巨型水轮发电机剪断销研发与质量控制

为获得设计需要的巨型水轮发电机剪断销的剪切力,得到剪切力波动受控的批量剪断销,通过拉伸试验、冲击试验、硬度试验和剪断销剪切试验等讨论了全尺寸剪断销剪切试验的可行性,分析了剪切试验时正常剪断和非正常剪断的剪断销材料性能差异,探究了剪断销的剪切力质量稳定性控制方法。结果表明:控制剪断销料坯的布氏硬度波动,可实现间接控制剪断销剪切强度的波动;通过试验总结的六步法可达到控制批量剪断销质量和剪切力波动的目的。     

燃气透平叶片尾缘内部冷却通道流动与换热特性研究

针对更为接近于真实叶片尾缘段的楔形内部冷却通道的流动与换热特性开展了数值研究,分析了不同冷却工质应用在楔形冷却通道中的性能表现以及不同扰流柱结构、柱肋组合冷却结构对尾缘内部冷却通道中的热力特性的影响.研究表明:区别于矩形内部冷却通道,楔形通道中壁面传热系数沿流动方向呈现逐渐升高的趋势;冷却工质对换热性能影响明显,蒸汽的...     

汽车活塞销用钢质量检验与改善试验

采用一种定性的塔形检测方法对活塞销用20CrH圆钢进行了检验分析,并与其他钢厂进行了对比。研究发现,该圆钢中心部分存在簇状黑线为中心的偏析线且较严重,不能满足用户要求。为改善中心偏析,对轧制加热工艺进行优化,效果不明显,需要进一步优化炼钢工艺,缓解铸坯中心偏析。通过这种定性的塔形检测方法,能够较为全面地反映活塞销的外工作面、内部质量和内孔质量,为活塞销用钢检验以及标准的制定提供了指导和参考。     

Research on the influences of torsional deformation on contour precision of the crank pin

The span and length to diameter ratio of the large-scale crankshaft are big,and the structure and the distribution of crank pins are complex.Thus it is easier for crankshaft to generate biggish torsional deflection which finally influences the contour precision of the crank pin in tangential point tracing grinding.Based on the analyses of force and torsional deformation of the crankshaft under different crankshaft driving modes of the headstock and the tailstock,the relationship between torsional deformation and rotation angle error of the crankshaft in tangential point tracing grinding is discussed in this paper.According to crankshaft rotational motion and wheel frame coordinated motion in tangential point tracing grinding,contour error of the crank pin caused by torsional deflection is established under different crankshaft driving modes.The simulation results show that minimum contour error of the crank pin can be obtained when crankshaft is synchronously driven by both the headstock and the tailstock,and speed error does not exist in tangential point tracing grinding.     

污秽地区玻璃绝缘子的选用

介绍了河南电网2001年1至2月发生大面积污闪的情况。分析了钟罩型绝缘子伞裙下棱槽容易积污,且不易自洁和人工清扫,容易引起污闪。提出了在某些污秽比较严重的地区,a、b、c、d四种形式的玻璃绝缘子不宜在直线串和耐张串上使用,e种形式的玻璃绝缘子可以在任何地区使用,选取原则必须遵从相应地区污秽水平爬距的要求。     

新型高温除尘技术的应用

高温烟气除尘技术落后,造成高温烟气污染治理处于十分尴尬的处境。机械转子离心除尘器是一种新型的超强离心耦合气动力分离高温烟气除尘技术,应用于手烧锅炉烟气除尘,意味着机械高温除尘技术取得了很大的进步。     

Operating principles of pin diodes

Analytical models of the pin diode in a small‐current operation are not known yet. This article presents a simple analytical model of the pin diode operation with its confirmation by a numerical simulation. At the onset, carrier recombinations are not included for the sake of simplicity. The exact J_F?V_F characteristic could have been induced only by accounting for the Boltzmann distribution of each carrier across the junctions and the diffusion current of each minority carrier in a p‐anode or n‐cathode. Based on this new model, the modifications of hole–electron densities product (n_en_h) across junctions, a rough estimation of the large operational current, its carrier distributions, and the effect of carrier recombination on the carrier distribution are plainly estimated and are also compared with the simulation results. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(4): 47–56, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20844     

MAX7000系列可编程器件应用技巧

MAX7000系列可编程器件的设计使用是一项实践性很强的专业技术,文中介绍了笔者在科研工作中的一些应用技巧心得。     

塑料上盖注射模设计

针对塑料上盖带有倒扣、侧凹坑、斜孔和表面质量要求高等特点,合理地选择了分型面和浇口形式,设计了镶拼式成型零件、弹簧侧抽芯机构以及斜推杆和推杆联合推出机构,解决了塑件脱模困难等问题,满足了塑件质量要求。     

活塞异型销孔轮廓测量仪的设计与应用

本文介绍了采用高精度杠杆测头测量活塞异型销孔轮廓的原理、测量仪硬件结构与配置,给出了测控软件模块构成。实际测量结果表明,该仪器能高效实现复杂销孔的精密测量,测量精度与国外先进测量仪器相当。