NUMERICAL ANALYSIS OF FLAME CHARACTERISTICS AND STABILITY FOR CONICAL NOZZLE BURNER

Abstract

The stability and the mean structure of methane partially premixed conical burner flames was investigated numerically using ANSYS Fluent. The study presents and discusses the stability curves of the partially premixed flame and maps the mean flame structure based on contours of mass fraction of O_2, CO and temperature. From the data obtained, it can be concluded that both premixed and non-premixed flames are less stable than the partially premixed flames. An optimum level of partially premixing was found and the flames beyond this threshold were found to be less stable. This optimum level was found, when the ratio of the mixing length to the nozzle diameter is equal to 5. At this specific degree of partially premixing, the flame exhibited triple interaction reaction zones. It was found that with an increase of the angle of the cone of the burner, the air entrainment increases which, in turns breaks the stabilization core and hence cause a reduction in the flame stability limit. The main role of the cone is to provide a protection from the surrounding environment at early phase of the reaction near the jet exit where turbulence with high intensity was observed.

Keywords

• Partially Premixed Flames,Flame Stability,Conical Burner

References

1. [1] Mansour, M. (2003). Stability characteristics of lifted turbulent partially premixed jet Flames, Combustion and Flame, 133, 236-274.
2. [2] INFORSE-EUROPE (2010), Regulation of air pollution from small biomass combustion, 17-19, [online] http://www.inforse.org/europe/pdfs/biomass-pollution-regulation-proposal.pdf
3. [3] Mansour, M. (2005). Mixing and nozzle geometry effects on flame structure and stability, Portugal, 6-10 October 2005. Lisbon, 23-34. http://scholar.cu.edu.eg/sites/default/files/ahmedabdelhafez/files/mixing_and_nozzle_geometry_effects_on_flame_structure_and_stability.pdf
4. [4] Miao, J. Leung, W. and Cheung, K. (2013). Flame Stability and Structure of Liquefied Petroleum Gas-Fired Inverse Diffusion Flame with Hydrogen Enrichment, International Journal of Mechanical, Aerospace, Industrial, Mechatronic and Manufacturing Engineering, 1, 121-129.
5. [5] Schefer, W. Wicksal, D.M. and Agrawal A.K. (2002) Combustion of hydrogen-enriched methane in a lean premixed swirl burner, Proceedings of the combustion institute, 29,1, 843-851
6. [6] Shoshin, Y. (2011). Stabilization of laminar inverted ultra -lean hydrogen-methane-air flames, Combustion Technology, 602-613, [online]. http://www.combustion-institute.it/proceedings/MCS-7/papers/PEC/PEC-11.pdf
7. [7] Alhashimi, M. (2012). Flashback and Blowoff Characteristics of Gas Turbine Swirl Combustor, 36-37. http://orca.cf.ac.uk/24193/1/2012%20Abdulsada%20M%20PhD.pdf
8. [8] Chaparro, A. and Cetegen, B. (2006). Blowoff characteristics of bluff-body stabilized conical premixed flames under upstream velocity modulation, Combustion and Flame, 144, 1-2, 318–335.

9. [9] Nair, S. and Muruganandam M. (2004). Lean Blowout Detection in a Single Nozzle Swirl Cup Combustor, 42nd AIAA Aerospace Sciences Meeting, 5, 138.
10. [10] Lieuwen, T. (2006), Chapter 3.1.1: Static and Dynamic Combustion Stablity, In: Gas Turbine Handbook. USA, Department of energy, office of fossil energy, 124-145.
11. [11] Noble, D. and Shareef, A. (2006) Syngas Mixture Composition Effects Upon Flashback and Blowout, ASME Conference Proceedings, 13, 357-368
12. [12] Sarli, V. and Bendetto, A. (2007). Laminar burning velocity of hydrogen–methane/air premixed flames,” International Journal of Hydrogen Energy, 32, 5, 637–646.
13. [13] Mansour, M. (2012). The stabilization mechanism of highly stabilised partially premixed flames in a concentric flow conical nozzle burner, Experimental thermal and fluid science, 43, 55-62.
14. [14] El-Mahallawy, F. (2005). Mixing and nozzle geometry effects on flame structure and stability, Combustion Science and Technology, 2, 60-12.
15. [15] Baudoin, E. (2011). Effect of partial premixing on stabilization and local extinction of turbulent methane/air flames. Chia Laguna, 4, 20-35.
16. [16] Elbaz, M.A. (2013). An Experimental Study of the Effect of Partial Premixing Level on the Interaction between the Flame Kernel and Flow Field, Computer Science Journals, 1, 121-145.
17. [17] El-Mahallawy, F. (2007). Mixing and nozzle geometry effects on flame structure and stability, Combustion Science and Technology, 2, 249-263.
18. [18] Peters, N. (2000). Turbulent Combustion, vol.II. 1st ed., Cambridge, Cambridge University Press. United Kingdom
19. [19]Mansour, M. (2004) The flow field structure at the base of lifted turbulent partially premixed jet flames, Experimental Thermal and Fluid Science, 7, 771-779.
20. [20] Joedicke, A. (2005) The stabilization mechanism and structure of turbulent, Proceedings of the Combustion Institute, 1, 901-909.
21. [21] Dutt, A. (2015). Effect of Mesh Size on Finite Element Analysis of Beam, International Journal of Mechanical Engineering (SSRG-IJME), 12, 8-9.
22. [22] Charles, M. (2006). Comparison of Pressure-Based and Density-Based Methods for low Mach number CFD computations, 3, 12-15.
23. [23] Pupo, R. (2011). Adiabatic Flame Temperature for Combustion of Methane, Journal of Mathematical Modelling, 2, 3-7.
24. [24] Khalil, R. (2010) Effect of Pressure and Inlet Velocity on the Adiabatic Flame Temperature of a Methane-Air Flame, Jordan Journal of Mechanical and Industrial Engineering, 4, 21-28.
25. [25] Jonathon, Z. (2009). Modelling Fluid Flow Using Fluent,” 35-38.
26. [26] Mathur, M.J. (2007). A pressure-based method for unstructured meshes, Numerical Heat Transfer, Part B: Fundamentals, 20-21. [online] http://www.tandfonline.com/doi/pdf/10.1080/10407799708915105?needAccess=true
27. [27] Salim, M. (2011). Comparison of RANS, URANS and LES in the Comparison of RANS, URANS and LES in the Prediction of Airflow and Pollutant Dispersion,” the World Congress on Engineering and Computer Science, 40-43.
28. [28] Baudoin, E. (2012). Effect of partial premixing on stabilization and local extinction of turbulent methane/air flames, Flow Turbulence Combust, 9, 269-284.
29. [29] Manera, J. (2008). Kelvin-Helmholtz instabilities occurring at a nacelle exhaust,” Aeroacoustics Conference, 14, 235-264.
30. [30] Almawali J. (2016, November). Numerical Analysis of Flame Characteristics and Stability for the Conical Nozzle Burner, Master thesis, Sheffield Hallam University.