Development of revolving drop surface tensiometer

A revolving drop surface tensiometer, which measures the surface tension of a small amount of liquid, is proposed. A remarkable feature of this device is that while using the pendant drop method, it employs a centrifugal force to deform the liquid droplet. The centrifugal force induces a large distortion of the droplet, which enables an accurate measurement of the surface tension to be made. In our experimental setup, the centrifugal force can be increased so that the apparent acceleration becomes up to 100 times larger than that due to gravity, and the capability of this method to measure surface tensions was demonstrated with ethylene glycol.     

A numerical study on the impact response and energy absorption of tapered thin-walled tubes

Tapered tubes have been considered desirable impact energy absorbers due to their relatively stable mean load–deflection response under dynamic loading. Relatively few studies have been reported on the energy absorption performance of tapered tubes compared with straight tubes. This paper compares the energy absorption response of straight and tapered thin-walled rectangular tubes under both quasi-static and dynamic axial impact loading, for variations in wall thickness, taper angle, impact mass and impact velocity. It is found that the dynamic response of tapered tubes is more sensitive to impact velocity and wall thickness than taper angle for lower impact velocities. Inertia effects influenced the dynamic response for both straight and tapered tubes, yet were less significant for the latter. Overall, the results indicate that the energy absorption response of tapered tubes can be controlled via their wall thickness and taper angle, and this highlights their potential for use as energy absorbers. Analysis has been undertaken using a finite element model, validated using existing theory.     

A multiplexed immunoassay system based upon reciprocating centrifugal microfluidics

A novel, centrifugal disk-based micro-total analysis system (μTAS) for low cost and high throughput semi-automated immunoassay processing was developed. A key innovation in the disposable immunoassay disk design is in a fluidic structure that enables very efficient micro-mixing based on a reciprocating mechanism in which centrifugal acceleration acting upon a liquid element first generates and stores pneumatic energy that is then released by a reduction of the centrifugal acceleration, resulting in a reversal of direction of flow of the liquid. Through an alternating sequence of high and low centrifugal acceleration, the system reciprocates the flow of liquid within the disk to maximize incubation/hybridization efficiency between antibodies and antigen macromolecules during the incubation/hybridization stage of the assay. The described reciprocating mechanism results in a reduction in processing time and reagent consumption by one order of magnitude.     

Application of gamma-ray computed tomography for the analysis of gas holdup distributions in centrifugal pumps

In this work, gas–liquid distributions in an industrial centrifugal pump operated at various steady state conditions have been quantitatively determined. Therefore, high-resolution gamma-ray computed tomography (HireCT) has been applied, operated in time-averaging rotation-synchronized CT scanning mode. Detailed studies have been performed on a hydraulic test facility providing authentic operating conditions for industrial centrifugal pumps. The gas phase distribution in the centrifugal pump has been studied for swirling gas–liquid two-phase flow as an inlet flow regime and at defined inlet gas volumetric flow rates between 0% and 5%. In this way, the influence of the inlet flow boundary conditions on the performance of the centrifugal pump as well as the gas holdup distribution within the impeller region could be successfully determined.     

Vibration-assisted filling capability in thin wall investment casting

Understanding the mechanism of the vibration needed to fill thin section and clarifying the dominant control parameters of the vibration in thin wall investment casting are the keys to producing sound casting. The filling capability in thin wall investment casting method can be assessed by the metal head. It was found that the effect of the vibration on the metal head is markedly dependent on acceleration of applied vibration. Two potential mechanisms were observed from the experimental results during the filling process in thin wall casting: discontinuous propagation flow in vibration conditions and continuous propagation flow without vibration. These mechanisms can modify the contact angles between liquid metal and a wall of the mold. Experiments also showed that two features of the transition can be observed from the front of the morphology: coherent liquid metal front, this occurs in thin wall investment casting when the acceleration due to vibration is less than (1?g) and jetting at the free surface, this occurs in thin wall investment casting when the acceleration due to vibration exceeds 1?g.     

内压作用下波纹换热管应力分析

用有限元法和实验应力分析法对波纹换热管在内压作用下的应力分布规律进行探讨。结果表明，光管加工成波纹换热管后，在波峰过渡处与波谷过渡处均产生了较严重的应力集中现象，最大应力出现在波谷过渡处附近，比相应条件下光管中的应力大许多，且在管的厚度方向有应力梯度存在。通过分析指出影响波纹管上最大应力强度值的因素，并得出最大应力强度值最小时的优化波形。     

螺旋式纸浆离心泵内部流动的数值模拟

为分析螺旋式纸浆离心泵内部流动状态,给优化过流部件结构的优化设计提供基础,采用CFD分析软件Fluent对螺旋式离心泵内部单相流动和固液两相流动进行了数值模拟。给出了螺旋式叶轮建模方法和流场分析方法,分析了泵内流体速度和压力的分布特性,并基于流动模拟结果预测了水力性能,单相输送条件下的计算结果与试验结果取得了较好的一致。通过对一定体积浓度和颗粒粒径下固液两相流的研究计算,分析了螺旋式离心泵叶片表面以及流道内的固液相分布状态,对螺旋式结构的优化具有一定的参考意义。     

儿童乘员约束系统台车碰撞试验设计与研究

为满足GB 27887-2011规定的儿童乘员用约束系统动态性能试验的台车加速度区间要求,提出组合不同长度、壁厚、直径的圆形薄壁吸能管来实现台车碰撞试验波形的方法。采用LS-DYNA软件建立台车和吸能管的有限元模型,并通过该模型获得能复现法规要求的前后碰撞加速度区间的吸能管组合参数,经台车碰撞试验验证其有效性和精确性。对碰撞过程中Q6儿童假人头部和胸部动态响应进行了致伤机理分析,同时基于像素分析法提取了假人头部质心位置的运动轨迹,最后通过分析试验结果,对该新型儿童约束系统提出了改进意见。     

Energy absorption of pressurized thin-walled circular tubes under axial crushing

By pressurizing cellular materials, honeycombs, or thin-walled structures, their energy absorption can be greatly enhanced, and this enhancement can be controlled by the applied pressure. This concept shines light on the possibility of achieving adaptive energy absorption. To investigate the effect of internal pressure on energy absorption of thin-walled structures, this paper presents a study of axial crushing of pressurized thin-walled circular tubes. In the experiments, three groups of circular tubes with radius/thickness ratio R/t=120-200 were axially compressed under different pressurizing conditions. The results show that with an increase of internal pressure, the deformation mode switches from diamond mode with sharp corners to that with round corners, and eventually to ring mode. In diamond mode, the mean force of the tubes increases linearly with internal pressure. The enhancement comes from two mechanisms: direct effect of pressure and indirect effect due to interaction between pressure and tube wall. After the deformation switches to ring mode, the enhancement resulting from the second mechanism becomes weaker. Based on experimental observations, the deformation mode, energy dissipation mechanisms as well as interaction between internal pressure and tube wall are analyzed theoretically and the theoretical results are in good agreement with the experimental ones.     

Annular flow in rod-bundle: Effect of spacer on disturbance waves

A high-speed camera technique is used to study the effect of spacers on the disturbance waves present in annular two-phase flow within a rod-bundle geometry. Images obtained using a backlight configuration to visualize the spacer-wave interactions at the micro-scale resolution (in time and space) are discussed. This paper also presents additional images obtained using a reflected light configuration which provides new observations of the disturbance waves. These images show the separation effect caused by the spacer on the liquid film in which the size of generated liquid droplets can be controlled by the gas superficial velocity. Furthermore, the data confirm that the spacer breaks the circumferential coherent structures of the waves.     

离心式液氢泵的动力特性与传热特性分析

对输运液氢的离心式液氢泵进行低温结构设计与动力单元分析,叶轮是速度能转变为压力能获得高压流体的重要部件,对离心泵的稳定输出特性有较大的影响。其中,转子(包括转轴和叶轮)是连动部件,也属于低温泵结构性传热部件。对应用于储运系统的某小流量高压头的离心式液氢泵的叶轮和转轴部件,进行功能分区,利用CFD内嵌模块对其进行数值计算。根据运行系统中输送载荷,对低温条件下的转子部件进行热-结构耦合瞬态应力应变分析,获得其动力特性;采用流固耦合方法,对叶轮区的流体域进行数值计算,分析不同流体载荷下叶轮表面应力分布;对低温离心泵轴-叶轮的传热区进行设计,分析低温-室温隔热效果,为离心式液氢泵的设计研发、结构优化和性能改进提供理论依据和参考。     

基于金属圆管扩胀变形的碰撞波形发生器设计

为模拟碰撞实验中的加速度波形的要求,以金属圆管扩胀变形原理,通过不同壁厚圆管的分段组合形式研究了波形发生器的设计方法.用实物的标定实验和有限元仿真计算相结合的方法,运用正交实验设计方法,分析了金属圆管扩胀变形的影响因素,并分析了壁厚、扩径量、碰撞质量等主要因素的影响规律.结合实际的算例,验证了设计方法的有效性.相关结论可以为类似的碰撞波形发生器的设计提供理论参考.     

An experimental investigation of a new method for protecting bends from erosion in gas-particle flows

This paper intends to introduce a new way of bend erosion protection: the ribbed bend erosion protection method. Experimental research has come out fixing ribs on the outer-wall of the inside bend as well as on the wall of the straight pipe extending behind the bend in order to decrease the erosion damage caused by the “bend effect”. The experiment shows that ribbed bend technology is a simple and efficient erosion protection method, which can greatly enhance bend erosion protection ability. It also shows that the rib relative height and the rib gap between two adjacent ribs are two important parameters in the ribbed bend erosion protection ability. The same result can be reached on the straight pipe extending from the bend.     

封闭玻璃管道内液体折射率的非接触测量

为了实时、原位和非接触测量工业生产过程中封闭管道系统内透明、半透明液体折射率,提出了一种简单的基于玻璃管壁光学特性的液体折射率测量方法。该方法通过涂覆在玻璃管壁外表面上的透射散射层,将入射激光束转换为进入玻璃管壁的大角度分布的透射散射光;透射散射光到达玻璃管壁与液体的界面上后,符合全反射条件的散射光反射到透射散射层上,自动形成与玻璃管内液体折射率值相关的椭圆形暗斑图像。根据椭圆形暗斑长轴长度与液体折射率之间的解析关系,即可实现玻璃管内液体折射率的原位、非接触测量。对几种常见的透明、半透明液体的折射率进行了实验测量,结果表明:该测量方法的准确性与目前商用数字阿贝折射仪相当(±2×10-4 RIU)。该测量方法具有成本低、稳定性好、抗干扰且光源稳定等优点,而且在处理与液体折射率相关的光学图像时无需调试,光照即显,有望用于封闭管道在非常温、非常压状态下液体折射率的实时、自动和非接触在线监测。     

基于FLUENT的离心加速度下气压场仿真研究

针对多参数复合环境试验系统中离心加速度会造成气压场分布不均匀的问题,提出了一种添加风扇搅拌来改善气压场分布均匀度的方法.通过研究离心加速度与气压场的耦合机理,以流体运动控制方程和标准k～ε湍流模型为基础,建立了环境舱内的流体运动模型.采用有限体积数值分析的方法,对无风扇搅拌和有风扇搅拌两种情况下气压场的分布进行了仿真,...     

一种新型离心式气液分离器分离性能的数值模拟与试验研究

为了研究该分离器的分离性能,通过搭建气液两级分离实验台架进行实验测量,同时应用计算流体力学(CFD)方法对分离器内的气液两相流动进行数值模拟.重点研究了流量、气液比、介质粘度、密度、气泡直径及转鼓转速等六个变量对离心式气液分离器分离效率的影响.通过比较数值计算与实验测定结果,验证了数值模拟方法的可行性.分析结果表明,预测的分离效率变化趋势与实测结果在总体上是一致的, CFD可作为离心式气液分离器设计的有效工具.     

低比转速开式叶轮高速离心泵的优化设计系统

提出基于Navier-Stokes方程和Spalart-allmaras湍流模型流动分析的低比转速开式叶轮高速离心泵优化设计系统,该系统由四个部分组成:基本参数的优化设计、性能预测、流动分析和信息反馈。根据提出的方法,对一台开式叶轮高速离心泵进行实例设计和实验研究,取得了较好的性指指标:泵的扬程流量H-qv特性线几乎是一条直线,扬程系数达到了0．7以上;汽蚀性能也满足要求;叶轮内部压力和速度分布合理,表明采用加大流量设计方法能设计出性能优异的低比转速开式叶轮高速离心泵,此设计方法是合理可行的,对开式叶轮高速离心泵的设计具有指导意义。     

单回路闭式脉动热管内流型的实验研究

对一个单回路闭式脉动热管进行了实验研究.该热管由铜管及玻璃管(内直径均为2mm)合制而成.两端的U形弯头是由细铜管弯曲而成,一端通电加热,另一端通水冷却.中间为两根直的平行玻璃管,采用酒精为工质.本实验目的是,揭示脉动热管内部所存在的复杂的气液两相现象,更好地理解其运行特性.实验表明流型及重力等对单回路系统的热力性能有着重要的影响.     

Adapter modification for a high-speed centrifuge rotor for use with standard medical polypropylene tubes

A rotor adapter for a Sartorius Sigma 3-30KS centrifuge (rotor 12158), which is used for centrifugal separation of detonation nanodiamond particles with different sizes at accelerations of 6 × 10⁴ g, was developed and tested. The developed adapter allows one to use common medical polypropylene test tubes after their simple modification instead of the expensive test tubes that are usually recommended by the manufacturer of the centrifuge. As a result, the use of the adapter significantly decreases expenses on experiments, where fractionation of various liquid dispersions is applied.     

管内螺旋导流板引发的气液两相旋流场

用数值模拟的方法研究某种螺旋导流板结构引发的管内气液两相旋流的流动特点。空气为主相,水为次相,入口为雾状流。研究旋转给流型转变、气液相分布、速度分布及旋流衰减带来的影响。发现雾状流在螺旋导流板的作用下,转变为环状流。螺旋导流板内有二次涡的生成,且二次涡结构不断发展变化,离心力分布不均匀而形成沿管壁周向不连续的液膜;流出螺旋导流板后,二次涡会衰减消失,流体做螺旋向前运动,液膜沿圆管周向逐渐分布均匀。管中心处气相切向速度小,气相切向速度较大的区域远离旋流中心区,旋流中心与圆管中心存在小的偏心距;与直管及螺旋纽带相比,螺旋导流板引发的气液两相旋流在圆管中心的气相轴向流速远高于光管和螺旋纽带;与螺旋纽带相比,螺旋导流板引发的旋流强度更大且衰减减慢。