Numerical simulation of a counterflow diffusion flame in supersonic airflow

A counterflow diffusion flame of hydrogen, developed in the forward stagnation-flow region of a porous cylinder in supersonic airflow (which can be considered as a flame of the "Tsuji-burner" in supersonic airflow), was analyzed numerically by solving the two-dimensional Navier-Stokes equations for multispecies. A counterflow diffusion flame, having a temperature distribution and concentration distributions of species in the direction of the burner surface, can be established in the very thin region behind a detached shock nave. It is shown that thermal quenching occurs when the flame approaches the surface of a porous cylindrical burner as in the case of a normal "Tsuji-burner." The decrease of static temperature or Mach number (equivalent to the flow velocity) of airflow causes flame extinction, in contrast to the case of subsonic airflow. Flame temperature approaches the stagnation temperature in the region of high static temperature and has maximum heat release at a certain static temperature. This is due to the increase of how velocity and stretch rate based on the increase of static temperature, but appreciable flame extinction does not occur even if the stretch rate becomes much higher, because the stagnation temperature exceeds the critical temperature, which has previously been discussed for a high-temperature subsonic airflow system.