基于虚拟仪器检测系统测射流冲击器性能参数

目前经常应用的液动冲击器冲击性能参数的测试方法有多种,但均存在某种缺陷。为此给出了一种测试射流冲击器性能参数的方法,即基于LabVIEW虚拟仪器平台的检测系统,用于测试射流冲击器的冲击功及频率。介绍了冲击频率检测电路、声音拾取电路、声音传送及变换电路。通过系统压力检测电路,可测得冲锤活塞上、下腔压力,求得冲锤活塞的单次冲击功。该方法具有操作简单、测试方便、成本低、开发周期短、测试可靠、精度较高等优点。     

大型电站叠梁门分层取水进水口水力特性研究

电站进口前加设叠梁门后引起局部水流条件复杂,本文以模型试验和数值模拟为研究手段,系统阐述了叠梁门分层取水进口水流流态、门顶最小运行水深、水头损失和叠梁门反向附加水击压力等。研究表明,加设叠梁门后机组各栅孔进流较为均化,门井水面波动加大,主要引流区间在门顶以下10 m—门顶以上25 m水域,叠梁门门顶最小运行水深一般为15~30 m,进口段水头损失1.20~1.95 m(水头损失系数为0.45~1.15),较无叠梁门时增大1.11~1.63 m,对机组发电经济效益将产生一定影响,机组甩负荷对叠梁门下游面板产生的附加水击压力(2.9~3.0)×9.81 k Pa。     

空气锤钎头齿孔过盈配合数值模拟研究

传统方法在研究空气锤钎头齿孔过盈量问题时大都是针对单个齿孔进行的,而且对模型进行了过度简化,没有考虑钎头本体的复杂几何外形和相邻孔间应力的相互影响,无法得出整个钎头体上的应力分布。为此,分别用弹塑性力学方法和有限元方法对齿孔在不同过盈量下的应力分布情况进行了计算。结果表明,弹塑性分析与有限元分析结果一致,钎头中心齿齿孔过盈量取0.05～0.06mm、边齿齿孔过盈量取0.06～0.07mm时较合理,弹塑性力学方法的计算值比较保守,但仍有重要的参考价值。利用ANSYS软件对钎头齿孔过盈配合进行有限元计算,是改进齿孔设计的有效方法,此方法也可用来分析PDC钻头和牙轮钻头齿孔过盈配合问题。     

TVD格式在上游调压室水击数值模拟中的应用

为了模拟含上游调压室水电站的水力过渡过程,采用TVD格式求解水击方程,并结合调压室系统的基本方程组和给定的边界条件来模拟水击压力变化。将此方法用于工程实例,其计算所得的水头与实测水头相吻合;并将计算所得的水头与MacCormark 格式和Lax-Friedrichs格式的计算结果比较,结果表明：TVD格式能有效模拟含上游调压室的水击现象,其结果具有耗散性低,不产生虚假数值震荡,计算精度高等优点。     

Scouring at Bed Sills as a Response to Flash Floods

The temporal development of clear-water local scour depth at bed sills in uniform gravel beds is considered. Experiments are presented on the development of scour holes under unsteady hydraulic conditions, with the triangular-shaped hydrographs tested being of different durations and different rates of flow variation. Based on the experimental results and a theoretical framework, a method is given for the definition and prediction of the scouring process under unsteady flows in terms of a dimensionless temporal parameter. A “flash flood” is here defined as an event for which the scour doesn’t attain its potential magnitude, i.e., the equilibrium value for the peak hydrograph flow rate. This flood nature is dependent on both the characteristics of the flood event itself and the characteristics of the stream. A quantitative measure of what constitutes a flash flood is given in terms of the identified temporal parameter. Results show that the ratio between the final scour depth and the potential scour depth at a bed sill for a given hydrograph can be estimated as a function of the identified temporal parameter.     

Phthalocyanine molecular nanowires that were prepared using porous alumina as a template: Development in the sample preparation procedure to evaluate electronic properties

We have proposed the synthesis of organic molecular nanowires using porous alumina as a template. We also proposed the use of a magnetic field to control the molecular packing structure in the nanowires. In this paper, we developed the method to evaluate the electronic properties of the nanowire of a phthalocyanine derivative that was synthesized using porous alumina as a template. The developed method facilitates the study in the organic molecular nanowires that were synthesized using templates and helps their use in future electronic devices.     

全套管薄壁灌注桩在山区某工程基坑支护中的应用

结合工程施工实例,介绍了全套管薄壁灌注桩的施工工艺流程、关键工序的主要事项,并与其它大直径灌注桩进行对比,说明该桩型作为基坑支护的围护桩具有较大的经济社会效益和广阔的市场前景,同时也对存在的问题做了总结。     

Precision emulsification for droplet and capsule production

Emulsions and microcapsules are typical structures in various dispersion formulations for pharmaceutical, food, personal and house care applications. Precise control over size and size distribution of emulsion droplets and microcapsules are important for effective use and delivery of active components and better product quality. Many emulsification technologies have been developed to meet different formulation and processing requirements. Among them, membrane and microfluidic emulsification as emerging technologies have the feature of being able to precisely manufacture droplets in a drop-by-drop manner to give subscribed sizes and size distributions with lower energy consumption. This paper reviews fundamental sciences and engineering aspects of emulsification, membrane and microfluidic emulsification technologies and their use for precision manufacture of emulsions for intensified processing. Generic application examples are given for single and double emulsions and microcapsules with different structure features.     

Hydraulics of Tangential Vortex Intake for Urban Drainage

A tangential vortex intake is a compact structure that can convey storm water efficiently as a swirling flow down a vortex dropshaft. It has been studied in physical models and successfully employed in urban drainage and hydroelectric plant applications, but a comprehensive account of the key flow characteristics has not been reported and a theoretical design guideline of a tangential intake is not available. In this study the hydraulics of tangential slot vortex intakes is investigated via extensive experiments. It is found that the flow in the tapering and downward sloping vortex inlet channel is strongly dependent on the geometry of the inlet and dropshaft. Under some conditions, hydraulic instability and overflow can occur, rendering the design ineffective. It is shown that the hydraulic stability depends on the discharge at which flow control shifts from upstream to downstream (Qc), as well as the free drainage discharge (Qf). A theoretical design criterion for stable flow is developed in terms of Qf and Qc as a function of the vortex inlet geometry. For a “stable” design, the flow in the tapering inlet evolves from supercritical flow to subcritical flow smoothly as the discharge increases. Fifteen different tangential vortex intake models are tested. The experimental observations are in excellent agreement with the theoretical prediction. The present study provides a general guideline for designing a tangential vortex intake that can convey the flow smoothly without unstable fluctuating flow associated with a hydraulic jump.     

Experimental and numerical study of ball size effect on restitution coefficient in low velocity impacts

In this article, the Coefficient of Restitution (COR) and Energy Loss Percentage (ELP) of one-dimensional impacts are determined experimentally for different ball sizes using a drop test apparatus. Ball diameters range from 6 to 12 mm, made of steel and aluminum dropped on steel and aluminum sheets.