Simulation of the Effects of a Plunge Ground Rod on Hydraulic Rod Seal Behavior

A numerical analysis of a reciprocating hydraulic rod seal with a plunge ground rod has been performed. It consists of coupled fluid mechanics, contact mechanics, and deformation analyses. The fluid mechanics analysis consists of a finite volume solution of the Reynolds equation. The deformation is computed with a finite element analysis. The contact of the seal asperities with the rod utilizes the Greenwood-Williamson model and the rod surface geometry is treated deterministically. The fluid transport, friction force, contact pressure distribution, and fluid pressure distribution in the sealing zone have been computed for a polyurethane U-cup seal and for a step seal with a polytetrafluoroethylene (PTFE) sealing element and a nitrile energizer. These have been compared with the results for a smooth rod.     

Physical and numerical modeling of the process of rolling off of a tapered shaft of aviation purpose

One of the most promising methods of manufacturing axisymmetric parts of gas turbine engines is local deformation on specialized rolling mills. To design this class of manufacturing operations and equipment, it is effective to use physical and numerical modeling. The article has provided the method and results of physical and numerical finite-element modeling of local deformation process of a detail of a cone-with-cylinder type made of EI962–Sh chromium steel. Analyses of the energy-power parameters of the technical process and the possibility of the destruction of a part during the deformation process have been carried out.     

热力耦合作用下水下井口连接器密封特性*

为研究海底高温高压复杂工况下金属密封圈在井口连接器中的密封性能，根据传热学理论建立传热学和热力耦合数学模型，运用ANSYS建立井口连接器温度场有限元模型；在温度场数值模拟的基础上，进行稳态和瞬态热结构耦合数值模拟分析，得到油气介质压力及温度对水下井口连接器密封性能的影响。结果表明：油气介质温度越高，密封圈内部的温度梯度越大，在温度冲击影响下，连接器各零部件和密封圈之间的温差波动要大于匀速变温及瞬间变温下产生的温差波动。稳态热-结构耦合分析表明，金属密封圈会因温度升高而产生膨胀变形，并且该变形大于不施加温度载荷时的变形，说明温度载荷在特定条件下将直接影响连接器的密封特性；瞬态热-结构耦合分析表明，油气介质温度的快速变化，导致密封圈中接触面受热产生的线膨胀比外圈的线膨胀大，从而导致密封圈内部的不协调变形，因此在实际工作环境中应避免温度升高速度过快的现象发生。     

悬臂式薄片动压润滑气体轴承性能研究——用薄壳非线性大变形法计算薄片的弹性变形

建立了计算弹性薄壳的非线性大变形方法 ,并将此方法用于求解悬臂式薄片动压气体润滑轴承的薄片弹性变形 ,通过实验验证并与其它计算方法相比较 ,表明本文所采用的方法是准确 ,可靠的 ,其结果更符合实际工况     

Large deformation analysis of anisotropic rubber hose along cyclic path by homogenization and path interpolation methods

Automotive braking hose used to deliver the hydraulic braking force to the drake disc is in a lamination composition of rubber and fabric braided layers to prevent the oil leakage and the excessive radial deformation. Currently, the configuration and durability become a hot issue in the design of braking hose, because both substantially affect the oil leakage caused by the micro cracks and the interference with other adjacent parts. The design of braking hose including its configuration has been relied on the trial-and-error experiment because there is no reliable numerical analysis technique. A main obstacle in developing the numerical analysis technique is the geometry modeling of braided layer which is woven with fabric cords of small diameter. The microstructure of braided layer has been simplified as an isotropic layer because of its painstaking modeling job and the necessity of huge number of finite elements. However, such a simple model could not successfully reproduce the out-of-deformation of braking hose which is produced by the orthotropic braided layers. Meanwhile, the braking hose undergoes cyclic large deformation during the steering motion and bump/rebound motions of vehicle. In this context, the goal of this study is to introduce a modeling-effective but reliable large deformation analysis method for braking hose along the specified cyclic path making use of the homogenization and path interpolation methods. The numerical results are also presented to illustrate the proposed numerical analysis method.

     

关于逆向车削加工细长轴误差的力学分析

针对细长轴车削加工，分别在两种不同装夹条件下(一端卡盘夹紧、一端顶尖支承和两端顶尖支承)进行正向切削和逆向切削时的工件变形进行了力学分析，建立了正逆向切削工件在切削力作用下产生弯曲变形的解析模型。具体算例表明：逆向切削时工件的弯曲变形以及由此引起的加工误差远小于同等条件下正向切削的变形和误差。该模型及分析结果可用于细长轴加工的工艺设计。     

Pore-scale visualization of gas trapping in porous media by X-ray CT scanning

Entrapment of the non-wetting phase in porous media has been observed in a variety of fields such as petroleum engineering, geological storage of carbon dioxide, and remediation of ground water. We investigated gas trapping in porous media from a microscopic point of view. High-resolution, three-dimensional images of pore structure and trapped gas bubbles in Berea sandstones were obtained using a micro-focused X-ray CT scanner. We used vertical and horizontal Berea sandstone cores, 8 mm in diameter and 15 mm long. Based on the three-dimensional image analysis, the statistical distribution of the trapped gas volume was estimated. Trapped bubbles have a pore-network scale size and distribute over several pores. In the case of the vertical core, the porosity fluctuates along the flow direction due to the layered structure. The residual gas saturation also fluctuates with porosity along the flow direction. The higher gas saturation in porous layers at the end of gas injection results in a higher trapped gas saturation compared to dense layers. On the other hand, in dense layers the gas saturation at the end of gas injection is almost the same as residual gas saturation. Therefore, most of the gas injected into the dense layers would be trapped. In the case of the horizontal core, the gas saturation at the irreducible water condition is lower than that for the vertical core, because the injected gas selectively passes through the more permeable layers. However, the residual gas saturation is 29.2% for the horizontal core, which is comparable with that for the vertical core (30.9%). Finally, the effect of capillary number on stability of trapped gas bubbles has been estimated. Trapped gas bubbles are stable against the increased flow rate up to a capillary number of 1.0×10^?5.     

石油生产光纤-电导组合探针阵列多分相测井仪研究

为解决石油生产多分相测量问题,基于课题组研制的创新型光纤-电导组合探针设计研制一种用于石油生产多参数测量的高精度、高灵敏度探测仪器。采用ZEMAX光线追迹方法和FEM数值分析方法对光纤-电导组合探针阵列多分相测井仪电场分布、响应特性进行了理论分析,且验证了其在流量为5、10、20、30 m~3/d,持气率为10%、20%、30%、40%,持水率为90%、80%、70%、60%等工况下良好的测量效果。为进一步证明其优良性能,以液相流量30 m~3/d,液相持水率25%、45%、65%及85%,气流量6、12、24 m~3/d等多相流工况为例进行动态实验分析,其持气率测量误差在5%以内,持水率误差在10%以内。实际动态实验与仿真模拟结果保持相同。充分表明光纤-电导组合探针阵列多分相测井仪的良好的性能。     

多场耦合作用下动涡旋盘的变形和应力研究

利用Pro/E建立了涡旋压缩机动涡旋盘的三维实体模型,基于有限元法分别对动涡旋盘在气体力、温度场和惯性力作用下的应力和变形分布情况进行分析,并对气体力、温度场、惯性力耦合作用下动涡旋盘的变形和应力进行了数值计算。结果表明温度场引起的轴向变形较大,惯性力使涡旋齿尾部的变形增加,多场耦合作用下最大变形发生在涡旋齿头,最大应力发生在涡旋齿头的底部和驱动轴承座孔内。     

基于时域反射的分布式地表变形探测技术

地表变形探测技术对于提高地质灾害监测能力具有重要的现实意义.通过对现有地表变形测量技术和时域反射测量技术的分析,提出一种基于时域反射技术的分布式地表变形探测方法并设计了一种螺旋结构的时域反射测量电缆.这种电缆由平行线缠绕而成.通过理论分析和实验证明电缆可以将其局部拉伸变形转化为电缆的局部阻抗变化.通过观测时域反射测量仪反射波形的变化定位阻抗变化点从而探测地表变形点的位置.     

An upper-bound analysis of friction in metal forming

In the analysis of metal forming processes, a knowledge of friction is important, especially when the microstructure evolution and criteria for limiting phenomena are predicted by numerical simulation. The friction wave model has been studied by several researchers. Their analyses are mainly based on the assumption that there is no plastic deformation of the bulk material. However, it is necessary to clarify the influence of bulk material deformation on the surface asperity deformation. This paper deals with the development of a friction wave model by considering the influence of bulk material on the surface asperity deformation. The situation of rough tool—smooth workpiece (RT—SW) contact during forming process has been investigated. Based on this condition, an admissible velocity field is constructed for the upper bound analysis. The relationship between the normal pressure and the sliding resistance is established over a large range of pressure. The role of surface roughness, bulk displacement and bulk strain on metal forming friction is analysed.     

汽轮机高压缸三维热弹性接触模型及其气密性分析

汽轮机高压缸中的高温和高压蒸气经常会造成缸体较大的变形,从而在汽缸法兰中分面产生漏气,为了分析汽缸的气密性,文中结合汽缸温度场和三维弹性接触理论,建立汽缸三维热弹性接触有限元模型。利用建立的模型完成一个100MW汽轮机高压缸的温度场及应力、变形计算,并且应用于实际的高压缸改造。实践表明这些计算结果可以作为汽缸设计的重要依据,从而提高运行中汽缸的安全可靠性。     

某重型装备多刚体建模及对地载荷研究

某重型装备工作对地面强度和变形有严格要求。借助Pro/Engineer和ADAMS,建立了装备的多体动力学模型,在装备与地面之间添加接触力和轴套力约束条件,通过执行装备工作过程仿真,计算得到与实际趋势吻合的装备千斤顶及轮组的对地载荷。研究表明,多体建模分析方法对于装备工作载荷的样本提取是可行的,有利于缩短研究周期和降低研究成本。研究成果可进一步用于装备与地面之间载荷效应的数值模拟研究。     

基于单板加强筋的焊接夹具设计与仿真

针对充气柜单板加强筋焊接变形问题,设计了焊接专用夹具,并对焊接过程进行了热固耦合数值求解,得到了两种不同焊接顺序下,气体保护焊和激光焊两种焊接方式的温度场和变形。结果表明,两种方案的焊接变形相差不大,激光焊接能明显减小变形,最大可减小达67.09%。充气柜以其优良的性能适用于环境恶劣的场所,在工矿企业变电所广泛安装使用。     

Development of three-dimensional numerical model for combustion-flow in interior ballistics

Interior ballistics analysis is required for the development of the gun system. Interior ballistics is a complex phenomenon containing the propellant combustion and gas flow and is completed in tens of milliseconds during gun firing. Thus, some data cannot be directly measured by experiment. Numerical analysis is therefore traditionally used to understand the complex gun firing phenomena. In previous studies, the two-dimensional axisymmetric numerical method for interior ballistics using the Eulerian-Lagrangian approach has been developed. There are some limits in depicting the actual phenomena with two-dimensional models. Therefore, a three-dimensional numerical model has been built in the present study. Unlike the conventional method, the calculation has been conducted by separating the physical phenomena into the combustion part and the flow part for simplicity and efficiency. The internal flow in the gun barrel has been calculated by using the STAR-CCM+ and the source terms produced by the propellant combustion has been computed by utilizing the existing code. The developed numerical model has been compared with the AGARD gun results and the simulation of 40 mm gun firings. The reliability of the developed model has been confirmed because the results of the numerical analysis greatly agree with the simulation results. The basis of the three-dimensional analysis of the interior ballistics has been formed through this study.     

IMTOS一体化计算机辅助光学设计软件系统

IMTOS软件系统用一体化数值方法完成光学仪器设计分析, 在日立的M-169机上把热、结构和光学分析程序连成一体, 解决光学仪器工程中常规问题, 对热变形、机械变形和光学元件本身变形及相对位置变形等进行分析, 快速地比较, 修改, 能加快仪器设计速度.对IMTOS的发展提出了设想.     

Three-dimensional computational fluid dynamic analysis of the conventional PEM fuel cell and investigation of prominent gas diffusion layers effect

A full three-dimensional, single phase computational fluid dynamics model of a proton exchange membrane fuel cell (PEMFC) with both the gas distribution flow channels and the membrane electrode assembly (MEA) has been developed. A single set of conservation equations which are valid for the flow channels, gas-diffusion electrodes, catalyst layers, and the membrane region are developed and numerically solved using a finite volume based computational fluid dynamics technique. In this research some parameters such as oxygen consumption, water production, velocity distribution, ohmic losses, liquid water activity and fuel cell performance for straight (base case) and prominent gas diffusion layers were investigated in more detail. The numerical simulations reveal that prominent gas diffusion layer improves the transport of the reactant gases through the porous layers; it is due to increase of the mentioned fuel cell efficiency, and prominent gas diffusion layers yield appreciably higher current density. Finally the numerical results of proposed CFD model (base case) are compared with the available experimental data that represent good agreement.     

船用水润滑推力轴承扇形推力瓦润滑性能数值分析

采用数值分析方法研究了船用水润滑推力轴承扇形推力瓦的润滑性能问题,计算得出了水膜厚度、压力分布、推力瓦位移场和温度场的三维分布规律.研究表明:在推力瓦不同位置有着较大温度差,水膜最大厚度和最大压力、推力瓦最高温度和最大变形均出现在推力瓦周向出水口的位置.     

弹性箔片动压气体推力轴承承载性能研究

气弹耦合解是准确预测弹性箔片动压气体轴承承载性能的有效方法。通过引入箔片的弹性变形以及联立求解动压气体润滑Reynolds方程和弹性箔片的变形方程,给出了弹性箔片动压气体推力轴承的气弹耦合解。应用气弹耦合解理论,将顶层箔片的局部弹性变形纳入考虑范围,对弹性箔片动压气体推力轴承的承载性能进行了计算和分析。有限元数值仿真结果表明:顶层箔片在气膜压力作用下的局部弹性变形直接导致弹性箔片动压气体推力轴承承载能力的降低;根据轴承瓦块上气膜压力分布的特点合理设计支承拱箔的结构形式,可以减小顶层箔片的局部弹性变形,有效提高轴承的承载能力。得到了一种承载能力较高的弹性箔片动压气体推力轴承支承拱箔结构设计方案。     

A numerical model for simulating temperature and speed effects in hot extrusion of rod

In this paper, a two-dimensional numerical model with upper-bound coupled thermal analysis has been developed. The model is capable of simulating the hot rod extrusion process with variable ram speeds. The temperature distributions and the speed effects in hot extrusion are predicted in detail by the proposed numerical model. A generalized kinematically-admissible velocity field without velocity discontinuity is adopted. The temperatures are calculated by considering simultaneously the heat generation due to deformation and friction and heat transfer. A finite-difference method with an implicit time integration scheme is utilized to solve the two-dimensional heat conduction problem. Two mathematical models for variable ram speed profiles are proposd. Ram speed profiles satisfying the exit temperature and the load requirements are obtained. The proposed numerical simulation has been demonstrated to be a powerful tool for the design of hot extrusion processes.