In this paper, the axial-flux permanent magnet driver is modeledand analyzed in a simple and novel way under three-dimensional cylindricalcoordinates. The inherent three-dimensional characteristics of the deviceare co...In this paper, the axial-flux permanent magnet driver is modeledand analyzed in a simple and novel way under three-dimensional cylindricalcoordinates. The inherent three-dimensional characteristics of the deviceare comprehensively considered, and the governing equations are solved bysimplifying the boundary conditions. The axial magnetization of the sectorshapedpermanent magnets is accurately described in an algebraic form bythe parameters, which makes the physical meaning more explicit than thepurely mathematical expression in general series forms. The parameters of theBessel function are determined simply and the magnetic field distribution ofpermanent magnets and the air-gap is solved. Furthermore, the field solutionsare completely analytical, which provides convenience and satisfactoryaccuracy for modeling a series of electromagnetic performance parameters,such as the axial electromagnetic force density, axial electromagnetic force,and electromagnetic torque. The correctness and accuracy of the analyticalmodels are fully verified by three-dimensional finite element simulations and a15 kW prototype and the results of calculations, simulations, and experimentsunder three methods are highly consistent. The influence of several designparameters on magnetic field distribution and performance is studied and discussed.The results indicate that the modeling method proposed in this papercan calculate the magnetic field distribution and performance accurately andrapidly, which affords an important reference for the design and optimizationof axial-flux permanent magnet drivers.展开更多
The CSU-RAMS-2A was used to simulate the meteorological fields over the Zhujiang River Delta in South China. Initialized from a horizontally homogeneous atmosphere,real topography and inhomogeneous surface boundary co...The CSU-RAMS-2A was used to simulate the meteorological fields over the Zhujiang River Delta in South China. Initialized from a horizontally homogeneous atmosphere,real topography and inhomogeneous surface boundary condi- tions,the model was run with thermal and terrain forcing.The modeling results of winter and summer cases are com- pared with those observed.The similarity of the predicted distributions of winds,temperatures and humidities to the ob- served patterns permits us to conclude that the mesoscale distribution of meteorological elements for the two study dates is the result of the thermal and dynamical forcing by the underlying surface and topography.展开更多
To address the problem that granular compound fertilizer is prone to agglomeration during mechanized direct seeding of oilseed rape in the middle and lower reaches of the Yangtze River,which causes clogging of the fer...To address the problem that granular compound fertilizer is prone to agglomeration during mechanized direct seeding of oilseed rape in the middle and lower reaches of the Yangtze River,which causes clogging of the fertilizer discharger and leads to a reduction in the uniformity and stability of fertilizer discharge,research on the crushing mechanism of caking compound fertilizer was performed.Considering that it is difficult to measure the bonding force between caking fertilizer particles directly,a simulation model of caking composite fertilizer was established with the bonding model in EDEM discrete element software.To decrease error between the simulation and physical test results,the normal contact stiffness,tangential contact stiffness,critical normal stress,critical tangential stress,bonding radius,and other parameters of the bonding model of caking composite fertilizer were calibrated.The three-dimensional structure of the caking composite fertilizer was obtained via three-dimensional scanning,the critical crushing displacement and critical crushing force of the caking composite fertilizer were measured via compression testing with a mass spectrometer,and the optimal parameter combination of the bonding model was determined via EDEM discrete element simulation of the Plackett-Burman test,steepest ascent test,and Box-Behnken test.The results of the simulated compression tests under the optimal parameter combination show that the relative errors of the critical crushing displacement and critical crushing force with respect to the physical test results were 0.296%and 0.343%,respectively.Using the crushing rate of caking compound fertilizer as an evaluation index,the feasibility of the calibrated parameters was verified for a four-head spiral two-row fertilizer discharger installed in a direct seeding machine for oilseed rape.The results show that the relative errors of the caking fertilizer crushing rates from the simulation relative to those of the bench and field tests were 5.81%and 5.06%,respectively,indicating that the calibration parameters of the discrete element model were accurate and could be used for parameter analysis of caking fertilizer with a discrete element model.These results can provide a reference for the structural optimization of fertilizer discharger crushing of caking fertilizer of direct seeding machine for oilseed rape.展开更多
This article presents a mathematical model of helical end-milling forces through experimental identification of the cutting coefficients and analyzes the changes of comer-milling forces under different conditions. In ...This article presents a mathematical model of helical end-milling forces through experimental identification of the cutting coefficients and analyzes the changes of comer-milling forces under different conditions. In allusion to the corner-milling process, the relationship between working parameters and the comer coordinates is investigated by way of combination of tool tracing and cutting geometrodynamics. The milling parameters are optimized by changing the coordinates of tool center and working parameters without altering curing forces. By applying the optimized parameters to milling practice, a comparison is made to show the improved product quality. Based on these optimized parameters, a finite element method （FEM） program is used to compute deformation values of a workpiece＇s comer, which evidences few effects that optimized parameters can exert on the comer deformation.展开更多
基金supported by the National Natural Science Foundation of China under Grant[52077027]Liaoning Province Science and Technology Major Project[No.2020JH1/10100020].
文摘In this paper, the axial-flux permanent magnet driver is modeledand analyzed in a simple and novel way under three-dimensional cylindricalcoordinates. The inherent three-dimensional characteristics of the deviceare comprehensively considered, and the governing equations are solved bysimplifying the boundary conditions. The axial magnetization of the sectorshapedpermanent magnets is accurately described in an algebraic form bythe parameters, which makes the physical meaning more explicit than thepurely mathematical expression in general series forms. The parameters of theBessel function are determined simply and the magnetic field distribution ofpermanent magnets and the air-gap is solved. Furthermore, the field solutionsare completely analytical, which provides convenience and satisfactoryaccuracy for modeling a series of electromagnetic performance parameters,such as the axial electromagnetic force density, axial electromagnetic force,and electromagnetic torque. The correctness and accuracy of the analyticalmodels are fully verified by three-dimensional finite element simulations and a15 kW prototype and the results of calculations, simulations, and experimentsunder three methods are highly consistent. The influence of several designparameters on magnetic field distribution and performance is studied and discussed.The results indicate that the modeling method proposed in this papercan calculate the magnetic field distribution and performance accurately andrapidly, which affords an important reference for the design and optimizationof axial-flux permanent magnet drivers.
文摘The CSU-RAMS-2A was used to simulate the meteorological fields over the Zhujiang River Delta in South China. Initialized from a horizontally homogeneous atmosphere,real topography and inhomogeneous surface boundary condi- tions,the model was run with thermal and terrain forcing.The modeling results of winter and summer cases are com- pared with those observed.The similarity of the predicted distributions of winds,temperatures and humidities to the ob- served patterns permits us to conclude that the mesoscale distribution of meteorological elements for the two study dates is the result of the thermal and dynamical forcing by the underlying surface and topography.
基金supported by the China Agricultural Research System of MOF and MARA(NO:CARS-12).
文摘To address the problem that granular compound fertilizer is prone to agglomeration during mechanized direct seeding of oilseed rape in the middle and lower reaches of the Yangtze River,which causes clogging of the fertilizer discharger and leads to a reduction in the uniformity and stability of fertilizer discharge,research on the crushing mechanism of caking compound fertilizer was performed.Considering that it is difficult to measure the bonding force between caking fertilizer particles directly,a simulation model of caking composite fertilizer was established with the bonding model in EDEM discrete element software.To decrease error between the simulation and physical test results,the normal contact stiffness,tangential contact stiffness,critical normal stress,critical tangential stress,bonding radius,and other parameters of the bonding model of caking composite fertilizer were calibrated.The three-dimensional structure of the caking composite fertilizer was obtained via three-dimensional scanning,the critical crushing displacement and critical crushing force of the caking composite fertilizer were measured via compression testing with a mass spectrometer,and the optimal parameter combination of the bonding model was determined via EDEM discrete element simulation of the Plackett-Burman test,steepest ascent test,and Box-Behnken test.The results of the simulated compression tests under the optimal parameter combination show that the relative errors of the critical crushing displacement and critical crushing force with respect to the physical test results were 0.296%and 0.343%,respectively.Using the crushing rate of caking compound fertilizer as an evaluation index,the feasibility of the calibrated parameters was verified for a four-head spiral two-row fertilizer discharger installed in a direct seeding machine for oilseed rape.The results show that the relative errors of the caking fertilizer crushing rates from the simulation relative to those of the bench and field tests were 5.81%and 5.06%,respectively,indicating that the calibration parameters of the discrete element model were accurate and could be used for parameter analysis of caking fertilizer with a discrete element model.These results can provide a reference for the structural optimization of fertilizer discharger crushing of caking fertilizer of direct seeding machine for oilseed rape.
基金National Defense Basic Research Program (D0620060433)
文摘This article presents a mathematical model of helical end-milling forces through experimental identification of the cutting coefficients and analyzes the changes of comer-milling forces under different conditions. In allusion to the corner-milling process, the relationship between working parameters and the comer coordinates is investigated by way of combination of tool tracing and cutting geometrodynamics. The milling parameters are optimized by changing the coordinates of tool center and working parameters without altering curing forces. By applying the optimized parameters to milling practice, a comparison is made to show the improved product quality. Based on these optimized parameters, a finite element method （FEM） program is used to compute deformation values of a workpiece＇s comer, which evidences few effects that optimized parameters can exert on the comer deformation.
