Application of the steady-state and unsteady-state lasers in reconstructing the geometrical characteristic parameters of soot fractal aggregates

• Published in: Optik (Stuttgart) 2020-02, Vol.202, p.163720, Article 163720
• Main Authors: He, Zhenzong, Dong, Chuanhui, Xu, Liang, Mao, Junkui, Tu, Zecan
• Format: Article
• Language: English
• Subjects: Geometrical morphology of aggregates; Inverse radiative problem; Laser measurement technique; Soot fractal aggregate
• ISSN: 0030-4026; 1618-1336
• DOI: 10.1016/j.ijleo.2019.163720

The unsteady-state laser, i.e. time-domain (TD) and frequency-domain (FD) lasers, and the steady-state (SS) laser are employed as the measurement lasers to reconstruct the geometrical characteristic parameters of soot fractal aggregates, i.e. the root mean square radius Rg and fractal dimension Df. The direct problems are solved by the finite volume method and Rayleigh-Debye-Gans fractal aggregate method, while an improved artificial bee colony algorithm is used as the inverse problem algorithm. The sensitivity analysis is employed to study the effective sampling region of the TD and FD laser measurement signals, and the results show that the time-resolved signals selected within [L, 0.5L + ctp] for the TD laser and the dimensionless frequency selected within [0.5, 5] for the FD laser are conducive to improving the retrieval accuracy. Then, the geometrical characteristic parameters of soot fractal aggregates are retrieved by using different measurement lasers, and the results reveal that the retrieval accuracy can be ensured by using the TD laser measurement technique. Moreover, the retrieval accuracy and robustness of Rg are better than those of Df. All the studies in the present manuscript supply an application plat of the laser measurement techniques in reconstructing the geometrical characteristic parameters of soot fractal aggregates.