康达效应对油气环状流分配特性的影响

基于Fluent流体力学软件对T型三通管道模型进行数值模拟,研究入口流型为环状流时,T型三通的气液相的质量流量、速度和压强的分布规律,特别是康达效应对以上分布规律的影响导致的油气分配的不均匀性。结果表明,连接处两支管曲率半径有差异时,康达效应导致油气环状流的分配出现不均性,曲率越小,支管内气相质量流量越大,液相质量流量越小;支管连接处曲率越小,曲率小的一侧支管出口的气相速度越大,反之,则越小;T型三通连接处入口的压强较高,压力梯度较小,水平支管中曲率小的一侧支管的压力梯度比曲率大的一侧大。     

喷嘴结构对高速滚动轴承油气润滑两相流特性的影响

基于油气两相流基本理论,采用 Fluent 仿真软件建立油气润滑系统喷嘴、轴承腔的油气两相流模型,分析油气两相流流经直接喷射型和内圈喷射型2种结构喷嘴后在轴承腔内的流动状态,分析内圈喷射型喷嘴的竖直管道与倾斜管道夹角及喷嘴出口结构等关键设计参数对轴承内部油气两相流分布状况的影响。仿真结果表明：内圈喷射型喷嘴具有更好的润滑效果,减小了油气润滑系统的耗油量和耗气量;竖管与倾斜管道夹角越小,越利于环状流的保持,供油均匀性越好;突扩管结构设计,有利于缓解因油气波动造成的供油不均匀。     

油气润滑输送管内环状流的特性分析

根据滑动轴承润滑工况．提出了油气润滑输送管内环状流的转变机理,利用小扰动法,对环状流气液界面的稳定性进行分析,并依据液膜平均厚度沿周向的分布规律,分析了环状流的均匀性,为环状流在管道内正确输送提供理论依据,为油气润滑工况下滑动轴承的性能研究提供了前提条件。     

喷嘴结构对油气润滑环状流特性的影响

油气润滑供油连续性与稳定性实际表现为输油管内部环状流的油膜连续性及油液波动程度的变化,为了研究喷嘴结构对油气润滑输油管内环状流特性的影响,基于气液两相流基本理论,利用流体力学计算软件FLUENT中VOF模型对高速滚动轴承油气润滑输油管中的油气分布状态及速度变化进行数值仿真。研究喷嘴结构参数对输油管中油气环状流特性的影响,得到了喷嘴结构参数对油气润滑环状流特性的影响关系。结果表明:影响油气润滑系统环状流特性的主要因素是喷嘴的入口和出口直径,两者越接近,对环状流特性影响越小;喷嘴突缩角对油气环状流特性的影响较小;通过研究喷嘴结构与油气环状流的影响关系,为喷嘴结构优化设计及油气润滑输油管内部流场的分析提供了理论基础与依据。     

油气润滑ECT系统的软场效应与成像精度分析

运用COMSOL和MATLAB对油气润滑系统水平管道环状流和中心流流型的ECT系统做了联合仿真,求解分析了软场效应,以及软场效应对图像成像精度的影响。结果表明:检测电极在远离介质突变层时,灵敏度场的值变化相对较小;检测电极在靠近介质突变层时,灵敏度场的值变化相对较大,且灵敏度场值在管道激励边缘远大于中心处。两相中心流的成像相对误差大于层流及环状流型,为提高成像精度需考虑软场效应。     

分配孔数对油气分配器分配性能的影响分析

建立了油气润滑系统油气分配器的流体域仿真模型,基于该模型仿真了均匀和不均匀环状流两种入口工况下分配器分配界面油气两相的流体分布,提取了不同分配孔数的出口油液和气体的质量流量,分析了分配孔数对油气分配器分配性能的影响。结果表明,分配孔数的增加提高了油气分配器对油液分配的均匀性和稳定性,分配孔增加到一定数目后,可以在一定程度上克服重力的影响,但对油气分配器的分配性能改善较小。     

油气润滑管道环状流形成及影响因素研究

建立了油气润滑系统中内径为6 mm的水平管模型,利用FLUENT仿真软件对管内油气两相环状流进行了数值模拟,研究分析了油液速度、气体速度对环状流质量的影响。结果表明,气体速度是影响环状流质量的主要因素,在油量一定时气体速度为60 m/s~80 m/s时形成的环状流品质较好。     

油气润滑系统中环状流流过突扩管时的流动特性

基于Fluent软件分析了油气润滑工况下环状流流过突扩管时的压力和油膜变化特点。结果表明,油气环状流流过突扩管时压力和油膜会发生突变,且突变的位置不会受到入口气速的影响,但是其变化的强度与入口气速的大小呈正比;油气环状流的液膜在管路突扩前分布的部分分布较为均匀,而在管路突扩后的分布受到气速和管径的影响较大,较大的气速和突扩管径会使环状液膜分散的程度增大。     

油气润滑系统油气两相流流型转变研究

依据Mandhane图中环状流转变阈值,利用MATLAB软件将选取的阈值与已有的无量纲准则数进行关联,拟合得到油气润滑工况下新的间歇流-环状流转变的无量纲准则式;借助Fluent软件仿真验证该准则式的合理性,并通过仿真得到油气润滑中分层流-环状流、间歇流-环状流的流型转变图。研究结果表明,两相流流型仿真图中气液相分布规律与文献中对流型的描述一致,压降分布规律也基本符合已有的结论;由于管径小的原因,新的流型图转变曲线位置较Mandhane图环状流部分偏下,但曲线走势基本相同,故该流型图可以作为研究油气润滑环状流流型转变的依据。     

渐扩管内气液环状流附壁特性研究

利用Fluent软件模拟了油气两相流在渐扩管内的液相的附壁情况,得到了渐扩管扩张段的速度场和压力的分布规律,并分析了改变渐扩管的扩张角对扩张段环状流液膜附壁的影响。结果表明,渐扩管扩张段的锥角对环状流液膜的附壁有很大的影响,扩张段横截面的速度差值和压降随扩张角增大而增大,但是轴向梯度力却随之减小。这些结论对油气润滑系统中的输运有指导意义。     

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。     

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.     

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...     

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。     

RLS and LMS blind adaptive multi-user detection method and comparison in acoustic communication

RLS and LMS blind adaptive multi-user detection algorithm and multi-user detector was proposed to solve the problem of multi-user signal detection problem encountered in underwater acoustic communication networks.In simulation analysis,RLS and the LMS blind adaptive multi-user detector were designed and tested for synchronous and asynchronous multi-user communication process.The results of SIR comparison and MMSE comparison show that,both of the two methods can realize blind adaptive detection when any user change in multi-user communication,during this process,the training communication sequences are not needed.The RLS algorithm has about 5 dB higher in SIR compared with LMS algorithm,and the convergence velocity of RLS algorithm is also higher than LMS algorithm when the communication users change.RLS algorithm has better ability in multi-user detection than that of LMS algorithm,and it has great attraction and guiding significance for solving the problem of multiple access interference(MAI) in multi-user communication.     

Robust Impedance Control of Robots Using an Adaptive Interaction Force Observer

For robot interaction control,the interaction force between the robot and the manipulated object or environment should be monitored.Impedance control is a type ...     

Research on key techniques of expendable conductivity temperature depth measuring system

This paper analysis the developing of expendable conductivity temperature depth measuring system(XCTD)and introduce its principle of measuring about temperature,salinity and depth of ocean.Some key techniques are put forward.According to the real needs of XCTD,conductivity sensor with high sensitivity is designed by principle of electromagnetic induce,the ocean conductivity from induced electromotive force has been calculated.Adding temperature correction circuit would help to reduce error of conductivity measurement because of sharply changing temperature.Advanced temperature measuring circuit of high precision and the constant current source is used to weaken effect of self-heating of resistance and fluctuation of the source.On respect of remote data transmission,LVDS is a good choice for the purpose of guarantee the quality of data transmitted and the transmission distance is reaching to thousand meters in the seawater.Modular programming method is also brought into this research aimed at improve the stability,reliability and maintainability of the whole measuring system.In February,2015,the trials in South China Sea demonstrate that the developed XCTD realize effective measurement at a speed of 6 knots and detection depth at 800 m.The consistency coefficient of the acquired data is greater than 0.99 and the success rate of probe launching is above 90%.     

CHARACTERISTCS OF FLUID FILM IN OPTIMIZED SPIRAL GROOVE MECHANICAL SEAL

In order to investigate the sealing performance variation resulted from the thermal deformation of the end faces, the equations to calculate the fluid film pressure distribution, the bearing force and the leakage rate are derived, for the fluid film both in parallel gap and in wedgy gap. The geometrical parameters of the sealing members are optimized by means of heat transfer analysis and complex method. The analysis results indicate that the shallow spiral grooves can generate hydrodynamic pressure while the rotating ring rotates and the bearing force of the fluid film in spiral groove end faces is much larger than that in the flat end faces. The deformation increases the bearing force of the fluid film in flat end faces, but it decreases the hydrodynamic pressure of the fluid film in spiral groove end faces. The gap dimensions which determine the characteristics of the fluid film is obtained by coupling analysis of the frictional heat and the thermal deformation in consideration of the equilibrium condition of the bearing force and the closing force. For different gap dimensions, the relationship between the closing force and the leakage rate is also investigated, based on which the leakage rate can be controlled by adjusting the closing force.