Shock Wave Compression Research Articles

Effects of discharge parameters on plasma acceleration and transmission characteristics of a coaxial gun operated in gas-prefilled mode

The effects of discharge parameters on the discharge process and plasma transport characteristics of a coaxial gun in the gas-prefilled mode are studied. The plasma optical intensity and ejection velocity are measured by photodiodes, the optical emission spectrum is taken by a spectroscopic system, and the plasma evolution in the transport process is captured by a high-speed camera. The plasma acceleration characteristics under different discharge parameters show that the velocity and electron density of the ejection plasma are mainly determined by the pre-filled pressure and discharge current, which is consistent with the snowplow model. The kinetic energy of ejection plasma can be significantly increased by reducing the outer loop inductance, which is conducive to increasing the energy utilization efficiency. The time-varying images of plasma radiation and the plasma density at different transport locations illuminate the transmission characteristics of coaxial gun discharge plasma. The results show that the snowplow effect continues to play a role in the plasma transport process, and the plasma accumulation is induced by the combination of shock wave compression. The current-driven magneto hydrodynamics instability occurs during the transport process, and the luminous signal of the plasma current sheet oscillates periodically. In addition, the plasma impact effect is obvious and the gas retarding effect is enhanced with the increase in the gas pressure. These results give us a more comprehensive view of the coaxial gun discharge process and plasma transport and provide a certain reference for optimizing the parameters selection and physical design of coaxial gun discharge plasma characteristics.

Ab initio simulation of the dynamic shock response of single crystal and lightweight multicomponent alloy

The dynamic response of shock wave impact on single crystal aluminium and lightweight multicomponent alloy Al-Cu-Li-Mg is simulated by using the combination of Ab initio Molecular Dynamics (AIMD) and Multi-Scale Shock Technique (MSST), with the analysis carried out at the atomic/electronic levels. The simulation is verified by comparing the particle velocity of single crystal obtained in this work with the data in literature. The shock compression process not only involves the migration of atoms, but also is related to electronic transition. Two stages could be found in the shock compression process: oscillatory compression of the crystal cell and oscillatory migration of the atoms. The crystal structure of the multicomponent alloy could be disordered even at low shock speed, due to the difference in the ability to migrate between different kinds of atoms. As the sample is shock-compressed, the contribution proportion of crystal orbitals shows a sharp decrease for D orbital, while it increases significantly for S orbital and P orbital. The electron structure shows a quicker response to the shock wave compression process than the crystal structure. The orbital contribution from P orbital of the crystal is mainly due to the P orbital of Al atoms, while the orbital contribution from D orbital of the crystal is mainly due to the D orbital of Cu atoms. Total Density of States (TDOS) is mainly contributed by the Projected Density of State (PDOS) of Cu atoms in the occupied state of energy levels, while it is close to the PDOS of Al atoms in the non-occupied state of energy levels.

Role of solid solution strengthening on shock wave compression of [111] copper crystals

Role of solid solution strengthening on shock wave compression of [111] copper crystals

INFLUENCE OF PARAMETERS OF OPERATING CONDITIONS OF SELECTIVE LASER MELTING ON SPALL FRACTURE KINETICS OF 12Cr18Ni10Ti STEEL

The results are presented with regard to experimental studies of dynamic strength characteristics of samples made of 12Cr18Ni10Ti steel powder. They were obtained through selective laser melting with various parameters of a technological process at shock-wave compression up to pressures of ~7 GPa. Critical parameters of a process, in addition to powder characteristics, include laser operating conditions: a laser spot diameter, laser power, a laser beam scanning velocity, as well as a powder layer thickness, protective atmosphere, etc. It has been demonstrated that an increase in the scan laser power and a decrease in a powder layer thickness bring about a decrease in a number of internal defects in initial structures of samples. The results are given, which compare strength characteristics of these steels with properties of steel produced by a traditional technique of hot rolling. Shock-wave experiments were carried out using a light gas gun-type facility, which makes it possible to accelerate flat impactors to speeds of ~700 m/s; internal wave processes in samples were reproduced when recording a rate of movement of the sample's free surface via a PDV laser interferometer; a degree of spall fracture was determined by the help of a metallographic analysis of samples recovered in tests. It has been showed that steel samples made through a selective laser melting technique have high spall strength and a lower degree of damage compared to hot-rolled steel under the same conditions of high-speed shock loading. According to the results of the metallographic studies, the presence of internal defects in initial structures of samples associated with a choice of operating conditions of a manufacturing process does not affect a degree of their spall damage. At the same time, a wave pattern of shock wave propagation differs significantly for samples with and without defects.

The role of κ‐deformed Kaniadakis distributed electrons on the dust ion‐acoustic waves in charge‐varying dusty plasma

AbstractThe one‐dimensional dynamics of nonlinear electrostatic dust‐ion acoustic waves (DIAWs), in a plasma containing Kaniadakis‐distributed electrons, fluid ions, and variable‐charge dust grains has been investigated. The κ−generalized electron charging current is derived based on the orbit‐motion limited approach. The reductive perturbation technique has been used to derive a KdV Burger equation of propagation. We have highlighted the dependence between the values of the dust particles charge Qd0 and the validity domain of the Kaniadakis parameter κ, where the Burger term C has positive. By integrating the KdV Burger equation numerically and assuming a laboratory dusty plasma, a transition from oscillatory to monotonic shock waves is observed with increasing values of κ. We have also found that the phase velocity of DIA shock waves decreases, and the dissipation can prevail over that of dispersion as the electrons move further away from thermal equilibrium (κ is increased). The coexistence of compressive and rarefactive of monotonic shock profile is observed. It is found that an increase in κ leads to an increase of the compressive monotonic shock wave and decrease the rarefactive monotonic shock wave.

Numerical Investigation on the Effect of Wet Steam and Ideal Gas Models for Steam Ejector Driven by Ship Waste Heat

Steam ejectors could improve the energy efficiency of ships by efficiently utilizing low-grade waste heat from ships for seawater desalination or cooling. The internal flow characteristics of steam ejectors can be deeply analyzed through numerical simulation, which is of great significance for improving their performance. Due to the influence of the nonequilibrium phase change, the results of the wet steam model and the ideal gas model are significantly different. In this paper, the flow field characteristics of the wet steam model and the ideal gas model under different primary flow pressures (Pm) are compared and analyzed. The results show that the structures of the shock wave train for the wet steam model and the ideal gas model are different under different Pm. When the first shock wave of the shock wave train changes from a compression shock wave to an expansion shock wave, the Pm for the ideal gas model is 75,000 Pa and that for the wet steam model is 55,000 Pa. The phase change reduces the energy loss of the shock wave. With the increase in the Pm, the variation in the length of the shock wave train for the wet steam model decreases by 61%, the variation of the primary temperature at the nozzle exit increases by 60% and the variation in the choke temperature decreases by 50% compared with the ideal gas model. The investigation in this paper provides guidance for the design theory of a ship waste heat steam ejector.

Effect of dimensionless vent ratio on the flame-shock wave evolution dynamics of blended LPG/DME gas explosion venting

To reveal the flow field-shock wave-flame coupling evolution law of LPG/DME blended gas explosion venting under different dimensionless vent ratio(KV), the numerical model for multi-blended gas explosion venting was established and research of blended gas explosion venting at KV = 0.02–0.21 was carried out based on experimental verification. The results show that, after the vent opens, the turbulence intensity increases, the velocity gradient of the flow field increases, the maximum explosion wind velocity(Vmax) of the outfield varies linearly with KV, and the flame of “mushroom shape” is elongated, and “break flame” occurs under the action of the relative motion of “primary and secondary vortex group”. When KV＞0.02, the flame propagation velocity increases locally because of the thermal-mass diffusion instability, and with increasing KV, the average flame propagation velocity decreases from 258.29 m/s to 226.58 m/s. In the process of explosion venting, a typical shock wave fluctuating pressure waveform curve is formed in the outfield. Under the combined action of the infield pressure venting effect and the outfield turbulence intensity, the maximum explosion overpressure in the outfield (Pmax) reaches maximum 423.97 kPa at KV = 0.07. Meanwhile, the larger the KV, the greater the shock wave velocity due to the lead role of the infield explosion venting shock wave and outfield flame compression shock wave on the shock wave propagation velocity.

МЕТАЛЛОКЕРАМИЧЕСКИЕ МАТЕРИАЛЫ, ПОЛУЧАЕМЫЕ ВЗРЫВНЫМ ПРЕССОВАНИЕМ СМЕСЕЙ ПОРОШКОВ КАРБИДОВ С ТИТАНОМ

The main principles of the formation of metal-ceramic materials of the Cr3C2-Ti and SiC-Ti systems during explosive pressing of powder mixtures on a steel base are considered. It has been established that the formation of strong interfaces between carbide (Cr3C2 or SiC) and titanium occurs at the temperature of heating the powder mixture as a result of shock wave compression to (0.35...0.4)Tm of the carbide phase. In this case, the chemical composition of the alloy components does not undergo changes, the redistribution of elements between phases in macrovolumes does not occur, and the hardness reaches its maximum level.

Enhancing Energy Efficiency in Jet Ejectors: A Computational Fluid Dynamics Investigation

Abstract: This study investigates the analysis of the operating modes of two distinct jet ejector types, namely, Constant Rate of Momentum Change (CRMC), Constant Pressure Mixing (CPM). Computational Fluid Dynamics (CFD) was employed to thoroughly examine and evaluate their respective geometrical attributes. Through our comprehensive scrutiny, we ascertained the notably superior performance of CRMC ejectors. This superiority is primarily linked to the continuous presence of compression shock waves within the flow processes of CRMC, which consequently lead to comparable or even diminished critical condenser pressures. The core objective of this research is to advance the application of jet-ejector refrigeration technology, especially for the efficient harnessing of low-grade waste heat, thereby contributing to enhanced energy efficiency and sustainable cooling solutions. We concentrated on two operational modes, CRMC and CPM, and employed CFD to analyze the geometry of these ejectors. We found a particular configuration called RSO-2 that demonstrated exceptional performance after carrying out extensive experiments encompassing 53 different parameter combinations using the Taguchi Design of Experiments. With regard to the throat inlet, RSO-2 demonstrated an exceptional mass flow rate of 5.28E+05 J kg-1 and a Mach number of 1.5418 at the throat exit. Furthermore, a strong correlation was found between the diameter of the throat and the radius of the mixing chamber, as revealed by our thorough sensitivity analysis. This discovery offers important new information for the development of jet ejector designs.

Ultrafast x-ray detection of low-spin iron in molten silicate under deep planetary interior conditions.

The spin state of Fe can alter the key physical properties of silicate melts, affecting the early differentiation and the dynamic stability of the melts in the deep rocky planets. The low-spin state of Fe can increase the affinity of Fe for the melt over the solid phases and the electrical conductivity of melt at high pressures. However, the spin state of Fe has never been measured in dense silicate melts due to experimental challenges. We report detection of dominantly low-spin Fe in dynamically compressed olivine melt at 150 to 256 gigapascals and 3000 to 6000 kelvin using laser-driven shock wave compression combined with femtosecond x-ray diffraction and x-ray emission spectroscopy using an x-ray free electron laser. The observation of dominantly low-spin Fe supports gravitationally stable melt in the deep mantle and generation of a dynamo from the silicate melt portion of rocky planets.

Анализ действия детонационного генератора низкоамплитудных импульсов давления регулируемой длительности

The paper presents results of the analysis conducted on the action of the low-amplitude pressure pulse detonation generator with adjustable duration, where the detonation wave affects the controlled compressible medium and propagates in the direction from the medium subjected to the shock wave compression. Analytical expressions are provided for a simple model of the process under study to calculate the pressure pulse amplitude-time characteristics on the compressible medium with the charge detonation product plane-symmetric flow and the compressible inert medium. The paper considers a scheme of experimental (laboratory) assembly. In its cylindrical channel, the detonation product quasi-one-dimensional effect on the controlled environment is realized. Results of registering dynamics of pressure alterations in the controlled environment were obtained. When comparing calculation and experiment results, the reasons causing their discrepancy were identified. If the assembly body is made of steel not subjected to heat treatment, then it becomes possible to use it five times (at least) with charges of the bulk explosives based on the hexogen with generating controlled pressure pulses of several kilobars in the condensed organic materials with duration of at least tens of microseconds. In this case, the pressure rise time at the pulse leading edge reaches approximately ten microseconds.

Selection of Material and Thickness of the Protective Wall in the Conditions of a Hydrogen Explosion of Various Power

The main purpose of this study is a numerical assessment of the consequences of an explosion of a hydrogen-air cloud on the personnel of a hydrogen fueling station and the strength of a protective solid wall of certain dimensions. An explosive gas mixture is formed as a result of the destruction of high-pressure cylinders, the number of which determines the size of the cloud, the power of the explosion, and the scale of the consequences of environmental impact. To obtain the spatio-temporal distribution of the maximum overpressure and the impulse of the shock wave compression phase, a mathematical model of the dispersion of an active gaseous admixture is used, taking into account the chemical interaction with air oxygen. The probable consequences of the shock-impulse impact on the personnel at the control point are carried out using probit analysis. The values of the maximum bending moment and stress at the base of the protective wall, which result from the impact of the blast wave, are used to deterministically estimate the minimum wall thickness necessary for the safe operation of the protective device. The mathematical model takes into account the complex terrain and the three-dimensional non-stationary nature of the shock wave propagation process, and it is a source of data necessary to solve the problem of the strength of solid objects located in the area of baric perturbation of the gaseous medium. The developed methodology makes it possible to carry out a comparative analysis of the effectiveness of protective structures in relation to the power of the explosion.

Equations of State for Calculating the Pressures of Shock-Wave Compression of Pentaerythritol Tetranitrate (PETN)

Equations of State for Calculating the Pressures of Shock-Wave Compression of Pentaerythritol Tetranitrate (PETN)

Investigation on improvement potential of steam ejector performance in refrigeration cycle via constant rate of momentum change design method

In this paper, an ejector created by the constant rate of the momentum change method (CRMC ejector) was experimentally studied and compared with the widely used constant pressure method (CPM ejector) under the same ejector area ratio. The influence of the boiler temperature, evaporator temperature, and primary nozzle size on the ability to improve the performance of the CRMC ejector was examined. The results indicated that at the same ejector area ratio, the CRMC ejector always performed a higher mass entrainment ratio than the CPM ejector. However, the critical condenser pressure was similar. The average percent improvement of the entrainment ratio via the CRMC ejector was approximately 20%. Based on the photograph taken from the transparent ejector, a compression shock wave was still found in the flow process of the CRMC ejector. This shows that an improvement potential of the CRMC ejector does not concern the compression shock wave as proposed in the design theory. The key to improvement was believed to be its ability to mitigate the momentum loss during the mixing process. In such a case, some simulation works based on computational fluid dynamics (CFD) were employed for explanation. This can also confirm that the compression shock wave via CRMC ejector is still found. In addition, this paper compared the experimental results with the theoretical results obtained from 1-D theory and CRMC theory to alternatively discuss that an improvement potential of the CRMC ejector was mainly the cause of a lower mixing loss.

Micro-holes’ effect on energy absorption ability in three-dimensional brittle materials under impact loading: A preliminary research

Brittle protective structures often fracture under shock wave compression, which will have a constraining effect on their structural design. A suitable three-dimensional micro-hole shape can improve the brittle materials' energy absorption ability. This paper uses a three-dimensional lattice point-spring model with rotating angle to study the effect of micro-holes’ shape and arrangement on energy absorption ability in three-dimensional brittle materials. In this paper, a three-dimensional lattice point-spring model with rotating angle is used to examine the effect of the micro-holes’ shape and arrangement on the three-dimensional brittle materials’ energy absorption ability. This model can effectively simulate brittle material’s elastic and fracture characteristics. The research results demonstrate that the evolution of the shock wave profile is strongly affected by the shape of the micro-holes. When arranged in a regular triangular prism, the concave decahedral holes, which have a negative Poisson’s ratio, can cause a strong impact deformation and have a good energy absorbing ability. This paper’s results can provide some ideas for designing brittle structures with the best impact resistance.

Effect of micro-hole shape and arrangement on the impact properties of three-dimensional isotropic brittle structures

Brittle structures often fracture under shock wave compression, which will have a constraining effect on their structural design. By introducing and designing suitable three-dimensional micro-hole shapes, the ability of brittle structures to resist impacts can be effectively improved. This paper examines the impact characteristics of the three-dimensional isotropic brittle structure's micro-hole shape and arrangement using the lattice spring model with rotational freedom degrees. The model effectively simulates brittle materials’ mechanical properties and fracture characteristics and overcomes the lattice point-spring model's fixed Poisson's ratio limitation. The research results demonstrate that micro-hole shape strongly affects shock wave profile evolution. When arranged in a regular triangular prism, the concave decahedral holes, which have a negative Poisson’s ratio, can cause a strong impact deformation and a good energy absorbing effect. This paper’s results can provide some ideas for designing brittle structures with the best impact resistance.

Combining the Tait equation with the phonon theory allows predicting the density of liquids up to the Gigapascal range

Predicting the density of liquids at ultrahigh pressures in the case when only the data measured at ambient pressure are available is a long-standing challenge for thermodynamic research. In this work, we archived this goal for molecular liquids by applying the half-sum of the Tait equation and the Murnagnan equation in the form coordinated with Tait’s at low pressure for predicting the density of molecular liquids up to the pressures more than 1 GPa with uncertainty comparable with the experimental one. It is shown that the control parameter, which is needed in addition to the initial density and the isothermal compressibility can be found using the speed of sound and the density at ambient pressure and has a clear physical interpretation in terms of the characteristic frequency of intermolecular oscillation mimicking the limiting frequency of Debye’s theory of heat conductivity of solids. This fact is discussed as arguing in favour of the modern phonon theory of liquid thermodynamics and expands it range of applicability to the volumetric properties of liquids at temperatures far below the critical one. The validity of the model is illustrated with the case study of classic Bridgman’s dataset as well as with some examples of ultrahigh-pressure data obtained by the diamond anvil cell and shock wave compression methods.

Injury and death to armored passenger-vehicle occupants and ground personnel from explosive shock waves

This study evaluated the risks for injury and death to occupants from blast waves to the side and underbody of an armored passenger-vehicle and to ground personnel from free-field blast waves. The Kingery-Bulmash empirical relationships for explosive shock waves were augmented by the Swisdak empirical relations for stand-off distances up to Z = 39.8 m/kg1/3 to tabulate shock-wave characteristics using the Friedlander wave-shape. A 15 kg, hemispherical explosion was analyzed in detail for the shock wave velocity and compression of air behind the wave front. An armored SUV was analyzed with Z = 1.6 m/kg1/3 (4 m) standoff distance from pressure loading on the near-side, far-side and underbody. The rigid body displacement was 0.36 m and 7.8° yaw for a side loading. When a segment of the occupant compartment accelerates inward, there are risks for injury from the intrusion. Energy is transferred to the occupant by deformation of their body (Ed) and by velocity increasing the kinetic energy of the body region (Ek). Body deformation injures an occupant by exceeding the tolerable compression (crush mechanism) or exceeding the rate-dependent tolerance, which is defined by the rate times the extent of compression (viscous mechanism). The risk for injury and death to ground personnel was analyzed for free-field blast waves by stand-off distance and TNT weight. A 15 kg charge posed a 99% risk of death at 3.9 m, 50% risk at 5.2 m, 1% risk at 7.8 m and injury threshold at 8.2 m. A 100 kg charge posed a 99% risk of death at 8.5 m, 50% risk at 11.6 m, 1% risk at 17.3 m and injury threshold at 18.0 m. The study describes the steps to analyze blast loading of an armored passenger-vehicle for risks of occupant injury. It describes the steps to analyze injury risks to ground personnel from blast wave pressure.

Application of fourier method to study propagation of compression shock wave in pipelines with damper

The transition problems from one mode of steady flow to another in a pipeline with a constant gradient are considered. The pressure value is set at the inlet to the section, and an air chamber of a certain volume is installed at the outlet. Modeling of the process of compression shock wave propagation in an elementary section of the pipeline was conducted according to the linearized quasi-one-dimensional N.E. Zhukovskymodel, and the damper was considered according to the I.A. Charny model. The problem is solved by the method of separation of variables. It is shown that at an increase in the volume of the damper, the amplitude and frequency of perturbations decrease due to the transient process.

A Review of Shock Wave Compression Rotary Engine Projects, Investigations and Prospects

Compression by shock waves is a specific way of compressing gases. It has been practically applied for many years in supersonic flying objects. The idea of using this method in rotary engines is extremely appealing because one disk can replace several or a dozen disks of an axial compressor, significantly reducing the weight and production costs of the engine and lowering the fuel consumption due to possible increased compression ratio. This paper presents a review of existing technical solutions and the results of published research devoted to the construction of shock wave compression rotary engines: patents, scientific publications describing various research methods, numerical calculations, and the experimental results of unusual technical solutions. The characteristic solutions and problems that arose during the implementation of these methods are presented and described. Judging from the presented overview, these have wide application possibilities, and an enormous intellectual and financial effort has been put into the construction of such engines. Conversely, there is a rather hermetic group of scientists involved in this activity.