Abstract:
The thesis describes the characterisation and application of the laser induced
incandescence
technique for making soot measurements in practical devices. Laser
induced incandescence is the phenomenon whereby particulates such a soot absorb
laser radiation and are heated to a
temperature much higher than the bath gas. The
broadband incandescence
signal from the hot particles can be detected and the signal is
proportional to volume fraction.
The
technique was used to study soot in partially premixed counterflow ethylene air
flames, iso-octane explosion flames, and to image soot in a D. I. Diesel engine. Mie
scattering, OH-LIF and absorption were used a complementary diagnostics.
Appropriate ratios of LII and Mie images allowed the relative particle size and number
density to be imaged. The counter flow burner measurements were used to study the
effects of strain on soot formation while the bomb work demonstrated soot production in
hydro-dynamically unstable cellular flames. The Diesel engine measurements are a
demonstration of optical diagnostics in a real device.
In order to characterise the LII signal behaviour two types of carbon aerosol generators
were built. The
liquid dispersion device produces almost spherical sub-micron carbon
black
particles. The device was used to characterise the soot field response, laser
fluence
response, signal decay and spectrum of the LII signal.
