A general acoustic framework for the assessment of noise emitted by combustors: a first case study

Abstract

This study proposes an alternative and general framework for the assessment of the sound generated within a combustion chamber. The novel approach is based on Doak's Momentum Potential Theory and combines the advantage of using the single assumption of a time-stationary fluctuating flow with a clear separation of turbulent, thermal and acoustic dynamics. The latter can furthermore be quantified by defining a generalised acoustic variable, which can be identified in the fluctuations of the stagnation enthalpy. The proposed model provides a new and more comprehensive explanation for the generation of combustion noise and is used here for the first time to analyse the acoustic properties of the turbulent and non-isentropic flow in a simplified combustion chamber, represented by LES data of a non-reacting combustor simulator. The application highlights the ability of the model to identify and clearly separate the main dynamical effects characteristic for the flow. Finally, the acoustic production can be quantified using the concept of the generalised acoustic field and related to the turbulent dynamics, which seems to represent the major acoustic generation mechanism for the considered setup.