Noise generation from methane/air premixed flames

Jin, Seong-Ho (2017) Noise generation from methane/air premixed flames. In: EKC 2017, 26 - 29 July 2017, Stockholm, Sweden.

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Item Type:Conference or Workshop contribution (Presentation)
Item Status:Live Archive

Abstract

Recent demands for high combustion loads and stringent emission requirements frequently induce combustion
instabilities. Since these are undesirable sources of noise and sometimes cause disastrous destruction of
combustion equipment, the active control of combustion instabilities becomes one of the key interests in
combustion research. In order to develop effective control technologies, it is required to understand the
mechanisms and the influencing factors governing combustion instabilities. Premixed methane/air flames in the
laminar thin annular jet burner have been studied experimentally to investigate the characteristics of self-excited
noise generation. The flame in the annular jets has various flame shapes, including ring shape, near conical shape,
crown shape, and oscillating crown shape depending on equivalence ratio, mixture velocity, and air velocity. The
regimes of the existence of these flames were identified. Self-excited noise with about 70 dB was generated for
the unsteady crown shape flame. The frequency of sound pressure depended on the equivalence ratio and mixture
velocity. Sound pressure and CH* chemiluminescence were measured by using a microphone and a photomultiplier
tube. The frequency of generated noise was measured as functions of equivalence ratio and pre-mixture
velocity. The frequency doubling behaviour was also observed. The variation of sound pressure with time showed
similar behaviour as that of the CH* chemiluminescence. The calculated sound pressure from the CH*
chemiluminescence signal was in satisfactory agreement with the measured one, demonstrating the source of
sound generation is from the flame surface fluctuation near the downstream part of the crown shape flames. The
present study demonstrated that significant noise can be generated when a rich fuel/air mixture propagate into air.
The flame stability regime was influenced sensitively to the supplying air through the inner tube. Further study is
needed in the future to identify the mechanism of flame surface corrugation, the noise source location, the
interaction with the diffusion flame surrounding it, and the mechanism of frequency doubling.

Keywords:Annular Jet, Laminar Premixed Flame, Sound Pressure, Stability
Subjects:H Engineering > H141 Fluid Mechanics
H Engineering > H800 Chemical, Process and Energy Engineering
H Engineering > H311 Thermodynamics
H Engineering > H341 Acoustics
Divisions:College of Science > School of Engineering
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ID Code:31205
Deposited On:12 Mar 2018 12:23

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