Simulation of Flame Acceleration and DDT

Abstract

This paper presents a combustion model and a simulation method for modeling flame acceleration (FA) and deflagration to detonation transition (DDT) in a premixed gas. The method is intended to produce the most important effects in FA and DDT without resolving the flame front on the computational mesh. The simulations presented here are of stoichiometric hydrogen-air mixtures in a channel with repeated obstacles. The channel is 2 m long and 110 mm wide, with a height of either 20 mm or 40 mm. The obstacles gives a blockage ratio of 0.5. These values are the same as for experiments by other researchers and is used for comparison. The combustion model combines a turbulent burning velocity model and a two-step Arrhenius kinetic rate. The simulations show similar flame speeds and pressures as seen in experiments, and the process of DDT is shown to be caused by shock focusing and shock flame interactions. The simulations show that the quasi detonation regime is a series of transition to detonation events followed by failure of the detonation. Results from both 2D and 3D simulations are presented, since the 2D simulations show how the method can reproduce important effects.