Analysis of the development of the flame brush in turbulent premixed spherical flames

Kulkarni, Tejas; Bisetti, Fabrizio

doi:10.1016/j.combustflame.2021.111640

Cited by 6 publications

(1 citation statement)

References 50 publications

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“…( 7), the thickness 𝛿 𝑡 is unknown a priori. Various experimental [39][40][41][42] and DNS 34,[43][44][45] data show that 𝛿 𝑡 𝐿 ⁄ > 1. Therefore, 𝐷𝑎 𝑐𝑟 should be less than (𝜎 − 1) −1 = O(10 −1 ).…”

Section: Accepted To Phys Fluids 101063/50123211mentioning

confidence: 99%

Effects of thermal expansion on moderately intense turbulence in premixed flames

et al. 2022

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The study aims at analytically and numerically exploring the influence of combustion-induced thermal expansion on turbulence in premixed flames. In the theoretical part, contributions of solenoidal and potential velocity fluctuations to the unclosed component of the advection term in the Reynolds-averaged Navier-Stokes equations are compared and a new criterion for assessing the importance of the thermal expansion effects is introduced. The criterion highlights a ratio of the dilatation in the laminar flame to the large-scale gradient of root-mean-square (rms) velocity in the turbulent flame brush. To support the theoretical study, direct numerical simulation (DNS) data obtained earlier from two complex-chemistry, lean H2-air flames are analyzed. In line with the new criterion, even at sufficiently high Karlovitz numbers, results show significant influence of combustion-induced potential velocity fluctuations on the second moments of the turbulent velocity upstream of and within the flame brush. In particular, the DNS data demonstrate that (i) potential and solenoidal rms velocities are comparable in the unburnt gas close to the leading edge of the flame brush and (ii) potential and solenoidal rms velocities conditioned to unburnt gas are comparable within the entire flame brush. Moreover, combustion-induced thermal expansion affects not only the potential velocity, but even the solenoidal one. The latter effects manifest themselves in a negative correlation between solenoidal velocity fluctuations and dilatation or in the counter-gradient behavior of the solenoidal scalar flux. Finally, a turbulence-in-premixed-flame diagram is sketched to discuss the influence of combustion-induced thermal expansion on various ranges of turbulence spectrum.

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Section: Accepted To Phys Fluids 101063/50123211mentioning

confidence: 99%

Effects of thermal expansion on moderately intense turbulence in premixed flames

et al. 2022

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Turbulence Intensity and Length Scale Effects on Premixed Turbulent Flame Propagation

Trivedi

Cant

2021

Flow Turbulence Combust

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The effects of varying turbulence intensity and turbulence length scale on premixed turbulent flame propagation are investigated using Direct Numerical Simulation (DNS). The DNS dataset contains the results of a set of turbulent flame simulations based on separate and systematic changes in either turbulence intensity or turbulence integral length scale while keeping all other parameters constant. All flames considered are in the thin reaction zones regime. Several aspects of flame behaviour are analysed and compared, either by varying the turbulence intensity at constant integral length scale, or by varying the integral length scale at constant turbulence intensity. The turbulent flame speed is found to increase with increasing turbulence intensity and also with increasing integral length scale. Changes in the turbulent flame speed are generally accounted for by changes in the flame surface area, but some deviation is observed at high values of turbulence intensity. The probability density functions (pdfs) of tangential strain rate and mean flame curvature are found to broaden with increasing turbulence intensity and also with decreasing integral length scale. The response of the correlation between tangential strain rate and mean flame curvature is also investigated. The statistics of displacement speed and its components are analysed, and the findings indicate that changes in response to decreasing integral length scale are broadly similar to those observed for increasing turbulence intensity, although there are some interesting differences. These findings serve to improve current understanding of the role of turbulence length scales in flame propagation.

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Effects of turbulence on variations in early development of hydrogen and iso-octane flame kernels under engine conditions

Chu

Berger

Grenga

et al. 2023

Combustion and Flame

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Analysis of the development of the flame brush in turbulent premixed spherical flames

Cited by 6 publications

References 50 publications

Effects of thermal expansion on moderately intense turbulence in premixed flames

Effects of thermal expansion on moderately intense turbulence in premixed flames

Turbulence Intensity and Length Scale Effects on Premixed Turbulent Flame Propagation

Effects of turbulence on variations in early development of hydrogen and iso-octane flame kernels under engine conditions

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