Measurement of the Mass Specific Extinction Coefficient of Acetylene, Toluene and Polymethyl Methacrylate Soot Particles in Visible and Near-Infrared Wavelengths

Abstract

An experimental set-up has been developed to determine the mass specific σs and the dimensionless extinction Kt coefficients of soot particles at visible (632 nm) and near-infrared (1064 nm) wavelengths. Near-infrared measurements have been carried out with a multiple-path extinction cell to increase the measurement accuracy. The extinction coefficient Kext has been analysed as a function of the mass concentration, measured by a Tapered Element Oscillating Microbalance (TEOM 1105 R&P) in order to retrieve the soot mass specific extinction coefficient, σe, in the smoke plume of acetylene, toluene and PolyMethyl MethAcrylate (PMMA) burning under turbulent, well-ventilated and small-scale conditions. Results for mass specific extinction coefficient σ e are consistent with previous measurements (Mulholland & Croarkin [1] and Newman & Steciak [2]) obtained for a variety of fuels for small-scale fires. The mobility diameter distribution of the soot particles is measured using a Scanning Mobility Particle Sizer (SMPS 3936 TSI). The soot aggregate morphology is determined from Transmission Electronic Microscopy picture analysis. From these measurements, the soot volume fraction is determined and so the dimensionless extinction coefficient. Values at 632 and 1064 nm are given and discussed in comparison to other published data. It is found the scattering contribution to the extinction process is important for the present experimental conditions. For this reason, the use of the dimensionless coefficient is expected to provide a more accurate soot volume fraction value than the calculation which assumes the scattering is negligible.