Technical Paper
Study of the Effect of the Residual Gas Fraction on Combustion in a S.I. Engine Using Simultaneous CARS Measurements of Temperature and CO2 Concentration
1992-10-01
922388
The aim of the work was to study the important issue of the residual gas mixing variations, using CO2 as a tracer for the residual gas fraction. Therefore simultaneous measurements of CO2 concentration and temperature have been performed inside a fired IC engine. Temperature is deduced from a broadband N2 CARS signal and the CO2 concentration from a narrowband CO2 CARS signal. To overcome the main difficulties encountered when making measurements in an engine (i.e. cycle-to-cycle variations and beam steering by density gradients), the shot-by-shot referencing technique and the in-situ referencing technique using the N2 CARS signal intensity to determine CO2 concentration were used. All the measurements were performed at the center of the combustion chamber, using different spark plug locations. Three locations were measured: 4cm, 0.5cm and 0.1cm from the plug. The first measurements were performed with three conventional spark plugs, regularly spaced around the combustion chamber.
