基于UG电机定子、转子冲片多工位级进模设计

利用UG软件的级进模向导(PDW)模块进行多工位级进模设计,可以极大地提高级进模设计效率.以电机定子、转子冲片为例,介绍模具设计过程.该设计方法简单、直观,结构合理、可靠,能保证制件质量,可为此类零件的级进模设计提供参考.

浅谈不同外径的电机定子在机壳中的替换

以某款电动扳手电机为例,介绍一种不同外径定子的替换方法。采用该方法,利用实物机壳,可尽早验证产品更换新电机的可行性,有利于缩短新品开发周期,降低快速成型中机壳的成本费用和避免可能发生的改模费用。

Y_2电动机轴向装配尺寸链的探讨

对Y2-315M-2电动机轴向装配尺寸链计算,发现设计的定、转子中心轴向距离偏差大。从定子铁心压入机座与转子铁心热套工艺入手,修改尺寸公差,将轴向距离偏差限制在较小范围内。

An Observing Method for Flux and Speed with Direct Torque Control

An observing method for stator flux and rotor flux is presented. Based on the proposed flux observing method, a novel speed estimator has been designed. At last, the speed estimator combined with the flux observing is applied in the direct torque control system without speed sensor. The simulation results show that these methods can improve the accuracy of speed observing and the low speed performance of direct torque control system, and strengthen the robustness of system.

电机能耗转差调速的研究

电能的生产、变换、传输、分配、使用和控制等都必须利用电机作为能量转换或信号变换的机电装置。电机是随着生产发展而产生和发展的,它的发展反过来又促进社会生产力的不断提高。随着生产的发展,对电动机的拖动系统也提出了更高的要求,如要求快速起动、制动及逆转,实现在很宽的范围内调速及整个生产过程自动化等。电机的调速方法有很多,本文就其中的能耗转差调速的方法进行相关研究讨论。能耗转差调速有转子电路串联电阻调速、改变定子电压调速、调压与变极相结合的调速、滑差电动机、串级调速及脉冲调速等。

Control of Doubly Fed Induction Generator under Unbalanced Voltages for Reduction of Torque Pulsation

The unbalanced voltages cause negative effects on the doubly fed induction generator （DFIG） sucn as torque pulsation,and increased stator current. Based on the symmetrical component theory, the torque pulsation is the consequence of the interaction of stator and rotor currents of different sequences. This paper presents a control technique to reduce the effect of unbalanced voltages on the DFIG in wind energy conversion systems. The negative sequence stator voltage is derived from the unbalanced three phase stator voltages. The compensated rotor voltage in terms of the derived negative sequence stator voltage and slip which minimizes the negative stator and rotor currents is proposed. The results from the simulation of control system with steady state model and dynamic model of the DFIG show that additional control loop with compensated voltage can significantly reduce torque and reactive power pulsations.

Continuous on-line adaptation of the rotor time constant in FOC induction machine system

Rotor time constant is an important parameter for the indirect lleld oraentateO control of mauc- tion motor. Incorrect rotor tittle constant value will cause the flux observer generating a wrong angu- lar orientation of the rotor field. A new approach serves for rotor time constant on-line adaptation by setting the stator current to be zero for a short period. A smooth eorrector is designed to prevent ab- normal detection result from making adaptation. Impact of zero current duration on detection error and rotor speed is analyzed by experiments.

The Slot Number and Air-Gap Effect on Performance of the High-Speed Brushless Permanent Magnet Motor

This paper describes the key issues of high-speed brushless permanent magnet motor design, such as rotor design, stator design, and determination of the main dimensions, and the overall design process was given. In this paper, a two-pole three-phase high-speed brushless PM （permanent magnet） motor with ratings air-gap length and stator slot number on the motor performance of 7.5 kW, 30,000 rpm is designed, and the effect of the different was analyzed. The results show that larger number of stator slot decreases the rotor loss and the rotor torque ripple. Larger air-gap length decreases the rotor loss.

Active Control of Fan Noise

In the wake-rotor interaction fan noise, a number of the interacting modes at the blade passing frequency （BPF） and its harmonics are generated which are prescribed by the number of stator and rotor blades etc. In the present study, the dominant mode is tried to be suppressed by the secondary sound from the loudspeaker actuators. One of the novel features of the present system is the adoption of the control board with the Field Programmable Gate Array （FP（3A） hardware and the LabVIEW software to synchronize the circumferentially installed loudspeaker actuators with the relative location of rotational blades under arbitrary fan rotational speeds. The experiments were conducted under the conditions of three rotational speeds of 2004, 3150, and 4002 [rpm]. The reduction in the sound pressure level （SPL） was observed for all three rotational speeds. The sound pressure level at the BPF was reduced approximately 13 [dB] for 2004 [rpm] case, but not so large reduction was attained for other cases probably due to the inefficiency of the loudspeaker actuators at high frequencies

Particle Image Velocimetry Experimental and Computational Investigation of a Blood Pump

Blood pumps have been adopted to treat heart failure over the past decades. A novel blood pump adopting the rotor with splitter blades and tandem cascade stator was developed recently. A particle image velocimetry （P1V） experiment was carried out to verify the design of the blood pump based on computational fluid dynamics （CFD） and further analyze the flow properties in the rotor and stator. The original sized pump model with an acrylic housing and an experiment loop were constructed to perform the optical measurement. The PIV testing was carried out at the rotational speed of 6952±50 r/rain with the flow rate of 3.1 l/rain and at 8186±50 r/min with 3.5 l/rain, respectively. The velocity and the Reynolds shear stress distributions were investigated by PIV and CFD, and the comparisons between them will be helpful for the future blood pump design.

Investigations of an enclosed annular rotor-stator system with LES method

In this study, the flows in an enclosed annular rotor-stator system with the Reynolds number ranging from 0.75×105 to 3.75×105 and an aspect ratio of 36.5 are investigated using the LES method. Few studies have explored such a rotor-stator system with this aspect ratio and the flow structure on the rotor side. The mean flow structure varies from a torsional Couette type to a Batchelor type as the Reynolds number increases. The onset of the instability in the B?dewadt layer adjacent to the stator is delayed,whereas it is promoted in the Ekman layer adjacent to the rotor. Both the layers demonstrate rich spiral structures. Turbulent spirals are observed to occur at the rotor disk side that also generates TS-wave-like(Tollmien-Schlichting) structures between adjacent spiral arms. Further, the turbulence at the stator is complex and interesting. Statistically, the turbulence is highly anisotropic near both the rotating and nonrotating disks, which is depicted by the Reynolds stresses.

Unsteady Rotor-Stator Interaction in High Speed Compressor and Turbine Stages

The blade row interaction can alter the time-mean flow and therefore be of interest for aerodynamic design analysis. Whereas results within low subsonic turbomachines are quite numerous in the literature, there have been far fewer works which give results of blade row interaction within high speed cases. Two cases are related in this paper. First, the effects of an incoming wake on the rotor flow field of a transonic compressor are analyzed. The blade row interaction proved to be positive regarding the total pressure ratio, but negative regarding the losses. The second case concerns a transonic turbine. Particular emphasis is placed on the assessment of the deterministic correlations included in the Averaged Passage Equation System.

Modal Decomposition for the Analysis of the Rotor-stator Interactions in Multi-stage Compressors

A modal analysis method of the rotor-stator interactions in multistage compressors has been developed by LMFA. This method, based on a double modal decomposition of the flow over space and time, has been applied to nu- merical and experimental results of the high-speed 3Y2-stage compressor CREATE based at LMFA, Lyon-France. It reveals the presence of a very strong rotor-stator interaction which completely drives the flow at casing behind all the rotors. This modal analysis method applied to an unsteady RANS simulation permits to calculate the en- ergy of the rotor-stator interactions and to plot energetic meridian maps to explain experimental results and to analyze the interaction in the whole machine.

An Extraction of the Dominant Rotor-Stator Interaction Modes by the Use of Proper Orthogonal Decomposition (POD)

The Proper Orthogonal Decomposition method is applied to the instantaneous velocity field within the rotor-stator inter-row region of a high-speed high-pressure centrifugal compressor. The processed data come from experiments and numerical simulations. In comparison with a Fourier transform, the POD gives the best modal approximation for both initial fields, in terms of the energy expressed on any given number of modes to be taken into account： to reach 98% of the total energy of the velocity field, the required number of POD modes is around nine times smaller than the number of Fourier harmonics. The individual POD modes are given and show that the unsteady rotor-stator interaction is already present in the very first modes.

Impeller-diffuser interaction:analysis of the unsteady flow structures based on their direction of propagation

The present study is focused on the analysis of the deterministic fluctuations arising from the rotor-stator interaction within a transonic centrifugal compressor stage. A spectral analysis applied to the unsteady flow field leads to the values of the rotation speed of most energetic modes. From these values, the various structures are classified according to their direction of propagation which leads to a comprehensive description of the underlying mechanisms involved in the interaction.

Three Dimensional Separation with Spiral-Focus in a Decelerating Duct Flow (Effect of Asymmetric Inlet Boundary Layer Thickness)

An experimental apparatus was developed to study the three dimensional separated flow with spiral-foci. The internal decelerating flow was generated by the air suction from a side wall to produce the separation on an opposite-side wall. The relation between the upstream boundary layer and the generation of spiral-foci in the separation region was observed by a tuft method. As a result, it was clarified that the spiral-focus type separation could be produced on the side wall and its behavior was closely related to the vortices supplied into the separation region from the boundary layer developing along top wall or bottom one.

Understanding human diseases with high-throughput quantitative measurement and analysis of molecular signatures

Microarray and deep sequencing technologies have provided unprecedented opportunities for mapping genome mutations,RNA transcripts,transcription factor binding,and histone modifications at high resolution at the genome-wide level.This has revolutionized the way in which transcriptomes,regulatory networks and epigenetic regulations have been studied and large amounts of heterogeneous data have been generated.Although efforts are being made to integrate these datasets unbiasedly and efficiently,how best to do this still remains a challenge.Here we review major impacts of high-throughput genome-wide data generation,their relevance to human diseases,and various bioinformatics approaches for data integration.Finally,we provide a case study on inflammatory diseases.

Investigation of the fluid flow in an isolated rotor-stator system with a peripheral opening

This paper deals with an experimental, theoretical and numerical study of a turbulent flow with separated boundary layers between a rotor and a stator. The system is not subjected to any superimposed radial flow. The periphery of the cavity is opened to the atmosphere so that the solid body rotation for infinite discs is not always observed. Emphasis was placed on develop- ment of an asymptotic approach and a step-by-step method to compute the radial distribution of the core swirl ratio and the static pressure on the stator side. The theory also includes the radial and axial velocities in the core region. The numerical simulation has been conducted with the commercial CFD code Fluent 6.1. The k- SST turbulence model is used, with the assumption of 2D-axisymmetric and steady flow. CFD validations have been performed by comparison of the numerical results with the corresponding theoretical results. Numerical and experimental results are in good agreement with analytical solutions.

Numerical Investigation of Influence of Rotor/Stator Interaction on Blade Boundary Layer Flow in a Low Speed Compressor

Numerical method was applied to the unsteady flow simulation at the mid span of a two-stage low speed compressor,and the blade boundary layer flow under rotor/stator interaction was investigated.By the model of wake/boundary layer interaction provided in this paper,the simulated blade frictional force and the boundary layer turbulent kinetic energy,the influence of wake/potential flow interaction on the blade boundary layer flow was analyzed in detail.The results show that under the condition of rotor/stator interaction,the wake is able to induce the stator laminar boundary layer flow to develop into turbulent flow within a certain range of wake interaction.In the stator suction boundary layer,an undisturbed region occurs behind the rotor wake,which extends the laminar flow range,and the wake with high turbulent intensity has the capability to control the boundary layer separation under adverse pressure gradient.

Effect of SGC on transient evolution of GWI in a Doppler broadened quasi Λ-type four-level system

In this paper,we study the effect of spontaneously generated coherence(SGC) on transient evolution of gain without inversion(GWI) in a Doppler broadened quasi Λ-type four-level atomic system.It is shown that transient evolution of GWI is very sensitive to the variation of SGC strength,and the transient maximum value and steady value of GWI both increase with SGC strength increasing.The transient and steady values of GWI with SGC are much larger than those without SGC.When Doppler broadening is present,the transient maximum value and steady value of GWI first increase and then decrease with Doppler broadening width(D) increasing,and the value of D which corresponds to the maximum transient GWI is different from that corresponding to the maximum steady GWI.The time needed for reaching the steady GWI increases with D increasing.The steady GWI,which is larger than that without Doppler broadening(D = 0),can be obtained by choosing appropriate D and SGC strength.