An automated light scattering system and a method for the i n s i t u measurement of the index of refraction of soot particles

An automated laser light scattering system which uses a single detector to measure both classical and dynamic light scattering from soot particles in flames was designed, fabricated, and tested. Measurements of classical and dynamic light scattering along with extinction for a premixed methane/oxygen flame are presented, as a function of position in the flame. It is demonstrated that by introducing a theoretical relationship between the real and imaginary parts of the complex index of refraction, the optical properties of Rayleigh size soot particles can be directly inferred from such in situ measurements. The sensitivity of the inferred quantities to the measured parameters is assessed. Soot particles sizes, number densities and optical properties were simultaneously inferred. The potential for determining the in situ refractive indices of soot has been demonstrated.