Affiliation:
1. Nordita, KTH Royal Institute of Technology and Stockholm University 2 , Hannes Alfvéns väg 12, 114 21 Stockholm, Sweden
Abstract
The initial stages of hydrogen–air flame propagation in tubes and the mechanism of tulip flame formation are investigated using a high-order numerical code to solve the fully compressible reactive Navier–Stokes equations for a spark or planar igniting flame at the closed end of a tube and propagating to the opposite closed or open end. It is shown that the mechanism of tulip flame formation is universal for both sparked and planar ignited flames in tubes with both ends closed. Flame front inversion results from the tulip-shaped profile of the unburned gas axial velocity near the flame front, which is the result of the superposition of the unburned gas flow generated by the accelerating flame and the reverse flow generated by the rarefaction wave during flame deceleration. In a half-open tube, this mechanism is valid for spark ignited flames. In the case of planar ignition, there is no rarefaction wave, but the growth of bulges on the sidewalls leads to the formation of a tulip flame.
Funder
no specific funds for this work
Subject
Condensed Matter Physics,Fluid Flow and Transfer Processes,Mechanics of Materials,Computational Mechanics,Mechanical Engineering