Heating of the fuel mixture due to viscous stress ahead of accelerating flames in deflagration-to-detonation transition

Valiev, Damir; Bychkov, Vitaly; Akkerman, V’yacheslav; Eriksson, Lars‐Erik; Marklund, Mattias

doi:10.1016/j.physleta.2008.04.066

Cited by 37 publications

(27 citation statements)

References 22 publications

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“…6, the flame tip curvature does not change significantly from the instant of the transition to the finger configuration and until the flame skirt touches the wall, thus justifying the assumption of almost constant tip curvature made in Section 4.1. It should be noted that formation of fingershaped laminar flame fronts in planar geometry due to essentially different Schelkin mechanism has been also obtained in simulations of premixed flames in channels with non-slip walls [31,36,40]. Furthermore similar shapes of the finger front were observed within the context of electrochemical doping in organic semiconductors [41,42], with the electric field playing conceptually the same role as the field of gas velocity in the present combustion problem.…”

Section: Numerical Results and Discussionsupporting

confidence: 71%

“…Outside the region of fine grid the mesh size increased gradually with 2% change in size between the neighboring cells. In order to keep the flame and pressure waves in the zone of fine grid we implemented the periodical mesh reconstruction during the simulation run [36]. Third-order splines were used for the re-interpolation of the flow variables during periodic grid reconstruction to preserve the second order accuracy of the numerical scheme.…”

Section: Numerical Method Basic Equations Boundary and Initial Condmentioning

confidence: 99%

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Influence of gas compression on flame acceleration in the early stage of burning in tubes

Valiev

Akkerman

Kuznetsov

et al. 2013

Combustion and Flame

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a b s t r a c tThe mechanism of finger flame acceleration at the early stage of burning in tubes was studied experimentally by Clanet and Searby [Combust. Flame 105 (1996) 225] for slow propane-air flames, and elucidated analytically and computationally by Bychkov et al. [Combust. Flame 150 (2007) 263] in the limit of incompressible flow. We have now analytically, experimentally and computationally studied the finger flame acceleration for fast burning flames, when the gas compressibility assumes an important role. Specifically, we have first developed a theory through small Mach number expansion up to the first-order terms, demonstrating that gas compression reduces the acceleration rate and the maximum flame tip velocity, and thereby moderates the finger flame acceleration noticeably. This is an important quantitative correction to previous theoretical analysis. We have also conducted experiments for hydrogenoxygen mixtures with considerable initial values of the Mach number, showing finger flame acceleration with the acceleration rate much smaller than those obtained previously for hydrocarbon flames. Furthermore, we have performed numerical simulations for a wide range of initial laminar flame velocities, with the results substantiating the experiments. It is shown that the theory is in good quantitative agreement with numerical simulations for small gas compression (small initial flame velocities). Similar to previous works, the numerical simulation shows that finger flame acceleration is followed by the formation of the ''tulip'' flame, which indicates termination of the early acceleration process.

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Section: Numerical Results and Discussionsupporting

confidence: 71%

Section: Numerical Method Basic Equations Boundary and Initial Condmentioning

confidence: 99%

Influence of gas compression on flame acceleration in the early stage of burning in tubes

Valiev

Akkerman

Kuznetsov

et al. 2013

Combustion and Flame

Self Cite

View full text Add to dashboard Cite

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“…Slowdown of the jet flow increases local pressure and temperature. Viscous dissipation of the vortices leads to additional temperature increase, which has the same effect as viscous heating at the wall in smooth tubes [20,34]. The important role of viscous heating in producing temperature peaks is especially obvious in Fig.…”

Section: Simulation Results and Discussionmentioning

confidence: 92%

“…The compression wave and the shock become stronger as the flame accelerates, until explosion starts and develops into detonation. Recent papers [20,34] on DDT in tubes with smooth adiabatic wall have also demonstrated the important role of viscous heating at the wall in addition to shock heating. Because of viscous heating, the temperature at the wall of a smooth adiabatic channel is larger than that at the axis, and numerical modeling demonstrates DDT onsets at the wall.…”

Section: Simulation Results and Discussionmentioning

confidence: 99%

Flame acceleration in channels with obstacles in the deflagration-to-detonation transition

Valiev

Bychkov

Akkerman

et al. 2010

Combustion and Flame

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149

100

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a b s t r a c tIt was demonstrated recently in Bychkov et al. [Bychkov et al., Phys. Rev. Lett. 101 (2008) 164501], that the physical mechanism of flame acceleration in channels with obstacles is qualitatively different from the classical Shelkin mechanism. The new mechanism is much stronger, and is independent of the Reynolds number. The present study provides details of the theory and numerical modeling of the flame acceleration. It is shown theoretically and computationally that flame acceleration progresses noticeably faster in the axisymmetric cylindrical geometry as compared to the planar one, and that the acceleration rate reduces with increasing Mach number and thereby the gas compressibility. Furthermore, the velocity of the accelerating flame saturates to a constant value that is supersonic with respect to the wall. The saturation state can be correlated to the Chapman-Jouguet deflagration as well as the fast flames observed in experiments. The possibility of transition from deflagration-to-detonation in the obstructed channels is demonstrated.

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“…It is however noted that, for flames in tubes/channels, the role of turbulence and flame instabilities is rather supplementary as compared to either the Shelkin mechanism in smooth tubes [3,7,[20][21][22][23][24] or acceleration in tubes with obstacles [25,26]. As such, hereafter we shall focus on smooth tubes and on the Shelkin scenario of the DDT, i.e.…”

Section: Introductionmentioning

confidence: 99%

Analysis of flame acceleration induced by wall friction in open tubes

2010

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Spontaneous flame acceleration leading to explosion triggering in open tubes/channels due to wall friction was analytically and computationally studied. It was first demonstrated that the acceleration is effected when the thermal expansion across the flame exceeds a critical value depending on the combustion configuration. For the axisymmetric flame propagation in cylindrical tubes with both ends open, a theory of the initial (exponential) stage of flame acceleration in the quasi-isobaric limit was developed and substantiated by extensive numerical simulation of the hydrodynamics and combustion with an Arrhenius reaction. The dynamics of the flame shape, velocity, and acceleration rate, as well as the velocity profile ahead and behind the flame, have been determined.

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Heating of the fuel mixture due to viscous stress ahead of accelerating flames in deflagration-to-detonation transition

Cited by 37 publications

References 22 publications

Influence of gas compression on flame acceleration in the early stage of burning in tubes

Influence of gas compression on flame acceleration in the early stage of burning in tubes

Flame acceleration in channels with obstacles in the deflagration-to-detonation transition

Analysis of flame acceleration induced by wall friction in open tubes

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