迷宫气封三维非定常流场及转子动特性数值仿真

通过计算流体力学方法,采用近似的解析变换网格,以及混合有限分析格式,对迷宫气封流场进行三维非定常数值求解,进而求得密封气流对转子的气流激振力,获得转子的动特性系数。将计算结果与试验结果以及双控制体计算结果相比较,结果令人满意,说明了该计算程序是正确可靠的。该方法精度较高,适用范围广,可以应用于各种复杂的涡动情况及各种齿型,对气封转子的深入研究有重要意义。计算结果还显示了主刚度、主阻尼对气流进口周向速度不敏感,而交叉刚度对气流进口周向速度非常敏感。由于交叉刚度对转子的稳定性影响相当大,这一点是值得注意和利用的。

粗糙度对大间隙环流偏心转子动特性系数的影响

基于作者建立的大间隙环流中转子运动的理论模型 ,用摄动法推导了大间隙环流流场非线性控制方程的一阶摄动方程 ,采用数值方法研究了静子和转子壁面粗糙度对大间隙环流中偏心转子动特性系数的影响 .研究结果表明 :静子和转子壁面粗糙度对大间隙环流中偏心转子动特性系数有较大影响 .所得到的数值结果与已有的解析解和实验结果具有较好的一致性 .

迷宫轴封气流周向剪切力对转子动态特性系数的影响

采用扰动法计算分析了透平机械直齿型轴封中非定常高压气流流动对涡动转子的气流激振问题,针对进口速度、进口压力、转子转速、涡动频率以及间隙大小对转子动特性系数的影响进行了详尽计算。结果表明,表面周向剪切力对转子动特性系数的影响不可忽略。

液体火箭发动机氢涡轮泵转子动力学特性研究

以运行在二阶临界转速以上的某低温氢涡轮泵柔性转子为研究对象,基于有限元法,通过建立的转子系统的动力学模型,对结构过盈配合与压紧力矩两个因素对轴系刚度的影响进行仿真研究,给出轴系弹性模量的等效方法,计算出转子系统临界转速,最终通过试验验证了该方法的有效性及实用性,所研究内容为涡轮泵转子系统的动力学特性研究及结构优化设计提供依据。

高低式迷宫密封转子动特性的数值模拟及优化

本文建立涡动转子-迷宫密封三维CFD模型,计算高低式迷宫密封流场及流体激振力,并计算密封转子动特性,计算结果经Pugachev试验数据验证可靠。分析不同结构的高低式迷宫密封转子动力学特征,尤其是广泛应用于汽轮机高压级围带密封的前后凸台高低式迷宫密封结构。结果显示,在高低式迷宫密封中,凸台位置越靠后,主阻尼系数越小;对于前后凸台的高低式迷宫密封结构,去掉后凸台能提高转子稳定性。

VIBRATION CHARACTERISTIC INVESTIGATION OF COUNTER-ROTATING DUAL-ROTOR IN AERO-ENGINE

Two methods for vibration characteristic investigation of the counter-rotating dual-rotors in an aero-en- gine are put forward. The two methods use DAMP tool on the MSC. NASTRAN platform and develope the re- solving sequence. Vibration characteristics of a turbofan engine are analyzed by using the two methods. Com- pared with results calculated using transfer matrix method and test results, the two methods are valuable and have great potential in practical applications for vibration characteristic investigation of aero-engines with high thrust-weight ratio.

COUPLED DYNAMIC CHARACTERISTICS AND CONTROL OF ROTOR-CONICAL MAGNETIC BEARING SYSTEM

The coupled dynamic characteristics of the conical electromagnetic bearing are presented and their definitions are given. On the basis of the analyses of the characteristics, the dynamic model of five degrees of freedom (five-DOF) rotor-conical electromagnetic bearing system is made, and the influence of the coupled characteristics on the system optimal controller is analyzed.

Isolation of a Genomic DNA for Gastrodia Antifungal Protein and Analyses of Its Promoter in Transgenic Tobacco

A genomic DNA containing 5'-upstream region and complete open reading frame of a Gastrodia antifungal protein was isolated by screening of a genomic library from Gastrodia elata B1. To investigate the promoter activity, the 5'-flanking region - 1 157 lip upstream from the putative transcription start site was fused to the coding sequence of beta-glucuronidase (GUS) gene and transformed into Nicotiana tabacum. The strongest GUS activity was detected in the roots of transgenic tobacco, followed by stems. The leaves only showed a low GUS activity. Furthermore, the promoter established inducible expression pattern in transgenic tobacco upon fungus Trichoderma viride inoculation and jasmonic acid and salicylic acid treatments.

Mammalian Models Based on RCAS-TVA Technique

The retroviral vector （RCAS） has been widely used in avian system to study development and diseases, but is not suitable for mammals which do not produce the retrovirus receptor TVA. In this review, we trace the current uses of RCAS-TVA approach in mammalian system with improved strategies, including generation of tv-a transgenic mice, use of soluble TVA receptor and retroviral receptor-ligand fusion proteins, improvement of RCAS vectors, and compare a series of mammalian models in variant studies of gene function, development, oncogenesis and gene therapy. All those studies demonstrate that the RCAS-TVA based mammalian models are powerful tools for understanding the mechanisms and target treating of human diseases.

A comprehensive comparative investigation of frictional force models for dynamics of rotor−bearing systems

Vibrations of a rotor-bearing system(RBS)can be affected by the frictional forces between the components of the inherent bearings.Thus,an in-depth investigation of the influences of the frictional moments of the bearings on the vibrations of the RBS can be helpful for understanding the vibration mechanisms in the rotating machinery.In this study,an improved dynamic model of a RBS considering different frictional force models is presented.A comparative investigation on the influences of the empirical and analytical frictional force models on the vibration characteristics of the RBS is proposed.The empirical frictional force models include Palmgren’s and SKF’s models.The analytical frictional force model considers the rolling friction caused by the radial elastic material hysteresis,slipping friction between the ball and races,viscosity friction caused by the lubricating oil,and contact friction between the ball and cage.The influences of the external load and rotational speed on the vibrations of the RBS are analyzed.The comparative results show that the analytical frictional force model can give a more reasonable method for formulating the effects of the friction forces in the bearings on the vibrations of the RBS.The results also demonstrate that the friction forces in the bearings can significantly affect the vibrations of the RBSs.

Numerical simulation on rotordynamic characteristics of annular seal under uniform and non-uniform flows

Currently, the flow field of annular seals disturbed by the circular whirl motion of rotors is usually solved using computational fluid dynamics(CFD) to evaluate the five rotordynamic coefficients. The simulations are based on the traditional quasi-steady method. In this work, an improved quasi-steady method along with the transient method was presented to compute the rotordynamic coefficients of a long seal. By comparisons with experimental data, the shortcomings of quasi-steady methods have been identified. Then, the effects of non-uniform incoming flow on seal dynamic coefficients were studied by transient simulations. Results indicate that the long seal has large cross stiffness k and direct mass M which are not good for rotor stability, while the transient method is more suitable for the long seal for its excellent performance in predicting M. When the incoming flow is non-uniform, the stiffness coefficients vary with the eccentric directions. Based on the rotordynamic coefficients under uniform incoming flow, the linearized fluid force formulas, which can consider the effects of non-uniform incoming flow, have been presented and can well explain the varying-stiffness phenomenon.

Vibration characteristics of rotor system with tilting-pad journal bearing of elastic and damped pivots

In view of an entire dynamic model of tilting-pad journal bearing(TPJB) in which the pads swing and vibrate along geometric direction of preload, a TPJB of elastic and damped pivots was designed and manufactured. Vibration experiments were carried out under the conditions of different rotor bending stiffness and oil supply pressure to find out the relationship between the new bearing's vibration depression effect and other dynamic parameters of the rotor. The result shows that critical amplitudes can be efficaciously reduced while system's stability can be remarkably improved by this bearing. Besides, the bearing's effect of vibration depression weakens as the rotor bending stiffness increases, but heightens it as the oil supply pressure increases.

Nonlinear dynamic behaviors of ball bearing rotor system

Nonlinear forces and moments caused by ball bearing were calculated based on relationship of displacement and deflection and quasi-dynamic model of bearing.Five-DOF dynamic equations of rotor supported by ball bearings were estimated.The Newmark-β method and Newton-Laphson method were used to solve the equations.The dynamic characteristics of rotor system were studied through the time response,the phase portrait,the Poincar?maps and the bifurcation diagrams.The results show that the system goes through the quasi-periodic bifurcation route to chaos as rotate speed increases and there are several quasi-periodic regions and chaos regions.The amplitude decreases and the dynamic behaviors change as the axial load of ball bearing increases;the initial contact angle of ball bearing affects dynamic behaviors of the system obviously.The system can avoid non-periodic vibration by choosing structural parameters and operating parameters reasonably.

Study of nonlinear dynamic characteristics of rotor-bearing systems

Based on the short-bearing model, the stability of a rigid Jeffcott rotor system is studied in a relatively wide parameter range by using Poincaré maps and the numerical integration method. The results of the calculation show that the period doubling bifurcation, quasi-periodic and chaotic motions may occur. In some typical parameter regions, the bifurcation diagrams, phase portrait, Poincaré maps and the frequency spectrums of the system are acquired with the numerical integration method. They demonstrate some motion state of the system. The fractal dimension concept is used to determine whether the system is in a state of chaotic motion. The analysis result of this paper provides the theoretical basis for qualitatively controlling the stable operating states of the rotors.

Influence of Rotor Structure and Number of Phases on Torque and Flux Weakening Characteristics of V-Shape Interior PM Electrical Machine

This paper investigates the influence of the rotor structure on torque and flux weakening region of V-shape IPM （interior permanent magnet） machine from TOYOTA PRIUS type. More specifically, always keeping the same magnet volume, the effect of the open angle between the two magnet segments of each V-shape pole on the machine performance is studied. Moreover, in order to examine the impact of phase number on the machine characteristics, PRIUS structure is transformed into 5-phase machine of the same type and dimensions. As well, an optimization procedure is carried out to determine the optimal open angle according to main characteristics. The previous investigation is done by using a free FEM （finite elements methods） program coupled with another optimization program. Using this obtained methodology, the study analyzes for 3-phase and 5-phase machine the average and pulsation of torque, cogging torque, phase EMF （electro-motive force）, constant power operating capability.

The dispersion characteristics of the waves propagating in a spinning single-walled carbon nanotube

As the nano-motor becomes a mechanical reality, its prototype can be envisaged as nano-sized rotating machinery at a situation,albeit for different purposes, like that in the first half of the 20th century during which rotor dynamics has contributed toboosting machine power capacity. Accordingly, we take the benefit of hindsight to develop a classical framework of vibrationanalysis. Essentially, the equations of motion are formulated to cope with both the special carbon-nanotube properties and thefirst author’s previously developed spinning beam formalism, establishing a model satisfactorily verified by some availablemolecular dynamics (MD) data and classical spinning beam results extracted from the literature. The model is inexpensivebased on continuum mechanics as an alternative to the less-flexible MD method for simulating wave motion of the spinningsingle-walled carbon nanotube, yielding several interesting phenomena, including the fall-off and splitting of the wave charac-teristic curves and the unexpected gyroscopic phase property. Potential applications are proposed.

The dynamical contact order:Protein folding rate parameters based on quantum conformational transitions

Protein folding is regarded as a quantum transition between the torsion states of a polypeptide chain.According to the quantum theory of conformational dynamics,we propose the dynamical contact order(DCO) defined as a characteristic of the contact described by the moment of inertia and the torsion potential energy of the polypeptide chain between contact residues.Conse-quently,the protein folding rate can be quantitatively studied from the point of view of dynamics.By comparing theoretical calculations and experimental data on the folding rate of 80 proteins,we successfully validate the view that protein folding is a quantum conformational transition.We conclude that(i) a correlation between the protein folding rate and the contact inertial moment exists;(ii) multi-state protein folding can be regarded as a quantum conformational transition similar to that of two-state proteins but with an intermediate delay.We have estimated the order of magnitude of the time delay;(iii) folding can be classified into two types,exergonic and endergonic.Most of the two-state proteins with higher folding rate are exergonic and most of the multi-state proteins with low folding rate are endergonic.The folding speed limit is determined by exergonic folding.

A system of matrix equations and its applications

We derive the solvability conditions and an expression of the general solution to the system of matrix equations A 1X=C1 , A2Y=C2 , YB2=D2 , Y=Y*, A3Z=C3 , ZB3=D3 , Z=Z*, B4X+(B4X)+C4YC4*+D4ZD4*=A4 . Moreover, we investigate the maximal and minimal ranks and inertias of Y and Z in the above system of matrix equations. As a special case of the results, we solve the problem proposed in Farid, Moslehian, Wang and Wu's recent paper (Farid F O, Moslehian M S, Wang Q W, et al. On the Hermitian solutions to a system of adjointable operator equations. Linear Algebra Appl, 2012, 437: 1854-1891).