Analysis of the Temperature Characteristics of High-speed Train Bearings Based on a Dynamics Model and Thermal Network Method

High-speed trains often use temperature sensors to monitor the motion state of bearings.However,the temperature of bearings can be affected by factors such as weather and faults.Therefore,it is necessary to analyze in detail the relationship between the bearing temperature and influencing factors.In this study,a dynamics model of the axle box bearing of high-speed trains is established.The model can obtain the contact force between the rollers and raceway and its change law when the bearing contains outer-ring,inner-ring,and rolling-element faults.Based on the model,a thermal network method is introduced to study the temperature field distribution of the axle box bearings of high-speed trains.In this model,the heat generation,conduction,and dispersion of the isothermal nodes can be solved.The results show that the temperature of the contact point between the outer-ring raceway and rolling-elements is the highest.The relationships between the node temperature and the speed,fault type,and fault size are analyzed,finding that the higher the speed,the higher the node temperature.Under different fault types,the node temperature first increases and then decreases as the fault size increases.The effectiveness of the model is demonstrated using the actual temperature data of a high-speed train.This study proposes a thermal network model that can predict the temperature of each component of the bearings on a high-speed train under various speed and fault conditions.

Analysis of temperature field for a surface-mounted and interior permanent magnet synchronous motor adopting magnetic-thermal coupling method

Aiming at obtaining high power density of surface-mounted and interior permanent magnet synchronous motor(SIPMSM),it is important to accurately calculate the temperature field distribution of SIPMSM,and a magnetic-thermal coupling method is proposed.The magnetic-thermal coupling mechanism is analyzed.The thermal network model and finite element model are built by this method,respectively.The effects of power frequency on iron losses and temperature fields are analyzed by the magnetic-thermal coupling finite element model under the condition of rated load,and the relationship between the load and temperature field is researched under the condition of the synchronous speed.In addition,the equivalent thermal network model is used to verify the magnetic-thermal coupling method.Then the temperatures of various nodes are obtained.The results show that there are advantages in both computational efficiency and accuracy for the proposed coupling method,which can be applied to other permanent magnet motors with complex structures.

Characteristic analysis of mechanical thermal coupling model for bearing rotor system of high-speed train

Based on Newton’s second law and the thermal network method,a mechanical thermal coupling model of the bearing rotor system of high-speed trains is established to study the interaction between the bearing vibration and temperature.The influence of lubrication on the vibration and temperature characteristics of the system is considered in the model,and the real-time relationship between them is built up by using the transient temperature field model.After considering the lubrication,the bearing outer ring vibration acceleration and node temperature considering grease are lower,which shows the necessity of adding the lubrication model.The corresponding experiments for characteristics of vibration and temperature of the model are respectively conducted.In the envelope spectrum obtained from the simulation signal and the experimental signal,the frequency values corresponding to the peaks are close to the theoretical calculation results,and the error is very small.In the three stages of the temperature characteristic experiment,the node temperature change of the simulation model is consistent with the experiment.The good agreement between simulation and experiments proves the effectiveness of the model.By studying the influence of the bearing angular and fault size on the system node temperature,as well as the change law of bearing lubrication characteristics and temperature,it is found that the worse the working condition is,the higher the temperature is.When the ambient temperature is low,the viscosity of grease increases,and the oil film becomes thicker,which increases the sliding probability of the rolling element,thus affecting the normal operation of the bearing,which explains the phenomenon of frequent bearing faults of high-speed trains in the low-temperature area of Northeast China.Further analysis shows that faults often occur in the early stage of train operation in the low-temperature environment.

Numerical Investigation of Thermal Behavior of CNC Machine Tool and Its Effects on Dimensional Accuracy of Machined Parts

The dimensional accuracy of machined parts is strongly influenced by the thermal behavior of machine tools (MT). Minimizing this influence represents a key objective for any modern manufacturing industry. Thermally induced positioning error compensation remains the most effective and practical method in this context. However, the efficiency of the compensation process depends on the quality of the model used to predict the thermal errors. The model should consistently reflect the relationships between temperature distribution in the MT structure and thermally induced positioning errors. A judicious choice of the number and location of temperature sensitive points to represent heat distribution is a key factor for robust thermal error modeling. Therefore, in this paper, the temperature sensitive points are selected following a structured thermomechanical analysis carried out to evaluate the effects of various temperature gradients on MT structure deformation intensity. The MT thermal behavior is first modeled using finite element method and validated by various experimentally measured temperature fields using temperature sensors and thermal imaging. MT Thermal behavior validation shows a maximum error of less than 10% when comparing the numerical estimations with the experimental results even under changing operation conditions. The numerical model is used through several series of simulations carried out using varied working condition to explore possible relationships between temperature distribution and thermal deformation characteristics to select the most appropriate temperature sensitive points that will be considered for building an empirical prediction model for thermal errors as function of MT thermal state. Validation tests achieved using an artificial neural network based simplified model confirmed the efficiency of the proposed temperature sensitive points allowing the prediction of the thermally induced errors with an accuracy greater than 90%.

Establishment of the thermo-mechanical coupling model of axle box bearings with track irregularity excitation and analysis of its temperature characteristics

As an important component of the running gear of high-speed trains,axle box bearings can cause lubricating grease failure and damage to bearing components under continuous high-temperature operation,which will affect the normal operation of highspeed trains.Therefore,bearing temperature is one of the key parameters to be monitored in the online monitoring system for trains.Based on the thermal network method,this paper establishes a thermal network model for the axle box bearing,considering the radial thermal deformation of the double-row tapered roller bearing components caused by the oil film characteristics and the temperature variations of the lubricating grease.A thermo-mechanical coupling model for the grease-lubricated double-row tapered roller axle box bearing of high-speed trains with track irregularity excitation is established.The correctness of the model is verified using the test bench data,and the temperature of the bearing at different rotational speeds,loads,fault sizes,and ambient temperatures are investigated.

设施园艺电驱移动平台轮毂电机设计及其磁-热耦合性能

针对设施园艺作业场景下电驱移动平台的低速大扭矩牵引作业需求,该研究设计了一种减速内转子轴向磁通轮毂电机,建立电机的电磁有限元模型并分析其电磁和损耗特性。考虑到绕组电阻率受温度变化影响,构建基于热网络法的轮毂电机磁-热耦合改进模型。与台架试验结果相比,基于改进模型获得的转矩预测值较传统模型的精度提高了5.33%,验证了模型的正确性。利用改进模型分析了温度和相电流对电机转矩特性的影响,仿真结果表明,输出转矩随电机温度增加而降低;在0~20 A,电机平均输出转矩与相电流呈线性关系。试验结果表明,轮毂电机功率随转速增加而增大,峰值功率可达4.59 kW,而转矩基本保持恒定;在转速450~900 r/min、转矩300~600 N·m时,电机效率高达93.2%。研究结果可为轴向磁通电机初步设计与多场耦合影响下电机性能分析提供思路。

考虑圆度误差的角接触球轴承温升特性研究

以往有关于轴承温升特性的研究多注重轴承温升以及圆度误差对轴承振动的影响,其中圆度误差对轴承温升影响的文献较少,且研究对象多针对的是低速、轻载轴承的温升。为此,建立了考虑圆度误差、轴承预紧力、离心效应、热力耦合等影响的角接触球轴承热-力耦合模型,研究了轴承沟道圆度误差对轴承温升的影响规律。首先,以轴承拟动力学、弹流润滑理论、传热学理论和基尔霍夫能量守恒定律为基础,建立了考虑圆度误差、轴承预紧力、离心效应、热力耦合等影响的角接触球轴承热-力耦合模型;然后,利用模型分析了不同工况条件、圆度误差对轴承温升特性影响;最后,将模型计算结果与试验结果进行了比较,验证了角接触球轴承热-力耦合模型的合理性。研究结果表明:模型计算结果和实验结果相比,最大相对误差为5.37%;随着圆度误差阶次的增加,轴承温度呈现波动性变化,且随着转速的增加,波动趋势愈加显著;随着润滑油温度的升高,温度波动逐渐减小;当圆度误差的阶次等于球数n/2±2(n=1,2,3…)时,轴承外圈温度比不考虑圆度误差时要低,因此将圆度误差控制在特定阶次内能有效降低轴承温升,从而提高工作效率;轴承外圈温度的波动性与外圈圆度误差的幅值成正比,为轴承设计提供了重要参考;外圈温度与沟道圆度误差阶次之间呈周期性变化,并与钢球的个数形成映射关系,当圆度误差阶次等于球数的(2 n-1)/4倍(n=1,2,3…)时,轴承外圈温度达到最高;当圆度误差阶次等于球数的n/2倍(n=1,2,3…)时,轴承外圈温度最低,这一规律可为轴承的优化提供具体参考方向。

计及IGBT模块键合线与芯片焊料层老化的热网络法结温计算

文中提出一种计及IGBT模块键合线与芯片焊料层老化的热网络法结温计算,基于Simulink对短时间尺度下损耗与结温的相互依赖关系进行更新,并分别通过双脉冲测试及有限元仿真修正长时间尺度下键合线与芯片焊料层老化对IGBT结温计算的影响,在此基础上,根据芯片焊料层不同老化状态下键合线的应力特征,实现两种老化模式的相互关联,较为准确地计算IGBT结温。最终利用试验平台与传统结温计算方法进行对比验证了所提结温计算方法的准确性。该结温计算方法有助于在实际运行工况及IGBT模块老化状态下精确计算结温。

牵引用永磁同步电机温度场集总参数热网络法分析

永磁同步牵引电机具有效率高、体积小、功率密度高等优点,在城际铁路运输领域应用越来越多,具有广阔的发展前景。但随着永磁同步牵引电机的单机容量日益增大,其内部损耗也随之不断增加,损耗的增加使得电机的温升不断增加。在高温环境下,永磁体有可能产生退磁等一系列问题,影响牵引电机的稳定安全运行。本文以一台永磁同步牵引电机为例,对电机转子内置转子等较复杂部件进行合理等效,其次使用集总参数热网络法,建立能够反映电机整体热量传递的热网络结构,该结构可快速计算电机不同工况下的温度分布情况,对电机的热设计有一定的帮助。

高速电主轴轴承热分析与实验研究

根据高速电主轴角接触球轴承中滚动体的运动情况,分析其受力状态,并考虑轴承预加载荷对滚动体在高速旋转状态下陀螺力矩的平衡效果,应用Palmgren经验公式计算轴承整体的摩擦热,然后依据传热学理论建立轴承的温升热模型,并用热网络法建立其热阻抗网络图,最后用120MD60Y6油雾润滑型电主轴的轴承进行试验验证。结果表明,轴承温升主要受转速、润滑油量、供气压力及载荷的影响,在主轴启动的初始阶段温升变化最快,且润滑油量和供气压力对轴承温升有一个最佳的适用范围。

飞机整体瞬态热状况的数值仿真研究

在分析飞机内外热环境的耦合传热机制基础上,建立了描述飞机整体瞬态热状况的物理数学模型。引入壁面热流函数,将飞机蒙皮外的气动对流与辐射换热作用转化为舱内热分析的浮动热边界条件,实现了飞机内外耦合热作用的解耦计算,避免了难以实现的直接耦合求解。采用区域分解技术,将飞机整体分解为特性不同的多个求解区域。采用蒙特卡罗法求解舱内设备之间的辐射换热,采用热网络法求解设备内部及各设备之间的辐射-导热-对流耦合换热。利用该方法对某型飞机飞行过程中的瞬态热状况进行了数值模拟,获得了飞机舱内的瞬态温度场,分析了相关因素的影响,为飞机设计及相关研究提供了重要依据。

某直升机齿轮传动系统的稳态热分析

以某直升机齿轮传动系统为研究对象，用热网络法建立了该传动系统的热平衡方程组；建立了热阻、功率损失、对流换热的计算模型；用自行编制的热分析程序计算了给定工况下的功率损失、对流换热系数和稳态温度场，为该传动系统的瞬态热分析提供了初始条件。

减速器齿轮传动系统的稳态热分析及试验研究

以ZD－10减速器齿轮传动系统为研究对象，用热网络法建立了该传动系统的热平衡方程组，建立了热阻，功率损失，对流换热系数计算模型，计算了该传动系统在有润滑条件下的稳态温度场，并进行了相应的试验研究。这对于武装直升机传动系统生存能力的研究是十分有意义的。

不同冷却结构的微型电动车用感应电机三维稳态温度场分析

以实际样机为实例,建立了微型电动车用风冷和水冷感应电机稳态温度场的热网络模型及有限元模型。以此模型为基础,计算了风冷、水冷电机额定负载运行下的热网络节点温度及稳态三维温度场分布。比较了热网络法与有限元法的计算精度及优缺点;探讨了风冷、水冷周向螺旋槽及轴向直槽冷却结构对电机温升的影响;分析了流体介质、转子鼠笼材料及机壳材料等与电机温度分布的关系和规律。用相应样机进行实验研究,实验结果与计算结果吻合,验证了仿真分析的正确性。

笔记本电脑散热模组的实验与热计算

对一笔记本电脑中的散热模组进行了实验研究,在给定CPU及北桥发热功率条件下,测量了CPU及北桥、热管和散热器出口空气的温度.同时,采用节点网络法对该散热模组进行了热计算,其中CPU至热管、北桥至热管的热阻由热阻测试仪测量得到参考值.在计算过程中对一些参数进行适当调整后,计算结果与实测结果基本一致.

高速球轴承热稳定性研究

基于球轴承拟静力学模型,考虑润滑油流变特性、热源和结构尺寸随温度的时变特性。利用热网格法建立了高速球轴承瞬态热计算模型,通过求解热平衡方程得到轴承瞬态变化特性,研究了工况参数对轴承生热量、温度和热诱导载荷的影响规律,为高速球轴承润滑参数选取、结构优化、热失效机理和故障分析提供了理论依据。结果表明:内圈转速和轴向载荷的变化均对轴承的热平衡温度和热诱导载荷有显著影响;适当降低润滑油的黏度、增大空气的对流系数有利于减小轴承热诱导载荷;预测结果和文献测试结果吻合较好。

等效热网络法和有限元法在轮毂电机温度场计算中的应用

轮毂电机温度场的准确计算对于轮毂电机的安全运行和性能提升至关重要。根据一般电动汽车用轮毂电机样机的结构,建立了等效热网络温度场分析模型和3D有限元模型。基于等效热网络法,编写了轮毂电机温度场计算程序,计算了额定工况下的稳态节点温度。通过有限元法,计算了轮毂电机额定工况下的稳态温度场分布和瞬态温升曲线。根据轮毂电机的温升实验,对比分析了两种方法的计算结果,验证了等效热网络分析模型和3D有限元模型的有效性,说明了等效热网络法和有限元法对于轮毂电机温度场计算的适应性和兼容性。

基于等效热网络法的定频双转子永磁风力发电机的热分析

定频双转子永磁风力发电机是近年来提出的一种新型特种电机,具有低速直驱、功率密度高、变换器功率小等优点,具有较好的应用前景。定频双转子发电机在定子和内转子上都设置有绕组,且内转子散热条件较差,热分析成为电机设计的关键环节。为此,本文提出了基于等效热网络法的定频双转子发电机的热分析,首先介绍了传热的基本定律,然后建立定频双转子发电机的热网络模型,并对模型中各个热参数比如热阻、热源等,进行分析和计算,最后对热网络图中的各个节点建立热平衡方程,求解方程组,得出电机各部分的稳态温升并通过实验进行了实验验证。

土压平衡盾构机行星减速器热平衡分析

土压平衡盾构行星减速器热平衡分析对保证行星减速器的正常运行和盾构机的运行可靠性具有重要意义。忽略各构件内部温差对传热性能的影响,将传动系统各构件转换为节点,综合考虑各构件间的耦合关系,在对热传递过程中的热阻进行研究的基础上,基于热网格法建立行星传动系统的热平衡数学模型,并对土压平衡盾构机行星减速器的热平衡过程进行计算。结果表明,齿轮啮合次数对齿轮温升具有重要影响。将仿真结果与测试结果进行对比,结果验证了基于热网格法的行星减速器热平衡模型的正确性。