抄録
Flame spreading over natural gas hydrate in a laminar boundary layer of air is experimentally investigated. The hydrate surface temperature when the pilot burner is ignited (T_<s,ig>) is varied between -90℃ and -20℃ and free stream velocity U_∞ is set at 0.4 ,0.7 or 1.1m/s. Two types of flame spreading is observed. One is the low speed linear spreading due to the heat transfer from the leading flame edge to the hydrate surface. This type of the flame spreading is observed when T_<s,ig> is relatively low and U_∞ is relatively high. The other is the high speed oscillating spreading. The leading flame edge spreads toward the upstream end of the hydrate with very high speed but suddenly disappear. This fast spreading and disappearance repeatedly occurs and finally the stable flame is formed. This type of the flame spreading is observed when T_<s,ig> is relatively high and U_∞ is relatively low.
