A method and related device for simultaneously measuring mass concentration of core-shell particles
By employing a photoacoustic measurement method involving dual-frequency excitation and multi-wavelength coupling, the measurement deviation problem caused by the core-shell structure was solved, enabling synchronous and accurate measurement of the mass concentration of the core and volatile shell layers of core-shell particles, thus improving measurement accuracy and practicality.
Patent Information
- Application Number
- CN202611210639.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-08-11
- Publication Date
- 2026-11-03
AI Technical Summary
When measuring non-volatile particulate matter emitted by aviation using the existing photoacoustic method, the optical and thermal heterogeneity of the core-shell structure leads to deviations in the measurement results, and existing preprocessing methods cannot completely eliminate interference and introduce new errors.
By employing a dual-frequency excitation and multi-wavelength coupling method, the photoacoustic signal is separated by spectral absorption differences. Combined with a multidimensional response signal inversion system, the mass concentration of the core and volatile shell of core-shell particles is simultaneously measured. The Levenberg-Marquardt algorithm is used for iterative solution.
It enables simultaneous, independent, and accurate measurement of the mass concentration of the core and volatile shell of core-shell particles, eliminating measurement distortion caused by core-shell heterogeneity and improving measurement accuracy and practicality.
Smart Images
Figure CN123028965A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of aerosol particulate matter detection technology, and in particular to a method and related apparatus for simultaneous measurement of the mass concentration of core-shell particulate matter. Background Technology
[0002] The current online measurement method for the mass concentration of non-volatile particulate matter (NVPM) in aviation emissions is photoacoustic. This method utilizes the absorption of modulated laser light by particulate matter to generate periodic temperature changes. The surrounding gas is heated, creating pressure fluctuations that excite sound waves of a specific frequency. Real-time online measurement of the mass concentration is achieved by detecting the amplitude of these sound waves. Compared to traditional methods such as filter weighing, photoacoustic methods offer advantages such as high sensitivity, rapid response, and continuous online measurement, making them a widely used method for detecting the mass concentration of aviation particulate matter internationally.
[0003] However, the photoacoustic method relies on the assumption of uniform spherical particles, meaning that the particles have uniform composition and consistent light absorption and thermal conductivity. In real aviation emissions, incomplete combustion of fuel produces a large amount of volatiles (such as polycyclic aromatic hydrocarbons and oxygenated organic compounds). These volatiles condense on the surface of NVPMs, forming an optically and thermally heterogeneous "core-shell structure"—the core being carbonaceous aggregates and the outer shell being condensed volatiles. At this point, the uniform spherical assumption no longer holds. Surface volatiles alter the light absorption and thermal conductivity processes of the particles, causing distortion in the photoacoustic response and leading to significant deviations in the measurement results. Existing detection techniques have obvious shortcomings in addressing the problem of distorted core-shell particle mass concentration measurements caused by volatile condensation: the photoacoustic method based on the uniform spherical assumption suffers from fundamental distortion due to the heterogeneity of particle absorption and thermal conductivity; VPR pretreatment methods cannot completely remove surface volatiles and cause particle deformation, introducing new errors. Summary of the Invention
[0004] The purpose of this application is to provide a method and related apparatus for simultaneous measurement of the mass concentration of core-shell particulate matter, which can realize the simultaneous and accurate measurement of the mass concentration of the non-volatile particles in the core and the volatile shell layer of core-shell particulate matter.
[0005] To achieve the above objectives, this application provides the following solution: In a first aspect, this application provides a method for simultaneous measurement of the mass concentration of core-shell particulate matter, comprising: The photoacoustic signals of the core-shell structure particles under test are acquired under the optimal combination of characteristic wavelengths and characteristic frequencies, as well as the photoacoustic signals of the zero-particle pure carrier gas under the same conditions. The optimal combination of characteristic wavelengths and the characteristic frequencies are obtained based on pre-calibration of pure carbon soot particles, pure volatile condensate particles, and standard core-shell particles.
[0006] Based on the photoacoustic signal of the zero-particle pure carrier gas under the optimal characteristic wavelength combination and the characteristic frequency conditions, the photoacoustic signal reference information is determined.
[0007] Based on the photoacoustic signal of the core-shell structured particulate matter under the optimal combination of characteristic wavelengths and characteristic frequencies, the photoacoustic signal reference information, and the optimal combination of characteristic wavelengths, the measured core-shell photoacoustic fingerprint spectrum is determined; the measured core-shell photoacoustic fingerprint spectrum includes measured amplitude data, measured phase data, and measured amplitude ratio data.
[0008] Based on the measured core-shell photoacoustic fingerprint spectrum, combined with the pre-constructed phase-thermal property mapping spectrum, the theoretical prediction value of the forward photo-thermal-acoustic coupling model is determined; the theoretical prediction value of the forward photo-thermal-acoustic coupling model includes theoretical prediction amplitude data, theoretical prediction phase data, and theoretical prediction amplitude ratio data.
[0009] A weighted least squares optimization objective function is constructed, and the Levenberg-Marquardt algorithm is used to iteratively solve the problem with the goal of minimizing the error between the theoretical prediction of the forward photo-thermal-acoustic coupling model and the measured core-shell photoacoustic fingerprint spectrum. The optimal measurement results of the core-shell structure particles to be measured are obtained. The optimal measurement results include the mass concentration of soot core, the mass concentration of volatile shell, and the thermal resistance of the core-shell interface.
[0010] Secondly, this application provides a computer device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the above-described method for synchronous measurement of the mass concentration of core-shell particles.
[0011] Thirdly, this application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the above-described method for synchronous measurement of the mass concentration of core-shell particulate matter.
[0012] Fourthly, this application provides a computer program product, including a computer program that, when executed by a processor, implements the above-described method for synchronous measurement of the mass concentration of core-shell particulate matter.
[0013] According to the specific embodiments provided in this application, this application has the following technical effects: This application provides a method and related apparatus for synchronous measurement of the mass concentration of core-shell particles. By selecting the optimal combination of characteristic wavelengths and conducting excitation detection on two types of characteristic frequencies that are sensitive to changes in shell thickness and resonance peak width, the method solves the problem that single-wavelength or single-frequency excitation cannot distinguish the optical and structural features of core-shell particles, achieving effective separation of the coupled photoacoustic signals of the core and shell. By collecting photoacoustic signals under pure carrier gas to determine reference data and combining the reference data with photoacoustic electrical signals to generate a measured core-shell photoacoustic fingerprint spectrum, the method solves the problems of inherent noise interference and difficulty in extracting effective signals, achieving complete preservation of the optical, thermal, and acoustic multidimensional response characteristics of core-shell particles. By retrieving a pre-constructed phase-thermal property mapping spectrum, the method obtains the forward photoacoustic-thermal response. The coupled model theoretical predictions address the problem of iterative divergence caused by random selection of initial values in nonlinear inversion, enabling rapid and reasonable estimation of initial parameters. By constructing a weighted least squares optimization objective function and using the Levenberg-Marquardt algorithm for iterative solution, the problem of simultaneous multi-parameter solution for the nonlinear mapping of photoacoustic response of core-shell particles is solved, enabling simultaneous solution of soot core mass concentration, volatile shell mass concentration, and core-shell interface thermal resistance. The overall technical solution of this application eliminates measurement distortion caused by core-shell heterogeneity in principle, avoids secondary errors without VPR preprocessing, and achieves synchronous, independent, and accurate measurement of the mass concentration of non-volatile particles in the core and the volatile shell of core-shell particles, significantly improving measurement accuracy and practicality. Attached Figure Description
[0014] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0015] Figure 1 This is an application environment diagram of a method for synchronous measurement of core-shell particulate matter mass concentration in one embodiment of this application; Figure 2 A schematic flowchart illustrating a method for simultaneous measurement of the mass concentration of core-shell particulate matter according to an embodiment of this application; Figure 3 A schematic diagram of the functional modules of a synchronous measurement device for the mass concentration of core-shell particulate matter provided in an embodiment of this application; Figure 4 A schematic diagram illustrating the iterative process of the particulate-volatile matter synchronous inversion method provided in an embodiment of this application; Figure 5 This is a schematic diagram of the structure of a computer device provided in an embodiment of this application.
[0016] Reference numerals: 101-Laser modulator; 201-First laser; 202-Second laser; 203-Third laser; 301-Spectroscopy system; 401-Carbide particle generation system; 501-Anti-particle adhesion pipe; 601-Photoacoustic cell; 701-Microphone; 801-Lock-in amplifier; 901-Signal processing module. Detailed Implementation
[0017] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0018] Traditional online measurement of the mass concentration of non-volatile particulate matter in aviation emissions uses the photoacoustic method. Although this method has detection advantages and is recognized by the industry, it is based on the assumption of uniform spherical particles, which cannot be adapted to core-shell structured particles in exhaust gas with volatile shells encasing carbonaceous cores. This can easily cause photoacoustic response distortion and measurement deviation. Furthermore, the accompanying preprocessing methods are difficult to completely eliminate interference and can easily introduce new errors.
[0019] Therefore, this application focuses on the measurement of NVPM and surface volatile matter mass concentrations in aviation emissions. It achieves simultaneous measurement of the mass concentrations of the core and volatile shell layers of core-shell particles using a "dual-frequency excitation + multi-wavelength coupling" method. Optical signal separation is achieved by utilizing the spectral absorption differences between the core NVPM and the volatile shell layer at different wavelengths. Multidimensional acoustic fingerprint features related to the core-shell structure are obtained through dual characteristic frequencies. A synchronous inversion mechanism is constructed based on the multidimensional response signal, ultimately achieving synchronous, independent, and accurate measurement of the mass concentrations of the core NVPM and the volatile shell layer of core-shell particles.
[0020] This application proposes a method for synchronously measuring the mass concentration of core-shell particles. By using the difference in spectral absorption between the two to separate photoacoustic signals, and relying on dual characteristic frequencies to extract multidimensional acoustic features corresponding to the core-shell structure, a multidimensional response signal synchronous inversion system is built to synchronously and accurately measure the mass concentration of the non-volatile particle core and the volatile shell layer.
[0021] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.
[0022] The method for simultaneous measurement of core-shell particulate matter mass concentration provided in this application embodiment can be applied to, for example... Figure 1In the application environment shown, terminal 102 communicates with server 104 via a network. A data storage system can store the data that server 104 needs to process. The data storage system can be set up independently, integrated into server 104, or placed in the cloud or on another server. Terminal 102 can send the photoacoustic signals of the core-shell structure particles under test under optimal characteristic wavelength combinations and characteristic frequency conditions, as well as the photoacoustic signals of zero-particle pure carrier gas under the same optimal characteristic wavelength combinations and characteristic frequency conditions, to server 104. After receiving the photoacoustic signals of the core-shell structure particles under test and the zero-particle pure carrier gas under the same optimal characteristic wavelength combinations and characteristic frequency conditions, server 104, based on the optimal characteristic wavelength combinations and characteristic frequency conditions of the zero-particle pure carrier gas, performs the following: The photoacoustic signals under the specified characteristic frequency conditions are combined to determine the photoacoustic signal reference information. Based on the photoacoustic signals of the core-shell structure particles under the optimal characteristic wavelength combination and characteristic frequency conditions, the photoacoustic signal reference information, and the optimal characteristic wavelength combination, the measured core-shell photoacoustic fingerprint spectrum is determined. Based on the measured core-shell photoacoustic fingerprint spectrum, combined with a pre-constructed phase-thermal property mapping spectrum, the theoretical prediction value of the forward photo-thermal-acoustic coupling model is determined. A weighted least squares optimization objective function is constructed, and the Levenberg-Marquardt algorithm is used to iteratively solve the problem with minimizing the error between the theoretical prediction value of the forward photo-thermal-acoustic coupling model and the measured core-shell photoacoustic fingerprint spectrum as the optimization objective, to obtain the optimal measurement result of the core-shell structure particles under test. The server 104 can feed back the obtained optimal measurement result of the core-shell structure particles to the terminal 102. Furthermore, in some embodiments, the method for synchronously measuring the mass concentration of core-shell particles can also be implemented separately by the server 104 or the terminal 102. For example, the terminal 102 can directly calculate the optimal measurement result of the core-shell particles under test based on the photoacoustic signals of the core-shell particles under test under the optimal characteristic wavelength combination and characteristic frequency conditions, as well as the photoacoustic signals of the zero-particle pure carrier gas under the same conditions. Alternatively, the server 104 can obtain the photoacoustic signals of the core-shell particles under test under the optimal characteristic wavelength combination and characteristic frequency conditions, as well as the photoacoustic signals of the zero-particle pure carrier gas under the same conditions from the data storage system, and calculate the optimal measurement result of the core-shell particles under test based on these signals.
[0023] The terminal 102 can be, but is not limited to, various desktop computers, laptops, smartphones, tablets, IoT devices, and portable wearable devices. IoT devices can include smart speakers, smart TVs, smart air conditioners, and smart in-vehicle devices. Portable wearable devices can include smartwatches, smart bracelets, and head-mounted devices. The server 104 can be implemented using a standalone server or a server cluster composed of multiple servers, or it can be a cloud server.
[0024] In one exemplary embodiment, such as Figure 2 As shown, a method for simultaneous measurement of the mass concentration of core-shell particulate matter is provided. This method is executed by a computer device, specifically by a terminal or server alone, or by both a terminal and a server. In this embodiment, the method is applied to... Figure 1 Taking server 104 as an example, the explanation includes the following steps 201 to 205.
[0025] Step 201: Obtain the photoacoustic signal of the core-shell structure particles to be tested under the optimal characteristic wavelength combination and characteristic frequency conditions, as well as the photoacoustic signal of the zero-particle pure carrier gas under the same optimal characteristic wavelength combination and characteristic frequency conditions; the optimal characteristic wavelength combination and characteristic frequency are obtained based on pre-calibration of pure carbon soot particles, pure volatile condensate particles, and standard core-shell particles.
[0026] Step 202: Determine the photoacoustic signal reference information based on the photoacoustic signal of the zero-particle pure carrier gas under the optimal characteristic wavelength combination and the characteristic frequency conditions.
[0027] Step 203: Based on the photoacoustic signal of the core-shell structured particles under the optimal characteristic wavelength combination and characteristic frequency conditions, the photoacoustic signal reference information, and the optimal characteristic wavelength combination, determine the measured core-shell photoacoustic fingerprint spectrum; the measured core-shell photoacoustic fingerprint spectrum includes measured amplitude data, measured phase data, and measured amplitude ratio data.
[0028] Step 204: Based on the measured core-shell photoacoustic fingerprint spectrum and combined with the pre-constructed phase-thermal property mapping spectrum, determine the theoretical prediction value of the forward photo-thermal-acoustic coupling model; the theoretical prediction value of the forward photo-thermal-acoustic coupling model includes theoretical prediction amplitude data, theoretical prediction phase data, and theoretical prediction amplitude ratio data.
[0029] Step 205: Construct a weighted least squares optimization objective function and use the Levenberg-Marquardt (LM) algorithm to iteratively solve the problem with the goal of minimizing the error between the theoretical prediction of the forward photo-thermal-acoustic coupling model and the measured core-shell photoacoustic fingerprint spectrum, to obtain the optimal measurement results of the core-shell structure particles to be measured; the optimal measurement results include the carbon soot core mass concentration, the volatile shell mass concentration, and the core-shell interface thermal resistance.
[0030] In another exemplary embodiment of this application, in order to accurately obtain the optimal combination of characteristic wavelengths and characteristic frequencies, the optimal combination of characteristic wavelengths and characteristic frequencies in step 201 above are replaced by the following steps 301-302: Step 301, the optimal characteristic wavelength combination is determined by measuring the absorption spectra of the pure carbon soot particles and the pure volatile matter condensate particles using an ultraviolet-visible-near-infrared absorption spectrometer, and based on the difference in spectral absorption between the pure carbon soot particles and the pure volatile matter condensate particles.
[0031] It should be noted that the absorption spectra of pure soot particles and pure volatile condensate particles were measured using an ultraviolet-visible-near-infrared absorption spectrometer. Based on their spectral absorption differences, an optimal combination of characteristic wavelengths was determined: λ1 is the ultraviolet band where pure volatile condensate particles have strong absorption; λ2 is the visible light band where pure soot particles have absolute dominance in absorption; and λ3 is the thermal relaxation excitation region in the near-infrared band. The thermal relaxation excitation region refers to the near-infrared characteristic band interval. In this band, the laser photon energy is lower, the light energy is deposited more uniformly inside the core-shell particles, and the thermal diffusion timescale is highly matched with the thermal relaxation process of heterogeneous thermal conduction in the particle core and shell. This can significantly amplify the thermal relaxation characteristic signals such as temperature rise lag and phase shift caused by the difference in thermal properties between the core soot and the outer volatile shell. It is convenient to transform the thermal resistance of the core-shell interface through photoacoustic phase and spectral distortion. It is a spectral observation window specifically used to capture and excite the variability of particle thermal conduction.
[0032] Step 302, the characteristic frequency is determined by sweeping and modulating the standard core-shell particles within a preset frequency range, and simultaneously acquiring the amplitude response curve and phase spectrum of the photoacoustic signal in the optimal characteristic wavelength combination under each preset frequency range; the standard core-shell particles are particles with known or controllable specific sizes of the core and volatile shell layers.
[0033] It should be noted that the characteristic frequency is determined by preparing a series of standard core-shell particles in this application embodiment. First, by fixing the carbonaceous core particle size and precisely controlling the thickness of the volatile shell layer, a series of standard core-shell particles are prepared to form a gradient sample. The standard core-shell particles generated by the soot particle generation system 401 are then introduced into the photoacoustic cell 601, and frequency sweep modulation is performed within the frequency range of 10Hz to 10kHz. The amplitude response curves and phase spectra of the three wavelength photoacoustic signals at each frequency are simultaneously acquired, and the characteristic frequency most sensitive to changes in shell thickness is determined. and the characteristic frequency most sensitive to the width of the resonance peak The standard core-shell particles are particles whose specific sizes of the core and volatile shell are known or controllable.
[0034] It should be noted that the soot particle generation system 401 uses a mini-CAST soot generator to prepare soot cores, obtains monodisperse particles through DMA sieving, and calibrates the particle size before and after condensation; selects polycyclic aromatic hydrocarbons, oxygen-containing polycyclic aromatic hydrocarbons, long-chain alkanes and alcohols as organic precursors, generates adjustable saturated vapor through a temperature-controlled diffuser tube, mixes and condenses with soot particles in a laminar flow tube condenser, and controls the type of volatiles, partial pressure, temperature and residence time to achieve precise control of shell thickness, thus realizing the preparation of standard core-shell particles.
[0035] In this embodiment of the application, after initializing the entire photoacoustic system, the laser modulator 101 outputs dual-frequency (… , The modulation signal drives three lasers to output λ1, λ2, and λ3 modulated lasers. The lasers output by each wavelength laser are combined by a dichroic mirror to achieve spatial collinear transmission and enter the photoacoustic cell 601. Then, the photoacoustic cell 601 is circulated with a zero-particle pure carrier gas to collect the background photoacoustic signal under the optimal characteristic wavelength combination and characteristic frequency conditions, and establish and store the photoacoustic signal reference information.
[0036] In another exemplary embodiment of this application, before step 203 described above, the method may further include steps 401 to 402. Wherein: Step 401: Convert the photoacoustic signal of the core-shell structured particles under the optimal combination of characteristic wavelengths and characteristic frequencies into an electrical signal.
[0037] Step 402: Filter the electrical signal and the characteristic frequency to obtain a photoacoustic electrical signal; the photoacoustic electrical signal serves as the photoacoustic signal of the core-shell structure particle under the optimal combination of characteristic wavelengths and characteristic frequencies, and is used to determine the measured core-shell photoacoustic fingerprint spectrum by combining the photoacoustic signal reference information and the optimal combination of characteristic wavelengths.
[0038] It should be noted that in this embodiment, a carbon soot particle generating system 401 generates core-shell structured particles that conform to aviation emission characteristics, which are then used as the core-shell structured particles to be tested. These particles are fed into a photoacoustic cell 601 at a constant speed and with low loss via an anti-particle adhesion pipe 501 to maintain stable concentration and uniform flow field within the cell. Then, the first laser 201 (λ1, ultraviolet), the second laser 202 (λ2, visible), and the third laser 203 (λ3, near-infrared) are periodically activated by a laser modulator 101. , Under dual-frequency conditions, intensity modulation is performed. The three modulated laser beams are combined into a single hybrid laser beam by the beam splitter 301 and focused onto the region of the core-shell structured particle under test in the photoacoustic cell 601 to excite the photoacoustic signal. Then, the microphone 701 synchronously collects the signal from the photoacoustic cell 601. , The photoacoustic signal at a certain frequency is converted into an electrical signal and then sent to the lock-in amplifier 801; the lock-in amplifier 801 is set to... , The signals are demodulated separately, and clutter and incoherent noise are filtered out to output a photoacoustic signal. The photoacoustic signal includes two independent sets of photoacoustic response amplitudes and phases with optimal characteristic wavelength combinations.
[0039] In another exemplary embodiment of this application, step 203 is replaced by steps 501 to 503: Step 501: Based on the photoacoustic signal and the photoacoustic signal reference information, baseline differential operation is used to filter out inherent noise to obtain the filtered photoacoustic signal.
[0040] Step 502: Based on the spectral absorption difference of the optimal characteristic wavelength combination, the filtered photoacoustic-electric signal is decoupled to obtain the core characteristic signal, the shell characteristic signal, and the core-shell interface thermal coupling characteristic signal.
[0041] Step 503: Based on the kernel feature signal, the shell feature signal and the core-shell interface thermal coupling feature signal, feature extraction is performed to obtain the measured core-shell photoacoustic fingerprint spectrum.
[0042] It should be noted that in this embodiment, the signal processing module 901 reads the multi-wavelength, dual-frequency original photoacoustic signal (i.e., photoacoustic signal) output by the lock-in amplifier 801, and retrieves the photoacoustic signal reference information under the zero-particle pure carrier gas condition that has been collected and stored in advance. The inherent noise of the system caused by the optical path, cavity and circuit is eliminated by baseline difference operation. Then, based on the spectral absorption difference of the optimal characteristic wavelength combination, the core, shell and core-shell thermal coupling characteristic signals are decoupled. The multi-dimensional features of photoacoustic amplitude, phase and resonance peak width after noise correction are extracted to generate the measured core-shell photoacoustic fingerprint spectrum that only reflects the optical, thermal and acoustic properties of the core-shell particles under test.
[0043] This application embodiment relies on an existing dual-frequency multi-wavelength photoacoustic measurement system. Experimental tests are conducted under conditions where the optimal combination of characteristic wavelengths and characteristic frequencies are selected. Three types of sensitive observation signals of the core-shell structure particles under test are simultaneously acquired wavelength by wavelength: the first at the resonant frequency... Measured amplitude data at each wavelength The measured amplitude data are used to characterize the spectral absorption characteristics of particles; the first amplitude at the resonance frequency. Measured phase data at each wavelength The measured phase data is used to characterize the thermal relaxation transfer properties of particles; and The next The measured amplitude ratio at each wavelength is compared to the data. The measured amplitude ratio data is used to characterize the acoustic distortion characteristics induced by the core-shell structure. For wavelength index, satisfying The system detection value, i.e. the measured core-shell photoacoustic fingerprint spectrum, is composed of all measured data of the three wavelengths.
[0044] The expression for the measured core-shell photoacoustic fingerprint spectrum is: (1); in, This represents the measured photoacoustic fingerprint spectrum of the core and shell.
[0045] Next, the carbon core mass concentration was... volatile shell mass concentration Core-shell interface thermal resistance The three key physical quantities to be determined are organized into a parameter vector to be inverted.
[0046] The expression for the parameter vector to be inverted is: (2); in, This represents the parameter vector to be inverted.
[0047] In another exemplary embodiment of this application, step 204 is replaced by steps 601 to 603: Step 601: Based on the measured phase data in the measured core-shell photoacoustic fingerprint spectrum and the pre-constructed phase-thermal property mapping spectrum, determine the initial value of the core-shell interface thermal resistance.
[0048] Step 602: Determine the initial values of the soot core mass concentration and the initial values of the volatile matter shell mass concentration based on the measured amplitude data in the measured core-shell photoacoustic fingerprint spectrum.
[0049] Step 603: Using a forward photo-thermal-acoustic coupling model, based on the initial values of the soot core mass concentration, the initial values of the volatile shell mass concentration, and the initial values of the core-shell interface thermal resistance, the theoretical predicted value of the forward photo-thermal-acoustic coupling model is determined.
[0050] It should be noted that, in order to improve the convergence of the nonlinear inversion iteration, this application employs a two-stage solution strategy of initial value estimation and regularized iterative optimization. First, rapid estimation of initial parameters is performed: based on the high sensitivity of phase signals to particle thermal properties, a pre-constructed phase-thermal property mapping spectrum (which is part of an existing database) is used to directly look up measured phase data and quickly determine the core-shell interface thermal resistance. The coarse interval significantly reduces the initial value deviation of the Levenberg-Marquardt algorithm and accelerates the convergence speed, thereby determining the core-shell interface thermal resistance. The initial range of values is used as the initial value of the thermal resistance at the core-shell interface; combined with the photoacoustic amplitude data in the near-infrared band at the resonance frequency (i.e., the measured amplitude data at the resonance frequency), the estimated value of the total particle mass concentration is calculated, and the initial values of the soot core mass concentration and the volatile shell mass concentration are obtained.
[0051] In another exemplary embodiment of this application, step 603 is replaced by steps 701 to 706: Step 701: Based on the initial values of the soot core mass concentration and the initial values of the volatile shell mass concentration, and combined with the particle number density of the core-shell structure particles to be tested, determine the particle core mass and particle shell mass.
[0052] Step 702: Based on the particle core mass, the particle shell mass, and the pre-calibrated core-shell material properties, and in conjunction with the initial value of the core-shell interface thermal resistance, determine the particle geometric characteristic parameters, complex dielectric parameters, and core-shell interface heat transfer boundary conditions.
[0053] It should be noted that the pre-calibrated core-shell material properties include: the complex refractive index of the core and shell (used to solve for the complex permittivity), the density parameters of the core and shell, the isobaric heat capacity, and the thermal conductivity.
[0054] Step 703: Using the Rayleigh concentric double-layer quasi-electrostatic model, based on the complex dielectric parameters and the particle geometric characteristic parameters, determine the transient heat source spatially distributed inside the particle.
[0055] Step 704: Based on the transient heat source distributed in the internal space of the particle and the heat transfer boundary conditions at the core-shell interface, the time-varying heat flow released outward by the particle is obtained as an equivalent time-varying point sound source.
[0056] Step 705: Substitute the equivalent time-varying point sound source into the acoustic wave equation of the photoacoustic resonator to obtain the periodic sound pressure inside the photoacoustic cavity.
[0057] Step 706: Perform orthogonal decomposition on the periodic sound pressure in the photoacoustic cavity to obtain theoretical predicted amplitude data, theoretical predicted phase data, and theoretical predicted amplitude ratio data.
[0058] It should be noted that, in this embodiment, the theoretical predicted value of the forward optical-thermal-acoustic coupling model is calculated based on the initial values of the soot core mass concentration, the initial values of the volatile shell mass concentration, and the initial values of the core-shell interface thermal resistance. First, the mass of the core and shell of a single particle is calculated based on the initial values of the soot core mass concentration and the volatile shell mass concentration. Then, the core and shell volumes are solved by combining the density parameters of the core and shell. The core radius, total outer diameter of the particle, shell thickness, and core volume fraction are calculated using the geometric relationship of concentric spheres, thus forming the particle's geometric characteristic parameters. Simultaneously, the complex dielectric parameters, isobaric heat capacity, thermal conductivity, and interface thermal resistance of the core and shell materials are calibrated. Subsequently, Rayleigh's concentric double-layer quasi-electrostatic theory is used, combined with the complex dielectric parameters and the incident light field, to construct the particle's internal structure. The spatial transient heat source distribution, combined with the heat transfer constraint conditions at the core-shell interface, is used to solve the unsteady temperature field of heterogeneous particles, yielding the time-varying heat flow released outward by the particles. This time-varying heat flow is the input of the equivalent time-varying point sound source, directly determining the amplitude and phase lag of the photoacoustic wave. This time-varying heat flow is substituted into the acoustic wave equation of the photoacoustic resonator as the sound source to obtain the periodic sound pressure inside the photoacoustic cavity. The periodic sound pressure inside the photoacoustic cavity is orthogonally decomposed to obtain the amplitude and phase, and the amplitude ratio is calculated. The results of multi-wavelength measurements are integrated to construct a theoretical prediction vector, obtaining the theoretical prediction value of the forward light-heat-sound coupling model.
[0059] The expression for the theoretical prediction of the forward optical-thermal-acoustic coupling model is: (3); in, This represents the theoretical prediction value of the forward optical-thermal-acoustic coupling model; The first output of the forward optical-thermal-acoustic coupling model Theoretical predicted amplitude data for each wavelength; The first output of the forward optical-thermal-acoustic coupling model Theoretical predicted phase data for each wavelength; The first output of the forward optical-thermal-acoustic coupling model The theoretical predicted amplitude ratio at each wavelength is greater than the data; For wavelength index, satisfying .
[0060] This application constructs a weighted least squares optimization objective function. Based on the nonlinear mapping relationship between the photoacoustic response of the core-shell structure particles under test and the parameters to be inverted, the weighted least squares method is used to quantify the residuals between the theoretical predictions of the forward photo-thermal-acoustic coupling model and the measured core-shell photoacoustic fingerprint spectrum. Amplitude weights are configured according to the anti-interference priority criterion. Phase weights Amplitude ratio weight We establish a weighted least squares optimization objective function.
[0061] The formula for calculating the weighted least squares optimization objective function is as follows: (4); in, The objective function is weighted least squares optimization. For amplitude weighting; For phase weights; The magnitude ratio is the weight.
[0062] Using the initial values of soot core mass concentration, volatile shell mass concentration, and core-shell interface thermal resistance as the starting points for iteration, the Levenberg-Marquardt algorithm is employed for iterative optimization. The parameters to be determined are continuously updated based on the gradient of the weighted least squares objective function until the weighted least squares objective function converges to a set residual threshold. Finally, the soot core mass concentration is simultaneously obtained. volatile shell mass concentration Core-shell interface thermal resistance The optimal solution was obtained, and the synchronous quantitative inversion of the mass concentration of kernel nvPM and shell volatiles was completed.
[0063] like Figure 3 As shown in the figure, an embodiment of this application provides an iterative schematic diagram of the particle-volatile matter synchronous inversion method. This embodiment of the application constructs a weighted least squares function (i.e., a weighted least squares optimization objective function) and performs Levenberg-Marquardt iterative calculation. During the iteration process, a fast initial value estimation step is performed. On the one hand, the interface thermal resistance value range is defined to obtain the initial value of the core-shell interface thermal resistance. On the other hand, the total particle mass concentration is estimated to obtain the initial value of the soot core mass concentration and the initial value of the volatile matter shell mass concentration. Based on the initial values of the soot core mass concentration, the initial values of the volatile matter shell mass concentration and the initial values of the core-shell interface thermal resistance, regularized joint optimization is performed. It is determined whether the optimization result has converged. If it has not converged, it returns to the Levenberg-Marquardt iterative step for recalculation. If the convergence condition is met, the soot and surface volatile matter mass concentration results are output.
[0064] This application embodiment achieves simultaneous measurement of core-shell particulate matter mass concentration based on dual-frequency excitation and multi-wavelength coupling. By decoupling differentiated photoacoustic excitation and multi-wavelength spectral signals, the mass concentration of the carbonaceous core and volatile shell of aviation emission particles can be measured simultaneously and accurately, eliminating measurement errors caused by the core-shell structure.
[0065] Traditional online measurement of the mass concentration of non-volatile particulate matter in aviation emissions uses the photoacoustic method. Although this method has detection advantages and is recognized by the industry, it is based on the assumption of uniform spherical particles, which cannot be adapted to core-shell structured particles in exhaust gas with volatile shells encasing carbonaceous cores. This can easily cause photoacoustic response distortion and measurement deviation. Furthermore, the accompanying preprocessing methods are difficult to completely eliminate interference and can easily introduce new errors.
[0066] This application embodiment achieves simultaneous measurement of the mass concentration of the core and volatile shell layers of core-shell particles through dual-frequency excitation and multi-wavelength coupling. By leveraging the difference in spectral absorption between the two, photoacoustic signals are separated, and multidimensional acoustic features corresponding to the core-shell structure are extracted based on dual characteristic frequencies. A multidimensional response signal synchronous inversion system is built, which eliminates measurement distortion caused by core-shell heterogeneity in principle. It eliminates the need for VPR preprocessing to avoid secondary errors and can simultaneously and independently determine the mass concentration of the core nvPM and volatile shell layers with high accuracy, significantly improving measurement precision and practicality.
[0067] Based on the same inventive concept, this application also provides a device for synchronously measuring the mass concentration of core-shell particles to implement the aforementioned method for synchronously measuring the mass concentration of core-shell particles. The solution provided by this device is similar to the solution described in the above method. Therefore, the specific limitations of one or more embodiments of the synchronous measurement device for the mass concentration of core-shell particles provided below can be found in the limitations of the synchronous measurement method for the mass concentration of core-shell particles described above, and will not be repeated here.
[0068] In one exemplary embodiment, such as Figure 4 As shown, a device for synchronous measurement of the mass concentration of core-shell particulate matter is provided, comprising: a laser modulator 101, a first laser 201, a second laser 202, a third laser 203, a beam splitting system 301, a carbon soot particle generation system 401, an anti-particle adhesion pipe 501, a photoacoustic cell 601, a microphone 701, a lock-in amplifier 801, and a signal processing module 901.
[0069] The laser modulator 101 is used to modulate the laser output from the laser to generate modulated light with a characteristic frequency.
[0070] The first laser 201 is used to emit an ultraviolet beam that can be strongly absorbed by volatile components.
[0071] The second laser 202 is used to emit a visible beam that can be strongly absorbed by soot components.
[0072] The third laser 203 is used to emit a near-infrared beam in the thermal relaxation excitation region.
[0073] The beam splitting system 301 is used to integrate three wavelength beams to complete the beam combining optical path synthesis.
[0074] The soot particle generation system 401 is used to generate core-shell structured particulate matter that meets the characteristics of aviation emissions.
[0075] The anti-particle adhesion pipe 501 is used to pass the core-shell structure particles to be tested generated by the carbon soot particle generation system 401 into the photoacoustic cell 601.
[0076] The photoacoustic cell 601 is used for amplification and measurement of photoacoustic signals generated after laser irradiation of a core-shell structure particle under test.
[0077] Microphone 701 is used to collect the photoacoustic signal generated by the absorption and modulation of light by the core-shell structure particles under test in the photoacoustic cell 601, and convert it into an electrical signal for output.
[0078] The lock-in amplifier 801 is used to extract photoacoustic signals at a specific frequency, filter out noise interference, and output an effective photoacoustic electrical signal.
[0079] The signal processing module 901 is used to analyze photoacoustic signal data and calculate the mass concentration of the two components.
[0080] The connection relationship of each part in the device for synchronous measurement of core-shell particulate matter mass concentration is as follows: the first laser 201, the second laser 202, and the third laser 203 generate three laser beams with specific wavelengths and powers under the control of the laser modulator 101. The three laser beams are combined by the beam splitting system 301 and then incident on the photoacoustic cell 601. The core-shell structured particulate matter to be measured generated by the soot particle generation system 401 enters the photoacoustic cell 601 through the anti-particle adhesion pipe 501. The core-shell structured particulate matter to be measured generates photoacoustic signals when irradiated by lasers in the photoacoustic cell 601. The microphone 701 collects the photoacoustic signals generated in the photoacoustic cell 601 and converts them into electrical signals, which are then transmitted to the lock-in amplifier 801. The lock-in amplifier 801 transmits the extracted effective photoacoustic electrical signals to the signal processing module 901 to analyze the multi-wavelength and multi-frequency photoacoustic signal data and calculate the dual-component mass concentration of the core nvPM and the volatile shell layer.
[0081] In one exemplary embodiment, a computer device is provided, which may be a server or a terminal, and its internal structure diagram may be as follows. Figure 5As shown, the computer device includes a processor, memory, input / output (I / O) interfaces, and a communication interface. The processor, memory, and I / O interfaces are connected via a system bus, and the communication interface is also connected to the system bus via the I / O interfaces. The processor provides computational and control capabilities. The memory includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores the operating system, computer programs, and a database. The internal memory provides an environment for the operation of the operating system and computer programs stored in the non-volatile storage medium. The database stores the photoacoustic signals of the core-shell particulate matter under optimal characteristic wavelength combinations and frequency conditions, the photoacoustic signals of zero-particle pure carrier gas under the same conditions, and the optimal measurement results of the core-shell particulate matter. The I / O interfaces are used for information exchange between the processor and external devices. The communication interface is used for communication with external terminals via a network connection. When executed by the processor, the computer program implements a method for synchronous measurement of the mass concentration of core-shell particulate matter.
[0082] Figure 5 The structures shown are merely block diagrams of some structures related to the present application and do not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than shown in the figures, or combine certain components, or have different component arrangements. In an exemplary embodiment, a computer device is provided, including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps in the above-described method embodiments.
[0083] In one exemplary embodiment, a computer-readable storage medium is provided storing a computer program that, when executed by a processor, implements the steps in the above-described method embodiments.
[0084] In one exemplary embodiment, a computer program product is provided, including a computer program that, when executed by a processor, implements the steps in the above-described method embodiments.
[0085] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of related data must comply with relevant regulations and be authorized by the owner of the corresponding device.
[0086] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments described above. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM).
[0087] The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, distributed databases based on blockchain. The processors involved in the embodiments provided in this application may be, but are not limited to, general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc.
[0088] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0089] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.
Claims
1. A method for simultaneous measurement of the mass concentration of core-shell particulate matter, characterized in that, The method for simultaneous measurement of the mass concentration of core-shell particulate matter includes: The photoacoustic signals of the core-shell structured particles under test are acquired under the optimal combination of characteristic wavelengths and characteristic frequencies, as well as the photoacoustic signals of the zero-particle pure carrier gas under the same conditions. The optimal combination of characteristic wavelengths and the characteristic frequencies are obtained based on pre-calibration of pure carbon soot particles, pure volatile condensate particles, and standard core-shell particles. Based on the photoacoustic signal of the zero-particle pure carrier gas under the optimal characteristic wavelength combination and the characteristic frequency conditions, determine the photoacoustic signal reference information; Based on the photoacoustic signal of the core-shell structured particulate matter under the optimal characteristic wavelength combination and characteristic frequency conditions, the photoacoustic signal reference information, and the optimal characteristic wavelength combination, the measured core-shell photoacoustic fingerprint spectrum is determined; the measured core-shell photoacoustic fingerprint spectrum includes measured amplitude data, measured phase data, and measured amplitude ratio data. Based on the measured core-shell photoacoustic fingerprint spectrum, combined with the pre-constructed phase-thermal property mapping spectrum, the theoretical prediction value of the forward photo-thermal-acoustic coupling model is determined; the theoretical prediction value of the forward photo-thermal-acoustic coupling model includes theoretical prediction amplitude data, theoretical prediction phase data, and theoretical prediction amplitude ratio data. A weighted least squares optimization objective function is constructed, and the Levenberg-Marquardt algorithm is used to iteratively solve the problem with the goal of minimizing the error between the theoretical prediction of the forward photo-thermal-acoustic coupling model and the measured core-shell photoacoustic fingerprint spectrum. The optimal measurement results of the core-shell structure particles to be measured are obtained. The optimal measurement results include the mass concentration of soot core, the mass concentration of volatile shell, and the thermal resistance of the core-shell interface.
2. The method for simultaneous measurement of core-shell particulate matter mass concentration according to claim 1, characterized in that, The optimal combination of characteristic wavelengths is determined by measuring the absorption spectra of the pure carbon soot particles and the pure volatile condensate particles using an ultraviolet-visible-near-infrared absorption spectrometer, and based on the difference in spectral absorption between the pure carbon soot particles and the pure volatile condensate particles. The characteristic frequency is determined by sweeping and modulating the standard core-shell particles within a preset frequency range, and simultaneously acquiring the amplitude response curve and phase spectrum of the photoacoustic signal in the optimal characteristic wavelength combination under each preset frequency range; the standard core-shell particles are particles with known or controllable specific sizes of the core and volatile shell layers.
3. The method for simultaneous measurement of core-shell particulate matter mass concentration according to claim 1, characterized in that, Before the step of determining the measured core-shell photoacoustic fingerprint spectrum based on the photoacoustic signal of the core-shell structured particulate matter under optimal characteristic wavelength combination and characteristic frequency conditions, the photoacoustic signal reference information, and the optimal characteristic wavelength combination, the method for synchronously measuring the mass concentration of core-shell particulate matter further includes: The photoacoustic signal of the core-shell structured particulate matter under the optimal combination of characteristic wavelengths and characteristic frequencies is converted into an electrical signal. Based on the electrical signal and the characteristic frequency, a photoacoustic electrical signal is obtained; the photoacoustic electrical signal serves as the photoacoustic signal of the core-shell structured particle under the optimal combination of characteristic wavelengths and characteristic frequencies, and is used to determine the measured core-shell photoacoustic fingerprint spectrum by combining the photoacoustic signal reference information and the optimal combination of characteristic wavelengths.
4. The method for simultaneous measurement of core-shell particulate matter mass concentration according to claim 3, characterized in that, Based on the photoacoustic signal of the core-shell structured particulate matter under optimal characteristic wavelength combination and characteristic frequency conditions, the photoacoustic signal reference information, and the optimal characteristic wavelength combination, the measured core-shell photoacoustic fingerprint spectrum is determined, specifically including: Based on the photoacoustic signal and the photoacoustic signal reference information, baseline differential operation is used to filter out inherent noise to obtain the filtered photoacoustic signal. Based on the spectral absorption difference of the optimal characteristic wavelength combination, the filtered photoacoustic-electric signal is decoupled to obtain the core characteristic signal, the shell characteristic signal, and the core-shell interface thermal coupling characteristic signal. Feature extraction is performed based on the kernel feature signal, the shell feature signal, and the core-shell interface thermal coupling feature signal to obtain the measured core-shell photoacoustic fingerprint spectrum.
5. The method for simultaneous measurement of core-shell particulate matter mass concentration according to claim 1, characterized in that, Based on the measured core-shell photoacoustic fingerprint spectrum, combined with the pre-constructed phase-thermal property mapping spectrum, the theoretical predicted values of the forward photo-thermal-acoustic coupling model are determined, specifically including: Based on the measured phase data in the measured core-shell photoacoustic fingerprint spectrum and the pre-constructed phase-thermal property mapping spectrum, the initial value of the core-shell interface thermal resistance is determined. Based on the measured amplitude data in the measured core-shell photoacoustic fingerprint spectrum, the initial values of the soot core mass concentration and the initial values of the volatile shell mass concentration are determined. Using a forward photo-thermal-acoustic coupling model, the theoretical predicted values of the forward photo-thermal-acoustic coupling model are determined based on the initial values of the soot core mass concentration, the initial values of the volatile shell mass concentration, and the initial values of the core-shell interface thermal resistance.
6. The method for simultaneous measurement of core-shell particulate matter mass concentration according to claim 5, characterized in that, Using a forward photo-thermal-acoustic coupling model, based on the initial values of the soot core mass concentration, the initial values of the volatile matter shell mass concentration, and the initial values of the core-shell interface thermal resistance, the theoretical predicted values of the forward photo-thermal-acoustic coupling model are determined, specifically including: Based on the initial values of the soot core mass concentration and the initial values of the volatile shell mass concentration, combined with the particle number density of the core-shell structure particles to be tested, the particle core mass and particle shell mass are determined. Based on the particle core mass, the particle shell mass, and the pre-calibrated core-shell material properties, and in conjunction with the initial value of the core-shell interface thermal resistance, the particle geometric characteristic parameters, complex dielectric parameters, and core-shell interface heat transfer boundary conditions are determined. Using the Rayleigh concentric double-layer spherical quasi-electrostatic model, the transient heat source spatially distributed inside the particle is determined based on the complex dielectric parameters and the particle geometric characteristic parameters; Based on the transient heat source distributed in the internal space of the particle and the heat transfer boundary conditions at the core-shell interface, the time-varying heat flow released outward by the particle is obtained as an equivalent time-varying point sound source. Substituting the equivalent time-varying sound source into the acoustic wave equation of the photoacoustic resonator, the periodic sound pressure inside the photoacoustic cavity is obtained. The periodic sound pressure within the photoacoustic cavity is orthogonally decomposed to obtain theoretical predicted amplitude data, theoretical predicted phase data, and theoretical predicted amplitude ratio data.
7. The method for simultaneous measurement of core-shell particulate matter mass concentration according to claim 1, characterized in that, The formula for calculating the weighted least squares optimization objective function is as follows: ； in, The objective function is weighted least squares optimization. Wavelength index; For amplitude weighting; The first resonant frequency Measured amplitude data at each wavelength; The first output of the forward optical-thermal-acoustic coupling model Theoretical predicted amplitude data for each wavelength; For phase weights; The first resonant frequency Measured phase data at each wavelength; The first output of the forward optical-thermal-acoustic coupling model Theoretical predicted phase data for each wavelength; The magnitude ratio is the weight; for and The next Measured amplitude ratio data at each wavelength; The first output of the forward optical-thermal-acoustic coupling model The theoretical predicted amplitude at each wavelength is greater than the data.
8. A computer device, comprising: A memory, a processor, and a computer program stored in the memory and capable of running on the processor, characterized in that the processor executes the computer program to implement the method for synchronous measurement of the mass concentration of core-shell particles according to any one of claims 1-7.
9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the computer program implements the method for synchronous measurement of the mass concentration of core-shell particulate matter as described in any one of claims 1-7.
10. A computer program product, comprising a computer program, characterized in that, When executed by a processor, the computer program implements the method for synchronous measurement of the mass concentration of core-shell particulate matter as described in any one of claims 1-7.