T-型微混合器的优化与仿真

设计了一种内置周期性挡板T-型微混合器,并采用ANSYS软件对其进行建模与仿真.主要针对不同挡板排数、高度、间距、角度、宽度、混合单元数和不同雷洛数对微混合器出口处温度的影响进行了对比分析,并采用田口分析方法,减少试验次数,根据信噪比大小找寻最优混合器结构.仿真结果表明:对于混合效率的影响,W_3(挡板高度)W_1(挡板宽度)W_2(相邻挡板水平距离)θ(挡板角度),双排正向双排反向单排无挡板;对压降的影响,W_3(挡板高度)θ(挡板角度)W_1(挡板宽度)W_2(相邻挡板水平距离),双排正向双排反向单排无挡板;因此选定W_1=60μm; W_2=500μm; W_3=100μm;θ=45°,挡板排数为双排正向,混合单元数4为最优设计参数.该结构在雷洛数达到150时,达到完全混合.     

前混合磨料水射流除鳞喷嘴混合腔内部流场

基于计算流体动力学多相流混合物模型,应用FLUENT软件对前混合磨料水射流除鳞喷嘴高压水与磨料混合腔内部流场进行数值模拟.比较了不同进料方式对流场均匀性的影响.分析了两侧为高压水入口条件下,磨料入口直径、高压水入口直径、高压水入口位置和角度以及收缩段锥角对流场混合均匀性的影响,得到了影响混合腔内部流场混合均匀性的合理结构参数.数值计算结果表明:入口速度一定的条件下,磨料中进式喷嘴混合腔的混合均匀性优于磨料侧进式喷嘴混合腔.随磨料入口和高压水入口直径增加,混合腔出口的射流速度均增加,但随高压水入口直径增加导致出口磨料浓度呈先增后减的趋势,磨料入口与高压水入口合理的质量流量比值约为3∶4,两侧高压水入口位置对流场混合均匀性影响较小,高压水入口角度和收缩段锥角均为30°时流场性能更佳.     

自浮颗粒三相体系的搅拌混合技术(Ⅱ)──挡板的影响

研究了不同高度、不同数量和不同布置方式的挡板组合对自浮颗粒三相体系的搅拌混合的影响，发现挡板对自浮颗粒的三相混合有很大的影响，其中不对称的３ 块全深度挡板对自浮颗粒的下拉是最有效的，此外回归得到了多种挡板条件下功耗和气含率的关联式     

自浮颗粒三相体系的搅拌混合技术（Ⅱ）：挡板的 …

研究了不同高度，不同数量和不同布置方式的挡板组合对自浮颗粒三相体系的搅拌混合的影响，发现挡板对自浮颗粒的三相混合有很大的影响，其中不对称的３块全深度挡板对自浮颗粒的下拉是最有效的。此外回归得到了多种挡板条件下功能和气含率的关联式。     

三角形微通道中环状冷凝过程的数值模拟

建立了三角形微通道中环状冷凝的一维稳态模型,给出了等边三角形微通道中环状冷凝过程的液相毛细半径沿轴向的变化曲线.计算发现,在等边三角形微通道中,气液界面毛细半径先沿程急剧增加,然后趋向平缓,最后再急剧上升,且毛细半径的平缓段占据了绝大部分冷凝段总长度.在接触角和通道热流密度较小或者通道水力直径和入口蒸气压力较大时,冷凝段长度较长.在冷凝过程中,流速和液相压力沿程变化剧烈.该模型较好地解释了三角形微通道环状冷凝机理,并能用于估算冷凝过程的部分参数,为进一步推导更完善的微通道冷凝模型奠定了基础.     

旋风式油气分离器分离特性影响因素的仿真研究

为提高旋风式油气分离器的分离效率,改善分离性能,研究了分离器入口形状(矩形、圆形)、入口混合气流速、圆锥段锥形角、出气管的直径和出气管插入深度对分离性能的影响。将搭建的旋风式油气分离器三维几何模型导入ANSYS体系下的Fluent软件中建立油气分离器的仿真计算模型,仿真分析了影响旋风式油气分离器分离特性的因素。得出以下结论:在同一条件下,对相同粒径微粒的分离效率,矩形入口式高于圆形入口式;入口气体流速的增加使得分离效率提高的同时,导致分离器内部整体压力损失增加,针对本文搭建的模型,在入口混合气流速为12.8 m/s左右时,压损较低,且分离效率较高;分离效率随着圆锥段锥形角度增大而缓慢增加,分离效率在锥形角度大于11.5°后基本保持不变;分离效率随出气管直径的增加而降低,并且下降的速度逐渐增加;分离效率随出气管插入深度的变化趋势呈现出抛物线式的变化规律,先增大后减小。     

挡板结构对微混合器内流动与混合的影响

对内置3种不同挡板的T型微混合器内的流动与混合进行数值模拟,比较流动与混合的发展过程,分析不同挡板结构的对流作用机理以及混合随通道长度方向的发展变化.讨论了不同雷诺数(Re)下,挡板结构对混合强度与压力损失的影响.结果表明,在5Re≤90范围内,3种挡板结构产生的混合强度与压力损失均随Re的增大而增大.矩形挡板产生的混合效果最佳,但结合压力损失评价,认为斜面梯形具备最优的综合性能.     

恒壁温下梯形硅微通道热沉流动换热特性

建立了恒壁温条件下微通道中层流流动换热的三维模型,对水力直径分别为108,160和200μm的梯形硅微通道内单相流动换热特性进行了数值模拟研究.研究结果表明:在恒壁温条件下,通道入口段Nu数最大,并沿流程逐渐减小,直至达到充分发展时,Nu数趋于定值;与大管道经典理论不同,充分发展段Nu数随Re数的增加而增加;通道尺度的减小能有效强化换热;恒壁温条件下的平均Nu数总是低于恒热流条件下平均Nu数.同时,对流动阻力损失的研究发现,Poiseuille数与经典值基本吻合.     

玻璃包覆纯铜微丝的力学性能

以实验室制备的玻璃包覆纯铜微丝为研究对象,对玻璃包覆纯铜微丝及去除包覆层的纯铜芯丝进行了力学性能评价和断口形貌分析.结果表明:外径45μm、包覆层厚度7.5μm和外径27μm、包覆层厚度6.0μm的玻璃包覆纯铜微丝极限拉伸载荷分别为0.268N和0.237N;纯铜芯丝的拉伸应力应变曲线表现出较低的加工硬化率,屈服强度与抗拉强度比值在0.75以上;纯铜芯丝抗拉强度随直径的减小而增大;直径10μm芯丝的平均抗拉强度可达547.9MPa,延伸率约为2.5%;芯丝断裂模式为滑移延伸断裂.     

粗糙元特征对风洞中大气表面层模拟的影响

采用不同尺度、不同铺设密度的二维正方形粗糙元,在环境风洞中对大气表面层进行了模拟.使用粒子图像速度场仪对所模拟的大气表面层风速廓线、湍流强度进行了测量.结果表明:当粗糙元的铺设长度达到实验段入口高度的12倍以上时,依靠自然形成法所模拟的对数风速廓线高度可达实验段高度的60%;空气动力学粗糙度Z0最高可达粗糙元尺度的0.4～0.5倍,且Z0随粗糙元铺设区到测量断面的距离呈指数变化;同一高度上湍流强度随粗糙元铺设间距的增加而减小,当廓线高度达到实验段高度的40%以上时,湍流强度不随粗糙元大小及铺设密度的变化而变化,其大小为12%～13%.实际应用中,在已知所需Z0和摩阻风速U*的情况下,可通过粗糙元尺度及铺设密度的不同组合获得满足要求的大气表面层,并确定实验模型区的位置和实验段的入口风速.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the