Influence of DPF Soot Loading on Engine Performance with a Pre-Turbo Aftertreatment Exhaust Line

The pressure drop across the aftertreatment systems directly affects the fuel economy as a function of the flow characteristics and also the soot loading in the case of the Diesel particulate filter. However, the relative position of this system with respect to the turbine has an additional effect which is dependent on the influence of the turbine expansion ratio. When the DPF is placed upstream of the turbine, its pressure drop is not affected by the multiplicative effect of the turbine expansion ratio to set the exhaust manifold pressure.

This work concentrates on the analysis of the influence that the aftertreatment pressure drop has on the engine performance depending on the DPF soot loading and the location of the aftertreatment with respect to the turbine. The interaction with the turbocharger and the EGR operation is also analyzed taking as reference a two stage turbocharger heavy duty Diesel engine. The running conditions comprise steady state operation and a wide range of load transient processes at constant engine speed, which includes several initial engine load conditions in order to properly evaluate the influence of heat losses and thermal inertia across the aftertreatment devices. These phenomena are combined with the effect of the pressure drop to finally determine the engine dynamic response in a pre-turbo aftertreatment architecture. The DPF soot loading, which highly influences the engine performance in the traditional post-turbo DPF placement, is shown to become a secondary parameter in the case of the pre-turbo DPF placement. The analysis of the engine response leads to define main control strategies to exploit advantages and overcome possible drawbacks of the proposed exhaust line configuration.