用RSM模拟旋风分离器内的三维湍流流场

为了选择更适合于旋风分离器流场数值模拟的湍流模型,采用多种湍流模型对旋风分离器的内流场进行数值模拟,并将计算值与试验值进行比较.结果显示:采用RSM(雷诺应力模型)得到的结果比采用标准k-ε模型的更贴近实验值,更适合用于强旋流流场的数值模拟,揭示了强旋流所具有的涡结构及各向异性的特点;采用雷诺应力模型及曲线坐标系下的SIMPLEC算法可以计算湍流各向异性的复杂三维流场.     

缝隙式排气管对旋风分离器的性能影响

为降低传统旋风分离器工作时排气管内气流高速旋转造成的大量能量损失,将Lapple型旋风分离器的排气管改进为缝隙式排气管,利用数值模拟和实验的方法分析了缝隙式排气管对旋风分离器的性能影响.采用RSM模型对气相流场的切向速度、静压、流动轨迹、湍流强度以及压降进行数值模拟,采用多相流模型中的DPM模型对分离器的分离效率和颗粒运动轨迹进行仿真分析.仿真分析结果与实验验证结果吻合度较好,有较高的预报精度.最终结果表明,缝隙式排气管可使传统旋风分离器的压降下降6.8%,分离效率提升5.5%;当排气管上缝隙长度或宽度增加至一定数值,分离器的分离效率达到最大.随着排气管上缝隙长度或宽度的增加,旋风分离器的分离效率逐渐趋于稳定,压降持续降低;排气管上的矩形缝隙可使排气管内产生旋进涡核(PVC)现象,随着缝隙长度的增加,旋进涡核现象有所减弱,缝隙宽度的变化对旋进涡核现象影响较小;缝隙式排气管可有效抑制普通排气管中心处回流区的产生,并使普通排气管底部以及外旋流的湍流强度降低,从而减少排气管底部的短路流,提高分离效率.通过观察不同颗粒粒径的电石渣颗粒的运动轨迹,可知Lapple型旋风分离器与新型旋风分离器内部流场呈现出有利于固体颗粒分离的组合涡结构,排气管结构的改变并未影响分离腔的原始涡流结构.     

旋风分离器内部流场及分离效率的数值仿真

为了研究旋风分离器内部气体和固体的运动状况与其分离机理,采用FLUENT软件对一旋风分离器内部气相流场和颗粒的运动状况进行三维数值仿真模拟.在仿真过程中,采用RNGk-ε方程来模拟其中的气相湍流流动,采用Lagrange方程模拟颗粒的运动.仿真结果表明,分离器内部的流动空间可分为内、外两个流动区域,在不同的流动区域中,气体压力、速度场的分布有较大的差异;固体颗粒的运动较为复杂,且带有一定的随机性;固体颗粒的分离效率与其进入分离器的具体位置有关.     

旋风分离器气相流场的数值模拟

为了考察适合旋风分离器流场模拟的湍流模型,采用三维贴体网格,应用ＰＨＯＥＮＩＣＳ程序对某旋风分离器气相流场进行了数值模拟,湍流模型分别采用标准ｋ－ε模型和Ｃｈｅｎ－Ｋｉｍ模型。通过计算结果与实验数据的对比发现,与标准ｋ－ε模型相比较,Ｃｈｅｎ－Ｋｉｍ模型更适合于模拟涡旋流动,可以用来进行旋风分离器流场模拟。     

旋风分离器内气相湍流流动的数值模拟

采用标准k-ε模型、雷诺应力模型(RSM)以及k-w模型对旋风分离器内部湍流流场进行了数值模拟.对比了采用两种不同的离散格式时的计算表现,分析了不同近壁模型对于模拟结果的影响.通过数值解与实验值进行的对比发现采用雷诺应力模型较k-w模型,k-ε模型能更准确地模拟分离器内强旋流场.     

CFD技术在旋风分离器内部流场中应用的可靠性分析

简要介绍了CFD技术,并利用CFD技术对旋风分离器进行数值研究,探讨了适用于旋风分离器的计算模型,包括湍流模型的选择、多项流模型的选取以及内部空气柱的分析方法。以锥形分离器为例进行数值计算和模拟,获得了旋风分离器中内部流场的静压云图、速度云图和速度矢量图,并用模拟结果与实际情况作为参照,得出可信性分析,这在以后对于旋风分离器的优化设计及性能分析有着重要的指导意义。     

旋风分离器压降数值分析

根据旋风分离器的结构和气流流动特点,在旋风分离器流场和浓度测定的基础上,以旋风分离器切向速度模型为基础,模拟进出口静压、动压,数值模拟结果与压力损失理论解析计算模型基本吻合,验证了旋风分离器内压降基本分布规律。     

轴入式旋风分离器分步湍流模型的 数值模拟与试验

针对轴入式旋风分离器的气相流场,提出了一种基于RNGκ-ε模型和雷诺应力模型的分布湍流模型并进行模拟研究.首先对5种分离器模型的气相流场采用RNGκ-ε模型进行模拟.待气相场趋于稳定时,加入离散颗粒相,对气相改用雷诺应力模型模拟;根据已得到的流场对颗粒相采用随机轨道模型,分析分离器阻力与效率性能.最后将典型模型的模拟结果与试验结果进行比较,二者吻合良好.基于分步湍流模型的数值模拟方法在研究轴入式旋风分离器的气相流场是可靠的.     

旋风分离器气固两相流动特性与最优管距

为提高旋风分离器的除尘效率,采用RSM湍流模型和相间耦合的随机轨道模型,模拟计算了不同排气管插入深度对旋风分离器内气相流场和除尘器中颗粒运行轨迹的影响。模拟计算结果显示:在相同条件下,与现有旋风分离器相比,排气管插入390mm时,可以在气流作用下提高颗粒物与筒锥体壁相撞的概率,除尘效率提高5%。根据模拟结果,调整旋风分离器进气管进行物理模型试验,与数值模拟结果相吻合。     

新型旋风分离器内颗粒的运动规律

分离效率是判定旋风分离器性能优劣最直接的一个参数,而分离效率的高低微观上由旋风分离器内颗粒的运动规律决定.采用离散颗粒模型研究了新型旋风分离器内颗粒的运动规律并估算了分离效率,结果发现:颗粒从入口不同区域进入该旋风分离器分离空间时有不同的运动轨迹,入口大致可划分为3个区域;被入口导流板碰撞分离的颗粒在发生二次分离时被再次捕集的可能性很大;分离效率实验值和模拟估算值变化趋势一致,但模拟估算值高于实验值.     

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…     

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.     

Tracking data management using topology of moving object database system for moving object constrained trajectory in LBS application

Advances in wireless technologies and positioning technologies and spread of wireless devices, an interest in LBS (Location Based Service) is arising. To provide location based service, tracking data should have been stored in moving object database management system (called MODBMS) with proper policies and managed efficiently. So the methods which acquire the location information at regular time intervals then, store and manage have been studied. In this paper, we suggest tracking data management techniques using topology that is corresponding to the moving path of moving object. In our techniques, we update the MODBMS when moving object arrived at a street intersection or a curved road which is represented as the node in topology and predict the location at past and future with attribute of topology and linear function. In this technique, location data that are corresponding to the node in topology are stored, thus reduce the number of update and amount of data. Also in case predicting the location,because topology are used as well as existing location information, accuracy for prediction is increased than applying linear function or spline function.