Mechanism of tulip flame formation in highly reactive and low reactive gas mixtures

TL;DR

This study uses high-fidelity simulations to explore how chemical kinetics and flame dynamics influence tulip flame formation in various gas mixtures and tube configurations, revealing key physical mechanisms behind this phenomenon.

Contribution

It provides detailed numerical insights into the physical and chemical factors driving tulip flame formation, which were previously not fully understood.

Findings

Faster flames lead to deeper tulip shapes.

Flame thickness and velocity significantly affect tulip formation.

Pressure wave interactions are crucial in the evolution of tulip flames.

Abstract

The early stages of flame dynamics and the development and evolution of tulip flames in closed tubes of various aspect ratios and in a semi-open tube are studied by solving the fully compressible reactive Navier-Stokes equations using a high-order numerical method coupled to detailed chemical models in a stoichiometric hydrogen/air and methane/air mixtures. The use of adaptive mesh refinement provides adequate resolution of the flame reaction zone, pressure waves, and flame-pressure wave interactions. The purpose of this study is to gain a deeper insight into the influence of chemical kinetics on the combustion regimes leading to the formation of a tulip flame and its subsequent evolution. The simulations highlight the effect of flame thickness, flame velocity, and reaction order on the intensity of the rarefaction wave generated by the flame during the deceleration phase, which is the principal physical mechanism of tulip flame formation. The obtained results explain most of the experimentally observed features of tulip flame formation, e.g. faster tulip flame formation with deeper tulip shape for faster flames compared to slower flames.