Thermoacoustic characterization of a swirl premixed flame using Doak's Momentum Potential Theory

Abstract

This study proposes a novel approach, based on Doak's Momentum Potential Theory, for the characterization of the thermoacoustic behavior of turbulent premixed flames. The novel approach has the following two advantages: firstly, an unambiguously separation of acoustic, thermal and turbulent dynamics is achieved by means of a Helmholtz decomposition of the momentum fluctuations density; secondly, the development as well as the interaction between the different dynamics are related to the fluxes of turbulent, acoustic, and thermal mean energies, which can be identified in the fluctuating stagnation enthalpy. The Momentum Potential Theory is applied here for the first time to describe the thermoacoustic behaviour of a confined turbulent flame, represented by large-eddy simulation data of a premixed CH4/Air model combustor. Interaction and energy exchange mechanisms between the fluctuations are analyzed in order to show the potential of the theory as a general framework for the characterization of thermoacoustic problems.