(600f) Impact of Drop to Idle On a Particulate Diesel Filter Fed by a Cone

Impact of Drop to Idle on a Particulate
Diesel Filter Fed by a Cone  

Mengting Yu and Dan Luss

Department of Chemical and
Biomolecular Engineering, University of Houston, Houston, TX, 77204

The Particulate Matter (PM) emitted by a
diesel engine is collected and then burned in a Diesel Particulate Filter
(DPF). A major technological challenge in the operation of the ceramic
cordierite filter is to avoid formation of high temperatures that may cause
local melting or cracking. Such high temperatures do not form under stationary
feed conditions but may be generated following a sudden drop to idle (DTI).
Almost all previous studies of temperature excursions during the DPF
regeneration (combustion of the deposited PM) were of cases in which the feed
to all the parallel channels was uniform. A wide-angled cone (diffuser) is
sometimes used to connect the diesel engine exhaust pipe to the DPF leading to
a non-uniform velocity to the inlet channels, with the highest attained at the
DPF center. We used a computational model of PM deposition and regeneration to
investigate the impact of the inlet cone on the DPF behavior. The cone led to
mal-distribution of the deposited PM, with the highest thickness in the DPF
center. Simulations revealed that following a DTI the highest regeneration
temperature in a DPF fed by a cone exceeded that in one not fed by a cone and
may exceed the cordierite DPF melting temperature (~1200⁰C).
Moreover, it may generate transient radial and axial temperature gradients
several times higher than under stationary regeneration that may crack the DPF.
The increase in the temperature gradients is especially large in the axial
direction. One of the surprising finding is that the highest temperature
attained following a DTI is not a monotonic function of the initial PM loading.