Large eddy simulation investigation of flame acceleration and deflagration to detonation transition of methane‐air mixture in rectangular channel

Abstract

Large eddy simulation is used to simulate flame acceleration and deflagration to detonation transition of methane-air mixtures in a small-scale 3D channel. The simulation results show the changing of the flame surface 3D structure in the stage of flame acceleration and deflagration to detonation transition. In the first stage, the flame velocity increases exponentially because of the expansion of combustion products and the wrinkle of flame surface. In the next stage, the interaction between flame and pressure wave makes flame accelerate continuously, and the acceleration rate of the flame velocity decreases first and then increases. As the pressure of the leading shock increases, the boundary layer is heated by the preheating area in front of the flame surface at the channel wall. Because the cross section of the channel is square, the ultrafast flame first appears in the boundary layer of the four inner edges between the channel wall, then it appears in the boundary layer on the channel wall. The ultrafast flame generates oblique shock waves continuously moving to the center of the channel and colliding with each other, which promote the occurrence of local explosion and the coupling of flame surface and leading shock wave.

A Conservative Approach for the Fast Deflagration Analysis in the Containment With GASFLOW-MPI

“…However, the flame speed, developing from a subsonic to isobaric sound speed, covers different regimes on the Borghi diagram, depending on the gas mixture compositions and boundary conditions like obstacle structures, indicating that it would be difficult to simulate the whole process with a certain combustion model. The capabilities of the combustion model for flame acceleration/deceleration have to be enhanced to a level providing reliable forecast (Zhao, 2017).…”