An Extinction Analysis of Counterflow Diffusion Flames in Supersonic Airflow.

Abstract

An extinction analysis of counterflow diffusion flames in supersonic airflow is presented. The flow configuration consists of supersonic airflow coming from an infinite distance and opposing a fuel stream ejected from the surface of a porous body. It is well known as the Tsuji burner, but airflow is supersonic. If airflow velocity is subsonic, the flame temperature decreases as airflow velocity increases because the flame stretch rate increases, and finally extinction takes place at a certain airflow velocity. In the case of supersonic airflow, however, the region in which a diffusion flame can be established between a detached shock wave and a porous body reappears, and flame extinction occurs when the airflow velocity decreases. This indicates that shock heating has a stronger effect than high stretch-rate flow. Moreover, the flame temperature changes increasingly with the Mach number when the airflow velocity is supersonic, in contrast to the case of subsonic airflow.