  Thermal radiation of the hot combustion products usually does not influence
noticeably the flame propagating through gaseous mixture. the situation is
changed drastically in the presence even small concentration of particles,
which absorb radiation, transfer the heat to the surrounding unburned gaseous
mixture by means of heat conduction, so that the gas phase temperature in front
of the advancing flame lags that of the particles. It is shown that radiative
preheating of unreacted mixture ahead of the flame results in a modest increase
of the advancing flame velocity for a highly reactive gaseous fuel, or to
considerable increase of the flame velocity in the case of a slow reactive
mixture. The effects of radiation preheating as stronger as smaller the normal
flame velocity. The radiation heat transfer can become a dominant mechanism
compared with molecular heat conduction, determining the structure and the
speed of combustion wave in the case of a small enough velocity of the
advancing flame. It is shown that in the case of non-uniform distribution of
the particles, such that time of the radiation heating is longer so that the
maximum temperature in the region of denser particles cloud ahead of the
advancing flame is sufficient for ignition, the thermal radiation may trigger
additional independent source of ignition. Depending on the steepness of the
temperature gradient formed in the unburned mixture, either deflagration or
detonation can be initiated via the Zeldovich's gradient mechanism. Ignition of
different combustion regimes, depending on the radiation absorption length, is
illustrated for the particle-laden hydrogen-oxygen flame.
