Simulation of the fluidic features for diffuser/nozzle involved in a PZT-based valveless micropump

PZT-based valveless micropump is a microactuator that can be used for controlling and delivering tiny amounts of fluids,and diffuser/nozzle plays an important role when this type of micropump drives the fluid flowing along a specific direction.In this paper,a numerical model of micropump has been proposed,and the fluidic properties of diffuser/nozzle have been simulated with ANSYS.With the method of finite-element analysis,the increased pressure drop between inlet and outlet of diffuser/nozzle induces the increment of flow rate in both diffuser and nozzle simultaneously,but the increasing rate of diffuser is faster than that of nozzle.The L/R,ratio of L(length of cone pipe) and R(radius of minimal cross section of cone pipe) plays an important role in fluidic performance of diffuser and nozzle as well,and the mean flow rate will decrease with increment of L/R.The mean flow rate reaches its peak value when L/R with the value of 10 regardless the divergence angle of diffuser or nozzle.The simulation results indicate that the fluidic properties of diffuser/nozzle can be defined by its geometric structure,and accordingly determine the efficiency of micropump.

Nozzle Spray Diffusivity Changing Law for Ultra Fast Cooling in Hot Strip Mill

Slot nozzle and intensive nozzle can be used in ultra fast cooling equipment. The spray cooling method with higher water pressure can be taken in order to achieve ultra fast cooling for hot rolled strip. Water will be diffused after it is sprayed out from ultra fast cooling nozzle. Spray diffusivity will affect water velocity and penetrability of water into residual water layer on top of the strip,and then it will affect strip cooling effect. Water spraying process can be simulated by Fluent and some conclusions were obtained. Slot nozzle width and outlet velocity within setting range could not affect the length of potential core zone and the spray diffusivity. Intensive nozzle diameter and outlet velocity will affect the length of potential core zone and the spray diffusivity with different extent. These conclusions will provide referenced role for confirming ultra fast cooling nozzle size and distance between ultra fast cooling nozzle and hot rolled strip.

Diffusion Behaviour of Fe-Cu Interface of Copper Brazed Double-wall Steel Tubes

By means of electron probe(EPMA),scanning electron microscope(SEM),and optical microscope (QM),the diffusion behaviour on the Fe-Cu interface of copper brazed double-wall steel tubes and the microstructure of the diffusion layer have been investigated.There are three kinds of metallurgical bonds between copper plating layer and steel substrate: (1)the Cu diffusing into steel substrate along grain boundary of ferrite;(2)the Cu diffusion into grain bulk of ferrite: (3)the Fe diffusing into Cu layer.The copper brazed double-wall steel tubes are formed by the combination of the diffusions mentioned above and this is the reason for excellent mechanical and technological properties of the copper brazed double-wall steel tubes.

Preparation of calibration standard of organic vapours using the diffusion tube method

This paper describe the theoretical consideration, experimental results and applications of diffusion tube, used for preparing the calibration standard of organic vapours. This dynamic procedure entirely eliminates the adsorption effect, which is important in static procedures. Its concentration range is wider than that of the permeation tube. The diffusion tube technique is therefore a very accurate, simple and easy-to-make device. It is quite useful in the determination of organic pollutants existing in the environment.

The Effect of Diffuser Angle on the Discharge Coefficient of a Miniature Critical Nozzle

Many researches on critical nozzles have been performed to accurately measure the mass flow rate of gas flow,and to standardize the performance as a flow meter.Recently,much interest is being paid on the measurement of very small mass flow rate in industry fields such as MEMS applications.However,the design and performance data of the critical nozzles obtained so far have been applied mainly to the critical nozzles with comparatively large diameters,and the works available on miniature critical nozzles are lacking.In the present study,a computational fluid dynamics method has been applied to investigate the influence of the diffuser angle on discharge coefficient of the miniature critical nozzles.In computations,the throat diameter of critical nozzle is varied from 0.2 mm to 5.0 mm and the diffuser angle is changed from 2 deg to 8 deg.The computational results are validated with some experimental data available.The results show that the present computational results predict appropriately the discharge coefficient of the gas flows through miniature critical nozzles.It is known that the discharge coefficient is considerably influenced by the diffuser angle,as the throat diameter of nozzle becomes small below a certain value.This implies that the miniature critical nozzles should be carefully designed.

Nosing process of empty and foam-filled circular metal tubes on semispherical die by theoretical and experimental investigations

Nosing process of circular metal tubes in empty and polyurethane foam-filled conditions on a semispherical rigid die was analyzed by theoretical and experimental methods.A new theoretical model of plastic deformation of circular metal tubes was demonstrated during the nosing process on a rigid semispherical die.Based on the analytical model,some theoretical relations were calculated to estimate instantaneous forming load and dissipated energy of empty and foam-filled circular metal tubes versus axial displacement.Some circular brazen and aluminum tubes were prepared and shaped into semispherical nosed nozzles to verify the present theory.Comparison of theoretical predictions and the corresponding experimental measurements reveals that predicted load?displacement and dissipated energy?displacement diagrams by theoretical formulas have a good correlation with the corresponding experimental curves and it proves verity of the theory.Also,the present theory shows that dissipated energy and axial load of empty tubes depend on material type,wall thickness and diameter of the tubes and they are independent of tube initial length.Furthermore,the experimental results show that the presence of polyethylene Teflon-constraints increases ultimate axial displacement of the forming process.

Numerical simulation of a thermal-bubble actuated diffuser-nozzle valveless pump

A valveless micropump actuated by thermal bubbles which are generated by an electrode heater mounted with a pair of diffuser nozzles has been numerically studied by commercial CFD software FLUENT. The relationships between the net flow rate and the superheating and heat supplying frequency have been investigated. The depth of the diffuser-nozzle micropump is 200 μm, the diameter of the actuating chamber is 1 mm, and a pair of diffuser nozzles whose gap has been expanded from 30 μm to 274 μm with an open angle of 7° are connected to the actuating chamber. The working fluid is methanol. In the numerical simulation, the flow pattern is laminar. The results show that the pump has different optimal driving frequencies at different superheating. A cycle resulting from bubble growth and shrinking costs more time at higher superheating temperature; different superheating has different optimal driving frequency; when the superheating increases, the maximum volume flow rate and the maximum pump pressure will increase simultaneously, and the optimal driving frequency decreases as well, the maximum volume flow rate and pump pressure also have the same tendency; in the condition of uncontrolled condensing, the bubble shrinking process is longer than the growth process, thus it is the determining factor to affect the pump performance. The maximum volume flow rate is 9.02 μL/min at ΔT = 15°C, and the maximum pump pressure is 680 Pa. With the increase of wall superheat, cycle including the bubble growth and condensation will become longer, resulting in a significant impact on the pumping flow; different wall superheat has different optimized frequency, increasing superheat will bring increased pumping flow and pump pressure, the optimized driving frequency will be reduced; liquid supply phase is longer than pumping phase.

Three-dimensional flow field simulation of steady flow in the serrated diffusers and nozzles of valveless micro-pumps

This paper presents a three-dimensional flow field simulation of the steady flows through diffusers and nozzles with straight or serrated-sided walls to analyze the effect of the channel structure on the flow characteristics.The pressure and velocity profiles in the diffusers and the nozzles as well as the net volumetric flow rate are determined.Our simulation demonstrates that the pressure and velocity profiles in the serrated diffuser/nozzles are more complicated than those with the straight-sided wall,while the net steady flow rate with the straight-sided wall increases monotonically with the increase of the pressure difference,the steady flow rate with serrated sided walls increases gradually to reach a maximum and then decreases with the increase of the pressure difference.The results suggest that the number of the sawteeth plays a significant role in optimizing the design of serrated diffusers and nozzles for improving the transport efficiency of valveless micro-pumps.

Visual analysis of flow and diffusion of hemolytic agents and hematomas

The elimination of intracranial hematomas has received widespread attention and the interactions between hemolytic agents and hematomas have become a hot research topic.In this study,we used the Navier-Stokes equation to describe the flow control equation for hemolytic agents in a tube and used Fick’s law and the Maxwell-Stefan diffusion theory to describe the diffusion and mass transfer of hemolytic agents and hematomas.The physical fields and initial boundary conditions were set according to the parametric properties of the fluid and drainage tube.The COMSOL Multiphysics software was used to simulate the streamline distribution of hemolytic agents in a bifurcated drainage tube.Additionally,the diffusion behaviors of the hemolytic agents into hematomas were simulated and visual analysis of coupled multiphysics was performed to realize the digitization and visualization of engineering fluid problems and contribute to the field of medical engineering.

Synthesis of Macroscopic Zr(C6H5PO3)2 Tubes

A new method of infiltration-diffusion is used to synthesize macroscopic α-Zr（C6H5PO3）2 （α-ZrBP） tube. Compared to the routine method, no HF was used and a fiberlike product with several millimeters in length was obtained. SEM （scanning electronic microscopy） result indicates that these fibers are tubes. The wall of the tubes is composed of the flake of α-ZrBP overlapped with each other. As we know, it is the first report on the synthesis of millimeter-scale supramolecular assembly of α-ZrBP.

钯合金阵列管束气密性焊接工艺方法研究

采用预先高频钎焊钯合金管过渡接头,再使用脉冲激光焊的方法,对钯合金扩散室密排列钯合金管束与不锈钢法兰进行了密封焊接工艺研究,通过对激光焊接接头的观察和气密性检测分析,确定了激光焊接功率、离焦量、脉冲频率、脉冲宽度及焊接速度等主要焊接参数。正式样件经气密性检测和氦质谱检漏达到了氢纯化分离用钯扩散装置的使用要求,从而确定激光焊技术可推广应用于钯合金扩散室密集阵列管束批量焊接生产。

不同结构空化射流喷嘴流场特性对比

喷嘴类型与结构是影响空化射流性能的关键因素。通过CFD数值模拟方法探究了风琴管自振空化射流喷嘴、Helmholtz型空化射流喷嘴、角形空化射流喷嘴、中心体空化射流喷嘴和叶轮式旋转空化射流喷嘴的流场特性。开展射流喷嘴流场室内测试,以射流扩散角为评价指标,验证了数值分析的可靠性。根据不同结构空化射流喷嘴的流场特性和现场工程应用需求,给出了适用于不同场景的空化射流喷嘴类型推荐和说明。研究结果表明:风琴管自振空化射流喷嘴射流冲击压力高且稳定性强(最高冲击压力12.165 MPa),适用于钻井过程中辅助破岩场景;Helmholtz型空化射流喷嘴脉冲频率高(2.0 kHz)且空泡运移距离远,适用于老井洗井解堵处理场景;角形空化射流喷嘴射流扩散能力强且空化程度高,适用于油田废水处理中乳化油破乳场景;中心体空化射流喷嘴具有集中于出口中心的空泡群和7.047 MPa的射流冲击压力,适用于煤层气开采中煤层瓦斯解吸渗流场景;叶轮式旋转空化射流喷嘴具有倒“U”形速度分布和空化作用范围大的特点,适用于水合物开采中径向分支钻孔场景。研究结果可为空化射流喷嘴选型提供理论依据。

喷嘴偏置角度对涡流管能量分离效应的影响分析

以理想空气为工质,对不同喷嘴偏置角度的涡流管进行了能量分离特性的数值模拟研究。此外,对涡流管内部速度场、温度场和压力场的分布规律进行了深入分析。模拟结果表明,不同偏置角度的喷嘴改变了涡流管切向速度和径向速度的分配,随着偏置角度的增大,轴向速度呈现增加趋势,轴向速度的变化会影响滞止点的位置,更大的轴向速度会使滞止点更加远离热端出口。涡流管中滞止点位置影响着冷流与热流的分界面大小,从而影响两股流体之间能量交换。随着冷流率的增大,4种不同涡流管的制冷效应逐渐减弱,且喷嘴偏置角度为0°时,涡流管表现出最佳制冷和制热效应。偏置角度在15°-45°变化时,随着喷嘴偏置角度增大,涡流管制冷和制热效应逐渐减弱。

紧耦合气雾化喷嘴流场特性研究

雾化喷嘴作为紧耦合气雾化法制备金属粉末的核心部件,其导液管末端压力及滞留点处压力对雾化过程中金属熔液的顺利流出和破碎至关重要。当导液管末端为正压时,金属熔液无法顺利流出导液管,严重时会造成金属熔液的反喷现象;滞留点处压力越大,流出导液管的金属熔液所受到雾化气体的冲击力越大,其破碎效果越佳。本文通过数学建模、实验验证及数值模拟的方法研究了雾化压力、导液管伸长量及导液管锥顶角对其末端压力及滞留点处压力的影响。结果表明:随着雾化压力的增大,负压区域长度基本不变,而滞留点处压力增大;导液管伸长量的增加会使负压区域长度增加且滞留点处压力减小;随着导液管锥顶角的增大,其末端压力会从负压过渡成正压,从而导致雾化失败。

TA15/YG8复合管扩散复合工艺设计及其施压阶段的有限元模拟

目的以制备钛合金/硬质合金叠层复合管为目标,基于钛合金和硬质合金的性能特点,解决使异种管材相互靠近的载荷难以直接施加的问题,设计开发钛合金/硬质合金复合管的扩散复合工艺。方法借鉴颗粒介质成形的基本原理,提出一种钛合金管-硬质合金管扩散复合方法,并以TA15钛合金和YG8硬质合金为原材料,通过有限元模拟研究了管间间隙、固体颗粒的填充度、固体颗粒的尺寸和管坯长径比等工艺参数对扩散复合施压过程中TA15钛合金管/YG8硬质合金管界面上径向应力分布的影响。结果有限元模拟结果表明,本文设计提出的钛/硬质合金异质管制备工艺确实能将轴向压力转变为径向贴合力,并且可以通过调控下压量满足扩散复合的压力需求(最小径向应力大于10 MPa)。沿轴线方向,钛合金管与硬质合金管之间的径向应力呈不均匀分布,并且受到管间间隙、颗粒填充度、颗粒的尺寸、管坯长径比等参数的影响。管间装配精度越高、固体颗粒尺寸越小、固体颗粒的填充度越多,越有益于管坯之间的扩散复合。试验结果表明,TA15钛合金/YG8硬质合金复合管在不同部位皆实现了良好的冶金结合。结论设计开发了一种钛合金/硬质合金复合管扩散复合方法,制备出具有良好冶金结合界面的TA15钛合金/YG8硬质合金复合管。

可调式节流喷嘴多规格内割刀水循环试验研究

为了提高油管内割刀切割效率,避免油管切割时发生割刀刀具伸出不足、刀片磨损失效快及喷嘴流量不可控等不良现象,研发了一种基于可调节式节流喷嘴的系列化互换多规格油管内割刀。对该工具设计了专用试验平台验证其使用可靠性,并对关键结构设计和试验步骤进行介绍。试验在水循环工况下由初试切割、正常切割、循环启停切割及磨损切割试验组成。研究结果表明:在主体结构及初始外径不变的情况下,系列化割刀能适应不同规格油管切割,可调式节流喷嘴能够满足现场泵组压力,保证割刀合理的转速;割刀能够在163 s内割断73.0 mm油管,多次启停切割73.0 mm油管时长为179 s,剧烈磨损后能在426 s内割断89.0 mm油管,刀具使用寿命达到4次;切割时割刀需要缓慢切入,靠近管壁时需停留23 s左右达到稳定状态,防止出现憋泵现象。试验验证了该刀具的伸出范围可以调节以适应不同外径油管,刀片在不同喷嘴流量下能够多次完成切割作业。研究结果表明该工具可为修井作业现场应用提供技术支撑。

CNTs/Cu层状复合材料的制备及其组织和性能研究

采用扩散结合法将分散后的碳纳米管附着在铜箔表面,经裁剪、堆叠和预压后使用真空热压烧结炉进行烧结,制备出具有优良导电性的CNTs/Cu层状复合材料。使用SEM、EDS和XRD等对样品的微观形貌和成分进行表征,使用显微硬度计和导电率检测仪等对样品性能进行测试。结果表明:在热压烧结过程中,一定量铜扩散到CNTs层中,有效改善了碳纳米管层和铜层的结合能力。相比于纯铜,CNTs/Cu层状复合材料在硬度提高45%的同时,在平行于碳纳米管层方向导电率达到91%IACS,而垂直于碳纳米管层方向也仍具有80.6%IACS的导电率。

输卵管和腹膜结核的MRI表现特征分析

目的探讨输卵管和腹膜结核的MRI表现特征。方法选21例经病理和实验室检查证实的输卵管和腹膜结核(TB)患者和27例卵巢癌(EOC)累及输卵管伴腹膜转移患者的临床和MRI及PET/CT表现进行比较分析,对病变形态、T1WI、T2WI和弥散加权成像(DWI)信号特点、表观弥散系数(ADC)值及强化特征进行分析研究。结果21例TB患者中,16例输卵管TB为单侧性(左侧9例,右侧7例),5例为双侧性。病变输卵管10例呈棒状,12例呈腊肠状S或L形,4例呈肿块状。病变输卵管于T1WI上呈略高信号,T2WI上呈软组织中等信号,DWI上呈高信号,ADC值测量范围为0.75-1.02×10-3mm2/s。结核性输卵管病变大小从0.7×2.2cm到1.5×4.5cm。TB性腹膜的厚度范围为1.6mm-3.2mm,呈薄层均匀平滑无结节增厚。结论输卵管呈管状、S/L形等非肿块样改变,在T1WI呈略高信号和腹膜呈薄层均匀性增厚并明显强化是输卵管和腹膜结核的特征表现。

一种适用于注射器和胃管接管的连接结构的设计及应用

鼻饲营养是临床常见的营养支持方法之一,能够为患者提供营养丰富的流质饮食或要素饮食,保证患者摄入足够的蛋白质和热量,还可避免肠道长期旷置造成的继发伤害。本研究介绍一款注射器和胃管接管连接结构的设计和使用方法,其结构新颖,呈分体式,方便组合使用,可再循环,不仅提升了可操作空间,且在一定程度上降低了使用成本。

老年女性原发性输卵管癌的MRI表现

目的分析老年女性原发性输卵管癌的MRI表现,提高其诊断准确率。方法回顾性分析2013年1月—2023年6月在复旦大学附属华东医院经病理证实的15例原发性输卵管癌MRI表现。测量病灶最大径,观察其信号强度、形态及增强后表现。测量其强化率、表观弥散系数(ADC)值,并与子宫肌层作统计学分析比较。结果15例输卵管癌病例共16个病灶。条管影伴结节5个,腊肠样病灶2个,肿块样9个。6个病灶见包膜强化。增强晚期病灶与子宫肌层强化率分别为(1.71±0.78)、(2.34±0.58),差异有统计学意义。病灶与子宫肌层ADC值分别为(0.788±0.133)×10^(-3)mm^(2)/s、(1.285±0.216)×10^(-3)mm^(2)/s,差异有统计学意义。输卵管积液5例,宫腔积液1例,未见正常卵巢。结论老年女性原发性输卵管癌MRI具特征性表现。正常卵巢在老年女性输卵管癌患者中不易显示,可能会增加诊断难度。