Temperature Mapping of an Acoustically Forced Laminar Diffusion Flame using Planar Laser Rayleigh Scattering

Abstract

Excitation of a combusting flow near its preferred mode to increase volumetric energy release has been studied for many years on internal systems. Excitation promotes the production and propagation of large scale vortices, which have been shown to improve combustion. Forcing on external systems is far less documented. Most studies employ chemiluminescence and Schlieren to image the flow, however neither technique provides a true cross sectional measurement.

Planar laser Rayleigh scattering was used to generate temperature maps of an acoustically forced laminar jet. Small scale enhancement was found to increase with frequency, while large scale vortices had competing effects in the range of the preferred mode. While vortices compacted the flame, increased the residence time of reactants, and entrained fresh reactants, straining of the reaction region and cooling from the entrained gases kept the temperature of the flame close to the unforced flame temperature.