基于回转椭球模型分析烟颗粒非球形性对光散射模式影响

针对火灾烟颗粒的链状结构特征,采用回转椭球模型,通过“T矩阵法”,分析其非球形性对光散射模式的影响.分别在固定取向与随机取向条件下,分析了“扁长”形回转椭球、球体及“扁圆”形回转椭球的散射光强分布.结果表明,在固定取向情况下,半轴比值a/b=1.0的球体对应的散射光强度分布的等高线均为直线;然而,对于半轴比值a/b＜1.0的“扁长”形椭球体对应的散射光强度分布的等高线为凸线,半轴比值a/b＞1.0的“扁圆”形椭球体对应的散射光强度分布的等高线为凹线.在随机取向条件下,球体（a/b=1.0）对应的取向平均散射光强度分布曲线的震荡最为剧烈,而a/b=0.5,2.0,4.0对应的三条曲线表明,非球形性越强的颗粒对应的散射光强分布曲线越平滑.

A spheroid model used to analyze effects of nonsphericity of smoke particles on light scattering patterns

A spheroid model was used to characterize the nonspherical morphology of smoke aggregates with an axis ratio a/b.Using the T-matrix method,the relative intensity distributions of the scattered light were analyzed for four spheroids with different a/b in a fixed orientation,as well as in a random orientation.The results indicate that the magnitude contours of the scattered light intensity distribution for spherical particles are straight lines.The corresponding magnitude contours of light scattering patterns would be convex for prolate spheroids(a/b<1) and be concave for the oblate spheroids(a/b>1).The results also show that the orientation-averaged scattered light intensity distribution for a sphere(a/b=1.0) oscillates much more strongly than those for the other spheroids with a/b of 0.5,2.0 and 4.0.The oscillation of orientation-averaged scattered light intensity distributions is an indication for nonspherical particles.