Abstract: Abstract: The combustion experiments of outdoor multiple fires and single pool fire were carried out under different pool diameter (1.0, 1.4, 1.7 m) and different pool spacing (1.5D, 1.75D, 2D). In the experiment, camera, electronic balance andthermocouples were used to monitor the flame height, the burning rate and the flame temperature respectively. Results show that the burning rate of each fire in the multiple-fire experiments is higher than that of a single pool fire with the same diameter, and when the flame mergence occurs at the distance of 1.5D, the merging flame height is higher than single pool fire flame height with the same diameter, indicating that the combustion risk of multiple-fire is greater. In addition, after the four flames mergence, the exponential changes of flame temperature at the geometric central axis with height are 0.13, [-1.02] and [-1.46], which is basically consistent with the recognized central axis temperature change of common buoyant pool fire, which indicates that multiple flames merge into a common buoyant pool fire.

Key words: Key words: outdoor multiple fires, burning rate, flame temperature, flame height, experimental study