Abstract: In order to investigate the influence of the high altitude low pressure environment on water mist fire extinguishing effectiveness. Carried out a series of fine water fog field characteristics of different environmental pressure experiments and fire extinguishing experiments, studied high altitude low pressure environmental conditions on the spray characteristics of the relationship, revealed the fire extinguishing mechanism of fine water mist in low-pressure environments. Research has shown that in high-altitude low-pressure environments, with a constant nozzle cone angle, increasing the nozzle flow coefficient K results in a higher water mist flow rate in low-pressure areas under the same working pressure. Compared with normal pressure, air density decreases with decreasing pressure, and the interaction between water mist and surrounding air weakens when sprayed out of the nozzle, resulting in an increase in water mist particle size. Through fire extinguishing experiments, it has been verified that fine water mist improves the cooling effect on high-temperature fuel surfaces in low-pressure environments without changing the dilution and oxygen isolation function. Therefore, fine water mist has better fire extinguishing efficiency in low-pressure environments.

Key words: plateau low-pressure environment, water mist, diesel fire, spray pressure, fog field characteristics