Experimental investigation on soot formation characteristics of n-heptane/butanol isomers blends in laminar diffusion flames

Biobutanol is a highly competitive alternative biofuel for fossil fuels in the future. However, there is no consensus on the soot formation of the four butanol isomers. The soot formation characteristics of the pure n-heptane (B00) and the volumetric mixture 50% n-heptane/50% butanol isomer (H50B50) flames were investigated on a coflow burner. The quantitative soot volume fraction, qualitative OH radical concentration, morphological parameters and nanostructures of soot particles were measured by the two-color laser induced incandescence (TC-LII) method, the planar laser induced fluorescence (PLIF) method, and transmission electron microscope (TEM) analysis. Compared with B00 flame, the soot loading of n-heptane/n-butanol (N50), n-heptane/s-butanol (S50) and n-heptane/i-butanol (I50) flames decreased by 62%, 40% and 33%, respectively, whereas the n-heptane/t-butanol (T50) flame increased by 57%. The oxidation of soot particles was jointly affected by the region and the peak concentration of OH radical. As the flame developed, the primary particle diameter initially increased and then decreased in the order T50 > I50 > S50 > N50. Regarding soot nanostructure, the fringe tortuosity and inter-fringe spacing of soot sampled in the three flames decreased in the order I50 > S50 > T50. (C) 2020 Elsevier Ltd. All rights reserved.