Effect of temporal pulsations of a turbulent flow on the flame velocity

Bychkov, Vitaly; Denet, Bruno

doi:10.1088/1364-7830/6/2/304

Cited by 12 publications

(28 citation statements)

References 22 publications

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“…The characteristic vortex size at the end of burning is much smaller than the original vortices. This is quite different from the model studies of turbulent "flames" with zero thermal expansion [13][14][15][16][17][18] where flame passes the vortices without changing them. Finally, the effect of pockets becomes even stronger at U rms,0 / U f = 20, see Figs.…”

Section: -9contrasting

confidence: 61%

“…44 A much more difficult question is how to imitate a turbulent flow, since turbulence in itself is one of the most unresolved and complicated problems in classical physics. Simulations performed in the approach of constant density [13][14][15][16][17][18] typically imitate the velocity field by a Fourier decomposition like…”

Section: T/tmentioning

confidence: 99%

“…͑1͒ was especially popular within the artificial model of turbulent "burning" with zero thermal expansion. [9][10][11][12][13][14][15][16][17][18] However, realistic flames involve considerable thermal expansion, with density ratio of the fuel mixture and the burnt matter about ⌰ ϵ f / b =5-8. In that case, the propagating flame strongly modifies the initial turbulent flow, and the dependence like Eq.…”

Section: Introductionmentioning

confidence: 99%

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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: -9contrasting

confidence: 61%

Section: T/tmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Flow-flame interaction in a closed chamber

et al. 2008

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“…The latter two limits are important to understand the behaviour of the effective flame speed U T for large values of the amplitude, say A, of the turbulent flow, and the corresponding bending effect of U T versus A, which is frequently, but somewhat inconclusively, discussed in the literature for parallel, vortical, and more general flows (see, e.g. [19][20][21][22][23][24]). The interested reader may consult these references for an instructive discussion of the bending effect and other aspects; of particular relevance to our study are references [22] and [23] since they consider time-dependent flows without addressing the limit → 0 however.…”

Section: Resultsmentioning

confidence: 99%

“…[19][20][21][22][23][24]). The interested reader may consult these references for an instructive discussion of the bending effect and other aspects; of particular relevance to our study are references [22] and [23] since they consider time-dependent flows without addressing the limit → 0 however. Here we simply point out that the bending effect is believed by Ronney and Yakhot [3] to be associated with the increasingly felt presence of the small scales in the (multi-scale) flow by the flame, as the turbulent intensity is increased; these authors seem however to have in mind a highly disrupted flame fronts similar to those investigated by Kagan and Sivashinsky [15] for vortical flows, which cannot be obtained within the model of the present study.…”

Section: Resultsmentioning

confidence: 99%

Flame propagation in a small-scale parallel flow

Daou

Sparks

2007

Combustion Theory and Modelling

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We consider the propagation of laminar premixed flames in the presence of a parallel flow whose scale is smaller than the laminar flame thickness. The study addresses fundamental aspects with relevance to flame propagation in narrow channels, to the emerging micro-combustion technology, and to the understanding of the effect of small scales in a (turbulent) flow on the flame structure. In part, the study extends the results of a previous analytical study carried out in the thick flame asymptotic limit which has in particular addressed the validity of Numerical contributions include a significant set of two-dimensional calculations which determine the range of validity of the asymptotic findings. In particular, these account for volumetric heat loss and differential diffusion effects. Good agreement between the numerics and asymptotics is found in all cases, both for steady and oscillatory flows, at least in the expected range of validity of the asymptotics. The effect of the frequency of oscillation is also discussed. Additional related aspects such as the difference in the response of thin and thick flames to the combined effect of heat loss and fluid flow are also addressed. It is found for example that the sensitivity of thick flames to volumetric heat loss is negligibly affected by the parallel flow intensity, in marked contrast to the sensitivity of thin flames. Interestingly, and somewhat surprisingly, thin flames are found to be more resistant to heat loss when a flow is present, even for unit Lewis number; this ceases to be the case, however, when the Lewis number is large enough.

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Turbulent Flow Produced by Piston Motion in a Spark-ignition Engine

Akkerman

Иванов

Bychkov

2008

Flow Turbulence Combust

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Turbulence produced by the piston motion in spark-ignition engines is studied by 2D axisymmetric numerical simulations in the cylindrical geometry as in the theoretical and experimental work by Breuer et al. (Flow Turbul Combust 74:145, 2005). The simulations are based on the Navier-Stokes gas-dynamic equations including viscosity, thermal conduction and non-slip at the walls. Piston motion is taken into account as a boundary condition. The turbulent flow is investigated for a wide range of the engine speed, 1,000-4,000 rpm, assuming both zero and non-zero initial turbulence. The turbulent rms-velocity and the integral length scale are investigated in axial and radial directions. The rms-turbulent velocity is typically an order-of-magnitude smaller than the piston speed. In the case of zero initial turbulence, the flow at the top-dead-center may be described as a combination of two large-scale vortex rings of a size determined by the engine geometry. When initial turbulence is strong, then the integral turbulent length demonstrates selfsimilar properties in a large range of crank angles. The results obtained agree with the experimental observations of Breuer et al. (Flow Turbul Combust 74:145, 2005).

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Effect of temporal pulsations of a turbulent flow on the flame velocity

Cited by 12 publications

References 22 publications

Flow-flame interaction in a closed chamber

Flow-flame interaction in a closed chamber

Flame propagation in a small-scale parallel flow

Turbulent Flow Produced by Piston Motion in a Spark-ignition Engine

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