INVESTIGATIONS ON A SPARK-IGNITED ENGINE USING 2-DIMENSIONAL LASER-INDUCED FLUORESCENCE

The method of laser-induced fluorescence (LIF) was applied to a modifi ed industrial two-stroke engine with a single cylinder and spark ignit ion. Together, the disc-shaped combustion chamber and the low clearanc e height of the piston ensure mainly two-dimensional flame propagation . Formaldehyde is used as a natural tracer species for detecting and s tudying exothermic centres (so-called ''hot spots'') in the end gas. T he latter contain a larger amount of formaldehyde than the enclosing e nd gas due to the slightly higher temperatures, To obtain two-dimensio nal excitation of the formaldehyde a laser light sheet enters from sid eways through a ring-shaped quartz window. The fluorescence is detecte d via a full-size top window by means of an ultrashort-exposure ICCD-c amera, and the frames are stored in a PC. Here, frames are presented w hich show 2D-LIF of formaldehyde in non-knocking as well as in knockin g cycles.