The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Vassili Novozhilov - One of the best experts on this subject based on the ideXlab platform.
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kinetic effects in Thermal Explosion with oscillating ambient conditions
Scientific Reports, 2018Co-Authors: Vassili NovozhilovAbstract:Thermal Explosion problem for a medium with oscillating ambient temperature at its boundaries is a new problem which was introduced in the preceding publication by the present author. It is directly applicable to a range of practical fire autoignition scenarios (e.g. in the storages of organic matter, explosives, propellants, etc.). Effects of kinetic mechanisms, however, need be further investigated as they are expected to alter critical conditions of Thermal Explosion. We consider several global kinetic mechanisms: first order reaction, second order reaction, and first order autocatalysis. It is demonstrated that kinetic effects related to reactants consumption do indeed shift respective critical boundaries. Effect of kinetics on oscillatory development of Thermal Explosion is of particular interest. In line with conclusions of the preceding publication, it is confirmed that temperature oscillations may develop during induction phase of Thermal Explosion when the effect of reactants consumption is properly taken into account. Moreover, development of Thermal Explosion instability through the prior oscillations is an inevitable and natural scenario. This fact is confirmed by a number of examples. Besides, effects of the other relevant parameter, Zeldovich number on critical conditions are also investigated.
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Effects of initial and boundary conditions on Thermal Explosion development
2017Co-Authors: Vassili NovozhilovAbstract:The paper investigates effects of non-uniform initial conditions, as well as oscillatory boundary conditions on critical conditions for Thermal Explosion. It is shown that natural convection plays significant role in case of initial non-uniformities in the temperature distribution. The role of convection is quantified considering critical Frank-Kamenetskii parameters at different Rayleigh numbers, relative to the same parameter at no-convection conditions. Preliminary results are presented for the effect of oscillatory boundary conditions. It is demonstrated that the system may develop Thermal Explosion if oscillations are imposed at the boundaries of otherwise Thermally stable medium.
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Thermal Explosion in oscillating ambient conditions
Scientific Reports, 2016Co-Authors: Vassili NovozhilovAbstract:Thermal Explosion problem for a medium with oscillating ambient temperature at its boundaries is considered. This is a new problem in Thermal Explosion theory, not previously considered in a distributed system formulation, but important for combustion and fire science. It describes autoignition of wide range of fires (such as but not limited to piles of biosolids and other organic matter; storages of munitions, explosives, propellants) subjected to temperature variations, such as seasonal or day/night variation. The problem is considered in formulation adopted in classical studies of Thermal Explosion. Critical conditions are determined by frequency and amplitude of ambient temperature oscillations, as well as by a number of other parameters. Effects of all the parameters on critical conditions are quantified. Results are presented for the case of planar symmetry. Development of Thermal Explosion in time is also considered, and a new type of unsteady Thermal Explosion development is discovered where Thermal runaway occurs after several periods of temperature oscillations within the medium.
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Critical Conditions for Conjugate Thermal Explosion
Combustion Theory and Modelling, 2008Co-Authors: Vassili NovozhilovAbstract:The Thermal Explosion problem is considered within the two Thermally interacting regions with different Thermal and kinetic properties. Thermal exchange with the surroundings is assumed to obey Newton's law. Critical conditions for such a problem are established for the planar, cylindrical and spherical geometries. The major conclusion of the present paper is that critical conditions in the two-media system differ both quantitatively and qualitatively from that of the single-media system. In particular, Thermal runaway may occur in the composite system at the parameters that are subcritical for both regions, considered as a single media. On the other hand, under certain conditions where a single-media system would experience Thermal Explosion, conjugate Thermal Explosion is preventable by adjusting the properties of the neighboring material and the rate of heat exchange with the surroundings. Different scenarios of Thermal Explosion development are presented for a typical (cylindrical geometry) case by wa...
G Jin - One of the best experts on this subject based on the ideXlab platform.
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Performance research on nano mechanics of electro-Thermal Explosion spraying coating
Journal of Functional …, 2006Co-Authors: S. Wei, Huaiyuan Wang, Bo Xu, G JinAbstract:The mechanical performance of three electro-Thermal Explosion spraying layers (FeAl, FeCrAl, Fe-CrAlRE) were tested and analyzed by adopting british nano multi-functional testing instrument type Nano Test 600. Meanwhile through comparing their loading and unloading curves, measuring the spring modulus and hardness, analyzing the surface rules of those three spraying layers, better technology parameter of electro-Thermal Explosion layer were found in this paper.
J L Maienschein - One of the best experts on this subject based on the ideXlab platform.
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Study of Thermal sensitivity and Thermal Explosion violence of energetic materials in the LLNL ODTX system
Journal of Physics: Conference Series, 2014Co-Authors: Gary A. Hust, H K Springer, M. X. Zhang, T K Lorenz, John G. Reynolds, Larry Fried, J L MaienscheinAbstract:Incidents caused by fire and combat operations can heat energetic materials that may lead to Thermal Explosion and result in structural damage and casualty. Some explosives may Thermally explode at fairly low temperatures (< 100 °C) and the violence from Thermal Explosion may cause significant damage. Thus it is important to understand the response of energetic materials to Thermal insults. The One Dimensional Time to Explosion (ODTX) system at the Lawrence Livermore National Laboratory has been used for decades to measure times to Explosion, threshold Thermal Explosion temperature, and determine kinetic parameters of energetic materials. Samples of different configurations (pressed part, powder, paste, and liquid) can be tested in the system. The ODTX testing can also provide useful data for assessing the Thermal Explosion violence of energetic materials. Recent ODTX experimental data are reported in the paper.
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A comparison of deflagration rates at elevated pressures and temperatures with Thermal Explosion results
2012Co-Authors: Elizabeth A. Glascoe, H K Springer, Joseph W. Tringe, J L MaienscheinAbstract:The deflagration rate of HMX-based explosives has previously been correlated with the violence of Thermal Explosion experiments. In particular, HMX-based materials that experience deconsolidative burning at elevated pressures (i.e. P = 200 - 600 MPa) also produce significantly more violent Thermal Explosions. We now report deflagration rates at elevated temperatures (i.e. T = 150 - 180C) and moderate pressures (i.e. P = 10 - 100 MPa). These conditions more closely mimic the pressures and temperatures of an explosive shortly after ignition of a Thermal Explosion. Here, we discuss the deflagration rates of HMX-based explosives at elevated temperatures and their usefulness to predict the Thermal Explosion violence of the same materials.
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test based Thermal Explosion model for hmx
Proceedings of the Combustion Institute, 2007Co-Authors: M A Mcclelland, J L Maienschein, Craig M TarverAbstract:Abstract We present a Thermal Explosion (cookoff) model for an HMX-based plastic bonded explosive (LX-10). The Thermal–chemical–mechanical response of LX-10 is modeled based on the measurements from the scaled Thermal Explosion experiment (STEX) at the Lawrence Livermore National Laboratory. Confined LX-10 is heated at a rate of 1 °C/h until an Explosion is observed. The modeled cookoff problem is simulated by the Arbitrarily Lagrangian–Eulerian hydrocode (ALE3D) that can handle a wide spectrum of time scales that vary from a structural to a high speed shock physics time scale. In addition to a comprehensive model for energetic material, the confinement material namely an AerMet 100 steel is modeled as a Steinberg–Guinan material with a Johnson–Cook failure model with a statistical failure distribution. By using the size distribution data from the fragmentation experiment, the metal fracture and fragmentation due to an Explosion are modeled. The Explosion temperature is predicted to within 1°. Calculated wall strain provides violence associated with the Thermal Explosion process and agrees favorably with the measured STEX data.
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simulating Thermal Explosion of cyclotrimethylenetrinitramine based explosives model comparison with experiment
Journal of Applied Physics, 2005Co-Authors: M A Mcclelland, J F Wardell, J L Maienschein, Craig M TarverAbstract:We compare two-dimensional model results with measurements for the Thermal, chemical, and mechanical behavior in a Thermal Explosion experiment. Confined high explosives (HEs) are heated at a rate of 1°C∕h until an Explosion is observed. The heating, ignition, and deflagration phases are modeled using an Arbitrarily Lagrangian-Eulerian code (ALE3D) that can handle a wide range of time scales that vary from a structural to a dynamic hydrotime scale. During the preignition phase, quasistatic mechanics and diffusive Thermal transfer from a heat source to the HE are coupled with the finite chemical reactions that include both endothermic and exothermic processes. Once the HE ignites, a hydrodynamic calculation is performed as a burn front propagates through the HE. Two cyclotrimethylenetrinitramine-based explosives, C-4 and PBXN-109, are considered, whose chemical-Thermal-mechanical models are constructed based on measurements of Thermal and mechanical properties along with small scale Thermal Explosion measu...
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Thermal Explosion Violence of HMX-Based and RDX-Based Explosives - Effects of Composition, Confinement, and Solid Phase Using the Scaled Thermal Explosion Experiment
2002Co-Authors: J L Maienschein, J F WardellAbstract:The Scaled Thermal Explosion Experiment (STEX) has been developed to quantify the violence of Thermal Explosion under well defined and carefully controlled initial and boundary conditions. Here we present results with HMX-based explosives (LX-04 and PBX-9501) and with Composition B. Samples are 2 inches (50 mm) in diameter and 8 inches (200 mm) in length, under confinement of 7,500-30,000 psi (50-200 MPa), with heating rates of 1-3 C/hr. We quantify reaction violence by measuring the wall velocity in the ensuing Thermal Explosion, and relate the measured velocity to that expected from a detonation. Results with HMX-based explosives (LX-04 and PBX-9501) have shown the importance of confinement and HMX solid phase, with reaction violence ranging from mild pressure bursts to near detonations. By contrast, Composition B has shown very violent reactions over a wide range of conditions.
S. Wei - One of the best experts on this subject based on the ideXlab platform.
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Performance research on nano mechanics of electro-Thermal Explosion spraying coating
Journal of Functional …, 2006Co-Authors: S. Wei, Huaiyuan Wang, Bo Xu, G JinAbstract:The mechanical performance of three electro-Thermal Explosion spraying layers (FeAl, FeCrAl, Fe-CrAlRE) were tested and analyzed by adopting british nano multi-functional testing instrument type Nano Test 600. Meanwhile through comparing their loading and unloading curves, measuring the spring modulus and hardness, analyzing the surface rules of those three spraying layers, better technology parameter of electro-Thermal Explosion layer were found in this paper.
M A Korchagin - One of the best experts on this subject based on the ideXlab platform.
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superadiabatic regime of the Thermal Explosion in a mechanically activated mixture of tungsten with carbon black
Combustion Explosion and Shock Waves, 2016Co-Authors: M A Korchagin, Natalia V. BulinaAbstract:A superadiabatic regime of the Thermal Explosion in mechanically activated stoichiometric mixtures of tungsten and carbon black is obtained. Regimes of preliminary mechanical activation of mixtures and the subsequent Thermal Explosion that allow obtaining a single-phase carbide WC with a submicron grain size are determined. The mechanical energy accumulated in the sample as a result of preliminary activation is estimated. Results of the x-ray diffraction analysis and electron microscopy of mechanically activated samples and Thermal Explosion products are reported.
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Thermal Explosion in mechanically activated low calorific value compositions
Combustion Explosion and Shock Waves, 2015Co-Authors: M A KorchaginAbstract:The effect of preliminary mechanical activation of low-calorific-value powdered formulations in a planetary ball mill on the main parameters of the subsequent Thermal Explosion has been studied. It has been found that in mechanically activated compositions, the initiation temperature of Thermal Explosion is reduced by hundreds of degrees. The maximum decrease (1300°C) is observed for the Ti + 4 wt.% C system. Regimes of preliminary mechanical activation of reaction mixtures and the subsequent Thermal Explosion conditions producing Ti3Al and Ni3Al single-phase intermetallic compounds with nanometer grain size were determined. For the 3Ni + Al composition, the energy accumulated during mechanical activation was evaluated. It is shown that the initiation temperature of Thermal Explosion in the MA compositions studied can be used to estimate the temperature that develops in the mill drums.
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Thermal Explosion and self propagating high temperature synthesis in mechanically activated sio2 al mixtures
Combustion Explosion and Shock Waves, 2014Co-Authors: M A Korchagin, E G Avvakumov, G G Lepezin, O B VinokurovaAbstract:A Thermal Explosion and self-propagating high-temperature synthesis in low-calorific SiO2-Al mixtures subjected to preliminary mechanical activation are obtained. Results of x-ray and electron-microscopic investigations of the microstructure and phase composition of activated mixtures and reaction products are reported. It is found that complete reduction of quartz by aluminum occurs only in the Thermal Explosion mode.
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Thermal Explosion of a mechanically activated 3ni al mixture
Combustion Explosion and Shock Waves, 2010Co-Authors: M A Korchagin, E. V. Smirnov, Yu V Filimonov, N. Z. LyakhovAbstract:Results of studying the Thermal Explosion of 3Ni-Al mixtures after their preliminary mechanical activation in a planetary ball mill are described. Reduction of the initiation temperature and effective energy of activation of interaction between the reagents to anomalously low values is found. Results of an x-ray diffraction analysis and an electron-microscope study of the Thermal Explosion products and initial mixtures with different times of mechanical activation are given.
