Detonation Process Research Articles

Heterogeneities in explosives affect detonation process

An explicit microstructure model reveals the role of heterogeneities in shock physics interactions.

Attenuation and Suppression of Detonation Waves in Reacting Gas Mixtures by Clouds of Inert Micro- and Nanoparticles

Physicomathematical models are proposed to describe the processes of detonation propagation, attenuation, and suppression in hydrogen–oxygen, methane–oxygen, and silane–air mixtures with inert micro- and nanoparticles. Based on these models, the detonation velocity deficit is found as a function of the size and concentration of inert micro- and nanoparticles. Three types of detonation flows in gas suspensions of reacting gases and inert nanoparticles are observed: steady propagation of an attenuated detonation wave in the gas suspension, propagation of a galloping detonation wave near the flammability limit, and failure of the detonation process. The mechanisms of detonation suppression by microparticles and nanoparticles are found to be similar to each other. The essence of these mechanisms is decomposition of the detonation wave into an attenuated frozen shock wave and the front of ignition and combustion, which lags behind the shock wave. The concentration limits of detonation in the considered reacting gas mixtures with particles ranging from 10 nm to 1 μm in diameter are also comparable. It turns out that the detonation suppression efficiency does not increase after passing from microparticles to nanoparticles.

Nanodiamonds for device applications: An investigation of the properties of boron-doped detonation nanodiamonds

The inclusion of boron within nanodiamonds to create semiconducting properties would create a new class of applications in the field of nanodiamond electronics. Theoretical studies have differed in their conclusions as to whether nm-scale NDs would support a stable substitutional boron state, or whether such a state would be unstable, with boron instead aggregating or attaching to edge structures. In the present study detonation-derived NDs with purposefully added boron during the detonation process have been studied with a wide range of experimental techniques. The DNDs are of ~4 nm in size, and have been studied with CL, PL, Raman and IR spectroscopies, AFM and HR-TEM and electrically measured with impedance spectroscopy; it is apparent that the B-DNDs studied here do indeed support substitutional boron species and hence will be acting as semiconducting diamond nanoparticles. Evidence for moderate doping levels in some particles (~1017 B cm−3), is found alongside the observation that some particles are heavily doped (~1020 B cm−3) and likely to be quasi-metallic in character. The current study has therefore shown that substitutional boron doping in nm NDs is in fact possible, opening-up the path to a whole host of new applications for this interesting class of nano-particles.

Growth mechanism and wave-absorption properties of multiwalled carbon nanotubes fabricated using a gaseous detonation method

Multiwalled carbon nanotubes (MWCNTs) were fabricated via the detonation of a mixed gas consisting of ferrocene vapor, methane, and oxygen. The samples were characterized using transmission electron microscopy, X-ray diffraction, Raman spectroscopy, vibrating sample magnetometry, and a vector network analyzer. The results indicate that the samples were MWCNTs that were about 30 nm in external diameter, about 15 nm in inner diameter. The ferrocene dosage had an obvious effect on the morphology, degree of graphitization, and magnetic property of the MWCNTs. The growth mechanism of the MWCNTs in the gaseous detonation process was discussed using the detonation Zeldovich-von Neumann-Döring model and a vapor-liquid-solid growth model. The minimum reflection loss of the MWCNTs was −6.1 dB at 11.2 GHz with a thickness of 2 mm, which is lower than that of the MWCNTs prepared via other methods, and the reasons for this result are analyzed in the paper.

On the deflagration-to-detonation transition (DDT) process with added energetic solid particles for pulse detonation engines (PDE)

In this paper, numerical simulations are performed to study the dynamics of the deflagration-to-detonation transition (DDT) in pulse detonation engines (PDE) using energetic aluminum particles. The DDT process and detonation wave propagation toward the unburnt hydrogen/air mixture containing solid aluminum particles is numerically studied using the Eulerian–Lagrangian approach. A hybrid numerical methodology combined with appropriate sub-models is used to capture the gas dynamic characteristics, particle behavior, combustion characteristics, and two-way solid-particle–gas flow interactions. In our approach, the gas mixture is expressed in the Eulerian frame of reference, while the solid aluminum particles are tracked in the Lagrangian frame of reference. The implemented computer code is validated using published benchmark problems. The obtained results show that the aluminum particles not only shorten the DDT length but also reduce the DDT time. The improvement of DDT is primarily attributed to the heat released from surface chemical reactions on the aluminum particles. The temperatures associated with the DDT process are greater than the case of non-reacting particles added, with an accompanying rise in the pressure. For an appropriate range of particle volume fraction, particularly in this study, the higher volume fraction of the micro-aluminum particles added in the detonation chamber can lead to more heat energy released and more local instabilities in the combustion process (caused by the local high temperature), thereby resulting in a faster DDT process. In essence, the aluminum particles contribute to the DDT process of successfully transitioning to detonation waves for (failure) cases in which the fuel gas mixture can be either too lean or too rich. With a better understanding of the influence of added aluminum particles on the dynamics of the DDT and detonation process, we can apply it to modify the geometry of the detonation chamber (e.g., the length of the detonation tube) accordingly to improve the operational performance of the PDE.

Laser intensity and absorbance measurements by tunable diode laser absorption spectroscopy based on non-line fitting algorithm

A novel approach to using tunable diode laser absorption spectroscopy (TDLAS) is developed for measuring the laser intensity and absorbance of gas with highly broadened and congested spectra by wavelength division multiplex (WDM) technology. Direct absorption spectroscopy with non-linear algorithm is utilized, because this fitting method offers benefits in dealing with blended spectral features according to the relationship between transmitted laser intensity and absorbance by Beer law. Compared with traditional TDLAS sensing with WDM, this approach has some advantages of transmissions demultiplexing without additional optic gratings and detectors. Following the published theory, the absorbance and transmitted laser intensity are incorporated into an improved non-linear fitting model. A solution to a simulation of CO2 blended spectrum at a pressure of 5 atm is exploited to demonstrate the ability to recover the absorption in a high pressure environment, inferring the optimal combination of parameters in the model. The influences of these nonideal laser effects, such as nonlinear and linear coefficients, are investigated by the multiplexed transmission simulations at rovibrational transitions of H2O near 7444 cm-1 and 7185 cm-1. Errors in absorbance fitting is larger when nonlinear or linear coefficients of two lasersbecome closer. The satisfied results can be obtained when linear coefficients ratio is limited whitin a range from 0.05 to 0.67. In addition, the essential transition spacing in multiplexed transmissions, larger than the full width of transitions, is considered to be able to improve the fitting accuracy. This approach is validated in a static absorption cell over a pressure range from 1 to 10 atm at room temperature to demonstrate the ability to measure the blended CO2 spectrum from 63307 cm-1 to 6337 cm-1 by a single DFB laser. The sensor method resolves laser intensity with a nonlinear coefficient of 1.4×10-4 and recovers absorbance with a root mean square (RMS) precision of 3.2%, which demonstrates the applicability of this sensor to high-pressure gas sensing systems. Another approach to validating the gas temperature and measuring H2O by WDM is presented in a gas-liquid two phase pulsed detonation engine running with a filling fraction of 100%. Two fiber coupled lasers, respectively, near 7185.6 cm-1 and 7444.35 cm-1 are scanned at 20 kHz to achieve a temporal resolution of 50 μs for monitoring detonation exhaust. A fixed spectrum interval (about 0.7 cm-1) of transitions in multiplexed transmission is created through temperature adjustment in DFB laser to provide more independent absorption information. Recovered linear coefficients of 0.18 and 0.46 in two DFB lasers are in good agreement with the results from the simulations. An instantaneous temperature measurement of 1183 K in the exhaust 7.45 ms after detonation wave provides the confirmation of the ability of this method to infer the temperature and H2O time histories in the whole detonation process. In conclusion, the novel approach based on TDLAS has tremendous potential applications in high pressure combustion diagnosis and WDM spectrum analysis.

Методика исследования процессов горения и детонации каменноугольной пыли в горных выработках

Методика исследования процессов горения и детонации каменноугольной пыли в горных выработках

Explosive detonation causes an increase in soil porosity leading to increased TNT transformation.

Explosives are a common soil contaminant at a range of sites, including explosives manufacturing plants and areas associated with landmine detonations. As many explosives are toxic and may cause adverse environmental effects, a large body of research has targeted the remediation of explosives residues in soil. Studies in this area have largely involved spiking ‘pristine’ soils using explosives solutions. Here we investigate the fate of explosives present in soils following an actual detonation process and compare this to the fate of explosives spiked into ‘pristine’ undetonated soils. We also assess the effects of the detonations on the physical properties of the soils. Our scanning electron microscopy analyses reveal that detonations result in newly-fractured planes within the soil aggregates, and novel micro Computed Tomography analyses of the soils reveal, for the first time, the effect of the detonations on the internal architecture of the soils. We demonstrate that detonations cause an increase in soil porosity, and this correlates to an increased rate of TNT transformation and loss within the detonated soils, compared to spiked pristine soils. We propose that this increased TNT transformation is due to an increased bioavailability of the TNT within the now more porous post-detonation soils, making the TNT more easily accessible by soil-borne bacteria for potential biodegradation. This new discovery potentially exposes novel remediation methods for explosive contaminated soils where actual detonation of the soil significantly promotes subsequent TNT degradation. This work also suggests previously unexplored ramifications associated with high energy soil disruption.

Experimental and Numerical Studies of Sheet Metal Forming with Damage Using Gas Detonation Process

Gas detonation forming is a high-speed forming method, which has the potential to form complex geometries, including sharp angles and undercuts, in a very short process time. Despite many efforts being made to develop detonation forming, many important aspects remain unclear and have not been studied experimentally, nor numerically in detail, e.g., the ability to produce sharp corners, the effect of peak load on deformation and damage location and its propagation in the workpiece. In the present work, DC04 steel cups were formed using gas detonation forming, and finite element method (FEM) simulations of the cup forming process were performed. The simulations on 3D computational models were carried out with explicit dynamic analysis using the Johnson–Cook material model. The results obtained in the simulations were in good agreement with the experimental observations, e.g., deformed shape and thickness distribution. Moreover, the proposed computational model was capable of predicting the damage initiation and evolution correctly, which was mainly due to the high-pressure magnitude or an initial offset of the workpiece in the experiments.

Failure modes and effect analysis of concrete gravity dams subjected to underwater contact explosion considering the hydrostatic pressure

Abstract To better understand damage characteristics of concrete gravity dams under contact explosion is a critical issue to evaluate the protective performance of dams. In this paper, a fully coupled Lagrangian-Eulerian numerical approach, incorporating the detonation process of underwater contact explosion, is performed to predict the damage propagation of a typical concrete gravity dam. In order to verify the validity of the coupled algorithm, damage profiles of a normal strength reinforced concrete (RC) slab subjected to contact explosion are predicted and compared with the published experimental results. The hydrostatic pressure of the reservoir is modeled by using the specific internal energy method. The interaction between detonation products and dam-foundation-reservoir systems is also considered. The detonation products development processes, shock wave propagation, and failure modes of the dam subjected to underwater contact explosion with and without considering the hydrostatic pressure are compared. In order to analyze the underwater contact explosion effects on failure modes and dynamic responses of the dam, three positions of the detonation point, i.e., upper blast point, middle blast point, and lower blast point, are considered in this study. The results show that the initial hydrostatic pressure has a significant influence on failure characteristics of the dam subjected to underwater contact explosion. Underwater contact explosion detonated in the lower zone will cause more serious damage to the dam heel and threaten the overall stability of the dam. Hence, more attention should be paid to the deep water contact explosion.

Boundary conditions in problems of studying the stability of a plane stationary detonation wave

The research’s problems of a plane stationary detonation wave’s stability are considered. It is shown that the boundary conditions for the two-front model allow estimating the main parameters of the internal structure of gas detonation. Such a model can serve as the basis for development of mathematical support and software for an intellectual decision support system for the problems of explosion-proof and explosion protection. An attempt has been made to systematize the problem of setting boundary conditions in studies of the stability of a detonation wave in order to further create a decision support system (DSS) on problems of explosion safety and explosion protection. The following models of a plane stationary detonation wave were considered, which the stability problem is stated for: 1) the Chapman-Jouget detonation model is the simplest model where the shock-detonation front is modeled by a direct shock wave, and all chemical transformations are assumed to occur instantaneously, directly at the front; 2) a two-front (single-stage, square-wave) model based on the assumption that chemical transformations also occur instantaneously, not on the leading shock front, but in a plane (called the instantaneous combustion front), which is separated from the leading shock front by the induction zone; 3) a multistage model that approximates the continuous distribution of parameters behind the leading shock front piecewise constant function; 4) a model with a continuous distribution of parameters behind the leading shock front, which most accurately reflects the real physical processes in a stationary detonation wave. These models are fundamentally different in boundary conditions, which small pertur-bations in the region separating the regions of the initial combustible medium and detona-tion products satisfy. The advantages and disadvantages of the models described above are both assessed from the standpoint of the correctness of the physical analysis of the detonation process and from the point of view of applicability for the mathematical support of DSS on problems of explosion safety and explosion protection. It is shown that the boundary conditions for the two-front model allow to estimate the main parameters of the internal structure of the gas detonation. Such model can be as the basis for the development of mathematical support and software of DSS for problems of explosion safety and explosion protection

Formation mechanism for oxidation synthesis of carbon nanomaterials and detonation process for core-shell structure

A novel formation mechanism according to the oxidative dehydrogenation of organics has been proposed for the low-temperature preparation of carbon-based nanomaterials. Several typical organics including ethanol, 1-butanol, p-cymene and liquid paraffin are used as precursors to react with ammonium persulfate (APS) in an autoclave, and carbon particles are obtained as a validation. The reaction characteristics are comprehensively investigated by the differential scanning calorimetric and thermogravimetric analysis. The strongly exothermic oxidation reaction below 200 °C is a common feature during the process. The organic molecules are cleaved into small carbon species and further transform to amorphous carbon. When the organometallic compound is used as a reactant instead, such as magnesocene and allyltriphenyltin, carbon encapsulated MgO and SnS nanocrystals with core-shell structure are synthesized, respectively. A detonation introduced by the violent reaction occurs in the process with a very rapid liberation of heat and large quantities of thermally expanding gases. The large amounts of free atomic/radical species and reactive intermediates are generated as sources for the core-shell structure. It is a common strategy for the large scale production of carbon encapsulated oxide/sulfide nanocrystals by means of the moderate detonation process of the organometallic compound and APS in an autoclave.

Mathematical description of ignition, combustion and propagation of detonation in reacting gas mixtures in the presence of micro- and nanoparticles

The physical and mathematical models for the description of the processes of ignition, combustion and propagation of detonation in mixtures of hydrogen-oxygen, methane-oxygen and silane-air in the presence of inert micro- and nanoparticles were proposed. On the basis of these models the dependencies of detonation velocity deficit vs the size and concentration of inert micro- and nanoparticles were found. Two modes of detonation flows in gas suspensions of reactive gases and inert nanoparticles were revealed: - propagation of weak detonation wave in the gas suspension, - destruction of the detonation process. It was determined that the mechanisms of detonation suppression by micro- and nanoparticles are closed and lies in the splitting of a detonation wave to frozen shock wave and ignition and combustion wave. Concentration limits of detonation were calculated. It turned out that in the transition from microparticles to nanoparticles the detonation suppression efficiency does not increase.

Numerical simulation of classical and rotating detonation waves in methane mixtures

A numerical simulations of a two-dimensional multi-front irregular structure of the detonation wave (DW) in methane-based mixtures at normal initial condition have been conducted. The computations have been performed in a wide range of channel height. From the analysis of the flow structure and the number of primary transverse waves in channel, the dominant size of the detonation cell for studied mixtures has been determined. We have simulated the cellular front structure in stoichiometric methane–air and methane–oxygen mixtures, and in a rich (equivalence ratio φ = 1.5) methane-air mixture. Based on the fundamental studies of front structure of the classical propagating DW in methane mixtures, numerical simulation of continuous spin detonation of rich (ϕ = 1.2) methane-oxygen mixture has been carried out in the cylindrical detonation chamber (DC) of the rocket-type engine. We studied the global flow structure in DC, and the detailed structure of the front of the continuous rotating DW. Integral characteristics of the detonation process - the distribution of average values of static and total pressure along the length of the DC, and the value of specific impulse have been obtained. The geometric limit of stable existence of rotating DW has been determined.

Study on the effects of ionization seeds on pulse detonation characteristics

Ionization phenomenon is happened on the wave front due to the presence of high temperature and pressure in the detonation process. Plasma produced in the detonation process can be used as magnetohydrodynamic (MHD) generator or flow controlled by the external magnetic field. However, it is necessary to increase the ionization efficiency by adding metal ions with lower ionization potential owing to the limited amount of plasma produced by detonation. In this paper, a model of pulse detonation engine with ionization seeds was established. The Conservation Element and Solution Element (CE/SE) method was deduced to simulate the interaction between plasma and detonation process. The influence of ionization seed contents on the electrical conductivity and detonation characteristic parameters was analyzed, and the MHD control of detonation process was realized by adding the external electromagnetic field device. The results showed that it had a little influence on the detonation process but a great influence on the generation of detonation plasma by the addition of a certain amount of ionized seed. The ion mass fraction and electrical conductivity in the detonation tube were first increased and then decreased with the increase of ionization seed content, which reached the maximum at the ionization seed mass fraction of 0.05. The acceleration and deceleration process could be achieved by the MHD control.

A comparison of methods for detonation pressure measurement

Detonation pressure is an important parameter describing the process of detonation. The paper compares three methods for determination of detonation pressure on the same explosive charge design. Pressed RDX/wax pellets with a density of $$1.66 \hbox { g cm}^{-3}$$ were used as test samples. The following methods were used: flyer plate method, impedance window method, and detonation electric effect. Photonic Doppler velocimetry was used for particle velocity measurements in the first two cases. The outputs of the three methods are compared to the literature values and to thermochemical calculation predictions.

2nd All-Russian Scientific Conference Thermophysics and Physical Hydrodynamics with the School for Young Scientists

10 September 2017Preface for the TPH 2017 – Thermophysics and physical hydrodynamics conferenceProceedings of the TPH 2017 – Thermophysics and physical hydrodynamics conferenceD. M. Markovich, S.V. GolovinThe origins of the Conference start from 1970 in the Soviet Union, Novosibirsk. It was organized by Kutateladze Institute of Thermophysics SB RAS. The name of the conference was “Actual problems of thermophysics and physical hydrodynamics”. The conference has been organized under this name up to 2015. The conference chairs were Academician V.E. Nakoryakov, Prof. D.M. Marckovich and Prof. S.V. Alekseenko. Peer reviewed proceedings of the conference have been published in the format of printed books. In 2016 the conference is reorganized in a new format with a shorter name: “Thermophysics and physical hydrodynamics”.The conference takes place in Yalta, a beautiful city in Crimea on the bank of the Black Sea. Lavrentev Institute of Hydrodynamics and the National committee on Heat and Mass Transfer are among other conference organizers besides Kutateladze Institute of Thermophysics. The present Conference covers the following topics: heat transfer and hydrodynamics in single phase and multiphase flows, reacting flows, detonation processes, experimental and numerical techniques in thermophysics and physical hydrodynamics, heat transfer and hydrodynamics in industrial processes. There are more than 150 participants. The proceedings contain 98 papers grouped by topic.The scientific committee appreciates the enormous work of the editorial board and reviewers in the preparation of this volume. We would like to express our sincere thanks to all authors for their research contributions, and also to organizers of the conference for their valuable spadework.

An experimental study on the onset of detonation downstream of a perforated plate with staggered orifices

The present study investigated the onset of detonation (OD) process which takes place downstream of a 0.9-mm-thick perforated plate. The orifice diameter of the plate is 1.6 mm with a blockage of 59%, and it was placed perpendicular to the axial direction of a smooth detonation tube. ‘Stable’ mixture C2H2 + 2.5O2 + 70%Ar and ‘unstable’ mixture C2H2 + 5N2O were tested, respectively. Ionization probes and smoked foils were used to record detonation velocities and corresponding cellular patterns. Excellent agreement of the velocity trends and smoked foil results shows that a critical pressure range exists to identify ‘go’ and ‘no go’ of OD downstream of the perforated plate. However, the OD mechanisms for these two gaseous mixtures are distinct: for the ‘stable’ mixture, OD occurs in the downstream near field (6 tube diameters in this study), whereas, OD in the ‘unstable’ mixture could also observed in the far field via the transition of deflagration to detonation after a long duration of quasi-steady regime. This distance reaches up to tens of tube diameters when close to the critical pressure.

Multiple Reaction Pathways in Shocked 2,4,6-Triamino-1,3,5-trinitrobenzene Crystal

Detonation processes probed with atomistic details have remained elusive due to highly complex reactions in heterogeneous shock structures. Here, we provide atomistic details of the initial reaction pathways during shock-induced decomposition of 2,4,6-triamino-1,3,5-trinitrobenzene (TATB) crystal using large reactive molecular dynamics simulations based on reactive force fields. Simulation results reveal the existence of three competing intermolecular pathways for the formation of N2. We also observe the formation of large nitrogen- and oxygen-rich carbon aggregates, which delays the release of final reaction products.

An experimental study of the propagation characteristics for a detonation wave of ethylene/oxygen in narrow gaps

To investigate the propagation characteristics of a detonation wave in a narrow gap, the detonation processes of a stoichiometric ethylene-oxygen mixture were studied at different initial pressures in narrow gaps ranging 1.0–4.0mm in height. Flame propagation through the narrow gap was observed with a high-speed camera, and the trajectories of triple points on the detonation waves were obtained using a soot-deposition plate. The results showed that both higher initial pressure p0 and lower narrow gap height h could accelerate the deflagration-to-detonation transition process and determine how the detonation wave propagates, e.g., galloping detonation, stuttering detonation, and stable detonation. To attain unstable detonation propagation, the corresponding range of initial pressures increased with decreasing height of the narrow gap. A smaller height of the narrow gap led to a higher initial pressure threshold corresponding to the detonability limit. This could be determined by the range of h/λ; the onset of galloping detonation occurred when 0.17<h/λ<0.27. Since the effect of the boundary layer on detonation propagation could not be neglected in narrow gaps, the velocity deficits were relatively large compared with those from a large scale channel. It was found that the velocity deficits were inversely proportional to the narrow gap height and initial pressure, and the relation between them was obtained by fitting the experimental data, i.e., ΔD=0.65h-0.8p0-0.5.