The maximum normal impact resultant force(NIRF)is usually regarded as the sum of the static earth pressure of the dead zone and the dynamic impact pressure of the flowing layer.The influence of the interaction between...The maximum normal impact resultant force(NIRF)is usually regarded as the sum of the static earth pressure of the dead zone and the dynamic impact pressure of the flowing layer.The influence of the interaction between the flowing layer and dead zone on the impact force is ignored.In this study,we classified two impact models with respect to the pileup characteristics of the dead zone.Then,we employed the discrete element method to investigate the influences of the pileup characteristics on the impact force of dry granular flow on a tilted rigid wall.If the final pileup height is equal to the critical value,the maximum NIRF can be estimated using a hydrostatic model,because the main contribution to the maximum NIRF is the static earth pressure of the dead zone.If the final pileup height is less than the critical value,however,the particles in the dead zone are squeezed along the slope surface by the impact ofthe flowing layer on the dead zone,and because of shear effects,the flowing layer causes an entrainment in the dead zone.This results in a decrease in the volume of the dead zone at the moment of maximum NIRF with increases in the slope angle.As such,the maximum NIRF mainly comprises the instant impact force of the flowing layer,so hydro-dynamic models are effective for estimating the maximum NIRF.Impact models will benefit from further study of the components and distribution of the impact force of dry granular flow.展开更多
为研究特高压线路绝缘子的自然积污状况及不同呼称高度杆塔上绝缘子的积污水平差异,在河南省郑州市境内的±800 k V哈郑直流线路的一基杆塔上,对1片悬挂在负极导线端的绝缘子和4串悬挂于不同高度处的不带电绝缘子进行了半年的自然...为研究特高压线路绝缘子的自然积污状况及不同呼称高度杆塔上绝缘子的积污水平差异,在河南省郑州市境内的±800 k V哈郑直流线路的一基杆塔上,对1片悬挂在负极导线端的绝缘子和4串悬挂于不同高度处的不带电绝缘子进行了半年的自然积污试验。试验结果表明:带电绝缘子表面污秽中的阳离子主要为2aC+和4NH+,阴离子主要为24SO-和3NO-;不可溶成分中2Si O约占80%,也含有少量2 3Al O、2 3Fe O等。工厂烟尘、汽车尾气中的2SO和氮氧化物是绝缘子污秽中24SO-和3NO-的重要来源。利用富集因子法计算得出了污秽中各金属元素的富集程度,发现Ca、Zn、Fe、Mg和Al等元素均受到不同程度的人为污染,其中Ca和Zn元素达到了严重污染的程度。化工厂废液中的2nZ+会通过污染周边土壤间接地影响绝缘子积污。绝缘子表面污秽颗粒粒度集中在10μm左右。同一地区,绝缘子表面自然积污程度随着悬挂高度的增加而逐渐降低。展开更多
文摘The maximum normal impact resultant force(NIRF)is usually regarded as the sum of the static earth pressure of the dead zone and the dynamic impact pressure of the flowing layer.The influence of the interaction between the flowing layer and dead zone on the impact force is ignored.In this study,we classified two impact models with respect to the pileup characteristics of the dead zone.Then,we employed the discrete element method to investigate the influences of the pileup characteristics on the impact force of dry granular flow on a tilted rigid wall.If the final pileup height is equal to the critical value,the maximum NIRF can be estimated using a hydrostatic model,because the main contribution to the maximum NIRF is the static earth pressure of the dead zone.If the final pileup height is less than the critical value,however,the particles in the dead zone are squeezed along the slope surface by the impact ofthe flowing layer on the dead zone,and because of shear effects,the flowing layer causes an entrainment in the dead zone.This results in a decrease in the volume of the dead zone at the moment of maximum NIRF with increases in the slope angle.As such,the maximum NIRF mainly comprises the instant impact force of the flowing layer,so hydro-dynamic models are effective for estimating the maximum NIRF.Impact models will benefit from further study of the components and distribution of the impact force of dry granular flow.
