Laminar Burning Speeds and Markstein Lengths of n-Decane/Air, n-Decane/O2/He, Jet-A/Air and S-8/Air Flames

Abstract

Laminar flame speeds and Markstein lengths of premixed n-Decane/air, n-Decane/O2/He, Jet-A/air and S8/air flames were measured at fuel equivalence ratios ranging from 0.7 to 1.6, at an initial temperature of 400K and pressure of 1 atm using a preheated spherical combustion chamber. The experimental results were compared with numerical simulations using the 1-D laminar premixed flame code PREMIX with existing detailed reaction mechanisms. For n-Decane/air flames the computations were performed using detailed kinetic mechanisms of Zhao et al., Honnet et al. and the JetSurF 0.2. The measured laminar flame speeds are best predicted by the mechanism of Honnet et al. over most of the range of experiments except at the extreme equivalence ratios. For Jet-A/air flames, the computations were performed based on the Aachen surrogate model and the computed flame speeds are lower than the measurements. The flame speed of Jet-A/air and S8/air flames are very similar for a given fuel equivalence ratio, while the flame speed of n-Decane/air flames is slightly higher at fuel lean conditions. Markstein lengths for these all the fuels considered decreases with increase in equivalence ratio and the transition from stable flames to unstable flames occurs at a fuel equivalence ratio of 1.2-1.3. This trend is consistent with other large hydrocarbon fuels and is opposite to that of light fuels such as hydrogen and methane. Substituting nitrogen in air with helium resulted in a fourfold increase in flame speed of n-decane and an approximately three-fold increase in the Markstein lengths.