Quantitative 2D Single-Shot Imaging of no Concentrations and Temperatures in a Transparent SI Engine

Abstract

The formation of nitric oxide in a transparent spark-ignition (SI) engine was studied experimentally using a combination of planar laser-induced fluorescence and Rayleigh scattering. Simultaneous images were obtained after excitation with a single pulse from a tunable KrF excimer laser. Tuning the laser to 247.9 nm allows excitation of the NO A-X (0,2) band, and subsequent fluorescence emission is spectrally well separated to image Rayleigh scattering from the same laser pulse. The advantages of using the (0,2) band for excitation of NO under engine conditions are demonstrated, and quantitative distributions of NO concentrations are shown along with temperature fields calculated from the Rayleigh images. We investigated various engine operation conditions with propane and iso-octane as fuels. Cycle-resolved measurements show strong cycle-to-cycle variations of the NO formation with peaks in the spatial NO distribution, whereas the temperature field is nearly homogeneous, leading to the conclusion that small variations in the temperature distributions lead to peak NO concentrations via the zeldovich mechanism.