The axial field hybrid permanent magnet memory machine(AFHPM-MM)employs a hybrid permanent magnet excitation combining NdFeB and AlNiCo,achieving high torque density and a wide flux adjustment range.A separated stator...The axial field hybrid permanent magnet memory machine(AFHPM-MM)employs a hybrid permanent magnet excitation combining NdFeB and AlNiCo,achieving high torque density and a wide flux adjustment range.A separated stator structure is adopted to enhance its antidemagnetization capability.To analyze the contributions of AlNiCo and NdFeB to the induced electromotive force(EMF)in the AFHPM-MM,a frozen permeability-based induced EMF calculation method is proposed.Theoretical analysis reveals that the conventional method exhibits substantial errors in calculating the AlNiCo-induced EMF,primarily attributed to its failure to adequately account for the dynamic magnetization characteristic discrepancies of AlNiCo under varying magnetization states.Through the analysis of magnetization variations in AlNiCo during the flux adjustment process under different magnetization states,an improved induced EMF calculation method is proposed.Comparative results indicate that,during the flux enhancement process,the average calculation error of the AlNiCo-induced EMF is reduced from 19.84%to 2.09%,whereas during the flux weakening process,the error is reduced from 3.87%to 1.67%.The proposed method achieves accurate induced EMF calculation for the AFHPM-MM.展开更多
With the development of aviation electrification,higher demands for electrical machines are put forward in aircraft electric propulsion systems.The aircraft electric propulsion requirements and propulsion motor featur...With the development of aviation electrification,higher demands for electrical machines are put forward in aircraft electric propulsion systems.The aircraft electric propulsion requirements and propulsion motor features are analyzed in this paper.Comparing with conventional PM machines,ironless stator axial flux permanent magnet(AFPM)machine topologies with Litz wire windings allow designs with higher compactness,lightness and efficiency,which are suitable for high-frequency and high-power density applications.Based on the motor requirements and constraints of aircraft electric propulsion systems,this paper investigates a high-power 1 MW multi-stack ironless stator AFPM machine,which is composed of four 250kW modular motors by stacking in axial.The design guidelines and special attentions are presented,in term of electromagnetic,thermal,and mechanical performance for the high-frequency coils and Halbach-array PM rotor.Finally,an ironless stator AFPM motor is manufactured,tested and evaluated with the consideration of cost and processing cycle.The results show that the output power is up to 53.8kW with 95%efficiency at 9000r/min at this stage.The proposed ironless stator AFPM machine with oil immersed forced cooling proves to be a favorable candidate for application in electric aircraft as propulsion motors.展开更多
Axial-flux permanent magnet synchronous machine(AFPMSM)enjoys the merits of high torque density and high efficiency,which make it one good candidate in the direct-drive application.The AFPMSM is usually analyzed based...Axial-flux permanent magnet synchronous machine(AFPMSM)enjoys the merits of high torque density and high efficiency,which make it one good candidate in the direct-drive application.The AFPMSM is usually analyzed based on the three-dimensional finite element method(3D FEM)due to its three-dimensional magnetic field distribution.However,the 3D FEM suffers large amount of calculation,time-consuming and is not suitable for the optimization of AFPMSM.Addressing this issue,a multi-layer quasi three-dimensional equivalent model of the AFPMSM is investigated in this paper,which could take the end leakage into consideration.Firstly,the multi-layer quasi three-dimensional equivalent model of the AFPMSM with single stator and single rotor is derived in details,including the equivalent processes and conversions of structure dimensions,motion conditions and electromagnetic parameters.Then,to consider the influence of end leakage on the performance,a correction factor is introduced in the multi-layer quasi three-dimensional equivalent model.Finally,the proposed multi-layer quasi three-dimensional equivalent model is verified by the 3D FEM based on an AFPMSM under different structure parameters.It demonstrates that the errors of flux linkage and average torque obtained by the multi-layer quasi three-dimensional equivalent model and 3D FEM are only around 2%although the structure parameters of the AFPMSM are varied.Besides,the computation time of one case based on the multi-layer quasi three-dimensional equivalent model is only 6 min,which is much less than that of the 3D FEM,1.8 h,under the same conditions.Thus,the proposed multi-layer quasi three-dimensional equivalent model could be used to optimize the AFPMSM and much time could be saved by this method compared with the 3D FEM.展开更多
Conventional fractional slot concentrated winding three-phase axial flux permanent magnet machines have an abundance of armature reaction magnetic field harmonics which deteriorate the torque performance of the machin...Conventional fractional slot concentrated winding three-phase axial flux permanent magnet machines have an abundance of armature reaction magnetic field harmonics which deteriorate the torque performance of the machine.This paper presents a double-stator dislocated axial flux permanent magnet machine with combined wye-delta winding.A wye-delta(Y-△)winding connection method is designed to eliminate the 6 th ripple torque generated by air gap magnetic field harmonics.Then,the accurate subdomain method is adopted to acquire the no-load and armature magnetic fields of the machine,respectively,and the magnetic field harmonics and torque performance of the designed machine are analyzed.Finally,a 6 k W,4000 r/min,18-slot/16-pole axial flux permanent magnet machine is designed.The finite element simulation results show that the proposed machine can effectively eliminate the 6 th ripple torque and greatly reduce the torque ripple while the average torque is essentially identical to that of the conventional three-phase machines with wye-winding connection.展开更多
In this paper,a performance comparison between the novel axial flux magnetically geared machines(AFMG)and the conventional axial flux YASA machine is presented.The AFMG and YASA machines have the same stator construct...In this paper,a performance comparison between the novel axial flux magnetically geared machines(AFMG)and the conventional axial flux YASA machine is presented.The AFMG and YASA machines have the same stator construction in which segments are equipped with concentrated windings to form the stator.However,the AFMG machine has two rotors with different pole-pair numbers.Magnetic gear effect can be obtained to increase the torque density.The performance comparisons at no-load and on-load conditions are then studied by 3D-finite element analysis(FEM).Moreover,both machines are prototyped,tested and compared.展开更多
With the cvolution of various high powerr-density machines, it beeomes important to optimize the power potential of machines of vastly different topologies with a variety of waveforms of back emf and current. The appr...With the cvolution of various high powerr-density machines, it beeomes important to optimize the power potential of machines of vastly different topologies with a variety of waveforms of back emf and current. The approach of tins paper is based oil the gencral-purpose sizing equations. which permit the optinlization method of machine power density to be applied to the axial-flux toroidal permanent-magnet (AFTPM) machine, and,furthermore, the power-production capabilities of the AFTPM machinc and the wen-known squirrel-cage indution machine are compared.展开更多
This paper describes the electric drive for an in-wheel fractional-slot axial flux machine,designed for achieving a wide flux-weakening operating region.By using a slotted stator with fractional-slot windings and addi...This paper describes the electric drive for an in-wheel fractional-slot axial flux machine,designed for achieving a wide flux-weakening operating region.By using a slotted stator with fractional-slot windings and additional cores enclosing end windings,the axial flux machine reaches a wide constant power speed range.The machine is designed for increasing flux-weakening capability while obtaining low harmonic back-electromotive force and low cogging torque.A 10 N.m axial flux machine exhibiting 3 to 1 flux-weakening speed range has been built.A flux-weakening controller,able to maximize the output torque in the flux-weakening region,is designed and implemented.The goodness of both design and control algorithm is proved by experimental tests.However,such a fractional-slot machine has not only advantages.Rotor losses are very high,and they have to be properly considered during the design process.展开更多
Titanium and its alloys have found very wide application in aerospace due to their excellent characteristics although their processing is still a challenge. Electrochemical machining is an important issue in the fabri...Titanium and its alloys have found very wide application in aerospace due to their excellent characteristics although their processing is still a challenge. Electrochemical machining is an important issue in the fabrication of titanium and titanium alloys. Wire electrochemical machining （WECM） is mainly used for workpiece cutting under the condition of different thickness plates. It has a great advantage over wire electro-discharge machining, which is the absence of heat-affected zone around the cutting area. Moreover, the wire electrode in WECM could be used repetitively because it is not worn out. Thus, much attention has been paid to WECM. The effective way of removing electrolysis products is of importance to WECM. In this paper, the axial electrolyte flushing is presented to WECM for removing electrolysis products and renewing electrolyte. The Taguchi experiment is conducted to optimize the machining parameters, such as wire feedrate, machining voltage, electrolyte concentration, etc. Experimental results show that WECM with axial electrolyte flushing is a promising issue in the fabrication of titanium alloy （TC1）. The feasibility of multi-wire electrochemical machining is also demonstrated to improve the machining productivity of WECM.展开更多
Wear is a major factor of disc cutters’ failure. No current theory offers a standard for the prediction of disc cutter wear yet. In the field the wear prediction method commonly used is based on the excavation length...Wear is a major factor of disc cutters’ failure. No current theory offers a standard for the prediction of disc cutter wear yet. In the field the wear prediction method commonly used is based on the excavation length of tunnel boring machine（TBM） to predict the disc cutter wear and its wear law, considering the location number of each disc cutter on the cutterhead（radius for installation）; in theory, there is a prediction method of using arc wear coefficient. However, the preceding two methods have their own errors, with their accuracy being 40% or so and largely relying on the technicians’ experience. Therefore, radial wear coefficient, axial wear coefficient and trajectory wear coefficient are defined on the basis of the operating characteristics of TBM. With reference to the installation and characteristics of disc cutters, those coefficients are modified according to penetration, which gives rise to the presentation of comprehensive axial wear coefficient, comprehensive radial wear coefficient and comprehensive trajectory wear coefficient. Calculation and determination of wear coefficients are made with consideration of data from a segment of TBM project（excavation length 173 m）. The resulting wear coefficient values, after modification, are adopted to predict the disc cutter wear in the follow-up segment of the TBM project（excavation length of 5621 m）. The prediction results show that the disc cutter wear predicted with comprehensive radial wear coefficient and comprehensive trajectory wear coefficient are not only accurate（accuracy 16.12%） but also highly congruous, whereas there is a larger deviation in the prediction with comprehensive axial wear coefficient（accuracy 41%, which is in agreement with the prediction of disc cutters’ life in the field）. This paper puts forth a new method concerning prediction of life span and wear of TBM disc cutters as well as timing for replacing disc cutters.展开更多
The underwater tapping machine is composed of a center bit, a tapping cutter, a seal box, a main drive box, a boring bar assembly, a envelop, a gear case, a counter and so on. The drive system in underwater tapping ma...The underwater tapping machine is composed of a center bit, a tapping cutter, a seal box, a main drive box, a boring bar assembly, a envelop, a gear case, a counter and so on. The drive system in underwater tapping machine consists of a worm drive, a gear drive system and a screw drive. The worm drive is in the main drive box. The worm is connected with a hydraulic motor and driven by the hydraulic motor. The gear drive system is a combined gear train which is the combinations of the fixed axes and differential gear train in the gear case. On the one hand, by means of the fixed axes gear trains the turn and power of transmission shaft are transferred to the boring bar and the screw rod, causing differential turn between the boring bar and the screw rod. On the other hand, the turns of the boring bar and the screw rod are transferred to the differential gear train. The differential gear train is used to drive a special counter to count axial travel of the boring bar. The screw drive is composed of a feed screw and a nut on the boring bar. There is the differential turn between the boring bar and the feed screw. By means of the nut, the boring bar can feed automatically. With the movement of the sliding gear 7 in the gear case, the designed drive system can also be provided with the ability of fast forward and fast backward movement of the boring bar in its idle motion, resulting in the increase of the tapping efficiency.展开更多
The excitation system of the homopolar inductor machine(HIM)is analyzed and designed to establish the design approach and evaluation criteria of the excitation system.The finite element method is used to calculate the...The excitation system of the homopolar inductor machine(HIM)is analyzed and designed to establish the design approach and evaluation criteria of the excitation system.The finite element method is used to calculate the three-dimensional electromagnetic field in the HIM,and the distribution and characteristics of the magnetic field are described.The analytical method is applied to investigate the design process of the excitation winding.The ratio of the axial length of the armature winding to the excitation winding and the ratio of the axial length of the working air-gap to the non-working air-gap are investigated by the numerical calculation method.A prototype HIM is designed and manufactured,and some experiments are implemented to verify the correctness of the theoretical analysis and numerical calculation results.The research results show that the established design method of the excitation winding is practical and feasible.Under the conditions of constant excitation magnetomotive force or constant excitation power,the optimum range of the axial length ratio of the armature winding and the excitation winding is 0.45 to 0.5.The optimal axial length of the non-working air-gap can be determined by the ratio of the stator inner diameter and pole-pairs.展开更多
The efficiency of energy conversion from mechanical to electrical in AC generators is not entirely optimal,as power losses are converted into heat.Accurate thermal modeling and temperature measurement of advanced elec...The efficiency of energy conversion from mechanical to electrical in AC generators is not entirely optimal,as power losses are converted into heat.Accurate thermal modeling and temperature measurement of advanced electric machines with complex structures are mandatory to confirm their reliability and safe operation.In a unique axial transverse flux switching permanent magnet(ATFSPM)generator,due to its high power density,large stray loss from leakage flux,compact topology,and totally enclosed structure,thermal analysis is of paramount significance.In this paper,thermal modeling and analysis of ATFSPM are carried out in detail using a three-dimensional(3D)finite element analysis(FEA)to evaluate the thermal condition for a precise performance improvement.To begin,all loss sources are accurately derived using 3-D FEA and analytical methods,taking into account the temperature dependence of material properties,and then losses are coupled to the thermal model as heat sources.Afterward,aiming for realistic thermal modelling,the convection heat transfer in the different regions of internal and external areas as well as thin layers of interface gaps between components are all considered.In addition,the prototype of ATFSPM is supplied to validate the accuracy of 3-D FEA temperature prediction.Furthermore,a novel technique is carried out to effectively improve thermal performance,enhance the efficiency,and limit hot-spot temperatures.The steady-state and transient temperature results demonstrate the high accuracy of the thermal modeling,enhance the secure operation of the ATFSPM,and facilitate increased loading utilizing the proposed technique.(1)展开更多
This paper investigates the application of the axial flux machine (AFM) to the wind energy conversion systems (WECS) to obtain high power and torque at reduced cost. By developing mathematical equations using the phas...This paper investigates the application of the axial flux machine (AFM) to the wind energy conversion systems (WECS) to obtain high power and torque at reduced cost. By developing mathematical equations using the phase and active transformations, the three-phase model is transformed to two-phase equations by making both the stator and rotor as reference frames, finally converting to arbitrary reference frame, which is useful for the modelling of the axial flux machine. The torque, current, and voltage equations are expressed to improve the simulation reliability. Based on the developed equations, the mathematical model for the axial flux machine is developed using the MATLAB/Simulink. Starting with the axial flux motor model, when the load on the motor increases, how the parameters like torque, current, and speed of the motor vary are explored in this paper. Then for the axial flux generator model, when the wind speed exceeds the rated speed how the torque, line voltages, currents, power and speed of the generator behave are investigated and presented in this paper. The developed model in this paper could be extended to a twin-rotor axial flux synchronous machine, which will lead to the development of more efficient WECS.展开更多
The three-dimensional(3D)analytical model of the magnetic field in an Axial Flux Permanent Magnets Maglev Motor(AFPMMM)is proposed and investigated the influence of the structural parameters on electromagnetic charact...The three-dimensional(3D)analytical model of the magnetic field in an Axial Flux Permanent Magnets Maglev Motor(AFPMMM)is proposed and investigated the influence of the structural parameters on electromagnetic characteristics.Firstly,the topology and working principle of the AFPMMM is introduced,and the model is transferred into a mathematical model in 3D cartesian coordinate.Then,the volume integral method and equivalent current sheets model is applied to find the 3D magnetic field distribution function of Halbach rotor.A unified form expression can be obtained by two dimensional discrete fourier transform(2-D DFT)is applied on the 3D magnetic field distribution function.Thirdly,the conductive and nonconductive regions of AFPMMM will be formulated by the second order vector potential(SOVP)to built the 3D analytic model.The expression of the lift force,torque and power losses was derived.Besides,the relationship between electromagnetic characteristics and structural parameters of the AFPMMM were analyzed based on 3D analytic model and validated using the 3D finite element analysis(FEA).Finally,the experiments based on a small scale prototype are carried out to verify the analytical results.展开更多
To achieve the utilization of torque components by current harmonics and the limitation of copper loss in a dual three-phase yokeless and segmented armature(YASA)axial flux permanent magnet(AFPM)machine,optimized 5th ...To achieve the utilization of torque components by current harmonics and the limitation of copper loss in a dual three-phase yokeless and segmented armature(YASA)axial flux permanent magnet(AFPM)machine,optimized 5th and 7th current harmonic injection is proposed.The torque component generated by the current harmonics is analyzed based on the vector space decomposition(VSD)model of the dual three-phase YASA machine,with consideration of the 5th and 7th harmonics of the open-circuit flux linkage.The optimization of 5th and 7th current harmonics,aiming for maximum torque with limited copper loss(MTLCL),is conducted and compared with existing optimization methods.Subsequently,simulations with and without current harmonic injection are conducted to compare and verify the proposed optimization.The simulation results show that the torque generated by the harmonics in the proposed method is 6.91%higher than that in the existing method,with 5th and 7th open-circuit flux-linkage harmonics of 17.72%and 5.3%of the fundamental component,respectively.A prototype is built,and the experimental results show that the torque component by current harmonics achieves 2.60%of that by the fundamental current with the limitation of copper loss,which further validates the proposed method.展开更多
基金The National Natural Science Foundation of China(No.52107039)the Fujian Provincial Natural Science Foundation for Youth(No.2021J05133)the Key Project of the National Natural Science Foundation of China(No.51937002)。
文摘The axial field hybrid permanent magnet memory machine(AFHPM-MM)employs a hybrid permanent magnet excitation combining NdFeB and AlNiCo,achieving high torque density and a wide flux adjustment range.A separated stator structure is adopted to enhance its antidemagnetization capability.To analyze the contributions of AlNiCo and NdFeB to the induced electromotive force(EMF)in the AFHPM-MM,a frozen permeability-based induced EMF calculation method is proposed.Theoretical analysis reveals that the conventional method exhibits substantial errors in calculating the AlNiCo-induced EMF,primarily attributed to its failure to adequately account for the dynamic magnetization characteristic discrepancies of AlNiCo under varying magnetization states.Through the analysis of magnetization variations in AlNiCo during the flux adjustment process under different magnetization states,an improved induced EMF calculation method is proposed.Comparative results indicate that,during the flux enhancement process,the average calculation error of the AlNiCo-induced EMF is reduced from 19.84%to 2.09%,whereas during the flux weakening process,the error is reduced from 3.87%to 1.67%.The proposed method achieves accurate induced EMF calculation for the AFHPM-MM.
基金This work was supported in part by National Natural Science Foundation for Excellent Young Scholar of China under Award 51622704,in part by Jiangsu provincial key research and development project under Award BE2017160。
文摘With the development of aviation electrification,higher demands for electrical machines are put forward in aircraft electric propulsion systems.The aircraft electric propulsion requirements and propulsion motor features are analyzed in this paper.Comparing with conventional PM machines,ironless stator axial flux permanent magnet(AFPM)machine topologies with Litz wire windings allow designs with higher compactness,lightness and efficiency,which are suitable for high-frequency and high-power density applications.Based on the motor requirements and constraints of aircraft electric propulsion systems,this paper investigates a high-power 1 MW multi-stack ironless stator AFPM machine,which is composed of four 250kW modular motors by stacking in axial.The design guidelines and special attentions are presented,in term of electromagnetic,thermal,and mechanical performance for the high-frequency coils and Halbach-array PM rotor.Finally,an ironless stator AFPM motor is manufactured,tested and evaluated with the consideration of cost and processing cycle.The results show that the output power is up to 53.8kW with 95%efficiency at 9000r/min at this stage.The proposed ironless stator AFPM machine with oil immersed forced cooling proves to be a favorable candidate for application in electric aircraft as propulsion motors.
基金the National Natural Science Foundation of China Grant No.52007055 and in part by the Fundamental Research Funds for the Central Universities under Grant 531118010386.
文摘Axial-flux permanent magnet synchronous machine(AFPMSM)enjoys the merits of high torque density and high efficiency,which make it one good candidate in the direct-drive application.The AFPMSM is usually analyzed based on the three-dimensional finite element method(3D FEM)due to its three-dimensional magnetic field distribution.However,the 3D FEM suffers large amount of calculation,time-consuming and is not suitable for the optimization of AFPMSM.Addressing this issue,a multi-layer quasi three-dimensional equivalent model of the AFPMSM is investigated in this paper,which could take the end leakage into consideration.Firstly,the multi-layer quasi three-dimensional equivalent model of the AFPMSM with single stator and single rotor is derived in details,including the equivalent processes and conversions of structure dimensions,motion conditions and electromagnetic parameters.Then,to consider the influence of end leakage on the performance,a correction factor is introduced in the multi-layer quasi three-dimensional equivalent model.Finally,the proposed multi-layer quasi three-dimensional equivalent model is verified by the 3D FEM based on an AFPMSM under different structure parameters.It demonstrates that the errors of flux linkage and average torque obtained by the multi-layer quasi three-dimensional equivalent model and 3D FEM are only around 2%although the structure parameters of the AFPMSM are varied.Besides,the computation time of one case based on the multi-layer quasi three-dimensional equivalent model is only 6 min,which is much less than that of the 3D FEM,1.8 h,under the same conditions.Thus,the proposed multi-layer quasi three-dimensional equivalent model could be used to optimize the AFPMSM and much time could be saved by this method compared with the 3D FEM.
基金supported in part by the National Natural Science Foundation of China Grant No.51877139。
文摘Conventional fractional slot concentrated winding three-phase axial flux permanent magnet machines have an abundance of armature reaction magnetic field harmonics which deteriorate the torque performance of the machine.This paper presents a double-stator dislocated axial flux permanent magnet machine with combined wye-delta winding.A wye-delta(Y-△)winding connection method is designed to eliminate the 6 th ripple torque generated by air gap magnetic field harmonics.Then,the accurate subdomain method is adopted to acquire the no-load and armature magnetic fields of the machine,respectively,and the magnetic field harmonics and torque performance of the designed machine are analyzed.Finally,a 6 k W,4000 r/min,18-slot/16-pole axial flux permanent magnet machine is designed.The finite element simulation results show that the proposed machine can effectively eliminate the 6 th ripple torque and greatly reduce the torque ripple while the average torque is essentially identical to that of the conventional three-phase machines with wye-winding connection.
文摘In this paper,a performance comparison between the novel axial flux magnetically geared machines(AFMG)and the conventional axial flux YASA machine is presented.The AFMG and YASA machines have the same stator construction in which segments are equipped with concentrated windings to form the stator.However,the AFMG machine has two rotors with different pole-pair numbers.Magnetic gear effect can be obtained to increase the torque density.The performance comparisons at no-load and on-load conditions are then studied by 3D-finite element analysis(FEM).Moreover,both machines are prototyped,tested and compared.
文摘With the cvolution of various high powerr-density machines, it beeomes important to optimize the power potential of machines of vastly different topologies with a variety of waveforms of back emf and current. The approach of tins paper is based oil the gencral-purpose sizing equations. which permit the optinlization method of machine power density to be applied to the axial-flux toroidal permanent-magnet (AFTPM) machine, and,furthermore, the power-production capabilities of the AFTPM machinc and the wen-known squirrel-cage indution machine are compared.
基金financed by the Electric'Drive Laboratory,Department of Electrical Engineering,University of Padova,Padova(haly).
文摘This paper describes the electric drive for an in-wheel fractional-slot axial flux machine,designed for achieving a wide flux-weakening operating region.By using a slotted stator with fractional-slot windings and additional cores enclosing end windings,the axial flux machine reaches a wide constant power speed range.The machine is designed for increasing flux-weakening capability while obtaining low harmonic back-electromotive force and low cogging torque.A 10 N.m axial flux machine exhibiting 3 to 1 flux-weakening speed range has been built.A flux-weakening controller,able to maximize the output torque in the flux-weakening region,is designed and implemented.The goodness of both design and control algorithm is proved by experimental tests.However,such a fractional-slot machine has not only advantages.Rotor losses are very high,and they have to be properly considered during the design process.
基金financial support from the National Natural Science Foundation of China (No. 51005120)Jiangsu Natural Science Foundation (Nos. BK2010508 and BE2010193)
文摘Titanium and its alloys have found very wide application in aerospace due to their excellent characteristics although their processing is still a challenge. Electrochemical machining is an important issue in the fabrication of titanium and titanium alloys. Wire electrochemical machining （WECM） is mainly used for workpiece cutting under the condition of different thickness plates. It has a great advantage over wire electro-discharge machining, which is the absence of heat-affected zone around the cutting area. Moreover, the wire electrode in WECM could be used repetitively because it is not worn out. Thus, much attention has been paid to WECM. The effective way of removing electrolysis products is of importance to WECM. In this paper, the axial electrolyte flushing is presented to WECM for removing electrolysis products and renewing electrolyte. The Taguchi experiment is conducted to optimize the machining parameters, such as wire feedrate, machining voltage, electrolyte concentration, etc. Experimental results show that WECM with axial electrolyte flushing is a promising issue in the fabrication of titanium alloy （TC1）. The feasibility of multi-wire electrochemical machining is also demonstrated to improve the machining productivity of WECM.
基金Supported by National Natural Science Foundation of China (Grant No.51075147)National Hi-tech Research and Development Program of China (863 Program,Grant No.2012AA041803)
文摘Wear is a major factor of disc cutters’ failure. No current theory offers a standard for the prediction of disc cutter wear yet. In the field the wear prediction method commonly used is based on the excavation length of tunnel boring machine（TBM） to predict the disc cutter wear and its wear law, considering the location number of each disc cutter on the cutterhead（radius for installation）; in theory, there is a prediction method of using arc wear coefficient. However, the preceding two methods have their own errors, with their accuracy being 40% or so and largely relying on the technicians’ experience. Therefore, radial wear coefficient, axial wear coefficient and trajectory wear coefficient are defined on the basis of the operating characteristics of TBM. With reference to the installation and characteristics of disc cutters, those coefficients are modified according to penetration, which gives rise to the presentation of comprehensive axial wear coefficient, comprehensive radial wear coefficient and comprehensive trajectory wear coefficient. Calculation and determination of wear coefficients are made with consideration of data from a segment of TBM project（excavation length 173 m）. The resulting wear coefficient values, after modification, are adopted to predict the disc cutter wear in the follow-up segment of the TBM project（excavation length of 5621 m）. The prediction results show that the disc cutter wear predicted with comprehensive radial wear coefficient and comprehensive trajectory wear coefficient are not only accurate（accuracy 16.12%） but also highly congruous, whereas there is a larger deviation in the prediction with comprehensive axial wear coefficient（accuracy 41%, which is in agreement with the prediction of disc cutters’ life in the field）. This paper puts forth a new method concerning prediction of life span and wear of TBM disc cutters as well as timing for replacing disc cutters.
基金supported by the National High Technology Research and Development Program of China(863 Program, Grant No.2002AA602012-2)
文摘The underwater tapping machine is composed of a center bit, a tapping cutter, a seal box, a main drive box, a boring bar assembly, a envelop, a gear case, a counter and so on. The drive system in underwater tapping machine consists of a worm drive, a gear drive system and a screw drive. The worm drive is in the main drive box. The worm is connected with a hydraulic motor and driven by the hydraulic motor. The gear drive system is a combined gear train which is the combinations of the fixed axes and differential gear train in the gear case. On the one hand, by means of the fixed axes gear trains the turn and power of transmission shaft are transferred to the boring bar and the screw rod, causing differential turn between the boring bar and the screw rod. On the other hand, the turns of the boring bar and the screw rod are transferred to the differential gear train. The differential gear train is used to drive a special counter to count axial travel of the boring bar. The screw drive is composed of a feed screw and a nut on the boring bar. There is the differential turn between the boring bar and the feed screw. By means of the nut, the boring bar can feed automatically. With the movement of the sliding gear 7 in the gear case, the designed drive system can also be provided with the ability of fast forward and fast backward movement of the boring bar in its idle motion, resulting in the increase of the tapping efficiency.
基金The National Natural Science Foundation of China(No.51977035)。
文摘The excitation system of the homopolar inductor machine(HIM)is analyzed and designed to establish the design approach and evaluation criteria of the excitation system.The finite element method is used to calculate the three-dimensional electromagnetic field in the HIM,and the distribution and characteristics of the magnetic field are described.The analytical method is applied to investigate the design process of the excitation winding.The ratio of the axial length of the armature winding to the excitation winding and the ratio of the axial length of the working air-gap to the non-working air-gap are investigated by the numerical calculation method.A prototype HIM is designed and manufactured,and some experiments are implemented to verify the correctness of the theoretical analysis and numerical calculation results.The research results show that the established design method of the excitation winding is practical and feasible.Under the conditions of constant excitation magnetomotive force or constant excitation power,the optimum range of the axial length ratio of the armature winding and the excitation winding is 0.45 to 0.5.The optimal axial length of the non-working air-gap can be determined by the ratio of the stator inner diameter and pole-pairs.
基金supported by research grants of the Iran National Science Foundation(INSF)under grant No.98002866。
文摘The efficiency of energy conversion from mechanical to electrical in AC generators is not entirely optimal,as power losses are converted into heat.Accurate thermal modeling and temperature measurement of advanced electric machines with complex structures are mandatory to confirm their reliability and safe operation.In a unique axial transverse flux switching permanent magnet(ATFSPM)generator,due to its high power density,large stray loss from leakage flux,compact topology,and totally enclosed structure,thermal analysis is of paramount significance.In this paper,thermal modeling and analysis of ATFSPM are carried out in detail using a three-dimensional(3D)finite element analysis(FEA)to evaluate the thermal condition for a precise performance improvement.To begin,all loss sources are accurately derived using 3-D FEA and analytical methods,taking into account the temperature dependence of material properties,and then losses are coupled to the thermal model as heat sources.Afterward,aiming for realistic thermal modelling,the convection heat transfer in the different regions of internal and external areas as well as thin layers of interface gaps between components are all considered.In addition,the prototype of ATFSPM is supplied to validate the accuracy of 3-D FEA temperature prediction.Furthermore,a novel technique is carried out to effectively improve thermal performance,enhance the efficiency,and limit hot-spot temperatures.The steady-state and transient temperature results demonstrate the high accuracy of the thermal modeling,enhance the secure operation of the ATFSPM,and facilitate increased loading utilizing the proposed technique.(1)
文摘This paper investigates the application of the axial flux machine (AFM) to the wind energy conversion systems (WECS) to obtain high power and torque at reduced cost. By developing mathematical equations using the phase and active transformations, the three-phase model is transformed to two-phase equations by making both the stator and rotor as reference frames, finally converting to arbitrary reference frame, which is useful for the modelling of the axial flux machine. The torque, current, and voltage equations are expressed to improve the simulation reliability. Based on the developed equations, the mathematical model for the axial flux machine is developed using the MATLAB/Simulink. Starting with the axial flux motor model, when the load on the motor increases, how the parameters like torque, current, and speed of the motor vary are explored in this paper. Then for the axial flux generator model, when the wind speed exceeds the rated speed how the torque, line voltages, currents, power and speed of the generator behave are investigated and presented in this paper. The developed model in this paper could be extended to a twin-rotor axial flux synchronous machine, which will lead to the development of more efficient WECS.
基金supported in part by the Fundamental Research Funds for the Central Universities of China under Grant No.2022JBMC050。
文摘The three-dimensional(3D)analytical model of the magnetic field in an Axial Flux Permanent Magnets Maglev Motor(AFPMMM)is proposed and investigated the influence of the structural parameters on electromagnetic characteristics.Firstly,the topology and working principle of the AFPMMM is introduced,and the model is transferred into a mathematical model in 3D cartesian coordinate.Then,the volume integral method and equivalent current sheets model is applied to find the 3D magnetic field distribution function of Halbach rotor.A unified form expression can be obtained by two dimensional discrete fourier transform(2-D DFT)is applied on the 3D magnetic field distribution function.Thirdly,the conductive and nonconductive regions of AFPMMM will be formulated by the second order vector potential(SOVP)to built the 3D analytic model.The expression of the lift force,torque and power losses was derived.Besides,the relationship between electromagnetic characteristics and structural parameters of the AFPMMM were analyzed based on 3D analytic model and validated using the 3D finite element analysis(FEA).Finally,the experiments based on a small scale prototype are carried out to verify the analytical results.
基金Supported in part by the National Natural Science Foundation of China(52207060,U2141223)in part by the Natural Science Foundation of Jiangsu Province(BK20220905)+1 种基金in part by the China Postdoctoral Science Foundation(2022M711609)in part by the Engineering Research Center of Low-Carbon Aerospace Power,Ministry of Education(CEPE2024016)。
文摘To achieve the utilization of torque components by current harmonics and the limitation of copper loss in a dual three-phase yokeless and segmented armature(YASA)axial flux permanent magnet(AFPM)machine,optimized 5th and 7th current harmonic injection is proposed.The torque component generated by the current harmonics is analyzed based on the vector space decomposition(VSD)model of the dual three-phase YASA machine,with consideration of the 5th and 7th harmonics of the open-circuit flux linkage.The optimization of 5th and 7th current harmonics,aiming for maximum torque with limited copper loss(MTLCL),is conducted and compared with existing optimization methods.Subsequently,simulations with and without current harmonic injection are conducted to compare and verify the proposed optimization.The simulation results show that the torque generated by the harmonics in the proposed method is 6.91%higher than that in the existing method,with 5th and 7th open-circuit flux-linkage harmonics of 17.72%and 5.3%of the fundamental component,respectively.A prototype is built,and the experimental results show that the torque component by current harmonics achieves 2.60%of that by the fundamental current with the limitation of copper loss,which further validates the proposed method.
