Dynamics of premixed confined swirling flames

Considerable effort is currently being extended to examine the fundamental mechanisms of combustion instabilities and develop methods allowing predictions of these phenomena. One central aspect of this problem is the dynamical response of the flame to incoming perturbations. This question is examined in the present article, which specifically considers the response of premixed swirling flames to perturbations imposed on the upstream side of the flame in the feeding manifold. The flame response is characterized by measuring the unsteady heat release induced by imposed velocity perturbations. A flame describing function is defined by taking the ratio of the relative heat release rate fluctuation to the relative velocity fluctuation. This quantity is determined for a range of frequencies and for different levels of incoming velocity perturbations. The flame dynamics is also documented by calculating conditional phase averages of the light emission from the flame and taking the Abet transform of these average images to obtain the flame geometry at various instants during the cycle of oscillation. These data can be useful to the determination of possible regimes of instability. To cite this article: P Palies et al., C. R. Mecanique 337 (2009). (C) 2009 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.