Spray Characteristics Determination of Water Mist for Suppressing Pool Fire

摘要

To optimize the design of a water mist fire suppression system or to provide input data and validation data for field models, the characteristics of the water mist field are needed. This data typically consists of the distribution of droplet sizes and velocities. In this research a LS2000 Laser Sizer has been proposed to simultaneously determine spray characteristics of 408 kinds of self-developed nozzles for fire suppression. The results of LS2000 Laser Sizer measurements to characterize the water mist produced by nozzles for suppressing pool fire are presented. These data can provide a foundation to the design and optimization of additive-containing WMFSS. To explore the effect of the water pressure on the droplet size distribution and spray velocity, data from three typical pressures of 0.9MPa, 1.2MPa and 1.5MPa have been obtained. With the measured average size and distribution of droplets, a comparison between three nozzles was made in the pressure of 1.5MPa to investigate the influence of the nozzle design parameters on atomizing characteristics. The results show that representative size of droplets decreases slightly and the water flow rate increases with the water pressure to the nozzle head P_(w), and the droplet velocity of water mist is approximately directly proportional to P_(w). The trends that the nozzles with the larger D_(32) have a wider range of droplet diameter distribution and their volume fraction curves shift towards the large diameter direction are also found in measurements. This will be favorable to the extinguishment of kerosene pool fire. The water flux density distribution results demonstrated that the water flux density over the cross section was very non-uniform when the water mist nozzle is improperly designed.