Appearance and stability of a laminar conical premixed flame subjected to an acoustic perturbation
- Bizerte Faculty of Sciences (Tunisia)
- CNRS, Meudon (France). Lab. d`Aerothermique
The paper describes an experimental study of quad-conical premixed air/methane flames vibrating under periodic fluctuations of the upstream flow. The flow field and the flame were characterized by an LDV system and image processing. The flow velocity fluctuations were created by an acoustic perturbation with a frequency between 20 and 1000 Hz and a perturbation intensity, defined as the ratio of the rms amplitude of the flow velocity fluctuations to the mean velocity at the exit of the burner, ranging from 0 to 150%. In the perturbation plane (frequency and intensity), a chart is established that shows the configurations assumed by the flame in response to the acoustic perturbation. Three configurations were studied. The wrinkled flame configuration exhibits a flame with undulations symmetrical about the vertical axis and vibrating at the perturbation frequency. This work completes previous studies. In particular, a critical value of the frequency is found. Above this acoustic amplitudes of deformation are damped at the front, which is unaffected by the wrinkling. The subharmonic flame configuration exhibits a flame whose front oscillates with half the perturbation frequency, symmetrical or not, about the burner centerline. The asymmetrical flame is composed of two half-fronts moving in opposition. This instability on Bunsen burners has never previously been observed or predicted. The chaotic flame configuration characterizes a flame not necessarily attached to the burner that exhibits a disordered geometry that leads to aperiodicity of its motion.
- OSTI ID:
- 669936
- Journal Information:
- Combustion and Flame, Journal Name: Combustion and Flame Journal Issue: 3-4 Vol. 114; ISSN CBFMAO; ISSN 0010-2180
- Country of Publication:
- United States
- Language:
- English
Similar Records
Upstream flow dynamics of a laminar premixed conical flame submitted to acoustic modulations
Experimental and theoretical study of a premixed vibrating flame