High propagation rates of explosions in large volumes of gaseous mixtures

Abstract

To account for the level of damage observed following unconfined vapour cloud explosions of the kind that occurred at Flixborough in 1974, flame speeds of the order 10² m s⁻¹ have had to be postulated^1,2. Detonations (in which reaction is initiated by adiabatic compression in a shock wave) are not thought to be involved, whilst deflagrations (in which molecular and turbulent transport processes from the flame bring the reactants to a state of rapid reaction) do not seem capable of producing sufficiently high velocities. We suggest here that radiation from a large enough body of burnt products could be sufficient to produce multi-point initiation ahead of the flame by igniting particles, especially those consisting of loose aggregates of fine fibres. Although we thought initially that the hazard would chiefly be due to particles of flammable materials, such as cotton waste and other ‘fluffy’ aggregates of cellulosic substances, we show below that non-flammable materials are also hazardous.