研究目的
To develop a novel in-situ optical method for measuring soot size distribution using spectrally resolved light scattering with only two scattering angles, overcoming limitations of ex-situ techniques.
研究成果
The spectral scattering technique successfully measures soot size distributions with only two scattering angles, validated against SMPS. It provides insights into soot optical properties and composition. Future improvements include extending the wavelength range and using more powerful light sources for application in high-pressure combustion environments.
研究不足
The technique has limitations in signal-to-noise ratio, especially in flame conditions due to weak light source power and thermal emissions. The wavelength range is narrow, and sensitivity decreases for small or highly polydisperse aggregates. The inversion process can be ill-posed and sensitive to noise, requiring high-quality data.
1：Experimental Design and Method Selection:
The study uses spectrally resolved elastic light scattering based on Rayleigh–Debye–Gans theory for Fractal Aggregates (RDG-FA). A Bayesian inversion approach is employed for data analysis to determine size distributions and quantify uncertainties.
2：Sample Selection and Data Sources:
Soot particles are generated using a miniCAST generator under three operating conditions (CAST 1, CAST 2, CAST 3) to produce aggregates with varying sizes, morphologies, and compositions. Independent validation is done using Scanning Mobility Particle Sizer (SMPS) measurements.
3：List of Experimental Equipment and Materials:
Equipment includes a polychromatic broadband light source (Energetiq EQ-99FC-LDLS), spectrometer (Acton SP2150i), intensified camera (Princeton Instruments PM4-1024EMB-HR-FO-P46-CM-FM-SM-SF), integrating sphere (Labsphere CA-13773-UJF), and miniCAST soot generator (miniCast 6200). Materials involve propane gas, air for oxidation and dilution, and soot particles.
4：0). Materials involve propane gas, air for oxidation and dilution, and soot particles.
Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: Scattered light spectra are collected at multiple scattering angles (e.g., 7°, 20°, 45°, 70°, 90°) over a wavelength range of 500-700 nm. The ratio of spectra at two angles is computed and analyzed using RDG-FA theory and Bayesian inference to extract size distribution parameters.
5：Data Analysis Methods:
Data is processed using power-law fitting (Eq. 11) and Bayesian inference to determine median diameter and geometric standard deviation of log-normal size distributions. Uncertainties are quantified statistically.
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