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Meeting the US Heavy-Duty EPA 2010 Standards and Providing Increased Value for the Customer
Abstract:
The paper will discuss the design and development of heavy-duty
diesel engines to meet the US EPA 2010 on-highway standards - 0.2
g/HP-hr NOx and 0.01 g/HP-hr particulate matter (PM). In meeting
these standards a combination of in-cylinder control and
aftertreatment control for both NOx and particulate has been
used.
For NOx control, a combination of cooled exhaust gas
recirculation (EGR) and selective catalytic reduction (SCR) is
used. The SCR catalyst uses copper zeolite to achieve high levels
of NOx conversion efficiency with minimal ammonia slip and
unparalleled thermal durability.
For particulate control, a diesel particulate filter (DPF) with
upstream oxidation catalyst (DOC) is used. While the DPF may be
actively regenerated when required, it operates predominantly with
passive regeneration - enabled by the high NOx levels between the
engine and the DPF, associated with high efficiency SCR systems and
NO₂ production across the DOC.
The engine features a proprietary high pressure common rail fuel
system (HPCR), developed jointly by Cummins and Scania. This HPCR
system was developed for medium- and heavy-duty engines and is
known as XPI. The XPI system was developed for very high pressure
injection required by heavy-duty engines at US EPA 2010, EURO 5 and
EURO 6 exhaust emission levels. Together with the variable geometry
turbocharger (VGT), the HPCR provides flexibility for thermal
management of the aftertreatment system. Thermal management is used
extensively to provide fast warm-up and optimum DPF and SCR
performance in use.
This system architecture is designed to minimize both fuel and
DEF consumption characteristics. With the adoption of copper
zeolite SCR, it has been possible to achieve the near-zero US EPA
2010 emission standards, while reducing overall operating costs
significantly (4-5%) when compared with the EPA 2007 engine it
replaces.
On-board diagnostics (OBD) has been fully implemented in these
HD engines for 2010. This has required that all emission control
systems be monitored for performance against emission thresholds,
and that all related actuators and sensors be monitored for correct
functionality.