http://arxiv.org/abs/1710.02843
We propose a theoretical substantiation of the alternative propagation mechanism explaining origin of the secondary explosion producing the high speeds of combustion and high overpressures in unconfined dust explosions. It is known that unconfined dust explosions consist of a relatively weak primary (turbulent) deflagrations followed by a devastating secondary explosion. The secondary explosions can propagate with a speed of up to 1000 m/s producing overpressures of over 8-10 atm. For example, the over-pressure and damages in the 2005 Buncefield explosion were much higher than that predicted by conventional flame propagation mechanisms. We show that clustering of dust particles in a turbulent flow gives rise to a significant increase of the thermal radiation absorption length ahead of the advancing flame front. This effect ensures that clusters of dust particles are sufficiently long time exposed to and heated by the radiation from hot combustion products of large gaseous explosions to become multi-point ignition kernels in a large volume ahead of the advancing flame front. The ignition times of fuel-air mixture by the radiatively heated clusters of particles is considerably reduced compared to the ignition time by a single isolated particle, so that the radiation-induced multipoint ignitions of a large volume of fuel-air ahead of the primary flame efficiently increase the total flame area, giving rise to the secondary explosion, which results in high rates of combustion and overpressures required to account for the observed level of overpressures and damages in unconfined dust explosions.
M. Liberman, N. Kleeorin, I. Rogachevskii, et. al.
Tue, 10 Oct 17
21/70
Comments: 32 pages, 7 Figures