Application of Laser-Induced Breakdown Spectroscopy to Engine Research

This report explained the local equivalence ratio (air fuel ratio) measurements of engine exhaust gas and direct fuel injection in engine cylinder using laser-induced breakdown spectroscopy (LIBS) and spark-induced breakdown spectroscopy (SIBS). When we use LIBS/SIBS in combustion system, we can discuss simultaneous laser/spark ignition and equivalence ratio measurement of premixed mixture. The intensity ratio of H/O or H/N showed a good agreement with preset equivalence ratio in engine exhaust gas and premixed mixture in engine cylinder. The influence of spark discharge characteristics on emission spectra was investigated by simultaneous measurement of spark discharge visualization and spectroscopy. The relationship between air-fuel ratio and the emission intensity ratio was obtained in premixed gas combustion in a spark ignition engine. There was a tendency that local air-fuel ratio decreases with advance of the injection timing from the fi xed ignition timing. It was observed that spark discharge was affected by the flow due to injection. LIBS/SIBS is very good tool to discuss the combustion characteristics in real engine researches.