Design, Development, and Analysis of a Twin-Fluid Fire Suppression Atomizer and Characterization of Electrostatically Charged Droplet Sprays

• Main Author: Moore, Chad Everett
• Other Authors: Sumanta Acharya
• Format: Others
• Language: en
• Published: LSU 2003
• Subjects: Mechanical Engineering
• Online Access: http://etd.lsu.edu/docs/available/etd-1112103-104824/

A twin-fluid water mist fire suppression atomizer is designed, developed, and analyzed. Of primary interest is the development of a twin-fluid atomizer that produces a large droplet diameter and velocity distribution and also produces a mist with sufficient cone angle to be effective in fire suppression applications. Spray characterization experiments are conducted utilizing Phase Doppler Particle Analysis (PDPA). The effect of atomizer nozzle geometry on internal two-phase flow and resulting spray pattern is investigated. National Fire Protection Association (NFPA) Standard 750 characterization experiments are conducted to verify that the sprays produced by the developed atomizer are classified as a water mist as defined by the Standard. Water mist sprays are produced using three different atomizing gases: Carbon Dioxide, Helium, and Nitrogen. PDPA measurements obtained utilizing all three gases are compared and analyzed. Full-scale fire suppression experiments are conducted using the developed twin-fluid atomizers. Identical experiments are conducted with a commercially available water mist atomizer to provide a basis for comparison. Fire tests are conducted on Class B fires consisting of pool, spray, jet, and simulated machinery space fires. The locations of the fires relative to the atomizer are varied to study the effects of atomizer position on fire suppression performance. The results reported herein indicate the atomizers ability to rapidly extinguish Class B fires. Also, the mechanisms of extinguishment for each fire scenario are described. Particle Image Velocimetry (PIV) measurements are conducted on charged droplet sprays. A Spray Triodeâ electrostatic atomizer is utilized to study the effects of charged droplet sprays with varying electrical boundary conditions near the exit of the atomizer. The boundary conditions near the atomizer are varied by placing grounded and ungrounded obstructions in the spray flow field. The experimental results indicate .the charged droplets ability to wrap around objects and sustain counter gravity flow.