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.

Oil oxidation in the whole temperature regions during oil reservoir air injection and development methods

The oil oxidation characteristics of the whole temperature regions from 30 ℃ to 600 ℃ during oil reservoir air injection were revealed by experiments. The whole oil oxidation temperature regions were divided into four different parts: dissolving and inflation region, low temperature oxidation region, medium temperature oxidation region and high temperature oxidation region. The reaction mechanisms of different regions were explained. Based on the oil oxidation characteristics and filed tests results, light oil reservoirs air injection development methods were divided into two types: oxygen-reducing air flooding and air flooding;heavy oil reservoirs air injection in-situ combustion development methods were divided into two types: medium temperature in-situ combustion and high temperature in-situ combustion. When the reservoir temperature is lower than 120 ℃, oxygen-reducing air flooding should be used for light oil reservoir development. When the reservoir temperature is higher than 120 ℃, air flooding method should be used for light oil reservoir development. For a normal heavy oil reservoir, when the combustion front temperature is lower than 400 ℃, the development method is medium temperature in-situ combustion. For a heavy oil reservoir with high oil resin and asphalting contents, when the combustion front temperature is higher than 450 ℃, the development method at this condition is high temperature in-situ combustion. Ten years field tests of air injection carried out by PetroChina proved that air has advantages in technical, economical and gas source aspects compared with other gas agents for oilfield gas injection development. Air injection development can be used in low/super-low permeability light oil reservoirs, medium and high permeability light oil reservoirs and heavy oil reservoirs. Air is a very promising gas flooding agent.

Analysis and Forecasting Model of Durative Hightemperature in Late Spring and Early Summer in 2009

This paper analyzed characteristics of Pingliang City's continuous hot weather from late spring to early summer in 2009.The result showed that,when the daily maximum temperature in some parts of cities had run up to 32℃ or above,the number of days reached the top in recent 40 years.The average temperature,average maximum temperature,surface maximum temperature and surface average temperature in most parts of the city broke history record.Based on the analysis of characteristics of the 500 hPa circulation,which resulted in durative high temperature weather,3 kinds of the high temperature circulation patterns were summarized.It was the continental warm high pressure that resulted in the durative high temperature weather in June,2009.Meanwhile,by using European numerical forecast product and MOS,the forecasting method of high temperature,from June to August,was set up.The method had been used in June,and its high-temperature forecasting accuracy in 24,48,72,96,120 hours had respectively amounted to 76.6%,69.5%,61.4%,58.1% and 51.9%.

Thermal stress and fracture temperature prediction for flexible pavement

Analytical solutions of thermal stresses in multilayered elastic system whose materials characteristics are dependent on temperature are derived by a transfer matrix and integral transformation method.The resulting formulation is used to calculate thermal stresses in the low temperature cracking problem of asphalt pavement.Numerical simulations and analyses are performed using different structural combinations and material characteristics of base course.And fracture temperatures are predicted for a given flexible pavement constructed with three types of asphalt mixtures based on the calculated results and experimental data.This approach serves as a better model for real pavement structure as it takes into account the relationships between the material characteristics and temperature in the pavement system.

复合助剂对低温喷雾干燥蓝靛果粉理化性质的影响

为保证低温喷雾干燥后蓝靛果粉品质,采用黄金分割法研究复合助剂(麦芽糊精、β-环糊精和乳清蛋白)对喷雾干燥蓝靛果粉理化性质的影响,分析低温进风温度(50~90℃)对蓝靛果粉花青素保留率、集粉率和含水率的影响规律。结果表明,在麦芽糊精、β-环糊精的质量比例为85.4%、14.6%时,集粉率高达37.96%;随进料溶液中麦芽糊精质量比例增加,蓝靛果粉玻璃化转变温度、水溶性指数、堆积密度、亮度L^(*)值、红度a^(*)值和色差值ΔE呈增加趋势,含水率、花青素含量和黄度b^(*)值呈下降趋势;在麦芽糊精、β-环糊精和乳清蛋白质量比例为72.9%、12.5%、14.6%时,集粉率达到最高(40.11%);随料液中乳清蛋白质量比例增加,蓝靛果粉含水率、花青素含量呈上升趋势,其玻璃化转变温度、水溶性指数、亮度L^(*)值、红度a^(*)值、黄度b^(*)值和色差值ΔE等指标呈下降趋势;复合助剂显著提高蓝靛果粉集粉率(P<0.05),对其中的花青素起到较强保护作用,其含水率、水溶性指数、堆积密度等理化指标均接近于最优水平。低温喷雾干燥研究发现,随进风温度上升,集粉率和含水率呈负相关,在进风温度90℃时,集粉率最高的配方中可实现较高花青素保留率(89.94%)。低频核磁共振波谱以及质子密度图像信息分析表明,加入的助剂与蓝靛果果汁中水分通过氢键、静电结合力和疏水作用等分子间作用力,形成稳定性高水合物、增强液滴聚结抵抗力,提高料液玻璃态转换温度,从而实现高集粉率和高花青素保留率的蓝靛果果粉低温喷雾干燥;红外光谱分析表明,复合助剂可在蓝靛果果粉中形成分子间氢键,并对花青素等活性物质进行固定包埋保护。研究结果可为蓝靛果粉喷雾干燥加工生产提供理论支撑和参考依据。

干湿循环与加载先后顺序对砂泥岩混合料压缩特性的影响

为研究干湿循环与加载先后顺序对砂泥岩混合料压缩特性的影响,针对不同干湿循环次数、浸水时间和水温处置下的砂泥岩混合料,开展先干湿循环后加载、先加载后干湿循环的单向压缩试验。结果表明,两种试验方法所得砂泥岩混合料压缩量均随干湿循环次数增加、浸水时间增长、水温增高而增大;压缩量与干湿循环次数呈对数关系、与浸水时间呈幂函数关系、与水温呈线性关系,并推导出相应的压缩量计算公式;试验结果及理论分析均得出先干湿循环后加载的压缩量大于先加载后干湿循环的压缩量。

基于标准火灾曲线和热释放率的衬砌温度分布数值计算研究

为探明火灾下衬砌温度的分布特性,基于隧道火灾-衬砌辐射对流传热数学模型建立了衬砌温度数值计算方法,并对HC标准火灾曲线和30 MW火灾热释放率火灾工况进行计算分析。结果表明,标准火灾曲线最高温度普遍大于目前我国规范的要求。采用火灾温度作为衬砌壁面边界条件将显著增大衬砌温度荷载,2小时HC火灾曲线和30 MW火灾工况衬砌最高温度分别为778℃和351℃。标准火灾曲线工况衬砌内部的高温影响范围和高温值均显著大于30 MW火灾工况。

Micro-macro evolution of mechanical behaviors of thermally damaged rock:A state-of-the-art review

The influence of thermal damage on macroscopic and microscopic characteristics of different rocks has received much attention in the field of rock engineering.When the rocks are subjected to thermal treatment,the change of macroscopic characteristics and evolution of micro-structure would be induced,ultimately resulting in different degrees of thermal damage in rocks.To better understand the thermal damage mechanism of different rocks and its effect on the rock performance,this study reviews a large number of test results of rock specimens experiencing heating and cooling treatment in the laboratory.Firstly,the variations of macroscopic behaviors,including physical parameters,mechanical parameters,thermal conductivity and permeability,are examined.The variations of mechanical parameters with thermal treatment variables(i.e.temperature or the number of thermal cycles)are divided into four types.Secondly,several measuring methods for microstructure,such as polarizing microscopy,fluorescent method,scanning electron microscopy(SEM),X-ray computerized tomography(CT),acoustic emission(AE)and ultrasonic technique,are introduced.Furthermore,the effect of thermal damage on the mechanical parameters of rocks in response to different thermal treatments,involving temperature magnitude,cooling method and thermal cycle,are discussed.Finally,the limitations and prospects for the research of rock thermal damage are proposed.

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。

原位式准静态压电材料温度特性测试系统研发

压电材料的压电-温度特性会直接影响到压电器件的工作稳定性,是压电器件研发的重要依据。文中基于准静态测量方法研制上、下位机系统,实现了原位压电-温度特性测试。其次,设计开发了变温管式炉、激振器驱动、信号调理与采集电路,构建了准确的滤波与工频陷波算法。实测结果表明,所设计系统测试结果稳定,能够准确测量压电-温度特性并标定压电材料相变温度,可为压电器件设计提供重要的参考。

三维球床几何稀疏条数长特征线加速方法

特征线法具有非常强的几何适应性,可用于三维球床高温气冷堆全堆芯求解,但存在迭代次数多、计算速度慢的缺点。本文将长特征线加速方法应用于三维球床高温气冷堆以解决非规则几何数值加速的问题,基于三维模型特征线布置较二维模型稠密的分析,提出了稀疏条数长特征线加速方法,极大地减少了加速方程的计算量,在不降低角度离散精度的前提下,获得了非常好的加速效果。通过基准题对加速参数的选取方式进行了研究,条数稀疏度取3~5、长特征线长度取2.0 cm左右、加速迭代步取20~60步可获得良好的加速效果。小型轻水堆三维基准题和球床堆芯简化模型的计算结果表明,采用稀疏条数长特征线加速可获得7倍左右的时间加速比,此时对应的迭代步加速比为20倍左右。

温度循环作用下石窟砂岩渗透特性试验

石窟岩体常年裸露在外,会受到多种自然因素的影响,尤其是温度变化和渗水等,可能导致岩体物理力学性质发生改变。针对温度循环作用下石窟砂岩的渗透特性开展研究,选取重庆大足石刻砂岩为研究对象,通过渗透试验,对多次冷热循环后石窟砂岩的渗透率进行测定和分析,并进一步研究了渗透试验后石窟砂岩的抗压强度特性。试验过程设计了不同冷热循环次数、不同高温持续时间、不同冷却方式等多种试验工况。研究结果表明:经过多次冷热循环,砂岩渗透率增加,并且渗透率变化幅度受循环次数和冷却方式的影响;当渗透压增大,砂岩渗透率增加;在高渗透压下渗透后,砂岩的强度稍小于低渗透压下的强度。

类金刚石碳基涂层热稳定性研究进展

类金刚石碳基(Diamond-like Carbon,DLC)涂层性能优异,前景广阔,但热稳定性不足制约了DLC涂层在严苛高温工况下的应用。首先,综述了DLC涂层热稳定性研究方法的发展现状,对比了热处理结合非原位测试、热分析、高温原位测试、模拟计算4种常用研究方法的优劣势。其次,归纳总结了组分、制备方法和退火环境对DLC涂层热稳定性的影响过程和作用机制,发现高sp^(3)含量的无氢DLC涂层呈现出最优异的热稳定性。而不同制备方法通过影响涂层结构、sp^(3)含量、氢含量获得热稳定性各异的DLC涂层。另外,涂层在真空及惰性气体环境中的热稳定性比含氧环境更好。通过异质第三元素掺杂、多层结构、梯度结构,可进一步提高DLC涂层热力学性能。其中,元素掺杂通过改变DLC组分和键态结构,实现对涂层热稳定性的调控;而多层及梯度结构设计主要通过降低涂层应力,突破厚膜关键制备技术,进而提高涂层热稳定性。结合涂层微结构的演变规律,进一步从涂层自身石墨化、氧化、脱氢和剥落行为,阐述了DLC涂层的高温失效机理。最后,对设计和发展DLC高温防护涂层材料技术的共性挑战和未来趋势做了分析展望。

中阶煤的孔隙特征研究

明确煤体的孔隙结构对煤层气的开采及瓦斯突出危险性评价有重要意义。为了解中阶煤孔隙特征,首先通过扫描电子显微镜测试煤层表面,后采用低温液氮吸附法和压汞法分析孔隙结构,并对测得实验数据进行绘图,研究其分形特征。结果表明:钱家营焦煤(QJY)、宁夏1/3焦煤(NX)、东欢坨气煤(DHT)三种煤样的吸附等温曲线均属于Ⅱ类吸附曲线,且呈倒"S"型。东欢坨煤的比表面积最大,宁夏煤次之,钱家营煤的比表面积较小,煤的变质程度与比表面积呈现明显的负相关性。孔径在≥50 nm的孔含量与平均孔径呈正相关;3个煤样中孔径≤10 nm的孔容占比均最大,煤孔隙主要是由微孔组成。孔隙发育情况:DHT>NX>QJY;钱家营煤与东欢坨煤的分形维数都呈现出吸附孔D _(2)>渗流孔D 1的特征,其微小孔的孔隙结构比较复杂,且无规则性。宁夏煤吸附孔的分形维数D_(2)=2.890,在2~3之间,微小孔具有分形特征。

燃气发生器弹射特性数值仿真与试验研究

为了研究燃气发生器弹射特性,基于改性双基固体推进剂装药结构和燃气发生器参数,建立了燃气底推弹射形式的数学模型,利用四阶龙格库塔法对数学模型进行求解,获得了燃气发生器弹射参数变化特性,结果表明:在常温条件下,载荷出简时的行程为7.7m,需要时间为0.53s,载荷出筒速度为31.1m/s,最大加速为81.7m/s^(2),满足弹射要求;同时,发现环境温度对燃气发生器弹射参数较大影响,随着环境温度增加,低压室压力峰值增加,载荷出筒时间缩短,出筒速度和最大过载增加;与常温弹射试验结果对比,低压力的压力峰值最大误差为5.2%,导弹载荷出筒速度最大误差为5.4%,表明所建立的燃气发生器弹射模型能够准确描述导弹载荷弹射参数特性。

土壤特性对圆环型直流接地极暂态温升的影响

温升是影响直流接地极安全运行的重要因素,为研究土壤特性对圆环型直流接地极暂态温升的影响,建立了水平圆环型直流接地极的有限元模型,对比分析了不同土壤特性下水平双圆环直流接地极的温升变化规律。仿真结果表明:土壤导热系数、比热容和土壤电阻率是重要影响因素;在水平双层土壤中,接地极的最高温升与土壤电阻率成正比,上层土壤电阻率的影响较下层土壤电阻率更为明显,而下层土壤电阻率对内环与外环的最高温升差值影响较大;上层土壤超过一定厚度后,上层土壤厚度的变化对极环最高温升的影响较小。研究成果可为特高压直流接地极选址及设计提供参考。

公共建筑供暖房间动态热负荷及热环境研究

建筑节能减碳是实现双碳目标两大战略的重要领域,寒冷地区公共建筑供热能耗普遍较高。公共建筑供暖目标是在节能减碳双控目标下实现精准补偿热负荷,并满足舒适要求。在调研公共建筑供热需求模式的基础上,根据反应系数法原理,应用特征温度法,研究分析高校供热与非供热房间各时间段不同人员工作状况下的动态热负荷和热环境,为北方公共建筑实现精准供热和热舒适提供了借鉴。

高温高湿环境下大规模海上风电机组零部件的防腐检测

受海上环境因素的干扰,风电机组零部件防腐状态的检测准确性难以得到保障。针对这一问题,提出了高温高湿环境下大规模海上风电机组零部件的防腐检测方法。将集红外热成像仪与可见光摄像机于一体的NC200NW红外相机作为监测装置,结合风电机组的运行时间和天气条件设定定时拍摄时间间隔,利用GPS定位功能标记数据采集位置。采用高斯滤波去除零部件红外数据噪声因素后,基于区域平均法将像素值转换为温度值,通过提取温度梯度特征和温度峰值特征确定防腐状态。测试结果表明,该方法能够有效识别腐蚀缺陷类型,抑制腐蚀缺陷信号,并准确定位腐蚀缺陷位置,能为及时维护或更换腐蚀零部件提供可靠指导。

正温度系数自控加热器耐久试验的方法浅析

本文首先对PTC自控加热器进行了产品介绍和工作原理的剖析。进而对现行国标GB/T 14536.1—2022《电自动控制器第1部分:通用要求》的附录J中PTC自控加热器的耐久试验方法进行了分析与研究,并按照产品种类总结了所需试验周期。希望本文能够帮助各方正确理解GB/T 14536.1—2022对PTC自控加热器产品耐久试验的要求。

1981-2020年北京地区气温时空变化特征分析

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