Simulation of Flame Acceleration and DDT in H2-air Mixture with a Flux Limiter Centred Method

Flame acceleration and deflagration to detonation transition (DDT) is simulated with a numerical code based on a flux limiter centred method for hyperbolic differential equations. The energy source term is calculated by a Riemann solver for the in homogeneous Euler equations for the turbulent combustion and a two-step reaction model for hydrogen-air. The transport equations are filtered for large eddy simulation (LES) and the sub filter turbulence is modelled by a transport equation for the the turbulent kinetic energy. The flame tracking is handled by the G-equation for turbulent flames. Numerical results are compared to pressure histories from physical experiments. These experiments are performed in a closed, circular, 4m long tube with inner diameter of 0.107m. The tube is filled with hydrogen-air mixture at 1atm, which is at rest when ignited. The ignition is located at one end of the tube. The tube is fitted with an obstruction with circular opening 1m down the tube from the ignition point. The obstruction has a blockage ratio of 0.92 and a thickness of 0.01m. The obstruction creates high pressures in the ignition end of the tube and very high gas velocities in and behind the obstruction opening. The flame experiences a detonation to deflagration transition (DDT) in the super sonic jet created by the obstruction. Pressure build-up in the ignition end of the tube is simulated with some discrepancies. The DDT in the supersonic jet is simulated, but the position of the DDT is strongly dependent on the simulated pressure in the ignition end.