Application of Boundary Element Methods in Modeling Multidimensional Flame- Acoustic Interactions Tim Lieuwen and Ben T. Zinn Depts. Of Mechanical and Aerospace Engineering Georgia Institute of Technology Atlanta, GA th World Conference on the Boundary Element Method Orlando, Fl., Aug , 1998

Flame - Acoustic Interactions n Combustion Noise n Pulse Combustors n Combustion Instabilities

Flame - Acoustic Interactions Visualization taken with Mr. Hector Torres Premixed Fuel+Air P’ time

Goal of Study n Develop relatively simple tool capable of semi-quantitative analysis of flame acoustic interactions n Develop insight to suggest simplifications for analytical approaches to problem

Approach n Noting that in typical systems –Discrepancy between acoustic and flame length scales Acoustic Wavelength ~ 1 m Flame Thickness ~ mm –Mach Numbers typically low e.g. gas turbine combustors, M~0.04 –Nearly Isothermal flow except for rapid heating near flame

Approach

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 n Acoustic velocity field near flame two dimensional n Acoustic pressure reasonably one dimensional n BEM methods useful tool for modeling flame acoustic interactions

Future Work n Flame Dynamics n Mean Flow Effects –May be significant in determining energy flux n Time Domain Formulation –Linear Acoustics / Nonlinear Flame Dynamics