Influence of water coupling coefficient on the blasting effect of red sandstone specimens

This study investigates the impact of different water coupling coefficients on the blasting effect of red sandstone.The analysis is based on the theories of detonation wave and elastic wave,focusing on the variation in wall pressure of the blasting holes.Using DDNP explosive as the explosive load,blasting tests were conducted on red sandstone specimens with four different water coupling coefficients:1.20,1.33,1.50,and 2.00.The study examines the morphologies of the rock specimens after blasting under these different water coupling coefficients.Additionally,the fractal dimensions of the surface cracks resulting from the blasting were calculated to provide a quantitative evaluation of the extent of rock damage.CT scanning and 3D reconstruction were performed on the post-blasting specimens to visually depict the extent of damage and fractures within the rock.Additionally,the volume fractal dimension and damage degree of the post-blasting specimens are calculated.The findings are then combined with numerical simulation to facilitate auxiliary analysis.The results demonstrate that an increase in the water coupling coefficient leads to a reduction in the peak pressure on the hole wall and the crushing zone,enabling more of the explosion energy to be utilized for crack propagation following the explosion.The specimens exhibited distinct failure patterns,resulting in corresponding changes in fractal dimensions.The simulated pore wall pressure–time curve validated the derived theoretical results,whereas the stress cloud map and explosion energy-time curve demonstrated the buffering effect of the water medium.As the water coupling coefficient increases,the buffering effect of the water medium becomes increasingly prominent.

Molecular Dynamics, Physical Properties, Diffusion Coefficients and Activation Energy of the Lithium Oxide (Li-O) and Sodium Oxide (Na-O) Electrolyte (Cathode)

This work is a simulation model with the LAMMPS calculation code of an electrode based on alkali metal oxides (lithium, sodium and potassium) using the Lennard Jones potential. For a multiplicity of 8*8*8, we studied a gap-free model using molecular dynamics. Physical quantities such as volume and pressure of the Na-O and Li-O systems exhibit similar behaviors around the thermodynamic ensembles NPT and NVE. However, for the Na2O system, at a minimum temperature value, we observe a range of total energy values;in contrast, for the Li2O system, a minimum energy corresponds to a range of temperatures. Finally, for physicochemical properties, we studied the diffusion coefficient and activation energy of lithium and potassium oxides around their melting temperatures. The order of magnitude of the diffusion coefficients is given by the relation Dli-O >DNa-O for the multiplicity 8*8*8, while for the activation energy, the order is well reversed EaNa-O > EaLi-O.

Performance of water-coupled charge blasting under different in-situ stresses

Water-coupled charge blasting is a promising technique to efficiently break rock masses.In this study,numerical models of double boreholes with water-coupled charge are established using LS-DYNA and are calibrated by the tests of rock masses subjected to explosion loads to examine its performance.The crack levels of rock mass induced by water-coupled charge blasting and air-coupled charge blasting are first compared.It is found that water-coupled charge blasting is more appropriate to fracture deep rock mass than air-coupled charge blasting.In addition,the effects of rock properties,water-coupled charge coefficients,and borehole connection angles on the performance of water-coupled charge blasting are investigated.The results show that rock properties and water-coupled charge coefficients can greatly influence the crack and fragmentation levels of rock mass induced by water-coupled charge blasting under uniform and non-uniform in-situ stresses.However,changing borehole-connection angles can only affect crack and fragmentation levels of rock mass under non-uniform in-situ stresses but barely affect those under uniform in-situ stresses.A formula is finally proposed by considering the above-mentioned factors to provide the design suggestion of water-coupled charge blasting to fracture rock mass with different in-situ stresses.

Diffusion Equations of the Electric Charges and Magnetic Flux

Innovative definitions of the electric and magnetic diffusivities through conducting mediums and innovative diffusion equations of the electric charges and magnetic flux are verified in this article. Such innovations depend on the analogy of the governing laws of diffusion of the thermal, electrical, and magnetic energies and newly defined natures of the electric charges and magnetic flux as energy, or as electromagnetic waves, that have electric and magnetic potentials. The introduced diffusion equations of the electric charges and magnetic flux involve Laplacian operator and the introduced diffusivities. Both equations are applied to determine the electric and magnetic fields in conductors as the heat diffusion equation which is applied to determine the thermal field in steady and unsteady heat diffusion conditions. The use of electric networks for experimental modeling of thermal networks represents sufficient proof of similarity of the diffusion equations of both fields. By analysis of the diffusion phenomena of the three considered modes of energy transfer;the rates of flow of these energies are found to be directly proportional to the gradient of their volumetric concentration, or density, and the proportionality constants in such relations are the diffusivity of each energy. Such analysis leads also to find proportionality relations between the potentials of such energies and their volumetric concentrations. Validity of the introduced diffusion equations is verified by correspondence their solutions to the measurement results of the electric and magnetic fields in microwave ovens.

Study and Implementation on Batteries Charging Method of Micro-Grid Photovoltaic Systems

In the micro-grid photovoltaic systems, the random changes of solar radiation enable lead-acid batteries to experience low SOC (State of Charge) or overcharged for periods of time if directly charged with such traditional methods as decreased charging current, which will reduce lifetime of batteries. What’s more, it’s difficult to find a proper reduction coefficient in decreasing charging current. To adapt to the random changes of circumstance and avoid selecting the reduction coefficient, a new fast charging method named decreased charging current based on SOC is proposed to apply into micro-grid photovoltaic systems. It combines batteries’ SOC with the maximum charging voltage to determine the charging rate without strictly selecting reduction coefficient. By close-loop current control strategy and related scheme, the experiment proves the new method is feasible and verifies that, comparing with decreased charging current, the improved method make batteries’ SOC reach 100% in shorter time as well as the temperature of batteries raise more slowly.

Non-Stokes drag coefficient in single-particle electrophoresis:New insights on a classical problem

We measured the intrinsic electrophoretic drag coefficient of a single charged particle by optically trapping the particle and applying an AC electric field,and found it to be markedly different from that of the Stokes drag.The drag coefficient,along with the measured electrical force,yield a mobility-zeta potential relation that agrees with the literature.By using the measured mobility as input,numerical calculations based on the Poisson-Nernst-Planck equations,coupled to the Navier-Stokes equation,reveal an intriguing microscopic electroosmotic flow near the particle surface,with a well-defined transition between an inner flow field and an outer flow field in the vicinity of electric double layer’s outer boundary.This distinctive interface delineates the surface that gives the correct drag coefficient and the effective electric charge.The consistency between experiments and theoretical predictions provides new insights into the classic electrophoresis problem,and can shed light on new applications of electrophoresis to investigate biological nanoparticles.

Non-coupled charge explosion and geo-mechanical dynamics

The non-coupled charge explosion and geo-mechanical dynamics problem in real air condition is studied in this paper. It analyzes and calculates the problem by using the real air state equations. Through researching on the non-coupled charge rock bench blasting with big clearance of air, its result indicates that the borehole wall reflection overpressure is far higher than strength of rock, but much lower than detonation front pressure of the charge. So non-coupled charge explosion blasting engineering is very successful. Furthermore, it introduces the method of shaft forming by blasting once and the new tube room technology. And the non-coupled charge explosion is used successfully in the method of shaft forming by blasting once. As it drills and blasts in the top and removes the broken rock from the bottom tunnel, it increases the construction efficiency significantly. This paper has important reference on the improvement of the large-span underground engineering construction.

径向不耦合装药孔壁冲击压力特性

径向不耦合装药结构广泛应用于实际爆破工程中,为探究径向不耦合装药孔壁冲击压力的变化规律,基于冲击波理论,利用激波管模型对径向不耦合装药条件下孔内波系作用过程进行简化分析。研究了孔内爆炸冲击波在各介质面的冲击压力,获得了径向不耦合装药条件下孔壁初始冲击压力的计算表达式,模拟了径向不耦合装药时冲击波的作用过程。研究结果表明:径向空气层的存在极大削减了爆炸冲击波压力,孔壁峰值压力在不耦合系数1~2时发生指数型衰减,在不耦合系数大于2时,其衰减速度较缓慢。冲击波作用在孔壁处时存在多个波峰,且初始峰值压力最大,后续峰值压力随时间的延长逐渐减小;随着不耦合系数的增大,初始峰值压力逐渐减小且到达峰值压力的出现时间也逐渐延后;不耦合系数越大,多波峰特性越明显,不耦合系数较小时峰值压力较大,会对围岩产生较大的破坏。为减小对围岩的破坏且满足相应的爆破要求,应充分利用不耦合系数较大时的多波峰特性,根据岩石性质选择合理的径向装药系数。

不耦合装药系数对岩体爆破损伤的影响

在爆破工程中,选择合适的装药结构能够有效提高炸药利用率,从而改善爆破效果。基于RHT(Riedel-Hiermaier-Thomamodel)动态响应力学关系,采用ANSYS/LS-DYNA软件研究了偏心不耦合装药条件下不耦合系数K对岩体爆破荷载的影响,以及爆破过程中岩体的损伤情况。通过建立单孔偏心不耦合爆破模型,分析了不耦合系数K为1.0、1.5、2.0、2.5、3.0和3.5条件下的有效应力、振动速度、爆破地震波能量和损伤状况。同时,研究了不同不耦合系数K条件下爆心距(l)与损伤度(D)、质点振动速度(PPV)与爆心距(l),以及振动速度(vpp)与损伤度(D)之间的关系。结果表明:随着不耦合系数K的增大,耦合侧与不耦合侧有效应力和峰值振动速度、地震波峰值能量略微减小;粉碎区和裂隙区范围逐渐减小,且粉碎区损伤半径较裂隙区减小速率更大。岩体损伤程度和质点振动速度(vpp)均随着爆心距的增大而逐渐减小。质点振动速度越大损伤程度也越大,当vpp=50.4 cm/s时,岩体中的损伤变量达到损伤破坏阈值(D=0.19);当vpp>140.6 cm/s时,损伤度D>0.80。

不耦合装药下岩石爆破块体尺寸的分布特征

通过不同装药结构下立方体红砂岩小型爆破实验,分析了岩石的损伤程度和破坏模式,同时引入三参数极值分布函数量化岩石爆破块体尺寸分布特征。此外,根据岩样R1的爆破实验结果进行了有限元数值模型验证,基于验证的模型展开了岩石单孔爆破损伤破裂行为的模拟,讨论了径向、轴向不耦合系数和耦合介质对岩石破碎效果的影响。结果表明,三参数极值分布函数可以较好地表征岩石爆破后破碎块体尺寸分布特征,块体平均尺寸随着不耦合系数的减小呈线性降低趋势,且破碎块度趋于均匀。通过比较不同耦合介质装药时岩石内部的能量分布特征和破坏体积发现,水作为耦合介质时,爆炸能量的传递效率最高,其次分别是湿砂和干砂,空气的能量传递效率最低。结合等效波阻法计算的理论应力透射系数可以很好地反映不耦合装药时岩石的破碎程度。

径向不耦合装药爆压消峰作用及其对岩石破裂范围影响

弄清单孔爆破岩石破裂规律是揭示群孔爆破岩石破碎机理的基础。从理论上阐明了单孔爆破岩石破裂机理,采用高能爆轰炸药模型和混凝土损伤模型,分别模拟了空气与水不耦合装药下单孔爆破的应力变化过程、裂纹扩展过程以及不耦合系数为1.0~3.5时岩石粉碎区与裂隙区大小;分析了炮孔壁上爆破压力峰值、粉碎区与裂隙区的大小随不耦合系数的变化规律。研究结果表明:由于不同介质的影响,空气不耦合装药结构对于爆压的削峰作用约是水不耦合装药结构的2倍;当不耦合系数介于1.0~3.5时(药卷直径不变),空气不耦合装药下粉碎区直径介于4.44~1.59倍炮孔直径,裂隙区直径介于22.5~7.62倍炮孔直径;水不耦合装药下粉碎区直径介于4.44~2.74倍炮孔直径,裂隙区直径介于22.5~10.67倍炮孔直径。

基于电场传感器阵列的输电线路电压非接触式测量方法

电压作为表征线路运行状态的重要参量,实现其灵活准确的测量对保证电力系统稳定运行至关重要。传统的接触式电压测量方法,因电压互感器体积较大、会产生电磁谐振和高频振荡、额外测量需断电安装等问题,对于海量化测量并不便利。相比较而言,非接触式测量不接触导线,更加安全和便捷,将成为未来电压测量的发展方向。文中提出了基于电场传感器阵列的输电线路电压非接触式测量方法,该方法为了解决导线位置信息未知的问题,设计了与导线方向垂直排列的电场传感器阵列;求解了含导线未知信息量的方程组;构建了比例系数矩阵,反推出导线电压瞬时值;分析了电场传感器对测量的影响;最后,进行了10 kV电压等级电压瞬时值仿真验证,结果显示最大测量误差为2.219%。

基于热化学烧蚀模型的身管寿命等效折算系数研究

针对当前等效全装药(Equivalent Full Charge,EFC)折算系数的国家军用标准预测值与实际测试结果差距较大的问题,基于热-化学烧蚀模型,研究不同工况下射击发数与EFC射击发数间的折算系数计算方法。射击一定发数后,假设身管内壁白层厚度及成分随射击发数呈周期性变化,由质量扩散定律建立膛线起始部热-化学烧蚀量与火药燃气侵蚀性、内膛表面瞬态温度的关系。通过经典内弹道模型获得弹后空间火药燃气平均温度及内壁面强制对流换热系数,在考虑后效期高温燃气影响的基础上,建立身管内壁瞬态温度计算模型。以对内弹道过程有重要影响的射速、药量和药温为重点,计算不同射速、不同药号和不同药温下的身管内壁烧蚀量,并据此获得不同工况下的折算系数。研究发现,射速越快,装药质量越大,装药初始温度越高,单发射击造成的身管烧蚀越严重,其对应的EFC折算系数越大,其中强装药的EFC折算系数可达2.131。以某型155 mm火炮身管实弹射击数据为例,验证了新模型的合理性。

不耦合空气间隔装药结构爆破机理分析

空气间隔装药爆破广泛应用于隧道掘进开挖,其中不耦合系数是保证光面爆破效果的关键因素。QBT工程现场仅有Φ32 mm直径的药卷,为改善爆破效果,采用LS-DYNA程序对轴向不耦合系数Kl进行数值研究,分析了轴向不耦合系数Kl取2.41、3.22、4.83时炮孔壁应力场、速度场及损伤特性,与光面爆破小直径药卷(Φ25 mm)连续装药结构进行对比,揭示轴向不耦合系数对爆破效果的影响,得到最优取值。结果表明:有效应力峰值与轴向不耦合系数成反比,应力衰减程度与轴向不耦合系数成正比;质点峰值速度下降率为64%~82%,有效降低了爆破振动,轴向不耦合系数越大,控制振动水平能力越强,但由于岩石损伤程度分布发育不充分,在孔口处可能存在挂门帘现象。

考虑分区域动态电价机制引导的电动汽车充电优化策略

为应对大规模电动汽车无序充电引起的配电网运行损耗增加问题,提出一种分区域动态电价机制引导的电动汽车(electric vehicle,EV)充电优化策略。该动态电价机制是根据不同区域内的负荷特点建立不同的动态电价,从而优化对应区域的EV充电。其中商业区建立计及充电站充电总功率的动态电价模型,居民区和办公区采用计及风光出力的动态电价模型。同时,提出充电效益系数模型以提升在居民区和办公区用户的充电时间满意度。最后,在IEEE33节点系统上进行仿真验证。结果表明,所提出的基于分区域动态电价机制的EV充电优化策略能够在保证车主利益的同时,降低网损、提高配网电压质量、促进风光消纳以及提升配网的经济性。

改善不同地应力下隧道轮廓爆破成型效果

含预切空腔的轮廓爆破技术被认为是改善高地应力下隧道轮廓成型的有效方法。然而,对这种爆破技术在不同地应力下性能的研究较少。本文通过校验后的公路隧道数值模型,调查了含预切空腔(PC)的两种典型轮廓爆破技术(即光面爆破(SB)和预裂爆破(PB))在不同地应力条件下的性能。结果表明,在耦合装药和50 MP地应力下,PCSB比PCPB能获得更好的隧道轮廓成型效果。此外,研究了两种轮廓爆破技术在不同的不耦合系数和地应力条件下的性能,发现随着地应力从30 MPa增加至50 MPa,PCSB和PCPB作用下隧道轮廓成型效果均逐渐改善。此外,在不同地应力条件下调整周边孔的不耦合系数能使PCPB形成有效的隧道轮廓。然而,对于PCSB,在不同地应力条件下,需调整所有炮孔的不耦合系数才能形成符合要求的隧道轮廓。最后通过多元非线性回归获得经验公式,本研究可以为不同地应力下使用PCSB和PCPB开挖隧道提供设计参考。

浅谈新建居住区充电桩配建比例提升的电气问题

2023年,国务院办公厅和北京市政府相继出台政策,要求进一步加强新建住宅小区充电桩配建,并提出了《电动汽车分散充电设施工程技术标准》DB11/T1455—2017的修编任务。作为规范参编人,笔者结合本规范在颁布执行以来遇到的问题进行总结,并通过对国家电网、消防救援局、建设单位、物业单位、充电设施制造商、平台运营商、电池厂商等进行的多方调研,对政策的落实方案提出了一些粗浅的分析和建议。

计及SOC影响的电化学储能系统低电压穿越控制策略

针对电化学储能现有低电压穿越控制策略未计及荷电状态(state of charge,SOC)动态特性导致其在低SOC场景下出现过放这一问题,设计并引入自适应调节系数来表征低电压穿越期间SOC对储能单元输出有功电流的影响,进而提出一种计及SOC动态特性与充放电状态的电化学储能系统低电压穿越控制策略。该控制策略基于并网规范的电压和频率要求,结合工程实际应用对自适应调节系数进行定量设计,使得系统故障期间储能单元输出的有功电流能够根据SOC大小动态调整。仿真结果表明,该控制策略在低SOC场景下能够有效限制有功电流输出,减缓放电速度,从而避免小容量、大放电倍率储能单元出现因SOC越限而退出运行的风险,并减小低电压穿越过程中多个储能单元之间的SOC极差。通过与传统的低电压穿越策略对比验证了所提策略的有效性。

基于主从博弈的考虑无线充电道规划的电网调度策略

该文研究无线充电道的规划问题,并在规划基础上研究电动汽车在无线充电道上充电对电网造成的影响。首先,基于道路、充电站的分布和交通情况,建立新型的路网交通模型,并通过分析各道路的拥堵系数,提出无线充电道的最优规划;其次,以电网运营商为领导者,以充电行为的变化规律符合改进需求响应函数的电动汽车用户为跟随者,建立主从博弈模型;最后,采用粒子群算法对其进行求解,得到最优的分时电价和充电策略,实现电网运营商收益最大与用户充电成本最小。研究结果表明,该方法解决无线充电道的利用率和收益低的问题,并为电动汽车通过无线充电道参与电网调度提供了理论依据。

地应力作用下隧道爆破周边孔参数优化研究

为探究在地应力作用下隧道爆破时周边孔最优参数,以白竹山隧道为工程背景,通过数值模拟方法研究当隧道地应力为5 MPa时的情况,将周边孔不耦合装药系数和空气间隔装药段数进行调整,确定合理的爆破参数指导现场施工。研究表明,在相同药量情况下,当不耦合系数为1.4时,粉碎区范围适中,岩体破碎充分,炮孔之间形成良好贯通;周边孔采用空气间隔装药时,孔底空气长度为0.6 m,每节药卷为0.3 m的4段间隔装药结构较为合适,能将平均超欠挖厚度控制在20 cm内,爆破效果较好。