Abstract: A single nozzle spray of compressed air foam and pure water experiments have been conducted with of five typical types of nozzles. The density distribution of the spray medium at the bottom surface and the 25% liquid separation time of the sprayed foam are compared and analyzed. It is found that the structural type and flow parameters of the nozzles will affect the foaming characteristics of the foam. The internal core of the nozzles will reduce the foam stability; the uniformity of the bottom surface of the suspended nozzles is relatively good, while the turbulent nozzle and two types of seven- hole nozzles are relatively uniform, besides, the uniformity of the bottom surface distribution of the suspended nozzle and the gas nozzle under higher pressure and flow conditions is reduced; Meanwhile, nozzles selection of the compressed air foam system can refer to the corresponding nozzle's water spray characteristics. Based on the research, optimal performance nozzle was selected, the fire model was established, and full- scale transformer hot oil fire test of the fixed compressed air foam system was carried out to verify the adaptability of the nozzle and the system.

Key words: compressed air foam, nozzle, distribution density;25% liquid separation time