DETONATION INITIATION INDUCED BY FLAME IMPLOSION AND SHOCK WAVE FOCUSING

Computational simulations on structurally different detonation generator are carried out to study the phenomena,the mechanism and the gas dynamics characteristics of flame implosion and shock wave focusing.Two-dimensional axisymmetric and unsteady Navier-Stokes equations are numerically solved and detailed chemical reaction kinetics of hydrogen/air mixture is used.The simulation results show that the laminar flame generated by low energy spark in the jet flame burner is accelerated under the narrow channel,the jet flame impinging on the axis strengthens shock wave and the shock wave enhances flame acceleration.Under the function of multiple shock waves and flame,a number of hot spots appear between the wave and the surface.The spots enlarge rapidly,thus forming an over-drive detonation with high pressure,and then declining to stable detonation.Through calculation and analysis,the length of detonation initiation and stable detonation are obtained,thus providing the useful information for further experimental investigations.

Numerical study on magneto-Rayleigh–Taylor instabilities for thin liner implosions on the primary test stand facility

The thin aluminum liners with an aspect ratio R/?r 1 have been imploded on the primary test stand(PTS) facility,where R is the outer radius of the liner and ?r is the thickness. The x-ray self-emission images present azimuthally correlated perturbations in the liner implosions. The experiments show that at-10 ns before the stagnation, the wavelengths of perturbation are about 0.93 mm and 1.67 mm for the small-radius and large-radius liners, respectively. We have utilized the resistive magnetohydrodynamic code PLUTO to study the development of magneto-Rayleigh–Taylor(MRT) instabilities under experimental conditions. The calculated perturbation amplitudes are consistent with the experimental observations very well. We have found that both mode coupling and long implosion distance are responsible for the more developed instabilities in the large-radius liner implosions.

Radiation characteristics and implosion dynamics of tungsten wire array Z-pinches on the YANG accelerator

We investigated the radiation characteristics and implosion dynamics of low-wire-number cylindrical tungsten wire array Z-pinches on the YANG accelerator with a peak current 0.8-1.1 MA and a rising time ～ 90 ns.The arrays are made up of（8-32）×5 μm wires 6/10 mm in diameter and 15 mm in height.The highest X-ray power obtained in the experiments was about 0.37 TW with the total radiation energy ～ 13 kJ and the energy conversion efficiency ～ 9%（24×5 μm wires,6 mm in diameter）.Most of the X-ray emissions from tungsten Z-pinch plasmas were distributed in the spectral band of 100-600 eV,peaked at 250 and 375 eV.The dominant wavelengths of the wire ablation and the magneto-Rayleigh-Taylor instability were found and analyzed through measuring the time-gated self-emission and laser interferometric images.Through analyzing the implosion trajectories obtained by an optical streak camera,the run-in velocities of the Z-pinch plasmas at the end of the implosion phase were determined to be about（1.3-2.1）×10 7 cm/s.

Comparison Between Mitigation Effects of the Finite Larmor Radius and Sheared Axial Flow on Rayleigh-Taylor Instability in Z-Pinch Implosions

A magnetohydrodynamic (MHD) formulation is derived to investigate and compare the mitigation effects of both the sheared axial flow and finite Larmor radius (FLR) on the Rayleigh-Taylor (RT) instability in Z-pinch implosions. The sheared axial flow is introduced into MHD equations in a conventional way and the FLR effect into the equations via /t → -i(w+ik⊥2pi2Ωi,), as proposed in our previous paper [Chin. Phys. Lett. 2002, 19:217] , where k⊥2 pi2 is referred to FLR effect from the general kinetic theory of magnetized plasma. Therefore the linearized continuity and momentum equations for the perturbed mass-density and velocity include both the sheared axial flow and the FLR effect. It is found that the effect of sheared axial flow with a lower peak velocity can mitigate RT instability in the whole wavenumber region and the effect of sheared axial flow with a higher one can mitigate RT instability only in the large wavenumber region (for normalized wavenumber k】2.4); The effect of FLR can mitigate RT instability in the whole wavenumber region and the mitigation effect is stronger than that of the sheared axial flow with a lower peak velocity in the almost whole wavenumber region.

Study of the asymmetry of hot-spot self-emission imaging of inertial confinement fusion implosion driven by high-power laser facilities

Implosion asymmetry is a crucial problem quenching ignition in the field of inertial confinement fusion.A forward-calculation method based on 1D and 2D hydrodynamic simulations has been developed to generate and study the x-ray images of hot-spot self-emission,indicating asymmetry integrated over the entire drive pulse.It is shown that the x-ray imaging photon energy should be higher to avoid the influence of the remaining shell.The contour level(percentage of the maximum emission intensity)and spatial resolution should be as low as possible,optimally less than 20%and 3μm,for characterization of higher-mode signatures such as Ps-P12 by x-ray self-emission images.On the contrary,signatures of lower-mode such as P2 remain clear at all contour levels and spatial resolutions.These key results can help determine the optimal diagnostics,laser,and target parameters for implosion experiments.Recent typical hot-spot asymmetry measurements and applications on the Shenguang 100 kJ class laser facility are also reported.

Effects of mode coupling between low-mode radiation flux asymmetry and intermediate-mode ablator roughness on ignition capsule implosions

The low-mode shell asymmetry and high-mode hot spot mixing appear to be the main reasons for the performance degradation of the National Ignition Facility(NIF)implosion experiments.The effects of the mode coupling between low-mode P2 radiation flux asymmetry and intermediate-mode L=24 capsule roughness on the implosion performance of ignition capsule are investigated by two-dimensional radiation hydrodynamic simulations.It is shown that the amplitudes of new modes generated by the mode coupling are in good agreement with the second-order mode coupling equation during the acceleration phase.The later flow field not only shows large areal density P2 asymmetry in the main fuel,but also generates large-amplitude spikes and bubbles.In the deceleration phase,the increasing mode coupling generates more new modes,and the perturbation spectrum on the hot spot boundary is mainly from the strong mode interactions rather than the initial perturbation conditions.The combination of the low-mode and high-mode perturbations breaks up the capsule shell,resulting in a significant reduction of the hot spot temperature and implosion performance.

内爆法(Implosion)拆除68m框剪结构大楼

上海地区一幢长85.4m、宽25.2m、高68m,建筑面积达28076m2的16层框剪结构仓储大楼被采用内爆法(Implosion)成功拆除。根据周边环境条件,在高楼重心无法移出原支撑面时,采用了沿高楼纵轴方向起爆,且纵向与横向分别设置不同延时间隔的逐柱起爆网路;通过对高楼底部、中部、上部局部楼层不同的爆前处理,实现了高楼近似于原地逐层坍塌,略向特定方向倾斜的理想爆破效果。借助于更多的爆破实践,内爆法将在国内日趋严峻的城市爆破拆除环境中进一步展现其控爆特色。

Scientometric Implosion that Leads to Explosion: Case Study of Armenian Journals

Purpose: The purpose of this study is to introduce a new concept and term into the scientometric discourse and research—scientometric implosion—and test the idea on the example of the Armenian journals. The article argues that the existence of a compressed scientific area in the country makes pressure on the journals and after some time this pressure makes one or several journals explode—break the limited national scientific area and move to the international arena. As soon as one of the local journals breaks through this compressed space and appears at an international level, further explosion happens, which makes the other journals follow the same path.Design/methodology/approach: Our research is based on three international scientific databases—WoS, Scopus, and RISC CC, from where we have retrieved information about the Armenian journals indexed there and citations received by those journals and one national database—the Armenian Science Citation Index. Armenian Journal Impact Factor(ArmJIF) was calculated for the local Armenian journals based on the general impact factor formula. Journals were classified according to Gl?nzel and Schubert(2003). Findings: Our results show that the science policy developed by the scientific authorities of Armenia and the introduction of ArmJIF have made the Armenian journals comply with international standards and resulted in some local journals to break the national scientific territory and be indexed in international scientific databases of RISC, Scopus, and WoS. Apart from complying with technical requirements, the journals start publishing articles also in foreign languages. Although nearly half of the local journals are in the fields of social sciences and humanities, only one journal from that field is indexed in international scientific databases. Research limitation: One of the limitations of the study is that it was performed on the example of only one state and the second one is that more time passage is needed to firmly evaluate the results. However, the introduction of the concept can inspire other similar case study. Practical implications: The new term and relevant model offered in the article can practically be used for the development of national journals.Originality/value: The article proposes a new term and a concept in scientometrics.

Numerical Analysis of Factors Influencing Implosion

-By using gas-liquid two-phase flow theory, a modified mathematical model based on the computational fluid dynamics method SIMPLE (Semi-Implicit Method for Pressure-Linked Equations) is introduced to investigate implosion phenomena in high pressure chambers systematically. A theoretical simulation-prediction method, which is independent of experimental data, is developed in the paper and great improvement has been made on the topic. In the paper, various implosion situations have been simulated and predicted. Effects of a series of factors influencing implosion results and methods of reducing implosion danger have been analysed. The analysis results are of importance to underwater engineering practice.

Diagnostic Technique of Neutron Doppler Broadening for Indirectly-Driven Implosions

The neutron Doppler broadening in inertial confinement fusion has been acquired from the time of flight for the neutron, from which the fuel ion temperature can be derived. An ultrafast-quenched plastic scintillation detector was used to measure the time of flight for the neutron at a low-imploded DT neutron yield (5×107-1×108) in the experiment performed on the Shenguang Ⅱ laser facility. The typical temperatures of ablating targets for indirect drive were around 2.8 keV and the uncertainties were ±30 % - ±40%. The detection efficiency of the detector for DT neutrons was calibrated at a K-400 accelerator. The time response function of the detection system was calibrated by imploded neutrons from a DT-filled capsule, which can be regarded as a S function pulsed neutron source due to its much narrower pulse width than that of the measured neutron time-of-flight spectrum.

Linear Rayleigh-Taylor instability analysis of double-shell Kidder's self-similar implosion solution

This paper generalizes the single-shell Kidder＇s self-similar solution to the double-shell one with a discontinuity in density across the interface. An isentropic implosion model is constructed to study the Rayleigh-Taylor instability for the implosion compression. A Godunov-type method in the Lagrangian coordinates is used to compute the one-dimensional Euler equation with the initial and boundary conditions for the double-shell Kidder＇s self-similar solution in spherical geometry. Numerical results are obtained to validate the double-shell implosion model. By programming and using the linear perturbation codes, a linear stability analysis on the Rayleigh-Taylor instability for the double-shell isentropic implosion model is performed. It is found that, when the initial perturbation is concentrated much closer to the interface of the two shells, or when the spherical wave number becomes much smaller, the modal radius of the interface grows much faster, i.e., more unstable. In addition, from the spatial point of view for the compressibility effect on the perturbation evolution, the compressibility of the outer shell has a destabilization effect on the Rayleigh-Taylor instability, while the compressibility of the inner shell has a stabilization effect.

Chimney ImplosionmA Case Study

Chimney implosion is the strategic planning of explosives and accessories materials and timings of its detonation so that chimney collapses on itself, minimising the physical damage to its immediate surroundings. Built in 1885, the brick chimney at kankanee colliery, Sijua area, BCCL （Bharat Collieries Company Limited） was demolished by felling method using the commercial explosives by adopting single-folding and toppling method. The chimney was 31.5 m in height and suffered structural weaknesses due to progressive deterioration over age, weathering and non maintenance. The chimney was posing potential threat to the safety of the nearby dwellings and surface structures, viz. main mechanical ventilator of Kankanee colliery, 11 KV electrical substation supplying power to Sijua area, BCCL, high tension cable line and busy Katras-Sijua-Dhanbad Dobari Road all failing within a radius of 30 m. About 75.22 kg of commercial explosive, 100 m of detonating fuse along with 0 and 25 ms delay detonators were used for controlled demolition of chimney. The chimney got demolished by vertically cascading on its own base without causing any damage to the nearby dwellings and surface structures.

激光间接驱动柱几何内界面减速段的流体力学不稳定性实验研究

研究收缩几何下的流体力学不稳定性增长对于惯性约束聚变靶丸降低流体力学不稳定性增长和混合的优化设计具有重要的作用。在神光100 kJ激光装置上开展了辐射驱动柱几何内界面减速段的流体力学不稳定性实验,观测到模耦合现象,以及收缩几何独有的Bell-Plesset(BP)效应,理论预估BP效应导致的扰动增长与实验结果基本一致。实验中观察到驱动不对称性引入的2阶模扰动,M2不对称性约为11%,提出了通过增加黑腔长度来优化驱动不对称性的方法。柱几何流体力学不稳定性增长研究将有助于理解收缩几何效应在高能量密度条件下对流体力学不稳定性增长的影响,为优化惯性约束聚变靶丸设计提供帮助。

多级柱面炸药内爆磁通量压缩技术研究

柱面内爆磁通量压缩发生器是利用炸药内爆压缩其内部磁通量至轴线附近小体积内从而实现超高磁场,传统的单级装置因受到金属套筒内爆失稳等影响性能指标受限。开展了多级内爆磁压缩技术研究,突破多项关键技术,包括研制特殊结构的密绕螺线管、脉冲功率源及大电流放电开关等,具备在直径135 mm套筒空间内实现20 T以上初始磁场产生能力,并建立了动态磁光测量系统。利用磁流体力学编码SSS-MHD开展多级装置设计,计算显示,设计的多级装置能够将约42%的初始磁通量压缩至轴线附近直径7 mm的空间内。最终研制成功多级内爆磁压缩装置CJ-150,在亚立方厘米以上空间实现轴向峰值磁场强度906 T,数据不确定度5.35%。10余发动态考核实验显示,CJ-150装置工作稳定,能够满足物理实验需要。利用经实验验证的磁流体模型计算显示,CJ-150具备1000 T以上超强磁场产生能力,能够对大尺寸样品实现500 GPa以上的准等熵加载。

航空餐车-织物袋组合装置的抗爆特性研究

为了提高民机客舱安保技术水平,提出将航空餐车与织物袋组合形成民机客舱爆炸包容装置,来作为客舱内应急处置疑似爆炸物的潜在解决方式。针对航空餐车及航空餐车-织物袋组合装置,开展了内爆试验且进行了有限元仿真,对比了内爆场下二者的响应历程及失效形式,通过试验验证有限元模型的准确性,并分析了内部填充物及织物袋厚度对结构抗爆性能的影响。研究结果表明:爆炸冲击载荷下,织物袋赋予了航空餐车显著的抗爆能力,航空餐车弥补了织物袋的易燃短板;增加座椅垫作为内部填充物时,座椅垫吸能占吸能总量的74%,并降低了航空餐车的变形及失效规模,对于爆炸能量的耗散起到了关键作用;航空餐车-织物袋组合装置各自可拆卸,织物袋厚度对相同药量下各部分的吸能能力影响不明显。组合装置可用作民机客舱爆炸包容装置,作为客舱内应急处置疑似爆炸物的解决方案。

消费主义情境下的符号操持——以盲盒消费为例

消费社会中,“物”的极大丰盛使得“物”摆脱了生产逻辑而进入符号逻辑的序列,并从此落入了整个语言学体系合理性的操控之中。以盲盒消费为切入点,正是以“物”的功能性的消解为契机,盲盒手办成为符号操持的对象,成为我们这个时代的现象级消费品,并且也成为人与人之间产生关联的契机。分别从消费逻辑、消费者和消费品三个维度来解读符号对于社会生活各个层面的介入,永恒自洽的符号逻辑将被升级为拟真模式,并最终导致意义的“内爆”,此种意义的荒芜恰是符号操持的必然后果。

深海浮球内部气压对水下内爆波的抑制机理

深海潜器常携带中空浮球来为其提供浮力。陶瓷因其高强度、低密度等优点成为浮球的理想材料。然而,中空结构在外部高压环境下易发生内爆,产生的内爆波会对周围结构产生毁灭性损害。为了探索浮球内部初始气压对内爆波的影响,首先,利用气泡动力学对其不考虑球壳影响时进行理论分析,得到内爆波压力脉冲沿径向以指数-1衰减,并指出其物理意义和隐含假设,进而从能量分析得到增加内压使压缩空气消耗的能量增加,从而减弱释放到水中的压力波能量;其次,采用三相流固耦合有限元模型进行计算,考虑水的可压缩性和球壳因挤压引起的脆性破裂的影响,得到更为接近实际的内爆压力的分布。由于两侧挤压球壳,外部的水在不断扩大的缺口处产生向内的射流,造成内部气体非球形塌缩,后续压力波呈现出与球壳碎裂方式有关的方向性差异。通过有限元模型对内部初始气压的研究表明,增加初始内部气体压力到1 MPa时,压力脉冲在球壳表面处下降了15.6%~24.8%。这一结果表明,在几乎不增加浮球质量的条件下,增加内部初始气压具有很好地抑制近端内爆波强度的效果。

基于显式动力学计算的储罐内爆破坏影响分析

储罐作为存储油气资源及其产品的主要设备,一旦发生爆炸并产生破坏,罐内燃烧的液体极有可能会从破坏位置流出,进而形成流淌火,将会造成无法挽回的大规模安全事故。以立式拱顶储罐为研究对象,考虑储罐结构与内外流体间的多相耦合,建立了罐内流体-储罐-罐外流体的内爆破坏三维有限元模型,并基于指数内聚力模型失效准则对储罐材料进行描述,通过在材料中插入黏结单元的方法模拟储罐的裂口扩展过程,开展内爆载荷作用下储罐的显式动力学破坏分析。结果表明:储罐起裂位置均位于液位以上,罐体起裂速度与起爆位置呈现正相关;随着内爆载荷的持续作用,储罐裂口不断扩展延伸至液位时,其扩展速度有所减缓;满罐液位状态下储罐未产生裂口,半罐液位降至空罐液位时,储罐平均破坏比由78.8%增至88.4%,储罐破坏程度与液位高度呈现负相关;储罐偏心起爆平均破坏比较中心起爆高1.6%,即储罐偏心起爆破坏程度更严重;储罐容积由1000m^(3)增至5000m^(3)时,若液位占储罐高度低于46%,储罐平均破坏比由88.2%增至88.6%,反之,储罐平均破坏比由86.4%降至84.4%。研究结果可为储罐爆炸事故的预防以及储罐弱顶结构的补强设计提供参考依据。

环肋布局对钛合金圆柱耐压壳内爆过程的影响研究

环肋圆柱壳是深潜器耐压结构的主要形式,但由于极限承载能力和振动特性的需求,存在不同的环肋布局形式。为探究环肋布局对钛合金圆柱耐压壳内爆的影响,基于任意拉格朗日欧拉方法开展数值研究。首先对比试验结果验证液-固-气三相流固耦合数值模型的准确性。然后分析3种环肋布局下圆柱耐压壳水下内爆过程中的结构动态响应、冲击波传播以及能量演化等特征。结果表明,环肋均布时,内爆中心由筒体中部向一端移动。而中部和端部加强时,内爆中心由环肋稀疏位置向密集位置移动,结构动能均存在显著的二次波峰现象。此外,中部加强能有效降低最大冲击波峰值。通过对环肋圆柱壳内爆响应特性的分析,对深海耐压结构的设计具有重要的工程意义。

迫-1甲引信工作过程仿真模拟

为研究迫-1甲引信运动和作用过程,对其引信工作进行仿真模拟。使用多体系统动力学仿真软件MSC.ADAMS建立引信虚拟样机模型,模拟其运动过程并得到击针对针刺雷管的撞击动能;使用显式动力学仿真软件Ansys Workbench LS-DYNA对引信传爆序列爆轰作用过程进行仿真模拟,验证针刺雷管→导爆管→传爆管→主装药之间传爆的可靠性。仿真结果表明,该仿真模拟可为迫-1甲引信的改进或智能化改造提供数据支撑。