A Simulation Study of an Aftertreatment System Level Model for Diesel Dual Fuel (DDF) Engine Emission Control

The diesel/natural gas engine configuration provides a potential alternative solution for PM and NO_x emissions reduction from typical diesel engine operations. However, their engine operations suffer from high NMHC/methane emissions and poor engine performance, especially at light loads. By increasing the diesel pilot quantity, the performance and reduction of NMHC/methane emissions can be improved but the emission levels are still very high. Clearly, a typical DOC is not good enough to treat NMHC/methane emissions. Methane has been known as one of most stable species that is difficult to catalytically oxidize in lean burn environment and low exhaust temperatures. An aftertreatment system exclusively designed for treating methane emissions from DDF operations is therefore necessary.

The current work is aimed to establish an effective computational tool in order to study the newly proposed catalytic converter system concept on treating methane from DDF operations. A system level model approach was chosen to found the proposed system. Thermal management of the proposed DDF catalytic converter system is done via raw diesel fuel injection ahead of the catalyst. The model was used to simulate exhaust-device and device-device interactions under steady-state operations with various raw fuel injection patterns. The results show the possibility of implementing the proposed concept to DDF emission control but the trade-off lies in fuel penalty. Good thermal management can be achieved by optimizing the amount of fuel injection, injection patterns, and geometric properties of the substrate.