Abstract: A temperature sensitive self-starting fire extinguishing pipe system with no power supply was designed for closed space fire accident of electric vehicle battery box. The fire source was simulated using n-heptane. The test was carried out in a test chamber using perfluorohexanone and hexafluoropropane as the extinguishing medium. The fire extinguishing process, pressure change in the pipe, use rate of fire extinguishing agent and fire extinguishing time were analyzed under the pressure of 0, 0.88 and 1.81 MPa. The results show that the fire extinguishing process of perfluorohexanone and hexafluoropropane fire pipe systems is similar, which can be divided into three stages: preheating-pipe rupture jet-flame extinguishing and continued jetting, that the actual use rate of extinguishing agent for hexafluoropropane fire extinguishing pipe system is 100%, that the actual use rate of perfluorohexanone fire extinguishing pipe system is between 50% and 95%, and the increase of pressure greatly increases the actual use rate of perfluorohexanone, that the hexafluoropropane fire extinguishing pipe system can extinguish the fire within 20 s, and that the fire extinguishing time of the perfluorohexanone fire extinguishing pipe system is longer than that of hexafluoropropane fire extinguishing pipe system.

Key words: electric vehicle fire, closed space, pressure change, extinguishing agent usage rate, temperature-sensing self-starting fire extinguishing pipe system, fire extinguishing time