Abstract
Natural gas engines have been attracting a lot of attention recently due to the development of unconventional natural gas sources. Achieving lean burn with supercharging is necessary to attain high thermal efficiency. Conventional spark plugs face difficulties with ignition because of the high pressure and lean air/fuel mixture. This paper describes studies on laser spark ignition which has been investigated at AIST as an alternative method for the achievement of stable ignition under such conditions. The extension of lean limit and improvement in thermal efficiency are demonstrated, and the possibilities of advanced laser ignition are also discussed.
