Engine exhaust photochemical aging evaluation system and method

Abstract

The application relates to the technical field of engine exhaust detection, in particular to an engine exhaust photochemical aging evaluation system and method, wherein the system comprises: a sampling device that samples initial engine exhaust, a dilution device that dilutes the initial engine exhaust, a reaction device that performs photochemical aging reaction on the diluted initial engine exhaust; a detection device that performs multi-dimensional detection on the initial engine exhaust and the reacted engine exhaust respectively, and obtains first characteristic parameters and second characteristic parameters respectively; and an electronic device that determines the total coating thickness of particulate matters in the exhaust based on the first characteristic parameters and the second characteristic parameters, decomposes the total coating thickness into organic coating thickness and inorganic coating thickness, and evaluates the photochemical aging characteristics of the engine exhaust based on the organic coating thickness and the inorganic coating thickness. Therefore, the problems that the real aging characteristics of engine exhaust particulate matters cannot be comprehensively and accurately reflected in the related art are solved.

Description

Technical Field

[0001] This application relates to the field of engine exhaust gas detection technology, and in particular to an engine exhaust gas photochemical aging assessment system and method. Background Technology

[0002] Engine combustion emits pollutants such as particulate matter, nitrogen oxides, and hydrocarbons, with BC (Black Carbon) being the main particulate component. The estimation of its atmospheric radiative forcing is subject to significant uncertainty. During atmospheric transport, BC is easily encapsulated by secondary organic aerosols and inorganic salts, forming a composite coating that significantly enhances light absorption and can have adverse effects. Therefore, it is necessary to assess the photo-aging characteristics of engine exhaust.

[0003] Research on photochemical aging assessment of engine exhaust particulate matter mainly falls into three technical categories. The first is the optical inversion method, which uses multi-wavelength AAE (Absorption Ångström Exponent) to exponentially separate the light absorption contributions of black carbon and brown carbon. However, this method is a purely optical indirect inference technique, relying on assumptions about the intrinsic optical parameters of black carbon and failing to provide direct structural evidence for coating growth. The second is the particle size inversion method, which uses a core-shell model and Mie scattering to calculate and invert coating thickness. However, this method significantly deviates from the fractal aggregation morphology of real black carbon, with particularly significant inversion errors for thin-coated particles. The third category involves multi-dimensional instrumentation methods, using SP-AMS (Soot Particle Aerosol Mass Spectrometer) and SMPS (Scanning Mobility Particle Sizer) to measure BC core mass, coating thickness, and chemical composition. However, these methods cannot distinguish between the lensing effect of SOA (Secondary Organic Aerosol) and the different contribution mechanisms of inorganic salts to enhanced light absorption. Furthermore, none of these techniques can comprehensively and accurately reflect the true aging characteristics of engine exhaust particulate matter. Summary of the Invention

[0004] This application provides a photochemical aging assessment system and method for engine exhaust gas to solve the problems in related technologies that cannot fully and accurately reflect the true aging characteristics of engine exhaust particulate matter.

[0005] The first aspect of this application provides an engine exhaust photochemical aging assessment system, comprising: a sampling device for collecting initial engine exhaust gas from an engine under test; a dilution device connected to the sampling device for diluting the initial engine exhaust gas with air; a reaction device connected to the dilution device for performing a photochemical aging reaction on the diluted initial engine exhaust gas and outputting the reacted engine exhaust gas, wherein the particulate matter in the reacted engine exhaust gas is coated with an inorganic coating and / or an organic coating; a detection device connected to the reaction device for performing particle size distribution detection, optical absorption detection, particulate morphology characterization detection, and chemical composition detection on the initial engine exhaust gas and the reacted engine exhaust gas, respectively, to obtain a first characteristic parameter of the initial engine exhaust gas and a second characteristic parameter of the reacted engine exhaust gas; and an electronic device communicatively connected to the detection device for receiving the first characteristic parameter and the second characteristic parameter from the detection device, calculating the total coating thickness of the particulate matter in the engine exhaust gas based on the first characteristic parameter and the second characteristic parameter, decomposing the total coating thickness into an organic coating thickness and an inorganic coating thickness, and evaluating the photochemical aging characteristics of the engine exhaust gas based on the organic coating thickness and the inorganic coating thickness.

[0006] Optionally, both the first characteristic parameter and the second characteristic parameter include at least one of particle size distribution characteristics, target electromobility particle size, light absorption coefficient at different wavelengths, black carbon mass concentration, morphology characterization image, and chemical composition. The electronic device is further used to: calculate the total coating thickness of particulate matter in engine exhaust gas based on the first target electromobility particle size and the second target electromobility particle size; calculate the organic component increment and inorganic component increment of particulate matter based on the first chemical composition and the second chemical composition, respectively; and calculate the organic coating thickness and inorganic coating thickness of particulate matter in engine exhaust gas based on the organic component increment, inorganic component increment, and total coating thickness.

[0007] Optionally, the formula for calculating the total coating thickness is: ; in, The second target electromobility particle size is the second characteristic parameter. The first target electromobility particle size in the first characteristic parameter, t This refers to the total coating thickness. The formula for calculating the increase in organic components is: ; in, For the increase of organic components, The concentration of the second organic component in the second characteristic parameter. The concentration of the first organic component in the first characteristic parameter; The formula for calculating the increment of inorganic components is: ; in, For the increment of inorganic components, The concentration of the second inorganic component in the second characteristic parameter. The concentration of the first inorganic component in the first characteristic parameter; The formula for calculating the thickness of the organic coating is: ; in, For the thickness of the organic coating, The total coating thickness, For the increase of organic components, This represents the increment of the inorganic component; The formula for calculating the thickness of inorganic coatings is: ; in, For the thickness of the inorganic coating, The total coating thickness, For the increase of organic components, This represents the increase in the inorganic component.

[0008] Optionally, the electronic device is also used to: calculate the absorption enhancement coefficient of particulate matter in engine exhaust gas at the corresponding wavelength based on the first and second light absorption coefficients at each wavelength, and calculate the Estrange absorption index of particulate matter based on the light absorption coefficients at multiple wavelengths; determine the surface coating characteristics of particulate matter in engine exhaust gas based on the first and second morphology characterization images; and evaluate the photochemical aging characteristics of engine exhaust gas based on at least one of organic coating thickness, inorganic coating thickness, particle size distribution characteristics, absorption enhancement coefficient, Estrange absorption index, black carbon mass concentration, surface coating characteristics, inorganic component increment, and organic component increment.

[0009] Optionally, the dilution device includes a first air compressor, a filter, and a multi-channel mass flow controller, wherein the first air compressor is used to generate first compressed air; the filter is used to filter the first compressed air to obtain dilution air; and the multi-channel mass flow controller is used to control the flow ratio of dilution air and initial engine exhaust gas to dilute the initial engine exhaust gas based on the dilution air.

[0010] Optionally, the reaction apparatus includes a reaction apparatus body, an ultraviolet lamp, a second air compressor, and a nitrogen supply device. The second air compressor is used to generate second compressed air; the nitrogen supply device is used to supply nitrogen; the ultraviolet lamp is used to irradiate the reaction apparatus body; the reaction apparatus body stores diluted initial engine exhaust gas, second compressed air, and nitrogen, and supplies the diluted initial engine exhaust gas, second compressed air, and nitrogen to carry out a photochemical aging reaction under the irradiation of the ultraviolet lamp.

[0011] Optionally, the detection device includes a first to a fourth detection module, wherein the first detection module is used to detect the particle size distribution characteristics and target electromobility particle size of particulate matter in engine exhaust gas; the second detection module is used to detect the light absorption coefficient and black carbon mass concentration of particulate matter in engine exhaust gas at different wavelengths; the third detection module is used to detect the morphological characterization image of single particulate matter in engine exhaust gas; and the fourth detection module is used to detect the chemical components in engine exhaust gas.

[0012] Optionally, the first detection module is a particle size spectrometer, and the second detection module is a black carbon analyzer. The particle size spectrometer includes a differential electromobility analyzer, a condensation nucleus particle counter, and an analysis unit. The differential electromobility analyzer is used to classify the particle size of the particulate matter in the engine exhaust gas according to the electromobility of the particulate matter. The condensation nucleus particle counter is used to count the particulate matter in each particle size group. The analysis unit is used to determine the particle size distribution characteristics and target electromobility particle size of the particulate matter in the engine exhaust gas according to the particle size classification results and the particle count values ​​of different particle sizes.

[0013] Optionally, the third detection module includes a single-particle sampler and an electron microscope, wherein the single-particle sampler is used to collect particulate matter in engine exhaust gas, and the electron microscope is used to generate morphological characterization images of the single particles; the fourth detection module includes a filter membrane sampler and at least one analyzer, wherein the filter membrane sampler is used to sample particulate matter in engine exhaust gas through a filter membrane, and at least one analyzer is used to analyze the chemical composition of the sampled single particles.

[0014] Optionally, the fourth detection module also includes a flow meter and a sampling pump, wherein the flow meter is used to regulate the sampling flow rate of the engine exhaust gas, and the sampling pump is used to generate suction to drive the engine exhaust gas through the filter membrane sampler.

[0015] A second aspect of this application provides a method for evaluating the photochemical aging of engine exhaust gas, applied to the aforementioned engine exhaust gas photochemical aging evaluation system, comprising the following steps: obtaining first characteristic parameters of the initial engine exhaust gas of the engine under test, and second characteristic parameters of the engine exhaust gas after photochemical aging reaction; calculating the total coating thickness of particulate matter in the engine exhaust gas based on the first and second characteristic parameters, and decomposing the total coating thickness into organic coating thickness and inorganic coating thickness; evaluating the photochemical aging characteristics of the engine exhaust gas based on the organic coating thickness and inorganic coating thickness.

[0016] A third aspect of this application provides a computer-readable storage medium having a computer program or instructions stored thereon, which is executed by a processor to perform the engine exhaust photochemical aging assessment method as described above.

[0017] The fourth aspect of this application provides a computer program product, including a computer program or instructions, which, when executed, implement the engine exhaust photochemical aging assessment method as described in the above embodiments.

[0018] Therefore, this application has at least the following beneficial effects: This application embodiment constructs an engine exhaust photochemical aging assessment system, including a sampling device, a dilution device, a reaction device, a detection device, and a processor. The dilution device is used to dilute the initial engine exhaust collected by the sampling device with air. The reaction device is used to perform a photochemical aging reaction on the diluted initial engine exhaust and output the reacted engine exhaust to simulate the photochemical aging process of engine exhaust in the atmospheric environment. The detection device is used to perform particle size distribution detection, optical absorption detection, particulate morphology characterization detection, and chemical composition detection on the unreacted initial engine exhaust and the reacted engine exhaust, respectively, to obtain a first characteristic parameter and a second characteristic parameter. Electronic equipment is then configured based on the first and second characteristic parameters. This method calculates the total coating thickness of particulate matter in engine exhaust using characteristic parameters. It achieves this calculation quickly and easily without complex models or optimization calculations. The total coating thickness is decomposed into organic and inorganic coating thicknesses. Based on these thicknesses, the photochemical aging process of engine exhaust is assessed, providing a quantitative and intuitive evaluation. The refined decomposition of organic and inorganic coating thicknesses improves the accuracy of the photoaging characteristics assessment, clearly distinguishing the contribution of the two different coating components to the photochemical aging evolution process. This comprehensively and meticulously reflects the true photochemical aging evolution characteristics of engine exhaust. Therefore, it solves the technical problem of not being able to comprehensively and accurately reflect the true aging characteristics of particulate matter in engine exhaust.

[0019] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0020] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 This is a schematic diagram of an engine exhaust photochemical aging assessment system provided according to an embodiment of this application; Figure 2 This is a schematic diagram of the composition of the engine exhaust photochemical aging assessment system provided according to an embodiment of this application; Figure 3 This is a schematic diagram illustrating the changes in particle size distribution before and after aging, according to an embodiment of this application. Figure 4 This is a flowchart of the engine exhaust photochemical aging assessment method provided according to an embodiment of this application. Detailed Implementation

[0021] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0022] Combustion processes in engines release a complex mixture of pollutants, including PM (particulate matter), NOx (nitrogen oxides), and hydrocarbons. Among these pollutants, carbon black (BC) is the main particulate component produced by incomplete combustion in engines, and its large emissions have adverse effects, making it a hot research topic. However, current estimates of black carbon radiative forcing have an uncertainty of up to 2 times. One of the main reasons is that black carbon particles are coated with an oxygen-air-base (SOA) layer during atmospheric transport, resulting in a significant increase in their light absorption capacity. This enhancement effect directly leads to more solar radiation being trapped by the atmosphere, exacerbating positive radiative forcing. SOA is formed by the oxidation of various gaseous organic emissions in the atmosphere, including SVOCs (semi-volatile organic compounds), IVOCs (intermediate volatile organic compounds), and VOCs (volatile organic compounds). In most environments, the reaction with hydroxyl radicals is the main decay pathway for various VOCs. To simulate atmospheric photochemical aging processes, OFR (Oxidation Flow Reactor) has been widely used in laboratory studies to simulate atmospheric aging over days to weeks by generating hydroxyl radicals (OH·) within minutes.

[0023] Research on the evaluation of enhanced light absorption of black carbon in related technologies can be mainly divided into three technical paths. The first category is optical inversion methods, which separate the light absorption contributions of black carbon and brown carbon through multi-wavelength AAE exponents. This method overcomes the limitation of traditional methods that fix the AAE at 1.0 by allowing the AAE of black carbon to vary within a certain range. Alternatively, it can achieve the inversion of spectral absorption contributions without pre-setting the intrinsic value of the AAE of black carbon through tracer-least square coupling methods. However, optical inversion methods are all purely optical indirect inference techniques, which rely on assumptions about the intrinsic optical parameters of black carbon. They cannot provide direct structural evidence of coating growth solely through absorption spectrum inversion.

[0024] The second type is particle size inversion. The core-shell model and Mie scattering calculations used in the SP2 inversion principle deviate significantly from the fractal aggregation morphology of real black carbon, resulting in inverted D... p / D c The inversion error is particularly significant for thin-coated particles, which are underestimated across most particle size ranges.

[0025] The third category is multidimensional instrument-coupled studies, where SP-AMS and SMPS measure BC nucleus mass, coating thickness, and chemical composition, but do not decompose the total coating thickness into contributions from organic and inorganic components.

[0026] Therefore, the main problems in the related technologies are as follows: optical inversion methods can only indirectly infer the contribution of brown carbon through absorption spectra and cannot provide direct structural evidence of coating growth; particle size inversion relies on complex Mie models and the spherical assumption, which introduces errors; and the chemical composition of the coating layer is not decomposed.

[0027] To address this issue, this application provides an engine exhaust photochemical aging assessment system to solve at least one of the above-mentioned technical problems.

[0028] Specifically, Figure 1 This is a schematic diagram of an engine exhaust photochemical aging assessment system provided in an embodiment of this application.

[0029] like Figure 1 As shown, the engine exhaust photochemical aging assessment system 100 includes: a sampling device 101, a dilution device 102, a reaction device 103, a detection device 104, and electronic equipment 105.

[0030] The sampling device 101, dilution device 102, reaction device 103, and detection device 104 are sequentially connected. An electronic device 105 is communicatively connected to the detection device 104. The sampling device 101 is used to collect initial engine exhaust gas from the engine under test; the dilution device 102 is used to dilute the initial engine exhaust gas with air; the reaction device 103 is used to perform a photochemical aging reaction on the diluted initial engine exhaust gas and output the reacted engine exhaust gas, wherein the particulate matter in the reacted engine exhaust gas is coated with inorganic and / or organic coatings; the detection device 104 is used to detect the initial engine exhaust gas... The initial engine exhaust gas and the reacted engine exhaust gas are subjected to particle size distribution detection, optical absorption detection, particulate morphology characterization detection, and chemical composition detection, respectively, to obtain the first characteristic parameters of the initial engine exhaust gas and the second characteristic parameters of the reacted engine exhaust gas. The electronic device 105 is used to receive the first characteristic parameters and the second characteristic parameters from the detection device 104, calculate the total coating thickness of the particulate matter in the engine exhaust gas based on the first characteristic parameters and the second characteristic parameters, and decompose the total coating thickness into organic coating thickness and inorganic coating thickness. The photochemical aging characteristics of the engine exhaust gas are evaluated based on the organic coating thickness and the inorganic coating thickness.

[0031] It is understood that this application embodiment constructs an engine exhaust photochemical aging assessment system 100, including a sampling device 101, a dilution device 102, a reaction device 103, a detection device 104, and an electronic device 105. The dilution device 102 is used to dilute the initial engine exhaust collected by the sampling device 101 using air. The reaction device 103 is used to perform a photochemical aging reaction on the diluted initial engine exhaust and output the reacted engine exhaust to simulate the photochemical aging process of engine exhaust in the atmospheric environment. The detection device 104 is used to perform particle size distribution detection, optical absorption detection, particulate matter morphology characterization detection, and chemical composition detection on the unreacted initial engine exhaust and the reacted engine exhaust, respectively, to obtain a first characteristic parameter and a second characteristic parameter. The electronic device 105 calculates the total coating thickness of particulate matter in engine exhaust gas based on the first and second characteristic parameters. It can calculate the coating thickness of particulate matter without complex models and optimization calculations, making the calculation simple and fast. The total coating thickness is decomposed into organic coating thickness and inorganic coating thickness. Then, the photochemical aging process of engine exhaust gas is evaluated based on the organic coating thickness and inorganic coating thickness. This achieves a quantitative and intuitive evaluation of the photochemical aging process of engine exhaust gas. By refining the decomposition of organic and inorganic coating thickness, the accuracy of the evaluation of the photo-aging characteristics of engine exhaust gas is improved. It clearly distinguishes the contribution of the two different types of component coatings in the photochemical aging evolution process, and comprehensively and meticulously reflects the true photochemical aging evolution characteristics of engine exhaust gas.

[0032] The initial engine exhaust gas in this application embodiment can also be referred to as fresh engine exhaust gas, engine exhaust gas before aging or oxidation, and the engine exhaust gas after the reaction can also be referred to as engine exhaust gas after aging or oxidation. The reaction device 103 in this application embodiment can be a PAM-OFR (Potential Aerosol Mass-Oxidation Flow Reactor) to simulate the photochemical aging process. The organic coating can be an SOA coating. The inorganic coating is mainly composed of gaseous inorganic pollutants such as nitrogen oxides and sulfur oxides contained in the engine exhaust gas, which are converted into nitrates and sulfates by ultraviolet and ozone oxidation, and then react with internal water vapor to generate inorganic salt aerosols.

[0033] It should be noted that the embodiments of this application are mainly for evaluating the photochemical aging characteristics of BC in engine exhaust gas; the embodiments of this application can be applied to the exhaust gas of engines such as diesel engines, gasoline engines and aircraft engines.

[0034] Furthermore, in one embodiment of this application, both the first characteristic parameter and the second characteristic parameter include at least one of particle size distribution characteristics, target electromobility particle size, light absorption coefficient at different wavelengths, black carbon mass concentration, morphology characterization image, and chemical composition.

[0035] The particle size distribution characteristics can include the particle size of different particles and the concentration of particles at different particle sizes; the target electromobility particle size can be the geometric median particle size or peak particle size in the particle number concentration particle size distribution, which is the core indicator for characterizing the overall particle size. When the particle size distribution shows a unimodal distribution, the peak particle size is used as the target electromobility particle size; when the particle size distribution shows a bimodal or multimodal distribution, the peak particle size of the aggregation mode is used as the target electromobility particle size. The particle size range of the aggregation mode is 50 nm to 500 nm. The particles corresponding to this mode are mainly non-volatile aggregated particles, and their particle size changes best reflect the coating thickening effect caused by the condensation and growth of secondary components during photochemical aging. Core mode particles (particle size < 50 nm) may disappear due to volatilization or agglomeration during the aging process and are not selected as the target electromobility particle size; the chemical components include the concentration of organic components and the concentration of inorganic components.

[0036] Furthermore, in one embodiment of this application, the electronic device 105 is further configured to: calculate the total coating thickness of particulate matter in engine exhaust gas based on a first target electromobility particle size and a second target electromobility particle size; determine the organic component increment and inorganic component increment of particulate matter based on a first chemical component and a second chemical component; and calculate the organic coating thickness and inorganic coating thickness of particulate matter in engine exhaust gas based on the organic component increment, the inorganic component increment and the total coating thickness.

[0037] The total coating thickness is the overall thickness of all coatings (i.e., the covering layer) outside the core of the particulate matter; the organic component increment is the difference between the organic components of the particulate matter before and after the reaction, used to characterize the content of newly generated organic matter during the aging process; the inorganic component increment is the difference between the inorganic components of the particulate matter before and after the reaction, used to characterize the content of newly generated inorganic matter during the aging process.

[0038] It is understood that the embodiments of this application can calculate the total coating thickness of particulate matter in engine exhaust gas based on the first target electromobility particle size before the reaction and the second target electromobility particle size after the reaction. The total coating thickness of particulate matter can be calculated directly through the target electromobility, which is simple and fast, without the need for complex models and optimization calculations. The organic component increment and inorganic component increment of particulate matter are determined based on the first chemical component and the second chemical component, and then the organic coating thickness and inorganic coating thickness of particulate matter are determined based on the organic component increment, inorganic component increment and total coating thickness.

[0039] Specifically, the formula for calculating the total coating thickness in this application embodiment can be: ; in, For the second target (after aging) electromobility particle size, For the primary target (before aging), the particle size with the highest electromobility. t This refers to the coating thickness.

[0040] The incremental formulas for the organic and inorganic components in this application embodiment are as follows: ; ; in, For the increase of organic components, For the increase of organic components, This refers to the concentration of the second organic component in the second characteristic parameter (i.e., the concentration of the organic component after aging). The concentration of the first organic component in the first characteristic parameter (i.e., the concentration of the organic component before aging). For the increment of inorganic components, This refers to the concentration of the second inorganic component in the second characteristic parameter (i.e., the concentration of the inorganic component after aging). The concentration of the first inorganic component in the first characteristic parameter (i.e., the concentration of the inorganic component before aging).

[0041] The formulas for calculating the thickness of the organic coating and the inorganic coating in this application embodiment are as follows: ; ; in, For the thickness of the organic coating, The total coating thickness, For the increase of organic components, For the increment of inorganic components, The thickness is the inorganic coating thickness.

[0042] Furthermore, in one embodiment of this application, the electronic device 105 is also configured to: calculate the absorption enhancement coefficient of particulate matter in engine exhaust gas at the corresponding wavelength based on the first light absorption coefficient and the second light absorption coefficient at each wavelength, and calculate the Estrange absorption index of particulate matter based on the light absorption coefficients at multiple wavelengths; determine the surface coating characteristics of particulate matter in engine exhaust gas based on the first morphology characterization image and the second morphology characterization image; and evaluate the photochemical aging characteristics of engine exhaust gas based on at least one of the following: total coating thickness, organic coating thickness, inorganic coating thickness, particle size distribution characteristics, absorption enhancement coefficient, Estrange absorption index, black carbon mass concentration, surface coating characteristics, inorganic component increment, and organic component increment.

[0043] Among them, the absorption enhancement coefficient is the ratio of the light absorption coefficient of the particles before and after the reaction at the same wavelength, which is used to characterize the enhancement effect of the coating on the light absorption capacity of the particles; AAE is calculated based on the multi-wavelength light absorption coefficient, which is used to characterize the wavelength dependence of the light absorption of the particles and distinguish the light absorption contribution of black carbon and brown carbon; the surface coating characteristics are the particle coating uniformity, core-shell structure and agglomeration morphology identified by the morphology characterization image.

[0044] It is understood that the embodiments of this application can calculate the absorption enhancement technology of engine exhaust particulate matter at each wavelength based on the first light absorption coefficient and the second light absorption dilution at each wavelength, and calculate the Estrand absorption index based on the light absorption coefficients of multiple wavelengths. At the same time, the morphological characterization images before and after the reaction are compared to determine the surface coating characteristics of the particulate matter. Then, the evolution law of photochemical aging is comprehensively evaluated based on multiple indicators such as total coating thickness, layered coating thickness, particle size, optical parameters, morphology, and chemical increment.

[0045] The formula for calculating the absorption enhancement coefficient of particulate matter at different wavelengths in this application embodiment can be: ; in, wavelength The absorption enhancement coefficient below, wavelength The second light absorption coefficient, i.e., the light absorption coefficient after aging. wavelength The first light absorption coefficient, i.e. the light absorption coefficient before aging.

[0046] The formula for calculating AAE in this application embodiment can be: ; in, , For two different wavelengths, , These are the light absorption coefficients at different wavelengths.

[0047] It is generally believed that AAE 1. The component is black carbon; AAE 2~8, the components are brown carbon.

[0048] Since BrC (Brown Carbon) exhibits significantly enhanced absorption in the ultraviolet and blue light bands (300–500 nm), a measured AAE value significantly greater than 1 usually indicates the presence of a BrC contribution.

[0049] Specifically, the embodiments of this application evaluate the photochemical aging characteristics of particulate matter in engine exhaust based on the above-mentioned parameters, including the following: 1. The relationship between absorption enhancement coefficient and aging.

[0050] The absorption enhancement factor is used to represent the multiple by which the light absorption capacity of aged particulate matter is enhanced relative to that of freshly emitted particulate matter.

[0051] when A value greater than 1 indicates that the absorption at that wavelength is enhanced after aging. This indicates that the aging process has enhanced the light absorption capacity of the particulate matter, suggesting that the particulate matter has undergone photochemical aging, such as the formation of secondary organic aerosols, inorganic salts, or organic / inorganic coatings, which causes a "lens effect" in black carbon. The larger the absorption enhancement coefficient, the more significant the absorption enhancement effect caused by the photochemical aging of the particulate matter.

[0052] when 1 indicates that the absorption capacity changes little before and after aging, and the degree of aging is weak.

[0053] when <1 indicates that absorption is weakened after aging, which may be related to the bleaching, volatilization loss of light-absorbing organic matter, or the breakage of particulate matter structure.

[0054] 2. The relationship between the Estrand absorption index and changes in brown carbon / organic absorption.

[0055] The evolution of particulate matter light-absorbing components can be judged by the changes in AAE before and after aging. AAE reflects the strength of absorption with wavelength. Generally speaking: when AAE is close to 1, it is determined that black carbon absorption is dominant; when AAE increases, it is determined that short-wavelength absorption is enhanced, indicating that brown carbon or light-absorbing organic matter may have increased; when AAE decreases, it is determined that the organic light-absorbing components have been oxidized and bleached after oxidation, or that the proportion of black carbon absorption has increased.

[0056] 3. The relationship between coating thickness and aging degree.

[0057] The degree of aging of particulate matter surfaces is assessed based on the thickness of organic and inorganic coatings. When the coating thickness on the particulate matter surface increases after aging, it is determined that secondary components generated by the photochemical reaction of gaseous precursors have condensed or deposited, and the degree of particulate matter aging increases. The greater the coating thickness, the more fully the particulate matter surface is covered, and the more significant the optical lens effect.

[0058] 4. Relationship between particle size distribution characteristics and aging degree.

[0059] When the peak particle size of the number concentration, the average particle size, or the proportion of cumulative modal particles increases after aging, it is determined that the particles have undergone condensation growth or multiphase reaction growth, and the degree of photochemical aging is enhanced.

[0060] 5. The relationship between the quality and aging degree of black charcoal.

[0061] The mass concentration of black carbon is used as a normalization parameter for calculating absorption enhancement and chemical increment, distinguishing between absorption changes caused by changes in particulate matter mass and changes in absorption capacity per unit of black carbon due to aging. When the light absorption coefficient corresponding to a unit mass of black carbon increases, it is determined that the absorption enhancement is caused by changes in the surface coating or mixing state of the black carbon particles.

[0062] 6. Relationship between surface coating characteristics and aging degree.

[0063] Based on the first and second morphological characterization images, the core-shell structure, surface attachments, degree of agglomeration compaction, and coating continuity of particulate matter are identified. When the aged particulate matter changes from a loose chain structure to a compact structure, or when a continuous organic / inorganic coating layer appears on the surface, it is determined that the mixing state of the particulate matter has changed from external mixing to internal mixing, and the degree of photochemical aging has increased.

[0064] 7. Relationship between the increase in inorganic / organic components and the degree of aging.

[0065] The degree of photochemical reaction product formation is determined by the increase in chemical components (i.e., the increase in inorganic and organic components). When the concentration increase of sulfate, nitrate, ammonium salt, oxygen-containing organic matter or secondary organic aerosol tracers after aging is positive and exceeds the set threshold, it is determined that the engine exhaust gas has undergone photochemical oxidation reaction and generated secondary particulate matter. The greater the increase in chemical components, the higher the degree of photochemical aging.

[0066] Furthermore, in one embodiment of this application, the dilution device 102 includes a first air compressor, a filter, and a multi-channel mass flow controller, wherein the first air compressor is used to generate first compressed air; the filter is used to filter the first compressed air to obtain dilution air; and the multi-channel mass flow controller is used to control the flow ratio of dilution air and initial engine exhaust gas to dilute the initial engine exhaust gas based on the dilution air.

[0067] It is understandable that, such as Figure 2 As shown, the dilution device 102 in this embodiment includes a first air compressor, a filter, and a multi-channel mass flow controller. The first air compressor is used to generate first compressed air, and the filter is used to filter and purify the first compressed air to obtain diluted air. Clean diluted air is prepared by the air compressor and the filter to eliminate the interference of impurities in the air on the engine exhaust gas and improve the subsequent detection accuracy. The multi-channel mass flow controller is used to control the dilution ratio to simulate the real atmospheric process.

[0068] Furthermore, in one embodiment of this application, the reaction device 103 includes a reaction device body, an ultraviolet lamp, a second air compressor, and a nitrogen supply device. The second air compressor is used to generate second compressed air; the nitrogen supply device is used to supply nitrogen; the ultraviolet lamp is used to irradiate the reaction device body; the reaction device body stores diluted initial engine exhaust gas, second compressed air, and nitrogen, and provides the diluted initial engine exhaust gas, second compressed air, and nitrogen for photochemical aging reaction under the irradiation of the ultraviolet lamp.

[0069] The reaction device body can be understood as the reaction chamber for photochemical aging.

[0070] It is understandable that, such as Figure 2 As shown, the reaction device 103 in this embodiment includes a reaction device body, an ultraviolet lamp, a second air compressor, and a nitrogen supply device. The second air compressor outputs second compressed air, the nitrogen supply device supplies nitrogen, the reaction device body contains engine exhaust, the second compressed air, and nitrogen, and the ultraviolet lamp irradiates the reaction device body to cause the gas inside the reaction device body to undergo a photochemical aging reaction. By irradiating the second compressed air, the ultraviolet lamp can excite the air to generate strong oxidants such as ozone and hydroxyl radicals, simulating atmospheric photo-oxidation conditions. Nitrogen can regulate the reaction atmosphere, stabilize the airflow and atmosphere inside the reaction device body, control the oxidation intensity, and thus achieve controllable aging reaction conditions to simulate different aging degrees.

[0071] Specifically, this application embodiment can use PAM-OFR as the reaction device, that is, as the core photochemical aging simulation device. The reactor has an effective internal container of 13.3 L and operates in OFR254 mode. In OFR254 mode, the ultraviolet lamp power is adjustable from 100-400W, and the gradient control of OH exposure is achieved by adjusting the ultraviolet lamp power and irradiation time. In this mode, an independent lamp outside the reactor irradiates oxygen (O2) with 185 nm ultraviolet light to generate ozone (O3). After entering the reactor, O3 is photolyzed by 254 nm ultraviolet light to produce excited-state oxygen atoms O(O2). 1 D), O( 1 D) It reacts with water vapor (H2O) in the reactor to generate hydroxyl radicals (OH·), and the specific reaction pathway is as follows: O3+h v 254 → O( 1 D) + O2; O( 1 D) + H₂O → 2OH; Among them, h v 254 This represents ultraviolet light with a wavelength of 254 nm.

[0072] The reactor is also equipped with a second air compressor and a nitrogen (N2) supply system for regulating the oxidizing atmosphere and carrier gas flow rate within the reactor. By controlling the ultraviolet light intensity and the relative humidity within the reactor, this embodiment can generate a high concentration of OH radicals (10). 8 -10 10 molecules / cm 3 This process allows aerosols to undergo a photochemical aging process equivalent to several days to several weeks of atmospheric conditions within minutes. The relative humidity inside the reactor is controlled in a closed loop using a humidifier and humidity sensor, adjustable within the range of 30%-70%, with a relative humidity control accuracy of ±3%. The ozone concentration at the reactor outlet is monitored in real time using an ultraviolet absorption ozone analyzer.

[0073] Based on the above-mentioned reaction device, the atmospheric photochemical aging process can be rapidly simulated to achieve time compression; a controllable oxidation environment can be generated to study the evolution of emissions under different aging degrees; and oxidation conditions can be provided for the generation of secondary organic aerosols.

[0074] Furthermore, it should be noted that a VPR (Volatile Particle Remover) can be connected between the reaction device 103 and the dilution device 102 in this embodiment of the application to remove interference from volatile substances and ensure that the particles entering the reactor represent non-volatile or semi-volatile components.

[0075] To avoid contamination of the oxidation flow reactor by high-concentration exhaust gas and to simulate atmospheric dilution, this application employs a two-stage dilution process. First-stage dilution: Engine exhaust gas is extracted using a gas sampling tube inserted into a large collection pipe. The dilution air flow is precisely controlled by a compressed air-driven MFS (Mass Flow Controller) to accurately adjust the dilution ratio. The dilution air is supplied by an air compressor after being filtered through a HEPA (High Efficiency Particulate Air Filter). Second-stage dilution: After entering the oxidation flow reactor, the engine exhaust gas mixes with ozone (O3) generated within the reactor, achieving further dilution. The combined dilution ratio after both stages is approximately 100 times.

[0076] Based on the above dilution process, the high-temperature exhaust gas can be quickly cooled to room temperature to avoid thermal secondary reaction; simulate the atmospheric dilution process to reduce the particulate matter concentration to the appropriate range of the detection instrument; (3) remove the interference of volatile substances through VPR to ensure that the particulate matter entering the reactor represents non-volatile or semi-volatile components.

[0077] Furthermore, in one embodiment of this application, the detection device 104 includes a first to a fourth detection module, wherein the first detection module is used to detect the particle size distribution characteristics and target electromobility particle size of particulate matter in engine exhaust gas; the second detection module is used to detect the light absorption coefficient and black carbon mass concentration of particulate matter in engine exhaust gas at different wavelengths; the third detection module is used to detect the morphological characterization image of single particulate matter in engine exhaust gas; and the fourth detection module is used to detect the chemical components in engine exhaust gas.

[0078] It is understood that the detection device 104 in this application embodiment can be divided into four detection modules, each performing different types of detection. The first detection module is used to detect particle size distribution characteristics and target electromobility particle size; the second detection module is used to detect multi-wavelength light absorption coefficient and black carbon mass concentration; the third detection module is used to acquire single particle morphology characterization images; and the fourth detection module is used to detect the chemical composition of particulate matter.

[0079] Furthermore, in one embodiment of this application, the first detection module is a particle size spectrometer, and the second detection module is a black carbon analyzer. The particle size spectrometer includes a differential electromobility analyzer, a condensation nucleus particle counter, and an analysis unit. The differential electromobility analyzer is used to classify the particle size of the particulate matter according to the electromobility of the particulate matter in the engine exhaust gas. The condensation nucleus particle counter is used to count the particulate matter in each particle size group. The analysis unit is used to determine the particle size distribution characteristics and target electromobility particle size of the particulate matter in the engine exhaust gas according to the particle size classification results and the particle count values ​​of different particle sizes.

[0080] Among them, the particle size analyzer can be an SMPS; the black carbon analyzer can be an AE33 seven-band black carbon analyzer.

[0081] Specifically, the first detection module in this application embodiment can be a particle size analyzer. The particle size analyzer measures the particle size number concentration distribution of particulate matter in engine exhaust gas before and after the reaction. The particle size analyzer consists of a DMA (Differential Mobility Analyzer) and a CPC (Condensation Particle Counter). The DMA can sieve particulate matter according to different electromobilities, and the CPC counts the sieved ultrafine particles. The detection particle size range can be set to 9.82~399.5 nm, and the single scan cycle is approximately 110 seconds. The particle size distribution changes of particulate matter before and after aging in this application embodiment are as follows: Figure 3 As shown.

[0082] Based on the analysis unit in the first detection module mentioned above, the particle size distribution characteristics of freshly emitted and aged particulate matter can be obtained; the peak electromobility particle sizes Dp,fresh and Dp,aged can be obtained, providing core input parameters for SOA coating thickness inversion; and the evolution trend of particle size distribution during aging can be monitored.

[0083] The second detection module in this application embodiment can be a black carbon analyzer, which measures the aerosol light absorption coefficient and equivalent BC concentration. This instrument is equipped with a sampling tube and performs real-time detection at seven wavelengths (370, 470, 520, 590, 660, 880, 950 nm) with a sampling flow rate of 5 L / min. The corresponding MAC (Mass Absorption Cross-section) for each wavelength are 18.47, 14.54, 13.14, 11.58, 10.35, 7.77, and 7.19 nm, respectively. 2 / g. The instrument works by measuring the ATN (Attenuation) of the sample spot on the filter membrane through which incident light passes, and then calibrating by simultaneously measuring a particulate-free reference spot to obtain the aerosol absorption coefficient. The BC concentration is measured at 880 nm (where BC is the main absorbing substance), the detection time resolution is 1 second, and the detection limit is 0.03 μg / m². 3 .

[0084] The black carbon mass concentration measured by the AE33 is calculated based on the absorption signal at a wavelength of 880 nm. Since black carbon is the main absorbing component at this wavelength, the instrument obtains the BC mass concentration by converting the 880 nm absorption coefficient with a preset mass absorption cross section. This BC concentration is used to characterize the level of atmospheric black carbon pollution and also serves as a reference parameter for optical inversion. It is used to extrapolate the BC absorption contribution at different wavelengths based on the wavelength dependence of black carbon absorption, and to subtract the BC absorption from the total absorption to estimate the brown carbon absorption contribution.

[0085] The calculation method for BC is as follows: ; Where BC represents the black carbon mass concentration, in μm / m³. 3 ; The absorption coefficient at 880 nm; This represents the mass absorption cross section of black carbon at 880 nm. In common optical inversions of brown carbon, the BC concentration or absorption coefficient measured at 880 nm is often used as a benchmark to estimate the absorption of BC in the short-wavelength band. ; It is generally assumed Then, subtract the BC absorption from the total absorption to obtain the brown carbon absorption: = ; If the concentration of OC (Organic Carbon) is measured simultaneously, it can be calculated that: ; in, The cross section of brown carbon mass absorption is given in meters. 2 g -1 The larger the MAC, the stronger the light absorption capacity per unit mass of brown carbon.

[0086] Therefore, the black carbon mass concentration detected by AE33 is not only a direct observation of the BC pollution level, but also a key basic parameter for estimating black carbon absorption and stripping non-black carbon absorption contribution in brown carbon optical inversion.

[0087] Based on the second module described above, the first light absorption coefficient at seven wavelengths before and after aging can be obtained. Second light absorption coefficient ; Calculate the absorption enhancement coefficient at each wavelength; Calculate the absorption Ångström exponent AAE to characterize the wavelength dependence of the absorption coefficient; Provide optical data for the quantitative correlation between coating thickness and absorption enhancement.

[0088] Furthermore, in one embodiment of this application, the third detection module includes a single-particle sampler and an electron microscope, wherein the single-particle sampler is used to collect particulate matter in engine exhaust gas, and the electron microscope is used to generate morphological characterization images of the single particles; the fourth detection module includes a filter membrane sampler and at least one analyzer, wherein the filter membrane sampler is used to sample particulate matter in engine exhaust gas through a filter membrane, and the at least one analyzer is used to analyze the chemical composition of the sampled single particles.

[0089] Among them, electron microscopes can include SEM (Scanning Electron Microscope) and TEM (Transmission Electron Microscope); the analyzer is used to detect the particulate chemical components in engine exhaust gas sampled on the filter membrane, and can include thermo-photonic carbon analyzers, ion chromatographs, etc.

[0090] It is understood that the third detection module in this application embodiment includes a single particle sampler and an electron microscope to achieve microscopic sampling and imaging of single particles, magnify and observe the surface structure of particles, so as to clearly present the core-shell structure and coating morphology of particles, and provide microscopic and intuitive evidence for aging assessment. The fourth detection module includes a filter membrane sampler and an analyzer, which enriches particulate matter through the filter membrane and then uses the analyzer to analyze the chemical composition to accurately determine the chemical composition of particulate matter for subsequent calculation of chemical increment and coating layering.

[0091] Specifically, the third detection module of this application introduces a single-particle sampler to directly deposit particles before and after aging onto a silicon wafer or transmission electron microscope (TEM) grid. The collected samples are characterized for high-resolution morphology using SEM and TEM. SEM is used to observe the particle surface coating state, agglomeration morphology, and surface texture, while TEM is used to observe the internal structure of the particles, core-shell layering, and coating uniformity. By comparing single-particle images before and after aging, the presence of a coating, the uniformity of coating coverage, and the evolution characteristics of particle morphology (such as whether chain-like agglomerates tend to become rounded due to coating) can be intuitively determined.

[0092] Based on the aforementioned third detection module, intuitive microscopic morphology evidence of coating presence can be provided, overcoming the limitations of the "black box" operation of pure optical inversion; qualitative verification of the reliability of coating thickness results based on particle size peak migration inversion; and revealing the evolution law of particle morphology during aging.

[0093] Furthermore, in one embodiment of this application, the fourth detection module further includes a flow meter and a sampling pump, wherein the flow meter is used to adjust the sampling flow rate of the engine exhaust gas, and the sampling pump is used to generate suction to drive the engine exhaust gas through the filter membrane sampler.

[0094] Among them, the sampling pump is used to provide negative pressure for air extraction; the flow meter is used to monitor and adjust the sampling flow rate of engine exhaust gas in real time.

[0095] It is understood that the fourth detection module in this application embodiment also includes a flow meter and a sampling pump. The sampling pump is used to generate negative pressure suction to drive the engine exhaust gas through the filter membrane sampler, and the flow meter is used to adjust the sampling flow rate to ensure that the sampling conditions of the engine exhaust gas before and after the reaction are consistent.

[0096] Specifically, the fourth detection module in this application embodiment can use a quartz filter membrane sampler to collect particulate matter samples before and after aging. The sampler is equipped with a flow meter and a sampling pump for precise control of the sampling flow rate. The collected filter membrane undergoes multi-dimensional chemical analysis, including: determining the concentrations of OC and EC (Elemental Carbon) using a thermoluminescent carbon analyzer, calculating the OC / EC ratio and its changes before and after aging; analyzing the elemental composition of metals using inductively coupled plasma mass spectrometry or X-ray fluorescence spectrometry; and analyzing water-soluble inorganic ions (including SO42-) using ion chromatography. 2- NO3 - NH4 + Cl - The concentrations of organic components (e.g., etc.) were determined; the organic components were analyzed using gas chromatography-mass spectrometry or liquid chromatography-mass spectrometry.

[0097] Based on the fourth detection module mentioned above, the condensation contribution of SOA on the particle surface can be quantitatively characterized by the OC increment after aging; the contribution of inorganic coating can be quantitatively characterized by the sulfate increment after aging; the total coating thickness t based on the particle size peak migration inversion can be decomposed into organic coating thickness and inorganic coating thickness; direct chemical evidence can be provided to distinguish the SOA lens effect from the contribution of sulfate to light absorption enhancement; and the role of different chemical components in coating formation can be analyzed.

[0098] It should be noted that the engine exhaust photochemical aging assessment system of this application embodiment can also be used to assess the photochemical aging process of engine exhaust under different operating conditions, which can be achieved simply by setting the operating conditions of the transmitter under test.

[0099] The following will combine Figure 2 The engine exhaust photochemical aging assessment system shown is used to describe the engine exhaust photochemical aging assessment process of this application embodiment, including: Step 1: Fresh emission baseline condition determination.

[0100] The engine operates under steady-state conditions. After two-stage dilution (total dilution ratio of approximately 100 times), the exhaust gas is diverted to each detection module: (1) SMPS measures the particle size distribution of freshly emitted particulate matter and obtains the peak electromobility particle size D. p,fresh(2) AE33 was used to measure the absorption coefficient of fresh emission light and the concentration of BC at 7 wavelengths; (3) a single particle sampler was used to collect samples, and SEM / TEM was used to observe the morphological characteristics and surface state of fresh emission particles; (4) a quartz filter membrane was used to collect samples and the background concentrations of OC, EC, metal elements, inorganic ions and organic components were measured.

[0101] OC and EC were determined using a thermo-photocatalytic carbon aerosol analysis method. During aging, gaseous precursors undergo oxidation to generate SOA, which condenses on the surface of particulate matter, leading to a significant increase in OC content. EC cores remain chemically stable during aging, and their mass remains essentially unchanged. Therefore, an increase in the OC / EC ratio is an important indicator for measuring the degree of aging and the amount of SOA generated.

[0102] Meanwhile, the embodiments of this application can use X-ray fluorescence to analyze the metal content in the filter membrane. The metals (such as calcium, sodium, potassium, etc.) mainly come from fuel, lubricating oil or mechanical wear. During the aging process, the concentration of these metal elements themselves does not change much, but they are often used as tracers. They can be combined with single particle analysis to track the aging path of specific types of particles.

[0103] Water-soluble inorganic ions were determined by ultrasonic extraction and ion chromatography. During the aging process, SO2 was photochemically oxidized to sulfate, and NO... x Oxidation produces nitrates, and these newly generated secondary inorganic aerosols coat the surface of particulate matter, causing its concentration to increase.

[0104] Organic components were extracted, concentrated, and subjected to necessary derivatization with organic solvents before being determined by GC-MS or LC-MS. Analysis revealed primary organic components such as polycyclic aromatic hydrocarbons (PAHs) in fresh emissions, as well as newly generated, more oxidizing SOA components after aging. All results were adjusted by subtracting field or laboratory blanks.

[0105] Step 2: Photochemical aging treatment.

[0106] The diluted engine exhaust gas was introduced into the PAM-OFR reactor and subjected to photochemical aging in OFR254 mode. By controlling the intensity of ultraviolet light, an OH exposure gradient was set (equivalent atmospheric aging for 0.5 days, 1 day, 2 days, 5 days, and 10 days), the relative humidity in the reactor was controlled at 50%, and the residence time was approximately 120 seconds.

[0107] Step 3: Multi-dimensional testing after aging.

[0108] After aging, the gas is diverted to each detection module under the same conditions, and the measurements in step S1 are repeated to obtain the D value after aging. p,aged , BC concentration, SEM / TEM images and chemical composition data.

[0109] In summary, the engine exhaust photochemical aging assessment system of this application embodiment can achieve the following: 1. To address the error issues inherent in particle size inversion techniques that rely on complex Mie models and sphericity assumptions, a direct inversion formula based on the rightward shift of the peak particle size distribution measured by SMPS is proposed. This method eliminates the need for complex models and optimization calculations, enabling simple and rapid assessment of coating thickness and demonstrating promising prospects for engineering applications.

[0110] 2. Regarding the problem that optical inversion methods in related technologies generally assume that the AAE of black carbon is 1, and can only extrapolate the absorption of black carbon through the absorption spectrum and attribute the remaining absorption to brown carbon, thus indirectly inferring the contribution of brown carbon, it cannot provide direct structural evidence of coating growth. In this application, the embodiment introduces a single-particle sampler to collect particulate matter and then performs SEM and TEM for morphological characterization. By comparing the changes in the surface coating state of particles before and after aging, intuitive microscopic morphological evidence of coating existence is provided, breaking through the limitations of the "black box" operation of pure optical inversion, and improving the attribution analysis of absorption enhancement from indirect speculation to direct observation.

[0111] 3. To address the issue of undecomposed chemical components of the coating layer in related technologies, this study measures the chemical components such as EC / OC, metals, inorganic ions, and organic matter using a quartz filter membrane. For the first time, the total coating thickness is decomposed into organic coating thickness and inorganic coating thickness, providing direct chemical evidence to distinguish between the SOA lens effect and the contribution of sulfate to light absorption enhancement.

[0112] The embodiments of this application employ a multi-dimensional comprehensive evaluation, which has the following significant advantages over single-dimensional evaluation methods: (1) Compared with the pure optical inversion method, this application directly calculates the total coating thickness by SMPS particle size peak migration, without relying on the assumption of the eigenvalue of black carbon AAE, and provides direct microstructure evidence of the existence of the coating by SEM / TEM single particle morphology characterization, breaking through the limitations of "black box" inversion. (2) Compared with the Mie scattering particle size inversion method, this application calculates the coating thickness by direct difference of the peak value of the particle size distribution. It does not require complex models and optimization algorithms, and the calculation is simple and fast, which is suitable for rapid evaluation in engineering field. (3) Compared with the existing SP-AMS / SMPS combined method, which can only obtain the total coating thickness, this application realizes the separate quantitative determination of organic coating thickness and inorganic coating thickness for the first time by calculating the chemical increment and the total coating thickness. It can clearly distinguish the different contribution mechanisms of SOA lens effect and inorganic salt to light absorption enhancement. However, if coating decomposition is not performed, the absorption enhancement coefficient will be uniformly attributed to the total coating and the contribution differences of different components cannot be distinguished. The black carbon radiative forcing error estimated in this way is extremely large.

[0113] The engine exhaust photochemical aging assessment system proposed in this application includes a sampling device, a dilution device, a reaction device, a detection device, and a processor. The dilution device uses air to dilute the initial engine exhaust collected by the sampling device. The reaction device performs a photochemical aging reaction on the diluted initial engine exhaust and outputs the reacted engine exhaust to simulate the photochemical aging process of engine exhaust in the atmospheric environment. The detection device performs particle size distribution detection, optical absorption detection, particulate morphology characterization detection, and chemical composition detection on the unreacted initial engine exhaust and the reacted engine exhaust, respectively, to obtain a first characteristic parameter and a second characteristic parameter. An electronic device is then configured to perform particle size distribution detection, optical absorption detection, particulate morphology characterization detection, and chemical composition detection on the first and second characteristic parameters. The characteristic parameter calculation method can calculate the total coating thickness of particulate matter in engine exhaust gas without the need for complex models and optimization calculations. The calculation is simple and fast. The total coating thickness is decomposed into organic coating thickness and inorganic coating thickness. Then, the photochemical aging process of engine exhaust gas is evaluated based on the organic coating thickness and inorganic coating thickness. This enables a quantitative and intuitive assessment of the photochemical aging process of engine exhaust gas. By refining the decomposition of organic and inorganic coating thickness, the accuracy of the assessment of the photo-aging characteristics of engine exhaust gas is improved. The method can clearly distinguish the contribution of the two different types of coating components in the photochemical aging evolution process, and comprehensively and meticulously reflect the true photochemical aging evolution characteristics of engine exhaust gas.

[0114] Next, referring to the accompanying drawings, a method for evaluating the photochemical aging of engine exhaust gas according to an embodiment of this application is described.

[0115] Figure 4 This is a schematic flowchart of the engine exhaust photochemical aging assessment method according to an embodiment of this application.

[0116] like Figure 4 As shown, the engine exhaust photochemical aging assessment method, based on the engine exhaust photochemical aging assessment system described above, includes the following steps: In step S101, the first characteristic parameters of the initial engine exhaust gas of the engine under test and the second characteristic parameters of the engine exhaust gas after photochemical aging reaction are obtained.

[0117] In step S102, the total coating thickness of particulate matter in engine exhaust gas is calculated based on the first characteristic parameter and the second characteristic parameter, and the total coating thickness is decomposed into organic coating thickness and inorganic coating thickness.

[0118] In step S103, the photochemical aging characteristics of engine exhaust gas are evaluated based on the thickness of the organic coating and the thickness of the inorganic coating.

[0119] It should be noted that the foregoing explanation of the embodiment of the engine exhaust photochemical aging assessment system also applies to the engine exhaust photochemical aging assessment method of this embodiment, and will not be repeated here.

[0120] The following specific embodiment describes the engine exhaust photochemical aging assessment method of this application.

[0121] I. Baseline measurement of engine exhaust before photochemical aging.

[0122] 1. Engine operating conditions.

[0123] This embodiment uses a YC173FB single-cylinder two-stroke diesel engine equipped with a 2.5-liter fuel tank. The engine operates stably at 1800 rpm, with an output power of 2.2 kW and a fuel consumption rate of 311.1 g / kWh. Automotive diesel fuel (freezing point -10℃) was used, and the engine was subsequently operated at four different speeds: 1200 rpm, 1800 rpm, 3000 rpm, and 3600 rpm.

[0124] A large collection tube, approximately 30 cm in diameter, is connected to the rear end of the engine exhaust pipe to collect engine exhaust gases and mix them with ambient air. This unit's function is to generate stable, repeatable engine combustion emissions, providing representative fresh emission samples for subsequent aging simulations. A gas sampling tube extends into the large collection tube to extract engine exhaust gases. The exhaust gases are then diluted by a two-stage jet diluter, with a total dilution ratio of approximately 100 times. The dilution air is supplied by an air pump through a HEPA filter.

[0125] 2. Particle size distribution determination.

[0126] The particle size number concentration distribution of freshly emitted particulate matter was measured using a TSI 3080 SMPS. The detection particle size range was 9.82–399.5 nm, with a single scan cycle of approximately 110 seconds and a sampling flow rate of 0.3–1.5 L / min. The peak electromobility particle size D of the freshly emitted particulate matter was determined. p,fresh .

[0127] 3. Measurement of light absorption coefficient.

[0128] The light absorption coefficient and equivalent black carbon (BC) concentration of freshly emitted aerosols were measured using an AE33-7 seven-band black carbon analyzer. The instrument, equipped with a data acquisition tube, performs real-time detection at seven wavelengths (370, 470, 520, 590, 660, 880, and 950 nm) at a sampling flow rate of 5 L / min. The corresponding MAC values ​​for each wavelength were 18.47, 14.54, 13.14, 11.58, 10.35, 7.77, and 7.19 m, respectively. 2 / g. The instrument obtains the aerosol absorption coefficient by measuring the attenuation of the sample spot on the incident light passing through the filter membrane, combined with the simultaneous measurement of the particulate-free reference spot. The concentration of BC was measured at a wavelength of 880 nm (where BC is the main absorbing substance), with a detection time resolution of 1 second and a detection limit of 0.03 μg / m³. 3 .

[0129] 4. Characterization of single-particle morphology.

[0130] Freshly emitted particulate matter was deposited onto a silicon wafer or transmission electron microscope grid using a single-particle sampler. High-resolution morphology characterization was performed using SEM and TEM to obtain the morphological features and background images of the surface coating state of the freshly emitted particulate matter.

[0131] 5. Determination of chemical composition.

[0132] Fresh particulate matter samples were collected using a quartz filter membrane sampler at a sampling flow rate of 4.5 L / min. The sampler was equipped with a mass flow controller and a sampling pump to precisely control the sampling flow rate. The collected filter membranes underwent the following chemical analyses: (1) the concentrations of OC and EC were determined using a thermoluminescent carbon analyzer, and the OC / EC baseline value was calculated; (2) the elemental composition of metals was analyzed using ICP-MS; (3) the concentration of water-soluble inorganic ions was analyzed using IC; and (4) the organic components were analyzed using GC-MS.

[0133] II. Determination of the state of engine exhaust after photochemical aging.

[0134] The diluted engine exhaust gas was subjected to photochemical aging treatment, and the various physicochemical properties after aging were measured.

[0135] 1. Photochemical aging treatment.

[0136] Diesel engine exhaust gas, after two-stage dilution (total dilution ratio approximately 100 times), was introduced into a PAM-OFR oxidation flow reactor, operating in OFR254 mode. The relative humidity inside the reactor was controlled at 50%, and the residence time was approximately 120 seconds. The ozone concentration at the reactor outlet was monitored in real time using an ultraviolet absorption ozone analyzer. The aforementioned OH· free radicals interact with O3 and precursors in the exhaust gas to generate low-volatility compounds, which then transform into the particulate phase, promoting SOA formation.

[0137] 2. Measurement after aging.

[0138] The particle size number concentration distribution of aged particles was measured using the same SMPS method as described above. The particle size range was 9.82–399.5 nm, and the single scan cycle was approximately 110 seconds. The peak electromobility particle size D of the aged particles was determined. p,aged Based on the peak particle size migration, according to the formula... Invert the SOA coating thickness.

[0139] The light absorption coefficient of aged aerosols was measured using an AE33-7 seven-band black carbon analyzer. and BC concentration. Based on the measurement results before and after aging, according to the formula Calculate the absorption enhancement coefficient at each wavelength. In this embodiment, three wavelengths—370 nm (containing BC + BrC), 660 nm, and 880 nm (containing BC only)—are selected to separate the BrC absorption and calculate the absorption Ångström index (AAE): using the formula... This characterizes the relationship between the absorption coefficient and wavelength.

[0140] Aging particulate matter was collected using a single-particle sampler and its morphology was characterized by SEM / TEM. The results were compared with the fresh emission background images to observe the changes in the surface coating state and the presence of coatings on the aged particles.

[0141] A quartz filter membrane sampler was used to collect particulate matter samples after aging. Chemical analysis was performed using the same method as described above to determine the concentrations of OC, EC, metal elements, inorganic ions, and organic matter after aging, and the values ​​before and after aging were calculated. and Based on the above results, the total coating thickness is... Decomposed into organic coating thickness and inorganic coating thickness .

[0142] This application also provides a computer-readable storage medium storing a computer program or instructions thereon, which, when executed by a processor, implements the above-described engine exhaust photochemical aging assessment method.

[0143] This application also provides a computer program product, including a computer program or instructions, which, when executed, implement the above-described engine exhaust photochemical aging assessment method.

[0144] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0145] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "N" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0146] Any process or method described in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or N executable instructions for implementing custom logic functions or processes, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as should be understood by those skilled in the art to which embodiments of this application pertain.

[0147] It should be understood that the various parts of this application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, the N steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or more of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (FPGAs), field-programmable gate arrays (FPGAs), etc.

[0148] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

Claims

1. An engine exhaust gas photo-chemical aging evaluation system, characterized by, include: A sampling device for collecting initial engine exhaust gas from the engine under test; A dilution device, connected to the sampling device, is used to dilute the initial engine exhaust gas with air; A reaction device, which is connected to the dilution device, is used to perform a photochemical aging reaction on the diluted initial engine exhaust gas and output the reacted engine exhaust gas, wherein the particulate matter in the reacted engine exhaust gas is coated with an inorganic coating and / or an organic coating. A detection device, which is connected to the reaction device, is used to perform particle size distribution detection, optical absorption detection, particulate morphology characterization detection and chemical composition detection on the initial engine exhaust gas and the reacted engine exhaust gas, respectively, to obtain the first characteristic parameter of the initial engine exhaust gas and the second characteristic parameter of the reacted engine exhaust gas. An electronic device, communicatively connected to the detection device, is configured to receive a first characteristic parameter and a second characteristic parameter from the detection device, calculate the total coating thickness of particulate matter in the engine exhaust gas based on the first characteristic parameter and the second characteristic parameter, decompose the total coating thickness into an organic coating thickness and an inorganic coating thickness, and evaluate the photochemical aging characteristics of the engine exhaust gas based on the organic coating thickness and the inorganic coating thickness. The first characteristic parameter includes a target electromobility particle size and a chemical composition. The electronic device is further configured to: calculate the total coating thickness of particulate matter in the engine exhaust gas based on a first target electromobility particle size and a second target electromobility particle size; calculate the organic component increment and the inorganic component increment of the particulate matter based on a first chemical composition and a second chemical composition, respectively; and calculate the organic coating thickness and the inorganic coating thickness of the particulate matter in the engine exhaust gas based on the organic component increment, the inorganic component increment, and the total coating thickness.

2. The engine exhaust gas photo-aging evaluation system according to claim 1, characterized by, The first characteristic parameter and the second characteristic parameter further include at least one of the following: particle size distribution characteristics, light absorption coefficient at different wavelengths, black carbon mass concentration, and morphology characterization image.

3. The engine exhaust photochemical aging assessment system according to claim 2, characterized in that, The formula for calculating the total coating thickness is as follows: ； in, The second target electromobility particle size is the second characteristic parameter. The first target electromobility particle size in the first characteristic parameter, t This refers to the total coating thickness. The formula for calculating the increase in the organic component is: ； in, For the increase of organic components, The concentration of the second organic component in the second characteristic parameter. The concentration of the first organic component in the first characteristic parameter; The formula for calculating the increment of the inorganic component is: ； in, For the increment of inorganic components, The concentration of the second inorganic component in the second characteristic parameter. The concentration of the first inorganic component in the first characteristic parameter; The formula for calculating the thickness of the organic coating is: ； in, For the thickness of the organic coating, The total coating thickness, For the increase of organic components, This represents the increment of the inorganic component; The formula for calculating the thickness of the inorganic coating is: ； in, For the thickness of the inorganic coating, The total coating thickness, For the increase of organic components, This represents the increase in the inorganic component.

4. The engine exhaust photochemical aging assessment system according to claim 2, characterized in that, The electronic device is also used for: The absorption enhancement coefficient of particulate matter in the engine exhaust gas at the corresponding wavelength is calculated based on the first and second light absorption coefficients at each wavelength, and the Estram absorption index of the particulate matter is calculated based on the light absorption coefficients at multiple wavelengths. The surface coating characteristics of particulate matter in the engine exhaust gas are determined based on the first morphological characterization image and the second morphological characterization image. The photochemical aging characteristics of the engine exhaust gas are evaluated based on at least one of the following: organic coating thickness, inorganic coating thickness, particle size distribution characteristics, absorption enhancement coefficient, Estrand absorption index, black carbon mass concentration, surface coating characteristics, inorganic component increment, and organic component increment.

5. The engine exhaust photochemical aging assessment system according to claim 1, characterized in that, The dilution device includes a first air compressor, a filter, and a multi-channel mass flow controller, wherein, The first air compressor is used to generate the first compressed air; The filter is used to filter the first compressed air to obtain diluted air; The multi-channel mass flow controller is used to control the flow ratio of the dilution air and the initial engine exhaust gas, so as to dilute the initial engine exhaust gas based on the dilution air.

6. The engine exhaust photochemical aging assessment system according to claim 1, characterized in that, The reaction apparatus includes a reaction apparatus body, an ultraviolet lamp, a second air compressor, and a nitrogen supply device. The second air compressor is used to generate the second compressed air; The nitrogen supply equipment is used to provide nitrogen. The ultraviolet lamp is used to irradiate the body of the reaction device; The reaction device body stores the diluted initial engine exhaust gas, the second compressed air, and the nitrogen gas, and supplies the diluted initial engine exhaust gas, the second compressed air, and the nitrogen gas to carry out a photochemical aging reaction under the irradiation of the ultraviolet lamp.

7. The engine exhaust photochemical aging assessment system according to claim 1, characterized in that, The detection device includes first to fourth detection modules, wherein, The first detection module is used to detect the particle size distribution characteristics and target electromobility particle size of particulate matter in the engine exhaust gas. The second detection module is used to detect the light absorption coefficient and black carbon mass concentration of particulate matter in engine exhaust at different wavelengths. The third detection module is used to detect the morphological characterization images of single particles in engine exhaust gas. The fourth detection module is used to detect chemical components in engine exhaust.

8. The engine exhaust photochemical aging assessment system according to claim 7, characterized in that, The first detection module is a particle size spectrometer, and the second detection module is a black carbon analyzer. The particle size spectrometer includes a differential electromobility analyzer, a condensation nucleus particle counter, and an analysis unit. The differential electromobility analyzer is used to classify the particle size of the particulate matter in the engine exhaust gas according to the electromobility of the particulate matter. The condensation nucleus particle counter is used to count the particulate matter in each particle size group. The analysis unit is used to determine the particle size distribution characteristics and target electromobility particle size of the particulate matter in the engine exhaust gas based on the particle size classification results and the particle count values ​​of different particle sizes.

9. The engine exhaust photochemical aging assessment system according to claim 7, characterized in that, The third detection module includes a single-particle sampler and an electron microscope, wherein the single-particle sampler is used to collect particulate matter in engine exhaust gas, and the electron microscope is used to generate morphological characterization images of the single particles. The fourth detection module includes a filter membrane sampler and at least one analyzer. The filter membrane sampler is used to sample particulate matter in engine exhaust gas through a filter membrane, and the at least one analyzer is used to analyze the chemical composition of the sampled single particulate matter.

10. The engine exhaust photochemical aging assessment system according to claim 9, characterized in that, The fourth detection module further includes a flow meter and a sampling pump. The flow meter is used to adjust the sampling flow rate of the engine exhaust gas, and the sampling pump is used to generate suction to drive the engine exhaust gas through the filter membrane sampler.

11. A method for evaluating the photochemical aging of engine exhaust gas, characterized in that, The method employs the engine exhaust photochemical aging assessment system as described in any one of claims 1-10, wherein the method includes the following steps: The first characteristic parameters of the initial engine exhaust gas of the engine under test, and the second characteristic parameters of the engine exhaust gas after photochemical aging reaction are obtained. The total coating thickness of particulate matter in the engine exhaust gas is calculated based on the first characteristic parameter and the second characteristic parameter, and the total coating thickness is decomposed into organic coating thickness and inorganic coating thickness. The photochemical aging characteristics of the engine exhaust gas were evaluated based on the thickness of the organic coating and the thickness of the inorganic coating.

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