CRANK-ANGLE-RESOLVED LASER-INDUCED FLUORESCENCE IMAGING OF NO IN A SPARK-IGNITION ENGINE AT 248 NM AND CORRELATIONS TO FLAME FRONT PROPAGATION AND PRESSURE RELEASE

Inside the combustion chamber of a spark-ignition engine, NO fluoresce nce is excited with a narrow-band tunable KrF excimer laser. The fluor escence light is detected by an intensified CCD camera that yields ima ges of the NO distributions. Rotational-vibrational transitions of NO are excited by the A (2) Sigma(+) <-- X (II)-I-2 (0, 2) band system ar ound 248 nm. Single laser shot planar NO distributions are obtained wi th good signal-to-noise ratio at all crank angles and allow us to loca te areas of NO formation during combustion. The pressure within the co mbustion chamber is measured simultaneously with the NO distributions, which allows the evaluation of correlations between indicated work an d NO formation. The crank-angle-resolved sequences of two-dimensional NO distributions and averaged pressure traces are presented for differ ent engine-operating conditions. In addition, laser-induced predissoci ation fluorescence of OH excited by the same laser source is measured in order to visualize the corresponding flame front propagation and to compare the time of formation of NO relative to that of OH. (C) 1996 Optical Society of America