A method for collecting metal particles in aviation working fluids

Abstract

This invention discloses a method for collecting metal particles in aviation working fluids, belonging to the field of experimental and testing technology. The method employs an improved filtration device, which forms a central sealed area by placing a metal disc at the center of the filter plate and filter membrane, and a linearly adjustable electric stirring device is installed in the upper funnel. The collection steps include: initial filtration to trap working fluid particles on the filter membrane; adding cleaning fluid and determining high and low speeds through speed testing; first, stirring at high speed to clean contaminants on the surface of the metal particles, then switching to low speed to utilize the "tea leaf paradox" effect generated by liquid rotation to cause the metal particles to aggregate in the center; secondary filtration while maintaining low speed to enrich the metal particles in the central region of the filter membrane; finally, using conductive tape to collect the central metal particles for energy dispersive spectroscopy (EDS) analysis. This invention achieves effective separation of metal and non-metal particles, reduces interference from non-metallic contaminants and electron beam drift, and improves the efficiency and accuracy of EDS analysis.

Description

Technical Field

[0001] This invention relates to the field of testing and experimental technology, and specifically to a method for collecting metal particles in aviation working fluids. Background Technology

[0002] Metal particles mainly originate from the surfaces of aero-engine components and from lubricating oil. The former may have adverse effects on the components during use, while the latter can characterize the wear of lubricating oil system components. Therefore, it is necessary to analyze the composition of the metal particles to determine their material grade or type. Due to the small size of the metal particles, energy dispersive spectroscopy (EDS) is required for analysis.

[0003] Currently, the detection of metal particulate matter in aviation working fluids typically employs a general filtration device as specified in GJB 380.5A-2004. The specific procedure involves: filtering the aviation working fluid onto a filter membrane, then using conductive tape to collect the filtered material, followed by energy dispersive spectroscopy (EDS) analysis. However, the filtered material usually contains a large amount of non-metallic particles, and non-metallic contaminants also adhere to the surface of the metallic particles. Non-metallic particles generally have poor conductivity, which can cause electron beam drift. Both electron beam drift and contaminants can affect the quantitative results of EDS analysis, making it difficult to determine the material grade or type of the metallic particles.

[0004] To address the problem of particulate matter separation, existing technologies include methods for separating fine mineral powders using spiral chute separation, which can achieve the separation of mineral powders with differences in specific gravity. However, the content of metal particles in aviation working fluids is extremely low, making this method unsuitable. Chinese invention patent CN118701302A discloses a method for disassembling and obtaining metal particles from an aviation piston engine lubricating oil filter element, but its focus is on the disassembly process of the filter element itself, without addressing the problem of separating metal particles from non-metal particles on the filter membrane after filtration, nor does it address technical means to improve the accuracy of subsequent energy dispersive spectroscopy analysis.

[0005] Therefore, how to provide a method for collecting metal particles in aviation working fluids that can effectively separate metal particles from non-metal particles, reduce interference from non-metallic contaminants, and improve the efficiency and accuracy of energy dispersive spectroscopy analysis has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a method for collecting metal particles in aviation working fluids, which facilitates subsequent energy dispersive spectroscopy (EDS) analysis, solves the problem of difficulty in separating metal particles from non-metal particles, and also shows that the distribution of collected particles has a certain regularity, which can improve the efficiency of EDS analysis.

[0007] The technical solution of the present invention: A method for collecting metal particles in aviation working fluids employs a filtration device. The filtration device includes an upper funnel, a lower funnel, and a filtration system disposed between the two. An electric stirring device is configured on the upper funnel. The filtration system includes a filter plate and a filter membrane disposed on the upper part of the filter plate. A metal disc is placed at the center of the clamping point between the filter plate and the filter membrane. The collection method includes the following steps: Step 1: Initial filtration. Pour the aviation working fluid to be treated into the upper funnel, start the vacuum pump for the first vacuum filtration, and then rinse the inner wall of the upper funnel with solvent until the liquid sample on the inner wall is clean. Step 2: Test the rotation speed. Add analytical grade solvent to the upper funnel, start the electric stirrer to test the rotation speed, and record the high rotation speed that makes most of the filter material at the bottom rotate with the liquid, and the low rotation speed that makes most of the non-metallic material rotate with the liquid while the metallic particles gather in the center. Step 3: Rotation separation. First, switch the stirring speed to the high speed recorded in Step 2 to wash away some of the contaminants attached to the metal particles. After maintaining this speed for a period of time, switch it to the recorded low speed. Use the secondary flow generated by the liquid rotation to make the metal particles gather at the center of the bottom. Step 4: Collect metal particles. While maintaining the low rotation speed, start the vacuum pump for a second vacuum filtration. The central area is enriched with metal particles, the outer area is enriched with non-metal particles, and there is a blank isolation zone between the two areas. Step 5: Sampling and analysis. Remove the filter membrane and use the adhesive side of carbon conductive tape to collect the metal particles in the central area of ​​the filter membrane. Attach the carbon conductive tape with the metal particles to the electron microscope sample stage and collect backscattered electron images or surface distribution maps under high voltage for observation and energy dispersive spectroscopy analysis.

[0008] Furthermore, in step 1, the aviation working fluid needs to be pretreated by shaking, mixing, and defoaming before being poured into the upper funnel; after rinsing the liquid sample on the inner wall with anhydrous ethanol, the filtration continues until the filter membrane is dry.

[0009] Furthermore, in step 2, the solvent added includes anhydrous ethanol, acetone, petroleum ether, or other solvents with similar functions; the stirring blades of the electric stirring device are immersed in the liquid to a depth of 5mm to 15mm to ensure that the liquid forms a stable vortex during stirring.

[0010] Furthermore, the rotational speed of the electric stirring device is linearly adjustable within the range of 0 to 500 r / min, and it can switch between at least two set rotational speeds with a linear switching time of 10s to 30s.

[0011] Furthermore, the metal disc is a thin metal sheet with a thickness of 0.05mm to 0.2mm and a diameter of 10mm to 25mm, and its material includes stainless steel, aluminum alloy, and copper alloy.

[0012] Furthermore, the filter membrane is a nylon mesh filter membrane with a pore size of 1μm to 10μm; the filter plate is a sand core filter plate.

[0013] Furthermore, the filtration device also includes: a vacuum bottle disposed at the lower end of the lower funnel, a funnel cover disposed at the upper end of the upper funnel, an electric stirring device disposed on the funnel cover, and an air hole provided on the funnel cover.

[0014] Furthermore, the stirring device includes: a stirring rod, a stirring blade disposed at the bottom end of the stirring rod, and a motor disposed at the upper end of the stirring rod; the height at which the stirring rod is inserted into the upper funnel is adjustable, and the stirring blade and the stirring rod are made of stainless steel.

[0015] Furthermore, the device also includes a clamp mounted on the filtration system, and a solvent-resistant rubber stopper is provided at the mouth of the vacuum bottle for sealing the lower funnel to the vacuum bottle.

[0016] Furthermore, a through hole is provided on the side wall of the vacuum bottle, and a connecting pipe is integrally formed at the through hole, which is connected to the vacuum pump.

[0017] The beneficial effects of this invention are as follows: The filtration device of this invention collects less non-metallic material, thus reducing electron beam drift; high-speed stirring can wash away some contaminants attached to metal particles, reducing interference from contaminants and improving the accuracy of energy dispersive spectroscopy (EDS) analysis results for metal particles. The metal particles collected by the device of this invention are more concentrated, resulting in more metal particles in a single field of view during EDS analysis, reducing the time spent switching fields of view to search for metal particles; simultaneously, lower-density materials such as aluminum alloys and titanium alloys are distributed on the periphery, while higher-density materials such as steel, high-temperature alloys, and large-sized particles are distributed in the middle, making EDS analysis more targeted and reducing the time wasted on blind analysis. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the specific embodiments of the present invention, the drawings used in the description of 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.

[0019] Figure 1 This is a schematic diagram of the filter device structure of the present invention; Figure 2 This is a partial schematic diagram of the filtration device of the present invention; Figure 3This is a schematic diagram of the filter membrane after filtration by a typical filtration device; Figure 4 This is a schematic diagram of the filter membrane after filtration by the filtration device of the present invention; Reference numerals: Vacuum pump-1, Metal disc-2, Upper funnel-3, Filter membrane-4, Support plate filter plate-5, Lower funnel-6, Clamp-7, Solvent-resistant rubber stopper-8, Vacuum bottle-9, Connecting pipe-10. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, it should not be construed that the scope of the subject matter of the present invention is limited to the following embodiments. All modifications, substitutions and alterations made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention are included within the scope of the present invention.

[0021] The method of this invention utilizes the secondary flow generated by liquid rotation, where heavy particles aggregate at the bottom, creating the "tea paradox." Separation is achieved through suction filtration when the rotation speed is just right to separate metal particles from non-metallic matter. The objective of this invention is achieved through the following technical solution: (1) A general filtration device, comprising an upper funnel 3, a filter membrane 4, a support plate filter plate 5 with a sealing ring, a lower funnel 6, a clamp 7, a solvent-resistant rubber stopper 8, a vacuum bottle 9, a vacuum pump 1 and a connecting pipe 10. The upper funnel 7 has a capacity of 250ml and is marked with graduations. The filter membrane has a diameter of 45-50mm. The vacuum degree of the vacuum pump 1 is adjustable and the vacuum degree is not greater than 0.087MPa.

[0022] (2) Unlike general filtration devices, the filter plate 5 with sealing ring is made of sand core filter plate, and a metal disc 2 of aluminum or other materials with a thickness of 0.05mm to 0.2mm and a diameter of 10mm to 25mm needs to be placed flat in the center of the filter plate. The metal disc is located below the filter membrane so that the liquid cannot pass through the filter membrane in this area during vacuum filtration. The filter membrane 4 is made of nylon mesh material with a pore size of 1 to 10μm. The nylon material can ensure that it will not be damaged when stirring and adhering to metal particles. The vacuum pump is placed in a far position to avoid its working vibration affecting the liquid flow channel.

[0023] (3) The funnel cover is equipped with a special electric stirring device and has an air hole that allows air to pass through. The rotation speed of the stirring device is linearly adjustable, with a speed range of 0 to 500 r / min. At least two speeds can be recorded and set at the same time. When switching from one speed to another, the speed changes linearly and slowly, with a switching time of 10 to 30 seconds. The stirring rod is located in the center of the funnel cover and passes through the central axis of the upper funnel after being covered. The stirring blade is 5 mm × 20 mm in size and 0.6 mm in thickness. The stirring blade is welded to the bottom of the stirring rod. The height of the stirring rod inserted into the funnel is adjustable. The stirring blade and stirring rod are made of stainless steel.

[0024] (4) When using, clean the filter device and stirrer, and install a new filter membrane. Soak, shake, and defoam the aviation working fluid. Pour the well-treated aviation working fluid into the upper funnel and vacuum filter. Rinse the inner wall of the funnel with anhydrous ethanol, acetone or petroleum ether until the liquid sample on the inner wall of the upper funnel is rinsed clean. Vacuum filter until dry and then turn off the vacuum pump.

[0025] (5) Add 100ml to 200ml of anhydrous ethanol, acetone or petroleum ether. The anhydrous ethanol, acetone or petroleum ether should be chemically pure or analytically pure. Adjust the height of the stirring rod inserted into the funnel so that the stirring blade is about 10mm below the liquid surface. The position of the stirring blade can be adjusted according to the rotation of the stirring liquid and the generation of vortices in the liquid.

[0026] (6) Cover the funnel with the electric stirring device, start the electric stirring device to test the speed, slowly increase the stirring speed to the speed at which most of the filtered material at the bottom rotates with the liquid and record it, slowly decrease the stirring speed to the speed at which most of the non-metallic material rotates with the liquid and the metallic particles gather in the center and record it.

[0027] (7) Switch the stirring speed to the recorded high speed. After reaching the high speed, switch the stirring speed to the recorded low speed. The liquid rotates and generates a secondary flow. Heavy particles gather at the bottom and form the tea paradox. The recorded low speed can just separate most of the metal particles and non-metals. If there are many contaminants attached to the metal particles, extend the stirring time of the high speed.

[0028] (8) When the low speed recorded is reached, start the vacuum pump for secondary filtration. Since the 10mm to 25mm area in the center of the filter plate with the sealing ring is sealed, the liquid can only be drawn down from the filter membrane outside the 10mm to 25mm area. When the liquid level is drawn close to the bottom, the secondary flow weakens, the central liquid flows to the edge and washes away the central metal particles in the 10mm to 25mm area to form a near-blank area. Continue filtration until dry.

[0029] (9) Take out the filter membrane. The central area of ​​the filter membrane obtained by the device is mainly composed of metal particles, while the area outside the 10mm to 25mm region is mainly composed of non-metallic particles. There is a near-blank area between the two, which can reduce the non-metallic particles that are picked up during sampling.

[0030] (10) Select carbon conductive tape with a width of 10mm to 25mm. The conductive material of the carbon conductive tape is carbon powder and the substrate is non-woven fabric. Cut a suitable length of carbon conductive tape and use the adhesive layer of the carbon conductive tape to stick the metal particles in the center of the filter membrane. If there are many metal particles, stick them again in another area of ​​the carbon conductive tape.

[0031] (11) The adhesive layer after removing the release layer is attached to the electron microscope sample stage, with the side of the adhesive layer with the metal particles facing the electron microscope tube. Backscattered electron images or surface distribution maps are collected under a high voltage of 20-30KV for observation and energy dispersive spectroscopy (EDS) analysis. The device collects fewer non-metallic materials, which reduces electron beam drift; high-speed stirring can wash away some contaminants attached to the metal particles, reducing interference from contaminants and thus improving the accuracy of the EDS analysis results of metal particles. The metal particles collected by this device are more concentrated, and there are more metal particles in one field of view during EDS analysis, which reduces the time spent switching fields of view to search for metal particles; at the same time, the less dense aluminum alloys, titanium alloys, etc. are distributed on the periphery, while the denser steel, high-temperature alloys, etc., and large-sized particles are distributed in the middle, making the EDS analysis more targeted and reducing the time wasted on blind analysis.

[0032] Example 1: A device for collecting metal particles from aviation working fluids. This device is an improved design based on a traditional filtration device, particularly suitable for separating and enriching trace metal particles from aviation working fluids for subsequent energy dispersive spectroscopy analysis. (Refer to...) Figure 1 and Figure 2 The device includes an upper funnel 3, a lower funnel 6, and a filtration system disposed between the two. The upper funnel 3 has a capacity of 250 ml and is marked with graduations for easy observation of the liquid volume. A vacuum bottle 9 is provided at the lower end of the lower funnel 6 for receiving the filtrate.

[0033] The filtration system includes a support plate filter 5 and a filter membrane 4 with a diameter of 47 mm, disposed on top of the support plate filter 5. The support plate filter 5 is a sand core filter plate, with a metal disc 2 flatly placed in its central area, directly below the filter membrane 4. The metal disc 2 is 0.1 mm thick, 18 mm in diameter, and made of aluminum. The function of the metal disc 2 is to create a sealed area in the central region of the filter membrane 4 during filtration, preventing liquid from passing through and forcing liquid to pass only through the edge region of the filter membrane 4.

[0034] The filter membrane 4 is made of nylon mesh with a pore size of 5μm. Nylon material has good mechanical strength, ensuring it will not break during subsequent stirring operations and when adhering to metal particles. The filtration system is clamped and fixed by clamps 7 to ensure a tight seal. The lower funnel 6 is sealed to the vacuum bottle 9 with a solvent-resistant rubber stopper 8 to prevent air leakage.

[0035] The upper funnel 3 is equipped with a funnel cover 31 at its upper end, and the funnel cover 31 has an air hole 35 to balance the air pressure. An electric stirring device is mounted on the funnel cover 31, which includes a motor 32, a stirring rod 33, and a stirring blade 34. The stirring rod 33 is located at the center of the funnel cover 31, and after the funnel cover 31 is closed, the stirring rod 33 extends into the funnel along the central axis of the upper funnel 3. The stirring blade 34 is welded to the bottom end of the stirring rod 33, and its dimensions are 5mm × 20mm with a thickness of 0.6mm. The insertion height of the stirring rod 33 into the funnel is adjustable to accommodate different liquid levels. The stirring blade 34 and the stirring rod 33 are made of 304 stainless steel, which has good corrosion resistance.

[0036] The electric stirring device has a linearly adjustable rotational speed, ranging from 0 to 500 r / min. It features speed recording and setting functions, capable of recording and setting at least two different speed values. The speed transition from one value to another is linear and gradual, with a switching time of 10 to 30 seconds.

[0037] A through hole is provided on the side wall of the vacuum bottle 9, and a connecting pipe 10 is integrally formed at the through hole, which is connected to the vacuum pump 1. The vacuum degree of the vacuum pump 1 is adjustable, and the vacuum degree is not greater than 0.087 MPa. To avoid the vibration of the vacuum pump affecting the liquid flow channel, the vacuum pump 1 is placed at a distance from the filter device.

[0038] The collection device provided in this embodiment provides a hardware foundation for the subsequent separation of metal and non-metal particles by adding a metal disc to the center of the filter plate of a traditional filtration device to form a central sealing area and configuring an electric stirring device with linearly adjustable speed.

[0039] Example 2: A method for collecting metal particles in aviation working fluids, using the device described in Example 1, includes the following steps: Step 1: Apparatus preparation and sample pretreatment. Clean the filter and stirrer, install a new filter membrane 4 (5μm pore size), and place an aluminum metal disc 2 with a diameter of 18mm and a thickness of 0.1mm in the center of the filter plate 5 on the support plate. Perform ultrasonic dispersion, shaking and mixing, and static defoaming pretreatment on the aviation working fluid to be treated to ensure that the sample is uniform and free of bubbles.

[0040] Step 2: The first filtration is the initial filtration. Pour the pretreated aviation working fluid into the upper funnel 3 and start the vacuum pump 1 for the first vacuum filtration. After filtration, rinse the inner wall of the upper funnel 3 several times with anhydrous ethanol until the residual liquid sample on the inner wall is washed away. Continue filtration until the filter membrane 4 is dry, then turn off the vacuum pump. At this point, the particulate matter in the aviation working fluid is trapped on the filter membrane 4.

[0041] Step 3: Speed ​​parameter calibration. Add 150 ml of analytical grade anhydrous ethanol to the upper funnel 3. Adjust the insertion height of the stirring rod 33 so that the stirring blade 34 is about 10 mm below the liquid surface. Cover the funnel with the lid 31 and start the electric stirring device to test the speed. Slowly increase the stirring speed and observe the movement of particles on the filter membrane 4. Record the high speed value (e.g., 200 r / min) that allows most of the filtered material at the bottom to rotate with the liquid. Then slowly decrease the stirring speed and record the low speed value (e.g., 80 r / min) that allows most of the non-metallic particles to rotate with the liquid while the metallic particles begin to aggregate in the center.

[0042] Step 4: Rotational separation. First, switch the stirring speed to the recorded high speed (200 r / min) and maintain stirring for 30 seconds. This high-speed stirring ensures that the particles on filter membrane 4 are fully suspended and uses liquid shear force to wash away some non-metallic contaminants attached to the surface of the metal particles. Then, slowly reduce the stirring speed to the recorded low speed (80 r / min) with a linear switching time of 20 seconds. At the low speed, the liquid rotation generates a secondary flow, creating the "tea leaf paradox" effect: denser metal particles accumulate in the central area at the bottom, while less dense non-metallic particles are distributed on the periphery.

[0043] Step 5: The second filtration is for enrichment and collection. While maintaining low-speed stirring (80 r / min), vacuum pump 1 is started for the second vacuum filtration. Because the central region of filter membrane 4 is sealed by the metal disc 2, the liquid can only be drawn downwards from the area outside the 18 mm diameter of filter membrane 4. As the liquid level gradually decreases, the secondary flow effect weakens, and the liquid in the central region flows towards the edge, further washing away and retaining the metal particles accumulated in the center. Simultaneously, a near-blank isolation zone is formed between the metal particle enrichment area and the non-metal particle area. Filtration continues until filter membrane 4 is dry.

[0044] Step 6: Sampling and Energy Dispersive Spectroscopy (EDS) analysis. Filter membrane 4 is removed. Observation reveals that the central region of the filter membrane is dominated by metallic particles, while the outer region is dominated by non-metallic particles, with a clear blank isolation zone between the two. Figure 4As shown. A 12mm wide carbon conductive tape was used to adhere the metal particles from the central region of filter membrane 4. The carbon conductive tape with the adhered metal particles was then attached to the electron microscope stage, with the side with the adhered metal particles facing the microscope tube. Backscattered electron images or surface distribution maps were acquired under a 25kV high voltage for observation and energy dispersive spectroscopy (EDS) analysis.

[0045] The method in this embodiment effectively separates metals and non-metals: through the "tea leaf paradox" effect, metal particles are enriched in the center of the filter membrane, significantly reducing interference from non-metallic particles; it improves the accuracy of energy dispersive spectroscopy (EDS) analysis: high-speed stirring cleans contaminants attached to the surface of metal particles, reducing electron beam drift; the centrally enriched metal particles are easy to locate quickly, and more metal particles can be observed within a single field of view, improving analysis efficiency; and it exhibits strong distribution regularity: among the enriched metal particles, less dense aluminum alloys and titanium alloys are distributed on the periphery, while denser steel, high-temperature alloys, and large-sized particles are distributed in the center, making EDS analysis more targeted and reducing the time spent on blind searches.

[0046] Comparative Example 1: Collection effect using a conventional filtration device. Metal particles were collected from the same batch of aviation working fluid using a conventional filtration device (without a stirring device or metal discs) as described in GJB 380.5A-2004 as a comparative example.

[0047] Operating procedure: After shaking the aviation working fluid well, pour it directly into the upper funnel of the conventional filtration device. Start the vacuum pump to perform filtration, trapping particulate matter in the working fluid onto the filter membrane. Rinse the inner wall of the funnel with anhydrous ethanol and continue filtration until dry.

[0048] Remove the filter membrane and use carbon conductive tape to collect the filtered material. Attach the conductive tape with the collected material to the electron microscope stage and perform energy dispersive spectroscopy (EDS) analysis under the same conditions.

[0049] Collection effect and comparison: On the filter membrane after filtration by the traditional device, metal particles and non-metal particles are mixed and distributed without obvious regional division (e.g., Figure 3 (As shown). In the filter membrane obtained in Example 2, metal particles are concentrated in the central region, surrounded by non-metallic particles, with a blank isolation area between them (as shown). Figure 4 (As shown). Traditional methods for energy dispersive spectroscopy (EDS) suffer from frequent electron beam drift due to the presence of numerous non-metallic particles with poor conductivity, requiring repeated field-of-view adjustments and consuming significant time to search for metallic particles. The method in Example 2, however, allows for the observation of multiple metallic particles within a single field of view due to the concentrated distribution of these particles, significantly improving analytical efficiency.

[0050] In traditional methods, non-metallic contaminants adhering to the surface of metal particles are not cleaned, directly interfering with the quantitative results of energy dispersive spectroscopy (EDS), making it difficult to determine the material grade of some samples. The method in Example 2 pre-cleans the contaminants on the surface of the metal particles through high-speed stirring, resulting in more accurate and reliable EDS analysis results.

[0051] In summary, this invention effectively solves the technical problem of separating metallic and non-metallic particles in aviation working fluids by improving the filtration device and introducing the "tea paradox" effect separation method. It provides high-quality samples for subsequent energy dispersive spectroscopy analysis and has significant practical value and prospects for promotion.

[0052] The method for collecting metal particles in aviation working fluids provided by this invention has been described in detail above. Specific examples have been used to illustrate the structure and working principle of this invention. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make several improvements and modifications to this invention without departing from the principles of this invention, and these improvements and modifications also fall within the scope of protection of the claims of this invention.

Claims

1. A method for collecting metal particles in aviation working fluids, characterized in that: The collection is carried out using a filtration device, which includes an upper funnel (3), a lower funnel (6), and a filtration system disposed between the two. An electric stirring device is disposed on the upper funnel (3). The filtration system includes a filter plate (5) and a filter membrane (4) disposed on the upper part of the filter plate (5). A metal disc (2) is placed at the center of the clamping point between the filter plate (5) and the filter membrane (4). The collection method includes the following steps: Step 1: Initial filtration. Pour the aviation working fluid to be treated into the upper funnel (3), start the vacuum pump to perform the first vacuum filtration, and then rinse the inner wall of the upper funnel (3) with solvent until the liquid sample on the inner wall is clean. Step 2: Test the rotation speed. Add solvent to the upper funnel (3), start the electric stirring device to test the rotation speed, and record the high rotation speed that makes most of the filter material at the bottom rotate with the liquid, and the low rotation speed that makes most of the non-metallic material rotate with the liquid while the metal particles gather in the center. Step 3: Rotation separation. First, switch the stirring speed to the high speed recorded in Step 2 to wash away some of the contaminants attached to the metal particles. After maintaining this speed for a period of time, switch it to the recorded low speed. Use the secondary flow generated by the liquid rotation to make the metal particles gather at the center of the bottom. Step 4: Collect metal particles. While maintaining the low rotation speed, start the vacuum pump for a second vacuum filtration. The central area is enriched with metal particles, the outer area is enriched with non-metal particles, and there is a blank isolation zone between the two areas. Step 5: Sampling and analysis. Take out the filter membrane (4), use the adhesive layer of carbon conductive tape to pick up the metal particles in the central area of ​​the filter membrane (4), stick the carbon conductive tape with the metal particles on it to the electron microscope sample stage, and collect backscattered electron images or surface distribution maps under high voltage for observation and energy spectrum analysis.

2. The method for collecting metal particles in aviation working fluids according to claim 1, characterized in that: In step 1, the aviation working fluid needs to be pretreated by shaking, rinsing and defoaming before being poured into the upper funnel (3); the liquid sample on the inner wall is rinsed clean with solvent and then filtered until the filter membrane (4) is dried.

3. The method for collecting metal particles in aviation working fluids according to claim 1, characterized in that: In step 2, the added solvent includes anhydrous ethanol, acetone, petroleum ether or other solvents with similar functions, and the solvent is analytically pure or chemically pure; the stirring blade of the electric stirring device is immersed in the liquid to a depth of 5mm to 15mm to ensure that the liquid forms a stable vortex during stirring.

4. The method for collecting metal particles in aviation working fluids according to claim 1, characterized in that: The rotation speed of the electric stirring device is linearly adjustable within the range of 0 to 500 r / min, and it can switch between at least two set rotation speeds with a linear switching time of 10s to 30s.

5. The method for collecting metal particles in aviation working fluids according to claim 1, characterized in that: The metal disc (2) is a thin metal sheet with a thickness of 0.05mm to 0.2mm and a diameter of 10mm to 25mm, and its material includes stainless steel, aluminum alloy and copper alloy.

6. The method for collecting metal particles in aviation working fluids according to claim 1, characterized in that: The filter membrane (4) is a nylon mesh filter membrane with a pore size of 1μm to 10μm; the filter plate (5) is a sand core filter plate.

7. The method for collecting metal particles in aviation working fluids according to claim 1, characterized in that: The filtration device further includes: a vacuum bottle (9) located at the lower end of the lower funnel (6), a funnel cover (31) located at the upper end of the upper funnel (3), an electric stirring device being provided on the funnel cover (31), and an air hole being provided on the funnel cover (31).

8. The method for collecting metal particles in aviation working fluids according to claim 1, characterized in that: The stirring device includes: a stirring rod (33), a stirring blade (34) disposed at the bottom of the stirring rod (33), and a motor (32) disposed at the upper end of the stirring rod (33); the height of the stirring rod (33) inserted into the upper funnel (3) is adjustable, and the stirring blade (34) and the stirring rod (33) are made of stainless steel.

9. The method for collecting metal particles in aviation working fluids according to claim 1, characterized in that: The device also includes a clamp (7) clamped to the filtration system, and a solvent-resistant rubber stopper (8) is provided at the mouth of the vacuum bottle (9) for sealing connection between the lower funnel (6) and the vacuum bottle (9).

10. The method for collecting metal particles in aviation working fluids according to claim 1, characterized in that: The vacuum bottle (9) has a through hole on its side wall, and a connecting pipe (10) is integrally formed and connected to the through hole. The connecting pipe (10) is connected to the vacuum pump (1).

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