A DPF (Diesel Particulate Filter) is a device designed to remove
diesel particulate matter or soot from the exhaust gas of a diesel
engine. Wall-flow diesel particulate filters usually remove 85% or
more of the soot. In addition to collecting the particulate, a
method must exist to clean the filter. Wall-flow filters are
designed to burn off the accumulated particulate at regular
intervals, and this can be achieved through engine modifications
such as in-cylinder post injections, throttling of the intake air,
and using the EGR valve during overrun all to achieve 630degC at
the DPF. Running the regeneration cycle too often, while keeping
the back pressure in the exhaust system low will use extra fuel,
with increased oil dilution, which will increases the chances of
diesel engine runaway and engine damage. Regenerating infrequently
runs the risk of blocking the DPF and also causing engine damage
and/or uncontrolled regeneration and possible DPF failure. Quality
regeneration control software is a necessity for longevity of the
active DPF system and control of the different techniques. The
overall system needs to be robust and function regardless of
environmental conditions, driver style, drive cycle, ambient
conditions such as altitude and also engine component tolerances
such as fuel injector delivery, all in all a challenging task.
This paper will discuss the details of some of the calibration
techniques for achieving all of the targets. This is based on
experience gained from calibrating for production a 2.0-liter 4cyl
diesel engine using common rail injection, EGR, DOC catalyst, VNT,
intake air throttling, T4 temperature sensor, Pre cDPF temperature
sensor and Delta-P sensor across the DPF. With the DPF being
packaged some 60 cm from Catalyst out. The schematic of the system
is shown.