Formalism for spatially averaged consumption speed considering spherically expanding flame configuration

Lefebvre, A. H.; Larabi, Hakim; Moureau, Vincent; Lartigue, Ghislain; Varéa, Emilien; Modica, Vincent; Renou, Bruno

doi:10.1016/j.combustflame.2016.08.024

Cited by 11 publications

(3 citation statements)

References 36 publications

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“…However, these surrogates are unequally appropriate (Najm et al 1998), and the relationship between fuel reaction rate and measured intensity of these surrogates may not hold in general. Here, we propose a novel approach inspired by previous work on spherical flames (Chung & Law 1988;Bradley, Gaskell & Gu 1996;Poinsot & Veynante 2011;Lefebvre et al 2016) or turbulent flames (Shepherd & Kostiuk 1994).…”

Section: Analytical Considerationsmentioning

confidence: 99%

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Isolating strain and curvature effects in premixed flame/vortex interactions

et al. 2017

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This study focuses on the response of premixed flames to a transient hydrodynamic perturbation in an intermediate situation between laminar stretched flames and turbulent flames: an axisymmetric vortex interacting with a flame. The reasons motivating this choice are discussed in the framework of turbulent combustion models and flame response to the stretch rate. We experimentally quantify the dependence of the flame kinematic properties (displacement and consumption speeds) to geometrical scalars (stretch rate and curvature) in flames characterized by different effective Lewis numbers. Whilst the displacement speed can be readily measured using particle image velocimetry and tomographic diagnostics, providing a reliable estimate of the consumption speed from experiments remains particularly challenging. In the present work, a method based on a budget of fuel on a well chosen domain is proposed and validated both experimentally and numerically using two-dimensional direct numerical simulations of flame/vortex interactions. It is demonstrated that the Lewis number impact neither the geometrical nor the kinematic features of the flames, these quantities being much more influenced by the vortex intensity. While interacting with the vortex, the flame displacement (at an isotherm close to the leading edge) and consumption speeds are found to increase almost independently of the type of fuel. We show that the total stretch rate is not the only scalar quantity impacting the flame displacement and consumption speeds and that curvature has a significant influence. Experimental data are interpreted in the light of asymptotic theories revealing the existence of two distinct Markstein numbers, one characterizing the dependence of flame speed to curvature, the other to the total stretch rate. This theory appears to be well suited for representing the evolution of the displacement speed with respect to either the total stretch rate, curvature or strain rate. It also explains the limited dependence of the flame displacement speed to Lewis number and the strong correlation with curvature observed in the experiments. An explicit relationship between displacement and consumption speeds is also given, indicating that the fuel consumption rate is likely to be altered by both the total stretch rate and curvature.

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Section: Analytical Considerationsmentioning

confidence: 99%

“…A proper method to quantify S c is to start by integrating the fuel mass fraction equation over a given control volume (Chung & Law 1988;Bradley et al 1996;Poinsot & Veynante 2011;Lefebvre et al 2016). This method is generally referred to as the integral approach (Chung & Law 1988).…”

Section: General Expression For the Flame Consumption Speedmentioning

confidence: 99%

Isolating strain and curvature effects in premixed flame/vortex interactions

et al. 2017

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“…where and 0 stand for the flame radius and the inner chamber radius, respectively and corresponds to the unburnt gas density. Experimental evaluation of the compression term ( 1) is possible but delicate [17]. Alternatively, assuming that the unburnt gas is isentropically compressed (with the heat capacity ratio of the unburnt gas) yields:…”

Section: Introductionmentioning

confidence: 99%

Development of an optically accessible apparatus to characterize the evolution of spherically expanding flames under constant volume conditions

Halter

Chen

Dayma

et al. 2020

Combustion and Flame

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Flame speed is extremely important as it affects the performances of many industrial systems. Moreover, its significance makes it a major target for the validation of kinetic mechanisms, which explains the necessity to provide ever more accurate data. Flame speed dependence on pressure and temperature conditions is interestingly assessed using, among others, spherically expanding flame in constant volume chambers. In these conditions, the flame speed derivation, based solely on the pressure evolution in the chamber, requires empirical models. The current study describes a perfectly spherical chamber with full optical access allowing simultaneous recording of the pressure inside the chamber and, fully innovative, of the flame radius evolution until the flame vanishes at wall. A careful description of the new set-up and of the accuracy of the measurements, in particular of the flame radius, are presented here. In parallel with experiments, one-dimensional transient simulations were carried out to identify the limits of the proposed new method. Then, the simultaneous use of pressure and flame radius information is compared to the traditional constant volume method based on empirical models. A first advantage relies in the direct detection of the development of instabilities during the flame propagation. In addition, although the flame speed is extremely sensitive to the flame radius determination, the actual experimental accuracy allows significant improvements in terms of accuracy, notably as initial pressure and temperature are elevated. This new set-up will allow major advances in the measurement of laminar flame velocity under extreme thermodynamic conditions.

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