2017 年 59 巻 189 号 p. 184-191
The lean combustion is one of the key techniques for the advanced internal combustion systems due to the requirement of the higher thermal efficiency. Since the successful ignition must be guaranteed even in the lean combustion, advanced ignition systems have been developed in this decade. Laser ignition is one of the advanced ignition systems which have the profits of the flexibility in the position and the timing of ignition. To develop this ignition system for the actual combustion system, it is required to reveal the underlying physics of the laser ignition. The effects of the initial conditions of the gas mixture and of the spatial and temporal laser profiles on ignition of a homogeneous lean methane/air mixture were examined using a constant volume combustion chamber (CVCC). Results show that the laser ignition has a benefit to ignite leaner mixture under high pressure condition compared to the ignition with conventional spark plug. However, the high incident energy for ignition in lean and high pressure condition was required for maintaining flame kernel and sustainable flame propagation. In addition, the results imply that the large scale and the long duration high temperature region is required for achieving self-sustainable flame propagation.
