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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.

An experimental study was performed to set up a new non intrusive technique to measure the rate of RBG (Residual Burnt Gases) in the cylinder of a firing SI (Spark Ignition) engine. The method is based on time-resolved in-cylinder CO2 concentration measurements; this molecule being used as an RBG tracer. The measurement technique that has been developed is based on the absorption of an IR (infrared) beam (around 4.3μm) that crosses the combustion chamber. The method was first set up in a heated and pressurized constant volume vessel that could be filled with controlled N2/CO2 mixture. Optical filters are used to select the useful part of the IR spectrum (the one which interacts with the CO2 absorption spectrum). It has been pointed out that the CO2 absorption coefficient is temperature and pressure dependent. Moreover, these dependencies vary with the absorption wavelength.