Microwave emission from explosive plasma jets

Microwave emission from explosive plasma jets excited by RF pulses has been observed. Plasma jets excited by frequency-modulated signals have been studied, and the distributions of the number and duration of emission pulses over the microwave frequency range have been determined.     

Electron beam induced explosive luminescence of PETN

We have studied the spectrum and kinetics of optical emission in the wavelength range from 550 to 1000 nm accompanying explosive decomposition of pentaerythritol tetranitrate (PETN) single crystals initiated by a nanosecond electron beam. The explosive luminescence kinetics reveals two components with a continuous spectrum, identified as luminescence accompanying the explosive decomposition, and a component with a linear spectrum due to molecular nitrogen formed as a result of explosion.     

Peculiarities of the kinetics of explosive decomposition of silver azide initiated by a pulsed electron beam

We have studied the spectrum and kinetics of optical emission accompanying the explosive decomposition of silver azide crystals initiated by a nanosecond electron beam (0.25 MeV, 20 ns, 0.1–2 kA/cm²). The emission kinetics reveals a component observed during the initiating pulse action, whose spectrum coincides with the spectrum of preexplosive luminescence observed in the subsequent stages of the initiation reaction. It is shown that the explosive decomposition reaction is initiated directly during the electron beam action and has a nonmonotonic kinetics.     

PETN detonation initiated by a high-power electron beam

We have studied for the first time the physicochemical processes developed in pentaerythritol tetranitrate (PETN) under the action of a pulsed electron beam in a broad range of the beam power densities. Data on the pulsed cathodoluminescence spectrum and kinetics, explosive optical emission kinetics, and thresholds of the mechanical fracture and explosive decomposition of PETN are presented.     

The physical nature of the optical emission and absorption accompanying explosive decomposition of heavy metal azides

The kinetics and spatial characteristics of the optical emission and absorption have been studied in the course of explosive decomposition of silver azide initiated by a pulsed electron beam. The emission and absorption observed after the induction period reflect the process of formation and expansion of the products of chemical decomposition of silver azide.     

对称双线型聚能爆破技术数值模拟研究及应用

以直径28mm的煤矿许用炸药为研究对象,通过理论分析和数值模拟技术,设计一种带有对称双线型聚能槽的装药结构,使普通炸药具有聚能爆破作用。模拟研究表明,带有对称双线型聚能槽(65°夹角)的炸药在聚能方向做功能力得到提高,爆炸产物速度提高了35.7%,爆压提高了2.5倍。将此技术在煤矿岩巷掘进光面爆破中进行了应用,提高了光面爆破效果。     

The effects of the failure diameter of an explosive on its response to shaped charge jet attack

In order to shed some light on the response of explosives to the attack of small-diameter projectiles such as shaped charge jets, we conducted a computational study using the 2DE code and the Forest Fire explosive initiation model. Simulations of copper-jet attack against Composition B were made in order to determine modes of initiation and critical velocity for initiation as a function of jet diameter. We modeled the jet as a nonstretching cylindrical projectile with a flat tip. Its diameter was varied between 0.3 mm and 12.0 mm and its velocity was varied between 0.8 km/s. and 15.0 km/s. We observed two modes of initiation: (1) prompt, impact-mode initiation for both subsonic and supersonic penetration and (2) delayed, penetration-mode initiation only for supersonic penetration by small-diameter jets. The velocity threshold for large subsonic jets agrees with the Jacob-Roslund formula. For jets with diameters smaller than the failure diameter of the explosive they attack, higher velocities than predicted by Jacobs-Roslund are required for initiation. A critical threshold between impact- and penetration-mode initiation was determined over the entire supersonic range. A similar threshold between penetration-mode initiation and initiation failure has not yet been determined due to limitations of the code.     

Determining the temperature of silver azide explosion products

The spectrum and kinetics of optical emission accompanying the explosive decomposition of silver azide initiated by a nanosecond pulsed electron beam (250 MeV, 1000 A/cm², 10 ns) have been studied. Based on these data, it is established that the temperature of silver azide explosion products in the stage of expansion reaches 3000–3500 K.     

Creation and simulation of very fast jets

We propose a concept in order to produce very fast metallic jets (which speed could exceed 20 km/s). It uses the detonation wave of an explosive cylinder to initiate a high compression on the rear face of a metallic target ; the jet is created on the front surface, in a cylindrical cavity. Many experiments were performed, in which we tested different metals and various geometries of cavity. Numerical calculations with PLEXUS (finite element 2D or 3D code) and CEL (finite difference 2D code) were used to understand the phenomenology of the creation and propagation of these jets ; the correlation with the experimental results (about the shape of the jets and their speed) is good.     

Fabrications of nanofibers as crossed arrays by electrospinning

We have developed a new method for obtaining nanofiber crossed arrays by exploiting an auxiliary electrode subjected to electrical frequencies, between the capillary tip and the grounded target in an electrospinning machine. The frequencies generated crossed arrays on a flat collector, used instead of a rotating wheel because of intersecting jets. We observed many straight and crossed structures. We determined the variation in morphology with changes in frequency, and characterized the samples using optical microscopy and a field emission scanning electron microscope. This paper reports on a simple, easy method for generating crossed array nanofibers on a flat substrate using electrical frequency in an auxiliary electrode.     

Features of explosive electron emission from a multipoint liquid-metal emitter

A multipoint liquid-metal (MLM) emitter operating in the explosive regime is characterized by a significantly greater working capacity than solid-state explosive cathodes. The MLM emitter described is capable of producing a series of blow-up emission pulses with a repetition period from 25 μs to 1 ms controlled by external circuit parameters. The high stability of the MLM emitter operation is explained by the explosive emission taking place simultaneously from several hundreds of emitting points.     

Various microplasma jets and their sterilization of microbes

Various microplasma jets including coplanar-electrodes device, hollow-electrode device, twin injection-needle device, jet from a flexible tube, and pencil-type electrode will be discussed. Argon plasma jets penetrate deep into ambient air and create a path for oxygen radicals to sterilize microbes including spores. A sterilization experiment with bacterial endospores indicates that an argon-oxygen plasma jet very effectively kills endospores of Bacillus atrophaeus (ATCC 9372), thereby demonstrating its capability to clean surfaces and its usefulness for reinstating contaminated equipment as free from toxic biological agents. The key element of the sterilization is the oxygen radicals. The pencil-type configuration produces a long cold plasma jet capable of reaching 3.5 cm and having various excited plasma species shown through optical emission spectrum. By introducing an appropriate gas flow rate, striated discharge patterns in the plasma jet from the pencil-type configuration are produced through ionization wave propagation. 2 W operation of an air plasma jet in pencil-type electrode provides an excellent opportunity for sterilization of microbes. Finally, the twin plasma columns in the twin injection-needle device will be introduced.     

水下线型聚能切割器内外炸高对射流侵彻性能的影响

借助ANSYS/LS-DYNA程序,对线型聚能切割器在水下切割钢板的性能进行了数值模拟研究,并通过试验对数值模拟仿真结果进行了验证。通过数值模拟和试验对比,重点分析了水下聚能切割器空气内炸高和水外炸高对射流侵彻靶板的特性影响。数值模拟和试验结果表明:聚能槽内的水介质会阻碍射流的形成,严重影响切割性能,设置适量的空气内炸高并减小水外炸高,可以提供射流形成的空间,大幅提高射流的侵彻能力;空气内炸高越小,射流的形成越不充分,形成射流的速度和动能越小,侵彻能力越弱。     

乳化炸药线型切割器对薄壳弹药销毁效果的数值模拟研究

针对目前的弹药销毁状况,为了减轻直接爆破的环境压力,利用理论分析及数值模拟的方法,首先对设计的简易乳化炸药线型切割器的药型罩材料进行确定,数值模拟表明:铝质药型罩所形成的射流侵彻能力要比紫铜材质的提高28%,而后利用ANSYS数值模拟得出该切割器最佳炸高为15 mm。最后对乳化炸药线型切割器切割薄壳弹药的过程进行数值模拟,证明该切割器可以达到切去弹药外壳而不产生剧烈爆轰及高速破片的效果。     

铝合金蒙皮聚能切割的数值计算与实验研究

为了在战场条件下实现飞机受损蒙皮不规则破孔的快速修整,引入聚能切割技术,通过数值计算,设计了针对铝合金板材的低能量聚能切割索;经聚能切割实验,获得了边缘整齐、线性良好的穿透性切割缝隙;同时,对切割索的安全性与可靠性进行了测试。     

Spectra and kinetics of emission from the products of explosive decomposition of silver azide

The spectrum and kinetics of optical emission from the products of explosive decomposition of silver azide (AgN₃) initiated by a pulsed electron beam (0.5 MeV, 1 kA/cm², 20 ns) have been experimentally studied. The stage of preexplosion luminescence is followed by the formation of a continuous emission spectrum due to a dense plasma of decomposition products. This spectrum exhibits variations within a time interval of 0.6–0.9 μs, which can be related to the self-heating of plasma from 3000 to 3600 K as a result of the exothermal reaction 2N₃ → 3N₂.     

Jet flames from noncircular burners

Gas jets from noncircular exits entrain more air from surroundings than jets from circular exits of equivalent area. Because the mixing rate of fuel and air governs the combustion and pollutant emission of diffusion flames and partially premixed flames, noncircular geometries offer a passive control of the flame characteristics. In this paper, the literature on nonburning, noncircular jets is reviewed and recent studies on noncircular jet flames are discussed with focus on the work conducted in the author’s laboratory. The funding for the studies from which the material for this paper is extracted was provided by the Gas Research Institute, Chicago, Illinois and the Oklahoma Center for Advancing Science and Technology, Oklahoma City, Oklahoma in USA.     

Jet emission from a capillary in a strong electric field

The phenomenon of multiple jet formation during a liquid efflux from a capillary in a strong electric field is considered. Conditions for the simultaneous emission of an arbitrary number of jets have been experimentally determined.     

Application to cleaning of waste plastic surfaces using atmospheric non-thermal plasma jets

The removal of paint on the surface of waste plastics is difficult by the conventional process; in this research, a new cleaning mechanism using atmospheric plasmas was examined through optical emission spectroscopy, electron spectroscopy for chemical analysis, and scanning electron microscopy. Results indicate that an increase of pulse frequency enables for a short processing time for the removal of the paint film, signifying that the production of radicals in plasma, especially oxygen radicals, can be controlled by pulse frequency.Plasma jets were generated under the experimental conditions of an input power of 250 W to 400 W, a pulse frequency of 2 kHz to 12 kHz, and a plasma gas flow rate of 30 L/min. Examination of the intensity ratio of the reactive species, as measured by emission spectroscopy, showed that the O/N value increased with an increase in pulse frequency. Results of analysis with electron spectroscopy for chemical analysis show that nitrogen atoms and molybdenum in only the paint film decreased through plasma processing.     

Determination of the Time Dependence of Periodic Optical Signals by Correlation Spectroscopy

A method is described for determining the time dependence of a periodic optical signal by measuring the autocorrelation function and counting rate distribution of the anode pulses of a photomultiplier, which is used as a light detector. The effect of amplitude and frequency fluctuations is discussed. The method is applied to the determination of fast periodic concentration variations generated by the mixing process of three free jets, one CO₂ jet and two air jets. The Raman technique is used as a molecular number density probe.