Laser Induced Fluorescence Detection of NO in the Combustion Chamber of an Optical GDI Engine with A-X(0,1) Excitation 2001-01-1926

Planar Laser Induced Fluorescence has been set up to study in-cylinder production of NO in a realistic optical GDI engine. The excitation in the A-X (0,1) band of NO around 236 nm has been used for the first time. This was possible by means of an optical parametric oscillator laser system. A very careful choice of the excitation wavelength has been made with the assistance of a spectral simulation code of NO and O₂ molecules. The first tests inside the engine running in the early injection mode were performed. Global equivalence ratio was set to 0.9 and NO concentration in the exhaust was about 3200 ppm. Pressure traces were recorded and a combustion analysis was performed. Direct flame and fluorescence images were acquired at numerous crank angle degrees between 320 CAD and 500 CAD (TDC=360CAD). Individual images depicted non-homogeneous NO distribution between 450 CAD and 500 CAD. Interference with oxygen seemed negligible whereas a strong absorption phenomenon was observed. Quantification possibilities were also discussed.