Abstract
Characteristics of polycyclic aromatic hydrocarbon (PAH) and soot formation for gasoline surrogate liquid fuels have been investigated in counterflow diffusion flames by using laser induced incandescence (LII) and laser induced fluorescence (LIF) techniques. Tested fuels were 3 binary fuel mixtures from primary reference fuels; toluene / iso-octane, toluene / n-heptane, and n-heptane / isooctane. The experiments were conducted for soot formation (SF) flame and soot formation/oxidation (SFO) flame. The experimental conditions are selected at (XO,0, XF,0) = (0.21, 0.30) and (0.07, 0.90) for SF and SFO flames, respectively. The profiles of LII signals were similar for the SF and SFO flames having mono-modal. However, the profiles of PAH LIF signals were different for the SF and SFO flames having mono-modal and bimodal nature, respectively. The result showed that LII and LIF signals maintained near zero level for all mixtures of n-heptane / iso-octane case. For toluene / iso-octane and toluene / n-heptane mixtures, however, even though, the LII and LIF signals were insensitive to the toluene ratio when it was small, the signals increases with the ratio over the threshold value of about 0.2. These results implied that even though toluene had a dominant role in soot and PAH formation, small percentage of toluene has minimal effect on the PAH and soot formation.
Keywords: Soot, Polycyclic aromatic hydrocarbon (PAH), Laser-induced incandescence, Laser-induced fluorescence, Gasoline surrogate fuel