基于时变载荷的齿轮摩擦功率损失计算研究

应用齿轮啮合原理、齿轮接触分析和摩擦学理论,提出考虑齿轮瞬态啮合过程中传动效率随齿面接触载荷时变的齿轮摩擦功率损失计算方法;建立了啮合齿面间的相对运动速度、接触压力、滑动摩擦系数及摩擦功率损失的计算模型,并编制了计算程序;分析了齿轮几何参数、运行工况及润滑油温度等对齿轮摩擦功率损失的影响规律.研究结果为齿轮传动及其润滑系统的合理设计提供理论依据.     

渐开线直齿轮的啮合冲击研究

本文用解析的方法,研究了直齿轮振动中的一种重要激励项——啮合冲量,找出了齿轮的误差、变形以及齿面载荷与啮合冲击的时间、冲击力以及啮合冲量之间的定量关系。从而为进一步研究齿轮的啮合冲击振动创造了条件。通过分析不同精度齿轮的基节误差对啮合冲量的影响,说明了精度高的齿轮应采用齿廓修形的方法以减小传动中的啮合冲击。     

波动转矩下渐开线直齿轮传动齿廓修形研究

分析了齿轮转速波动和齿面、齿背啮合相位差对啮合点的影响,结合单、双齿啮合和修形边界条件并采用解析法计算啮合刚度,建立了与齿轮实际运动状态和啮合状态相关的非线性啮合刚度模型,该模型可与齿轮非线性动力学方程实时反馈,更加准确地描述齿轮传动过程中的啮合刚度。建立了考虑间隙、非线性啮合刚度的2自由度单级齿轮传动非线性动力学模型,在波动转矩的作用下,对比研究齿廓修形参数对齿轮动态特性的影响。研究结果表明:修形量对齿轮动态特性影响显著,存在最优修形量使动载系数达到最小;当修形量超过某临界值齿轮产生单边或双边冲击现象,齿轮动载荷明显增加;外载荷一定,增加修形长度可降低动载系数最小值;波动转矩作用下,齿轮的最大修形量为最小转矩作用下单齿啮合最高点的变形量。     

齿轮传动啮合接触冲击解析

齿轮传动在工业生产中广泛的应用,关于齿轮啮合的动态特性研究,受到了各界的广泛关注。对于齿轮传动而言,为了能够进一步的提高性能,必须在传统系统的振动、噪声两个方面进行努力。啮合接触的冲击,是这两个方面的重要体现。相对而言,齿轮传动过程中,啮合冲击是不可避免的,关键在于如何将啮合冲击降到最低。今后,需针对齿轮传动本身开展深入的研究,并针对啮合冲击进行全面的讨论,寻找多元化的方法,将啮合冲击进一步降低,提高齿轮传动的效果,减少损伤,提高工作效率。     

在高压工况下通过应用齿轮传动压缩机节省功率和成本

ＧＨＨ ＢＯＲＳＩＧ透平机械公司建造了世界上首台１０级齿轮传动压缩机，并且成功地进行了试验。该机器在一个箩斯的 纱合成中用于压缩二氧化碳至２００ｂａｒ。与在这种情况下通常使用的多室式单轴压缩机相比，新的解法明显地降低了成本和功率，本文介绍了新式压缩机的特点，特别着重于齿轮传导 控制方面，此外还叙述了压缩机各级的热动力设计特色。     

硬齿面渐开线齿轮强度的优化设计

本文对目前日益广泛应用的硬齿面齿的弯曲强度与接触强度进行了分析，提出了加权因子的方法来统一齿轮的弯曲强度与接触强度，使之符合等强度设计原则，进而构造优化设计的目标函数，进行硬齿面齿轮的参数设计，对硬齿面齿轮的强度设计具有一定的实际意义。     

渐开线圆柱直齿轮传动的重合度计算

本文阐述了渐开线圆柱直齿轮传动的重合度的概念及具体计算方法，重合度受那些因素的影响。     

偏心渐开线齿轮在高速包装机上的应用

采用偏心渐开线齿轮传动作为高速包装机横封机构，与其它变速传动机构相比，这种机构不仅结构简单，拆装方便；而且速度变化范围较大，传动较平稳，容易进行动平衡，从而能较好地改善封头和切刀的寿命，它最诱人的优点是容易制成可调变速范围的结构，以便适应不同的物料和包装材料，并且它的制作成本非常低，与普通齿轮传动的制造成本几乎相同。     

偏心渐开线齿轮在高速包装机上的应用

采用偏心渐开线齿轮传动作为高速包装机横封机构，与其它变速传动机构相比，这种机构不仅结构简单，拆装方便，而且速度变化范围较大，传动较平稳，容易进行动平衡。从而能较好地改善封头和切刀的寿命。它最诱人的优点是容易制成可调变速范围的结构，以慢适应不同的物料和包装材料，并且它的制造成本非常低，与普通齿轮传动的制造成本几乎相同。     

Time-varying mesh stiffness calculation of cracked spur gears

Considering the misalignment of gear root circle and base circle and accurate transition curve, an improved mesh stiffness model for a healthy gear pair is proposed and validated by the finite element method (FEM). Based on the improved method, three mesh stiffness calculation methods (method 1: straight lines for crack path and limiting line; method 2: straight line for crack path and parabolic curve for limiting line proposed in Ref. [1]; method 3: parabolic curves for crack path and limiting line) for cracked gear pair are presented and compared with FEM. The results show that there is a significant difference between method 1 and FEM under large crack condition and the results of methods 2 and 3 are quite close to FEM result, which also shows that the parabolic curve as a limiting line is appropriate. Mesh stiffness of method 2 is very close to that of method 3, which also shows that it is acceptable to assume the crack path to be a straight line.     

基于有限元分析的直齿轮搅油损失计算及实验验证

搅油损失的影响因素包括润滑油的运动粘度、工作温度,齿轮的模数、齿数、齿宽,旋转速度、齿轮的浸油深度,当地重力数值等,多种因素并存且形成了复杂的函数关系,难以直接用理论确定解析解。在对上述各种影响进行分析的基础上使用流体力学中边界层理论对齿轮搅油功率损失进行了理论分析,使用FLUENT软件中的多相流VOF模型、涡流K_ε模型对建立的搅油流动偏微分方程进行数值仿真计算分析,最后通过齿轮搅油功率损失实验对仿真结果进行了验证。分析结果表明,在低转速条件下使用仿真计算的方法可以有效地预测搅油功率损失数值。     

考虑动载荷和表面粗糙度的渐开线齿轮摩擦因数的研究

 进行齿面摩擦因数的研究,对于减少摩擦损失、改善系统传动性能等具有重要的意义．建立渐开线圆柱齿轮的非线性时变单自由度动力学模型,求解得到动态啮合力和单对轮齿的受力．结合载荷分担概念和弹流润滑理论,得到考虑表面粗糙度和动态载荷的不同啮合位置处的齿面摩擦因数,并与静态载荷条件的结果进行对比．同时分析转速、表面粗糙度和润滑剂黏度等工作条件对摩擦因数的影响．研究结果表明：动态载荷对油膜厚度、油膜承载比例和摩擦因数均有一定程度的影响．进入啮合段,油膜较薄,油膜承载比例较低.退出啮合段,油膜增厚,油膜承载比例增高.转速对摩擦因数的影响并非单调的,摩擦因数先是随着转速的增大显著减小,而后随着转速的增大而增大．随着表面粗糙度的增大,摩擦因数随之明显增大．在一定的黏度范围内,随着润滑剂黏度的增大,摩擦因数随之明显减小．     

Effect of the load location along the involute curve of spur gears on the applied stress at the fillet radius

In this study, attempts are carried out to determine the amount of stress at the fillet radius region of spur gears when the applied load location changes, along the involute curve, from the top surface to the bottom. For this purpose the photoelastic method and numerical MSC/NASTRAN software are used. The gears with pressure angle (ϕ) 20^o, and 25^o were prepared from photoelastic material type PLM‐4B in this study. Practical calibration is used to determine the fringe order value of this material. Four different modules (m); 6, 10, 14, and 20 mm were prepared for two different numbers of teeth (N); 18 and 26, with different face widths (B₁, B₂, B₃); 10, 17, 25.4 mm respectively. Four load values were applied on each tooth at five to six different load locations along the involutes curve profile. In order to accomplish the comparison between the results for different methods, the same sample dimensions and parameters were prepared again for the MSC/NASTRAN software. The results showed that the maximum applied stress at the fillet radius occur when the applied load location is on the top land of a tooth, and then that amount is decreased when the applied load positions change toward the bottom land. The results of the NASTRAN method showed that the applied stress at the fillet radius would be minimum when the loading point locates between the pitch circle and dedendum circle, in particular around 1.5 times module (1.5 m) of the total tooth height which equals 2.25 module, and then the applied stresses are increased again. However, in the photoelastic method the applied stresses were decreased continuously to the bottom land. The reasons behind such results can be attributed to the type of failure theories that can be used in NASTRAN software for characterization the applied stresses, i.e. considering types of applied stresses into account, such as bending, direct compressive, and shear stresses. Moreover, in order to compare the applied stress values at fillet regions, obtained by theoretical and practical approaches, four different standard mathematical equations are used for stress calculation at fillet radius of spur gears to show the difference of the parameters and variables that can affect the applied stress results.     

同功重比修形斜齿和直齿面齿轮性能对比研究

为深入了解同功重比修形斜齿与直齿面齿轮的性能差异,选择更适合于高速重载工况下的面齿轮传动.基于啮合原理推导了修形斜齿与直齿面齿轮齿面方程,基于CATIA建立了修形斜齿与直齿面齿轮三维模型,采用有限元接触分析方法,以接触应力、弯曲应力和重合度为面齿轮传动性能指标展开研究.研究结果表明:修形斜齿面齿轮相比修形直齿面齿轮接触应力大幅降低,算例最大接触应力降低16.3%;修形斜齿面齿轮相比修形直齿面齿轮弯曲应力大幅降低,算例最大弯曲应力降低32.4%;修形斜齿面齿轮相比修形直齿面齿轮重合度大幅提高,算例重合度提高10.3%.所以同功重比情况下,修形斜齿面齿轮传动性能优于修形直齿面齿轮,前者更适合于高速重载工况下的轻量化设计.     

Effect of shaft misalignment and friction force on time varying mesh stiffness of spur gear pair

Shaft misalignment and sliding friction between meshing teeth are considered as primary excitation to generate vibrations and extra dynamic loads on transmitting gear teeth. Time varying mesh stiffness (TVMS) is an important parameter to understand the dynamics of meshing gear pair. Potential energy method is one of the most acceptable methods to calculate TVMS. This paper proposes a computer simulation based approach to study the effect of shaft misalignment and friction on total effective mesh stiffness for spur gear pair. The results showed clearly that misalignment and friction affect TVMS of gear pair. The effect of misalignment and friction has also been studied for cracked gear pair and results are discussed.     

Numerical analysis of the AC losses of 500-m HTS power cable in Super-ACE project

The alternating current (AC) losses of 500-m high-T_C superconducting (HTS) power cable in Super-ACE project are calculated by using an electric-circuit model. The cable core is consisted of a former (copper-stranded wire conductor), HTS conductor (Ag/Bi-2223 tapes, 1 layer), electrical insulation (LN₂-impregnated laminated paper), HTS shield (Ag/Bi-2223 tapes, 1 layer) and protection (copper-braided wire). Numerically calculated AC loss (the total loss) is obtained by a sum of the self-field loss and external-field loss (hysteresis losses) consumed at the HTS conductor and HTS shield, the ohmic loss caused by a resistance of copper of the former and protection, and the eddy-current loss caused by an axial field at the former. The calculations are compared with experimental results measured by a calorimetric method. The calculations are almost equal to the measurements at wide transport-current range. At transporting 1 kA_rms to the cable, the calculation indicates that the total loss of 1.29 W m⁻¹ (the measurement is 1.3 W m⁻¹) is obtained by a sum of 0.89 W m⁻¹ as the self-field loss, 0.32 W m⁻¹ as the external-field loss, 0.06 W m⁻¹ as the ohmic loss and 0.02 W m⁻¹ as the eddy-current loss. On the other hand, Central Research Institute of Electric Power Industry (CRIEPI) has estimated that the AC loss is obtained by a sum of 0.5 W m⁻¹ consumed at the HTS conductor and HTS shield as the hysteresis loss, and 0.8 W m⁻¹ consumed at the former as the eddy-current loss. The author’s result contradicts CRIEPI’s estimation. It is considered that the difference is caused by an overestimation of the axial field at the former in CRIEPI’s loss calculation.     

Parallel power paths and compactness of gear transmissions

Developments in mechanical power transmission have hinged around better materials and processes, new design ideas and effective new application of enduring scientific design principles and ideas. The current presentation aims at showing how deliberate measures to optimize load distribution have increased the compactness and capabilities of present day gear transmissions. Exploitation of parallel power paths, packing of gears in annular spaces and the effective use of epicyclic action by reducing the number of gear meshes and substituting rolling friction are explained. Deceased     

Evaluation of coolant power losses in a thermal plasma arc reactor

Coolant power losses, associated with the operation of a research prototype plasma arc reactor, have been studied experimentally and are described herein. These power losses were measured in four separate fluid-cooled plasma arc reactor zones while plasma power input levels were increased from 4.8 to 13.7 k W. During this increase, all other controllable variables, such as plasma gas flow rate and coolant fluid flow rate were held constant. As operating power levels were increased, the coolant power losses in all four fluid-cooled zones of the plasma arc reactor also increased. However, the relative distribution of power losses changed significantly as the plasma power input levels were increased.