Download or read book On the Stability of Deflagration Through a Porous Energetic Material written by Stephen B. Margolis and published by . This book was released on 1995 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Over pressure Effects on the Stability of Deflagrations on Confined Porous Energetic Materials written by Alexander M. Telengator and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Structure and Stability of Deflagrations in Porous Energetic Materials written by and published by . This book was released on 1999 with total page 49 pages. Available in PDF, EPUB and Kindle. Book excerpt: Theoretical two-phase-flow analyses have recently been developed to describe the structure and stability of multi-phase deflagrations in porous energetic materials, in both confined and unconfined geometries. The results of these studies are reviewed, with an emphasis on the fundamental differences that emerge with respect to the two types of geometries. In particular, pressure gradients are usually negligible in unconfined systems, whereas the confined problem is generally characterized by a significant gas-phase pressure difference, or overpressure, between the burned and unburned regions. The latter leads to a strong convective influence on the burning rate arising from the pressure-driven permeation of hot gases into the solid/gas region and the consequent preheating of the unburned material. It is also shown how asymptotic models that are suitable for analyzing stability may be derived based on the largeness of an overall activation-energy parameter. From an analysis of such models, it is shown that the effects of porosity and two-phase flow are generally destabilizing, suggesting that degraded propellants, which exhibit greater porosity than their pristine counterparts, may be more readily subject to combustion instability and nonsteady deflagration.

Download or read book Stability of Quasi Steady Deflagrations in Confined Porous Energetic Materials written by and published by . This book was released on 2000 with total page 53 pages. Available in PDF, EPUB and Kindle. Book excerpt: Previous analyses have shown that unconfined deflagrations propagating through both porous and nonporous energetic materials can exhibit a thermal/diffusive instability that corresponds to the onset of various oscillatory modes of combustion. For porous materials, two-phase-flow effects, associated with the motion of the gas products relative to the condensed material, play a significant role that can shift stability boundaries with respect to those associated with the nonporous problem. In the present work, additional significant effects are shown to be associated with confinement, which produces an overpressure in the burned-gas region that leads to reversal of the gas flow and hence partial permeation of the hot gases into the unburned porous material. This results in a superadiabatic effect that increases the combustion temperature and, consequently, the burning rate. Under the assumption of gas phase quasi-steadiness, an asymptotic model is presented that facilitates a perturbation analysis of both the basic solution, corresponding to a steadily propagating planar combustion wave, and its stability. The neutral stability boundaries collapse to the previous results in the absence of confinement, but different trends arising from the presence of the gas-permeation layer are predicted for the confined problem. Whereas two-phase-flow effects are generally destabilizing in the unconfined geometry, the effects of increasing overpressure and hence combustion temperature associated with confinement are shown to be generally stabilizing with respect to thermal/diffusive instability, analogous to the effects of decreasing heat losses on combustion temperature and stability in single-phase deflagrations.

Download or read book Investigation on Deflagration to Detonation Transition in Porous Energetic Materials Final Report written by and published by . This book was released on 1995 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Two step Asymptotic Analysis of Deflagration in Porous Energetic Materials written by Stephen B. Margolis and published by . This book was released on 1996 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Analysis of a Two temperature Model of Deflagrations in Confined Porous Energetic Materials written by Stephen B. Margolis and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effects of Two phase Flow on the Deflagration of Porous Energetic Materials written by Stephen B. Margolis and published by . This book was released on 1995 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 500 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Modeling and Numerical Simulation of Deflagration to detonation Transition in Porous Energetic Materials written by Shaojie Xu and published by . This book was released on 1996 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt: An understanding of the deflagration-to-detonation transition (DDT) in porous energetic materials is important for various engineering applications. Safety issues for damaged explosives is one example. In this work, two topics related to multi-dimensional simulation of DDT in energetic materials are presented. The objective of the first part is to develop a simple and predictive model for multidimensional simulations. Models constructed by two-phase mixture theory usually have complicated mathematical formulation, and admit complex dispersive wave structures. Three simplified single-velocity models, named BKS, SVG and GISPA, are considered in this work. The BKS model was derived--using asymptotic theory--from the two-phase theory by assuming a large interphase drag. The SVG model is newly developed, based on solid-void-gas three-phase formulation. The GISPA model is a new single-phase model which utilizes two independent rate processes for compaction and reaction. In addition to model simplification, a new reaction rate law is developed which describes the slow and the fast energy-release processes during DDT. A comparative study is carried out and the study shows that the SVG and GISPA models are able to predict all the events measured in 1-D DDT-tube experiments. The second part of the study describes the development of a high-quality numerical method for two-dimensional DDT simulations. The new fourth-order method integrates total variation diminishing and essentially non-oscillatory schemes with an extension to a general equation of state. In order to handle complex geometry, an internal boundary algorithm is developed on a structured grid, which allows a two-dimensional, non-deformable body of an arbitrary shape to be inserted in a flow field. A DDT simulation is carried out for cases of both blunt-body and sharp-body impact on porous energetic materials. The radius effect (in the case of blunt-body impact) and the angle effect (in the case of sharp-body impact) on detonation properties are studied.

Download or read book Effects of Two phase Flow on the Deflagration of Porous Energetic Materials written by and published by . This book was released on 1994 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Eigen value Calculations for Porous Energetic Material Deflagration in the Merged flame Regime written by Nenad Ilincic and published by . This book was released on 1997 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Analyses of Combustion Processes in Porous Energetic Materials written by Alexander M. Telengator and published by . This book was released on 2000 with total page 314 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Intrusive and Nonintrusive Deflagrations in Confined Porous Energetic Materials written by Stephen B. Margolis and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Combustion of Porous Energetic Materials in the Merged flame Regime written by and published by . This book was released on 1996 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: The structure and burning rate of an unconfined deflagration propagating through a porous energetic material is analyzed in the limit of merged condensed and gas-phase reaction zones. A global two-step reaction mechanism, applicable to certain types of degraded nitramine propellants and consisting of sequential condensed and gaseous steps, is postulated. Taking into account important effects due to multiphase flow and exploiting the limit of large activation energies, a theoretical analysis based on activation energy asymptotics leads to explicit formulas for the deflagration velocity in a specifically identified regime that is consistent with the merged-flame assumption. The results clearly indicate the influences of two-phase flow and the multiphase, multi-step chemistry on the deflagration structure and the burning rate, and define conditions that support the intrusion of the primary gas flame into the two-phase condensed decomposition region at the propellant surface.

Download or read book Eigenvalue Analysis and Calculations for the Deflagration of Porous Energetic Materials in the Merged flame Regime written by and published by . This book was released on 1996 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt: Analytical and numerical calculations of the structure and burning rate of a deflagrating porous energetic material are presented for the limiting case of merged condensed and gas-phase reaction zones. The reaction scheme is modeled by a global two-step mechanism, applicable to certain types of degraded nitramine propellants and consisting of sequential condensed and gaseous steps. Taking into account important effects due to multiphase flow and exploiting the limit of large activation energies, a theoretical analysis may be developed based on activation-energy asymptotics. For steady, planar deflagration, this leads to an eigenvalue problem for the inner reaction-zone, the solution of which determines the burning rate. Numerical solutions give a reasonably complete description of the dependence of the structure and burning rate on the various parameters in the problem, and show excellent agreement with analytical results that are obtained in a more limited parameter regime in which most of the heat release is produced by the condensed-phase reaction and the porosity of the solid is small. These calculations indicate the significant influences of two-phase flow and the multiphase, multi-step chemistry on the deflagration structure and the burning rate, and thus serve to define an important parameter regime that supports the intrusion of the primary gas flame into the two-phase condensed decomposition region at the propellant surface.

Download or read book Nano and Micro Scale Energetic Materials written by Weiqiang Pang and published by John Wiley & Sons. This book was released on 2023-01-26 with total page 1005 pages. Available in PDF, EPUB and Kindle. Book excerpt: Provides an up-to-date account of innovative energetic materials and their potential applications in space propulsion and high explosives Most explosives and propellants currently use a small number of ingredients, such as TNT and nitrocellulose. In comparison to conventional materials, nano- and micro-scale energetic materials exhibit superior burning characteristics and much higher energy densities and explosive yields. Nano and Micro-scale Energetic Materials: Propellants and Explosives provides a timely overview of innovative nano-scale energetic materials (nEMs) and microscale energetic materials (μEMs) technology. Covering nEMs and μEMs ingredients as well as formulations, this comprehensive volume examines the preparation, characterization, ignition, combustion, and performance of energetic materials in various applications of propellants and explosives. Twenty-two chapters explore metal-based pyrotechnic nanocomposites, solid and hybrid rocket propulsion, solid fuels for in-space and power, the sensitivity and mechanical properties of explosives, new energetic materials, and more. Explores novel energetic materials and their potential for use in propellants and explosives Summarizes the most recent advances of leading research groups currently active in twelve countries Discusses how new environmentally friendly, high-combustion energetic materials can best be used in different applications Explains the fundamentals of energetic materials, including similarities and differences between composite propellants and explosives Nano and Micro-scale Energetic Materials: Propellants and Explosives is an important resource for materials scientists, explosives specialists, pyrotechnicians, environmental chemists, polymer chemists, physical chemists, aerospace physicians, and aerospace engineers working in both academia and industry.