Experimental study on enhancing the foam spray range of compressed air foam nozzle

As the core equipment in power systems, ultra-high voltage (UHV) transformers pose a high fire risk. The compressed-air foam spray nozzle is a novel end-release device that, due to its high efficiency and excellent suppression effect on oil-based fires, has been increasingly applied in UHV substations. This study is based on a self-developed experimental platform for compressed-air foam firefighting systems. To meet practical engineering needs, the longitudinal maximum of the contour line at the threshold of 12 L/(min·m²) was selected as the spray range. The study systematically explored the factors influencing the spray range of the spray nozzle. Experimental results revealed that when the hole elevation angle was 60°, the average spray range increased by 59 % compared to 0°. When the nozzle aperture was 10 mm and the outlet pressure was 0.15 MPa, the spray range improved by 17 %. Additionally, as the outlet pressure increased, the foam spray range grew significantly, with a 35.2 % increase at 0.3 MPa compared to 0.1 MPa, indicating that the outlet pressure had a substantial effect on the spray range. To predict the spray range increase, an empirical model is developed for the outlet pressure versus the spray range. After analyzing the above three influencing factors, all the data of various working conditions were integrated into a single dataset, a prediction model of the spray range was established, and the importance of the factors affecting the range was ranked. These findings provide a theoretical foundation for the optimized design and engineering application of compressed-air foam systems (CAFSs).