Turbulence-Flame Interactions in Lean Premixed Dodecane Flames

Turbulent lean premixed dodecane/air flames are simulated in a doubly-periodic domain using detailed kinetics and transport over a range of Karlovitz number. We observe extensive thickening of thermal profiles through the flames that increases with turbulent intensity. The high Lewis number of the flames acts to suppress wrinkling of the flame resulting in considerably lower turbulent flame speeds than is observed for lower molecular weight fuels. The impact of high Lewis number is also reflected in a negative correlation of local consumption-based flame speed with curvature. Characteristic of heavy hydrocarbons, pyrolysis of the fuel into smaller fuel fragments is separated in temperature from the primary consumpution of oxygen, which peaks at a higher temperature where the fuel fragments are consumed. The resulting intermediate species are partially entrained within the cool region ahead of the flame, but the overall pyrolysis-oxidation sequence appears essentially unaffected by turbulent mixing; however, the peak rates of these reactions are dramatically reduced.