- Author
- Prasad, K. R. | Li, C. | Kailasanath, K.
- Title
- Numerical Modeling of Fire Suppression Using Water Mist. Part 2. An Optimization Study on Jet Diffusion Flames. NRL Memorandum Report.
- Coporate
- Naval Research Laboratory, Washington, DC Science Application International Corp., VA
- Sponsor
- Office of Naval Research, Arlington, VA
- Report
- NRL/MR/6410-98-8159, June 22, 1998, 26 p.
- Keywords
- water mist | fire suppression | numerical models | diffusion flames | jet flames | droplets | vapor phases | equations | flame suppression | extinction | water supply | fuel flow rate
- Identifiers
- base injection configuration: co-flow injection; symmetric/asymmetric injection configuration; base injection configuration: angle injection; side injection configuration; top injection configuration
- Abstract
- This report is the second in a series that discusses the numerical modeling of fire suppression using water-mist. In the first report, a numerical study was described for obtaining a detail understanding of the physical processes involved during the interaction of water-mist and flames. The relative contribution of the various suppression mechanisms for methane-air diffusion flames was studied and detailed comparison with experimental results was provided in the first report. The present report describes a computational study for optimizing water-mist injection characteristics for suppression of co-flow diffusion flames. A two-continuum formulation is used in which the gas phase and the water-mist are both described by equations of the Euletian form. Numerical simulations are performed to optimize various water-mist injection characteristics for maximum flame suppression. The effects of droplet diameter, mist in injection angle (throw angle), mist density and velocity on water-mist entrainment into the flame and flame suppression are quantified. Droplet sectional trajectories and density contours are used to identify the regions of the flame where the droplets evaporate and absorb energy. Numerical results are presented for symmetric and asymmetric spray pattern geometries resulting from base injection and side injection nozzle orientation. Results indicate that smaller droplet diameters produce optimum suppression under base injection configuration, while larger droplet diameters are needed for optimum suppression for the side injection configuration. For all cases, the model is used to determine the water-mist required for extinction, and this is reported in terms of the ratio of the water supply rate to the fuel flow rate.