Measurement of organic carbon content during the growth of soot particles in propane normal and inverse diffusion flames using a multi-wavelength light extinction method

Abstract

This paper proposes a novel method for in situ determination of the organic carbon (OC) content in soot particles using a multi-wavelength light extinction method for propane normal diffusion flames (NDFs) and inverse diffusion flames (IDFs). Light extinction at wavelengths of 450–900 nm was measured using white light and a spectrometer. The light extinction coefficient plotted as a function of the reciprocal wavelength revealed the extinction characteristics of the soot particles. Additionally, the wavelength dependency of the OC content in soot was determined using the ratio of the slopes at short and long wavelengths. For the NDF, the slope ratio was higher near the flame center and upstream of the flame, whereas for the IDF, a constant of slope ratio was observed in all measurement positions. By comparing the slope ratio with the soot component analysis, a quantitative relationship was derived between the organic mass fraction (OMF) of the soot and the slope ratio. The OMF was 0.1–0.27 depending on the position in the NDF, and the IDF showed a similar OMF of 0.25–0.32 at all measurement positions. The results of transmission electron microscopy and electron energy loss spectroscopy also confirmed the validity of the OMF measurement.