Microwave resonant oil debris detection sensor, system and method with electromagnetic enrichment

Abstract

The application discloses a kind of microwave resonance oil abrasive particle detection sensors with electromagnetic enrichment, system and method, sensor includes: medium substrate surface is provided with microstrip transmission line and planar microwave resonance structure, microstrip transmission line and planar microwave resonance structure electromagnetic coupling;Oil liquid flow pipe is through two ends of medium substrate, for the oil liquid to be measured to flow through;Electromagnet is arranged in the one side of oil liquid flow pipe detection section, for forming magnetic field gradient in the detection section of oil liquid flow pipe;The central axis of electromagnet and the geometric center of planar microwave resonance structure and the center position of oil liquid flow pipe detection section intersect or approximately intersect;Radio frequency connector, including first radio frequency connector and second radio frequency connector, respectively with the input end and output end of microstrip transmission line connection, for receiving input microwave excitation signal and output resonance response signal.The application combines planar microwave resonance structure with electromagnet active enrichment, and realizes the enhanced detection of ferromagnetic metal abrasive particles in lubricating oil.

Description

Technical Field

[0001] This invention relates to the field of microwave detection and oil condition monitoring technology, specifically to a microwave resonant oil wear particle detection sensor, system, and method with electromagnetic enrichment. Background Technology

[0002] Lubricating oil is widely used in industrial equipment such as engines, gearboxes, bearings, and hydraulic transmissions, serving the functions of lubrication, heat dissipation, and sealing. During equipment operation, metal abrasive particles generated by friction pair wear will circulate with the oil. The number and size of these abrasive particles are directly related to the wear condition of the equipment. Therefore, oil metal abrasive particle detection is an important means of assessing the health status of equipment and predictive maintenance.

[0003] Existing technologies for detecting metal abrasive particles in oil mainly include electrical detection, optical imaging detection, and ultrasonic detection. Electrical detection methods, such as inductive methods, are sensitive to flow channel size, installation gaps, and external electromagnetic environment. Under conditions of low concentration of small particles, the signal amplitude is insufficient and the stability is poor. Optical imaging methods are easily affected by oil transparency, bubbles, and contamination of the observation window, resulting in high long-term maintenance costs. Ultrasonic detection methods are affected by bubbles, flow disturbances, temperature changes, and fluctuations in transducer coupling conditions, resulting in insufficient quantitative accuracy and long-term stability.

[0004] In recent years, microwave resonant sensing technology has been gradually applied to the field of oil detection due to its advantages such as compact structure, ease of integration, and insensitivity to oil transparency. However, existing microwave oil detection schemes still have significant drawbacks: planar resonant structures are sensitive to the spatial distribution of abrasive particles, and at low concentrations, the random distribution of ferromagnetic abrasive particles makes it difficult to stably enter the resonant sensitive region, resulting in weak detection response and poor repeatability; high-frequency resonant schemes suffer from prominent connection losses and parasitic coupling, making them susceptible to electromagnetic interference and temperature drift; cavity resonant structures are large and complex, requiring precise sample loading positions, which is not conducive to integration in confined spaces and online deployment.

[0005] Therefore, there is an urgent need to explore a microwave oil abrasive detection scheme that is easy to integrate, has high detection stability, and enhances the detection capability for low-concentration ferromagnetic abrasive particles. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a microwave resonant oil abrasive particle detection sensor, system, and method with electromagnetic enrichment, aiming to solve at least some of the problems mentioned above.

[0007] In a first aspect, the present invention provides a microwave resonant oil abrasive particle detection sensor with electromagnetic enrichment, comprising: A dielectric substrate having a microstrip transmission line and a planar microwave resonant structure disposed on its surface, wherein the microstrip transmission line and the planar microwave resonant structure are electromagnetically coupled. An oil flow tube is disposed along the length of the dielectric substrate in the microwave sensitive region of the planar microwave resonant structure, and the oil flow tube passes through both ends of the dielectric substrate for supplying the oil to be tested. An electromagnet is disposed on one side of the detection section of the oil flow pipe to form a magnetic field gradient near the detection section of the oil flow pipe. The central axis of the electromagnet intersects or approximately intersects the geometric center of the planar microwave resonant structure and the center of the detection section of the oil flow pipe, so that the magnetic field enrichment area formed when the electromagnet is energized, the microwave sensitive area of ​​the planar microwave resonant structure, and the oil flow area in the oil flow pipe spatially overlap or partially overlap.

[0008] The radio frequency connector includes a first radio frequency connector and a second radio frequency connector, which are respectively connected to the input end and the output end of the microstrip transmission line to receive the input microwave excitation signal and the output resonant response signal.

[0009] Furthermore, the planar microwave resonant structure is a complementary split-ring resonator, i.e., a CSRR resonant structure. The CSRR resonant structure and the microstrip transmission line are respectively disposed on two opposite surfaces of the dielectric substrate, and the two are electromagnetically coupled through the dielectric substrate.

[0010] Furthermore, the central axis of the electromagnet is perpendicular to the plane of the planar microwave resonant structure, the central axis of the oil flow pipe is parallel to the plane of the planar microwave resonant structure, and the oil flow direction in the oil flow pipe is perpendicular to the central axis of the electromagnet.

[0011] Furthermore, the oil flow pipe is composed of a complete and continuous insulating tube, and the oil to be tested and the abrasive particles it carries flow inside the oil flow pipe.

[0012] Furthermore, the sensor also includes a protective housing, with the dielectric substrate, the oil flow pipe, and the electromagnet disposed within the internal mounting cavity of the protective housing; a conductive shielding seal is provided between the mating surfaces of the protective housing, and the conductive shielding seal is conductively connected to the protective housing, the reference ground of the dielectric substrate, and the outer conductor of the RF connector to form an electromagnetic shielding structure.

[0013] Secondly, the present invention provides a microwave resonant oil abrasive particle detection method with electromagnetic enrichment, comprising the following steps: Obtain the reference resonant frequency of the reference lubricating oil with non-ferromagnetic metal abrasive particles under the same electromagnet excitation state as the lubricating oil to be tested for enrichment detection; Electromagnetic enrichment of ferromagnetic metal abrasive particles in the lubricating oil under test was performed, and the actual resonant frequency under enrichment was obtained. Based on the reference resonant frequency and the actual resonant frequency, the enriched state resonant frequency shift is determined; Based on the enriched state resonant frequency shift and the pre-established calibration relationship between the resonant frequency shift and the concentration of ferromagnetic metal abrasive particles, the concentration of ferromagnetic metal abrasive particles in the lubricating oil to be tested is determined.

[0014] Furthermore, the determination of the concentration of ferromagnetic metal abrasive particles includes correcting the resonant frequency shift of the enriched state and the calibration relationship using a focusing degree coefficient; The process of determining the focus coefficient includes: Obtain the first model frequency shift corresponding to the uniform arc enrichment model and the second model frequency shift corresponding to the central bulge-type focusing model; The focusing coefficient is calculated based on the frequency shift of the first model, the frequency shift of the second model, and the frequency shift of the standard oil sample experiment.

[0015] Furthermore, the formula for calculating the focus level coefficient is as follows:

[0016] in, For the first model frequency shift; For the second model frequency shift; For a known concentration (C) i The experimental average frequency shift was measured from the standard oil sample.

[0017] Furthermore, after determining the concentration of ferromagnetic metal abrasive particles in the lubricating oil to be tested, the method further includes: Cut off the excitation current of the electromagnet so that the accumulated ferromagnetic metal abrasive particles are released with the flow of oil. The resonant frequency is reacquired under power failure. When the reacquired resonant frequency recovers to the preset baseline tolerance range, it is determined that the abrasive release is complete and the next detection cycle begins. If the frequency does not recover to the preset baseline tolerance range, extend the oil circulation flushing time until the resonant frequency recovers to the preset baseline tolerance range.

[0018] Thirdly, the present invention provides a microwave resonant oil abrasive particle detection system with electromagnetic enrichment, comprising: The microwave resonant oil abrasive particle detection sensor with electromagnetic enrichment is connected to the oil circuit; A vector network analyzer, connected to the first and second RF connectors of the sensor, is used to provide a swept-frequency microwave excitation signal and acquire the amplitude-frequency response. A DC power supply, connected to the electromagnet of the sensor, is used to provide excitation current; The data processing equipment is connected to the vector network analyzer and the DC power supply, respectively, and is used to execute the microwave resonant oil abrasive particle detection method with electromagnetic enrichment.

[0019] The beneficial effects of this invention are: This invention places an electromagnet near the local strong field sensitive region of the planar microwave resonant structure, and spatially aligns the magnetic field gradient enrichment region, the oil flow channel in the oil pipe, and the microwave sensitive region. When the electromagnet is energized, it exerts a directional attraction on ferromagnetic metal abrasive particles, causing them to migrate and accumulate from a randomly dispersed state towards the resonant sensitive region. This increases the probability of abrasive particles entering the effective microwave detection region and enhances the resonant characteristic changes induced by the particles. Simultaneously, this invention uses a complete and continuous insulating oil flow pipe as the oil channel, preventing direct contact between the lubricating oil and abrasive particles and the metal layer of the planar microwave resonant structure. This facilitates series or bypass integration of the sensor with the lubrication circuit. The complete and continuous insulating oil pipe design prevents direct contact between the oil and the microwave structure, avoiding the impact of oil corrosion and contamination on sensor performance. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments will be briefly introduced below. Obviously, the drawings described below only relate to some embodiments of the present invention, and are not intended to limit the present invention.

[0021] Figure 1 This is a schematic diagram of the overall structure of the sensor of the present invention; Figure 2 This is a schematic diagram of the CSRR resonant structure of the sensor in this invention; Figure 3 This is a schematic diagram of the microstrip line structure of the sensor in this invention; Figure 4 This is a schematic diagram of the detection system of the present invention; In the figure: 1. Dielectric substrate; 2. Microstrip transmission line; 3. Planar microwave resonant structure; 4. Oil flow pipe; 5. Electromagnet. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0024] like Figure 1-3 As shown, the present invention provides a microwave resonant oil abrasive particle detection sensor with electromagnetic enrichment, comprising: a dielectric substrate 1, an oil flow pipe 4, an electromagnet 5, and an RF connector. A dielectric substrate 1 has a microstrip transmission line 2 and a planar microwave resonant structure 3 disposed on its surface, wherein the microstrip transmission line 2 and the planar microwave resonant structure 3 are electromagnetically coupled. In this embodiment, the dielectric substrate 1 is an F4B double-sided copper-clad microwave dielectric substrate with a relative permittivity of 3.5, a total thickness of 3.6 mm, and a copper layer thickness of 35 μm. The dielectric substrate 1 consists of a first dielectric substrate and a second dielectric substrate that cooperate with each other. Semi-circular grooves extending along the length direction are respectively provided on the opposing surfaces of the two dielectric substrates. After assembly, they form a through-hole installation channel adapted to the outer diameter of the oil flow pipe 4, reducing the difficulty of machining long-distance small holes and facilitating the assembly and replacement of the oil flow pipe 4.

[0025] like Figure 2 As shown, the planar microwave resonant structure 3 is a three-ring octagonal complementary split-ring resonator (CSRR), etched on the lower surface metal layer of the dielectric substrate 1. The CSRR consists of three concentric octagonal slots, each with an opening, and the openings of adjacent slots are staggered along the same axis. The openings and slots together form an equivalent capacitance, and the ring current path forms an equivalent inductance, generating a localized enhanced electric field in the slot, opening, and central coupling region near the resonant frequency. The geometric center of the CSRR almost coincides with the projection of the center of the detection section of the oil flow pipe 4 and the central axis of the electromagnet 5 onto the plane of the substrate. The present invention preferably uses a CSRR, but is not limited to a CSRR of a specific shape, number of rings, or opening direction. Any planar resonant structure that can generate a strong local electromagnetic field near the oil channel and convert the equivalent electromagnetic parameter changes caused by abrasive particles into measurable resonant characteristic changes can be used, including circular or square CSRRs, single-ring or multi-ring CSRRs, complementary spiral resonators, complementary open-ring resonators, etc. When using an alternative structure, the spatial correspondence between the oil channel, the magnetic field enrichment region, and the microwave strong field region is still maintained.

[0026] like Figure 3As shown, the microstrip transmission line 2 is disposed on the upper surface of the dielectric substrate 1, and is U-shaped in overall form. It includes a first side transmission segment, a second side transmission segment, a lateral coupling segment connecting the two side transmission segments, and a loading coupling structure disposed in the middle of the lateral coupling segment. The ends of the two side transmission segments constitute the RF input terminal and the RF output terminal, respectively, designed with a characteristic impedance of 50Ω. The middle loading coupling structure is continuously connected to the lateral transmission segment and can adopt a combination of circular, elliptical, polygonal, or arc-gradient structures. Its center coincides with the projection of the geometric center of the CSRR in the substrate thickness direction. It is used to adjust the surface current distribution in the central region, enhance the local electromagnetic coupling between the microstrip transmission line 2 and the back CSRR, and adjust the external quality factor, resonant notch depth, and operating frequency. An arc-gradient transition is used between the middle loading structure and the two side transmission segments to reduce additional reflections caused by abrupt changes in linewidth.

[0027] In this embodiment, the oil flow tube 4 is composed of a complete and continuous insulating tube, and the oil to be tested and the abrasive particles it carries flow inside the oil flow tube 4. The oil flow tube 4 is made of PU tube with an outer diameter of 3.0 mm, an inner diameter of 2.0 mm, and a wall thickness of 0.5 mm, and is installed through the through mounting channel of the dielectric substrate 1. The central axis of the PU tube passes through the geometric center of the CSRR resonant structure and is basically parallel to the plane of the CSRR, and the oil flows along the axial direction of the PU tube. The interior of the PU tube forms the actual flow channel for lubricating oil and ferromagnetic metal abrasive particles. During the test, the lubricating oil and abrasive particles are always located inside the PU tube and do not directly contact the microstrip transmission line 2 and the CSRR metal structure on the surface of the dielectric substrate 1. Both ends of the PU tube are connected to the external oil circuit through quick-connect connectors, and the connection is sealed with O-rings. In addition to PU tube, PTFE, FEP, PFA, PEEK, polyethylene, quartz capillary tube, glass tube, or other lubricating oil-resistant, insulating, and non-magnetic materials can also be used.

[0028] In this embodiment, electromagnet 5 is disposed on one side of the detection section of the oil flow pipe 4. A cylindrical DC electromagnet 5, model WF-06 / 06, with a diameter of 6mm and a height of 6mm, is used. It is positioned above the center of the CSRR resonant structure, with the magnetic end face facing the CSRR metal plane. The central axis of electromagnet 5 is perpendicular to the CSRR metal plane, aligned with the geometric center of the CSRR resonant structure, and intersects with the center of the PU tube detection section. This ensures that the magnetic field enrichment area formed by electromagnet 5, the abrasive particle movement area within the PU tube, and the CSRR local strong field sensitive area correspond spatially. A 0.03mm thick polytetrafluoroethylene (PTFE) film is disposed between the magnetic end face of electromagnet 5 and the CSRR metal plane to electrically isolate electromagnet 5 from the CSRR metal layer, preventing direct contact that could cause short circuits, surface wear, or changes in assembly position.

[0029] In this invention, the sensor further includes a protective housing. The dielectric substrate 1, the oil flow pipe 4, and the electromagnet 5 are disposed within the internal mounting cavity of the protective housing. A conductive shielding seal is provided between the mating surfaces of the protective housing. The conductive shielding seal is conductively connected to the protective housing, the reference ground of the dielectric substrate 1, and the outer conductor of the RF connector to form an electromagnetic shielding structure. The protective housing is made of 6061 aluminum alloy non-ferromagnetic conductive material and includes a top cover and a base that are connected to each other. After the two are connected, they form an internal mounting cavity. The dielectric substrate 1, the microstrip transmission line 2, the CSRR resonant structure, the electromagnet 5, and its mounting components are all disposed within the internal mounting cavity. The top cover and the base are connected by multiple screws. A conductive rubber pad is provided between their mating surfaces, continuously distributed along the mating surfaces, to achieve electrical continuity of the housing and reduce electromagnetic leakage at the joints. A first oil pipe through hole and a second oil pipe through hole are respectively provided on two opposite sidewalls along the extension direction of the PU pipe. The PU pipe passes through and exits through the through holes. An elastic sealing sleeve is provided inside the through holes to achieve oil pipe positioning and environmental sealing.

[0030] In this embodiment, the RF connectors include a first RF connector and a second RF connector, both of which are through-plate SMA connectors with a characteristic impedance of 50Ω. They are respectively installed on the protective housing at positions corresponding to the input and output ends of the microstrip transmission line 2. The center conductor of the SMA connector is connected to the input / output end of the microstrip transmission line 2, and the outer conductor forms a low-resistance electrical connection with the reference ground of the dielectric substrate 1 and the metal protective housing, establishing a continuous RF return path. The SMA RF connector maintains a 10-15mm isolation distance from the electromagnet 5 coil and its power supply leads to reduce interference of the electromagnet 5 power supply circuit to the RF signal. The protective housing is also provided with an electromagnet 5 power supply lead hole. The positive and negative power supply wires of the electromagnet 5 are led out through the lead hole and connected to an external DC power supply. An insulating threaded sleeve and a sealed connector are provided inside the lead hole.

[0031] Secondly, the present invention provides a microwave resonant oil abrasive particle detection method with electromagnetic enrichment, comprising the following steps: S1. Obtain the reference resonant frequency of the reference lubricating oil with non-ferromagnetic metal abrasive particles under the same excitation state of electromagnet 5 as the lubricating oil to be tested for enrichment detection; when the electromagnet 5 is de-energized, collect the de-energized blank reference resonant frequency of the reference lubricating oil; energize according to the excitation current used in the formal test, and after enrichment waiting time and stabilization waiting time, collect the energized blank reference resonant frequency of the reference lubricating oil; based on the de-energized blank reference resonant frequency and the energized blank reference resonant frequency, evaluate the inherent reference changes caused by the metal structure of electromagnet 5 and the energized temperature rise.

[0032] Lubricating oil, free of ferromagnetic metal abrasive particles and of the same type as the oil to be tested, is supplied at a stable flow rate through the PU tube, while maintaining stable oil temperature, circulation flow rate, and sweep frequency parameters. First, electromagnet 5 is de-energized, and at least three S21 amplitude-frequency response curves are continuously acquired and averaged to obtain the blank reference resonant frequency with electromagnet 5 de-energized. Subsequently, electromagnet 5 was switched on using the excitation current employed in the formal test, and kept energized for 30 seconds. Then, approximately 0.5 seconds were allowed for the excitation current, sensor temperature, and resonant response to stabilize. With the excitation current of electromagnet 5 unchanged, at least three S21 amplitude-frequency response curves were continuously collected and averaged to obtain the blank reference resonant frequency of electromagnet 5 under energized conditions. The inherent reference change caused by the electromagnet 5 itself and its excitation state can be expressed as: Δ = -

[0033] The Δ This is used to evaluate the effects of the electromagnet's metal structure, excitation current, and energized temperature rise on the resonant response, and is not used as the response for detecting abrasive particles in ferromagnetic metals. The baseline acquisition temperature is preferably maintained at 25±1 ℃, or near the actual operating temperature of the equipment; the same temperature, flow rate, and excitation conditions should be used for standard oil sample calibration and unknown oil sample testing.

[0034] S2. Electromagnetically enrich the ferromagnetic metal abrasive particles in the lubricating oil to be tested, and obtain the actual resonant frequency under enrichment state. Measure 200 mL of thoroughly mixed lubricating oil (without significant air bubbles) and place it in a storage container. Use an oil delivery device to circulate the oil sample between the storage container, connecting pipe, and oil flow pipe 4. Maintain a stable oil flow rate during the test. Keep electromagnet 5 de-energized, allowing the 200 mL oil sample to continue circulating through the PU tube. After the oil flow rate and sensor response stabilize, continuously acquire at least three S21 amplitude-frequency response curves. Average the measurement results to obtain the resonant frequency of the oil sample when electromagnet 5 is de-energized. A 200 mL sample of oil was circulated at the set flow rate. Electromagnet 5 (model WF-06 / 06) was connected, creating a magnetic field gradient near the detection section of the PU tube. This attracted the ferromagnetic abrasive particles flowing with the oil to positions corresponding to the CSRR strong field sensitive area. The enrichment time for electromagnet 5 was set to 30 s. During the enrichment process, the oil flow rate, the excitation current of electromagnet 5, and the oil sample mixing state were kept constant to minimize the impact of flow fluctuations, abrasive particle settling, and changes in excitation conditions on the enrichment degree. After 30 s of enrichment, the excitation current of electromagnet 5 was kept constant, and approximately 0.5 s was allowed for the excitation current and abrasive particle enrichment state to stabilize. Subsequently, a vector network analyzer was used to perform an S21 amplitude-frequency response scan within 1–3 s to extract the resonant frequency under enrichment conditions. .

[0035] S3. Based on the reference resonant frequency and the actual resonant frequency, determine the enriched state resonant frequency shift to reduce the influence of the inherent loading of electromagnet 5 on the resonant response; the resonant frequency shift of the enriched state relative to the reference state of electromagnet 5 under energization is: Δ = -

[0036] In the formula, The resonant frequency of the oil sample after enrichment by electromagnet 5 is the actual frequency measured. This is the reference resonant frequency of the energized state, measured under the same conditions of oil temperature, circulation flow rate, excitation current of electromagnet 5, energizing time, and sweep frequency parameters for the same type of lubricating oil with non-ferromagnetic metallic abrasive particles. During the S21 scan, electromagnet 5 is kept stably energized without changing the excitation current or oil circulation flow rate to ensure consistency between the measured state of the oil sample and the blank baseline and standard oil sample calibration state. Using a consistent energized blank baseline for comparison reduces the influence of the electromagnet 5's metal core, electrical loading, and energizing temperature rise on the abrasive particle frequency shift results.

[0037] S4. Based on the enriched state resonant frequency shift and the pre-established calibration relationship between the resonant frequency shift and the concentration of ferromagnetic metal abrasive particles, determine the concentration of ferromagnetic metal abrasive particles in the lubricating oil to be tested. The process of determining the focusing degree coefficient includes: obtaining the first model frequency shift corresponding to the uniform arc-shaped enrichment model and the second model frequency shift corresponding to the centrally raised focusing model; calculating the focusing degree coefficient based on the first model frequency shift, the second model frequency shift, and the experimental frequency shift of the standard oil sample; wherein, the focusing degree coefficient is used to characterize the degree to which the actual abrasive particle distribution state is close to the uniform arc-shaped enrichment model or the centrally raised focusing model. The focusing degree coefficient can be obtained through standard oil sample experimental calibration, and the calculation formula of the focusing degree coefficient is as follows:

[0038] in, For the first model frequency shift; For the second model frequency shift; For a known concentration (C) i The experimental average frequency shift was measured from the standard oil sample.

[0039] If the focus coefficient is a fixed value The corrected concentration-frequency shift relationship is then:

[0040] The resonant frequency of an unknown oil sample was measured under conditions where the electromagnet was energized and the excitation parameters were consistent with the calibration conditions. The reference resonant frequency of the same type of blank oil sample with non-ferromagnetic metal abrasive particles under the same energized state is: Then the resonant frequency shift of the enrichment state of the unknown oil sample is:

[0041] By solving:

[0042] The concentration of metal abrasive particles in an unknown oil sample can then be obtained. ; If the focusing coefficient changes with concentration, then the correction formula is:

[0043] Passed again:

[0044] Inverse calculation of unknown concentration .

[0045] The uniform arc-shaped enrichment model represents the relatively uniform spread of metal abrasive particles along the sensitive area at the bottom of the PU tube; the centrally raised focusing model represents the state where metal abrasive particles accumulate more in the central region of the magnetic field and are thinner on both sides. These two abrasive particle distribution models serve as two reference endpoints for the actual abrasive particle aggregation state. The focusing degree coefficient is used to correct the detection model based on experimental calibration results, thereby reducing the impact of abrasive particle distribution uncertainty on the metal abrasive particle content detection results.

[0046] Based on the uniform arc-shaped enrichment model, the central bulge-type focusing model, and the calculation method of the focusing degree coefficient, the obtained resonant frequency of the actual enrichment state is processed. Combining the pre-established resonant frequency-abrasive particle concentration calibration relationship and the focusing degree coefficient, the concentration of ferromagnetic metal abrasive particles in the oil sample to be tested is obtained using table lookup, interpolation, or numerical solution methods. The computer outputs the concentration of ferromagnetic metal abrasive particles in the oil sample to be tested and the resonant frequency of the actual enrichment state. Resonant frequency in power-off state The resonant frequency shift Δ relative to the electromagnet 5 in its energized blank reference state Focusing degree coefficient. When the detected abrasive particle concentration, resonant frequency shift, or abrasive particle concentration change exceeds the preset threshold, an abnormality prompt is output. Simultaneously, the original S21 amplitude-frequency response curve, 200 mL oil sample volume, oil temperature, circulation flow rate, electromagnet 5 excitation parameters, enrichment time, focusing degree coefficient, and detection time are saved for traceability and analysis of the detection results.

[0047] Under the established simulation model and parameter settings, when the content of ferromagnetic metal abrasive particles increases from 0 to 200 ppm, the resonant frequency of the uniform arc-shaped enrichment model decreases from 1.8041 GHz to 1.7892 GHz, corresponding to a total frequency shift of 14.9 MHz and an average frequency shift change of approximately 74.5 kHz / ppm. The resonant frequency of the centrally raised focusing model decreases to 1.7846 GHz under the 200 ppm condition, corresponding to a total frequency shift of 19.5 MHz. These simulation results demonstrate that, under the established model conditions, an increase in abrasive particle content can cause a identifiable change in resonant frequency, and the concentration of abrasive particles in the CSRR-sensitive region can further enhance the resonant disturbance. This provides a theoretical and simulation basis for establishing concentration calibration relationships through subsequent standard oil sample tests.

[0048] S5. After determining the concentration of ferromagnetic metal abrasive particles in the lubricating oil to be tested, the excitation current of the electromagnet 5 is cut off, so that the enriched ferromagnetic metal abrasive particles are released with the flow of oil. The resonant frequency is reacquired in the power-off state. When the reacquired resonant frequency recovers to the preset baseline tolerance range, it is determined that the abrasive particle release is complete and the next detection cycle begins. When it does not recover to the preset baseline tolerance range, the oil circulation flushing time is extended until the resonant frequency recovers to the preset baseline tolerance range.

[0049] This invention employs a periodic working mode of energized enrichment, constant current measurement, power-off release, and state recovery confirmation. After the enrichment measurement is completed, the abrasive particles are released by power-off and oil circulation, which can reduce the risk of long-term abrasive particle retention, local accumulation, and flow channel blockage.

[0050] like Figure 4As shown, the present invention provides a microwave resonant oil wear particle detection system with electromagnetic enrichment, comprising: a sensor, a vector network analyzer, a DC power supply, and a data processing device; The microwave resonant oil abrasive particle detection sensor with electromagnetic enrichment described in this invention is connected to the oil circuit. The sensor can be installed in series in the main lubricating oil circuit, or it can be installed in a branch pipe or bypass position via a tee connector, flow restrictor valve, and bypass pipeline. A bypass installation method is preferred to facilitate stable flow control, power-off flushing, and sensor replacement. The oil pipe in the sensor is connected to the external oil circuit. The oil to be tested enters the oil pipe through the sensor inlet, passes through the core detection section defined by the CSRR strong field region and the electromagnet enrichment region, and then flows back to the equipment oil circuit or sampling container from the sensor outlet.

[0051] In this embodiment, a vector network analyzer is connected to the first and second RF connectors of the sensor to provide a swept-frequency microwave excitation signal and acquire the amplitude-frequency response. The vector network analyzer is connected to the first and second RF connectors of the sensor via two SMA RF coaxial cables with a characteristic impedance of 50 Ω. The scanning frequency range of the vector network analyzer is set to 1.75–1.85 GHz, and the number of sampling points is set to 801 or 1601.

[0052] In this embodiment, a DC power supply is connected to the electromagnet 5 of the sensor to provide excitation current.

[0053] In this embodiment, the data processing device is connected to the vector network analyzer and the DC power supply, respectively, and is used to execute the microwave resonant oil abrasive particle detection method with electromagnetic enrichment. A data processing program is set up in the computer to read the S21 amplitude-frequency curve, determine the resonant frequency in the curve, calculate the resonant frequency shift, and invert the abrasive particle concentration by combining the calibration model and the focusing degree coefficient.

[0054] This invention places an electromagnet 5 near the local strong field sensitive region of the CSRR, and spatially aligns the magnetic field gradient enrichment region, the PU tube oil flow channel, and the CSRR microwave sensitive region. When energized, the electromagnet 5 exerts a directional attraction on the ferromagnetic metal abrasive particles, causing them to migrate and accumulate from a randomly dispersed state towards the resonant sensitive region. This increases the probability of abrasive particles entering the effective microwave detection region and enhances the resonant characteristic changes induced by the particles. This invention uses a complete and continuous insulated PU tube as the oil channel, preventing direct contact between the lubricating oil and abrasive particles and the microstrip transmission line 2 and the CSRR metal structure. Simultaneously, it employs a periodic operating mode of energized enrichment—constant current measurement—power-off release—state recovery confirmation. After completing the enrichment measurement, the abrasive particles are released through power-off and oil circulation, reducing the risks of long-term abrasive particle retention, local accumulation, and flow channel blockage.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A microwave resonant oil abrasive particle detection sensor with electromagnetic enrichment, characterized in that, include: A dielectric substrate having a microstrip transmission line and a planar microwave resonant structure disposed on its surface, wherein the microstrip transmission line and the planar microwave resonant structure are electromagnetically coupled. An oil flow tube is disposed along the length of the dielectric substrate in the microwave sensitive region of the planar microwave resonant structure, and the oil flow tube passes through both ends of the dielectric substrate for supplying the oil to be tested. An electromagnet is disposed on one side of the detection section of the oil flow pipe to form a magnetic field gradient near the detection section of the oil flow pipe. The central axis of the electromagnet intersects or approximately intersects with the geometric center of the planar microwave resonant structure and the center of the detection section of the oil flow pipe, so that the magnetic field enrichment area formed when the electromagnet is energized, the microwave sensitive area of ​​the planar microwave resonant structure, and the oil flow area in the oil flow pipe spatially overlap or partially overlap. The radio frequency connector includes a first radio frequency connector and a second radio frequency connector, which are respectively connected to the input end and the output end of the microstrip transmission line to receive the input microwave excitation signal and the output resonant response signal.

2. The sensor according to claim 1, characterized in that, The planar microwave resonant structure is a complementary split-ring resonator, i.e., a CSRR resonant structure. The CSRR resonant structure and the microstrip transmission line are respectively disposed on two opposite surfaces of the dielectric substrate, and the two are electromagnetically coupled through the dielectric substrate.

3. The sensor according to claim 1, characterized in that, The central axis of the electromagnet is perpendicular to the plane of the planar microwave resonant structure, the central axis of the oil flow pipe is parallel to the plane of the planar microwave resonant structure, and the oil flow direction in the oil flow pipe is perpendicular to the central axis of the electromagnet.

4. The sensor according to claim 1, characterized in that, The oil flow pipe is composed of a complete and continuous insulating tube, and the oil to be tested and the abrasive particles it carries flow inside the oil flow pipe.

5. The sensor according to claim 1, characterized in that, The sensor also includes a protective housing, and the dielectric substrate, the oil flow pipe and the electromagnet are disposed in the internal mounting cavity of the protective housing; a conductive shielding seal is provided between the mating surfaces of the protective housing, and the conductive shielding seal is conductively connected to the protective housing, the reference ground of the dielectric substrate and the outer conductor of the radio frequency connector to form an electromagnetic shielding structure.

6. A microwave resonant oil abrasive particle detection method with electromagnetic enrichment, characterized in that, Includes the following steps: Obtain the reference resonant frequency of the reference lubricating oil with non-ferromagnetic metal abrasive particles under the same electromagnet excitation state as the lubricating oil to be tested for enrichment detection; Electromagnetic enrichment of ferromagnetic metal abrasive particles in the lubricating oil under test was performed, and the actual resonant frequency under enrichment was obtained. Based on the reference resonant frequency and the actual resonant frequency, the enriched state resonant frequency shift is determined; Based on the enriched state resonant frequency shift and the pre-established calibration relationship between the resonant frequency shift and the concentration of ferromagnetic metal abrasive particles, the concentration of ferromagnetic metal abrasive particles in the lubricating oil to be tested is determined.

7. The detection method according to claim 6, characterized in that, The determination of the concentration of ferromagnetic metal abrasive particles includes correcting the resonant frequency shift of the enriched state and the calibration relationship using a focusing degree coefficient; The process of determining the focus coefficient includes: Obtain the first model frequency shift corresponding to the uniform arc enrichment model and the second model frequency shift corresponding to the central bulge-type focusing model; The focusing coefficient is calculated based on the frequency shift of the first model, the frequency shift of the second model, and the frequency shift of the standard oil sample experiment.

8. The detection method according to claim 7, characterized in that, The formula for calculating the focus coefficient is as follows: in, For the first model frequency shift; For the second model frequency shift; For a known concentration (C) i The experimental average frequency shift was measured from the standard oil sample.

9. The detection method according to claim 6, characterized in that, After determining the concentration of ferromagnetic metal abrasive particles in the lubricating oil to be tested, the method further includes: Cut off the excitation current of the electromagnet so that the accumulated ferromagnetic metal abrasive particles are released with the flow of oil. The resonant frequency is reacquired under power failure. When the reacquired resonant frequency recovers to the preset baseline tolerance range, it is determined that the abrasive release is complete and the next detection cycle begins. If the frequency does not recover to the preset baseline tolerance range, extend the oil circulation flushing time until the resonant frequency recovers to the preset baseline tolerance range.

10. A microwave resonant oil abrasive particle detection system with electromagnetic enrichment, characterized in that, include: The microwave resonant oil abrasive particle detection sensor with electromagnetic enrichment as described in any one of claims 1-5 is connected to the oil circuit. A vector network analyzer, connected to the first and second RF connectors of the sensor, is used to provide a swept-frequency microwave excitation signal and acquire the amplitude-frequency response. A DC power supply, connected to the electromagnet of the sensor, is used to provide excitation current; The data processing device is connected to the vector network analyzer and the DC power supply respectively, and is used to perform the microwave resonant oil abrasive particle detection method with electromagnetic enrichment as described in any one of claims 6-9.

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