Showing papers by "Piotr Wolanski published in 1984"

The shock wave ignition of dusts

Abstract: Dust explosions pose a serious hazard in many industries. The detonability and flam inability of dust/oxidizer mixtures depend on the ignition delay of the dust particles when suddenly exposed to a high temperature environment. Consequently, the ignition delay time of dust particles behind a shock wave in the Mach number range of 4.0-5.0 has been measured using a photomultiplier tube to determine the onset of ignition. The dusts investigated included Pittsburgh Seam Coal, graphite, diamond, oats, and RDX. The experimental arrangement, consisting of a shock tube and two different dust injection devices, is described in detail, and experimental results for dusts ranging in particle size from 2 to 74 /*m are presented. In the Mach number range considered, ignition delay times varied from 2 to 100 /*s. A detailed analytical model based on a solution of the heat conduction equations for the particle interior coupled with a solution of the particle equation of motion has been developed. Heterogeneous reactions occurring on the particle surface and in the pores within the particle are used to model the chemistry. The results were in reasonable agreement with most of the data. Approximate analyses based on a comparison of characteristi c thermal and chemical times were also developed. A key conclusion is that the ignition delay is determined mainly by the heat-up time of the particle surface.