弯管顺序输送影响因素研究

相邻批次的油品在进行成品油顺序输送时会产生一定量的混油。通过CFD软件,针对弯管顺序输送的条件下通过改变流速、粘度和弯径比来进行研究比较。结果表明,流速越小混油油头越尖锐,并且流速越大混油油头越靠近管道弯曲处;而后行油品粘度较大的比粘度较小的混油油头的位置相对滞后;弯径比较大的管道混油流经下游管段时混油段长度越长。其结果与工程现象基本吻合。为实际生产提供了一定的理论参考。     

开敞式混流泵内流的数值模拟与出水机构选择

为了给新型开敞式混流泵的设计积累经验并为特殊出水流道结构设计提供方法,对具有不同出水机构的开敞式混流泵进行数值模拟,分析从小流量到最大流量下的内部流动和水力性能,提出适应特殊液压动力需求的开敞式出水机构方案。给出内部流动数值模拟和性能预测的方法,通过外特性预测结果与模型试验数据的比较,验证数值计算的可靠性。在模型分析基础上,针对轴向有导叶、轴向无导叶和径向无导叶等不同的开敞式出水结构形式,进行整机内部流动分析和外特性预测,对不同结果进行比较分析,给出不同出水机构对于特定结构和动力需求的适应性。     

多目标追逐问题的一种混合整数线性规划解

研究多车辆多目标追逐的路径规划问题。提出两个基于混合整数线性规划 (Mixed integer linear programming, MILP) 的多目标追逐 (Multi-target pursuit, MTP) 模型：就近追逐和“一对一”使能追逐。在两个MIP追逐模型中,小车运动的状态方程考虑为具有线性阻尼的质点动力学方程。采用整数变量描述小车与障碍物的相对位置信息,提出 “目标膨胀尺寸”的概念来描述对目标的追逐,定义小车的“追逐方向”。采用选取整变量的等高面法求解MILP追逐问题,并给出初始内点整变量的确定方法。最后给出仿真试验1对两个多目标追逐模型进行对比研究,仿真试验2证实了算法的效率。     

Confidence bounds on component reliability in the presence of mixed uncertain variables

Uncertainties in a physical system can be modeled and analyzed by using probability theory or possibility theory, depending on the amount of information available. In probability theory, uncertain variables are modeled using probability density functions (PDFs) and then propagated through the system to obtain its reliability. In the absence of sufficient data to model a PDF, possibility theory, in which variables are represented using fuzzy membership functions, can be used to propagate uncertainty. However, when dealing with a combination of both probability distributions and fuzzy membership functions, the computational cost involved in estimating the membership function of reliability increases exponentially because one reliability analysis, which is a computationally expensive procedure, is performed at each possibility level to obtain the bounds on the reliability of the structure. To improve the computational efficiency, a technique that uses response surface models and transformations of possibility functions is presented in this paper. The efficiency and accuracy of the proposed methodology is demonstrated using numerical examples.     

Global and local analysis of gear scuffing tests using a mixed film lubrication model

Gear tests were performed in a FZG test rig in order to evaluate the influence of the operating conditions (torque, speed and oil bath temperature), gear geometry and base oil viscosity on gear scuffing.A mixed film lubrication model was used to evaluate the normal pressures and shear stresses in several points along the gear meshing line, for each load stage and for all the gear scuffing tests performed.The gear scuffing results were analyzed using two different approaches: one considering global gear parameters defined at the meshing line scale and another based on local parameters at the roughness asperity scale, determined using the mixed film lubrication model.The analysis at the roughness asperity level was used to complete the scuffing study performed with global gear contact parameters, explaining the occurrence of scuffing during ‘running-in’, justifying the zones in teeth flanks where the first scuffing marks appear and supplying indicators for low scuffing resistance at high oil bath temperatures.     

Film-forming capability in rough surface EHL investigated using contact resistance

Highly loaded machine elements such as gears and cams have a non-smooth surface topography that is created during manufacturing. It is well known that the film-building properties of such surfaces may be different from those that are perfectly smooth. The capability to form a separating film may also be altered in time due to run-in phenomena. In this study, a smooth steel ball was loaded against rough steel discs and run under pure rolling as well as sliding conditions. Several different steel surfaces were tested under nominal EHL conditions, where the contact was monitored by means of its electrical resistance and capacitance. Each surface was first run in for 15 min, followed by a sweep-in speed determining the lift-off curve. Electrical contact measurements were continuously conducted during run in as well as lift-off. Fully formulated gear oil and its base fluid were used as test lubricants. Results show that run in of a surface seems to be a competition between conformation of surface topography and tribofilm formation. At the tested conditions, the formation of a tribofilm is dependent on the initial surface topography and is created rapidly causing less metal–metal contact. This film also seems to effectively prohibit changes in surface topography causing less structural run in than expected.     

气质联用仪的微分流技术测定混合芳烃中的三甲苯含量

针对进口混合芳烃中的"X"类有毒物质,建立混合芳烃中三甲苯含量的气质联用(GC-MS)测定方法。运用气相色谱质谱的微分流技术,对混合芳烃中的3种三甲苯的同分异构体进行定性和定量分析,该方法准确度高,回收率99.06~101.8%,最大标准偏差0.04%。     

基于四叉树法和波前法的曲面网格剖分算法

提出了一种基于四叉树法和波前法的有限元网格生成算法。该算法首先将裁剪曲线边界离散成多边形,然后使用四叉树法对待划分裁剪参数曲面按细分要求进行递归分解,最终生成规则的栅格点,最后利用波前法的原理生成三角形网格,通过合并处理生成三角形与四边形混合网格。     

高喷雾化机风源的比较研究

采用Fluent软件计算了斜流式风机和轴流式风机在相同的叶轮尺寸和进气条件下叶轮内部及通流部分的流场.计算结果说明:高喷雾化机风源,斜流式风机比较适宜.     

Identification of material hardening parameters by three-point bending of metal sheets

Calibration of hardening and partly viscoplastic parameters of the previously published material model was the primary concern of this paper. The method used for identification of the material hardening parameters for metals, the three-point cyclic bending of sheets, constitutes a basis for this work. Plastic hardening parameters were determined by comparing load–displacement curves from FE simulations with those from the tests. Since viscoplasticity is assumed, stress–strain curves from uniaxial tension tests at selected strain rates for strain-rate sensitive materials were employed to calibrate corresponding viscoplastic parameters. The optimization problems are solved by means of a commercial optimization code, LS-OPT, using a response surface methodology. The objective is to minimize (by the least-squares method) the sum of the differences between measured and simulated loads. The material parameters were identified for two high-strength steel alloys (ZSte340 and DP600, strain-rate sensitive materials), and one aluminium alloy (AA5182).