- Author
-
Goldmeer, J. S.
- Title
- Extinguishment of a Diffusion Flame Over a PMMA Cylinder by Depressurization in Reduced-Gravity.
- Coporate
- Case Western Reserve Univ., Cleveland, OH
- Sponsor
- National Aeronautics and Space Administration, Lewis Research Center, Cleveland, OH
- Report
-
NASA Contractor Report 198550
December 1996
194 p.
- Keywords
-
diffusion flames
|
polymethyl methacrylate
|
reduced gravity
|
combustion
|
low pressure
|
flammability
|
extinction
|
numerical analysis
- Abstract
- Extinction of a diffusion flame burning over horizontal PMMA (Polymethyl methacrylate) clinders in low-gravity was examined experimentally and via numerical simulations. Low-gravity conditions were obtained using the NASA Lewis Research Center's reduced-gravity aircraft. The effects of velocity and pressure on the visible flame were examined. The flammability of the burning solid was examined as a function of pressure and the solid-phase centerline temperature. As the solid temperature increased, the extinction pressure decreased, and with a centerline temperature of 525 K, the flame was sustained to 0.1 atmospheres before extinguishing. The numerical simulation iteratively coupled a two-dimensional quasi-steady, gas-phase model with a transient solid-phase model which included conductive heat transfer and surface regression. This model employed an energy balance at the gas/solid interface that included the energy conducted by the gas-phase to the gas/solid interface,Arrhenius pyrolysis kinetics, surface radiation, and the energy conducted into the solid. The ratio of the solid and gas-phase conductive fluxes was a boundary condition for the gas-phase model at the solid-surface. Initial simulaitons modeled conditions similar to the low-gravity experiments and predicted low-pressure extinction limits consistent with the experimental limits. Other simulaitons examined the effects of velocity, depressurization rate and on extinction.