- Author
-
Prasad, K. R.
|
Li, C.
|
Kailasanath, K.
|
Ndubizu, C.
|
Ananth, R.
|
Tatem, P. A.
- Title
- Numerical Modeling of Fire Suppression Using Water Mist. Part 3. Methanol Liquid Pool Fire Model. NRL Memorandum Report.
- Coporate
- Naval Research Laboratory, Washington, DC
Science Application International Corp., VA
GEO-Centers, Inc., Fort Washington, MD
- Sponsor
- Office of Naval Research, Arlington, VA
- Report
-
NRL/MR/6410-98-8190
October 30, 1998
37 p.
- Keywords
-
water mist
|
fire suppression
|
numerical models
|
diffusion flames
|
methanol
|
liquid fires
|
pool fires
|
fire models
|
mathematical models
|
equations
|
vapor phases
|
thermodynamics
|
kinetics
|
burning rate
|
flame structure
|
temperature profiles
- Identifiers
- boundary and interphase conditions; unsteady pulsating pool fires; steady pool fires
- Abstract
- This report is the third in a series dealing with 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 methane-air diffusion flames. The relative contribution of the various suppression mechanisms was studied and detailed comparison with experimental results was provided. The second report described a computational study for optimizing water-mist injection characteristics for suppression of co-flow diffusion flames. The effect of droplet diameter, mist injection angle (throw angle), mist density and velocity on water-mist entrainment into the flame and flame suppression were quantified. Numerical results were presented for symmetric and asymmetric spray pattern geometries resulting from base injection and side injection nozzle orientation. The focus of this report is on numerical modeling of methanol liquid pool fires. A mathematical model is first developed to describe the evaporation and burning of liquid methanol. Then, the complete set of unsteady, compressible Navier-Stokes equations for reactive flows are solved in the gas phase to describe the convection of the fuel gases away from the pool surface, diffusion of the gases into the surrounding air and the oxidation of the fuel molecules into product species. Heat transfer into the liquid pool and the metal container through conduction, convection and radiation are modeled by solving a modified form of the energy equation. Clausius-Clapeyron relationships are invoked to model the evaporation rate of a two-dimensional pool of pure liquid methanol. The governing equations along with appropriate boundary and interface conditions are solved using the Flux Corrected Transport algorithm. Numerical results exhibit a flame structure that compares well with experimental observations. Temperature profiles and burning rates were found to compare favorably with experimental data from single compartment and three compartment laboratory burners. The model predicts a puffing frequency of approximately 12 hz for a 1 cm diameter methanol pool in the absence of any air-co-flow. It is also observed that increasing air co-flow velocity helps in stabilizing the diffusion flame, by pushing the vertical structures away from the flame region.