Imaging and post-processing of laser-induced fluorescence from NO in a diesel engine

The imaging of in-cylinder NO distributions in a steadily running optically accessible diesel engine operated on standard diesel fuel is performed by means of the 2D-LIF technique and a tunable ArF excimer laser at 193 nm. Simultaneous excitation at 226 nm showed that no sizable photo-chemical effects are induced by the excimer laser. In order to account for the gradually decreasing transparency of the windows due to soot deposits and for the in-cylinder attenuation of the laser intensity, signal processing procedures for the imaged distributions are presented. In addition to the more realistic depictions of NO distributions at selected crank angles and loads resulting from these procedures, the latter are an essential step towards a quantitative interpretation of the corresponding in-cylinder NO concentrations.