单-双蜗壳泵隔舌区压力脉动及径向力特性分析

为揭示单-双蜗壳离心泵的不同水力特性,应用商业软件FLUENT,采用RNGk-ε湍流模型和滑移网格技术,对单-双蜗壳双吸离心泵进行不同工况下三维非定常湍流数值模拟,得到不同蜗壳隔舌区计算点的压力脉动情况,并对其进行频域分析.结果表明:单蜗壳离心泵在设计工况及大流量工况下,压力脉动频率以叶片通过频率为主;在小流量工况下,压力脉动频率以低于1倍叶片通过频率为主,在0.6倍设计流量工况下,其压力脉动最大幅值约为设计工况下1.13倍.双蜗壳离心泵在小流量、设计流量及大流量工况下,压力脉动频率均以叶片通过频率为主,在0.6、0.8和1.2倍设计工况下,其压力脉动最大幅值分别约为设计工况的6.59、3.12和4.55倍.相比较于单蜗壳泵,双蜗壳泵能有效地平衡径向力,在偏离设计工况下径向力变化不大.     

不同径向间隙对双蜗壳泵径向力影响的数值模拟

通过改变蜗壳基圆直径改变叶轮与隔舌之间的间隙,采用CFD软件Fluent对5种蜗壳基圆直径的双蜗壳离心泵作全流场计算.计算采用雷诺时均方程和RNGk-ε湍流模型,压力和速度耦合采用SIMPLEC算法.通过离心泵径向力的数学计算模型获得不同基圆直径离心泵叶轮所受的径向力大小,并对其进行比较分析.结果表明:相比于单蜗壳泵,双蜗壳结构泵能有效地减小径向力,在设计点运行时径向力最小且不为0,偏离设计工况下径向力逐渐增大,但不同工况下径向力的变化不大,验证了双蜗壳能有效地平衡径向力;不同基圆直径工况下,随着基圆直径的增大,叶轮所受的径向力大小先减小后增大,说明适当增大蜗壳基圆直径能减小作用在叶轮上的径向力,起到降低振动和噪音的作用,并使效率有所提高.同时针对蜗壳基圆直径为397mm的泵进行性能试验,与数值模拟结果对比分析表明数值模拟的方法可行.     

仿生蜗壳结构对离心泵隔舌区域脉动特性的影响

为了有效降低离心泵隔舌区域压力脉动特性,基于长耳鸮特殊的羽翼形态,建立仿生蜗壳结构计算模型.采用数值模拟的方法对标准蜗壳、仿生蜗壳离心泵全流场进行瞬态计算,对比分析了设计工况下不同蜗壳结构隔舌区域各监测点脉动特性,研究了不同工况下不同蜗壳结构隔舌头部的脉动特性.结果表明:不同工况下,各监测点的压力脉动频率基本与叶片通过频率一致;设计工况下,采用仿生蜗壳时相对于标准蜗壳各监测点脉动幅值均有所下降,最大降幅达56.1%;3种工况下,采用仿生蜗壳时隔舌头部脉动幅值在标准工况及大流量工况下均会降低;设计工况下采用仿生蜗壳可以显著改善其叶轮流道及扩散段流体的流动状态,使离心泵内部流场更平缓,提高其运行的稳定性.     

离心泵蜗壳内部清水流动测量

利用ＬＤＶ分别测量了最优和小流量工况下矩形断面蜗壳内３个断面内的清水平均流动．实 验发现,蜗壳内部液体绝对速度的圆周分速度比径向分速度大一个数量级;蜗壳内存在螺旋运动; 蜗壳断面内流体角动量不守恒;无论在最优还是在小流量工况,蜗壳内部流动都是扩压流动;在小 流量工况,扩压更为严重．     

基于CFD的离心泵关死点流动性能分析

 流体动力学数值计算（CFD）被广泛用于研究离心泵内部的流场和外特性预测,在设计工况下计算准确性较高,近年在流体机械领域的研究中占有重要位置。然而针对关死点工况离心泵流场的CFD 模拟,现有研究都是采用极小流量作为边界条件,难以得到水泵关死点的真实流动性能。本文采用完全零流量的边界条件,以常用的IS125 型管道离心水泵为例,借助于瞬态CFD 流场计算技术,进行关死点及其附近工况的非定常流场数值模拟和性能预测,并得到实测结果的验证。研究结果发现,在非设计工况尤其是关死点和小流量工况下,叶轮每个通道内具有不同的流场分布和过流能力,导致水泵性能参数出现较大的脉动现象。在关死点工况下,蜗壳隔舌所承受的流动冲击最为严重,靠近蜗壳上游的叶轮通道是排水状态,而靠近蜗壳下游的叶轮通道则是吸水状态。本文提出的关死点和小流量工况下离心泵流场计算方法能较为有效的预测该工况下泵的扬程和轴功率,得到的叶轮流道过流能力大小的结论,具有一定的学术和工程价值。     

隔舌对离心泵压力脉动特性及内部流场的影响

为了明确隔舌对离心泵内部流场影响,采用滑移网格技术,对离心泵不同隔舌蜗壳情况下的外特性进行数值模拟,并结合试验分析隔舌形状对离心泵效率和扬程的影响。同时,对不同工况下单隔舌蜗壳、双隔舌蜗壳离心泵压水室各截面上压力脉动特性及其内部流场特性进行研究。研究结果表明:双隔舌蜗壳相比于单隔舌蜗壳对离心泵外特性的影响很小;单隔舌蜗壳、双隔舌蜗壳离心泵压水室各截面的压力脉动频率以叶片通过频率为主,各压力脉动幅值以近隔舌处尤为激烈;采用双隔舌蜗壳时压水室各截面压力脉动幅值明显减小,压力脉动频率多集中在中低频;在偏离设计工况下,单隔舌蜗壳离心泵的某些截面上压力脉动幅值有锐增现象,双隔舌蜗壳时其压力脉动最大降幅达45.5%;双隔舌蜗壳离心泵内部流场流动状态较好,隔舌处速度梯度变化均匀,更利于流体流动。     

径向力对螺旋离心泵转子系统动力学响应的影响

为了研究流体激励力对螺旋离心泵转子系统动力学响应的影响,以一台单叶片螺旋离心泵为研究对象,利用CFX 14.5对泵的内部流场进行了非定常计算,得到了不同流量工况下叶轮所受的径向力随时间的变化情况.建立了转子系统的有限元模型,对转子的临界转速和振型进行了分析,研究了以不同流量工况下的径向力作为外部激励时,转子系统的瞬态响应.结果表明:不同流量工况下,叶轮的径向力均呈周期性变化,周期和叶轮旋转的周期相同;径向力可以分解为恒定量和脉动量,随着频率的增加,脉动峰值逐渐减小;在设计转速下,转子系统不会发生共振;当考虑径向力的作用时,叶轮上监测点处的径向位移呈现复杂的周期性变化,径向力的频率成分会在振动过程中体现出来.     

基于OpenFOAM的离心泵内部流动数值模拟

分析了离心泵内流模拟中存在的问题,指出开源CFD软件是提高离心泵内流模拟精度的必然选择.通过在开源计算流体力学软件OpenFOAM的求解器中添加GGI动静耦合处理程序,实现了OpenFOAM在泵内流数值模拟中的应用.应用修改后的OpenFOAM求解程序对一比转数为117.8的离心泵不同工况下的内流场进行数值模拟,并将数值计算结果与试验结果进行了对比,同时分析了叶轮内部流场的分布规律.研究结果表明,设计工况下的计算扬程相对误差最小,约为-3.5%,而小流量工况下误差最大-6.4%;各工况下的计算效率绝对误差范围均在-0.5%以内.这说明设计工况下的模拟结果优于非设计工况下的计算结果.同时,叶轮内部压力分布和相对速度分布规律符合离心泵内部流动的一般规律.     

前向多翼离心风机叶片尾迹和蜗壳二次流动的试验研究

对前向多翼式离心风机建立了性能及流场测试台位 性能试验及流场测试表明,性能试验重复性良好,曲线符合理论性能曲线.用粒子图像速度场仪技术对叶片尾迹区及蜗壳出口横截面上的二次流做了详细的变工况测量与分析.结果表明:叶片尾迹区脉动强度达20%～70%;在设计工况附近叶片尾迹影响区域小,在非设计工况下叶片尾迹影响区域大,尾迹区域占到蜗壳径向宽度的15%～25%,约是叶片弦高的2～3倍;在蜗壳横截面上明显存在二次流旋涡;沿着蜗壳旋出方向二次流对称分布,但是到达出口时,小流量下两侧旋涡结合成一个旋涡,大流量下两侧旋涡一直保持到蜗壳出口.     

复杂泵体压力脉动特性的数值模拟

为了揭示复杂泵体水力的不稳定性,以减压塔底泵为例,利用计算流体动力学（CFD）对泵内部非定常流场进行数值模拟计算.根据得到的蜗壳内压力脉动情况,对其时域和频域进行分析.结果表明：各工况下压力脉动频率均以叶片通过频率为主,且次级蜗壳内的压力脉动比首级要明显;蜗壳内压力脉动最大值出现在隔舌附近,且沿蜗壳流道螺旋线方向压力脉动幅值依次减小;设计工况下蜗壳内压力脉动强度小于非设计工况下的,次级蜗壳隔舌处小流量工况下压力脉动幅值约为设计流量时的2.63倍.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

海南岛地体及其毗邻陆缘晚中生代—新生代古地磁研究和构造演化

本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。     

Exciton Seebeck in Molecular Systems

Various applications relevant to the exciton dynamics,such as the organic solar cell,the large-area organic light-emitting diodes and the thermoelectricity,are operating under temperature gradient.The potential abnormal behavior of the exicton dynamics driven by the temperature difference may affect the efficiency and performance of the corresponding devices.In the above situations,the exciton dynamics under temperature difference is mixed with     

Achieving Unusual States of Matter Under High Pressure

The elongation method,originally proposed by Imamura was further developed for many years in our group.As a method towards O(N)with high efficiency and high accuracy for any dimensional systems.This treatment designed for one-dimensional(ID)polymers is now available for three-dimensional(3D)systems,but geometry optimization is now possible only for 1D-systems.As an approach toward post-Hartree-Fock,it was also extended to     

《Chinese Science Bulletin》SUBJECT INDEX TO VOLUME 59(2014)

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An on-line scaling method for improving scalability of a database cluster

The explosive growth of the Internet and database applications has driven database to be more scalable and available, and able to support on-line scaling without interrupting service. To support more client's queries without downtime and degrading the response time, more nodes have to be scaled up while the database is running. This paper presents the overview of scalable and available database that satisfies the above characteristics. And we propose a novel on-line scaling method. Our method improves the existing on-line scaling method for fast response time and higher throughputs. Our proposed method reduces unnecessary network use, i.e. , we decrease the number of data copy by reusing the backup data. Also, our on-line scaling operation can be processed parallel by selecting adequate nodes as new node. Our performance study shows that our method results in significant reduction in data copy time.     

An improved R-tree based on childnode''s probability

R-Tree is a good structure for spatial searching. But in this indexing structure,either the sequence of nodes in the same level or sequence of traveling these nodes when queries are made is random. Since the possibility that the object appears in different MBR which have the same parents node is different, if we make the subnode who has the most possibility be traveled first, the time cost will be decreased in most of the cases. In some case, the possibility of a point belong to a rectangle will shows direct proportion with the size of the rectangle. But this conclusion is based on an assumption that the objects are symmetrically distributing in the area and this assumption is not always coming into existence. Now we found a more direct parameter to scale the possibility and made a little change on the structure of R-tree, to increase the possibility of founding the satisfying answer in the front sub trees. We names this structure probability based arranged R-tree (PBAR-tree).     

Integrating GIS Web services based on mediating architecture

The geographic information service is enabled by the advancements in general Web service technology and the focused efforts of the OGC in defining XML-based Web GIS service. Based on these models, this paper addresses the issue of services chaining,the process of combining or pipelining results from several interoperable GIS Web Services to create a customized solution. This paper presents a mediated chaining architecture in which a specific service takes responsibility for performing the process that describes a service chain. We designed the Spatial Information Process Language (SIPL) for dynamic modeling and describing the service chain, also a prototype of the Spatial Information Process Execution Engine (SIPEE) is implemented for executing processes written in SIPL. Discussion of measures to improve the functionality and performance of such system will be included.