进气畸变对压气机稳定性的影响

在低速大尺寸单级压气机实验器上,实验研究了动态进气畸变对压气机稳定边界的影响。并采取在静子叶片表面埋入微型压力传感器的方法,分析了压气机流场的动态压力特性。实验结果表明,动态总压畸变的旋转频率和旋转方向对压气机稳定性有很大的影响,当畸变相对转速n在0~+0．5之间时,压气机失速推迟;分析动态压力的频谱特性后知道,在压气机失速前一般存在与失速相关的压力扰动,动态总压畸变影响这种压力扰动,从而影响压气机的不稳定流动状态。     

轴向间距对压气机失速特性的影响

采取在静子叶片表面埋入微型压力传感器的方法,对叶尖、叶中和叶根三个截面上的动态压力进行测量,实验研究了六个轴向间距下压气机的旋转失速特性。实验结果表明:轴向间距对压气机失速点的流量系数影响很大,转静子轴向间距减少,压气机失速推迟;压气机刚进入旋转失速的模态与轴向间距有关,轴向间距较大时,压气机首先进入多团全叶高旋转失速,当轴向间距为21％CR时,压气机直接进入单团全叶高旋转失速;轴向间距不同,近失速点的压力扰动也存在差别。     

基于电接触法的行波超声电机接触特性研究

电接触法是测试超声电机定转子接触状态的有效方法,但目前该方法主要用来研究电机堵转时的定转子接触状态,没有进行电机旋转时的接触状态的测试。针对该问题,对电接触法进行改进,使之可以测试电机旋转时的接触状态。基于改进后的电接触法分别对超声电机堵转和空载情况下定转子相对接触长度进行测试。结果表明,空载时定转子相对接触长度要小的多,与堵转时的最大差值约为36%。说明负载对超声电机接触状态有不可忽视的影响。最后,基于黏弹性接触模型对电机空载时定转子接触状态进行仿真计算,结果与实验值有很好的一致性,表明改进后的电接触法可有效的测试电机动态接触状态。      

Dynamic analysis of a BLDC motor with mechanical and electromagnetic interaction due to air gap variation

In this study, the dynamic behaviors of a BLDC motor are analyzed, when the motor undergoes mechanical and electromagnetic interaction due to an air gap variation between the stator and rotor. When considering the air gap variation caused by the translational motion of the rotor relative to the stator, the kinetic and potential energies, Rayleigh dissipation function, and the magnetic coenergy are expressed in terms of the rotor displacements and stator currents. With these energies and function, new equations of motion are derived using Lagrange’s equation. The equations for the proposed model are nonlinear equations in which the displacements and currents are coupled. The time responses for the displacements and currents are computed for the proposed and previous models. Furthermore, the effects of rotor eccentricity are also investigated. It is found that, when the air gap varies with time, the time responses for the proposed and previous models have small differences in the stator currents, electromagnetic torques, and rotating speeds. However, the time responses have large differences in the rotor displacements. Therefore, this paper claims that the proposed model describes the dynamic behaviors of the motor more accurately than the previous model. It is also shown that rotor eccentricity increases the stator current period and the electromagnetic torque, while it decreases the rotating speed of the rotor.     

Aspects of noise in rotary vacuum pumps

In this paper the authors describe a detailed spectral analysis of noise in a rotary vacuum pump. The noise sample studied could help to identify various noise sources in different frequency regions. The importance of correct balancing/machining of the rotor and the stator and the optimisation of the oil flow rate are also stressed. The quantitative data thus obtained are indicative of trends in the design of modern rotary vane vacuum pumps.     

A finite volume method and experimental study of a stator of a piezoelectric traveling wave rotary ultrasonic motor

Piezoelectric traveling wave rotary ultrasonic motors are motors that generate torque by using the friction force between a piezoelectric composite ring (or disk-shaped stator) and a metallic ring (or disk-shaped rotor) when a traveling wave is excited in the stator. The motor speed is proportional to the amplitude of the traveling wave and, in order to obtain large amplitudes, the stator is excited at frequencies close to its resonance frequency. This paper presents a non-empirical partial differential equations model for the stator, which is discretized using the finite volume method. The fundamental frequency of the discretized model is computed and compared to the experimentally-measured operating frequency of the stator of Shinsei USR60 piezoelectric motor.     

轴流压气机转子叶尖泄漏涡和尾迹在静子尖区的传播

用三维激光多普勒测速系统测量了轴流压气机设计状态转子叶尖泄漏涡和尾迹在静子尖区的传播过程。结果表明,转子叶尖泄漏涡和转子尾迹周期地扫过静子通道尖区,导致该区出现周期性的流动阻塞和脉动。转子尾迹在静子通道内追赶上从前一转子叶片通道内下来的叶尖泄漏涡,二者的相互作用和掺混导致静子尖区更为复杂的二次流动。同转子尾迹相比,转子叶尖泄漏涡对静子尖区的影响更为明显和深远。静叶尾部吸力面出现流动分离,分离流同低能物质之间发生相互作用和掺混。     

跨音速轴流压气机级三维粘性流场全工况数值模拟

采用一种快速求解三维粘性流场的计算方法求解跨音速轴流压气机级内部流场及全工况特性。该方法以LU-SGS-GE隐式格式和MUSCL TVD迎风格式为基础,结合壁面函数方法和简单的混合长度湍流模型,对三维可压缩雷诺平均Navie-Stokes方程进行求解。叶列间参数的传递采用混合平面方法并应用了微机网络并行计算技术。计算得到了NASA 37号低展弦比、跨音速轴流压气机级70％设计转速下的全工况性能曲线,并重点分析了其中一些典型工况下的内部流场。计算与实验结果的对比表明此方法能快速得到三维粘性流场的流动特性且计算精度较高,可用来模拟跨音速轴流压气机级内的全工况三维粘性流动。     

Development and study of novel non-contact ultrasonic motor based on principle of structural asymmetry

The article presents novel design of non-contact rotary ultrasonic motor consisting of ring-shaped stator vibrating in in-plane flexural mode and rotor provided with blades. In contrast to other motors with similar design proposed motor relies on the use of standing ultrasonic waves. This simplifies design and electronic control of motor and becomes possible due to introduction of artificial asymmetry, for example by tilting one or several blades of the rotor relative to the surface normal. Operating principle of the proposed motor is based on acoustic radiation torque exerted on rotor by ultrasonic waves propagating in air or fluid gap between rotor and stator. This torque is calculated using finite element method by means of COMSOL Multiphysics software. Dynamics of rotor is studied using MathCad software and general theory of nonlinear conservative oscillators. Role of asymmetry is explained on the basis of comparative analysis of potential functions and phase trajectories for symmetric and asymmetric cases. It is shown that direction of rotation is determined by structural parameters of motor, particularly tilting direction (clockwise or counter-clockwise) of the blades. Conceptual design of motor with bidirectional rotation is described. Direction and velocity of rotation in the proposed conceptual design can be potentially controlled by changing excitation frequency of stator.     

单级高负荷向心透平三维黏性非定常计算

对一台单级高负荷向心透平进行了三维黏性定常和非定常计算,计算得到的动叶出口以及下游的周向平均流场与文献提供的实验结果符合良好。在此基础上对流动的非定常特性进行了分析,发现由于动叶转速较高,且动叶下游不存在下一级静叶的干涉,流动的非定常效应主要体现在叶片排之间的区域以及动叶通道进口,动叶出口以及下游流动的非定常特性并不明显。非定常计算结果透平的级效率随时间的波动幅度达到了1.3%。     

Modal balancing of flexible rotors with bow and distributed unbalance

Unbalance and bow are found to be one of the most common causes of synchronous machinery vibrations in rotating systems. Concentrated lumped mass models are adopted in most of the finite element approach for modeling unbalances and subsequent balancing in rotating systems. But this assumption may not be appropriate for long slender rotors with unbalances distributed along the length of the rotor. A polynomial curve for eccentricity distribution with finite element modeling is used to identify the distributed unbalance. The unbalance eccentricity distributions are estimated using the measured vibration responses at a speed below the balancing speed. Modal correction mass required to balance a rotor at its first bending critical speed, having both distributed unbalance and bow is computed knowing the amplification factor at critical speed. The rotor is balanced at its first bending critical speed using modal balancing method in a single trial run and using a single balancing plane. The method thus avoids multiple trial runs required for modal balancing of flexible rotors. This method is verified on an experimental rotor having both bow and unbalance. The concept of quantifying the distributed unbalance using ‘Norm’ of eccentricity polynomial function is also introduced for the first time.     

单级跨声速压气机旋转失速模拟方法

为了研究多排跨声轴流压气机旋转失速先兆的表现形式与失速演化规律,基于自主研发的CFD软件AS-PAC,通过发展动态重叠网格技术,流量出口边界条件以及节流阀边界条件,对单级跨声速压气机NASA Stage 35由近失速状态到完全失速状态的过程进行了模拟.结果表明,发展的数值模拟方法能准确地模拟多排压气机的旋转失速发展过程...     

Unified modelling of passive homopolar and heteropolar electrodynamic bearings

A model of passive electrodynamic bearings based on the R–L dynamics of the eddy currents inside a conductor is presented. The model is derived from an analytical solution of the magnetic field in the air region surrounding the rotor for electrodynamic bearings having an even number of magnetic pole pairs. It allows homopolar and heteropolar electrodynamic bearings to be considered in a single unified way that accounts for the electromechanical interactions between the rotating conductor and the magnetic field of the stator. The model of the bearings is then coupled to a Jeffcott rotor model using complex coordinates in a state-space representation, allowing the dynamics of rotors supported by electrodynamic bearings to be studied. The number of magnetic pole pairs is found to influence rotordynamic stability, unbalance responses and frequency responses. The results demonstrate that homopolar electrodynamic bearings have a unique characteristic of passively filtering the transmission of forces due to residual unbalance of the rotor to the machine supports. The models are also used to perform a stability analysis of a case study presented in literature, and results from experimental observation are compared to those obtained analytically.     

Theoretical simulation of a rotary motor driven by surface acoustic waves

A simulation model for theoretically studying the operation behavior of a rotary motor driven by surface acoustic waves (SAWs) is proposed. According to the model, some simulation results are obtained as follows: (1) as the rotor is excited by the SAWs, the motor experiences two phases, i.e., the acceleration phase and the steady phase; (2) the normal vibration amplitude A of SAWs has a very weak effect on the acceleration in the first phase but an enhancing effect on the steady velocity of the rotary motor; (3) as the number of the contact points between the rotor and the stator increases, the motor rotates more steadily; (4) as the rotor radius becomes smaller, both the acceleration and the steady angular velocity become greater. These features are in agreement with the experimental results.     

压气机转子三维紊流流场

在低速大尺寸压气机试验台上，用单斜热丝、高频压力探针及由旋转四坐标全电动探针位移机构带动的五孔气动探针，测量了单级压气机转子出口和单转子压气机叶片通道尖区在不同流量状态下三维平均和亲流流场。设计状态，叶尖泄漏涡的发展及其与端壁附面层的交混决定了尖区的流动特性。小流量状态，叶片吸力面附面层增厚，近失速状态尖部吸力面附面层发生分离，吸力而附面层内径向潜移强烈，叶尖吸力面角区产生大范围强旋涡，角区部分低能流体移向叶尖通道中部，与端壁附面层、泄漏涡、刮削涡及主流发生交混．     

Performances estimation of a rotary traveling wave ultrasonic motor based on two-dimension analytical model

The understanding of ultrasonic motor performances as a function of input parameters, such as the voltage amplitude, driving frequency, the preload on the rotor, is a key to many applications and control of ultrasonic motor. This paper presents performances estimation of the piezoelectric rotary traveling wave ultrasonic motor as a function of input voltage amplitude and driving frequency and preload. The Love equation is used to derive the traveling wave amplitude on the stator surface. With the contact model of the distributed spring-rigid body between the stator and rotor, a two-dimension analytical model of the rotary traveling wave ultrasonic motor is constructed. Then the performances of stead rotation speed and stall torque are deduced. With MATLAB computational language and iteration algorithm, we estimate the performances of rotation speed and stall torque versus input parameters respectively. The same experiments are completed with the optoelectronic tachometer and stand weight. Both estimation and experiment results reveal the pattern of performance variation as a function of its input parameters.     

轴流压缩机转子叶栅内粒子沉积及对其性能影响的数值研究

计算了一轴流压缩机入口级的三维流场,在此基础上,通过UDF引入作用于旋转坐标系下固体粒子上的附加 力,计算了该入口级动叶内粒子的运动轨迹和叶面上粒子的沉积分布情况,并在此基础上模拟了由于粒子沉积所引起的压 缩机动叶叶栅的性能恶化,为发展气动防沉三维叶片的优化设计提供了研究基础。     

A matrix model of the axle vibration of a piezoelectric motor

In this work, a matrix model of the axle vibration of a piezoelectric motor is proposed. The stator of this motor is composed of a thin piezoelectric membrane and a steel axle fitted at the center of the membrane. The rotor consists of a cylinder-shaped permanent magnet, pressed in contact with the other end of the axle by means of the magnetic forces. A travelling wave is excited in the membrane by using four electrodes and four, properly delayed, driving signals. The rotating flexural displacement of the membrane produces a wide precessional motion of the axle. In this way, a continuous slipping takes place between the axle and the rotor, and therefore, a torque is transmitted to the rotor. In this paper, the precessional motion of the axle is modeled as the composition of two transverse vibrations belonging to two perpendicular planes passing through the axle. The axle, vibrating in its transverse mode, is modeled as a two-port system: the input is the bending moment supplied by the membrane, and the output is the transverse force at the terminal end of the axle. With this model, we have computed the trasmission transfer function as a function of frequency, and the transversal displacement along the axle at its resonance frequency. The computed results are in reasonable agreement with experimental interferometric measurements carried out on a prototype.     

叶顶间隙大小和壁面相对运动对低速轴流压气机孤立转子性能的影响

本文针对一低速轴流压气机孤立转子,利用数值方法分析了不同叶顶间隙大小、机匣和叶顶之间相对运动对其总体性能的影响。 结果表明存在着最佳顶部间隙,原因是顶部区域吸力面边界层引起的损失由于叶顶间隙流的作用而减少,虽然存在泄漏损失,但总损失却小于无顶部间隙时的损失。壁面相对静止和相对运动时的顶部区域二次流和损失分布有着明显的区别,因此某些没有考虑壁面相对运动的平面叶栅实验或计算结果在用于压气机转子设计时,需要经过一定的修正。     

A 3D finite element model for the vibration analysis of asymmetric rotating machines

This paper suggests a 3D finite element method based on the modal theory in order to analyse linear periodically time-varying systems. Presentation of the method is given through the particular case of asymmetric rotating machines. First, Hill governing equations of asymmetric rotating oscillators with two degrees of freedom are investigated. These differential equations with periodic coefficients are solved with classic Floquet theory leading to parametric quasimodes. These mathematical entities are found to have the same fundamental properties as classic eigenmodes, but contain several harmonics possibly responsible for parametric instabilities. Extension to the vibration analysis (stability, frequency spectrum) of asymmetric rotating machines with multiple degrees of freedom is achieved with a fully 3D finite element model including stator and rotor coupling. Due to Hill expansion, the usual degrees of freedom are duplicated and associated with the relevant harmonic of the Floquet solutions in the frequency domain. Parametric quasimodes as well as steady-state response of the whole system are ingeniously computed with a component-mode synthesis method. Finally, experimental investigations are performed on a test rig composed of an asymmetric rotor running on nonisotropic supports. Numerical and experimental results are compared to highlight the potential of the numerical method.