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).     

前缘弯掠轴流转子简化设计及其内流分析

应用环壁边界层理论及其速度分布图形,在不变更常规设计系统下,研究并构造一种前缘动力学弯掠轴流转子新叶片,使用N-S方程数值分析并考察了新叶片内的流动状态和内流机制,它与常规转子的比较结果初步证实了设计方法的可行性．     

风扇前缘曲线前掠程度对风扇性能的影响

根据风扇前缘曲线的相对前掠概念，将其应用于NASA67风扇叶片的改型，通过数值模拟研究了三种不同前缘曲线掠弯程度对叶片通道内气流流动的影响，计算结果表明。前掠叶片的等熵效率高于无掠叶片；前掠叶片的稳定工作裕度及流量范围比无掠叶片有很大提高，并随着前掠程度的增大而增大；前掠叶片的增压比低于无掠叶片，且增压比随前掠程度的增大而降低。     

轴向尺寸限制下的低压轴流风扇自动优化设计

针对空调低压轴流风扇轴向尺寸受限制情况下的自动优化设计问题,基于B样条曲线,采用基元级设计和复合弯掠技术相结合的参数化方法构建轴流风扇三维模型.将轴流风扇叶轮参数化方法、商用数值计算软件ANSYS和第二代非支配排序遗传算法(NSGA-II)耦合.在叶轮轴向尺寸限制下以容积流量和静压效率为目标函数,建立起集参数化建模、网格划分、流场计算和多目标优化于一体的自动优化设计平台.在设计工况下,采用该优化平台对一款低压轴流风扇展开优化设计,并通过数值模拟和实验方法对比分析了优化前后模型的气动性能,结果表明:优化后的轴流风扇减小了轴向尺寸,在设计工况下实验流量提升10.4%、静压效率增加1.7%,具有较宽的工作范围,并且减弱了叶尖涡的强度,提高了通流能力.     

Bezier函数型弯叶片的轴流风扇气动性能研究

为了研究轴流叶片前缘段保凸性对风扇性能的影响,采用Bezier曲线对某空调开式轴流风扇叶片子午面进行参数设计,结合大涡模拟中声类比积分求解方法,对轴流风扇原型叶轮及改进新型叶轮进行三维非定常流场计算.两种叶轮结构的内流分析表明:在相同流量下,新型叶轮涡度分布小于原型叶轮,流场性能较好.最后通过实验测试,得到了不同转速下的流量及总声级曲线图,发现改进后叶轮具有较好的外部特性,并能有效降噪1.1 dB.     

轴流风扇转子叶片优化设计

针对一通用型轴流风扇的转子叶片,以三维粘性流场的数值计算程序为平台,利用人工神经网络BP算法和遗传算法,通过叶片弯掠技术对叶片的周向弯曲角度进行寻优,以使风扇的性能进一步提高.通过对比优化前、后的叶轮发现,优化之后的叶片形成明显的沿周向顺叶轮旋转方向弯曲.试验结果表明,其全压效率提高了1.27%,全压升提高了3.56%,上、下端部的流动损失进一步降低.     

弯掠翼叶轮内流压力场的计算机数值仿真

采用计量流线曲率和旋转流动的改进的曲率时间尺度k-ε湍流模型和Navier-Stokcs方程组求解，对宇宙航空弯掠翼型叶轮和对比用基准叶轮的内流压力梯度场进行了计算机数值仿真，分析了压力梯度场的变化规律及其作用机制．仿真结果表明：弯掠叶轮数值仿真必须选择计量曲率和旋转影响的改进湍流模型；弯掠翼型形成的C型压力梯度场有益于抑制低效流；可以通过移动积迭点位置调整压力梯度以控制内流场．     

前缘弯掠(扭)斜流转子叶尖脱落涡的PIV研究

应用PIV技术测量了一开式前缘弯掠(扭)斜流转子的叶尖脱落涡的结构及其发展演化趋势,测量结果表明,叶尖脱落涡产生于叶片顶部区域,沿着一条与转子旋转方向相反的斜线向下游发展．叶尖脱落涡的强度随叶轮转速的提高而增强,随背压的提高而减弱,当背压增加到一定程度时,叶尖脱落涡消失．实验结果为前缘弯掠(扭)斜流转子在大型中央空调室外机上的应用和优化设计及其降噪提供重要的内流实验数据．     

基于弯掠参数控制的压气机动叶优化设计

通过数值模拟方法对NASA Stage35单级轴流压气机原型性能进行计算,选取合理的Bezier和B样条拟合曲线控制点个数来完成压气机动叶参数化拟合,获得参数化叶型.基于人工神经网络和遗传算法相结合的优化设计体系,通过控制叶片的弯掠特性参数对动叶进行寻优计算,最终提高压气机绝热效率.对比发现,对动叶的弯掠特性进行优化可以改变激波位置,减小叶片表面附面层的分离区,优化流场通道内的流动结构,减少流动损失,从而有效提高压气机的绝热效率.     

弯掠动叶气动—声学优化设计及实验研究

给出适于工程计算的弯掠动叶气动－声学优化设计方法，总结归纳了亚音速弯掠动叶的弯掠角方向、弯－掠角度值、叶片重心型线联线以及加功量沿径向分布等主要结构和气动参数的合理选择。根据优化设计方法，加工了３个叶轮（周向前弯动叶叶轮、轴向前掠动叶叶轮及径向动叶叶轮）。实验结果表明：弯或掠动叶叶轮气动－声学性能均优于径向动叶叶轮，并且周向前弯动叶的稳定工作范围扩大２０％以上，同时验证了优化设计中所讨论的结构和气     

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.     

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     

An affordable accurate evaluation of the binding conformations predicted by molecular docking studies in bio-system

Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with