly reduced and efficient measurement in seconds is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of blade film hole measurement, and in particular to a non-contact measurement system and method for the aperture of a turbine blade film hole. Background Art

[0002] Aircraft engines are known as the "crown jewel of industry," and their performance directly determines an aircraft's thrust, fuel economy, and reliability. Turbine blades are among the key components in the hot end of aircraft engines, bearing the harshest loads and operating environments. To operate reliably at ever-increasing turbine inlet temperatures, turbine blades widely employ complex cooling structures. Film cooling technology, among other things, involves machining a large number of tiny film holes on the blade surface, guiding relatively cool air to form a protective film on the blade surface, insulating it from high-temperature combustion gases and effectively reducing the blade surface temperature. The geometric parameters of the film holes, such as their aperture and position, directly affect cooling efficiency. Therefore, accurate and efficient measurement of the film hole diameter is a key step in blade manufacturing and quality control.

[0003] Current technologies for measuring the diameter of film holes on turbine blades can be categorized into two main types: contact and non-contact. Contact measurement techniques primarily rely on direct contact between a probe and the hole to obtain dimensional information. A common method is a coordinate measuring machine (CMM). A precision probe scans the hole's contour to calculate the hole's diameter. Its advantages are high measurement accuracy and good repeatability; however, its disadvantage is that contact with the measured surface can damage the hole. Non-contact measurement techniques avoid direct contact with the hole, reducing the potential for damage and improving measurement efficiency. Common methods include optical microscopes and industrial CT. Optical microscopes offer the advantages of ease of operation and low cost, but their accuracy is limited by optical diffraction, making it difficult to measure the diameter of tiny, deep holes. Industrial CT can perform non-destructive testing of film holes inside blades, obtaining three-dimensional topographic information. However, the equipment is expensive and the measurement resolution is relatively low, typically above 10μm. Therefore, faced with increasingly demanding film hole diameter measurement requirements, there is an urgent need for a non-contact measurement technology that can accommodate micro-holes with large aspect ratios. This application proposes a system and method for non-contact measurement of the diameter of film holes on turbine blades. Summary of the Invention

[0004] The purpose of the present invention is to address the problem in the background technology that there is no non-contact measurement method that can adapt to the non-contact measurement of micro-holes with a large aspect ratio, and to propose a non-contact measurement system and method for the aperture of turbine blade film holes.

[0005] In a first aspect, the present application provides a non-contact measurement system for the aperture of a film hole in a turbine blade, comprising a tunable laser, a three-dimensional displacement device, and a dual-axis turntable, wherein the output end of the tunable laser is connected to a polarization controller, and the output end of the polarization controller is connected to a fiber circulator;

[0006] The through output end of the optical fiber circulator is connected to a vertically coupled whispering gallery microcavity, which is fixed on the three-dimensional displacement device, and the reflection output end of the optical fiber circulator is connected to a photodetector;

[0007] A turbine blade is fixed on the dual-axis turntable, and the dual-axis turntable is used to adjust the spatial orientation of the turbine blade so that the axis of the air film hole coincides with the probe axis of the vertically coupled whispering gallery microcavity.

[0008] Optionally, the vertically coupled whispering gallery microcavity is formed by fusing the ends of micro-nano optical fibers to form a microsphere structure, wherein the probe diameter is 0.3-2 μm and the microsphere diameter is 0.01-1 mm.

[0009] Optionally, the vertically coupled whispering gallery microcavity is configured as follows:

[0010] When the probe penetrates deep into the air film hole and the gap between the microsphere and the inner wall of the hole is at the subwavelength scale, its evanescent field is disturbed by the hole wall, causing the characteristic parameters of the reflection spectrum to change.

[0011] Optionally, the characteristic parameter includes at least one of maximum reflectivity and resonant wavelength.

[0012] Optionally, the diameter of the microsphere of the vertically coupled whispering gallery microcavity is 20 μm, and the diameter of the probe is 0.4 μm.

[0013] Optionally, the operating wavelength of the tunable laser is 1530-1536 nm, and the line width is 280-320 kHz.

[0014] Optionally, the photoelectric detector is configured to: monitor the change in characteristic parameters of the reflection spectrum to detect the gap between the microsphere and the inner wall of the air film hole with nanometer precision, and the gap value corresponding to the optimal detection sensitivity range is 0.2 μm.

[0015] In a second aspect, the present application provides a method for non-contact measurement of the aperture of a film hole on a turbine blade, which is applied to the non-contact measurement system for the aperture of a film hole on a turbine blade described in the first aspect, comprising the following steps:

[0016] S1: Adjust the turbine blades using a dual-axis turntable to make the axis of the air film hole coincide with the axis of the probe of the vertically coupled whispering gallery microcavity;

[0017] S2: The tunable laser emits a laser with continuously adjustable wavelength, which is then input into the fiber circulator after the polarization state is adjusted by the polarization controller.

[0018] S3: Laser light is input into a vertically coupled whispering gallery microcavity through a fiber circulator. The light wave that meets the resonance conditions resonates in the microcavity, and the reflected light wave is transmitted to the photodetector through the fiber circulator.

[0019] S4: The photodetector converts the reflected light wave into an electrical signal to obtain a reflection spectrum;

[0020] S5: Under the control of the three-dimensional displacement device, the vertically coupled whispering gallery microcavity is driven to move along the diameter direction of the air film hole to the first measurement position to obtain the first gap between the microsphere and the inner wall of the hole. ;

[0021] S6: Continue to drive the vertically coupled whispering gallery microcavity to move to the second measurement position opposite in the diameter direction to obtain the second gap between the microsphere and the inner wall of the hole ;

[0022] S7: Calculate the air film pore diameter according to the formula : ,in, is the microsphere diameter, The displacement of the probe in the diameter direction recorded by the three-dimensional displacement device.

[0023] Optionally, the first gap and the second gap The acquisition specifically includes:

[0024] The maximum reflectivity change or resonant wavelength drift of the reflection spectrum is converted into a gap value through the mapping relationship between the reflection spectrum characteristic parameters and the preset calibration curve;

[0025] The calibration curve is established by experimentally measuring characteristic parameters of reflection spectra under different known gaps.

[0026] Optionally, the displacement in step S7 Nanometer-level precision measurement is achieved through the built-in grating ruler or laser interferometer of the three-dimensional displacement device.

[0027] Compared with the prior art, this application has at least one of the following beneficial technical effects:

[0028] The turbine blade film hole aperture measurement scheme based on the whispering gallery microcavity adopted in the present invention is a non-contact measurement, which avoids the disadvantage that the contact force caused by contact measurement may damage the surface of the measured object;

[0029] The gap between the whispering gallery microcavity and the inner wall of the air film hole in the present invention is measured by monitoring the characteristic parameters of the reflection spectrum, with an accuracy of nanometers, which greatly improves the measurement accuracy.

[0030] The whispering gallery microcavity in the present invention has a slender probe structure, which is suitable for measuring the aperture of micropores with a large aspect ratio, overcoming the problem that the traditional probe radius is too large to measure micropores.

[0031] The measuring system of the present invention is easy to miniaturize, simple to manufacture and low in cost.

[0032] The present invention leverages the evanescent field sensitivity of a subwavelength-scale whispering gallery microcavity probe to achieve nanometer-level precision non-contact measurement of the aperture of turbine blade air film holes. This breakthrough addresses the industry's measurement challenges of large aspect ratio microholes caused by contact damage, optical diffraction limitations, and insufficient industrial CT accuracy. It improves detection accuracy to the nanometer level with zero damage. At the same time, with its miniaturized fiber optic system and dual-axis dynamic calibration structure, it significantly reduces the cost of complex deep hole detection and achieves efficient measurement in seconds. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A diagram of a non-contact measurement system for the diameter of film holes in turbine blades is given.

[0034] Figure 2 is the field distribution diagram of the vertically coupled whispering gallery microcavity resonance mode;

[0035] Figure 3 is the reflection spectrum of the vertically coupled whispering gallery microcavity;

[0036] Figure 4 This is the resonant mode field distribution diagram when the vertically coupled whispering gallery microcavity is close to the inner wall of the air film hole;

[0037] Figure 5 is the reflection spectrum of the vertically coupled whispering gallery microcavity at different gaps;

[0038] Figure 6 It is the maximum reflectivity variation curve at different gaps;

[0039] Figure 7 This is a curve of the resonant wavelength change at different gaps.

[0040] Figure numerals: 1. tunable laser; 2. polarization controller; 3. fiber circulator; 4. vertically coupled whispering gallery microcavity; 5. photodetector; 6. three-dimensional displacement device; 7. turbine blade; 8. dual-axis turntable. DETAILED DESCRIPTION

[0041] The technical solution of the present invention is further described below with reference to the accompanying drawings and specific embodiments.

[0042] Example

[0043] See also Figure 1 As shown, the present invention proposes a non-contact measurement system for the aperture of a turbine blade air film hole, comprising a tunable laser 1, a polarization controller 2, a fiber circulator 3, a vertically coupled whispering gallery microcavity 4, a photodetector 5, a three-dimensional displacement device 6, a turbine blade 7, and a dual-axis turntable 8.

[0044] Among them, the output end of the tunable laser 1 is connected to the input end of the polarization controller 2, and the tunable laser 1 is used to generate a laser with continuously tunable wavelength and input it into the polarization controller 2; the output end of the polarization controller 2 is connected to the input end of the fiber circulator 3, and the polarization controller 2 is used to adjust the polarization state of the laser light wave and input it into the fiber circulator 3.

[0045] Furthermore, the direct output of the fiber circulator 3 is connected to the input of the vertically coupled whispering gallery microcavity 4, and the reflected output of the fiber circulator 3 is connected to the input of the photodetector 5. The fiber circulator 3 is used to transmit the laser light wave into the vertically coupled whispering gallery microcavity 4 and input the laser light wave reflected from the vertically coupled whispering gallery microcavity 4 into the photodetector 5. The vertically coupled whispering gallery microcavity 4 is used to generate laser resonance and reflect the resonant light wave signal back to the fiber circulator 3. The vertically coupled whispering gallery microcavity 4 is fabricated directly on a micro-nano optical fiber and has a microspherical structure, which facilitates deep detection of the micropore wall.

[0046] In this embodiment, the photodetector 5 is used to convert the reflected laser light into an electrical signal to obtain a reflection spectrum. The three-dimensional displacement device 6 is implemented by a high-precision nano-translation stage to accurately obtain the displacement of the vertically coupled whispering gallery microcavity 4. The vertically coupled whispering gallery microcavity 4 is fixed to the three-dimensional displacement device 6, which can achieve high-precision three-dimensional displacement.

[0047] It is worth noting that the turbine blade 7 is fixed on the dual-axis turntable 8 to ensure that the air film hole on the turbine blade 7 can be adjusted to be coaxial with the vertically coupled whispering gallery microcavity 4;

[0048] In this embodiment, the tunable laser 1 operates at a wavelength of approximately 1533 nm and a linewidth of 300 kHz. The microsphere in the vertically coupled whispering gallery microcavity 4 has a diameter of 20 μm, and the probe has a diameter of 0.4 μm. The microsphere is obtained by arc discharge. Before measurement, the air film hole is adjusted coaxially with the probe in the vertically coupled whispering gallery microcavity 4 using a dual-axis turntable 8.

[0049] Furthermore, the wavelength-continuously changing laser light emitted from the tunable laser 1 is polarized by the polarization controller 2 and then enters the fiber circulator 3, and then enters the vertically coupled whispering gallery microcavity 4. The light wave that meets the resonance condition resonates in the microspherical cavity and is strengthened, such as Figure 2 As shown, part of the light waves are reflected back to the fiber circulator 3, and the light waves that do not meet the resonance conditions will be scattered to the outside and cannot be reflected, which appears as a peak in the reflection spectrum, such as Figure 3As shown, it is a resonant mode. The characteristic parameters of the peak, such as the maximum reflectivity or the resonant wavelength, are affected by the gap between the vertically coupled whispering gallery microcavity 4 and the inner wall of the film hole of the turbine blade 7. Changes in the gap will cause changes in the characteristic parameters of the reflection spectrum. Therefore, by monitoring the characteristic parameters of the reflection spectrum, the gap between the vertically coupled whispering gallery microcavity 4 and the inner wall of the film hole of the turbine blade 7 can be obtained with an accuracy of nanometers. In a non-contact manner, by moving the vertically coupled whispering gallery microcavity 4 along the diameter direction of the film hole, the two gap sizes between the vertically coupled whispering gallery microcavity 4 and the inner wall of the film hole at both ends of the diameter are obtained respectively, and then the microsphere diameter and the displacement are superimposed to obtain the aperture value of the film hole, thereby solving the problem of non-contact high-precision measurement of the aperture of micropores with a large aspect ratio that is difficult to achieve with existing technologies.

[0050] like Figure 4 The figure shows the resonant mode field distribution when the vertically coupled whispering gallery microcavity 4 is close to the inner wall of the air film hole in this embodiment. The gap between the two is denoted as d. It can be seen that the inner wall of the air film hole has a significant impact on the evanescent field.

[0051] like Figure 5 Figure 2 shows the reflection spectra of a vertically coupled whispering gallery microcavity at different gaps. It can be seen that a small change in the gap has a significant impact on the reflection spectrum. As the gap decreases, the maximum reflectivity of the reflection spectrum decreases, and the resonant wavelength also decreases.

[0052] In order to more intuitively see the change of the characteristic parameters of the resonance mode with the gap, such as Figure 6 and Figure 7 As shown in the figure, the curves of the maximum reflectivity and resonant wavelength of the reflection spectrum are respectively given as a function of the gap. It can be seen that both the maximum reflectivity and the resonant wavelength decrease as the gap decreases. The sensitivity of the maximum reflectivity change remains basically unchanged, while the sensitivity of the resonant wavelength change gradually increases.

[0053] In order to maximize the non-contact measurement accuracy of the turbine blade film hole aperture based on the whispering gallery microcavity proposed in the present invention, the detection value of the gap d between the vertically coupled whispering gallery microcavity 4 and the inner wall of the film hole needs to be set in the highest sensitivity area. Figure 7 It is shown in Figure 2 that the sensitivity of the resonant wavelength change increases as the gap decreases, but if the gap is too small, the peak of the reflection spectrum will be broadened and the peak value will be reduced (e.g. Figure 5 ), which results in a decrease in the accuracy of resonant wavelength extraction. Therefore, considering the sensitivity and peak parameter extraction accuracy, the detection value of the gap d is set to 0.2μm, as shown in Figure 6 and Figure 7 The diameter of the probe of the vertically coupled whispering gallery microcavity 4 of the present invention is 0.3-2 μm, and the diameter of the microsphere on the vertically coupled whispering gallery microcavity 4 is 0.01-1 mm;

[0054] The above-mentioned embodiment of the present invention provides a non-contact measurement system for the aperture of the film hole of a turbine blade. The system is based on the principle of interaction between the evanescent field of the whispering gallery microcavity and external matter, and utilizes the characteristic that changes in the gap between the external matter and the whispering gallery microcavity will cause changes in the characteristic parameters of the resonance mode. By monitoring the maximum reflectivity and resonance wavelength of the resonance mode in the reflection spectrum, the gap between the vertically coupled whispering gallery microcavity 4 and the inner wall of the film hole of the turbine blade 7 is monitored; under the control of the three-dimensional displacement device 6, the vertically coupled whispering gallery microcavity 4 is moved along the diameter direction of the film hole, and the gaps between the vertically coupled whispering gallery microcavity 4 and the inner wall of the film hole at both ends of the film hole diameter are measured respectively; the gaps at both ends are superimposed on the microsphere diameter and the displacement to obtain the aperture of the film hole.

[0055] The above is an embodiment of the non-contact measurement system of the turbine blade film hole diameter based on the whispering gallery microcavity of the present invention. The following is an embodiment of the non-contact measurement method of the turbine blade film hole diameter of the present invention.

[0056] An embodiment of the present invention further provides a method for non-contact measurement of the aperture of a film hole in a turbine blade, which is applied to the above-mentioned non-contact measurement system for the aperture of a film hole in a turbine blade, and includes the following steps:

[0057] S1: Adjust the turbine blade 7 by using the dual-axis turntable 8 so that the axis of the air film hole coincides with the axis of the probe of the vertically coupled whispering gallery microcavity 4;

[0058] S2: Tunable laser 1 emits laser light with continuously adjustable wavelength, which is then polarized by polarization controller 2 and input into fiber circulator 3;

[0059] S3: The laser is input into the vertically coupled whispering gallery microcavity 4 through the fiber circulator 3. The light wave that meets the resonance condition resonates in the microcavity, and the reflected light wave is transmitted to the photodetector 5 through the fiber circulator 3.

[0060] S4: The photodetector 5 converts the reflected light wave into an electrical signal to obtain a reflection spectrum;

[0061] S5: Under the control of the three-dimensional displacement device 6, the vertically coupled whispering gallery microcavity 4 is driven to move along the diameter direction of the air film hole to the first measurement position to obtain the first gap between the microsphere and the inner wall of the hole. ;

[0062] S6: Continue to drive the vertically coupled whispering gallery microcavity 4 to move to the second measurement position opposite in the diameter direction to obtain the second gap between the microsphere and the inner wall of the hole ; First gap and the second gap The acquisition specifically includes: converting the maximum reflectivity change or the resonant wavelength drift of the reflection spectrum into a gap value through a mapping relationship between the reflection spectrum characteristic parameters and a preset calibration curve; the calibration curve is established by experimentally measuring the reflection spectrum characteristic parameters under different known gaps;

[0063] S7: Calculate the air film pore diameter according to the formula : ,in, is the microsphere diameter, The displacement ΔL is the displacement of the probe in the diameter direction recorded by the three-dimensional displacement device 6. The displacement ΔL is measured by the built-in grating ruler or laser interferometer of the three-dimensional displacement device 6.

[0064] By leveraging the subwavelength evanescent field sensitivity of a vertically coupled whispering gallery microcavity (probe diameter 0.3-2μm), this method overcomes the size limitations of traditional contact probes (such as CMMs) and the optical diffraction limit (such as microscopes), enabling non-destructive measurement of air film holes with aspect ratios greater than 10:1 and avoiding the risk of contact damage.

[0065] This invention leverages the nanometer-level sensitivity of microcavity reflection spectrum characteristic parameters (maximum reflectivity / resonant wavelength) to gap detection, improving gap detection accuracy to the nanometer scale (optimal range 0.2μm), two orders of magnitude higher than industrial CT (resolution approximately 10μm). By combining microspheres with diameters of 0.01-1mm with an ultrafine probe, it can penetrate deep into the curved channels within turbine blades. A dual-axis turntable dynamically adjusts the blade's position, ensuring precise alignment of the microcavity with the axis of the air film hole, overcoming the inability of traditional equipment to locate deep holes.

[0066] The present invention does not require a complex optical path. All components are connected by optical fiber, which is resistant to environmental interference and easy to package. The calibration-free algorithm directly outputs the aperture by superimposing the displacement ΔL (recorded by the nano-translation stage) and the gap value (formula: ), reducing manual calibration steps. A single measurement requires only two displacement positionings (at both ends of the diameter). Combined with high-sensitivity real-time analysis of the reflection spectrum, the measurement cycle is shortened to seconds, significantly improving efficiency compared to industrial CT (which requires 3D scanning and reconstruction).

[0067] The above specific embodiments are merely several optional embodiments of the present invention. Based on the technical solutions of the present invention and the relevant inspirations of the above embodiments, those skilled in the art may make various alternative improvements and combinations to the above specific embodiments.

Claims

1. A non-contact measurement system for the diameter of film holes of turbine blades, characterized in that: It comprises a tunable laser (1), a three-dimensional displacement device (6) and a dual-axis turntable (8), wherein the output end of the tunable laser (1) is connected to a polarization controller (2), and the output end of the polarization controller (2) is connected to an optical fiber circulator (3); The through output end of the optical fiber circulator (3) is connected to a vertically coupled whispering gallery microcavity (4), the vertically coupled whispering gallery microcavity (4) is fixed on the three-dimensional displacement device (6), and the reflection output end of the optical fiber circulator (3) is connected to a photodetector (5); A turbine blade (7) is fixed on the dual-axis turntable (8), and the dual-axis turntable (8) is used to adjust the spatial orientation of the turbine blade (7) so that the axis of the air film hole coincides with the probe axis of the vertically coupled whispering gallery microcavity (4); The vertically coupled whispering gallery microcavity (4) is formed by melting the end of a micro-nano optical fiber to form a microsphere structure, wherein the probe diameter is 0.3-2 μm and the microsphere diameter is 0.01-1 mm; The vertically coupled whispering gallery microcavity (4) is configured as follows: When the probe penetrates deep into the air film hole and the gap between the microsphere and the inner wall of the hole is at a subwavelength scale, its evanescent field is disturbed by the hole wall, causing the characteristic parameters of the reflection spectrum to change. The microsphere diameter of the vertically coupled whispering gallery microcavity (4) is 20 μm, and the probe diameter is 0.4 μm; The photoelectric detector (5) is configured to detect the gap between the microsphere and the inner wall of the air film hole with nanometer precision by monitoring the change in the characteristic parameters of the reflection spectrum, and the gap value corresponding to the optimal detection sensitivity range is 0.2 μm.

2. The non-contact measurement system for the diameter of film holes of turbine blades according to claim 1, characterized in that: The characteristic parameter includes at least one of a maximum reflectivity and a resonance wavelength.

3. The non-contact measurement system for the diameter of film holes of turbine blades according to claim 1, characterized in that: The tunable laser (1) has an operating wavelength of 1530-1536 nm and a line width of 280-320 kHz.

4. A method for non-contact measurement of the diameter of film holes of turbine blades, applied to a non-contact measurement system for the diameter of film holes of turbine blades according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1: Adjust the turbine blade (7) by means of a dual-axis turntable (8) so that the axis of the air film hole coincides with the axis of the probe of the vertically coupled whispering gallery microcavity (4); S2: The tunable laser (1) emits a laser with a continuously adjustable wavelength, which is then input into the fiber circulator (3) after the polarization state is adjusted by the polarization controller (2); S3: The laser is input into the vertically coupled whispering gallery microcavity (4) through the optical fiber circulator (3). The light wave that meets the resonance condition resonates in the microcavity, and the reflected light wave is transmitted to the photodetector (5) through the optical fiber circulator (3). S4: Photodetector (5) converts the reflected light wave into an electrical signal to obtain a reflection spectrum; S5: Under the control of the three-dimensional displacement device (6), the vertically coupled whispering gallery microcavity (4) is driven to move along the diameter direction of the air film hole to the first measurement position to obtain the first gap between the microsphere and the inner wall of the hole. ; S6: Continue to drive the vertically coupled whispering gallery microcavity (4) to move to the second measurement position opposite in the diameter direction to obtain the second gap between the microsphere and the inner wall of the hole ; S7: Calculate the air film pore diameter according to the formula : ,in, is the microsphere diameter, The displacement of the probe in the diameter direction recorded by the three-dimensional displacement device (6).

5. The non-contact measurement method for the diameter of film holes of turbine blades according to claim 4, characterized in that: The first gap and the second gap The acquisition specifically includes: The maximum reflectivity change or resonant wavelength drift of the reflection spectrum is converted into a gap value through the mapping relationship between the reflection spectrum characteristic parameters and the preset calibration curve; The calibration curve is established by experimentally measuring characteristic parameters of reflection spectra under different known gaps.

6. The non-contact measurement method for the diameter of film holes of turbine blades according to claim 4, characterized in that: The displacement in step S7 The measurement is performed by a grating ruler or laser interferometer built into the three-dimensional displacement device (6).

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