Influence of Swirl Number on Flame Stability of an LPG Premixed Swirl Burner under Free-Flame Conditions

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Published: Sep 7, 2026
DOI: https://doi.org/10.14416/j.kmutnb.2026.09.003
Keywords:
Flame Structure Computational Fluid Dynamics Premixed Swirl Burner Swirl Number

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Sumeta Sribun
Department of Mechanical Engineering, Faculty of Engineering, Ubon Ratchathani University, Ubon Ratchathani, Thailand
Anirut Matthujak
Department of Mechanical Engineering, Faculty of Engineering, Ubon Ratchathani University, Ubon Ratchathani, Thailand
Chakrit Pongarm
Department of Mechanical Engineering, Faculty of Engineering, Ubon Ratchathani University, Ubon Ratchathani, Thailand
Thanarath Sriveerakul
Department of Mechanical Engineering, Faculty of Engineering, Ubon Ratchathani University, Ubon Ratchathani, Thailand
Chayut Nuntadusit
Department of Mechanical Engineering, Faculty of Engineering, Prince of Songkla University, Songkhla, Thailand
Sutthisak Phongthanapanich
Department of Mechanical Engineering Technology, College of Industrial Technology, King Mongkut's University of Technology North Bangkok, Bangkok, Thailand

Abstract


Swirl burners are widely used in energy and industrial applications due to their ability to enhance fuel–air mixing and stabilize flames. However, a detailed understanding of Liquefied Petroleum Gas (LPG) combustion in premixed swirl burners under free-flame conditions remains limited. Free-flame operation minimizes wall-confinement effects and allows clearer observation of intrinsic swirl-induced flame stabilization mechanisms. This study numerically investigates the combustion behavior of an LPG-fueled premixed swirl burner, focusing on the effects of equivalence ratio, Reynolds number, and swirl number on flame structure and stability. Computational Fluid Dynamics (CFD) simulations were performed by solving the governing equations of mass, momentum, energy, and species transport. Turbulence was modeled using the RNG k–ε approach, while combustion was represented by the partially premixed combustion model coupled with the discrete ordinates radiation model. The numerical model was validated against experimental data, showing good agreement with a mean error of 8.19%, indicating its reliability. Simulations were conducted for Reynolds numbers of 2,000, 4,000 and 6,000 and equivalence ratios of 0.8, 1.0 and 1.2. The results indicate that lean flames are elongated, stoichiometric flames are compact and symmetric, and rich flames exhibit thicker reaction zones. Increasing Reynolds number improves fuel–air mixing and flame stability. The condition at Reynolds number 6,000 and equivalence ratio 0.8 yields the highest swirl number, producing a strong central recirculation zone, a well-anchored flame, and a maximum temperature of 2,079 K. These findings confirm that swirl number is a key parameter in the design of premixed swirl burners to improve combustion efficiency and flame stability.


Article Details

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Vol. 36 No. 4 (2026): October-December, 2026 (In progress)
Section
Engineering Research Articles
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