Flame dynamics of equivalence ratio oscillations in a laminar stagnating lean methane/air premixed flame

Hisashi Tomita, Mohd Rosdzimin Abdul Rahman, Sotaro Miyamae, Takeshi Yokomori, Toshihisa Ueda

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

This study investigates the effect of fuel concentration oscillation on laminar stagnating premixed flames by both experiment and numerical simulation. The numerical analysis is conducted using ANSYS Fluent 14.5. The equivalence ratio oscillation in the experiments is formed by a novel oscillator with two cylinder piston units that can produce alternating ejections of leaner and richer pre-mixtures. Velocity fluctuation is well suppressed by installing screens on the burner exit. The fuel concentration oscillation between the stagnation plate and the burner exit is visualized and analyzed by acetone ultraviolet light-induced fluorescence in the isothermal condition. The oscillator frequency is varied in the range 2-20 Hz, and the oscillation wavelength is much longer than the flame thickness. The flame oscillates with the fuel concentration, and in the experiment, the amplitude of the flame oscillation attenuates as the frequency of fuel concentration oscillation increases above 5 Hz, which corresponds to a Strouhal number of unity. This indicates that the Strouhal number distinguishes quasi-steadiness for St < 1 and unsteadiness for St > 1. The flame oscillation pattern is a closed loop, which might be attributable to variation of the back support effect on the flame. The numerical results show a similar trend for the flame response to oscillations in fuel concentration. This study finds the flame motion is significantly affected by fuel concentration oscillations, even at low frequencies; in other words, the oscillation wavelength is much longer than the flame thickness, as a result of the back support effect.

Original languageEnglish
Pages (from-to)989-997
Number of pages9
JournalProceedings of the Combustion Institute
Volume35
Issue number1
DOIs
Publication statusPublished - 2015

Fingerprint

premixed flames
Methane
equivalence
flames
methane
oscillations
air
Air
Strouhal number
Fuel burners
burners
Wavelength
Experiments
Acetone
Pistons
oscillators
Numerical analysis
Fluorescence
pistons
ejection

Keywords

  • Acetone ultraviolet light-induced fluorescence
  • Equivalence ratio oscillation
  • Flame dynamics
  • Laminar premixed flame
  • Stagnating flame

ASJC Scopus subject areas

  • Mechanical Engineering
  • Chemical Engineering(all)
  • Physical and Theoretical Chemistry

Cite this

Flame dynamics of equivalence ratio oscillations in a laminar stagnating lean methane/air premixed flame. / Tomita, Hisashi; Abdul Rahman, Mohd Rosdzimin; Miyamae, Sotaro; Yokomori, Takeshi; Ueda, Toshihisa.

In: Proceedings of the Combustion Institute, Vol. 35, No. 1, 2015, p. 989-997.

Research output: Contribution to journalArticle

Tomita, Hisashi ; Abdul Rahman, Mohd Rosdzimin ; Miyamae, Sotaro ; Yokomori, Takeshi ; Ueda, Toshihisa. / Flame dynamics of equivalence ratio oscillations in a laminar stagnating lean methane/air premixed flame. In: Proceedings of the Combustion Institute. 2015 ; Vol. 35, No. 1. pp. 989-997.
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