水电站过渡过程计算中水轮机尾水管进口最小压强须控制在-8 m H2O以上,以防止危险的水柱分离。对于水泵水轮机,压力脉动大且成份复杂,确定此最小压强时应该计入哪些压力脉动尚无明确答案。针对某直锥尾水管水泵水轮机模型,在转轮进口施...水电站过渡过程计算中水轮机尾水管进口最小压强须控制在-8 m H2O以上,以防止危险的水柱分离。对于水泵水轮机,压力脉动大且成份复杂,确定此最小压强时应该计入哪些压力脉动尚无明确答案。针对某直锥尾水管水泵水轮机模型,在转轮进口施加不同脉动流速,分析尾水管进口空化腔生成发展规律。发现尾水管最大空化腔体积与进口脉动流速频率相关;随频率增大,空腔体积有先快速增大后缓慢减小变化趋势;空化腔变化周期受压力脉动频率和尾水管出口压强波动共同影响。在实际转轮进口可能的压力脉动频率对尾水管空化腔波动都有较大影响,但频率与尾水涡频率一致时会有共振效应。尾水管水锤波动是产生空腔涡的根本因素。展开更多
Nanoporous copper with nano-scale pore size was synthesized by dealloying Mn-Cu precursor alloy using a free corrosion method. The effects of heat treatment of Mn-Cu precursors on alloy phase, morphology and compositi...Nanoporous copper with nano-scale pore size was synthesized by dealloying Mn-Cu precursor alloy using a free corrosion method. The effects of heat treatment of Mn-Cu precursors on alloy phase, morphology and composition of the resultant nanoporous copper were investigated. It is revealed that the compositions distribute homogeneously in the bulk Mn-Cu precursors, which consequently results in a more fully dealloying for forming nanoporous copper. The alloy phase changes from Cuo.a9Mno.51 and Cuo.21Mno.79 of non-thermally treated precursor to Cuo.33Mn0.67 of heat treated alloy. The residual Mn content in nanoporous copper is decreased from 12.97% to 2.04% （molar fraction） made from the precursor without and with 95 h heat treatment. The typical pore shape of nanoporous copper prepared by dealloying the precursor without the heat treatment is divided into two different zones： the uniform bi-continuous structure zone and the blurry or no pore structure zone. Nanoporous copper is of a uniform sponge-like morphology made from the heat-treated precursor, and the average ligament diameter is 40 nm, far smaller than that from the non-thermally treated precursor, in which the average ligament diameter is estimated to be about 70 nm.展开更多
文摘水电站过渡过程计算中水轮机尾水管进口最小压强须控制在-8 m H2O以上,以防止危险的水柱分离。对于水泵水轮机,压力脉动大且成份复杂,确定此最小压强时应该计入哪些压力脉动尚无明确答案。针对某直锥尾水管水泵水轮机模型,在转轮进口施加不同脉动流速,分析尾水管进口空化腔生成发展规律。发现尾水管最大空化腔体积与进口脉动流速频率相关;随频率增大,空腔体积有先快速增大后缓慢减小变化趋势;空化腔变化周期受压力脉动频率和尾水管出口压强波动共同影响。在实际转轮进口可能的压力脉动频率对尾水管空化腔波动都有较大影响,但频率与尾水涡频率一致时会有共振效应。尾水管水锤波动是产生空腔涡的根本因素。
基金Project(10804101) supported by the National Natural Science Foundation of ChinaProject(9140C6805021008) supported by the State Key Development Program for Basic Research of ChinaProject(2007B08007) supported by the Science and Technology Development Foundation of Chinese Academy of Engineering Physics
文摘Nanoporous copper with nano-scale pore size was synthesized by dealloying Mn-Cu precursor alloy using a free corrosion method. The effects of heat treatment of Mn-Cu precursors on alloy phase, morphology and composition of the resultant nanoporous copper were investigated. It is revealed that the compositions distribute homogeneously in the bulk Mn-Cu precursors, which consequently results in a more fully dealloying for forming nanoporous copper. The alloy phase changes from Cuo.a9Mno.51 and Cuo.21Mno.79 of non-thermally treated precursor to Cuo.33Mn0.67 of heat treated alloy. The residual Mn content in nanoporous copper is decreased from 12.97% to 2.04% （molar fraction） made from the precursor without and with 95 h heat treatment. The typical pore shape of nanoporous copper prepared by dealloying the precursor without the heat treatment is divided into two different zones： the uniform bi-continuous structure zone and the blurry or no pore structure zone. Nanoporous copper is of a uniform sponge-like morphology made from the heat-treated precursor, and the average ligament diameter is 40 nm, far smaller than that from the non-thermally treated precursor, in which the average ligament diameter is estimated to be about 70 nm.
