Soot temperature and the local integrated soot volume fraction can also be measured optically using the spectral soot emission (SSE) technique that has recently been developed in our lab. It does this by taking a line-of-sight measurement through a chord in the flame and uses an Abel inversion to get point measurements. The thermal radiation of the soot produced in the flame chord is imaged onto a narrow entrance slit of a spectrometer. An optical grating inside the spectrometer divides the incident flame radiation into a spectrum and images it onto the pixels of a charge-couple device (CCD) detector [1].
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1. D. R. Snelling, K. A. Thomson, G. J. Smallwood, Ö L. Gülder, E. J. Weckman and R. A. Fraser, “Spectrally Resolved Measurement of Flame Radiation to Determine Soot Temperature and Concentration,” AIAA Journal, vol. 40, pp. 1789-1795, 2002.
A schematic of the SSE setup, Taken from the PhD thesis of Dr. Ahmet Emre Karatas, University of Toronto