Analysis of the critical conditions for ignition of gas–particle mixtures by a heated body with pulsed energy supply

The critical conditions for the ignition of solid particles suspended in a gas by a heated body with pulsed energy supply are determined using numerical and approximate methods. It is shownthat in the kinetic (one-temperature) ignition regime, the critical duration of the thermal pulse is equal to the time of establishment of a zero gradient on the interface between the heaterand the gas–particle mixture. In the diffusive (two-temperature) ignition regime (small coefficients of heat transfer between the particles and the gas), the critical duration of the thermal pulse is much shorter than the time of establishment of a zero gradient. It is established that the critical duration of the thermal pulse is determined from the condition that the time of complete particle burnout on the interface between the heater and the gas–particle mixture is equal to the time of repeated heating of the gas to the temperature of the transition of the particle oxidation reaction tothe diffusive reaction regime. An approximate method for calculating the critical duration of the thermal pulse for the diffusive ignition regime is proposed. Numerical calculations show that the minimum time of establishment of the high-temperature combustion regime is reached when the thermal pulse duration is equal to the time of attainment of a zero pressure gradient on the interface between the heater and the gas–particle mixture.