Ignition study of acetone/air mixtures by using laser-induced spark.

The breakdown and the laser-induced spark ignition of acetone-air mixtures were experimentally studied using a nanosecond pulse at 1064 nm from a Q-switched Nd:YAG laser. The breakdown was first characterized for different mixtures with acetone and air. This part of the work highlighted the wide variation in the energy absorbed by the plasma during a breakdown. We also demonstrated that the presence of acetone in air tends to reduce the energy required to obtain a breakdown. Next, the ignition of acetone-air mixtures in the equivalence ratio range 0.9-2.4 was investigated. The probabilities of ignition were calculated in function to the laser energy. However, according to the variability of energy absorption by the plasma, we preferred to present the result according to the energy absorbed by the plasma. The minimum ignition energies were also provided. The minimum ignition energy was obtained for an equivalence ratio of 1.6 and an absorbed energy of 1.15 mJ. Finally the characteristics of the plasma (absorption coefficient and kernel temperature) were calculated for the experiments corresponding to minimum ignition energies.