Concerns about the harmful exhaust emissions of internal combustion engines have imposed the employment of aftertreatment devices to reduce their impacts both on health and environment.
System modeling of engine and aftertreatment devices is required not only to provide an accurate assessment of the engine and aftertreatment devices performances as single elements but also to quantify the complex interaction of these components from a thermo fluid perspective.
The work focuses on development of a model capable of predicting temporal and spatial evolution of thermo-fluid quantities and chemical species in a diesel oxidation catalyst (DOC). The developed model allows to investigate the influence of thermal characteristics and gas composition on the evolution of the phenomena occurring in the device which deeply reflect on the particulate filter behavior during regeneration phase.
A hybrid approach has been implemented to predict molar fractions and temperatures in the monolith under isobaric and adiabatic conditions. Lax-Wendroff scheme has been used to solve the channel fluid-dynamics. The time-discretization of the differential equations related to the solid phase has allowed to analyze their properties evolution.
The model has been at first calibrated using measured engine test data; then, it has been employed in simulations to predict the behavior of DOC under different engine out conditions during an active regeneration process of the DPF, in order to highlight the role of the oxidation catalyst on the conditions upstream the filter that have to be carefully managed in order to ensure an efficient filter response, preventing DPF regeneration damage and reducing the fuel economy penalty.