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Flame–sound interaction in tubes with nonslip walls
Umeå University, Faculty of Science and Technology, Physics.
Umeå University, Faculty of Science and Technology, Physics.
Umeå University, Faculty of Science and Technology, Physics.
2007 (English)In: Combustion and Flame, ISSN 0010-2180, Vol. 149, no 4, 418-434 p.Article in journal (Refereed) Published
Abstract [en]

Flame interaction with sound is studied for a premixed flame propagating to the closed end of a tube with nonslip walls. The flow geometry is similar to that in the classical Searby experiments on flame–acoustic interaction [Combust. Sci. Technol. 81 (1992) 221]. The problem is solved by direct numerical simulations of the combustion equations. The flame–sound interaction strongly influences oscillations of the flame front. Particularly, sound noticeably increases the oscillation amplitude in comparison with that in an open tube with nonreflecting boundary conditions at the ends studied previously. Oscillations become especially strong in the second part of the tube, where flame pulsations are in resonance with the acoustic wave. Parameters of the flame oscillations are investigated for different values of the tube width and length. It is demonstrated that the oscillations are stronger in wider tubes, though the investigated tube width is limited by the computational facilities. In sufficiently wide tubes, violent folding of a flame front is observed because of the flame–acoustic resonance. By increasing the Lewis number, one also increases the oscillation amplitude.

Place, publisher, year, edition, pages
2007. Vol. 149, no 4, 418-434 p.
Keyword [en]
Premixed burning, Flame–sound interactions, Direct numerical simulations
URN: urn:nbn:se:umu:diva-2484DOI: 10.1016/j.combustflame.2007.02.003OAI: diva2:140627
Available from: 2007-08-28 Created: 2007-08-28Bibliographically approved
In thesis
1. Numerical study of flame dynamics
Open this publication in new window or tab >>Numerical study of flame dynamics
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Modern industrial society is based on combustion with ever increasing standards on the efficiency of burning. One of the main combustion characteristics is the burning rate, which is influenced by intrinsic flame instabilities, external turbulence and flame interaction with walls of combustor and sound waves.

In the present work we started with the problem how to include combustion along the vortex axis into the general theory of turbulent burning. We demonstrated that the most representative geometry for such problem is a hypothetic “tube” with rotating gaseous mixture. We obtained that burning in a vortex is similar to the bubble motion in an effective acceleration field created by the centrifugal force. If the intensity of the vortex is rather high then the flame speed is determined mostly by the velocity of the bubble. The results obtained complement the renormalization theory of turbulent burning. Using the results on flame propagation along a vortex we calculated the turbulent flame velocity, compared it to the experiments and found rather good agreement.

All experiments on turbulent combustion in tubes inevitably involve flame interaction with walls. In the present thesis flame propagation in the geometry of a tube with nonslip walls has been widely studied numerically and analytically. We obtained that in the case of an open tube flame interaction with nonslip walls leads to the oscillating regime of burning. The oscillations are accompanied by variations of the curved flame shape and the velocity of flame propagation. If flame propagates from the closed tube end, then the flame front accelerates with no limit until the detonation is triggered. The above results make a good advance in solving one of the most difficult problems of combustion theory, the problem of deflagration to detonation transition. We developed the analytical theory of accelerating flames and found good agreement with results of direct numerical simulations. Also we performed analytical and numerical studies of another mechanism of flame acceleration caused by initial conditions. The flame ignited at the axis of a tube acquires a “finger” shape and accelerates. Still, such acceleration takes place for a rather short time until the flame reaches the tube wall. In the case of flame propagating from the open tube end to the closed one the flame front oscillates and therefore generates acoustic waves. The acoustic waves reflected from the closed end distort the flame surface. When the frequency of acoustic mode between the flame front and the tube end comes in resonance with intrinsic flame oscillations the burning rate increases considerably and the flame front becomes violently corrugated.

Place, publisher, year, edition, pages
Umeå: Fysik, 2007. 73 p.
combustion, Direct Numerical Simulation (DNS), turbulence, flame-vortex interaction, flame acceleration, flame-acoustic interaction
National Category
Physical Sciences
urn:nbn:se:umu:diva-1313 (URN)978-91-7264-351-2 (ISBN)
Public defence
2007-09-21, KB3A9, KBC-huset, SE-901 87, Umeå University, Sweden, Umeå, 13:00 (English)
Available from: 2007-08-28 Created: 2007-08-28 Last updated: 2009-08-19Bibliographically approved

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