Based on the triaxial testing machine and discrete element method, the effects of embedded crack on rock fragmentation are investigated in laboratory tests and a series of numerical investigations are conducted on the...Based on the triaxial testing machine and discrete element method, the effects of embedded crack on rock fragmentation are investigated in laboratory tests and a series of numerical investigations are conducted on the effects of discontinuities on cutting characteristics and cutting efficiency. In laboratory tests, five propagation patterns of radial cracks are observed. And in the numerical tests, firstly, it is similar to laboratory tests that cracks ahead of cutters mainly initiate from the crushed zone, and some minor cracks will initiate from joints. The cracks initiating from crushed zones will run through the thinner joints while they will be held back by thick joints. Cracks tend to propagate towards the tips of embedded cracks, and minor cracks will initiate from the tips of embedded cracks, which may result in the decrease of specific area, and disturbing layers play as ‘screens', which will prevent cracks from developing greatly. The peak penetration forces, the consumed energy in the penetration process and the uniaxial compression strength will decrease with the increase of discontinuities. The existence of discontinuities will result in the decrease of the cutting efficiency when the spacing between cutters is 70 mm. Some modifications should be made to improve the efficiency when the rocks containing groups of discontinuities are encountered.展开更多
The separation characteristics of the PVA-CS (polyvinyl alcohol-chitosan) blended composite membrane for dehydration of ethanol-water mixture are examined. The relationships of flux and separation factor with the feed...The separation characteristics of the PVA-CS (polyvinyl alcohol-chitosan) blended composite membrane for dehydration of ethanol-water mixture are examined. The relationships of flux and separation factor with the feed concentration and operation temperature are established. Using this correlated equation, the continuous-flow pervaporation process about 500 kilolitres/year dehydrated ethanol is designed. The numbers of stage and reheater are calculated by stage-by-stage method for two kinds of cascades: one with equal membrane area and the other with 10℃ of temperature decrement per section. The results show that when the numbers of stage and reheater are the same, the cascade with 10℃ of temperature decrement has more advantages than that with equal membrane area. The influences of feed concentration and flow rate on the numbers of stage and reheater in the cascades are discussed.展开更多
基金Project(2013CB035401) supported by the National Basic Research Program of ChinaProject(51174228) supported by the National Natural Science Foundation of China+1 种基金Project(71380100003) supported by Hunan Provincial Innovation Foundation for Postgraduate,ChinaProject(201304) supported by Open Research Fund of Hunan Province Key Laboratory of Safe Mining Techniques of Coal Mines(Hunan University of Science and Technology),China
文摘Based on the triaxial testing machine and discrete element method, the effects of embedded crack on rock fragmentation are investigated in laboratory tests and a series of numerical investigations are conducted on the effects of discontinuities on cutting characteristics and cutting efficiency. In laboratory tests, five propagation patterns of radial cracks are observed. And in the numerical tests, firstly, it is similar to laboratory tests that cracks ahead of cutters mainly initiate from the crushed zone, and some minor cracks will initiate from joints. The cracks initiating from crushed zones will run through the thinner joints while they will be held back by thick joints. Cracks tend to propagate towards the tips of embedded cracks, and minor cracks will initiate from the tips of embedded cracks, which may result in the decrease of specific area, and disturbing layers play as ‘screens', which will prevent cracks from developing greatly. The peak penetration forces, the consumed energy in the penetration process and the uniaxial compression strength will decrease with the increase of discontinuities. The existence of discontinuities will result in the decrease of the cutting efficiency when the spacing between cutters is 70 mm. Some modifications should be made to improve the efficiency when the rocks containing groups of discontinuities are encountered.
基金Supported by the National Natural Science Foundation of China(No.29836160) and Commission of Science & Technology of Zhejiang Province(No.924010,No.85-12-02-05).
文摘The separation characteristics of the PVA-CS (polyvinyl alcohol-chitosan) blended composite membrane for dehydration of ethanol-water mixture are examined. The relationships of flux and separation factor with the feed concentration and operation temperature are established. Using this correlated equation, the continuous-flow pervaporation process about 500 kilolitres/year dehydrated ethanol is designed. The numbers of stage and reheater are calculated by stage-by-stage method for two kinds of cascades: one with equal membrane area and the other with 10℃ of temperature decrement per section. The results show that when the numbers of stage and reheater are the same, the cascade with 10℃ of temperature decrement has more advantages than that with equal membrane area. The influences of feed concentration and flow rate on the numbers of stage and reheater in the cascades are discussed.
基金Supported by the Natural Science Foundation of China （No. 10375044, 10435060） and by Specialized Research Fund for the Doctoral Program of Higher Education （No. 20050486054）. L. P. Guo greatfully acknowledges the support of K. C. Wong Education Foundation, HongKong.
