LOAD CAPACITY OF OILFILM——LUBRICATED BALL-BEARING WITH SPIRAL GROOVES

In order to improve load capacity and stability of a fluid moving-pressure bearing, at present, measure of cutting grooves on a turning-shaft is generally adopted.The performances of spiral grooves are better in various groovetypes. Therefore, a theoretical analysis and an experimental investigation of the bearing with spiral grooves attract general attention. But the results of most articles published in china are numerical solutions of the computer. Using the methods of parameter perturbation in the paper, an approaching analytical solution of Reynolds equation of the moving-pressure oilfilm-lubricated ball-bearing with spiral grooves has been obtained. We have combined the numerical solutions of the computer, and the influence of the bearing parameters upon the load capacity is discussed; the optimum values of the groove parameter are obtained. The theoretical conclusion of this paper is in good agreement with the experimental data obtained by 651 Institute.     

Flexible shaft whirl induced by dry friction and its stability

This paper is devoted to the study of the whirling phenomena of flexible rotors due to dry friction. The mechanical model used here is a two-degree-of-freedom system in which the rubbing plane is not coincident with the rotating plane of the lumped mass. The characteristic equation of whirl speeds is derived and the whirling modes are obtained. The dynamic stability of each admissible whirling motion is also discussed. The results show that the whirl speeds are always higher than the critical speed of the shaft.     

迷宫密封湍流增阻的数值研究

迷宫密封是依靠节流间隙中的节流过程和迷宫空腔内的动能耗散过程来实现密封的,这两个流体流动过程从本质上规定了迷宫密封的密封性能。通过密封内部流动本质的研究,合理利用湍流流动的规律和特点,能够发挥密封内部湍流的增阻作用,提高密封性能。本文数值计算了一种锯齿型径向迷宫密封的内部流动,得到了密封内部的流动形态,揭示了密封内部流动与密封性能的关系。结果表示,密封存在一个最佳的齿插入长度。在最佳齿插入长度时,尽管节流间隙较大,但由于节流间隙内流动收缩和偏转,间隙的有效通流面积却很小,泄漏介质可以在间隙中获得较大的速度,在迷宫空腔内形成正确的耗散涡流,密封具有最佳的密封效果。所以,充分发挥湍流增阻的作用,可以突破节流间隙的微小尺寸限制,实现较大间隙下的良好密封。这不仅会给迷官密封的制造、安装及运行等带来很大的方便,而且可以为发展新的迷宫密封技术奠定理论基础。     

Reflection from 1D quasi-periodical structures

A theoretical investigation of 1D stationary and transient quasi-periodical dielectric structures is presented. A new approach for solving the problem of field interaction with such structures common for both stationary and transient cases, based on integral equations for the fields in transient media, is proposed. Some special cases of quasi-periodical structures with doubled quasi-periodicity are investigated numerically, showing that an additional complexity of the structure allows to obtain good filtering properties with a small number of quasi-periods. Transient structures with the same spatial dependencies, but with a time-dependent permittivity were also investigated.     

用STC格式求解二维激波─边界层相互作用问题

将空间－时间守恒（ＳＴＣ）格式应用于求解Ｎ－Ｓ方程,并对激波－边界层相互作用问题进行了计算．结果表明,该方法可捕获激波与边界层相互作用的各种现象,显示了优良的数值模拟性能。     

气液两相瞬变流数值计算及试验研究

在气液两相流计算中,人们通常给出气泡在液体中均匀分布的,与工程实际不符的假设,致使计算与试验结果之间相差较大。两相瞬变流计算也常看作均质的单相流来处理．本文由试验求得不同空间系数与波逐关系曲线,取消了均匀分布假设,改进了特性曲线法以适用于非均质的两相流计算,并将计算值与试验值进行比较,结果表明两者吻合得较好。     

波前延拓剪切干涉的数学原理与数值模拟

从数值方法的角度分析了常规剪切干涉存在的缺陷,通过数学原理和数值分析方法提出波前延拓剪切干涉,并证明了它的可行性及其对常规剪切干涉缺陷的克服。最后用数值方法模拟了波前恢复过程。     

纤维/金属网增强层板低速冲击损伤机理和演化

本文首先通过落锤低速冲击实验测试了纯玻璃纤维增强环氧树脂复合材料和304不锈钢丝网(SSWM)/玻璃纤维混杂复合材料的力学性能,探究了SSWM嵌入数量对混杂复合材料抗冲击性能的影响．随后采用Abaqus有限元软件建立了混杂复合材料的低速冲击模型,分别采用三维Hashin失效准则和Jason-Cook破坏准则模拟了纤维/基体和SSWM的损伤;建立了基于表面接触的内聚力模型来模拟界面分层;编写了VUMAT用户子程序定义混杂复合材料层合板的渐进失效过程．结果表明：相较于纯玻璃纤维增强环氧树脂层合板,SSWM/玻璃纤维混杂增强环氧树脂层合板的抗冲击性能更优,其中铺层形式为铺层III的混杂复合材料抗冲击性能最佳．通过对比发现有限元仿真结果与实验结果吻合良好,表明建立的模型适用于SSWM/玻璃纤维混杂增强环氧树脂复合材料低速冲击损伤的评估．通过分析仿真结果发现混杂复合材料的低速冲击损伤主要是冲击区域的纤维断裂、基体破坏和层间分层;SSWM通过吸收和传递冲击能量从而提升了混杂复合材料的抗冲击性能．     

660 MW超临界W火焰锅炉低负荷稳燃特性研究

"碳中和"、"碳达峰"的提出预示着未来煤电机组将在更低的负荷运行,用于燃烧无烟煤、贫煤等低挥发份煤种的W火焰锅炉低负荷运行时会出现燃烧稳定性问题.以某660MW超临界W型火焰锅炉为对象开展了针对低负荷稳燃特性的研究,进行了100％、60％、55％、45％ THA工况的试验研究与数值模拟解析,35％ THA工况理论预报....     

一维流体饱和粘弹性多孔介质层的动力响应

本文研究了不可压流体饱和粘弹性多孔介质层的一维动力响应问题。基于粘弹性理论和多孔介质理论,在流相和固相微观不可压、固相骨架服从粘弹性积分型本构关系和小变形的假定下,建立了不可压流体饱和粘弹性多孔介质层一维动力响应的数学模型,利用Laplace变换,求得了原初边值问题在变换空间中的解析解,并利用Laplace逆变换的Crump数值反演方法,得到原动力响应问题的数值解。数值研究了饱和标准线性粘弹性多孔介质层的动力响应,分析了固相位移、渗流速度、孔隙压力及固相有效应力等的响应特征。结果表明,与不可压流体饱和弹性多孔介质相同,不可压流体饱和粘弹性多孔介质中亦只存在一个纵波,并且固相骨架的粘性对动力行为有显著的影响。