Initial transient process in a simple helical flux compression generator

An analytical scheme on the initial transient process in a simple helical flux compression generator, which includes the distributions of both the magnetic field in the hollow of an armature and the conducting current density in the stator, is developed by means of a diffusion equation. A relationship between frequency of the conducting current, root of the characteristic function of Bessel equation and decay time in the armature is given. The skin depth in the helical stator is calculated and is compared with the approximate one which is widely used in the calculation of magnetic diffusion. Our analytical results are helpful to understanding the mechanism of the loss of magnetic flux in both the armature and stator and to suggesting an optimal design for improving performance of the helical flux compression generator.

Calculation of time-varying equivalent inductance and resistance of helical flux compression generators using the 2D filamentary method and dynamic matrix concept in the frequency domain

In this paper we present an approach to calculate the time-varying equivalent inductance and resistance of helical flux compression generators accurately. This approach is based on the 2D filamentary method and uses the dynamic matrix concept. By using this method, it is possible to consider both the effects of the armature presence and frequency on the inductance and resistance of the HFCGs. The latter effect has not been discussed in previous open literature. The validation of the presented method has been verified by measurement results.

Explosive Ferroelectric Power Supply of Flux Compression Generator

Useful electrical pulses of a few hundred kilowatts lasting for several microseconds can be obtained by the depolarization process of PZT95/5 ferroelectric ceramics. In this paper, taking account of the dielectric relaxation, and finite resistance, a new mathematical model of PZT95/5 ferroelectric ceramics subjected to normal-mode shock wave is suggested. Explosive shock wave techniques have also been used to investigate the response of PZT95/5 ferroelectric ceramics with inductive loads in experiments. The predictions from the model have a good agreement with observed results. In addition, an explosive ferroelectric generator composed of explosive shock wave generators, electric units, and additional capacitors is design to power small-size helical flux compression generators. The test results with the maximal output energy of up to 80 J are given and experimental results are also considered.

Flux Limiter Lattice Boltzmann Scheme Approach to Compressible Flows with Flexible Specific-Heat Ratio and Prandtl Number

We further develop the lattice Boltzmann (LB) model [Physica A 382 (2007) 502] for compressible flows fromtwo aspects.Firstly,we modify the Bhatnagar-Gross-Krook (BGK) collision term in the LB equation,which makes themodel suitable for simulating flows with different Prandtl numbers.Secondly,the flux limiter finite difference (FLFD)scheme is employed to calculate the convection term of the LB equation,which makes the unphysical oscillations atdiscontinuities be effectively suppressed and the numerical dissipations be significantly diminished.The proposed modelis validated by recovering results of some well-known benchmarks,including (i) The thermal Couette Row;(ii) One- andtwo-dimensional Riemann problems.Good agreements are obtained between LB results and the exact ones or previouslyreported solutions.The Rexibility,together with the high accuracy of the new model,endows the proposed modelconsiderable potential for tracking some long-standing problems and for investigating nonlinear nonequilibrium complexsystems.

Flux Limiter Lattice Boltzmann for Compressible Flows

In this paper,a new flux limiter scheme with the splitting technique is successfully incorporated into amultiple-relaxation-time lattice Boltzmann (LB) model for shacked compressible Hows.The proposed flux limiter schemeis efficient in decreasing the artificial oscillations and numerical diffusion around the interface.Due to the kinetic nature,some interface problems being difficult to handle at the macroscopic level can be modeled more naturally through theLB method.Numerical simulations for the Richtmyer-Meshkov instability show that with the new model the computedinterfaces are smoother and more consistent with physical analysis.The growth rates of bubble and spike present asatisfying agreement with the theoretical predictions and other numerical simulations.

千特斯拉级内爆磁压缩装置初始磁场电源系统研制

初始磁场电源系统用于激励千特斯拉级内爆磁压缩装置的初级线圈产生初始磁场,是内爆磁压缩装置的关键设备。在分析千特斯拉级内爆磁压缩装置初始磁场电源需求和技术难点的基础上,系统设计了核心部件选择方案和主脉冲电路及控制系统结构,研制成功一套输出电压1~40 kV可调、主放电电流脉冲上升沿约60μs、总峰值电流达3.2 MA的初始磁场电源系统,已应用于千特斯拉级内爆磁压缩装置动态试验。

不同尺度纤维复合增强水泥基材料的抗氯离子渗透性能

为研究不同尺度纤维复合增强水泥基材料的抗氯离子渗透性能,对单掺和复掺碳酸钙晶须、聚乙烯醇(PVA)纤维的水泥基材料分别进行电通量试验、电镜扫描观测及基本力学性能试验,分析不同纤维尺度、掺量及复合比例对水泥基材料抗氯离子渗透性能和基本力学性能的影响规律,并基于试验结果给出了多纤维复合增强水泥基材料的氯离子侵蚀深度计算模型。结果表明,不同尺度纤维可在不同结构层次上发挥对水泥基材料的增强作用,使得多纤维复合增强水泥基材料的抗氯离子渗透性能明显优于单一纤维增强水泥基材料;多纤维复合材料的抗压强度与氯离子侵蚀深度及电通量大致呈反比例关系;当复合材料的抗压强度提高13.6%时,其氯离子侵蚀深度和总电通量则分别降低39.1%和44.7%;建立的氯离子侵蚀深度计算模型,可用于多纤维复合增强水泥基材料的抗氯离子渗透和侵蚀性能评估。

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。

钒钛磁铁矿制备熔剂性球团工艺优化

为探究合理的钒钛磁铁矿熔剂性球团造球工艺制度及生球冷态性能,以钒钛磁铁矿为原料制备熔剂性球团。结果表明:随着造球时间由10 min增加至18 min,生球抗压强度和落下强度均得到提高,爆裂温度降低了95℃,且在造球时间为14 min时,生球抗压强度为11.6 N/个,落下强度为5.1次/个,生球性能较好;随着造球水分由7%增加至10%,生球抗压强度先升高后降低,落下强度逐渐升高,爆裂温度降低了63℃,且在造球水分为8%时,生球抗压强度为10.2 N/个,落下强度为4.2次/个,均能够满足生球质量要求;随着膨润土用量由0.6%增加至1.4%时,生球抗压强度和落下强度均得到提高,爆裂温度升高了89℃,且在膨润土用量为1.0%时,生球抗压强度为10.4 N/个,落下强度为4.8次/个,均满足质量要求。

Lattice Boltzmann Flux Solver:An Efficient Approach for Numerical Simulation of Fluid Flows

A lattice Boltzmann flux solver(LBFS)is presented for simulation of fluid flows.Like the conventional computational fluid dynamics(CFD)solvers,the new solver also applies the finite volume method to discretize the governing differential equations,but the numerical flux at the cell interface is not evaluated by the smooth function approximation or Riemann solvers.Instead,it is evaluated from local solution of lattice Boltzmann equation(LBE)at cell interface.Two versions of LBFS are presented in this paper.One is to locally apply one-dimensional compressible lattice Boltzmann(LB)model along the normal direction to the cell interface for simulation of compressible inviscid flows with shock waves.The other is to locally apply multi-dimensional LB model at cell interface for simulation of incompressible viscous and inviscid flows.The present solver removes the drawbacks of conventional lattice Boltzmann method(LBM)such as limitation to uniform mesh,tie-up of mesh spacing and time interval,limitation to viscous flows.Numerical examples show that the present solver can be well applied to simulate fluid flows with non-uniform mesh and curved boundary.

电磁驱动高能量密度动力学实验的一维磁流体力学多物理场数值模拟平台:SSS-MHD

超高压、超高密度物质状态生成和性质研究是当代极端物理学的重要前沿领域,电磁驱动的高能量密度物理实验对于该领域的意义尤为重要。这类实验虽然形式上多种多样,但在物理上有内在统一性,即均以力学守恒定律和宏观电磁理论为基本框架。为了建立统一数值模拟平台、依靠负载电流实验数据(或驱动电路真实数据)确定各种极端实验条件下负载构形的力学运动及其与各个物理场的耦合问题,将经受大量实际检验的冲击、爆轰动力学和激光效应计算的一维拉格朗日编码SSS,实质性扩展成为磁流体力学多物理场耦合编码SSS-MHD。对于具有典型意义的平面准等熵斜波压缩、高速平面固体飞片发射、固体套筒电磁内爆和炸药内爆磁通量压缩实验等各类高能量密度动力学实验案例的模拟计算结果表明,编码SSS-MHD计算与美国Z装置、中国CQ和CJ系列装置的实验及美国编码ALEGRA-1D和2D计算数据的相对偏差基本不超过5%。该数值模拟平台为极端材料动力学实验(包括气体、液体、化合物和金属)提供了有力的支撑,还将有助于多维磁流体力学多物理场编码的开发。

电流切换型等离子体套筒驱动磁通压缩电流放大实验0维模型数值模拟

为利用雷电驱动Z箍缩产生聚变,调查了相关脉冲压缩技术,尤其是新型的磁通压缩电流放大技术。本文提出一个0维模型,用于描述文献中的电流切换型等离子体套筒驱动磁通压缩电流放大实验,模型计算的结果与实验符合很好。模型成功的关键是其中包含一个定性先升后降的开关电感模型。推测开关断路过程中等离子体壳层的长度先增后减对应于电感的先升后降,这需进一步通过1维和2维建模模拟来确认。

A Re-examination of Density Effects in Eddy Covariance Measurements of CO_2 Fluxes

Corrections of density effects resulting from air-parcel expansion/compression are important in interpreting eddy covariance fluxes of water vapor and CO2 when open-path systems are used. To account for these effects, mean vertical velocity and perturbation of the density of dry air are two critical parameters in treating those physical processes responsible for density variations. Based on various underlying assumptions, different studies have obtained different formulas for the mean vertical velocity and perturbation of the density of dry air, leading to a number of approaches to correct density effects. In this study, we re-examine physical processes related to different assumptions that are made to formulate the density effects. Specifically, we re-examine the assumptions of a zero dry air flux and a zero moist air flux in the surface layer, used for treating density variations, and their implications for correcting density effects. It is found that physical processes in relation to the assumption of a zero dry air flux account for the influence of dry air expansion/compression on density variations. Meanwhile, physical processes in relation to the assumption of a zero moist air flux account for the influence of moist air expansion/compression on density variations. In this study, we also re-examine mixing ratio issues. Our results indicate that the assumption of a zero dry air flux favors the use of the mixing ratio relative to dry air, while the assumption of a zero moist air flux favors the use of the mixing ratio relative to the total moist air. Additionally, we compare different formula for the mean vertical velocity, generated by air-parcel expansion/compression, and for density effect corrections using eddy covariance data measured over three boreal ecosystems.

电磁能与炸药联合加载药型罩基础理论

为提高聚能射流对炸药能量的利用率,结合电磁加载药型罩以及爆磁压缩发生器原理,提出一种电磁能与炸药联合加载药型罩的原理结构。联合加载分为两个阶段:第1阶段,电容器放电,在爆磁压缩发生器中形成初始磁通;第2阶段,炸药1爆轰,压缩磁场,电流增大,同时爆轰波传播至药型罩部分引爆炸药2,电磁力与爆轰压力共同压垮药型罩。结合炸药爆轰理论、传统PER射流成型理论以及电磁加载特性,建立电磁与炸药联合加载下药型罩射流成型的理论模型。利用理论模型计算?56 mm聚能装药在联合加载结构下的射流成型,并通过理论计算分析联合加载时序对联合加载射流成型的影响。计算结果表明:电磁与炸药联合加载能够增加成型射流的速度以及动能,提高聚能射流对炸药的利用率,并且优化联合加载时序能够进一步提高射流速度和动能;联合加载下射流动能相对传统聚能装药提升了34.5%,对炸药的能量利用率提高了36%。

石粉种类及含量对C60机制砂混凝土性能的影响

为研究不同机制砂粗颗粒(0.075~4.75 mm)与石粉(<75μm)的质量比(砂粉比)对岩石粉混凝土性能的影响,使用岩石粉(石灰石粉和花岗岩石粉)以不同质量比取代机制砂制备高强混凝土,测试不同砂粉比条件下混凝土流动性能、抗压强度和耐久性能(干燥收缩率及电通量)的演变规律。结果表明,机制砂的砂粉比不低于9时,砂粉比降低有利于改善混凝土拌合物的和易性,增强混凝土抗压强度和耐久性能。进一步降低砂粉比对混凝土的干燥收缩性能影响较小,但对混凝土流动性、力学性能和抗氯离子渗透性不利。降低砂粉比有利于提高机制砂混凝土的密实性,但过低的砂粉比容易造成混凝土需水量升高,游离态石粉颗粒含量增大,对混凝土性能不利。

塑性膨胀剂对海上风电超高性能灌浆料性能的影响

分别采用偶氮化合物类塑性膨胀剂(PEA1)及亚硝基化合物类塑性膨胀剂(PEA2)配制了C125海上风电超高性能灌浆料,对比研究了塑性膨胀剂种类及掺量对C125海上风电超高性能灌浆料流动度、膨胀率、抗压强度、电通量及孔结构分布的影响规律。结果表明,随着塑性膨胀剂掺量的增加,灌浆料的流动度先增大后减小,抗压强度逐渐降低,竖向膨胀率和电通量逐渐增加。当PEA1、PEA2掺量相同时,PEA1对灌浆料的流动度、抗压强度、竖向膨胀率和电通量的影响幅度更大,掺入PEA1后灌浆料的总孔隙率、平均孔径及大孔比例增幅更明显。

唐钢带式焙烧工艺生产熔剂性球团矿

球团矿具有铁品位高、冶金性能优良、粒度均匀、冷态强度高、冶炼过程渣铁比低和燃料比低等特点。随着球团矿入炉比例的提升、环保要求的不断提高,带式焙烧机以其大型化、自动化、集约化、低能耗等特点成为球团生产线的首选。本文基于唐钢自身铁精粉中MgO、TiO2含量高的资源状况,分析了MgO、TiO2含量对熔剂性球团矿熔滴性能、低温还原粉化指标、转鼓指数、抗压强度、膨胀指数、筛分指数等指标的影响。结果表明,在膨润土配比0.6%、SiO23.0%~3.20%,熔剂性球团矿碱度1.2,且TiO2含量为0.6%时,MgO含量从1.5%提高至2.1%,球团矿抗压强度变化不大,膨胀指数略有降低,低温还原粉化率(RDI+6.3 mm)明显提高;在相同生产条件下,熔剂性球团矿中MgO含量为1.5%时,TiO2含量从0.2%提高至0.9%,球团矿转鼓指数、筛分指数变化不明显,抗压强度略有下降,膨胀指数略有提高,低温还原粉化率明显下降。通过采取优化配矿结构,唐钢3座3 000 m^(3)高炉在配加40%以上球团矿的情况下,炉况顺行,状况良好。

不同预湿再生细骨料对UHPC的力学与自收缩性能影响

研究了不同预湿和不同取代率再生细骨料对超高性能混凝土(UHPC)的抗压强度、自收缩、抗氯离子渗透性能影响。结果表明:再生细骨料的预湿程度和掺量是影响UHPC力学性能和自收缩的关键因素。不同预湿程度再生细骨料均能降低其早期自收缩,而对其早期抗压强度和抗氯离子侵蚀能力有不利影响,但提升其28d抗压强度;随着预湿再生细骨料掺量增大,UHPC自收缩逐渐降低,其中掺20%全预湿再生细骨料制备的UHPC抗压强度与抗氯离子渗透性能更优,与未掺再生细骨料UHPC相比,其28d抗压强度提升16.6%,自收缩降低了74.5%;预湿再生细骨料体孔隙水释放出来起到内养护的作用,降低UHPC内部自干燥进程,提高水化反应程度,优化界面过渡区组成结构,提高抗压强度和耐久性。

高增益螺旋形爆炸磁通量压缩发生器

从爆炸磁通量压缩发生器的工作原理和有效利用炸药能入手，探讨爆炸磁通量压缩发生器运行性能的影响因素和设计制造过程应注意的问题。

电磁轨道炮军事应用综述

从电炮实用电源、电枢与烧蚀、复杂轨道设计、与线圈炮对比、磁场增强措施、应用要求和军事使用效果等角度分析了当前电磁轨道炮的技术特征。结论为:活塞式螺旋绕组磁通压缩发电机(MFCG)适合作轨道炮电源,该电磁轨道炮在采用固态电枢、无烧蚀高效率、高射速、超高速发射小质量射弹方面有无可比拟的优势。通过对比分析了高空小质量弹丸与地面大质量射弹的弹道学特征,提出了轨道炮可能优先应用于高空飞机平台上用于自卫、防空、近程反导的电磁发射动能武器,它具有响应快、作战半径大、高精度、抗电磁干扰等优势,对未来作战效果和作战模式有广泛影响。