Dynamics of a Transversely Excited Swirling, Lifted Flame: Part II — Flame Response Modeling and Comparison With Experiments

Abstract

This paper is the second of a two-part series, describing work to model the response of a swirling, lifted flame to transverse flow excitation. The problem is motivated by combustion instabilities associated with transverse acoustic modes of combustors. This paper develops a formulation that relates the unsteady flame response characteristics to both the spatially filtered disturbance field and mean flow field characteristics. The flow and flame features from Part I [1] of this paper are used as model inputs in order to compare the global heat release fluctuations with those measured from the experiment, showing quite good agreement. As such, this paper shows that, given a nearly axisymmetric configuration and sufficient flow field information, the dynamic flame response can be reasonably predicted. However, we also show that the strongly helical disturbances present in the flow have minimal impact on the global response of axisymmetric flames, as the local heat release fluctuations that they induce cancel each other azimuthally. An important needed next step is a similar exercise on a more strongly non-axisymmetric configuration (such as a multi-nozzle configuration), where the helical nature of the flow disturbances manifest themself in the global unsteady heat release more significantly.