PREVOST H 2018 Series, Operator'S Manual

Page: 117 / 258

OTHER FEATURES 5-3
PA1628 H3-41, H3-45 Operator’s Manual
EXHAUST AFTERTREATMENT SYSTEM
The exhaust aftertreatment system consists of
two units, the filtration and regeneration unit
and the selective catalytic reduction SCR unit.
FILTRATION AND REGENERATION UNIT
The main purpose of the filtration and
regeneration unit is to capture and oxidize
(regenerate) the particulate matter (soot) in the
engine exhaust gas. The exhaust gas first enters
the Diesel Oxidation Catalyst (DOC) and then
flow through the Diesel Particulate Filter (DPF);
together they capture and regenerate the soot
on a regular or passive basis. Through constant
monitoring of the exhaust gas temperature and
the system back pressure, the engine control
module is able to manage regeneration.
PASSIVE REGENERATION
Passive regeneration is the process by which the
particulate matter is oxidized due to the heat
generated by the engine internal combustion
process. During normal highway operation,
exhaust temperatures alone are usually high
enough to oxidize accumulating soot. In low
ambient temperatures, however, or in some
stop-and-go applications, the system needs a
little help to regenerate, or clean itself. This
process is called “active” regeneration.
Active regeneration
Active regeneration is necessary when the
engine internal combustion process alone does
not generate enough heat. A dosing system
injects a mist of diesel fuel into the exhaust
system to increase and maintain the
aftertreatment system temperature. Exhaust
temperature must be above 572°F (300°C) to
initiate the oxidation catalyst, which in turn
oxidizes the injected diesel fuel molecules to
achieve up to 1200°F (650°C) exhaust
temperature at the particulate filter. This
process of active regeneration takes place
during the normal operation cycle of the vehicle
without charges in performance or control for
the operator. EPA2010 compliant Volvo engines
produce less soot, so less active or stationary
regeneration will be required.
Stationary (parked) regeneration
In a small number of specific engine duty cycles,
engine control module may not be capable of
completing an active regeneration. In these
situations, the operator will be notified that a
stationary or parked regeneration may be
required. A DPF telltale light will illuminate
indicating the need for user interaction. The
lamp gives the operator a grace period to allow
this process to take place at a time when most
convenient for the operator. This process
requires the vehicle to be parked while a driver
or maintenance technician initiates the
regeneration process using the DID menus. Once
initiated, the stationary regeneration process
will be complete in about 45 minutes.
The driver will be notified of the need for a
stationary regeneration (parked) by illumination
of the DPF REGENERATION telltale light.