ALBERT

Description: High speed BLDC has the characteristic as larger air gap smaller armature inductance, traditional PWM modulation will produce a great number of high frequency current harmonics which led problem like large torque ripple and serious motor heat. In the meantime traditional PWM modulation use the diode rectifier which cause harmonic pollution in electric power net. To solve the problem above, proposes a new motor controller topology. Using the IGBT device to replace the diode on frequency converter rectifier side, apply the power factor correction technology, reduce the pollution on the grid. Using busbar current modulation on the inverter, driving bridge-arm use 3-phase 6-state open as driving Mode, realize the control on a 10000r/min,10kw BLDC. The results of Simulation on matlab show the topological structure as proposed can effectively improve the network side power factor and reduce the motor armature winding harmonic and motor torque ripple.

Description: The influence of blade angle distribution along leading edge on cavitation performance of centrifugal pumps is analysed in the present paper. Three sets of blade angle distribution along leading edge for three blade inlet angles are chosen to design nine centrifugal pump impellers. The RNG k- ##IMG## [http://ej.iop.org/icons/Entities/epsilon.gif] {epsilon} turbulence model and the Zwart-Gerber-Belamri cavitation model are employed to simulate the cavitation flows in centrifugal pumps with different impellers and the same volute. The numerical results are compared with the experimental data, and the comparison proves that the numerical simulation can accurately predict the cavitation performance of centrifugal pumps. On the basis of the numerical simulations, the pump head variations with pump inlet pressure, and the flow details in centrifugal pump are revealed to demonstrate the influence of blade an...

Description: The influence of prewhirl regulation by inlet guide vanes (IGVs) on cavitation performance and flow characteristic in a centrifugal pump is investigated. At the impeller inlet, the streamlines are regulated by the IGVs, and the axial velocity distribution is also influenced by the IGVs. Due to the total pressure loss on the IGVs, the cavitation performance of the centrifugal pump degrades. The cavitation area in impeller with IGVs is larger than one without IGVs. The specify values of total pressure loss between the suction pipe inlet and impeller inlet for three cavitation conditions show that the IGVs will generate additional pressure loss, which is related to the IGVs angles and cavitation conditions.

Description: The plunger valve of colliding energy dissipation is one of the important parts in pipeline system. In the operation condition of low backpressure and high pressure difference, cavitation phenomenon is easy to come into being, which may result in noise and vibration and even lead to damage to valve. This article aims to decrease and even eliminate the cavitation phenomenon in plunger valve which may occur in this operation condition. Mathematical models including basic control equation, standard k-ε model, equation model of fluid, cavitation model and so on, are used to calculate flow field. Then, the physical model of plunger valve of colliding energy dissipation is built and numerical simulation study on valve’s inside flow is conducted in using software on the view of hydraulics. The physical model of plunger valve is built by using Pro/E, ICEM CFD and finally simulation is carried out by using Pumplinx software. Two calculations are performed in this study. One is calculatio...

Description: A new concept of power generator using autorotation of elliptic cylinder to extract energy from fluid is proposed in the present study. Numerical simulation studies Fluid-Structure Interaction of the fixed-axis autorotation of rigid elliptic cylinder using a coupled Computational Fluid Dynamics (CFD) – Rigid Body Dynamics (RBD) solver. This solver requires no solid mesh to setup FSI (Fluid Structure Interaction) simulation. Based on solving two-dimensional unsteady incompressible N-S equations and SST k - ω turbulent governing equations, the power generator of elliptic cylinder was investigated in different axis rations, eccentric distance ratios and Reynolds number conditions. Numerical results reveal that autorotation of elliptic cylinder can achieve energy extraction. With optimal parameters, the power generator can reach maximum energy extraction efficiency of 34%. The investigation results provided fundamental support for utilization of ocean current energy.

Description: The unreasonable pumping scheme of the pump-treat technology can lead to high repair cost and poor performance in contaminated groundwater remediation. In order to improve the cost effectiveness of the technology, we took a heavily nitrate-polluted informal domestic waste landfill site in North China as an example, and optimized the pumping scheme using Visual MODFlOW software combined with genetic algorithm (GA) in MGO module. By designing the constant pumping rate scheme and phased pumping rate scheme, optimal layout of pumping wells were determined with the minimum total pumping capacity as the optimal target. The result showed that the two wells which located near the central axis and in the middle and lower reaches of the plume with a constant pumping rate of 13.2 m 3 /d and continuous pumping for 75 days was the optimal pumping solution in constant pumping rate scheme. While the pump schedule as Q 1 = 19.8 m 3 /d, Q 2 =...

Description: The pressure fluctuations in a centrifugal compressor with different inlet guide vanes (IGV) pre-whirl angles were investigated numerically, as well as the pre-stress model and static structural of blade. The natural frequency was evaluated by pre-stress model analysis. The results show that, the aero-dynamic pressure acting on blade surface is smaller than rotation pre-stress, which wouldn't result in large deformation of blade. The natural frequencies with rotation pre-stress are slightly higher than without rotation pre-stress. The leading mechanism of pressure fluctuations for normal conditions is the rotor-stator (IGVs) interaction, while is serious flow separations for conditions that are close to surge line. A few frequency components in spectra are close to natural frequency, which possibly result in resonant vibration if amplitude is large enough, which is dangerous for compressor working, and should be avoided.

Description: 〈span〉〈div〉Abstract〈/div〉The NE–SW-trending Qin-Hang Belt and east–west-trending Nanling Range are two critical magmatic and mineralization zones in the southeastern South China Block (SCB). However, the formation timing and petrogenesis of the magmatism in these zones, along with the relationship with the Pacific subduction, remain hotly debated. Herein, this study presents a set of zircon U–Pb geochronological, Lu–Hf isotopic and whole-rock geochemical data for the Late Jurassic Mashan and Nandu shoshonitic intrusions in the Qin-Hang Belt. All the samples are enriched in large ion lithophile elements and light rare earth elements. They have high 〈span〉ε〈/span〉Nd〈sub〉(〈span〉t〈/span〉)〈/sub〉 (from −1.4 to +4.4) and zircon 〈span〉ε〈/span〉Hf〈sub〉(〈span〉t〈/span〉)〈/sub〉 values (from −1.0 to +3.4) and low initial 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr (0.70426–0.70696), distinct from those of the Triassic shoshonitic rocks but comparable with those of the Jurassic shoshonitic rocks in the region. Such signatures suggest that the Mashan and Nandu igneous rocks mainly derived from a Jurassic metasomatized lithospheric mantle in response to asthenospheric upwelling, without significant contribution from subducted slab-derived components. Our new data, together with other geological observations, reveal a spatial change of magmatic activities, structural patterns, sedimentary basins and palaeocurrent directions during the Middle–Late Jurassic, probably associated with the far-field effects of the Pacific subduction in the interior SCB.〈/span〉

Description: Lower Cretaceous pedogenic carbonates exposed in SE China have been dated by U–Pb isotope measurements on single zircons taken from intercalated volcanic rocks, and the ages integrated with existing stratigraphy. 13 C values of calcretes range from –7.0 to –3.0 and can be grouped into five episodes of increasing–decreasing values. The carbon isotope proxy derived from these palaeosol carbonates suggests p CO 2 mostly in the range 1000–2000 parts per million by volume (ppmV) at S ( z ) (CO 2 contributed by soil respiration) = 2500 ppmV and 25°C during the Hauterivian–Albian interval ( c . 30 Ma duration). Such atmospheric CO 2 levels are 4–8 times pre-industrial values, almost double those estimated by geochemical modelling and much higher than those established from stomatal indices in fossil plants. Rapid rises in p CO 2 are identified for early Hauterivian, middle Barremian, late Aptian, early Albian and middle Albian time, and rapid falls for intervening periods. These episodic cyclic changes in p CO 2 are not attributed to local tectonism and volcanism but rather to global changes. The relationship between reconstructed p CO 2 and the development of large igneous provinces (LIPs) remains unclear, although large-scale extrusion of basalt may well be responsible for relatively high atmospheric levels of this greenhouse gas. Suggested levels of relatively low p CO 2 correspond in timing to intervals of regional to global enrichment of marine carbon in sediments and negative carbon isotope ( 13 C) excursions characteristic of the oceanic anoxic events OAE1a (Selli Event), Kilian and Paquier events (constituting part of the OAE 1b cluster) and OAE1d. Short-term episodes of high p CO 2 coincide with negligible carbon isotope excursions associated with the Faraoni Event and the Jacob Event. Given that episodes of regional organic carbon burial would draw down CO 2 and negative 13 C excursions indicate the addition of isotopically light carbon to the ocean–atmosphere system, controls on the carbon cycle in controlling p CO 2 during Early Cretaceous time were clearly complex and made more so by atmospheric composition also being affected by changes in silicate weathering intensity.

Description: 〈span〉〈div〉Abstract〈/div〉The NE–SW-trending Qin-Hang Belt and east–west-trending Nanling Range are two critical magmatic and mineralization zones in the southeastern South China Block (SCB). However, the formation timing and petrogenesis of the magmatism in these zones, along with the relationship with the Pacific subduction, remain hotly debated. Herein, this study presents a set of zircon U–Pb geochronological, Lu–Hf isotopic and whole-rock geochemical data for the Late Jurassic Mashan and Nandu shoshonitic intrusions in the Qin-Hang Belt. All the samples are enriched in large ion lithophile elements and light rare earth elements. They have high 〈span〉ε〈/span〉Nd〈sub〉(〈span〉t〈/span〉)〈/sub〉 (from −1.4 to +4.4) and zircon 〈span〉ε〈/span〉Hf〈sub〉(〈span〉t〈/span〉)〈/sub〉 values (from −1.0 to +3.4) and low initial 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr (0.70426–0.70696), distinct from those of the Triassic shoshonitic rocks but comparable with those of the Jurassic shoshonitic rocks in the region. Such signatures suggest that the Mashan and Nandu igneous rocks mainly derived from a Jurassic metasomatized lithospheric mantle in response to asthenospheric upwelling, without significant contribution from subducted slab-derived components. Our new data, together with other geological observations, reveal a spatial change of magmatic activities, structural patterns, sedimentary basins and palaeocurrent directions during the Middle–Late Jurassic, probably associated with the far-field effects of the Pacific subduction in the interior SCB.〈/span〉