Journal of Electromagnetic Analysis and Applications, 2014
Experimental observations indicate that electromagnetic (EM) radiation is emitted after the deton... more Experimental observations indicate that electromagnetic (EM) radiation is emitted after the detonation of high explosives (HE) charges. The movement of ionized atoms, particles and electrons seems to be the underlying cause. Expansion of the detonation products (DP) drives a strong (~1 kb) shock in surrounding air. This forms an intense thermal wave (T ~11,000 K) with duration of ~20 microseconds. Such temperatures create significant ionization of the air. According to Ohm's Law, movement of ionized patches generates current; and according to the Biot-Savart Law, such currents induce electric and magnetic fields. We investigate these effects through numerical simulations of TNT explosions. A high-order Godunov scheme is used to integrate the one-dimensional conservation laws of gasdynamics. An extremely fine grid (10 microns) was needed to get converged temperature and conductivity profiles. The gasdynamic solution provided a source current, which was fed into a time-domain Green's function code to predict three-dimensional electromagnetic waves emanating from the TNT explosion. This analysis clearly demonstrates one mechanism-the Boronin current-as the source of EM emissions from TNT explosions, but other mechanisms are also possible.
A phase-plane method is proposed to model flow fields bounded by constant-velocity detonation wav... more A phase-plane method is proposed to model flow fields bounded by constant-velocity detonation waves propagating in TNT charges. Similarity transformations are used to formulate the problem in the phase plane of non-dimensional sound speed Z versus non-dimensional velocity F. The formulation results in two coupled ordinary differential equations that are solved simultaneously. The solution corresponds to an integral curve Z(F) in the phase plane, starting at the Chapman-Jouguet (CJ) point and terminating at the singularity A, which is the sonic point within the wave. The system is closed by computing thermodynamic variables along the expansion isentrope passing through the CJ point, forming, in effect, the complete equation of state of the thermodynamic system. The CJ condition and isentropic states are computed by the Cheetah thermodynamic code. Solutions are developed for planar, cylindrical, and spherical detonations. Species profiles are also computed; carbon graphite is found to be the predominant component (≈10 mol/kg). The similarity solution is used to initialize a 1D gas-dynamic simulation that predicts the initial expansion of the detonation products and the formation of a blast wave in air. Such simulations provide an insight into the thermodynamic states and species concentrations that create the initial optical emissions from TNT fireballs.
Volcanic jet flows in explosive eruptions emit radio frequency signatures, indicative of their fl... more Volcanic jet flows in explosive eruptions emit radio frequency signatures, indicative of their fluid dynamic and electrostatic conditions. The emissions originate from sparks supported by an electric field built up by the ejected charged volcanic particles. When shock-defined, low-pressure regions confine the sparks, the signatures may be limited to high-frequency content corresponding to the early components of the avalanche-streamer-leader hierarchy. Here, we image sparks and a standing shock together in a transient supersonic jet of micro-diamonds entrained in argon. Fluid dynamic and kinetic simulations of the experiment demonstrate that the observed sparks originate upstream of the standing shock. The sparks are initiated in the rarefaction region, and cut off at the shock, which would limit their radio frequency emissions to a tell-tale high-frequency regime. We show that sparks transmit an impression of the explosive flow, and open the way for novel instrumentation to diagnos...
SHOCK COMPRESSION OF CONDENSED MATTER - 2019: Proceedings of the Conference of the American Physical Society Topical Group on Shock Compression of Condensed Matter
Optical emissions from 50 and 100-g spherical charges were investigated. When the detonation prod... more Optical emissions from 50 and 100-g spherical charges were investigated. When the detonation products (DP) expand, they act like a spherical piston-driving a spherical blast wave into the atmosphere. Emissions from this blast wave come from: shock-heated air molecules, detonation-products molecules, combustion products molecules, and carbon particles formed in the detonation wave. Six HEs were studied: TNT, Comp B, PBX-N5, Comp A5, Tritonal, and AP-NM. HE powder was pressed in hemispherical molds. For TNT and Tritonal, a central booster of PBXN-5 and a RP-80 were used to detonate the charges. Experiments were conducted in air versus N 2 to control combustion, and at different pressures (1, 0.1 and 0.01 bars) to control emissions from the shock-heated air. Emission histories were measured with an Andor fast kinetics spectrometer. In the visible regime, emission spectra were well fit by a Planckian function-thereby allowing us to compute the evolution of the emission temperature of the fireball. Maximum temperatures in the 1 st peak correlate with CJ temperature of the particular explosive. Estimated temperatures fall due to the adiabatic expansion of the fireball gases. The 2 nd optical peak was caused by reheating of the fireball and carbon particles by the shock reflections from the chamber floor.
SHOCK COMPRESSION OF CONDENSED MATTER - 2019: Proceedings of the Conference of the American Physical Society Topical Group on Shock Compression of Condensed Matter
We describe a hydrodynamic model of the flow field created by pyrotechnic explosions. It is based... more We describe a hydrodynamic model of the flow field created by pyrotechnic explosions. It is based on a 3-phase version of our AMR code. It contains the following elements: (i) a gas-dynamic model of the expansion and mixing in the fireball, (ii) a Discrete Lagrangian Particles model of the burning projectiles, and (iii) a heterogeneous continuum model of the particle wakes. The 3 sets of conservation laws are coupled through drag and heat transfer with the gas; also, the projectiles loose mass, creating a mass source for the wakes. Adaptive Mesh Refinement: AMR (Bell et al., 1996) is used to capture turbulent mixing and combustion on the grid. The grid was initialized with similarity solutions for: (i) the detonation products (Kuhl 2015) and (ii) the particles (Stanyukovich 1960)-thereby defining the particular pyrotechnic charge configuration to be studied. The 3 sets of hyperbolic conservation laws were integrated with our high-order Godunov schemes (Bell et al. 1989). Results of the numerical simulations are compared with data from pyrotechnic explosion tests. Most striking is the bright turbulent combustion structures in the fireball and the bright streamers formed by combustion of the DLP-wake systems.
SHOCK COMPRESSION OF CONDENSED MATTER - 2019: Proceedings of the Conference of the American Physical Society Topical Group on Shock Compression of Condensed Matter
Finding small density gradients in high explosives non-destructively using x-ray computed tomogra... more Finding small density gradients in high explosives non-destructively using x-ray computed tomography AIP Conference Proceedings 2272, 060035 (2020);
Proposed here is a gaseous detonation tube blast simulator. A disposable (or reusable) shock tube... more Proposed here is a gaseous detonation tube blast simulator. A disposable (or reusable) shock tube would be constructed on an in-situ ground surface of interest. The tube would be sealed and filled with a detonatable as mixture. henlaar 00 'n 1473 BoTo, o, Iov oSoAVI UNCLASSIFIED 5saU*.1YI CIMPAFICATIOA OFr Itls P"6 ffte Do Icw•eme" !ii, tIUNCLAS S IF IED IECURITY CLASSIFICATION OF THIS PAGE(Whm Date Entstd) 20. ABSTRACT (Continued) wave is initiated at one end of the tube, it induces a peaked blast wave which expands self-similarly with time-the longer the detonation run distance, the longer the blast wave duration. Similarity analysis of such a wave (which consists of a constantvelocity Chapman-Jouguet detonation followed by an adiabatic rarefaction wave expressed in terms of a Riemann characteristic) results in a closed-form analytic solution for the flow field time history. It is shown that the static and dynamic pressure wave-T forms associated with this detonation give a high fidelity simulation of a nuclear surface burst. ecan achieve peak overpressures from 14 to 55 atm and pea dynamic pressures from 6 to 35 atm, depending on the detonatable gas selected. Detonation run lengths from 25 to 100 m/KTSBl/ 3 are required for kiloton-level simulations. The principal simulation deficiency involves the detonation temperature ("3000K) which is considerably larger than its airblast counterpart ('xI1000K). Small dust particles have the potential for melting and/or vaporizing, due to convective heat transfer from the detonation products, while in the nuclear case such effects are caused by radiative heating from the fireball. These effects can be ameliorated somewhat by choosing air as the oxidizer, and by employing large diameter dust particles. Lk UNCLMSSZFIED 1IGUMI ., C.458UtCA (0O 4
fligh-explosive-driven blast waves contain a contact surface (denoting the interface between the ... more fligh-explosive-driven blast waves contain a contact surface (denoting the interface between the detonation products and thu air) which is Rayleigh-Taylor unstable. The kinematics of the mixing at this surface was studied numerically with a onedimensional hydrocode. A k-C turbulence model was used to simulate the growth and decay of turbulence for this problem; source terms were included to model the Rayleigh-Taylor instability Smechanism. The numerical calculations demonstrate that this k-£ JDAM"0"W3 tMvw or I OVO',sOVshOisO.LETz UNCLASSIFIED SECuFAYY CL&S=fICAVIGO o, T•is #Aria (¢wwi ziea Eowm,. UNCLASSIFIED sIuCUQITy CLA.UPICATION OF TWIS *&AG[(11e 0&af SE,SE)
Our calculations of complex and double Mach reflection are in close agreement with measurements f... more Our calculations of complex and double Mach reflection are in close agreement with measurements for shocks reflecting in air from wedges. Because of the accuracy and speed of FCT algorithms and the effectiveness of adaptive rezoning, the calculations are accurate and economical even when the Mach stem develops very slowly. All of the important features (location of surfaces of discontinuity, pressure loading on the wedge surface, density contours) are correctly predicted. The results do not depend sensitively on whether the L-T or FAST2D code is used. Of the advances discussed in Section 1, multidimensional flux limiting and the adaptive regridding technique seem to be the most efficacious for reflections in nonreactive media. We conclude that FCT algorithms reduce numerical diffusion dramatically, assuring qualitative improvements in accuracy. We believe that to achieve comparable accuracy and efficiency, other hydrocodes must employ similar nonlinear algorithms and rezoning techniques.
In Ref. [1] fundamental hexane droplets/vapour-air explosion data were obtained by measuring the ... more In Ref. [1] fundamental hexane droplets/vapour-air explosion data were obtained by measuring the explosion overpressure variation in closed chambers. Tests in the chambers of volumes of 5.6, 40, 150 and 1250 dm 3 were performed. The experimental overpressure histories can be applied to analyse the combustion of hexane-air mixtures. However, the theoretical model of the combustion process is also required. The purpose of this work is to apply the thermodynamic model of closed combustion for describing the rapid combustion of aerosol/vapour hexane-air mixtures. The relations between thermodynamic parameters and hexane (air) consumption are determined. These relations and experimental overpressure histories enable us to estimate the rate of combustion and fuel burned. Moreover, the law of combustion of hexane particles in rich hexane-air mixtures is proposed. To determine the rate of combustion of hexane vapour and hexane droplets dispersed in air closed inside a chamber, the theoretical model proposed in Refs. [2-4] is applied. In this model, the analysis of the combustion and determination of combustion characteristics on the basis on the pressure history are possible. Fuel (hexane vapour), F, and oxidizer (air), W, take part in reactions. In a closed combustion system they form non-stoichiometric mixture-charge, C. Therefore, the system, S, consisting of fuel, oxidizer and combustion products, is a multicomponent medium, in which the distribution of components in space is not taken into account. The exothermic processes take place as a result of transformation of reagents, R, into products, P. Let us assume that the reaction proceeds in two-steps. During the first stage, liquid fuel (hexane) evaporates and, in the second one, it reacts with oxygen from air. A rate of chemical reactions is so fast, that the transition from R to P, if fuel evaporates, is instant. Thermodynamic properties of the components are presented on the so-called Le Chatelier diagram. The Le Chatelier diagrams for mixtures tested are obtained by the use of the CHEETAH code [5]. We assumed that the thermochemical properties of gaseous components are characterised by the equation of state for the ideal gas. The thermochemical data for hexane and hexane vapour are taken from Ref. [6].
Here we review experimental data and models of the ignition of aluminum (Al) particles and clouds... more Here we review experimental data and models of the ignition of aluminum (Al) particles and clouds in explosion fields. The review considers: (i) ignition temperatures measured for single Al particles in torch experiments; (ii) thermal explosion models of the ignition of single Al particles; and (iii) the unsteady ignition Al particles clouds in reflected shock environments. These are used to develop an empirical ignition model appropriate for numerical simulations of Al particle combustion in shock dispersed fuel explosions.
Charges of 0.5 g PETN were used to disperse 1 g of flake aluminum in a rectangular test chamber o... more Charges of 0.5 g PETN were used to disperse 1 g of flake aluminum in a rectangular test chamber of 4 liter inner volume and inner dimensions of approximately 10 cm x 10 cm x 40 cm. The subsequent combustion of the flake aluminum with the ambient air in the chamber gave rise to a highly luminous flame. The evolution of the luminous region was studied by means of high-speed cinematography. The high-speed camera is responsive to a broad spectral range in the visible and near infra-red. For a number of tests this response range was narrowed down by means of a band-pass filter with a center wavelength of 488 nm and a half-width of 23 nm. The corresponding images were expected to have a stronger temperature dependence than images obtained without the filter, thus providing better capability to highlight hot-spots. Emission in the range of the pass-band of the filter can be due to continuous thermal radiation from hot Al and AlâOâ particles or to molecular band emission from gaseous AlO. A...
2009 IEEE Conference on Technologies for Homeland Security, 2009
Page 1. Securing Infrastructure from High Explosive Threats Lee G. Glascoe, Ph.D., PE 1., Charles... more Page 1. Securing Infrastructure from High Explosive Threats Lee G. Glascoe, Ph.D., PE 1., Charles Noble, Ph.D., John G. Reynolds, Ph.D., Allen Kuhl, Ph.D., and Joseph Morris, ... 254 Page 6. [10] C. Noble, E. Kokko, I. Darnell, T. Dunn, L. Hagler, and L. Leininger, Concrete model ...
ABSTRACT An empirical model for the ignition of aluminum particle clouds is developed and applied... more ABSTRACT An empirical model for the ignition of aluminum particle clouds is developed and applied to the study of particle ignition and combustion behavior resulting from explosive blast waves. This model incorporates both particle ignition time delay as well as cloud concentration effects on ignition. The total mass of aluminum that burns is found to depend on the model, with shorter ignition delay times resulting in increased burning of the cloud. A new mass-averaged ignition parameter is defined and is observed to serve as a useful parameter to compare cloud ignition behavior. Investigation of this variable reveals that both peak ignition as well as time required to attain peak ignition are sensitive to the model parameters. Overall, this study demonstrates that the new ignition model developed captures effects not included in other combustion models for the investigation of shock-induced ignition of aluminum particle clouds.
Journal of Electromagnetic Analysis and Applications, 2014
Experimental observations indicate that electromagnetic (EM) radiation is emitted after the deton... more Experimental observations indicate that electromagnetic (EM) radiation is emitted after the detonation of high explosives (HE) charges. The movement of ionized atoms, particles and electrons seems to be the underlying cause. Expansion of the detonation products (DP) drives a strong (~1 kb) shock in surrounding air. This forms an intense thermal wave (T ~11,000 K) with duration of ~20 microseconds. Such temperatures create significant ionization of the air. According to Ohm's Law, movement of ionized patches generates current; and according to the Biot-Savart Law, such currents induce electric and magnetic fields. We investigate these effects through numerical simulations of TNT explosions. A high-order Godunov scheme is used to integrate the one-dimensional conservation laws of gasdynamics. An extremely fine grid (10 microns) was needed to get converged temperature and conductivity profiles. The gasdynamic solution provided a source current, which was fed into a time-domain Green's function code to predict three-dimensional electromagnetic waves emanating from the TNT explosion. This analysis clearly demonstrates one mechanism-the Boronin current-as the source of EM emissions from TNT explosions, but other mechanisms are also possible.
A phase-plane method is proposed to model flow fields bounded by constant-velocity detonation wav... more A phase-plane method is proposed to model flow fields bounded by constant-velocity detonation waves propagating in TNT charges. Similarity transformations are used to formulate the problem in the phase plane of non-dimensional sound speed Z versus non-dimensional velocity F. The formulation results in two coupled ordinary differential equations that are solved simultaneously. The solution corresponds to an integral curve Z(F) in the phase plane, starting at the Chapman-Jouguet (CJ) point and terminating at the singularity A, which is the sonic point within the wave. The system is closed by computing thermodynamic variables along the expansion isentrope passing through the CJ point, forming, in effect, the complete equation of state of the thermodynamic system. The CJ condition and isentropic states are computed by the Cheetah thermodynamic code. Solutions are developed for planar, cylindrical, and spherical detonations. Species profiles are also computed; carbon graphite is found to be the predominant component (≈10 mol/kg). The similarity solution is used to initialize a 1D gas-dynamic simulation that predicts the initial expansion of the detonation products and the formation of a blast wave in air. Such simulations provide an insight into the thermodynamic states and species concentrations that create the initial optical emissions from TNT fireballs.
Volcanic jet flows in explosive eruptions emit radio frequency signatures, indicative of their fl... more Volcanic jet flows in explosive eruptions emit radio frequency signatures, indicative of their fluid dynamic and electrostatic conditions. The emissions originate from sparks supported by an electric field built up by the ejected charged volcanic particles. When shock-defined, low-pressure regions confine the sparks, the signatures may be limited to high-frequency content corresponding to the early components of the avalanche-streamer-leader hierarchy. Here, we image sparks and a standing shock together in a transient supersonic jet of micro-diamonds entrained in argon. Fluid dynamic and kinetic simulations of the experiment demonstrate that the observed sparks originate upstream of the standing shock. The sparks are initiated in the rarefaction region, and cut off at the shock, which would limit their radio frequency emissions to a tell-tale high-frequency regime. We show that sparks transmit an impression of the explosive flow, and open the way for novel instrumentation to diagnos...
SHOCK COMPRESSION OF CONDENSED MATTER - 2019: Proceedings of the Conference of the American Physical Society Topical Group on Shock Compression of Condensed Matter
Optical emissions from 50 and 100-g spherical charges were investigated. When the detonation prod... more Optical emissions from 50 and 100-g spherical charges were investigated. When the detonation products (DP) expand, they act like a spherical piston-driving a spherical blast wave into the atmosphere. Emissions from this blast wave come from: shock-heated air molecules, detonation-products molecules, combustion products molecules, and carbon particles formed in the detonation wave. Six HEs were studied: TNT, Comp B, PBX-N5, Comp A5, Tritonal, and AP-NM. HE powder was pressed in hemispherical molds. For TNT and Tritonal, a central booster of PBXN-5 and a RP-80 were used to detonate the charges. Experiments were conducted in air versus N 2 to control combustion, and at different pressures (1, 0.1 and 0.01 bars) to control emissions from the shock-heated air. Emission histories were measured with an Andor fast kinetics spectrometer. In the visible regime, emission spectra were well fit by a Planckian function-thereby allowing us to compute the evolution of the emission temperature of the fireball. Maximum temperatures in the 1 st peak correlate with CJ temperature of the particular explosive. Estimated temperatures fall due to the adiabatic expansion of the fireball gases. The 2 nd optical peak was caused by reheating of the fireball and carbon particles by the shock reflections from the chamber floor.
SHOCK COMPRESSION OF CONDENSED MATTER - 2019: Proceedings of the Conference of the American Physical Society Topical Group on Shock Compression of Condensed Matter
We describe a hydrodynamic model of the flow field created by pyrotechnic explosions. It is based... more We describe a hydrodynamic model of the flow field created by pyrotechnic explosions. It is based on a 3-phase version of our AMR code. It contains the following elements: (i) a gas-dynamic model of the expansion and mixing in the fireball, (ii) a Discrete Lagrangian Particles model of the burning projectiles, and (iii) a heterogeneous continuum model of the particle wakes. The 3 sets of conservation laws are coupled through drag and heat transfer with the gas; also, the projectiles loose mass, creating a mass source for the wakes. Adaptive Mesh Refinement: AMR (Bell et al., 1996) is used to capture turbulent mixing and combustion on the grid. The grid was initialized with similarity solutions for: (i) the detonation products (Kuhl 2015) and (ii) the particles (Stanyukovich 1960)-thereby defining the particular pyrotechnic charge configuration to be studied. The 3 sets of hyperbolic conservation laws were integrated with our high-order Godunov schemes (Bell et al. 1989). Results of the numerical simulations are compared with data from pyrotechnic explosion tests. Most striking is the bright turbulent combustion structures in the fireball and the bright streamers formed by combustion of the DLP-wake systems.
SHOCK COMPRESSION OF CONDENSED MATTER - 2019: Proceedings of the Conference of the American Physical Society Topical Group on Shock Compression of Condensed Matter
Finding small density gradients in high explosives non-destructively using x-ray computed tomogra... more Finding small density gradients in high explosives non-destructively using x-ray computed tomography AIP Conference Proceedings 2272, 060035 (2020);
Proposed here is a gaseous detonation tube blast simulator. A disposable (or reusable) shock tube... more Proposed here is a gaseous detonation tube blast simulator. A disposable (or reusable) shock tube would be constructed on an in-situ ground surface of interest. The tube would be sealed and filled with a detonatable as mixture. henlaar 00 'n 1473 BoTo, o, Iov oSoAVI UNCLASSIFIED 5saU*.1YI CIMPAFICATIOA OFr Itls P"6 ffte Do Icw•eme" !ii, tIUNCLAS S IF IED IECURITY CLASSIFICATION OF THIS PAGE(Whm Date Entstd) 20. ABSTRACT (Continued) wave is initiated at one end of the tube, it induces a peaked blast wave which expands self-similarly with time-the longer the detonation run distance, the longer the blast wave duration. Similarity analysis of such a wave (which consists of a constantvelocity Chapman-Jouguet detonation followed by an adiabatic rarefaction wave expressed in terms of a Riemann characteristic) results in a closed-form analytic solution for the flow field time history. It is shown that the static and dynamic pressure wave-T forms associated with this detonation give a high fidelity simulation of a nuclear surface burst. ecan achieve peak overpressures from 14 to 55 atm and pea dynamic pressures from 6 to 35 atm, depending on the detonatable gas selected. Detonation run lengths from 25 to 100 m/KTSBl/ 3 are required for kiloton-level simulations. The principal simulation deficiency involves the detonation temperature ("3000K) which is considerably larger than its airblast counterpart ('xI1000K). Small dust particles have the potential for melting and/or vaporizing, due to convective heat transfer from the detonation products, while in the nuclear case such effects are caused by radiative heating from the fireball. These effects can be ameliorated somewhat by choosing air as the oxidizer, and by employing large diameter dust particles. Lk UNCLMSSZFIED 1IGUMI ., C.458UtCA (0O 4
fligh-explosive-driven blast waves contain a contact surface (denoting the interface between the ... more fligh-explosive-driven blast waves contain a contact surface (denoting the interface between the detonation products and thu air) which is Rayleigh-Taylor unstable. The kinematics of the mixing at this surface was studied numerically with a onedimensional hydrocode. A k-C turbulence model was used to simulate the growth and decay of turbulence for this problem; source terms were included to model the Rayleigh-Taylor instability Smechanism. The numerical calculations demonstrate that this k-£ JDAM"0"W3 tMvw or I OVO',sOVshOisO.LETz UNCLASSIFIED SECuFAYY CL&S=fICAVIGO o, T•is #Aria (¢wwi ziea Eowm,. UNCLASSIFIED sIuCUQITy CLA.UPICATION OF TWIS *&AG[(11e 0&af SE,SE)
Our calculations of complex and double Mach reflection are in close agreement with measurements f... more Our calculations of complex and double Mach reflection are in close agreement with measurements for shocks reflecting in air from wedges. Because of the accuracy and speed of FCT algorithms and the effectiveness of adaptive rezoning, the calculations are accurate and economical even when the Mach stem develops very slowly. All of the important features (location of surfaces of discontinuity, pressure loading on the wedge surface, density contours) are correctly predicted. The results do not depend sensitively on whether the L-T or FAST2D code is used. Of the advances discussed in Section 1, multidimensional flux limiting and the adaptive regridding technique seem to be the most efficacious for reflections in nonreactive media. We conclude that FCT algorithms reduce numerical diffusion dramatically, assuring qualitative improvements in accuracy. We believe that to achieve comparable accuracy and efficiency, other hydrocodes must employ similar nonlinear algorithms and rezoning techniques.
In Ref. [1] fundamental hexane droplets/vapour-air explosion data were obtained by measuring the ... more In Ref. [1] fundamental hexane droplets/vapour-air explosion data were obtained by measuring the explosion overpressure variation in closed chambers. Tests in the chambers of volumes of 5.6, 40, 150 and 1250 dm 3 were performed. The experimental overpressure histories can be applied to analyse the combustion of hexane-air mixtures. However, the theoretical model of the combustion process is also required. The purpose of this work is to apply the thermodynamic model of closed combustion for describing the rapid combustion of aerosol/vapour hexane-air mixtures. The relations between thermodynamic parameters and hexane (air) consumption are determined. These relations and experimental overpressure histories enable us to estimate the rate of combustion and fuel burned. Moreover, the law of combustion of hexane particles in rich hexane-air mixtures is proposed. To determine the rate of combustion of hexane vapour and hexane droplets dispersed in air closed inside a chamber, the theoretical model proposed in Refs. [2-4] is applied. In this model, the analysis of the combustion and determination of combustion characteristics on the basis on the pressure history are possible. Fuel (hexane vapour), F, and oxidizer (air), W, take part in reactions. In a closed combustion system they form non-stoichiometric mixture-charge, C. Therefore, the system, S, consisting of fuel, oxidizer and combustion products, is a multicomponent medium, in which the distribution of components in space is not taken into account. The exothermic processes take place as a result of transformation of reagents, R, into products, P. Let us assume that the reaction proceeds in two-steps. During the first stage, liquid fuel (hexane) evaporates and, in the second one, it reacts with oxygen from air. A rate of chemical reactions is so fast, that the transition from R to P, if fuel evaporates, is instant. Thermodynamic properties of the components are presented on the so-called Le Chatelier diagram. The Le Chatelier diagrams for mixtures tested are obtained by the use of the CHEETAH code [5]. We assumed that the thermochemical properties of gaseous components are characterised by the equation of state for the ideal gas. The thermochemical data for hexane and hexane vapour are taken from Ref. [6].
Here we review experimental data and models of the ignition of aluminum (Al) particles and clouds... more Here we review experimental data and models of the ignition of aluminum (Al) particles and clouds in explosion fields. The review considers: (i) ignition temperatures measured for single Al particles in torch experiments; (ii) thermal explosion models of the ignition of single Al particles; and (iii) the unsteady ignition Al particles clouds in reflected shock environments. These are used to develop an empirical ignition model appropriate for numerical simulations of Al particle combustion in shock dispersed fuel explosions.
Charges of 0.5 g PETN were used to disperse 1 g of flake aluminum in a rectangular test chamber o... more Charges of 0.5 g PETN were used to disperse 1 g of flake aluminum in a rectangular test chamber of 4 liter inner volume and inner dimensions of approximately 10 cm x 10 cm x 40 cm. The subsequent combustion of the flake aluminum with the ambient air in the chamber gave rise to a highly luminous flame. The evolution of the luminous region was studied by means of high-speed cinematography. The high-speed camera is responsive to a broad spectral range in the visible and near infra-red. For a number of tests this response range was narrowed down by means of a band-pass filter with a center wavelength of 488 nm and a half-width of 23 nm. The corresponding images were expected to have a stronger temperature dependence than images obtained without the filter, thus providing better capability to highlight hot-spots. Emission in the range of the pass-band of the filter can be due to continuous thermal radiation from hot Al and AlâOâ particles or to molecular band emission from gaseous AlO. A...
2009 IEEE Conference on Technologies for Homeland Security, 2009
Page 1. Securing Infrastructure from High Explosive Threats Lee G. Glascoe, Ph.D., PE 1., Charles... more Page 1. Securing Infrastructure from High Explosive Threats Lee G. Glascoe, Ph.D., PE 1., Charles Noble, Ph.D., John G. Reynolds, Ph.D., Allen Kuhl, Ph.D., and Joseph Morris, ... 254 Page 6. [10] C. Noble, E. Kokko, I. Darnell, T. Dunn, L. Hagler, and L. Leininger, Concrete model ...
ABSTRACT An empirical model for the ignition of aluminum particle clouds is developed and applied... more ABSTRACT An empirical model for the ignition of aluminum particle clouds is developed and applied to the study of particle ignition and combustion behavior resulting from explosive blast waves. This model incorporates both particle ignition time delay as well as cloud concentration effects on ignition. The total mass of aluminum that burns is found to depend on the model, with shorter ignition delay times resulting in increased burning of the cloud. A new mass-averaged ignition parameter is defined and is observed to serve as a useful parameter to compare cloud ignition behavior. Investigation of this variable reveals that both peak ignition as well as time required to attain peak ignition are sensitive to the model parameters. Overall, this study demonstrates that the new ignition model developed captures effects not included in other combustion models for the investigation of shock-induced ignition of aluminum particle clouds.
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Papers by Allen Kuhl