Model for High Rate Gas Flows in Deformable and Reactive Porous Beds

摘要

This report presents the development of a one dimensional planar Lagrange hydrodynamic computer model which describes the processes preceding detonation. The model treats gas flow, deflagration, and compaction in a porous bed of reactive material. The early part of deflagration to detonation experiment with porous HMX is simulated. Sensitivity of the simulation calculation to ignition and burn rate parameters is illustrated and discussed. The effects of changing the mean particle size of the porous material are investigated. There is widespread interest in runaway reaction hazards that may be associated with porosity in propellant and explosive materials. Experimentally, such reactions are initiated and observed in long, thick walled hollow tubes, filled with a granular porous bed of reactive material. We will present comparisons with an experiment on porous HMX to illustrate details of the model and to point out what we believe are important features of the observed phenomenon. A geometric finite element cell is devised that allows gas to flow through a compacting matrix. The experimental simulation considers the DDT process from initial squib burn through the onset of general matrix deflagration (convective burning), to the development of a fully dense compaction wave. While this simulation did not calculate turnover to detonation, it did illustrate that the transition occurred as soon as the compaction wave became fully dense. It is shown that deflagration and gas permeation lags compaction at the time of transition. This suggests that the actual transition involves an additional compaction dependent process. 18 references, 20 figures, 3 tables. (ERA citation 10:011582)