摘要:
基于自主研制的结合偏振调制和锁相检测技术的光散射实验装置,测量了两种典型火灾烟雾颗粒（棉绳阴燃烟雾和正庚烷池火烟雾）及超声雾化水滴颗粒的532nm光散射矩阵元素随散射角的分布.通过水滴颗粒测量结果与数值计算结果的比较验证了实验装置的可靠性.对比分析了棉绳阴燃烟雾和正庚烷池火烟雾光散射矩阵元素随散射角的分布特征,讨论了该特征在颗粒区分上的应用.研究了烟雾颗粒微观形貌特征对光散射矩阵的影响,发现可以利用Lorenz-Mie理论描述棉绳阴燃烟雾的光散射,表明其形貌为球形,并利用模拟退火拟合的方法得到了棉绳阴燃烟雾颗粒的粒径分布参数和复折射率.
Abstract:
Based on polarization modulation and lock-in detection,an experimental apparatus is built to determine several important angular dependent scattering matrix elements at 532 nm.The apparatus is tested by water droplets through comparing measurement results with Mie calculations.Measurement results of scattering matrix elements and element ratios between smoke particles produced by smoldering cotton test fire and those produced from flaming n-heptane test fire are presented.We find that results of Mie calculations are able to describe the experimental data of smoldering cotton test fire smoke,which indicates that the particles generated by smoldering cotton test fire are mostly spherical in shape with considering the particle size relative to the wavelength.Using the optimization method,we estimate the refractive index （m=1.49＋i0.01） and size distribution （lognormal distribution,σg=2.335 and dg=0.17μm） of smoldering cotton test fire smoke.Contrarily,the experimental data of flaming n-heptane fire smoke cannot be described by Mie scattering,which is interpreted by the nonspherical,fractal aggregate morphology of the particulates.
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