The Influence of Cycle-to-Cycle Hydrocarbon Emissions on Cyclic NO:NO2 Ratio From a HSDI Diesel Engine

Abstract Knowledge of the NO:NO2 ratio emitted from a diesel engine is particularly important for ensuring highest performance selective catalytic reduction (SCR) NOx after-treatment systems. As real driving emissions vehicles increase in importance, need to understand during transient operation similarly increases. Previous work by authors identified significant differences throughout exhaust period single-engine cycle, with proportionally more NO2 being blowdown compared rest stroke. At time it was not known what caused this effect. In study, crank-angle resolved NO and measurements using fast response chemiluminescence detector (CLD) (for NO) new laser-induced fluorescence (LIF) instrument NO2) have been taken single-cylinder high-speed light-duty at three different speed load points including point without gas recirculation (EGR). addition, unburned hydrocarbon (UHC) simultaneously flame ionization detection (FID). The per cycle peak cylinder pressure that shown high correlation coefficients (R2 < 0.97 all test points) work. variation through engine's stroke also observed indicative in-cylinder stratification NO2. A link between UHC an individual - results show where there are higher levels first part (blowdown), perhaps injector dribble or release crevices, proportion increased. This effect analyzed across EGR. LIF analyzer has evaluated, comparison previous state-of-the-art standard “slow” measurement apparatus showing noise order magnitude.