Download or read book Generating Detonation Waves in an Annulus Via Phased Adiabatic Shocks written by Joseph D. Heath and published by . This book was released on 2015 with total page 83 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis documents the design and development of a continuous rotating detonation combustor. The design of the combustor incorporates a new system to initiate and control detonation waves within an annular duct. This system known as the wave controller functions by generating phased adiabatic shocks using an azimuthal array of spark plugs. The main intent of the research was to determine the effectiveness and usability of the wave controller in developing transverse waves to initiate a detonation wave. Imaging data of the adiabatic shocks in the annulus was obtained using a high-speed camera and optical setup. The data presented here illustrates the wave controller's capability in creating transverse shock waves traveling circumferentially. Another aspect of the research is to introduce a new injection scheme and provide experimental results on its effectiveness in mixing fuel and oxidizer.

Download or read book Shock Waves Science and Technology Library Vol 6 written by F. Zhang and published by Springer Science & Business Media. This book was released on 2012-03-28 with total page 482 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book, as a volume of the Shock Wave Science and Technology Reference Library, is primarily concerned with the fundamental theory of detonation physics in gaseous and condensed phase reactive media. The detonation process involves complex chemical reaction and fluid dynamics, accompanied by intricate effects of heat, light, electricity and magnetism - a contemporary research field that has found wide applications in propulsion and power, hazard prevention as well as military engineering. The seven extensive chapters contained in this volume are: - Chemical Equilibrium Detonation (S Bastea and LE Fried) - Steady One-Dimensional Detonations (A Higgins) - Detonation Instability (HD Ng and F Zhang) - Dynamic Parameters of Detonation (AA Vasiliev) - Multi-Scaled Cellular Detonation (D Desbordes and HN Presles) - Condensed Matter Detonation: Theory and Practice (C Tarver) - Theory of Detonation Shock Dynamics (JB Bdzil and DS Stewart) The chapters are thematically interrelated in a systematic descriptive approach, though, each chapter is self-contained and can be read independently from the others. It offers a timely reference of theoretical detonation physics for graduate students as well as professional scientists and engineers.

Download or read book Phase Velocity Techniques for the Implosion of Pressurized Linear Drivers written by Jason Loiseau and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Toward Detonation Theory written by Anatoly N. Dremin and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 163 pages. Available in PDF, EPUB and Kindle. Book excerpt: It is known that the Chapman-Jouguet theory of detonation is based on the assumption of an instantaneous and complete transformation of explosives into detonation products in the wave front. Therefore, one should not expect from the theory any interpretations of the detonation limits, such as shock initiation of det onation and kinetic instability and propagation (failure diameter). The Zeldovich-Von Neuman-Doring (ZND) theory of detonation appeared, in fact, as a response to the need for a theory capable of interpreting such limits, and the ZND detonation theory gave qualitative interpretations to the detonation limits. These interpretations were based essentially on the theoretical notion that the mechanism of explosives transformation at detonation is a combustion of a layer of finite thickness of shock-compressed explosive behind the wave shock front with the velocity of the front. However, some experimental findings turned out to be inconsistent with the the ory. A very small change of homogeneous (liquid) explosives detonation velocity with explosive charge diameter near the rather sizable failure diameter is one of the findings. The elucidation of the nature of this finding has led to the discovery of a new phenomenon. This phenomenon has come to be known as the breakdown (BD) of the explosive self-ignition behind the front of shock waves under the effect of rarefaction waves.

Download or read book Detonation Initiation by Annular Jets and Shock Waves written by and published by . This book was released on 2005 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: This project was an experimental test of the concept of initiating detonations in PDEs with imploding shock waves. The existing 6-inch shock tube at Caltech was used to create hot, high pressure air behind a reflected shock wave. The hot air created an imploding annular shock wave when it jetted through an annular orifice into a 76 mm diameter, 1 m long tube attached to the end of the shock tube. The test tube was filled with either stoichiometric ethylene-oxygen or propane-oxygen diluted with nitrogen. Piezoelectric pressure transducers and ionization gauges were used to determine the type of combustion event initiated by the annular jet of hot air. The stagnation conditions in the shock tube and the amount of dilution with nitrogen in the test section were varied to find the critical conditions for the onset of detonation in each test mixture. Less sensitive (high dilution) mixtures required larger stagnation pressures in order to initiate a detonation. We were unable to initiate either ethylene or propane-air mixtures within our facility limits. Extrapolation of the low-dilution data indicates that very high stagnation pressures (> 16 bar) are required.

Download or read book Shock Wave Science and Technology Reference Library Vol 4 written by F. Zhang and published by Springer Science & Business Media. This book was released on 2009-06-12 with total page 407 pages. Available in PDF, EPUB and Kindle. Book excerpt: The fourth of several volumes on solids in this series, the six extensive chapters here are more specifically concerned with detonation and shock compression waves in reactive heterogeneous media, including mixtures of solid, liquid and gas phases.

Download or read book Simulation of Air Shocks with Detonation Waves written by Gerald P. D'Arcy and published by . This book was released on 1966 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presented theoretically and experimentally are (1) the feasibility of simulating a nuclear blast environment by detonating a gas and (2) determination of the initial conditions of hydrogen-oxygen mixtures to yield blast waves of the same pressure-velocity relationship as that in air shock waves. When the theory was derived by predicting the characteristics of the simulated blast waves, a computer program was written. Experimental data were used to adjust the computed data. The experiments were conducted in a 13-inch-diameter, high-pressure shock tube and yielded four mixtures of hydrogen and oxygen capable of simulating shock waves with overpressures of from 300 to 1,200 psi. It was found that detonation waves may be substituted for air shock waves when the incident loading is important and that applications are generally limited to instances in which only one characteristic of an air shock is simulated. (Author)

Download or read book Initiation of Orderly Spinning Detonation Waves Via Phased Sparking written by Jacob A. Boening and published by . This book was released on 2016 with total page 58 pages. Available in PDF, EPUB and Kindle. Book excerpt: A Continuous Rotating Detonation Engine (CRDE) was tested with two unique features. First, the conventional pre-detonator was replaced by a novel detonation wave generator. This generator sequentially fired spark plugs at a speed near the acoustic speed of a reactant gas mixture thereby producing free radicals ready to partake in detonation. The generator produced high speed detonation waves traveling with homogenous direction in gaseous mixtures of H2 and O2. Detonation waves continued to spin in a self-sustained fashion after turning off the wave generator. The number of simultaneous sparks did not influence the number of detonation waves observed. Instead the number of observed detonation waves was a strong function of the mass flow rate of reactants. Second, the fuel and oxidizer were injected radially. To avoid the thrust-area loss of conventional axial injection, all injection holes were oriented along the annulus radially, thereby allowing the high pressure to work over the entire front end area. Furthermore, radial injection modulated the mixing of fuel and oxidizer to adjust the axial location of detonation zones avoiding damage to the wave generator.

Download or read book Unsteady Interaction of Shock and Detonation Waves in Gases written by Viktor Pavlovich Korobeĭnikov and published by CRC Press. This book was released on 1989 with total page 256 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Shock and Detonation Waves in Two phase Media written by Mervin John Edwards and published by . This book was released on 1986 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book CONSIDERATIONS FOR THE ATTAINMENT OF A STANDING DETONATION WAVE written by J. Rutowaki, J.A. Nicholls and published by . This book was released on 1955 with total page 33 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Detonation Shock and Ignition Dynamics in Condensed Phase Explosives written by Juan A. Saenz and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We investigate the ignition and dynamics of detonation waves in condensed phase explosives using direct numerical simulations and asymptotic analysis. We develop a model to simulate deflagration to detonation transition in pentaerythritol tetranitrate powders. The model uses a continuum mechanics formulation of conservation laws for a mixture of solid reactants and gas products, written in terms of mixture quantities, plus two independent variables used to account for exothermic conversion of solid reactants into gas products, and compaction associated with pore collapse and grain rearrangement. We propose a simple empirical dependence of the reaction rate on the initial bed compaction that allows us to calibrate the model for a wide range of initial conditions. For the solid reactants we use a wide ranging equation of state. We suggest phenomenological closure relations, consistent with the limit of a compressible inert material and of a solid fully reactive material, such that the equation of state can be posed only in terms of mixture quantities and the reaction and compaction variables. We demonstrate the model's ability to capture deflagration to detonation transition in pentaerythritol tetranitrate powders by matching transients typically observed in experiments, through simulation. We develop an asymptotic formulation to calculate an intrinsic relation between the shock acceleration, velocity and curvature of self-sustained detonation waves in the limit of small time variation and small curvature of the lead shock front in condensed phase explosives. The formulation is developed in terms of a general, incomplete equation of state with composition variables to represent scalar quantities for a general range of phenomena. The results presented here are the first calculations obtained from asymptotic detonation shock dynamics relations for general material models. The formulation is a generalization of an asymptotic theory for a polytropic equation of state and a single step Arrhenius reaction rate model. We discuss the assumptions and justify the generalizations made that allow the use of general form incomplete equations of state. We test the proposed theory by calculating quasi-steady relations between detonation velocity and curvature and the dynamics of ignition events in a reactive hydrogen-oxygen mixture using an ideal equation of state and single step Arrhenius reaction rate model, and compare the results with those obtained using the original asymptotic theory. We find that quasi-steady relations between detonation velocity and curvature calculated using the proposed theory are in better agreement with numerical calculations than the original theory. We also use an equation of state that realistically represents condensed phase explosives, and two composition variables to track reaction and compaction processes, to perform calculations of quasi-steady relations between detonation velocity and curvature, detonation shock acceleration fields as a function of detonation velocity and curvature, and the dynamics of ignition events in solid PBX9501 and in PETN powders. We compare our results with numerical calculations of detonation shock dynamics and direct numerical simulations. We find that the time it takes an ignition wave to become quasi-steady is short, explaining why the quasi-steady relation between the detonation velocity and curvature can sometimes be a good approximation for a speed rule.

Download or read book Dynamics of Shock Waves Explosions and Detonations written by J. Raymond Bowen and published by . This book was released on 1984 with total page 632 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Dynamics of Shock Waves Explosions and Detonations written by J. Raymond Bowen and published by . This book was released on 1984 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Detonation in Spatially Inhomogeneous Media written by XiaoCheng Mi and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "Detonation propagation in a compressible medium wherein the energy release has been made spatially inhomogeneous is examined via numerical simulations. The inhomogeneity is introduced via concentrating reactive material into regions which are separated by inert gaps while maintaining the same average energy density. The propagation velocity and propagation limit of detonation waves under the influence of these imposed inhomogeneities are put to a rigorous examination.Spatial inhomogeneities are introduced to adiabatic detonation systems with a hierarchy of complexities. In a system governed by one-dimensional Euler equations with a simplified mechanism of instantaneous energy deposition, i.e., a source triggered by the passage of leading shock after a prescribed delay time, the resulting averaged propagation speed over hundreds of spatially discrete sources is compared to the ideal Chapman-Jouguet (CJ) speed for an equivalent amount of energy release. Velocities in excess of the CJ speed are found as the reactive regions are made increasingly discrete, with deviation above CJ being as great as 15%. The deviation above the CJ value increases with decreasing values of specific heat ratio [gamma]. When the sources are sufficiently spread out so as to make the energy release of the media nearly continuous, the classic CJ solution is obtained for the average wave speed. In the limit of highly discrete sources, time-averaged mean wave structure shows that the effective sonic surface does not correspond to an equilibrium state. The average state of the flow leaving the wave in this case does eventually reach the equilibrium Hugoniot, but only after the effective sonic surface has been crossed. Thus, the super-CJ waves observed in the limit of highly discretized sources can be understood as weak detonations due to the non-equilibrium state at the effective sonic surface. The investigation on how detonation velocity is influenced by the presence of spatial inhomogeneities is then extended to one- and two-dimensional systems with a more realistic mechanism of energy release, i.e., single-step Arrhenius kinetics. In the case of sufficiently inhomogeneous media wherein the spacing between the reactive zones is greater than the inherent reaction zone length, average wave speeds significantly greater than the corresponding CJ speed of the homogenized medium are obtained. If the shock transit time between reactive zones is less than the reaction time scale, then the classical CJ detonation velocity is recovered. The super-CJ wave propagation is also identified in the cases with a two-dimensional arrangement of spatial inhomogeneities. The correspondence of the super-CJ behavior identified in this study with real detonation phenomena that may be observed in experiments is discussed. Finally, a random distribution of spatially discrete sources is implemented into a two-dimensional detonation system confined by an inert, compressible layer of gas. In this system, detonation waves experience losses due to lateral expansion behind a curved shock front and, thus, propagate at a velocity lower than the ideal CJ velocity. As the thickness of the reactive layer within the confinement decreases, the deficit in propagation velocity increases; below a critical thickness, detonations can no longer propagate in a self-sustained manner. The critical thickness for a steady propagation is determined for a homogeneous reactive medium and a mixture with randomly distributed, discrete reactive sources. The simulation results show that, for a sufficiently high activation energy, the spatial inhomogeneities assist a detonation wave to propagate beyond the limit that is encountered in a homogeneous reactive medium. This enhancing effect of the spatial inhomogeneities on the near-limit propagation of detonation waves is found to be more pronounced with increasing activation energy." --

Download or read book Temperature Studies in Shock and Detonation Waves written by and published by . This book was released on 1972 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Viscous Triple Shock Reflections Relevant to Detonation Waves and Detonation Dynamics Predicted by the Fickett Model written by Sébastien She-Ming Lau-Chapdelaine and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Two aspects of detonation dynamics are addressed in this thesis by articles. The first part of the thesis investigates shock reflection phenomena believed to be responsible for enhancing reaction rates in detonations, namely Kelvin-Helmholtz instability and Mach stem bifurcation caused by forward jetting. Three papers are presented. The first numerically investigates shock reflections from a wedge under detonation-like conditions. A state of the art solver of the Euler equations is used. The shock reflection configuration is shown to depend on solver type, wedge implementation, and resolution. The type of reflection (i.e. regular or irregular) is found to depend on corner geometry, even far from the corner, showing initial conditions can play important roles in shock reflections. These complications are addressed with shock-resolved viscous simulations and a new initial condition: the triple point reflection. The numerical method is demonstrated in the second paper, and the presence of Kelvin-Helmholtz instability is investigated. Viscosity is found to play an important role in delaying the instability, which is found not to be a likely source of reaction acceleration on time scales commensurate with autoignition behind the Mach stem, but may become important on scales associated with the detonation cell. Mach stem bifurcations are investigated experimentally and numerically in the third paper. Experimental shock reflections are performed from a free-slip boundary in gases with differing isentropic exponents. Bifurcations are found in experiments, viscous and inviscid simulations. Viscosity is found to delay bifurcations. Inviscid simulations are used to approximate the limits of Mach stem bifurcation in the phase space of Mach number, isentropic exponent, and reflection angle. A maximum isentropic exponent is found beyond which bifurcations do not occur, matching the irregular/regular boundary of the detonation cellular structure. Flow field instability is found in experiments at high Mach number and low isentropic exponent. The second part of the thesis, comprised of one paper, investigates the dynamics of detonations with multiple thermicity peaks using Fickett's detonation analogue. Steady state analysis predicts multiple possible steady states, but only the fastest is singularity-free. Simulations show other solutions develop shock waves that eventually establish a detonation travelling at the fastest velocity allowed by the generalized Chapman-Jouguet criterion. Characteristic and linear stability analysis shows these shocks are found to arise due to instability at the sonic points.