The temperature and pressure changes of nitrogenfire extinguishing agent two- phase transient flow under different discharge pressures were obtained by setting up a fixed pipeline agent discharge and flow experimental device. The spraying process, pressure behavior, and thermal properties of Halon 1301 were analyzed. In the agent discharge process, the following pressure behaviors occur in sequence A: The flow front moves to the nozzle. B-C: The phenomenon of nitrogen degassing and nucleation occurs in the metastable extinguishing agent. D: Halon 1301 is sprayed from the nozzle with a mixture of nitrogen. E: Liquid Halon 1301 is drained from the fire extinguisher. F: Gas phase Halon 1301 moves with nitrogen mixture to the nozzle. G: The flow state of the mixture at the nozzle reaches critical flow. The discharge pressure has little effect on the dimensionless pressure of pressure behavior and thermal

properties in the nozzle except for nitrogen degassing and nucleation. In the liquid holdup phase, the A, D, E, and F pressure behavior's dimensionless pressure are not related to the discharge pressure but only to the experimental conditions. The density of Halon 1301 at the nozzle fluctuates between 1 660 kg/m³ and 1 800 kg/m³ , while the superheat remains between -18 ℃ and -

23 ℃. Discharge pressure mainly affects the occurrence time of pressure behavior, and there is an exponential change law between them. Therefore, increasing discharge pressure can effectively shorten the discharge time.

aircraft fire suppression, transient two- phase flow, Halon 1301, discharge pressure, pressure behavior