Laser-Induced Spark Ignition of Gaseous and Quiescent N-Decane-Air Mixtures

Non-resonant breakdown ignition of quiescent mixtures of n-decane vapors and air is characterized by focusing the beam of a Nd:YAG laser operating at 1064 nm within a closed vessel. Breakdown and ignition are considered following a statistical approach: percentages of ignition are determined for different fuel equivalence ratios and pressures (phi = 0.65-2; P-0 = 0.5-4 bar) at constant initial temperature T-0 = 347 K. Significant influence of these parameters is reported. The domain of systematic ignition is characterized in terms of equivalence ratio and energy delivered by the laser, i.e., parameters relevant to propulsion applications. From a more fundamental point of view, absorbed energy is considered and the minimum ignition energy value equals 0.95 mJ. Effects of air chemical composition on ignition probabilities are evidenced by employing ambient or synthetic air, with argon or water vapor. This work brings useful complements to existing studies mainly focused on decane spray ignition.