レーザー誘起ブレークダウンの物理とそれがもたらす点火特性

抄録

For understanding the characteristics of the ignition of a combustible gas mixture by laser-induced gaseous breakdown, fundamental physical processes in laser-induced gaseous breakdown and comparison between laser-spark ignition and electrode-spark ignition were described. Regarding the laser-induced gaseous breakdown, the threshold laserpower density, the plasma development during the laser pulse, and the fluid motion induced just after the end of the laser pulse were discussed. On the comparison between laser-spark ignition and electrode-spark ignition, the ignition ability and processes were compared between the two ignition schemes at the same deposited energy near the lean-fuel ignitable limit in quiescent gas mixtures. The ignition ability of the laser-induced spark was superior to that of the electrode-induced spark, due not only to the lack of heat loss to the electrodes but also to the augmentation of the flame-kernel energy by rapid heat release from the combustible gas mixture sucked into the flame kernel by the laser-spark-induced non-spherical gas flow.