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<p>This study presents an experimental and numerical investigation of the stability of an unconfined annular premixed swirl burner operating with a premixed n-butane-air mixture at an equivalence ratio (<i>ϕ</i>) = 1, 1 bar, and 300 K. The key variable, the annular exit area, was varied while maintaining constant Reynolds number, exit velocity, and equivalence ratio. Three burner heads with exit areas of 98 mm<sup>2</sup>, 157 mm<sup>2</sup>, and 216 mm<sup>2</sup> were analyzed. Particle image velocimetry (PIV), formaldehyde planar laser induced fluorescence (CH<sub>2</sub>O PLIF) and CH* chemiluminescence were utilized to characterize the turbulent reactive flow field. A numerical simulation using the Delayed Detached Eddy Simulation (DDES) turbulence model and the Flamelet Generated Manifold (FGM) model, coupled with a reduced USC Mech, was performed to capture turbulence-chemistry interactions. Q-criterion was used to visualize the 3D flow structures. Results indicate that the burner with an annular area of 157 mm<sup>2</sup> exhibited higher entrainment and strain rates, leading to increased turbulence intensity and vortex stretching. This resulted in a more unstable flame root, frequent extinction-reignition events, and a narrower lean blowoff (LBO) limit. These findings highlight the impact of exit annular area modification on key combustion dynamics.</p>

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Effect of Burner Exit Annular Area on Swirl/Bluff Body Stabilized n-Butane/Air Premixed Flame

  • 期刊论文

  • 发表日期：

    2025年9月8日

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  • Vishnu Raj,
  • Chockalingam Prathap

摘要

This study presents an experimental and numerical investigation of the stability of an unconfined annular premixed swirl burner operating with a premixed n-butane-air mixture at an equivalence ratio (ϕ) = 1, 1 bar, and 300 K. The key variable, the annular exit area, was varied while maintaining constant Reynolds number, exit velocity, and equivalence ratio. Three burner heads with exit areas of 98 mm2, 157 mm2, and 216 mm2 were analyzed. Particle image velocimetry (PIV), formaldehyde planar laser induced fluorescence (CH2O PLIF) and CH* chemiluminescence were utilized to characterize the turbulent reactive flow field. A numerical simulation using the Delayed Detached Eddy Simulation (DDES) turbulence model and the Flamelet Generated Manifold (FGM) model, coupled with a reduced USC Mech, was performed to capture turbulence-chemistry interactions. Q-criterion was used to visualize the 3D flow structures. Results indicate that the burner with an annular area of 157 mm2 exhibited higher entrainment and strain rates, leading to increased turbulence intensity and vortex stretching. This resulted in a more unstable flame root, frequent extinction-reignition events, and a narrower lean blowoff (LBO) limit. These findings highlight the impact of exit annular area modification on key combustion dynamics.