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Application of Boundary Element Methods in Modeling Multidimensional Flame-Acoustic Interactions.
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Application of Boundary Element Methods in Modeling Multidimensional Flame-Acoustic Interactions Tim Lieuwen and Ben T. ZinnDepts. Of Mechanical and Aerospace EngineeringGeorgia Institute of TechnologyAtlanta, GA 3031820th World Conference on the Boundary Element MethodOrlando, Fl., Aug. 19-22, 1998
Flame - Acoustic Interactions • Combustion Noise • Pulse Combustors • Combustion Instabilities
Flame - Acoustic Interactions 3 1 Premixed Fuel+Air 7 5 3 5 1 P’ 7 time Visualization taken with Mr. Hector Torres 1
Goal of Study • Develop relatively simple tool capable of semi-quantitative analysis of flame acoustic interactions • Develop insight to suggest simplifications for analytical approaches to problem
Approach • Noting that in typical systems • Discrepancy between acoustic and flame length scales • Acoustic Wavelength ~ 1 m • Flame Thickness ~ 0.1- 1 mm • Mach Numbers typically low • e.g. gas turbine combustors, M~0.04 • Nearly Isothermal flow except for rapid heating near flame
Results No flame response to perturbations
Results With Flame Response to Perturbations
Results Ratio of transverse and axial velocity component over the flame surface
Results Comparison of magnitude of the acoustic pressure along the combustor wall and flame surface
Conclusions • Acoustic velocity field near flame two dimensional • Acoustic pressure reasonably one dimensional • BEM methods useful tool for modeling flame acoustic interactions
Future Work • Flame Dynamics • Mean Flow Effects • May be significant in determining energy flux • Time Domain Formulation • Linear Acoustics / Nonlinear Flame Dynamics