氯苯基硅油润滑球轴承在真空环境下摩擦性能与泄漏量研究

阐明氯苯基硅油润滑球轴承的润滑机理,对不同真空度和转速下的轴承摩擦力矩进行研究.在真空度3×10 ^-5Pa条件下,选用FY-3卫星“紫外臭氧垂直探测仪”光学调制器电机样机和进口电机进行8个月工程试验后,利用高倍显微镜分析试验轴承表观状态,并分析氯苯基硅油的泄漏量.结果表明:在3×10^-5Pa下,所用试验轴承的摩擦力矩值随着转速的增大而趋向稳定;氯苯基硅油润滑球轴承摩擦力矩的变化量为9.8×10^-4Nm,小于采用Maplub101润滑的进口电机轴承摩擦力矩变化量;试验期间氯苯基硅油的泄漏量为1.92mg,证明采用氯苯基硅油润滑适合光学调制器在真空环境下长期运转     

金沙江某水电站坝址区水化学特征研究

为解决开发大西南水能遇到的最大问题岩溶渗漏,以云南省金沙江某水电站为例,应用区域水文地球化学理论,分析了其坝址区水化学特征。结果表明,该区地表水与地下水化学特征比较类似,为判定大区域内岩溶系统是否属于同一流动系统,解决岩溶渗漏问题提供了可靠的基础地质资料。     

Solution of incompressible flows with or without a free surface using the finite volume method on unstructured triangular meshes

An incompressible Navier–Stokes solver based on a cell‐centre finite volume formulation for unstructured triangular meshes is developed and tested. The solution methodology makes use of pseudocompressibility, whereby the convective terms are computed using a Godunov‐type second‐order upwind finite volume formulation. The evolution of the solution in time is obtained by subiterating the equations in pseudotime for each physical time step, with the pseudotime step set equal to infinity. For flows with a free surface the computational mesh is fitted to the free surface boundary at each time step, with the free surface elevation satisfying a kinematic boundary condition. A ‘leakage coefficient’, ε, is introduced for the calculation of flows with a free surface in order to control the leakage of flow through the free surface. This allows the assumption of stationarity of mesh points to be made during the course of pseudotime iteration. The solver is tested by comparing the output with a wide range of documented published results, both for flows with and without a free surface. The presented results show that the solver is robust. © 1999 John Wiley & Sons, Ltd.     

基于分布式光纤的埋地自来水管多点泄漏定位方法分析

基于拉曼散射测温原理,利用分布式光纤对UPVC（硬脂聚氯乙烯）和铸铁自来水管道进行模拟泄漏点定位实验。首先对采集到的原始Anti-Stokes光信号进行滤波平滑处理,再利用相关系数法对温度检测信号进行分类分析,识别自来水管有无泄漏发生,最后通过选择性阈值法识别出UVPC管以及铸铁管中的泄漏点位置。实验结果表明,该系统运行稳定且能够准确识别自来水管泄漏情况。选择性平均阈值法的使用,能够对200 m的埋地自来水管道准确地进行泄漏点的定位,定位误差为0.25 m～0.65 m。     

多级轴流压气机间隙流动数值模拟

本文对某亚音轴流压气机的中间三排叶片进行定常与非定常数值模拟,分析在不同的动叶叶顶间隙和静叶气封间隙组合下压气机的流动特性。计算结果表明:定常计算条件下,叶顶间隙由0．5％叶高增大到2％叶高时,压气机的效率下降1．028％-1．034％,相同的气封间隙变化使效率下降0．108％-0．114％;非定常计算条件下,效率比定常计算高出 1％左右,并且叶顶间隙与气封间隙同时增大1％叶高时,效率下降约1％,与定常计算的规律相同。     

加载形式对涡轮叶尖泄漏损失的影响

本文通过改变90%叶高截面叶型的安装角和厚度分布获得了不同的加载形式,并采用数值模拟方法对比分析了加载形式对叶尖泄漏流动和损失的影响。结果表明,叶尖加载形式影响了泄漏流的流量和法向/流向速度差沿轴向的分布,进而影响泄漏流动损失。随着叶尖负荷向前缘移动,叶尖泄漏总流量增大,当泄漏量和动量差沿轴向分布相对均匀,当地峰值减小,叶中附近所占比重增加;在泄漏量与动量差共同作用下,泄漏涡卷起位置向上游移动,但与主流掺混强度减弱,损失减小;采用均匀加载和前加载形式能有效降低泄漏流与主流的动量差,减小泄漏损失,提高涡轮性能。     

基于Kriging代理模型的DBD等离子体控制叶顶泄漏流动研究

本文采用数值方法研究了布置于涡轮动叶叶顶的多个等离子体激励器组合对间隙泄漏流动的影响。结果表明:不同的极板数目和位置组合对间隙泄漏流量有着十分明显的影响。在叶顶沿吸力边布置等离子体激励器的最佳位置在大约55%S/Sps处,布置相同数目的等离子体激励器,在靠近尾缘处的控制效果要远好于在前缘附近的控制效果;等离子体激励器在叶顶靠近吸力边处产生诱导涡,阻碍了间隙内流体的流动,使泄漏流体的速度降低。同时还会使得分离泡的破碎提前,有利于减小掺混损失;对泄漏流动的控制效果不会随着等离子体极板数增加而持续增强,而存在一定限度,最优布置方式的泄漏流量较原型下降约46%,相应的出口截面能量损失下降了15.7%。     

Cryptanalysis and improvement of several quantum private comparison protocols

Recently, Wu et al(2019 Int. J. Theor. Phys. 58 1854) found a serious information leakage problem in Ye and Ji's quantum private comparison protocol(2017 Int. J. Theor. Phys. 561517), that is, a malicious participant can steal another's secret data without being detected through an active attack means. In this paper, we show that Wu et al's active attack is also effective for several other existing protocols, including the ones proposed by Ji et al and Zha et al(2016 Commun. Theor. Phys. 65 711; 2018 Int. J. Theor. Phys. 57 3874). In addition,we propose what a passive attack means, which is different from Wu et al's active attack in that the malicious participant can easily steal another's secret data only by using his own secret data after finishing the protocol, instead of stealing the data by forging identities when executing the protocol. Furthermore, we find that several other existing quantum private comparison protocols also have such an information leakage problem. In response to the problem, we propose a simple solution, which is more efficient than the ones proposed by Wu et al, because it does not consume additional classical and quantum resources.     

Mn掺杂对多铁性BiFeO_3薄膜铁电性能以及漏电流的影响

本文利用脉冲激光沉积技术在(LaAlO3)0.3(Sr2AlTaO6)0.7(001)衬底上生长了BiFe1-xMnxO3(x=0～5%)外延薄膜,研究了Mn掺杂对BiFeO3(BFO)薄膜结构、铁电特性和漏电流的影响.XRD和SEM结果表明薄膜具有良好的结晶质量.漏电流测量显示Mn掺杂有效地减小了BFO薄膜的漏电流密度,因而在室温下5%Mn掺杂的BFO薄膜能够获得饱和的电滞回线.XPS分析证明,Mn掺杂改善BFO薄膜性能的可能原因在于其极大地减少了BFO薄膜中的Fe2+离子.     

Effects of camberwise varying tip injection on loss and wake characteristics of a low pressure turbine blade

This paper presents the results of an experimental study that investigates the effects of camberwise varying tip injection on the total pressure loss and wake flow characteristics downstream of a row of Low Pressure Turbine (LPT) blades. This injection technique involves spanwise jets at the tip that are issued from a series of holes distributed along the camber line. The injection from each hole is individually and separately controlled using a computer driven solenoid valve and therefore the flow injection geometrical pattern at the tip can be adjusted to any desired variation. Three different injection cases are investigated including triangular, reversed triangular and uniform injection patterns. Here, triangular and reversed triangular cases refer to discrete blowing from the blade tip in which the blowing velocity increases (triangular) or decreases (reverse triangular) linearly from the leading to trailing edge along the camber. For uniform injection, the injection velocity is kept constant for all injection holes. The total mass injection from the tip is kept the same for all injection cases. The experiments are conducted in a continuous-flow wind tunnel with a linear cascade test section and measurements involve Kiel probe traverses 0.5 axial chords downstream of the blades covering a region between 85% and 100% span as well as two-dimensional Particle Image Velocimetry (PIV) measurements on 50%, 85% and 95% spanwise planes. For all injection cases, results show that tip injection reduces the total pressure loss levels in general. Highest measured overall loss reduction occurs in the case of reversed-triangular injection. The least effective waveform is observed to be triangular injection. There is significant reduction in the extent of the low momentum zone of the leakage vortex with injection. This effect is much less pronounced for the passage vortex. On the other hand, complex flow patterns are observed within the passage vortex, especially in the case of reversed-triangular injection, such as a possible embedded vortical structure along the passage vortex core, which creates double peaks in the velocity and turbulent kinetic energy fields.