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1

Structure and maintenance threshold of laser supported detonation waves  

Microsoft Academic Search

A novel method is used to calculate laser supported detonation (LSD) wave thicknesses, as a function of laser irradiance, for a variety of gases that are being considered as propellant materials for laser propulsion. A computational scheme for studying the structure of LSD waves is developed. The derivation of structures of an LSD wave is described. Results are presented for

G. Weyl; C. Rollins; D. Resendes

1990-01-01

2

Structure and maintenance threshold of laser supported detonation waves  

Microsoft Academic Search

Maintenance of a Chapman Jouguet laser supported detonation (LSD) wave requires complete absorption of the laser beam in an absorption front travelling supersonically with respect to the upstream gas. A requirement for LSD maintenance is that this distance be less than the radius of the beam. A computational scheme was developed to study the structure of LSD waves in various

G. Weyl; C. Rollins; D. Resendes

1990-01-01

3

Laser-supported detonation waves and pulsed laser propulsion  

SciTech Connect

A laser thermal rocket uses the energy of a large remote laser, possibly ground-based, to heat an inert propellant and generate thrust. Use of a pulsed laser allows the design of extremely simple thrusters with very high performance compared to chemical rockets. The temperatures, pressures, and fluxes involved in such thrusters (10{sup 4} K, 10{sup 2} atmospheres, 10{sup 7} w/cm{sup 2}) typically result in the creation of laser-supported detonation (LSD) waves. The thrust cycle thus involves a complex set of transient shock phenomena, including laser-surface interactions in the ignition of the LSD wave, laser-plasma interactions in the LSD wave itself, and high-temperature nonequilibrium chemistry behind the LSD wave. The SDIO Laser Propulsion Program is investigating these phenomena as part of an overall effort to develop the technology for a low-cost Earth-to-orbit laser launch system. We will summarize the Program's approach to developing a high performance thruster, the double-pulse planar thruster, and present an overview of some results obtained to date, along with a discussion of the many research question still outstanding in this area.

Kare, J. (Lawrence Livermore National Laboratory, Livermore, California 94550 (United States))

1990-07-30

4

Laser-supported detonation waves and pulsed laser propulsion  

SciTech Connect

A laser thermal rocket uses the energy of a large remote laser, possibly ground-based, to heat an inert propellant and generate thrust. Use of a pulsed laser allows the design of extremely simple thrusters with very high performance compared to chemical rockets. The temperatures, pressures, and fluxes involved in such thrusters (10{sup 4} K, 10{sup 2} atmospheres, 10{sup 7} w/cm{sup 2}) typically result in the creation of laser-supported detonation (LSD) waves. The thrust cycle thus involves a complex set of transient shock phenomena, including laser-surface interactions in the ignition if the LSD wave, laser-plasma interactions in the LSD wave itself, and high-temperature nonequilibrium chemistry behind the LSD wave. The SDIO Laser Propulsion Program is investigating these phenomena as part of an overall effort to develop the technology for a low-cost Earth-to-orbit laser launch system. We will summarize the program's approach to developing a high performance thruster, the double-pulse planar thruster, and present an overview of some results obtained to date, along with a discussion of the many research questions still outstanding in this area. 16 refs., 7 figs.

Kare, J.T.

1989-01-01

5

Energy Absorption Structure of Laser Supported Detonation Wave  

NASA Astrophysics Data System (ADS)

In Repetitive Pulsed (RP) laser propulsion, when the high energy laser beam is focused in the thruster, Laser Supported Detonation (LSD) wave is generated. This LSD wave converts the laser energy to the enthalpy of the blast wave, which will then apply impulse to the wall of the thruster. Therefore, the energy absorption structure and sustaining condition of LSD wave are important to be understood, which was still not clear though some visualized experiments have been conducted by Ushio et al. before. In this paper, 2-wavelength Mach-Zehnder interferometry is brought to investigate the electron density distribution of LSD area. At the same time, the temperature of the laser induced plasma is measured by an emission spectroscopy experiment, and calculated based on the assumption of local thermal equilibrium. The results show that in LSD, the electron density has a peak (as high as 2×1024[m-3]) behind the shock wave. The irradiated laser can be entirely absorbed before reaching the position of this peak. As a result, a new peak is always generating in front of the old one and this propagating has the same velocity as that of the blast wave. In this way, high heating ratio is sustained right after the shock front. However, as the laser pulse energy becomes lower, the propagating peak cannot catch up with the blast wave anymore, which leads to a termination of the LSD wave. From this study, it is found that for sustaining the LSD wave, a sufficiently thin laser absorption layer is necessary.

Wang, Bin; Yamaguchi, Toshikazu; Hatai, Keigo; Komurasaki, Kimiya; Arakawa, Yoshihiro

2010-05-01

6

Analysis of Laser-Supported Detonation Waves and Laser Beam Propagation in Two Dimensions.  

National Technical Information Service (NTIS)

It is shown that the Flux-Corrected Transport (FCT) algorithm correctly computes the propagation velocity and Chapman-Jouguet pressure for a laser-supported detonation (LSD) wave, even for zone size large compared to the radiation absorption length. A two...

J. R. Triplett M. H. Rice

1978-01-01

7

Lateral expansion of a laser-supported detonation wave in a gas.  

NASA Technical Reports Server (NTRS)

A model satisfying the conditions in the burnt (ionized) and ambient undisturbed gases is presented for the two-dimensional case of the absorption wave resulting from the interaction of a laser beam with the plasma it generates in the gas through which the beam propagates. The flowfield of the rarefaction wave resulting from the laser-supported detonation is discussed, along with the computed shock and flow deflection angles.

Howe, J. T.

1972-01-01

8

Internal structure of laser supported detonation waves by two-wavelength Mach-Zehnder interferometer  

Microsoft Academic Search

Characteristics of the internal structure of the laser supported detonation (LSD) waves, such as the electron density ne and the electron temperature Te profiles behind the shock wave were measured using a two-wavelength Mach-Zehnder interferometer along with emission spectroscopy. A TEA CO2 laser with energy of 10 J\\/pulse produced explosive laser heating in atmospheric air. Results show that the peak

Kohei Shimamura; Keigo Hatai; Koichi Kawamura; Akihiro Fukui; Akio Fukuda; Bin Wang; Toshikazu Yamaguchi; Kimiya Komurasaki; Yoshihiro Arakawa

2011-01-01

9

Numerical Analysis on Non-Equilibrium Mechanism of Laser-Supported Detonation Wave Using Multiply-Charged Ionization  

SciTech Connect

Laser-Supported Detonation (LSD), one type of Laser-Supported Plasma (LSP), is considered as the most important phenomena because it can generate high pressure and high temperature for laser absorption. In this study, I have numerically simulated the 1-D LSD waves propagating through a helium gas, in which Multiply-charged ionization model is considered for describing an accurate ionization process.

Shiraishi, Hiroyuki [Department of Mechanical Engineering, Daido Institute of Technology (Japan)

2006-05-02

10

Fundamental Properties of Non-equilibrium Laser-Supported Detonation Wave  

SciTech Connect

For developing laser propulsion, it is very important to analyze the mechanism of Laser-Supported Detonation (LSD), because it can generate high pressure and high temperature to be used by laser propulsion can be categorized as one type of hypersonic reacting flows, where exothermicity is supplied not by chemical reaction but by radiation absorption. I have numerically simulated the 1-D and Quasi-1-D LSD waves propagating through an inert gas, which absorbs CO2 gasdynamic laser, using a 2-temperature model. Calculated results show the fundamental properties of the non-equilibrium LSD Waves.

Shiraishi, Hiroyuki [Department of Mechanical Engineering, Daido Institute of Technology, 10-3 Taki-haru-cho, Minami-ku, Nagoya (Japan)

2004-03-30

11

Laser supported detonation wave source of atomic oxygen for aerospace material testing  

NASA Technical Reports Server (NTRS)

A pulsed high-flux source of nearly monoenergetic atomic oxygen was developed to perform accelerated erosion testing of spacecraft materials in a simulated low-earth orbit (LEO) environment. Molecular oxygen is introduced into an evacuated conical expansion nozzle at several atmospheres pressure through a pulsed molecular beam valve. A laser-induced breakdown is generated in the nozzle throat by a pulsed CO2 TEA laser. The resulting plasma is heated by the ensuing laser-supported detonation wave, and then it rapidly expands and cools. An atomic oxygen beam is generated with fluxes above 10 to the 18th atoms per pulse at 8 + or - 1.6 km/s with an ion content below 1 percent for LEO testing. Materials testing yielded the same surface oxygen enrichment in polyethylene samples as observed on the STS mission, and scanning electron micrographs of the irradiated polymer surfaces showed an erosion morphology similar to that obtained on low earth orbit.

Krech, Robert H.; Caledonia, George E.

1990-01-01

12

Internal structure of laser supported detonation waves by two-wavelength Mach-Zehnder interferometer  

SciTech Connect

Characteristics of the internal structure of the laser supported detonation (LSD) waves, such as the electron density n{sub e} and the electron temperature T{sub e} profiles behind the shock wave were measured using a two-wavelength Mach-Zehnder interferometer along with emission spectroscopy. A TEA CO{sub 2} laser with energy of 10 J/pulse produced explosive laser heating in atmospheric air. Results show that the peak values of n{sub e} and T{sub e} were, respectively, about 2 x 10{sup 24} m{sup -3} and 30 000 K, during the LSD regime. The temporal variation of the laser absorption coefficient profile estimated from the measured properties reveals that the laser energy was absorbed perfectly in a thin layer behind the shock wave during the LSD regime, as predicted by Raizer's LSD model. However, the absorption layer was much thinner than a plasma layer, the situation of which was not considered in Raizer's model. The measured n{sub e} at the shock front was not zero while the LSD was supported, which implies that the precursor electrons exist ahead of the shock wave.

Shimamura, Kohei; Kawamura, Koichi; Fukuda, Akio; Wang Bin; Yamaguchi, Toshikazu; Komurasaki, Kimiya [Department of Advanced Energy, University of Tokyo, 5-1-5 Kashiwa-no-ha, Kashiwa, Chiba 277-8561 (Japan); Hatai, Keigo; Fukui, Akihiro; Arakawa, Yoshihiro [Department of Aeronautics and Astronautics, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan)

2011-04-15

13

Internal structure of laser supported detonation waves by two-wavelength Mach-Zehnder interferometer  

NASA Astrophysics Data System (ADS)

Characteristics of the internal structure of the laser supported detonation (LSD) waves, such as the electron density ne and the electron temperature Te profiles behind the shock wave were measured using a two-wavelength Mach-Zehnder interferometer along with emission spectroscopy. A TEA CO2 laser with energy of 10 J/pulse produced explosive laser heating in atmospheric air. Results show that the peak values of ne and Te were, respectively, about 2 × 1024 m-3 and 30 000 K, during the LSD regime. The temporal variation of the laser absorption coefficient profile estimated from the measured properties reveals that the laser energy was absorbed perfectly in a thin layer behind the shock wave during the LSD regime, as predicted by Raizer's LSD model. However, the absorption layer was much thinner than a plasma layer, the situation of which was not considered in Raizer's model. The measured ne at the shock front was not zero while the LSD was supported, which implies that the precursor electrons exist ahead of the shock wave.

Shimamura, Kohei; Hatai, Keigo; Kawamura, Koichi; Fukui, Akihiro; Fukuda, Akio; Wang, Bin; Yamaguchi, Toshikazu; Komurasaki, Kimiya; Arakawa, Yoshihiro

2011-04-01

14

Numerical Analysis on Thermal Non-Equilibrium Process of Laser-Supported Detonation Wave in Axisymmetric Nozzle  

SciTech Connect

Numerical Analyses on Laser-Supported Plasma (LSP) have been performed for researching the mechanism of laser absorption occurring in the laser propulsion system. Above all, Laser-Supported Detonation (LSD), categorized as one type of LSP, is considered as one of the most important phenomena because it can generate high pressure and high temperature for performing highly effective propulsion. For simulating generation and propagation of LSD wave, I have performed thermal non-equilibrium analyses by Navier-stokes equations, using a CO{sub 2} gasdynamic laser into an inert gas, where the most important laser absorption mechanism for LSD propagation is Inverse Bremsstrahlung. As a numerical method, TVD scheme taken into account of real gas effects and thermal non-equilibrium effects by using a 2-temperature model, is applied. In this study, I analyze a LSD wave propagating through a conical nozzle, where an inner space of an actual laser propulsion system is simplified.

Shiraishi, Hiroyuki [Daido Institute of Technology, Dept. of Mechanical Engineering 10-3 Takiharu-cho, Minami-ku, Nagoya 457-8530 (Japan)

2008-04-28

15

Calculation of laser induced impulse based on the laser supported detonation wave model with dissociation, ionization and radiation  

NASA Astrophysics Data System (ADS)

In the laser intensity range that the laser supported detonation (LSD) wave can be maintained, dissociation, ionization and radiation take a substantial part of the incidence laser energy. There is little treatment on the phenomenon in the existing models, which brings obvious discrepancies between their predictions and the experiment results. Taking into account the impact of dissociation, ionization and radiation in the conservations of mass, momentum and energy, a modified LSD wave model is developed which fits the experimental data more effectively rather than the existing models. Taking into consideration the pressure decay of the normal and the radial rarefaction, the laser induced impulse that is delivered to the target surface is calculated in the air; and the dependencies of impulse performance on laser intensity, pulse width, ambient pressure and spot size are indicated. The results confirm that the dissociation is the pivotal factor of the appearance of the momentum coupling coefficient extremum. This study focuses on a more thorough understanding of LSD and the interaction between laser and matter.

Li, Gan; Cheng, Mousen; Li, Xiaokang

2014-03-01

16

Numerical Analysis of Threshold between Laser-Supported Detonation and Combustion Wave Using Thermal Non-Equilibrium and Multi-Charged Ionization Model  

NASA Astrophysics Data System (ADS)

Laser-supported Detonation (LSD), which is one type of Laser-supported Plasma (LSP), is an important phenomenon because it can generate high pressures and temperatures for laser absorption. In this study, using thermal-non-equilibrium model, we numerically simulate LSPs, which are categorized as either LSDs or laser-supported combustion-waves (LSCs). For the analysis model, a two-temperature (heavy particle and electron-temperature) model has been used because the electronic mode excites first in laser absorption and a thermal non-equilibrium state easily arises. In the numerical analysis of the LSDs, laser absorption models are particularly important. Therefore, a multi-charged ionization model is considered to evaluate precisely the propagation and the structure transition of the LSD waves in the proximity of the LSC-LSD threshold. In the new model, the transition of the LSD construction near the threshold, which is indicated by the ionization delay length, becomes more practical.

Shiraishi, Hiroyuki; Kumagai, Yuya

17

Laser Wavelength Dependency of Laser Supported Detonation  

NASA Astrophysics Data System (ADS)

The development of high power Neodymium glass (Nd:glass) laser allows for application in laser propulsion. The Nd:glass laser is one of a candidate of the driver for the propulsion. However, there is a lack of study with using the solid state laser. Previous studies found that plasma induced using the glass laser absorbs the laser energy during a short laser supported detonation (LSD) regime compared with CO2 lasers. To investigate a laser wavelengths dependency of LSD in comparison with the CO2 laser, we used plasma emission spectroscopy and measured the electron temperature and electron density. As a result, these parameters of the glass laser appear to be higher value than those for the CO2 laser plasma. Besides, the absorption depth behind the shock wave is longer than that one of the CO2 laser. The results reveal that the long depth absorbs the energy conversion efficiency at almost same order despite a short LSD duration, as compared with the CO2 laser.

Shimamura, Kohei; Michigami, Keisuke; Wang, Bin; Yamaguchi, Toshikazu; Komurasaki, Kimiya; Arakawa, Yoshihiro

2011-11-01

18

Influence of the gaseous form on the precursor heating layer of a laser-supported detonation wave using half self-emission half shadowgraph visualization  

NASA Astrophysics Data System (ADS)

After breakdown one of the possible mechanisms of occurrence of laser-produced plasma is noted as laser-supported detonation (LSD) wave. This wave consisting of the shock wave and the beam absorbing plasma travels at 1-10 km/s along the beam channel in the direction opposite to the laser incidence. The laser heating structure is recognized as the ZND model of chemical detonation. However, Shimamura et. al, showed that the plasma proceeds the shock wave during LSD regime. The role of shock compression is relatively smaller than preheating by laser. The conventional model is inconsistent with our paper. To investigate the heating structure of a LSD wave, half self-emission half shadowgraph (HSHS) methods provides the self-emission image from the plasma on the top half and the shadowgraph image of the induced shock wave on the bottom half simultaneously. A TEA CO2 laser was used at 10 J incident energy. The locations of both wave fronts were detected from the brightness distribution of the HSHS images. As a result, the propagation of ionization front precedes that of shock wave front by the order of 10-4 m in air and N2. Preheating layer of N2 is shorter than that of air because O2 in air has the lowest ionization energy. Thus, a characteristic of preionization layer depends on the ionization properties because photoionization by the UV radiation generate the seed electrons ahead of shock wave.

Shimamura, Kohei; Michigami, Keisuke; Ofoso, Joseph; Komursaki, Kimiya

2012-10-01

19

Terminating Conditions of Laser Supported Detonation in Two Different Lasers  

NASA Astrophysics Data System (ADS)

Laser Supported Detonation (LSD) wave is the major efficient energy conversion structure in Repetitively Pulsed Laser Propulsion, which is known as one of the promising candidates for future space launching system. In order to advance the launching performance, it is quite important to find out the terminating condition of LSD. It is known that feature of high power lasers is one of the crucial factors for LSD wave. Former studies were concentrated on the LSD wave generated by CO2 laser, however, the structure of LSD induced by solid laser haven't been well investigated yet. In this paper, by applying the visual technique of Schlieren, images of LSD wave generated by Nd:Glass laser were obtained around its ending time. After which, a compare of the LSD termination condition between the using of CO2 laser and Glass laser were given from experimental aspects.

Yamaguchi, Toshikazu; Wang, Bin; Shimada, Yutaka; Shimamura, Kohei; Hatai, Keigo; Komurasaki, Kimiya; Arakawa, Yoshihiro

2010-05-01

20

Understanding curved detonation waves  

SciTech Connect

The reaction zone of a detonation wave is very small compared to the dynamic length scale for a typical application. Consequently, it is impractical for numerical calculations to fully resolve the reaction zone. A non-zero reaction zone width is critical to describe curved detonation waves because it affects the wave speed. The curvature effect is the result of an the interaction between the rate of energy release and geometric source terms within the reaction zone. When the reaction zone width is determined by the computational cell size rather than the physical scale, the numerics introduces an artificial curvature effect which frequently dominates the physical effect and leads to mesh dependence of simulations. Modified Hugoniot jump conditions are derived which characterize the curvature effect. They express the conservation laws and are not sensitive to the detailed reaction dynamics but instead depend only on the reaction zone width, and averages of pressure and of mass, momentum and energy densities.

Bukiet, B.G. [New Jersey Inst. of Tech., Newark, NJ (United States); Lackner, K.S.; Menikoff, R. [Los Alamos National Lab., NM (United States)

1993-06-01

21

Understanding curved detonation waves  

SciTech Connect

The reaction zone of a detonation wave is very small compared to the dynamic length scale for a typical application. Consequently, it is impractical for numerical calculations to fully resolve the reaction zone. A non-zero reaction zone width is critical to describe curved detonation waves because it affects the wave speed. The curvature effect is the result of an the interaction between the rate of energy release and geometric source terms within the reaction zone. When the reaction zone width is determined by the computational cell size rather than the physical scale, the numerics introduces an artificial curvature effect which frequently dominates the physical effect and leads to mesh dependence of simulations. Modified Hugoniot jump conditions are derived which characterize the curvature effect. They express the conservation laws and are not sensitive to the detailed reaction dynamics but instead depend only on the reaction zone width, and averages of pressure and of mass, momentum and energy densities.

Bukiet, B.G. (New Jersey Inst. of Tech., Newark, NJ (United States)); Lackner, K.S.; Menikoff, R. (Los Alamos National Lab., NM (United States))

1993-01-01

22

Steady, oblique, detonation waves  

NASA Astrophysics Data System (ADS)

. Normal and oblique, steady planar detonation waves have been theoretically and computationally examined using the Zeldovich, von Neumann, Döring model. Combustion is between a methane/hydrogen mixture and dry air assuming, first, complete combustion, then an equilibrium solution. Prescribed parameters are the upstream values for the pressure, temperature, and Mach number, the fuel/air equivalence ratio, a hydrogen/methane ratio, and the detonation wave angle. For a given upstream state, the angle varies from its normal wave value in increments of 10o to non-integer wave angles that correspond to the Chapman-Jouguet state for complete combustion and for an equilibrium solution. For each solution, detailed results are provided for the upstream state, the state just downstream of the shock, and the two downstream states. Over 340 solutions in a report (Emanuel and Tuckness 2002) are provided, thereby establishing, for the first time, comprehensive tables that can be used to provide quick estimates, establish trends, and check CFD results. This paper describes the basis for the model, briefly outlines the analytical and numerical method, and discusses several insights.

Emanuel, George; Tuckness, Dan G.

23

Photoionization in the Precursor of Laser Supported Detonation by Ultraviolet Radiation  

NASA Astrophysics Data System (ADS)

The propagation mechanism of laser-supported detonation (LSD) is important for designing laser propulsion for a detonation type thruster. The purpose of this work to was to confirm that photo-ionization in precursor is the predominant LSD sustainment mechanism. First of all, we tried to investigate the dependency of LSD duration on ambient gas species, air and argon. We took a series of high-speed images using the laser shadow-graphy. Besides, to estimate the UV photons emitted from the plasma, we used plasma emission spectroscopy and determined the electron temperature and density. As a result, the LSD duration of argon plasma and air plasma are 0.7 ?s and 0.3 ?s, resp. Besides, argon plasma emitted 1010 to 1014 photons/seconds, which was higher than air plasma. These results reveal that LSD propagation depends on the photon-contributing photoionization. The threshold photon-emission rate of LSD termination gives the elucidation of the LSD termination condition.

Shimamura, Kohei; Michigami, Keisuke; Wang, Bin; Komurasaki, Kimiya; Arakawa, Yoshihiro

2011-11-01

24

Research on Detonation Wave Mechanics.  

National Technical Information Service (NTIS)

An analysis leading to an extension of the Taylor-Stanyukovich simularity solution for detonation waves having circular symmetries is given. The extension utilizes the continuum mechanical field equations written in intrinsic coordinate form without appro...

M. W. Burnham

1966-01-01

25

Transient Studies of Detonation Waves.  

National Technical Information Service (NTIS)

The smoked foil technique is being used to study the transient behavior of transverse wave systems on propagating detonations that encounter either compositional or tube area changes. A technique has been developed which allows the measurement of the stre...

A. A. Adamczyk R. A. Strehlow R. J. Stiles

1972-01-01

26

A reexamination of the laser supported combustion wave  

NASA Technical Reports Server (NTRS)

Kantrowitz (1972) and Minovitch (1972) have proposed the use of laser sustained plasmas as a means to heat a rocket propellant. Recent studies of laser-powered propulsion have been directed toward the application of high-specific-impulse space propulsion systems for orbital transfer missions. Analyses of rocket performance relied heavily on the concept of the laser-supported combustion (LSC) wave. Raizer (1971) first drew the analogy between laser-sustained plasmas and combustion waves in an analysis. The Raizer model was later applied to hydrogen by Kemp and Root (1979). In connection with certain problems arising with the approach considered by Kemp and Root, the present investigation is concerned with a reexamination of the Raizer model. Attention is given to a numerical approach for the entire LSC wave in hydrogen, taking into account the incorporation of the proper boundary conditions far downstream of the wave.

Keefer, D.; Peters, C.; Crowder, H.

1983-01-01

27

Analytical study of laser-supported combustion waves in hydrogen  

NASA Technical Reports Server (NTRS)

Laser supported combustion (LSC) waves are an important ingredient in the fluid mechanics of CW laser propulsion using a hydrogen propellant and 10.6 micron lasers. Therefore, a computer model has been constructed to solve the one-dimensional energy equation with constant pressure and area. Physical processes considered include convection, conduction, absorption of laser energy, radiation energy loss, and accurate properties of equilibrium hydrogen. Calculations for 1, 3, 10 and 30 atm were made for intensities of 10 to the 4th to 10 to the 6th W/sq cm, which gave temperature profiles, wave speed, etc. To pursue the propulsion application, a second computer model was developed to describe the acceleration of the gas emerging from the LSC wave into a variable-pressure, converging streamtube, still including all the above-mentioned physical processes. The results show very high temperatures in LSC waves which absorb all the laser energy, and high radiative losses.

Kemp, N. H.; Root, R. G.

1978-01-01

28

Detonation-generated shock wave  

Microsoft Academic Search

UDC 533.932 Let us consider a cylindrical explosive charge of sufficiently large dimensions in which aplane detonation wave traveling along the axis is initiated. When this wave emerges at the charge endface, decay of the discontinuity occurs. Let a condensed explosive charge be in contact with an inert medium of lower dynamic stiffness (gas, water, organic material). Then a shock

N. N. Kalitkin; V. M. Sinenko

1980-01-01

29

Change in Continuous Detonation Wave Propagation Mode from Rotating Detonation to Standing Detonation  

NASA Astrophysics Data System (ADS)

We perform a three-dimensional numerical simulation based on a one-step chemical reaction model to investigate changes in the mode of H2-Air detonation wave propagation from rotating detonation wave (RDW) mode to standing detonation wave mode. The physical characteristics of an RDW with injection velocity of 500m/s are analyzed to investigate the physical mechanisms involved. We find that with increasing injection velocity, the detonation wave gradually changes from perpendicular to the head wall to parallel to the head wall. When the injection velocity exceeds the Chapman-Jouguet velocity VCJ (about 1984m/s), the detonation wave changes orientation to become perpendicular to the fuel injection direction, and the rotating mode changes accordingly to a standing mode. Finally, the plane detonation characteristic triple-wave structures can be found from the standing mode.

Shao, Ye-Tao; Wang, Jian-Ping

2010-03-01

30

Interaction of oblique shock and detonation waves  

Microsoft Academic Search

The interaction of an oblique shock wave and an oblique detonation wave which deflect the flow in the same direction is analyzed. The detonation wave is assumed to be an exothermic gasdynamic discontinuity. A criterion is developed and used to determine whether or not a theoretical solution of the problem describes a physically realizable interaction configuration. It is found that

Y. Sheng

1982-01-01

31

Evaluation of the oblique detonation wave ramjet  

NASA Technical Reports Server (NTRS)

The potential performance of oblique detonation wave ramjets is analyzed in terms of multishock diffusion, oblique detonation waves, and heat release. Results are presented in terms of thrust coefficients and specific impulses for a range of flight Mach numbers of 6 to 16.

Morrison, R. B.

1978-01-01

32

Detonation waves induced by a confined wedge  

Microsoft Academic Search

An auto-ignition detonation phenomenon can be initiated by a wedge confined in a channel. A new, self-sustaining, normal detonation wave engine concept is proposed. The detonation processes were numerically modeled with a simplified two-dimensional wedged channel flow that was deemed to emulate a real three-dimensional configuration. The results showed that within certain ranges of incoming flow Mach number or wedge

Frank K. Lu; Huiyuan Fan; Donald R. Wilson

2006-01-01

33

Detonation wave profiles in HMX based explosives  

Microsoft Academic Search

Detonation wave profiles have been measured in several HMX based plastic bonded explosives including PBX9404, PBX9501, and EDC-37, as well as two HMX powders (coarse and fine) pressed to 65% of crystal density. The powders had 120 and 10 ?m average grain sizes, respectively. Planar detonations were produced by impacting the explosive with projectiles launched in a 72-mm bore gas

R. L. Gustavsen; S. A. Sheffield; R. R. Alcon

1998-01-01

34

Detonation wave profiles in HMX based explosives  

Microsoft Academic Search

Detonation wave profiles have been measured in several HMX based plastic bonded explosives including PBX9404, PBX9501, and EDC-37, as well as two HMX powders (coarse and fine) pressed to 65% of crystal density. The powders had 120 and 10 mum average grain sizes, respectively. Planar detonations were produced by impacting the explosive with projectiles launched in a 72-mm bore gas

R. L. Gustavsen; S. A. Sheffield; R. R. Alcon

1998-01-01

35

Detonation wave augmentation of gas turbines  

NASA Technical Reports Server (NTRS)

The results of a feasibility study that examined the effects of using detonation waves to augment the performance of gas turbines are reported. The central ideas were to reduce compressor requirements and to maintain high performance in jet engines. Gasdynamic equations were used to model the flows associated with shock waves generated by the detonation of fuel in detonator tubes. Shock wave attenuation to the level of Mach waves was found possible, thus eliminating interference with the compressor and the necessity of valves and seals. A preliminary parametric study of the performance of a compressor working at a 4:1 ratio in a conceptual design of a detonation wave augmented jet engine in subsonic flight indicated a clear superiority over conventional designs in terms of fuel efficiency and thrust.

Wortman, A.

1984-01-01

36

Detonation wave compression in gas turbines  

NASA Technical Reports Server (NTRS)

A study was made of the concept of augmenting the performance of low pressure ratio gas turbines by detonation wave compression of part of the flow. The concept exploits the constant volume heat release of detonation waves to increase the efficiency of the Brayton cycle. In the models studied, a fraction of the compressor output was channeled into detonation ducts where it was processed by transient transverse detonation waves. Gas dynamic studies determined the maximum cycling frequency of detonation ducts, proved that upstream propagation of pressure pulses represented no problems and determined the variations of detonation duct output with time. Mixing and wave compression were used to recombine the combustor and detonation duct flows and a concept for a spiral collector to further smooth the pressure and temperature pulses was presented as an optional component. The best performance was obtained with a single firing of the ducts so that the flow could be re-established before the next detonation was initiated. At the optimum conditions of maximum frequency of the detonation ducts, the gas turbine efficiency was found to be 45 percent while that of a corresponding pressure ratio 5 conventional gas turbine was only 26%. Comparable improvements in specific fuel consumption data were found for gas turbines operating as jet engines, turbofans, and shaft output machines. Direct use of the detonation duct output for jet propulsion proved unsatisfactory. Careful analysis of the models of the fluid flow phenomena led to the conclusion that even more elaborate calculations would not diminish the uncertainties in the analysis of the system. Feasibility of the concept to work as an engine now requires validation in an engineering laboratory experiment.

Wortman, A.

1986-01-01

37

Diffraction effects in weakly nonlinear detonation waves  

Microsoft Academic Search

In the limit of small heat release, large activation energy and weak nonlinearity, the propagation of detonation waves obeys\\u000a a Geometrical Optics approximation. These equations develop caustic singularities, where the approximation fails. Here we\\u000a present a derivation of a modified set of equations for weakly nonlinear detonation waves incorporating lateral diffraction\\u000a effects. The modified set of equations does not fail

Rodolfo Rosales

38

Detonation waves in pentaerythritol tetranitrate  

Microsoft Academic Search

Fabry–Perot laser interferometry was used to obtain nanosecond time resolved particle velocity histories of the free surfaces of tantalum discs accelerated by detonating pentaerythritol tetranitrate (PETN) charges and of the interfaces between PETN detonation products and lithium fluoride crystals. The experimental records were compared to particle velocity histories calculated using very finely zoned meshes of the exact dimensions with the

Craig M. Tarver; R. Don Breithaupt; John W. Kury

1997-01-01

39

Detonation waves in pentaerythritol tetranitrate  

Microsoft Academic Search

FabryâPerot laser interferometry was used to obtain nanosecond time resolved particle velocity histories of the free surfaces of tantalum discs accelerated by detonating pentaerythritol tetranitrate (PETN) charges and of the interfaces between PETN detonation products and lithium fluoride crystals. The experimental records were compared to particle velocity histories calculated using very finely zoned meshes of the exact dimensions with the

Craig M. Tarver; R. Don Breithaupt; John W. Kury

1997-01-01

40

On the propagation of detonation waves along wedges  

Microsoft Academic Search

It is shown through a series of detonation tube experiments that there are important differences between the wave diffraction trajectories of detonation waves and shock waves. Smoked-foil recordings are presented in order to illustrate the structures of detonation waves behind an overdriven Mach stem, and the peak pressures of the waves are shown. The effect of varying recombination and induction

D. H. Edwards; J. R. Walker; M. A. Nettleton

1984-01-01

41

Reinitiation process of detonation wave behind a slit-plate  

Microsoft Academic Search

The propagation phenomenon of a detonation wave is particularly interesting, because the detonation wave is composed of a\\u000a 3D shock wave system accompanied by a reaction front. Thus, the passage of a detonation wave draws cellular patterns on a\\u000a soot-covered plate. The pressure and temperature behind the detonation wave are extremely high and may cause serious damages\\u000a around the wave.

T. Obara; J. Sentanuhady; Y. Tsukada; S. Ohyagi

2008-01-01

42

Detonation wave profiles in HMX based explosives  

Microsoft Academic Search

Detonation wave profiles have been measured in several HMX based plastic bonded explosives including PBX9404, PBX9501, and EDC-37, as well as two HMX powders (coarse and fine) pressed to 65% of crystal density. The powders had 120 and 10 μm average grain sizes, respectively. Planar detonations were produced by impacting the explosive with projectiles launched in a 72-mm bore gas

R. L. Gustavsen; S. A. Sheffield; R. R. Alcon

1998-01-01

43

On the Structure of Plane Detonation Waves  

Microsoft Academic Search

A steady planar detonation wave, considered to be a shock wave followed by a reaction zone, is studied with both irreversible and reversible first-order reaction kinetics. A perturbation solution with first-order transport effects, valid in the reaction zone for those cases where the ratio of the characteristic collision time to the characteristic chemical time is small compared to one, is

T. C. Adamson

1960-01-01

44

Mach reflection of detonation waves  

NASA Astrophysics Data System (ADS)

The diffraction of a nominally planar gaseous detonation at a wedge was investigated to determine the critical wedge angle for transition from regular to Mach reflection. Experiments were conducted in a square 83-mm cross-section detonation tube using stoichiometric mixtures of hydrogen-oxygen at 0.2 bars. Experimental results for the triple-point trajectory angle produced during Mach reflection were obtained using the smoke foil technique and are compared with analytic calculations made using three-shock theory and the oblique detonation polars. Measurements of the cell size behind the overdriven Mach stem are also reported. Both analytic and experimental results are compared with work from previous investigations to address apparent discrepancies in the existing literature.

Meltzer, J.; Shepherd, J. E.; Akbar, R.; Sabet, A.

45

Detonation wave profiles in HMX based explosives  

NASA Astrophysics Data System (ADS)

Detonation wave profiles have been measured in several HMX based plastic bonded explosives including PBX9404, PBX9501, and EDC-37, as well as two HMX powders (coarse and fine) pressed to 65% of crystal density. The powders had 120 and 10 ?m average grain sizes, respectively. Planar detonations were produced by impacting the explosive with projectiles launched in a 72-mm bore gas gun. Impactors, impact velocity, and explosive thickness were chosen so that the run distance to detonation was always less than half the explosive thickness. For the high density plastic bonded explosives, particle velocity wave profiles were measured at an explosive/window interface using two VISAR interferometers. PMMA windows with vapor deposited aluminum mirrors were used for all experiments. Wave profiles for the powdered explosives were measured using magnetic particle velocity gauges. Estimates of the reaction zone parameters were obtained from the profiles using Hugoniots of the explosive and window.

Gustavsen, R. L.; Sheffield, S. A.; Alcon, R. R.

1998-07-01

46

Detonation wave profiles in HMX based explosives  

SciTech Connect

Detonation wave profiles have been measured in several HMX based plastic bonded explosives including PBX9404, PBX9501, and EDC-37, as well as two HMX powders (coarse and fine) pressed to 65% of crystal density. The powders had 120 and 10 {micro}m average grain sizes, respectively. Planar detonations were produced by impacting the explosive with projectiles launched in a 72-mm bore gas gun. Impactors, impact velocity, and explosive thickness were chosen so that the run distance to detonation was always less than half the explosive thickness. For the high density plastic bonded explosives, particle velocity wave profiles were measured at an explosive/window interface using two VISAR interferometers. PMMA windows with vapor deposited aluminum mirrors were used for all experiments. Wave profiles for the powdered explosives were measured using magnetic particle velocity gauges. Estimates of the reaction zone parameters were obtained from the profiles using Hugoniots of the explosive and window.

Gustavsen, R.L.; Sheffield, S.A.; Alcon, R.R.

1997-11-01

47

On the Existence of Pathological Detonation Waves  

SciTech Connect

Pathological detonation waves with velocities greater than Chapman-Jouguet (C-J) have been proposed theoretically but never observed experimentally in gaseous, liquid or solid explosives. Two types of pathological chemical reaction zones have been identified within the Zeldovich-von Neumann-Doring (ZND) model: an exothermic chemical decomposition with a mole decrease during from the von Neumann spike state to the C-J state and an exothermic reaction followed by an endothermic reaction (eigenvalue detonation). The high temperatures reached in detonation reaction zones cause sufficient radial and atom formation to insure overall mole increases in gaseous H{sub 2} + O{sub 2} detonations. Aluminized explosives exhibit a slight mole decrease when the solid aluminum particles are oxidized, but this does not negate the large mole increase that occurs during explosive decomposition. Porous solid explosives whose products form with more cold compression energy than that of the solid are an unlikely possibility for pathological detonation. Eigenvalue detonations have been postulated for H{sub 2} + Cl{sub 2} gas phase detonations and for plastic bonded solid explosives if endothermic binder decomposition follows exothermic explosive decomposition. Chemical kinetic and physical arguments are presented to eliminate these possible pathological detonations. In the case of H{sub 2} + Cl{sub 2}, highly vibrationally excited HCl molecules dissociate Cl{sub 2} molecules during the exothermic portion of the reaction zone rather than later in the flow process. In the plastic bonded explosives, the binders are located on the surfaces of explosive particles and thus are exposed to ''hot spots'' created by the three-dimensional Mach stem shock front. Any remaining binder material rapidly reacts in collisions with the high, vibrationally excited reaction products formed during explosive decomposition. Therefore eigenvalue detonations are extremely unlikely to occur in gaseous, liquid or solid explosives.

Tarver, C M

2003-07-11

48

On the Existence of Pathological Detonation Waves  

NASA Astrophysics Data System (ADS)

Pathological detonation waves with velocities greater than Chapman-Jouguet (C-J) have been proposed theoretically but never observed experimentally in gaseous, liquid or solid explosives. Two types of pathological chemical reaction zones have been identified within the Zeldovich - von Neumann - Doring (ZND) model: an exothermic chemical decomposition with a mole decrease from the von Neumann spike state to the C-J state; and an exothermic reaction followed by an endothermic reaction (eigenvalue detonation). The high temperatures reached in detonation reaction zones cause sufficient radial and atom formation to insure that enough moles are formed in gaseous 2H2 + O2 detonations. Aluminized explosives exhibit a slight mole decrease when the solid aluminum particles are oxidized, but this does not negate the large mole increase that occurs during explosive decomposition. Porous solid explosives whose products form with more cold compression energy than that of the solid are still a possibility for pathological detonation. Eigenvalue detonations have been postulated for H2 + Cl2 gas phase detonations and for plastic bonded solid explosives if endothermic binder decomposition follows exothermic explosive decomposition. Chemical kinetic and physical arguments are presented to eliminate these possible pathological detonations. In the case of H2 + Cl2, highly vibrationally excited HCl molecules dissociate Cl2 molecules during the exothermic portion of the reaction zone rather than later in the flow process. In the plastic bonded explosives, the binders are located on the surfaces of explosive particles and thus are exposed to hot spots created by the three-dimensional Mach stem shock front. Any remaining binder material rapidly reacts in collisions with the high, vibrationally excited reaction products formed during explosive decomposition. Therefore eigenvalue detonations are extremely unlikely to occur in gaseous, liquid or solid explosives.

Tarver, Craig M.

2004-07-01

49

Mach Waves in Shock Wave Systems from Detonating Explosives  

Microsoft Academic Search

WE have recently obtained many photographs of Mach waves1, known alternatively as `bridge' or `Y' waves2, in the shock wave systems resulting from the detonation of unconfined charges of solid explosive. Waves of this type, which Mach postulated from the observation of soot patterns, are produced when supersonic waves intersect at obtuse angles of incidence. Instead of the simple intersection

D. W. Woodhead; R. Wilson

1947-01-01

50

Dynamic characteristics of spherically converging detonation waves  

NASA Astrophysics Data System (ADS)

The spherically converging detonation wave was numerically investigated by solving the one-dimensional multi-component Euler equations in spherical coordinates with a dispersion-controlled dissipative scheme. Finite rate and detailed chemical reaction models were used and numerical solutions were obtained for both a spherical by converging detonation in a stoichiometric hydrogen-oxygen mixture and a spherically focusing shock in air. The results showed that the post-shock pressure approximately arises to the same amplitude in vicinity of the focal point for the two cases, but the post-shock temperature level mainly depends on chemical reactions and molecular dissociations of a gas mixture. While the chemical reaction heat plays an important role in the early stage of detonation wave propagation, gas dissociations dramatically affect the post-shock flow states near the focal point. The maximum pressure and temperature, non-dimensionalized by their initial value, are approximately scaled to the propagation radius over the initial detonation diameter. The post-shock pressure is proportional to the initial pressure of the detonable mixture, and the post-shock temperature is also increased with the initial pressure, but in a much lower rate than that of the post-shock pressure.

Jiang, Zonglin; Chang, Lina; Zhang, Fan

2007-02-01

51

On the Existence of Pathological Detonation Waves  

Microsoft Academic Search

Pathological detonation waves with velocities greater than Chapman-Jouguet (C-J) have been proposed theoretically but never observed experimentally in gaseous, liquid or solid explosives. Two types of pathological chemical reaction zones have been identified within the Zeldovich - von Neumann - Doring (ZND) model: an exothermic chemical decomposition with a mole decrease from the von Neumann spike state to the C-J

Craig M. Tarver

2004-01-01

52

Performance Characteristics of Hypersonic Detonation Wave Ramjets.  

National Technical Information Service (NTIS)

One method of heat addition to a supersonic flow is by means of shock-induced combustion or in this particular study a detonation wave. In order to assess the performance potential of a propulsion utilizing such a mode of heat addition a first order invis...

T. M. Atamanchuk J. P. Sislian

1990-01-01

53

Detonation.  

National Technical Information Service (NTIS)

A brief definition of detonation is followed by a detailed discussion of how it occurs and how it can be made to occur in simple tubular apparatuses. Three basic types and detonation--weak, strong and Chapman-Jouguet--are described. The role of shock wave...

K. I. Shchelkin

1968-01-01

54

PETN Particles in a Gas-Detonation Wave  

Microsoft Academic Search

To account for the development pattern of detonation by weakly initiating powdered high explosives (HE) an investigation of interacting HE particles with a high-enthalpy gas flow was performed. The results of experiments of an ignition of PETN particles by gas-detonation wave is reported. The radiation intensity of detonation products (DP) was recorded by several wave lengths simultaneously with using of

Vladimir Grigoriev; Leonid Lukyanchikov; Eduard Pruuel

1997-01-01

55

The flow field in a rotating detonation-wave engine  

NASA Astrophysics Data System (ADS)

Rotating detonation-wave engines (RDE) are a form of continuous detonation-wave engine. They potentially provide further gains than an intermittent or pulsed detonation--wave engine (PDE). However, significantly less work has been on this concept when compared to the PDE. In this talk, we present the detailed flow field in an idealized RDE, primarily consisting of two concentric cylinders. A premixed detonable mixture is injected into the annulus between the two concentric cylinders. Once a detonation is initiated, it keeps travelling around in the annulus as long as there is fresh detonable mixture ahead of it. Hence, the injection process is critically important to the stability and performance of the RDE. Furthermore, we show that the flow field is quite complex consisting of multiple shock waves and the outflow is primarily axial, although the detonation-wave is travelling around circumferentially.

Kailasanath, Kazhikathra; Schwer, Douglas

2011-11-01

56

On the Existence of Pathological Detonation Waves  

Microsoft Academic Search

Pathological detonation waves with velocities greater than Chapman-Jouguet (C-J) have been proposed theoretically but never observed experimentally in gaseous, liquid or solid explosives. Two types of pathological chemical reaction zones have been identified within the Zeldovich-von Neumann-Doring (ZND) model: an exothermic chemical decomposition with a mole decrease during from the von Neumann spike state to the C-J state and an

Tarver

2003-01-01

57

Spherically imploding detonation waves initiated by two-step divergent detonation  

NASA Astrophysics Data System (ADS)

The detonation chamber developed by K. Terao and H. G. Wagner in Göttingen has been improved, in order to concentrate the combustion energy more effectively to a focus, so that imploding detonation waves are initiated by two-step divergent detonation waves in a hemispherical space having an effective diameter of 500 mm. The imploding detonation waves are investigated by measuring their propagation velocity using ion probes and pressure variations at different positions in the space by a piezoelectric pressure transducer, while the temperature in the implosion center is measured by a laser light scattering method. The results suggest that the peak pressure at the detonation front increases with the propagation to the center more rapidly than that in the Göttingen apparatus, while the propagation velocity is almost the same. A temperature from 107 K to 108 K is also observed in the focus of the imploding detonation waves.

Terao, K.; Akaba, H.; Shiraishi, H.

1995-07-01

58

Detonation wave profiles in HMX based explosives  

SciTech Connect

Detonation wave profiles have been measured in several HMX based plastic bonded explosives including PBX9404, PBX9501, and EDC-37, as well as two HMX powders (coarse and fine) pressed to 65{percent} of crystal density. The powders had 120 and 10 {mu}m average grain sizes, respectively. Planar detonations were produced by impacting the explosive with projectiles launched in a 72-mm bore gas gun. Impactors, impact velocity, and explosive thickness were chosen so that the run distance to detonation was always less than half the explosive thickness. For the high density plastic bonded explosives, particle velocity wave profiles were measured at an explosive/window interface using two VISAR interferometers. PMMA windows with vapor deposited aluminum mirrors were used for all experiments. Wave profiles for the powdered explosives were measured using magnetic particle velocity gauges. Estimates of the reaction zone parameters were obtained from the profiles using Hugoniots of the explosive and window. {copyright} {ital 1998 American Institute of Physics.}

Gustavsen, R.L.; Sheffield, S.A.; Alcon, R.R. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

1998-07-01

59

The strength of transverse waves in marginal planar detonation waves  

Microsoft Academic Search

The structure of planar detonation waves propagating in a narrow rectangular channel, of cross section 3×¼ in2, has been studied for a mixture of stoichiometric oxyhydrogen diluted with 60% argon. It is confirmed that at an initial pressure of 80 torr the waves generated are self-sustaining and possess either two or three Mach interactions along the broad wall of the

D H Edwards; R J Meddins

1971-01-01

60

MHD Control of Oblique Detonation Waves  

NASA Astrophysics Data System (ADS)

Based on the Euler equation, the hybrid Roe/HLL scheme is employed to simulate the oblique detonation waves (ODWs). Furthermore, magnetohydrodynamic (MHD) control of both stable and unstable ODWs is investigated. It is shown that the stable ODW wave front can be controlled to the desired position under different inflow Mach numbers. However, for an unstable ODW, it is difficult for the MHD control to return the ODW front, but the unstable ODW turns to be stable with the Lorentz force applied in proper direction.

Sun, Xiao-Hui; Chen, Zhi-Hua; Zhang, Huan-Hao

2011-01-01

61

Wave dynamic processes in cellular detonation reflection from wedges  

Microsoft Academic Search

When the cell width of the incident detonation wave (IDW) is comparable to or larger than the Mach stem height, self-similarity\\u000a will fail during IDW reflection from a wedge surface. In this paper, the detonation reflection from wedges is investigated\\u000a for the wave dynamic processes occurring in the wave front, including transverse shock motion and detonation cell variations\\u000a behind the

Zongmin Hu; Zonglin Jiang

2007-01-01

62

The quasi-steady regime in critically initiated detonation waves  

Microsoft Academic Search

Experimental work is described on the initiation of spherical detonation waves, in oxyacetylene with various diluents, using an exploding wire and a lead azide pellet as sources. The transition of the spherical blast wave to a detonation, when the source energy is either above or at the critical value, is studied by three methods. Changes in wave structure are inferred

D. H. Edwards; G. Hooper; J. M. Morgan; G. O. Thomas

1978-01-01

63

Mach Reflection of Detonation Waves in Condensed High Explosives. II  

Microsoft Academic Search

Reflection parameters are derived for two colliding plane detonation waves in a condensed high explosive. The pressure and angle of the reflected shock wave are calculated as a function of the detonation-wave angle to the line of collision. The critical angle for the onset of Mach reflection and the pressure in the center of the Mach stem are also determined.

Brian Dunne

1964-01-01

64

Numerical modeling of divergent detonation wave  

NASA Astrophysics Data System (ADS)

The indefinite nature of divergent detonations under the assumption of instantaneous stable detonation is described. In the numerical modeling method for divergent detonation, the artificial cohesiveness was improved and the Cochran reaction rate and the JWL equations of state were used to describe the ignition process of the explosion. Several typical divergent detonation problems were computed obtaining rather satisfying results.

Li, Zhiwei; Liu, Bangdi

1987-11-01

65

Propagation of detonation waves from an impact region  

Microsoft Academic Search

An experimental system was developed to study the propagation of a detonation wave away from a region that is initiated by the impact of a thin flyer plate. The propagation of detonation waves away from this region in pressed pellets of TATB and in RX-26-AF, a TATB\\/HMX formulation is studied. The system permits measurements at elevated, ambient, and low temperatures.

R. S. Lee; W. C. Tao; L. D. Crouch

1989-01-01

66

Model of Hypersonic Two-Dimensional Oblique Detonation Wave Ramjet.  

National Technical Information Service (NTIS)

The possibility of using an oblique detonation wave ramjet as a power plant for a hypersonic vehicle is examined. The performance of a model of a two dimensional oblique detonation wave ramjet is analyzed in terms of thrust, lift and fuel consumption.

Y. Sheng J. P. Sislian

1985-01-01

67

Dynamics and Stability of a Weak Detonation Wave  

Microsoft Academic Search

:  One dimensional weak detonation waves of a basic reactive shock wave model are proved to be nonlinearly stable, i.e. initially\\u000a perturbed waves tend asymptotically to translated weak detonation waves. This model system was derived as the low Mach number\\u000a limit of the one component reactive Navier-Stokes equations by Majda and Roytburd [SIAM J. Sci. Stat. Comput. 43, 1086–1118 (1983)], and

Anders Szepessy; Kungl Tekniska Hogskolan; S Stockholm

1999-01-01

68

On the propagation of detonation waves along wedges  

NASA Astrophysics Data System (ADS)

It is shown through a series of detonation tube experiments that there are important differences between the wave diffraction trajectories of detonation waves and shock waves. Smoked-foil recordings are presented in order to illustrate the structures of detonation waves behind an overdriven Mach stem, and the peak pressures of the waves are shown. The effect of varying recombination and induction zone lengths on the spacing behind the overdriven Mach stem are described, and a simple numerical relation is derived for the spacing of transverse waves and the induction time of the chain-branching reaction H + O2 gives OH + O. It is found that the numerical relation provides an adequate description of the observed spacing in the case of overdriven detonation.

Edwards, D. H.; Walker, J. R.; Nettleton, M. A.

69

Gasdynamic characteristics of toroidal shock and detonation wave converging  

Microsoft Academic Search

The modified CCW relation is applied to analyzing the shock, detonation wave converging and the role of chemical reactions\\u000a in the process. Results indicate that the shock wave is strengthened faster than the detonation wave in the converging at\\u000a the same initial Mach number. Euler equations implemented with a detailed chemical reaction model are solved to simulate toroidal\\u000a shock and

Honghui Teng; Zonglin Jiang

2005-01-01

70

Mach Reflection of Detonation Waves in Condensed High Explosives  

Microsoft Academic Search

By preshocking a condensed high explosive before the passage of a detonation front, it is possible to increase the peak pressure in the front to a level at which reflection phenomena can be readily observed by means of the Dautriche effect. Also, by the use of a tracer detonation wave, which intersects the shock configuration, it is possible to observe

B. B. Dunne

1961-01-01

71

Numerical simulations of a pulsed detonation wave augmentation device  

NASA Technical Reports Server (NTRS)

We present here the concept of a hybrid engine for Single Stage To Orbit (SSTO) air-breathing hypersonic vehicle. This concept relies on the use of pulsed detonation waves, both for thrust generation and mixing/combustion augmentation. We describe the principles behind the engine concept, which we call the Pulsed Detonation Wave Augmentor (PDWA). We demonstrate the principles of operation for two possible configurations through numerical simulations. We also attempt a first approximation to engine design, and propose various applications.

Cambier, Jean-Luc; Adelman, Henry; Menees, Gene P.

1993-01-01

72

Propagation of detonation waves from an impact region  

NASA Astrophysics Data System (ADS)

An experimental system was developed to study the propagation of a detonation wave away from a region that is initiated by the impact of a thin flyer plate. The propagation of detonation waves away from this region in pressed pellets of TATB and in RX-26-AF, a TATB/HMX formulation is studied. The system permits measurements at elevated, ambient, and low temperatures. The the distance-time trajectory and arrival time of the detonation front at the downstream face of the explosive pellets is measured for pellets with thicknesses of 1 to 16 mm over the temperature range -80 to +80 C.

Lee, R. S.; Tao, W. C.; Crouch, L. D.

73

Wavelets for uncertainty estimates of propagating shock and detonation waves  

NASA Astrophysics Data System (ADS)

The propagation speed of a shock or detonation wave in a shock or detonation tube is usually determined by a time-of-flight method by dividing the distance between two transducers with the propagation time of the disturbance signal. Some arbitrariness is inherent in determining the propagation time by this method. A new method based on Haar and Morlet wavelet transforms is reported. The method was applied to shock and detonation waves representing a step and a decaying spike discontinuity. The wavelet methods can be applied to the step discontinuity provided that the SNR ratio is good. The wavelet methods worked well for a decaying spike in the presence of noise.

Lu, F. K.; Ortiz, A. A.

2012-01-01

74

Dynamics and Stability of a Weak Detonation Wave  

NASA Astrophysics Data System (ADS)

One dimensional weak detonation waves of a basic reactive shock wave model are proved to be nonlinearly stable, i.e. initially perturbed waves tend asymptotically to translated weak detonation waves. This model system was derived as the low Mach number limit of the one component reactive Navier-Stokes equations by Majda and Roytburd [SIAM J. Sci. Stat. Comput. 43, 1086-1118 (1983)], and its weak detonation waves have been numerically observed as stable. The analysis shows in particular the key role of the new nonlinear dynamics of the position of the shock wave, The shock translation solves a nonlinear integral equation, obtained by Green's function techniques, and its solution is estimated by observing that the kernel can be split into a dominating convolution operator and a remainder. The inverse operator of the convolution and detailed properties of the traveling wave reduce, by monotonicity, the remainder to a small L1 perturbation.

Szepessy, Anders

75

Gasdynamic characteristics of toroidal shock and detonation wave converging  

NASA Astrophysics Data System (ADS)

The modified CCW relation is applied to analyzing the shock, detonation wave converging and the role of chemical reactions in the process. Results indicate that the shock wave is strengthened faster than the detonation wave in the converging at the same initial Mach number. Euler equations implemented with a detailed chemical reaction model are solved to simulate toroidal shock and detonation wave converging. Gasdynamic characteristics of the converging are investigated, including wave interaction patterns, observable discrepancies and physical phenomena behind them. By comparing wave diffractions, converging processes and pressure evolutions in the focusing area, the different effects of chemical reactions on diffracting and converging processes are discussed and the analytic conclusion is demonstrated through the observation of numerical simulations.

Teng, Honghui; Jiang, Zonglin

2005-11-01

76

Shock Tube Using Free Piston Driven by Detonation Waves  

Microsoft Academic Search

In order to improve and simplify the Stalker tube, a shock tube having a free piston driven by detonation waves is developed and examined. The free piston accelerated in a long vacuum tube enters into the He shock driver gas with a velocity higher than 300 m\\/s, producing a shock wave at its front. Due to the repeating shock wave

Kunio Terao; Tomonobu Furushoh

1994-01-01

77

Analytical and Experimental Investigations of the Oblique Detonation Wave Engine Concept.  

National Technical Information Service (NTIS)

Wave combustors, which include the Oblique Detonation Wave Engine (ODWE), are attractive propulsion concepts for hypersonic flight. These engines utilize oblique shock or detonation waves to rapidly mix, ignite, and combust the air-fuel mixture in thin zo...

G. P. Menees H. G. Adelman J. Cambier

1991-01-01

78

Analytical and Experimental Investigations of the Oblique Detonation Wave Engine Concept.  

National Technical Information Service (NTIS)

Wave combustors, which include the oblique detonation wave engine (ODWE), are attractive propulsion concepts for hypersonic flight. These engines utilize oblique shock or detonation waves to rapidly mix, ignite, and combust the air-fuel mixture in thin zo...

G. P. Menees H. G. Adelman J. Cambier

1990-01-01

79

Application of steady and unsteady detonation waves to propulsion  

NASA Astrophysics Data System (ADS)

The present work investigates the applications of steady and unsteady detonation waves to air-breathing propulsion systems. The efficiency of ideal detonation-based propulsion systems is first investigated based on thermodynamics. We reformulate the Hugoniot analysis of steady combustion waves for a fixed initial stagnation state to conclude that steady detonation waves are less desirable than deflagrations for propulsion. However, a thermostatic approach shows that unsteady detonations have the potential for generating more work than constant-pressure combustion. The subsequent work focuses on specific engine concepts. A flow path analysis of ideal steady detonation engines is conducted and shows that their performance is limited and poorer than that of the ideal ramjet or turbojet engines. The limitations associated with the use of a steady detonation in the combustor are drastic and such engines do not appear to be practical. This leads us to focus on unsteady detonation engines, i.e., pulse detonation engines. The unsteady generation of thrust in the simple configuration of a detonation tube is first analyzed using gas dynamics. We develop one of the first models to quickly and reliably estimate the impulse of a pulse detonation tube. The impulse is found to scale directly with the mass of explosive in the tube and the square root of the energy release per unit mass of the mixture. Impulse values for typical fuel-oxidizer mixtures are found to be on the order of 160 s for hydrocarbon-oxygen mixtures and 120 s for fuel-air mixtures at standard conditions. These results are then used as a basis to develop the first complete system-level performance analysis of a supersonic, single-tube, air-breathing pulse detonation engine. We show that hydrogen- and JP10-fueled pulse detonation engines generate thrust up to a Mach number of 4, and that the specific impulse decreases quasi-linearly with increasing flight Mach number. Finally, we find that the performance of our pulse detonation engine exceeds that of the ramjet below a Mach number of 1.35.

Wintenberger, Eric

80

The role of compressible turbulence in detonation waves  

NASA Astrophysics Data System (ADS)

Detonation waves are supersonic combustion waves, observable in both terrestrial and astrophysical settings. The present study investigates experimentally and numerically the turbulent structure of gaseous detonation waves. Due to hydrodynamic instabilities, the front exhibits pulsations over a large range of scales. During the negative pulsations of the leading front, chemical induction delay times increase dramatically. Nevertheless, the gas shocked during these negative pulsations ignites before its adiabatic ignition delay times, following the turbulization of burned/unburned gas interfaces and increase of transport rates. The nature of the turbulent interactions responsible for the gas ignition are identified. Shock-shock interactions produce vorticity layers which enhance mixing via Kelvin-Helmholtz instabilities. Shock-density layer interactions favor Richtmyer-Meshkov instabilities. Large vortical flows entrain hot reacted gases into un-reacted gases and enhance their burning rates. A statistical description of the turbulent energy budget within the detonation wave structure is obtained from the two-dimensional numerical simulations.

Radulescu, Matei I.; Sharpe, Gary J.; Law, Chung K.

2004-11-01

81

Laser-initiated conical detonation wave for supersonic combustion. II  

NASA Astrophysics Data System (ADS)

Further theoretical studies are undertaken of the feasibility of an air-breathing supersonic combustor based on a stabilized, conically configured (oblique) detonation wave. The conical wave is the resultant of the interaction of a train of spherical detonation waves, each directly initiated by a very rapidly repeated pulsed laser, which is tightly focused on a fixed site in a steady uniform supersonic stream of combustible gaseous mixture. Here, the length of an axisymmetric (nearly conical) nozzle required to exhaust the reacted mixture at ambient-atmosphere pressure is estimated by a steady isentropic ideal-gas flow calculation. Then the thrust-to-drag ratio achievable with such a combustor for upper-atmospheric flight is roughly characterized. Finally, proof-of-principle laboratory experiments needed to establish the capacity of existing laser sources to achieve the direct initiation of detonation in hydrogen/air mixtures under conditions of practical interest are outlined.

Fendell, F.; Mitchell, J.; McGregor, R.; Magiawala, K.; Sheffield, M.

1992-01-01

82

Links between detonation wave propagation and reactive flow models.  

SciTech Connect

An accurate reactive flow model is necessary to be able to predict the initiation properties of explosives by complicated shock structures, but a very fine the spatial resolution is needed in reactive flow to reproduce the detailed dynamics of a detonation wave. However, it is not often necessary to use a reactive flow model to simulate the motion of a fully-developed detonation wave. In many situations the same results can be obtained with a coarse computational mesh using programmed burn techniques. In the WBL model [Lambourn89,Swift93], an eikonal detonation wave propagates through a body of explosive at a speed which depends on the curvature of the wave. The model describes the motion of the leading shock of the detonation wave. Here we use the level set method for integrating the WBL equations in time [Collyer98,Bdzil93,Osher88,Aslam98]. This method is attractive because complicated detonation wave shapes can be represented simply. It was found possible to initialize the level set field by a set of source points derived from a reactive flow simulation, by taking 'trigger states' from the reactive flow. The level set scheme was generalized further to take account of motion of the material behind the detonation wave, allowing it to be used for simulations coupled with reactive flow, where detonation may propagate through preshocked and moving material. The modified level set scheme was implemented in 1D and 2D Lagrangian hydrocodes. Trial calculations were performed of initiation and detonation in the TATB-based explosive LX-17, using the Lee - Tarver model. A CJ detonation was simulated in order to verify that the modified level set algorithm operated correctly. The detonation speed was in very good agreement with the expected value. Single-shock initiation was simulated. The position - time history of the leading shock from the coupled model was in excellent agreement with full reactive flow; the pressure profiles were similar but not identical, because of the difference in material properties behind the WBL wave and the omission of the von Neumann spike from the WBL profiles. As a more interesting test, we simulated the shock-to-detonation transition on reflection of a weak shock from a rigid boundary. The position - time history of the leading shock was in good agreement. The pressure profiles varied much more than in the single-shock case, because the WBL calculation used the same propagation parameters and for simplicity imposed the same state at the end of the detonation zone as was used in the single-shock simulation. We have previously used quasisteady flow analysis to derive a reaction rate from experimental measurements of the relation between detonation speed and wave curvature, or vice versa [Swift93]. Reactive flow models have been developed for HMX-based explosives based on mesoscale representations of the components of the explosive [Mulford01], and using a temperature-dependent reaction rate which should be valid over a wide range of loading conditions. The quasisteady analysis scheme was extended to allow arbitrary reaction models to be investigated.

Swift, D. C. (Damian C.); White, S. J. (Stephen J.)

2002-01-01

83

Propagation of detonation waves from an impact region  

SciTech Connect

We have developed an experimental system for studying the propagation of a detonation wave away from a region that is initiated by the impact of a thin flyer plate. We have studied the propagation of detonation waves away from this region in pressed pellets of TATB and in RX-26-AF, a TATB/HMX formulation. The system permits measurements at elevated, ambient and low temperatures. We measured the distance-time trajectory and arrival time of the detonation front at the downstream face of the explosive pellets for pellets with thicknesses of 1-16 mm over the temperature range -80{degree}C to +80{degree}C. 9 refs., 10 figs.

Lee, R.S.; Tao, W.C.; Crouch, L.D.

1989-01-01

84

Mechanism of Detonation Wave propagation in PBX with Energetic Binder  

NASA Astrophysics Data System (ADS)

The complex phenomena of Detonation Wave (DW) propagation in PBX of 82% of HMX, with successively HTPB, as inert binder, and GAP as Energetic Binder (EB), with an initial density 99.5% TMD was studied. A thin optical multifibre strip (250 ?m each fibre), connected to a fast electronic streak camera, allows the nanosecond temporal resolution not only of the behavior of coarse HMX particles, surrounded by binder, but also the fine geometrical structure of detonation and its subsequent shock waves. The results obtained with micro gap and corner turning tests, prove the influence of EB in the mechanisms of DW formation in PBX, especially in the interaction zone between binder and particles. Detonation in PBX with GAP binder shows the shock front interacting earlier in the EB space, between the coarse particles, and DW oscillations with a mean period of 23+/-5 ns, 1.5 times less than those observed in PBX with HTPB. .

Plaksin, I.; Campos, J.; Mendes, R.; Ribeiro, J.; Gois, J.

2000-04-01

85

Transverse waves in numerical simulations of cellular detonations  

Microsoft Academic Search

In this paper the structure of strong transverse waves in two-dimensional numerical simulations of cellular detonations is investigated. Resolution studies are performed and it is shown that much higher resolutions than those generally used are required to ensure that the flow and burning structures are well resolved. Resolutions of less than about 20 numerical points in the characteristic reaction length

Gary J. Sharpe

2001-01-01

86

Numerical simulation of standing detonation induced by oblique shock wave  

Microsoft Academic Search

The induction of standing detonation in a gaseous mixture in a convergent-divergent nozzle by an oblique shock wave is investigated theoretically by means of numerical simulations using a multilevel-grid method. The approaches used to model the chemical reactions, the thermodynamic properties, the transport properties, and the combustion chamber is described; the derivation of the fundamental equations are outlined; and the

Shiro Taki

1989-01-01

87

The variation in strength of transverse shocks in detonation waves  

Microsoft Academic Search

The variation of strength along a transverse shock associated with a Mach stem interaction at the detonation front in 2CO + O2 at 50 torr was measured by analysis of interferograms. An approximate solution to the flow behind the nonsteady reactive wave is obtained on the assumption of a power-law form for the density profile which is a reasonable representation

D. H. Edwards; A. T. Jones

1978-01-01

88

Direct Calculation of Wave Implosion for Detonation Initiation in Pulsed Detonation Engines  

Microsoft Academic Search

One- and two-dimensional imploding waves are numerically simulated by using the space- time CESE method. One-dimensional calculations show that a Mach 1.3 converging shock is capable to initiate the detonation in a 2:1:7 H2\\/O2\\/Ar gas mixture, initially at 0.2 standard atmospheric pressure. Results also clearly show a two-shock implosion system, resulting from interactions between the reflected main shock and the

Bao Wang; S.-T. John Yu

89

Simulations of a Detonation Wave in Transverse Magnetic Fields  

NASA Astrophysics Data System (ADS)

Numerical simulations of magneto-hydrodynamic (MHD) effects on detonation wave structures are performed, with applications to flow control and MHD power extraction in Pulse Detonation Engines (PDE) and their design variations. In contrast to prior studies of MHD interactions in PDEs,ootnotetextCambier, et al., AIAA-2008-4688 the effects of the finite relaxation length scale for ionization on the stability of the detonation wave are examined. Depending on the coupling parameters, the magnetic field can quench the detonation and effectively act as a barrier to its propagation. Conversely, an applied transient magnetic field can exert a force on a pre-ionized gas and accelerate it. The dynamics are subject to non-linear effects; a propagating transverse magnetic field will initially exert a small force if the gas has a low conductivity and the magnetic Reynolds number (Rem) is low. Nevertheless, the gas accelerated by the "piston" action of the field can pre-heat the ambient gas and increase its conductivity. As the wave progresses, Rem increases and the magnetic field becomes increasingly effective. The dynamics of this process are examined in detail with a high-order shock-capturing method and full kinetics of combustion and ionization. The complex chemical kinetics calculations are ported onto a GPU using the CUDA language, and computational performance is compared with standard CPU-based computations.

Cole, Lord; Karagozian, Ann; Cambier, Jean-Luc

2010-11-01

90

Impact waves and detonation. Part I  

NASA Technical Reports Server (NTRS)

Among the numerous thermodynamic and kinetic problems that have arisen in the application of the gaseous explosive reaction as a source of power in the internal combustion engine, the problem of the mode or way by which the transformation proceeds and the rate at which the heat energy is delivered to the working fluid became very early in the engine's development a problem of prime importance. The work of Becker here given is a notable extension of earlier investigations, because it covers the entire range of the explosive reaction in gases - normal detonation and burning.

Becker, R

1929-01-01

91

Mach reflection in a detonating gas with a stem in the form of a shock wave  

Microsoft Academic Search

The reflection of a plane shock wave from a solid wall in a detonating gas mixture is investigated for the case of the formation of a triple wave configuration with a reflected detonation wave and a Mach stem in the form of a shock wave. Systems of equations describing flow of gas behind the reflected wave are presented, as are

N. D. Vysk; N. N. Smirnov

1986-01-01

92

Velocity of spherically-diverging detonation waves in RX-26-AF, LX-17 and LX-10  

SciTech Connect

The velocity of spherically-diverging detonation waves was measured in RX-26-AF, LX-17 and LX-10 explosives at 20/sup 0/C and -54/sup 0/C for detonation wave radii from 13 to 50 mm. At the smaller radii the measured velocities were lower than published steady detonation velocities by as much as 4%. The detonation velocities measured at -54/sup 0/C were usually higher than those measured at room temperature. These results indicate that a significant part of the excess transit time observed when an explosive is initiated by a point or hemispherical detonator may be due to a low detonation velocity.

Bahl, K.L.; Lee, R.S.; Weingart, R.C.

1983-07-15

93

Velocity of spherically-diverging detonation waves in RX26AF, LX17 and LX10  

Microsoft Academic Search

The velocity of spherically-diverging detonation waves was measured in RX-26-AF, LX-17 and LX-10 explosives at 20°C and -54°C for detonation wave radii from 13 to 50 mm. At the smaller radii the measured velocities were lower than published steady detonation velocities by as much as 4%. The detonation velocities measured at -54°C were usually higher than those measured at room

K. L. Bahl; R. S. Lee; R. C. Weingart

1983-01-01

94

Re-Initiation Mechanisms of a Detonation Wave in the PDE Initiator Using a Reflecting Board  

NASA Astrophysics Data System (ADS)

Quick initiation of a detonation wave in a combustion chamber is important to realize high-performance pulse detonation engine. A possible method is to generate a detonation wave in a pre-detonator and release the detonation wave into the chamber. In this paper, a reflecting board is installed in the combustion chamber near the pre-detonator exit where the tube diameter expands abruptly. It prevents the detonation wave from disappearing at the expanding region near the tube exit. The re-initiation mechanisms of a detonation wave near the reflecting board were observed by using the soot film method. Main results obtained in this study are in the followings: Re-initiation of a detonation wave due to the Mach reflection of a shock wave is observed on the surface of the reflecting board and the propagation promoting effect is observed. The effectiveness of the reflecting board is a strong function of the clearance between the pre-detonator exit and the reflecting board, and the promotion effect sharply decreases with increasing the clearance beyond the distance, in which the incident planar detonation wave maintains. By equipping with a reflective board with a suitable clearance, the critical cell size increases by 2 or 3 times.

Wakita, Masashi; Numakura, Ryusuke; Ito, Yusuke; Nagata, Harunori; Totani, Tsuyoshi; Kudo, Isao

95

Ignition of petn particles by a gas-detonation wave  

Microsoft Academic Search

Ignition ofPETN particles by a gas-detonation wave in a gas suspension has been studied experimentally. The critical pressure at which the\\u000a total rate ofPETN decomposition increases sharply has been found using a method of multiwave pyrometry with variation in the pressure of the\\u000a initial gas mixture from 0.1 to 0.4MPa. It is shown that this can occur owing to a

V. V. Grigor’ev; L. A. Lukyanchikov; É. P. Pruuel

1997-01-01

96

Numerical investigation of oblique detonation waves for a shcramjet combustor  

NASA Astrophysics Data System (ADS)

Research in hypersonic airbreathing propulsion strives to provide an efficient, cost-effective alternative to rocket propulsion for space transportation systems. The supersonic combustion ramjet (scramjet) is one of the most common hypersonic airbreathing propulsion concepts, but its massive combustor could have detrimental effects on its efficiency. The shock-induced combustion ramjet (shcramjet) overcomes this drawback by using standing oblique detonation waves (coupled shock-combustion fronts) as a means of nearly instantaneous heat addition. A numerical investigation of standing oblique detonation waves for their use in shcramjet propulsion is the main purpose of this investigation. The laminar, two-dimensional Navier-Stokes equations coupled with non-equilibrium hydrogen/air combustion models based on chemical kinetics are used to represent the physical system. The combustion models are incorporated into an in-house computational fluid dynamics solver based on a shock-capturing scheme by Yee scheme and an approximate factorization algorithm with a dual-time stepping technique to regain time-accuracy. The solver is validated with experimental data found in the literature. A time accurate simulation of the formation of a standing oblique detonation wave (ODW) near the Chapman Jouguet (minimum entropy) condition yields a non-oscillatory, stable structure. The stability of the ODW to inhomogeneities in the oncoming fuel/air mixture is assessed through other time-accurate simulations by artificially introducing small disturbances consisting of pure air just upstream of the ODW structure. The ODW is shown to be resilient to these disturbances: an upstream displacement is observed followed by the return of the ODW to its original position. Steady-state simulations are carried out to determine the effect of laminar boundary layers on ODW structures and properties above and below the Chapman-Jouguet point. A comparison with analogous inviscid simulations shows that the effect is minimal and that the shorter induction distance in laminar flow does not entail a significantly earlier onset of the ODW. A novel shcramjet combustor design that makes use of oblique detonation waves stabilized over wedge-shaped flame-holders and configured such that detonation wave-wall interactions are avoided, is presented and analyzed through steady-state simulations. The design is shown to be a viable one for shcramjet propulsion by means of thrust potential calculations.

Fusina, Giovanni

97

Shock Tube Using Free Piston Driven by Detonation Waves  

NASA Astrophysics Data System (ADS)

In order to improve and simplify the Stalker tube, a shock tube having a free piston driven by detonation waves is developed and examined. The free piston accelerated in a long vacuum tube enters into the He shock driver gas with a velocity higher than 300 m/s, producing a shock wave at its front. Due to the repeating shock wave reflections between the piston and diaphragm set at the end of the driver-gas tube, the He driver gas is compressed and heated to a pressure and temperature much higher than those produced by isentropic compression. Applying this driver gas of high pressure and temperature, strong shock waves having a Mach number from 10 to 15 are produced in argon in the low-pressure tube. The results also suggest that much stronger shock waves can be produced in low-pressure argon by enlarging the size and honing the inner sides of the tubes.

Terao, Kunio; Furushoh, Tomonobu

1994-05-01

98

DETONATION WAVE STRUCTURE IN LIQUID HOMOGENEOUS, SOLID HETEROGENEOUS AND AGATIZED HE  

Microsoft Academic Search

Heterogeneous HE decomposition mechanism in hot spots in detonation wave front is considered. Study of detonation wave structure of HE (HMX, RDX, PETN, etc.) with various porosity values (1-10%) is performed. Different structures of detonation wave with both pressure sharply raising and pressure smoothly growing for several tens of nanoseconds are recorded in liquid HE (nitromethane, tetranitromethane and fuel\\/oxidizer-type mixtures

A. V. Fedorov

99

Mechanism of low-speed detonation wave propagation in gas-drop mixtures  

Microsoft Academic Search

Results are offered from an experimental study of propagation of a low-speed detonation wave through a chain of liquid hydrocarbon drops in a pure oxygen atmosphere. Detonation was initiated by a planar shock wave at Mach numbers M=2.0–3.5. The detonation wave structure is reflected by the x, t-diagrams obtained. The propagation of the flame front was found to be pulsating

V. M. Boiko; V. V. Lotov; A. N. Papyrin

1993-01-01

100

PETN Particles in a Gas-Detonation Wave  

NASA Astrophysics Data System (ADS)

To account for the development pattern of detonation by weakly initiating powdered high explosives (HE) an investigation of interacting HE particles with a high-enthalpy gas flow was performed. The results of experiments of an ignition of PETN particles by gas-detonation wave is reported. The radiation intensity of detonation products (DP) was recorded by several wave lengths simultaneously with using of a multiwave pyrometer. This enabled us to define the time of the reaction beginning in HE by change in a spectrum of DP radiation with particles and without them. The PETN decomposition was recorded in all experiments under varying of the initial pressure P of a gaseous mixture from 0.1 to 0.4 MPa. But from P = 0.3 Mpa the velocity of PETN combustion increased more than in 10 times. It was shown, as a result of breaking the melted layer at particles the sharp extension of HE surface occurs. The HE surface increases by more than one order of magnitude. It causes the increase of the integral reaction rate. The process is of a threshold nature: a fragmentation will occur if the melted layer thickness greater than some critical value.

Grigoriev, Vladimir; Lukyanchikov, Leonid; Pruuel, Eduard

1997-07-01

101

Experimental study on transmission of an overdriven detonation wave from propane/oxygen to propane/air  

SciTech Connect

Two sets of experiments were performed to achieve a strong overdriven state in a weaker mixture by propagating an overdriven detonation wave via a deflagration-to-detonation transition (DDT) process. First, preliminary experiments with a propane/oxygen mixture were used to evaluate the attenuation of the overdriven detonation wave in the DDT process. Next, experiments were performed wherein a propane/oxygen mixture was separated from a propane/air mixture by a thin diaphragm to observe the transmission of an overdriven detonation wave. Based on the characteristic relations, a simple wave intersection model was used to calculate the state of the transmitted detonation wave. The results showed that a rarefaction effect must be included to ensure that there is no overestimate of the post-transmission wave properties when the incident detonation wave is overdriven. The strength of the incident overdriven detonation wave plays an important role in the wave transmission process. The experimental results showed that a transmitted overdriven detonation wave occurs instantaneously with a strong incident overdriven detonation wave. The near-CJ state of the incident wave leads to a transmitted shock wave, and then the transition to the overdriven detonation wave occurs downstream. The attenuation process for the overdriven detonation wave decaying to a near-CJ state occurs in all tests. After the attenuation process, an unstable detonation wave was observed in most tests. This may be attributed to the increase in the cell width in the attenuation process that exceeds the detonability cell width limit. (author)

Li, J.; Lai, W.H. [National Cheng Kung University, Institute of Aeronautics and Astronautics, Tainan (China); Chung, K. [National Cheng Kung University, Aerospace Science and Technology Research Center, Tainan (China); Lu, F.K. [University of Texas at Arlington, Mechanical and Aerospace Engineering Department, Aerodynamics Research Center, TX 76019 (United States)

2008-08-15

102

Transverse waves in numerical simulations of cellular detonations  

NASA Astrophysics Data System (ADS)

In this paper the structure of strong transverse waves in two-dimensional numerical simulations of cellular detonations is investigated. Resolution studies are performed and it is shown that much higher resolutions than those generally used are required to ensure that the flow and burning structures are well resolved. Resolutions of less than about 20 numerical points in the characteristic reaction length of the underlying steady detonation give very poor predictions of the shock configurations and burning, with the solution quickly worsening as the resolution drops. It is very difficult and dangerous to attempt to identify the physical structure, evolution and effect on the burning of the transverse waves using such under-resolved calculations. The process of transverse wave and triple point collision and reflection is then examined in a very high-resolution simulation. During the reflection, the slip line and interior triple point associated with the double Mach configuration of strong transverse waves become detached from the front and recede from it, producing a pocket of unburnt gas. The interaction of a forward facing jet of exploding gas with the emerging Mach stem produces a new double Mach configuration. The formation of this new Mach configuration is very similar to that of double Mach reflection of an inert shock wave reflecting from a wedge.

Sharpe, Gary J.

2001-11-01

103

Initiation and propagation of detonation waves in combustible high speed flows  

Microsoft Academic Search

The initiation and propagation of detonation waves in combustible high speed flows were studied experimentally. A planar detonation wave traveling in an initiation tube was transmitted into a test section where a combustible high speed flow was induced by an incident shock wave generated in a shock tube. In this study, the flow Mach numbers were obtained as 0.9 and

K. Ishii; H. Kataoka; T. Kojima

2009-01-01

104

A study on planar blast waves initiated by gaseous detonations. I - Estimation of initiation energy  

Microsoft Academic Search

An experimental study has been made of the initiation of planar blast waves by gaseous detonations. A gaseous detonation initiated by a DDT process is submitted into a long tube filled with air at various initial pressures. The measurement of the decay process of a produced shock wave indicates that it can be treated as a 'plane source' blast wave,

S. Ohyagi; T. Yoshihashi; Y. Harigaya

1985-01-01

105

The Use of Steady and Unsteady Detonation Waves for Propulsion Systems  

NASA Technical Reports Server (NTRS)

Detonation wave enhanced supersonic combustors such as the Oblique Detonation Wave Engine (ODWE) are attractive propulsion concepts for hypersonic flight. These engines utilize detonation waves to enhance fuel-air mixing and combustion. The benefits of wave combustion systems include shorter and lighter engines which require less cooling and generate lower internal drag. These features allow air-breathing operation at higher Mach numbers than the diffusive burning scramjet delaying the need for rocket engine augmentation. A comprehensive vehicle synthesis code has predicted the aerodynamic characteristics and structural size and weight of a typical single-stage-to-orbit vehicle using an ODWE. Other studies have focused on the use of unsteady or pulsed detonation waves. For low speed applications, pulsed detonation engines (PDE) have advantages in low weight and higher efficiency than turbojets. At hypersonic speeds, the pulsed detonations can be used in conjunction with a scramjet type engine to enhance mixing and provide thrust augmentation.

Adelman, Henry G.; Menees, Gene P.; Cambier, Jean-Luc; Bowles, Jeffrey V.; Cavolowsky, John A. (Technical Monitor)

1995-01-01

106

Mechanism of Detonation Wave Propagation in PBX with Energetic Binders  

NASA Astrophysics Data System (ADS)

The complex phenomenon of detonation wave (DW) propagation in PBX-EB (filler - 85% RDX or HMX, energetic binder (EB) - GAP or POLYNIMMO, initial density >95% TMD) has been studied in comparison experiments simultaneously with PBX-HTPB and pseudo PBX (85% inert filler, as a RDX or HMX simulator, and EB). A thin optical fibre strip (spatial resolution of each fibre corresponds to two particle characteristics sizes), connected to a fast electronic streak camera, and the printed erosion figure on an witness plate allows clear quantification, with nanosecond temporal resolution, of DW fine structure in PBX-EB, namely: 1 - the previous front traversing in EB interparticle space followed by particles detonation with time delay 5-7 ns, and 2 - DW oscillations with mean period 30 ns. The results obtained in modified gap tests and corner turning tests prove a significant distinction between the mechanisms of DW formation in PBX-EB and PBX-HTPB, in particular case of interaction between binder and particles in detonation front formation.

Plaksin, I.; Mendes, R.; Campos, J.; Ribeiro, J.; Gois, J.

1999-06-01

107

The irregular reflection from the symmetrical collision of two plane detonation waves in high explosive  

NASA Astrophysics Data System (ADS)

The obliquely symmetrical collision of the plane detonation wave in high explosive was observed by means of a high-speed camera in framing mode. The plane detonation wave is generated by two kinds of devices: one using the plane wave generators; the other being the newly devised set-up. The collision angle is set to values greatly larger than the critical angle for irregular reflection of detonation wave from the theoretical prediction. The experimental results show that Mach reflection of detonation wave indeed occurs, but the length of Mach stem is short and the stem shape is smoothly curved. At the same time, the results also illustrate that the collision of detonation wave in high explosive indicates somewhat more complexity than shock reflection in gases and solids. .

Itoh, S.; Liu, Z.; Nakamura, Y.; Nagano, S.; Nadamitsu, Y.

2000-04-01

108

The Ignition of Carbon Detonations via Converging Shock Waves in White Dwarfs  

NASA Astrophysics Data System (ADS)

The progenitor channel responsible for the majority of Type Ia supernovae is still uncertain. One emergent scenario involves the detonation of a He-rich layer surrounding a C/O white dwarf, which sends a shock wave into the core. The quasi-spherical shock wave converges and strengthens at an off-center location, forming a second, C-burning, detonation that disrupts the whole star. In this paper, we examine this second detonation of the double detonation scenario using a combination of analytic and numeric techniques. We perform a spatially resolved study of the imploding shock wave and outgoing detonation and calculate the critical imploding shock strengths needed to achieve a core C detonation. We find that He detonations in recent two-dimensional simulations yield converging shock waves that are strong enough to ignite C detonations in high-mass C/O cores, with the caveat that a truly robust answer requires multi-dimensional detonation initiation calculations. We also find that convergence-driven detonations in low-mass C/O cores and in O/Ne cores are harder to achieve and are perhaps unrealized in standard binary evolution.

Shen, Ken J.; Bildsten, Lars

2014-04-01

109

Velocity of Spherically-Diverging Detonation Waves in RX-26-AF, LX-17 and LX-10.  

National Technical Information Service (NTIS)

The velocity of spherically-diverging detonation waves was measured in RX-26-AF, LX-17 and LX-10 explosives at 20 exp 0 C and -54 exp 0 C for detonation wave radii from 13 to 50 mm. At the smaller radii the measured velocities were lower than published st...

K. L. Bahl R. C. Weingart R. S. Lee

1983-01-01

110

Detonation Wave Profiles in Plastic Bonded Explosives Measured using 1550 nm Heterodyne Velocimetry  

Microsoft Academic Search

We have measured detonation wave profiles in several triaminotrinitrobenzene (TATB) and cyclotetramethylene tetranitramine (HMX or octogen) based plastic bonded explosives using 1550 nm Heterodyne Velocimetry. (Heterodyne Velocimetry is also called Photon Doppler Velocimetry or PDV.) Planar detonations were produced by impacting the explosive with projectiles launched in a gas gun. Particle velocity wave profiles were measured at the mirror\\/interface of

Rick Gustavsen

2009-01-01

111

Shock-wave initiation of heated plastified TATB detonation  

NASA Astrophysics Data System (ADS)

Explosive, plastified TATB, attracts attention with its weak sensitivity to shock loads and high temperature stability ( Pthreshold ? 6.5 GPa and Tcrit ? 250 0Q). However, at its cooling to T 250 0Q plastified TATB becomes as sensitive to shock load as octogen base HE: the excitation threshold reduces down to Pthreshold 2.0 GPa. The main physical reason for the HE sensitivity change is reduction in density at heating and, hence, higher porosity of the product (approximately from 2Moreover, increasing temperature increases the growth rate of uhotf spots which additionally increases the shock sensitivity [1]. Heated TATB experiments are also conducted at VNIIEF. The detonation excitation was computed within 1D program system MAG using EOS JWL for HE and EP and LLNL kinetics [1,2,3]. Early successful results of using this kinetics to predict detonation excitation in heated plastified TATB in VNIIEF experiments with short and long loading pulses are presented. Parameters of the chemical zone of the stationary detonation wave in plastified TATB (LX-17) were computed with the data from [1]. Parameters Heated In shell Cooled Unheated ?0 , g/cm3 1.70 1.81 1.84 1.905 D , km/s 7.982 7.764 7.686 7.517 PN, GPa 45.4 45.8 35.7 32.9 PJ, GPa 27.0 27.3 27.2 26.4 ?x , mm 0.504 0.843 1.041 2.912 ?t , ns 63.1 108.6 135.5 387.4 [1] Effect of Confinement and Thermal Cycling on the Shock Initiation of LX-17 P.A. Urtiew, C.M. Tarver, J.L. Maienschein, and W.C. Tao. LLNL. Combustion and Flame 105: 43-53 (1996) [2] C.M. Tarver, P.A. Urtiew and W.C. Tao (LLNL) Effects of tandem and colliding shock waves on initiation of triaminotrinitrobenzene. J.Appl. Phys. 78(5), September 1995 [3] Craig M. Tarver, John W. Kury and R. Don Breithaupt Detonation waves in triaminotrinitrobenzene J. Appl. Phys. 82(8) , 15 October 1997.

Kuzmitsky, Igor; Rudenko, Vladimir; Gatilov, Leonid; Koshelev, Alexandr

1999-06-01

112

Micro-blast waves using detonation transmission tubing  

NASA Astrophysics Data System (ADS)

Micro-blast waves emerging from the open end of a detonation transmission tube were experimentally visualized in this study. A commercially available detonation transmission tube was used (Nonel tube, M/s Dyno Nobel, Sweden), which is a small diameter tube coated with a thin layer of explosive mixture (HMX + traces of Al) on its inner side. The typical explosive loading for this tube is of the order of 18 mg/m of tube length. The blast wave was visualized using a high speed digital camera (frame rate 1 MHz) to acquire time-resolved schlieren images of the resulting flow field. The visualization studies were complemented by computational fluid dynamic simulations. An analysis of the schlieren images showed that although the blast wave appears to be spherical, it propagates faster along the tube axis than along a direction perpendicular to the tube axis. Additionally, CFD analysis revealed the presence of a barrel shock and Mach disc, showing structures that are typical of an underexpanded jet. A theory in use for centered large-scale explosions of intermediate strength (10 < ? {p}/{p}_0 ? 0.02) gave good agreement with the blast trajectory along the tube axis. The energy of these micro-blast waves was found to be 1.25 ± 0.94 J and the average TNT equivalent was found to be 0.3. The repeatability in generating these micro-blast waves using the Nonel tube was very good (± 2 %) and this opens up the possibility of using this device for studying some of the phenomena associated with muzzle blasts in the near future.

Samuelraj, I. Obed; Jagadeesh, G.; Kontis, K.

2013-07-01

113

Nonlinear Dynamics of Self-Sustained Supersonic Reaction Waves: Fickett's Detonation Analogue  

NASA Astrophysics Data System (ADS)

The present study investigates the spatiotemporal variability in the dynamics of self-sustained supersonic reaction waves propagating through an excitable medium. The model is an extension of Fickett’s detonation model with a state-dependent energy addition term. Stable and pulsating supersonic waves are predicted. With increasing sensitivity of the reaction rate, the reaction wave transits from steady propagation to stable limit cycles and eventually to chaos through the classical Feigenbaum route. The physical pulsation mechanism is explained by the coherence between internal wave motion and energy release. The results obtained clarify the physical origin of detonation wave instability in chemical detonations previously observed experimentally.

Radulescu, M. I.; Tang, J.

2011-10-01

114

Nonlinear dynamics of self-sustained supersonic reaction waves: Fickett's detonation analogue.  

PubMed

The present study investigates the spatiotemporal variability in the dynamics of self-sustained supersonic reaction waves propagating through an excitable medium. The model is an extension of Fickett's detonation model with a state-dependent energy addition term. Stable and pulsating supersonic waves are predicted. With increasing sensitivity of the reaction rate, the reaction wave transits from steady propagation to stable limit cycles and eventually to chaos through the classical Feigenbaum route. The physical pulsation mechanism is explained by the coherence between internal wave motion and energy release. The results obtained clarify the physical origin of detonation wave instability in chemical detonations previously observed experimentally. PMID:22107392

Radulescu, M I; Tang, J

2011-10-14

115

Shock wave dynamics of novel aluminized detonations and empirical model for temperature evolution from post-detonation combustion fireballs  

NASA Astrophysics Data System (ADS)

Optical forensics of explosion events can play a vital role in investigating the chain of events leading up to the explosion by possibly identifying key spectral characteristics and even molecules in the post-detonation fireball that may serve as the fingerprint for a particular explosive type used. This research characterizes the blast wave and temperature evolution of an explosion fireball in order to improve the classification of aluminized conventional munitions based on a single explosive type such as RDX. High speed 4 kHz visible imagery is collected for 13 field detonations of aluminized novel munitions to study fireball and shock wave dynamics. The 238 mus temporal resolution visible imagery and the 12 ms temporal resolution FTS spectra are the data sets upon which shock wave dynamics and the time dependence of the fireball temperature are studied, respectively. The Sedov-Taylor point blast theory is fitted to data where a constant release (s = 1) of energy upon detonation suggests shock energies of 0.5--8.9 MJ corresponding to efficiencies of 2--15 percent of the RDX heats of detonation with blast dimensionalities indicative of the spherical geometry observed in visible imagery. A drag model fit to data shows initial shock wave speeds of Mach 4.7--8.2 and maximum fireball radii ranging from 4.3--5.8 m with most of the radii reached by 50 ms upon detonation. Initial shock speeds are four times lower than theoretical maximum detonation speed of RDX and likely contributes to the low efficiencies. An inverse correlation exists between blast wave energy and overall aluminum or liner content in the test articles. A two-color best fit Planckian is used to extract temperature profiles from collected Fourier-transform spectrometer spectra. The temperatures decay from initial values of 1290--1850 K to less than 1000 K within 1 s after detonation. A physics-based low-dimensionality empirical model is developed to represent the temperature evolution of post-detonation combustion fireballs. Using a radiative cooling term and a secondary combustion term, the model is able to reduce 82 data points down to five fit parameters. The fit-derived heat of combustion has a 96% correlation with the calculated heat of combustion but has a slope of 0.49 suggesting that only half of the theoretical heat of combustion is realized. Initial temperature is not a good discriminator of detonation events but heat of combustion holds promise as a potential variable for event classification. This model and corresponding analyses might improve the ability of sensing platforms to identify explosive types and sources.

Gordon, J. Motos

116

Application of detonation wave theory to subcritical vapor explosions  

SciTech Connect

Detonation wave theory was applied to the physical process of a vapor explosion. Initially, the experimental observations using hot water as the fuel and saturated refrigerant liquid as the coolant were analyzed with this technique. These tests are notable since peak explosion pressures were far below the critical pressure of the coolant. From the analysis, the volume fractions of the coolant vapor and the volume ratio of the two liquids prior to the explosion were estimated from the measured peak explosion pressures and associated explosion propagation velocities under the assumption that the process was steady and one-dimensional. Complete Hugoniot curves were constructed, and the detonation condition was initially determined under the assumption that flow velocity behind the shock was equal to the mixture sound speed. This assumption was checked with the tangency condition between the Rayleigh line and Hugoniot curve at the Chapman-Jouguet point, as well as the existence of a minimum in the entropy change across the shock wave. The point of minimum entropy showed good agreement with the graphical tangency point, but was slightly different than the sound speed criteria in pressure (<2%) with a larger difference in propagation speed (50%). This discrepancy between the three criteria becomes insignificant as the explosion pressure rises. This is demonstrated by examining a tin-water explosion experiment. This technique appears to be a useful tool to estimate initial conditions for subcritical vapor explosions.

Tibkin, L.; El-Beshbeeshy, M.; Bonazza, R.; Corradini, M.L. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Nuclear Engineering and Engineering Physics

1995-07-01

117

An Experimental Investigation of Shock Initiated Detonation Waves in a Flowing Combustible Mixture.  

National Technical Information Service (NTIS)

The investigation was concerned with the initiation of detonation waves in a subsonically flowing mixture of gaseous hydrogen and oxygen by means of shock waves injected opposite to the direction of the flow. Nominally stoichiometric mixtures at near ambi...

L. A. Hamilton

1967-01-01

118

Conical detonation waves - A comparison of theoretical and numerical results  

NASA Technical Reports Server (NTRS)

A predictive capability for conical oblique detonation waves (ODWs) is discussed with particular attention given to the special case of an axisymmetric conical projectile, which yields necessary conditions for attached waves. A multidimensional numerical model was used to study the influence of a finite Damkoehler number (Da) and viscosity on the formation of a conical ODW. The ODW is predicted for Da on the order of 10, and is found to be important in the ODW formation. For a Da of 1, shock induced combustion is predicted. Simulations of the experimental geometry showed general agreement with experimental flow features, but underpredicted the shock angle. It is suggested that this difference may be caused by inadequate boundary layer resolution, lack of grid orthogonality at the cone surface, and an inappropriate chemical mechanism.

Fort, James A.; Pratt, David T.

1992-01-01

119

Hydrodynamic instabilities and transverse waves in propagation mechanism of gaseous detonations  

NASA Astrophysics Data System (ADS)

The present study examines the role of transverse waves and hydrodynamic instabilities mainly, Richtmyer-Meshkov instability (RMI) and Kelvin-Helmholtz instability (KHI) in detonation structure using two-dimensional high-resolution numerical simulations of Euler equations. To compare the numerical results with those of experiments, Navier-Stokes simulations are also performed by utilizing the effect of diffusion in highly irregular detonations. Results for both moderate and low activation energy mixtures reveal that upon collision of two triple points a pair of forward and backward facing jets is formed. As the jets spread, they undergo Richtmyer-Meshkov instability. The drastic growth of the forward jet found to have profound role in re-acceleration of the detonation wave at the end of a detonation cell cycle. For irregular detonations, the transverse waves found to have substantial role in propagation mechanism of such detonations. In regular detonations, the lead shock ignites all the gases passing through it, hence, the transverse waves and hydrodynamic instabilities do not play crucial role in propagation mechanism of such regular detonations. In comparison with previous numerical simulations present simulation using single-step kinetics shows a distinct keystone-shaped region at the end of the detonation cell.

Mahmoudi, Y.; Mazaheri, K.; Parvar, S.

2013-10-01

120

Lifetime of a multifront structure in overcompressed detonation waves in gases  

NASA Astrophysics Data System (ADS)

Manzhalei and Subbotin (1976) have observed a multifront structure of compressed detonation waves in a CH4 + 202 + 7Ar mixture in the presence of negative heat release. In the present paper, a physical interpretation of this phenomenon is proposed. A stability criterion for supercompressed detonations is derived, and the possibility, in principle, of the existence of a self-sustaining detonation in the presence of negative heat release is demonstrated.

Manzhalei, V. I.

1980-01-01

121

Numerical study on the self-organized regeneration of transverse waves in cylindrical detonation propagations  

Microsoft Academic Search

Cylindrical detonation propagation was numerically investigated by solving the two-dimensional multi-component Euler equations\\u000a implemented with a one-step chemical reaction model. The numerical results demonstrate the evolution of cellular cell bifurcation\\u000a of cylindrical detonation, and indicate that new cellular cells are generated from the self-organized transverse waves. The\\u000a local curvature of the cylindrical cellular detonation is found to be a critical

C. Wang; Z. Jiang

122

Oblique interactions of detonation waves with explosive/metal interfaces  

SciTech Connect

The interaction of a detonation wave with an explosive/metal interface is considered. Theoretical models are discussed, and calculated results are given for PBX 9501 onto uranium, tantalum, copper, 304 stainless steel, aluminum, and nickel. For PBX 9501 onto aluminum and copper, regular shock reflection (in the PBX 9501) at small angles changes to regular rarefaction reflection (Prandtl-Meyer flow) at large angles, and the curve of metal-shock pressure vs incidence angle is smooth. For the other metals, there is a discontinuity in shock pressure where low-angle, regular reflection transists to Mach reflection, and a smaller discontinuity where the Mach reflection changes back to high-angle regular reflection.

Walsh, J.M.

1982-12-01

123

Instability Criterion of One-Dimensional Detonation Wave with Three-Step Chain Branching Reaction Model  

Microsoft Academic Search

One-dimensional detonation waves are simulated with the three-step chain branching reaction model, and the instability criterion is studied. The ratio of the induction zone length and the reaction zone length may be used to decide the instability, and the detonation becomes unstable with the high ratio. However, the ratio is not invariable with different heat release values. The critical ratio,

Hong-Hui Teng; Zong-Lin Jiang

2011-01-01

124

Instability Criterion of One-Dimensional Detonation Wave with Three-Step Chain Branching Reaction Model  

NASA Astrophysics Data System (ADS)

One-dimensional detonation waves are simulated with the three-step chain branching reaction model, and the instability criterion is studied. The ratio of the induction zone length and the reaction zone length may be used to decide the instability, and the detonation becomes unstable with the high ratio. However, the ratio is not invariable with different heat release values. The critical ratio, corresponding to the transition from the stable detonation to the unstable detonation, has a negative correlation with the heat release. An empirical relation of the Chapman—Jouguet Mach number and the length ratio is proposed as the instability criterion.

Teng, Hong-Hui; Jiang, Zong-Lin

2011-08-01

125

Calculation of Chemical Detonation Waves With Hydrodynamics and Thermochemical Equation of State  

SciTech Connect

We model detonation waves for solid explosives, using 2-D Arbitrary Lagrange Eulerian (ALE) hydrodynamics, with an equation of state (EOS) based on thermochemical equilibrium, coupled with simple kinetic rate laws for a few reactants. The EOS for the product species is based on either a BKWC EOS or on an exponential-6 potential model, whose parameters are fitted to a wide range of shock Hugoniot and static compression data. We show some results for the non ideal explosive, urea nitrate. Such a model is a powerful tool for studying such processes as initiation, detonation wave propagation and detonation wave propagation as a function of cylindrical radius.

Howard, W M; Fried, L E; Souers, P C; Vitello, P A

2001-08-01

126

A double-front structure of detonation wave as the result of phase transitions  

NASA Astrophysics Data System (ADS)

Using thermochemical code calculations, we show that the nanographite nanodiamond phase transition, which may occur in the detonation products of a number of carbon containing explosives, can affect the detonation properties and can cause a specific detonation regime with some unusual peculiarities. Among them, we first note the failure of the Chapman Jouguet condition and the presence of the sonic plane, where the Mach number is equal to unity, in a detonation product expansion wave at a lower pressure than that at the Chapman Jouguet point. The peculiarities of this detonation regime are demonstrated by the example of TNT, HNS, and RDX. The computed detonation velocities are in excellent agreement with experiments over a wide range of initial charge densities for all of the investigated explosives. The results of this work allow one to explain, e.g., contradictory experimental data on the detonation pressure and on the length of the reaction zone for TNT. We believe that some other solid solid, solid liquid, and liquid liquid phase transformations in the detonation products may also cause a detonation regime with the same features as shown here for the nanographite nanodiamond transition. We suggest a computational study that should facilitate proposing detonation experiments strongly arguing in favor of the model presented.

Victorov, Sergey B.; Gubin, Sergey A.

2006-06-01

127

Simulation of laser interaction with ablative plasma and hydrodynamic behavior of laser supported plasma  

NASA Astrophysics Data System (ADS)

When an intense laser beam irradiates on a solid target, ambient air ionizes and becomes plasma, while part of the target rises in temperature, melts, vaporizes, ionizes, and yet becomes plasma. A general Godunov finite difference scheme WENO (Weighted Essentially Non-Oscillatory Scheme) with fifth-order accuracy is used to simulate 2-dimensional axis symmetrical laser-supported plasma flow field in the process of laser ablation. The model of the calculation of ionization degree of plasma and the interaction between laser beam and plasma are considered in the simulation. The numerical simulations obtain the profiles of temperature, density, and velocity at different times which show the evolvement of the ablative plasma. The simulated results show that the laser energy is strongly absorbed by plasma on target surface and that the velocity of laser supported detonation (LSD) wave is half of the ideal LSD value derived from Chapman-Jouguet detonation theory.

Tong, Huifeng; Yuan, Hong; Tang, Zhiping

2013-01-01

128

Simulation of Laser Interaction with Ablative Plasma and ydrodynamic of Laser Supported Plasma(LSP)  

NASA Astrophysics Data System (ADS)

A general Godunov finite difference schemes-WENO(Weighted Essentially Non-Oscillatory) Schemes which have fifth-order accuracy was used to make a numerical calculation for 2-dimensional axis symmetrical laser-supported plasma flow field under laser ablated solid target. The models of the calculation of ionization degree of plasma and the interaction between laser beam and plasma and the simplified eos(equation of state) of plasma were considered in the simulation. The plasma field parameters during and after laser duration variation with time are also obtained. The simulation results show that the laser beam power was strong absorbed by plasma of target surface, and the velocity of LSD(Laser Supported Detonation) wave is half of ideal LSD value which derived from C-J detonation theory.

Huifeng, Tong; Zhiping, Tang

2011-06-01

129

Head-on Collision of a Detonation with a Planar Shock Wave  

NASA Astrophysics Data System (ADS)

The phenomenon that occurs when a Chapman Jouguet (CJ) detonation collides with a shock wave is discussed. Assuming a one-dimensional steady wave configuration analogous to a planar shock shock frontal interaction, analytical solutions of the Rankine Hugoniot relationships for the transmitted detonation and the transmitted shock are obtained by matching the pressure and particle velocity at the contact surface. The analytical results indicate that there exist three possible regions of solutions, i.e. the transmitted detonation can have either strong, weak or CJ solution, depending on the incident detonation and shock strengths. On the other hand, if we impose the transmitted detonation to have a CJ solution followed by a rarefaction fan, the boundary conditions are also satisfied at the contact surface. The existence of these multiple solutions is verified by an experimental investigation. It is found that the experimental results agree well with those predicted by the second wave interaction model and that the transmitted detonation is a CJ detonation. Unsteady numerical simulations of the reactive Euler equations with both simple one-step Arrhenius kinetic and chain-branching kinetic models are also carried out to look at the transient phenomena and at the influence of a finite reaction thickness of a detonation wave on the problem of head-on collision with a shock. From all the computational results, a relaxation process consisting of a quasi-steady period and an overshoot for the transmitted detonation subsequent to the head-on collisions can be observed, followed by the asymptotic decay to a CJ detonation as predicted theoretically. For unstable pulsating detonations, it is found that, due to the increase in the thermodynamic state of the reactive mixture caused by the shock, the transmitted pulsating detonation can become more stable with smaller amplitude and period oscillation. These observations are in good agreement with experimental evidence obtained from smoked foils where there is a significant decrease in the detonation cell size after a region of relaxation when the detonation collides head-on with a shock wave.

Ng, H. D.; Botros, B. B.; Chao, J.; Yang, J. M.; Nikiforakis, N.; Lee, J. H. S.

2006-09-01

130

Millimeter-Wave Measurements of the Transmission and Reflection of Detonation Plasmas Produced by Solid Explosives.  

National Technical Information Service (NTIS)

Transmission and reflection coefficients of detonation plasmas produced by solid explosives are measured by means of millimeter waves and used to calculate their conductivity and relative permittivity. Because of the limited spatial resolution correspondi...

H. D. vom Stein B. Koch

1977-01-01

131

Experimental study and numerical simulation of cellular structures and Mach reflection of gaseous detonation waves  

NASA Astrophysics Data System (ADS)

In this paper the Deflagration to Detonation Transition (DDT) process of gaseous H2-O2 mixture and Mach reflection of gaseous detonation wave on a wedge have been conducted experimentally. The cellular pattern of DDT process and Mach reflection were obtained from experiments with wedge angle ?= 10° ˜ 40° and initial pressure of gaseous mixture 16kPa ˜ 26.7kPa. The 2-D numerical simulations of DDT process and Mach reflection of detonation wave were performed by using the simplified ZND model and improved space-time conservation element and solution element (CE/SE) method. The numerical cellular structures were compared with the cellular patterns of soot track. Compared results were shown that it is satisfactory. The characteristic comparisons on Mach reflection of air shock wave and detonation wave were carried also out and their differences were given.

Zhang, D.; Guo, C. M.

132

The cellular structure of a two-dimensional H2\\/O2\\/Ar detonation wave  

Microsoft Academic Search

In this paper, the cellular structure of a two-dimensional detonation wave in a low pressure H2\\/O2\\/Ar mixture calculated with a detailed chemical reaction model, high order scheme and high resolution grids is investigated. The regular cellular structure is produced about 1 ms after introducing perturbations in the reaction zone of a steady one-dimensional detonation wave. It is found from the

X. Y. Hu; B. C. Khoo; D. L. Zhang; Z. L. Jiang

2004-01-01

133

A numerical simulation of reflection processes of a detonation wave on a wedge  

Microsoft Academic Search

  \\u000a \\u000a \\u000a Abstract. A two dimensional numerical simulation has been performed to study reflection processes of detonation waves on a wedge. The\\u000a numerical scheme adopted is the flux corrected transport scheme and a two-step chemical reaction is assumed for a stoichiometric\\u000a oxyhydrogen mixture diluted with argon. Transverse wave structures of the detonation are produced by artificial disturbances\\u000a situated in front of

S. Ohyagi; T. Obara; F. Nakata; S. Hoshi

2000-01-01

134

Study of Detonation Wave Structure in Solid and Liquid Tetranitromethane (TNM)  

NASA Astrophysics Data System (ADS)

Investigations of detonation front structure and parameters in solid and liquid tetranitromethane were done using Doppler Fabry-Perot velocimeter. We recorded the particle velocity of explosion products, braking on the HE/window interface. Smooth front of the detonation wave and concave negative-going particle velocity profile were recorded for liquid TNM. The experimental records indicate that because of solid TNM heterogeneity flow, turbulization occurs behind detonation wave front what appears in the form of velocity fluctuations on the U(t) profile.

Fedorov, A. V.; Mikhailov, A. L.; Nazarov, D. V.; Finyushin, S. A.; Men'shikh, A. V.; Davydov, V. A.; Govorunova, T. A.

2006-07-01

135

Detonation Structure for Unstable Waves in Condensed Phase HE  

NASA Astrophysics Data System (ADS)

In gases, propagating detonations develop a distinct three-dimensional cellular structure, characterized by triple point shock (Mach, incident and transverse) interactions that propagate transverse to the front. An oblique shock polar theory for equations of state appropriate to a mixture of gaseous reactants confirms the existence of such triple shock structures for detonation velocities appropriate to gases. A stability analysis of detonation for some EOS and reaction models appropriate to condensed phase systems have also indicated the possibility of unstable non-planar detonations; however an oblique shock polar analysis indicates that triple shock configurations may not be feasible. High resolution numerical simulations are used to examine the structure of condensed phase unstable detonations in such cases.

Kiyanda, Charles; Short, Mark

2009-06-01

136

Numerical simulation of flow during compression of cylindrical samples by a glancing detonation wave  

Microsoft Academic Search

The parameters of shock waves created in cylindrical samples of various materials during detonation of explosive charges surrounding them have been determined experimentally [1–3]. It was established that in a number of materials the reflection of a conical shock wave from the symmetry axis of a sample leads to the formation of a Mach triple shock-wave configuration which gives rise

V. F. Lobanov

1975-01-01

137

Numerical simulation of flow during compression of cylindrical samples by a glancing detonation wave  

Microsoft Academic Search

The parameters of shock waves created in cylindrical samples of various materials during detonation of explosive charges surrounding them have been determined experimentally [1 3]. It was established that in a number of materials the reflection of a conical shock wave from the symmetry axis of a sample leads to the formation of a Mach triple shock-wave configuration which gives

V. F. Lobanov

1975-01-01

138

Instrumentation techniques for monitoring shock and detonation waves  

SciTech Connect

CORRTEX (Continuous Reflectometry for Radius Versus Time Experiments), SLIFER (Shorted Location Indication by Frequency of Electrical Resonance), and pin probes were used to monitor several conditions of blasting such as the detonation velocity of the explosive, the functioning of the stemming column confining the explosive, and rock mass motion. CORRTEX is a passive device that employs time-domain reflectometry to interrogate the two-way transit time of a coaxial cable. SLIFER is an active device that monitors the changing frequency resulting from a change in length of a coaxial cable forming an element of an oscillator circuit. Pin probes in this application consist of RG-174 coaxial cables, each with an open circuit, placed at several known locations within the material. Each cable is connected to a pulse-forming network and a voltage source. When the cables are shorted by the advancing wave, time-distance data are produced from which a velocity can be computed. This paper describes each technique, installation of the gauge, examples of the signals, and interpretation of the records. 11 refs., 11 figs.

Dick, R.D.; Parrish, R.L.

1985-01-01

139

Decoupling and recoupling of detonation waves associated with sudden expansion  

NASA Astrophysics Data System (ADS)

Detonation propagation behavior associated with sudden expansions has been investigated both experimentally and numerically. Different mechanisms, from sustained propagation to detonation failure and reinitiation including shock and flame front decoupling and recoupling have been observed with the schlieren technique. The shock-induced flame propagation has been modeled with two-step chemistry and structured two-dimensional CFD on arbitrary geometries. The results of the numerical simulations show good correspondence to the variety of phenomena observed in experiments. Thus the numerical simulation can be used to study detonation propagation in complex geometries. It provides a tool for the design of safety devices and aids experimental investigations.

Pantow, E. G.; Fischer, M.; Kratzel, Th.

1996-09-01

140

The Feasibility of a Rotating Detonation Wave Rocket Motor.  

National Technical Information Service (NTIS)

A study has been conducted which deals with the feasibility of utilizing exclusively the detonative mode of combustion in a rocket motor rather than the deflagrative mode used in conventional, chemical rocket motors. The configuration adopted consists of ...

J. A. Nicholls R. E. Cullen

1964-01-01

141

Damage in low alloy steel produced by sweeping, interacting detonation waves  

NASA Astrophysics Data System (ADS)

Detonation waves that sweep along the surface of a metal plate induce reduced pressure and enhanced shear, relative to the same detonation at normal incidence. Detonation waves at intermediate obliquity impress intermediate combined stress states. Release waves from the free surfaces may enter into play and contribute to the damage. Initiation of explosive at discrete points produces strong pressure, density, and velocity gradients in the gaseous explosive products in areas where the waves collide, are impressed in an adjacent metal, causing similar stress gradients within the metal that often leading to intense damage. In this work, we investigate damage generated in AISI 4130 steel by the combined effects of oblique drive and interacting detonation waves. The experimental data consist of multipoint velocimetry points probing the free surface in regions loaded by interacting detonation waves and regions between the interactions. Metallography on recovered plate records the plastic flow and damage correlated with the velocimetry data. Spall is indicated in most regions, but not some, and the alpha-epsilon stress-induced phase transformation appears in most regions, but not all.

Hull, L.; Gray, G.; Faulkner, J.; Briggs, M.

2014-05-01

142

The formation and propagation of super-compressed gas detonation waves in conical converging channels  

Microsoft Academic Search

The two-dimensional unsteady problem of the formation and propagation of a super-compressed detonation wave during a transition\\u000a of the detonation from a large round pipe into a narrow one through a conical converging connecting piece has been formulated\\u000a and solved numerically. It was shown for the first time that in the narrow pipe portion the degree of super-compression of\\u000a the

S. A. Zhdan; E. S. Prokhorov

1995-01-01

143

Numerical simulation of shock-wave initiation of heterogeneous detonation in aerosuspensions of aluminum particles  

Microsoft Academic Search

Numerical simulations of flows of reacting two-phase media in a two-velocity, twotemperature approximation are used to study\\u000a the shock-wave initiation of detonation in aerosuspensions of aluminum particles in oxygen. The conditions in a high pressure\\u000a chamber under which detonation can develop after rupture of a diaphragm are determined. Two initiation scenarios are established\\u000a that depend on the localization of the

A. V. Fedorov; T. A. Khmel

1999-01-01

144

Particle response to shock waves in solids: dynamic witness plate/PIV method for detonations  

NASA Astrophysics Data System (ADS)

Studies using transparent, polymeric witness plates consisting of polydimethlysiloxane (PDMS) have been conducted to measure the output of exploding bridge wire (EBW) detonators and exploding foil initiators (EFI). Polymeric witness plates are utilized to alleviate particle response issues that arise in gaseous flow fields containing shock waves and to allow measurements of shock-induced material velocities to be made using particle image velocimetry (PIV). Quantitative comparisons of velocity profiles across the shock waves in air and in PDMS demonstrate the improved response achieved by the dynamic witness plate method. Schlieren photographs complement the analysis through direct visualization of detonator-induced shock waves in the witness plates.

Murphy, Michael J.; Adrian, Ronald J.

2007-08-01

145

Photographic investigation into the mechanism of combustion in irregular detonation waves  

NASA Astrophysics Data System (ADS)

Irregular detonations are supersonic combustion waves in which the inherent multi-dimensional structure is highly variable. In such waves, it is questionable whether auto-ignition induced by shock compression is the only combustion mechanism present. Through the use of high-speed schlieren and self-emitted light photography, the velocity of the different components of detonation waves in a {{ CH}}_4+2{ O}_2 mixture is analyzed. The observed burn-out of unreacted pockets is hypothesized to be due to turbulent combustion.

Kiyanda, C. B.; Higgins, A. J.

2013-03-01

146

The criterion of the existence or inexistence of transverse shock wave at wedge supported oblique detonation wave  

NASA Astrophysics Data System (ADS)

A simplified theoretic method and numerical simulations were carried out to investigate the characterization of propagation of transverse shock wave at wedge supported oblique detonation wave. After solution validation, a criterion which is associated with the ratio ? ( u 2/ u CJ) of existence or inexistence of the transverse shock wave at the region of the primary triple was deduced systematically by 38 cases. It is observed that for abrupt oblique shock wave (OSW)/oblique detonation wave (ODW) transition, a transverse shock wave is generated at the region of the primary triple when ? < 1, however, such a transverse shock wave does not take place for the smooth OSW/ODW transition when ? > 1. The parameter ? can be expressed as the Mach number behind the ODW front for stable CJ detonation. When 0.9 < ? < 1.0, the reflected shock wave can pass across the contact discontinuity and interact with transverse waves which are originating from the ODW front. When 0.8 < ? < 0.9, the reflected shock wave can not pass across the contact discontinuity and only reflects at the contact discontinuity. The condition (0.8 < ? < 0.9) agrees well with the ratio ( D ave/ D CJ) in the critical detonation.

Wang, Ai-Feng; Zhao, Wei; Jiang, Zong-Lin

2011-10-01

147

Simplified version of the Barthel model for transverse wave spacings in gaseous detonation  

Microsoft Academic Search

The acoustic theory of Barthel and Strehlow for transverse wave spacing prediction is investigated in one-dimensional detonation waves. Based on a simple model in which heat is released uniformly in the reaction zone, the cell spacings are found to be dependent upon the following parameters: the induction zone length, reaction zone length, Mach number and specific heat ratio. For high

K. W. Chiu; J. H. Lee

1976-01-01

148

A Simplified Version of the Barthel Model For Transverse Wave Spacings in Gaseous Detonation.  

National Technical Information Service (NTIS)

The acoustic theory of Barthel and Strehlow for transverse wave spacing prediction is investigated in one-dimensional detonation waves. Based on a simple model in which heat is released uniformly in the reaction zone, the cell spacings are found to be dep...

K. W. Chiu J. H. Lee

1975-01-01

149

Atomistic Studies of Shock-Wave and Detonation Phenomena in Energetic Materials  

NASA Astrophysics Data System (ADS)

The major goal of this PhD project is to investigate the fundamental properties of energetic materials, including their atomic and electronic structures, as well as mechanical properties, and relate these to the fundamental mechanisms of shock wave and detonation propagation using state-of-the-art simulation methods. The first part of this PhD project was aimed at the investigation of static properties of energetic materials (EMs) with specific focus on 1,3,5-triamino-2,4,6-trinitrobenzene (TATB). The major goal was to calculate the isotropic and anisotropic equations of state for TATB within a range of compressions not accessible to experiment, and to make predictions of anisotropic sensitivity along various crystallographic directions. The second part of this PhD project was devoted to applications of a novel atomic-scale simulation method, referred to as the moving window molecular dynamics (MW-MD) technique, to study the fundamental mechanisms of condensed-phase detonation. Because shock wave is a leading part of the detonation wave, MW-MD was applied to demonstrate its effectiveness in resolving fast non-equilibrium processes taking place behind the shock-wave front during shock-induced solid-liquid phase transitions in crystalline aluminum. Next, MW-MD was used to investigate the fundamental mechanisms of detonation propagation in condensed energetic materials. Due to the chemical complexity of real EMs, a simplified AB model of a prototypical energetic material was used. The AB interatomic potential, which describes chemical bonds, as well as chemical reactions between atoms A and B in an AB solid, was modified to investigate the mechanism of the detonation wave propagation with different reactive activation barriers. The speed of the shock or detonation wave, which is an input parameter of MW-MD, was determined by locating the Chapman-Jouguet point along the reactive Hugoniot, which was simulated using the constant number of particles, volume, and temperature (NVT) ensemble in MD. Finally, the detonation wave structure was investigated as a function of activation barrier for the chemical reaction AB+B ? A+ BB. Different regimes of detonation propagation including 1-D laminar, 2-D cellular, and 3-D spinning and turbulent detonation regimes were identified.

Budzevich, Mikalai M.

150

The Irregular Reflection from the Symmetrical Collision of Two Plane Detonation Waves in High Explosive  

NASA Astrophysics Data System (ADS)

A simple device being able to generate two oblique symmetrical plane detonation waves in high explosive was developed. Through the high-speed camera with both streak and framing capacities, the reflection configurations of these two plane detonation waves were observed under different incidence angle conditions. The result shows that even in the collision of plane detonation waves, the Mach stem in irregular reflection is always of the curved shape. This phenomenon very resembles the features of the von Nemann reflection of weak shock in gases. Furthermore, the lengths of Mach stem in the irregular refection are not consistent with the predicted values from whether von Nemann three-shock theory or Whitham\\x81fs shock-shock theory. A tentative explanation for this discrepancy is given finally.

Itoh, Shigeru; Nakamura, Yuichi; Liu, Zhi-Yue; Nagano, Shiro

1999-06-01

151

Chemical reaction and equilibration mechanisms in detonation waves  

SciTech Connect

Experimental and theoretical evidence for the nonequilibrium Zeldovich-von Neumann-Doring (NEZND) theory of self-sustaining detonation is presented. High density, high temperature transition state theory is used to calculate unimolecular reaction rate constants for the initial decomposition of gaseous norbornene, liquid nitromethane, and solid, single crystal pentaerythritol tetranitrate as functions of shock temperature. The calculated rate constants are compared to those derived from experimental induction time measurements at various shock and detonation states. Uncertainties in the calculated shock and von Neumann spike temperatures are the main drawbacks to calculating these reaction rates. Nanosecond measurements of the shock temperatures of unreacted explosives are necessary to reduce these uncertainties.

Tarver, C. M., LLNL

1997-07-01

152

Detonation and shock-wave front temperature measurement by two-wave pyrometer based on optical fibers  

Microsoft Academic Search

In this work we employed two-wave optical pyrometer to record characteristics of light emission and brightness temperature in shock and detonation waves. Light is transmitted to photoelectronic multiplier over a fiber light conductor with its end located in the immediate neighborhood of a light source. Error in brightness temperature determination does not exceed value (Delta) T equals +\\/- 5%. Limit

M. D. Tarasov; A. I. Tolshmyakov; F. O. Kuznetsov; O. N. Petrushin; V. S. Petushkov; Yu. A. Savel'Ev; M. Y. Tarakanov; V. A. Til'Kunov

1997-01-01

153

Formation of Detonation Waves in Flowing Combustible Gaseous Mixtures.  

National Technical Information Service (NTIS)

Detonation induction distances were measured in hydrogen-oxygen and methane-oxygen mixtures flowing at various velocities through a 9 stainless steel tube, 9 mm inside diam. The linear flow velocities of the gas mixture ranged from 0-100 m/sec in hydrogen...

L. E. Bollinger G. C. Smith F. J. Tomazic R. Edse

1965-01-01

154

Dynamic compaction of powders by an oblique detonation wave in the cylindrical configuration  

SciTech Connect

A new method has been applied to dynamically compact ceramic powders in the cylindrical configuration. In this method, a converging oblique detonation is used instead of the sliding detonation used in the standard method. The oblique detonation is generated by a configuration using two explosive layers. X-ray flash photographs have been made that show the detonation and shock fronts in both the standard and new configuration. In the present article, the shock wave and particle velocities in the B{sub 4}C powder have been calculated using the shock and detonation angles obtained from the photographs in combination with the measured detonation velocity. In the two-layer configuration, the pressure applied to the powder was increased by a factor of 3.5 compared to the one-layer configuration, in agreement with calculations. The working principle of the two-layer configuration is discussed and compared with a computer simulation of the process. {copyright} {ital 1997 American Institute of Physics.}

Carton, E.P. [TNO-Prins Maurits Laboratory, Post Office Box 45, 2280 AA, Rijswijk (The Netherlands)] [TNO-Prins Maurits Laboratory, Post Office Box 45, 2280 AA, Rijswijk (The Netherlands); [Laboratory for Applied Inorganic Chemistry, Delft University of Technology, Post Office Box 5045, 2600 GA, Delft (The Netherlands); Verbeek, H.J.; Stuivinga, M. [TNO-Prins Maurits Laboratory, Post Office Box 45, 2280 AA, Rijswijk (The Netherlands)] [TNO-Prins Maurits Laboratory, Post Office Box 45, 2280 AA, Rijswijk (The Netherlands); Schoonman, J. [Laboratory for Applied Inorganic Chemistry, Delft University of Technology, Post Office Box 5045, 2600 GA, Delft (The Netherlands)] [Laboratory for Applied Inorganic Chemistry, Delft University of Technology, Post Office Box 5045, 2600 GA, Delft (The Netherlands)

1997-04-01

155

Periodic oscillation and fine structure of wedge-induced oblique detonation waves  

NASA Astrophysics Data System (ADS)

An oblique detonation wave for a Mach 7 inlet flow over a long enough wedge of 30° turning angle is simulated numerically using Euler equation and one-step rection model. The fifth-order WENO scheme is adopted to capture the shock wave. The numerical results show that with the compression of the wedge wall the detonation wave front structure is divided into three sections: the ZND model-like strcuture, single-sided triple point structure and dual-headed triple point strucuture. The first structure is the smooth straight, and the second has the characteristic of the triple points propagating dowanstream only with the same velocity, while the dual-headed triple point structure is very complicated. The detonation waves facing upstream and downstream propagate with different velocities, in which the periodic collisions of the triple points cause the oscillation of the detonation wave front. This oscillation process has temporal and spatial periodicity. In addition, the triple point trace are recorded to obtain different cell structures in three sections.

Gui, Ming-Yue; Fan, Bao-Chun; Dong, Gang

2011-12-01

156

The influence of small additions of diethylenetriamine on the detonation waves stability for nitromethane/acetone solution  

NASA Astrophysics Data System (ADS)

Instability of detonation front in the nitromethane/acetone (NM/A) solution was observed in our previous work: at 10% of acetone the amplitude of heterogeneities was about 20 microns and at 20% of acetone this size was 50 microns. It is known that small additions of diethylenetriamine (DETA) considerably increase the initial rate of chemical reaction in detonation waves for NM. It was expected that DETA would influence the stability of detonation waves in the NM/A solution too. To investigate this phenomenon the laser interferometer VISAR was used for the recording of particle velocity profiles in detonation waves for NM/A. It was found that at the addition of 0.5% DETA to NM/A 90/10 the oscillations in the velocity profile decreased several times over. At the addition of 1% DETA the profile is smooth, i.e. the heterogeneities disappear and detonation wave becomes steady-state. In NM/A 80/20 at the addition of 5% DETA the heterogeneities size is reduced by the order. The increase of detonation wave velocity of NM/A grater than 1% was observed at small concentrations of DETA. Thus it was found that small additions of DETA to the NM/A solution with an unstable detonation front resulted not only in the decrease of heterogeneities size but in their disappearance and stabilization of detonation waves.

Mochalova, V.; Utkin, A.

2014-05-01

157

The criterion of the existence or inexistence of transverse shock wave at wedge supported oblique detonation wave  

Microsoft Academic Search

A simplified theoretic method and numerical simulations were carried out to investigate the characterization of propagation\\u000a of transverse shock wave at wedge supported oblique detonation wave. After solution validation, a criterion which is associated\\u000a with the ratio ? (u\\u000a 2\\/u\\u000a CJ) of existence or inexistence of the transverse shock wave at the region of the primary triple was deduced systematically

Ai-Feng Wang; Wei Zhao; Zong-Lin Jiang

158

The Transitional Structure of Detonation Waves in Multi-Phase Reactive Media  

Microsoft Academic Search

The transitional structure of two-phase detonations initiated by strong blast waves in decane sprays in oxygen and in clouds of wheat and RDX particles in air is investigated numerically. A one-dimensional unsteady code based on the flux corrected transport algorithm is employed. Detailed profiles of mass velocity, particle velocity, sound velocity and Mach number are presented for the reaction zone

SHMUEL EIDELMAN; MARTIN SICHEL

1981-01-01

159

Numerical prediction of oblique detonation wave structures using detailed and reduced reaction mechanisms  

Microsoft Academic Search

Modelling of the structure and the limiting flow turning angles of an oblique detonation wave, established by a two-dimensional wedge, requires the implementation of detailed chemical kinetic models involving a large number of chemical species. In this paper, a method of reducing the computational effort involved in simulating such high-speed reacting flows by implementing a systematically reduced reaction mechanism is

A. A. Thaker; H. K. Chelliah

1997-01-01

160

Experimental researches of mechanism of decomposition of heterogeneous HE in detonation wave front  

NASA Astrophysics Data System (ADS)

The following hypotheses of hot spots formation are usually considered as the basic hypotheses: 1. pores collapse, hot area formation and subsequent surface burning of HE; 2. friction between HE particles, shifts and dislocations. In this report, basing on the experimental researches of the mechanism of decomposition of such HE as HMX, RDX, PETN, etc. with various initial values of porosity (1-10%), it is shown that jets are the reason of formation of locally heated areas (hot spots). These jets are formed under pores cumulation. Smooth increase of HE-window interface velocity before detonation wave arrival was recorded. These jets possibly penetrate into the initial HE, and the chemical reaction begins in hot spots even before arrival of the detonation wave. Jets catalyze the process of HE decomposition and increase rate of chemical reactions. Perturbations in profile of particle velocity of detonation wave are also recorded. These perturbations are caused by deceleration of jets in unreacted HE. In the report the other experimental data associated with the mechanism of decomposition of heterogeneous HE in detonation wave front are discussed.

Fedorov, Alexey

2001-06-01

161

Operation Hardtack. Project 6. 4. Wave form of electromagnetic pulse from nuclear detonations  

Microsoft Academic Search

The wave form of the electromagnetic pulse resulting from nuclear detonations, especially at very high altitudes is analyzed. In particular, broadband measurements were made from 0 to 10 Mc at ranges up to 460 statue miles. The measurements were a continuation of those made during Operation Plumbbob, although improvements in equipment were incorporated wherever possible. The increased cataloging of EM-pulse

F. Lavicka; G. Lang

1985-01-01

162

Particle response to shock waves in solids: dynamic witness plate\\/PIV method for detonations  

Microsoft Academic Search

Studies using transparent, polymeric witness plates consisting of polydimethlysiloxane (PDMS) have been conducted to measure the output of exploding bridge wire (EBW) detonators and exploding foil initiators (EFI). Polymeric witness plates are utilized to alleviate particle response issues that arise in gaseous flow fields containing shock waves and to allow measurements of shock-induced material velocities to be made using particle

Michael J. Murphy; Ronald J. Adrian

2007-01-01

163

On the existence of fast strong and fast weak ionizing detonation waves in magnetohydrodynamics  

Microsoft Academic Search

The existence of structure for ionizing fast-strong and fast-weak detonation waves in magnetohydrodynamics are proved. The reactions are assumed to be one step exothermic reactions with a natural discontinuous reaction rate function. The problem is studied for a general gas, considering some general thermodynamics rules which described by a fairly mild set of hypotheses. The uniqueness and nonuniqueness of structure

A. Aghajani; Y. Farjami; M. Hesaaraki

2009-01-01

164

Blast Wave Measurements from Detonating Spherical 8.4 Kg Comp B Charges.  

National Technical Information Service (NTIS)

Air blast wave measurements were made at distances 4 to 17 m from detonating 8.4 kg spherical Comp B charges suspended at 0.75 and 1.0 m over a plain ground surface. Pressure-time histories, peak pressures, durations and impulses are presented. A comparis...

I. Aaseborn

1983-01-01

165

Shock and detonation wave diffraction at a sudden expansion in gas–particle mixtures  

Microsoft Academic Search

Numerical modeling of the propagation of shock and detonation waves is carried out in a duct with an abrupt expansion for\\u000a a heterogeneous mixture of fine particles of aluminum and oxygen. A considerable difference from corresponding flows in pure\\u000a gas is found. The influence of the size and mass loading of particles on the flow and shock wave structure behind

A. V. Fedorov; T. A. Khmel; Yu. V. Kratova

2008-01-01

166

Effect of reflection type on detonation initiation at shock-wave focusing  

Microsoft Academic Search

  \\u000a \\u000a \\u000a Abstract. From practical and theoretical standpoints, the initiation of combustion in gaseous media due to the shock waves focusing\\u000a process at various reflectors is a subject of much current interest. The complex gas flowfield coupled with chemical kinetics\\u000a provides a wide spectrum of possible regimes of combustion, such as fast flames, deflagration, detonation etc. Shock wave\\u000a reflection at concave

A. M. Bartenev; S. V. Khomik; B. E. Gelfand; H. Grönig; H. Olivier

2000-01-01

167

Conditions of detonation initiation by focusing shock waves in a combustible gas mixture  

Microsoft Academic Search

Based on experiments on focusing shock waves in hydrogen-air mixtures and available publications, the critical shock-wave\\u000a Mach number at which detonation is initiated near the apex of a concave reflector is analyzed as a function of the reflector\\u000a size and reactivity of the mixture. The effect of the reflector shape and size on the value of this Mach number is

S. V. Khomik; S. P. Medvedev; A. N. Polenov; B. E. Gelfand

2007-01-01

168

Experimental measurements of the detonation wave profile in a TATB based explosive  

NASA Astrophysics Data System (ADS)

We report results of the experimental measurements of the detonation wave profile of the TATB based plastic bonded explosive T2 (97 w. % of TATB) using VISAR and Heterodyne Velocimetry (HV - same as Photon Doppler Velocimetry). The experiment consists in initiating a detonation wave in a 15 mm diameter cylinder of explosive using an explosive wire detonator and an explosive booster. In order to obtain the particle velocity history in the reaction zone, we measure particle velocity at the interaction of the detonation front with an aluminized window or the free surface velocity of a metallic foil. Lithium Fluoride (LIF), PMMA and steel have been tested. Several shots have been performed for different lengths of explosive. We compare the VISAR and HV measurements. With LIF and steel, VISAR and HV diagnostics give very similar profiles. The ZND profile obtained on LIF is resolved with both techniques. With PMMA, HV gives a more accurate profile than VISAR in the reaction zone. There is no evidence of the influence of the explosive cylinder length.

Bouyer, V.; Doucet, M.; Decaris, L.

169

An Asymptotic Derivation of the Linear Stability of the Square-Wave Detonation using the Newtonian Limit  

Microsoft Academic Search

The two-dimensional linear stability of a detonation wave characterized by a one-step irreversible Arrhenius reaction is examined by a two-parameter asymptotic approach. The first is the limit of high activation energy in which the underlying steady detonation structure tends to the classical square-wave profile. The second is due to Blythe & Crighton (Proc. R. Soc. Lond. A 426, 189-209 (1989))

Mark Short

1996-01-01

170

Relation Between Spark-Ignition Engine Knock, Detonation Waves, and Autoignition as Shown by High-Speed Photography  

NASA Technical Reports Server (NTRS)

A critical review of literature bearing on the autoignition and detonation-wave theories of spark-ignition engine knock and on the nature of gas vibrations associated with combustion and knock results in the conclusion that neither the autoignition theory nor the detonation-wave theory is an adequate explanation of spark-ignition engine knock. A knock theory is proposed, combining the autoignition and detonation-wave theories, which introduces the idea that the detonation wave develops in autoignited or after-burning gases, and ascribes comparatively low-pitched heavy knocks to autoignition but high-pitched pinging knocks to detonation waves with the possibility of combinations of the two types of knocks. Analysis of five shots of knocking combustion, taken with the NACA high-speed motion-picture camera at the rate of 40,000 photographs per second reveals propagation speeds ranging from 3250 to more than 5500 feet per second. The range of propagation speeds from 3250 to more than 5500 feet per second is held to be considered with the proposed combined theory but not with either the simple autoignition theory or the simple detonation-wave theory.

Miller, Cearcy D

1946-01-01

171

Particle response to shock waves in solids: dynamic witness plate\\/PIV method for detonations  

Microsoft Academic Search

Studies using transparent, polymeric witness plates consisting of polydimethlysiloxane (PDMS) have been conducted to measure\\u000a the output of exploding bridge wire (EBW) detonators and exploding foil initiators (EFI). Polymeric witness plates are utilized\\u000a to alleviate particle response issues that arise in gaseous flow fields containing shock waves and to allow measurements of\\u000a shock-induced material velocities to be made using particle

Michael J. Murphy; Ronald J. Adrian

2007-01-01

172

Computational and theoretical analysis of weak and strong transverse-wave structures in gaseous detonations  

SciTech Connect

Two-dimensional simulation results are presented that capture at great detail the temporal evolution of Mach reflection triple point sub-structures intrinsic to gaseous detonation waves. The observed patterns are classified by shock polar analysis for realistic, thermally perfect but nonreactive gases. A diagram of the transition boundaries between possible Mach reflection structures is constructed and found to be in good agreement with the computational results.

Deiterding, Ralf [ORNL

2011-01-01

173

The Attenuation of a Detonation Wave by an Aircraft Engine Axial Turbine Stage  

NASA Technical Reports Server (NTRS)

A Constant Volume Combustion Cycle Engine concept consisting of a Pulse Detonation Combustor (PDC) followed by a conventional axial turbine was simulated numerically to determine the attenuation and reflection of a notional PDC pulse by the turbine. The multi-stage, time-accurate, turbomachinery solver TURBO was used to perform the calculation. The solution domain consisted of one notional detonation tube coupled to 5 vane passages and 8 rotor passages representing 1/8th of the annulus. The detonation tube was implemented as an initial value problem with the thermodynamic state of the tube contents, when the detonation wave is about to exit, provided by a 1D code. Pressure time history data from the numerical simulation was compared to experimental data from a similar configuration to verify that the simulation is giving reasonable results. Analysis of the pressure data showed a spectrally averaged attenuation of about 15 dB across the turbine stage. An evaluation of turbine performance is also presented.

VanZante, Dale; Envia, Edmane; Turner, Mark G.

2007-01-01

174

The cellular structure of a two-dimensional H2/O2/Ar detonation wave  

NASA Astrophysics Data System (ADS)

In this paper, the cellular structure of a two-dimensional detonation wave in a low pressure H2/O2/Ar mixture calculated with a detailed chemical reaction model, high order scheme and high resolution grids is investigated. The regular cellular structure is produced about 1 ms after introducing perturbations in the reaction zone of a steady one-dimensional detonation wave. It is found from the present resolution study that the discrepancies concerning the structure type arising from the coarser grid employed can be resolved using a sufficiently fine grid size of 0.05 mm and below and shows a double-Mach-like strong-type configuration. During the structure evolution process, the structure configuration does not change much in the periods before and after the triple point collision. Through the triple point collision, three regular collision processes are observed and are followed by a quick change to the double-Mach-like configuration. The simulated structure tracks show that there are three different tracks associated with different triple points or the kink on the transverse wave. Comparisons with previous work and experiments indicate the presence of a strong structure for an ordinary detonation. EHPRG Award Lecture.

Hu, X. Y.; Khoo, B. C.; Zhang, D. L.; Jiang, Z. L.

2004-06-01

175

Detonation wave profiles measured in plastic bonded explosives using 1550 nm photon doppler velocimetry (PDV)  

SciTech Connect

We present detonation wave profiles measured in two TATB based explosives and two HMX based explosives. Profiles were measured at the interface of the explosive and a Lithium-Fluoride (LiF) window using 1550 nm Photon Doppler Velocimetry (PDV). Planar detonations were produced by impacting the explosive with a projectile launched in a gas-gun. The impact state was varied to produce varied distance to detonation, and therefore varied support of the Taylor wave following the Chapman-Jouget (CJ) or sonic state. Profiles from experiments with different support should be the same between the Von-Neumann (VN) spike and CJ state and different thereafter. Comparison of profiles with differing support, therefore, allows us to estimate reaction zone lengths. For the TATB based explosive, a reaction zone length of {approx} 3.9 mm, 500 ns was measured in EDC-35, and a reaction zone length of {approx} 6.3 mm, 800 ns was measured in PBX 9502 pre-cooled to -55 C. The respective VN spike state was 2.25 {+-} 0.05 km/s in EDC-35 and 2.4 {+-} 0.1 km/s in the cooled PBX 9502. We do not believe we have resolved either the VN spike state (> 2.6 km/s) nor the reaction zone length (<< 50 ns) in the HMX based explosives.

Gustavsen, Richard L [Los Alamos National Laboratory; Bartram, Brian D [Los Alamos National Laboratory; Sanchez, Nathaniel (nate) J [Los Alamos National Laboratory

2009-01-01

176

Modelling detonation waves in condensed energetic materials: multiphase CJ conditions and multidimensional computations  

NASA Astrophysics Data System (ADS)

A hyperbolic multiphase flow model with a single pressure and a single velocity but several temperatures is proposed to deal with the detonation dynamics of condensed energetic materials. Temperature non-equilibrium effects are mandatory in order to deal with wave propagation (shocks, detonations) in heterogeneous mixtures. The model is obtained as the asymptotic limit of a total non-equilibrium multiphase flow model in the limit of stiff mechanical relaxation only (Kapila et al. in Phys Fluids 13:3002-3024, 2001). Special attention is given to mass transfer modelling, that is obtained on the basis of entropy production analysis in each phase and in the system (Saurel et al. in J Fluid Mech 607:313-350, 2008). With the help of the shock relations given in Saurel et al. (Shock Waves 16:209-232, 2007) the model is closed and provides a generalized ZND formulation for condensed energetic materials. In particular, generalized CJ conditions are obtained. They are based on a balance between the chemical reaction energy release and internal heat exchanges among phases. Moreover, the sound speed that appears at sonic surface corresponds to the one of Wood (A textbook of sound, G. Bell and Sons LTD, London, 1930) that presents a non-monotonic behaviour versus volume fraction. Therefore, non-conventional reaction zone structure is observed. When heat exchanges are absent, the conventional ZND model with conventional CJ conditions is recovered. When heat exchanges are involved interesting features are observed. The flow behaviour presents similarities with non ideal detonations (Wood and Kirkwood in J Chem Phys 22:1920-1924, 1950) and pathological detonations (Von Neuman in Theory of detonation waves, 1942; Guenoche et al. in AIAA Prog Astron Aeronaut 75: 387-407, 1981). It also present non-conventional behaviour with detonation velocity eventually greater than the CJ one. Multidimensional resolution of the corresponding model is then addressed. This poses serious difficulties related to the presence of material interfaces and shock propagation in multiphase mixtures. The first issue is solved by an extension of the method derived in Saurel et al. (J Comput Phys 228(5):1678-1712, 2009) in the presence of heat and mass transfers. The second issue poses the difficult mathematical question of numerical approximation of non-conservative systems in the presence of shocks associated to the physical question of energy partition among phases for a multiphase shock. A novel approach is used, based on extra evolution equations used to retain the information of the material initial state. This method insures convergence in the post-shock state. Thanks to these various theoretical and numerical ingredients, one-dimensional and multidimensional unsteady detonation waves computations are done, eventually in the presence of material interfaces. Convergence of the numerical hyperbolic solver against ZND multiphase solution is reached. Material interfaces, shocks, detonations are solved with a unified formulation where the same equations are solved everywhere with the same numerical scheme.

Petitpas, F.; Saurel, Richard; Franquet, E.; Chinnayya, A.

2009-10-01

177

Gaseous Detonation. I. Initiation of Detonation  

Microsoft Academic Search

By means of piezoelectric gauges, a study has been made of the development of detonation from a shock wave propagated into a mixture. With a sufficiently strong shock, detonation above the stable velocity is immediately established which decays smoothly to the steady state. When the shock is weaker than required for detonation the phenomena which ensue depend upon the strength

A. J. Mooradian; W. E. Gordon

1951-01-01

178

Reaction Zone Structure of Steady-State Detonation Wave for Tetranitromethane  

NASA Astrophysics Data System (ADS)

The investigation of the reaction zone structure at steady-state detonation in liquid TNM by means of laser interferometer VISAR was conducted. The initial density and detonation velocity of TNM were 1.64 g/cm^3 and 6.4 km/s respectively. Laser beam reflected from Al foil with thickness 7-400 mkm placed between the charge and water window. Velocity profiles with Von Neumann spike were determined. The transition from the reaction zone to unloading wave is smooth and it doesn't allow to define correctly the parameters of Chapman-Jouguet point. Approximate reaction time is 300 ns, and pressure in Von Neumann spike (26,4 GPa) exceeds the pressure in Chapman-Jouguet point (14,5 GPa) 1,8 times. Behind the shock jump a maximum gradient of particle velocity is observed which is equal to 10^7 1/s, it is a typical value for powerful HE. Although TNM has low parameters in Chapman-Jouguet point and a large duration of chemical reaction zone, the high initial decomposition rate provides the existence of steady-state detonation front in tetranitromethane.

Utkin, Alexander; Mochalova, Valentina; Garanin, Victor

2007-06-01

179

Parametric study of an ODW scramaccelerator for hypersonic test facilities. [obligation detonation wave  

NASA Technical Reports Server (NTRS)

A parametric study has been conducted for an oblique detonation-wave (ODW) 'scramaccelerator' suitable for projectile aerothermodynamics studies in real gas hypersonic test facilities. The results of the present analytical design evaluation indicate that an ODW scramaccelerator using conventional gaseous propellants can accelerate projectiles of 0.1 to 1000 kg masses to speeds in the 6-10 km/sec range. Potential applications for such an accelerator encompass a hypersonic ballistic test range, kinetic energy weapon accelerators, mass drivers to LEO, projectile terminal ballistics testing, projectile/target interaction studies, inertial welders, and shock compactors.

Humphrey, Joseph W.

1990-01-01

180

Numerical prediction of oblique detonation wave structures using detailed and reduced reaction mechanisms  

NASA Astrophysics Data System (ADS)

Modelling of the structure and the limiting flow turning angles of an oblique detonation wave, established by a two-dimensional wedge, requires the implementation of detailed chemical kinetic models involving a large number of chemical species. In this paper, a method of reducing the computational effort involved in simulating such high-speed reacting flows by implementing a systematically reduced reaction mechanism is presented. For a hydrogen - air mixture, starting with an elementary mechanism having eight species in 12 reactions, three alternate four-step reduced reaction mechanisms are developed by introducing the steady-state approximation for the reaction intermediates HO2, O and OH, respectively. Additional reduction of the computational effort is achieved by introducing simplifications to the thermochemical data evaluations. The influence of the numerical grid used in predicting the induction process behind the shock is also investigated. Comparisons of the induction zone predicted by two-dimensional oblique detonation wave calculations with that of a static reactor model (with initial conditions of the gas mixture specified by those behind the nonreactive oblique shock wave) are also presented. The reasonably good agreement between the three four-step reduced mechanism predictions and the starting mechanism predictions indicates that further reduction to a two-step mechanism is feasible for the physical flow time scales (corresponding to inflow Mach numbers of 8 - 10) considered here, and needs to be pursued in the future.

Thaker, A. A.; Chelliah, H. K.

1997-12-01

181

Detonation Wave Profiles in Plastic Bonded Explosives Measured using 1550 nm Heterodyne Velocimetry  

NASA Astrophysics Data System (ADS)

We have measured detonation wave profiles in several triaminotrinitrobenzene (TATB) and cyclotetramethylene tetranitramine (HMX or octogen) based plastic bonded explosives using 1550 nm Heterodyne Velocimetry. (Heterodyne Velocimetry is also called Photon Doppler Velocimetry or PDV.) Planar detonations were produced by impacting the explosive with projectiles launched in a gas gun. Particle velocity wave profiles were measured at the mirror/interface of the explosive and either a LiF or PMMA window. Mirrors consisted of either a thin vapor deposited aluminum layer, or a 6 micron thick aluminum foil. Focusing and collimating light collection probes were used. Time-Frequency-Analysis of the fringe data was carried out using both Wavelet and Short-Time-Fourier-Transform (STFT) methods. With clean fringe data, good profiles can be obtained with a 1 ns full width half maximum (FWHM) analysis window (STFT) or about 3 to 4 oscillations in the wavelet. Some profiles, however, have a noisy character which is correlated with intensity fluctuations in the raw fringe data. Wave profiles show a ZND reaction zone structure with a single reaction in the HMX based explosives and both fast and slow reactions in the TATB based explosives.

Gustavsen, Rick

2009-06-01

182

Features of the Shock and Detonation Waves in Cylindrical Explosive Compaction  

NASA Astrophysics Data System (ADS)

Despite of the significant amount of the work that is being done in the field of the explosive consolidation, a considerable lack of time and spatial resolved experimental data is being feel by the people working in the area; moreover, many of the attempts made to overcome this problem were done in conditions far way from the ones used in real consolidation experiments. To fill this gap is necessary to perform the characterization of both, the consolidation and the detonation waves, in conditions close to the ones used in real experiments and with a spatial resolution approaching the characteristic size of the powder. Using an experimental technique developed at our laboratory, based on the utilization of a 64 channels optical fiber strip, connected to an electronic streak camera, spatial and temporal resolved details of the compaction and detonation waves front shape and pressure, were obtained and are presented. The results refer to a cylindrical configuration set-up and alumina powder, two values of the initial density, two characteristic sizes of the powder particles and two powder container materials.

Ribeiro, J. B.; Mendes, R. L.; Plaksin, I. Ye.; Campos, J. A.

2006-07-01

183

Shock wave physics and detonation physics --- a stimulus for the emergence of numerous new branches in science and engineering  

Microsoft Academic Search

In the period of the Cold War (1945-1991), Shock Wave Physics and Detonation Physics (SWP&DP) --- until the beginning of WWII mostly confined to gas dynamics, high-speed aerodynamics, and military technology (such as aero- and terminal ballistics, armor construction, chemical explosions, supersonic gun, and other firearms developments) --- quickly developed into a large interdisciplinary field by its own. This rapid

Peter O. K. Krehl

2011-01-01

184

A virtual test facility for the efficient simulation of solid material response under strong shock and detonation wave loading  

Microsoft Academic Search

A virtual test facility (VTF) for studying the three-dimensional dynamic response of solid materials subject to strong shock and detonation waves has been constructed as part of the research program of the Center for Simulating the Dynamic Response of Materials at the California Institute of Technology. The compressible fluid flow is simulated with a Carte- sian finite volume method and

Ralf Deiterding; Raul Radovitzky; Sean P. Mauch; Ludovic Noels; Julian C. Cummings; Daniel I. Meiron

2006-01-01

185

A double-front structure of detonation wave as the result of phase transitions  

Microsoft Academic Search

Using thermochemical code calculations, we show that the nanographite nanodiamond phase transition, which may occur in the detonation products of a number of carbon containing explosives, can affect the detonation properties and can cause a specific detonation regime with some unusual peculiarities. Among them, we first note the failure of the Chapman Jouguet condition and the presence of the sonic

Sergey B. Victorov; Sergey A. Gubin

2006-01-01

186

Application of K008 camera within measuring complex of laser diagnostics of shock and detonation waves  

NASA Astrophysics Data System (ADS)

In May 2001 the K008 camera/1,2/ being a part of a laser Doppler velocity meter (LDVM) experimental complex of the Russion Federation Nuclear Center, the All-Russian Research Institute of Experimental Physics (RFNC-VNIIEF), was tested under real conditions of gas-dynamic experiments. Some tasks typical to explosion physics were solved during these experiments: the record of velocities of the plates thrown by an explosion; the record of shock and detonation wave fronts; the record of elastic-plastic properties of constructional materials. At the same time the following camera's characterstics were checke: resistance to electromagnetic, acoustic and light interference; conformity of real characteristics to Documentation data; convenience in operation and reliability.

Lebedev, Vitaly B.; Feldman, Grigory G.; Karpov, Maxim A.; Fedorov, Alexey V.; Menshikh, Alexey V.; Nazarov, Dmitriy V.; Finyushin, Stanislav A.; Davidov, Valeriy A.

2005-03-01

187

The structure and evolution of galacto-detonation waves - Some analytic results in sequential star formation models of spiral galaxies  

NASA Technical Reports Server (NTRS)

Waves of star formation in a uniform, differentially rotating disk galaxy are treated analytically as a propagating detonation wave front. It is shown, that if single solitary waves could be excited, they would evolve asymptotically to one of two stable spiral forms, each of which rotates with a fixed pattern speed. Simple numerical solutions confirm these results. However, the pattern of waves that develop naturally from an initially localized disturbance is more complex and dies out within a few rotation periods. These results suggest a conclusive observational test for deciding whether sequential star formation is an important determinant of spiral structure in some class of galaxies.

Cowie, L. L.; Rybicki, G. B.

1982-01-01

188

DSD technology: A detonation reactive Huygens code.  

National Technical Information Service (NTIS)

The length of the reaction zone strongly influences the speed of propagation of detonation in multidimensional explosive pieces. Detonation Shock Dynamics (DSD) properly accounts for these effects in detonation wave-spreading problems when the radius of c...

J. Bdzil W. Fickett

1992-01-01

189

A double-front structure of detonation wave as the result of phase transitions  

Microsoft Academic Search

Using thermochemical code calculations, we show that the nanographite–nanodiamond phase transition, which may occur in the\\u000a detonation products of a number of carbon containing explosives, can affect the detonation properties and can cause a specific\\u000a detonation regime with some unusual peculiarities. Among them, we first note the failure of the Chapman–Jouguet condition\\u000a and the presence of the sonic plane, where

Sergey B. Victorov; Sergey A. Gubin

2006-01-01

190

Shock wave physics and detonation physics — a stimulus for the emergence of numerous new branches in science and engineering  

Microsoft Academic Search

In the period of the Cold War (1945?1991), Shock Wave Physics and Detonation Physics\\u000a (SWP&DP) — until the beginning of WWII mostly confined to gas dynamics, high-speed\\u000a aerodynamics, and military technology (such as aero- and terminal ballistics, armor\\u000a construction, chemical explosions, supersonic gun, and other firearms developments) —\\u000a quickly developed into a large interdisciplinary field by its own. This rapid

Peter O. K. Krehl

2011-01-01

191

Parallel Adaptive Simulation of Weak and Strong Transverse-Wave Structures in H2-O2 Detonations  

SciTech Connect

Two- and three-dimensional simulation results are presented that investigate at great detail the temporal evolution of Mach reflection sub-structure patterns intrinsic to gaseous detonation waves. High local resolution is achieved by utilizing a distributed memory parallel shock-capturing finite volume code that employs block-structured dynamic mesh adaptation. The computational approach, the implemented parallelization strategy, and the software design are discussed.

Deiterding, Ralf [ORNL

2010-01-01

192

Dynamic behavior of lead driven by head-on detonation waves  

NASA Astrophysics Data System (ADS)

The dynamic behavior of Pb driven by head-on sweeping detonation waves is studied in comparison with the behavior of Cu and W alloy. High-speed frame photography and pulsed X-ray radiography records have shown that a jet-like spiking is formed in the collision region of Pb flyer and the length of spiking extends rapidly from mm to cm size because of the significant speed gradients of mass particles inside the spiking body. Multi-layered structures of the spiking are recorded, which reflect the details of shock wave fronts inside the flyer and the melting, fracture related parameters. The typical mass densities inside the spiking structure fixed by the pulsed X-ray radiography are evaluated as about 7%~17% of the initial density of Pb. The dynamic strength and shock melting should have played a dominant role in the initial spiking formation stage. The cavitation and fragmentation process inside the molten or near molten Pb flyer in the collision region elapse only in sub-microsecond, during which the continuum of shocked Pb turns into porous and dispersed state under intense tensional release wave and the later evolution pattern of the spiking at the late stages of experimental diagnostics is preliminarily defined. The vertical bundles in the crown-like spiking pattern caused by K-H instabilities in Pb flyer can be clearly observed under more intense loading. In the collision region of Cu and W flyer jet-like spiking is also observed, which reflects multidimensional spalling mechanism in un-melting metal with its own flow strength and fracture strength.

Zhang, Chongyu; Hu, Haibo; Tang, Tiegang; Sun, Xuelin; Zhang, Zhengtao

2012-03-01

193

Interaction Between a Steady Detonation Wave in Nitromethane and Geometrical Complex Confinement Defects  

Microsoft Academic Search

Two copper cylinder expansion tests were carried out on nitromethane. They differ from the classical cylinder test in that the liner includes evenly-spaced protruding circular defects. The aim is to study how a detonation front propagating in the liquid explosive interacts with the confining material defects. The subsequent motion of the metal, accelerated by the expanding detonation products, is measured

B. Crouzet; L. Soulard; N. Carion; P. Manczur

2007-01-01

194

Analysis of oblique shock-detonation wave interactions in the supersonic flow of a combustible medium  

Microsoft Academic Search

Shock polar analysis is used to analyze the interaction which occurs when a detonation propagates past a bounding layer of inert or explosive gas. The oblique shock or detonation which is transmitted into the bounding medium is reflected from the lower bounding wall either regularly or as a Mach reflection. Such interactions occur in layered explosives and will also arise

B. C. Fan; M. Sichel; C. W. Kauffman

1988-01-01

195

Shock Wave Dynamics of Novel Aluminized Detonations and Empirical Model for Temperature Evolution from Post-Detonation Combustion Fireballs.  

National Technical Information Service (NTIS)

This research characterizes the blast wave and temperature evolution of an explosion fireball in order to improve the classification of aluminized conventional munitions based on a single explosive type such as RDX. A drag model fit to data shows initial ...

J. M. Gordon

2011-01-01

196

Internal Detonations  

Microsoft Academic Search

\\u000a Detonations inside structures present a number of complicating factors. Multiple reflections from walls, floors and ceilings\\u000a interact and enhance the overpressure. In a structure which has few internal walls or partitions such as a parking garage,\\u000a the blast wave reflects from the floor and ceiling. Mach stems form on both surfaces. As the triple points grow away from\\u000a each surface,

Charles E. Needham

197

Steady One-Dimensional Detonations  

NASA Astrophysics Data System (ADS)

While treatments of detonation wave propagation using control volume analysis, such as the Chapman-Jouguet (CJ) detonation solution presented in the prior chapter, are very successful in predicting the steady-state, equilibrium properties of detonations, they provide no information about the limits of detonation propagation or the dynamics of detonation waves. Addressing these issues necessitates investigating the structure of the detonation front. To illustrate this point, consider an extremely dilute concentration of fuel in air (e.g., 0.1% of methane in air by volume). If this mixture is entered into a thermochemical equilibrium code, a unique equilibrium CJ detonation solution will be generated. In practice, however, such a dilute mixture is highly unlikely to be able to support detonation wave propagation, since the low post-shock temperatures from the weak leading shock front would result in very slow reaction rates or no perceptible reaction at all.

Higgins, Andrew

198

Reaction Zone of Steady-State Detonation Waves in Dinitrodiazapentane and RDX  

NASA Astrophysics Data System (ADS)

The detonation waves structure of pressed high explosives (HE) dinitrodiazapentane (DNP) and RDX with different initial densities was investigated by the laser interferometric system VISAR. The experimental results are the profiles of surface velocity of foils placed at the boundary between a HE sample and a water ``window''. In DNP the Von Neumann spike was observed for all studied initial densities, and one of the most interesting features in these results is the unexpectedly large ratio (reaching two) of the von Neumann peak to C-J point parameters. Earlier it was found that in RDX with initial particle size of ~80 ?m existed the critical initial density of 1.73 g/cm3 above which the monotone increase of parameters in the reaction zone was observed. Now it is shown that in acetone-recrystallized RDX with initial particle size of ~5 ?m this critical density is much lower (~1.30-1.35 g/cm3). Above this density the Von Neumann spike was observed. The experimental results are explained by chemical reaction in the shock front and influence of initial density, particle sizes and preparation conditions of samples on the efficiency of the ``hot spots'' and thus on the rate of this reaction.

Kolesnikov, Sergey A.; Utkin, Alexander V.; Ananin, Alexander V.; Pershin, Sergey V.; Fortov, Vladimir E.

2004-07-01

199

Portable fiber optic coupled doppler interferometer system for detonation and shock wave diagnostics  

SciTech Connect

Testing and analysis of shock wave characteristics such as produced by detonators and ground shock propagation frequently require a method of measuring velocity and displacement of the surface of interest. One method of measurement is doppler interferometry. The VISAR (Velocity Interferometer System for Any Reflector) uses doppler interferometry and has pined wide acceptance as the preferred tool for shock measurement. An important asset of VISAR is that it measures velocity and displacement non intrusively. The conventional VISAR is not well suited for portability because of its sensitive components, large power and cooling requirements, and hazardous laser beam. A new VISAR using the latest technology in solid state lasers and detectors has been developed and tested. To further enhance this system`s versatility, the unit is fiber optic coupled which allows remote testing, permitting the VISAR to be placed over a kilometer away from the target being measured. Because the laser light is contained in the fiber optic, operation of the system around personnel is far less hazardous. A software package for data reduction has also been developed for use with a personal computer. These new advances have produced a very versatile system with full portability which can be totally powered by batteries or a small generator. This paper describes the solid state VISAR and its peripheral components, fiber optic coupling methods and the fiber optic coupled sensors used for sending and receiving laser radiation.

Fleming, K.J.

1993-03-01

200

Surface chemical reaction of laser ablated aluminum sample for detonation initiation  

SciTech Connect

We explore the evolution of metal plasma generated by high laser irradiances and its effect on the surrounding air by using shadowgraph images after laser pulse termination; hence the formation of laser supported detonation and combustion processes has been investigated. The essence of the paper is in observing initiation of chemical reaction between ablated aluminum plasma and oxygen from air by inducing high power laser pulse (>1000 mJ/pulse) and conduct a quantitative comparison of chemically reactive laser initiated waves with the classical detonation of exploding aluminum (dust) cloud in air. Findings in this work may lead to a new method of initiating detonation from metal sample in its bulk form without the need of mixing nano-particles with oxygen for initiation.

Kim, Chang-hwan; Yoh, Jack J. [School of Mechanical and Aerospace Engineering, Seoul National University, 599 Kwanakro, Kwanakgu, Seoul, Korea 151-742 (Korea, Republic of)

2011-05-01

201

Detonation in Liquid Explosives  

Microsoft Academic Search

DURING the War a general investigation was commenced at the Road Research Laboratory, on the initiative of Dr. A. H. Davis, into the process of detonation in explosives, the programme including a photographic study of the detonation Waves in transparent liquid explosives-the sensitivity of some of which can be varied by adjusting the constitution-and their relation to primers of different

D. Croney

1948-01-01

202

Analytical study of subcritical vapor explosions using thermal detonation wave theory  

SciTech Connect

Experimental observation has shown that the assumption of complete fuel fragmentation in a vapor explosion by the shock adiabatic thermodynamic model results in predicting upper bounds for the shock pressure, propagation velocity, and work output. This model has been modified by considering the condition where the assumption of complete fragmentation of the fuel is relaxed. A methodology is adopted using experimental values of the shock pressure and propagation velocity to estimate the initial mixture conditions of the experiment and the mass fraction of the materials participating in the explosion. Analysis of a steady-state subcritical vapor explosion in one dimension has been carried out by applying the conservation laws of mass, momentum, and energy and the appropriate equation of state for a homogeneous mixture of molten tin and water. The KROTOS-21 experiment, conducted at the Joint Research Center at Ispra, Italy, was used as the initial benchmark experiment in this analysis. A quasi-steady explosion pressure of {approximately}3 MPa and a propagation velocity of {approximately}200 m/s were obtained in this experiment. Using this model, the estimated minimum mass of the fragmented fuel was found to be 0.21 kg (3.2%) of the total mass of the fuel. The predicted work output by this model corresponding to the aforementioned fragmented fuel mass was found to be 9.8 kJ. The estimated initial void fraction of the vapor was found to be 11.5%. In these analyses, a comparison is made of the various possible closure relations applied to the detonation wave theory for a vapor explosion and associated concerns of model stability in the two-phase region.

Shamoun, B.I.; Corradini, M.L. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Nuclear Engineering and Engineering Physics

1996-07-01

203

Numerical investigation of the propagation of light-induced detonation waves during the absorption of high-power laser radiation in air at elevated density  

Microsoft Academic Search

Spatiotemporal gasdynamic plasma structures formed in quiescent air of elevated density by high-power unfocused laser radiation absorbed in the light-induced detonation (LID) wave regime have been numerically studied using a model of inviscid, equilibrium emitting air. Laser radiation intensity and air density serve as parameters of the model. Dependences of the velocity of LID wave on the laser radiation intensity

S. Yu. Pirogov; D. G. Belyanin; A. S. Yur'ev; V. V. Tipaev; A. V. Filatov

2010-01-01

204

Fundamentals of rotating detonations  

NASA Astrophysics Data System (ADS)

A rotating detonation propagating at nearly Chapman-Jouguet velocity is numerically stabilized on a two-dimensional simple chemistry flow model. Under purely axial injection of a combustible mixture from the head end of a toroidal section of coaxial cylinders, the rotating detonation is proven to give no average angular momentum at any cross section, giving an axial flow. The detonation wavelet connected with an oblique shock wave ensuing to the downstream has a feature of unconfined detonation, causing a deficit in its propagation velocity. Due to Kelvin-Helmholtz instability existing on the interface of an injected combustible, unburnt gas pockets are formed to enter the junction between the detonation and oblique shock waves, generating strong explosions propagating to both directions. Calculated specific impulse is as high as 4,700 s.

Hishida, Manabu; Fujiwara, Toshi; Wolanski, Piotr

2009-04-01

205

Interaction between a steady detonation wave in nitromethane and geometrical complex confinement defects.  

NASA Astrophysics Data System (ADS)

It is well known that detonation propagation is altered if the explosive is encased in an inert confining material. But in practice, explosives are rarely used without confinement and particular attention must be paid to the problem of explosive/confinement interactions. In this work, we have carried out two copper cylinder expansion tests on nitromethane. They differ from the classical cylinder test in that the liner includes evenly-spaced protruding circular defects. The aim is to study how a detonation front propagating in the liquid explosive interacts with the confining material defects. The subsequent motion of the metal, accelerated by the expanding detonation products, is measured using a range of diagnostic techniques: electrical probes, rapid framing camera, glass block associated with streak camera and velocity laser interferometers. The different experimental records have been examined in the light of a simple 2D theoretical shock polar analysis and 2D numerical simulations.

Crouzet, Blandine; Carion, Noel; Manczur, Philippe

2007-06-01

206

Excitation of ignition foci in a detonation relaxation zone  

Microsoft Academic Search

The interactions in a detonation wave include collisions between ignition foci and the renewal of ternary Mach reflections. It is shown in this paper that such a mechanism occurs in the relaxation zone of a shock wave not only in a detonation already formed by also on detonation formation. The relaxation zone in a detonation wave is examined by a

V. S. Avduevskii; Yu. N. Denisov; I. I. Podtynkov; A. M. Frolov

1987-01-01

207

Interaction between a steady detonation wave in nitromethane and geometrical complex confinement defects  

Microsoft Academic Search

It is well known that detonation propagation is altered if the explosive is encased in an inert confining material. But in practice, explosives are rarely used without confinement and particular attention must be paid to the problem of explosive\\/confinement interactions. In this work, we have carried out two copper cylinder expansion tests on nitromethane. They differ from the classical cylinder

Blandine Crouzet; Noel Carion; Philippe Manczur

2007-01-01

208

Experimental Investigation of the Initiation of Detonation Behind a Reflected Shock Wave.  

National Technical Information Service (NTIS)

The purpose of this work was to develop an experimental apparatus for the study of the initiation of detonation in a gaseous medium as a result of shock compression. The design of the apparatus is described, and results of some preliminary experiments are...

T. J. Krusic

1966-01-01

209

Interaction Between a Steady Detonation Wave in Nitromethane and Geometrical Complex Confinement Defects  

NASA Astrophysics Data System (ADS)

Two copper cylinder expansion tests were carried out on nitromethane. They differ from the classical cylinder test in that the liner includes evenly-spaced protruding circular defects. The aim is to study how a detonation front propagating in the liquid explosive interacts with the confining material defects. The subsequent motion of the metal, accelerated by the expanding detonation products, is measured using a range of diagnostic techniques: electrical probes, a rapid framing camera, a glass block associated with a streak camera and velocity laser interferometers. The different experimental records have been examined in the light of previous classical cylinder test measurements, simple 2D theoretical shock polar analysis results and 2D numerical simulations.

Crouzet, B.; Soulard, L.; Carion, N.; Manczur, P.

2007-12-01

210

Exploratory study of flow domains arising from detonation waves induced in a wedged channel  

Microsoft Academic Search

Detonation of the flow of a combustible mixture over a wedged channel is numerically simulated. A two-dimensional, time accurate, finite-volume-based method is used to perform the computations, and a five-species, two-step chem- ical reaction is assumed for a stoichiometric hydrogen-air mixture. The combus- tion channel is made of a wedged section followed by a constant area section. The simulation was

H. Y. Fan; F. K. Lu

211

SHOCK-INDUCED DETONATION WAVE DRIVER FOR ENHANCING SHOCK TUBE PERFORMANCE  

Microsoft Academic Search

An existing pressure-driven hypersonic shock tunnel at the University of Texas at Arlington (UTA) was converted to a detonation-driven shock tube. The specific goal was to create a test environment to investigate electrical properties of high-pressure seeded air plasmas to support development of a test facility concept involving the use of MHD augmentation of high-pressure arc heaters for hypersonic engine

W. S. Stuessy; F. K. LuT; D. R. Wilson

212

Maetning av Luftstoetvagens Tryck-Tidfoerlopp fran Detonerande 48 kg Sfaeriska Hexotol-Trotylladdingar (Blast Wave Measurements from Detonating Spherical 48 kg Comp B/TNT Charges),  

National Technical Information Service (NTIS)

Air blast wave measurements 1.1 m above ground have been made at distances 5.5 - 25 m from detonating 48 kg spherical Comp B/TNT charges suspended at 1.05 - 1.32 m over a plain ground surface. Pressure-time histories, peak pressures, durations and impulse...

K. Edin I. Aseborn

1988-01-01

213

Optically detonated explosive device  

NASA Technical Reports Server (NTRS)

A technique and apparatus for optically detonating insensitive high explosives, is disclosed. An explosive device is formed by containing high explosive material in a house having a transparent window. A thin metallic film is provided on the interior surface of the window and maintained in contact with the high explosive. A laser pulse provided by a Q-switched laser is focussed on the window to vaporize the metallic film and thereby create a shock wave which detonates the high explosive. Explosive devices may be concurrently or sequentially detonated by employing a fiber optic bundle to transmit the laser pulse to each of the several individual explosive devices.

Yang, L. C.; Menichelli, V. J. (inventors)

1974-01-01

214

Global modelling of heat release during initiation and propagation of detonation and deflagration waves in methane-air-particle systems  

NASA Astrophysics Data System (ADS)

In the present paper the direct initiation of a self supporting detonation and propagation of a low-speed combustion in methane-air-coal particles mixtures are solved. For particles, a heterogeneous regime of combustion is used, for methane one overall chemical reaction is taken into account: CH 4 + 2O 2 = CO 2 + 2H 2O. The heat release rate is assumed to be defined as a delay time based on the well-known thermal theory of Frank-Kamenetsky (1967). The proposed model allows one to investigate the influence inert particles or coal dust on the explosion limits of methane-air mixtures. It is shown that the addition of a limited quantity of particles leads to detonation stability. In low speed combustion problems this method allows one to get a good correlation between theoretical and experimental velocities of steady flame propagation in carbon-hydrogen gaseous mixtures. Coal dust influence on gasdynamics of a methane-air mixture combustion is investigated in an unsteady problem by using of the global modelling. It is shown that limited coal dust concentration increases the flame wave intensity in lean methane-air mixtures in contrast to inert particles. In stoichiometric gas mixtures, sand and coal dusts decrease a flame velocity. Far from the ignition point flame, the velocity is largely defined by the dust mass concentration and not by the size of particles.

Tunik, Yu. V.

215

Gaseous detonation initiation and stabilization by hypervelocity projectiles  

Microsoft Academic Search

An experimental investigation of gaseous detonations initiated and stabilized by high-speed spherical projectiles has been carried out. Detonation initiation by projectiles is closely related to propulsion concepts such as the ram accelerator and the oblique detonation wave engine, in which, theoretically, rapid combustion occurs in detonation waves stabilized on solid objects. The criteria for initiation and stabilization by projectiles are

Michael Jiro Kaneshige

1999-01-01

216

Numerical investigation of the propagation of light-induced detonation waves during the absorption of high-power laser radiation in air at elevated density  

Microsoft Academic Search

Spatiotemporal gasdynamic plasma structures formed in quiescent air of elevated density by high-power unfocused laser radiation\\u000a absorbed in the light-induced detonation (LID) wave regime have been numerically studied using a model of inviscid, equilibrium\\u000a emitting air. Laser radiation intensity and air density serve as parameters of the model. Dependences of the velocity of LID\\u000a wave on the laser radiation intensity

S. Yu. Pirogov; D. G. Belyanin; A. S. Yur’ev; V. V. Tipaev; A. V. Filatov

2010-01-01

217

Detonation and deflagration initiation at the focusing of shock waves in combustible gaseous mixture  

Microsoft Academic Search

  \\u000a \\u000a \\u000a Abstract. Detonation and deflagration initiation under focusing conditions in a lean hydrogen-air mixture was experimentally investigated.\\u000a The experiments were carried out in a shock tube equipped with the laser schlieren system and pressure transducers. Two-dimensional\\u000a wedges (53 and 90), semi-cylinder and parabola, were used as the focusing elements. The peculiarities of mild and strong\\u000a ignition inside the reflector cavity

B. E. Gelfand; S. V. Khomik; A. M. Bartenev; S. P. Medvedev; H. Grönig; H. Olivier

2000-01-01

218

Molecular dynamics and kinetic study of carbon coagulation in the release wave of detonation products  

NASA Astrophysics Data System (ADS)

We present a combined molecular dynamics and kinetic study of a carbon cluster aggregation process in thermodynamic conditions relevant for the detonation products of oxygen deficient explosives. Molecular dynamics simulations with the LCBOPII potential under gigapascal pressure and high temperatures indicate that (i) the cluster motion in the detonation gas is compatible with Brownian diffusion and (ii) the coalescence probability is 100% for two clusters entering the interaction cutoff distance. We used these results for a subsequent kinetic study with the Smoluchowski model, with realistic models applied for the physical parameters such as viscosity and cluster size. We found that purely aggregational kinetics yield too fast clustering, with moderate influence of the model parameters. In agreement with previous studies, the introduction of surface reactivity through a simple kinetic model is necessary to approach the clustering time scales suggested by experiments (1000 atoms after 100 ns, 10 000 atoms after 1 ?s). However, these models fail to reach all experimental criteria simultaneously and more complex modelling of the surface process seems desirable to go beyond these current limitations.

Chevrot, Guillaume; Sollier, Arnaud; Pineau, Nicolas

2012-02-01

219

Detonation Performance of Aluminium - Ammonium Nitrate Explosives  

Microsoft Academic Search

The research on an effect of aluminium contents on detonation characteristics of ammonium nitrate explosives was carried out. Measurements of detonation velocity were performed. Parameters of blast waves produced by charges of the investigated explosives detonating in an open space were measured by the use of piezoelectric gauges. Quasi-static pressure measurements were conducted in a steel chamber of 0.15 m

Józef PASZULA; Waldemar A. TRZCI?SKI

220

Bidirectional slapper detonators in spherical explosion systems  

NASA Astrophysics Data System (ADS)

A bidirectional slapper detonator has been proven effective for producing a spherically expanding shock wave. Two bridge foils are used to propel flyers in opposite directions, thereby initiating two explosive pellets, each embedded in one hemisphere of a spherical system. This detonation system produces a nearly perfect spherically expanding detonation front.

Martinez, Ernest C.

1990-11-01

221

Bidirectional slapper detonators in spherical explosion systems  

Microsoft Academic Search

A bidirectional slapper detonator has been proven effective for producing a spherically expanding shock wave. Two bridge foils are used to propel flyers in opposite directions, thereby initiating two explosive pellets, each embedded in one hemisphere of a spherical system. This detonation system produces a nearly perfect spherically expanding detonation front.

Ernest C. Martinez

1990-01-01

222

Numerical Simulation of Detonation Initiation with a Shock Wave Entering a Cloud of Aluminum Particles  

Microsoft Academic Search

Based on the mathematical model of a reacting two-phase medium in the two-velocity, two-temperature approximation, the process of planar shock wave entering a cloud of aluminum particles is numerically studied. The incident shock wave may have either a rectangular or a triangular profile, i.e., it may be accompanied by a rarefaction wave. An analysis of numerical data allowed us to

A. V. Fedorov

2002-01-01

223

Reaction zone structure in supracompressed detonating explosives  

Microsoft Academic Search

Nanosecond time resolved particle velocity histories of supracompressed detonation waves in TNT-, TATB-, and HMX-based explosives are measured using a VISAR laser velocimeter and calculated using the ignition and growth reactive flow hydrodynamic computer code model. The Zeldovich-von Neumann-Doering (ZND) detonation wave structure is observed at pressures more than twice the self-sustaining detonation wave pressure. TNT and TATB exhibited a

L. G. Green; C. M. Tarver; D. J. Erskine

1989-01-01

224

The generation and role of detonation front pulsations  

Microsoft Academic Search

The independence of the generation mechanism for detonation front pulsations from the role of these pulsations in the maintenance of undamped detonation is discussed. It is shown that pulsations are not a necessary property of undamped detonation, that elemetary Mach configurations, which form detonation front discontinuities, arise upon every shock wave reflection from a wall and that when a reactive

V. E. Gordeev

1979-01-01

225

Detailed structure of spinning detonation in a circular tube  

Microsoft Academic Search

A single spinning detonation wave propagating in a circular tube, discovered experimentally in 1926, is simulated three-dimensionally with a detailed chemical reaction mechanism. The detonation front obtained numerically rotates periodically with a Mach leg, whiskers, and a transverse detonation. A long pressure trail, which is distributed from the transverse detonation to downstream, was reproduced, clearly showing that the pressure trail

N. Tsuboi; K. Eto; A. K. Hayashi

2007-01-01

226

Dynamic aspects of detonations; International Colloquium on Dynamics of Explosions and Reactive Systems, 13th, Nagoya, Japan, July 28-Aug. 2, 1991, Technical Papers  

NASA Astrophysics Data System (ADS)

Various papers on the dynamic aspects of detonations are presented. Individual subjects addressed include: high-resolution numerical simulations for 2D unstable detonations, simulation of cellular structure in a detonation wave, Mach reflection of detonation waves, mechanism of unstable detonation front origin, numerical modeling of galloping detonation, experimental study of the fine structure in spin detonation, influence of fluorocarbon on H2O2Ar detonation, digial signal processing analysis of soot foils, cylindrical detonations in methane-oxygen-nitrogen mixtures, structure of reaction waves behind oblique shocks, ignition in a complex Mach structure, simulations for detonation initiation behind reflected shock waves. Also discussed are: limiting tube diameter of gaseous detonation, mechanisms of detonation propagation in a porous medium propagation and extinction of detonation waves in tube bundles, structure and velocity deficit of gaseous detonation in rough tubes, possible method for quenching of a gaseous detonation, effect of hollow heterogeneities on nitromethane detonation.

Kuhl, A. L.; Leyer, J.-C.; Borisov, A. A.; Sirignano, W. A.

227

Planar Reflection of Gaseous Detonations  

NASA Astrophysics Data System (ADS)

Pipes containing flammable gaseous mixtures may be subjected to internal detonation. When the detonation normally impinges on a closed end, a reflected shock wave is created to bring the flow back to rest. This study built on the work of Karnesky (2010) and examined deformation of thin-walled stainless steel tubes subjected to internal reflected gaseous detonations. A ripple pattern was observed in the tube wall for certain fill pressures, and a criterion was developed that predicted when the ripple pattern would form. A two-dimensional finite element analysis was performed using Johnson-Cook material properties; the pressure loading created by reflected gaseous detonations was accounted for with a previously developed pressure model. The residual plastic strain between experiments and computations was in good agreement. During the examination of detonation-driven deformation, discrepancies were discovered in our understanding of reflected gaseous detonation behavior. Previous models did not accurately describe the nature of the reflected shock wave, which motivated further experiments in a detonation tube with optical access. Pressure sensors and schlieren images were used to examine reflected shock behavior, and it was determined that the discrepancies were related to the reaction zone thickness extant behind the detonation front. During these experiments reflected shock bifurcation did not appear to occur, but the unfocused visualization system made certainty impossible. This prompted construction of a focused schlieren system that investigated possible shock wave-boundary layer interaction, and heat-flux gauges analyzed the boundary layer behind the detonation front. Using these data with an analytical boundary layer solution, it was determined that the strong thermal boundary layer present behind the detonation front inhibits the development of reflected shock wave bifurcation.

Damazo, Jason Scott

228

Surface shear strains induced by quasi-steady sweeping detonation waves  

NASA Astrophysics Data System (ADS)

Sweeping wave experiments create conditions of greater shear than corresponding onedimensional motion experiments, and are of current interest for material damage characterization. Sweeping waves are also important with regards to the spectrum of applications of explosives driving metals. The intensity of the shear developed in a sweeping wave experiment may be monitored using crossed beams of Photon Doppler Velocimetry (PDV). During the time the material is traversing the volume defined by the crossed beams, the interferometer is measuring the velocity of the same mass element (approximately) from two directions. It is known that PDV measures the velocity component that lies along the beam direction, so that with crossed beams, two independent directions are simultaneously measured and therefore the vector velocity (both magnitude and direction) are captured. The vector velocity is readily related to the strain rates on the surface (after removing the rigid rotation rates), and the equations are integrated to obtain the strains.

Hull, Lawrence; Briggs, Matthew; Faulkner, James

2012-03-01

229

Instrumented Floret Tests of Detonation Spreading  

NASA Astrophysics Data System (ADS)

The floret test was originally devised to permit comparison of detonation-spreading performance of various insensitive explosive materials, using only the dent in a copper witness plate as a metric. Dent depth in the copper plate is directly related to the fraction of a thin acceptor pellet that was detonated by impact of a small explosive-driven flyer plate. We have now added instrumentation to quantitatively measure the detonation corner-turning behavior of IHEs. Results of multi-fiber optical probe measurements are shown for LLM-105 and UF-TATB explosive materials. Results are interpreted and compared with predictions from one reaction-rate model used to describe detonation spreading, and may be advantageous for comparison with other reactive-flow wave-code models. Detonation spreading in UF-TATB occurred with formation of a non-detonating region surrounding a detonating core, and re-establishment of detonation in a ``lateral'' direction beyond that region.

Kennedy, James; Plaksin, Igor; Thomas, Keith; Martin, Eric; Lee, Kien-Yin; Akinci, Adrian; Asay, Blaine; Campos, Jose; Direito, Jose

2004-07-01

230

Initiation of propagating detonations  

SciTech Connect

The initiation of propagating detonation in PBS 9404, PBX 9502, and X0219 by hemispheric intiators of PBX 9404, 1.8 g/cm/sup 3/-TATB, and X0351 is described numerically, using the two-dimensional Lagrangian code, 2DL, and the Forest Fire rate to describe the heterogeneous explosive shock initiation process. The initiation of propagating detonation in the insensitive explosive PBX 9502 by triple-shock-wave interaction from three initiators has been modeled using the three-dimensional, reactive, Eulerian hydrodynamicd code, 3DE.

Mader, C.L.

1981-01-01

231

Behavior of the surface of a bubbly liquid after detonation wave impact  

Microsoft Academic Search

In safety engineering, one position of interest inside heterogeneous systems of the type liquid–gas is the contact surface between these two phases. Under certain conditions, e.g. shock wave impact, phenomena can take place at this position that can have a significant influence on the explosion behavior of the system. In this work an investigation is presented about the existence of

K. Mitropetros; P. A. Fomin; H. Hieronymus

2006-01-01

232

Mach reflection of shock and detonation waves in steady supersonic chemically reacting flows  

Microsoft Academic Search

Numerical simulations have been performed to study regular and Mach reflections of oblique shock waves (SW) in a steady supersonic flow of a homogeneous combustible gas mixture and different inflow Mach numbers Min. The dynamics of the compressible medium was described by two-dimensional unsteady Euler equations. Chemical transformations in the gas mixture were described by a two-stage reaction model. The

A. V. Trotsyuk; A. N. Kudryavtsev; M. S. Ivanov

2003-01-01

233

PRELUDE TO A DOUBLE DEGENERATE MERGER: THE ONSET OF MASS TRANSFER AND ITS IMPACT ON GRAVITATIONAL WAVES AND SURFACE DETONATIONS  

SciTech Connect

We present the results of a systematic numerical study of the onset of mass transfer in double degenerate binary systems and its impact on the subsequent evolution. All investigated systems belong to the regime of direct impact, unstable mass transfer. In all of the investigated cases, even those considered unstable by conventional stability analysis, we find a long-lived mass transfer phase continuing for as many as several dozen orbital periods. This settles a recent debate sparked by a discrepancy between earlier smoothed particle hydrodynamics (SPH) calculations that showed disruptions after a few orbital periods and newer grid-based studies in which mass transfer continued for tens of orbits. The number of orbits a binary survives sensitively depends on the exact initial conditions. We find that the approximate initial conditions that have been used in most previous SPH calculations have a serious impact on all stages of the evolution from the onset of mass transfer up to the final structure of the remnant. We compare 'approximate' initial conditions where spherical stars are placed at an initial separation obtained from an estimate of the Roche lobe size with 'accurate' initial conditions that were constructed by carefully driving the binary system to equilibrium by a relaxation scheme. Simulations that use the approximate initial conditions underestimate the initial separation when mass transfer sets in, which yields a binary that only survives for only a few orbits and thus a rapidly fading gravitational wave signal. Conversely, the accurate initial conditions produce a binary system in which the mass transfer phase is extended by almost two orders of magnitude in time, resulting in a gravitational wave signal with amplitude and frequency that remain essentially constant up until merger. As we show that these binaries can survive at small separation for hundreds of orbital periods, their associated gravitational wave signal should be included when calculating the gravitational wave foreground (although expected to be below Laser Interferometer Space Antenna's sensitivity at these high frequencies). We also show that the inclusion of the entropy increase associated with shock heating of the accreted material reduces the number of orbits a binary survives given the same initial conditions, although the effect is not as pronounced when using the appropriate initial conditions. The use of accurate initial conditions and a correct treatment of shock heating allows for a reliable time evolution of the temperature, density, and angular momentum, which are important when considering thermonuclear events that may occur during the mass transfer phase and/or after merger. Our treatment allows us to accurately identify when surface detonations may occur in the lead-up to the merger, as well as the properties of final merger products.

Dan, Marius; Rosswog, Stephan [School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, 28759 Bremen (Germany); Guillochon, James; Ramirez-Ruiz, Enrico, E-mail: m.dan@jacobs-university.de, E-mail: rosswog@jacobs-university.de, E-mail: jfg@ucolick.org, E-mail: enrico@ucolick.org [TASC, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)

2011-08-20

234

Numerical study of detonation in CH 4 (H 2 ) + air mixtures behind shock waves  

Microsoft Academic Search

A comparative analysis is performed of the variation of the gas-dynamic parameters and of the dynamics of formation of nitrogen-containing components during combustion ofCH4 + air andH2 + air mixtures in supersonic flow behind a shock wave. The sizes of the induction and combustion zones at different initial values of the Mach number of are calculated and the possibility of

N. G. Dautov; A. M. Starikov

1996-01-01

235

Burning and detonation  

SciTech Connect

The effect of confined burning explosive abutting nonburning explosive in a variety of one-dimensional geometries has been studied by numerical simulation, demonstrating the effects of confinement, burning rate, and shock sensitivity. The model includes porous bed burning, compressible solids and gases, shock-induced decomposition with possible transition to detonation, and constant velocity ignition waves. Two-phase flow, gas relative to solid, is not allowed. Because the shock sensitivity of an explosive changes with explosive density and because such experimental data is rarely available over a range of densities, a method for the calculation of the density effect on the initial-shock-pressure, distance-to-detonation (wedge test) measure of shock sensitivity is given. The calculation uses the invariance with density of the shock particle velocity as a function of time to detonation, and the experimental data at some high density.

Forest, C.A.

1981-01-01

236

Study on Performance of Detonation-Driven Shock Tube  

NASA Astrophysics Data System (ADS)

A detonation-driven shock tube firstly designed by H. R. Yu is considered to be a useful apparatus for producing high-enthalpy flow. In this apparatus, a strong shock wave is generated by detonating an oxygen-hydrogen mixture (oxy-hydrogen) and the driver gas temperature and pressure are extremely high compared with those of a conventional shock tube. However, the structure of the detonation wave is not uniform, e. g., the detonation wave has three-dimensional cellular structures and multiple transverse waves. Furthermore, the detonation wave is followed by a Taylor expansion fan and the performance of detonation-driven shock tube is not well understood. In this preliminary study, a detonation-driven shock tube is constructed and its performance is experimentally investigated by measuring pressure histories and the profile of the ionization current behind the detonation wave. As a result, (i)the pressure history of the detonation wave is clarified and shows reasonable agreement with the result obtained by the KASIMIR shock tube simulation code. (ii)The propagation velocity of the detonation wave coincides well with the theoretical prediction assuming a Chapman-Jouguet detonation wave. (iii)The equivalence ratio of the oxy-hydrogen mixture to produce the highest Mach number of the shock wave is evaluated to be ? approximately equal to 1.7.

Yamanaka, Akio; Ariga, Yosuke; Obara, Tetsuro; Cai, Pin; Ohyagi, Shigeharu

237

Folded Detonation Initiator for Constant Volume Combustion Device.  

National Technical Information Service (NTIS)

In the present invention, at least one detonation initiator is positioned downstream of a main combustion chamber, with the initiator oriented such that it projects a detonation initiation wave forward into the main combustion chamber. The main combustion...

A. J. Dean K. R. McManus V. E. Tangirala

2004-01-01

238

Burning and detonation  

Microsoft Academic Search

The effect of confined burning explosive abutting nonburning explosive in a variety of one-dimensional geometries has been studied by numerical simulation, demonstrating the effects of confinement, burning rate, and shock sensitivity. The model includes porous bed burning, compressible solids and gases, shock-induced decomposition with possible transition to detonation, and constant velocity ignition waves. Two-phase flow, gas relative to solid, is

Charles A. Forest

1981-01-01

239

Formation of unburnt pockets in gaseous detonations  

Microsoft Academic Search

Formation of unburnt pockets in gaseous detonations is caused by two mechanisms: longitudinal and transverse mechanisms. The\\u000a longitudinal mechanism is based on longitudinal instability of the detonation front. In the transverse mechanism, interactions\\u000a between transverse waves lead to the formation of unburnt pockets. In this paper, the transverse mechanism is investigated\\u000a via two-dimensional numerical simulations of propagation of gaseous detonation

M. Sabzpooshani; K. Mazaheri

2009-01-01

240

Detonation transformations in an aerated liquid  

SciTech Connect

The propagation of detonation waves (DW) in aerated fluid systems, capable of exothermal chemical reaction, is of great interest both from the theoretical standpoint and for providing safe conditions in chemical production. In this work the conditions for detonation transformations in liquid organic nitrogen derivatives - diethylene glycol dinitrate (DEGDN) and nitromethane - are studied. Initiation of detonation in porous nitromethane is described. The porosity was created by continuously passing air bubbles through the liquid.

Kondrikov, B.N.; Kozak, G.D.; Oblomskii, V.B.; Savkin, A.V.

1987-09-01

241

Excitation of ignition foci in a detonation relaxation zone  

SciTech Connect

The interactions in a detonation wave include collisions between ignition foci and the renewal of ternary Mach reflections. It is shown in this paper that such a mechanism occurs in the relaxation zone of a shock wave not only in a detonation already formed by also on detonation formation. The relaxation zone in a detonation wave is examined by a correlation method, with analysis of the fine structure and comparison of the thicknesses of the collision zones for detonation waves on recordings, where the authors have calculated the relaxation zone thicknesses. They also examined nucleated ignition and the reactions in the ignition in the relaxation zone on detonation formation. They processed the measurements for various times in a 2H/sub 2//O/sub 2/ detonation mixture for normal initial conditions.

Avduevskii, V.S.; Denisov, Yu.N.; Podtynkov, I.I.; Frolov, A.M.

1987-03-01

242

Theory of Detonations. III. Ignition Temperature Approximation  

Microsoft Academic Search

This paper is one of a series in which we discuss the effect of viscosity, diffusion, and heat conductivity on the structure of steady-state plane detonation waves. It is shown that the consideration of these phenomena may lead to considerable overlapping of the reaction and shock zones and also to the existence of detonation limits.In order to discuss in more

C. F. Curtiss; J. O. Hirschfelder; M. P. Barnett

1959-01-01

243

Specific Features of Synthesis of Detonation Nanodiamonds  

Microsoft Academic Search

It is demonstrated that the Chapman-Jouguet parameters for high explosives used in nanodiamond synthesis are located in the region of liquid nanocarbon; therefore, the chemical reaction zone of the detonation wave involves formation of carbon nanodroplets, which are later crystallized into nanodiamonds on the segment of the isentrope of expansion of detonation products, passing through the region of stability of

V. V. Danilenko

2005-01-01

244

Detonation safety in microchannels  

US Patent & Trademark Office Database

The proper sizing of microchannel dimensions and the management of internal features offer the possibility of inherently safe operation within the flammable limits of a combustible fluid stream while preserving the largest-possible flow dimensions for industrial-scale process capacity. Specifically, the microchannel dimensions need not be restricted to gap distances below the quenching distance to be operated safely. Microchannel performance can be engineered to provide adequate heat transfer for flame propagation. However, it is essential to maintain flame characteristics in such a manner that it cannot transition to a detonation flame front. A detonation takes place when the combustion wave propagates at supersonic speeds at the existing local temperature and pressure conditions in the system. It results in a much larger energy release over a much smaller period of time as compared to a laminar flame or deflagration, the later of which is a combustion wave propagating at subsonic speed. Detonations can be potentially highly destructive and very hazardous and therefore should be avoided for most industrial applications.

2013-08-27

245

Investigation of the adiabat of heterogeneous two-phase detonation  

Microsoft Academic Search

The authors construct a mathematical model for the adiabatic heterogeneous detonation and detonation wave propagation of a suspension of fuel droplets in gas under the influence of nonequilibrium in the two-phase flow. The nonideality of the model results in difficulties in the selection of the detonation velocity and the location of the Chapman-Jouguet plane. The following rules are proposed for

A. E. Medvedev; A. V. Fedorov; V. M. Fomin

1987-01-01

246

Some aspects of nonideal detonation in composite explosives  

Microsoft Academic Search

A theoretical treatment is formulated for steady-state planar detonation waves in composite explosives such as Amatex 20. This treatment provides a more definitve and realistic description of detonation in such explosives, and extends the classical Zeldovich-von Neumann-Doering model of ideal detonation into a propotype model for nonideal detonation. Incomplete decomposition of the slowest reacting component, and incomplete attainment of chemical

M. Cowperthwaite

1983-01-01

247

Detonator Performance Characterization using Multi-Frame Laser Schlieren Imaging  

Microsoft Academic Search

Multi-frame Laser Schlieren Imaging of shock waves produced by detonators in transparent witness materials can be used to evaluate detonator performance. We use inverse calculations of the 2D propagation of shock waves in the EPIC finite element model computer code to calculate a temporal-spatial-pressure profile on the surface of the detonator that is consistent with the experimental shock waves from

Steven Clarke; Colin Landon; Michael Murphy; Michael Martinez; Thomas Mason; Keith Thomas

2009-01-01

248

Initiation of Gaseous Detonation by Conical Projectiles  

NASA Astrophysics Data System (ADS)

Initiation and stabilization of detonation by hypersonic conical projectiles launched into combustible gas mixtures is investigated. This phenomenon must be understood for the design and optimization of specific hypersonic propulsion devices, such as the oblique detonation wave engine and the ram accelerator. The criteria for detonation initiation by a projectile is also related to fundamental aspects of detonation research, such as the requirement for direct initiation of a detonation by a blast wave. Experimental results of this problem also offer useful references for validation of numerical and theoretical modeling. Projectiles with cone half angles varying from 15° to 60° were launched into stoichiometric mixtures of hydrogen/oxygen with 70% argon dilution at initial pressures between 10 and 200 kPa. The projectiles were launched from a combustion-driven gas gun at velocities up to 2.2 km/s (corresponding to 133% of the Chapman Jouguet velocity). Pictures of the flowfields generated by the projectiles were taken via Schlieren photography. Five combustion regimes were observed about the projectile ranging from prompt and delayed oblique detonation wave formation, combustion instabilities, a wave splitting, and an inert shock wave. Two types of transition from the prompt oblique detonation wave regime to the inert shock regime were observed. The first (the delayed oblique detonation wave regime) showed an inert shock attached to the tip of the projectile followed by a sharp kink at the onset of an oblique detonation wave; this regime occurred by decreasing the cone angle at high mixture pressures. The second (the combustion instabilities regime) exhibited large density gradients due to combustion ignition and quenching phenomena; this regime occurred by decreasing the mixture pressure at large cone angles. A number of theoretical models were considered to predict critical conditions for the initiation of oblique detonations. The Lee-Vasiljev model agreed qualitatively well with the experimental results for relatively blunt projectiles (cone half-angle larger than 35°) and low mixture pressures (lower than 100 kPa). The trend of the critical Damköhler number calculated along the projectile cone surface was similar to that of the experimental results for slender cones (cone half-angles lower 35°) and high mixture pressures (higher than 100 kPa). Steady 2D simulations of reacting flows over finite wedges using the method of characteristics with a one-step Arrhenius chemical reaction model reproduced the three regimes observed for direct initiation of a detonation: the subcritical, critical and supercritical regimes. It is shown that in order for a 2D wedge to be equivalent to the problem of blast initiation of a detonation (which is the essence of the Lee-Vasiljev model), the Mach number normal to the oblique shock needs to be greater than 50 and the wedge angle has to be smaller than 30°. Simulations of reacting flows over semi-infinite wedges and cones were validated with CFD results. Excellent agreement was reached between the angle of overdriven oblique detonations obtained from the simulations and those from a polar analysis. For wedge or cone angles equal or lower than the minimum angle for which an oblique detonation is attached (according to the polar analysis), a Chapman-Jouguet oblique detonation was initiated. In the conical configuration, the curvature around the cone axis allowed an oblique detonation to be self-sustained at an angle less than without the curvature effect. At larger activation energies, the initiation process of an oblique detonation wave at the tip of a semi-infinite wedge or cone was identified. Unsteady 2D computational simulations were also conducted and showed the cellular structure of an oblique detonation wave. Instabilities in the form of transverse shock waves along the oblique detonation front arise for large activation energies.

Verreault, Jimmy

249

CIT: Detonators  

Microsoft Academic Search

Detonators are: (1) exploding bridge wire (EBW) initiators, (2) exploding foil initiators (EFI), and (3) explosive surface initiators (covered under 'high explosives'). Controls are: (1) NSG DUL: 6.A.1., (2) WA: 1.A.7, (3) EU: 1A007, 3A232, and (4) HS: 3603.00. Nuclear uses are to initiate HE charge of an implosion-type nuclear weapon. Other uses are commercial mining operations (EBWs), and downhole

Davis R. Thomsen; Loretta A. Weiss

2012-01-01

250

Cellular structure of detonation utilized in propulsion system  

NASA Astrophysics Data System (ADS)

How to confine a detonation in a combustor is a key issue of detonation applications in propulsion systems. Based on achieving schemes, detonations applied in the combustor, including pulse detonation wave (PDW), oblique detonation wave (ODW) and rotating detonation wave (RDW), are different from that described by the classic CJ theory in fine structures and its self-sustaining mechanisms. In this work, the cellular structures and flow fields of ODW and RDW were obtained numerically, and the fundamental characteristics and self-sustaining mechanisms of the detonations were analyzed and discussed. ODW front consists of three parts: the ZND-like front, the single-headed triple point front and the dual-headed triple point front. Cellular structures of RDW are heterogeneous, and the cell size near the outer wall is smaller than that near the inner wall.

Zhang, XuDong; Fan, BaoChun; Gui, MingYue; Pan, ZhenHua

2012-10-01

251

Oxyhydrogen combustion and detonation driven shock tube  

NASA Astrophysics Data System (ADS)

The performance of combustion driver ignited by multi-spark plugs distributed along axial direction has been analysed and tested. An improved ignition method with three circumferential equidistributed ignitors at main diaphragm has been presented, by which the produced incident shock waves have higher repeatability, and better steadiness in the pressure, temperature and velocity fields of flow behind the incidence shock, and thus meets the requirements of aerodynamic experiment. The attachment of a damping section at the end of the driver can eliminate the high reflection pressure produced by detonation wave, and the backward detonation driver can be employed to generate high enthalpy and high density test flow. The incident shock wave produced by this method is well repeated and with weak attenuation. The reflection wave caused by the contracted section at the main diaphragm will weaken the unfavorable effect of rarefaction wave behind the detonation wave, which indicates that the forward detonation driver can be applied in the practice. For incident shock wave of identical strength, the initial pressure of the forward detonation driver is about 1 order of magnitude lower than that of backward detonation.

Hongru, Yu

1999-05-01

252

Bidirectional slapper detonators in spherical explosion systems.  

National Technical Information Service (NTIS)

A bidirectional ''slapper detonator'' has been proven effective for producing a spherically expanding shock wave. Two bridge foils are used to propel flyers in opposite directions, thereby initiating two explosive pellets, each embedded in one hemisphere ...

E. C. Martinez

1990-01-01

253

The Formation Kinetics of Detonation Nanodiamonds  

Microsoft Academic Search

We report experimental data on small angle X-ray scattering behind the detonation wave front in the high pressure zone, obtained using synchrotron radiation. A series of detonation experiments with ultradisperse diamond in oxygen and oxygen-free media have led us to the conclusion that diamond cannot be produced immediately behind the wave front. We believe that here there is a diamond-free

V. M. Titov; B. P. Tolochko; K. A. Ten; L. A. Lukyanchikov; P. I. Zubkov

254

Detailed structure of spinning detonation in a circular tube  

SciTech Connect

A single spinning detonation wave propagating in a circular tube, discovered experimentally in 1926, is simulated three-dimensionally with a detailed chemical reaction mechanism. The detonation front obtained numerically rotates periodically with a Mach leg, whiskers, and a transverse detonation. A long pressure trail, which is distributed from the transverse detonation to downstream, was reproduced, clearly showing that the pressure trail also spins synchronously with the transverse detonation. The formation of an unburned gas pocket behind the detonation front was not observed in the present simulations because the rotating transverse detonation completely consumed the unburned gas. The calculated profiles of instantaneous OH mass fraction have a keystone shape behind the detonation front. The numerical results for pitch, track angle, Mach stem angle, and incident shock angle on the tube wall agree well with the experimental results. (author)

Tsuboi, N. [Space Transportation Engineering Department, Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Yoshinodai 3-1-1, Sagamihara, Kanagawa 229-8510 (Japan); Eto, K.; Hayashi, A.K. [Department of Mechanical Engineering, Aoyama Gakuin University, Fuchinobe 5-10-1, Sagamihara, Kanagawa 229-8558 (Japan)

2007-04-15

255

Series Detonator Initiation System.  

National Technical Information Service (NTIS)

The purpose of this thesis was to design, build, and test a high voltage detonator initiation system capable of firing a series modular detonator array. This initiation system was designed to optimally fire a detonator array of 25 detonators, but is capab...

K. Olmscheid

1983-01-01

256

Preliminary Experimental Investigation on Detonation Initiation in the Ejector of a Pulse Detonation Rocket Engine  

NASA Astrophysics Data System (ADS)

A small pulse detonation rocket engine (PDRE) was used as a predetonator to initiate detonation in its ejector. The detonation products discharged from the PDRE was not only ignition source for the ejector but also primary flow which entrained air from environment into the ejector. Stoichiometric liquid kerosene and gaseous oxygen were used as reactants for the PDRE. While in the ejector injected liquid kerosene was used as fuel and entrained air was used as oxidizer. Reactants in the ejector were ignited by the detonation wave and products discharged from the PDRE. Detonation was successfully initiation in present experiments. It was found that flame propagation upstream at the entrance of the ejector was inevitable, which affected the detonation initiation process in the ejector. Disks with orifices were placed at the entrance of the ejector to weaken the flame propagation upstream effect, which would affect the air flow entraining process, but the results show it worked.

Yan, Yu; Fan, Wei; Mu, Yang

2012-12-01

257

Stability of Detonation Profiles in the ZND Limit  

Microsoft Academic Search

Confirming a conjecture of Lyng–Raoofi–Texier–Zumbrun, we show that stability of strong detonation waves in the ZND, or small-viscosity,\\u000a limit is equivalent to stability of the limiting ZND detonation together with stability of the viscous profile associated\\u000a with the component Neumann shock. Moreover, on bounded frequencies the nonstable eigenvalues of the viscous detonation wave\\u000a converge to those of the limiting ZND

Kevin Zumbrun

2011-01-01

258

Detonation performance of high-dense BTF charges  

NASA Astrophysics Data System (ADS)

New experimental data on detonation wave parameters and explosive performance for benzotrifuroxan are presented. Optical pyrometry was applied in order to measure the temperature and pressure of BTF detonation products. Chapman-Jouguet temperature was obtained as 3990 – 4170 K (charge densities 1.82 – 1.84 g/cc). The heat of explosion and the acceleration ability were measured also. It is also considered the hypothesis of formation of nanodiamond particles in detonation products directly behind the detonation front and influence of these processes on the temperature-time history in detonation products.

Dolgoborodov, A.; Brazhnikov, M.; Makhov, M.; Gubin, S.; Maklashova, I.

2014-05-01

259

Simulation of multidimensional gaseous detonations with a parallel adaptive method  

Microsoft Academic Search

A detonation wave is a self-sustained, violent form of shock-induced combustion that is characterized by a subtle energetic interplay between leading hydrodynamic shock wave and following chemical reaction. Multidimensional gaseous detonations never remain planar and instead exhibit transverse shocks that form triple points with transient Mach reflection patterns. Their accurate numerical simulation requires a very high resolution around shock and

Ralf Deiterding

2008-01-01

260

Two phase detonation studies  

NASA Technical Reports Server (NTRS)

An experimental study of the passage of a shock wave over a burning fuel drop is described. This includes high speed framing photographs of the interaction taken at 500,000 frames per second. A theoretical prediction of the ignition of a fuel drop by a shock wave is presented and the results compared with earlier experimental work. Experimental attempts to generate a detonation in a liquid fuel drop (kerosene)-liquid oxidizer drop (hydrogen peroxide)-inert gas-environment are described. An appendix is included which gives the analytical prediction of power requirements for the drop generator to produce certain size drops at a certain mass rate. A bibliography is also included which lists all of the publications resulting from this research grant.

Nicholls, J. A.; Pierce, T. H.; Miyajima, H.; Oza, R.; Patil, P.

1974-01-01

261

Mach reflection bifurcations as a mechanism of cell multiplication in gaseous detonations  

Microsoft Academic Search

Detonation waves in gases are unstable and form cellular structures. The cellular structure can range from being very regular, to very irregular, where new modes are continuously formed on the front of the detonation wave. The present work addresses the mechanism of new cell formation in irregular structure detonations. Using idealized one-step chemistry calculations on sufficiently wide domains, as to

P. Mach; M. I. Radulescu

2011-01-01

262

The influence of detonation cell size and regularity on the propagation of gaseous detonations in granular materials  

NASA Astrophysics Data System (ADS)

This paper presents results from an experimental study of transmission of gaseous detonation waves through various granular filters. Spherical glass beads of 4 and 8 mm diameter and crushed rock of 7.5 mm volume averaged diameter were used as filter material. Varying the initial pressure of the detonating gas mixture controlled the detonation cell size. Dilution with argon was used to vary the detonation cell regularity. The complete range from almost no detonation velocity deficit to complete extinction of the combustion wave was observed. The existing correlation for gaseous detonation velocity deficit V/VCJ = [1-0.35 (d_ c/dps)] +/- 0.1 where dc is the critical diameter for the gaseous detonation and dps is the pore size, is found to be applicable for both smooth spherical particles and irregular crushed rock when considering irregular detonation structures. Soot films and pressure measurements show that as the detonation cell size is increased, reinitiation of a reanular filter until it finally no longer occurs at V/VCJ ~ 0.4--0.45. Complete extinction of the combustion wave occurs at V/VCJ ~ 0.25--0.3. These two limits appear to be about the same for irregular and regular detonation cell structures. For irregular structures without argon dilution, dc/dps ~ 50 can be found for detonation wave failure, and dc/dps ~ 100 can be found for complete extinction of the combustion wave. For argon dilution these limits are changed to dc/dps ~ 10 and dc/dps ~ 40, respectively. The data are a bit scarce as a basis for proposing a new correlation for regular structures, but as a first approximation V/VCJ =[0.8--0.35log(dc/dps)] +/- 0.1 is suggested for regular structures. The detonation or combustion wave is found to approach a constant velocity in the granular filter if not extinguished.

Slungaard, T.; Engebretsen, T.; Sønju, O. K.

263

Characterizing Detonator Output Using Dynamic Witness Plates  

Microsoft Academic Search

A sub-microsecond, time-resolved micro-particle-image velocimetry (PIV) system is developed to investigate the output of explosive detonators. Detonator output is directed into a transparent solid that serves as a dynamic witness plate and instantaneous shock and material velocities are measured in a two-dimensional plane cutting through the shock wave as it propagates through the solid. For the case of unloaded initiators

Michael John Murphy; Ronald J. Adrian

2009-01-01

264

CHARACTERIZING DETONATOR OUTPUT USING DYNAMIC WITNESS PLATES  

Microsoft Academic Search

A sub-microsecond, time-resolved micro-particle-image velocimetry (PIV) system is developed to investigate the output of explosive detonators. Detonator output is directed into a transparent solid that serves as a dynamic witness plate and instantaneous shock and material velocities are measured in a two-dimensional plane cutting through the shock wave as it propagates through the solid. For the case of unloaded initiators

Michael J. Murphy; Ronald J. Adrian

2009-01-01

265

Detonation properties of the insensitive explosive TATB  

Microsoft Academic Search

The detonation properties of various compositions of the insensitive explosive TATB were investigated using thin flyer plates. These flyer plates were accelerated by electrically exploding metal foils. The divergence of the detonation wave in TATB is improved for compositions of lower-density, lower-binder-percentage, and smaller HE particle size. Increasing the velocity or the diameter of the flyer plate or increasing the

R. K. Jackson; R. C. Weingart

1976-01-01

266

Gaseous detonation propagation in a bifurcated tube  

NASA Astrophysics Data System (ADS)

Gaseous detonation propagation in a bifurcated tube was experimentally and numerically studied for stoichiometric hydrogen and oxygen mixtures diluted with argon. Pressure detection, smoked foil recording and schlieren visualization were used in the experiments. Numerical simulation was carried out at low initial pressure (8.00kPa), based on the reactive Navier-Stokes equations in conjunction with a detailed chemical reaction model. The results show that the detonation wave is strongly disturbed by the wall geometry of the bifurcated tube and undergoes a successive process of attenuation, failure, re-initiation and the transition from regular reflection to Mach reflection. Detonation failure is attributed to the rarefaction waves from the left-hand corner by decoupling leading shock and reaction zones. Re-initiation is induced by the inert leading shock reflection on the right-hand wall in the vertical branch. The branched wall geometry has only a local effect on the detonation propagation. In the horizontal branch, the disturbed detonation wave recovers to a self-sustaining one earlier than that in the vertical branch. A critical case was found in the experiments where the disturbed detonation wave can be recovered to be self-sustaining downstream of the horizontal branch, but fails in the vertical branch, as the initial pressure drops to 2.00kPa. Numerical simulation also shows that complex vortex structures can be observed during detonation diffraction. The reflected shock breaks the vortices into pieces and its interaction with the unreacted recirculation region induces an embedded jet. In the vertical branch, owing to the strength difference at any point and the effect of chemical reactions, the Mach stem cannot be approximated as an arc. This is different from the case in non-reactive steady flow. Generally, numerical simulation qualitatively reproduces detonation attenuation, failure, re-initiation and the transition from regular reflection to Mach reflection observed in experiments.

Wang, C. J.; Xu, S. L.; Guo, C. M.

267

Flash x-ray radiography study of the dynamic fracture of metallic discs at the interface between two colliding detonation wave fronts  

NASA Astrophysics Data System (ADS)

In this paper the dynamic fragmentation behavior of a metal disc, positioned at the interface between colliding detonation wave fronts, is investigated. Flash x-ray radiography images from both 150kV and 450kV sytems were obtained to study the break-up phenomena of the metal disc between two similar explosive charges initiated simultaneously. The study was limited to discs of oxygen free high purity copper and an aluminium alloy (6061 T6). During the inititial shock loading phase the disc is stretched accompanied by the formation of spalling fragment rings. At a later stage discrete fragment rings are formed, which fly outward in an expanding disc fashion. The measured discrete fragment velocities ranged between 0.19 mm/?s and 2.7 mm/?s, depending on the material type. Flash x-ray radiography data at specific times is compared with numerical simulations performed using 3D-AutodynTM. Experimental techniques, procedures and results will be presented for the different metals.

Reddy, Kevin J. P.; Terblanche, Cornelis J.; Konig, Pieter J.

2005-03-01

268

Detonation Phenomena of PBX Microsamples  

NASA Astrophysics Data System (ADS)

Detonation study of PBX micro-samples, based on HMX with an inert (HTPB, epoxy) or energetic (GAP) binder was developed on the mesoscale level, using the multifiber optical probes, of 50 ?m resolution, connected directly to a fast electronic streak camera with 0.5 ns of temporal resolution. This record system allows the 2D direct observation of particle-to-particle successive transition of ?-waves through the interparticle binder space. The obtained results show, when the individual coarse HMX particles are subjected to a strong shock wave (30 GPa), the pulsed, double phase, process of energy release (a fast initial phase followed by relatively slow second phase). Also it can be observed the cooperative formation of a multi-head detonation front (DF) in collections of particles surrounded by the binder and the synergetic effect, behind the DF, by the appearing of spatial-temporal dissipative structures, followed by the self-organization of DF oscillations.

Plaksin, Igor; Campos, Jose; Ribeiro, Jose; Mendes, Ricardo

2001-06-01

269

Methods for proving the equivalency of detonator performance  

SciTech Connect

One of the challenges facing engineers is developing newer, safer detonators that are equivalent to devices currently in use. There is no clear consensus on an exact method for drawing equivalence of detonators. This paper summarizes our current efforts to develop diagnostics addressing various aspects of detonator design to better quantify and prove equivalency. We consider various optical techniques to quantify the output pressure and output wave shape. The development of a unique interpretation of streak camera breakouts, known as the apparent center of initiation, will be discussed as a metric for detonation wave shape. Specific examples apply these techniques to the comparison of a new laser-driven detonator with an existing exploding bridgewire (EBW) detonator. Successes and short-comings of the techniques will be discussed.

Munger, Alan C [Los Alamos National Laboratory; Akinci, Adrian A [Los Alamos National Laboratory; Thomas, Keith A [Los Alamos National Laboratory; Clarke, Steve A [Los Alamos National Laboratory; Martin, Eric S [Los Alamos National Laboratory; Murphy, Michael J [Los Alamos National Laboratory

2009-01-01

270

Detonator Performance Characterization using Multi-Frame Laser Schlieren Imaging  

NASA Astrophysics Data System (ADS)

Multi-frame Laser Schlieren Imaging of shock waves produced by detonators in transparent witness materials can be used to evaluate detonator performance. We use inverse calculations of the 2D propagation of shock waves in the EPIC finite element model computer code to calculate a temporal-spatial-pressure profile on the surface of the detonator that is consistent with the experimental shock waves from the schlieren imaging. Examples of calculated 2D temporal-spatial-pressure profiles from a range of detonator types (EFI --exploding foil initiators, DOI -- direct optical initiation, EBW -- exploding bridge wire, hotwire), detonator HE materials (PETN, HMX, etc), and HE densities. Also pressure interaction profiles from the interaction of multiple shock waves will be shown. LA-UR-09-00909.

Clarke, Steven; Landon, Colin; Murphy, Michael; Martinez, Michael; Mason, Thomas; Thomas, Keith

2009-06-01

271

The Physical Effects of Detonation in a Closed Cylindrical Chamber  

NASA Technical Reports Server (NTRS)

Detonation in the internal-combustion engine is studied as a physical process. It is shown that detonation is accompanied by pressure waves within the cylinder charge. Sound theory is applied to the calculation of resonant pressure-wave frequencies. Apparatus is described for direct measurement of pressure-wave frequencies. Frequencies determined from two engines of different cylinder sizes are shown to agree with the values calculated from sound theory. An outline of the theoretically possible modes of vibration in a right circular cylinder with flat ends is included. An appendix by John P. Elting gives a method of calculating pressure in the sound wave following detonation.

Draper, C S

1935-01-01

272

The physical effects of detonation in a closed cylindrical chamber  

NASA Technical Reports Server (NTRS)

Detonation in the internal-combustion engine is studied as a physical process. It is shown that detonation is accompanied by pressure waves within the cylinder charge. Sound theory is applied to the calculation of resonant pressure-wave frequencies. Apparatus is described for direct measurement of pressure-wave frequencies. Frequencies determined from two engines of different cylinder sizes are shown to agree with the values calculated from sound theory. An outline of the theoretically possible modes of vibration in a right circular cylinder with flat ends is included. An appendix by John P. Elting gives a method of calculating pressure in the sound wave following detonation.

Draper, C S

1935-01-01

273

Generation of the patterns in gaseous detonations  

Microsoft Academic Search

The problem addressed here is the mode of formation of the first initial regular pattern and its spacing in a detonation front. It is generally accepted that these patterns derive from a self-sustaining process of formation of Mach stems by colliding blast waves and blast waves from secondary local explosions initiated by these Mach stems. The reason for the very

F. Schultz-Grunow

1982-01-01

274

Numerical simulation of spinning detonation in square tube  

Microsoft Academic Search

A single spinning detonation wave propagating in a square tube is simulated three-dimensionally with the detailed chemical\\u000a reaction mechanism for hydrogen\\/air mixture proposed by Petersen and Hanson. The spinning detonation is composed of a transverse\\u000a detonation rotating around the wall normal to the tube axis, triple lines propagating partially out of phase, and a short\\u000a pressure trail. The formation of

Nobuyuki Tsuboi; Makoto Asahara; Keitaro Eto; A. Koichi Hayashi

2008-01-01

275

Study on Performance of Detonation-Driven Shock Tube  

Microsoft Academic Search

A detonation-driven shock tube firstly designed by H. R. Yu is considered to be a useful apparatus for producing high-enthalpy flow. In this apparatus, a strong shock wave is generated by detonating an oxygen-hydrogen mixture (oxy-hydrogen) and the driver gas temperature and pressure are extremely high compared with those of a conventional shock tube. However, the structure of the detonation

Akio Yamanaka; Yosuke Ariga; Tetsuro Obara; Pin Cai; Shigeharu Ohyagi

2002-01-01

276

Experimental studies of ignition and transition to detonation induced by the reflection and diffraction of shock waves  

Microsoft Academic Search

.   This paper presents results from a program of experimental studies of ignition induced by the interaction of an initially\\u000a planar shock wave with an obstacle in its path. With the aid of pressure measurements, spark schlieren photography and smoked\\u000a foil techniques it is shown how, given favourable initial conditions, the two-dimensional multiple shock reflection and diffraction\\u000a can promote ignition

C. J. Brown; G. O. Thomas

2000-01-01

277

Stability Affects of Artificial Viscosity in Detonation Modeling  

SciTech Connect

Accurate multi-dimensional modeling of detonation waves in solid HE materials is a difficult task. To treat applied problems which contain detonation waves one must consider reacting flow with a wide range of length-scales, non-linear equations of state (EOS), and material interfaces at which the detonation wave interacts with other materials. To be useful numerical models of detonation waves must be accurate, stable, and insensitive to details of the modeling such as the mesh spacing, and mesh aspect ratio for multi-dimensional simulations. Studies we have performed show that numerical simulations of detonation waves can be very sensitive to the form of the artificial viscosity term used. The artificial viscosity term is included in our ALE hydrocode to treat shock discontinuities. We show that a monotonic, second order artificial viscosity model derived from an approximate Riemann solver scheme can strongly damp unphysical oscillations in the detonation wave reaction zone, improving the detonation wave boundary wall interaction. These issues are demonstrated in 2D model simulations presented of the 'Bigplate' test. Results using LX-I 7 explosives are compared with numerical simulation results to demonstrate the affects of the artificial viscosity model.

Vitello, P; Souers, P C

2002-06-03

278

State parameter distribution of spherical detonation products  

SciTech Connect

The authors consider an expanding self-maintaining spherical detonation wave within a gas, determining the distribution of the state parameters of products produced by spherical detonation analytically. Until the detonation is completed, product motion is self-similar. Considering the products to be an ideal gas, equations are derived using the detonation velocity, speed of sound in the products, and velocity of the products themselves. An approximate solution to the resulting system is achieved using the method of asymptotic expansions. The approximate solution is compared to a numerical solution, showing a high degree of accuracy. For the solution obtained, the laws of conservation of mass and energy are satisfied to an accuracy of 1%. Using the solution, the energy distribution is calculated: the kinetic energy comprises 3% of the total energy, while the energy of the nonmoving core is 7% of the total.

Bystrov, S.A.; Gorev, V.A.

1983-05-01

279

Reaction zone structure in supracompressed detonating explosives  

SciTech Connect

Nanosecond time resolved particle velocity histories of supracompressed detonation waves in TNT-, TATB-, and HMX-based explosives are measured using a VISAR laser velocimeter and calculated using the ignition and growth reactive flow hydrodynamic computer code model. The Zeldovich-von Neumann-Doering (ZND) detonation wave structure is observed at pressures more than twice the self-sustaining detonation wave pressure. TNT and TATB exhibited a fast reaction which liberates approximately 80% of the total available exothermicity within 50 ns, followed by a slower reaction which lasts another 100--200 ns. These reaction rates are not strongly dependent on the initial shock pressure. The slower reaction is attributed to diffusion controlled solid carbon coagulation. The ignition and growth model using a ZND type model with a fast reaction preceding a slower reaction to the fully reacted product state accurately calculates the VISAR experimental data for TNT, LX-17, PBX 9404 and RX-26-AF. 21 refs., 15 figs., 3 tabs.

Green, L.G.; Tarver, C.M.; Erskine, D.J.

1989-08-18

280

A Simplified Analysis on a Pulse Detonation Engine Model  

NASA Astrophysics Data System (ADS)

The performance of pulse detonation engines was analytically estimated by using a simple model. A pulse detonation engine was modeled as a straight tube. One end of the tube was closed and the other was open, and a detonation wave was ignited at the closed end. One cycle of the pulse-detonation-engine operation was divided into three phases: combustion, exhaust, and filling phases. The combustion and exhaust phases were theoretically analyzed with some simplifications, using the Hugoniot relation for the Chapman-Jouguet detonation wave and flow relations for self-similar rarefaction waves. Based on the simplified theoretical analysis, useful formulas for impulse density per one-cycle operation and time-averaged thrust density were derived.

Endo, Takuma; Fujiwara, Toshi

281

Stability of Chapman Jouguet detonations for a stiffened-gas model of condensed-phase explosives  

NASA Astrophysics Data System (ADS)

The analysis of the linear stability of a planar Chapman Jouguet detonation wave is reformulated for an arbitrary caloric (incomplete) equation of state in an attempt to better represent the stability properties of detonations in condensed-phase explosives. Calculations are performed on a ‘stiffened-gas’ equation of state which allows us to prescribe a finite detonation Mach number while simultaneously allowing for a detonation shock pressure that is substantially larger than the ambient pressure. We show that the effect of increasing the ambient sound speed in the material, for a given detonation speed, has a stabilizing effect on the detonation. We also show that the presence of the slow reaction stage, a feature of detonations in certain types of energetic materials, where the detonation structure is characterized by a fast reaction stage behind the detonation shock followed by a slow reaction stage, tends to have a destabilizing effect.

Short, Mark; Bdzil, John B.; Anguelova, Iana I.

2006-04-01

282

Detonation in An Aluminized Explosive and Its Modeling  

Microsoft Academic Search

Detonation properties of an aluminized explosive cannot be described by a simple theory, such as the Chapman-Jouguet theory, which assumes energy release to be instantaneous. Aluminum reacts very slowly, and, thus, the energy released from the aluminum reaction does not contribute much to the leading shock wave. As a result, detonation velocity and pressure of an aluminized explosive are much

J. Lee; J. H. Kuk; S.-Y. Song; K. Y. Choi

1997-01-01

283

Effect of Explosive Detonation Characteristics on Shaped Charge Performance.  

National Technical Information Service (NTIS)

The jet formation caused by the collapse of a shaped charge liner is dependent upon the pressure delivered to the liner wall by the detonating explosive. As a shaped charge liner is collapsed axisymmetrically to the charge axis by a detonation wave to for...

J. Simon

1974-01-01

284

Computation of a diverging Comp-B detonation  

SciTech Connect

The expansion which occurs in diverging detonations weakens the wave and yields pressures and densities below those occurring in planar geometry. We study the problem of a spherically expanding detonation of Comp-B. The effect of varying the order of reaction as well as the rate law parameters (using an Arrhenius burn model) is studied. 14 refs., 3 figs.

Bukiet, B.G.

1989-01-01

285

Detonation chemistry studies of energetic materials using laboratory scale samples  

Microsoft Academic Search

We describe an apparatus by which the detonation products of an explosive can be identified and whose relative concentrations can be determined quantitatively. These measurements can be made on products that have been formed in less than one microsecond after the passage of the detonation wave. The technique is based on the rapid quenching of chemical reactions by virtue of

N. C. Blais; N. R. Greiner; W. J. Fernandez

1989-01-01

286

Detonation front in homogeneous and heterogeneous high explosives  

NASA Astrophysics Data System (ADS)

The present report describes the results of experimental researches of detonation wave structure in homogeneous liquid HE: tetranitromethane (TNM), its mixtures with nitromethane and nitrobenzene (TNM/NM, TNM/NB) and plastified compositions based on HMX, RDX, PETN and TNT (heterogeneous HE). Researches were carried out using laser interferometry techniques with nanosecond time resolution. Neumann spike parameters were found for investigated HE. Two types of detonation wave profiles were found in the mixtures of liquid HE based on TNM/NB. Maximums for the registered particle velocity for these profiles differed essentially. Complex 3D-structure of detonation wave front was registered. .

Fedorov, A. V.; Zotov, E. V.; Krasovsky, G. B.; Menshikh, A. V.; Yagodin, N. B.

2000-04-01

287

Asymmetry and the Nucleosynthetic Signature of Nearly Edge-lit Detonation in White Dwarf Cores  

Microsoft Academic Search

Most of the leading explosion scenarios for Type Ia supernovae involve the nuclear incineration of a white dwarf star through a detonation wave. Several scenarios have been proposed as to how this detonation may actually occur, but the exact mechanism and environment in which it takes place remain unknown. We explore the effects of an off-center initiated detonation on the

David A. Chamulak; Casey A. Meakin; Ivo R. Seitenzahl; James W. Truran

2012-01-01

288

Dynamics of the formation of the condensed phase particles at detonation of high explosives  

Microsoft Academic Search

The article presents the results of the experimental study SAXS on condensed carbon particles that appear at the detonation of a high explosive. It was shown that the SAXS signal rises for 1.5–4?s after the detonation front passing. The SAXS signal in trotyl and its alloys with hexogen starts just after the compression of the material in the detonation wave.

O. V. Evdokov; M. G. Fedotov; G. N. Kulipanov; L. A. Luckjanchikov; N. Z. Lyakhov; S. I. Mishnev; M. R. Sharafutdinov; M. A. Sheromov; K. A. Ten; V. M. Titov; B. P. Tolochko; P. I. Zubkov

2001-01-01

289

Detonation duct gas generator demonstration program  

NASA Technical Reports Server (NTRS)

The feasibility of the generation of detonation waves moving periodically across high speed channel flow is experimentally demonstrated. Such waves are essential to the concept of compressing requirements and increasing the engine pressure compressor with the objective of reducing conventional compressor requirements and increasing the engine thermodynamic efficiency through isochoric energy addition. By generating transient transverse waves, rather than standing waves, shock wave losses are reduced by an order of magnitude. The ultimate objective is to use such detonation ducts downstream of a low pressure gas turbine compressor to produce a high overall pressure ratio thermodynamic cycle. A 4 foot long, 1 inch x 12 inch cross-section, detonation duct was operated in a blow-down mode using compressed air reservoirs. Liquid or vapor propane was injected through injectors or solenoid valves located in the plenum or the duct itself. Detonation waves were generated when the mixture was ignited by a row of spark plugs in the duct wall. Problems with fuel injection and mixing limited the air speeds to about Mach 0.5, frequencies to below 10 Hz, and measured pressure ratios of about 5 to 6. The feasibility of the gas dynamic compression was demonstrated and the critical problem areas were identified.

Wortman, Andrew; Brinlee, Gayl A.; Othmer, Peter; Whelan, Michael A.

1991-01-01

290

Over-Driven Detonation Phenomenon in High Explosive  

NASA Astrophysics Data System (ADS)

The overdriven detonation is referred to such detonation phenomenon in which the main detonation parameters such as detonation pressure, velocity and particle velocity of detonation products immediately behind the detonation front exceeds the corresponding Chapman-Jouguet (C-J) values. Theoretically speaking, this detonation state can be realized by the impingement of high flying object. This paper presents our initial survey on the confirmation of the occurrence of overdriven detonation in high explosive. The PBX is used for driven explosive to accelerate the metal plate as the impactor. The target explosive studied is the so-called SEP, simplified from the term of the \\x81esafety explosive\\x81f, with the composition of PETN wt.65paraffin 35 wt.explosive, it makes us to obtain different impinging velocities. The propagation of the detonation wave under these impinging velocities is recorded by the streak camera. It is found out that the detonation velocity not only at the vicinity of impacting end but also at the later range has a long increase stage until decreasing to the normal C-J value.

Liu, Zhi-Yue; Nagano, Shiro; Itoh, Shigeru

1999-06-01

291

Detonation Phenomena of PBX Microsamples  

NASA Astrophysics Data System (ADS)

Detonation study of PBX micro-samples, based in HMX with an inert (HTPB, epoxy) or energetic (GAP) binder was performed on the meso-scale level, using the multifiber optical probes of 50 mum of maximum resolution, connected directly to a fast electronic streak camera with 0.6 ns resolution. The direct 2D observation of particle to particle successive transition of transmitted shock wave, through the binder, allows to analyse and to discuss, not only the cooperative formation of a multihead detonation front (DF), in the collection of particles surrounded by binder, but also the synenergetic effect, behind the DF, by the appearing of dissipative structures drawing spatial and temporal DF oscillations.

Plaksin, I.; Campos, J.; Ribeiro, J.; Mendes, R.

2002-07-01

292

Numerical simulation of spinning detonation in square tube  

NASA Astrophysics Data System (ADS)

A single spinning detonation wave propagating in a square tube is simulated three-dimensionally with the detailed chemical reaction mechanism for hydrogen/air mixture proposed by Petersen and Hanson. The spinning detonation is composed of a transverse detonation rotating around the wall normal to the tube axis, triple lines propagating partially out of phase, and a short pressure trail. The formation of an unburned gas pocket behind the detonation front was not observed in the present simulations because the rotating transverse detonation completely consumed the unburned gas. The calculated profiles of instantaneous OH mass fraction have a keystone shape behind the detonation front. The numerical results for the pitch and track angle on the tube wall agree well with the experimental results.

Tsuboi, Nobuyuki; Asahara, Makoto; Eto, Keitaro; Hayashi, A. Koichi

2008-09-01

293

Detonation diffraction from an annular channel  

NASA Astrophysics Data System (ADS)

In this study, gaseous detonation diffraction from an annular channel was investigated with a streak camera and the critical pressure for transmission of the detonation wave was obtained. The annular channel was used to approximate an infinite slot resulting in cylindrically expanding detonation waves. Two mixtures, stoichiometric acetylene-oxygen and stoichiometric acetylene-oxygen with 70% Ar dilution, were tested in a 4.3 and 14.3 mm channel width ( W). The undiluted and diluted mixtures were found to have values of the critical channel width over the cell size around 3 and 12 respectively. Comparing these results to values of the critical diameter ( d c ), in which a spherical detonation occurs, a value of critical d c / W c near 2 is observed for the highly diluted mixture. This value corresponds to the geometrical factor of the curvature term between a spherical and cylindrical diverging wave. Hence, the result is in support of Lee's proposed mechanism [Lee in Dynamics of Exothermicity, pp. 321, Gordon and Breach, Amsterdam, 1996] for failure due to diffraction based on curvature in stable mixtures such as those highly argon diluted with very regular detonation cellular patterns.

Meredith, James; Ng, Hoi Dick; Lee, John H. S.

2010-12-01

294

Types and stability of detonation flows of aluminum particles in oxygen  

Microsoft Academic Search

The problem of detonation-wave structure is studied on the basis of a mathematical model for the detonation of aluminum particles in oxygen within the framework of a single-velocity two-temperature continuum. An analysis of flow types in the form of the Chapman-Jouguet strong-detonation and weak-detonation regimes is given. A chart of the mixture flow regimes in the plane of the Mach

A. V. Fedorov

1996-01-01

295

Shock Wave Initiation of Mixture Liquid Explosives  

NASA Astrophysics Data System (ADS)

We investigated initiation of liquid HE consisting of tetranitromethane (TNM) and nitrobenzene (NB). Smooth stable (when mass of NB<20%) and pulsing unstable detonation wave front was registered (20-50% NB). We registered shock wave, shock compressed explosive (SCE) detonation wave and normal detonation wave for unstable detonation front on different parts of the front. In case of normal and SCE detonation wave we registered parameters rise during 3-25 nsec until the start of chemical reaction. We consider it to be the induction period of thermal explosion inside detonation wave front.

Fedorov, A. V.; Mikhailov, A. L.; Nazarov, D. V.; Finyushin, S. A.; Men'shikh, A. V.; Davydov, V. A.

2006-07-01

296

Obturator and detonation experiments in the subdetonative ram accelerator  

NASA Astrophysics Data System (ADS)

An experimental investigation has been undertaken to improve understanding of the role of the obturator and detonations in the subdetonative ram accelerator starting process. Ram accelerator start experiments were conducted with various obturator geometries to determine the obturator dynamics and assess its effect on the outcome of a start attempt. The obturator rapidly decelerates upon entrance and then moves backwards. Reversal of direction occurs more rapidly after propellant ignition, for less massive obturators, and solid geometries. Perforated geometries and decreasing obturator mass are less conducive to igniting a given propellant, as evidenced by the flowfield and start attempt outcome data presented. Wave unstarts were observed to occur with and without detonations, indicating more than one mechanism responsible for this type of start failure. Piston-initiated detonation experiments were conducted by firing the obturators without the ram accelerator projectile. The piston experiments identified the detonation limits for a wide range of propellants, but were found to not always be indicative of the upper Mach number at which a ram accelerator can be successfully started. In some instances a successful start or wave fall-off would occur at Mach numbers above which a piston alone detonated the propellant. Thus, the projectile can play a mitigating role in detonation initiation and use of piston detonation limits to quantitatively define a detonation wave unstart limit was not realized.

Schultz, E.; Knowlen, C.; Bruckner, A. P.

297

Features of the Detonation of Explosive Aerosuspensions  

NASA Astrophysics Data System (ADS)

The detonation activity of aerosuspensions of particles of a secondary explosive (pentaerythritol tetranitrate) with a mean-volume density of 0.14-1.28 mg/cm3 at the initial pressure of the air in a shock tube of 0.01-0.3 MPa was considered. The dependence of the structure and the main parameters of the detonation wave in an explosive aerosuspension on the concentration of the explosive in it and the initial air pressure as well as the mechanism of propagation of this wave were investigated. The critical (lowest) mean-volume density of an explosive aerosuspension, at which its detonation is still possible, was determined experimentally for different initial air pressures.

Pinaev, A. V.

2014-03-01

298

Theory of Detonations. I. Irreversible Unimolecular Reaction  

Microsoft Academic Search

The composition, temperature, and pressure as functions of distance in a steady-state, plane gaseous detonation wave are studied. The effects of the coefficients of viscosity, diffusion, and thermal conductivity are included. The basic equations are set up for a gas in which the irreversible unimolecular reaction A?B takes place with the release of energy. The topological nature of the solutions

Joseph O. Hirschfelder; Charles F. Curtiss

1958-01-01

299

Generation of the Patterns in Gaseous Detonations.  

National Technical Information Service (NTIS)

The problem is the mode of formation of the first initial regular pattern and its spacing in a detonation front. It is generally accepted that these patterns are due to a selfsustaining process of formation of Mach stems by colliding blast waves by second...

F. Schultz-Grunow

1981-01-01

300

Reactive Molecular Dynamics of Detonating Petn  

Microsoft Academic Search

We investigate the initial chemical events sustaining a detonation in shock-compressed PETN resulting from intermolecular collisions behind the shock wave using first-principles reactive molecular dynamics. The reaction dynamics of bimolecular collisions was studied as a function of collision velocities and crystallographic orientations. For each orientation, threshold collision velocities of reaction, and products of decomposition were determined. The timescale of reaction

A. C. Landerville; I. I. Oleynik; C. T. White

2009-01-01

301

REACTIVE MOLECULAR DYNAMICS OF DETONATING PETN  

Microsoft Academic Search

We investigate the initial chemical events sustaining a detonation in shock-compressed PETN resulting from intermolecular collisions behind the shock wave using first-principles reactive molecular dynamics. The reaction dynamics of bimolecular collisions was studied as a function of collision velocities and crystallographic orientations. For each orientation, threshold collision velocities of reaction, and products of decomposition were determined. The timescale of reaction

A. C. Landerville; I. I. Oleynik; C. T. White

2009-01-01

302

Numerical simulation of detonation initiation in a contoured tube  

Microsoft Academic Search

The effect of the wall contours in an axisymmetric tube on the transition from the shock wave to the detonation wave is studied\\u000a numerically. Qualitative features and quantitative characteristics of the detonation initiation mechanism realized in a tube\\u000a with a parabolic segment of the wall contour and conical expansion are found. The calculated results are presented in the\\u000a form of

I. V. Semenov; P. S. Utkin; V. V. Markov

2009-01-01

303

The development of a sonic boom simulator with detonable gases  

NASA Technical Reports Server (NTRS)

A sonic boom pressure profile was simulated in the far-field by detonation of a methane-oxygen mixture contained in a slender, shaped Mylar envelope. Ideal N-waves were synthesized with peak overpressures from two to five psf and durations of 30 to 75 milliseconds. The detonation of the gas mixture was initiated by a single Primacord strand running the length of balloon. The N-wave producing balloon was synthesized as a composite structure, utilizing experimental pressure profiles obtained from the detonations of slender, axisymmetric balloons with elementary, non-cylindrical shapes.

Strugielski, R. T.; Fugelso, L. E.; Holmes, L. B.; Byrne, W. J.

1971-01-01

304

Mach reflection of gaseous detonations  

NASA Astrophysics Data System (ADS)

The phenomenon of Mach reflection in gaseous detonations was investigated experimentally and numerically using laser shadowgraphy and calculations based on extensions of theories of shock wave reflection. Three different reactive mixtures were used in the experiments: mix 1 was stoichiometric hydrogen and oxygen at 295 K and 20 kPa, mix 2 was a stoichiometric hydrogen and oxygen with 77.5% argon dilution, at 295 K and 20 kPa. Mix 3 consisted of stoichiometric acetylene and oxygen with 80% argon dilution, at 50 kPa and 295 K. Detonations in each mixture were imaged interacting with wedges, with the wedge angle, ?, ranging from 15 degrees to 50 degrees. Triple point trajectory angles, ?, were inferred from the shadowgraphs. ? was also obtained from soot foil records for wedge angles of 20, 25 and 30 degrees. Relationships between ? and ? were calculated, using 3-shock theory and Whitham's shock dynamics theory, both with and without energy release. Contours of the leading waves were obtained from the shadowgraphs to investigate the self-similarity assumption. It was found that the Mach reflections mostly exhibited self-similar behavior, with the exception of ? of 30o for mix 1, where the Mach reflection seems to be changing shape, within the field of observation. The calculated /chi-/theta relations did not agree with those from the experiments, except in the case of mix 2, where, the relation calculated assuming frozen chemistry was in good agreement with the experiments. These results are discussed with regard to, the presence of an intrinsic length scale in gaseous detonations and the behavior of the transverse waves.

Akbar, Raza

305

Exploding bridgewire detonator simulator  

NASA Technical Reports Server (NTRS)

Tests indicate that electric detonator simulators of the exploding bridgewire type will not fire as a result of the application of a direct current power of one watt for 5 minutes. The detonator also will not fire if the protective gap fails and the firing stimulus is inadvertently applied.

Sullivan, R. R.; Tarley, R. C.; Tarpley, R. C.

1969-01-01

306

Bidirectional slapper detonator  

DOEpatents

The disclosure is directed to a bidirectional slapper detonator. One embodiment utilizes a single bridge circuit to detonate a pair of opposing initiating pellets. A line generator embodiment uses a plurality of bridges in electrical series to generate opposing cylindrical wavefronts.

McCormick, Robert N. (Los Alamos, NM); Boyd, Melissa D. (Los Alamos, NM)

1984-01-01

307

Investigation of hypersonic flow of a detonable gas mixture ahead of a forward facing step  

NASA Astrophysics Data System (ADS)

The hypersonic flow of a detonable gas mixture, which includes the establishment of shock and detonation waves, over a forward facing step is investigated. The positions and shapes of the shock and detonation waves are calculated for a hydrogen-oxygen mixture for initial pressures of 1 atm to 50 atm and for hypersonic Mach numbers. The detonation wave is seen to approach the shock wave as the Mach number and/or initial pressure increase. It is found that these wave practically unite as the Mach number is increased beyond 10 and when the initial pressure is increased to above 10-20 atm. This shock-detonation wave is seen to become an oblique wave as it emerges from the face of the step into the flow above the step.

Tivanov, Genadi; Rom, Josef

1993-01-01

308

Experimental investigation of deflagration to detonation transition in hydrocarbon-air gaseous mixtures  

SciTech Connect

The paper presents the results of investigation of deflagration to detonation transition in gas mixtures with exothermic chemical reaction using the experimental method of nonintrusive diagnostics of the process. Schlieren photochronography in the optical sections in different places of the tube is performed using the laser as a source of light. Experimental results of visualization of the transition process in hydrocarbon-air gas mixtures show several different flow patterns: (1) The detonation wave originates in the flame zone. (2) The detonation wave originates between the flame zone and primary shock wave. (3) The secondary combustion zone originates between primary shock and the flame and causes the detonation. (4) Spontaneous flame occurs that leads to the combustion to detonation transition. The influence of the flame zone on the originating strong detonation wave is noticed.

Smirnov, N.N.; Tyurnikov, M.V. [Moscow State Univ. (Russian Federation). Dept. of Mechanics and Mathematics] [Moscow State Univ. (Russian Federation). Dept. of Mechanics and Mathematics

1995-03-01

309

Detonation propagation in a high loss configuration  

SciTech Connect

This work presents an experimental study of detonation wave propagation in tubes with inner diameters (ID) comparable to the mixture cell size. Propane-oxygen mixtures were used in two test section tubes with inner diameters of 1.27 mm and 6.35 mm. For both test sections, the initial pressure of stoichiometric mixtures was varied to determine the effect on detonation propagation. For the 6.35 mm tube, the equivalence ratio {phi} (where the mixture was {phi} C{sub 3}H{sub 8} + 50{sub 2}) was also varied. Detonations were found to propagate in mixtures with cell sizes as large as five times the diameter of the tube. However, under these conditions, significant losses were observed, resulting in wave propagation velocities as slow as 40% of the CJ velocity U{sub CJ}. A review of relevant literature is presented, followed by experimental details and data. Observed velocity deficits are predicted using models that account for boundary layer growth inside detonation waves.

Jackson, Scott I [Los Alamos National Laboratory; Shepherd, Joseph E [CALTECH

2009-01-01

310

The Cellular Structure of Carbon Detonations  

NASA Astrophysics Data System (ADS)

We compare two and three-dimensional simulations of the cellular structure of carbon detonations. The initial density of the carbon is taken to be 107 g cm-3. This value has been suggested as the density at which a deflagration to detonation transition may occur in Type Ia supernovae. An initial planar detonation front becomes unstable and develops a complex structure due to the generation of transverse waves. Differences in the amount of asymmetry between the 2D and 3D cases, as well as the relative sizes of individual cells will be discussed. This work was supported in part by the Department of Energy Grant No. B341495 to the Center for Astrophysical Thermonuclear Flashes at the University of Chicago under the ASCI Strategic Alliances Program.

Fryxell, B.; Timmes, F. X.; Zingale, M.; Dursi, L. J.; Ricker, P.; Olson, K.; Calder, A. C.; Tufo, H.; MacNeice, P.; Truran, J. W.; Rosner, R.

2000-05-01

311

Modified Multiprocess Model of Detonation  

NASA Astrophysics Data System (ADS)

New powerful teraflops computers require hydrocodes of new generation with material models of new generation, i.e., high precision models based on perfect physical description of shock wave processes. Presented here Modified Multiprocess model of detonation (MMP model) is certain step in this strategical project. It is model for classical explosive compositions of PBX type. The MMP model describes process of explosive decomposition as a sum of two parallel processes, namely, heterogeneous and homogeneous decompositions. The heterogeneous process, i.e., hot spot process (which dominates at low pressure P<200 kbar) is described by two-modes mechanism. It is a new developed mechanism. It consists from the low pressure mode (when switching from outward to inward birn topology occurs at decomposition fraction equals about 0.76) and from high pressure mode (when switching occurs at decomposition fraction equals about 0.1). The homogeneous process (which dominates at high pressure P>200 kbar) is described by the so-called frontal mechanism. This mechanism consists from two stages: (1) intra-frontal stage and (2) post-frontal stage. The first stage describes process of electron excitation of explosive molecules (i.e., HMX, RDX, TNT molecules) in shock wave front and fast break-up of excited molecules with creation of primary radicals. The MMP model takes into account effect of decreasing excitation energy under compression. At the second stage these radicals generate some set of consecutive-parallel reactions which produce final products. The developed MMP model was incorporated into the DYNA3D hydrocode and demonstrates high accuracy in simulation of detonation processes. In particular, it reproduces extraordinarily well experimental profiles of particle velocity for shock to detonation transition process. It is consequence of high physical level of the MMP model.

Klimenko, Vladimir

2001-06-01

312

Reignition of detonations by reflected shocks  

NASA Astrophysics Data System (ADS)

Numerical simulations are used to study the diffraction, decay, and reignition that occurs when a detonation propagates past an increase in cross-sectional area in a rectangular tube. The computations solve the time-dependent two-dimensional equations describing a reactive flow in an argon-diluted stoichiometric hydrogen-oxygen mixture at atmospheric pressure. Previous studies have shown that soon after transmission to a larger area, the reaction front decouples from the leading shock and forms a decaying blast wave (“bubble”) in the larger tube. Then, depending on the initial conditions, the detonation either continues to decay or is reignited as the bubble reflects off confining surfaces. For a strongly overdriven initiating detonation, reignition occurs through an interaction between the bubble and the original contact surface. For a more weakly driven system, reignition can occur in two ways: either in the slip line and Mach stem of the Mach reflection formed when the bubble reflects off the bottom surface of the tube, or by multiple shock interactions that occur when the reflected bubble overtakes the initial detonation front. The computations show the evolution and development of the cellular structure of the steady detonation front.

Jones, D. A.; Sichel, M.; Oran, E. S.

1995-06-01

313

Detonation Meso-Scale Tests for Energetic Materials  

NASA Astrophysics Data System (ADS)

The objective of the present study is to characterize, on the meso-scale level, the detonation behaviour of PBX based on HMX , based in the minimisation of the test samples of energetic materials up to 10 mg. The development of a non-intrusive, high resolution, optical metrology procedures, using multi-fibber strip, allows the testing of PBX micro-samples, formed by few crystals surrounded by binder, with the simultaneous registration of parameters as local detonation velocity and pressure, geometrical shape of detonation front and the structure of the shock-to-detonation transition zone. The enhanced information allows a better understanding of the processes of formation and propagation of detonation wave. This procedure can be applied to the study of new advanced energetic materials.

Plaksin, I.; Campos, J.; Ribeiro, J.; Mendes, R.; Gois, J.; Portugal, A.; Simoes, P.; Pedroso, L.

2002-07-01

314

Hypervelocity reactive dynamics in detonating PETN, RDX, and HMX energetic materials  

Microsoft Academic Search

Despite intensive experimental and theoretical efforts, the first chemical events that trigger the chemistry behind the shock wave front in detonating materials are still largely unknown. We investigate the chemical initiation of detonation in shock compressed PETN, RDX, and HMX which results from intermolecular collisions behind the shock wave using first-principles reactive molecular dynamics. The reaction dynamics of bimolecular collisions

Aaron Landerville; Ivan Oleynik; Carter White

2009-01-01

315

Computer modeling of detonators.  

National Technical Information Service (NTIS)

A mathematical model of detonators which describes the resistance of the exploding bridgewire or exploding foil initiator as a function of energy deposition will be described. This model includes many parameters that can be adjusted to obtain a close fit ...

C. M. Furnberg

1994-01-01

316

Pulse Detonation Engine Modeled.  

National Technical Information Service (NTIS)

Pulse Detonation Engine Technology is currently being investigated at Glenn for both airbreathing and rocket propulsion applications. The potential for both mechanical simplicity and high efficiency due to the inherent near-constant-volume combustion proc...

D. E. Paxson

2001-01-01

317

Detonation structures generated by multiple shocks on ram-accelerator projectiles  

SciTech Connect

The detailed detonation structure generated by multiple shocks on ram-accelerator projectiles is studied using highly resolved numerical simulations. The simulations show that the detonation structure on the projectile consists of the following basic elements: nonreactive shocks, induction regions, deflagration waves, and detonation waves. The shape and location of these basic elements strongly depends on the projectile Mach number. In some cases, the induction region and the related detonation wave are primarily associated with one single shock. In other cases, the induction region extends across several shocks and the detonation structure is much more complex. These simulations also confirm that the detonations on the projectile are stable in a wide range of flow conditions and, therefore, can be used to generate the high pressure needed for projectile propulsion.

Li, C.; Kailasanath, K.; Oran, E.S. [Naval Research Lab., Washington, DC (United States). Lab. for Computational Physics and Fluid Dynamics] [Naval Research Lab., Washington, DC (United States). Lab. for Computational Physics and Fluid Dynamics

1997-01-01

318

Phase detonated shock tube (PFST)  

SciTech Connect

The simple, cylindrically imploding and axially driven fast shock tube (FST) has been a basic component in the high velocity penetrator (HVP) program. It is a powerful device capable of delivering a directed and very high pressure output that has been successfully employed to drive hypervelocity projectiles. The FST is configured from a hollow, high-explosive (HE) cylinder, a low-density Styrofoam core, and a one-point initiator at one end. A Mach stem is formed in the core as the forward-propagating, HE detonation wave intersects the reflected radial wave. This simple FST has been found to be a powerful pressure multiplier. Up to 1-Mbar output pressure can be obtained from this device. Further increase in the output pressure can be achieved by increasing the HE detonation velocity. The FST has been fine tuned to drive a thin plate to very high velocity under an impulse per unit area of about 1 Mbar[mu]s/cm[sup 2]. A 1.5-mm-thick stainless steel disk has been accelerated intact to 0.8 cm/[mu]s under a loading pressure rate of several Mbar/[mu]s. By making the plate curvature slightly convex at the loading side the authors have successfully accelerated it to almost 1.0 cm/[mu]s. The incorporation of a barrel at the end of the FST has been found to be important as confinement of the propellant gas by the barrel tends to accelerate the projectile to higher velocity. The desire to accelerate the plate above 1.0 cm/[mu]s provided the impetus to develop a more advanced fast shock tube to deliver a much higher output pressure. This report describes the investigation of a relatively simple air-lens phase-detonation system (PFST) with fifty percent higher phase-detonation velocity and a modest 2 Mbar output. Code calculations have shown that this PFST acceleration of a plate to about 1.2 cm/[mu]s can be achieved. The performance of these PFSTs has been evaluated and the details are discussed.

Zerwekh, W.D.; Marsh, S.P.; Tan, Tai-Ho.

1993-01-01

319

Phase detonated shock tube (PFST)  

SciTech Connect

The simple, cylindrically imploding and axially driven fast shock tube (FST) has been a basic component in the high velocity penetrator (HVP) program. It is a powerful device capable of delivering a directed and very high pressure output that has been successfully employed to drive hypervelocity projectiles. The FST is configured from a hollow, high-explosive (HE) cylinder, a low-density Styrofoam core, and a one-point initiator at one end. A Mach stem is formed in the core as the forward-propagating, HE detonation wave intersects the reflected radial wave. This simple FST has been found to be a powerful pressure multiplier. Up to 1-Mbar output pressure can be obtained from this device. Further increase in the output pressure can be achieved by increasing the HE detonation velocity. The FST has been fine tuned to drive a thin plate to very high velocity under an impulse per unit area of about 1 Mbar{mu}s/cm{sup 2}. A 1.5-mm-thick stainless steel disk has been accelerated intact to 0.8 cm/{mu}s under a loading pressure rate of several Mbar/{mu}s. By making the plate curvature slightly convex at the loading side the authors have successfully accelerated it to almost 1.0 cm/{mu}s. The incorporation of a barrel at the end of the FST has been found to be important as confinement of the propellant gas by the barrel tends to accelerate the projectile to higher velocity. The desire to accelerate the plate above 1.0 cm/{mu}s provided the impetus to develop a more advanced fast shock tube to deliver a much higher output pressure. This report describes the investigation of a relatively simple air-lens phase-detonation system (PFST) with fifty percent higher phase-detonation velocity and a modest 2 Mbar output. Code calculations have shown that this PFST acceleration of a plate to about 1.2 cm/{mu}s can be achieved. The performance of these PFSTs has been evaluated and the details are discussed.

Zerwekh, W.D.; Marsh, S.P.; Tan, Tai-Ho

1993-07-01

320

Direct observation detonator operation  

NASA Astrophysics Data System (ADS)

The analysis of detonator-timing performance has involved the use of rotating-mirror cameras (RMC) used in the streak mode and high-speed film. Fiducial timing marks are applied to the film to provide temporal references. The use of a RMC for detonator analysis requires aligning the camera, performing an exposure test, capturing light from the detonation and then processing the film. This procedure can take up to an hour for two technicians. After the film is possessed another technician compares each light streak on the film with the fiducial timing marks also recorded on the film. Capturing light from a detonator and recording it directly to a digitizer can improve detonator-timing measurement in several ways. The digitized signals can then be directly analyzed with software. The direct recording method reduces the need for expensive rotating mirror cameras, film processing and subjective optical measurement comparison. Furthermore, an extensive support facility requiring several specialized technicians is reduced to a single technician in a modest laboratory. This technician is then capable of performing several tests an hour. Tests were preformed to measure light intensity at detonation. An optical method of capturing the light was designed using a remote microscope coupled to optical fiber to bring the light to an optical/electrical converter and a digitizer then records the signal. This system is presently used in parallel with a RMC. The results are compared for accuracy.

Hall, Charles R.

2001-11-01

321

Multiple-Cycle Simulation of a Pulse Detonation Engine Ejector  

NASA Technical Reports Server (NTRS)

This paper presents the results of a study involving single and multiple-cycle numerical simulations of various PDE-ejector configurations utilizing hydrogen-oxygen mixtures. The objective was to investigate the thrust, impulse and mass flow rate characteristics of these devices. The results indicate that ejector systems can utilize the energy stored in the strong shock wave exiting the detonation tube to augment the impulse obtained from the detonation tube alone. Impulse augmentation ratios of up to 1.9 were achieved. The axial location of the converging-diverging ejectors relative to the end of the detonation tube were shown to affect the performance of the system.

Yungster, S.; Perkins, H. D.

2002-01-01

322

Numerical analysis of a two-dimensional nonsteady detonations  

NASA Technical Reports Server (NTRS)

In the present work a system of two-dimensional nonsteady hydrodynamic and chemical kinetic equations was numerically integrated for an exothermic system. Assumed two-step reaction model simulates practically an oxyhydrogen mixture. The calculation starts from a plane Chapman-Jouguet detonation as an initial condition. Two-dimensional disturbances are generated by artificially placing nonuniformities ahead of the detonation front. Regardless of the difference of the given initial disturbances, a fixed number of triple shock waves were produced for a fixed combination of mixture model and geometry when the transition period was over. This shows that for a given detonation tube geometry any exothermic system has its own characteristic multidimensional structure. The obtained number of triple shock waves contained in the detonation front was in agreement with existing experimental observations under the same condition.

Taki, S.; Fujiwara, T.

1976-01-01

323

Recent developments with gaseous detonation drivers for a shock tunnel  

NASA Astrophysics Data System (ADS)

Early researches on the detonation driven shock tube are reviewed briefly. Calculation results demonstrated that an improvement in attenuation of incident shock wave generated by forward driver can be obtained, provided the diameter of the driver is larger than that of the driven section and an abrupt reduction of cross-section area is placed just beyond the diaphragm and were verified by the experiments. Inserting a cavity ring between the driver and the driven section can make the flow field parameters behind a detonation rather uniform. An additional backward-detonation driver was proposed to attach to primary forward-detonation driver. The Taylor wave in the primary driver can be eliminated completely, if the ratios of initial pressure in additional driver to that in primary driver exceed the threshold value (about 7 times).

Yu, H.-R.

324

The Incidental Effects of Gaps in Detonating PBX 9501  

NASA Astrophysics Data System (ADS)

The incidental effects of gaps in detonating explosives have been observed for many years, yet the root cause of peripheral damage due to these features has been a partial mystery. To evaluate such damage for PBX 9501, a test series has been performed that examines single and multiply-directed detonations both crossing and moving along gaps of varying widths, lengths, and angles relative to the detonation wave fronts. Damage is evaluated with steel witness plates and quantified through trench profiling, volume, and mass decrement measurements. In addition, streak camera traces are used to track detonation wave speeds along explosive material surfaces and across gaps. Such traces allow the quantification of timing delays due to gap reinitiation processes for both confined and unconfined explosives. For some reinitiation tests, a second detonation wave is directed to interfere at varying times with the post-gap run-up process of the first wave, thus allowing complex wave-wave interactions to be investigated in detail. With these cumulative observations, further insight into the mechanism of extrinsic damage due to gaps is gained.

Salyer, Terry; Hill, Larry

2007-06-01

325

Rapid detonation initiation by sparks in a short duct: a numerical study  

NASA Astrophysics Data System (ADS)

Rapid onset of detonation can efficiently increase the working frequency of a pulse detonation engine (PDE). In the present study, computations of detonation initiation in a duct are conducted to investigate the mechanisms of detonation initiation. The governing equations are the Euler equations and the chemical kinetic model consists of 19 elementary reactions and nine species. Different techniques of initiation have been studied for the purpose of accelerating detonation onset with a relatively weak ignition energy. It is found that detonation ignition induced by means of multiple sparks is applicable to auto-ignition for a PDE. The interaction among shock waves, flame fronts and the strip of pre-compressed fresh (unburned) mixture plays an important role in rapid onset of detonation.

Hu, Z. M.; Dou, H. S.; Khoo, B. C.

2010-06-01

326

Transition to detonation in a model problem  

SciTech Connect

It is shown, within the context of a model problem, how an initial low-Mach-number combustion wave develops into a detonation when subjected to an externally applied gasdynamic disturbance. Explicit criteria are given that the external disturbance must satisfy in order for transition to be achieved. The governing equations are the unsteady equations for an ideal reacting gas. The reaction is assumed to be fuel going into product plus heat. The reaction terms are modeled that appear in the energy and species equations by using an ignition temperature, flame-sheet model that is derived from Arrehnius kinetics in the limit of large activation energy. A small-amplitude theory is then used to take advantage of the standard techniques of linear and nonlinear acoustics by assuming that the heat released during combustion is small. A description of one of the essential criteria for transition follows. The initial disturbance applied to the reacting front is comprised of right-going and stationary progressive waves. Each wave, in isolation, produces a temperature, pressure field. For transition to detonation to occur it is necessary that the progressive wave, traveling in the direction of the ultimate detonation, produce a temperature that is equal to or greater than the ignition temperature. In particular, an example is given of a shock overtaking and accelerating an unsteady deflagration. In this case the criteria requires that the shock strength exceeds a critical value in order for transition to occur.

Stewart, D.S.

1985-01-01

327

Estimation of critical conditions for the detonation-to-deflagration transition  

Microsoft Academic Search

An estimate is proposed for the critical Mach number of the shock wave that can ensure the deflagration-to-detonation transition\\u000a (DDT): Mmin ? 0.56M0 for expanding waves and Mmin ? 0.33M0 for plane waves propagating in a constant-section straight tube (M0 is the Mach number of an ideal Chapman—Jouguet detonation wave). The condition M > Mmin ensures the DDT mode, whereas

A. A. Vasil’ev

2006-01-01

328

Studies on the thermal behaviour of detonating fuse and detonators  

Microsoft Academic Search

Investigations of the thermal stability of detonating fuse containing 10 g pentaerythrol tetranitrate (PETN) revealed that the cord burnt under unconfinement at 403 K. Under confinement in a steel pipe or copper tube there was a partial detonation at 403 K. In order to characterize the thermal stability of PETN and pyrotechnic composition used in fuse head of electric detonators

R. N. Gupta; B. Singh

1989-01-01

329

Detonation in Sub-Chandrasekhar Mass SN Ia  

NASA Astrophysics Data System (ADS)

A possible formation channel for type Ia supernovae involves a sub-Chandrasekhar mass carbon-oxygen white dwarf that has accumulated an outer layer of helium from a companion star. It is assumed that a thermonuclear runaway starts in a local region in the (turbulently convecting) helium shell, setting off a detonation which at first only affects the helium. While this helium detonation is not likely to cross the core/shell boundary and light the core directly, it induces compressional waves inside the core. These waves may converge and produce a hot spot that initiates a secondary detonation wave in the core. Only the incineration of the core produces the necessary amounts of the radioactive isotope nickel-56 which are needed for a type Ia SN. I have performed multi-dimensional simulations of this so-called double detonation scenario, showing that core detonation is induced even in circumstances which do not assume symmetries, as would arise if the helium is ignited at multiple points. However, the helium detonation is hard to set off in dwarfs with low-mass helium shells which yield the kind of spectra that are most typical for Ia's.

Moll, Rainer; Woosley, S. E.

2013-01-01

330

Analytical study of idealized two-dimensional cellular detonations  

NASA Astrophysics Data System (ADS)

In this study, the idealized two-dimensional detonation cells were decomposed into the primary units referred to as sub-cells. Based on the theory of oblique shock waves, an analytical formula was derived to describe the relation between the Mach number ratio through triple-shock collision and the geometric properties of the cell. By applying a modified blast wave theory, an analytical model was developed to predict the propagation of detonation waves along the cell. The calculated results show that detonation wave is, first, strengthened at the beginning of the cell after triple-shock collision, and then decays till reaching the cell end. The analytical results were compared with experimental data and previous numerical results; the agreement between them appears to be good, in general.

Hu, X. Y.; Zhang, D. L.; Jiang, Z. L.

331

On the theory of the propagation of detonation in gaseous systems  

NASA Technical Reports Server (NTRS)

The existing theory of detonation is critically examined. It is shown that the considerations with which the steady value of the velocity of detonation is chosen are not convincing. In connection with the problem of the process of the chemical reaction in a detonation wave, the objections raised against the conceptions of Le Chatelier and Vieille of the 19th century with regard to the ignition of the gas by the shock wave are refuted. On the basis of this concept, it is possible to give a rigorous foundation for the existing method of computing the detonation velocity. The distributions of the temperature, the pressure, and the velocity in the detonation wave front as the chemical reaction proceeds, are considered. On the assumption of the absence of losses, the pure compression of the gas in the shock wave at the start of the chemical reaction develops a temperature that is near the temperature of combustion of the given mixture at constant pressure.

Zeldovich, Y B

1950-01-01

332

Deflagration-to-detonation transition in isopropyl nitrate mist\\/air mixtures  

Microsoft Academic Search

The characteristics and stages of the deflagration-to-detonation transition (DDT) in isopropyl nitrate (IPN) mist\\/air mixtures\\u000a are studied and analyzed. A self-sustained detonation wave forms, as is observed from the existence of a transverse wave and\\u000a a spinning wave structure. The run-up distance of the DDT process and the pitch size of the self-sustained spinning detonation\\u000a wave in IPN\\/air mixtures are

Qingming Liu; Chuhua Bai; Wenxi Dai; Li Jiang

2011-01-01

333

Deflagration to detonation  

NASA Astrophysics Data System (ADS)

Thermonuclear explosions of Type Ia supernovae (SNIa) involve turbulent deflagrations, detonations, and possibly a deflagration-to-detonation transition. The physics of these processes is discussed. A phenomenological delayed detonation model of SNIa successfully explains many observational properties of SNIa including monochromatic light curves, spectra, brightness - decline and color - decline relations. Observed variations among SNIa are explained as a result of varying nickel mass synthesized in an explosion of a Chandrasekhar mass C/O white dwarf. Based on theoretical models of SNIa, the value of the Hubble constant H0 ~= 67 km s-1 Mpc-1 was determined without the use of secondary distance indicators. The cause for the nickel mass variations is still debated. It may be a variation of the initial C/O ratio in a supernova progenitor, rotation, or other effects.

Khokhlov, A. M.

334

Low voltage nonprimary explosive detonator  

Microsoft Academic Search

A low voltage, electrically actuated, nonprimary explosive detonator is disclosed wherein said detonation is achieved by means of an explosive train in which a deflagration-to-detonation transition is made to occur. The explosive train is confined within a cylindrical body and positioned adjacent to low voltage ignition means have electrical leads extending outwardly from the cylindrical confining body. Application of a

Robert H. Dinegar; John Kirkham

1982-01-01

335

DETONATION PRESSURE MEASUREMENTS ON PETN  

Microsoft Academic Search

PETN is widely recognized as an example of nearly ideal detonation performance. The chemical composition is such that little or no carbon is produced in the detonation products. The reaction zone width is less than currently detectable. (<1 ns) Observations on PETN have thus become a baseline for EOS model predictions. It has therefore become important to characterize the detonation

L G Green; E L Lee

2006-01-01

336

In-Situ Continuous Detonation Velocity Measurements Using Fiber-optic Bragg Grating Sensors  

SciTech Connect

In order to fully calibrate hydrocodes and dynamic chemistry burn models, initiation and detonation research requires continuous measurement of low order detonation velocities as the detonation runs up to full order detonation for a given density and initiation pressure pulse. A novel detector of detonation velocity is presented using a 125 micron diameter optical fiber with an integral chirped fiber Bragg grating as an intrinsic sensor. This fiber is embedded in the explosive under study and interrogated during detonation as the fiber Bragg grating scatters light back along the fiber to a photodiode, producing a return signal dependant on the convolution integral of the grating reflection bandpass, the ASE intensity profile and the photodetector response curve. Detonation velocity is measured as the decrease in reflected light exiting the fiber as the grating is consumed when the detonation reaction zone proceeds along the fiber sensor axis. This small fiber probe causes minimal perturbation to the detonation wave and can measure detonation velocities along path lengths tens of millimeters long. Experimental details of the associated equipment and preliminary data in the form of continuous detonation velocity records within nitromethane and PBX-9502 are presented.

Benterou, J; Udd, E; Wilkins, P; Roeske, F; Roos, E; Jackson, D

2007-07-25

337

Supporting Structure of the LSD Wave in an Energy Absorption Perspective  

NASA Astrophysics Data System (ADS)

In Repetitively Pulsed (RP) Laser Propulsion, laser energy irradiated to a vehicle is converted to blast wave enthalpy during the Laser Supported Detonation (LSD) regime. Based on the measured post-LSD electron number density profiles by two-wavelength Mach Zehnder interferometer in a line-focusing optics, electron temperature and absorption coefficient were estimated assuming Local Thermal Equilibrium. A 10J/pulse CO2 laser was used. As a result, laser absorption was found completed in the layer between the shock wave and the electron density peak. Although the LSD-termination timing was not clear from the shock-front/ionization-front separation in the shadowgraph images, there observed drastic changes in the absorption layer thickness from 0.2 mm to 0.5 mm and in the peak heating rate from 12-17×1013 kW/m3 to 5×1013 kW/m3 at the termination.

Fukui, Akihiro; Hatai, Keigo; Cho, Shinatora; Komurasaki, Kimiya; Arakawa, Yoshihiro

2008-04-01

338

The role of unsteadiness in direct initiation of gaseous detonations  

Microsoft Academic Search

An analytical model is presented for the direct initiation of gaseous detonations by a blast wave. For stable or weakly unstable mixtures, numerical simulations of the spher- ical direct initiation event and local analysis of the one-dimensional unsteady reaction zone structure identify a competition between heat release, wave front curvature and unsteadiness. The primary failure mechanism is found to be

A. ECKETT; JAMES J. Q UIRK; JOSEPH E. SHEPHERD

2000-01-01

339

Effects of Solid to Gas Conversion in Detonator Delay Elements  

Microsoft Academic Search

We investigate the passage of a deflagration wave down a porous delay element in a detonator where a small part of the pyrotechnic mixture is converted to gas A one dimensional model is formulated with the wave propagated by thermal conduction and with the reaction rate described by a single step kinetic equation. Numerical solutions are obtained and compared with

A. H. C. NORGROVE; A. F. JONES; J. A. KING-HELE

1991-01-01

340

Advances in detonation driving techniques for a shock tube\\/tunnel  

Microsoft Academic Search

Early works on the detonation driven shock tube are reviewed briefly. High initial pressure detonable mixture can be used\\u000a in backward-detonation driver when the buffer tube is attached to the end of the driver for eliminating the excessive reflected\\u000a peak pressure. Experimental data showed that an improvement on attenuation of the incident shock wave generated by the forward\\u000a driver can

H. R. Yu; H. Chen; W. Zhao

2006-01-01

341

Characterizing Detonator Output Using Dynamic Witness Plates  

NASA Astrophysics Data System (ADS)

A sub-microsecond, time-resolved micro-particle-image velocimetry (PIV) system is developed to investigate the output of explosive detonators. Detonator output is directed into a transparent solid that serves as a dynamic witness plate and instantaneous shock and material velocities are measured in a two-dimensional plane cutting through the shock wave as it propagates through the solid. For the case of unloaded initiators (e.g. exploding bridge wires, exploding foil initiators, etc.) the witness plate serves as a surrogate for the explosive material that would normally be detonated. The velocity-field measurements quantify the velocity of the shocked material and visualize the geometry of the shocked region. Furthermore, the time-evolution of the velocity-field can be measured at intervals as small as 10 ns using the PIV system. Current experimental results of unloaded exploding bridge wire output in polydimethylsiloxane (PDMS) witness plates demonstrate 20 MHz velocity-field sampling just 300 ns after initiation of the wire. Successful application of the PIV system to full-up explosive detonator output is also demonstrated.

Murphy, Michael; Adrian, Ronald

2009-06-01

342

RESPONSE OF ALUMINUM SPHERES IN SITU TO DETONATION  

SciTech Connect

Time sequence x-ray imaging was utilized to determine the response of aluminum spheres embedded in a detonating high-explosive cylinder. The size of these spheres ranged from 3/8-inch to 1/32-inch in diameter. These experiments directly observed the response of the spheres as a function of time after interaction with the detonation wave. As the spheres are entrained in the post-detonation flow field, they are accelerating and their velocity profile is complicated, but can be determined from the radiography. Using the aluminum spheres as tracers, radial velocities of order 1.6 mm/us and horizontal velocities of order 0.08 mm/us were measured at early times post detonation. In terms of response, these data show that the largest sphere deforms and fractures post detonation. The intermediate size spheres suffer negligible deformation, but appear to ablate post detonation. Post detonation, the smallest spheres either react, mechanically disintegrate, atomize as a liquid or some combination of these.

Molitoris, J D; Garza, R G; Tringe, J W; Batteux, J D; Wong, B M; Villafana, R J; Cracchiola, B A; Forbes, J W

2010-03-26

343

An experimental study of laser supported hydrogen plasmas  

NASA Technical Reports Server (NTRS)

The rudiments of a rocket thruster which receives its enthalpy from an energy source which is remotely beamed from a laser is described. An experimental study now partially complete is discussed which will eventually provide a detailed understanding of the physics for assessing the feasibility of using hydrogen plasmas for accepting and converting this energy to enthalpy. A plasma ignition scheme which uses a pulsed CO2 laser has been developed and the properties of the ignition spark documented, including breakdown intensities in hydrogen. A complete diagnostic system capable of determining plasma temperature and the plasma absorptivity for subsequent steady state absorption of a high power CO2 laser beam are developed and demonstrative use is discussed for the preliminary case study, a two atmosphere laser supported argon plasma.

Vanzandt, D. M.; Mccay, T. D.; Eskridge, R. H.

1984-01-01

344

High-speed photographic study on overdriven detonation of high explosive  

NASA Astrophysics Data System (ADS)

On the common circumstances the detonation of explosives has a steady propagation rate and can be satisfactorily explained by Chapman-Jouguet's theory on this phenomenon. Hence, this type of detonation is more frequently called the Chapman- Jouguet (C-J) detonation. The detonation properties such as pressure, density, and temperature, of the detonation products are often characterized as the C-J values of the explosive that represent the corresponding maximums of the variables in the detonation products. However, when an explosive is initiated in some special ways, for instance, high velocity impact of a flyer plate, a strong detonation with properties higher than C-J values will be induced in the explosive. This strong detonation is what we called the overdriven detonation of explosive. The use of overdriven detonation expects to provide much more work to the surrounding matter than does the common C-J detonation. In order to have a basic knowledge of this detonation phenomenon, we designate an experimental set- up for the purpose of acquiring the overdriven detonation in high explosive. The set-up uses a circular metal plate accelerated by a piece of cylinder explosive (donor) to impact another cylinder explosive (acceptor), inducing a detonation wave in the acceptor explosive. The donor explosive used is PBX (85%wt HMX and 15%wt binder) explosive cylinder that has the detonation velocity of 7.84 km/s and the detonation pressure of 25.24 GPa and the acceptor explosive cylinder is SEP (65%wt PETN and 35%wt paraffin) with the detonation velocity of 6.97 km/s and the detonation pressure of 15.9 GPa. The impactor is the copper disc with the same diameter of the donor explosive and 1 mm and 2 mm thicknesses respectively. The detonations occurred in the acceptor explosive from the impact of copper flyer were recorded by the high-speed camera (IMACON 790). The photographs make us possible to estimate the detonation velocities from the distance and time data on them. In addition, we also make a numerical visualization on this phenomenon using a 2-D Lagrangian hydrodynamic code. The calculation, to somewhat extent, reproduces the consequences of the current experimental results.

Liu, Zhi-Yue; Kubota, Shiro; Nagano, Shirou; Itoh, Shigeru

2001-04-01

345

New detonation concepts for propulsion and power generation  

NASA Astrophysics Data System (ADS)

A series of related analytical and experimental studies are focused on utilizing detonations for emerging propulsion and power generation devices. An understanding of the physical and thermodynamic processes for this unsteady thermodynamic cycle has taken over 100 years to develop. An overview of the thermodynamic processes and development history is provided. Thermodynamic cycle analysis of detonation-based systems has often been studied using surrogate models. A real gas model is used for a thermal efficiency prediction of a detonation wave based on the work and heat specified by process path diagrams and a control volume analysis. A combined first and second law analysis aids in understanding performance trends for different initial conditions. A cycle analysis model for an airbreathing, rotating detonation wave engine (RDE) is presented. The engine consists of a steady inlet system with an isolator which delivers air into an annular combustor. A detonation wave continuously rotates around the combustor with side relief as the flow expands towards the nozzle. Air and fuel enter the combustor when the rarefaction wave pressure behind the detonation front drops to the inlet supply pressure. To create a stable RDE, the inlet pressure is matched in a convergence process with the average combustor pressure by increasing the annulus channel width with respect to the isolator channel. Performance of this engine is considered using several parametric studies. RDEs require a fuel injection system that can cycle beyond the limits of mechanical valves. Fuel injectors composed of an orifice connected to a small plenum cavity were mounted on a detonation tube. These fuel injectors, termed fluidic valves, utilize their geometry and a supply pressure to deliver fuel and contain no moving parts. Their behavior is characterized in order to determine their feasibility for integration with high-frequency RDEs. Parametric studies have been conducted with the type of fuel injected, the orifice diameter, and the plenum cavity pressure. Results indicate that the detonation wave pressure temporarily interrupts the fluidic valve supply, but the wave products can be quickly expelled by the fresh fuel supply to allow for refueling. The interruption time of the valve scales with injection and detonation wave pressure ratios as well as a characteristic time. The feasibility of using a detonation wave as a source for producing power in conjunction with a linear generator is considered. Such a facility can be constructed by placing a piston--spring system at the end of a pulsed detonation engine (PDE). Once the detonation wave reflects off the piston, oscillations of the system drive the linear generator. An experimental facility was developed to explore the interaction of a gaseous detonation wave with the piston. Experimental results were then used to develop a model for the interaction. Governing equations for two engine designs are developed and trends are established to indicate a feasible design space for future development.

Braun, Eric M.

346

Minimum tube diameters for steady propagation of gaseous detonations  

NASA Astrophysics Data System (ADS)

Recent experimental results on detonation limits are reported in this paper. A parametric study was carried out to determine the minimum tube diameters for steady detonation propagation in five different hydrocarbon fuel-oxygen combustible mixtures and in five polycarbonate test tube diameters ranging from 50.8 mm down to a small scale of 1.5 mm. The wave propagation in the tube was monitored by optical fibers. By decreasing the initial pressure, hence the sensitivity of the mixture, the onset of limits is indicated by an abrupt drop in the steady detonation velocity after a short distance of travel. From the measured wave velocities inside the test tube, the critical pressure corresponding to the limit and the minimum tube diameters for the propagation of the detonation can be obtained. The present experimental results are in good agreement with previous studies and show that the measured minimum tube diameters can be reasonably estimated on the basis of the ? /3 rule over a wide range of conditions, where ? is the detonation cell size. These new data shall be useful for safety assessment in process industries and in developing and validating models for detonation limits.

Gao, Y.; Ng, H. D.; Lee, J. H. S.

2014-04-01

347

Detonation of gas jets  

SciTech Connect

The authors experimentally and mathematically assess the detonation processes occurring in acetylene, methane, acetaldehyde, ethane, propane, butane, hydrogen, oxygen and their mixtures toward the end of increasing worker safety and decreasing the possibility of explosion in the handling of these gases.

Vasil'ev, A.A.; Zak, D.V.

1987-01-01

348

Computer modeling of detonators  

Microsoft Academic Search

A mathematical model of detonators which describes the resistance of the exploding bridgewire or exploding foil initiator as a function of energy deposition will be described. This model includes many parameters that can be adjusted to obtain a close fit to experimental data. This has been demonstrated using recent experimental data taken within Sandia National Laboratories

C. M. Furnberg

1994-01-01

349

Numerical simulation of triple shock behavior of gaseous detonation  

SciTech Connect

A numerical analysis is performed on the nonsteady two-dimensional behavior of self-sustaining detonations. In order to produce realistic two-dimensional structures during propagation in a finite width channel, an initially assumed plane one-dimensional Chapman-Jouguet detonation was perturbed by locating up to five pairs of exothermicity spots in the passage of the detonation. The most interesting feature of the simulation was the number of triple shock waves existing after a certain time of transition from plane to periodically nonsteady two-dimensional structures. The final number of transverse shock waves becomes mostly two, which are nearly irrelevant to the assumed number of initial exothermicity spots. Details of the disappearance of several transverse waves during their rearrangement were clearly observed and are discussed. 13 refs.

Taki, S.; Fujiwara, T.

1981-01-01

350

Environmentally Benign Stab Detonators  

SciTech Connect

Many energetic systems can be activated via mechanical means. Percussion primers in small caliber ammunition and stab detonators used in medium caliber ammunition are just two examples. Current medium caliber (20-60mm) munitions are detonated through the use of impact sensitive stab detonators. Stab detonators are very sensitive and must be small, as to meet weight and size limitations. A mix of energetic powders, sensitive to mechanical stimulus, is typically used to ignite such devices. Stab detonators are mechanically activated by forcing a firing pin through the closure disc of the device and into the stab initiating mix. Rapid heating caused by mechanically driven compression and friction of the mixture results in its ignition. The rapid decomposition of these materials generates a pressure/temperature pulse that is sufficient to initiate a transfer charge, which has enough output energy to detonate the main charge. This general type of ignition mix is used in a large variety of primers, igniters, and detonators.[1] Common primer mixes, such as NOL-130, are made up of lead styphnate (basic) 40%, lead azide (dextrinated) 20%, barium nitrate 20%, antimony sulfide 15%, and tetrazene 5%.[1] These materials pose acute and chronic toxicity hazards during mixing of the composition and later in the item life cycle after the item has been field functioned. There is an established need to replace these mixes on toxicity, health, and environmental hazard grounds. This effort attempts to demonstrate that environmentally acceptable energetic solgel coated flash metal multilayer nanocomposites can be used to replace current impact initiated devices (IIDs), which have hazardous and toxic components. Successful completion of this project will result in IIDs that include innocuous compounds, have sufficient output energy for initiation, meet current military specifications, are small, cost competitive, and perform as well as or better than current devices. We expect flash metal multilayer and sol-gel to be generic technologies applicable to a wide range of devices, especially in small caliber ammunition and sub-munitions. We will replace the NOL-130 mixture with a nanocomposite that consists of a mechanically robust energetic multilayer foil that has been coated with a sol-gel energetic material. The exothermic reactions are activated in this nanocomposite are the transformation of the multilayer material to its respective intermetallic alloy and the thermite reaction, which is characterized by very high temperatures, a small pressure pulse, and hot particle ejection. The proposed materials and their reaction products consist of, but are not limited to aluminum, nickel, iron, aluminum oxide, titanium, iron oxide and boron. These materials have much more desirable environmental and health characteristics than the NOL-130 composition.

Gash, A

2005-12-21

351

The role of instability in gaseous detonation  

NASA Astrophysics Data System (ADS)

In detonation, the coupling between fluid dynamics and chemical energy release is critical. The reaction rate behind the shock front is extremely sensitive to temperature perturbations and, as a result, detonation waves in gases are always unstable. A broad spectrum of behavior has been reported for which no comprehensive theory has been developed. The problem is extremely challenging due to the nonlinearity of the chemistry-fluid mechanics coupling and extraordinary range of length and time scales exhibited in these flows. Past work has shown that the strength of the leading shock front oscillates and secondary shock waves propagate transversely to the main front. A key unresolved issue has emerged from the past 50 years of research on this problem: What is the precise nature of the flow within the reaction zone and how do the instabilities of the shock front influence the combustion mechanism?This issue has been examined through dynamic experimentation in two facilities. Key diagnostic tools include unique visualizations of superimposed shock and reaction fronts, as well as short but informative high-speed movies. We study a range of fuel-oxidizer systems, including hydrocarbons, and broadly categorize these mixtures by considering the hydrodynamic stability of the reaction zone. From these observations and calculations, we show that transverse shock waves do not essentially alter the classic detonation structure of Zeldovich-von Neumann-Doring (ZND) in weakly unstable detonations, there is one length scale in the instability, and the combustion mechanism is simply shock-induced chemical-thermal explosion behind a piecewise-smooth leading shock front. In contrast, we observe that highly unstable detonations have substantially different behavior involving large excursions in the lead shock strength, a rough leading shock front, and localized explosions within the reaction zone. The critical decay rate model of Eckett et al. (JFM 2000) is combined with experimental observations to show that one essential difference in highly unstable waves is that the shock and reaction front may decouple locally. It is not clear how the ZND model can be effectively applied in highly unstable waves. There is a spectrum of length scales and it may be possible that a type of "turbulent" combustion occurs. We consider how the coupling between chemistry and fluid dynamics can produce a large range of length scales and how possible combustion regimes within the front may be bounded.

Austin, Joanna Maria

352

A Hydrodynamic Theory for the Interaction of a Gaseous Detonation with a Compressible Boundary.  

National Technical Information Service (NTIS)

Detonations through an explosive of finite width are curved and propagate at a lower velocity than an ideal one-dimensional plane wave. A theory relating the velocity decrement and curvature of a gaseous detonation to the conditions at the explosive inert...

M. Sichel

1965-01-01

353

A Hydrodynamic Theory for the Propagation of Gaseous Detonations Through Charges of Finite Width.  

National Technical Information Service (NTIS)

Detonations through an explosive of finite width are curved and propagate at a lower velocity than an ideal one-dimensional plane wave. A theory relating the velocity decrement and curvature of a gaseous detonation to the conditions at the explosive inert...

M. Sichel

1965-01-01

354

Propagation of Two-Dimensional Nonsteady Detonation in a Channel with Backward-Facing Step.  

National Technical Information Service (NTIS)

Re-establishment or quenching of a detonation at a corner is conceivably caused by the interaction of numerous triple shock waves contained in the frontal structure of the detonation; a combined effect of Prandtl-Meyer expansion and the disappearance of c...

T. Sugimura S. Taki T. Fujiwara

1981-01-01

355

Dynamically adaptive simulation of regular detonation structures using the Cartesian mesh renemen t framework AMROC  

Microsoft Academic Search

Numerical simulations can be the key to the thorough understanding of the multi-dimensional nature of transient detonation waves. But the accurate approxima- tion of realistic detonations is extremely demanding, because a wide range of dieren t scales needs to be resolved. This paper describes an entire solution strategy that is based on a generic implementation of a dynamically adaptive mesh

Ralf Deiterding

356

The mach reflection of a detonation based on soot track measurements  

Microsoft Academic Search

This paper presents a series of soot tracks formed by gaseous detonation waves diffracting around wedges with different wedge angles. These cellular structure patterns describe the Mach-reflection processes of a detonation and reveal some unique characteristics. They can be used to analyze the relationship between the trajectory angle of the triple point, wedge angle, and initial pressure in Mach reflection.

Guo Changming; Zhang Deliang; Xie Wei

2001-01-01

357

Physical–chemical model of processes at detonation synthesis of nanodiamonds  

Microsoft Academic Search

This article presents a principally new physical–chemical model of nanodiamond formation at explosion, which describes adequately all the existing experimental data on detonation synthesis of diamonds. According to this model, the detonation wave performs activation rapidly; then the reaction mixture composition keeps varying. In the diagram C – H – O this process results in continual motion of the point

B. P. Tolochko; V. M. Titov; A. P. Chernyshev; K. A. Ten; E. R. Pruuel; I. L. Zhogin; P. I. Zubkov; N. Z. Lyakhov; L. A. Lukyanchikov; M. A. Sheromov

2007-01-01

358

Application of a Schlieren diagnostic to the behavior of exploding bridge wire and laser detonators  

SciTech Connect

Even though the exploding bridge wire (EBW) detonator has been in use for over 60 years, there are still discussions about the mechanism for achieving detonation. Los Alamos has been developing a high-power laser detonator to function in a manner similar to an EBW. Schlieren imaging techniques are applied to laser-driven detonator output in polydimethylsiloxane (POMS) samples to investigate the time-dependent geometry of the shock wave and to obtain instantaneous measurements of shock-front velocity. Velocity Hugoniot data are used to convert measured shock velocities to corresponding particle velocities, allowing instantaneous shock pressures to be obtained via Rankine-Hugoniot relations across the shock.

Murphy, Michael J [Los Alamos National Laboratory; Clarke, Steven A [Los Alamos National Laboratory; Munger, Alan C [Los Alamos National Laboratory; Thomas, Keith A [Los Alamos National Laboratory

2009-01-01

359

Dynamics of the formation of the condensed phase particles at detonation of high explosives  

NASA Astrophysics Data System (ADS)

The article presents the results of the experimental study SAXS on condensed carbon particles that appear at the detonation of a high explosive. It was shown that the SAXS signal rises for 1.5-4 ?s after the detonation front passing. The SAXS signal in trotyl and its alloys with hexogen starts just after the compression of the material in the detonation wave. In octogen, hexogen and PETN, the SAXS signal appears in 0.5 ?s and is much smaller than the signal at the detonation of trotyl and its alloys with hexogen.

Evdokov, O. V.; Fedotov, M. G.; Kulipanov, G. N.; Luckjanchikov, L. A.; Lyakhov, N. Z.; Mishnev, S. I.; Sharafutdinov, M. R.; Sheromov, M. A.; Ten, K. A.; Titov, V. M.; Tolochko, B. P.; Zubkov, P. I.

2001-09-01

360

The Use of Steady and Pulsed Detonations for Propulsion Systems  

NASA Technical Reports Server (NTRS)

Objectives of the ODWE concept studies are: demonstrate the feasibility of the oblique detonation wave engine (ODWE) for hypersonic propulsion; demonstrate the existance and stability of an oblique detonation wave in hypersonic wind tunnels; develop engineering codes which predict the performance characteristics of the ODWE including specific impulse and thrust coefficients for various operating conditions; develop multi-dimensional computer codes which can model all aspects of the ODWE including fuel injection, mixing, ignition, combustion and expansion with fully detailed chemical kinetics and turbulence models; and validate the codes with experimental data use the simulations to predict the ODWE performance for conditions not easily obtained in wind tunnels.

Adelman, Henry G.; Menees, Gene P.; Cambier, Jean-Luc; Bowles, Jeffrey V.

1996-01-01

361

Analytical Estimation of Performance Parameters of an Ideal Pulse Detonation Engine  

NASA Astrophysics Data System (ADS)

The cycle of an ideal pulse detonation engine (PDE) was theoretically analyzed. A PDE was modeled as a straight tube, one end of which was closed and the other end open. A detonation wave was ignited at the closed end and simultaneously started to propagate toward the open end. When the detonation wave broke out from the open end, a rarefaction wave started to propagate from the open end toward the closed end. We analytically obtained a functional form of the thrust-density history, showing a plateau followed by decay. Using the obtained history of the thrust density, we formulated some PDE performance parameters such as impulse density per cycle.

Endo, Takuma; Fujiwara, Toshi

362

Using Schlieren Visualization to Track Detonator Performance  

Microsoft Academic Search

Several experiments that are part of a phased plan to understand the evolution of detonation in a detonator from initiation shock through run to detonation to full detonation to transition to booster and booster detonation will be presented. High Speed Laser Schlieren Movies have been used to study several explosive initiation events, such as exploding bridgewires (EBW), Exploding Foil Initiators

Steven Clarke; Keith Thomas; Michael Martinez; Adrian Akinci; Michael Murphy; Ronald Adrian

2007-01-01

363

Using Schlieren Visualization to Track Detonator Performance  

Microsoft Academic Search

Several experiments will be presented that are part of a phased plan to understand the evolution of detonation in a detonator from initiation shock through run to detonation, to full detonation, to transition, to booster and booster detonation. High-speed multiframe schlieren imagery has been used to study several explosive initiation events, such as exploding bridgewires (EBWs), exploding foil initiators (EFIs

S. A. Clarke; C. A. Bolme; M. J. Murphy; C. D. Landon; T. A. Mason; R. J. Adrian; A. A. Akinci; M. E. Martinez; K. A. Thomas

2007-01-01

364

USING SCHLIEREN VISUALIZATION TO TRACK DETONATOR PERFORMANCE  

Microsoft Academic Search

Several experiments will be presented that are part of a phased plan to understand the evolution of detonation in a detonator from initiation shock through run to detonation, to full detonation, to transition, to booster and booster detonation. High-speed multiframe schlieren imagery has been used to study several explosive initiation events, such as exploding bridgewires (EBWs), exploding foil initiators (EFIs

S. A. Clarke; C. A. Bolme; M. J. Murphy; C. D. Landon; T. A. Mason; R. J. Adrian; A. A. Akinci; M. E. Martinez; K. A. Thomas

2007-01-01

365

Numerical study on three-dimensional flow field of continuously rotating detonation in a toroidal chamber  

NASA Astrophysics Data System (ADS)

Gaseous detonation propagating in a toroidal chamber was numerically studied for hydrogen/oxygen/nitrogen mixtures. The numerical method used is based on the three-dimensional Euler equations with detailed finiterate chemistry. The results show that the calculated streak picture is in qualitative agreement with the picture recorded by a high speed streak camera from published literature. The three-dimensional flow field induced by a continuously rotating detonation was visualized and distinctive features of the rotating detonations were clearly depicted. Owing to the unconfined character of detonation wavelet, a deficit of detonation parameters was observed. Due to the effects of wall geometries, the strength of the outside detonation front is stronger than that of the inside portion. The detonation thus propagates with a constant circular velocity. Numerical simulation also shows three-dimensional rotating detonation structures, which display specific feature of the detonationshock combined wave. Discrete burning gas pockets are formed due to instability of the discontinuity. It is believed that the present study could give an insight into the interesting properties of the continuously rotating detonation, and is thus beneficial to the design of continuous detonation propulsion systems.

Zhang, Xu-Dong; Fan, Bao-Chun; Gui, Ming-Yue; Pan, Zhen-Hua; Dong, Gang

2012-02-01

366

Precursors in detonations in porous explosives  

SciTech Connect

Photographs of detonation waves in low-density HMX and PETN, made with an image-intensifier camera, show a brilliant band of light in front of the pressure jump. The radiation temperature is estimated to be 12,000 to 14,000/sup 0/K. The spectrum of this light is continuous. A quartz gauge shows a gradual buildup of pressure from the material producing the light. The material has little effect on the propagation of detonation. Further observations, using pellets of plastic-bonded HMX and single crystals of PETN, show that the material thrown off the free surface is transparent, with a leading edge moving at approximately 20 mm/..mu..s. Collision of this material with polymethyl methacrylate (PMMA) produces a brilliant light with a spectrum that is initially a narrow H/sub ..cap alpha../ line. Quartz gauges measure the rate of pessure buildup of this material.

Spaulding, R.L. Jr.

1981-01-01

367

Homogeneous Mechanisms for Detonation of Heterogeneous HE  

NASA Astrophysics Data System (ADS)

To prepare a precise numerical model of detonation it is necessary to take into account all mechanisms of the detonation process. Hot spot mechanism is a conventional one, but there are classical experiments, which indicate that at high pressure the decomposition is homogeneous in nature. Recent experiments also show that the width of the chemical spike depends greatly on the porosity of the HE. The analysis of these results leads to the conclusion that explosive decomposition is different for low (<0.05) and high (>0.05) porosities. Two-dimensional numerical simulations of shock wave propagation in porous HMX were carried out, which showed that at low porosity the fast frontal mechanism dominates in explosive decomposition. At high porosity a standard thermal decomposition takes place.

Klimenko, Vladimir Yu.

2004-07-01

368

Initial hydrogen detonation data from the High-Temperature Combustion Facility  

SciTech Connect

The Brookhaven National Laboratory High-Temperature Combustion Facility (HTCF) is described and data from initial hydrogen detonation experiments are presented. Initial phase of the inherent detonability experimental program is described. Test gases thus far tested are hydrogen-air mixtures at one atmosphere initial pressure and temperatures 300K-650K. Detonation pressure, wave speed, and detonation cell size were measured. Data were consistent with earlier SSDA (small-scale development apparatus) test results. HTCF results confirm the conclusion from the SSDA program that the gas temperature decreases the cell size and, therefore, increases the sensitivity of mixtures to detonation. Data from the larger HTCF test vessel, however, also demonstrates that the effect of increased scale is to extend the range of detonable mixtures to lower concentration.

Ginsberg, T.; Ciccarelli, G.; Boccio, J. [and others

1994-12-31

369

Detonation Shock Dynamics for Porous Explosives and Energetic Materials  

NASA Astrophysics Data System (ADS)

An explosive powder subjected to mechanical or thermal loading undergoes microstructural changes that cause the density to increase and the material to be compacted. The energy that drives compaction is absorbed by the material as the microstructure changes and the specific internal energy of the solid-void mixture increases due to the increase in density as voids become occupied by solids. These changes affect the reactive properties of the material and the mechanics and dynamics of detonation waves in explosive powders. The effects of explosive powder compaction on detonation wave dynamics have not been well characterized. Here we use the theory of Detonation Shock Dynamics (DSD) to analyze the effects of compaction on the dynamics and geometry of detonation waves in explosive powders. We apply DSD theory using a simplified equation of state (EOS) that has been shown to represent the effects of compaction that lead to deflagration to detonation transition in explosive powders. We will show results from the numerical solution of the DSD theory equations as well as from asymptotic DSD theory.

Saenz, Juan; Stewart, D. Scott

2009-06-01

370

Detonation Shock Dynamics for Porous Explosives and Energetic Materials  

NASA Astrophysics Data System (ADS)

An explosive powder subjected to mechanical or thermal loading undergoes micro structural changes that cause the density to increase and the material to be compacted. The energy that drives compaction is absorbed by the material as the microstructure changes and the specific internal energy of the solid-void mixture increases due to the increase in density as voids become occupied by solids. These changes affect the reactive properties of the material and the mechanics and dynamics of detonation waves in explosive powders. The effects of explosive powder compaction on detonation wave dynamics have not been well characterized. Here we use the theory of Detonation Shock Dynamics (DSD) to analyze the effects of compaction on the dynamics and geometry of detonation waves in explosive powders. We apply DSD theory using a simplified equation of state (EOS) that has been shown to represent the effects of compaction that lead to deflagration to detonation transition in explosive powders. We will show results from the numerical solution of the DSD theory equations as well as from asymptotic DSD theory.

Saenz, Juan A.; Stewart, D. Scott

2009-12-01

371

Experimental Study on DDT Characteristics in Spiral Configuration Pulse Detonation Engines  

NASA Astrophysics Data System (ADS)

This work investigated features of the deflagration to detonation transition in a curved tube. A number of experiments were performed to acquire the transition rule of DDT, which would provide the design data and theoretical basis for the curved detonation chamber. The content of research is as follows: (1) Flow resistance experiments of nine detonation chambers have been explored. The results show that the spiral configuration can reduce the axial length of DC, and the total pressure recovery coefficient increases with the spiral pitch. (2) Single-cycle detonation experiments have been conducted using the 9 tubes in the resistance experiments. Liquid-gasoline/air is used as the detonative mixture in all the experiments. The detonation experimental results indicate that there is no detonation wave formed in the straight tube, but in all the selected spiral tubes fully-developed detonation waves have been obtained; compared to the straight tube case, the DDT time decrease with the decreasing of the radius of curvature (RC) by 6.2%˜19.8% in the spiral detonation tubes.

Wang, Wei; Qiu, Hua; Fan, Wei; Xiong, Cha

2013-09-01

372

Miniature plasma accelerating detonator and method of detonating insensitive materials  

DOEpatents

The invention is a detonator for use with high explosives. The detonator comprises a pair of parallel rail electrodes connected to a power supply. By shorting the electrodes at one end, a plasma is generated and accelerated toward the other end to impact against explosives. A projectile can be arranged between the rails to be accelerated by the plasma. An alternative arrangement is to a coaxial electrode construction. The invention also relates to a method of detonating explosives. 3 figs.

Bickes, R.W. Jr.; Kopczewski, M.R.; Schwarz, A.C.

1985-01-04

373

Miniature plasma accelerating detonator and method of detonating insensitive materials  

DOEpatents

The invention is a detonator for use with high explosives. The detonator comprises a pair of parallel rail electrodes connected to a power supply. By shorting the electrodes at one end, a plasma is generated and accelerated toward the other end to impact against explosives. A projectile can be arranged between the rails to be accelerated by the plasma. An alternative arrangement is to a coaxial electrode construction. The invention also relates to a method of detonating explosives.

Bickes, Jr., Robert W. (Albuquerque, NM); Kopczewski, Michael R. (Albuquerque, NM); Schwarz, Alfred C. (Albuquerque, NM)

1986-01-01

374

Synchro-ballistic recording of detonation phenomena  

NASA Astrophysics Data System (ADS)

Synchro-ballistic use of rotating-mirror streak cameras allows for detailed recording of high-speed events of known velocity and direction. After an introduction to the synchro-ballistic technique, this paper details two diverse applications of the technique as applied in the field of high-explosives research. In the first series of experiments detonation-front shape is recorded as the arriving detonation shock wave tilts an obliquely mounted mirror, causing reflected light to be deflected from the imaging lens. These tests were conducted for the purpose of calibrating and confirming the asymptotic detonation shock dynamics (DSD) theory of Bdzil and Stewart. The phase velocities of the events range from ten to thirty millimeters per microsecond. Optical magnification is set for optimal use of the film's spatial dimension and the phase velocity is adjusted to provide synchronization at the camera's maximum writing speed. Initial calibration of the technique is undertaken using a cylindrical HE geometry over a range of charge diameters and of sufficient length-to- diameter ratio to insure a stable detonation wave. The final experiment utilizes an arc-shaped explosive charge, resulting in an asymmetric denotation-front record. The second series of experiments consists of photographing a shaped-charge jet having a velocity range of two to nine millimeters per microsecond. To accommodate the range of velocities it is necessary to fire several tests, each synchronized to a different section of the jet. The experimental apparatus consists of a vacuum chamber to preclude atmospheric ablation of the jet tip with shocked-argon back lighting to produce a shadow-graph image.

Critchfield, Robert R.; Asay, Blaine W.; Bdzil, John B.; Davis, William C.; Ferm, Eric N.; Idar, Deanne J.

1997-12-01

375

Gaseous detonation initiation and stabilization by hypervelocity projectiles  

NASA Astrophysics Data System (ADS)

An experimental investigation of gaseous detonations initiated and stabilized by high-speed spherical projectiles has been carried out. Detonation initiation by projectiles is closely related to propulsion concepts such as the ram accelerator and the oblique detonation wave engine, in which, theoretically, rapid combustion occurs in detonation waves stabilized on solid objects. The criteria for initiation and stabilization by projectiles are also related to other initiation and propagation criteria such as blast initiation and failure of diffracting detonations. Experimental data of this type are useful for identifying relevant assumptions and important processes, and for providing validation for computational and analytical models. Experiments were performed in the Caltech T5 shock tunnel laboratory. T5 was used in a shock-compression light gas gun mode, with 25.4-mm diameter nylon spheres and velocities around 2300 m/s. Gaseous mixtures studied included 2H2+O2+?N2 (1 >= ? >= 13.76), C2H4+3O2+5N2, and C2H 2+2.5O2+9.4N2 at initial pressures of 0.08-2.56 bar. Flow visualization results obtained by differential interferometry, shadowgraphy, and intensified CCD imaging were augmented by wall pressure records. A wide variety of results were observed, including non- detonative shock-induced combustion, unstably initiated detonations, stabilized prompt initiations, and stabilized delayed initiations. These results can be roughly correlated in terms of the ratio of projectile velocity to mixture Chapman-Jouguet detonation speed, and the ratio of projectile diameter to detonation cell size or reaction zone thickness, although the effects of confinement and unsteadiness complicate this categorization. Two basic approaches to modeling the results have been attempted. In the first, a global model for initiation is based on an existing blast-initiation model using the hypersonic blast-wave analogy. This model is simple, and roughly predicts the experimental results, but suffers from a number of assumptions and approximations that restrict its usefulness and accuracy. The second approach, based on the local shock curvature, is not directly capable of predicting global initiation and failure, but illustrates the mechanism responsible for decoupling of the reaction zone from the shock front in cases of detonation failure. Coupled with a separate model for the shock shape, shock-curvature theory can be used for quantitative global predictions.

Kaneshige, Michael Jiro

376

Chemical Equilibrium Detonation  

NASA Astrophysics Data System (ADS)

Energetic materials are unique for having a strong exothermic reactivity, which has made them desirable for both military and commercial applications. The fundamental principles outlined in this chapter pertain to the study of detonation in both gas-phase and condensed-phase energetic materials, but our main focus will be on the condensed ones, particularly on high explosives (HEs). They share many properties with other classes of condensed energetic compounds such as propellants and pyrotechnics, but a detailed understanding of detonation is especially important for numerous HE applications. The usage and study of HE materials goes back more than a century, but many questions remain to be answered, e.g., on their reaction pathways at high pressures and temperatures, chemical properties, etc.

Bastea, Sorin; Fried, Laurence E.

377

Semiconductor bridge (SCB) detonator  

Microsoft Academic Search

The present invention is a low-energy detonator for high-density secondary-explosive materials initiated by a semiconductor bridge igniter that comprises a pair of electrically conductive lands connected by a semiconductor bridge. The semiconductor bridge is in operational or direct contact with the explosive material, whereby current flowing through the semiconductor bridge causes initiation of the explosive material. Header wires connected to

Bickes Jr. Robert W; Mark C. Grubelich

1999-01-01

378

Semiconductor bridge (SCB) detonator  

Microsoft Academic Search

The present invention is a low-energy detonator for high-density secondary-explosive materials initiated by a semiconductor bridge (SCB) igniter that comprises a pair of electrically conductive lands connected by a semiconductor bridge. The semiconductor bridge is in operational or direct contact with the explosive material, whereby current flowing through the semiconductor bridge causes initiation of the explosive material. Header wires connected

R. W. Jr. Bickes; M. C. Grubelich

1999-01-01

379

Detonation in TATB Hemispheres  

Microsoft Academic Search

Streak camera breakout and Fabry-Perot interferometer data have been taken on the outer surface of 1.80 g\\/cm³ TATB hemispherical boosters initiated by slapper detonators at three temperatures. The slapper causes breakout to occur at 54{sup o} at ambient temperatures and 42{sup o} at -54 C, where the axis of rotation is 0{sup o}. The Fabry velocities may be associated with

B Druce; P C Souers; C Chow; F Roeske; P Vitello; C Hrousis

2004-01-01

380

Initiation of detonation regimes in hybrid two-phase mixtures  

NASA Astrophysics Data System (ADS)

The problem of detonation initiation is studied in the case of hybrid two-phase mixtures consisting of a hydrogen-air gaseous mixture with suspended fine aluminium particles. In preceding works on this subject, investigation of the steady propagation regimes has shown that three main propagation regimes could exist: the Pseudo-Gas Detonation (PGD), the Single-Front Detonation (SFD), and the Double-Front Detonation (DFD). In the present study, a one-dimensional unsteady numerical code has been improved to study the build-up of the detonation in a heterogeneous solid particle gas mixture contained in a tube. The initiation is simulated by the deposition of a given energy in a point source explosion, and the formation of the detonation is observed over distances of 15 m to 30 m. As the code has been designed to run on a micro-computer, memory limitations preclude sufficient accuracy for quantitative results, however, good qualitative agreement has been found with the results of the steady analysis. In addition, it has been demonstrated that when both PGD and SFD could exist at the same particle concentration, the PGD regime was unstable and was able to exist only over a limited distance (a few meters): after some time, the reaction of aluminium particles in the unsteady flow perturbs the leading wave and accelerates it to the SFD regime. Influence of particle diameter and of initiation energy are examined.

Khasainov, B. A.; Veyssiere, B.

1996-06-01

381

Detonation Front in Homogeneous and Geterogeneous High Explosives.  

NASA Astrophysics Data System (ADS)

We have measured detonation wave structure in heterogeneous plasticized HE (HMX, RDX, PETN, TNT) and homogeneous liquid HE (tetranitromethane, nitrobenzol and others). Detonation wave particle velocity profiles and Neumann spike value were measured by laser velocymeter on HE-window interface. Neumann spike exceeding over Chapman- Jouget state was 1.2:1.4 for heterogeneous HE and 1.5:1.7 for homogeneous HE. For liquid HE compression waves with different profiles passing ahead of detonation front were recorded. Compression waves duration in different experiment was equal to 5-20 ns. Hypotheses explaining the existence of such waves in liquid HE are given in the paper. Complex three-dimensional detonation front structure and two types of particle velocity profiles on HE-window interface for heterogeneous HE were recorded. The types of particle velocity profiles are: a) quickly falling down concave profiles which indicate the high reaction rate immediately after Neumann spike and b) stepped convex profiles with period of 2.5-30 ns which indicate the many-stages chemical reaction in the front and slow reaction rate immediately after Neumann spike.

Fedorov, A. V.; Zotov, E. V.; Krasovsky, G. V.; Menshikh, A. V.; Yagodin, N. B.

1999-06-01

382

Detonation failure characterization of non-ideal explosives  

NASA Astrophysics Data System (ADS)

Non-ideal explosives are currently poorly characterized, hence limiting the modeling of them. Current characterization requires large-scale testing to obtain steady detonation wave characterization for analysis due to the relatively thick reaction zones. Use of a microwave interferometer applied to small-scale confined transient experiments is being implemented to allow for time resolved characterization of a failing detonation. The microwave interferometer measures the position of a failing detonation wave in a tube that is initiated with a booster charge. Experiments have been performed with ammonium nitrate and various fuel compositions (diesel fuel and mineral oil). It was observed that the failure dynamics are influenced by factors such as chemical composition and confiner thickness. Future work is planned to calibrate models to these small-scale experiments and eventually validate the models with available large scale experiments. This experiment is shown to be repeatable, shows dependence on reactive properties, and can be performed with little required material.

Janesheski, Robert S.; Groven, Lori J.; Son, Steven

2012-03-01

383

Design and optimization of a deflagration to detonation transition (ddt) section  

NASA Astrophysics Data System (ADS)

Throughout the previous century, hydrocarbon-fueled engines have used and optimized the `traditional' combustion process called deflagration (subsonic combustion). An alternative form of combustion, detonation (supersonic combustion), can increase the thermal efficiency of the process by anywhere from 20 - 50%. Even though several authors have studied detonation waves since the 1890's and a plethora of papers and books have been published, it was not until 2008 that the first detonation-powered flight took place. It lasted for 10 seconds at 100 ft. altitude. Achieving detonation presents its own challenges: some fuels are not prone to detonate, severe vibrations caused by the cyclic nature of the engine and its intense noise are some of the key areas that need further research. Also, to directly achieve detonation either a high-energy, bulky, ignition system is required, or the combustion chamber must be fairly long (5 ft. or more in some cases). In the latter method, a subsonic flame front accelerates within the combustion chamber until it reaches supersonic speeds, thus detonation is attained. This is called deflagration-todetonation transition (DDT). Previous papers and experiments have shown that obstacles, such as discs with an orifice, located inside the combustion chamber can shorten the distance required to achieve detonation. This paper describes a hands-on implementation of a DDT device. Different disc geometries inside the chamber alter the wave characteristics at the exit of the tube. Although detonation was reached only when using pure oxygen, testing identified an obstacle configuration for LPG and air mixtures that increased pressure and wave speed significantly when compared to baseline or other obstacle configurations. Mixtures of LPG and air were accelerated to Mach 0.96 in the downstream frame of reference, which would indicate a transition to detonation was close. Reasons for not achieving detonation may include poor fuel and oxidizer mixing, and/or the need for a longer DDT section.

Romo, Francisco X.

384

Low voltage nonprimary explosive detonator  

SciTech Connect

A low voltage, electrically actuated, nonprimary explosive detonator is disclosed wherein said detonation is achieved by means of an explosive train in which a deflagration-to-detonation transition is made to occur. The explosive train is confined within a cylindrical body and positioned adjacent to low voltage ignition means have electrical leads extending outwardly from the cylindrical confining body. Application of a low voltage current to the electrical leads ignites a self-sustained deflagration in a donor portion of the explosive train which then is made to undergo a transition to detonation further down the train.

Dinegar, Robert H. (Los Alamos, NM); Kirkham, John (Newbury, GB2)

1982-01-01

385

Modeling two-dimensional detonations with detonation shock dynamics  

Microsoft Academic Search

In any explosive device, the chemical reaction of the explosive takes place in a thin zone just behind the shock front. The finite size of the reaction zone is responsible for the pressure generated by the explosive being less near the boundaries, for the detonation velocity being lower near a boundary than away from it, and for the detonation velocity

J. B. Bdzil; D. S. Stewart

1988-01-01

386

Integrated Pulse Detonation Propulsion and Magnetohydrodynamic Power  

NASA Technical Reports Server (NTRS)

The prospects for realizing an integrated pulse detonation propulsion and magnetohydrodynamic (MHD) power system are examined. First, energy requirements for direct detonation initiation of various fuel-oxygen and fuel-air mixtures are deduced from available experimental data and theoretical models. Second, the pumping power requirements for effective chamber scavenging are examined through the introduction of a scavenging ratio parameter and a scavenging efficiency parameter. A series of laboratory experiments were carried out to investigate the basic engineering performance characteristics of a pulse detonation-driven MHD electric power generator. In these experiments, stoichiometric oxy-acetylene mixtures seeded with a cesium hydroxide/methanol spray were detonated at atmospheric pressure in a 1-m-long tube having an i.d. of 2.54 cm. Experiments with a plasma diagnostic channel attached to the end of the tube confirmed the attainment of detonation conditions (p2/p1 approximately 34 and D approximately 2,400 m/sec) and enabled the direct measurement of current density and electrical conductivity (approximately = 6 S/m) behind the detonation wave front, In a second set of experiments, a 30-cm-long continuous electrode Faraday channel, having a height of 2.54 cm and a width of 2 cm, was attached to the end of the tube using an area transition duct. The Faraday channel was inserted in applied magnetic fields of 0.6 and 0.95 T, and the electrodes were connected to an active loading circuit to characterize power extraction dependence on load impedance while also simulating higher effective magnetic induction. The experiments indicated peak power extraction at a load impedance between 5 and 10 Omega. The measured power density was in reasonable agreement with a simple electrodynamic model incorporating a correction for near-electrode potential losses. The time-resolved thrust characteristics of the system were also measured, and it was found that the NM interaction exerted a negligible influence on system thrust and that the measured I(sub sp) of the system (200 see) exceeded that computed for an equivalent nozzleless rocket (120 see).

Litchford, Ron J.

2001-01-01

387

Integrated Pulse Detonation Propulsion and Magnetohydrodynamic Power  

NASA Technical Reports Server (NTRS)

The prospects for realizing an integrated pulse detonation propulsion and magnetohydrodynamic (MHD) power system are examined. First, energy requirements for direct detonation initiation of various fuel-oxygen and fuel-air mixtures are deduced from available experimental data and theoretical models. Second, the pumping power requirements for effective chamber scavenging are examined through the introduction of a scavenging ratio parameter and a scavenging efficiency parameter. A series of laboratory experiments were carried out to investigate the basic engineering performance characteristics of a pulse detonation-driven MHD electric power generator. In these experiments, stoichiometric oxy-acetylene mixtures seeded with a cesium hydroxide/methanol spray were detonated at atmospheric pressure in a 1-m-long tube having an i.d. of 2.54 cm. Experiments with a plasma diagnostic channel attached to the end of the tube confirmed the attainment of detonation conditions (p(sub 2)/p(sub 1) approx. 34 and D approx. 2,400 m/sec) and enabled the direct measurement of current density and electrical conductivity (=6 S/m) behind the detonation wave front. In a second set of experiments, a 30-cm-long continuous electrode Faraday channel, having a height of 2.54 cm and a width of 2 cm, was attached to the end of the tube using an area transition duct. The Faraday channel was inserted in applied magnetic fields of 0.6 and 0.95 T. and the electrodes were connected to an active loading circuit to characterize power extraction dependence on load impedance while also simulating higher effective magnetic induction. The experiments indicated peak power extraction at a load impedance between 5 and 10 Ohm. The measured power density was in reasonable agreement with a simple electrodynamic model incorporating a correction for near-electrode potential losses. The time-resolved thrust characteristics of the system were also measured, and it was found that the MHD interaction exerted a negligible influence on system thrust and that the measured I(sub sp) of the system (200 sec) exceeded that computed for an equivalent nozzleless rocket (120 sec).

Litchford, R. J.; Lyles, Garry M. (Technical Monitor)

2001-01-01

388

Interaction of oblique shock and detonatin waves  

Microsoft Academic Search

The interaction between an oblique shock wave and an oblique detonation wave that deflect the flow in the same direction is analyzed. It is assumed that the detonation wave is an exothermic gasdynamic discontinuity. A criterion is developed and used in determining whether a theoretical solution to the problem describes a physically realizable interaction configuration. The reflected wave is found

J. P. Sislian; Y. Sheng

1983-01-01

389

Detonation Failure Characterization of Non-Ideal Explosives  

NASA Astrophysics Data System (ADS)

Non-ideal explosives are currently poorly characterized, which limits the modeling of them. Current characterization requires large-scale testing to obtain detonation wave characterization for analysis due to the relatively thick reaction zones. Use of a microwave interferometer applied to small-scale confined experiments is being implemented to allow for time resolved characterization of a failing detonation. The microwave interferometer measures the failing detonation wave in a tube, and this experiment only requires small amounts of non-ideal explosives. A non-ideal explosive is initiated with a booster charge and a measurement of the failure distance and a continuous position-time trace of the detonation front location can be obtained. Initial tests have been performed that show this method is feasible using an ammonium perchlorate (AP) composite propellant as a model non-ideal explosive. Future work will apply this approach to non-ideal explosives. Successful results of this method would allow for the calibration of detonation models for many different non-ideal explosives.

Janesheski, Robert; Son, Steven; Groven, Lori

2011-06-01

390

Characterizing detonator output using dynamic witness plates  

SciTech Connect

A sub-microsecond, time-resolved micro-particle-image velocimetry (PIV) system is developed to investigate the output of explosive detonators. Detonator output is directed into a transparent solid that serves as a dynamic witness plate and instantaneous shock and material velocities are measured in a two-dimensional plane cutting through the shock wave as it propagates through the solid. For the case of unloaded initiators (e.g. exploding bridge wires, exploding foil initiators, etc.) the witness plate serves as a surrogate for the explosive material that would normally be detonated. The velocity-field measurements quantify the velocity of the shocked material and visualize the geometry of the shocked region. Furthermore, the time-evolution of the velocity-field can be measured at intervals as small as 10 ns using the PIV system. Current experimental results of unloaded exploding bridge wire output in polydimethylsiloxane (PDMS) witness plates demonstrate 20 MHz velocity-field sampling just 300 ns after initiation of the wire.

Murphy, Michael John [Los Alamos National Laboratory; Adrian, Ronald J [Los Alamos National Laboratory

2009-01-01

391

Characterizing Detonator Output Using Dynamic Witness Plates  

NASA Astrophysics Data System (ADS)

A sub-microsecond, time-resolved micro-particle-image velocimetry (PIV) system is developed to investigate the output of explosive detonators. Detonator output is directed into a transparent solid that serves as a dynamic witness plate and instantaneous shock and material velocities are measured in a two-dimensional plane cutting through the shock wave as it propagates through the solid. For the case of unloaded initiators (e.g. exploding bridge wires, exploding foil initiators, etc.) the witness plate serves as a surrogate for the explosive material that would normally be detonated. The velocity-field measurements quantify the velocity of the shocked material and visualize the geometry of the shocked region. Furthermore, the time-evolution of the velocity-field can be measured at intervals as small as 10 ns using the PIV system. Current experimental results of unloaded exploding bridge wire output in polydimethylsiloxane (PDMS) witness plates demonstrate 20 MHz velocity-field sampling just 300 ns after initiation of the wire.

Murphy, Michael J.; Adrian, Ronald J.

2009-12-01

392

Attempts to initiate detonations in metal-sulfur mixtures  

NASA Astrophysics Data System (ADS)

Deflagration waves, which convert solid reactants into solid products, have been observed in certain inorganic mixtures. The possibility of self-sustained "gasless" detonation waves has yet to be experimentally demonstrated. The present study attempts to initiate detonation in metal-sulfur mixtures. Specifically, manganese-sulfur mixtures are used because they are extremely energetic with flame temperature as high as 4000 K and all their detonation products exist in a condensed phase. The charges were 50 mm in diameter and 250 mm long, and were confined with a heavy walled steel pipe. At one end, a short length of bare Mn-S charge was wrapped with sheet explosive. Upon initiation of the sheet explosive, a strong Mach disk was driven into the Mn-S charge. Contact gauges and ion probes were used to monitor the shock and reaction front in the charge. The results indicate that the speed of the reaction front in the part of the charge surrounded by explosive was 6-7 km/sec, but quickly decelerated to below 2.5 km/s as it propagated into steel-confined charge. The results indicate that self-sustained "gasless" detonation is not observed even using an overdriven Mach disk for initiation. Rapid reactions can be initiated by shock wave, but the shock wave apparently cannot be maintained without significant volume expansion in the products.

Goroshin, Samuel; Jiang, Junping; Lee, John H. S.; Romano, Massimiliano

1999-06-01

393

On Gas Flow Circulation in Detonator Delay Elements  

Microsoft Academic Search

We study theoretically the pressure and gas flow fields produced by a deflagration wave as it passes down a cylindrical detonator delay element filled with a porous pyrotechnic. We model the flame front as a planar source of heat and gas which travels down the element with constant speed, thus eliminating the detailed chemistry of the reaction. It is shown

J. A. KING-HELE; J. WILLIAMS

2000-01-01

394

Recent developments with gaseous detonation drivers for a shock tunnel  

Microsoft Academic Search

Early researches on the detonation driven shock tube are reviewed briefly. Calculation results demonstrated that an improvement in attenuation of incident shock wave generated by forward driver can be obtained, provided the diameter of the driver is larger than that of the driven section and an abrupt reduction of cross-section area is placed just beyond the diaphragm and were verified

H.-R. Yu

2005-01-01

395

Pulse Detonation Rocket Magnetohydrodynamic Power Experiment  

NASA Technical Reports Server (NTRS)

The production of onboard electrical power by pulse detonation engines is problematic in that they generate no shaft power; however, pulse detonation driven magnetohydrodynamic (MHD) power generation represents one intriguing possibility for attaining self-sustained engine operation and generating large quantities of burst power for onboard electrical systems. To examine this possibility further, a simple heat-sink apparatus was developed for experimentally investigating pulse detonation driven MHD generator concepts. The hydrogen oxygen fired driver was a 90 cm long stainless steel tube having a 4.5 cm square internal cross section and a short Schelkin spiral near the head end to promote rapid formation of a detonation wave. The tube was intermittently filled to atmospheric pressure and seeded with a CsOH/methanol prior to ignition by electrical spark. The driver exhausted through an aluminum nozzle having an area contraction ratio of A*/A(sub zeta) = 1/10 and an area expansion ratio of A(sub zeta)/A* = 3.2 (as limited by available magnet bore size). The nozzle exhausted through a 24-electrode segmented Faraday channel (30.5 cm active length), which was inserted into a 0.6 T permanent magnet assembly. Initial experiments verified proper drive operation with and without the nozzle attachment, and head end pressure and time resolved thrust measurements were acquired. The exhaust jet from the nozzle was interrogated using a polychromatic microwave interferometer yielding an electron number density on the order of 10(exp 12)/cm at the generator entrance. In this case, MHD power generation experiments suffered from severe near-electrode voltage drops and low MHD interaction; i.e., low flow velocity, due to an inherent physical constraint on expansion with the available magnet. Increased scaling, improved seeding techniques, higher magnetic fields, and higher expansion ratios are expected to greatly improve performance.

Litchford, R. J.; Jones, J. E.; Dobson, C. C.; Cole, J. W.; Thompson, B. R.; Plemmons, D. H.; Turner, M. W.

2003-01-01

396

Steady Non-Ideal Detonation  

Microsoft Academic Search

Highly non-ideal explosives, such as commercial ammonium nitrate based explosives used in mining and blasting, have critical charge diameters of several centimetres and relatively low detonation speeds. Shock polar match analyses between these explosives and confining inert materials give two main types of interactions. For the first type (denoted here by case I), the detonation drives an oblique shock into

G. J. Sharpe; M. Y. Luheshi; M. Braithwaite; S. A. E. G. Falle

2009-01-01

397

STEADY NON-IDEAL DETONATION  

Microsoft Academic Search

Highly non-ideal explosives, such as commercial ammonium nitrate based explosives used in mining and blasting, have critical charge diameters of several centimetres and relatively low detonation speeds. Shock polar match analyses between these explosives and confining inert materials give two main types of interactions. For the first type (denoted here by case I), the detonation drives an oblique shock into

G. J. Sharpe; M. Y. Luheshi; M. Braithwaite; S. A. E. G. Falle

2009-01-01

398

Detonator-activated ball shutter  

SciTech Connect

A detonator-activated ball shutter for closing an aperture in about 300 ..mu..seconds is disclosed. The ball shutter containing an aperture through which light, etc., passes, is closed by firing a detonator which propels a projectile for rotating the ball shutter, thereby blocking passage through the aperture.

McWilliams, R.A.; Von Holle, W.G.

1981-05-14

399

Light-initiated detonation systems  

Microsoft Academic Search

Numerous light sources could be employed in detonation systems, but lasers have the most efficient coupling to optical fibers and can generate energetic light pulses required for detonation. Flash lamp-pumped, solid state lasers are presently the most useful light source for explosive initiation. Laser diodes in current production cannot generate enough energy for practical applications. The most useful optical fiber

Stafford S. Cooper; Philip G. Malone; Stephen W. Bartholomew; William J. Necker

1986-01-01

400

Detonator-activated ball shutter  

DOEpatents

A detonator-activated ball shutter for closing an aperture in about 300.mu. seconds. The ball shutter containing an aperture through which light, etc., passes, is closed by firing a detonator which propels a projectile for rotating the ball shutter, thereby blocking passage through the aperture.

McWilliams, Roy A. (Livermore, CA); von Holle, William G. (Livermore, CA)

1983-01-01

401

Investigation of the detonation regimes in gaseous mixtures with suspended starch particles  

NASA Astrophysics Data System (ADS)

The existence of a secondary discontinuity at the rear of a detonation front shown in experiments by Peraldi and Veyssiere (1986) in stoichiometric hydrogen-oxygen mixtures with suspended 20- ? m starch particles has not been explained satisfactorily. Recently Veyssiere et al. (1997) analyzed these results using a one-dimensional (1-D) numerical model, and concluded that the heat release rate provided by the burning of starch particles in gaseous detonation products is too weak to support a double-front detonation (DFD), in contrast to the case of hybrid mixtures of hydrogen-air with suspended aluminium particles in which a double-front detonation structure was observed by Veyssiere (1986). A two-dimensional (2-D) numerical model was used in the present work to investigate abovementioned experimental results for hybrid mixtures with starch particles. The formation and propagation of the detonation has been examined in the geometry similar to the experimental tube of Peraldi and Veyssiere (1986), which has an area change after 2 m of propagation from the ignition point from a 69 mm dia. section to a 53 mm × 53 mm square cross section corresponding to a 33% area contraction. It is shown that the detonation propagation regime in these experiments has a different nature from the double-front detonation observed in hybrid mixtures with aluminium particles. The detonation propagates as a pseudo-gas detonation (PGD) because starch particles release their heat downstream of the CJ plane giving rise to a non-stationary compression wave. The discontinuity wave at the rear of the detonation front is due to the interaction of the leading detonation front with the tube contraction, and is detected at the farthest pressure gauge location because the tube length is insufficient for the perturbation generated by the tube contraction to decay. Thus, numerical simulations explain experimental observations made by Peraldi and Veyssiere (1986).

Veyssiere, B.; Khasainov, B. A.; Arfi, P.

402

Semiconductor bridge (SCB) detonator  

SciTech Connect

The present invention is a low-energy detonator for high-density secondary-explosive materials initiated by a semiconductor bridge (SCB) igniter that comprises a pair of electrically conductive lands connected by a semiconductor bridge. The semiconductor bridge is in operational or direct contact with the explosive material, whereby current flowing through the semiconductor bridge causes initiation of the explosive material. Header wires connected to the electrically-conductive lands and electrical feed-throughs of the header posts of explosive devices, are substantially coaxial to the direction of current flow through the SCB, i.e., substantially coaxial to the SCB length. 3 figs.

Bickes, R.W. Jr.; Grubelich, M.C.

1999-01-19

403

Detonation diffraction in gases  

SciTech Connect

We have experimentally investigated detonation diffraction out of a round tube into an unconfined half-space. The focus of our study is examining how the extent of detonation cellular instability influences the quantitative and qualitative features of diffraction. Detailed quantitative and qualitative measurements were obtained through simultaneous schlieren imaging, multiple-exposure chemiluminescence imaging, and planar laser-induced fluorescence imaging of OH molecules. Two types of stoichiometric mixtures, highly diluted H{sub 2}-O{sub 2}-Ar and H{sub 2}-N{sub 2}O, were studied in the sub-critical, critical and super-critical regime. These mixture types represent extreme cases in the classification of cellular instability with highly diluted H{sub 2}-O{sub 2}-Ar mixtures having very regular instability structures and H{sub 2}-N{sub 2}O having very irregular instability structures. The most striking differences between the mixtures occur in the sub-critical and critical regimes, for which the detonation fails to transition into the unconfined half-space. For the H{sub 2}-O{sub 2}-Ar mixture, the velocity on the center line was found to decay significantly slower than for the H{sub 2}-N{sub 2}O mixture. In case of the H{sub 2}-O{sub 2}-Ar mixture, it was evident from simultaneous schlieren-fluorescence images that the reaction front was coupled to the lead shock front up to 2.3 tube diameters from the exit plane. For the H{sub 2}-N{sub 2}O mixture, the reaction front velocity decreased to 60% of the corresponding Chapman-Jouguet value at 1.1 tube diameters from the tube exit plane. A geometric acoustic model showed that the observed differences in failure patterns are not caused by the differences in thermodynamic properties of the two mixtures but is linked to the larger effective activation energy and critical decay time in the H{sub 2}-N{sub 2}O mixture as compared to the H{sub 2}-O{sub 2}-Ar mixture. The re-initiation events appear similar for the two mixtures and are a consequence of local fluctuations at random locations within the region between the lead shock and decoupled reaction zone, resulting in strong transverse detonations sweeping through shocked but largely unreacted gas. (author)

Pintgen, F.; Shepherd, J.E. [California Institute of Technology, Mail stop 105-50, 1200 E California Blvd, Pasadena, CA 91125 (United States)

2009-03-15

404

Stability of detonations for an idealized condensed-phase model  

NASA Astrophysics Data System (ADS)

The stability of travelling wave Chapmanvon Neumannring type is formulated for a general system that incorporates the idealized gas and condensed-phase (liquid or solid) detonation models. The general model consists of a two-component mixture with a one-step irreversible reaction between reactant and product. The reaction rate has both temperature and pressure sensitivities and has a variable reaction order. The idealized condensed-phase model assumes a pressure-sensitive reaction rate, a constant-=3, and invokes the strong shock limit. A linear stability analysis of the steady, planar, ZND detonation wave for the general model is conducted using a normal-mode approach. An asymptotic analysis of the eigenmode structure at the end of the reaction zone is conducted, and spatial boundedness (closure) conditions formally derived, whose precise form depends on the magnitude of the detonation overdrive and reaction order. A scaling analysis of the transonic flow region for ChapmanJouguet detonations. Neutral stability boundaries are calculated for the idealized condensed-phase model for one- and two-dimensional perturbations. Comparisons of the growth rates and frequencies predicted by the normal-mode analysis for an unstable detonation are made with a numerical solution of the reactive Euler equations. The numerical calculations are conducted using a new, high-order algorithm that employs a shock-fitting strategy, an approach that has significant advantages over standard shock-capturing methods for calculating unstable detonations. For the idealized condensed-phase model, nonlinear numerical solutions are also obtained to study the long-time behaviour of one- and two-dimensional unstable Chapman-Jouguet ZND waves.

Short, M.; Anguelova, I. I.; Aslam, T. D.; Bdzil, J. B.; Henrick, A. K.; Sharpe, G. J.

405

The role of cellular structure on increasing the detonability limits of three-step chain-branching detonations  

SciTech Connect

In [1], the dynamics of a pulsating three-step chain-branching detonation were studied. The reaction model consists of, sequentially, chain-initiation, chain-branching and chain-termination steps. The chain-initiation and chain-branching steps are taken to be thermally neutral, with chemical energy release occuring in the chain-termination stage. The purpose of the present study is to examine whether cellular detonation structure can increase the value of the chain-branching cross-over temperature T{sub b} at which fully coupled detonation solutions are observed over those in 1 D. The basic concept is straightforward and has been discussed in [1] and [3]; if T{sub s} drops below T{sub b} at the lead shock, the passage of a transverse shock can increase both the lead shock temperature and the temperature behind the transverse wave back above T{sub b}, thus sustaining an unstable cellular detonation for values of T{sub b} for which a one-dimensional pulsating detonation will fail. Experiments potentially supporting this hypothesis with irregular detonations have been shown in [3] in a shock tube with acoustically absorbing walls. Removal of the transverse waves results in detonation failure, giving way to a decoupled shock-flame complex. A number of questions remain to be addressed regarding the possibility of such a mechanism, and, if so, about the precise mechanisms driving the cellular structure for large T{sub b}. For instance, one might ask what sets the cell size in a chain-branching detonation, particularly could the characteristic cell size be set by the chain-branching cross-over temperature T{sub b}: after a transverse wave shock collision, the strength of the transverse wave weakens as it propagates along the front. If the spacing between shock collisions is too large (cell size), then the transverse shocks may weaken to the extent that the lead shock temperature or that behind the transverse waves is not raised above T{sub b}, losing chemical energy to drive the front in those regions. Failure may result if less than sufficient of the lead shock be driven above n to sustain reaction. Our starting point for generating cellular solutions is as in [I], consisting of an initial ZND wave in the channel, but perturbed here by a density non-uniformity to generate a cellular structure. Exactly how far the detonability limits (value of T{sub b}) can be extended is not addressed here, as such issues relate in part to the way the cellular structure is generated [6]. Our concern here is to investigate the mechanisms of self-sustained cellular detonation for values of T{sub b} above those that lead to 1D pulsating wave failure that can be generated from the initial ZND wave. Finally, we do not consider cellular propagation driven by a process of apparent thermal ignition of hot-spots downstream that tends to appear close to the 20 detonability limit. Such events are subject to the lack of correct thermal diffusive physics in the model and thus to the form of numerical dissipation in the underlying flow algorithm.

Short, Mark [Los Alamos National Laboratory; Kiyanda, Charles B [Los Alamos National Laboratory; Quirk, James J [Los Alamos National Laboratory; Sharpe, Gary J [UNIV OF LEEDS, UK

2011-01-27

406

The influence of structural response on sympathetic detonation  

NASA Technical Reports Server (NTRS)

The role that a munition's structural response plays in the ignition process and the development of violent reactions and detonations is explored. The munition's structural response is identified as one of the factors that influences reaction violence. If the structural response of a round is known, this knowledge can be used to redstruce the probability that a large explosion would result from the sequential detonation of individual rounds within a large storage array. The response of an acceptor round was studied. The castings fail in the same manner regardless of whether or not there is a fill material present in the round. These failures are caused by stress waves which are transformed from compressive waves to tensile waves by reflection as the impact energy moves around the casting. Since these waves move in opposite directions around the projectile circumference and collide opposite the point of impact, very high tensile forces are developed which can crack the casing.

Watson, J. L.

1980-01-01

407

Diamonds in detonation soot  

NASA Technical Reports Server (NTRS)

Diamonds 4 to 7 nm in diameter have been identified and partially isolated from soot formed in detonations of carbon-forming composite explosives. The morphology of the soot has been examined by transmission electron microscopy (TEM), and the identity of the diamond has been established by the electron diffraction pattern of the TEM samples and by the X-ray diffraction (XRD) pattern of the isolated solid. Graphite is also present in the form of ribbons of turbostatic structure with a thickness of 2 to 4 nm. A fraction, about 25 percent of the soot by weight, was recovered from the crude soot after oxidation of the graphite with fuming perchloric acid. This fraction showed a distinct XRD pattern of diamond and the diffuse band of amorphous carbon. The IR spectrum of these diamonds closely matches that of diamonds recovered from meteorites (Lewis et al., 1987), perhaps indicating similar surface properties after the oxidation. If these diamonds are produced in the detonation itself or during the initial expansion, they exhibit a phenomenal crystal growth rate (5 nm/0.00001 s equal 1.8 m/hr) in a medium with a very low hydrogen/carbon ratio. Because the diamonds will be carried along with the expanding gases, they will be accelerated to velocities approaching 8 km/s.

Greiner, N. Roy; Phillips, Dave; Johnson, J. D.; Volk, Fred

1990-01-01

408

DEtonation gas delivery unit  

SciTech Connect

The detonation gas for gas-detonatable blasting charges used in surface mining and the like is supplied by a portable self-contained delivery unit connected to the blasting charges by a network of small flexible tubing, which unit blends pressurized fuel and oxidizing gases from separate supply sources in predetermined proportions and regulates the separate flows of such gases in response to the backpressure imposed by the tubing network to maintain such proportions in the gas blend delivered to the tubing network. The separate gas flows are controlled by servo-actuated flow control valves actuated by a control gas pressure which is applied or released in response to such backpressure. Preferably, the control gas pressure is regulated by a pair of pilot valves, one normally open and the other normally closed, connected in parallel between the servo actuators of such flow control valves and the control gas source and the atmosphere, respectively, the state of the pilot valves being reversed in response to the occurrence of a backpressure exceeding a predetermined maximum to disconnect the control gas from and release the existing gas pressure on the flow control valve servo actuators. A preferred safety feature assures complete filling of the tubing network before the gas therein can be ignited to initiate detonation of the explosive charges.

Emmett, G. C.

1984-12-04

409

Explosive Mixtures Detonating at Low Velocity  

Microsoft Academic Search

Summary Same explosive mixtures detonating at a low velocity and not containing high explosives were experimentally investigated. As a system providing detonation capability, a mixture of ammonium nitrate and powdered aluminium was employed. Glass or urea-form- aldehyde resin beads or lead oxides were used to reduce detonation parameters. Detonation velocity and critical diameter were measured for mixtures differentiated in composition

Andrzej Maranda; Stanis?aw Cudzi?o

2001-01-01

410

Analytical study of idealized two-dimensional cellular detonations  

Microsoft Academic Search

.   In this study, the idealized two-dimensional detonation cells were decomposed into the primary units referred to as sub-cells.\\u000a Based on the theory of oblique shock waves, an analytical formula was derived to describe the relation between the Mach number\\u000a ratio through triple-shock collision and the geometric properties of the cell. By applying a modified blast wave theory, an\\u000a analytical

X. Y. Hu; D. L. Zhang; Z. L. Jiang

2002-01-01

411

Analytical study of idealized two-dimensional cellular detonations  

Microsoft Academic Search

In this study, the idealized two-dimensional detonation cells were decomposed into the primary units referred to as sub-cells. Based on the theory of oblique shock waves, an analytical formula was derived to describe the relation between the Mach number ratio through triple-shock collision and the geometric properties of the cell. By applying a modified blast wave theory, an analytical model

X. Y. Hu; D. L. Zhang; Z. L. Jiang

2002-01-01

412

A thermochemically derived global reaction mechanism for detonation application  

NASA Astrophysics Data System (ADS)

A 4-species 4-step global reaction mechanism for detonation calculations is derived from detailed chemistry through thermochemical approach. Reaction species involved in the mechanism and their corresponding molecular weight and enthalpy data are derived from the real equilibrium properties. By substituting these global species into the results of constant volume explosion and examining the evolution process of these global species under varied conditions, reaction paths and corresponding rates are summarized and formulated. The proposed mechanism is first validated to the original chemistry through calculations of the CJ detonation wave, adiabatic constant volume explosion, and the steady reaction structure after a strong shock wave. Good agreement in both reaction scales and averaged thermodynamic properties has been achieved. Two sets of reaction rates based on different detailed chemistry are then examined and applied for numerical simulations of two-dimensional cellular detonations. Preliminary results and a brief comparison between the two mechanisms are presented. The proposed global mechanism is found to be economic in computation and also competent in description of the overall characteristics of detonation wave. Though only stoichiometric acetylene-oxygen mixture is investigated in this study, the method to derive such a global reaction mechanism possesses a certain generality for premixed reactions of most lean hydrocarbon mixtures.

Zhu, Y.; Yang, J.; Sun, M.

2012-07-01

413

Investigation of the adiabat of heterogeneous two-phase detonation  

SciTech Connect

The authors construct a mathematical model for the adiabatic heterogeneous detonation and detonation wave propagation of a suspension of fuel droplets in gas under the influence of nonequilibrium in the two-phase flow. The nonideality of the model results in difficulties in the selection of the detonation velocity and the location of the Chapman-Jouguet plane. The following rules are proposed for the selection of the Chapman-Jouguet plane location: the site of complete drop burnup; the plane of drop shattering and ignition; equality of the Mach numbers; utilization of approximate chemical equilibrium; using boundary conditions for the gradients in the reaction zone; and dependence on the relationship between the characteristic relaxation times of the phase velocities, the heat transfer between the phases and the heat liberation, by one of four possible equilibrium-frozen speeds of sound.

Medvedev, A.E.; Fedorov, A.V.; Fomin, V.M.

1987-09-01

414

Preparation of C60 by Detonation Technique  

NASA Astrophysics Data System (ADS)

A mixture of TNT (Trinitrotoluene) and natural graphite was detonated in a vacuum container which was immersed into cooling water; detonation products were collected for detecting. The results of mass spectroscopy, high performance liquid chromatography showed significant signals of C60, which proved that C60 could be synthesized by detonating the mixture of TNT/graphite and the detonation pressure was around 12.3 GPa and the detonation temperature was around 1985 K.

Wei, Xianfeng; Han, Yong; Long, Xinping

2012-11-01

415

Detonation spreading in fine TATBs  

SciTech Connect

A test has been devised that permits rapid evaluation of the detonation-spreading (or corner-turning) properties of detonations in insensitive high explosives. The test utilizes a copper witness plate as the medium to capture performance data. Dent depth and shape in the copper are used as quantitative measures of the detonation output and spreading behavior. The merits of the test are that it is easy to perform with no dynamic instrumentation, and the test requires only a few grams of experimental explosive materials.

Kennedy, J.E.; Lee, K.Y.; Spontarelli, T.; Stine, J.R.

1998-12-31

416

Approximate Equation of State for Overdriven and Reflected Detonation Products  

NASA Astrophysics Data System (ADS)

Approximate Equation of State for Overdriven and Reflected Detonation Products Zhi-Yue Liu and Shigeru Itoh Shock Wave and Condensed Matter Research Center, Kumamoto University, 2-39-1 Kurokami, Kumamoto, 860-8555, Japan ABSTRACT There are several types of equations of state (EOS) to describe the isentropic expansion behavior of the detonation products after the explosive is exploded. Of which, Jones-Wilkins-Lee (or JWL) equation and polytropic gas (or gamma-law) equation are most popularly employed owing to either the completely experimental calibration or simple form in expression. However, both equations fail to correctly describe the behavior of detonation products above the Chapman-Jouguet (C-J) state. For this reason, a new form of equation of state is proposed for overcoming this deficiency. The new equation of state is simply a linear combination of JWL and gamma-law equations. The coefficient appeared in the EOS can be obtained by fitting to the data from the overdriven detonation experiments. Results show that this form of EOS not only gives the satisfactory description to the variation of the detonation products in overdriven or reflected state also can simply be incorporated into the hydrodynamic computer codes.

Liu, Zhi-Yue; Itoh, Shigeru

2001-06-01

417

Development of an Actuator for Flow Control Utilizing Detonation  

NASA Technical Reports Server (NTRS)

Active flow control devices including mass injection systems and zero-net-mass flux actuators (synthetic jets) have been employed to delay flow separation. These devices are capable of interacting with low-speed, subsonic flows, but situations exist where a stronger crossflow interaction is needed. Small actuators that utilize detonation of premixed fuel and oxidizer should be capable of producing supersonic exit jet velocities. An actuator producing exit velocities of this magnitude should provide a more significant interaction with transonic and supersonic crossflows. This concept would be applicable to airfoils on high-speed aircraft as well as inlet and diffuser flow control. The present work consists of the development of a detonation actuator capable of producing a detonation in a single shot (one cycle). Multiple actuator configurations, initial fill pressures, oxidizers, equivalence ratios, ignition energies, and the addition of a turbulence generating device were considered experimentally and computationally. It was found that increased initial fill pressures and the addition of a turbulence generator aided in the detonation process. The actuators successfully produced Chapman-Jouguet detonations and wave speeds on the order of 3000 m/s.

Lonneman, Patrick J.; Cutler, Andrew D.

2004-01-01

418

Detonation tube impulse in sub-atmospheric environments.  

SciTech Connect

The thrust from a multi-cycle, pulse detonation engine operating at practical flight altitudes will vary with the surrounding environment pressure. We have carried out the first experimental study using a detonation tube hung in a ballistic pendulum arrangement within a large pressure vessel in order to determine the effect that the environment has on the single-cycle impulse. The air pressure inside the vessel surrounding the detonation tube varied between 100 and 1.4 kPa while the initial pressure of the stoichiometric ethylene-oxygen mixture inside the tube varied between 100 and 30 kPa. The original impulse model (Wintenberger et al., Journal of Propulsion and Power, Vol. 19, No. 1, 2002) was modified to predict the observed increase in impulse and blow down time as the environment pressure decreased below one atmosphere. Comparisons between the impulse from detonation tubes and ideal, steady flow rockets indicate incomplete expansion of the detonation tube exhaust, resulting in a 37% difference in impulse at a pressure ratio (ratio of pressure behind the Taylor wave to the environment pressure) of 100.

Cooper, Marcia A.; Shepherd, Joseph E. (California Institute of Technology, Pasadena, CA)

2005-04-01

419

Numerical simulation of three-dimensional gas detonation  

NASA Astrophysics Data System (ADS)

We investigate the characteristics of the three-dimensional detonation in an argon-diluted mixture of hydrogen and oxygen. The three-dimensional Euler equations with a simple chemical reaction model are used as the governing equations for the detonation problem. The spatial derivatives are evaluated using the WENO scheme, and the temporal derivative is calculated using the TVD Runge-Kutta method. It is verified that the detonation front is composed of incident shocks and Mach stems, joined at the lines of triple points by transverse waves. And the clear cellular structure is displayed by using a three-dimensional numerical visualization. The process of generating unburned gas pockets is shown by the spatial isosurface profiles of the reaction progress parameter in the exothermic period, and it is explained that the triple lines play a role of "shutter". Furthermore, the rectangles, enclosed by the triple lines, vary with the movement of the triple lines. Consequently, the evolution between the diagonal detonation and the rectangular detonation is realized.

Wang, C.; Lu, J.; Ye, T.

2008-02-01

420

Detonation initiation of JP-8-oxygen mixtures at different initial temperatures  

NASA Astrophysics Data System (ADS)

Liquid fuel with sufficient vapor proportion at micron scale is essentially required to increase specific energy density and reduce volume requirements for application of pulse detonation engine. For JP-8, the fully vaporized temperature ranges from 380 to 410 K. In this study, the fuel vapor with oxygen is not enough to induce the reaction and leads to failure of detonation initiation at the initial temperature of 373 K. Condensed fuel was also observed on the bottom of detonation tube. At 393 K, the detonation wave was successfully generated even though a portion of fuel was in a liquid state. The deflagration-to-detonation run-up distance and the pressure trace at fully vaporized conditions, in which the initial temperatures were at 413, 433, and 453 K, were similar to those of gaseous mixtures, such as propane-oxygen mixture.

Wen, C.-S.; Chung, K.-M.; Lai, W.-H.

2012-09-01

421

Experiments on spinning detonations with detailed analysis of the shock structure  

NASA Astrophysics Data System (ADS)

Spinning detonations are characteristic of detonation limit phenomena in round tubes. In this work we study experimentally the structure of the transverse wave of single-headed spinning detonations. The flow field is experimentally analysed and an original approach enables us to calculate the overall shock structure. The calculations and experimental results indicate that the actual structure of the spinning detonation tries to match closely to the condition where the state parameters (pressure and temperature) reach their maximum values. This condition corresponds to a spinning head where the Mach stem is normal to the incoming flow and could be readily used as boundary condition by further investigators to determine the structure of spinning detonations.

Huang, Z. W.; Lefebvre, M. H.; Van Tiggelen, P. J.

422

Nonlinear Development of Low Frequency One-Dimensional Instabilities for Reacting Shock Waves. (Reannouncement with New Availability Information).  

National Technical Information Service (NTIS)

It has been postulated that detonation waves are steady traveling waves with a quasi one-dimensional structure of an ordinary fluid dynamic shock followed by a reaction zone. In contrast, the detonations observed in many experimental circumstances demonst...

A. Bourlioux A. J. Majda V. Roytburd

1991-01-01

423

High-speed photography for pressure generation using the underwater explosion of spiral detonating cord  

NASA Astrophysics Data System (ADS)

In recent years we have devoted our efforts to the studies on the various shock processing techniques using explosives for the objectives of gaining materials with the good properties. Those techniques include the punch of pipes, shock consolidation of metallic and ceramic powders, explosive welding of amorphous ribbon on the steel or copper substrate, explosive engraving for the art objects and explosive forming of shells and spheres, and the improvement of the permeability of wood by shock wave. However, to a specific processing technique, it needs to control the shock wave for meeting the demands of that processing purpose. One important control is how to increase the strength of underwater shock wave. Therefore, we propose the following method to converge the underwater shock wave by putting a piece of detonating cord in a spiral way. First, the assignment of the spiral shape of detonation was determined from the geometrical consideration and the basic features of the detonation cord itself. Second, the converging process of the underwater shock wave from the explosion of such designed shape of detonating cord was photographically observed by using the high speed camera in the framing form. The spiral shape with the 100 mm distance from detonating start point to the center of the spiral (indicated by r1) was selected. They were amounted together with the electric detonator and the detonating cord. The photographs confirm that the underwater shock wave moves toward the spiral center in a convergence way. Third, the pressure nearing the spiral center was measured experimentally by means of the pressure transducers. The distance, Dh, between the detonating cord and the transducer was set to be 272 mm. Compared to the case that the detonating cord was placed in straight way, the maximum pressure in the case with the spiral shape is verified to be unchanged, but the impulse, however, is much improved. This reason may be due to over- greatly set Dh. When the distance Dh was set to 50 mm, the pressure measurement was made again and as a result, the large pressure value was record. Compared to the straightly placed detonating cord, it is shown that 3 times higher peak pressure is available in the spiral detonation cord. The results demonstrate that in a small range the pressure of underwater shock wave is indeed converged and higher pressure value is obtained.

Itoh, Shigeru; Nagano, Shirou; Hamada, Toru; Murata, Kenji; Kato, Yukio

2001-04-01

424

Theoretical analysis of rotating two phase detonation in a rocket motor  

NASA Technical Reports Server (NTRS)

Tangential mode, non-linear wave motion in a liquid propellant rocket engine is studied, using a two phase detonation wave as the reaction model. Because the detonation wave is followed immediately by expansion waves, due to the side relief in the axial direction, it is a Chapman-Jouguet wave. The strength of this wave, which may be characterized by the pressure ratio across the wave, as well as the wave speed and the local wave Mach number, are related to design parameters such as the contraction ratio, chamber speed of sound, chamber diameter, propellant injection density and velocity, and the specific heat ratio of the burned gases. In addition, the distribution of flow properties along the injector face can be computed. Numerical calculations show favorable comparison with experimental findings. Finally, the effects of drop size are discussed and a simple criterion is found to set the lower limit of validity of this strong wave analysis.

Shen, I.; Adamson, T. C., Jr.

1973-01-01

425

The Los Alamos detonating pellet test (DPT): PBX 9501 evaluation tests  

NASA Astrophysics Data System (ADS)

High explosive (HE) Velocity of Detonation (VOD) measurements are usually conducted using rate-stick-type tests. This method is highly accurate if carefully implemented, but is relatively costly and may require kilograms or more of HE depending on its sensitivity. We present a novel technique for inferring VOD using a single HE pellet, which for Conventional High Explosives (CHEs) can use 10 gm of HE or even less. This attribute makes the Detonating Pellet Test (DPT) ideal for the preliminary performance characterization of newly synthesized HE materials. On the other end of the size spectrum, the DPT can be scaled to very large dimensions so as to minimize the HE load necessary to characterize highly insensitive HEs such as ANFO. The DPT exploits the fact that the detonation emerging from the pellet face can be made highly spherical over some central region. Spherical detonation breakout on the Sample Pellet (SP) face is described by a simple analytic equation, which depends on the VOD and the Center Of Initiation (COI). The latter is determined by separate characterization of the detonator, with a wave refraction correction at the detonator/SP interface. The SP VOD is then determined by fitting the ideal breakout equation, with specified detonator COI, to detonation breakout data obtained via streak camera. We develop the DPT method and appraise it using sample PBX 9501 data in particular, while discussing its benefits and limitations in general.

Preston, D. N.; Hill, L. G.; Tappan, B. C.

2014-05-01

426

Fine structure in nitromethane/acetone detonations  

SciTech Connect

Dark waves in the detonation front of nitromethane/acetone mixtures, known for 30 years, have been photographed using pairs of image intensifier cameras, triggered at slightly different times. The photographs show the motions and changes of the complex wave structure. Intriguing results are that the average brightness doesn't change as much from center to edge as simple theory would predict, and brightness goes down rather than up when a reflected shock from a glass plate enters the explosive products. The structure remains visible in the products stagnated against a glass plate, showing that the bright regions are high temperature regions, not just areas where less absorbing material is present ahead of the emitting layer.

Davis, W.C.

1981-01-01

427

Generation of the patterns in gaseous detonations  

NASA Astrophysics Data System (ADS)

The problem addressed here is the mode of formation of the first initial regular pattern and its spacing in a detonation front. It is generally accepted that these patterns derive from a self-sustaining process of formation of Mach stems by colliding blast waves and blast waves from secondary local explosions initiated by these Mach stems. The reason for the very first explosions and their spacing, however, are not known. It is shown here that this is caused by temperature perturbations as they are introduced with any kind of ignition. A steady mode of perturbation is derived which initiates the first local explosions at the extreme end of the combustion zone. They are substitutes for what is considered unrealistic asymptotic decrease. The concept is shown to be in agreement with measurements of the reaction time and of the spacing of soot patterns.

Schultz-Grunow, F.

428

Steady non-ideal detonations  

Microsoft Academic Search

Theories for determining the velocity of detonation (VoD) in highly non-ideal explosives, e.g. commercial explosives used in mining, are discussed. Such explosives have critical charge diameters of several centimetres. An analysis of the interaction between detonations and confining materials along the explosive-confiner interface reveals there a two main types of interaction. In the first (denoted here by case 1) the

Gary Sharpe

2009-01-01

429

Infrared signatures from bomb detonations  

Microsoft Academic Search

Remote observations of the temporal and spectral characteristics of the infrared emissions from bomb detonations have been correlated with explosion conditions. A Fourier transform interferometer was used to record spectra in the 1.6-20 \\/mum range at spectral resolutions of 4-16 cm-1 and temporal resolutions of 0.047-0.123 s. Field observations of 56 detonation events included a set of aircraft delivered ordinance

Jay A. Orson; William F. Bagby; Glen P. Perram

2003-01-01

430

Infrared signatures from bomb detonations  

Microsoft Academic Search

Remote observations of the temporal and spectral characteristics of the infrared emissions from bomb detonations have been correlated with explosion conditions. A Fourier transform interferometer was used to record spectra in the 1.6–20 ?m range at spectral resolutions of 4–16 cm?1 and temporal resolutions of 0.047–0.123 s. Field observations of 56 detonation events included a set of aircraft delivered ordinance

Jay A. Orson; William F. Bagby; Glen P. Perram

2003-01-01

431

Applications of classical detonation theory  

SciTech Connect

Classical detonation theory is the basis for almost all calculations of explosive systems. One common type of calculation is of the detailed behavior of inert parts driven by explosive, predicting pressures, velocities, positions, densities, energies, etc as functions of time. Another common application of the theory is predicting the detonation state and expansion isentrope of a new explosive or mixtures, perhaps an explosive that has not yet been made. Both types of calculations are discussed.

Davis, W.C.

1994-09-01

432

Mechanisms of detonation transmission in layered H2-O2 mixtures  

NASA Astrophysics Data System (ADS)

When a plane detonation propagating through an explosive comes into contact with a bounding explosive, different types of diffraction patterns, which may result in the transmission of a detonation into the bounding mixture, are observed. The nature of these diffraction patterns and the mode of detonation transmission depend on the properties of the primary and bounding explosives. An experimental and analytical study of such diffractions, which are fundamental to many explosive applications, has been conducted in a two channel shock tube, using H2-O2 mixtures of different equivalence ratios as the primary and bounding or secondary explosive. The combination of mixtures was varied from rich primary / lean secondary to lean primary / rich secondary since the nature of the diffraction was found to depend on whether the Chapman-Jouguet velocity of the primary mixture, D p, was greater than or less than that of the secondary mixture, D s. Schlieren framing photographs of the different diffraction patterns were obtained and used to measure shock and oblique detonation wave angles and velocities for the different diffraction patterns, and these were compared with the results of a steady-state shock-polar solution of the diffraction problem. Two basic types of diffraction and modes of detonation reinitiation were observed. When D p> D s, an oblique shock connecting the primary detonation to an oblique detonation in the secondary mixture was observed. With D p< D s, two modes of reinitiation were observed. In some cases, ignition occurs behind the Mach reflection of the shock wave, which is transmitted into the secondary mixture when the primary detonation first comes into contact with it, from the walls of the shock tube. In other cases, a detonation is initiated in the secondary mixture when the reflected shock crosses the contact surface behind the incident detonation. These observed modes of Mach stem and contact surface ignition have also been observed in numerical simulations of layered detonation interactions, as has the combined oblique-shock oblique-detonation configuration when D p> D s. When D p> D s, the primary wave acts like a wedge moving into the secondary mixture with velocity D p after steady state has been reached, a configuration which also arises in oblique-detonation ramjets and hypervelocity drivers.

Tonello, N. A.; Sichel, M.; Kauffman, C. W.

1995-12-01

433

Light-initiated detonation systems  

NASA Astrophysics Data System (ADS)

Numerous light sources could be employed in detonation systems, but lasers have the most efficient coupling to optical fibers and can generate energetic light pulses required for detonation. Flash lamp-pumped, solid state lasers are presently the most useful light source for explosive initiation. Laser diodes in current production cannot generate enough energy for practical applications. The most useful optical fiber for blast line application is a step index fiber with a large core-to-cladding ratio. The large core minimizes energy losses due to misalignment core of fibers in connectors. Couplers that involve mechanically crimped connectors and cleaved fibers, rather than the epoxy-cemented connectors with polished fibers, provide superior energy transmission due to the reduced carbonization at the fiber end. Detonators for optical initiation systems are similar in basic construction to those employed in electrical initiation systems. Explosive and pyrotechnic charges can also be similar. Either primary or secondary explosives can be initiated in present laser-based systems. Two laser detonation systems are presently accessible; a multiple-shot laser with a single-shot, single fiber system designed for use with detonators containing primary explosives. Additional research related to development of low-energy, photoreactive detonators, continuity checking techniques and improved connectors and fibers can produce significant improvements in presently fielded systems.

Cooper, Stafford S.; Malone, Philip G.; Bartholomew, Stephen W.; Necker, William J.

1986-09-01

434

Analysis of the shock structures in a regular detonation  

NASA Astrophysics Data System (ADS)

Time-dependent two-dimensional numerical simulations have been used to investigate the detailed shock structures and patterns of energy release in the regions of the triple points and transverse waves in a planar detonation. As the system of shock triple points evolves between collisions, they trace a well shaped cellular pattern characteristic of detonations in argon-diluted, low-pressure mixtures of hydrogen and oxygen. In the region of the triple points, the shock structure evolves continuously from a single Mach structure to a double Mach structure and finally to a complex Mach structure characteristic of spinning detonations. Most of the energy released in the region of the triple points. The amount of energy release increases as the triple point comes closer to a collision with a wall or another triple point. Just before the collision, there is a large region of energy release that covers the length of the interacting transverse waves. The result is a rectangular high-energy region which boosts the propagation of the new detonation cell.

Lefebvre, M. H.; Oran, E. S.

1995-03-01

435

Towards Integrated Pulse Detonation Propulsion and MHD Power  

NASA Technical Reports Server (NTRS)

The interest in pulse detonation engines (PDE) arises primarily from the advantages that accrue from the significant combustion pressure rise that is developed in the detonation process. Conventional rocket engines, for example, must obtain all of their compression from the turbopumps, while the PDE provides additional compression in the combustor. Thus PDE's are expected to achieve higher I(sub sp) than conventional rocket engines and to require smaller turbopumps. The increase in I(sub sp) and the decrease in turbopump capacity must be traded off against each other. Additional advantages include the ability to vary thrust level by adjusting the firing rate rather than throttling the flow through injector elements. The common conclusion derived from these aggregated performance attributes is that PDEs should result in engines which are smaller, lower in cost, and lighter in weight than conventional engines. Unfortunately, the analysis of PDEs is highly complex due to their unsteady operation and non-ideal processes. Although the feasibility of the basic PDE concept has been proven in several experimental and theoretical efforts, the implied performance improvements have yet to be convincingly demonstrated. Also, there are certain developmental issues affecting the practical application of pulse detonation propulsion systems which are yet to be fully resolved. Practical detonation combustion engines, for example, require a repetitive cycle of charge induction, mixing, initiation/propagation of the detonation wave, and expulsion/scavenging of the combustion product gases. Clearly, the performance and power density of such a device depends upon the maximum rate at which this cycle can be successfully implemented. In addition, the electrical energy required for direct detonation initiation can be significant, and a means for direct electrical power production is needed to achieve self-sustained engine operation. This work addresses the technological issues associated with PDEs for integrated aerospace propulsion and MHD power. An effort is made to estimate the energy requirements for direct detonation initiation of potential fuel/oxidizer mixtures and to determine the electrical power requirements. This requirement is evaluated in terms of the possibility for MHD power generation using the combustion detonation wave. Small scale laboratory experiments were conducted using stoichiometric mixtures of acetylene and oxygen with an atomized spray of cesium hydroxide dissolved in alcohol as an ionization seed in the active MHD region. Time resolved thrust and MHD power generation measurements were performed. These results show that PDEs yield higher I(sub sp) levels than a comparable rocket engine and that MHD power generation is viable candidate for achieving self-excited engine operation.

Litchford, Ron J.; Thompson, Bryan R.; Lineberry, John T.

1999-01-01

436

Thermodynamic Calculations of Hydrogen-Oxygen Detonation Parameters for Various Initial Pressures  

NASA Technical Reports Server (NTRS)

Composition, temperature, pressure and density behind a stable detonation wave and its propagation rate have been calculated for seven hydrogen-oxygen mixture at 1, 5, 25 and 100 atm initial pressure, and at an initial temperature of 40C. For stoichiometric mixtures that calculations also include an initial temperature of 200C. According to these calculations the detonation velocities of hydrogen-oxygen mixtures increase with increasing initial pressure, but decrease slightly when the initial temperature is raised from 40 to 200 C. The calculated detonation velocities agree satisfactorily with values determined experimentally. These values will be published in the near future.

Bollinger, Loren E.; Edse, Rudolph

1961-01-01

437

Deflagration-to-detonation transition in gases in tubes with cavities  

NASA Astrophysics Data System (ADS)

The existence of a supersonic second combustion mode — detonation — discovered by Mallard and Le Chatelier and by Berthélot and Vieille in 1881 posed the question of mechanisms for transition from one mode to the other. In the period 1959-1969, experiments by Salamandra, Soloukhin, Oppenheim, and their coworkers provided insights into this complex phenomenon. Since then, among all the phenomena related to combustion processes, deflagration-to-detonation transition is, undoubtedly, the most intriguing one. Deflagration-to-detonation transition (DDT) in gases is connected with gas and vapor explosion safety issues. Knowing mechanisms of detonation onset control is of major importance for creating effective mitigation measures addressing two major goals: to prevent DDT in the case of mixture ignition, or to arrest the detonation wave in the case where it has been initiated. A new impetus to the increase in interest in deflagration-to-detonation transition processes was given by the recent development of pulse detonation devices. The probable application of these principles to creation of a new generation of engines put the problem of effectiveness of pulse detonating devices at the top of current research needs. The effectiveness of the pulse detonation cycle turned out to be the key factor characterizing the Pulse Detonation Engine (PDE), whose operation modes were shown to be closely related to periodical onset and degeneration of a detonation wave. Those unsteady-state regimes should be self-sustained to guarantee a reliable operation of devices using the detonation mode of burning fuels as a constitutive part of their working cycle. Thus deflagration-to-detonation transition processes are of major importance for the issue. Minimizing the predetonation length and ensuring stability of the onset of detonation enable one to increase the effectiveness of a PDE. The DDT turned out to be the key factor characterizing the PDE operating cycle. Thus, the problem of DDT control in gaseous fuel-air mixtures became very acute. This paper contains results of theoretical and experimental investigations of DDT processes in combustible gaseous mixtures. In particular, the paper investigates the effect of cavities incorporated in detonation tubes at the onset of detonation in gases. Extensive numerical modeling and simulations allowed studying the features of deflagration-to-detonation transition in gases in tubes incorporating cavities of a wider cross section. The presence of cavities substantially affects the combustion modes being established in the device and their dependence on the governing parameters of the problem. The influence of geometrical characteristics of the confinement and flow turbulization on the onset of detonation and the influence of temperature and fuel concentration in the unburned mixture are discussed. It was demonstrated both experimentally and theoretically that the presence of cavities of wider cross section in the ignition part of the tube promotes DDT and shortens the predetonation length. At the same time, cavities incorporated along the whole length or in the far-end section inhibit detonation and bring about the onset of low-velocity galloping detonation or galloping combustion modes. The presence of cavities in the ignition section turns an increase in the initial mixture temperature into a DDT-promoting factor instead of a DDT-inhibiting factor.

Smirnov, N. N.; Nikitin, V. F.; Phylippov, Yu. G.

2010-12-01

438

The structure and evolution of a two-dimensional H 2 \\/O 2 \\/Ar cellular detonation  

Microsoft Academic Search

This paper reports on two-dimensional numerical simulation of cellular detonation wave in a \\u000a\\/\\u000a\\/\\u000a mixture with low initial pressure using a detailed chemical reaction model and high order WENO scheme. Before the final equilibrium structure is produced, a fairly regular but still non-equilibrium mode is observed during the early stage of structure formation process. The numerically tracked detonation cells

X. Y. Hu; D. L. Zhang; B. C. Khoo; Z. L. Jiang

2005-01-01

439

A statistical mechanical theory of chemically reacting multiphase mixtures: Application to the detonation properties of PETN  

Microsoft Academic Search

We present a new statistical mechanical theory of multiphase, multicomponent systems. It is based on Ross’s modification of the Mansoori–Canfield–Rasaiah–Stell hard-sphere variational theory and the improved one-fluid van der Waals mixture model. Next, the new theory and exponential-6 potentials that accurately reproduce shock wave data of major detonation-product species are used to compute the detonation properties of PETN (pentaerythritol tetranitrate).

Francis H. Ree

1984-01-01

440

Statistical mechanical theory of chemically reacting multiphase mixtures: Application to the detonation properties of PETN  

Microsoft Academic Search

We present a new statistical mechanical theory of multiphase, multicomponent systems. It is based on Ross's modification of the Mansoori--Canfield--Rasaiah--Stell hard-sphere variational theory and the improved one-fluid van der Waals mixture model. Next, the new theory and exponential-6 potentials that accurately reproduce shock wave data of major detonation-product species are used to compute the detonation properties of PETN (pentaerythritol tetranitrate).

Ree

2009-01-01

441

On the role of turbulence in detonation induced by Mach stem reflection  

Microsoft Academic Search

.   A series of experiments conducted by Chan has shown that while some shock waves may not be strong enough to induce detonation\\u000a when they collide with an obstacle the resulting Mach stem will induce detonation if it collides with a subsequent obstruction.\\u000a A series of numerical simulations, however, failed to demonstrate the expected results if either the Euler or

D. Ingram; B. Jiang; D. Causon

1998-01-01

442

Detonation in TATB Hemispheres  

SciTech Connect

Streak camera breakout and Fabry-Perot interferometer data have been taken on the outer surface of 1.80 g/cm{sup 3} TATB hemispherical boosters initiated by slapper detonators at three temperatures. The slapper causes breakout to occur at 54{sup o} at ambient temperatures and 42{sup o} at -54 C, where the axis of rotation is 0{sup o}. The Fabry velocities may be associated with pressures, and these decrease for large timing delays in breakout seen at the colder temperatures. At room temperature, the Fabry pressures appear constant at all angles. Both fresh and decade-old explosive are tested and no difference is seen. The problem has been modeled with reactive flow. Adjustment of the JWL for temperature makes little difference, but cooling to -54 C decreases the rate constant by 1/6th. The problem was run both at constant density and with density differences using two different codes. The ambient code results show that a density difference is probably there but it cannot be quantified.

Druce, B; Souers, P C; Chow, C; Roeske, F; Vitello, P; Hrousis, C

2004-03-17

443

Numerical study of chemically reacting viscous flow relevant to pulsed detonation engines  

NASA Astrophysics Data System (ADS)

A computational fluid dynamics code for two-dimensional, multi-species, laminar Navier-Stokes equations is developed to simulate a recently proposed engine concept for a pulsed detonation based propulsion system and to investigate the feasibility of the engine of the concept. The governing equations that include transport phenomena such as viscosity, thermal conduction and diffusion are coupled with chemical reactions. The gas is assumed to be thermally perfect and in chemically non-equilibrium. The stiffness due to coupling the fluid dynamics and the chemical kinetics is properly taken care of by using a time-operator splitting method and a variable coefficient ordinary differential equation solver. A second-order Roe scheme with a minmod limiter is explicitly used for space descretization, while a second-order, two-step Runge-Kutta method is used for time descretization. In space integration, a finite volume method and a cell-centered scheme are employed. The first-order derivatives in the equations of transport properties are discretized by a central differencing with Green's theorem. Detailed chemistry is involved in this study. Two chemical reaction mechanisms are extracted from GRI-Mech, which are forty elementary reactions with thirteen species for a hydrogen-air mixture and twenty-seven reactions with eight species for a hydrogen-oxygen mixture. The code is ported to a high-performance parallel machine with Message-Passing Interface. Code validation is performed with chemical kinetic modeling for a stoichiometric hydrogen-air mixture, an one-dimensional detonation tube, a two-dimensional, inviscid flow over a wedge and a viscous flow over a flat plate. Detonation is initiated using a numerically simulated arc-ignition or shock-induced ignition system. Various freestream conditions are utilized to study the propagation of the detonation in the proposed concept of the engine. Investigation of the detonation propagation is performed for a pulsed detonation rocket and a supersonic combustion chamber. For a pulsed detonation rocket case, the detonation tube is embedded in a mixing chamber where an initiator is added to the main detonation chamber. Propagating detonation waves in a supersonic combustion chamber is investigated for one- and two-dimensional cases. The detonation initiated by an arc and a shock wave is studied in the inviscid and viscous flow, respectively. Various features including a detonation-shock interaction, a detonation diffraction, a base flow and a vortex are observed.

Yi, Tae-Hyeong