With the introduction of particulate matter emissions regulations for
gasoline engines, most car manufacturers are considering using
Gasoline Particulate Filters (GPF). Although very similar to Diesel
Particulate Filters (DPF), GPFs operate at higher temperatures and
generally have thinner monolith walls. In order to estimate the
pressure loss through the filter, filter wall permeability is needed.
This presents a number of challenges since wall losses cannot be
efficiently isolated from other losses in a full scale filter or filter core.
Thin wall wafers have been used for DPF characterisation. However,
GPF wafers are generally thinner, which makes the testing less
straightforward. This paper presents a novel effective methodology
for estimation of GPF wall permeability using thin wafers cut from
the filter monolith. Both cold and hot flow permeability can be
estimated, which allows to account for the change of apparent
permeability due to the slip effect. The flow through the wafer is also
modelled numerically to assess the effect of the uneven wafer surface
resulting from wafer preparation method. A technique for calculating
corrected permeability is suggested which is estimated to provide
values within 5% of the "nominal" value. Combining experimental
results with the applied correction, consistent permeability values
have been obtained for seven wafer samples. Maximum variation in
the permeability values was 10%, with a standard error of ±2.5% of
the mean. Being able to assess filter wall permeability from a simple
cold flow pressure testing procedure will allow development of more
efficient flow and pressure loss models for Gasoline Particulate
Filters, which in turn will facilitate design of efficient aftertreatment
systems with lower back pressure.
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- Particulate Matter
- Particulate Filter
- Pressure Loss
- Automotive Engineering