To study the transient response of a diffusion flame to an unsteady flowfield, quantitative measurements of velocity, using particle-imaging velocimetry, and OH measurements, using planar laser-induced fluorescence, were made simultaneously in an oscillating counterflow diffusion flame. These non-intrusive measurements were performed to spatially and temporally resolve flowfield and flame characteristics as a function of initial steady strain rate and forcing frequency. For the forcing frequencies considered in this study, the strain rate fluctuations were found to lag the velocity fluctuations, but the phase difference decreased with increasing forcing frequency. At lower forcing frequencies, the width of the OH field responded quasi-steadily, but as the forcing frequency increased, the OH field showed transient effects. The dilatation velocity, defined as the difference between the minimum velocity in the preheat zone and the maximum velocity in the reaction zone, was used as a flame temperature indicator. The dilatation velocity revealed that the phase difference between the velocity and the temperature increased with increasing forcing frequency, confirming the existence of a diffusion limited response. The results presented here help to illuminate the interconnecting relationships between the chemistry, fluid dynamics, and reactant transport times.
|Original language||English (US)|
|Number of pages||7|
|Journal||Proceedings of the Combustion Institute|
|State||Published - 2000|
|Event||30th International Symposium on Combustion - Chicago, IL, United States|
Duration: Jul 25 2004 → Jul 30 2004
Bibliographical noteFunding Information:
This work was supported by the Army Research Office, ARO grant number DAAH04-95-10230, under the technical monitoring of Dr. David Mann.
ASJC Scopus subject areas
- Chemical Engineering(all)
- Mechanical Engineering
- Physical and Theoretical Chemistry