Velocity and Flame Wrinkling Characteristics of a Transversely Forced, Bluff-Body Stabilized Flame, Part I: Experiments and Data Analysis

Abstract

This article describes measurements of the response of bluff-body stabilized flames subjected to transverse acoustic waves. It is the first of a two-article series. The objective of this work was to extend prior studies of this nature to much higher Reynolds numbers and more severe environments that more closely mimic conditions encountered in applications. To this end, experiments were performed at flow velocities of 50 m/s and 100 m/s with inlet air temperatures ranging from 475–750 K. Two different modes of acoustic excitation were applied, corresponding to velocity and pressure nodes/antinodes along the combustor centerline. High-speed imaging and phase-locked particle image velocimetry (PIV) were used to characterize the spatio-temporal flame front and velocity field response. The data show that the disturbance field and the flame front response amplitude exhibit a nonmonotonic spatial distribution with interference patterns. The phase of the flame front response at the forcing frequency varies nearly linearly with downstream distance, and corresponds to a phase speed that is slightly less than the mean flow velocity. Significantly, these results show that the key features of the flame's magnitude and phase characteristics are quite similar to those observed in much lower flow velocities.

Keywords:

• Bluff-body stabilized
• Premixed flame response
• Transverse excitation

ACKNOWLEDGMENTS

The authors gratefully acknowledge the U.S. Air Force (Contract FA-8650-07-M-2784, Contract monitor Barry Kiel) and the U.S. Department of Energy (Contract DEFG26-07NT43069 and DE-NT5054, Contract Monitors: Mark Freeman and Richard Wenglarz) for their financial support of this research.