Experimental and LES investigation of premixed methane/air flame propagating in an obstructed chamber with two slits

The paper aims at revealing the interaction of twin premixed methane/air jet flames in a closed duct, in which a thin obstacle with two slits is mounted to generate two free jet flames. In the experiment, a high-speed video camera and pressure transducers are used to study the flame shape changes and pressure dynamics. In the numerical simulations, large eddy simulation (LES) with a Power-Law model is applied to investigate the interaction between the moving flame and vortices induced by the obstacle. The results indicate that the flame propagation for all obstacle configurations in a closed duct can be divided into four typical stages, i.e. hemispherical flame, finger-shaped flame, jet flame and bidirectional propagation flame. For three obstacle configurations, the merged jet flames, paralleling jet flames, and separated jet flames are observed after twin jet flames are formed downstream of the two slits. The Power-Law model can well reproduce the flame shape changes, the dynamics of flame front, and the pressure growth rates. By analyzing the predicted flow structure and vorticity magnitude, the premixed methane/air flame propagation in an obstructed tube can be explained in the view of pure hydrodynamics. In addition, the transition from a "corrugated flamelets" to a "thin reaction zones" is observed in the simulation. (C) 2016 Elsevier Ltd. All rights reserved.