1. 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 30318 20th World Conference on the Boundary Element Method Orlando, Fl., Aug. 19-22, 1998

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

3. Flame - Acoustic Interactions Visualization taken with Mr. Hector Torres 7 3 1 5 7 5 3 1 1 Premixed Fuel+Air P’ time

4. 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

5. Approach n 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

6. Approach

7. Results No flame response to perturbations

8. Results With Flame Response to Perturbations

9. Results Ratio of transverse and axial velocity component over the flame surface

10. Results Comparison of magnitude of the acoustic pressure along the combustor wall and flame surface

11. 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

12. 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