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Nordita Astrophysics seminars

Influence of radiative preheating on combustion regimes of flames propagating in gaseous mixtures seeded with inert particles

by Mikhail Liberman (Nordita)

122:026 ()


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.