Understanding the dynamics of premixed flames that propagates in confined systems is important in a wide range of applications. The study of premixed flames propagating in a closed channel covers a variety of thermochemical complexities related to flame ignition, laminar flame development, and strong non-linear interaction between the flame and the surrounding walls. Accordingly, to study the dynamics of premixed flames propagating in closed channels, numerical simulations of the propagation of distorted tulip flames are carried out in this work. All the numerical simulations are performed using the open-source computational tool PeleC, which is part of the Exascale Computing Project (ECP). More specifically, the fully reactive compressible Navier – Stokes equations are solved here using the high-order PPM (piecewise parabolic method). A 21-step chemical kinetic mechanism is employed to model the chemical kinetics and the energy release in a stoichiometric air/hydrogen mixture. Computational mesh independence studies are carried out in this work by both refining grid elements and employing different levels of adaptive mesh refinements (AMR). The final mesh employed here features an element size of 1/96 cm with 5 levels of refinement performed based on density gradients. The main results show that the classic tulip flame behavior evolves into a distorted one. Indeed, two consecutive collapses on the flame front are observed, which are related to wave pressure and the presence of reverse flow. Important aspects of the flame formation and propagation process analyzed include (i) the initial evolution of the tulip flame and its comparison with previous experimental and analytical results, (ii) the propagation of acoustic waves and its influence on flame evolution, and (iii) the formation of the distorted tulip flame and the collapse of flame cups. It is particularly found that the pressure wave produced by the interaction of the flame skirt with the side walls reduces the flame velocity and contributes to the formation of tulip flames. This is consistent with the reduction in both flame area and pressure gradient at the flame tip. Furthermore, the collapse of flame cups is associated with the vortex’s formation near the channel side walls and the increase of pressure waves.
Autor(es):ILLACANCHI, Fernando
VALENCIA, Sebastian
CELIS, Cesar
MENDIBURU, Andres
BRAVO, Luis
KHARE, Prashant
Año: 2023
Título de la revista: 27th International Congress of Mechanical Engineering, COBEM2023 (ABCM)
Ciudad: Florianópolis, SC, Brazil
Url: https://doi.org/10.48550/arXiv.2309.05893