Wavelike gas dispersion in a liquid in a compressor-free environment

An experimental investigation has been performed regarding the operation of a new type of wave-generating gas disperser in a liquid in entrainment mode in a compressor-free environment. The wave-generating disperser and ejector-caused gas flow relationship with the water pressure at the disperser inlet under different design factors has been obtained. The gas bubbles’ average size has been measured in a biphase stream leaving the disperser. Recommendations for the selection of the disperser parameters have been submitted. The goal of this work is the simplification of plants intended for dispersing gas in a liquid, diminishing the gas bubbles’ size, and reducing the dispersion energy flow. This is a pressing problem for many chemical technology targets, for wastewater biological treatment systems, and for chlorinating or ozonizing tap water.     

An electric arc in a helium flow in a high-current plasmatron

Experimental studies of an electric arc in a helium flow are described. A generalized dependence of the electric field on the determining criteria has been obtained on the basis of the experimental data, and a plasmatron has been designed on the basis of the technique developed. Its thermal efficiency is 0.68–0.74, and the mass-averaged temperature of the helium flow is T = 3700–4200 K. The plasmatron can be used in various technological processes involving energy conversion.     

Analysis of a mitered joint in a cylindrical shell in bending

The problem of in-plane bending of a single unreinforced mitered joint between two cylindrical shells of equal diameter is analyzed according to thin shell theory. The solution is constructed by the method of matched asymptotic expansions. Formulas for the stress amplification factor and flexibility factor are derived and comparisons are made with available test results.     

Operation of a Dilution Refrigerator in a Micromode

Two design versions of a ³He-in-⁴He dilution refrigerator with ³He pumping out through its condensation on a cold wall are described: a classical refrigerator with a heat exchanger and a refrigerator with a collector that allows for operation in a quasi-single mode. The refrigerator operated stably in both cases when a power of 30 W was fed to the still, i.e., at a circulation rate of ³He of a few micromoles per second. In this case, the mixing chamber was cooled down to a temperature below 0.05 K.     

Diagnostics of a cavity in a prismatic beam

A beam with a cross section in the form of a hollow rectangular box is considered. A method for calculation of the dimensions of a cavity in a beam by two natural bending frequencies that are taken from different spectra is proposed. These are the spectra of vibrations in two mutually perpendicular planes that are chosen in such a way that the neutral axis of the cross section is parallel to the sides in both cases. The dependence of the natural frequency on the cavity’s parameters is studied. It is proven that the frequency values of the beam under investigation and of an identical beam with a solid cross section do not coincide at any size of the cavity and the natural frequency values of the former beam are always higher than those of the latter one.     

PIV measurements in a turbulent wall jet over a backward-facing step in a three-dimensional,non-confined channel

A study of a turbulent wall jet over a backward-facing step is especially of interest because it shows a rich phenomenon flow and a mechanism to alter the flow characteristics downstream of the step. However, studies on this flow configuration are rare. In this paper, we considered this flow configuration in a non-confined channel as the specific engineering applications of electrical rotating machines and alternator that can be found in modern wind generators of the power production industry and automobile engines. The turbulent wall jet over a backward-facing step in a non-confined wind tunnel had the jet Reynolds number of 24,100 and the step Reynolds number of 11,900. Particle image velocity (PIV) and stereoscopic PIV measurements were performed along the central plane and several cross-stream planes. Numerical simulation of the test configuration was conducted by solving the three-dimensional Reynolds Averaged Navier–Stokes (RANS) equations with the second-order closure Reynolds stress model (RSM). The mean flow fields and second-order statistical moments from the RSM simulation were compared to results that were obtained through the PIV and stereo-PIV experiments. The mean reattachment length obtained from the current configuration was much shorter than those from the backward-facing step in the plane channel. The stereo-PIV measurements in the cross-stream planes revealed a high three-dimensionality of the flow, a high population of streamwise vortice in the upper region, near the side walls and the corners formed by the side walls and the bottom wall. The obtained results also confirmed the presence of the wall-jet formation on the bottom wall.     

The field of a finite defect in a plate

An equation for determining the magnetic field of a plate inside which there is a cavity of finite dimensions with a smooth boundary has been obtained on the basis of the integro-differential equation of magnetostatics. A particular problem has been solved for a spherical cavity and an external uniform magnetizing field directed parallel to the plate surface.     

Remote control of a robot in a map network

The automated control of manufacturing devices on a common communications network is a necessity for the factory of the future. The manufacturing automation protocol (MAP) represents a major effort by a group of companies towards meeting this need, and apparently is becoming a standard for factory-floor communications. In this project, an ASEA 2000 robot was used with a computer-controlled ply-cutting machine in a simulated factory sheet-metal cell to demonstrate coordinated inter- and intra-cell communications. Both machines used a MAP network to send and receive information from the cell-controller computer, and to coordinate cell operation. The methodology, hardware and software required to adapt the ASEA robot to the MAP network are described. This methodology will be useful in adapting other computer-controlled manufacturing devices to MAP networks.     

Laminar Flow in a Recess of a Hydrostatic Bearing

The flow in a recess of a hydrostatic journal bearing is studied in detail. The Navier-Stokes equations for the laminar flow of an incompressible liquid are solved numerically in a two-dimensional plane of a typical bearing recess. Pressure- and shear-induced flows, as well as a combination of these two flow conditions, are analyzed. Recess friction, pressure-ram effects at discontinuities in the flow region, and film entrance pressure loss effects are calculated. Entrance pressure loss coefficients over a forward-facing step are presented as functions of the mean flow Reynolds number for pure-pressure and shear-induced laminar flows.     

Flow around a flexible plate in a free stream

This paper presents a numerical scheme for fluid-structure interaction, especially for flexible structures. The lattice Boltzmann method with an immersed boundary technique using a direct forcing scheme is used for the fluid, and a finite element method with Euler beam elements is used for the flexible plate. The direct forcing scheme of the lattice Boltzmann method was improved for the immersed boundary scheme by introducing the occupation ratio of fluid lattices among the interpolated lattices. We compared the results of our proposed scheme with the known results of conventional schemes. Using the proposed numerical scheme, the flow around the flexible plate in a free stream is simulated for the effect of flexibility. Our results show that the major role of the flexibility of the flexible plate is the reduction of the resistance from flow. From the unsteady flow around a flexible plate, we found that the St of the flexible plate up to Re < 80 increased regardless of plate flexibility, but the St in the range of Re > 120 was dependent on plate flexibility. In the range of Re > 120, the St of very flexible plate increased with increasing Re, while the St of rigid plate decreased with increasing Re.     

装载机铲掘作业的轨迹规划

为给装载机的铲掘作业寻找一条能耗较小的铲掘轨迹,根据经验及有关文献给出的较理想的直线和曲线两种铲掘作业的轨迹方程,经过对装载机铲掘作业的轨迹规划及运动学建模,实现铲掘轨迹由直角坐标空间向关节空间转换以及由关节空间向驱动空间转换,得到动臂油缸和转斗油缸的驱动方程,并给出铲斗在实现铲掘轨迹的过程中所受的作用力。对在ADAMS环境下ZL40装载机仿真模型进行仿真,结果表明,装载机在同样时间内完成同样的作业量下,直线铲掘轨迹所作的总功小于曲线铲掘轨迹。     

Synthesis of a precision coupling in a piston transmission

A design for a precision coupling in a piston transmission is proposed. A method is outlined for the geometric synthesis of the mechanism when the piston’s working part has a circular profile.     

Steady rotation of a sphere in a paramagnetic fluid

The steady rotation of a non-conducting sphere in an unbounded electrically non-conducting incompressible paramagnetic fluid was investigated. An external magnetic field acted parallel to the axis of rotation. The non-dimensional partial differential equations governing the magnetic field, magnetization and velocity were solved numerically. The magnetic field is comparatively weak in the radial direction and strong in the transverse direction over regions nearer the sphere. At points equidistant from the sphere the radial component of the magnetic field is maximum at an angle 14° from the axis. At points equidistant from the centre of the sphere the transverse component of the magnetic field is maximum at points near the equator and minimum at points near the axis. The magnetization increases with the applied magnetic field. At points near the equator and the axis the dipoles are oriented almost parallel to the applied magnetic field. In the remaining region they make an angle with the direction of the applied field which decreases with increasing applied magnetic field until at saturation magnetization they are oriented in the direction of the applied field. At points very near to the sphere the velocity is not affected by the magnetic field. Away from the sphere magnetization retards the flow.     

What's in a network

Ever wondered what all this networking business is all about? Angela Grigson takes you back to basics.     

某变速箱内齿圈加工技术

通过数据分析找出影响内齿圈变形的因素,提高机械加工尺寸精度,改善加工方法,优化热处理工艺参数和调整装料方式,减少渗碳时热应力引起的变形,确定采用整体花键芯模定位滑块挤压外圆淬火,控制薄壁内齿圈淬火变形,确保不磨齿,满足精度要求。     

How to obtain a thickness-independent image in a STEM

"Z" contrast is independent of thickness only for extremely thin specimens (3 nm of carbon). Following Egerton [Ultramicroscopy 10 (1983) 293], we propose a new method of imaging which is really independent of thickness and which provides absolute values. It consists of a mixing of the unscattered, the annular darkfield and the inelastic signal. Two-dimensional histograms are used to determine the relative efficiency factors of the different images. Thus, in addition to the obtaining of lambda i/lambda e images, the method allows the calculations of the ratios of the detection factors, of the primary beam intensity image and the production of image free of beam fluctuations. An example of such a treatment is given for a biological specimen with knife-marks.     

集散控制系统在啤酒厂糖化车间的应用

本文简介了工控组态软件 T350 0、欧陆下位机的特点 ,给出了一个在啤酒厂糖化车间应用的实例。