Water hammer occurs whenever the fluid velocity in vertical lifting pipe systems for deep-sea mining suddenly changes. In this work, the shock wave was proven to play an important role in changing pressures and period...Water hammer occurs whenever the fluid velocity in vertical lifting pipe systems for deep-sea mining suddenly changes. In this work, the shock wave was proven to play an important role in changing pressures and periods, and mathematical and numerical modeling technology was presented for simulated transient pressure in the abnormal pump operation. As volume concentrations were taken into account of shock wave speed, the experiment results about the pressure-time history, discharge-time history and period for the lifting pipe system showed that： as its concentrations rose up, the maximum transient pressure went down, so did its discharges; when its volume concentrations increased gradually, the period numbers of pressure decay were getting less and less, and the corresponding shock wave speed decreased. These results have highly coincided with simulation results. The conclusions are important to design lifting transporting system to prevent water hammer in order to avoid potentially devastating consequences, such as damage to components and equipment and risks to personnel.展开更多
Based on the deep understanding of the requirements of cutting conditions on ceramic tools, a design model for functionally gradient ceramic tool materials with symmetrical composition distribution was presented in th...Based on the deep understanding of the requirements of cutting conditions on ceramic tools, a design model for functionally gradient ceramic tool materials with symmetrical composition distribution was presented in this paper, according to which an Al 2O 3-TiC functionally gradient ceramic tool material FG-1 was synthesized by powder-laminating and uniaxially hot-pressing technique. The thermal shock resistance of the Al 2O 3-TiC functionally gradient ceramics FG-1 was evaluated by water quenching and subsequent three-point bending tests of flexural strength diminution. Comparisons were made with results from parallel experiments conducted using a homogeneous Al 2O 3-TiC ceramics. Functionally gradient ceramics exhibited higher retained strength under all thermal shock temperature differences compared to homogeneous ceramics, indicating the higher thermal shock resistance. The experimental results were supported by the calculation of transient thermal stress field. The cutting performance of the Al 2O 3-TiC functionally gradient ceramic tool FG-1 was also investigated in rough turning the cylindrical surface of exhaust valve of diesel engine in comparison with that of a common Al 2O 3-TiC ceramic tool LT55. The results indicated that the tool life of FG-1 increased by 50 percent over that of LT55. Tool life of LT55 was mainly controlled by thermal shock cracking which was accompanied by mechanical shock. While tool life of FG-1 was mainly controlled by mechanical fatigue crack extension rather than thermal shock cracking, revealing the less thermal shock susceptibility of functionally gradient ceramics than that of common ceramics.展开更多
失水事故(lose of coolant accident,LOCA)试验中极端热冲击测试作为核设备安全检测中的关键测试之一,能够模拟LOCA事故中高温高压蒸汽对核设备造成的损害程度和设备运行工况的影响情况。在LOCA试验过程中的温度变化对热冲击实验研究尤...失水事故(lose of coolant accident,LOCA)试验中极端热冲击测试作为核设备安全检测中的关键测试之一,能够模拟LOCA事故中高温高压蒸汽对核设备造成的损害程度和设备运行工况的影响情况。在LOCA试验过程中的温度变化对热冲击实验研究尤为重要,实际测试中很难测量出整个压力容器中的温度变化,需要在整个环境中多点布置温度传感器才能测得。如何分析极端温度冲击下的压力容器温度场分布和优化传感器布局成为LOCA测试系统的关键问题。因此采用ANSYS Fluent软件对LOCA热冲击测试环境进行仿真模型,提取极端热冲击的瞬态参数,验证实验仓内流体运动状态和紊流情况,研究测试环境中温度分布特性和温度传感器摆放位置。在仿真测试中LOCA仿真模型中试验品表面温度与实际测试环境表面温度偏差小于2℃,仿真模型符合实际测试需求。展开更多
基金supported by the National Natural Science Foundation of China(Grant No.50875081)China Postdoctoral Science Foundation(Grant No.20080440992)+1 种基金the Planned Science and Technology Support Project of Hunan Province(Grant No.2009SK3159)Graduate Innovation Fund of Hunan University of Science and Technology(Grant No.S100109)
文摘Water hammer occurs whenever the fluid velocity in vertical lifting pipe systems for deep-sea mining suddenly changes. In this work, the shock wave was proven to play an important role in changing pressures and periods, and mathematical and numerical modeling technology was presented for simulated transient pressure in the abnormal pump operation. As volume concentrations were taken into account of shock wave speed, the experiment results about the pressure-time history, discharge-time history and period for the lifting pipe system showed that： as its concentrations rose up, the maximum transient pressure went down, so did its discharges; when its volume concentrations increased gradually, the period numbers of pressure decay were getting less and less, and the corresponding shock wave speed decreased. These results have highly coincided with simulation results. The conclusions are important to design lifting transporting system to prevent water hammer in order to avoid potentially devastating consequences, such as damage to components and equipment and risks to personnel.
文摘Based on the deep understanding of the requirements of cutting conditions on ceramic tools, a design model for functionally gradient ceramic tool materials with symmetrical composition distribution was presented in this paper, according to which an Al 2O 3-TiC functionally gradient ceramic tool material FG-1 was synthesized by powder-laminating and uniaxially hot-pressing technique. The thermal shock resistance of the Al 2O 3-TiC functionally gradient ceramics FG-1 was evaluated by water quenching and subsequent three-point bending tests of flexural strength diminution. Comparisons were made with results from parallel experiments conducted using a homogeneous Al 2O 3-TiC ceramics. Functionally gradient ceramics exhibited higher retained strength under all thermal shock temperature differences compared to homogeneous ceramics, indicating the higher thermal shock resistance. The experimental results were supported by the calculation of transient thermal stress field. The cutting performance of the Al 2O 3-TiC functionally gradient ceramic tool FG-1 was also investigated in rough turning the cylindrical surface of exhaust valve of diesel engine in comparison with that of a common Al 2O 3-TiC ceramic tool LT55. The results indicated that the tool life of FG-1 increased by 50 percent over that of LT55. Tool life of LT55 was mainly controlled by thermal shock cracking which was accompanied by mechanical shock. While tool life of FG-1 was mainly controlled by mechanical fatigue crack extension rather than thermal shock cracking, revealing the less thermal shock susceptibility of functionally gradient ceramics than that of common ceramics.
文摘失水事故(lose of coolant accident,LOCA)试验中极端热冲击测试作为核设备安全检测中的关键测试之一,能够模拟LOCA事故中高温高压蒸汽对核设备造成的损害程度和设备运行工况的影响情况。在LOCA试验过程中的温度变化对热冲击实验研究尤为重要,实际测试中很难测量出整个压力容器中的温度变化,需要在整个环境中多点布置温度传感器才能测得。如何分析极端温度冲击下的压力容器温度场分布和优化传感器布局成为LOCA测试系统的关键问题。因此采用ANSYS Fluent软件对LOCA热冲击测试环境进行仿真模型,提取极端热冲击的瞬态参数,验证实验仓内流体运动状态和紊流情况,研究测试环境中温度分布特性和温度传感器摆放位置。在仿真测试中LOCA仿真模型中试验品表面温度与实际测试环境表面温度偏差小于2℃,仿真模型符合实际测试需求。
