Evolution of size distribution of nascent soot in n- and i-butanol flames

Abstract

The impact of fuel bound oxygen on the sooting behavior of butanol fuels was examined by following the evolution of the particle size distribution function (PSDF) of nascent soot produced in atmospheric pressure burner stabilized stagnation (BSS) flames of n-butanol and i-butanol. Similar experiments were carried out for i-butane and n-butane flames to better understand the influence of fuel structure and the presence of the alcohol group on detailed processes of soot nucleation and growth. In terms of fuel structure, the branched chain functionality has the most observable effect on soot formation. The onset of soot nucleation is faster in the branched fuels in comparison to the straight-chain counterparts. Under the same C/O ratio, however, the butanol flames were found to nucleate soot earlier and have higher soot volume fraction than the butane flames. A combustion reaction model for i-butanol and n-butanol was used to explore the precursor chemistry. Similar to the measured PSDF, benzene is computed to rise earlier in flames of the branched fuels than the straight-chain fuels.