Evaluation of Fire-Extinguishing Performance of HFC-125a Gas Hydrate Fire-Extinguishing Projectiles Based on Discharge Method

This study evaluated the effects of fire class and discharge method on the fire-extinguishing characteristics of HFC-125a gas hydrate fire-extinguishing projectiles. Direct and indirect discharge tests were conducted for Class A and Class B liquid fires using a Grade 4 fire test model based on the “Technical Standards for Type Approval and Product Inspection of Automatic Gas and Powder Fire-Extinguishing Systems.” Fire temperature, oxygen concentration, extinguishing time, and reignition were analyzed. In the Class A Grade 4 direct-discharge test, visible flame was extinguished within approximately 1 s after discharge, and the temperature directly above the fire source decreased from approximately 780 ℃ to 105 ℃ without reignition. In the Class A indirect-discharge test, visible flame was extinguished at 482 s. In the Class B Grade 4 direct-discharge test, fuel scattering and rapid flame spread occurred. Additionally, sustained flaming was observed in the Supplementary Grade 3 test, thus indicating the limited extinguishing applicability of direct discharge. By contrast, indirect discharge extinguished Class B fire at 430 s, thereby reducing the extinguishing time by 153 s—or approximately 26.2%—compared with that (583 s) under natural burning conditions. Therefore, direct discharge is considered suitable for Class A wood fires, whereas indirect discharge is more appropriate for Class B liquid fires.