轴流压气机平面叶栅气动特性的数值研究

以轴流压气机DMU37动叶根部5%叶高典型截面叶型为研究对象,采用Fluent软件,计算分析不同冲角和进口等熵马赫数下叶栅流场损失及气动特性.结果表明:同一冲角下,进口等熵马赫数的提高增加了叶片负荷和扩压能力,同时也使出口总压损失增加,失速冲角范围变小;相同进口马赫数时,随着冲角增加,出口总压损失先减小后增大,-4°冲角时总压损失最小.同时,验证了轴流压气机平面叶栅马赫数、冲角损失特性规律具有相似性,并且,叶栅端壁区域受进口马赫数和冲角变化影响较大.     

后加载和高负荷前加载叶型气动性能的试验研究

采用平面叶栅和环形叶栅吹风试验对后加载和高负荷前加载叶型的气动性能进行了详细的测量和研究.在平面叶栅吹风试验中,测量了2种叶型的压力系数分布,研究了攻角、相对栅距、安装角和马赫数的变化对叶型能量损失系数的影响规律.在环形叶栅吹风试验中,测量了2种叶型的近叶顶、中叶高和近叶根处的压力系数分布以及能量损失系数沿叶高的变化规律.对后加载和高负荷前加载叶型的三维成型规律进行了讨论.试验结果表明:高负荷前加载叶型相对于后加载叶型具有更大的负荷特性;高负荷前加载叶型在采用较大的切向弯曲后可以抑制二次流的发展和减少二次流损失;前加载叶型和后加载叶型均具有优良的气动性能.研究结果对于拓宽高性能叶型在汽轮机中的应用提供了理论基础和技术支持.     

载荷分布对可控扩散叶型性能的影响

叶型吸力面和压力面等熵马赫数分布符合控制扩散规律,则其设计点损失小、低损失攻角范围大。为了研究可控扩散叶型载荷分布对叶栅气动性能的影响,建立了可控扩散叶型自动优化设计方法;并对叶栅进口马赫数为0.7的静子和转子叶型进行多个载荷分布设计,分析载荷分布规律对叶栅性能的影响。结果表明对于静子及转子叶型,载荷前移(至0.1倍相对轴向弦长位置)可抑制吸力面附面层发展,降低设计进气角损失、增大低损失攻角范围;吸力面峰值马赫数增大,吸力面靠前缘凸起程度越大,小攻角损失增加、最低损失对应进气角增大。     

分流叶片位置对平面叶栅流动分离的影响

为更好地控制叶栅流动分离,提出一种在叶栅内部设置分流叶片的流动控制方法.采用数值模拟方法对比在不同攻角下有无分流叶片对叶栅性能及流动损失的影响,结果表明:分流叶片在大攻角条件下,更能提高叶栅的气动性能;选取攻角为11.7°,设计具有不同位置分流叶片的平面叶栅,对比分析发现分流叶片能够提高叶栅的做功能力.分流叶片轴向位置与周向位置存在最优组合,当分流叶片在周向与大叶片吸力面距离为28％弦长时,叶栅气动性能最佳,距离增大或减小均会恶化叶栅性能;轴向位置上,当分流叶片位于大叶片前缘处时,能够抑制尾缘边界层分离,减少流动损失.     

叶片前缘造型对压气机平面叶栅气动特性的影响

为探究叶片前缘造型对压气机平面叶栅气动性能的影响规律,基于Fluent软件,采用一种径向参数造型方法对轴流压气机DMU37动叶根部5%叶高平面叶栅进行前缘改型,分析不同冲角下造型参数变化对叶栅流场气动性能的影响规律.结果表明:切削后的叶栅流场出口截面质量平均的总压损失系数变大,但较小切削深度使可计算正冲角范围扩大2°;在0°及正冲角时,切削后的叶栅静压比提高,端部区域低能流体向叶高中间位置迁移,端部区域总压损失变小;切削后的叶栅流场损失特性变化开始于前缘附近,进而影响整个流道,证明前缘对整个流场气动特性变化具有重要作用,为进一步探索前缘造型方法提供了参考方向.     

临界攻角下锯齿尾缘压气机叶片气动特性

基于Smagorinsky亚格子应力模型的大涡模拟,研究不同攻角下某型压气机叶栅的性能变化规律,获得临界攻角.分析临界攻角下不同齿高比(1.0～2.0)的锯齿尾缘叶片的气动特性及锯齿结构抑制流动分离的物理机理.研究表明：当攻角增至临界攻角时,叶栅的升压、扩压能力达到最大值,但此时伴随着流动分离、涡脱落等复杂流动现象,导致流动损失增加;锯齿尾缘结构能够改善叶片吸力面的流动分离,从而有效地减少吸力面边界层的厚度,延缓叶片失速,并能在不影响压气机增压能力的情况下降低损失;综合考虑流动损失及增压、扩压能力,齿高比在1.2左右时锯齿叶片的性能最佳;相较于基准叶片,最佳锯齿叶片的扩压能力基本相同,但是至少可以减少28.1%的流动损失,并提高1.2%的增压能力.     

串列叶栅前后排叶型对叶片损失的影响

为了研究串列叶栅前后排叶片叶型变化对叶片损失的影响,采用数值模拟方法,对三种不同叶型组合的平面串列叶栅在0°攻角工况下,进行了总压损失分布和损失机理分析。研究结果表明,前排叶片的叶型,尤其是前缘形状的改变对串列叶栅的总压损失分布有显著影响;而后排叶片的叶型变化造成的影响较小;参数L=ρV03/T反映了附面层内熵增的难易程度。由于前排叶片前缘附近的L值要远大于后排叶片,从而导致串列叶栅的总压损失对前排叶片的叶型变化更加敏感。     

不同马赫数下非轴对称端壁扇形叶栅流场

以某一高压涡轮导叶扇形叶栅为研究对象,通过数值和实验方法研究非轴对称端壁造型对涡轮叶栅内二次流的控制机制,分析出口马赫数增加对二次流损失特性的影响规律.结果表明:不同出口马赫数下,非轴对称端壁造型可有效降低总压损失,抑制周向二次流,削弱通道涡强度.出口总压损失系数和涡量随出口马赫数的变化而变化;出口马赫数为0.85时,改善效果最好,出口总压损失系数减小10.81%.     

叶片弯曲对压气机叶栅损失与速度的影响

进行了带尾板的由常规直叶片、正倾斜叶片、正弯曲叶片、反弯曲叶片、S形叶片组成的5种矩型压气机叶栅在低速风洞上的实验研究，测量了叶栅出口流场，分析了零冲角下不同叶片弯曲形式对叶栅出口总压损失分布情况和主流速度的影响．结果表明，弯曲叶片对压气机叶栅出口流场有很大的影响，正弯曲叶栅可以降低叶栅的端壁损失，反弯曲叶栅加大了角区分离，恶化了两端区流动，总损失高于直叶栅．     

涡轮叶栅叶顶间隙泄漏流动实验研究

针对一种高负荷涡轮叶栅,利用低速矩形叶栅风洞实验研究叶顶间隙泄漏流动。研究了不同叶顶间隙和不同来流冲角情况下,涡轮叶栅的流场结构和气动性能。研究工况包括无间隙, 0.5%、1.0%、1.5%叶高间隙和±10°、±5°、0°冲角。通过五孔探针获得矩形叶栅出口截面上总压、气流角以及速度分布;通过叶片表面开设的静压孔,获得叶片中部以及靠近叶顶截面的叶片表面静压分布。实验结果表明:叶顶间隙的存在增强了叶栅顶部的二次流动,恶化了上半叶展的流动状况,涡系结构发生了改变。随着叶顶间隙的增大,叶栅总压损失增加,气流偏转不足/过偏现象加剧;随着冲角的增大叶栅总压损失增加。     

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.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

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