Weakly Turbulent, Wrinkled Flames in Premixed Gases

Searby, Geoffrey; Clavin, Paul

doi:10.1080/00102208608959799

Cited by 82 publications

(92 citation statements)

References 10 publications

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“…In agreement with the previous theory, 29,30,60,61 experiments 24,62 and simulations, 34,63 the role of small vortices decreases strongly with decreasing vortex size. Even in the case of strong vortex intensity, burning rate approaches the laminar value for small vortices.…”

Section: -19supporting

confidence: 79%

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Flow-flame interaction in a closed chamber

et al. 2008

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Numerous studies of flame interaction with a single vortex and recent simulations of burning in vortex arrays in open tubes demonstrated the same tendency for the turbulent burning rate ϰU rms 2/3 , where U rms is the root-mean-square velocity and is the vortex size. Here, it is demonstrated that this tendency is not universal for turbulent burning. Flame interaction with vortex arrays is investigated for the geometry of a closed burning chamber by using direct numerical simulations of the complete set of gas-dynamic combustion equations. Various initial conditions in the chamber are considered, including gas at rest and several systems of vortices of different intensities and sizes. It is found that the burning rate in a closed chamber ͑inverse burning time͒ depends strongly on the vortex intensity; at sufficiently high intensities it increases with U rms approximately linearly in agreement with the above tendency. On the contrary, dependence of the burning rate on the vortex size is nonmonotonic and qualitatively different from the law 2/3 . It is shown that there is an optimal vortex size in a closed chamber, which provides the fastest total burning rate. In the present work, the optimal size is six times smaller than the chamber height.

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Section: -19supporting

confidence: 79%

“…34 correlated strongly with the cutoff wavelength c of the DL instability. This correlation is not a coincidence; it follows from the theory, 60 see also, Refs. 29, 30, and 61 and it was supported by experiments.…”

Section: How Does the Burning Rate Depend On The Vortex Size?mentioning

confidence: 95%

Flow-flame interaction in a closed chamber

et al. 2008

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“…This is an important effect, which has been addressed theoretically in the literature. We shall demonstrate it by calculating the flame response to smallamplitude enthalpy fluctuations in the same spirit as Searby & Clavin (1986) and Aldredge & Williams (1991) did for vortical disturbances. The flame is assumed to be intrinsically stable.…”

Section: Hydrodynamic Regionmentioning

confidence: 99%

Large-activation-energy theory for premixed combustion under the influence of enthalpy fluctuations

Moin

2010

J. Fluid Mech.

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This paper presents a mathematical theory for premixed combustion under the influence of enthalpy fluctuations in the oncoming fresh mixture. Based on the assumptions of large activation energy and small Mach number, an analysis of the thermal, hydrodynamic and acoustic regions of a flame is performed to derive an interactive system that describes, on the first-principles basis, the intricate coupling between the flame and its spontaneously emitted acoustic waves. The system, in its general form, is strongly nonlinear and requires a numerical attack. In this paper, it is employed to analyze several fundamental physical processes in relatively simple cases in order to provide useful insights into the role of enthalpy fluctuations in combustion. Firstly, the linear response of the flame to two-or three-dimensional small-amplitude enthalpy fluctuations is considered, and they are found to generate hydrodynamic motion. Secondly, enthalpy fluctuations are shown to radiate sound waves through their interaction with the flame. Thirdly, enthalpy fluctuations and the sound waves emitted by them modify the flame stability, and the analysis shows that a moderate level of enthalpy fluctuation may cause a strong subharmonic parametric instability. Finally, in the small-heat-release limit, an extended Michelson-Sivashinsky equation is derived to describe the nonlinear evolution of the flame under the influence of both the imposed enthalpy fluctuations and the induced acoustic waves. Numerical solutions suggest that the flame evolves into a time-periodic state and acquires a curved profile, which primarily vibrates in the longitudinal direction, while its overall shape remains almost unaltered.

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“…Hence, in this case the fractional increase in the burning speed of the quasi-planar flame above S L is a result of and equal to the fractional increase in the flame-surface area above A yz caused by the transient, nonuniform advection field U, as described earlier (Williams, 1985). Equation provides for more generally applicable results beyond the case of Huygens propagation (S N = S L ), accounting for variations of the reactant density and local normal propagation speed along the flame (e.g., caused by effects of local flow-field strain and flame-surface curvature) (Aldredge, 2005;Aldredge and Killingsworth, 2004;Aldredge and Williams, 1991;Clavin, 1985;Clavin and Garcia-Ybarra, 1983;Clavin and Williams, 1982;Joulin and Clavin, 1979;Kwon et al, 1992;Law, 1988;Lewis and von Elbe, 1961;Markstein, 1953Markstein, , 1964Markstein and Squire, 1955;Searby and Clavin, 1986;Sivashinsky, 1983;Tseng et al, 1993;Williams, 1985). Consider now the propagation of a wrinkled, quasi-planar surface described by x = f 0 (y, z, t).…”

Section: Introductionmentioning

confidence: 99%

Flame-Surface Advection in Transient Periodic Flow

Aldredge

2014

Combustion Science and Technology

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The advection of an interface by a known transient periodic excitation flow is investigated in the present study, the results of which are relevant to the propagation of nearly isothermal premixed flames in turbulent flow. The relation between the corrugated-surface area and the intensity of the excitation flow is obtained numerically and compared with exact analytically derived solutions. The results elucidate the relation between the surface area and the intensity of spatial and temporal flow-field variations at low, moderate, and large intensities and highlight the stabilizing influence of Huygens surface propagation (e.g., of premixed flames) on the rate of surface-area increase, which is found to be otherwise unbounded in time.

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Weakly Turbulent, Wrinkled Flames in Premixed Gases

Cited by 82 publications

References 10 publications

Flow-flame interaction in a closed chamber

Flow-flame interaction in a closed chamber

Large-activation-energy theory for premixed combustion under the influence of enthalpy fluctuations

Flame-Surface Advection in Transient Periodic Flow

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