Influence of radiative preheating on combustion regimes of flames propagating in gaseous mixtures seeded with inert particles
by
Mikhail Liberman(Nordita)
→
Europe/Stockholm
122:026
122:026
Description
At normal terrestrial conditions the radiation of hot combustion products
has negligibly small effect and does not influence the flame propagation
because the unburned gaseous fuel is almost fully transparent for radiation.
The situation changes drastically in the presence of particulates suspended
in the gaseous mixture, which is typical for e.g., coal mine, chemical
industry, forest fire, etc. In the latter case the radiant energy flux is
absorbed by the particles. Particles preheated by the radiation heat the
surrounding unburned gaseous mixture affecting the flame dynamics. The
radiative preheating in the presence of suspended micro particles may result
in different scenarios depending on the spatial distribution of the
particles, radiation absorption length and reactivity of the mixture (highly
reactive e.g. hydrogen/oxygen or slow flames). The result of radiative
preheating can be a modest increase of the temperature ahead of the flame
and corresponding modest increase of the combustion velocity for the fast
flames or noticeable increase and oscillation of the flame velocity for slow
flames in the case of uniform spatial distribution of the particles. For the
case of non-uniform spatial distribution it is ignition of either
deflagration or detonation initiated via the Zeldovich's gradient mechanism
far ahead of the flame. I will show the results of our numerical simulation
for the case of gaseous H2/O2 with a detailed chemical kinetics and discuss
possibility of the radiative transfer as a propagation mechanism of
combustion wave.