Conductivity for Soot
Sensing: Possibilities and Limitations
- Publication date
- Publisher
Abstract
In this study we summarize the possibilities and limitations
of
a conductometric measurement principle for soot sensing. The electrical
conductivity of different carbon blacks (FW 200, lamp black 101, Printex
30, Printex U, Printex XE2, special black 4, and special black 6),
spark discharge soot (GfG), and graphite powder was measured by a
van der Pauw arrangement. Additionally the influence of inorganic
admixtures on the conductivity of carbonaceous materials was proven
to follow the percolation theory. Structural and oxidation characteristics
obtained with Raman microspectroscopy and temperature programmed oxidation,
respectively, were correlated with the electrical conductivity data.
Moreover, a thermophoretic precipitator has been applied to deposit
soot particles from the exhaust stream between interdigital electrodes.
This combines a controlled and size independent particle collection
method with the conductivity measurement principle. A test vehicle
was equipped with the AVL Micro Soot Sensor (photoacoustic soot sensor)
to prove the conductometric sensor principle with an independent and
reliable technique. Our results demonstrate promising potential of
the conductometric sensor for on-board particle diagnostic. Furthermore
this sensor can be applied as a simple, rapid, and cheap analytical
tool for characterization of soot structure