Online detection system for abrasive particles in aircraft engine lubricating oil

Abstract

This invention provides an online detection system for aero-engine lubricating oil abrasive particles, comprising an upper-layer three-dimensional imaging module and a lower-layer trace metal analysis module. The three-dimensional imaging module is used to irradiate the lubricating oil sample in the abrasive particle detection area and perform three-dimensional imaging of the abrasive particles therein. The trace metal analysis module is used to analyze the metal composition of the abrasive particles in the sample cell. The abrasive particle detection area and the sample cell are connected in series. The lubricating oil sample from the aero-engine is pumped into the abrasive particle imaging detection area by a peristaltic pump, and then flows into the sample cell through a connecting pipe. After detection, the lubricating oil sample flows out from the outlet of the sample cell. This invention reduces the instrument size, can simultaneously measure the three-dimensional size of particles and the metal composition, and improves detection sensitivity and equipment stability.

Description

Technical Field

[0001] This invention relates to the field of spectroscopic instrument technology, and in particular to an online detection system for abrasive particles in aero-engine lubricating oil. Background Technology

[0002] Aero engines are critical components of aircraft, with complex internal structures. Under high temperatures and heavy loads, they are prone to component wear, seriously threatening operational safety. Of major aircraft accidents caused by mechanical reasons, approximately 40% are due to engine failure, with wear-related failures accounting for over 80%. Therefore, real-time monitoring of aero engine wear is crucial for accelerating aero engine development, ensuring service safety, and preventing catastrophic accidents. Lubricating oil in aero engines is used to lubricate, cool, and clean bearings, gears, and other moving parts. When engine wear occurs, abrasive particles enter the lubricating oil system. The size, shape, and material composition of these particles are closely related to the location, degree, and manner of wear. Therefore, aero engine lubricating oil testing is an important means of diagnosing and detecting wear faults in aero engines. Researchers worldwide have developed various lubricating oil testing devices based on different principles.

[0003] Currently available oil testing instruments can be categorized into online and offline types based on their testing methods. Online testing instruments primarily detect large particles in lubricating oil, and most can only perform online counting and size detection, unable to obtain three-dimensional morphological information of the particles. Offline testing instruments mainly use atomic emission spectrometry to detect the composition of small abrasive particles in lubricating oil. Sampling and testing can only be performed after the engine is shut down, resulting in a longer sampling and testing time. This allows for the detection of only early potential engine faults, but these instruments are also bulky and difficult to use for online detection, making it hard to detect potential faults in a timely manner. Information acquisition is also untimely. Therefore, existing lubricating oil testing instruments have limited functionality and cannot meet the requirements for real-time online monitoring of multiple parameters related to wear in service aircraft. Summary of the Invention

[0004] In view of the above problems, the purpose of this invention is to propose an online detection system for aero-engine lubricating oil abrasive particles. This system employs a three-dimensional imaging module for lubricating oil abrasive particles, composed of micro-optical elements capable of static phase modulation, and a trace metal analysis module to achieve multi-parameter online detection of aero-engine lubricating oil. The three-dimensional imaging module performs three-dimensional imaging and reconstruction of large-sized particles in the lubricating oil, while the trace metal analysis module analyzes the type and content of small-sized metal abrasive particles. The proposed solution reduces the instrument size, simultaneously measures the three-dimensional size of particles and the metal composition, and improves detection sensitivity and equipment stability.

[0005] To achieve the above objectives, the present invention adopts the following specific technical solution:

[0006] This invention provides an online detection system for aero-engine lubricating oil wear particles, comprising a three-dimensional imaging module in the upper layer and a trace metal analysis module in the lower layer;

[0007] The three-dimensional imaging module is used to irradiate the lubricating oil sample on the oil abrasive detection area and perform three-dimensional imaging of the abrasive particles therein; the trace metal analysis module is used to perform metal composition analysis on the abrasive particles in the sample cell.

[0008] The oil abrasive detection area is connected in series with the sample cell. The lubricating oil sample from the aero-engine is pumped into the abrasive imaging detection area by a peristaltic pump, and then flows into the sample cell through a connecting pipe. After the detection is completed, the lubricating oil sample flows out from the outlet of the sample cell.

[0009] Preferably, the three-dimensional imaging module includes: a light source submodule, a beam splitter, a sampling submodule, a first phase modulation submodule, and a detection submodule;

[0010] The parallel beam emitted by the light source submodule is incident on the beam splitter and split into a first reflected beam and a first transmitted beam; the first reflected beam is incident on the sampling submodule to provide linear illumination to the abrasive particle imaging detection area, and then a sample beam containing abrasive particle information of the lubricating oil sample to be tested is returned to the beam splitter along the original path; the first transmitted beam is incident on the first phase modulation submodule and, after phase modulation, forms a reference beam that returns to the beam splitter along the original path.

[0011] The sample beam and the reference beam interfere at the exit position of the beam splitter to form an interference beam, which is then incident on the detector submodule to obtain interference spectral information.

[0012] Preferably, the trace metal analysis module includes: a graphite disk electrode, a graphite rod electrode, an optical fiber, a second collimating lens, a second phase modulation submodule, and an imaging submodule;

[0013] The graphite disk electrode is placed perpendicular to the sample cell, and the bottom of the graphite disk electrode is in partial contact with the lubricating oil sample in the sample cell.

[0014] A discharge gap is provided between the top of the graphite disk electrode and the graphite rod electrode.

[0015] When the graphite disk electrode rotates, the lubricating oil sample in the sample cell is brought to the discharge gap by the graphite disk electrode. By applying a high voltage alternating current between the two electrodes, the metal abrasive particles in the lubricating oil sample are plasmaized to generate a radiation beam.

[0016] The radiated beam is collected by the optical fiber and transmitted to the second collimating mirror. After being collimated by the second collimating mirror, it becomes a parallel beam and is incident on the second phase modulation submodule.

[0017] The second phase modulation submodule is used to phase modulate the radiation beam to form an interference light field with N×N interference channels;

[0018] After the interference light field is incident on the imaging submodule, an interference image array is obtained. By performing interference data processing such as Fourier transform on the interference image data, the spectral information of the radiation beam can be obtained, thereby realizing the compositional analysis of the oil sample abrasive particles.

[0019] Preferably, the light source submodule includes: a broadband light source and a first collimating lens; the broadband light source is a near-infrared light source, and the broadband low-coherence beam emitted by the broadband light source is collimated into a parallel beam by the first collimating lens.

[0020] Preferably, the sampling submodule includes a scanning mirror and an objective lens; the scanning mirror is used to scan the lubricating oil sample, the scanning mirror is rectangular and rotates around its axis of symmetry, the center of the rectangle coincides with the image-side focal point of the objective lens, and the objective lens adopts an object-side telecentric optical path design;

[0021] After the first reflected beam is reflected by the scanning mirror and converged by the objective lens, it linearly irradiates the lubricating oil sample on the abrasive detection area, generating a scattered echo with abrasive information in the lubricating oil sample to be tested, thus obtaining the sample beam to return to the beam splitter along the original path.

[0022] The oil abrasive detection area is made of a material that is transparent to the imaging wavelength and has a rectangular cross-section.

[0023] Preferably, the first phase modulation submodule includes: a focusing mirror and a phase-shifting micromirror;

[0024] The phase-shifting micromirror is fabricated using the MOEMS process and consists of steps. The surface of each step is coated with a reflective film. Each step corresponds to a phase modulation channel, and the beam in each phase modulation channel travels through different optical paths under the modulation effect of the phase-shifting micromirror.

[0025] The focusing lens is designed with an image-side telecentric optical path.

[0026] The first transmitted beam is refracted by the focusing lens and converged to the phase-shifting micromirror. After being reflected by the stepped surfaces at different spatial positions, it returns to the beam splitter as a reference beam.

[0027] Preferably, the detection submodule comprises a dispersive grating, an imaging mirror, and a first array detector;

[0028] The interference beam is incident on the dispersion grating and dispersed, and then refracted by the imaging mirror and converged to the first array detector to obtain interference spectral information of different channels and different spectral bands.

[0029] When the number of steps in the phase-shifting micromirror is n: the spatial arrangement of the steps causes each phase modulation channel to generate a phase shift of π / 2. Interference spectral signals from n channels at the test point are obtained through a single imaging operation. The amplitude A and phase of the interference signals are then calculated. Construct the complex function of the interference signal:

[0030]

[0031] By performing a Fourier transform on the complex function I of the interference signal, the depth information of the lubricating oil abrasive particles is obtained after eliminating the interference of mirror images and parasitic images.

[0032] Preferably, the second phase modulation submodule includes: a beam splitter, a high-order echelle micromirror, and a low-order echelle micromirror;

[0033] The parallel beam is split into a second transmitted beam and a second reflected beam by the beam splitter. The second transmitted beam is incident on the higher-order echelle micromirror and returns to the beam splitter after being reflected by the higher-order echelle micromirror. The second reflected beam is incident on the lower-order echelle micromirror and returns to the beam splitter after being reflected by the lower-order echelle micromirror.

[0034] Preferably, the high-step multi-stage micromirrors and the low-step multi-stage micromirrors have the same number of steps N and the same step width.

[0035] Let the sub-step height of the low-step multi-stage micromirror be d:

[0036] The optical path difference sampling interval is then Δ = 2d;

[0037] The sub-step height of the high-step multi-stage micromirror is N×d;

[0038] The high-order multi-level micromirrors and low-order multi-level micromirrors orthogonally form N×N optical path difference sampling units, which are used to modulate the optical field into an interference optical field with N×N interference channels.

[0039] The optical path difference of the interference channel formed by the orthogonal high-order multi-stage micromirror x-th order and the low-order multi-stage micromirror y-th order is:

[0040] δ(x,y)=2(Nx-y)d.

[0041] Preferably, the second reflected beam and the second transmitted beam interfere at the exit position of the beam splitter to form an interference light field with N×N interference channels that is incident on the imaging submodule.

[0042] Preferably, the imaging submodule includes: a beam-shrinking system and a second array detector;

[0043] The interfering light field is converged onto the second array detector after being compressed by the beam-shrinking system to obtain an interferometric image array.

[0044] Let the radiated beam be I, then the interference light field distribution after interference modulation by the phase modulation submodule is as follows:

[0045]

[0046] in,

[0047] ν = 1 / λ is the spatial frequency of the radiated beam;

[0048] B(ν) is the power spectral density distribution function of the radiated beam.

[0049] Preferably, the interference light field I(n) is subjected to a discrete Fourier transform to obtain:

[0050]

[0051] The spectral information of the radiation beam signal is reconstructed based on the power spectral density distribution function B(ν) of the radiation beam, and then fitted with a standard database to achieve the analysis of the metal element composition of the oil sample abrasive particles.

[0052] Compared with existing technologies, this invention achieves multi-parameter online detection of aviation lubricating oil through a three-dimensional imaging module for lubricating oil abrasive particles composed of micro-optical elements capable of static phase modulation and a trace metal analysis module. The three-dimensional imaging module performs three-dimensional imaging and reconstruction of large-sized particles in the lubricating oil, while the trace metal analysis module analyzes the type and content of small-sized metal abrasive particles. The proposed solution reduces the instrument size, simultaneously measures particle three-dimensional size and metal composition, and improves detection sensitivity and equipment stability. Attached Figure Description

[0053] Figure 1 This is a schematic diagram of the structure of an online detection system for abrasive particles in aero-engine lubricating oil provided according to an embodiment of the present invention.

[0054] Figure 2 This is a block diagram illustrating the working principle of an online detection system for abrasive particles in aero-engine lubricating oil provided according to an embodiment of the present invention.

[0055] Figure 3 This is a schematic diagram of the structure of a three-dimensional imaging module provided according to an embodiment of the present invention.

[0056] Figure 4This is a schematic diagram of the oscillation of the scanning mirror in the three-dimensional imaging module provided by an embodiment of the present invention.

[0057] Figure 5 This is a schematic diagram of the spectral distribution of the interferogram of the area array detector in the three-dimensional imaging module provided by the present invention.

[0058] Figure 6 This is a schematic diagram of the structure of a trace metal analysis module provided according to an embodiment of the present invention.

[0059] Figure 7 This is a schematic diagram of the interferogram distribution of the area array detector in the trace metal analysis module provided according to an embodiment of the present invention.

[0060] The reference numerals in the figures include: broadband light source 1, first collimating lens 2, beam splitter 3, oscillating scanning imaging lens group 4, scanning mirror 5, objective lens 6, oil abrasive detection area 7, focusing lens 8, phase shifting micromirror 9, dispersive grating 10, imaging mirror 11, first array detector 12.

[0061] Sample cell 13, graphite disk electrode 14, graphite rod electrode 15, optical fiber 16, second collimating mirror 17, beam splitter 18, high-step multi-stage micromirror 19, low-step multi-stage micromirror 20, beam shrinking system 21, and second array detector 22. Detailed Implementation

[0062] In the following description, embodiments of the invention will be described with reference to the accompanying drawings. In the description below, the same modules are denoted by the same reference numerals. Where the same reference numerals are used, their names and functions are also the same. Therefore, their detailed description will not be repeated.

[0063] To make the objectives, technical solutions, and advantages of this invention clearer, the 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 merely illustrative of the invention and do not constitute a limitation thereof.

[0064] Figure 1 The structure of an online detection system for abrasive particles in aero-engine lubricating oil provided according to an embodiment of the present invention is shown.

[0065] Figure 2 The working principle of the online detection system for abrasive particles in aero-engine lubricating oil provided according to an embodiment of the present invention is illustrated.

[0066] like Figure 1-2 As shown, the online detection system for aero-engine lubricating oil wear particles provided in this embodiment of the invention has a two-layer structure, including: a three-dimensional imaging module and a trace metal analysis module;

[0067] The 3D imaging module is located on the upper layer, and the trace metal analysis module is located on the lower layer.

[0068] The three-dimensional imaging module is used to irradiate the lubricating oil sample in the oil abrasive detection area and perform three-dimensional imaging of the abrasive particles therein, while the trace metal analysis module is used to perform metal composition analysis on the abrasive particles in the sample cell.

[0069] The aforementioned oil abrasive detection area and sample cell are connected in series. The lubricating oil sample from the aero-engine is first pumped into the abrasive imaging detection area by a peristaltic pump, and then flows into the sample cell through the connecting pipe between the oil abrasive detection area and the sample cell. The three-dimensional imaging module and the trace metal analysis module analyze the abrasive particles and metal components of the lubricating oil, respectively. After the detection is completed, the lubricating oil sample flows out from the outlet of the sample cell.

[0070] Figure 3 The structure of a three-dimensional imaging module provided according to an embodiment of the present invention is shown.

[0071] like Figure 3 As shown, the three-dimensional imaging module adopts a Michelson interferometer structure, including: a light source submodule, a beam splitter 3, a sampling submodule 4, a first phase modulation submodule, and a detector submodule.

[0072] The light source submodule includes: a broadband light source 1 and a first collimating lens 2; the broadband light source 1 can be a near-infrared light source with strong penetration capability for lubricating oil, and the broadband low-coherence beam emitted by the broadband light source 1 becomes a parallel beam after being collimated by the first collimating lens 2.

[0073] The parallel beam emitted by the light source submodule is incident on beam splitter 3 and split into a reflected beam and a transmitted beam. The beam splitter is placed at 45° to the optical axis, with a splitting ratio of 1:1.

[0074] The first reflected beam is incident on the sampling submodule 4; the first transmitted beam is incident on the first phase modulation submodule.

[0075] The sampling submodule 4 includes a scanning mirror 5 and an objective lens 6.

[0076] After being reflected by the scanning mirror 5 and converged by the objective lens 6, the first reflected beam illuminates the lubricating oil sample on the abrasive detection area 7. The first reflected beam produces linear illumination of the abrasive particles in the abrasive detection area 7, generating a scattered echo carrying the abrasive particle information in the lubricating oil sample to be tested, thus obtaining the sample beam returning to the beam splitter 3 along the original path.

[0077] The oil abrasive detection area 7 is made of a material that is transparent to the imaging wavelength and has a rectangular cross-section.

[0078] The first phase modulation submodule includes a focusing mirror 8 and a phase-shifting micromirror 9. The phase-shifting micromirror 9 is fabricated using MOEMS technology and consists of multiple steps. Each step surface is coated with a reflective film, and each step corresponds to a phase modulation channel. The beam in each phase modulation channel travels through different optical paths under the modulation effect of the phase-shifting micromirror. The phase-shifting micromirror 9 used in this invention achieves multi-channel static modulation of the beam phase through the spatial arrangement of different positions on each step, without adding any additional movable structures, thus ensuring the stability of the system. Furthermore, this invention can achieve phase modulation of multiple channels at the same measurement point simultaneously, significantly improving the imaging efficiency of the system.

[0079] To ensure that the light rays reflected by the phase-shifting micromirror 9 can return along the incident path, the focusing mirror 8 adopts an image-side telecentric optical path design.

[0080] The first transmitted beam, after being refracted by the focusing mirror 8, converges to the phase-shifting micromirror 9. After being reflected by the stepped surfaces at different spatial positions, it returns to the beam splitter 3 as a reference beam.

[0081] The reference beam and the sample beam interfere at the exit position of beam splitter 3, resulting in an interference beam that is incident on the detector submodule.

[0082] The detector submodule includes a dispersive grating 10, an imaging mirror 11, and a first array detector 12.

[0083] The interference beam is incident on the dispersion grating 10 and produces dispersion. After being refracted by the imaging mirror 11, it converges to the first array detector 12 to obtain interference spectral information of different channels and different spectral bands.

[0084] Figure 4 The scanning process of the scanning mirror in the three-dimensional imaging module provided according to an embodiment of the present invention is illustrated.

[0085] The aforementioned three-dimensional imaging module can achieve parallel imaging of the line field of view. It uses a scanning mirror 5 to scan the object surface (i.e., the abrasive particles in the lubricating oil sample) to acquire three-dimensional information of all abrasive particles flowing through the oil abrasive particle detection area 7. The scanning mirror 5 is set as a rectangle and rotates around its axis of symmetry. The center of the rectangle coincides with the image-side focal point of the objective lens 6. The objective lens 6 adopts an object-side telecentric optical path design.

[0086] Figure 5 The spectral distribution of the interferogram of the area array detector in the three-dimensional imaging module provided according to an embodiment of the present invention is shown.

[0087] When the number of steps in the phase-shifting micromirror 9 is n: the spatial arrangement of the steps can generate a phase shift of π / 2 in each phase modulation channel. Interference spectral signals of n channels at the test point are obtained through a single imaging operation. The amplitude A and phase of the interference signal are then calculated. A complex function of the interference signal is constructed, and a Fourier transform is performed on the complex function of the interference signal to obtain the depth information of the lubricating oil abrasive particles.

[0088] When the number of steps in the phase-shifting micromirror 9 is 5: Let the spectra of the five channels obtained on the first array detector 12 be:

[0089]

[0090] Then we have:

[0091]

[0092]

[0093] The complex function of the interference signal can then be constructed:

[0094]

[0095] By performing a Fourier transform on the complex function of the interference signal, the depth information of the lubricating oil abrasive particles can be obtained, eliminating the interference from mirror images and parasitic images.

[0096] Figure 6 The structure of a trace metal analysis module provided according to an embodiment of the present invention is shown.

[0097] like Figure 6 As shown, the trace metal analysis module includes: a graphite disk electrode 14, a graphite rod electrode 15, an optical fiber 16, a second collimating lens 17, a second phase modulation submodule, and an imaging submodule.

[0098] The graphite disk electrode 14 is placed perpendicular to the sample cell 13, and the bottom of the graphite disk electrode 14 is in partial contact with the lubricating oil sample in the sample cell 13. A discharge gap is provided between the top of the graphite disk electrode 14 and the graphite rod electrode 15.

[0099] When the graphite disk electrode 14 rotates, the lubricating oil sample in the sample cell 13 is brought by the graphite disk electrode 14 to the discharge gap between the graphite rod electrode 15. By applying a high voltage AC current of 10k-25kV between the two electrodes, the metal abrasive particles in the lubricating oil sample to be tested are plasmaized to generate a radiation beam.

[0100] After being collected by the optical fiber 16, the radiated beam is transmitted to the position of the second collimating mirror 17. After being collimated by the second collimating mirror 17, the radiated beam becomes a parallel beam and is incident on the second phase modulation submodule.

[0101] The second phase modulation submodule includes: a beam splitter 18, a high-step multi-stage micromirror 19, and a low-step multi-stage micromirror 20; the beam splitter is placed at 45° to the optical axis and has a beam splitting ratio of 1:1.

[0102] The high-echelon multi-stage micromirror 19 and the low-echelon multi-stage micromirror 20 have the same number of steps N and the same step width. The sub-step height follows the Nyquist sampling theorem, that is, the sampling interval must be less than or equal to half of the minimum wavelength. The sub-step height of the low-echelon multi-stage micromirror 20 is d, so the optical path difference sampling interval is Δ = 2d. In order to ensure the continuity of optical path difference (OPD) sampling, that is, to satisfy the optical path difference complementarity principle, the sub-step height of the high-echelon multi-stage micromirror 19 is N×d. The two multi-stage micromirrors orthogonally form N×N optical path difference sampling units, which are used to modulate the optical field into an interference optical field with N×N interference channels.

[0103] The trace metal analysis module employs orthogonal multi-stage micromirrors that achieve static interference modulation of the excitation light through a sub-step spatial arrangement. The height of the sub-step determines the sampling interval of the online detection system. According to the Nyquist sampling theorem, the sampling interval must be less than or equal to half of the system's minimum wavelength, i.e., the sub-step height d of the low-step multi-stage micromirror 20 ≤ λ. min / 4, which in turn determines the spectral detection band range of the system; the total height of the steps determines the maximum optical path difference of the system sampling, and the spectral resolution of the interferometric spectrometer is the reciprocal of the maximum optical path difference, i.e., Δν=1 / OPDmax, which in turn determines the spectral detection accuracy of the system.

[0104] In one embodiment of the trace metal analysis module: the sub-step height of the low-step multi-level micromirror 20 is designed to be 0.05 μm, and the number of sub-steps N is designed to be 700. Similarly, the sub-step height of the high-step multi-level micromirror 19 is designed to be 35 μm, and the number of sub-steps N is also 700. This parameter design enables spectral analysis with a spectral resolution <0.013 nm in the spectral range of 300 nm to 800 nm.

[0105] The parallel beam is split into a second transmitted beam and a second reflected beam by the beam splitter 18. The second transmitted beam is incident on the high-order multi-stage micromirror 19 and returns to the beam splitter 18 after being reflected by the high-order multi-stage micromirror 19. The second reflected beam is incident on the low-order multi-stage micromirror 20 and returns to the beam splitter 18 after being reflected by the low-order multi-stage micromirror 20.

[0106] The optical path difference of the interference channel formed orthogonally by the x-th order of the high-order multi-stage micromirror 19 and the y-th order of the low-order multi-stage micromirror 20 is:

[0107] δ(x,y)=2(Nx-y)d

[0108] The second reflected beam and the second transmitted beam interfere at the exit position of the beam splitter 18, forming an interference light field with multiple interference channels that is incident on the imaging submodule.

[0109] The imaging submodule includes: a beam-shrinking system 21 and a second array detector 22.

[0110] After the interference light field is focused by the beam-shrinking system 21, it converges onto the second array detector 22 to obtain an interference image array.

[0111] Let the radiation beam emitted by the lubricating oil sample be I. Then the interference light field distribution after interference modulation by the phase modulation submodule can be expressed as:

[0112]

[0113] in,

[0114] ν = 1 / λ is the spatial frequency of the radiated beam;

[0115] B(ν) is the power spectral density distribution function (spectrum) of the radiation beam.

[0116] Figure 7 The diagram shows the interferogram distribution of the area array detector in the trace metal analysis module provided according to an embodiment of the present invention.

[0117] Interferometric image arrays and their path difference distributions are as follows Figure 7 As shown. The discrete Fourier transform of the interference light field I(n) yields:

[0118]

[0119] The spectral information of the radiation beam signal can be reconstructed from the power spectral density distribution function B(ν), and then fitted with a standard database to achieve the analysis of the metal element composition of the oil sample abrasive particles.

[0120] By integrating the three-dimensional morphological features of lubricating oil particles and the metal element composition information of oil samples extracted by the integrated online detection system, fault information such as wear location, wear degree and wear type of aero-engines can be analyzed more accurately, effectively improving the accuracy of engine wear fault diagnosis.

[0121] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

[0122] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. An online detection system for abrasive particles in aero-engine lubricating oil, characterized in that, It includes a three-dimensional imaging module located on the upper layer and a trace metal analysis module located on the lower layer; The three-dimensional imaging module is used to irradiate the lubricating oil sample on the oil abrasive detection area and perform three-dimensional imaging of the abrasive particles therein; the trace metal analysis module is used to perform metal composition analysis on the abrasive particles in the sample cell. The oil abrasive detection area and the sample cell are connected in series. The lubricating oil sample from the aero-engine is pumped into the abrasive imaging detection area by a peristaltic pump, and then flows into the sample cell through a connecting pipe. After the detection is completed, the lubricating oil sample flows out from the outlet of the sample cell. The three-dimensional imaging module includes: a light source submodule, a beam splitter, a sampling submodule, a first phase modulation submodule, and a detection submodule; The parallel beam emitted by the light source submodule is incident on the beam splitter and split into a first reflected beam and a first transmitted beam; the first reflected beam is incident on the sampling submodule to provide linear illumination to the abrasive particle imaging detection area, and the resulting sample beam containing abrasive particle information in the lubricating oil sample returns to the beam splitter along the original path; the first transmitted beam is incident on the first phase modulation submodule and, after phase modulation, forms a reference beam that returns to the beam splitter along the original path. The sample beam and the reference beam interfere at the exit position of the beam splitter to form an interference beam, which is then incident on the detector submodule to obtain interference spectral information. The sampling submodule includes a scanning mirror and an objective lens; the scanning mirror is used to scan the lubricating oil sample. The scanning mirror is rectangular and rotates around its axis of symmetry. The center of the rectangle coincides with the image-side focal point of the objective lens. The objective lens adopts an object-side telecentric optical path design. After the first reflected beam is reflected by the scanning mirror and converged by the objective lens, it linearly irradiates the lubricating oil sample on the abrasive detection area, generating a scattered echo with abrasive information in the lubricating oil sample to be tested, thus obtaining the sample beam to return to the beam splitter along the original path. The oil abrasive detection area is made of a material that is transparent to the imaging wavelength and has a rectangular cross-section. The first phase modulation submodule includes: a focusing mirror and a phase-shifting micromirror; The phase-shifting micromirror is fabricated using the MOEMS process and consists of steps. The surface of each step is coated with a reflective film. Each step corresponds to a phase modulation channel, and the beam in each phase modulation channel travels through different optical paths under the modulation effect of the phase-shifting micromirror. The focusing lens is designed with an image-side telecentric optical path. The first transmitted beam is refracted by the focusing lens and converged to the phase-shifting micromirror. After being reflected by the stepped surfaces at different spatial positions, it returns to the beam splitter as a reference beam.

2. The online detection system for abrasive particles in aero-engine lubricating oil according to claim 1, characterized in that, The trace metal analysis module includes: a graphite disk electrode, a graphite rod electrode, an optical fiber, a second collimating lens, a second phase modulation submodule, and an imaging submodule. The graphite disk electrode is placed perpendicular to the sample cell, and the bottom of the graphite disk electrode is in partial contact with the lubricating oil sample in the sample cell. A discharge gap is provided between the top of the graphite disk electrode and the graphite rod electrode. When the graphite disk electrode rotates, the lubricating oil sample in the sample cell is brought to the discharge gap by the graphite disk electrode. By applying a high voltage alternating current between the two electrodes, the metal abrasive particles in the lubricating oil sample are plasmaized to generate a radiation beam. The radiated beam is collected by the optical fiber and transmitted to the second collimating mirror. After being collimated by the second collimating mirror, it becomes a parallel beam and is incident on the second phase modulation submodule. The second phase modulation submodule is used to phase modulate the radiation beam to form an interference light field with N×N interference channels; After the interference light field is incident on the imaging submodule, an interference image array is obtained. By performing Fourier transform interference data processing on the interference image data, the spectral information of the radiation beam can be obtained, thereby realizing the compositional analysis of the oil sample abrasive particles.

3. The online detection system for abrasive particles in aero-engine lubricating oil according to claim 1, characterized in that, The light source submodule includes: a broadband light source and a first collimating lens; the broadband light source is a near-infrared light source, and the broadband low-coherence beam emitted by the broadband light source is collimated into a parallel beam by the first collimating lens.

4. The online detection system for abrasive particles in aero-engine lubricating oil according to claim 1, characterized in that, The detection submodule consists of a dispersive grating, an imaging mirror, and a first array detector; The interference beam is incident on the dispersion grating and dispersed, and then refracted by the imaging mirror and converged to the first array detector to obtain interference spectral information of different channels and different spectral bands. When the number of steps in the phase-shifting micromirror is n: the spatial arrangement of the steps causes each phase modulation channel to generate The phase shift is obtained by acquiring the interference spectrum signals of n channels at the test point through a single imaging process, and the amplitude of the interference signal is then calculated. and phase Construct the complex function of the interference signal: By performing a Fourier transform on the complex function I of the interference signal, the depth information of the lubricating oil abrasive particles is obtained after eliminating the interference of mirror images and parasitic images.

5. The online detection system for abrasive particles in aero-engine lubricating oil according to claim 2, characterized in that, The second phase modulation submodule includes: a beam splitter, a high-order echelle micromirror, and a low-order echelle micromirror; The parallel beam is split into a second transmitted beam and a second reflected beam by the beam splitter. The second transmitted beam is incident on the higher-order echelle micromirror and returns to the beam splitter after being reflected by the higher-order echelle micromirror. The second reflected beam is incident on the lower-order echelle micromirror and returns to the beam splitter after being reflected by the lower-order echelle micromirror.

6. The online detection system for aero-engine lubricating oil wear particles according to claim 5, characterized in that, The high-step multi-stage micromirrors and the low-step multi-stage micromirrors have the same number of steps N and the same step width. Let the sub-step height of the low-step multi-stage micromirror be d: The optical path difference sampling interval is =2d; The sub-step height of the high-step multi-stage micromirror is N×d; The high-order multi-level micromirrors and low-order multi-level micromirrors orthogonally form N×N optical path difference sampling units, which are used to modulate the optical field into an interference optical field with N×N interference channels. The optical path difference of the interference channel formed by the orthogonal high-order multi-stage micromirror x-th order and the low-order multi-stage micromirror y-th order is: 。 7. The online detection system for aero-engine lubricating oil wear particles according to claim 6, characterized in that, The second reflected beam and the second transmitted beam interfere at the exit position of the beam splitter, forming an interference light field with N×N interference channels that is incident on the imaging submodule.

8. The online detection system for abrasive particles in aero-engine lubricating oil according to claim 7, characterized in that, The imaging submodule includes: a beam-shrinking system and a second array detector; The interfering light field is converged onto the second array detector after being compressed by the beam-shrinking system to obtain an interferometric image array. Let the radiated beam be I, then the interference light field distribution after interference modulation by the phase modulation submodule is as follows: in, ν=1 / λ is the spatial frequency of the radiated beam; B(ν) is the power spectral density distribution function of the radiated beam.

9. The online detection system for abrasive particles in aero-engine lubricating oil according to claim 8, characterized in that, The discrete Fourier transform of the interference light field I(n) yields: The spectral information of the radiation beam signal is reconstructed based on the power spectral density distribution function B(ν) of the radiation beam, and then fitted with a standard database to achieve the analysis of the metal element composition of the oil sample abrasive particles.

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