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Dynamic torque response analysis of IPMSM in flux weakening region for HEV applications
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作者 刘晓红 张幽彤 黄文卿 《Journal of Beijing Institute of Technology》 EI CAS 2015年第3期355-360,共6页
An over-modulation based vector control strategy for interior permanent magnet synchronous machine( IPMSM) is proposed and investigated. The strategy increases the reference flux weakening voltage to improve efficie... An over-modulation based vector control strategy for interior permanent magnet synchronous machine( IPMSM) is proposed and investigated. The strategy increases the reference flux weakening voltage to improve efficiency in flux weakening region of IPMSMwith the same dynamic torque response performance in standard SV Mtechnique. The relationship between dynamic torque performance and the reference flux weakening voltage is also discussed. In order to achieve fast and smooth shift process,the torque response must be less than 20 ms in the parallel hybrid electric vehicle( HEV),according to this,modeling and experimental studies were carried out. The results show that the proposed strategy can achieve the same dynamic and steady state torque performance with higher reference flux weakening voltage,which means higher efficiency. 展开更多
关键词 interior permanent magnet synchronous machine(IPMSM) over-modulation flux weakening dynamic torque response hybrid electric vehicle(HEV)
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Asymmetry of the water flux induced by the deformation of a nanotube 被引量:1
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作者 何俊霞 陆杭军 +4 位作者 刘扬 吴锋民 聂雪川 周晓艳 陈艳燕 《Chinese Physics B》 SCIE EI CAS CSCD 2012年第5期372-377,共6页
The behavior of nano-confined water is expected to be fundamentally different from the behavior of bulk water.At the nanoscale,it is still unclear whether water flows more easily along the convergent direction or the ... The behavior of nano-confined water is expected to be fundamentally different from the behavior of bulk water.At the nanoscale,it is still unclear whether water flows more easily along the convergent direction or the divergent one,and whether a hourglass shape is more convenient than a funnel shape for water molecules to pass through a nanotube.Here,we present an approach to explore these questions by changing the deformation position of a carbon nanotube.The results of our molecular dynamics simulation indicate that the water flux through the nanotube changes significantly when the deformation position moves away from the middle region of the tube.Different from the macroscopic level,we find water flux asymmetry(water flows more easily along the convergent direction than along the divergent one),which plays a key role in a nano water pump driven by a ratchet-like mechanism.We explore the mechanism and calculate the water flux by means of the Fokker-Planck equation and find that our theoretical results are well consistent with the simulation results.Furthermore,the simulation results demonstrate that the effect of deformation location on the water flux will be reduced when the diameter of the nanochannel increases.These findings are helpful for devising water transporters or filters based on carbon nanotubes and understanding the molecular mechanism of biological channels. 展开更多
关键词 single-walled carbon nanotube deformation position molecular dynamics simulation water flux
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Causal mechanism behind the stall delay by airfoil's pitching-up motion 被引量:1
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作者 Shufan Zou Ankang Gao +1 位作者 Yipeng Shi Jiezhi Wu 《Theoretical & Applied Mechanics Letters》 CAS CSCD 2017年第5期311-315,共5页
Why the stall of an airfoil can be significantly delayed by its pitching-up motion? Various attempts have been proposed to answer this question over the past half century, but none is satisfactory. In this letter we ... Why the stall of an airfoil can be significantly delayed by its pitching-up motion? Various attempts have been proposed to answer this question over the past half century, but none is satisfactory. In this letter we prove that a chain of vorticity-dynamics processes at accelerating boundary is fully responsible for the causal mechanism underlying this peculiar phenomenon. The local flow behavior is explained by a simple potential-flow model. 展开更多
关键词 dynamic stall Boundary vorticity flux Unsteady aerodynamics
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Ocean dynamic noise energy flux directivity in the 400 Hz to 700 Hz frequency band 被引量:1
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作者 Vladimir A. Shchurov Galina F. Ivanova +1 位作者 Marianna V. Kuyanova Helen S. Tkachenko 《Chinese Journal of Acoustics》 2007年第2期102-110,共9页
Results of field studies of underwater dynamic noise energy flux directivity at two wind speeds, 6 m/s and 12 m/s, in the 400 Hz to 700 Hz frequency band in the deep open ocean are presented. The measurements were mad... Results of field studies of underwater dynamic noise energy flux directivity at two wind speeds, 6 m/s and 12 m/s, in the 400 Hz to 700 Hz frequency band in the deep open ocean are presented. The measurements were made by a freely drifting telemetric combined system at 500 m depth. Statistical characteristics of the horizontal and vertical dynamic noise energy flux directivity are considered as functions of wind speed and direction. Correlation between the horizontal dynamic noise energy flux direction and that of the wind was determined; a mechanism of the horizontal dynamic noise energy flux generation is related to the initial noise field scattering on ocean surface waves. 展开更多
关键词 Ocean dynamic noise energy flux directivity in the 400 Hz to 700 Hz frequency band
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A simulation study of mercury release fluxes from soils in wet–dry rotation environment 被引量:3
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作者 Peng Liang Cheng Zhang +1 位作者 Yongkui Yang Dingyong Wang 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2014年第7期1445-1452,共8页
A simulative mesocosm study was conducted to evaluate the influence of wet-dry rotation on mercury(Hg) flux from soil/water to air and the distribution of Hg species in water as well as Hg chemical fractions in soil... A simulative mesocosm study was conducted to evaluate the influence of wet-dry rotation on mercury(Hg) flux from soil/water to air and the distribution of Hg species in water as well as Hg chemical fractions in soil. Three types of soil were employed including two kinds of paddy soil, Typic Purpli-Udic Cambosols(TPUC) and Xanthi-Udic Ferralosols(XUF), as well as the Alluvial Soil(AS) from Three Gorge reservoir area in Chongqing, China. The results showed that Hg fluxes in wetting periods were significantly higher than that in drying periods. It might be due to the formation of a layer of stable air over the water surface in which some redox reactions promote evasion processes over the water surface. This result indicated that more Hg would be evaporated from the Three Gorge reservoir and paddy soil field during the flooding season. Hg fluxes were positively correlated with air temperature and solar irradiation, while negatively correlated with air humidity and the electronic conductivity of water. Hg fluxes from AS and TPUC were significantly higher than that from XUF, which might be due to the higher organic matter(OM) contents in XUF than TPUC and AS. The reduction processes of oxidized Hg were restrained due to the strong binding of Hg to OM, resulting in the decrease in Hg flux from the soil. 展开更多
关键词 Mercury flux dynamic flux chamber Wet-dry rotation
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Statistics of Polymer Capture by a Nanopore:A Brownian Dynamics Simulation Study 被引量:2
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作者 Ming-ming Ding Xiao-zheng Duan +1 位作者 卢宇源 石彤非 《Chinese Journal of Polymer Science》 SCIE CAS CSCD 2015年第5期674-679,共6页
We investigate the statistics of polymer capture by a nanopore using Brownian dynamics simulations. It is found that when the velocity flux is greater than a critical velocity flux, the capture picture is a random sel... We investigate the statistics of polymer capture by a nanopore using Brownian dynamics simulations. It is found that when the velocity flux is greater than a critical velocity flux, the capture picture is a random selection process, otherwise it tends to a statistical process governed by energetic considerations. In addition, the chain ends capture probability decreases as the chain length increases and satisfies a power-law scaling of P0(N)-N^-0.8. 展开更多
关键词 Polymer capture Critical velocity flux Brownian dynamics
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Reargument over E~j relation of high temperature superconductors
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作者 JIN Hao 《Science China Mathematics》 SCIE 2001年第4期513-527,共15页
The E ~ j relation of an HTSC slab is solved strictly within the Bean’s model in two different situations where the system does and does not reach equilibrium state under the magnetic relaxation respectively, with b... The E ~ j relation of an HTSC slab is solved strictly within the Bean’s model in two different situations where the system does and does not reach equilibrium state under the magnetic relaxation respectively, with both forward and backward hopping taken into consideration (the backward hopping means the hopping from the barriers with low energy to high ones). Our results suggest and rigorously prove that the In E ~ In j curves show only positive curvature on the side of slab where the directions of current-created field and the applied field are the same, while they show both positive and negative curvatures at a certain field range on the other side where the directions are opposite. The relationship of the positive and negative curvatures with the critical current, applied field and temperature is also discussed. 展开更多
关键词 flux dynamics thermal activated creep magnetic relaxation
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Analysis on capabilities of density-based solvers within OpenFOAM to distinguish aerothermal variables in difusion boundary layer 被引量:4
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作者 Shen Chun Sun Fengxian Xia Xinlin 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2013年第6期1370-1379,共10页
Open source feld operation and manipulation(OpenFOAM)is one of the most prevalent open source computational fluid dynamics(CFD)software.It is very convenient for researchers to develop their own codes based on the... Open source feld operation and manipulation(OpenFOAM)is one of the most prevalent open source computational fluid dynamics(CFD)software.It is very convenient for researchers to develop their own codes based on the class library toolbox within OpenFOAM.In recent years,several density-based solvers within OpenFOAM for supersonic/hypersonic compressible flow are coming up.Although the capabilities of these solvers to capture shock wave have already been verifed by some researchers,these solvers still need to be validated comprehensively as commercial CFD software.In boundary layer where diffusion is the dominant transportation manner,the convective discrete schemes'capability to capture aerothermal variables,such as temperature and heat flux,is different from each other due to their own numerical dissipative characteristics and from viewpoint of this capability,these compressible solvers within OpenFOAM can be validated further.In this paper,frstly,the organizational architecture of density-based solvers within OpenFOAM is analyzed.Then,from the viewpoint of the capability to capture aerothermal variables,the numerical results of several typical geometrical felds predicted by these solvers are compared with both the outcome obtained from the commercial software Fastran and the experimental data.During the computing process,the Roe,AUSM+(Advection Upstream Splitting Method),and HLLC(Harten-Lax-van Leer-Contact)convective discrete schemes of which the spatial accuracy is 1st and 2nd order are utilized,respectively.The compared results show that the aerothermal variables are in agreement with results generated by Fastran and the experimental data even if the1st order spatial precision is implemented.Overall,the accuracy of these density-based solvers can meet the requirement of engineering and scientifc problems to capture aerothermal variables in diffusion boundary layer. 展开更多
关键词 Aerothermal variables Boundary layer Computational fluid dynamics(CFD) Heat flux Open source Supersonic
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