FLAME SPREAD OVER CHARRING THIN CYLINDRICAL FUELS IN OXYGEN-ENRICHED NORMAL AND MICROGRAVITY ENVIRONMENTS

In this study, we investigated flame spread phenomena over charring combustible rods (cellulose) of sub-millimeter diameter (0.6 mm). The ambient oxygen concentration was varied in the range of 25%-40% in both normal and microgravity environments. The flame spread phenomena were recorded using a camera and the flame characteristics and spread rates were obtained using image processing of the captured frames. The numerical simulation of the flame spread processes was also carried out using a two-dimensional axisymmetric in-house computational fluid dynamics code in order to understand the details of the flow and heat transfer processes in the spreading flame. Gravity influenced the flow field in and around the flame; therefore, the flame size, heat transport and spread rate were also affected. Increases in the oxygen level also influenced the flame temperature and flow and heat transport phenomena. Despite having lower temperatures compared to normal gravity flames, the microgravity flames were larger and spread faster. The results of this work explain the transport processes leading to the observed phenomena.