Effect of the Wet Outlet Geometry on the Shockwave Position in Supersonic Separators

Supersonic separators (3Ss) are applied in gas separation processes. Two-dimensional simulation is employed to investigate the effect of operational and thermophysical parameters on the shockwave position. In addition, the impact of the cyclonic part and wet outlet geometry is evaluated by proposing four cases. Increasing the length of the cyclonic part exerts positive and negative influences on the performance of the 3S and the pressure recovery coefficient, respectively. The optimum length is determined between 10 and 15 cm. To demonstrate negative effects of wasted air from the wet outlet, its flow has been increased from 3.6 to 8.1 % of the inlet flow. Improved performance of the 3S is obtained by reducing the flow disturbances around the wet outlet and moving the shockwave towards the outlet.     

Effect of Samples Cutting Position and Gage Length or Specimen Geometry on the Mechanical Properties of Woven Thermoplastic Prepreg

Abstract

Woven composites are getting acceptance in many engineering applications such as tranportation, construction and automotive, albeit in most instances are rather confined to those of thermoset matrices. In view of many favourable circumstances, thermoplastic based systems are slowly gaining recognition which can be easily attributed to their unique properties. For example, these include better damage tolerence, ease of handling, recyclability, etc. However, they are always referred to those derived from fabrics, either impregnated or otherwise. Here, an alternative system was realized by utilizing the impregnated towpreg or simply continuous fiber impregnated thermoplastic (COFIT). Results on composite testing, using tensile measurement as an example apart from type of towpregs, weave characteristics, etc., it clearly shows that the tensile properties of any woven structures are dependent on specimen cutting position coupled with gage length too. Generally, the woven system's properties are manifested by the presence of what is called weave characteristics such as interlaces, floats length, crimps, etc.     

旋流燃烧室内冷态和热态流场的三维数值模拟分析

采用RNGk-ε湍流模型以及有限化学反应速率涡破碎模型(Eddy break up)对Allied Signal公司75 kW微型燃气轮机旋流燃烧室内冷态和热态时气流三维流动过程进行了模拟计算。结果表明,燃烧室火焰筒内热态时与冷态时的流场相似,烧室火焰筒内都有3个回流区,3个回流区的存在将有助于燃料的连续点火和火焰的稳定;燃烧室内热态三维流场的中心回流区长度小于冷态时的中心回流区长度,气流的轴向速度也大于相应的冷态轴向速度,而且掺冷孔空气射流对环向速度分布的影响小于冷态时的影响。     

Swirling effects on the performance of the micro-particle acceleration and penetration: parametric studies

A unique biomedical delivery system (biolistics), for micro-sized powder formulation of drugs (typically protein- and/or DNA-based macromolecules) to be effectively and efficiently delivered into human skin or mucosal tissue for the treatment of a scope of diseases, has been proposed. One of the key concerns for designing and evaluating the biolistic system is to warrant that micro-particles are accelerated and penetrated in to the skin with a controllable velocity range and uniform spatial distribution for optimal targeting the cells of interest. In this paper, we numerically interrogate the performance of a prototype biolistic device, designed for a uniform micro-particle acceleration and penetration. Swirling effects on the gas-particle dynamics, the particle acceleration and penetration as well as the device performance are presented and interpreted. Variations of the micro-particle velocity range and spatial distribution with swirl ratios are examined. The ability of the micro-particles penetrating in to a model skin target is demonstrated and discussed.     

旋流器和喷嘴对燃烧器性能影响的数值模拟研究

旋流器和喷嘴是多通道燃烧器的重要部件,其性能参数直接决定了燃烧器的使用性能。通过用FLUENT方法数值模拟多通道燃烧器的旋流器和喷嘴,研究了旋流角度和喷嘴数量对燃烧器性能的影响,所得结果用于燃烧器的设计,可以优化燃烧器的性能,提升煤粉的燃烧效率,更加灵活地调整火焰形状,确保熟料的煅烧效果。     

化工压力容器开孔接管区过渡圆角的研究

利用ANSYS有限元分析软件,对化工压力容器的开孔接管区进行数值模拟,研究不同的内外侧过渡圆角对开孔区域应力的影响。分析结果表明外侧圆角越大,开孔区域应力越小,内侧圆角对应力的影响较小。     

The Effect of Catalytic Washcoat Geometry on Light-off in Monolith Reactors

This paper presents the results of a series of simulations of the light-off of carbon monoxide in excess oxygen in a single channel monolith reactor. The catalytic washcoat geometry is tested for its effect on the light-off position and shape. The simulations used a combination of two and three-dimensional modelling with non-linear oxidation kinetics. Different temperature ramp rates were employed. It is seen that the shape of the washcoat has an influence on the shape of the light-off curve, especially for high values of gas hourly space velocity and larger temperature ramp rates. The washcoat geometry that gives the fastest rise to complete conversion is the one that is the most non-uniform in shape; that is, the one that has thin sections.     

氧化锆质定径水口在使用温度下矿物组成分析

为研究连铸用氧化锆质定径水口在使用温度下矿物组成和微观结构,对以氧化镁部分稳定氧化锆(Mg-PSZ)为原料制备的定径水口产品进行模拟实验研究.实验条件为:模拟浇钢使用条件试样在1540℃×5h后水淬冷却,模拟翻包后自然冷却条件试样在1540℃×5h后随炉冷却.借助X-ray荧光分析仪、X-ray衍射仪、扫描电子显微镜对试样的矿物组成及显微结构进行表征.研究结果表明:以Mg-PSZ制备的氧化锆质定径水口产品在1540℃浇钢温度下矿物相以立方相为主,在翻包自然冷却过程中,缓慢的冷却速率导致部分立方相转变为单斜相,矿物相以单斜相氧化锆为主.氧化锆质定径水口产品在高温使用环境中结构均匀,平均颗粒尺寸10 μm,而翻包自然冷却后,由于缓慢的冷却速率,定径水口产品中稳定剂脱溶,导致立方相转变为单斜相氧化锆,平均颗粒尺寸7 μm.即通过翻包自然冷却后所取试样的研究结果不能代表氧化锆质定径水口在中间包浇注过程中实际使用状态.     

空气层对干喷湿法聚丙烯腈原丝喷头稳定性的影响

为提高聚丙烯腈碳纤维原丝干喷湿法喷头的稳定性,从空气层高度、温度、湿度、空气流动状态等角度,综合分析了空气层对喷头稳定性的影响。通过试验,确定了各干扰因素的控制范围,为控制喷头稳定性,提供了重要的理论和试验数据基础。     

旋风分离器入口结构改进及其对“短路流量”的影响

常规切向进口旋风分离器的气流进入旋风分离器后必定要经过排气芯管外壁和筒体内壁之间,因此不可避免会使得相当一部分气流没有经过分离空间而直接从排气芯管底部排出(短路流量),这也是影响旋风分离器分离效率的重要因素之一。在前人工作的基础上,对旋风分离器的进口结构进行了改进:使得旋风分离器的入口具有一定截面角,并借助数值计算技术,分别对传统的和具有一定入口截面角旋风分离器内的三维流场进行了数值模拟,计算了芯管底部的"短路流量",结果表明:进口具有一定截面角可以明显减小芯管底部的"短路流量",这对改善旋风分离器的分离效率具有重要的实际意义。     

Influence of Different Woven Geometry and Ply Effect in Woven Thermoplastic Composite Behaviour-Part 2

Abstract

Works on woven composite both thermoset and thermoplastic are numerous, however in most instances they involve the use of preimpregnated fabric. It is apparent that woven thermoplastic system has significant potential due to the combined properties such as better damage tolerence, recyclability, easy processing, storage, etc. Here work on woven thermoplastic composites based on Continuous Fiber Impregnated towpreg (COFIT) tape rather than conventional approach is reported. The influences of different woven geometry and ply effect were investigated. Correlations between different woven geometry and weave characteristics were also noted. In general, the woven composite properties are influenced by many process variables such as type of towpreg, woven geometry, number of plies etc.     

Investigations of effect of radial flow impeller type swirl generator fitted in an electronic heat sink and Al2O3/water nanofluid on heat transfer enhancement

In this paper experimental investigations on convective heat transfer and pressure drop characteristics in a novel electronic heat sink fitted with dynamic mixers using water and Al₂O₃/water nanofluid are presented. For this, Al₂O₃ nanoparticles of average size 47 nm are synthesized using microwave assisted chemical precipitation method and characterized using XRD and SEM. Heat transfer and pressure drop characteristics of water and nanofluid are studied in the electronic heat sink of base size 60 mm × 60 mm made of copper with and without the dynamic mixer. The enhancements in the heat transfer and pressure drop results are compared with water and the heat sink without any mixer. The results reveal that there is significant increase in the convective heat transfer when the dynamic mixer is used for enhancing the heat transfer and further increase in heat transfer is found for the nanofluid. The rise in pressure drop compared with the increase of heat transfer is less.     

液体火箭发动机喷管化学反应黏性流场数值模拟和实验验证

运用耦合点隐式方法的MacCormak两步差分格式求解N-S方程,对喷管中的可压、黏性、湍流流体的流动,进行了数值模拟,得到了一些实验不能得到的参数分布,研究结果对发动机的设计、性能和理论研究具有重要的实际意义和参考价值,最后用实验对数值模拟结果进行了验证。     

Measurement of Consumed Energy Due to the Two-Phase Pressure Drop in a Pulsed Semi-Industrial Column: Effect of Geometry

This article deals with the evaluation of pressure drop and consumption of energy for a steady-state solvent extraction in a horizontal pulsed sieve-plate column, which are important for the design and optimization of the periodic-flow processes for industrial applications. In this study, the pressure drop and the position of loading points are investigated. Moreover, a mathematical evaluation on the energy consumption in the case of a pulsed flow is conducted, and besides the influence of pulsation intensity, the effect of geometrical parameters including the plate spacing and plate-free area is investigated as well. The results of this study are helpful for optimization of column geometry targeted to higher performance and lower energy consumption.     

Effects of co- and counter-swirl on the droplet characteristics in a spray flame

This paper reports measurements of droplet characteristics and flow field in a spray flame with inner and outer swirling air streams. The spatial distribution of droplet characteristics produced by the burner's airblast atomizer was measured using dual-phase Doppler anemometry (PDA). The spray flame was operated near the lean blow-out limit at two flow conditions: co-swirling (flow rotation in the same direction) and counter-swirling (flow rotation in opposite directions). In both cases, the flame exhibited a U-shaped form and was marked by a large central recirculation zone. Based on the measurements of the droplet velocity components, differences between both configurations appeared for the counter-rotational setup mainly in the near burner region, where the decrease of total swirl causes deeper penetration of the droplets from the inner duct into the combustion chamber, resulting in a much more homogeneous distribution than the other one. The droplet size in terms of the Sauter mean diameter (SMD) shows little variation in the change of the direction swirl condition. Application of counter-swirl results in more turbulent droplet motion.     

泡沫发生器内气液不稳定流动规律研究

泡沫发生器是冲砂洗井的主要应用设备,对于泡沫发生器结构的设计,目前国内外学者设计的泡沫发生器多用于煤矿井下,结合油田实际生产情况特点,在同心管式泡沫发生器结构上进行设计优化,建立泡沫发生器实验模型,利用PIV技术系统来研究泡沫发生器内的液体不同表观速度、气体的不同表观速度对泡沫液流的影响。     

下引式连续定向凝固薄壁铜管中具有温度梯度的结晶器对固液界面位置影响的数值模拟与分析

根据凝固原理建立了下引式连续定向凝固薄壁铜管过程中具有温度梯度的结晶器下二维稳态温度场的物理、数学模型,并通过数值计算与绝热结晶器、恒温结晶器下工艺参数对固液界面位置的影响进行对比分析,结果表明在保证熔体温度稳定的条件下,使用具有温度梯度的结晶器能够获得相对较宽的适宜工艺参数范围以及较高的极限拉坯速度.     

磷炉停炉时电极位置的处理方法浅析

简介了磷炉停炉时电极位置的处理方法，并以5000kVA磷炉为例,通过对熔池的分析，指出了停炉时处理电极位置应注意的一些问题。     

Numerical Simulation of the Two‐Phase Fluid Field in a Gas‐Around‐Liquid Spray Nozzle

A new gas‐around‐liquid spray nozzle (GLSN) was designed, and the two‐phase flow fluid field in this nozzle was simulated numerically. Flow characteristics under different structural parameters were obtained by changing the L/D ratio of the premixing chamber, incident angle, and inlet pressures. Increasing the L/D ratio and incident angle improved flow characteristics such as atomization flow, outlet velocity, and turbulence intensity. The nozzle performed optimally at an L/D ratio of 0.5 and incident angle of 60°. The atomization flow decreased with higher gas pressure and increased with higher liquid pressure. The outlet velocity mainly depended on the inlet gas pressure, not on the inlet liquid pressure. These results provide an indication for optimum structures and parameters of the GLSN.