Application of Boundary Element Methods in Modeling Multidimensional Flame-Acoustic Interactions

1
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
2
Flame - Acoustic Interactions

• Combustion Noise
• Pulse Combustors
• Combustion Instabilities

3
Flame - Acoustic Interactions
3
1
Premixed FuelAir
7
5
3
5
1
7
P
time
Visualization taken with Mr. Hector Torres
1
4
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

5
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, M0.04
• 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

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

12
Future Work

• Flame Dynamics
• Mean Flow Effects
• May be significant in determining energy flux
• Time Domain Formulation
• Linear Acoustics / Nonlinear Flame Dynamics