1. 13th Int Symp on Applications of Laser Techniques to Fluid Mechanics Lisbon, Portugal, 26-29 June, 2006 Project supported by MinKnock Project nº ENK6-CT-2003-00643 Ilídio S. Guerreiro Edgar C. Fernandes Laboratory of Thermofluids, Combustion and Environmental Systems Instituto Superior Técnico -Technical University of Lisbon, Portugal http://in3.dem.ist.utl.pt Time-resolved description of a flame front propagation toward an inclined wall - The effect of local stretch on flame speed

2. 13th Int Symp on Applications of Laser Techniques to Fluid Mechanics Lisbon, Portugal, 26-29 June, 2006 Background overview Objectives Experimental Setup Global setup Laser and camera characteristics Combustion chamber condition Intermediary results Data treatment Sample visualizations Final results Flame speed/stretch correlations Relevant effects of stretch on flame speed Effect of flame/wall interaction Conclusions Presentation Outline

3. 13th Int Symp on Applications of Laser Techniques to Fluid Mechanics Lisbon, Portugal, 26-29 June, 2006 Recent works Foucher, et al., 2002 Wall Methane

4. 13th Int Symp on Applications of Laser Techniques to Fluid Mechanics Lisbon, Portugal, 26-29 June, 2006 Recent works wall flame U wall Non-Wrinkled Symmetric flame Wrinkled Symmetric flame Wrinkled Non-Symmetric flame Rolo, N., 2005 Propane

5. 13th Int Symp on Applications of Laser Techniques to Fluid Mechanics Lisbon, Portugal, 26-29 June, 2006 Flame/wall interaction wall n U W SuSu burned unburned Flame Front Objectives: - Obtain stretch/flame speed (S u ) sorrelations -Flow effect on flame/wall interaction Markstein Length

6. 13th Int Symp on Applications of Laser Techniques to Fluid Mechanics Lisbon, Portugal, 26-29 June, 2006 Experimental Setup

7. 13th Int Symp on Applications of Laser Techniques to Fluid Mechanics Lisbon, Portugal, 26-29 June, 2006 Technical characteristics Spectra Physics Ar-Ion Laser-5W Seeding: DANTEC Safex Inside Nebelfluid Kodak CCD High speed camera - 240x256 Typical data: 1000fps ; 1/1000s Spatial resolution for flame front displacement: 0.5mm Spatial resolution for velocity vectors: 29vectors/20mm  1.5vector/mm Propane/air mixtures: Eq. Ratios 0.86 and 1.52

8. 13th Int Symp on Applications of Laser Techniques to Fluid Mechanics Lisbon, Portugal, 26-29 June, 2006 Data processing 1 m/s Flow PIV Processing Flame front detection - Thresh detection; - Noise reduction Original image (PIV) W

9. 13th Int Symp on Applications of Laser Techniques to Fluid Mechanics Lisbon, Portugal, 26-29 June, 2006 Data processing k c (curvature) Flame Front r k s (flow) Flame Front U Total stretch

10. 13th Int Symp on Applications of Laser Techniques to Fluid Mechanics Lisbon, Portugal, 26-29 June, 2006 Inclined-wall / Non-Symmetric Flame k and S u along a flame front

11. 13th Int Symp on Applications of Laser Techniques to Fluid Mechanics Lisbon, Portugal, 26-29 June, 2006 Plane-wall / Flame n U W SuSu Lean (  =0.86 ) L exp( 0.86 ) = 0.059 mm L theo( 0.7 ) = 0.340 mm Rich (  =1.52 ) L exp( 1.52) = 0.031 mm L theo( 1.7 ) = 0.014 mm k=[-3000, 0] k=[-100, 0] Present results Law & Sung, 2000

12. 13th Int Symp on Applications of Laser Techniques to Fluid Mechanics Lisbon, Portugal, 26-29 June, 2006 Flow variations in wall interaction

13. 13th Int Symp on Applications of Laser Techniques to Fluid Mechanics Lisbon, Portugal, 26-29 June, 2006 Relevance of flow stretch Lean (  =0.86 ) Rich (  =1.52 ) Total stretch

14. 13th Int Symp on Applications of Laser Techniques to Fluid Mechanics Lisbon, Portugal, 26-29 June, 2006 Flow stretch distributions Lean (  =0.86 ) Rich (  =1.52 ) PDF

15. 13th Int Symp on Applications of Laser Techniques to Fluid Mechanics Lisbon, Portugal, 26-29 June, 2006 Conclusions Time-resolved PIV was used to characterize flame-wall interaction The flow between flame and wall is not stagnant, and induces aerodynamic effects Linearity between S u and k for very high stretch values –k c >>>>k s –k s increases when flame is close to the wall