Quantitative in-cylinder NO-LIF imaging in a realistic gasoline engine with spray-guided direct injection

Quantitative in-cylinder imaging measurements of NO mole fractions in a gasoline engine with spray-guided direct injection were presented. The optical engine design was kept close to that of a serial four-cylinder engine. Optical access was achieved via sapphire windows, requiring only minor modifications to the engine block. The engine was operated with commercial gasoline and fired continuously. Temperature-dependent CO₂ absorption cross-sections were used to correct for laser and signal attenuation. A sensitivity analysis of the quantitative NO concentrations on the different parameters entering the evaluation was presented. The laser-induced fluorescence (LIF) measurements were compared to results from in-cylinder fast gas sampling through a modified spark plug. The two techniques showed good quantitative agreement. The LIF measurements were also compared to charge-averaged working-cycle-resolved NO chemiluminescence measurements in the exhaust port. NO-LIF imaging results were presented for stratified engine operation with different levels of exhaust gas recirculation (EGR), showing the large impact of EGR on in-cylinder NO formation. This is an abstract of a paper presented at the 30th International Symposium on Combustion (Chicago, IL 7/25-30/2004).