Transient and Geometrical Effects in Expanding Turbulent Flames

Lipatnikov, Andrei; Chomiak, Jerzy

doi:10.1080/00102200008947273

Cited by 37 publications

(18 citation statements)

References 49 publications

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“…Similar trend has been observed in [36] for propane-air mixtures, however, magnitudes of this ratio reported in that work are lower because they refer to smaller flame kernels. Steady increase of the ratio of the burning rate to the effective rms velocity is qualitatively compatible with the findings of [30,35,36] that the reduction in the mean flame brush curvature increases flame acceleration, nonetheless this question deserves a further quantitative analysis. Figure 5 shows clearly that the burning rate increases with pressure, so that the faster turbulent flames correspond to the slower laminar flames.…”

Section: Resultssupporting

confidence: 79%

“…5. The strong acceleration of a turbulent spherical flame is not a new observation [28][29][30]35]. The magnitude of the flame acceleration is further illustrated in Figs.…”

Section: Resultsmentioning

confidence: 91%

“…There are additional factors which can contribute to the observed growth of burning velocity, such as the growth of the flame thickness affecting the averaged thermal expansion ratio and the gradual increase in mean flame curvature [30,35]. Direct verification of these hypothesis requires measuring of the profile of the mean temperature across the flame brush, however, it may be argued that if a growing flame accelerates in such a way that the ratio of its burning velocity to either u k or u ef f remains constant, it means that other mechanisms are negligible.…”

Section: Resultsmentioning

confidence: 99%

See 2 more Smart Citations

Turbulent Combustion of Hydrogen–CO Mixtures

Burluka

Hussin

Sheppard

et al. 2011

Flow Turbulence Combust

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Laminar and turbulent burning velocities were measured in a closedvolume fan-stirred vessel for H 2 -CO mixtures using two independent methods of flame definition. It has been shown that the unsteady flame development is an important factor and it needs to be taken into account for comparison of the burning rates obtained in different experiments. For the atmospheric pressure flames, the mixtures with faster laminar flame velocities burnt faster in turbulent flow despite the fact that the lean flames exhibit cellular structures. However, even a modest increase of the initial pressure promotes strongly cellularity and causes a significant acceleration of a lean laminar flame. The same lean flame burns faster in turbulent flow as well and this increase in the rate of combustion is greater that can be deduced from variation of the molecular heat diffusivity and laminar flame speed.

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Section: Resultssupporting

confidence: 79%

“…5. The strong acceleration of a turbulent spherical flame is not a new observation [28][29][30]35]. The magnitude of the flame acceleration is further illustrated in Figs.…”

Section: Resultsmentioning

confidence: 91%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Turbulent Combustion of Hydrogen–CO Mixtures

Burluka

Hussin

Sheppard

et al. 2011

Flow Turbulence Combust

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“…The RANS calculations of spherical turbulent flames of Hainsworth (1985) were done by Schmid et al (1998) using a turbulent flame speed closure. A similar approach was also used by Lipatnikov and Chomiak (2000) to study turbulent spherical flames in various configurations. A transported joint velocity-scalar pdf approach was used by Pope and Cheng (1986) to compute the spherical flames of Hainsworth (1985) and showed a very good agreement with the measurements.…”

Section: Introductionmentioning

confidence: 92%

Simulation of Spherically Expanding Turbulent Premixed Flames

Ahmed

Swaminathan

2013

Combustion Science and Technology

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Statistically spherical expanding turbulent premixed flames are computed using an unsteady Reynolds-averaged Navier-Stokes (URANS) approach. Mean reaction rate is closed using strained and unstrained flamelet models and an algebraic model. The flamelets are parametrized using the scalar dissipation rate in the strained flamelet model. It is shown that this model is able to capture the measured growth rate of methane-air turbulent flame ball, which is free of thermo-diffusive instability. The spherical flames are observed to accelerate continuously. The flame brush thickness grows in time and the role of turbulent diffusion on this growth seems secondary compared to the convection due to the fluid velocity induced by the chemical reaction. The spherical flames have larger turbulent flame speed, the leading-edge displacement speed s t , compared to the planar flames for a given turbulence and thermochemical condition. The computational results suggest s t =s 0 L $ Re n t with 0.57 n 0.58, where Re t is the turbulence Reynolds number and s 0 L is the unstrained planar laminar flame speed, for both spherical and planar flames.

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“…The above equations were solved employing the numerical approach used in Refs. [11,58] and the independence of numerical results on the grid size was checked.…”

mentioning

confidence: 99%

Testing Premixed Turbulent Combustion Models by Studying Flame Dynamics

Lipatnikov

2009

International Journal of Spray and Combustion Dynamics

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First, the following universal feature of premixed turbulent flame dynamics is highlighted: During an early stage of flame development, the burning velocity grows much faster than the mean flame brush thickness, because the two processes are controlled by the small-scale and large-scale turbulent eddies, respectively. Second, this feature of developing flames is exploited in order to test a number of different models of premixed turbulent combustion by theoretically and numerically studying an interaction of an initially laminar, planar, one-dimensional flame with a statistically stationary, planar, one-dimensional, and spatially uniform turbulent flow not affected by combustion. To test as many models as possible in a simple and unified manner, various combustion models are divided into three generalized groups: (i) algebraic models, which invoke an algebraic expression for the mean rate of product creation, (ii) gradient models, which involve a gradient-type source term in a balance equation for the mean combustion progress variable, and (iii) two-equation models, which deal not only with a balance equation for the mean combustion progress variable but also with either a balance equation for the flame surface density or a balance equation for the mean scalar dissipation rate. Analytical and numerical results reported in the paper indicate that solely the gradient models are able to yield substantially different growth rates of the turbulent burning velocity and the mean flame brush thickness.

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Transient and Geometrical Effects in Expanding Turbulent Flames

Cited by 37 publications

References 49 publications

Turbulent Combustion of Hydrogen–CO Mixtures

Turbulent Combustion of Hydrogen–CO Mixtures

Simulation of Spherically Expanding Turbulent Premixed Flames

Testing Premixed Turbulent Combustion Models by Studying Flame Dynamics

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