Spectral Characterization of Flame Instability Induced by Acoustically Excited Fuel in Diffusion Flames with Different Burner Diameters

Mohammed Al-Bakoush; Hanan Mohamed Edawi

doi:10.66411/jer.v41i1.144

Authors

Mohammed Al-Bakoush Mechanical and Industrial Engineering Department-University of Tripoli -Libya Author
Hanan Mohamed Edawi Mechanical and Industrial Engineering Department-University of Tripoli -Libya Author

DOI:

https://doi.org/10.66411/jer.v41i1.144

Keywords:

Thermoacoustic instability, chemiluminescence, spectral analysis, diffusion flame

Abstract

This study investigated the impact of acoustically excited fuel on the instability of diffusion flames in continuous combustion systems, focusing on burner geometry. Its design significantly influenced combustion instability, particularly thermo-acoustic instabilities. A controlled acoustic excitation system was employed to introduce fuel perturbations at specific, frequencies and acoustic intensities. The experiment at constant fuel flow rate was conducted while varying burner diameters (0.5 mm, 0.75 mm, and 1.0 mm) to assess their influence on flame dynamics. Results indicated that flame instability was consistent across all configurations, with the highest instability observed at 90 Hz, flame strongly stable at 150 Hz, and intermediate behavior at 175 Hz. Smaller burner diameters exhibited greater instability, as evidenced by reduced signal correlation and increased spectral complexity. Stable flames exhibited a single dominant frequency, whereas unstable flames showed multiple distinct frequency peaks. These findings highlight the critical role of acoustic excitation and burner geometry in governing flame stability, offering insights relevant to the design and control of combustion systems.

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