结合放电影像观测的土壤冲击散流性能评估方法

已有研究表明雷电冲击电流作用下,接地装置冲击散流性能受接地极近区土壤的影响显著,主要表现为土壤出现显著的火花放电现象,而目前对不同类型土壤的冲击散流性能评估还缺乏有效的方法。实际工程中主要是采用经验公式将土壤火花放电效应折算到接地装置的冲击系数中,但该系数是冲击电流作用下接地导体自身电感效应和近区土壤火花放电效应的综合反映结果,并不能准确反映土壤的冲击散流性能。因此,针对该问题采用X射线透视成像技术,开展了接地导体近区土壤冲击散流性能评估方法研究,提出了结合土壤试品冲击放电区域与冲击电流幅值的量化评估指标,即单位电流下土壤放电体积等效值V_I,并对该方法的合理性与有效性进行了验证,分析了不同性质土壤试品中接地装置散流能力的变化规律。结果表明,结合土壤冲击放电影像观测的V_I能够直观地分析土壤试品参数变化对接地装置冲击散流能力的影响规律,并为增强近区土壤冲击散流能力,降低接地装置冲击接地阻抗提供了新的思路。

Electrochemical Properties of Electrodes with Different Shapes and Diffusion Kinetic Analysis of Microbial Fuel Cells on Ocean Floor

Microbial fuel cell(MFC) on the ocean floor is a kind of novel energy-harvesting device that can be developed to drive small instruments to work continuously.The shape of electrode has a great effect on the performance of the MFC.In this paper,several shapes of electrode and cell structure were designed,and their performance in MFC were compared in pairs:Mesh(cell-1) vs.flat plate(cell-2),branch(cell-3) vs.cylinder(cell-4),and forest(cell-5) vs.disk(cell-6) FC.Our results showed that the maximum power densities were 16.50,14.20,19.30,15.00,14.64,and 9.95 mWm-2 for cell-1,2,3,4,5 and 6 respectively.And the corre-sponding diffusion-limited currents were 7.16,2.80,18.86,10.50,18.00,and 6.900 mA.The mesh and branch anodes showed higher power densities and much higher diffusion-limited currents than the flat plate and the cylinder anodes respectively due to the low diffusion hindrance with the former anodes.The forest cathode improved by 47% of the power density and by 161% of diffusion-limited current than the disk cathode due to the former's extended solid/liquid/gas three-phase boundary.These results indicated that the shape of electrode is a major parameter that determining the diffusion-limited current of an MFC,and the differences in the elec-trode shape lead to the differences in cell performance.These results would be useful for MFC structure design in practical applica-tions.

New development of Einstein′s viscose law for powder suspension systems

Through the analysis of the present situation of the rheology of suspension disperse systems, the classical Einstein′s viscosity law was developed into the generalized Einstein′s viscosity law which can be further developed into universalized form, called the universalized Einstein′s viscosity law by introducing modification function f(φ) . Some rational forms of the function f(φ) were discussed according to functional approximation method, and were consequently developed into a few suspension disperse system rheological equations suitable for high particle concentration. These equations all keep good consistence with the models acquired in experiments or other mathematical physics analysis.

高土壤电阻率地区柔性石墨复合接地材料与圆钢接地材料的有效长度对比研究

改善杆塔接地能够有效的降低输电线路雷击跳闸率,对于高土壤电阻率地区的杆塔,减小冲击接地电阻是降低雷击跳闸率的关键,而减小接地体冲击接地电阻可以通过延长接地体长度来实现,但是当长度超过一定值时,延长将不再有效。因此研究接地体的有效长度、选取有效长度更长的接地材料,对降低接地电阻有着重要意义。首先分析了接地体有效长度的物理意义,然后运用CDEGS仿真软件计算工程中常用的镀锌钢和柔性石墨复合材料水平接地体的工频接地电阻与接地体长度、冲击接地电阻与接地体长度之间的关系。由此对比在高土壤电阻率情况下柔性石墨复合接地材料的和镀锌钢材料的有效长度,并分析其原因。此后采用冲击散流试验加以验证,最后得出结论,高土壤电阻率情况并通以冲击电流时,柔性石墨复合材料接地体有更长的有效长度。