Numerical Study of Distorted Tulip Flame Propagation in Confined Systems
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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 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. More specifically, a set of fully reactive compressible transport equations are solved here using the high-order PPM. A 21-step chemical kinetic mechanism is employed to model the chemical kinetics and the energy release in an 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 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. 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 formation of the vortex near the channel side walls and the increase of pressure waves.
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