The overcurrent (OC) protection limit is set usually accorging to a OC protection setting table on digital integrated protection equipment in mine explode isolation high voltage (HV) vacuum switch. For digital integra...The overcurrent (OC) protection limit is set usually accorging to a OC protection setting table on digital integrated protection equipment in mine explode isolation high voltage (HV) vacuum switch. For digital integrated protection equipment, OC protection setting table must be converted to be a microcomputer algorithm. This paper first intro-duced a method of the fitting OC protection setting table to be OC relay inverse time characteristics equations using MATLAB least square fitting. On the basis of analyzing these fitting equations, a notion, “integral limit rate” was put forward initially and a OC in-verse time digital algorithm was developed. MATLAB simulation results and a digital signal processor (DSP) based digital integrated protection equipment running test indicate that this algorithm has less calculation amount, less taking up memory, high control accuracy, implements the no-grade setting of OC delay values, suits for all kinds of low-middle mi-crocomputer system implementation.展开更多
This paper summarizes some of the typical riser vortex-induced vibration （VIV） problems in subsea oil and gas developments, and presents the corresponding computational fluid dynamics （CFD） time domain simula- tio...This paper summarizes some of the typical riser vortex-induced vibration （VIV） problems in subsea oil and gas developments, and presents the corresponding computational fluid dynamics （CFD） time domain simula- tion results to address these problems. First, the CFD time domain simulation approach was applied to analyze the wake field behind a stationary cylinder and a vibrating cylinder. Then a vertical riser VIV response under uniform current was studied. The VIV response time histories revealed some valuable clues that could lead to explanation of the higher harmonics. After that, a vertical riser VIV response under shear current was investigated. A 3 000 ft （1 ft=-0.304 8 m） water depth top tensioned riser was sized, and its VIV responses under uniform and shear current were studied. Then this paper continues to discuss one catenary flexible riser VIV response during normal lay. Last, the time domain simulation approach was applied to a partially submerged flexible jumper, to study the jumper VIV behavior, and dynamic motion envelopes. It was demonstrated that the time domain simulation ap- proach is able to disclose details of the flow field, vortex shedding pattern, and riser dynamic behavior, and han- dle different tvoes of risers under different Woe of currents.展开更多
To investigate the differences and the development trends of the 400 kA aluminum reduction cell, four representative cells were deeply analyzed. By using numerical simulation methods in ANSYS software, the structure p...To investigate the differences and the development trends of the 400 kA aluminum reduction cell, four representative cells were deeply analyzed. By using numerical simulation methods in ANSYS software, the structure parameters were firstly compared, and then three-dimensional models of electric-magnetic-flow field were built and solved with finite element method(FEM). The comparison of the structures reveals that the cell bodies are similar while the current flow path and distribution ratio of bus bars are different. It appears that most of the current(70%-80%) in side A are used as the magnetic field compensation current and flow through two ends. The numerical simulation results indicate that the distributions of magnetic fields are different but all satisfy with the magnetohydrodynamics(MHD) stabilization, and the flow patterns are all two or multi vortexes with appropriate velocities. The comparison shows that all studied cells can satisfy with the physical field requirement, and the commercial applications also verify that the 400 kA cells have become the product of the mature and world's leading technology.展开更多
文摘The overcurrent (OC) protection limit is set usually accorging to a OC protection setting table on digital integrated protection equipment in mine explode isolation high voltage (HV) vacuum switch. For digital integrated protection equipment, OC protection setting table must be converted to be a microcomputer algorithm. This paper first intro-duced a method of the fitting OC protection setting table to be OC relay inverse time characteristics equations using MATLAB least square fitting. On the basis of analyzing these fitting equations, a notion, “integral limit rate” was put forward initially and a OC in-verse time digital algorithm was developed. MATLAB simulation results and a digital signal processor (DSP) based digital integrated protection equipment running test indicate that this algorithm has less calculation amount, less taking up memory, high control accuracy, implements the no-grade setting of OC delay values, suits for all kinds of low-middle mi-crocomputer system implementation.
文摘This paper summarizes some of the typical riser vortex-induced vibration （VIV） problems in subsea oil and gas developments, and presents the corresponding computational fluid dynamics （CFD） time domain simula- tion results to address these problems. First, the CFD time domain simulation approach was applied to analyze the wake field behind a stationary cylinder and a vibrating cylinder. Then a vertical riser VIV response under uniform current was studied. The VIV response time histories revealed some valuable clues that could lead to explanation of the higher harmonics. After that, a vertical riser VIV response under shear current was investigated. A 3 000 ft （1 ft=-0.304 8 m） water depth top tensioned riser was sized, and its VIV responses under uniform and shear current were studied. Then this paper continues to discuss one catenary flexible riser VIV response during normal lay. Last, the time domain simulation approach was applied to a partially submerged flexible jumper, to study the jumper VIV behavior, and dynamic motion envelopes. It was demonstrated that the time domain simulation ap- proach is able to disclose details of the flow field, vortex shedding pattern, and riser dynamic behavior, and han- dle different tvoes of risers under different Woe of currents.
基金Projects(51104187,51274241,61321003) supported by the National Natural Science Foundation of ChinaProject(20100162120008) supported by Doctoral Fund of Ministry of Education of China
文摘To investigate the differences and the development trends of the 400 kA aluminum reduction cell, four representative cells were deeply analyzed. By using numerical simulation methods in ANSYS software, the structure parameters were firstly compared, and then three-dimensional models of electric-magnetic-flow field were built and solved with finite element method(FEM). The comparison of the structures reveals that the cell bodies are similar while the current flow path and distribution ratio of bus bars are different. It appears that most of the current(70%-80%) in side A are used as the magnetic field compensation current and flow through two ends. The numerical simulation results indicate that the distributions of magnetic fields are different but all satisfy with the magnetohydrodynamics(MHD) stabilization, and the flow patterns are all two or multi vortexes with appropriate velocities. The comparison shows that all studied cells can satisfy with the physical field requirement, and the commercial applications also verify that the 400 kA cells have become the product of the mature and world's leading technology.
