Research On High-pressure Water Mist Nozzle And Its Characteristics Of Fire Suppression

As development of morden society and advance of science & technology, methods to suppress and extinguish fire bring up the higher requirement. Halon will be banned by most countries worldwide due to its adverse effect on the ozone layer. It has brought the development of alternative fire-fighting methods into focus. In view of its significant advantages including environment-friendly, fast and effective fire suppression, etc., water mist fire extinguishing system has been recognized as the most potential substitute of halon fire-fighting system. Nozzle is a key component that is essential to all kinds of high-pressure water mist fire extinguishing systems. Therefore, research on nozzle's atomizing mechanisms and characteristics and its fire suppression characteristics in this dissertation has great significance for the development and application of the high-pressure water mist fire extinguishing technology. The mechanisms and advantages of high-pressure water mist fire extinguishing technology are analysed. Atomizing mechanisms of liquid is discussed. After comparison of various atomizers, centrifugal nozzle is selected for the spray head used in the high-pressure water mist fire extinguishing systems. The inner flow field of centrifugal nozzle is theoretically analysed. Conclusions that are useful for the design of nozzles are deduced. Lots of experiments on the atomizing characteristics of several types of nozzles are carried out by the use of a laser particle size analyzer. The results show that: The increase of pressure can lead to the decrease of particle size and it is beneficial to particle size distribution. The increase of pressure can result in the increase of flux, but the flow coefficient of nozzle is constant. With the increase of measure distance, particle size of mist droplets becomes bigger. Meanwhile it decreases the coefficient of uniformity degree of mist droplets. The augment of spray angle can lead to the decrease of particle size. Particle size of droplets is in direct proportion to the square of the diameter of spout. These conclusions lay the foundation for the design and application of nozzles. Different extinguishing systems are proposed to meet various application requirements. The prototype of a portable high-pressure water mist fire extinguisher is designed. Experiments of fire suppression characteristics are carried out with fixed extinguishing systems and portable extinguisher. The results show that high-pressure water mist fire extinguishing systems perform well in extinguishing fires. It has advantages such as less water consume, fast and effective fire suppression, no harm to human beings and little damage to equipments.