Application of laser diagnostics to engine combustion phenomena

Three carmakers of direct-injection gasoline engines put direct injection gasoline engines on the Japanese market in 1996 and 1997. This paper describes the role played by optical diagnostics in the development of direct-injection SI gasoline engine. Optical diagnostic techniques are instrumental in understanding combustion phenomena in a spark ignition engine and in developing some aspects of the combustion concept. This is because the combination of combustion elements such as gas flow fields and concentration of air-fuel ratio fields, including residual gas, must be fully controlled under different driving conditions with the aim of achieving the best thermal efficiency and lowest exhaust emissions. This kind of optimization is not easy to accomplish without diagnostic tools. Laser-based visualization techniques such as particle image velocimetry (PIV), laser-induced fluorescence (LIF) and so on are useful tools for minimizing the optimization process and development period.