Spatially-Resolved Soot Measurements in Gas Turbine Combustors

Abstract

The difficulties in making spatially-resolved measurements of soot concentration inside practical combustors, which do not rely on sample extraction techniques, are highlighted. Restricted optical access presents the principal constraint to the adoption of established tomographic techniques. A novel hybrid approach, which combines a traversable laser shielding tube and conventional integrated absorption measurement, is demonstrated in two tubular combustors operating at a range of AFRs, inlet air temperatures and pressures. Measurements are reported which have been taken through existing primary and dilution ports and through additional line-of-sight holes drilled in the liner specifically for that purpose. Distinctive radial profiles of soot volume fraction emerge, reflecting the annular development of richer mixtures, which favour soot formation, downstream of the fuel injector.

Stochastic Modelling of NOx and Smoke Production in Gas Turbine Combustors

“…Here the trace species chemistry is substantially decoupled from the turbulent heat release and plausible levels are predicted by post-processing the additional scalar balance equations needed. The processes of particulate surface growth and oxidation, which determine soot production, are also comparatively slow, but at high power conditions primary zone concentrations are not small [5,6] and the influence on local temperature is non-negligible. Chemical source term closures for sooting processes based, for example, on laminar flamelet models [7] then inevitably reinstate some of the difficulties so carefully circumvented by the conserved scalar approach.…”