Thermal expansion effect on the propagation of premixed flames in narrow channels of circular cross-section: Multiplicity of solutions, axisymmetry and non-axisymmetry

• Published in: Proceedings of the Combustion Institute Vol. 37; no. 2; pp. 1927 - 1935
• Main Authors: Dejoan, Anne, Kurdyumov, Vadim N.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 2019
• Subjects: Flashback; Non-axisymmetry; Premixed laminar flame propagation; Three-dimensional simulations; Flashback; Premixed laminar flame propagation; Non-axisymmetry; Three-dimensional simulations
• ISSN: 1540-7489; 1873-2704
• DOI: 10.1016/j.proci.2018.06.153

The present study examines, in presence of thermal expansion effects, the existence of the multiplicity of solutions previously reported within the context of diffusive-thermal modeling in [15], for lean premixed flames with low Lewis number (Le < 1) propagating in narrow circular adiabatic channels subject to a Poiseuille flow. For this, direct numerical simulations have been carried out within the framework of variable-density Navier–Stokes equations and zero-Mach-number approximation. The simulations, conducted for both axisymmetric and three-dimensional cylindrical geometries, confirm the coexistence of multiple steady flame structures for a given flow rate. They show that axisymmetric flames concave towards the upstream are more unstable to three-dimensional perturbations than convex (toward the upstream) flames. This result evinces earlier findings obtained from stability analysis. The non-axisymmetry property of the flame is also found to push back the critical flashback limits at larger flow rate when compared to those predicted under the assumption of flame axisymmetry.