Current commercial vehicles' engines are complex systems
with multiple degrees of freedom. In conjunction with current
emissions regulations manufacturers are forced to combine highly
developed engines with complex aftertreatment systems.
A comprehensive simulation model including the engine and
aftertreatment system has been set up in order to study and
optimize the overall system. The model uses a phenomenological
spray combustion model to predict fuel consumption and NO
emissions. In addition physical models for the material
temperatures and the reaction kinetics were generated for the
aftertreatment system. Steady state and transient measurements were
used to calibrate the engine as well as the aftertreatment
model.
The aim for a system-level optimization was a reduction of fuel
consumption while meeting emission standards. Different parameters
influencing the overall process of engine and aftertreatment have
been chosen for optimization with parameter variations and the DoE
method.
Different configurations regarding length and insulation of the
exhaust pipes have been studied and the best possible solution for
reduction of NOx emissions has been evaluated.
EGR temperature directly influences the engine process. The
influence of EGR temperature on the overall process has been
evaluated and the potential of reduced EGR temperature could be
shown.
Another important factor for the reduction of NOx is
the volume of the catalyst brick which has been varied and
optimized together with engine operating parameters using the
neural-network-based model. Finally, reduced fuel consumption could
be found taking into account emission restrictions.