null  User manual
Volvo Trucks North America
Greensboro, NC USA
D
Service Bulletin
Trucks
Date
Group
No.
Page
1.2007
258
42
1(6)
Exhaust After-Treatment System
Design and Function
D13F
Exhaust After-Treatment System
W2005779
This information covers the design and function of the Exhaust After-Treatment System
(EATS) on the Volvo D13F engine.
Contents
• “Exhaust After-Treatment System, (EATS)” page 2
Note: Information is subject to change without notice.
Illustrations are used for reference only and can differ slightly from the actual vehicle
being serviced. However, key components addressed in this information are represented
as accurately as possible.
PV776-20178666
USA24525.ihval
Volvo Trucks North America
Service Bulletin
D
Date
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No.
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1.2007
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42
2(6)
Design and Function
Exhaust After-Treatment System, (EATS)
The Exhaust After-Treatment System (EATS) consists
of many engine and exhaust components and sensors
working together to lower emissions to meet the stringent
2007 emission requirements for the heavy truck industry.
The following bulletin provides a brief description of each
of the main components and how these components
interact with each other to allow the EATS system to lower
emissions and provide optimal fuel economy. This bulletin
also provides a list of the various modes of operation
that the emission system passes through during normal
engine operation.
EATS Operational Modes Definitions
Normal Mode
The engine is controlled by its normal calibration. The
engine exhaust forms Particulate Matter (PM) or soot,
most of which gets trapped in the Diesel Particulate
Filter (DPF). Eventually the soot needs to be removed
or oxidized.
In the normal mode no active regeneration is in progress,
however passive regeneration may be occurring.
Passive Regeneration
A continuous, slow oxidation (burning) process of soot
due to sufficient filter temperature and NOx/soot ratio. The
engine exhaust supplies the required heat under normal
engine operating conditions.
Heat Mode
An engine control mode that allows the exhaust
temperature to raise to a minimum temperature required
to allow hydrocarbon (aftertreatment fuel) injection (active
regeneration mode). Heat mode is activated when an
active regeneration is required.
Active Regeneration Mode
A hydrocarbon (aftertreatment fuel) injector is used
to inject fuel into the exhaust flow to raise the DPF
filter temperature to a controlled value, currently about
575 C to 625 C (1067 F to 1157 F). The increased
temperature is used to allow oxygen oxidation (burning)
of the soot to occur in the DPF. The active regeneration
mode is used when the passive regeneration mode is
insufficient to allow the filter from reaching certain soot
levels.
Service Mode
The service mode is performed by a trained service
technician at the service center. The technician
determines whether the filter ash accumulation is
excessive and if the filter should be removed from the
DPF and cleaned externally or exchanged. If the ash
accumulation is below the removal level, the service
technician could initiate a manual stationary regeneration
through the use of the VCADS service tool.
CAUTION
The service technician must ensure that the truck
is in a safe and suitable location to withstand the
high temperatures that occur during the regeneration
process. Equipment damage or personal injury may
occur if combustibles are too close to the exhaust pipe
or muffler.
Volvo Trucks North America
Service Bulletin
System Components
EGR System
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The EGR system is designed to recirculate exhaust gases
into the combustion chambers to reduce the nitrogen
oxide (NOx) emissions.
The NOx content increases with higher combustion
temperatures. Recirculating cooled exhaust gases
reduces the temperature in the combustion chamber and
lowers the level of NOx emissions. To be able to do this,
the pressure must be higher in the exhaust side than in
the inlet side — this is controlled by the VGT turbo.
On the exhaust manifold an EGR valve (Exhaust Gas
Recirculation) is mounted. This valve is managed by the
oil pressure and regulates recirculation of exhaust gases.
A portion of the exhaust gas is redirected from the exhaust
manifold into the exhaust gas (EGR) cooler, through the
Venturi pipe, which measures the gas flow, and into the
EGR mixing chamber. There the exhaust gas is mixed
with intake air cooled by the charge air cooler before it is
led into the intake manifold.
W2005851
The amount of recirculated exhaust gases is controlled
by the engine Electronic Control Unit (ECU) and depends
on engine load, coolant temperature and various other
factors.
1
2
3
4
5
6
7
EGR Valve
EGR Valve Exhaust Pipe
EGR Cooler
Differential Pressure Sensor
Venturi Tube
Crossover Pipe
EGR Mixing Chamber
Variable Geometry Turbocharger
In order to be able to quickly regulate the charge air
pressure and drive the EGR, a new type of turbocharger
unit with variable geometry has been introduced. This
turbocharger contributes to lower emissions, provides
optimal fuel consumption and increases power output.
The extent of turbocharger function can be varied by
the speed of the gases entering into the turbine. This
is controlled by an electrically-operated actuator. The
turbocharger bearing housing and the actuator are both
cooled by engine coolant.
The variable geometry turbocharger (VGT) has a set of
vanes and a sliding nozzle ring that maintains sufficient
backpressure in the exhaust manifold for proper operation
of the EGR system. A certain amount of backpressure is
required to push the exhaust gases into the pressurized
intake air at the EGR mixer.
Additionally, the sliding nozzle ring of the turbocharger
controls exhaust backpressure not only for proper
operation of the EGR system, but also for enhanced
braking. By fully closing the VG nozzle mechanism, the
turbocharger performs as an exhaust brake.
W2005653
Volvo Trucks North America
Service Bulletin
Particulate Filter
The Diesel Particulate Filter (DPF) with oxidation catalyst
and particulate trap greatly reduces the emission of
particulate (soot), hydrocarbons (HC) and carbon
monoxide (CO).
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The use of Ultra Low Sulphur Diesel (ULSD) meeting a
limit of 15 parts per million sulphur is required to prevent
fouling of the DPF. Additionally, the maximum allowable
blending of biodiesel is 5%.
In the DPF system, soot is trapped within a catalyzed
ceramic monolith, particulate filter with unique noble
metal coating. The particulate filter is regenerated either
passively, or actively by the means of a “hydrocarbon
injector” that injects a small amount of diesel fuel to
reburn the exhaust gases using catalytic reaction. This
will reduce the soot quantity and extend the function of
the filter.
The DPF system has been designed to provide primarily
“passive” regeneration in order to increase fuel economy.
During passive regeneration, the soot is chemically
removed out of the monolith by an ongoing catalytic
reaction process that uses no additional fuel.
If the duty cycle is more “stop-and-go”, it may be
insufficient to remove the soot passively, and “active”
regeneration will sometimes occur. In this process,
additional diesel fuel is introduced into the exhaust stream
at the turbocharger outlet by a “hydrocarbon injector”. The
fuel travels to the precatalyst, where a chemical reaction
occurs which raises temperatures in the monolith to the
oxidation level, and the soot is simply consumed. Active
regeneration takes about 20-30 minutes and consumes
a liter or two of fuel. The driver will have the ability to
postpone regeneration until later if one is not desired. To
increase the exhaust temperature and to keep it during
regeneration, a Discharge Recirculation Valve (DRV) is
connected on the compressor side of the turbocharger. It
recirculates a portion of warm charge air from the outlet to
the inlet of the turbo. The on/off of the DRV is controlled
by a solenoid valve.
There are two variants of the muffler with particulate filter:
the Compact DPF that is frame mounted behind the right
front wheel, and the Vertical DPF that can be mounted
behind the cab for certain chassis configurations. The
Vertical DPF includes the NOx sensor, while the Compact
DPF has this sensor mounted on a separate pipe.
The particulate filter continuously oxidizes the trapped
particles in the filter module. A small amount of the
particulate trapped in the filter consists of inorganic
material (ash) that cannot be oxidized. If the filter is not
serviced, this ash will eventually build up and block the
filter, causing exhaust gas back pressure. This leads to
increased fuel consumption and can also lead to de-rate
and possibly excessive engine wear or damage and can
damage the particulate filter itself.
Note: All gaskets must be replaced every time they are
loosened.
W2005786
Volvo Trucks North America
Service Bulletin
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Discharge Recirculation Valve (DRV)
Under some conditions the exhaust temperature is not
hot enough for the Diesel Oxidation Catalyst (DOC) to
oxidize, or burn, the hydrocarbons (fuel) that are being
injected into the exhaust flow. Typically the condition
where more heat is needed is at lower torque levels. Heat
mode is automatically activated as necessary during
active regenerations.
One method of achieving higher exhaust temperatures
requires reducing turbocharger effectiveness. This is
done by using the Discharge Recirculation Valve (DRV).
The DRV allows boosted air to be re-circulated back into
the turbocharger compressor inlet. This function is used
to help elevate the exhaust temperature and maintain
the DOC temperature to a level which supports active
regeneration.
W2005903
Aftertreatment Fuel Injector (AFI)
The aftertreatment fuel (hydrocarbon) injector is used
with the DPF muffler systems to inject diesel fuel into the
exhaust stream to increase the exhaust temperature to
the extent needed to allow active regeneration. Active
regeneration mode is used when the passive regeneration
is insufficient to prevent the filter from reaching certain
soot levels. Active regeneration can be triggered
automatically by the engine ECU or manually by a service
technician in a suitable location.
W2005917
Volvo Trucks North America
Service Bulletin
Electronic Control Unit (ECU)
The engine Electronic Control Unit (ECU) provides total
control of the exhaust after-treatment system. The
engine ECU monitors lapsed time, distance traveled, fuel
consumption and soot accumulation, plus many other
sensor signals to determine when conditions are right to
trigger a DPF regeneration event.
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The engine ECU is also responsible for monitoring all the
valves and components that are required to ensure that
DPF regeneration is controlled and successful. These
would include, but are not limited to control of the DRV,
turbocharger actuator and EGR valve position. Control of
these and many other components are all important to a
successful DPF regeneration.
W2005598
Emission Control Sensors
The engine control unit could not provide the total control
of the emissions system without the feedback provided by
the many sensors throughout the EATS system. These
include monitoring of the turbocharger, EGR system,
engine coolant, engine position and the DPF muffler.
Additionally, many chassis-mounted sensors are required,
including the ambient air temperature and turbocharger
wheel speed sensor. An example of some of the main
engine sensors are listed below. However, sensors will
vary dependent upon the DPF system used.
1
Engine Position
•
•
3
Turbocharger Wheel Speed Sensor
VGT Position Sensor
Boost Pressure Sensor
Boost Temperature Sensor
Camshaft Speed Sensor
Crankshaft Speed Sensor
Engine Coolant
•
Coolant Temperature Sensor
Diesel Particulate Filter
•
•
•
•
•
•
5
Turbocharger
•
•
•
•
2
4
EGR System
•
•
6
Pre-Oxidation Catalyst Temperature Sensor
Downstream Oxidation Catalyst Temperature
Sensor
Downstream DPF Temperature Sensor
Differential Pressure Sensor
NOx Sensor
AFI Pressure Sensor
EGR Temperature Sensor
EGR Flow Sensor (Differential Pressure Sensor)
Inlet Air Sensors
•
•
•
•
Inlet Air Temperature Sensors
Inlet Air Humidity Sensors
Ambient Air Temperature Sensors
Ambient Air Pressure Sensors
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