Volvo VAH 2013, Руководство оператора, Страница: 101 / 175

Operator's Manual Vehicle Maintenance
VN, VHD 97
New stringent standards for exhaust emission control begin with the 2010 model year.
The Diesel Particulate Filter (DPF) system has been developed to act in combination
with Ultra Low Sulphur Diesel (ULSD) fuel to reduce particulate emissions to meet
the requirement. The Exhaust After-Treatment System (EATS) includes all the engine
and exhaust emissions control components that are required to meet the stringent
2010 standard.
Particulate matter consists of soot and ash in the exhaust that engines with an EGR
system alone, are not equipped to handle. The particulate matter is considered
a contaminant that contains undesirable elements. The DPF system reduces the
unwanted elements to a more acceptable level defined in the regulations. There are
multiple methods of reducing these emissions. VOLVO has selected to use a Diesel
Oxidation Catalyst (DOC) with a catalyzed diesel particulate filter. The other uses
a diesel particulate filter of a different kind without a DOC and in its place uses a
combustion chamber to heat the exhaust mixture thus causing active regeneration.
The particulate matter removed from the exhaust collects on the filter surfaces. To
avoid eventual blockage, which would increase exhaust back pressure and affect power
and fuel economy, the filter must be cleaned. The DPF is cleaned automatically. The
soot breaks down to safer substances before being released to the atmosphere. Some
of the ash remains, but takes a long time to reach the point where ash clogs the filter.
Cleaning a filter so it can continue to function is called “regeneration.” Either system
uses high heat to break down the chemical properties. Depending on vehicle usage,
the engine is equipped with a passive or active regeneration system.
In “passive regeneration,” the exhaust produces enough heat continuously to convert
the soot, with approximately 260 °C (500 °F) being required. The process is slow and
continues indefinitely. Passive regeneration is possible only in vehicle applications
where the temperature is likely to remain at or above the required temperature level,
making active regeneration unnecessary.
Active regeneration occurs when the vehicle is parked and is initiated automatically
by the aftertreatment system. During an active regeneration, the temperature of the
filter must be raised to 500 °C (932 °F). To produce this temperature, the system uses
a hydrocarbon injector or Aftertreatment Fuel (AF) injector to introduce fuel into
the exhaust stream as it leaves the turbocharger. The hot exhaust ignites the fuel
which produces the regeneration temperature. When the DPF becomes restricted to a
minimum volume, the engine ECU starts the fuel injection into the exhaust. When the
air flow rate returns to normal through the DPF, the engine ECU turns the injector off.
WARNING
Prior to ever working on the exhaust,
allow time for the entire exhaust system
to cool. Failure to do so may result in
personal injury. Severe burns can occur.