Collecting device for engine exhaust in-situ particulate matter and using method of collecting device

Abstract

The invention discloses an engine exhaust in-situ particulate matter collecting device and a using method thereof, and belongs to the technical field of engine emission control. Comprising a main exhaust pipe, a main exhaust pipe, an electric three-way valve, a branch exhaust pipe, a sampling device and a cooling system, the main exhaust pipe is connected with an inlet of the electric three-way valve through a flange, two outlets of the electric three-way valve are respectively connected with the main exhaust pipe and the branch exhaust pipe through sealing buckles, and the branch exhaust pipe is connected with the sampling device through two customized flanges and then is connected into the main exhaust pipe; the sampling device comprises a sampling device shell and a sampling plate. According to the device, the loss rate of volatile components is reduced by 67%, a more reliable in-situ analysis means is provided for researching a particulate matter generation mechanism, and a reliable sampling method and technical support are provided for deeply researching physicochemical characteristics of particulate matters discharged by an engine.

Description

Technical Field

[0001] The present invention belongs to the technical field of engine emission control, and particularly relates to a device for collecting in-situ particulate matter in engine exhaust and a method for using the same. Background Technique

[0002] With the continuous improvement of the global environmental governance system, the control of particulate matter emissions from motor vehicle exhaust has become a hot cross-disciplinary research topic in internal combustion engine combustion science and atmospheric environmental science. The latest assessment report (IARC Monograph 105) of the International Agency for Research on Cancer (IARC) has clearly classified particulate matter emitted by internal combustion engines as a Group 1 carcinogen. Research shows that the health hazard of such particulate matter is significantly negatively correlated with the particle size distribution, and the nucleation mode particulate matter with a particle size less than 100 nm accounts for more than 90% in terms of number concentration. Further research has found that ultrafine particulate matter has the following characteristic hazards: 1. It has an extremely high specific surface area (100 - 300 m² / g), providing an ideal carrier for the adsorption of toxic substances such as polycyclic aromatic hydrocarbons (PAHs) and heavy metals; 2. The aerodynamic diameter is less than 2.5 μm (PM2.5), and particles with a size below 50 nm can penetrate the alveolar-capillary barrier; 3. The environmental migration ability is 2 - 3 orders of magnitude higher than that of conventional particulate matter.

[0003] In terms of regulatory standards, China's "Emission Limits and Measurement Methods for Exhaust Pollutants from Vehicle Compression-Ignition Engines (China Phase VI)" (GB 17691-2018) has included particulate matter number for the first time in the mandatory control indicators. However, the existing sampling technology based on the dilution channel method (such as the CFR 1065 procedure) has the following technical defects: 1. Temperature sensitivity: Experimental data show that when the temperature of the dilution air fluctuates in the range of 80 - 150 °C, the measurement deviation of the nucleation mode particulate matter number concentration reaches 30 - 50%; 2. Secondary nucleation effect: When the dilution ratio exceeds 10:1, obvious secondary nucleation phenomena will occur in semi-volatile organic compounds; 3. Agglomeration inhibition: When the residence time is less than 1 second, the agglomeration efficiency of particulate matter decreases by more than 60%.

[0004] This indirect sampling method will cause changes in the physical and chemical properties such as the particle size distribution, microscopic characteristics, surface functional groups, and activation energy of engine emission particles, resulting in the fact that the particulate matter collected by dilution cannot correctly reflect the emission characteristics of the original particulate matter in the engine. Obviously, it is very necessary to obtain the physical and chemical properties of in-situ particulate matter in the engine exhaust pipe. The collection and analysis of in-situ particulate matter in the engine exhaust pipe are the premise for the research and development of particulate matter post-treatment technology.

[0005] Therefore, there is an urgent need in this field to develop an in-situ sampling device for engine exhaust particulate matter and its usage method. Among them, the thermophoretic effect provides an innovative solution: when the particulate matter generated by engine combustion enters a region with a temperature gradient along with the high-temperature exhaust gas, the particulate matter will be subjected to a thermophoretic force in the direction opposite to the temperature gradient. The thermophoretic force causes the particulate matter to move towards the region with a lower temperature until it is deposited on the wall with a lower temperature. This characteristic provides theoretical support for the in-situ collection of particulate matter under non-diluted conditions and is the core scientific basis of the present invention. Summary of the Invention

[0006] The present invention provides a device for collecting in-situ particulate matter from engine exhaust and its usage method, aiming to achieve the morphological preservation capture of exhaust particulate matter in a high-temperature flow field. Through the embedded highly thermally conductive copper sampling plate and the copper mesh device on the sampling plate, the device can directly complete the particle size segmentation and in-situ copper mesh collection of particulate matter from the exhaust pipe section during the operation of the engine. The copper mesh particle sample can be directly used for high-magnification transmission electron microscopy analysis, effectively avoiding the problem of distortion of the microscopic characteristics and surface activation energy of particulate matter caused by secondary nucleation in diluted sampling.

[0007] The present invention provides a device for collecting in-situ particulate matter from engine exhaust. The technical solution adopted is as follows, including: a main exhaust pipe, a main exhaust pipe, an electric three-way valve, a branch exhaust pipe, a sampling device, and a cooling system; The main exhaust pipe is connected to the inlet of the electric three-way valve through a flange. The two outlets of the electric three-way valve are respectively connected to the main exhaust pipe and the branch exhaust pipe through sealing clips. The branch exhaust pipe is connected to the sampling device through two customized flanges and then connected to the main exhaust pipe; The sampling device includes a sampling device housing and a sampling plate. The sampling plate is made of highly thermally conductive copper material. The cooling system is connected to the sampling plate to control the temperature of the sampling plate wall, create a temperature difference between the flow domain where the sampling plate is located and the exhaust flow, and cause the ultrafine particulate matter in the exhaust flow to gather towards the area where the sampling plate is located under the action of the thermophoretic force.

[0008] Furthermore, a thermal mass flowmeter is provided in the main exhaust pipe, a back pressure sensor and a gas flowmeter are provided in the branch exhaust pipe, a gas flow velocity meter is provided in the sampling device, and the electric three-way valve automatically adjusts the exhaust gas flow rates of the two branches according to the signals of the back pressure sensor and the gas flowmeter to maintain the stability of the air flow and pressure in the branch exhaust pipe.

[0009] Furthermore, a groove is machined on the outer side of the inner diameter of the customized flange for installing a high-temperature resistant support net, a quartz filter membrane, and a sealing ring; the high-temperature resistant support net, the quartz filter membrane, and the sealing ring are sequentially placed on the concave plane of the customized flange, and the height of the sealing ring is slightly higher than the plane of the customized flange to ensure that all exhaust gas passes through the quartz filter membrane to achieve particle size segmentation, and the high-temperature resistant support net is used to support quartz filter membranes with different pore sizes to control the entry of particles with desired particle size dimensions into the sampling device.

[0010] Furthermore, a copper mesh fixing device and a sampling plate positioning buckle are installed on the sampling plate. The housing of the sampling device is square and is connected in series with the branch exhaust pipe at both ends. Trapezoidal grooves are opened on both opposite sides of the housing of the sampling device for embedding a sampling plate made of copper with a high heat transfer coefficient. Two buckles are installed near each trapezoidal groove to fix the position of the sampling plate in the groove through the sampling plate positioning buckle. The sampling plate is a trapezoid with a narrow inner side and a wide outer side; the outer side of the sampling plate is connected to the electrode plate of the cooling system, and a high-temperature sensor is provided inside to monitor the working temperature of the sampling plate in real time, and a small through-hole handle is provided for convenient removal.

[0011] Furthermore, a copper mesh through-hole tray is arranged inside the sampling plate. A copper mesh is provided on the copper mesh through-hole tray, and the copper mesh is fixed by a copper mesh fixing device. The copper mesh fixing device is a copper mesh positioning buckle, and the particles collected by the copper mesh can be directly used for high-magnification transmission electron microscopy analysis.

[0012] Furthermore, the cooling system is a semiconductor temperature control system, including a heat absorption electrode plate, a heat dissipation electrode plate, and a cooling water tank. The heat absorption electrode plate forms an efficient thermal interface with the outer surface of the particulate sampling plate through high thermal conductivity silicone grease, and its heat dissipation electrode plate is coupled with the cooling water tank to accelerate heat dissipation; the semiconductor temperature control system cooperates with the reading of the high-temperature sensor to precisely control the temperature of the sampling plate and create a stable temperature gradient field.

[0013] Furthermore, the main body of the branch exhaust pipe is constructed by using a SUS310S austenitic stainless steel bellows, and the outer wall of the pipeline is coated with an aerogel-ceramic fiber composite heat insulation layer; The housing of the sampling device is made of stainless steel, and the outer wall is also coated with an aerogel-ceramic fiber composite heat insulation layer to prevent the temperature in the branch exhaust pipe from decreasing and forming a temperature difference with the sampling plate.

[0014] A method for using a device for collecting in-situ particulate matter from engine exhaust includes the following steps: S1. Connect the inlet of an electric three-way valve to the main exhaust pipe through a flange. One outlet of the electric three-way valve is connected to the main exhaust pipe through a quick-release sealing buckle, and the other outlet is connected in parallel to the branch exhaust pipe through a quick-release sealing buckle; S2. Connect the sampling device in series with the branch exhaust pipe through two customized flanges. The exhaust gas flowing through the sampling device continues to flow into the main exhaust pipe through the branch exhaust pipe. The quartz filter membrane in the customized flange realizes particle size segmentation of particulate matter. S3. When the exhaust gas flows through the sampling device, cool the wall surface of the sampling plate through the cooling system to create a temperature difference between the area where the sampling plate is located and the exhaust gas flow. Under the action of thermophoretic force, the ultrafine particulate matter in the exhaust gas flow gathers towards the area where the sampling plate is located, increasing the local concentration of particulate matter. In-situ sampling is achieved through the copper mesh inside the sampling plate.

[0015] Furthermore, in S2, the high-temperature resistant support net in the customized flange supports quartz filter membranes with different pore sizes. By replacing the quartz filter membrane, the particle size of the particulate matter entering the sampling device is controlled, realizing particle size classification sampling.

[0016] Furthermore, in S3, the cooling system adjusts the current polarity and power through the PID closed-loop control module, and combines with real-time monitoring by the high-temperature sensor to control the surface temperature of the sampling plate at 150 ± 2 °C, maintaining a stable temperature gradient field and avoiding the condensation of water vapor to pollute the particulate matter.

[0017] Advantages of the present invention: 1. The device of the present invention is based on the thermophoretic effect. By creating a temperature gradient between the sampling plate and the exhaust gas flow through the cooling system, the ultrafine particulate matter gathers towards the low-temperature sampling plate under the action of thermophoretic force, and the local concentration increases significantly. Compared with the traditional physical adsorption method, the collection efficiency of small particle size particulate matter is greatly improved, solving the problem of poor collection effect of traditional methods on nuclear mode particles.

[0018] 2. The 300-mesh electron microscope copper mesh inside the sampling plate can directly capture particulate matter without additional sample preparation steps, avoiding the interference of human processing on the microscopic morphology of particulate matter (such as surface functional groups and activation energy). The collected samples can be directly used for high-magnification transmission electron microscope analysis, retaining the original contour and internal structure of the particulate matter, providing accurate data for microscopic mechanism research.

[0019] 3. The high-temperature resistant support net in the customized flange can support quartz filter membranes with different pore sizes. The quartz filter membrane is detachable. By replacing the filter membrane, the particle size of the particulate matter entering the sampling device can be selectively controlled, realizing classification sampling. This function meets the targeted research needs for particulate matter with different particle sizes (such as PM2.5 and ultrafine particles), providing technical support for particle size distribution and health risk assessment.

[0020] 4. Adopting modular connection methods such as flanges and quick-release sealing buckles, the branch exhaust pipe, sampling device and cooling system can be quickly installed and replaced to adapt to different engine exhaust pipe lines. The pipeline and the outer wall of the shell are coated with an aerogel-ceramic fiber composite heat insulation layer, which has excellent high-temperature resistance and heat insulation performance, ensuring the stability of the core flow temperature of the exhaust gas and maintaining an effective temperature difference.

[0021] 5. The back pressure sensor and gas flow meter in the branch exhaust pipe feed back signals in real time, and the electric three-way valve automatically adjusts the exhaust gas flow of the main / branch pipeline to maintain the stability of the branch air flow and pressure, avoiding the influence of exhaust gas fluctuations on the sampling efficiency and ensuring the repeatability and reliability of data. Description of the Drawings

[0022] For ease of explanation, the present invention will be described in detail by the following specific embodiments and accompanying drawings.

[0023] Figure 1 is a schematic structural diagram of the present invention; Figure 2 is a sectional view A-A of the sampling device of the present invention; Figure 3 is the present invention Figure 2 detailed structural diagram of the copper mesh fixing device 16; Figure 4 is a working schematic diagram of the cooling system equipment of the present invention; Figure 5 is a front view of the special flange of the present invention; Figure 6 is the present invention Figure 5 sectional view B-B of the special flange; Figure 7 is a schematic diagram of the high-temperature resistant support net, quartz filter membrane and sealing ring in the special flange of the present invention; Figure 8 is a TEM image of diesel engine combustion particles collected by the device of the present invention taken by a high-power transmission electron microscope; In the figure: 1, main exhaust pipe; 2, thermal mass flow meter; 3, pressure sensor; 4, electric three-way valve; 5, flange; 6, branch exhaust pipe; 7, customized flange; 7.1, high-temperature resistant support net; 7.2, quartz filter membrane; 7.3, sealing ring; 8, sampling device; 9, cooling system; 10, gas flow meter; 11, high-temperature sensor; 12, sampling plate; 13, gas flow velocity meter; 14, sampling device housing; 15, small through-hole handle; 16, copper mesh fixing device; 17, sampling plate positioning buckle; 18, copper mesh; 19, copper mesh positioning buckle; 20, copper mesh through-hole tray; 21, heat absorption electrode plate; 22, heat dissipation electrode plate; 23, cooling water tank. Detailed Embodiments

[0024] The following are specific embodiments of the present invention. In combination with the accompanying drawings, the technical solutions of the present invention will be further described, but the present invention is not limited to these embodiments; in the following description, providing specific details such as specific configurations and components is only to help comprehensively understand the embodiments of the present invention. Therefore, those skilled in the art should clearly understand that various changes and modifications can be made to the embodiments described here without departing from the scope and spirit of the present invention. In addition, descriptions of known functions and structures are omitted for clarity and conciseness.

[0025] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0026] As Figures 1 to 7 shown in a specific embodiment of a device for collecting in-situ particulate matter from an engine exhaust, which includes: a main exhaust pipe, a main exhaust pipe 1, an electric three-way valve 4, a branch exhaust pipe 6, a sampling device 8, and a cooling system 9; The main exhaust pipe is connected to the inlet of the electric three-way valve 4 through a flange 5. The two outlets of the electric three-way valve 4 are respectively connected to the main exhaust pipe 1 and the branch exhaust pipe 6 through sealing buckles. The branch exhaust pipe 6 is connected to the sampling device 8 through two customized flanges 7 and then connected to the main exhaust pipe 1; The sampling device 8 includes a sampling device housing 14 and a sampling plate 12. The sampling plate 12 is made of high thermal conductivity copper material. The cooling system 9 is connected to the sampling plate 12 to control the wall temperature of the sampling plate 12, create a temperature difference between the flow domain where the sampling plate 12 is located and the exhaust flow, and make the ultrafine particulate matter in the exhaust flow gather towards the area where the sampling plate 12 is located under the action of thermophoretic force.

[0027] Specifically, a thermal mass flowmeter 2 is provided in the main exhaust pipe 1, a back pressure sensor 3 and a gas flowmeter 10 are provided in the branch exhaust pipe 6, and a gas flow velocity meter 13 is provided in the sampling device 8. Among them, the gas flow velocity meter 13 is arranged at the lower part of the sampling device housing 14, and the gas flowmeter 10 is arranged at the upper part of the sampling device housing 14. The electric three-way valve 4 automatically adjusts the exhaust gas flow rates of the two branches according to the signals of the back pressure sensor 3 and the gas flowmeter 10 to keep the air flow and pressure in the branch exhaust pipe 6 stable.

[0028] Specifically, the gas flow velocity meter 13 in the sampling device 8 monitors the local flow velocity, and cooperates with the precise control of the temperature of the sampling plate 12 by the cooling system 9 to ensure that the temperature gradient field in the sampling area is not affected by air flow fluctuations. A stable temperature difference is the key to effectively driving the aggregation of particulate matter by the thermophoretic effect, avoiding the disorder of the temperature gradient caused by pressure or flow rate changes, and thus affecting the collection efficiency.

[0029] Specifically, the thermal mass flowmeter 2 monitors the total flow rate of the main exhaust pipe 1 in real time. Combining the data of the gas flowmeter in the branch exhaust pipe 6, the electric three-way valve 4 automatically adjusts the split ratio through the PID algorithm. The back pressure sensor 3 feeds back the pressure of the branch exhaust pipe 6 in real time. When the pressure of the main exhaust pipe 1 suddenly rises due to load changes, the electric three-way valve 4 automatically increases the branch opening to prevent negative pressure or excessive positive pressure in the branch exhaust pipe 6.

[0030] Specifically, in the present invention, in the branch exhaust pipe 6, the sampling device 8 directly collects the in-situ particulate matter emitted by the engine and realizes particle size segmentation, avoiding the influence of environmental factors such as dilution and secondary nucleation on the original morphology and physical and chemical properties of the particulate matter; this method is efficient, fast, simple to operate, and supports particle size classification sampling for particulate matter of different particle sizes, and can minimize the influence of factors such as dilution on the physical and chemical properties of the particulate matter emitted by the engine during the collection process.

[0031] In other preferred embodiments, the customized flange 7 is processed with a groove along the outer diameter of the flange inner diameter for installing the high-temperature resistant support net 7.1, the quartz filter membrane 7.2, and the sealing ring 7.3; the high-temperature resistant support net 7.1, the quartz filter membrane 7.2, and the sealing ring 7.3 are sequentially placed on the recessed plane of the customized flange 7. The height of the sealing ring 7.3 is slightly higher than the plane of the customized flange 7 to ensure that all the exhaust gas passes through the quartz filter membrane 7.2 to achieve particle size segmentation of the particulate matter. The high-temperature resistant support net 7.1 is used to support the quartz filter membranes 7.2 with different pore diameters to control the particulate matter with the desired particle size to enter the sampling device 8.

[0032] Specifically, the customized flange 7 selects a DN32 type flange with an inner diameter of 42.4 mm. A recessed plane with a depth of 3 mm and a diameter of 47 mm is processed with its center as the reference. On the plane, the high-temperature resistant support net 7.1 with a diameter of 47 mm and a thickness of 1 mm, the quartz filter membrane 7.2 with a diameter of 47 mm, and the sealing ring 7.3 with an inner diameter of 43 mm, an outer diameter of 47 mm, and a thickness of 2.5 mm are sequentially placed. The height of the sealing ring 7.3 is slightly higher than the flange plane to ensure that all the exhaust gas passes through the quartz filter membrane 7.2 to achieve particle size segmentation of the particulate matter. After installing the sealing ring 7.3, the flow domain diameter of the quartz filter membrane 7.2 is at least 38 mm, and quartz filter membranes 7.2 with different pore diameters can be selected according to needs to segment the particle size of the particulate matter.

[0033] In other preferred embodiments, a copper mesh fixing device 16 and a sampling plate positioning buckle 17 are installed on the sampling plate 12. The sampling device housing 14 is square and is connected in series with the branch exhaust pipe 6 at both ends. Trapezoidal grooves are formed on both opposite sides of the sampling device housing 14 for embedding the sampling plate 12 made of copper with a high heat transfer coefficient. Two buckles are installed near each trapezoidal groove to fix the position of the sampling plate 12 in the groove through the sampling plate positioning buckle 17. The sampling plate 12 is a trapezoid with a narrow inner side and a wide outer side. The outer side of the sampling plate 12 is connected to the electrode plate of the cooling system 9, and a high-temperature sensor 11 is arranged inside to monitor the working temperature of the sampling plate 12 in real time, and a small through-hole handle 15 is provided for convenient removal.

[0034] Specifically, a copper mesh through-hole tray 20 is arranged inside the sampling plate 12. A copper mesh 18 is provided on the copper mesh through-hole tray 20. The copper mesh 18 is fixed by the copper mesh fixing device 16. The copper mesh fixing device 16 is a copper mesh positioning buckle 19. The particulate matter collected by the copper mesh 18 can be directly used for high-magnification transmission electron microscopy analysis.

[0035] Specifically, the sampling device housing 14 is made of stainless steel, and the outer wall is coated with an aerogel-ceramic fiber composite heat insulation layer to prevent the temperature in the branch exhaust pipe 6 from decreasing and form a temperature difference with the sampling plate 12. Trapezoidal grooves are formed on both opposite sides of the sampling device housing 14 for embedding the sampling plate 12 made of copper with a high heat transfer coefficient. Two buckles are installed near each trapezoidal groove to fix the position of the sampling plate 12 in the groove through the sampling plate positioning buckle 17 to ensure the sealing of the sampling device 8 and prevent the sampling plate 12 from falling off. The sampling plate 12 is a trapezoid with a narrow inner side and a wide outer side, the length of the internal sampling surface is 50 mm, the width is 25 mm, and the inclination angle of the hypotenuse is 45°. It fits tightly with the sampling box groove. Micro-convex point arrays (diameter 0.5 mm, height 0.1 mm, spacing 1 mm) are arranged on the outer side of the sampling plate 12, and a metal bonding layer is formed by hot pressing and sintering, and the interfacial contact thermal resistance is reduced to 8.7×10 -6 m²·K / W, which improves the heat transfer efficiency by 5 times compared with planar contact. A copper mesh through-hole tray 20 is installed inside the sampling plate 12. A 300-mesh copper mesh 18 that can be directly used for high-magnification transmission electron microscopy shooting is placed in the copper mesh through-hole tray 20 and fixed inside the copper mesh through-hole tray 20 by the copper mesh positioning buckle 19. A small through-hole handle 15 is welded at the outer boundary of the sampling plate 12. After each sampling, the sampling plate 12 is taken out by using a pair of pointed tweezers as a fulcrum.

[0036] In other preferred embodiments, the cooling system 9 is a semiconductor temperature control system, including a heat absorption electrode plate 21, a heat dissipation electrode plate 22 and a cooling water tank 23. The heat absorption electrode plate 21 forms an efficient thermal interface with the outer surface of the particulate sampling plate 12 through high thermal conductivity silicone grease, and its heat dissipation electrode plate 22 is coupled to the cooling water tank 23 to accelerate heat dissipation; the semiconductor temperature control system cooperates with the reading of the high-temperature sensor to precisely control the temperature of the sampling plate 12, creating a stable temperature gradient field.

[0037] Specifically, when the system is running, the heat absorption electrode plate 21 continuously absorbs the heat of the sampling plate 12, making its surface temperature significantly lower than the inner wall temperature of the branch exhaust pipe 6, so as to form a stable temperature gradient field at the gas-solid interface. This gradient drives the exhaust particles to migrate directionally to the low-temperature surface area through the thermophoretic effect, and the concentration increases. As the exhaust flow field flows through the surface of the sampling plate 12 and impacts the 300-mesh copper mesh 18, a large number of particulate matters can be successfully captured by this copper mesh 18.

[0038] Specifically, to ensure sampling stability, a high-precision temperature sensor and a PID closed-loop control module are integrated in the system: the temperature sensor monitors the surface temperature of the sampling plate 12 (set value 150 ± 2 °C) in real time, and the controller dynamically adjusts the power of the semiconductor module to maintain a constant temperature; this temperature control strategy has two advantages: ensuring the continuous action of the thermophoretic force by controlling the temperature difference; avoiding the condensation and liquefaction of high-temperature water vapor in the branch exhaust pipe 6 on the surface of the sampling plate 2, and preventing the re-dissolution or surface contamination of particulate matters caused by condensation. When the temperature of the sampling plate 12 decreases while the exhaust temperature remains relatively high due to the heat preservation of the sampling box, the thermophoretic effect occurs, and the particulate matters in the exhaust gas spontaneously approach the flow field around the sampling plate.

[0039] In other preferred embodiments, the main body of the branch exhaust pipe 6 is constructed of SUS310S austenitic stainless steel bellows, and the outer wall of the pipeline is coated with an aerogel-ceramic fiber composite thermal insulation layer; constructed of SUS310S austenitic stainless steel bellows, the outer wall of the pipeline is coated with an aerogel-ceramic fiber composite thermal insulation layer, and its equivalent heat transfer coefficient ≤ 0.035 W / (m·K), which is more than 60% lower than that of traditional aluminosilicate fiber, ensuring that the temperature of the core exhaust flow is stably higher than 300 °C to avoid the condensation of moisture and unburned hydrocarbon components in the exhaust gas on the inner wall of the pipeline. The sampling device housing 14 is made of stainless steel structure, and the outer wall is also coated with an aerogel-ceramic fiber composite thermal insulation layer to prevent the temperature in the branch exhaust pipe 6 from decreasing and forming a temperature difference with the sampling plate 12.

[0040] A method for using a device for collecting in-situ particulate matter from engine exhaust gas includes the following steps: S1. Connect the inlet of the electric three-way valve 4 to the main exhaust pipe through the flange 5 on the main exhaust pipe. One outlet of the electric three-way valve 4 is connected to the main exhaust pipe 1 through a quick-release seal buckle, and the other outlet is connected in parallel to the branch exhaust pipe 6 through a quick-release seal buckle; S2. Connect the sampling device 8 in series with the branch exhaust pipe 6 through two customized flanges 7. The exhaust gas flowing through the sampling device 8 continues to flow into the main exhaust pipe 1 through the branch exhaust pipe 6. The quartz filter membrane 7.2 in the customized flange 7 realizes particle size segmentation; S3. When the exhaust gas flows through the sampling device 8, cool the wall surface of the sampling plate 12 through the cooling system 9 to create a temperature difference between the area where the sampling plate 12 is located and the exhaust gas flow. Under the action of thermophoretic force, the ultrafine particles in the exhaust gas flow gather towards the area where the sampling plate 12 is located, increasing the local concentration of particles. In-situ sampling is realized through the copper mesh 18 inside the sampling plate 12.

[0041] Specifically, in S2, the high-temperature resistant support net 7.1 in the customized flange 7 supports quartz filter membranes 7.2 with different pore sizes. By replacing the quartz filter membrane 7.2, the particle size of the particles entering the sampling device 8 is controlled to achieve particle size classification sampling.

[0042] Specifically, in S3, the cooling system adjusts the current polarity and power through the PID closed-loop control module, and combines with the real-time monitoring of the high-temperature sensor 11 to control the surface temperature of the sampling plate 12 at 150 ± 2 °C, maintaining a stable temperature gradient field and avoiding the condensation of water vapor to pollute the particles.

[0043] Specifically, the electric three-way valve, the main exhaust pipe and the branch exhaust pipe are quickly connected through the flange and the quick-release sealing buckle. The pipeline can be built without complex tools, adapting to the exhaust pipe layout of different models of engines, and significantly improving the installation efficiency and system compatibility.

[0044] Specifically, the electric three-way valve 4 automatically adjusts the diversion ratio according to the signals of the back pressure sensor 3 and the gas flow meter 10 in the branch exhaust pipe 6 to ensure the stable exhaust gas flow in the main / branch pipelines, avoiding the influence of airflow fluctuations caused by engine condition changes on the sampling accuracy, and ensuring the reliability and repeatability of the sampling process.

[0045] Specifically, the high-temperature resistant support net 7.1 in the customized flange 7 supports quartz filter membranes 7.2 with different pore sizes. By replacing the filter membrane, particles with the target particle size can be selectively intercepted to achieve the classification sampling of nucleation mode and accumulation mode particles, meeting the targeted research needs of particles with different particle sizes.

[0046] Specifically, the height of the sealing ring 7.3 is slightly higher than the flange plane, forcing all the exhaust gas to pass through the quartz filter membrane 7.2 to avoid the failure of particle size segmentation caused by bypass air leakage; the high-temperature resistant support net 7.1 evenly supports the quartz filter membrane 7.2 to prevent the filter membrane from being damaged by the impact of high-flow exhaust gas, ensuring the accuracy and stability of particle size segmentation.

[0047] Specifically, the cooling system 9 stabilizes the temperature of the sampling plate 12 at 150±2°C through PID closed-loop control, forming a significant temperature gradient with the exhaust flow (core temperature > 300°C), driving the thermophoretic force to cause ultrafine particles to migrate to the surface of the low-temperature sampling plate 12, thereby increasing the local concentration and solving the problem of low efficiency of traditional physical sampling in capturing small-size particles.

[0048] Specifically, the temperature above 150° C. avoids condensation of water vapor in the branch exhaust pipe 6 , prevents liquid water from dissolving or contaminating the functional groups on the surface of the particles and adsorbed pollutants (such as PAHs), and ensures the original physical and chemical properties of the sample.

[0049] Specifically, the copper mesh 18 on the inner side of the sampling plate 12 directly captures the particles without the need for subsequent transfer or sample preparation steps, thereby avoiding particle breakage or agglomeration caused by human operation. The collected samples can be directly used for high-magnification transmission electron microscopy (TEM) analysis, and the microscopic morphology (such as graphitized structure and pore distribution) is completely preserved.

[0050] Specifically, the high-temperature sensor 11 monitors the temperature of the sampling plate 12 in real time, and dynamically adjusts the current polarity and power of the semiconductor temperature control system in combination with the PID algorithm. It has a short response time and a temperature control accuracy of ±2°C, ensuring the long-term stability of the temperature gradient field and adapting to the exhaust temperature fluctuations when the engine is running under variable operating conditions.

[0051] like Figure 8 The figure shows a TEM image of diesel engine combustion particles collected by the device of the present invention using a high-magnification transmission electron microscope. The particle morphology shown in the figure is highly consistent with what traditional research has shown, and maintains a relatively clear outline and internal structure, providing more rigorous technical support and broader research ideas for subsequent research.

[0052] In summary, the main innovations of the present invention include: modular graded sampling design; thermophoresis capture based on temperature gradient field; and non-destructive sampling technology.

[0053] It should be noted that the device of the present application has been proven through multiple experiments that the device can reduce the loss rate of volatile components by 67%, providing a more reliable in-situ analysis method for studying the mechanism of particle formation, and providing a reliable sampling method and technical support for in-depth research on the physical and chemical properties of engine exhaust particles.

[0054] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0055] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by terms such as "upper", "lower", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention.

[0056] In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0057] Those skilled in the art to which the present invention pertains can make various modifications, supplements, or use similar ways to substitute the described specific embodiments, but will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. An in-situ particulate matter collection device for engine exhaust, characterized in that, It includes a main exhaust pipe, a main exhaust pipe (1), an electric three-way valve (4), a branch exhaust pipe (6), a sampling device (8) and a cooling system (9); The main exhaust pipe is connected to the inlet of the electric three-way valve (4) through a flange (5). The two outlets of the electric three-way valve (4) are respectively connected to the main exhaust pipe (1) and the branch exhaust pipe (6) through sealing buckles. The branch exhaust pipe (6) and the sampling device (8) are connected through two customized flanges (7) and then connected to the main exhaust pipe (1); The sampling device (8) includes a sampling device housing (14) and a sampling plate (12). The sampling plate (12) is made of high thermal conductivity copper material. The cooling system (9) is connected to the sampling plate (12) to control the wall temperature of the sampling plate (12), create a temperature difference between the area where the sampling plate (12) is located and the exhaust gas flow, and make the ultrafine particles in the exhaust gas flow gather towards the area where the sampling plate (12) is located under the action of thermophoretic force.

2. The collection device for in-situ particulate matter of an engine exhaust according to claim 1, wherein, A thermal mass flowmeter (2) is provided in the main exhaust pipe (1). A back pressure sensor (3) and a gas flowmeter (13) are provided in the branch exhaust pipe (6). A gas flow velocity meter (13) is provided in the sampling device (8). The electric three-way valve (4) automatically adjusts the exhaust gas flow of the two branches according to the signals of the back pressure sensor (3) and the gas flowmeter (13) to keep the gas flow and pressure in the branch exhaust pipe (6) stable.

3. The collection device for in-situ particulate matter in the engine exhaust according to claim 1, characterized in that, The customized flange (7) is processed with a groove along the outer diameter of the flange for installing a high-temperature resistant support net (7.1), a quartz filter membrane (7.2) and a sealing ring (7.3); The high-temperature resistant support net (7.1), the quartz filter membrane (7.2) and the sealing ring (7.3) are sequentially placed on the recessed plane of the customized flange (7). The height of the sealing ring (7.3) is slightly higher than the plane of the customized flange (7) to ensure that all the exhaust gas passes through the quartz filter membrane (7.2) to achieve particle size segmentation. The high-temperature resistant support net (7.1) is used to support quartz filter membranes (7.2) with different pore sizes to control the entry of particles with expected particle size into the sampling device (8).

4. The collection device for in-situ particulate matter of engine exhaust according to claim 1, characterized in that, A copper mesh fixing device (16) and a sampling plate positioning buckle (17) are installed on the sampling plate (12). The sampling device housing (14) is square and is connected in series with the branch exhaust pipe (6) at both ends. Trapezoidal grooves are opened on both opposite sides of the sampling device housing (14) for installing the sampling plate (12) made of copper with a high heat transfer coefficient. Two buckles are installed near each trapezoidal groove to fix the position of the sampling plate (12) in the groove through the sampling plate positioning buckle (17). The sampling plate (12) is a trapezoid with a narrow inner side and a wide outer side; The outer side of the sampling plate (12) is connected to the electrode plate of the cooling system (9). A high-temperature sensor (11) is provided inside to monitor the working temperature of the sampling plate in real time, and a small through-hole handle (15) is provided for convenient extraction.

5. The collection device for in-situ particulate matter of an engine exhaust according to claim 1, characterized in that, Inside the sampling plate (12), a copper mesh through-hole tray (20) is arranged. A copper mesh (18) is provided on the copper mesh through-hole tray (20). The copper mesh (18) is fixed by a copper mesh fixing device (16). The copper mesh fixing device (16) is a copper mesh positioning buckle (19). The particulate matter collected by the copper mesh (18) can be directly used for high-magnification transmission electron microscopy analysis.

6. The collection device for in-situ particulate matter in the engine exhaust according to claim 1, wherein, The cooling system (9) is a semiconductor temperature control system, including a heat absorption electrode sheet (21), a heat dissipation electrode sheet (22) and a cooling water tank (23). The heat absorption electrode sheet (21) forms an efficient thermal interface with the outer surface of the particulate matter sampling plate (12) through high thermal conductivity silicone grease. Its heat dissipation electrode sheet (22) is coupled with the cooling water tank (23) to accelerate heat dissipation. The semiconductor temperature control system cooperates with the reading of the high-temperature sensor (11) to precisely control the temperature of the sampling plate (12) and create a stable temperature gradient field.

7. The collection device for in-situ particulate matter of engine exhaust according to claim 1, characterized in that, The main body of the branch exhaust pipe (6) is constructed of SUS310S austenitic stainless steel bellows, and the outer wall of the pipe is coated with an aerogel-ceramic fiber composite heat insulation layer. The sampling device housing (14) is made of stainless steel, and the outer wall is also coated with an aerogel-ceramic fiber composite heat insulation layer to prevent the temperature in the branch exhaust pipe from decreasing and forming a temperature difference with the sampling plate.

8. The usage method of a device for collecting in-situ particulate matter in the exhaust gas of an engine according to any one of claims 1-7, characterized in that, It includes the following steps: S1. Connect the inlet of the electric three-way valve (4) to the main exhaust pipe through a flange (5). One outlet of the electric three-way valve (4) is connected to the main exhaust pipe (1) through a quick-release seal buckle, and the other outlet is connected in parallel to the branch exhaust pipe (6) through a quick-release seal buckle. S2. Connect the sampling device (8) in series with the branch exhaust pipe (6) through two customized flanges (7). The exhaust gas flowing through the sampling device (8) continues to flow into the main exhaust pipe (1) through the branch exhaust pipe (6). The quartz filter membrane (7.2) in the customized flange (7) realizes the particle size segmentation of the particulate matter. S3. When the exhaust gas flows through the sampling device (8), the cooling system (9) cools the wall surface of the sampling plate (12) to create a temperature difference between the area where the sampling plate (12) is located and the exhaust gas flow. Under the action of thermophoretic force, the ultrafine particulate matter in the exhaust gas flow gathers towards the area where the sampling plate (12) is located, increasing the local concentration of the particulate matter. The in-situ collection is realized through the copper mesh (18) inside the sampling plate (12).

9. The method of using a device for collecting in-situ particulate matter in the exhaust of an engine according to claim 8, characterized in that In S2, the high-temperature support net (7.1) in the customized flange (7) supports quartz filter membranes (7.2) with different pore sizes. By replacing the quartz filter membrane (7.2), the particle size of the particulate matter entering the sampling device (8) is controlled to achieve particle size classification sampling.

10. The method of using a device for collecting in-situ particulate matter from an engine exhaust according to claim 8, characterized in that, In S3, the cooling system (9) adjusts the current polarity and power through a PID closed-loop control module, and combines the real-time monitoring of the high-temperature sensor (11) to control the surface temperature of the sampling plate (12) at 150 ± 2 °C, maintaining a stable temperature gradient field and avoiding the condensation of water vapor to contaminate the particulate matter.

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