Computational Modeling of Coupled Acoustic and Combustion Phenomena Inherent to Gas Turbine Engines

ABSTRACT: Combustion instabilities can be a serious problem in combustion devices including augmentors/afterburners. Their prediction is very challenging due to nonlinear interactions between various complex phenomena, including acoustics, combustion, and turbulence. The goal of this project is to provide a framework that will allow the development of new models of combustion instabilities benefiting from an open, large, and multi-disciplinary community of researchers, a framework needed to tackle difficult multi-physics problems such as combustion instabilities. To accomplish this goal, OpenFOAM will be used to develop two models for combustion instabilities: a CFD model and a nonlinear acoustics model. A CFD model is needed as it has the potential to be truly predictive; however, they are computationally complex and expensive. A nonlinear acoustic model is more computationally tractable in the short term and provides a viable validation tool for the CFD model. Linear models are not considered because they have been amply studied and cannot provide information about limit cycles. For Phase I, this work will use simple combustion-instabilities problems to evaluate current CFD models in OpenFOAM, plan potential modifications to these models, and develop a nonlinear acoustic model in OpenFOAM. A plan to conduct new experiments for Phase II will be devised. BENEFIT: Combustion instabilities are thermo-acoustic phenomena characterized by pressure oscillations with well-defined frequencies and with amplitudes that can be large enough to cause damage to a combustor. Tools that can predict potential combustion instabilities in early design stages will considerably reduce costs associated with the design and testing of gas turbine engines. Hence, the tools developed here will be of considerable interest to the gas turbine industry. From a broader perspective, again due to the multi-physics nature of combustion instabilities, the expertise developed by CSE in this project about these instabilities and OpenFOAM can be easily extended to other projects of interest such as prediction of blow-off in augmentors, study of basic aspects of flame extinction and reignition, prediction of pollutant formation from flames, and design of industrial burners with CFD. This expertise can be sold to a wide variety of industries, something which CSE has been doing for more than ten years. The market size for the technology developed in this project is over $10M due to the many potential applications and the pervasiveness of these issues.