双联平动转子式压缩机的结构探讨

介绍一种新型压缩机的工作原理和结构特点,该压缩机具有一对双联转动的转子并用一个叶片将它们连接在一起,转子及叶片均采用平动转动的工作方式,其主要运动副如转子与气缸、转子与端盖、叶片与端盖的相对运动速度比较小,因此压缩机的摩擦和磨损亦较小。对压缩机的结构工艺要点及运动学特点进行了探讨,为该类装置的设计提供了良好的基础。

平动转子式压缩机的平动机构及其分析

介绍了一种新型旋转式压缩机的工作原理,该压缩机的转子采用平动转动的工作方式,因此它的主要运动副如转子与滑片、转子与气缸、转子与端盖之间的相对运动速度很小,故压缩机的摩擦和磨损亦小.论文对该类压缩机的平动机构进行了探讨,推导并分析了平动机构的运动学公式.

平动转子式压缩机的设计研究

针对传统滑片式压缩机存在较大摩擦损失的缺陷,设计了一种平动转子式压缩机,该压缩机的最大特点是转子采用平动转动的运转方式,与传统滑片式压缩机相比其主要运动副如转子与气缸、转子与端盖、滑片与缸孔之间的相对运动速度要小很多,因此它具有较少的摩擦和磨损。介绍了该类压缩机的工作原理和结构特点,推导并分析了滑片相对于缸孔的滑移速度,最后讨论了该类压缩机的结构设计要点。

Identification and Balancing of Flexible Rotors by Boundary Element Method

In this paper, an identification method to estimate the unbalances is introduced, which is based on the boundary element method (BEM). By using the vibration response measured at some points on the flexible rotor the unbalances can be identified conveniently. Therefore, the rotor can be balanced without test runs.

Simulation Study of Passive Rod Diffusion in Active Bath:Nonmonotonic Length Dependence and Abnormal Translation-Rotation Coupling

Diffusion of tracer particles in active bath has attracted extensive attention in recent years.So far,most studies have considered isotropic spherical tracer particles,while the diffusion of anisotropic particles has rarely been involved.Here we investigate the diffusion dynamics of a rigid rod tracer in a bath of active particles by using Langevin dynamics simulations in a two-dimensional space.Particular attention is paid to how the translation(rotation)diffusion coefficient D_(T)(D_(R))change with the length of rod L and active strength Fa.In all cases,we find that rod exhibits superdiffusion behavior in a short time scale and returns to normal diffusion in the long time limit.Both D_(T) and D_(R) increase with Fa,but interestingly,a nonmonotonic dependence of D_(T)(D_(R))on the rod length has been observed.We have also studied the translation-rotation coupling of rod,and interestingly,a negative translation-rotation coupling is observed,indicating that rod diffuses more slowly in the parallel direction compared to that in the perpendicular direction,a counterintuitive phenomenon that would not exist in an equilibrium counterpart system.Moreover,this anomalous(diffusion)behavior is reentrant with the increase of Fa,suggesting two competitive roles played by the active feature of bath particles.

Dynamic balancing of dual-rotor system with very little rotating speed difference

Unbalanced vibration in dual-rotor rotating machinery was studied with numerical simulations and experiments. A new method is proposed to separate vibration signals of inner and outer rotors for a system with very little difference in rotating speeds. Magnitudes and phase values of unbalance defects can be obtained directly by sampling the vibration signal synchronized with reference signal. The balancing process is completed by the reciprocity influence coefficients of inner and outer rotors method. Results showed the advantage of such method for a dual-rotor system as compared with conventional balancing.

Analysis of Heat Transfer of a Flat Plate Oscillating Heat Pipe, for Different Surfaces

Recent and constant demands for greater power densities and smaller sizes of electronic systems have stimulated the growth of new designs of different passive heat transfer methods such as heat pipes. Particularly, OHPs （Oscillating Heat Pipes） are relatively novel devices, capable of removing high heat rates over long and short distances with not much temperature drop. This study concentrates on the design, building and assembling a test rig in order to analyse the flow pattern ofdeionised water through a 5 turns flat plate oscillating heat pipe under different heat inputs, which was made in the school of engineering and materials science of the Queen Mary University of London by two energy M.Sc. students. The filling ratio of the water is 40%. Furthermore an experimental study on the OHP thermal performance is carried out in order to examine the effects of different surface wet conditions： super hydrophilic, hydrophilic and cleaned brass. It is demonstrated the formation of liquid slugs and vapour plugs of the water along the channels. The experimental results showed that the hydrophilic surface tends to be more energy efficient. The heat transfer performance of the super-hydrophilic and hydrophilic is higher than brass by 5-12% and 15-20% respectively.

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.

Acoustic Noise from Tandem Wind Rotors of Intelligent Wind Power Unit

The authors had invented the unique wind power unit composed of the large-sized front wind rotor,the small-sized rear wind rotor and the peculiar generator with the inner and the outer rotational armatures without the conventional stator.This unit is called "Intelligent Wind Power Unit" by the authors.The front and the rear wind rotors drive the inner and the outer armatures,respectively,while the rotational torque is counter-balanced between both armatures/wind rotors.This paper discusses experimentally the acoustic noise from the front and the rear wind rotors.The acoustic noise,in the counter-rotating operation,is induced mainly from the flow interaction between both rotors,and has the dominant power spectrum density at the frequency of the blade passing interaction.The noise is caused mainly from the turbulent fluctuation due to the flow separation on the blade,when the rear wind rotor stops or rotates in the same direction as the front wind rotor.

The Torsional Vibration of Turbo Axis Induced by Unsteady Aerodynamic Force on Rotor blade

An algorithm for computing the 3-D oscillating flow field of the blade passage under the torsional vibra-tion of the rotor is applied to analyze the stability in turbomachines. The induced fiow field responding to blade vibration is computed by Oscillating Fluid Mechanics Method and ParaInetric Polynomial Method. After getting the solution of the unsteady flow field, the work done by the unsteay aerody natnic force acting on the blade can be obtained. The negative or positive work is the criterion of the aeroelastic stability Numerical results indicate that there are instabilities of the torsional vibration in some boency bands.

Atomic scale electronic structure of the ferromagnetic semiconductor Cr2Ge2Te6

Cr_2Ge_2Te_6is an intrinsic ferromagnetic semiconductor with van der Waals type layered structure,thus represents a promising material for novel electronic and spintronic devices.Here we combine scanning tunneling microscopy and first-principles calculations to investigate the electronic structure of Cr_2Ge_2Te_6.Tunneling spectroscopy reveals a surprising large energy level shift and change of energy gap size across the ferromagnetic to paramagnetic phase transition,as well as a peculiar double-peak electronic state on the Cr-site defect.These features can be quantitatively explained by density functional theory calculations,which uncover a close relationship between the electronic structure and magnetic order.These findings shed important new lights on the microscopic electronic structure and origin of magnetic order in Cr_2Ge_2Te_6.