Laser diffraction and scattering based lubricating oil liquid particle measurement method and system

Abstract

This invention discloses a method and system for measuring abrasive particles in lubricating oil based on laser diffraction and scattering, belonging to the field of oil abrasive particle analysis technology. It includes: emitting laser light from a laser source; filtering the laser light in a specific direction using a laser beam control unit to form a diverging beam and control the amount of light entering the system; the laser light passing through a visualized oil path, causing diffraction and scattering on the abrasive particles within the oil path; acquiring the light intensity signal using a photoelectric detection device and converting it into an electrical signal; amplifying the electrical signal and converting it into a digital signal using an A / D converter; transmitting the digitized signal to a digital signal processor for preprocessing; using a multilayer medium optical correction algorithm to eliminate interference caused by the light passing through glass twice; and then transmitting the preprocessed digital signal to a calculator where a specialized algorithm analyzes the particle size distribution and concentration of the abrasive particles. This invention provides a novel technical infrastructure for online analysis of abrasive particle information in lubricating oil in mechanical engineering.

Description

Technical Field

[0001] This invention relates to the field of oil abrasive analysis technology, and in particular to a method and system for measuring abrasive particles in lubricating oil based on laser diffraction and scattering. Background Technology

[0002] The lubrication system is an indispensable "circulatory system" for modern machinery, and its reliability directly affects the overall safe operation of the machine. Studies show that over 80% of equipment failures originate from abnormal wear caused by lubrication malfunctions. The accumulation of wear particles can lead to component failure, hindering the long-term stable operation of machinery. Traditional lubricating oil monitoring mainly relies on offline detection methods, such as periodic sampling followed by laboratory spectral analysis and ferrography to assess oil physicochemical properties (e.g., viscosity, moisture content) and abrasive characteristics. While offline detection offers advantages such as comprehensive parameters and high accuracy, it suffers from long analysis cycles, poor timeliness, and an inability to capture real-time dynamic changes in equipment lubrication status. Furthermore, the sampling process is susceptible to human error, leading to delayed fault warnings. With the increasing demands for condition-based maintenance and intelligent operation and maintenance, offline detection can no longer meet the requirements for long-term continuous monitoring of steam turbines. In recent years, online oil monitoring technology has gradually developed, using sensors to collect abrasive information in the oil in real time, overcoming the latency problem of offline analysis. However, these technologies still have limitations. Therefore, those skilled in the art urgently need a system capable of online monitoring of various types of lubricating oil abrasive particles to achieve comprehensive analysis of the abrasive particles, thereby improving fault diagnosis of mechanical equipment in engineering. Summary of the Invention

[0003] The purpose of this invention is to provide a method and system for measuring abrasive particles in lubricating oil based on laser diffraction and scattering, so as to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following solution: On one hand, it provides a method for measuring abrasive particles in lubricating oil based on laser diffraction and scattering, the specific steps of which include the following:

[0005] After being filtered, the laser beam forms a diverging beam, passes through the visualized oil path, and undergoes diffraction and scattering on the abrasive particles in the oil path to obtain the light intensity signal;

[0006] The light intensity signal is first converted into an electrical signal, and then the electrical signal is amplified and converted into a digital signal.

[0007] The digital signal is preprocessed to obtain a preprocessed digital signal;

[0008] For the preprocessed digital signal, a multilayer dielectric optical correction algorithm is used to eliminate the interference caused by the beam passing through the visualized oil path. Then, the particle size distribution and concentration of the abrasive particles are obtained by analysis through inversion algorithm and extinction method.

[0009] Preferably, converting the light intensity signal into a light intensity signal in an electrical signal includes the following:

[0010] The light intensity signal generated by the Mie scattering of a laser beam on abrasive grains :

[0011] ;

[0012] in, , Let be a function of the intensity of the scattered light. , Let be the amplitude function of the scattered light, and r be the radius of the abrasive grain. The scattering angle is the angle between the direction of the incident light and the direction of the scattered light. The azimuth angle describes the orientation of the scattered light in the plane perpendicular to the incident light. The wavelength of the incident light;

[0013] The intensity signal generated when a laser beam irradiates abrasive grains and undergoes diffraction is calculated using Fraunhofer diffraction theory. :

[0014] ;

[0015] in, Where is the incident light intensity, and F is the focal length of the lens. The diffraction angle, Where is the particle radius, For wave number, The intensity of the diffracted light at the transmission center of the photodetector. For dimensionless particle size parameters, It is a first-order Bessel function of the first kind;

[0016] When a laser penetrates the abrasive particle system under test, the incident light intensity Attenuation will occur, as shown in the formula:

[0017] ;

[0018] in, Turbidity of particulate matter. The thickness of the particulate medium.

[0019] Preferably, the preprocessing operations include filtering, noise reduction, and signal averaging.

[0020] Preferably, the use of a multi-layer medium optical correction algorithm to eliminate interference caused by the light beam passing through the visualized oil path specifically includes: using Snell's law to eliminate the light path offset caused by the laser passing through the glass of the visualized oil path; and using Lambert-Beer's law to attenuate the light intensity.

[0021] On the other hand, a lubricating oil abrasive particle measurement system based on laser diffraction and scattering is provided, including a laser, a laser beam control unit, a visual oil circuit, a photoelectric detection device, an A / D converter, a digital signal processor, and a central processing unit; wherein,

[0022] The laser is used to emit laser light;

[0023] The laser beam control unit is used to filter the laser beam to form a divergent beam;

[0024] The visualized oil path is used for laser beams to pass through, causing diffraction and scattering on the abrasive grains of the oil path;

[0025] The photoelectric detection device is used to convert light intensity signals into electrical signals;

[0026] The A / D converter is used to amplify the electrical signal and convert it into a digital signal;

[0027] The digital signal processor is used to preprocess the digital signal;

[0028] The central processing unit is used to analyze the pre-processed digital signal to determine the particle size distribution and concentration of the abrasive particles using a built-in specialized algorithm.

[0029] Preferably, the laser beam control unit includes a polarizer, a beam expander and collimator, and a variable aperture.

[0030] Preferably, a Fourier lens with a known focal length is provided in front of the photoelectric detection device.

[0031] Preferably, the visualized oil circuit is made of a high-transmittance material and is directly embedded in the lubrication circuit of the mechanical equipment to achieve in-situ monitoring.

[0032] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0033] (1) It realizes continuous in-situ monitoring of abrasive particles in lubricating oil, overcomes the shortcomings of traditional offline detection with long cycle and poor timeliness, and can capture the dynamic changes of equipment wear status in real time.

[0034] (2) By combining laser scattering diffraction signals with extinction method, the particle size distribution and concentration parameters of abrasive particles in lubricating oil can be obtained simultaneously. Moreover, compared with traditional inductive sensors that can only measure ferromagnetic metal abrasive particles, the present invention can also detect non-ferromagnetic non-metallic abrasive particles at the same time.

[0035] (3) The present invention adopts a visual oil circuit that can be directly used in the oil circuit of mechanical equipment without changing the existing pipeline, which can reduce the installation cost. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a system structure diagram of the present invention.

[0038] Among them, 1. Laser; 2. Polarizer; 3. Beam expander collimator; 4. Variable aperture; 5. Visualization oil circuit; 6. Fourier lens; 7. Photoelectric detection device; 8. A / D converter; 9. Digital signal processor; 10. Central processing unit. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] like Figure 1 As shown, this embodiment of the invention provides a lubricating oil abrasive particle measurement system based on laser diffraction and scattering, including a laser 1, a laser beam control unit, a visual oil circuit 5, a photoelectric detection device 7, an A / D converter 8, a digital signal processor 9, and a central processing unit 10; wherein,

[0041] Laser 1, used to emit laser light;

[0042] A laser beam control unit is used to filter laser beams and form divergent beams.

[0043] Visualized oil path 5 is used for laser beams to pass through, causing diffraction and scattering on the abrasive grains of the oil path;

[0044] Photoelectric detection device 7 is used to convert light intensity signals into electrical signals;

[0045] A / D converter 8 is used to amplify electrical signals and convert them into digital signals;

[0046] Digital signal processor 9 is used for preprocessing digital signals;

[0047] The central processing unit 10 is used to analyze the pre-processed digital signal to determine the particle size distribution and concentration of the abrasive particles using a built-in specialized algorithm.

[0048] Furthermore, the laser beam control unit includes a polarizer 2, a beam expander collimator 3, and a variable aperture 4; a Fourier lens 6 with a known focal length is provided in front of the photoelectric detection device 7.

[0049] This invention also provides a method for measuring abrasive particles in lubricating oil based on laser diffraction and scattering. The method utilizes the aforementioned abrasive particle measurement system and includes the following specific steps:

[0050] S1. Laser is emitted by laser 1, and the required laser is screened out by the laser beam control unit to form a diverging beam.

[0051] S2. The laser passes through the visualized oil path 5, and diffraction and scattering occur on the abrasive particles in the oil path;

[0052] S3, the photoelectric detection device 7 receives the light intensity signal and converts it into a corresponding electrical signal;

[0053] S4. Use A / D converter 8 to amplify the electrical signal and convert it into a digital signal;

[0054] S5. Input the digitized signal into the digital signal processor 9 for preprocessing;

[0055] S6. The pre-processed digital signal is then processed using a multi-layer medium optical correction algorithm to eliminate interference caused by light passing through the glass twice. The signal is then transmitted to the central processing unit 10, where a specialized algorithm is used to analyze the particle size distribution and concentration of the abrasive particles.

[0056] Furthermore, the specific steps of S1 include the following:

[0057] S11. A laser beam with good monochromaticity is emitted by laser 1. Laser 1 can preferably be a He-Ne laser or a semiconductor laser, which can emit a laser beam with good monochromaticity, strong directionality and concentrated energy, providing a stable and reliable optical signal source for the entire measurement system.

[0058] S12. The monochromatic laser emitted by laser 1 is then passed through a laser beam control unit, which includes: a polarizer 2: filtering out laser light with a specific polarization direction to reduce stray light interference and improve the signal-to-noise ratio; a beam expander and collimator 3: expanding and collimating the laser beam to form a uniform divergent beam, increasing the irradiation area and improving the coverage of particle detection; and a variable aperture 4: adjusting the amount of light entering the oil path to adapt to the measurement needs of different oil paths and particle concentrations. This effectively improves the clarity and consistency of the subsequent light intensity signal and allows the system to adapt to more synovial fluid environments and particle types.

[0059] Furthermore, as the S2 laser passes through the visualized oil passage 5, diffraction and scattering occur on the abrasive particles within the oil passage. This visualized oil passage 5 is made of a high-transmittance material (preferably quartz or special engineering glass), possessing excellent optical properties and mechanical strength. It can be directly embedded into the lubrication circuit of mechanical equipment, enabling in-situ monitoring without requiring redesign or modification of the original oil passage. The laser sequentially passes through "glass-oil passage-glass," and within the oil passage, diffraction and scattering occur with the abrasive particles (including metallic and non-metallic particles) in the oil. The intensity distribution is influenced by the particle size, shape, and concentration of the abrasive particles.

[0060] Furthermore, the scattered and diffracted light intensity signals are converged by a Fourier lens 6 with a known focal length before entering the photodetector 7. This lens preferably has a focal length between 50 and 200 mm to ensure a clear diffraction ring pattern is formed on the photosensitive surface of the photodetector. The photodetector 7 (preferably a ring photodiode array or a CCD sensor) receives the light intensity signal and converts it into a corresponding electrical signal. The light intensity signal mainly consists of three parts:

[0061] 1) The light intensity signal generated by Mie scattering when a laser beam illuminates abrasive grains. :

[0062] ;

[0063] in, , Let be a function of the intensity of the scattered light. , Let be the amplitude function of the scattered light, and r be the radius of the abrasive grain. The scattering angle is the angle between the direction of the incident light and the direction of the scattered light. The azimuth angle describes the orientation of the scattered light in the plane perpendicular to the incident light. The wavelength of the incident light;

[0064] 2) The light intensity signal generated when a laser beam irradiates abrasive grains and undergoes diffraction is calculated using Fraunhofer diffraction theory. :

[0065] ;

[0066] in, Where is the incident light intensity, and F is the focal length of the lens. The diffraction angle, Where is the particle radius, For wave number, The intensity of the diffracted light at the transmission center of the photodetector. For dimensionless particle size parameters, It is a first-order Bessel function of the first kind;

[0067] 3) When the laser penetrates the abrasive particle system under test, the incident light intensity Attenuation will occur, as shown in the formula:

[0068] ;

[0069] in, Turbidity of particulate matter. The thickness of the particulate medium.

[0070] Furthermore, in S4, the A / D converter 8 is preferentially selected with high sampling rate and high resolution to ensure accurate capture of signal changes and reduce quantization errors. In S5, preprocessing operations include filtering, noise reduction, and signal averaging to improve the efficiency of the entire measurement system.

[0071] Furthermore, the specific steps of S6 include the following:

[0072] S61. Pre-calibrate the refractive index and attenuation coefficient of the visualization oil circuit glass and the lubricating oil to be tested for the laser wavelength used. Then, based on the scattering angle / diffraction angle corresponding to the received light intensity distribution signal, and using Snell's law (the law of refraction), the refraction angles of the laser at the glass-oil and oil-glass interfaces are calculated sequentially, as shown in the following formula. This allows for the deduction of the true scattering angle / diffraction angle, thereby eliminating the optical path offset caused by different media.

[0073] Snell's Law (Law of Refraction) formula is:

[0074] ;

[0075] in, denoted as the refractive index of the incident medium; is the refractive index of the refracting medium; Angle of incidence; It is the angle of refraction.

[0076] Then, based on the effective propagation path of laser in glass and oil... Using the Lambert-Beer law, the following formula can be used to calculate the total intensity attenuation of the laser light as it passes through multiple media, thus obtaining the true light intensity and eliminating the intensity attenuation caused by multiple media.

[0077] Lambert-Beer's Law Formula:

[0078] ;

[0079] in, The incident light intensity; The intensity of transmitted light. The attenuation coefficient of the medium, The thickness of the medium.

[0080] S62. Based on the corrected received scattering and diffraction ring intensity distribution signals, an inversion algorithm (preferably least squares method or iterative fitting method) is used to establish a linear inversion equation, which is as follows:

[0081]

[0082] in, This is a column vector composed of light intensity signals at different angles after correction; For the response matrix, Indicates the first Abrasive grains in the first particle size range... The characteristic light intensity generated by the angle is pre-calculated and calibrated using Mie scattering theory and Fraunhofer diffraction theory; Let be the particle size distribution vector, and be the vector to be solved. Indicates the first The volume / quantity percentage of each particle size range; This is the error vector.

[0083] Based on the typical particle size range of abrasive particles in lubricating oil for construction machinery, the particle size is divided into: A continuous number of cells determines the vector to be solved. The dimension; based on Mie scattering and Fraunhofer diffraction formulas, combined with the laser parameters and oil medium parameters of this invention, the characteristic light intensity of abrasive particles in each particle size range at different angles is pre-calculated, and a kernel matrix is ​​constructed. Extract the light intensity signal after optical correction in the multilayer medium, arrange the sampling points according to angle, and construct the light intensity vector. The least squares method is used to solve for the particle size distribution vector. The solution obtained Convert it into a volume / quantity particle size distribution curve or a table of the proportion of each particle size range.

[0084] S63. Based on the light intensity signal attenuated after passing through the oil path, and combined with the extinction method theory centered on Lambert-Beer law, the attenuation coefficient is calculated. And based on its calculation formula, the concentration distribution of abrasive particles in the oil is calculated, where the attenuation coefficient is... The calculation formula is:

[0085]

[0086] in, The inversion algorithm obtained the first The volume percentage of abrasive particles in each particle size range; The abrasive particle concentration is an unknown quantity to be solved. For the first Average extinction cross section of abrasive grains in each grain size range; This represents the number of particle size intervals, consistent with the inversion algorithm.

[0087] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for measuring abrasive particles in lubricating oil based on laser diffraction and scattering, characterized in that, The specific steps include the following: After being filtered, the laser beam forms a diverging beam, passes through the visualized oil path, and undergoes diffraction and scattering on the abrasive particles in the oil path to obtain the light intensity signal; The light intensity signal is first converted into an electrical signal, and then the electrical signal is amplified and converted into a digital signal. The digital signal is preprocessed to obtain a preprocessed digital signal; For the preprocessed digital signal, a multilayer dielectric optical correction algorithm is used to eliminate the interference caused by the beam passing through the visualized oil path. Then, the particle size distribution and concentration of the abrasive particles are obtained by analysis through inversion algorithm and extinction method.

2. The method for measuring abrasive particles in lubricating oil based on laser diffraction and scattering according to claim 1, characterized in that, Converting the light intensity signal into a light intensity signal in an electrical signal includes the following: The light intensity signal generated by the Mie scattering of a laser beam on abrasive grains : ； in, , Let be a function of the intensity of the scattered light. , Let be the amplitude function of the scattered light, and r be the radius of the abrasive grain. The scattering angle is the angle between the direction of the incident light and the direction of the scattered light. The azimuth angle describes the orientation of the scattered light in the plane perpendicular to the incident light. The wavelength of the incident light; The intensity signal generated when a laser beam irradiates abrasive grains and undergoes diffraction is calculated using Fraunhofer diffraction theory. : ； in, Where is the incident light intensity, and F is the focal length of the lens. The diffraction angle, Where is the particle radius, For wave number, The intensity of the diffracted light at the transmission center of the photodetector. For dimensionless particle size parameters, It is a first-order Bessel function of the first kind; When a laser penetrates the abrasive particle system under test, the incident light intensity Attenuation will occur, as shown in the formula: ； in, Turbidity of particulate matter. The thickness of the particulate medium.

3. The method for measuring abrasive particles in lubricating oil based on laser diffraction and scattering according to claim 1, characterized in that, The preprocessing operations include filtering, noise reduction, and signal averaging.

4. The method for measuring abrasive particles in lubricating oil based on laser diffraction and scattering according to claim 1, characterized in that, The multi-layer medium optical correction algorithm is used to eliminate interference caused by the light beam passing through the visualized oil path. Specifically, it includes: using Snell's law to eliminate the light path offset caused by the laser passing through the glass of the visualized oil path; and using Lambert-Beer's law to attenuate the light intensity.

5. A lubricating oil abrasive particle measurement system based on laser diffraction and scattering, characterized in that, This includes a laser, a laser beam control unit, a visual oil circuit, a photoelectric detection device, an A / D converter, a digital signal processor, and a central processing unit; among which, The laser is used to emit laser light; The laser beam control unit is used to filter the laser beam to form a divergent beam; The visualized oil path is used for laser beams to pass through, causing diffraction and scattering on the abrasive grains of the oil path; The photoelectric detection device is used to convert light intensity signals into electrical signals; The A / D converter is used to amplify the electrical signal and convert it into a digital signal; The digital signal processor is used to preprocess the digital signal; The central processing unit is used to analyze the pre-processed digital signal to determine the particle size distribution and concentration of the abrasive particles using a built-in specialized algorithm.

6. The lubricating oil abrasive particle measurement system based on laser diffraction and scattering according to claim 5, characterized in that, The laser beam control unit includes a polarizer, a beam expander and collimator, and a variable aperture.

7. The lubricating oil abrasive particle measurement system based on laser diffraction and scattering according to claim 5, characterized in that, A Fourier lens with a known focal length is placed in front of the photoelectric detection device.

8. The lubricating oil abrasive particle measurement system based on laser diffraction and scattering according to claim 5, characterized in that, The visualized oil circuit is made of a high-transmittance material and is directly embedded in the lubrication circuit of mechanical equipment to achieve in-situ monitoring.

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