UNSTEADY RANS MODELING OF WATER-SPRAY SUPPRESSION FOR LARGE-SCALE COMPARTMENT POOL FIRES

摘要

This paper presents a computational study of the effect of water-spray characteristics on the suppression of a large-scale (2 m X 2 m) JP-8 pool fire in a 10 m x 10 m X 10 m compartment with an open ceiling.The numerical model is based on an unsteady Reynolds-averaged Navier-Stokes formulation using a stochastic separated flow approach for the droplets that includes detailed descriptions of the interaction between water droplets and fire plume.Simulation results indicate that water-spray injection causes the gas temperature to rise due to the initial enliancement of the turbulent mixing.A threshold suppression condition is achieved when the injected droplet carries enough momentum (injection speed range is 20-80 m/s) to penetrate the fire plume and evaporate in the flame regions where most of the gas-phase combustion is taking place.In addition,the droplet size (ranging from 100-800 mu m) should be small enough to yield quick evaporation when in contact with the flame surface for efficient cooling.Based on a parametric study,a preferred fire suppression configuration is recommended for the systems considered.