In this paper a fully parametrized finite element simulation model of the stator bar end is created using the COMSOL Multiphysics.The model allows conducting the comparison of different corona protection structures’d...In this paper a fully parametrized finite element simulation model of the stator bar end is created using the COMSOL Multiphysics.The model allows conducting the comparison of different corona protection structures’design,various materials properties,and finally optimizing the corona protection system.Several samples of SiC based nonlinear conductivity materials for corona protection were fabricated in laboratory and then investigated.The conductivity dependencies on electric field(0.05 to 1 kV/mm)and temperature(20 to 155℃)were measured.By comparing the heat-resistant grades of the corona protection material and the insulating material,the maximum working temperature of the corona protection material corresponds to the heat-resistant grade F of the insulating material.As the temperature increases,the nonlinear characteristics of the corona protection material in the experiment decrease dramatically,reducing the heat-resistant grade of the corona protection material.The decrease in the nonlinear characteristics of the corona protection material at the maximum operating temperature causes the maximum electric field strength at the end of the HV rotating machines end corona protection(ECP)exceeding the corona discharge electric field strength,resulting in corona phenomenon.展开更多
This article investigates the anti-disturbance and stabilization problems for the nonlinear uncertain permanent magnet synchronous motor(PMSM)with stator voltage saturation and unknown load.A smooth switching mechanis...This article investigates the anti-disturbance and stabilization problems for the nonlinear uncertain permanent magnet synchronous motor(PMSM)with stator voltage saturation and unknown load.A smooth switching mechanism is presented to structure the adaptive integral terminal sliding mode control(SMC)strategy.The control design consists of compensation control and nominal control,which improves the rapidity and accuracy of trajectory tracking.The smooth saturation model based on the error function is applied to approximate the voltage saturation phenomenon.Additionally,to deal with the adverse effects of various unknown disturbances,including model parameter uncertainties and unknown external load disturbances,an improved disturbance observer(DO)is proposed.This observer effectively suppresses the fluctuations caused by fixed gain during the starting period of the system.Finally,the experimental results under different conditions show that the proposed strategy has good tracking and disturbance suppression performances.展开更多
The coupling effect of dual-parallel rotor connected stator permanent magnet synchronous motor not only affects the magnetic field in the coupling area, but also generates an additional magnetic field in the uncoupled...The coupling effect of dual-parallel rotor connected stator permanent magnet synchronous motor not only affects the magnetic field in the coupling area, but also generates an additional magnetic field in the uncoupled area.The characteristics of the additional magnetic field and its influence on electromagnetic torque are studied in this paper.The topology and parameters of motor are described briefly.The existence of additional magnetic field is proved by the simulation models under two boundary conditions, and its characteristics and source are analyzed. The analytical model is established, and the influence of key parameters on the additional magnetic field is discussed. On this basis, the influence of the additional magnetic field on the electromagnetic torque of the motor is studied, and the analytical expression of the additional torque is constructed.The fluctuation rule is analyzed, and the additional magnetic field separation model is proposed. The theoretical analysis and simulation results reveal and improve the internal mechanism of reducing motor torque ripple by optimizing the duty angle and coupling distance. Finally, a prototype test platform is built to verify the correctness of the proposed theory and the accuracy of the simulation model.展开更多
Clarifying the gas ingestion mechanism in the turbine disc cavity of marine gas turbines is crucial for ensuring the normal operation of turbines.However, the ingestion is influenced by factors such as the rotational ...Clarifying the gas ingestion mechanism in the turbine disc cavity of marine gas turbines is crucial for ensuring the normal operation of turbines.However, the ingestion is influenced by factors such as the rotational pumping effect, mainstream pressure asymmetry, rotor–stator interaction,and unsteady flow structures, complicating the flow. To investigate the impact of rotor–stator interaction on ingestion, this paper decouples the model to include only the mainstream. This research employs experiments and numerical simulations to examine the effects of varying the flow coefficient through changes in rotational speed and mainstream flow rate. The main objective is to understand the influence of different rotor–stator interactions on the mainstream pressure field, accompanied by mechanistic explanations. The findings reveal inconsistent effects of the two methods for changing the flow coefficient on the mainstream pressure field. Particularly, the pressure distribution on the vane side primarily depends on the mainstream flow rate, while the pressure on the blade side is influenced by the mainstream flow rate and the attack angle represented by the flow coefficient. A larger angle of attack angle can increase pressure on the blade side, even surpassing the pressure on the vane side. Assessing the degree of mainstream pressure unevenness solely based on the pressure difference on the vane side is insufficient. This research provides a basis for subsequent studies on the influence of coupled real turbine rotor–stator interaction on gas ingestion.展开更多
Tip clearances of multistage rotors and stators greatly affect aero-engines’ aerodynamic efficiency, stability and safety. The inevitable machining and assembly errors, as well as the complicated error propagation me...Tip clearances of multistage rotors and stators greatly affect aero-engines’ aerodynamic efficiency, stability and safety. The inevitable machining and assembly errors, as well as the complicated error propagation mechanism, cause overproof or non-uniform tip clearances. However, it is generally accepted that tip clearances are difficult to predict, even under assembly state. In this paper, a tip clearance prediction model is proposed based on measured error data. Some 3 D error propagation sub-models, regarding rotors, supports and casings, are built and combined. The complex error coupling relationship is uncovered using mathematical methods. Rotor and stator tip clearances are predicted and analyzed in different phase angles. The maximum, minimum and average tip clearances can be calculated. The proposed model is implemented by a computer program,and a case study illustrates its performance and verifies its feasibility. The results can be referred by engineers in assembly quality judgement and decision-making.展开更多
Bowed-twisted stators with large camber angles have been developed to replace the conventional tandem stators in an axial transonic fan stage working at high subsonic speeds. Experimental study is carried out on both ...Bowed-twisted stators with large camber angles have been developed to replace the conventional tandem stators in an axial transonic fan stage working at high subsonic speeds. Experimental study is carried out on both stages with tandem stators and with bowed-twisted stators. Compared to the tandem stators, the bowed-twisted stators change the distribution of the low-energy fluid and the potential high-energy fluid at the compressor outlets, reduce the endwall loss significantly, improve the aerody- namic matching of rotors and stators, and eventually increase the fan stage performances. The aerodynamic performances of the fan stage at different operating points are compared and contrasted. The results show that the transonic fan stage with bowed-twisted stators has better aerodynamic performances. It is thus suggested that the bowed-twisted stators with large camber angles be popularized into the high-loaded transonic fan designs.展开更多
Vector-controlled AC motor drives utilize pulse width modulation(PWM)to synthesize the desired output voltage of the voltage source inverter(VSI).In space vector PWM(SVPWM)techniques,the average realization of the spa...Vector-controlled AC motor drives utilize pulse width modulation(PWM)to synthesize the desired output voltage of the voltage source inverter(VSI).In space vector PWM(SVPWM)techniques,the average realization of the space vector applying the volt-sec balance principle results in an instantaneous error voltage that generates high frequency torque ripple.It may lead to an increase in motor vibration and acoustic noise.This article presents a high frequency torque ripple prediction model based on stator flux ripple and proposes a targeted designed variable switching frequency PWM(VSFPWM)strategy to diminish high frequency torque ripple.The switching frequency is dynamically adjusted according to the peak value of the predicted stator flux ripple to mitigate high frequency torque ripple.In contrast to existing strategies,the strategy outlined in this article directly suppresses high frequency torque ripple,thus remaining unaffected by inaccurate motor parameters.Additionally,due to the introduction of the power factor angle,the proposed strategy can better adapt to the full speed range operating conditions of the motor.Detailed simulations and experiments are provided to validate the effectiveness of the proposed strategy.展开更多
Coal mine conveyor belt and other low-speed large torque system,the torque density and torque stability of the motor requirements are higher,permanent magnet/magnet reluctance hybrid rotor double stator synchronous mo...Coal mine conveyor belt and other low-speed large torque system,the torque density and torque stability of the motor requirements are higher,permanent magnet/magnet reluctance hybrid rotor double stator synchronous motor(PM/MRHRDSSM)is just adapted to this requirement,however,the traditional close winding single inverter vector control system control PM/MRHRDSSM provides large torque ripple,high speed fluctuation and large total harmonic distortion(THD)of the current,difficult to be used in actual production and life,this paper proposes a large torque open winding-permanent magnet/magnet reluctance hybrid rotor double stator synchronous motor(OW-PM/MRHRDSSM)based on SVPWM dual inverter control strategy,and analysis of open winding double inverter structure,and its voltage vector mathematical model,using the existing two-level inverter as a basis,the bilateral inverter separately discussed its role and control method,as well as the decomposition method of synthetic voltage vector and the inverter device in the small sector on-time,the end of this paper through simulation to compare the traditional close winding single inverter vector control system control PM/MRHRDSSM and the large torque OW-PM/MRHRDSSM based on SVPWM dual inverter control strategy to prove the effectiveness of the proposed method in reducing torque ripple,speed fluctuation and THD of current during motor operation.展开更多
The outlet flow fields of a low-speed repeating-stage compressor with bowed stator stages are measured with five-hole probe under the near stall condition when the rotor/stator axial gap varies. The performances of th...The outlet flow fields of a low-speed repeating-stage compressor with bowed stator stages are measured with five-hole probe under the near stall condition when the rotor/stator axial gap varies. The performances of the straight stator stages are investigated and compared to those of the bowed stator stages. The results show that using bowed stator stages could alleviate the flow separation at both upper and low corners of the suction surface and the endwalls, and decrease the losses along the flow passage as well as the outlet flow angle. As the rotor/stator axial gap decreases, although the diffusion capacity of the compressor increases obviously, the outlet flow field in the straight stator stages deteriorates quickly. By contrast, little changes occur in the bowed stator stages, indicating that as the rotor/stator axial gap decreases, improved performance is achieved in the bowed stator stages.展开更多
The control platform of the induction motor （IM） with low costs is developed by using DSP MC56F8013 with a good performance/price rtaio. The control algorithm for the speed sensorless IM is studied based on the stat...The control platform of the induction motor （IM） with low costs is developed by using DSP MC56F8013 with a good performance/price rtaio. The control algorithm for the speed sensorless IM is studied based on the stator flux orientation （SFO）. The algorithm structure is simple to be implemented and cannot be influenced by motor parameters, The improved stator flux estimation is used to compensate errors caused by the low pass filter （LPF）. A new speed regulator is designed to ensure the system working with the maximal torque in the transient state. The system simulation and the prototype experiment are made. Results show that the con- trol system has good dynamic and static performance.展开更多
A two-degree-of-freedom（2-DOF） linear ultrasonic motor （USM） consists of a cylinder-shaped stator and a slider. Two bending vibration modes with orthogonality and one longitudinal vibration mode are excited in the...A two-degree-of-freedom（2-DOF） linear ultrasonic motor （USM） consists of a cylinder-shaped stator and a slider. Two bending vibration modes with orthogonality and one longitudinal vibration mode are excited in the stator by three groups of piezoelectric ceramic elements. The combinations of any one bending mode and the longitudinal mode mentioned above push the slider to move linearly in direction x or y. Some key issues for improving the motor output properties and efficiency are given. They include selection of the vibration modes, consistency of the modal frequencies, placement of the piezoelectric ceramic elements and the supporting plane, setting of pre-pressure, and influence of interfering modes.展开更多
This paper put forward a new fault-tolerant hybrid switched-flux PM(HSFPM)machine design employing the synergy of NdFeB and Ferrite Magnet.The key of the proposed HSFPM designed machine is the unique design E-core lam...This paper put forward a new fault-tolerant hybrid switched-flux PM(HSFPM)machine design employing the synergy of NdFeB and Ferrite Magnet.The key of the proposed HSFPM designed machine is the unique design E-core laminated stator with the hybrid magnet to ensure a drastic reduction of NdFeB magnet without compromising the output performances and efficiency in the conventional SFPM machine design to avert the huge demand of NdFeB and its associated volatile high price increase.Additionally,the fault-tolerant stator teeth designed principle implemented in the proposed HSFPM machine provides enhanced segregation among the various phases and ensures continuity of operation with acceptable operating performance under fault-condition.For fair evaluation and comparison,both the proposed HSFPM and the conventional SFPM(CSFPM)machine have the same slot-pole combination,winding arrangements,and stator/rotor dimensions except for the unique outer-stator of the proposed design.Meanwhile,compared to the CSFPM machine,the proposed HSFPM machine design makes use of only 60%of the PM(NdFeB)length.Finally,the evaluation of the no-load in conjunction with the load condition performances was carefully investigated by the Finite Element Method(FEM)of the ANSYS Maxwell software.The results depicted that the proposed HSFPM exhibits similar sinusoidal back electromotive force,comparable output torque,and slightly higher efficiency compared to that of the CSFPM machine.展开更多
This article proposes a tandem cascade constructed to tackle the thorny problem of designing the high-loaded stator with a supersonic inflow and a large turning angle. The front cascade adopts a supersonic profile to ...This article proposes a tandem cascade constructed to tackle the thorny problem of designing the high-loaded stator with a supersonic inflow and a large turning angle. The front cascade adopts a supersonic profile to reduce the shock wave intensity turning the flow into subsonic,while the rear cascade adopts a subsonic profile with a large camber offering the flow a large turning angle. It is disclosed that the losses would be minimized if the leading edge of the rear cas- cade lies close to the pressure side of the front cascade at a distance of 20% pitch in pitch-wise direction without either axial spacing or overlapping in axial direction. The 2D numerical test results show that,with the inflow Mach number of 1.25 and the turning angle of 52° ,the total pressure loss coefficient of the tandem cascade reaches 0. 106 ,and the diffusion factor 0. 745. Finally,this article has designed and simulated a high-loaded fan stage with the proposed tandem stator,which has the pressure ratio of 3.15 and the efficiency of 86.32% at the rotor tip speed of 495.32 m/s.展开更多
The direct torque control theory has achieved great success in the control ofinduction motors. However, in the DTC drive system of Permanent Magnet Synchronous Machine (PMSM)proposed a few years ago, there are many ba...The direct torque control theory has achieved great success in the control ofinduction motors. However, in the DTC drive system of Permanent Magnet Synchronous Machine (PMSM)proposed a few years ago, there are many basic theoretical problems that must be clarified. Thispaper describes an investigation about the effect of the zero voltage space vectors in the DTCsystem of PMSM and points out that if using the zero voltage space vectors rationally, not only canthe DTC system be driven successfully but also the torque ripple is reduced and the performance ofthe system is improved. This paper also studies the sensorless technique in the DTC system of PMSMand configures the DTC system of PMSM with sensorless technique including zero voltage spacevectors. Numerical simulations and experimental tests have proved the theory correct. In thecondition of sensor-less, the DTC system of PMSM is wide-rangely speed adjusting, and the ratio ofspeed adjustment is 1: 100.展开更多
This paper is focused on the experimental study of the effects of stator clocking on the performance of a low-speed repeating stage axial compressor with compound-lean stators as well as the one with conventional stat...This paper is focused on the experimental study of the effects of stator clocking on the performance of a low-speed repeating stage axial compressor with compound-lean stators as well as the one with conventional stators （the baseline） for comparison. The experimental results show that as the clocking positions vary, the upstream stator wake enters the following passage at different circumferential positions, and then mixes with the local fluid in the following passage. This is the main reason for the variation of the compressor performance resulted from the stator clocking effects. The variation of the compressor performance due to the clocking effect is less pronounced for the compressor with compound-lean stators than with the baseline. At a certain clocking position, the efficiency of the compressor with compound-lean stators is increased in comparison with that of the baseline, especially on small mass flow rate conditions, e.g., 0.7% at design condition and 3.5% at near-surge condition in this case. The maximum 1.22% and the minimum 0.07% increases in efficiency on design condition are obtained through the combined effects of the stator compound-lean and the stator clocking in this case.展开更多
In this paper, the effect of different amount of protrusion on various parameters in rotor–stator system was experimentally studied by measuring CO_2 concentration and pressure, in order to obtain the optimal protrus...In this paper, the effect of different amount of protrusion on various parameters in rotor–stator system was experimentally studied by measuring CO_2 concentration and pressure, in order to obtain the optimal protrusion amount.The parameters of different dimensionless sealing flow were measured under the condition that the annulus Reynolds number was 4.39 × 10~5 and the rotating Reynolds number was 1.05 × 10~6.The results show that the change of the amount of protrusions has little effect on the static pressure in the cavity, and the static pressure change near the sealing ring is almost negligible.But the total pressure and sealing efficiency increase first and then decrease with the increase of the amount of protrusion.The variation of power consumption is the same.A complex vortex structure will appear at the high radius region when the protrusion is installed.On the other hand, the protrusion can effectively reduce the minimum sealing flow of the rotor–stator cavity.Furthermore, considering the sealing efficiency and power consumption,the best range of the protrusion amount is about 36.The ratio near this range can optimally balance the alleviation of the gas ingestion and the reduction of the power consumption.展开更多
A hydraulic experimental platform for the assembly of stator components was developed,and the simulation on this system was performed based on software AMEsim.Characteristics of the system,such as the pressure and the...A hydraulic experimental platform for the assembly of stator components was developed,and the simulation on this system was performed based on software AMEsim.Characteristics of the system,such as the pressure and the displacement,were analyzed.The results guide design of the hydraulic system of experiment platform for the assembly of the stator.展开更多
This paper analyzes lightning surge on the stator windings of wind turbine generators.The path of lightning in the wind turbines was analyzed.An equivalent circuit model for megawatt direct-driven wind turbine system ...This paper analyzes lightning surge on the stator windings of wind turbine generators.The path of lightning in the wind turbines was analyzed.An equivalent circuit model for megawatt direct-driven wind turbine system was developed,in which high-frequency distributed parameters of the blade conducts,tower,power cables and stator windings of generator were calculated based on finite element method,and the models of converter,grounding,loads, surge protection devices and power grid were established.The voltage distribution along stator windings,when struck by lightning with 10/350μs wave form and different amplitude current between 50 kA and 200 kA,was simulated using electro-magnetic transient analysis method.The simulated results show that the highest coil-to-core voltage peak appears on the last coil or near the neutral of stator windings,and the voltage distribution along the windings is nonuniform initially.The voltage drops of each coil fall from first to last coil,and the highest voltage drop appears on the first coil.The insulation damage may occur on the windings under lightning overvoltage.The surge arresters can restrain the lightning surge in effect and protect the insulation.The coil-to-core voltage in the end of windings is nearly 19.5 kV under the 200 kA lightning current without surge arresters on the terminal of generator,but is only 2.7 kV with arresters.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
文摘In this paper a fully parametrized finite element simulation model of the stator bar end is created using the COMSOL Multiphysics.The model allows conducting the comparison of different corona protection structures’design,various materials properties,and finally optimizing the corona protection system.Several samples of SiC based nonlinear conductivity materials for corona protection were fabricated in laboratory and then investigated.The conductivity dependencies on electric field(0.05 to 1 kV/mm)and temperature(20 to 155℃)were measured.By comparing the heat-resistant grades of the corona protection material and the insulating material,the maximum working temperature of the corona protection material corresponds to the heat-resistant grade F of the insulating material.As the temperature increases,the nonlinear characteristics of the corona protection material in the experiment decrease dramatically,reducing the heat-resistant grade of the corona protection material.The decrease in the nonlinear characteristics of the corona protection material at the maximum operating temperature causes the maximum electric field strength at the end of the HV rotating machines end corona protection(ECP)exceeding the corona discharge electric field strength,resulting in corona phenomenon.
基金supported by the National Natural Science Foundation under Grant 62273189the Shandong Province Natural Science Foundation under Grant ZR2021MF005Systems Science Plus Joint Research Program of Qingdao University under Grant XT2024201 of China supporting this research work.
文摘This article investigates the anti-disturbance and stabilization problems for the nonlinear uncertain permanent magnet synchronous motor(PMSM)with stator voltage saturation and unknown load.A smooth switching mechanism is presented to structure the adaptive integral terminal sliding mode control(SMC)strategy.The control design consists of compensation control and nominal control,which improves the rapidity and accuracy of trajectory tracking.The smooth saturation model based on the error function is applied to approximate the voltage saturation phenomenon.Additionally,to deal with the adverse effects of various unknown disturbances,including model parameter uncertainties and unknown external load disturbances,an improved disturbance observer(DO)is proposed.This observer effectively suppresses the fluctuations caused by fixed gain during the starting period of the system.Finally,the experimental results under different conditions show that the proposed strategy has good tracking and disturbance suppression performances.
基金supported in part by the Natural Science Foundation of Heilongjiang Province under Grant LH2023E084by the National Natural Science Foundation of China under Grant 51777048。
文摘The coupling effect of dual-parallel rotor connected stator permanent magnet synchronous motor not only affects the magnetic field in the coupling area, but also generates an additional magnetic field in the uncoupled area.The characteristics of the additional magnetic field and its influence on electromagnetic torque are studied in this paper.The topology and parameters of motor are described briefly.The existence of additional magnetic field is proved by the simulation models under two boundary conditions, and its characteristics and source are analyzed. The analytical model is established, and the influence of key parameters on the additional magnetic field is discussed. On this basis, the influence of the additional magnetic field on the electromagnetic torque of the motor is studied, and the analytical expression of the additional torque is constructed.The fluctuation rule is analyzed, and the additional magnetic field separation model is proposed. The theoretical analysis and simulation results reveal and improve the internal mechanism of reducing motor torque ripple by optimizing the duty angle and coupling distance. Finally, a prototype test platform is built to verify the correctness of the proposed theory and the accuracy of the simulation model.
基金the National Natural Science Foundation Outstanding Youth Foundation (Grant No.52122603)the National Science and Technology Major Project (J2019-Ⅲ-0003–0046)。
文摘Clarifying the gas ingestion mechanism in the turbine disc cavity of marine gas turbines is crucial for ensuring the normal operation of turbines.However, the ingestion is influenced by factors such as the rotational pumping effect, mainstream pressure asymmetry, rotor–stator interaction,and unsteady flow structures, complicating the flow. To investigate the impact of rotor–stator interaction on ingestion, this paper decouples the model to include only the mainstream. This research employs experiments and numerical simulations to examine the effects of varying the flow coefficient through changes in rotational speed and mainstream flow rate. The main objective is to understand the influence of different rotor–stator interactions on the mainstream pressure field, accompanied by mechanistic explanations. The findings reveal inconsistent effects of the two methods for changing the flow coefficient on the mainstream pressure field. Particularly, the pressure distribution on the vane side primarily depends on the mainstream flow rate, while the pressure on the blade side is influenced by the mainstream flow rate and the attack angle represented by the flow coefficient. A larger angle of attack angle can increase pressure on the blade side, even surpassing the pressure on the vane side. Assessing the degree of mainstream pressure unevenness solely based on the pressure difference on the vane side is insufficient. This research provides a basis for subsequent studies on the influence of coupled real turbine rotor–stator interaction on gas ingestion.
基金co-supported by the Equipment Pre-Research Foundation (No. 61409230204)the National Basic Research Project (No. 2017-VII-0010-0104)+2 种基金the Defense Industrial Technology Development Program (No. XXXX2018213A001)the National Natural Science Foundation of China(No. 51875475)the Key Development Program of Shaanxi Province (Nos. 2018ZDXM-GY-068 and 2016KTZDGY4-02)。
文摘Tip clearances of multistage rotors and stators greatly affect aero-engines’ aerodynamic efficiency, stability and safety. The inevitable machining and assembly errors, as well as the complicated error propagation mechanism, cause overproof or non-uniform tip clearances. However, it is generally accepted that tip clearances are difficult to predict, even under assembly state. In this paper, a tip clearance prediction model is proposed based on measured error data. Some 3 D error propagation sub-models, regarding rotors, supports and casings, are built and combined. The complex error coupling relationship is uncovered using mathematical methods. Rotor and stator tip clearances are predicted and analyzed in different phase angles. The maximum, minimum and average tip clearances can be calculated. The proposed model is implemented by a computer program,and a case study illustrates its performance and verifies its feasibility. The results can be referred by engineers in assembly quality judgement and decision-making.
基金National Natural Science Foundation of China (50236020)
文摘Bowed-twisted stators with large camber angles have been developed to replace the conventional tandem stators in an axial transonic fan stage working at high subsonic speeds. Experimental study is carried out on both stages with tandem stators and with bowed-twisted stators. Compared to the tandem stators, the bowed-twisted stators change the distribution of the low-energy fluid and the potential high-energy fluid at the compressor outlets, reduce the endwall loss significantly, improve the aerody- namic matching of rotors and stators, and eventually increase the fan stage performances. The aerodynamic performances of the fan stage at different operating points are compared and contrasted. The results show that the transonic fan stage with bowed-twisted stators has better aerodynamic performances. It is thus suggested that the bowed-twisted stators with large camber angles be popularized into the high-loaded transonic fan designs.
基金supported in part by the National Key Laboratory of Electromagnetic Energy Foundation under Grant 614221722050501 and 61422172220503。
文摘Vector-controlled AC motor drives utilize pulse width modulation(PWM)to synthesize the desired output voltage of the voltage source inverter(VSI).In space vector PWM(SVPWM)techniques,the average realization of the space vector applying the volt-sec balance principle results in an instantaneous error voltage that generates high frequency torque ripple.It may lead to an increase in motor vibration and acoustic noise.This article presents a high frequency torque ripple prediction model based on stator flux ripple and proposes a targeted designed variable switching frequency PWM(VSFPWM)strategy to diminish high frequency torque ripple.The switching frequency is dynamically adjusted according to the peak value of the predicted stator flux ripple to mitigate high frequency torque ripple.In contrast to existing strategies,the strategy outlined in this article directly suppresses high frequency torque ripple,thus remaining unaffected by inaccurate motor parameters.Additionally,due to the introduction of the power factor angle,the proposed strategy can better adapt to the full speed range operating conditions of the motor.Detailed simulations and experiments are provided to validate the effectiveness of the proposed strategy.
基金supported in part by the National Natural Science Foundation of China under Grant U22A20215 and 51877139Applied Basic Research Program of Liaoning Province under Grant 2023JH2/101300219。
文摘Coal mine conveyor belt and other low-speed large torque system,the torque density and torque stability of the motor requirements are higher,permanent magnet/magnet reluctance hybrid rotor double stator synchronous motor(PM/MRHRDSSM)is just adapted to this requirement,however,the traditional close winding single inverter vector control system control PM/MRHRDSSM provides large torque ripple,high speed fluctuation and large total harmonic distortion(THD)of the current,difficult to be used in actual production and life,this paper proposes a large torque open winding-permanent magnet/magnet reluctance hybrid rotor double stator synchronous motor(OW-PM/MRHRDSSM)based on SVPWM dual inverter control strategy,and analysis of open winding double inverter structure,and its voltage vector mathematical model,using the existing two-level inverter as a basis,the bilateral inverter separately discussed its role and control method,as well as the decomposition method of synthetic voltage vector and the inverter device in the small sector on-time,the end of this paper through simulation to compare the traditional close winding single inverter vector control system control PM/MRHRDSSM and the large torque OW-PM/MRHRDSSM based on SVPWM dual inverter control strategy to prove the effectiveness of the proposed method in reducing torque ripple,speed fluctuation and THD of current during motor operation.
基金National Natural Science Foundation of China (50646021)Chinese Specialized Research Fund for the Doctoral Pro-gram of Higher Education (20060213007)
文摘The outlet flow fields of a low-speed repeating-stage compressor with bowed stator stages are measured with five-hole probe under the near stall condition when the rotor/stator axial gap varies. The performances of the straight stator stages are investigated and compared to those of the bowed stator stages. The results show that using bowed stator stages could alleviate the flow separation at both upper and low corners of the suction surface and the endwalls, and decrease the losses along the flow passage as well as the outlet flow angle. As the rotor/stator axial gap decreases, although the diffusion capacity of the compressor increases obviously, the outlet flow field in the straight stator stages deteriorates quickly. By contrast, little changes occur in the bowed stator stages, indicating that as the rotor/stator axial gap decreases, improved performance is achieved in the bowed stator stages.
文摘The control platform of the induction motor （IM） with low costs is developed by using DSP MC56F8013 with a good performance/price rtaio. The control algorithm for the speed sensorless IM is studied based on the stator flux orientation （SFO）. The algorithm structure is simple to be implemented and cannot be influenced by motor parameters, The improved stator flux estimation is used to compensate errors caused by the low pass filter （LPF）. A new speed regulator is designed to ensure the system working with the maximal torque in the transient state. The system simulation and the prototype experiment are made. Results show that the con- trol system has good dynamic and static performance.
文摘A two-degree-of-freedom（2-DOF） linear ultrasonic motor （USM） consists of a cylinder-shaped stator and a slider. Two bending vibration modes with orthogonality and one longitudinal vibration mode are excited in the stator by three groups of piezoelectric ceramic elements. The combinations of any one bending mode and the longitudinal mode mentioned above push the slider to move linearly in direction x or y. Some key issues for improving the motor output properties and efficiency are given. They include selection of the vibration modes, consistency of the modal frequencies, placement of the piezoelectric ceramic elements and the supporting plane, setting of pre-pressure, and influence of interfering modes.
基金This work was supported in part by the National Natural Science Foundation of China(51707083)the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘This paper put forward a new fault-tolerant hybrid switched-flux PM(HSFPM)machine design employing the synergy of NdFeB and Ferrite Magnet.The key of the proposed HSFPM designed machine is the unique design E-core laminated stator with the hybrid magnet to ensure a drastic reduction of NdFeB magnet without compromising the output performances and efficiency in the conventional SFPM machine design to avert the huge demand of NdFeB and its associated volatile high price increase.Additionally,the fault-tolerant stator teeth designed principle implemented in the proposed HSFPM machine provides enhanced segregation among the various phases and ensures continuity of operation with acceptable operating performance under fault-condition.For fair evaluation and comparison,both the proposed HSFPM and the conventional SFPM(CSFPM)machine have the same slot-pole combination,winding arrangements,and stator/rotor dimensions except for the unique outer-stator of the proposed design.Meanwhile,compared to the CSFPM machine,the proposed HSFPM machine design makes use of only 60%of the PM(NdFeB)length.Finally,the evaluation of the no-load in conjunction with the load condition performances was carefully investigated by the Finite Element Method(FEM)of the ANSYS Maxwell software.The results depicted that the proposed HSFPM exhibits similar sinusoidal back electromotive force,comparable output torque,and slightly higher efficiency compared to that of the CSFPM machine.
基金National Natural Science Foundation of China(10577002)Innovation Foundation of BUAA for PhD Graduates
文摘This article proposes a tandem cascade constructed to tackle the thorny problem of designing the high-loaded stator with a supersonic inflow and a large turning angle. The front cascade adopts a supersonic profile to reduce the shock wave intensity turning the flow into subsonic,while the rear cascade adopts a subsonic profile with a large camber offering the flow a large turning angle. It is disclosed that the losses would be minimized if the leading edge of the rear cas- cade lies close to the pressure side of the front cascade at a distance of 20% pitch in pitch-wise direction without either axial spacing or overlapping in axial direction. The 2D numerical test results show that,with the inflow Mach number of 1.25 and the turning angle of 52° ,the total pressure loss coefficient of the tandem cascade reaches 0. 106 ,and the diffusion factor 0. 745. Finally,this article has designed and simulated a high-loaded fan stage with the proposed tandem stator,which has the pressure ratio of 3.15 and the efficiency of 86.32% at the rotor tip speed of 495.32 m/s.
基金Aeronautical Science Emphasis foundation of China( 98Z5 2 0 0 1) Delta Power Electronics Science &Education DevelopmentF und
文摘The direct torque control theory has achieved great success in the control ofinduction motors. However, in the DTC drive system of Permanent Magnet Synchronous Machine (PMSM)proposed a few years ago, there are many basic theoretical problems that must be clarified. Thispaper describes an investigation about the effect of the zero voltage space vectors in the DTCsystem of PMSM and points out that if using the zero voltage space vectors rationally, not only canthe DTC system be driven successfully but also the torque ripple is reduced and the performance ofthe system is improved. This paper also studies the sensorless technique in the DTC system of PMSMand configures the DTC system of PMSM with sensorless technique including zero voltage spacevectors. Numerical simulations and experimental tests have proved the theory correct. In thecondition of sensor-less, the DTC system of PMSM is wide-rangely speed adjusting, and the ratio ofspeed adjustment is 1: 100.
基金National Natural Science Foundation of China (50236020)
文摘This paper is focused on the experimental study of the effects of stator clocking on the performance of a low-speed repeating stage axial compressor with compound-lean stators as well as the one with conventional stators （the baseline） for comparison. The experimental results show that as the clocking positions vary, the upstream stator wake enters the following passage at different circumferential positions, and then mixes with the local fluid in the following passage. This is the main reason for the variation of the compressor performance resulted from the stator clocking effects. The variation of the compressor performance due to the clocking effect is less pronounced for the compressor with compound-lean stators than with the baseline. At a certain clocking position, the efficiency of the compressor with compound-lean stators is increased in comparison with that of the baseline, especially on small mass flow rate conditions, e.g., 0.7% at design condition and 3.5% at near-surge condition in this case. The maximum 1.22% and the minimum 0.07% increases in efficiency on design condition are obtained through the combined effects of the stator compound-lean and the stator clocking in this case.
文摘In this paper, the effect of different amount of protrusion on various parameters in rotor–stator system was experimentally studied by measuring CO_2 concentration and pressure, in order to obtain the optimal protrusion amount.The parameters of different dimensionless sealing flow were measured under the condition that the annulus Reynolds number was 4.39 × 10~5 and the rotating Reynolds number was 1.05 × 10~6.The results show that the change of the amount of protrusions has little effect on the static pressure in the cavity, and the static pressure change near the sealing ring is almost negligible.But the total pressure and sealing efficiency increase first and then decrease with the increase of the amount of protrusion.The variation of power consumption is the same.A complex vortex structure will appear at the high radius region when the protrusion is installed.On the other hand, the protrusion can effectively reduce the minimum sealing flow of the rotor–stator cavity.Furthermore, considering the sealing efficiency and power consumption,the best range of the protrusion amount is about 36.The ratio near this range can optimally balance the alleviation of the gas ingestion and the reduction of the power consumption.
基金the National Basic Research Program(973)of China(No.2009CB724300)
文摘A hydraulic experimental platform for the assembly of stator components was developed,and the simulation on this system was performed based on software AMEsim.Characteristics of the system,such as the pressure and the displacement,were analyzed.The results guide design of the hydraulic system of experiment platform for the assembly of the stator.
基金Supported by National Natural Science Foundation of China(50877063)
文摘This paper analyzes lightning surge on the stator windings of wind turbine generators.The path of lightning in the wind turbines was analyzed.An equivalent circuit model for megawatt direct-driven wind turbine system was developed,in which high-frequency distributed parameters of the blade conducts,tower,power cables and stator windings of generator were calculated based on finite element method,and the models of converter,grounding,loads, surge protection devices and power grid were established.The voltage distribution along stator windings,when struck by lightning with 10/350μs wave form and different amplitude current between 50 kA and 200 kA,was simulated using electro-magnetic transient analysis method.The simulated results show that the highest coil-to-core voltage peak appears on the last coil or near the neutral of stator windings,and the voltage distribution along the windings is nonuniform initially.The voltage drops of each coil fall from first to last coil,and the highest voltage drop appears on the first coil.The insulation damage may occur on the windings under lightning overvoltage.The surge arresters can restrain the lightning surge in effect and protect the insulation.The coil-to-core voltage in the end of windings is nearly 19.5 kV under the 200 kA lightning current without surge arresters on the terminal of generator,but is only 2.7 kV with arresters.
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.
