A computational study on flame extinction limits and behavior of a heated air slab burner

A solid-fueled ramjet (SFRJ) is a type of air-breathing engine that provides suitable advantages for supersonic flight, primarily in the aspects of simplistic design and performance. The simplicity of a ramjet engine lies in the minimal usage of moving parts and coupled with the usage of solid fuel, further progresses towards a theoretically simpler design. Furthermore, ramjets have a higher specific impulse than chemical rockets making them an advantageous engine for atmospheric supersonic flight. However, because of the high Mach numbers attained and shockwaves generated in supersonic flight, substantial discontinuities in flow characteristics exist. One such discontinuity is temperature, where the oxidizer (air) inlet temperature directly behind the generated shockwave becomes larger than the freestream temperature. There has been little investigation into the implications of these high inlet temperatures on the flame characteristics and combustion stability of an SFRJ. As a result, the goal of this study is to examine the phenomenon through computational modeling. The present study utilized the open-source software OpenFOAM to model the in-house slab burner combustion chamber using the UCSD combustion mechanism to model the reactions and combustion process. The oxidizer inlet temperatures to be studied are 300 K to 1000 K in increments of 100 K; with the fuel held at a constant 300 K. The present research desires data pertaining to flame strain rates to observe the correlation between species formation, extinction strain rates, and inlet temperature.