Dynamic Response of Premixed Flames

Perforated-plate stabilized premixed flames are used extensively in industrial and compact household burners. In these systems, the coupling between the acoustics and the unsteady heat release rate often leads to self-excited oscillations, which in extreme cases may result in fatal structural damage. The dynamic response of the flame to the velocity perturbations in the system determines the nature of the combustion instability, and has thus received significant attention in the recent years. This response is typically characterized by the flame transfer function (FTF). From experimental investigtations by many researchers, it has been well established that at certain low frequencies, the heat release amplitude (non-dimensionalized by the mean) is greater than the non-dimensional amplitude of the imposed velocity oscillations. We are investigating the physical mechanisms behind such resonance like behavior of the system.

In our recent work, we have shown that the dynamic response of a premixed flame stabilized on a heat-conducting perforated plate depends critically on their coupled thermal interaction. We are investigating this problem using detailed numerical simulations with thermal coupling between the heat-conducting solid burner and the fluid domain. We are also developing simplified analytical models to predict the dynamic response of the flames.