| A numerical model was developed in this Ph.D. project to simulate waterfog fire suppression systems in a shipboard machinery room. The methodology for modelling such a two-phase interactive transient process is based on the Euterian-Lagrangian formulations for the gas phase and liquid (droplets) phase, relatively, and a Gaussian approach for the turbulence dispersion of the droplets. The development and suppression of the turbulent diffusion flame, originating from the evaporation of liquid fuel pool in the machinery room, were fully simulated using appropriate combustion and radiation models. The rate of fuel vapour combustion is determined using a modified eddy dissipation model, which takes into account the effect of gas-phase temperature drop due to droplet cooling on the chemical reaction during the fire suppression. A convergence criterion was established for the two-phase interactive process with intensive inter-phase exchanges of mass, momentum and energy. Techniques were developed to stabilise and accelerate the numerical iterative process. Basic validations of the program were conducted, and the overall model for fire suppression with waterfog was validated on a preliminary basis. The mechanisms of fire suppression with fine water sprays within the machinery room were analysed. The example for application of the numerical model in an obstructed room has shown the capability of the present model for effective design of the waterfog system. |
