Investigation Into Fixed High Pressure Single-Phase Water Mist Fire Suppression System

Water mist fire suppression systems are composed water hydraulic parts, atomization spray heads and some accessories. They only need low water consumption with no environmental pollution and have high extinguishing abilities. As increasing attentions are paid in environment protection and fire fighting, water mist fire suppression technology is developed quickly and has become one of the most important fire control techniques in recent years. There are two problems taking troubles to the rapid advancement of water mist fire suppression technology. One is that the extinguishing abilities of water mist can not be exerted sufficiently, because the atomization effects of water mist spray head are not well satisfied, especially the problem of small spray protecting radius. The other is that people have not grasped all the extinguishing mechanism of water mist, so they can not establish a scientific standard of water mist fire suppression systems. It is necessary to develop highly effective spray heads with larger protection diameter and to provide guideline for the standard of designing and installing water mist fire suppression systems with the help of fire tests and simulations.In this thesis, a fixed high pressure single-phase water mist fire suppression system is investigated by means of theoretical analysis, simulations and experiments. A water mist fire suppression system driven by water hydraulic piston pump is developed and the water hydraulic parts are successfully applied in fire-fighting field. A new two-stage atomizing structure is brought forward and a new two-stage atomizing water mist spray head is developed. The results of CFD spray simulation and spray parameter measurements show that the developed spray head has good fire extinguishing abilities, whose effective protecting radius is 2 m, two times of the radius of common swirl spray heads. Series of water mist extinguishing tests of pool and wood fires are carried out while the dimensional temperature fields of the fire enclosure are measured. The test results show that the shield condition of fire, spray pressure and fire power have important effects on water mist fire suppression. Gasification and suffocation of water mist play a critical role in the process of water mist suppression of pool fires, whereas cooling shows stronger ability for wood fires. CFD water mist fire simulations are done and some results are compared with tests'. Furthermore, the effects of room dimensions, locations of spray head and spray parameters on fire extinguishing time are studied. It is discussed and suggestions are given about how to determine spry intensity of system design. The research achievements can provide referenced basis for both the development of spray heads and the design and installment of water mist fire suppression systems in the future.In chapter 1, the definition, extinguishing mechanism, characters, system classification of water mist fire suppression are introduced. The current research status and the existing problems are summarized. Also the research aim and significance are described.In chapter 2, a fixed high pressure single-phase water mist fire suppression system driven by water hydraulic piston pump is developed. The calculation of system parameters, design of system control and 3D design of system structure are done and the details which should be paid attention to in the progress of system design are explained.