Modeling Premixed Combustion-Acoustic Wave Interactions: A Review

The interactions between acoustic waves and a premixed combustion process can play an important role in the characteristicunsteadinessofcombustiondevices.Inparticular,theyareoftenresponsiblefortheoccurrenceofselfexcited, combustion-driven oscillations that are detrimental to combustor life and performance. A tutorial review is provided of current understanding of these interactions. First, the mutual interaction mechanisms between the combustion process and acoustic, vorticity, and entropy waves are described. Then, the acoustic‐ e ame interaction literatureisreviewed,primarily focusingon modeling issues.Thisliteratureisessentially organized into fourparts, depending on its treatment of 1) linear or 2) nonlinear analyses of 1) e amelets or 2) distributed reaction zones. A sizeable theoretical literature has accumulated to model the unsteady response of the laminar e ame structure, for example, the burning rate response to pressure perturbations. However, essentially no serious experimental effort has been performed to critically assess these predictions. As such, it is dife cult to determine the state of understanding in this area. On the other hand, good agreement has been achieved between well-coordinated experiments and theory describing the interactions between inherent e ame instabilities and acoustically induced e ow oscillations. Similarly, both the linear and nonlinear kinematic response of simple laminar e ames to acoustic velocity disturbances appear to be well understood, as evidenced by the agreement between surprisingly simple theory and experiment. Other than kinematic nonlinearities, additional potential mechanisms that introduce heat release‐ acoustic nonlinearities, such as e ame holding, or extinction, have been analyzed theoretically, but lack experimentalverie cation.Unsteadyreactormodelshavebeenusedextensivelytomodelcombustionprocessesinthe distributed reaction zone regimes. None of thesepredictionsappears to have been subjected to direct experimental scrutiny. Itisunlikelythatthismodeling approach willbeusefulforquantitativecombustion responsecalculations, due to their largely heuristic nature and the dife culty in rationally modeling the key interactions between reaction rate and the global characteristics of the combustion region, such as its volume. Several areas in need of work are particularly highlighted. These include e nite amplitude effects, modeling approaches for interactions outside of the e amelet regime, turbulent e ame wrinkling effects, and unsteady vortex‐ e ame interactions.