Étude des instabilités de combustion au moyen des méthodes Lattice-Boltzmann (Thèse 2022 - 2025)
Activités
Mécanique des fluides;
Flammes de combustions;
Instabilité
thermoacoustique;
Lattice-Boltzmann Method.
Publications scientifiques au M2P2
2025
Ziyin Chen, Song Zhao, Bruno Denet, Christophe Almarcha, Pierre Boivin. A three-dimensional study on premixed flame propagation in narrow channels considering hydrodynamic and thermodiffusive instabilities. Combustion and Flame, 2025, 281, pp.114392. ⟨10.1016/j.combustflame.2025.114392⟩. ⟨hal-05344216⟩ Plus de détails...
In numerical studies of quasi-2D problems, such as laminar flame propagation through a slit, the quasi-2D assumption is commonly applied to simplify the problem. However, the impact of the third dimension (in the thickness between walls) can be significant due to strong curvature. The intrinsic Darrieus-Landau instability, the Saffman-Taylor instability, and the thermodiffusive instability lead to curved flame fronts in both the transverse and normal directions and radically change the global flame speed. This study investigates the interaction of these instabilities and their impact on premixed flames freely propagating in narrow channels. Two lean fuel-air mixtures are considered: one with unity Lewis number Le = 1 and another with Le = 0.5. A single-step Arrhenius-type reaction is used for combustion modeling. Joulin Sivashinsky's model [1], termed the 2D+ model, is implemented to capture the confinement effect due to walls. By comparing 3D Direct Numerical Simulations (DNS) and 2D simulations at unity Le, we find that the 2D+ model accurately reproduces confinement effects for channel width h up to 3.6δ T (δ T : thermal flame thickness), extending the validity of Darcy's law.
However, for larger h, interactions between flame curvatures in two directions result in higher flame surface increment and consumption speed. Besides, for 3D cases with Le = 0.5, positive curvature regions on the flame front primarily contribute to the global reaction due to the Lewis effect. Statistical studies on flame dynamics between walls in 3D cases are also
Ziyin Chen, Song Zhao, Bruno Denet, Christophe Almarcha, Pierre Boivin. A three-dimensional study on premixed flame propagation in narrow channels considering hydrodynamic and thermodiffusive instabilities. Combustion and Flame, 2025, 281, pp.114392. ⟨10.1016/j.combustflame.2025.114392⟩. ⟨hal-05344216⟩
Ziyin Chen, Yves Ballossier, Song Zhao, Bruno Denet, Christophe Almarcha, et al.. Study on symmetric/asymmetric hydrogen flame shapes in the thickness of a Hele-Shaw burner. Combustion and Flame, 2025, 277, pp.114208. ⟨10.1016/j.combustflame.2025.114208⟩. ⟨hal-05086359⟩ Plus de détails...
Premixed flame front shape, which drastically depends on boundary conditions, is closely related to its propagation speed. In this work, we focus on the symmetry of steady premixed hydrogen-air flames propagating in a narrow channel, like a Hele-Shaw burner. A wide range of equivalence ratios (0.35 -2.0) and channel widths (1.8 mm -4.8 mm) are analyzed by performing detailed simulations validated by experiments. A multiplicity of steady flame shape is found for channel widths above a certain critical value, that is related to flame cutoff wavelength. Our numerical results successfully reproduce steady flame fronts observed in experiments. Notably, transitions from symmetric to asymmetric with equivalence ratio are reproduced. Additionally, an increase in channel width reduces the region of symmetric solutions. Furthermore, The study explores the effects of the Darrieus-Landau instability and thermodiffusive effects on flame shapes, presenting a stability diagram for symmetric/asymmetric flame configurations. Throughout the study, an increase in flame area is associated with the asymmetry level of the flame front, showing a trend that first increases and then decreases with the equivalence ratio. The global consumption rate relative to laminar flame speed decreases monotonously with increasing equivalence ratio. It is determined by the flame area increment and stabilizing (destabilizing) effects on convex flame fronts at Lewis number greater (smaller) than 1. This effect is quantified and proved independent of flame symmetry and channel width. For very lean mixtures, the differential species diffusion significantly strengthens the consumption rate. A prediction model is established to determine the flame front length given a certain equivalence ratio and channel width.
Ziyin Chen, Yves Ballossier, Song Zhao, Bruno Denet, Christophe Almarcha, et al.. Study on symmetric/asymmetric hydrogen flame shapes in the thickness of a Hele-Shaw burner. Combustion and Flame, 2025, 277, pp.114208. ⟨10.1016/j.combustflame.2025.114208⟩. ⟨hal-05086359⟩
