An orifice is used widely as a flow meter or a contraction device in pipeline systems in hydro-power plants, thermal power plants, and chemical plants because of its simple construction, high reliability, and low cost...An orifice is used widely as a flow meter or a contraction device in pipeline systems in hydro-power plants, thermal power plants, and chemical plants because of its simple construction, high reliability, and low cost. However, it is well known that flow-accelerated corrosion (FAC) occurs on the pipe wall downstream of the orifice. Some of the authors have examined FAC through experimental and numerical analyses and have reported that one of the major governing parameters of FAC for single-phase water flow is the pressure fluctuation p’ on the pipe wall, and also that pipe wall thinning rate TR can be estimated by p’. In addition, they have presented the effects of the ori-fice geometry on p’ or TR, and have described a method for suppressing p’ or TR. In the present study, FAC for a two-phase air-water bubble flow is examined and compared with the single-phase water flow experimentally. Further, it is shown that because p’ is also considered a governing parameter of FAC for a two-phase air-water bubble flow, TR can be estimated using p’. It is also indicated that, by using a downstream pipe with a smaller diameter than that of the upstream pipe, p’ or TR can be suppressed.展开更多
The environmental conditions and the biotic crisis during the Permo-Triassic (Tr/P) transition received increasing attention in the past decades. Presented herein are the molecular fossil records of cyano-bacteria and...The environmental conditions and the biotic crisis during the Permo-Triassic (Tr/P) transition received increasing attention in the past decades. Presented herein are the molecular fossil records of cyano-bacteria and green sulfur bacteria,the base of the marine ecosystem,to highlight the episodic nature of both the environment and the biotic crisis during this critical period. At least two episodes of cyano-bacterial expansion are documented by 2-methylhopanes ranging from C28 to C32 in carbon number,indicative of the instable marine ecosystem and the fluctuant aquatic nutrients. Meanwhile,the index of 2-alkyl-1,3,4-trimethylbenzenes (biomarkers of green sulfur bacteria) and the ratio of pristane to phy-tane (Pr/Ph) witness the fluctuation of sedimentary environmental redox conditions. The above mo-lecular evidence suggests the occurrence of highly fluctuating environmental conditions during the Tr/P transition,which is consistent with,and probably the cause of,the multi-phased biotic crisis and the prolonged faunal recovery.展开更多
文摘An orifice is used widely as a flow meter or a contraction device in pipeline systems in hydro-power plants, thermal power plants, and chemical plants because of its simple construction, high reliability, and low cost. However, it is well known that flow-accelerated corrosion (FAC) occurs on the pipe wall downstream of the orifice. Some of the authors have examined FAC through experimental and numerical analyses and have reported that one of the major governing parameters of FAC for single-phase water flow is the pressure fluctuation p’ on the pipe wall, and also that pipe wall thinning rate TR can be estimated by p’. In addition, they have presented the effects of the ori-fice geometry on p’ or TR, and have described a method for suppressing p’ or TR. In the present study, FAC for a two-phase air-water bubble flow is examined and compared with the single-phase water flow experimentally. Further, it is shown that because p’ is also considered a governing parameter of FAC for a two-phase air-water bubble flow, TR can be estimated using p’. It is also indicated that, by using a downstream pipe with a smaller diameter than that of the upstream pipe, p’ or TR can be suppressed.
基金Supported by the National Natural Science Foundation of China (Grant Nos.40525008 and 40232025)NCET Program of Ministry of Education of China (Grant No. NCET-04-0729)Fok Ying Tung Education Foundation
文摘The environmental conditions and the biotic crisis during the Permo-Triassic (Tr/P) transition received increasing attention in the past decades. Presented herein are the molecular fossil records of cyano-bacteria and green sulfur bacteria,the base of the marine ecosystem,to highlight the episodic nature of both the environment and the biotic crisis during this critical period. At least two episodes of cyano-bacterial expansion are documented by 2-methylhopanes ranging from C28 to C32 in carbon number,indicative of the instable marine ecosystem and the fluctuant aquatic nutrients. Meanwhile,the index of 2-alkyl-1,3,4-trimethylbenzenes (biomarkers of green sulfur bacteria) and the ratio of pristane to phy-tane (Pr/Ph) witness the fluctuation of sedimentary environmental redox conditions. The above mo-lecular evidence suggests the occurrence of highly fluctuating environmental conditions during the Tr/P transition,which is consistent with,and probably the cause of,the multi-phased biotic crisis and the prolonged faunal recovery.
