Flame Front Speed of a Decane Cloud under Microgravity Conditions
In this study, a piezo disk was used to generate a cloud of n-decane fuel drops, which were mixed with air, then carried into a combustion chamber and ignited by a platinum wire. Microgravity data obtained at the Japan Microgravity Center (JAMIC) were compared to normal gravity data, all at 1Atm pressure and 20+/-1°C initial temperature. Under normal gravity the lean limit was found to be 7.6x106/mm3 (Φ = 1.0), and from this point the flame front speed steadily increased from 20cm/s up to a maximum flame front speed of 210cm/s at a fuel drop density of about 14x106/mm3 (Φ = 1.85). Microgravity data showed a much richer lean limit - about 14.5x106/mm3 (Φ = 1.9), and the flame front speed did not gradually rise to a peak value. Instead, the measurements indicated a peak value of about 250cm/s, with a steep increase followed by a gradual decrease at richer fuel air ratios. A cellular flame structure appeared, and the cell size decreased as the mixture density increased.