An a priori model for the effective species Lewis numbers in premixed turbulent flames

Savard, Bruno; Blanquart, Guillaume

doi:10.1016/j.combustflame.2013.12.014

Cited by 51 publications

(49 citation statements)

References 30 publications

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“…Little work has been done on direct numerical simulation of high molecular weight hydrocarbon fuels, particularly for high Karlovitz number premixed flames. In a sequence of papers, Savard et al [9,10] and Lapointe et al [11] discuss simulations of premixed heptane flames at high Karlovitz numbers with detailed chemistry and transport, building on previous work [12] based on the hydrogen simulations in [1]. The focus of these papers is on the impact of differential diffusion on flame response, even at high Karlovitz numbers; the authors note a broadening of the flame and a transition to composition versus temperature profiles characteristic of a unity Lewis number flame and a reduction in heat release and fuel consumption rates.…”

Section: Introductionmentioning

confidence: 99%

Turbulence–flame interactions in lean premixed dodecane flames

Aspden

Bell

Day

et al. 2017

Proceedings of the Combustion Institute

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Turbulent lean premixed dodecane/air flames are simulated in a doubly-periodic domain using detailed kinetics and transport over a range of Karlovitz number. We observe extensive thickening of thermal profiles through the flames that increases with turbulent intensity. The high Lewis number of the flames acts to suppress wrinkling of the flame resulting in considerably lower turbulent flame speeds than is observed for lower molecular weight fuels. The impact of high Lewis number is also reflected in a negative correlation of local consumption-based flame speed with curvature. Characteristic of heavy hydrocarbons, pyrolysis of the fuel into smaller fuel fragments is separated in temperature from the primary consumpution of oxygen, which peaks at a higher temperature where the fuel fragments are consumed. The resulting intermediate species are partially entrained within the cool region ahead of the flame, but the overall pyrolysis-oxidation sequence appears essentially unaffected by turbulent mixing; however, the peak rates of these reactions are dramatically reduced.

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Section: Introductionmentioning

confidence: 99%

Turbulence–flame interactions in lean premixed dodecane flames

Aspden

Bell

Day

et al. 2017

Proceedings of the Combustion Institute

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“…There is a growing body of work using DNS with detailed kinetics to study the canonical flame-ina-box configurations examining a wide range of fuels and conditions; examples include [1][2][3] in hydrogen, [4][5][6] in methane, and [7,8] in heavier fuels like heptane and dodecane. A common theme that comes out of this work is the importance of the global Lewis number (the Lewis number of the deficient species) and how its influence is moderated (or enhanced) by turbulence, but it is becoming increasingly clear that there are secondary effects that cannot be explained by the global Lewis number, e.g.…”

Section: Introductionmentioning

confidence: 99%

A numerical study of diffusive effects in turbulent lean premixed hydrogen flames

Aspden

2017

Proceedings of the Combustion Institute

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Three-dimensional direct numerical simulation of lean premixed hydrogen flames is used to explore the influence of species and thermal diffusion and viscosity on the flame structure and turbulent flame response. The leadingorder flame response is shown to be due to the global Lewis number with little influence from the other species. The previously-reported observation of decorrelation of fuel consumption and heat release at high Karlovitz numbers is shown to be solely due to atomic hydrogen diffusion. Finally, it is shown that the suppression of turbulence through the flame cannot be attributed to an increase in viscosity due to the increase in temperature, but that the effect is not negligible. It is further argued that turbulence-flame interactions are better described considering Kolmogorov's second similarity hypothesis (rather than the first); specifically, by a Karlovitz number that is defined based on the inertial subrange (i.e. the energy dissipation rate) rather than the dissipation subrange (i.e. viscosity or equivalently Kolmogorov scale quantities).

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“…In [16] and [9], it was shown that in high Karlovitz number flames, turbulence leads to a reduction in variation in local equivalence ratio, and the fuel mass fraction collapses to a unity Lewis number curve. In Savard et al [26], 380 an a priori model for effective species Lewis number is proposed based on data from [16], which tends towards unity for high Karlovitz numbers. Srinivasan et al [27] also observe a tendency towards unity Lewis number behaviour using the one-dimensional LEM approach.…”

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confidence: 99%