阶梯动压滑动轴承油膜流态可视化试验研究

阶梯动压滑动轴承深腔和浅腔油膜厚度相差较大,油膜流态会随之发生变化。采用可视化试验方案,利用气泡示踪法研究阶梯动压滑动轴承在深、浅腔及边界处的油膜流态变化规律,考察主轴转速、最小半径间隙对油膜流态的影响。结果表明:阶梯轴承的台阶突变处易导致油膜涡旋,出现紊流、层流混合现象;随着转速增加,深腔处油膜紊流现象加剧,随半径间隙增大,浅腔处容易产生紊流现象。试验数据与理论判据计算结果趋势一致。     

混合流态下径向滑动轴承的静态特性研究

以无限宽径向滑动轴承为研究对象,考虑油膜中同时存在层流和紊流两种流态,基于层流、紊流润滑理论,联立求解雷诺方程、能量方程和温黏方程,分析油膜中流态变化,得到压力分布、承载力、摩擦力和最高温度等特性参数。结果表明:随着转速的升高和偏心率的增大,油膜内流体从完全层流转变为完全紊流要经过一个复杂的流态变化过程;与单一层流流态相比,混合流态下油膜承载力和摩擦力较大,温升较高,黏度变化较大,这表明流态的改变和热效应对轴承特性有着不可忽略的影响,在计算轴承特性时,应准确判断油膜中流态,并考虑热效应的影响。     

层流、紊流共存时雷利阶梯轴承静特性分析

以具有深浅腔的高速阶梯轴承为研究对象,在考虑油膜中同时存在层流、紊流两种流态以及轴承两端存在不同静压力的条件下,采用连续性方程推导了油膜深浅腔的压力分布,进而求出轴承上的压力分布、承载力和摩擦力等静态特性参数。研究结果表明,油腔最优结构参数随深腔紊流因子和轴承两端静压力的不同而变化。将特定条件下混合流态时油膜静态特性结果与单一层流流态时的结果进行了比较。     

混合流态下鲨鱼皮织构滑动轴承静特性分析

轴瓦表面的织构会导致油膜厚度分布不均匀，整个流场中雷诺数差异较大，形成紊流和层流并存的混合流态。另外在高速运转工况下润滑油温度会大幅升高，从而影响其黏度及轴承承载能力等性能。鉴于鲨鱼皮结构在减阻、防污方面的成功应用，根据鲨鱼的盾鳞结构抽象建立了类鲨鱼皮二维织构的数学模型；同时考虑紊流以及油膜温度的作用，将类鲨鱼皮织构用于滑动轴承轴瓦形面的设计上，从鲨鱼皮织构的周向和轴向分布位置、织构深度、转速4个方面，对比分析了鲨鱼皮织构与球坑以及圆柱坑织构对滑动轴承静特性的影响。结果表明：1)织构位置分布对径向滑动轴承的性能影响非常大；2)不同织构深度下，鲨鱼皮织构始终表现出良好的减摩效果；3)高速紊流状态下的鲨鱼皮织构滑动轴承相比其他轴承减阻效果更加明显。     

混合流态下高速径向动静压轴承静特性分析

以具有深浅腔的高速动静压轴承为研究对象,分析在计入润滑油黏温特性时高转速下油膜层流、紊流共存时的混合流态对油膜特性的影响;建立层流、紊流共存时油膜的Reynolds方程、能量守恒方程、润滑油黏温特性方程以及相应的边界条件,综合利用有限元法和差分法求解以上方程,得出不同工况下油膜的特性参数。结果表明:在一定转速范围内,轴承内部油膜紊流区域随着转速的升高而增大;相同工况下混合流态模型计算出的油膜特性数值大于层流状态模型计算出的数值,数值之差随着转速的升高而增大,因此,高转速引起的润滑油膜流态的变化对轴承特性有一定的影响,在计算轴承特性时,考虑油膜流态的改变有利于得出与实际工况相近的理论数值。     

不同流态下高速动静压径向轴承静特性研究

针对深浅腔动静压径向轴承建立了层流、紊流共存时的油膜数学模型,采用有限元法计算了油膜的静态特性,并与完全层流和完全紊流两种状态下的计算结果进行了比较.结论表明:除流量外,静特性参数紊流工况下最大,混合流态次之,层流最小.     

挤压油膜阻尼器—滑动轴承—刚性转子系统的动力学建模

对挤压油膜阻尼器－滑动轴承－刚性转子系统的动力学模型进行了研究。提出在这一强非线性系统中,对于流体变化较大的挤压油膜层应考虑惯性力的影响,采用紊流短轴理论来分析;对于流体变化较小的滑动轴承油膜层,采用层流长轴理论来分析。文中从运动流体的动量微分方程及其质量连续性方程出发,推导出油膜层考虑惯性力的影响条件下的紊流压力分布函数。在模型的建立过程中,还考虑了旋转机械中出现的外界阻尼力、间隙激励力、外界异频干扰力和外界静态载荷。这对进一步研究系统的动力特性有一定的裨益。     

紊流工况下椭圆轴承性能研究

本文以紊流工况下的大型椭圆轴承为对象,通过试验和计算:(1)探讨了椭圆轴承中润滑油膜的流态由层流向紊流的转变点、影响转变的因素和判据,紊流系数的选取;热态工况和紊流流道中出现层流段对轴承性能的影响等;(2)分折了紊流工况下椭圆轴承的性能以及长径比、间隙比、椭圆比、进油压力、温度等时轴承性能的影响。在研究的过程中建立了一套适用于紊流工况轴承性能研究的试验手段和计算方法,为今后进一步研究大型透平发电机组径向滑动轴承的设计、计算和运行提供可靠的基础。     

基于流固耦合的离心压缩机轴系振动特性分析

为探究滑动轴承结构参数对离心压缩机轴系振动特性的影响规律,以某型离心压缩机轴承-转子系统为研究对象,首先采用多参考系模型、mixture两相流模型、liner层流模型以及UDF程序,利用隐式耦合求解法对考虑黏温特性的滑动轴承油膜流场进行求解,得到油膜流场压力分布进而对转子系统进行了单向稳态流固耦合分析,探究了轴承间隙比、宽径比对轴系振动特性的影响规律。结果表明：(1)油膜压力随轴承间隙比的增大而减小;临界转速随轴承间隙比的增大而小幅度减小,最大降幅为0.89%;轴系稳定性随间隙比增大呈现先减后增的变化趋势,研究轴系在间隙比为0.0014处稳定性最好。(2)油膜压力随轴承宽径比的增大而增大;临界转速随轴承宽径比的增大而增大,最大增幅为6.9%;轴系稳定性并未随轴承宽径比的增大而呈现规律性变化,研究轴系在宽径比为0.8处稳定性最佳。因此,轴承结构参数对轴系振动特性的影响并非是完全规律性的,我们需要根据旋转机械的实际工况选择合适的轴承结构参数。     

动压滑动轴承油膜不同流态时的油膜力场研究

为了研究高转速滑动轴承的油膜压力场,利用计算流体动力学软件FLUENT建立动压滑动轴承的油膜流场模型,计算油膜处于层流和湍流状态时的油膜压力分布,比较相同转速条件下轴颈随油膜涡动时的轴承承载能力变化.结果表明:在相同参数条件下,油膜处于湍流状态下的承载能力大于层流状态,模拟结果与前人理论研究一致,证明FLUENT对动压滑动轴承油膜压力分布模拟有效;轴颈随油膜涡动时,轴承承载能力降低,轴承端部泄油量减小,转轴涡动是影响轴承稳定性的主要原因.     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

Quantum Cooperative Robotics and Autonomy

The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci...     

On the Relation of Load to Average Gap in the Contact Between Surfaces with Longitudinal Roughness

A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load.     

三绕组变压器的双绕组等效建模及在Matpower中的应用

针对实际电网存在着大量的三绕组变压器,但国际上一些著名商业软件,如BPA仿真软件、Matpower这一权威潮流计算开源软件,均只提供双绕组变压器模型,限制了其在具有三绕组变压器的电力系统中的应用的问题,潮流计算是自主开发的电力系统各种应用软件的核心模块,因此依托国际权威开源程序进行二次开发,是一种较好的选择。对Matpower要求的数据格式进行了归纳,对变压器的一般的等值电路及带理想变压器的等值电路和带标幺值的等值电路进行了分析研究,提出了三绕组变压器转换为双绕组等效模型的建模方法,使得原先只适应双绕组变压器的潮流计算软件可以适用于三绕组变压器电网的潮流计算;最后以Matpower软件为例进行了案例计算,并用PSASP仿真软件进行对比验证。研究结果证明,所提出的建模方法是有效的。     

电站锅炉模糊风险评价方法研究与应用

针对电站锅炉风险等级评价问题,将模糊综合评价技术应用到电站锅炉风险等级评价中。开展了电站锅炉失效影响因素及模糊评价因素的重要程度分析,建立了一套科学合理适于在线评价的电站锅炉风险评价体系,提出了模糊综合评价技术与改进的模糊层次分析法相结合的模糊风险评价方法,利用改进的模糊层次分析法计算了指标体系中各层指标权重。对某一台电站锅炉的实际运行工况影响子因素进行了模糊风险评价,采用模糊合成算子进行模糊综合运算得到电了站锅炉运行工况影响子因素的评价向量。研究结果表明:电站锅炉的运行工况影响子因素的风险评价等级为第6级,失效可能性等级为小,该电站锅炉运行工况良好。     

考虑进油孔有限长滑动轴承油膜力的近似解析解

针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

交通荷载作用下桥梁结构参数识别方法

应用动力节点加载法,将作用在桥梁上的交通荷载转化为等效节点荷载,再用两步构造法识别结构物理参数.第1步,用Newmark-β方法变换结构运动方程,并用结构的加速度响应求得变换空间内的位移、速度和加速度响应;第2步,基于最小二乘原理,构造出变换空间内求解结构参数的递推式,进行结构物理参数识别.数值模拟结果表明,在交通荷载作用下,该方法能够快速、准确地进行桥梁结构参数识别.     

Fifth International Summer School on Screw-Theory Based Methods in Robotics

正3-11 September,2014University of Bologna,Bologna,Italy www.summerscrews.org summerscrews2014.ing.unibo.it SUMMER 20SCREWS 14In 2014,our screw-theory school comes to the world's oldest university.In early September,Summer Screws'14 will gather six experts in the application of screw theory in robotics and up to 40 participants at the University of Bologna,Bologna,Italy.The school will teach attendees how to apply existing methods and empower them to develop new ones in their own research.The basic theoretical notions will be introduced in a rigorous manner,emphasizing examples,applications,and exercises.Scholarships are available.     

INDUSTRIAL ENGINEERING AND VISUALISATION-A PRODUCT DEVELOPMENT PERSPECTIVE

Taking the actual project of teaching and researching process for example, the relationship between the industrial engineering and product development is discussed. And use the novel visualization technology to support the industrial engineering and product development. How to use the new computer modeling and simulating technologies to support the product development and industrial engineering, is introduced especially. The support includes both domestic products and industrial systems. The visualization and computer technologies take a very important role in some system or multi-direction modeling, those technologies mentioned above can help the industrial engineers study the effect of design on the whole life circle, including the producing steps. So the engineers can avoid making the wrong decision which may cause bad effects on the whole industrial engineering.