Use of Laser-Induced Ionization to Detect Soot Inception in Premixed Flames.
Use of Laser-Induced Ionization to Detect Soot Inception
in Premixed Flames.
Manzello, S. L.; Lee, E. J.; Mulholland, G. W.
Applied Optics, Vol. 44, No. 24, 5105-5111, August 20,
premixed flames; lasers; ionization; soot; instruments;
Experimental measurements of laser-induced ionization
were performed for ethene-air premixed flames operated
near the soot inception point. Soot was ionized with a
pulsed laser operated at 532 nm. The ionization signal
was collected with a tungsten electrode located in the
postflame region. Ionization signals were collected by
use of both single-electrode and dual-electrode
configurations. Earlier laser-induced- ionization
studies focused on the use of a single biased electrode
to generate the electric field, with the burner head
serving as the path to ground. In many practical
combustion systems, a path to ground is not readily
available. To apply the laser-induced- ionization
diagnostic to these geometries, a dual-electrode
geometry must be employed. The influence of electrode
configuration, flame equivalence ratio, and flame height
on ionization signal detection was determined. The
efficacy of the laser-induced-ionization diagnostic in
detecting soot inception in the postflame region of a
premixed flame by use of a dual-electrode configuration
was investigated. Of the dual-electrode configurations
tested, the dual-electrode geometry oriented parallel to
the laser beam was observed to be most sensitive for
detecting the soot inception point in a premixed flame.