Observation of Flame Spreading over Electric Wire under Reduced Gravity Condition Given by Parabolic Flight and Drop Tower Experiments

Abstract

Ground-based, microgravity experiments attained by aircraft parabolic flight and drop tower on flame spread phenomenon over electric wire are performed. These are the preliminary tests for expected long-term microgravity experiments by sub-orbital or on orbit microgravity experiment. The main objectives of this study are (1) to confirm the apparatus can be work properly in microgravity and (2) to show the necessity of long-term microgravity experiments in order to observe the unsteady phenomenon. The flame spread rate and the total soot volume are important items as fundamental characteristics of the spreading flame. From the parabolic flight test, which can provide relatively long microgravity period, it is confirmed that the apparatus can work properly in microgravity. On the other hand, the quality of microgravity provided by aircraft is fair including G-jitters, and dependable data in the slow external flow velocity regime is hardly expected. Flame spread rate and the total soot volume are measured by drop tower, which can provide 10-4G microgravity environment. Although, in some conditions, the flame spread phenomenon seems to reach steady-state within the available microgravity time with the drop tower (∼ five seconds), the phenomenon includes periodical change in flame shape in reality. Consequently, to confirm the actual steadiness of the spread phenomenon, at least 10-4G microgravity environment and long-term microgravity environment is necessary.