Combined Catalytic Hot Wires Probe and Fuel-Air-Ratio-Laser Induced-Exciplex Fluorescence Air/Fuel Ratio Measurements at the Spark Location Prior to Ignition in a Stratified GDI Engine 1999-01-3536

Combined Catalytic Hot Wires Probe (CHWP) and Fuel Air Ratio Laser Induced Exciplex Fluorescence (FARLIEF) techniques have been applied to a Gasoline Direct Injection Engine to characterize temporal and spatial evolution of the fuel/air ratio in the vicinity of the spark plug. The engine ran below stoichiometric with early injection (homogenous case taken as a reference) or late injection timing with a global equivalence ratio as low as 0.3. Under lean and late injection conditions, the temporal CHWP signal indicates that a rich vapor cloud is carried to the vicinity of the spark plug. CHWP and FARLIEF techniques show that the maximum equivalence ratio in the fuel cloud reaching the spark does not depend on the injection duration. Instead, the duration appeared to affect the size of this rich vapor pocket.