Opposed-Flow Ignition and Flame Spread Over Melting Polymers With Navier-Stokes Gas Flow.
Opposed-Flow Ignition and Flame Spread Over Melting
Polymers With Navier-Stokes Gas Flow.
Zheng, G.; Wichman, I. S.; Benard, A.
Combustion Theory and Modelling, Vol. 6, No. 2,
317-337, June 2002.
Sponsor:National Institute of Standards and Technology,
Available from:ONLINE AT: http://stacks.iop.org/CTM/6/317
gas flow; ignition; flame spread; polymers; numerical
models; polymethyl methacrylate; mathematical models;
equations; physical models; flame spread rate; flame
A numerical model is constructed to predict transient
opposed-flow flame spread behaviour in a channel flow
over a melting polymer. The transient flame is
established by initially applying a high external
radiation heat flux to the surface. This is followed by
ignition, transition and finally steady opposed-flow
flame spread. The physical phenomena under consideration
include the following: gas phase: channel flow, thermal
expansion and injection flow from the pyrolyzed fuel;
condensed phase: heat conduction, melting, and
discontinuous thermal properties (heat capacity and
thermal conductivity) across the phase boundary;
gas-condensed phase interface: radiation loss. There is
no in-depth gas radiation absorption in the gas phase.
It is necessary to solve the momentum, species, energy
and continuity equations in the gas along with the
energy equation(s) in the liquid and solid. Agreement is
obtained between the numerical spread rate and a flame
spread formula. The influence of the gas flow is
explored by comparing the Navier-Stokes (NS) and Oseen
(OS) models. An energy balance analysis describes the
flame-spread mechanism in terms of participating heat