Identification of a model for thermoacoustic instabilities in a Rijke tube

Abstract

In a large class of processes characterized by the presence of a heating source placed in a finite volume, the interaction between the flow field and the heat release mechanism can lead to unsteady fluctuations, known as thermoacoustic instabilities. This paper deals with the development of a model of such phenomenon, here observed in a laboratory scale facility. The test rig is constituted by a tube where air flows and an electric gauze provides heat, generally known as Rijke tube. The model is built via a thorough description of both the gasdynamics and the heat release process, which is concisely outlined. The validation is carried out on the basis of real experimental data, and it is founded on a mixed linear/nonlinear identification method with the support of the describing function theory for the detection of limit cycle behavior.