Experimental and kinetic modeling study of laminar coflow diffusion methane flames doped with iso-butanol

Abstract

In this work, laminar coflow diffusion flames fueled with methane/iso-butanol were investigated with synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). Mole fractions of C2–C16 flame species, including small hydrocarbons, oxygenates and aromatics were measured along the flame centerline. The enhancement in the formation of aromatics was observed through the increment of the iso-butanol doping ratio (1.95% and 3.90% in two flames) in the inlet fuel gas mixture. A detailed kinetic model was developed from previous models to help understand the experimental findings. According to rate of production analysis in laminar coflow diffusion flames, unimolecular decomposition and H abstraction reactions provide equivalent contributions to the consumption of iso-butanol. Compared to the coflow flames doped with other butanol isomers with the identical condition, the water elimination reaction of iso-butanol has the lowest contribution to fuel consumption. Two reaction pathways provide major contribution to the formation of propargyl radical, i.e. iC4H9OH→iC3H7→C3H6→aC3H5→aC3H4→C3H3 and iC4H9OH→βC4H8OH→iC4H8→iC4H7→aC3H4→C3H3. Propargyl is concluded as the key precursor for aromatics, while phenyl and benzyl radicals are the main PAH precursors. Finally, based on the studies of laminar coflow flames fueled with butanol isomers, the sooting tendency of butanol isomers relates strictly to the efficiency of the propargyl formation pathways in fuel decomposition.