卫生型泵内部流道流场分析

针对广东日新泵业两台不同参数卫生泵的实测结果，对叶轮内部三维不可压湍流流动进行了数值模拟．通过商用软件Fluent 5．0对两台泵的叶轮进行数值计算，计算过程采用标准k-ε湍流模型及SIMPLEC算法．通过对两台泵流动状况的研究与分析，揭示了叶轮内湍流流动的速度分布、压力分布情况，指出了两台泵叶轮结构的合理性，并提出了第二台泵叶轮的修改方案，同时对泵的水力性能进行了预测，从而为卫生型泵的优化设计奠定了基础．     

低比速疏水泵改善汽蚀性能的CFD优化设计

为提高热力发电厂低压加热器疏水泵的汽蚀性能,将CFD（计算流体动力学）技术与传统抗汽蚀方法相结合,利用商业软件FLUENT对具有不同布置形式的四种叶轮模型内三维湍流场进行数值计算。根据计算所得流场分布,通过比较找出具有良好汽蚀性能的设计方案。试验数据表明,泵的汽蚀性能得到改善。     

叶轮型式对超低比转速高速离心泵性能的影响

为了分析不同叶轮型式对超低比转速高速离心泵性能的影响,对采用普通叶轮与复合叶轮离心泵内部流动进行数值模拟.计算基于连续方程和雷诺时均N-S方程,采用标准的k-ε湍流模型和SIMPLEC算法.模拟采用不同长短叶片的复合叶轮的超低比转速高速离心泵在设计工况下的全三维流场,得到短叶片径向和周向偏置位置的最佳组合.着重分析比较采用普通叶轮和复合叶轮两种离心泵模型方案在不同流量下叶轮内部的速度场和压力场,得到其内部流动的主要特征.研究结果表明,在其他过流部件相同的条件下,采用长短叶片的复合式叶轮离心泵其性能比普通常规叶轮更佳.     

半螺旋吸入室隔舌形状对叶轮吸入性能的影响

为了研究半螺旋吸入室隔舌对叶轮进口介质流动的影响,基于计算流体动力学(CFD)技术,Reynolds时均化,湍流模型采用RNG k-ε模型,速度、压力耦合用SIMPLEC算法,对三种隔舌方案进行全流场数值模拟,得到叶轮进口处的速度场,并对其进行分析.将其中流动状态最好的一种方案进行真机性能试验,并与CFD计算结果进行对比验证.数值计算结果表明:半螺旋吸入室隔舌与叶轮进口边的距离影响叶轮的吸入性能;当该距离较远时叶轮进口处速度分布均匀,进口流动预旋较大,泵的扬程较低;当该距离较近时隔舌部位产生明显的漩涡,介质圆周速度周向分布波动大,预旋不明显,扬程相对较高;通过数值计算结果,为吸入室设计提供参考.     

离心泵内部流场的三维空化湍流的数值计算

采用Singhal等人发展的一种三维混合流体完整空化湍流模型,基于RNG的k-ε湍流模型和SIMPLEC算法,对离心泵内部的全流道三维空化流动进行定常和非定常数值模拟.根据空化流动模拟计算的结果,得到定常和非定常情况下空化余量和扬程的曲线,与实验结果进行对比,说明计算结果能够真实反映离心泵内部空化流动的性能.进而有效地预测叶轮内部流道空化发生的部位和空化流动的发展情况,分析空化余量的降低对离心泵空化性能的影响.研究结果表明,所采用的空化模型和数值计算方法能够用于离心泵在设计工况下的空化性能的计算.     

离心泵叶轮内部三维湍流流动的分析

为研究离心泵内部伴有盐析的复杂液固两相流动问题,首先需要了解在清水状态下,其内部真实流动现象的物理本质．为此,基于N—S方程和标准的k—ε湍流模型,利用FLUENT6．1对清水状态下离心泵叶轮内部的三维湍流场进行了数值模拟,并运用先进的测量仪器PIV对改进设计后的化工离心泵叶轮内部流场进行了测量,给出了其相对速度分布图．同时,结合数值计算与试验研究。对离心泵叶轮内部流场进行了初步分析．试验结果表明,计算所采用的模型的修正方法基本符合离心泵内部流动的实际情况．     

200 km/h电力机车气动性能风洞试验与数值模拟

采用模型风洞试验和数值计算方法研究了200 km/h机车外形的气动性能.试验风洞为FD-09单回流低速风洞,模型缩尺比为1:8.873.数值计算采用流体动力学软件FLUENT,数学模型为三维粘性不可压缩流体雷诺时均方程和κ-ε双方程湍流模型.数值模拟结果与模型风洞试验结果基本吻合.在此基础上对多个外形的设计参数进行了优化,并对优化后的模型流场作了数值计算,得出了一些有益的结论.     

低压轴流风扇性能的改善

在轴流叶轮常规准三维设计方法的基础上,采用前缘弯掠技术,运用CFD/CAD方法对空调器轴流风扇进行耦合设计,并且应用三维纳维-斯托克斯方程和Spalart-Allmaras湍流模型分别对国外样机风扇和新风扇进行了数值分析与性能实验.实验测试结果和内流计算结果符合较好,验证了设计方法的可行性和数值计算的有效性.研究结果还表明,采用大前弯角度和前掠角度的新轴流风扇减小了叶道中二次涡的影响范围,主流区域增大,基本消除了前缘分离现象;在气动性能基本保持不变的情况下,风扇噪声可降低0.5～1.3dB(A级声压级).     

叶顶泄漏流对半开式离心泵叶轮流动结构的影响

为研究不同叶顶间隙下叶顶泄漏流对半开式叶轮离心泵流动结构的影响,设计5种不同尺寸叶顶间隙方案,采用SST k-ω湍流模型,对半开式叶轮离心泵进行全流道三维数值计算,分析半开式叶轮叶顶间隙内部流动结构并进行可视化实验验证.结果表明:随着叶顶间隙的减小,离心泵的扬程和效率明显上升,间隙值减小到0.7 mm时,进一步减小叶顶...     

离心压气机流场的数值分析研究

以某离心压气机叶轮为基础,通过反设计形成的几何模型,采用kω湍流模型计算流场的湍流效应,对微型的离心压气机流场进行了数值模拟。结果表明:采用大小叶片技术的叶轮在较宽的工作范围内有很好的性能,入口攻角增大以及叶尖间隙二次流与压气机叶轮流场的失速有直接的关系。     

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