评价半流体润滑剂性能的齿轮台架

作者对全尺寸功率流封闭式齿轮试验台架成功地进行了改进和完善,发展了一种测试方法齐全、测量精度高的齿轮试验台架与测试系统,并以其进行了00~#半流体润滑脂、50~#机械油等润滑时啮合齿面间的油膜电压、齿轮传动效率、减速器的振动和噪声、润滑剂的温升和抗磨性能等多方面的对比分析和评价。结果表明,这种全尺寸齿轮试验台架与测试系统对半流体润滑剂性能的评价分析是可靠的,适合作为各种半流体润滑剂性能的全尺寸试验台架推广应用。     

Nomographs for synthesis of epicyclic-type automatic transmissions

This paper presents a MATLAB optimization technique for the determination of the gear ratios of epicyclic-type transmission mechanisms for a given set of velocity ratios. First, all of the feasible clutching sequences are enumerated directly without using complicated techniques. Then, for the transmission mechanism with the associated clutching sequence graph, the overall velocity ratios are derived and expressed in terms of the gear ratios of all the mating gears. Next, following the general trend of increased shift stages and a wider range of velocity ratios, the numbers of teeth of all gears are estimated by MATLAB optimization technique in a single run. Ravigneaux gear mechanisms are used as design examples. The methodology can be applied to any transmission mechanism depending on its kinematic and geometric constraints. New five- and six-velocity automatic transmissions are enumerated from the Ravigneaux gear mechanism. It is a major breakthrough to design a completely satisfactory six-speed automatic transmission from the Ravigneaux gear mechanism since it has only eight links. The new design makes use of the benefits of the Ravigneaux gear train and overcomes the previous art difficulties. This structural design has realized a six-speed automatic transmission, while having minimal number of clutches, and brakes. It is also low cost due to adoption of the conventional available Ravigneaux gear train.     

Selecting gas dynamics channel parameters for electrical discharge fast flowrate lasers

Using lasers with powers over l kW has become common in industry. Compactness and high efficiency are important requirements to take into account when designing lasers. Fast flowrate CO₂ lasers with independent discharges have wide application in industry, whose radiators are quite large because of the low density of the working gas. When considering the compactness and efficiency of these lasers, one must not ignore questions concerning the optimal correspondence of the characteristics for the pumping device (PD) of the gas and for the closed gas dynamics channel (CGDC) of the laser radiator. The PD must ensure circulation of the gas at a rate determined by the assigned power of the laser for the smallest size of the radiator and for small noise and vibration levels. The configuration and dimensions of the CGDC, the means of arranging its elements, the characteristics of the gas flow in the pumping zone, and the power of the active medium all determine the gas resistance of the closed channel and the loss of power at pump, which is 5 to 25% of the total power required in lasers with powers up to 10 kW [1, 2]. One may find information on the application of various PD in fast flowrate lasers [3–9], but there is no data on the characteristics of closed CGDC, which are determined by the PD parameters. There is currently an absence of literature dealing with the selection of optimal parameters for the electrical discharge, the gas flow, and the configuration of the flow section of the CGDC. We will take a comprehensive approach to determine the parameters for the gas flow in the pumping zone and the gas characteristics for the contour elements and the pumping device.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 6, pp. 3–8, November–December, 1986.     

Analysis of shifting performance of power shuttle transmission

This study was conducted to investigate the effects on the shifting performance of the design parameters of a power shuttle tractor using a computer simulation technique. The EASY 5 models of the hydraulic control system and power shuttle transmission were developed, and combined with a tractor model to complete a simulation model for a power shuttle tractor. The models for the hydraulic control system and power shuttle transmission were verified using an experimental power train constructed for the validation purpose.The design parameters included the terminal pressure and time for the modulation of the hydraulic control system, and forward speed, weight, shuttle gear ratio and torsional damping of the tractor. The shift performance was evaluated in term of the peak torques of the input shaft of the transmission and tractor axles, and power transmitted per unit area of the clutch and the time required for the power transmission.     

The response of a layered half-space to traffic loads moving along its surface

Summary The dynamic behaviour of a railway system is influenced by the interaction of its three subsystems: the vehicles, the rail construction itself and the subsoil. In this paper, the subsoil is considered as a linear-elastic layered half-space. Integral transformations are used for the analysis of this system: Fourier transformation for the time/frequency domain and for the space/wavenumber domains with respect to the horizontal coordinates. One arrives at an ordinary differential equation for the vertical direction, by which different layers or continuously changing elastic properties can be taken into account in an efficient manner. The efficiency of the transformation technique depends substantially on the effort necessary for the inverse transformation. A substantial reduction of data can be achieved in an error-controlled procedure if a wavelet transformation is applied as an additional transformation. The calculations are illustrated by solutions of several examples of moving time-dependent loads, particularly of a train model with four vehicles idealized by moving forces, time depending as if they were passing a rigid surface with a given roughness. Received 23 December 1997; accepted for publication 22 July 1998     

Flow and coupled heat transfer in the cavity between the rotor and stator

The turbulent flow and coupled heat transfer in the cavity between the rotor and stator is numerically simulated. Reynolds-averaged Navier-Stokes equations closed with equations of the k-ɛ turbulence model are used to calculate the viscous compressible gas flow characteristics and heat transfer; the unsteady heat conduction equation is used to calculate the temperature field in the metal. The influence of the mass flow rate of the coolant on the flow structure and efficiency of cooling of the rotor and stator walls is studied. The calculated results are compared with experimental data.     

复杂激励下平置板式浮筏功率流传递特性研究

针对隔振理论研究领域中舰船的振动和噪声控制问题，建立六维^[1、2]平置板式弹性浮筏的多机组隔振理论分析计算模型，导出了弹性浮筏传递功率流的表达式，从振动能量传输的角度来评价浮筏系统隔振效果，绘制了功率谱曲线，揭示机组的布置，筏架刚度等结构参数对功率流传递的影响，给出了浮筏设计中结构参数选择的一般准则。     

Global bifurcation and chaos analysis in nonlinear vibration of spur gear systems

The global homoclinic bifurcation and transition to chaotic behavior of a nonlinear gear system are studied by means of Melnikov analytical analysis. It is also an effective approach to analyze homoclinic bifurcation and detect chaotic behavior. A generalized nonlinear time varying (NLTV) dynamic model of a spur gear pair is formulated, where the backlash, time varying stiffness, external excitation, and static transmission error are included. From Melnikov method, the threshold values of the control parameter for the occurrence of homoclinic bifurcation and onset of chaos are predicted. Additionally, the numerical bifurcation analysis and numerical simulation of the system including bifurcation diagrams, phase plane portraits, time histories, power spectras, and Poincare sections are used to confirm the analytical predictions and show the transition to chaos.     

Non-Newtonian mixed elastohydrodynamics of differential hypoid gears at high loads

Prediction of friction and transmission efficiency are design objectives in transmission engineering. Unlike spur and helical involute gears, there is a dearth of numerical analysis in the case of hypoid gear pairs. In particular, it is important to take into account the side leakage of the lubricant from the contact as the result of the lubricant entrainment at an angle to the elliptical contact footprint. In the automobile differential hypoid gears, high loads result in non-Newtonian behaviour of the lubricant, which may exceed its limiting shear stress, a fact which has not been taken into account in the open literature. This results in conditions which deviate from observed experimental tractive behaviour. The paper takes into account these salient practical features of hypoid gear pair analysis under high load. It highlights a non-Newtonian shear model, which limits the lubricant shear behaviour. Prediction of friction and transmission efficiency is in line with those reported in the literature.     

Dynamics analysis of the Minuteman cover drive

Recursive matrix relations in kinematics and dynamics analysis of a 1-DOF compound planetary gear train are established in the paper. The mechanism of the Minuteman cover drive is a system with four moving links and three gear pairs controlled by one electric motor. Knowing the rotation motion of the output link, the inverse dynamic problem is solved using an approach based on the principle of virtual work, but it has been verified the results in the framework of the Lagrange equations. Finally, some simulation graphs for the input and output angles of rotation, the torque and the power of the actuator are obtained.     

Nonlinear vibration of the spiral bevel gear with a novel tooth surface modification method

Meccanica - The issue of gear noise is fairly common in power transmission systems. This noise largely stems from the gear pairs vibration triggered by transmission error excitation. This is mainly...     

Analysis of flow instabilities at the natural circulation loop DANTON with regard to non-linear effects

The natural circulation loop DANTON at the Dresden University of Technology was designed to investigate the thermohydraulic properties of integrated reactor concepts with a natural circulation driven primary loop. It is not possible to reach a stable two-phase flow in the loop without passing flow instabilities. At an equilibrium of heating and cooling power the flow oscillations can exist at nearly constant frequencies and amplitudes. The oscillating mass flow signal had been investigated by various methods: (a) autocorrelation function, (b) Fast Fourier transformation, (c) estimation of a temporal Liapunov-exponent and (d) reconstruction of the system attractor in a three-dimensional phase space. The selected time-series express a non-linear behaviour, however, they are not chaotic. In comparison to the usual methods the applied analysing methods yield additional information about system frequencies, sensitiveness to disturbances and properties due to non-linear and chaotic behaviour in a natural circulation loop. Received on 17 January 2000     

Bifurcation and chaos analysis of multistage planetary gear train

A nonlinear time-varying dynamic model for a multistage planetary gear train, considering time-varying meshing stiffness, nonlinear error excitation, and piece-wise backlash nonlinearities, is formulated. Varying dynamic motions are obtained by solving the dimensionless equations of motion in general coordinates by using the varying-step Gill numerical integration method. The influences of damping coefficient, excitation frequency, and backlash on bifurcation and chaos properties of the system are analyzed through dynamic bifurcation diagram, time history, phase trajectory, Poincaré map, and power spectrum. It shows that the multi-stage planetary gear train system has various inner nonlinear dynamic behaviors because of the coupling of gear backlash and time-varying meshing stiffness. As the damping coefficient increases, the dynamic behavior of the system transits to an increasingly stable periodic motion, which demonstrates that a higher damping coefficient can suppress a nonperiodic motion and thereby improve its dynamic response. The motion state of the system changes into chaos in different ways of period doubling bifurcation, and Hopf bifurcation.     

Comparison of spur,helical and curvilinear gear drives by means of stress and tooth contact analyses

Involute tooth surfaces are a successful technical solution for both spur and helical gear drives since they provide linear contact and a low-level function of transmission errors under good conditions of meshing. Tip relief is usually required to improve contact conditions during the transfer of meshing between adjacent pairs of teeth. Yet, unfavorable conditions of contact appear when shaft deflections and misalignments are present. Localization of contact through lead crowning is a solution that increases the cost of machining in both spur and helical gear drives. In this sense, the generation process of curvilinear gear drives provides localization of contact with no additional cost. Comparison of stresses and transmission error functions in spur, helical and curvilinear gear drives is investigated to show if the application of curvilinear gear drives yields some advantages respect to spur and helical gear drives. The three mentioned types of cylindrical parallel-axis gear drives are provided, firstly, with linear contact, and, secondly, with localized contact, for the purpose of comparison. Different misalignments conditions are taken into account by means of several numerical examples.     

On aerodynamic noises radiated by the pantograph system of high-speed trains

Pantograph system of high-speed trains become significant source of aerodynamic noise when travelling speed exceeds 300 km/h. In this paper, a hybrid method of non-linear acoustic solver （NLAS） and Ffowcs Williams-Hawkings （FW-H） acoustic analogy is used to predict the aerodynamic noise of pantograph system in this speed range. When the simulation method is validated by a benchmark problem of flows around a cylinder of finite span, we calculate the near flow field and far acoustic field surrounding the pantograph system. And then, the frequency spectra and acoustic attenuation with distance are analyzed, showing that the pantograph system noise is a typical broadband one with most acoustic power restricted in the medium-high frequency range from 200 Hz to 5 kHz. The aerodynamic noise of pantograph systems radiates outwards in the form of spherical waves in the far field. Analysis of the overall sound pressure level （OASPL） at different speeds exhibits that the acoustic power grows approximately as the 4th power of train speed. The comparison of noise reduction effects for four types of pantograph covers demonstrates that only case 1 can lessen the total noise by about 3 dB as baffles on both sides can shield sound wave in the spanwise direction. The covers produce additional aerodynamic noise themselves in the other three cases and lead to the rise of OASPLs.     

Self-sustaining thermoconvective flows in the absence of external force fields

It is shown, analytically and numerically, that if there are no external force fields and the hydraulic resistance is low, sustained thermoconvective subsonic flows may exist in a closed channel of variable cross section, in the wider part of which the medium is heated while in the narrower part it is cooled. The flow parameters depend on the equation of state of the medium, the channel geometry and the amount of heat transferred by the flow from the heated to the cooled part. Steady thermoconvective flows exist up to a certain critical value of the thermal power transported by the flow. The relation between the results obtained and the mechanism by which the motion of the medium is sustained in natural convection is discussed. Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No.2, pp. 11–17, March–April, 1994.     

Dynamic behavior of an agricultural power take-off driveline for rattle noise reduction: Part 1. Effect of spline tolerance on the power take-off rattle noise

An agricultural tractor has a power take-off (PTO) driveline that is directly connected to the engine to improve its power transmission efficiency. The PTO driveline comprises various mechanical components coupled by a spline joint. The spline coupling tolerance causes collisions between various mechanical parts of the PTO driveline and affects gear collision, thereby causing rattle noise. Therefore, the aim of this study is to conduct a dynamic behavior analysis to predict the gear rattle noise level of a PTO driveline. The dynamic behavior of the PTO driveline was analyzed through 1D simulations, and the results confirmed that the dynamic behavior changes according to rotation speed. Experimental verification of the dynamic behavior analysis results confirmed that the dynamic behavior changes as the main engine excitation-component amplification changes and then decreases at a relatively high rotation speed. Additionally, the dynamic behavior changes of the PTO driveline resulted in a jumping phenomenon that occurs rapidly at a specific rotation speed. The amplification of the engine’s main components was reduced from 3 to 4 times to 1.2 times owing to the jumping phenomenon; the noise level of the gear rattle was also reduced by approximately 10.9 dB(A).     

双圆柱斜置排列时下游圆柱压力分布和振荡频率的实验研究

当两个圆柱斜置排列并靠得较近时,绕流下游圆柱的流动明显地不同于单一圆柱.本文研究了下游圆柱压力分布受到的影响,并着重于用FFT来分析圆柱表面某些特征点上的压力频谱,研究频谱与圆柱之间的相对距离和位置的关系.当圆柱间距较远时,压力振荡的频率与单圆柱卡门涡节的频率相接近,随着横向间距的接近,频率逐渐降低,然而当两圆柱十分接近时,外侧压力振荡的频率继续降低,但圆柱内侧压力振荡的频率却突然提高,出现了一个圆柱体两侧作用有不同频率压力的情况.     

EXPERIMENTAL INVESTIGATION ON LIFT INCREMENT OF A PLASMA CIRCULATION CONTROL AIRFOIL

利用等离子体激励器发展了新型的环量增升技术,并对二维NACA0012翼型绕流实施控制。由于NACA0012翼型为尖后缘构型,环量增升装置由2个非对称型介质阻挡放电等离子体激励器构成。一个等离子体激励器贴附于翼型吸力面靠近后缘处,其诱导的壁面射流沿来流方向指向下游;另一个等离子体激励器贴附于翼型压力面靠近后缘处,其诱导的壁面射流与来流方向相反指向上游。在风洞中通过时间解析二维PIV系统对翼型绕流流场进行了测量,基于翼型弦长的雷诺数Re=20 000。结果表明在等离子体激励器的控制下,翼型压力面靠近后缘处可以形成一个定常回流区,从而起到虚拟气动外形的作用,因此翼型吸力面的流场得到加速,压力面的流场得到减速,使得翼型压力面的吸力以及压力面的压力都得到增加,进而增加了翼型的环量。风洞天平测力实验进一步验证了该环量增升技术的有效性。在整个攻角范围内,施加控制的翼型的升力系数相比没有控制的工况有明显的提高。     

基于斐波那契数积分计算非等径颗粒视角系数

热辐射是颗粒间热量传递的基本方式之一,视角系数计算的效率和精度是颗粒热辐射数值模拟中的主要难点。本文采用斐波那契数列对非等径颗粒表面进行离散,在此基础上计算视角系数,并且对z方向的积分使用非均匀变换以提高计算精度。结果表明,在具有不同球体数的粉末床中,用该方法计算的视角系数的相对误差为5%,与传统的蒙特卡洛方法相比,计算效率提升约30%。