Thermoacoustic instability analysis for a laminar flat flame combustor based on nonlinear flame transfer function

Abstract

Most practical combustion systems such as industrial boilers, furnaces, land-based gas turbine engines, aero-engines and rocket motors often face the problem of high amplitude oscillations. These oscillations occur due to the development of thermoacoustic instability. The instability establishes through a feedback mechanism between the acoustic field of the combustor and the unsteady heat release rate fluctuations from the combustion source. Understanding the mechanisms responsible for the occurrence of the phenomenon of nonlinear thermoacoustic instability, so that it can be predicted beforehand, is presently of interest to researchers in this field. For the prediction of the thermoacoustic instability, it’s important to know the flame response to disturbances (most often acoustic perturbations). This can be obtained in terms of a flame transfer function (FTF). Since our interest is to predict the nonlinear features of the instability of a prototypical combustor, the task will be to determine the response of the premixed flat flame to various frequencies at different amplitude levels (i.e. nonlinear flame transfer function).