Laser induced fluorescence (LIF) is a useful method for visualizing the distribution of the air-fuel ratio in the combustion chamber. The way this method is applied mainly depends on the fluorescent tracer used, such as biacetyl, toluene, various aldehydes, fluoranthene or diethylketone, among others.
Gasoline strongly absorbs light in the UV region, for example, at the 248-nm wavelength of broadband KrF excimer laser radiation. Therefore, when using this type of laser, iso-octane is employed as the fuel because it is transparent to 248-nm UV light. However, since the distillation curves of iso-octane and gasoline are different, it can be expected that their vaporization characteristics in the intake port and cylinder would also be different. The aim of this study was to find a better fuel for use with LIF at a broadband wavelength of 248 nm.
Three tasks were undertaken in this study. First, a compound fuel was developed that has a distillation curve similar to that of gasoline and is more transparent to 248-nm UV light. Second, an effort was made to develop a new fluorescent tracer having a lower boiling point and suitable for use in observing gasoline vaporization and mixing characteristics. Third, the new compound fuel with and without tracers was compared with different combinations of iso-octane and fluorescent tracers.