Laser induced spark ignition of coaxial methane/oxygen/nitrogen diffusion flames.

We report the laser induced spark ignition (LSI) of coaxial methane/oxygen/nitrogen diffusion flames using the 1064 nm output of a Q-switched Nd:YAG laser. The minimum ignition energy (MIE) and ignition time of the LSI has been determined by measuring the emission signals due to the ignited flames. The effects of the gas mixture properties, including the overall equivalence ratio (Ф), oxygen concentration and flow rate, and the ignition positions on the two parameters have been investigated systematically. The variation of the MIE and ignition time with the experimental conditions has been compared with the existing results and discussed with a special concentration on the effects of the local Ф.