In order to study the fire suppression effectiveness of the ammonium phosphate superfine powder with different kinds of nozzles, a 3 m×3 m×4 m experimental platform was set up according to the standard. One oil pool and three small tanks filled with n-heptane were used as the fire sources, and the total flooding fire extinguishing experiment was carried out under different nozzle configurations. The fire extinguishing time, flame temperature and smoke component concentration changes during the fire extinguishing process were measured, and the influence of the ultra- fine dry powder nozzle structure on the fire extinguishing effectiveness was analyzed and compared. The experimental results show that the single-orifice nozzles fail to extinguish the flame in the upper part of the space, and the multiorifices nozzles are difficult to extinguish the flame between the powder jet. The sprinkler nozzle has the best total flooding fire extinguishing effectiveness due to the best uniformly distribution of the powder. The flame temperatures drop rapidly after spraying powder in all experiments. However, the pool fire temperatures rise again and remain at a temperature slightly below the normal combustion state for multi-orifices nozzles and insufficient powder extinguishing agent conditions. The concentrations of O₂ and CO in space depends mainly on the fire extinguishing time of the pool fire.

superfine powder, nozzle structure, fire extinguishing effectiveness, pool fire, total flooding