温度补偿对提高航天微电机转速稳定性能的影响

某型号的航天微电机在太空中高速运行工作时转速不稳定，尤其在润滑油量不足的情况下甚至停机；而当要结束工作，缓慢停机时转速却变得很稳定。有限元方法提供了一种寻找该问题原因的手段。本文从润滑性能引起电机结构温升的角度出发，基于SKF轴承摩擦力矩计算方法，使用MARC软件，计算了电机在运转和和停机状态下各部件的温度分布情况。分析结果显示，由于轴承内圈温度高于端盖，润滑油向端盖扩散，轴承系统润滑性能降低，引起电机转速不稳定。通过对不同位置施加温度补偿的计算，最终确定在支架端面施加8W的温度补偿，使得轴承内圈温度始终低于轴承端盖。实验证明，施加温度补偿是一种很有效的方法，使得电机转速稳定性能满足设计要求     

组件温度对球轴承热冲击流变润滑特性的影响

为了研究组件温度对球轴承热冲击流变润滑性能的影响,考虑轴承组件温度与供油温度之间的差异,采用Eyring剪稀流体建立了球轴承热冲击流变弹流润滑模型,利用多重网格方法与时变性、流变性和温度场的分析技术研究了组件温度对动态油膜热流变弹流润滑性能的影响,并对极端工况下的热失效现象进行分析.结果表明:滚动体温度越高,其油膜厚度及摩擦系数越小;在极端工况下,轴承内圈与滚动体之间出现了高压、高温和低膜厚现象;轴承内圈温度达到边界膜脱附时的第1临界温度,且轴承内圈与滚动体之间处于混合润滑状态.因此,分析滚动轴承的非稳态热流变弹流润滑特性时需考虑轴承温度场的影响.     

CFX和Fluent在径向滑动轴承润滑计算中的异同探讨

基于CFD(计算流体动力学)理论,以径向滑动轴承润滑性能计算为例,分析了ANSYS中CFD模块CFX与Fluent在轴承润滑计算结果的异同.为此,建立了润滑计算模型,并采用两种模块对比分析了不同偏心率、转速及长径比工况下滑动轴承的摩擦学性能.结果表明:两种模块轴承润滑性能计算结果总体趋势基本吻合,但相对Fluent,CFX计算得到较小的最大油膜压力、轴承承载力和较大的摩擦系数;两种模块在大偏心率、小转速及小长径比工况下的计算结果偏差较大.     

轴承润滑调节装置

1．引言轴承的润滑有润滑脂润滑(脂润滑)、稀油润滑和油雾润滑等,一般转速较低或工作负荷较轻或运转条件较好的轴承多采用脂润滑。轴承的可靠运转除轴承的类型、本身的质量、轴承周围的结构、外圈与端盖轴承室的配合、内圈与转轴的配合以及润滑脂的品质等外,维持轴承滚动元件不间断的良好润滑是轴承可靠运行的重要条件之一。2．轴承润滑情况剖析及课题的提出一般情况下电机装配时,2极电机轴承填抹润滑脂的数量是轴承内腔的一半左右,4极及以上为2／3左右。当电机起动运转几分钟之     

一般速度条件下球轴承工作特性分析

速度通过惯性力作用于轴承,对其内部工作特性影响很大.高速时滚动体与内外圈接触角不再相等,内圈接触角大于外圈接触角.接触载荷的变化情况与接触角变化不同,在一定的转速条件下,外圈接触载荷大于内圈接触载荷.由于内圈接触角随转速的增加而减小,导致轴承径向刚度随转速的增加而降低.转速越高,轴承的工作情况变化越大.     

深沟球轴承内圈及滚动体运动噪声的计算方法

以深沟球轴承为研究对象,建立了一种对内圈轴心轨迹以及每个滚动体中心运动轨迹计算的轴承数学模型,结合声学理论,将轴承内圈看作圆柱声源,将滚动体看作球声源,建立了能够对深沟球轴承内圈和滚动体振动噪声进行定量计算的计算模型。通过一个具体的算例,研究了转速和径向载荷对固定点上噪声大小的影响,以及噪声沿滚动轴承轴线方向的变化规律,绘制了这些影响的变化曲线。发现随着轴承转速的增大,轴承声压值会随之增大;随着轴承所受径向载荷的增大,轴承声压值会随之增大,其变化趋势由快到慢;轴承内圈和滚动体运动所产生的声压在轴承轴线方向上逐渐减小,呈非线性关系变化。     

高速球轴承?转子系统动态性能的分析与优化

针对轴承刚度随转速呈非线性变化的特点,基于角接触球轴承拟静力学模型,考虑轴承内圈离心位移的影响,运用数值方法对轴承和轴承组的动刚度进行了计算。在此基础上,根据轴承-转子系统的有限元模型建立了动力学方程,并编制数值迭代程序求解其特征值,进而得到了系统的临界转速。由于转速对轴承(组)动刚度的影响,在每一次迭代计算中,需根据前次迭代计算出的临界转速求解前、后轴承(组)的动刚度,重建系统的有限元模型,因此结合Matlab优化工具箱,运用单纯形法对转子内径与轴承跨距进行了优化。分析结果表明:通过优化转子内径与轴承跨距,轴承-转子系统的一阶临界转速提高了7.65%,由于转速与内圈离心位移对轴承或轴承组动刚度的影响很大,因此在高速轴承-转子系统的动态分析中应考虑该影响因素。     

多参数监测智能轴承的设计与研究

研制了一种多参数监测智能轴承。该智能轴承对轴承实际工况中的振动加速度、转速和温度进行实时监测,并将测量数据传递给云端数据管控平台,实现对轴承运转状态的监控与故障预警,重点研究了轴承振动加速度的测量方式,通过对轴承工况下振动特性的研究与轴承内部结构的分析,选择采用三轴振动加速度计作为研究基础进行测量;通过对轴承内圈结构的改造,采用霍尔传感器与磁编码体相结合的方式测量轴承转速;采用温度传感器测量轴承内圈的温度。通过将该智能轴承与传统轴承座监测系统的对比,可知研发的智能轴承性能相较于传统轴承监测系统有显著的提升,其中振动加速度的监测信号幅值达到了传统轴承监测系统的3倍以上,能更好地判断轴承的运转状态,具有优秀的故障预测预警能力。     

微沟槽形貌对水润滑轴承混合润滑特性影响的研究

建立了计入轴承内表面微沟槽形貌的水润滑轴承混合润滑(Mixed-EHDL)数值计算模型,着重研究了不同运行工况下,半椭圆形、矩形、等腰三角形、左三角形、右三角形等多种微沟槽形貌对水润滑轴承混合润滑特性的影响.研究表明:在所有微沟槽形貌中,混合润滑性能与承载性能优劣排序依次为右三角形、等腰三角形、左三角形、半椭圆形、矩形;在弹流润滑阶段,微沟槽形貌对水润滑轴承摩擦系数几乎无影响,而在混合润滑阶段,不同微沟槽形貌下接触载荷以及摩擦系数之间的差异随转速的增加呈现出先增大后减小最后趋于统一的规律性;在承载区,由于沟槽内水膜增压能力以及抽吸作用的不同引起了水润滑轴承混合润滑性能的差异,其中右三角形表现最优,而矩形最差.     

角接触球轴承热特性分析及试验

为了预测并控制轴承运转过程中热态特性对进给系统精度的影响,基于球轴承拟静力学和摩擦生热理论,计算了包括自旋摩擦力矩在内的摩擦生热,分析了热传递方式,并建立了热传递模型和一种考虑接触热阻的球轴承组件有限元热结构模型。采用有限元法仿真轴承组件稳态温度场,搭建试验台测试了不同转速和载荷下轴承的稳态温度分布及轴向热位移。结果表明:转速和轴向载荷对轴承温升及轴向热位移影响较大,其中温升在10℃以内时,轴向热位移与温度线性关系明显;在温度场中,滚珠温度最高,内圈温度次之,外圈温度最低;仿真结果与测试结果相对误差在7%以内,可有效预测轴承在不同工况下的稳态温度场及轴向热位移。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that