Some 3-D gas flow effects in detonator delay elements

Abstract

In a previous paper, Norgrove et al [1], we studied theoretically the one- dimensional propagation of a flame front down a detonator delay element when there is significant gas production. The heat and mass balance equations were solved numerically to determine the effect of axial gas flow on the flame speed under various confinement conditions and the results were compared with experimental results obtained by Beck [2], Beck and Brown [3], and with theoretical asymptotic results. The purpose of this paper is to extend the one-dimensional model to a three dimensional axisymmetric situation in which there is radial heat transfer by conduction to and from the aluminium wall of the detonator delay element. This is a much more complex situation since gas produced in the reaction can flow both radially and axially convecting heat. Moreover heat can flow axially in the metal wall, preheating the cold unreacted pyrotechnic ahead of the flame front. These two effects are strongly coupled. A typical detonator is illustrated in Fig.1.1.