Effects of Turbulence and Fuel Properties on Pre-vaporized Jet Flame Surface Statistics

This research effort presents a detailed and systematic analysis of the impact of turbulence on surface characteristics of premixed flames produced with vaporized liquid fuels. The turbulent Reynolds Number (ReT) varied between 760 and 4,200, with equivalence ratios of 0.9 and 1.1. Hydroxyl (OH) planar laser-induced fluorescence (PLIF) was employed to mark the flame front. Flame surface density (FSD), average progress variable ( $$\overline{c}$$ ), flame-front curvature (κ), fractal dimension (FD), and inner cut-off scale (εi) were extracted from those images, which enabled additional analysis, including: turbulent flame area ratio and brush thickness. It was found that increasing the turbulent Karlovitz Number (KaT) broadened probability density functions (PDFs) of flame-front curvature, increased FSD across reaction variable space, increased turbulent area ratio and decreased brush thickness. Notably, for lean conditions, all surface statistics converged as KaT exceeded 10. Similarly, global consumption speed was analyzed and found to be consistent with previous findings in methane-air mixtures. Analysis of “flamelet” consumption speed shows that despite having different thermochemical properties, all of the flames considered behave similarly at a macroscopic level when properly normalized by a suitable SL. Lastly, a fractal analysis revealed consistent FD values that approximately equal the theoretical value of 7/3 for these types of flames. Also, such analysis indicated that the normalized inner cut off scales are not sensitive to fuel type and, as in prior studies of gaseous fueled flames, decrease with increasing KaT.