Abstract

It is widely known that unsteady combustion flame front generates acoustic, vortical and entropic disturbances. Previous research shows that an interaction between unsteady heat release and fluid disturbance near the flame front may result in, to some extent, intrinsic thermoacoustic instability. Meanwhile, interactions between acoustic modes of combustor cavity and unsteady heat release may generate combustor-induced thermoacoustic instabilities. Their features have been comprehensively analyzed in a uniform-radius combustor with a stationary flame front. The author gives mathematical modeling of a nonuniform-radius combustor where the flame front is moving. Three tasks are addressed in this talk. Firstly, quasi-one-dimensional mathematical modeling of disturbance generation of acoustic, entropic and vortical modes caused by unsteady heat release are given under the consideration of flow separation due to nonuniform-radius combustor. Secondly, their effects on the intrinsic and combustor-induced thermoacoustic instabilities are mathematically modeled. Finally, attentions are imposed on the interactions between these two types of thermoacoustic oscillations.