Evaluation of Buoyant Flow Velocity Induced by Centrifugal and Coriolis Acceleration During Downward Flame Spread Over Thin Wire in a Centrifuge

Centrifuges are effective devices for observing physical phenomena in various gravitational fields. This study discusses the effectiveness of observing flame spread phenomena along the solid materials in centrifuges as a basis for spacecraft fire safety. Flame spread tests are carried out on the ground in the present study. Thin wires which consist of a metallic core and polymer insulation are used as test samples. A sample is supported vertically in a chamber at 120 mm apart from the axis of rotation. The upper end of the sample is ignited by a hot wire and subsequent downward flame spread under varied centrifugal force is observed. A spreading flame leans to the radial direction due to centrifugal force, but also to the circumferential direction due to the Coriolis force. By measuring the flame tilt angle, we attempt to predict the buoyant flow velocity affecting the spreading flame, based on the scale analysis at the location of sample. The buoyant flow velocities obtained in this study are similar to those reported in previous studies, indicating the validity of analysis method. Those results show that the centrifuge can be used not only to investigate the material flammability under arbitrary gravitational field, but also to evaluate the buoyant flow velocity that affects the flame spreading along the solid materials.