Numerical Study of Thermal Decomposition and Pressure Generation in Charring Solids Undergoing Opposed-Flow Flame Spread.
Numerical Study of Thermal Decomposition and Pressure
Generation in Charring Solids Undergoing Opposed-Flow
Park, W. C.; Atreya, A.; Baum, H. R.
Volume 31; Part 2;
Combustion Institute, Symposium (International) on
Combustion, 31st. Proceedings. Volume 31. Part 2.
August 5-11, 2006, Heidelberg, Germany, Combustion
Institute, Pittsburgh, PA, Barlow, R. S.; Sick, V.;
Glarborg, P.; Yetter, R. A., Editor(s)(s), 2643-2652 pp,
combustion; fire research; flame spread; thermal
decomposition; pressure; solids; wood; charring; char;
pyrolysis; equations; mathematical models; conservation;
kinetics; reaction kinetics; temperature
Thermal decomposition and pressure generation in
charring solids undergoing opposed-flow flame spread
have been numerically studied with a detailed
physics-based model. The physical problem is modeled as
a steady state two-dimensional process including three
parallel finite rate reactions and volatiles convection.
Local thermal equilibrium is assumed between char matrix
and volatiles. For pressure calculation, the volatiles
are assumed to follow the ideal gas law and Darcy's law.
Numerical result indicates that the char density and
product yields are functions of depth due to an
insulating char layer. In addition, the characteristics
of various simplifying assumptions such as global
reaction, infinite rate kinetics and no convective gas
transport have been investigated. The global reaction
model shows excellent agreement on char layer thickness
with the detailed model. However, it predicts higher
pressure inside the charring solid. Infinite reaction
rate model shows thicker char layer in the fore region
and thinner char layer in the downstream region due to
constant pyrolysis temperature. Also, it shows lower
pressure in the char. Simplified
energy model predicts thicker char and higher pressure
than the detailed model.