Download or read book Deflagrationo Detonation Transition in HMX Based Propellants written by M. Cowperthwaite and published by . This book was released on 1978 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt: Research on the deflagration-to-detonation transition (DDT) is important to the Air Force because many of the energetic propellants required for present and future long-range delivery systems are explosively filled compositions that are capable of undergoing DDT. HMX-based propellant, for example, usually burns reliably in rocket motors but has detonated and destroyed the motor on several occasions. Possible steps leading to detonation in the rocket motor are fracture of propellant ahead of the flame and the subsequent formation of shock waves produced by the increased burning rate of fractured propellant. But even in this case, the mechanism of DDT and the conditions for its initiation are not adequately understood. The long-range objective of the present research program is to develop a computational capability for assessing the DDT hazard in explosively filled propellants. The program is based on the concept that a basic understanding of the physical and chemical processes involved in DDT is necessary to achieve this objective. Combined theoretical and experimental studies to determine the pressure fields behind and ahead of the flame and to establish mechanisms of DDT are required to develop such understanding. (Author).
Download or read book The Deflagration to detonation Transition in Granular HMX written by and published by . This book was released on 1991 with total page 66 pages. Available in PDF, EPUB and Kindle. Book excerpt: The transition from deflagration to detonation in porous beds of explosive and propellant has received considerable attention both experimentally and theoretically. In many cases, the use of a hot-gas-producing igniter complicates the interpretation and subsequent modeling of experiments because considerable effort is required to account for the effect of the igniter gases on the granular bed. Hot-wire ignition is less intrusive; however, the ignition front is not planar. Thus the early events in these experiments cannot be approximated as one-dimensional. We have studied the deflagration-to-detonation behavior of granular HMX confined in steel tubes with x-radiography, light emission, stress gauges, and various pin techniques. Simplification and consistency of results were obtained by igniting the HMX with a piston (initially at rest and in contact with the HMX) driven into the bed. A gasless igniter is used to stare the burning of the piston propellant (low-density HMX) providing the piston with a smooth initial motion. Analysis of the data gives a detailed picture of the DDT process under these conditions. The qualitative and quantitative experimental results show the transition from the burning to detonation is discontinuous. The results are discussed in terms of a descriptive model.
Download or read book Deflagration to Detonation in HMX Based Propellants written by and published by . This book was released on 1982 with total page 73 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of the research was to develop the capability of assessing the deflagration-to-detonation transistion (DDT) hazard in HMX-based propellants. Theoretical and experimental studies were undertaken to elucidate mechanisms of DDT, to establish conditions for its occurrence, and to formulate a satisfactory model for its quantitative description. The theoretical studies were concerned with the thermo-hydrodynamic treatment of DDT. Equations governing flames treated as reactive discontinuities were derived, and conditions were established for shock formation in front of an accelerating flame. Model solutions to the one-dimensional equations governing an accelerating flame in a closed table were constructed and examined to gain an insight into DDT. In the experimental study, an assembly was designed to allow incorporation of stress gages into propellant charges during the casting process, thereby eliminating the expensive machining and grooving operations conventionally used in constructing targets for Lagrange gage experiments. DDT experiments were performed in steel and Lexan confinement with propellant supplied by Edwards Air Force Base. However, internal pressure histories were recorded for the first time in a DDT experiment in the compressed propellant confined by steel. The gages recorded time periods of 300-500 microns, and peak pressure in the 2.5 to 4 kbar region. The limited pressure buildup is attributed to the small percentage of HMX in the propellant.
Download or read book Deflagration to detonation Transition in Granular HMX written by and published by . This book was released on 1980 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Experimental studies of the deflagration-to-detonation transition (DDT) in chemical explosives, specifically, granular HMX, are reviewed. The picture of the DDT process as presented here results from an attempt to incorporate common experimental observations which have heretofore been puzzling. It differs from that presented by G.B. Kistiakowsky in that the role of convective combustion is terminated and mechanical processes are postulated as the means of continuing the reaction buildup until shock waves are formed. In order to validate this picture it will be necessary both to review the experimental literature for observations which may not be reconcilable with it, and to subject each step in the proposed DDT process to detailed scrutiny. (LCL).
Download or read book The Deflagration to detonation Transition in PETN and HMX written by Robert H. Dinegar and published by . This book was released on 1983 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Deflagration to Detonation Transition in Granular HMX written by Nathan Burnside and published by . This book was released on 2001 with total page 82 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Deflagration to detonation Transition in Granular Double base Propellant written by Jason D. Rogers and published by . This book was released on 2012 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Deflagration to Shock to Detonation Transition of Energetic Propellants written by H. Krier and published by . This book was released on 1984 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt: It is well known that explosive-based propellants are susceptible to detonation from the controlled deflagration mode of combustion. In some instances a confined zone of granulated propellant adjacent to a zone of cast propellant can provide a rapid enough pressure-rise rate to shock initiate the cast material. If the cast propellant has voids, the detonation will initiate at some location ahead of the granulated bed/cast material interface. This report is a summary of the research activities that focus on the analysis and modeling of the physics of such highly transient flows.
Download or read book Prediction of Detonation Transition in Porous Explosives from Rapid Compression Loadings written by and published by . This book was released on 1985 with total page 70 pages. Available in PDF, EPUB and Kindle. Book excerpt: Increasing the nitramine content of solid rocket propellants increases the overall performance of the system as well as the sensitivity to Shock to Detonation Transition (SDT) and Deflagration to Detonation Transition (DDT). This report deals primarily with the analysis and numerical modeling of a combined SDT/DDT event. The results show that in some instances a zone of burning granulated propellant, confined and adjacent to a zone of cast propellant, can provide a rapid enough pressure-rise rate to shock initiate the cast material. This type of detonation hazard scenario is a real possibility in any high-energy rocket motor environment. The modeling study also indicates areas where important assumptions need to be further researched. These include: (a) relations for dynamic (transient) collapse of the voids or pores; (b) relations for setting the volume percent of hot spots based on initial porosity; (c) the evaluation and expression for the chemical rate of decomposition of the reactive, shocked material; and (d) the assessment of two-phase mixture equilibrium. The predicted run-to detonation distance as a function of porosity for HMX explosive compares favorably with limited shock initiation experiments. There is no data available to check whether the predictions of ramp-wave compressions (where rise times exceed several microseconds) presented here are valid.
Download or read book Analysis of Deflagration to Detonation Transition in High energy Solid Propellants written by Patrick Barry Butler and published by . This book was released on 1984 with total page 344 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Modeling of Deflagration to Shock to Detonation Transition DSDT in Porous High Energy Solid Propellants and Explosives written by Herman W. Krier and published by . This book was released on 1982 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: This annual report represents the summary of work done on the modeling of processes leading from deflagration to detonation in porous or granular high energy propellants. Particular attention is paid to the analysis of shock development from compression waves forming ahead of confined burning in the original material. It is summarized that if the shock is sufficiently strong, it will lead to shock to detonation transition (SDT). During the development of the shock wave, the porous material may collapse into a solid plug of void free propellant because the speed at which the wave propagates increases as the material is compressed. The modeling effort presented indicates how two-phase unsteady combustion processes in granular material can couple to the solid mechanics of shock formation and eventually to a steady-state detonation. (Author).
Download or read book Deflagration to Detonation Transition Behavior of Aluminized HMX written by Donna Price and published by . This book was released on 1979 with total page 45 pages. Available in PDF, EPUB and Kindle. Book excerpt: The effect of fine (5 microns) and coarse (95 microns) Al on the deflagration-to-detonation (DDT) behavior of HMX, is charges pressed to 90% theoretical maximum density (TMD), was studied. It was found that Al slows down the DDT process increasingly as the content of Al increases; that is, it increases predetonation column length and the relative times to detonation. Fine Al is more effective than coarse in delaying DDT, at a given content, but both are inferior to wax in this respect.
Download or read book Shock Wave Science and Technology Reference Library Vol 5 written by Blaine Asay and published by Springer Science & Business Media. This book was released on 2009-12-16 with total page 630 pages. Available in PDF, EPUB and Kindle. Book excerpt: Los Alamos National Laboratory is an incredible place. It was conceived and born amidst the most desperate of circumstances. It attracted some of the most brilliant minds, the most innovative entrepreneurs, and the most c- ative tinkerers of that generation. Out of that milieu emerged physics and engineering that beforehand was either unimagined, or thought to be f- tasy. One of the ?elds essentially invented during those years was the science of precision high explosives. Before 1942, explosives were used in munitions and commercial pursuits that demanded proper chemistry and con?nement for the necessary e?ect, but little else. The needs and requirements of the Manhattan project were of a much more precise and speci?c nature. Spatial and temporal speci?cations were reduced from centimeters and milliseconds to micrometers and nanoseconds. New theory and computational tools were required along with a raft of new experimental techniques and novel ways of interpreting the results. Over the next 40 years, the emphasis was on higher energy in smaller packages, more precise initiation schemes, better and safer formulations, and greater accuracy in forecasting performance. Researchers from many institutions began working in the emerging and expanding ?eld. In the midst of all of the work and progress in precision initiation and scienti?c study, in the early 1960s, papers began to appear detailing the ?rst quantitative studies of the transition from de?agration to detonation (DDT), ?rst in cast, then in pressed explosives, and ?nally in propellants.
Download or read book Initiation Combustion and Transition to Detonation in Homogeneous and Heterogeneous Reactive Mixtures A Summary written by and published by . This book was released on 1981 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt: Certain aspects of ignition source effects in reactive fuel-air mixtures are discussed. These aspects include effects of chemical sensitizers, flame acceleration, flame area, and ignition point location. The other area involves the hydrodynamic modeling of ignition and flamespreading in granular energetic solids to predict the potential for deflagration-to-detonation transition (DDT). Key results in the first area are that chemically sensitized clouds can lead to detonation, that flame acceleration or a large increase in the time rate of increase of the flame area are needed for transition from deflagration to detonation and that it is very difficult to generate damaging overpressure from edge-ignited combustion even for very high subsonic burning velocities. The research dealing with analysis of DDT in porous high energy solid propellant has shown (for the first time) actual steady-state detonation solutions, following the unsteady flow, for materials with sufficient porosity and critical burning rate properties. Limits of the run-up length to detonation are predicted as a function of propellant chemical energy, burning rate, bed porosity, and granulation (size). The detonation states conform to realistic measured conditions for porous HMX and RDX propellants.
Download or read book Proceedings written by and published by . This book was released on 1982 with total page 1126 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Proceedings written by and published by . This book was released on 1989 with total page 892 pages. Available in PDF, EPUB and Kindle. Book excerpt: Papers presented in this publication cover special problems in the field of energetic materials, particularly detonation phenomena in solids and liquids. General subject areas include shock-to-detonation transition, time resolved chemistry, initiation modeling, deflagration-to-detonation transition, equation of state and equation of state and performance, composites and emulsions, and composites and emulsions/underwater explosives, reaction zone, detonation wave propagation, hot spots, detonation products, chemistry and compositions, and special initiation.
Download or read book Modeling of Deflagration to shock to detonation Transition DSDT in Porous High Energy Solid Propellants and Explosives written by Herman Krier and published by . This book was released on 1982 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt:
