'American Institute of Aeronautics and Astronautics (AIAA)'
Abstract
The determination of an internal feedback mechanism which leads to combustion instability inside a small scale
laboratory combustor is presented in this paper. During combustion instability, the experimental findings show that a large vortical structure is formed at an acoustic resonant mode of the system. The subsequent unsteady burning, within the vortex as it is convected downstream,
feeds energy into the acoustic field and sustains the large resonant oscillations. These vortices are formed when the
acoustic velocity fluctuation at the flameholder is a large fraction of the mean flow velocity. The propagation of
these vortices is not a strong function of the mean flow speed and appears to be dependent upon the frequency of the
instability. Continued existence of large vortical structures which characterize unstable operation depends upon the fuel-air ratio, system acoustics, and fuel type