MD3-3: Distribution of Unburned Hydrocarbons for Low Temperature Light-Duty Diesel Combustion(MD: Measurement and Diagnostics,General Session Papers)

Abstract

In-cylinder imaging of unburned hydrocarbon (UHC) distributions was performed via planar laser-induced fluorescence (PLIF) in a light-duty diesel engine employing a partially-premixed compression ignition (PPCI) combustion scheme.Measurernents were acquired in the bowl and clearance volume at a light load baseline condition with optimized iniectiontiming. With the fueling rate held constant, the iniection timing was both advanced and retarded to help clarify the source of high level UHC emissions. The UHC composition was fhrther investigated by spectral analysis of the fluorescence signal, Three major UHC sources were identified: nozzle dribble from the iniector tip, low-temperature mixture ofincomplete reactants within the cylinder core surrounding the iajectoT and crevice region fuel accumulation along the cylinder sidewalls. Iajection timing was fbund to infiuence UHC composition and concentration in each ofthe identified regions, amounts of CH20 are present only in low-temperature regions (T< 1200 K), associated with overly-lean (ip < O.5) or excessively-rich (ta > 3.S) mixtures. Since PAHs are forrned in hot, panially-reacted rich regions (T> 1500 K, ip>2) [15], they are expected to co-exist with fbrmaldehyde only