Fire suppression using water mist with ultrafine size droplets

Abstract

An improved method and apparatus for producing an extremely fine micron and sub-micron size water mist using an electronic ultrasonic device that produces the mist at ambient-pressure and delivering the mist for application in suppressing fire. A piezoelectric transducer is arranged to produce a water mist having at least a portion of sub-micron size droplets. The water mist is produced by high frequency pressure waves or ultrasonic waves of predetermined or variable frequency, including frequencies which may exceed 2.5 MHz. The water mist is directed to a firebase to be self-entrained by the fire's flame. The momentum provided the water mist in directing the mist is minimized to enhance the ability of the fire to entrain the mist, and the flow of the carrier medium is usually directed tangentially about the water fountain creating the mist. Further, the throughput and concentration of the mist is controlled to ensure that the entrained mist will be sufficient to cool and suppress the fire. The water mist may be effectively utilized for mitigating blast and reducing over pressures. The fine water mist may also be utilized for humidification because of its fast vaporization and efficient cooling behavior. The apparatus may be modified in its physical design and direction of output, and the method may be modified by adjusting the throughput of mist, composition of mist, concentration of mist, and momentum of mist, whereby fire may be suppressed under many different scenarios.