Effects of thermal radiation on near-limit flame spread in a low convective microgravity environment

A numerical study is conducted to investigate the effects of thermal radiation on flame spread phenomenon close to limiting oxygen conditions in a low convective spacecraft environment. To understand the role of radiative heat loss from the flame, a set of simulations is performed where gas radiation is completely suppressed. The results show that radiation exerts a dual influence on flame spread rate depending on oxygen concentration. If there is more radiative heat loss from the flame, the limiting oxygen concentration increases, and the size of the flamelet decreases. It was observed that in the absence of gas radiation, oscillating near-limit flamelets stabilise and merge into a single flame. Further, the effects of surface radiation were studied by varying emissivity of the solid fuel and it was noted that a more emissive fuel is more susceptible to the formation of flamelets.