Numerical investigation on dynamic behavior of premixed hydrogen/air flame propagation in a closed tube

In this paper, the large eddy simulation (LES) model of OpenFOAM was used to study the flame propagation characteristics of hydrogen-air premixed flame in a closed tube with an aspect ratio of 12. The numerical simulation reproduces the characteristic flame shape evolution observed in the experiment, such as classical tulip flame, T-shaped flame, and distorted tulip deformation. The predicted flame front velocity, overpressure, and its fluctuation are all in good agreement with the measurements. The simulation demonstrates that after the classic tulip flame is formed, a series of waves cause an obvious adverse pressure gradient at the front of the flame. This adverse pressure gradient drives reverse flow which pulls the backward tip further into the combustion zone, forming an elongated tulip flame. A small amount of unburnt gas trapped in the cusp rapidly consumes to form a featured T-shaped flame. Then the T-shaped flame transforms into the second finger-shaped flame, and finally the tulip distortion occurs. The vortex and the reverse flow near the flame front generated by the interaction between the pressure field and the flow field accounts primarily for the formation of distorted tulip flame.