To obtain dynamic characteristics of cavitation and study the relationship between the cavitation and inlet pressure, large-eddy simulation(LES) is utilized to calculate unsteady flow field in the pilot stage. Lamb-Os...To obtain dynamic characteristics of cavitation and study the relationship between the cavitation and inlet pressure, large-eddy simulation(LES) is utilized to calculate unsteady flow field in the pilot stage. Lamb-Oseen vortex is observed. Simulation results show that vortex cavitation exists, and cloud cavitation begins to occur when inlet pressure reaches 7 MPa. Cavitation and cavitation-shedding are enhanced by the increment of inlet pressure. The main frequencies of the pressure oscillations of vortex cavitation and cloud cavitation increase with inlet pressure increasing. By comparing results of local cavitation and facet cavitation, it is known that cloud cavitation has a greater influence than vortex cavitation. Upon increasing the wedge length, the main frequency of vortex cavitation increases whereas that of cloud cavitation decreases, the volume fraction of the vapor phase and the energy efficiency decrease. Considering the above characteristics and the easiness of the process, the optimal wedge length is 0.03 mm.展开更多
提出了一种新的静止同步串联补偿器(staticsynchronous series compensator,SSSC)的恒功率控制模型,并将此模型运用于电力系统潮流计算中。仿真计算了IEEE-14节点系统在安装SSSC前后的有功、无功损耗变化;在线路的P-Q约束条件下,推导了...提出了一种新的静止同步串联补偿器(staticsynchronous series compensator,SSSC)的恒功率控制模型,并将此模型运用于电力系统潮流计算中。仿真计算了IEEE-14节点系统在安装SSSC前后的有功、无功损耗变化;在线路的P-Q约束条件下,推导了一种新的基于线路P-Q曲线的电压稳定计算公式,得出了相应的电压稳定指标,计算分析了SSSC安装前后对电压稳定的影响。通过仿真和计算分析可以得到,安装SSSC后能明显地改善系统的电压稳定。与其他方法相比,文中所提方法具有快速简洁的优点,进而具备一定的实际应用价值。展开更多
基金Supported by the National Natural Science Foundation of China(No.51475338)the Natural Science Foundation of Hubei Province(No.ZRZ2014000117)。
文摘To obtain dynamic characteristics of cavitation and study the relationship between the cavitation and inlet pressure, large-eddy simulation(LES) is utilized to calculate unsteady flow field in the pilot stage. Lamb-Oseen vortex is observed. Simulation results show that vortex cavitation exists, and cloud cavitation begins to occur when inlet pressure reaches 7 MPa. Cavitation and cavitation-shedding are enhanced by the increment of inlet pressure. The main frequencies of the pressure oscillations of vortex cavitation and cloud cavitation increase with inlet pressure increasing. By comparing results of local cavitation and facet cavitation, it is known that cloud cavitation has a greater influence than vortex cavitation. Upon increasing the wedge length, the main frequency of vortex cavitation increases whereas that of cloud cavitation decreases, the volume fraction of the vapor phase and the energy efficiency decrease. Considering the above characteristics and the easiness of the process, the optimal wedge length is 0.03 mm.
文摘提出了一种新的静止同步串联补偿器(staticsynchronous series compensator,SSSC)的恒功率控制模型,并将此模型运用于电力系统潮流计算中。仿真计算了IEEE-14节点系统在安装SSSC前后的有功、无功损耗变化;在线路的P-Q约束条件下,推导了一种新的基于线路P-Q曲线的电压稳定计算公式,得出了相应的电压稳定指标,计算分析了SSSC安装前后对电压稳定的影响。通过仿真和计算分析可以得到,安装SSSC后能明显地改善系统的电压稳定。与其他方法相比,文中所提方法具有快速简洁的优点,进而具备一定的实际应用价值。
