Optical investigations of low-pressure acetylenefluorine flames, 2. Soot formation and particle temperature

Profiles of absorption due to soot have been measured at various wavelengths in the visible in quasi-premixed, flat C 2H 2F 2 flames at C/F = 0.25, 0.30, and 0.33 burning at 7.0 mbar. The rate of soot formation is largest within the main reaction zone. The total conversion of fuel carbon into soot, ca. 50% for C/F = 0.3 and 60% for C/F = 0.33, is much larger than for comparable C 2H 2/O 2 flames. The maximum flame temperature decreases rapidly from 2650K to about 2000K when the C/F ratio is increased beyond the threshold for soot formation (0.198). Increasing C/F above 0.25 does not result in a further temperature decrease but leads to a stronger soot formation. The large soot yield and the decrease in temperature are discussed on the basis of previous mass spectrometric measurements of gaseous species.