Multiple-scale thermo-acoustic stability analysis of a coaxial jet combustor

Magri, L., See, Y.-C., Tammisola, Outi, Ihme, M. and Juniper, M.P. (2016) Multiple-scale thermo-acoustic stability analysis of a coaxial jet combustor. Proceedings of the Combustion Institute . ISSN 1540-7489

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In this paper, asymptotic multiple-scale methods are used to formulate a mathematically consistent set of thermo-acoustic equations in the low-Mach number limit for linear stability analysis. The resulting sets of nonlinear equations for hydrodynamics and acoustics are two-way coupled. The coupling strength depends on which multiple scales are used. The double-time-double-space (2T-2S), double-time-single-space (2T-1S) and single-time-double-space (1T-2S) limits are revisited, derived and linearized. It is shown that only the 1T-2S limit produces a two-way coupled linearized system. Therefore this limit is adopted and implemented in a finite-element solver. The methodology is applied to a coaxial jet combustor. By using an adjoint method and introducing the intrinsic sensitivity, (i) the interaction between the acoustic and hydrodynamic subsystems is calculated and (ii) the role of the global acceleration term, which is the coupling term from the acoustics to the hydrodynamics, is analysed. For the confined coaxial jet diffusion flame studied here, (i) the growth rate of the thermo-acoustic oscillations is found to be more sensitive to small changes in the hydrodynamic field around the flame and (ii) increasing the global acceleration term is found to be stabilizing in agreement with the Rayleigh Criterion.

Item Type: Article
Keywords: Thermo-acoustics; Stability; Adjoint methods; Multiple-scale analysis; Sensitivity analysis
Schools/Departments: University of Nottingham, UK > Faculty of Engineering
Identification Number:
Depositing User: Tammisola, Outi-leena
Date Deposited: 03 Jun 2016 08:42
Last Modified: 04 May 2020 17:56

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