Burning-Rate Models and Their Successors: A Personal Perspective
Final rept. 1 Sep 2002-25 Mar 2003
ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
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The development of models to compute the burning rate of energetic materials has undergone a paradigm shift in the last 15 years from treating the gas-phase reactions as a few global reactions to attempting to describe all of the elementary reactions involved. This shift toward chemical specificity has brought the promise of true predictive capability in such models. Thwarting this promise, however, has been the unattainability of treating the condensed-phase and surface processes with commensurate detail and assurance. In this work, it is shown that limited predictability has recently been achieved by a semi- empirical finesse of the condensed-phase reactions and surface gasification through the agency of a universal pyrolysis law for certain families of propellant ingredients. It is also argued that the long-range prognosis for generalized predictability arising from a first-principles three-phase model lies with developing submodels for the condensed-phase and surface phenomena based on molecular dynamics MD. However, since a continuum description of the gas-phase processes will always be preferable, the mating of these MD submodels with the continuum gas-phase description will be a non-trivial research issue. To facilitate the coming dialogue between current continuum modelers and future MD modelers, this work describes the conceptual and mathematical basis of the continuum models in considerable detail. It is suggested that the mating of these disparate descriptions might be accomplished by developing simple, idealized continuum submodels whose parameters and assumptions might be justified by the MD submodels. An example of such a continuum submodel is developed for the process of multicomponent evaporation as a surface-gasification mechanism.
- Combustion and Ignition