1D/3D Simulation in the Development of DeNOx Aftertreatment Systems for US10 Heavy Duty Application

Johann Christian  Wurzenberger, AVL List GmbH

1D/3D Simulation in the Development of DeNOx Aftertreatment Systems
for US 2010 Heavy Duty Applications

J. C. Wurzenberger, R. Wanker, M. Schuessler

The fulfillment of significantly reduced US emission limits for heavy
duty diesel engines as imposed by US 2010 emission legislation
presents a great challenge for the next development period. The
individual technology elements necessary to achieve these stringent
targets (engine-related measures as well as aftertreatment systems)
are available on the market. However, the pre-requisite for future
business success will be an optimised combination of these elements to
fully cover the customers' needs and expectations.

From today's point of view a combination of DOCs, a wall flow DPF and
a urea SCR system seems to be the most promising aftertreatment
concept to meet future emission limits. The application of complex
aftertreatment systems requires not only highly effective
aftertreatment components but also a systematic approach for the
integration of entire systems. At early development stages,
computationally efficient 1D simulation models can be used not only to
deepen the insight into all physical and chemical effects but also to
investigate and optimize the layout of entire systems. At later
development stages especially highly resolved 3D simulations are used
to investigate more-dimensional effects given by e.g. the urea
injection system and to perform final design tuning.

This paper presents a comprehensive simulation framework using 1D and
3D simulations by the example of a heavy-duty exhaust system. The
deNOx performance of the entire exhaust gas line during a drive cycle
is investigated by a 1D model consisting of pipes, DOC, DPF, SCR and
a dosing control unit. The models of the individual components are
discussed and compared to experimental data. The impact of different
pipe wall insulations on the overall NOx reduction is compared for
different engine operating phases. A 3D model is applied to describe
the behavior of a urea injection system. The model covers injection of
urea-water droplets, evaporation of water, thermolysis of urea,
droplet wall interaction, build-up of wall-films and the influence of
mixing devices. The model is used to investigate the impact of the
urea injection system on ammonia formation and distribution in front
of the SCR converter. Due to the combined and systematic application
of 1D/3D simulation tools both the overall system and the detailed
urea injection performance can be calculated with sufficient physical
details and an appropriate computational effort.

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