Laser induced fast ignition made realistic by relativistic velocities-dream or reality?

Due to the recent developments in high power lasers it is suggested to accelerate a micro-foil by the laser pressure to relativistic velocities. The time dependent velocity of this micro-foil is calculated analytically for pulsed constant laser intensity. The accelerated foil collides with a target creating a shock wave on impact. The shock wave parameters are calculated within the context of relativistic fluid dynamics.It is suggested to use the energy of the relativistic micro-foil to ignite a pre-compressed target with a density relevant for fusion ignition. The equations are written and solved for the collision between the micro-foil and the very dense target. The criteria for shock wave ignition and heat wave ignition are used to show that one needs significantly less laser energy for heat wave ignition.The present scheme shows that nuclear fast ignition by micro-foil impact could be attained in the near future with lasers that are currently under construction.     

基于振动实测的非均质地层钻头失效分析与对策

四川盆地作为国内页岩气开发的重点区域,通过近几年的不断攻关和实践,机械钻速得到了提高,但由于受地层复杂、可钻性差、非均质性强等地质因素的影响,导致井下钻柱系统不良振动剧烈,容易出现钻头损坏严重、钻速较低等问题,严重影响了钻井时效。为了解决上述难题,以该盆地涪陵工区上二叠统龙潭组—中二叠统茅口组为例,采用井下振动高频测量工具的实测手段,测量了钻头—钻柱系统的动态振动加速度参数,结合地层的岩性和矿物组分分析,研究钻头失效原因与对策,并开展了现场试验。研究结果表明:①在非均质地层中钻进的钻头—钻柱系统产生了大于40 m/s~2的高幅值瞬时冲击振动,高幅值的瞬时冲击是导致钻头先期失效的主要原因;②提出了抑制高幅值的瞬时冲击振动采用"减振+增压"工具组合和避免井下工具共振的钻井参数;③采用钻井新参数的试验井比邻井的高幅值瞬时振动降低了17%,单只钻头进尺增加24%,钻头工作环境得到了较大的改善,钻头使用数量减少。结论认为,该研究成果能够有效地改善钻头—钻柱系统的振动状态,有利于达成延长钻头使用寿命的目标。     

管道流体瞬态—水汽锤计算原理

文中介绍了核电站管道中流体瞬态——水汽锤的计算原理;既适用于液体介质的水锤计算,也适用于可压汽体的汽锤计算.对于一些典型管道部件的处理方法,文中也作了讨论。     

Shock-induced phase transitions of C70 fullerite

Shock-induced phase transitions of C₇₀ fullerite were studied at the pressure range up to 52 GPa with use of recovery assemblies of planar geometry. The starting material consists of two crystalline phases: phase with hexagonal close-packed (HCP) and phase with rhombohedral structure. We have found that C₇₀ fullerite undergoes a series of polymorphic phase transitions in conditions of step-like shock-wave compression. In the specimens, recovered from 9, 14 and 19 GPa, a dominant phase was fullerite C₇₀ with cubic structure. Also, some amount of C₇₀ with HCP structure was observed. The quantity of HCP phase was decreasing with increasing of intensity of shock loading. With further growth of shock pressure, destruction of C₇₀ molecules occurs. In the samples, recovered after shock loading, the main phase was graphite with a low degree of three-dimensional regularity.     

六通道瞬态光学高温计

六通道瞬态光学高温计是在可见光和近红外光谱范围内 ,把光源的热辐射取出六个波段进行测量。每个波段信号通过各自的光纤传输、光电倍增管探测和记录仪器记录。系统的时间分辨率小于 30 ns,冲击温度测量范围为 2 30 0～ 90 0 0 K,测量误差小于 5 % ,给出了以碘化钠、硝基甲烷和空气为样品的若干实验结果     

双模态燃烧室激波链/附面层相互干扰研究

研究优化燃烧室控制问题,燃烧引起的压力升高扰动对于双模态燃烧室流场内激波链/附面层相互干扰强度影响,同时由于喷油调节对燃烧效率也影响较大。为解决上述问题,采用变换燃烧室出口反压。计算出燃烧室内燃烧引起压力升高的实际情况,对不同出口反压条件下的双模态燃烧室冷流流场进行了数值仿真,并与试验结果进行对比,两者相互吻合。结果表明,燃烧室内激波链结构强度及位置对于出口反压的变化非常敏感,在实际燃烧室工作中可通过选择合适的供油规律来获得燃烧引起压力扰动对激波链结构强度及位置的气动控制,可实现双模态燃烧室的模态转换,使得燃烧室工作在最优模态。     

Development of the meshless finite volume particle method with exact and efficient calculation of interparticle area

The Finite Volume Particle Method (FVPM) is a meshless method based on a definition of interparticle area which is closely analogous to cell face area in the classical finite volume method. In previous work, the interparticle area has been computed by numerical integration, which is a source of error and is extremely expensive. We show that if the particle weight or kernel function is defined as a discontinuous top-hat function, the particle interaction vectors may be evaluated exactly and efficiently. The new formulation reduces overall computational time by a factor between 6.4 and 8.2. In numerical experiments on a viscous flow with an analytical solution, the method converges under all conditions. Significantly, in contrast with standard FVPM and SPH, error depends on particle size but not on particle overlap (as long as the computational domain is completely covered by particles). The new method is shown to be superior to standard FVPM for shock tube flow and inviscid steady transonic flow. In benchmarking on a viscous multiphase flow application, FVPM with exact interparticle area is shown to be competitive with a mesh-based volume-of-fluid solver in terms of computational time required to resolve the structure of an interface.     

JOB-9003炸药"激热"冲击损伤破坏及超声特征

进行了未经热处理的JOB-9003塑料粘结炸药(PBX)标准压缩试样的"激热"冲击损伤破坏试验,对试样热冲击试验前后的超声波特性参量进行了检测,试验显示出JOB-9003炸药存在一个明显的"激热"冲击损伤破坏临界温度差,并获得了试样热冲击损伤破坏的超声波参量特征.     

3200MVA冲击发电机励磁控制系统运行分析

论述了冲击发电机励磁系统组成及原理,励磁调节器调节电压的原理,以及强励的作用,论述了冲击发电机灭磁的必要性,分析了放电电阻灭磁和灭弧栅灭磁的灭磁原理。     

车辆悬架减震优化设计方法仿真

车辆在不同路况和不同车速等情况下,悬架系统弹性元件受到的冲击大小差异很大,无法形成固定的振动规则,振动剧烈程度与阻尼系数无法关联.传统车辆悬架减振设计方法,采用固定阻尼系数来减少弹性元件的振动,没有考虑不同路况及车速产生的振动剧烈程度不同的问题,减振效果较差.提出一种车辆悬架减震优化有限元设计方法,分析车辆悬架减震器的功能和结构,塑造车辆悬架减震优化模型,采用ANSYS有限元软件中一阶优化方法进行车辆悬架减振优化设计,以悬架减震器阻尼力为优化目标,以减震器阻尼系数为优化设计变量,以静强度和最大减震强度为约束条件,对车辆悬架减震进行有限元优化设计,确保车辆车身振动迅速衰弱,使车身能够很快达到一种稳定状态.实验结果表明,上述方法使车辆减震阻尼力和最大减震强度都优于传统方法,具有较高的稳定性和控制精度.