大型水轮发电机通风发热场模型研究及通风结构优化计算

将大型水轮发电机的转子三维温度场与电机整体通风网络联系起来,形成通风发热综合计算过程,旨在准确地得到部件中的温度及其分布。并利用优化技术调整结构尺寸,使各部件中温度分布趋于均匀。本文的研究工作对于提高电机设计制造中材料利用率以及电机运行中的可靠性,具有重要意义。     

防爆型高功率密度电机温度场与流体场综合计算

根据对防爆型高功率密度电机额定运行状态的分析,建立其传热数学物理模型。通过电机气隙流体场计算给出了气隙换热面的表面散热系数,借此用有限元法对电机温度场进行了模拟;模拟结果与实验结果对比,两者能够很好地吻合,说明该传热模型可以真实有效地反映实际传热过程。根据计算结果分析电机的温度场分布规律,找出额定工作时温升最大的位置作为监控点,其结果可以为电机热控制的优化提供理论依据。     

Al基准晶薄膜/涂层研究进展∗

准晶材料固有脆性限制其作为结构性材料的应用,广泛用于表面薄膜/ 涂层,而得到高纯度准晶相与控制准晶相变仍是应用难点。 围绕 Al 基准晶在表面薄膜/ 涂层应用方面,介绍真空蒸镀、溅射镀膜、热喷涂、激光熔覆等常用制备工艺,总结各工艺的特点。 分析准晶薄膜/ 涂层的成分、冷却速度、热处理对准晶相变的影响,合理的制备工艺和适当的后续热处理对薄膜/ 涂层中形成高纯度准晶有显著提升。 讨论相变对薄膜/ 涂层的力学性能、疏水性、摩擦性、耐腐蚀性和抗氧化性的影响,分析准晶薄膜/ 涂层在减磨耐磨涂层、热障涂层、太阳能选择性吸收薄膜等领域的应用前景。 综述了近 30 年准晶薄膜/ 涂层的制备技术及改性研究的重要结果和研究现状,提出了准晶薄膜/ 涂层应用方面存在的问题并进行了展望。     

DEH在齐鲁热电厂60MW汽轮机上的应用

简介DEH-ⅢA型纯电液调节系统的优越性。针对齐鲁热电厂一期60 MW汽轮机液压调节系统上实施改造后暴露出来的问题进行了逐项分析,及时找出了解决办法,保证了4台机组的安稳运行。     

An energy conservative symplectic methodology for buckling of cylindrical shells under axial compression

This study concerns a theoretical analysis on the buckling of cylindrical shells under axial compression in a new energy conservative symplectic system. By introducing four pairs of dual variables and employing the Legendre transformation, the governing equations that are expressed in stress function and radial displacement are re-arranged into Hamiltonian’s canonical equations. The critical loads and buckling modes are reduced to solving for symplectic eigenvalues and eigensolutions, respectively. The obtained results conclude that buckling solutions are mainly grouped into two types according to their nature of different buckling modes: non-uniform buckling with deflection localized at the vicinity of the ends and uniform buckling with deformation waves distributed uniformly along the axial direction, and the complete solving space only consists of the basic eigensolutions. The influence of geometric parameters and boundary conditions on the critical loads and buckling modes is discussed in detail, and some insights into this problem are analyzed.     

保温时间对CaO-Al2O3-SiO2系多孔陶瓷显微结构和性能的影响

以二氧化硅微粉和高岭土为原料,纳米CaCO3为造孔剂,纸浆废液为结合剂,采用冷等静压成型,烧结温度为1000℃,保温时间分别为1、2和3h,制备出了CaO-Al2O3-SiO2系多孔陶瓷.采用扫描电镜观测试样的显微结构,对试样的体积密度、显气孔率和耐压强度进行了表征.结果表明:当烧结温度为1000℃时,保温时间越短,试样显微结构所呈微小孤立浑圆状气相越多,分布越均匀；当保温时间为1h,试样的体积密度为1.65 g/cm3,显气孔率为37.0％,耐压强度为77.18 MPa,具有较好的高强隔热综合性能.     

高速动车组速度传感器的电磁干扰测试与分析

结合现场实测,对CRH380BL型动车组速度传感器的电磁干扰问题进行了研究。首先分析了开关型霍尔传感器自身具有良好的抗干扰能力,指出当降弓时产生的电弧放电在车体上产生过电压时将会对其产生干扰。然后采用电偶极子理论分析了降弓时激发的电磁场的特性,从磁场在介质表面切向分量不连续的角度分析了车体过电压产生的原因,最后从传感器传输电缆屏蔽层接地方式的角度分析了车体过电压对传感器的干扰耦合机理。结果表明:降弓时产生的磁场强度最大值为54.07 d BμA/m,且频率主要分布在5 MHz附近,2号车厢车体过电压达600 V以上。车体骚扰电压会通过电缆屏蔽层与芯线间的寄生电容耦合到芯线内,对芯线中传输的速度信号造成干扰。通过在1车新增保护接地线后,有效地减小了电弧放电对速度传感器的电磁干扰。     

In situ biaxial stretching for the platelet formation of an ethylene–vinyl alcohol copolymer through multistage stretching extrusion and its effect on the gas‐barrier properties of polyethylene

The morphological evolution of ethylene–vinyl alcohol copolymer (EVOH) and its effect on the gas‐barrier properties of high‐density polyethylene (HDPE) were investigated. HDPE/EVOH blends were prepared through a multistage stretching extrusion, which combined an assembly of force‐assembling elements (FAEs) with an extruder. Scanning electron microscopy confirmed that with an increasing number of FAEs, the biaxial‐stretching field existing in each FAE transformed the dispersed EVOH phase into well‐defined platelets along the flowing plane. Dynamic rheological results further revealed that the formation of the platelets enlarged the interfaces between the dispersed barrier phase and the matrix; this not only led to the decline of the complex viscosity but also created more tortuous paths for the diffusion of gas molecules. Compared with that of the non‐FAE specimen blended with 25 wt % EVOH, the oxygen permeability coefficient decreased more than one order of magnitude when one FAE was applied. The structural model for permeability indicated that the enhanced barrier resulted from the increased tortuosity of the diffusion pathway, which was provided by the aligned high‐aspect‐ratio platelets. Compared with the previous biaxial‐stretching method, multistage stretching extrusion provided a simple and economical way to generate a laminar structure of the dispersed phase in the matrix phase without the application of an external stretching force. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40221.     

回收聚丙烯基复合材料的耐候性与阻燃性能

以回收聚丙烯（RPP）为基体,添加茶粉、纳米二氧化钛（Nano-TiO2）及聚磷酸铵（APP）制备了茶塑复合材料,并考察了茶粉、Nano-TiO2用量对茶塑复合材料性能的影响。结果表明,适量茶粉可提高RPP的抗拉强度,茶粉质量分数10%时,抗拉强度增加了26.1%;Nano-TiO2既能增加茶塑复合材料的抗拉强度,也可抑制热老化过程中抗拉强度的下降,从而增加了材料的耐候性。考察了Nano-TiO2与APP对茶塑复合材料阻燃性能的协同作用,发现Nano-TiO2与APP共同作用能进一步降低茶塑复合材料的水平燃烧速度。在Nano-TiO2质量分数为4%时,水平燃烧速度最低,仅有23.3 mm/min,比不含Nano-TiO2时降低了40.6%。当固定Nano-TiO2质量分数为4%,改变APP用量时,在APP质量分数为15%时,水平燃烧速度仅为20.2 mm/min。