Thermoacoustic characterization of the PRECCINSTA combustor using Doak's Momentum Potential Theory

Abstract

The dynamics of a confined, partially premixed flame is analyzed in this study using a novel approach based on an extension to multi-components and reactive flows of Doak's Momentum Potential Theory. The main advantage of this novel approach lies in the unambiguous identification of turbulent, acoustic, thermal, and mixture fluctuations. Starting with an Helmholtz decomposition of the momentum fluctuations vector, a clear separation in turbulent, acoustic, thermal, and mixture components can be achieved for all model quantities described by the theory. These quantities can be used to characterize the thermoacoustic behavior of the combustor system.

The Momentum Potential Theory is applied to LES data of the flow inside the PRECCINSTA combustor in stable operating conditions. The most of the contents presented in this paper are based on a more comprehensive study presented by the authors at the ASME Turbo Expo 2023. The following main results are demonstrated here: (i) turbulent, acoustic, thermal, and mixture dynamics can be effectively separated from each others; (ii) in particular, the acoustics of the combustor can be better highlighted using the concept of the Generalized Acoustic Field, defined as the acoustic component of the Total Fluctuating Enthalpy; (iii) turbulent, acoustic, and thermal Total Fluctuating Enthalpy components can be used to characterize the thermoacoustic behavior of the combustor.

All of these findings intend to demonstrate the potential of the proposed approach as a more general and consistent framework for the thermoacoustic characterization of combustors.