Measurement of the size distribution, volume fraction and optical properties of soot in an 80 kW propane flame

This work presents measurements of the size distribution, volume fraction, absorption and scattering coefficients of soot in an 80 kW swirling propane-fired flame. Extractive measurements were performed in the flame using an oil-cooled particle extraction probe. The particle size distribution was measured with a Scanning Mobility Particle Sizer (SMPS) and the optical properties were measured using a Photo Acoustic Soot Spectrometer (PASS-3). A detailed radiation model was used to examine the influence of the soot volume fraction on the particle radiation intensity. The properties of the gas were calculated with a statistical narrow-band model and the particle properties were calculated using Rayleigh theory with four different complex indices of refraction for soot particles. The modelled radiation was compared with measured total radiative intensity, the latter which was measured with a narrow angle radiometer. The results show that the measured soot volume fraction yields particle radiation that corresponds well with the determined difference between gas and total radiation. This indicates that the presented methodology is capable of quantifying both the particle and gaseous radiation in a flame of technical size.