Abstract: In this paper, FDS is used to study the temperature and flame height of annular pool fire under flame fusion and non-fusion. The results show that the variation trend of the maximum temperature rise of the plume is closely related to the flame state. Introduced the ratio of internal radius to external radius δ,and a new dimensionless flame height H^* is defined. With the same δ, H^* increases with the increase of heat release rate. When the heat release rate of fire source is the same and the flame is fused, H^* shows an upward trend with the increase of δ, and the greater the heat release rate of fire source is, the more obvious the upward trend is. When the fire heat release rate is the same and the flame is not fused, the H^* decreases with the increase of δ. And the empirical characterization models of flame height were proposed under the flame fusion and non-fusion.

Key words: annular pool fire, flame fusion, flame temperature, flame height, numerical simulation