PREDICTIONS OF RADIATIVE PROPERTIES FOR FLY-ASH POLYDISPERSIONS IN COMBUSTION GAS

Monochromatic radiative properties of anisotropically scattering fly-a sh polydispersions in combustion gas, such as an extinction coefficien t, a scattering coefficient, a scattering albedo and Legendre expansio n coefficients for a phase function, are calculated by the Mie scatter ing computer code with the monochromatic complex refractive index meas ured and arranged in a wavelength region of 0.7 similar to 13 mu m and with a measured or an estimated bimodal particle distribution of fly- ash. Extinction and absorption coefficients calculated for fly-ash pol ydispersions closely agree with the results obtained by a small-partic le (x much less than 1) approximation when the Sauter diameter D-32 fo r polydispersions is much smaller than the incident wavelength (x(32)< 0.1). They also agree with the approximations of the complex refractiv e index near 1 (\m-1\much less than 1) when D-32 is much larger than t he wavelength (x(32)>10); in the intermediate region (0.1<x(32)<10), h owever, exact Mie scattering calculations are required.