Optical-microphysical properties of mixed smokes from a few spatially separated sources

Abstract

A series of experiments is performed to study the specific features of formation of the mixed-composition smokes from a few spatially separated sources of thermal decomposition of various types of wood material. It is shown that, in order to make an adequate prediction of the optical properties of the smoke aerosols, it is necessary to take into account not only the complex inhomogeneous structure of the disperse composition (the smoke particle size distribution density s(r)), but also variations in the complex refractive index (CRI) m = n − iχ over the smoke particle-size spectrum. Mixing the products of thermal decomposition of combustible forest materials generates smoke, consisting primarily of two aerosol components separated on the size scale: the finely dispersed component ( 300 nm) with the imaginary part χ ∼ 0.005–0.08. It is shown that the effective average n and χ values over the size range increase not due to external mixing of disperse components, but rather to penetration of the finely dispersed absorbing component into the structure of particles of other size ranges.