某电厂不同供水系统输水的水锤仿真模拟研究

以长距离输水和循环水系统输水管线为例,在管线中无任何水锤防护措施,仅在泵出口处安装两阶段关闭的蝶阀的情况下,对比了两阶段关阀时间的区别.模拟计算结果表明,两种工况下的关阀时间相差不大,长距离输水系统采用一个水锤相的时间来全部关闭阀门的措施符合分析结论;循环水系统管线较短,可不采用一个水锤相的时间来关阀,水锤发生时的管内...     

Cost–benefit analysis of constructing a filtration plant for the National Water Carrier in Israel

The paper presents an economic cost–benefit analysis (CBA) of the construction of a filtration plant for the Israeli National Water Carrier (NWC). Its main contribution lies in the comparison between the costs and the benefits of filtration in the context of a concrete policy choice. The first part of the paper presents a cost analysis of two alternative engineering systems: central filtration and localized filtration. The analysis shows that the costs of constructing and operating a central filtration plant are significantly lower than those of a system of local plants. The second part of the paper presents a two‐stage method for assessing the benefits of filtration. First, we valuate the damages caused by consumption of unfiltered water; then we estimate consumers' willingness to pay (WTP) for improved water quality, taking into account households' potential risk aversion. The main result is that total WTP significantly outweighs the costs of constructing and operating the plant.     

某电厂循环水系统瞬态过程分析研究

针对某电厂循环水供水系统特点,应用AFT ImpulseTM4.0动态流体(水锤或汽锤)分析软件,对系统事故停泵水力过渡过程进行了计算机仿真.从仿真结果看,最大水锤升压发生在循环水泵事故关阀,备用泵投运工况,此时需要设置水锤防护设施,避免过大的水锤压力破坏设备.经计算机仿真计算得出的结论,是系统设备选型及相应设计参数选取的依据,对提高电厂循环水系统的可靠性和运行稳定性具有重要的意义.     

A systematic approach towards the structural behaviour of a lightweight deck–side shell system

Lightweight structures are increasingly used for high-speed ships. This paper presents a systematic approach to analyse the structural behaviour of a lightweight deck–side shell system using high strength steel. An analytical model of the deck–side shell system was first given, which includes the effects of stiffeners for the deck and side shell, the support conditions of the centreline girder (CL-girder), the influence of transverse beams, and the interaction between the side shell and the lightweight deck as parts of problems to the solution. By changing several geometric parameters, the sensitivity of both overall and local stress and deflection for the deck–side shell system was investigated. The different geometric parameters analysed comprise the influence for variation in the thickness of the web for transverse beams, longitudinal stiffeners and the CL-girder, the thickness of lower flange for the transverse beam and, the thickness for the panel. Furthermore, the influence of the lightweight deck and loads from the deck above on the side shell, the effects of the side shell and loads from top deck on the deck, the support conditions for the CL-girder, and the influence of deck loads on the eigenmodes were also analysed. By evaluating the results obtained from FE simulation, the support conditions of the CL-girder, the thickness of the panels and the lower flange of the transverse beams were found to be the most relevant parameters affecting both the stress and the deflection distribution of the structure. The dynamic characteristics of the structure were also analysed. The FE analysis concerning buckling of the structure was present. The results enable naval architects and structural engineers to design new extreme lightweight deck structure more reliable and economical. And some suggestions for future research are also given.     

A study on the energy performance of a cooling plant system: Air-conditioning in a semiconductor factory

This paper will focus on the energy performance evaluation of a cooling plant system in a semiconductor factory. Several energy saving technologies namely: integrated cooling towers, free cooling systems, control of the chilled water quantity, etc., have been adopted to improve efficiency of the cooling plant system. We have collected actual operating data for 2 years and evaluated the performance of chillers’ COP and the whole cooling plant system's COP and they showed satisfactory results even if the thermal load of the factory was about half compared with design phase assumption.

We also have verified each effect of the energy saving technologies through model-based simulation analysis. The annual electric power consumption dropped about 35% compared to conventional cooling plant systems in case of design phase thermal load. And the faulty status operation of the chiller's number control miss occurred while we monitored. Electric power consumption increased about 17% compared to normal status operation at the same period.     

Morphological and physicochemical characteristics of iron corrosion scales formed under different water source histories in a drinking water distribution system

The corrosion scales on iron pipes could have great impact on the water quality in drinking water distribution systems (DWDS). Unstable and less protective corrosion scale is one of the main factors causing “discolored water” issues when quality of water entering into distribution system changed significantly. The morphological and physicochemical characteristics of corrosion scales formed under different source water histories in duration of about two decades were systematically investigated in this work. Thick corrosion scales or densely distributed corrosion tubercles were mostly found in pipes transporting surface water, but thin corrosion scales and hollow tubercles were mostly discovered in pipes transporting groundwater. Magnetite and goethite were main constituents of iron corrosion products, but the mass ratio of magnetite/goethite (M/G) was significantly different depending on the corrosion scale structure and water source conditions. Thick corrosion scales and hard shell of tubercles had much higher M/G ratio (>1.0), while the thin corrosion scales had no magnetite detected or with much lower M/G ratio. The M/G ratio could be used to identify the characteristics and evaluate the performances of corrosion scales formed under different water conditions. Compared with the pipes transporting ground water, the pipes transporting surface water were more seriously corroded and could be in a relatively more active corrosion status all the time, which was implicated by relatively higher siderite, green rust and total iron contents in their corrosion scales. Higher content of unstable ferric components such as γ-FeOOH, β-FeOOH and amorphous iron oxide existed in corrosion scales of pipes receiving groundwater which was less corroded. Corrosion scales on groundwater pipes with low magnetite content had higher surface area and thus possibly higher sorption capacity. The primary trace inorganic elements in corrosion products were Br and heavy metals. Corrosion products obtained from pipes transporting groundwater had higher levels of Br, Ti, Ba, Cu, Sr, V, Cr, La, Pb and As.     

Occurrence of aromatic amines and N-nitrosamines in the different steps of a drinking water treatment plant

The occurrence of 24 amines within a full scale drinking water treatment plant that used chlorinated agents as disinfectants was evaluated for the first time in this research. Prior to any treatment (raw water), aniline, 3-chloroaniline, 3,4-dichloroaniline and N-nitrosodimethylamine were detected at low levels (up to 18 ng/L) but their concentration increased ∼10 times after chloramination while 9 new amines were produced (4 aromatic amines and 5 N-nitrosamines). Within subsequent treatments, there were no significant changes in the amine levels, although the concentrations of 2-nitroaniline, N-nitrosodimethylamine and N-nitrosodiethylamine increased slightly within the distribution system. Eleven of the 24 amines studied were undetected either in the raw and in the treatment plant samples analysed. There is an important difference in the behaviour of the aromatic amines and N-nitrosamines with respect to water temperature and rainfall events. Amine concentrations were higher in winter due to low water temperatures, this effect being more noticeable for N-nitrosamines. Aromatic amines were detected at their highest concentrations (especially 3,4-dichloroaniline and 2-nitroaniline) in treated water after rainfall events. These results may be explained by the increase in the levels of amine precursors (pesticides and their degradation products) in raw water since the rainfall facilitated the transport of these compounds from soil which was previously contaminated as a result of intensive agricultural practices.     

安徽李楼铁矿矿床充水因素及地下水三维流数值模拟研究

安徽李楼铁矿地质、水文地质研究程度较低,随着生产规模扩大,给安全生产带来隐患,所以需进一步查明该矿区的水文地质条件,预测该矿区的矿坑涌水量,为矿山建设提供科学依据。本文通过分析矿区水文地质条件,研究矿床充水水源、充水通道以及影响充水强度的各种因素;依据有限差分法,利用Modflow数值模拟软件建立了地下水数值模型,并运用该模型预测了-200m深度开采的矿坑涌水量。预测结果合理,可以做为矿山开发规划的依据,并对该矿山防、治水措施提出了建议。     

地铁小系统空调负荷动态模拟与分析

建立了地铁小系统空调负荷动态模拟分析的传热模型,以Visual Basic 6.0和Compaq Visual Fortran等计算机语言为工具,开发出了地铁小系统空调负荷的逐时计算和能耗分析软件.介绍了软件开发的总体思路、主要界面及相关核心内容,通过实际工程的应用阐述了该软件的主要功能,为地铁小系统空调设计和能耗分析提供了理论依据.     

Influence of the depth and shape of a tunnel in the application of the convergence–confinement method

One of the most widely used methods in tunnel support analysis and design is the convergence–confinement method (CCM). For its practical application, it is necessary to study the influence of the depth and cross-section of the tunnel and to confirm the calculations with two- or three-dimensional simulations carried out with finite elements or explicit finite differences programs. These simulations require elevated calculation times. In this paper, a modification of the CCM is proposed that directly introduces the effect of depth and the shape of the tunnel cross-section in the determination of the radial displacement of the tunnel. To do so, a series of functions are determined that approximate the radial displacement at points situated on the perimeter of the cross-section of the tunnel, considering several cross-sections at different distances from the working face. Should the cross-section of the tunnel or its depth be modified, it will not be necessary to perform new numerical simulations in order to apply the CCM. It will only be necessary to use the calculated shape functions. It is thus possible to use the CCM in the analysis and design of the support elements in a quite precise and significantly faster way.     

架空炕采暖作用下建筑热过程的模拟与分析

建立了架空炕采暖作用下建筑热过程的耦合流动和传热模型,并对控制方程进行数值求解。通过实验数据验证,提供了一种准确地分析架空炕采暖系统热性能及预测室内温度的计算方法,可为架空炕采暖系统的优化设计及此种住宅的能耗分析提供工具和指导。     

A numerical study on differences in using Navier–Stokes and Reynolds equations for modeling the fluid flow and particle transport in single rock fractures with shear

The study on fluid flow and transport processes of rock fractures in most practical applications involves two fundamental issues: the validity of Reynolds equation for fluid flow (as most often assumed) and the effects of shear displacements on the magnitudes and anisotropy of the fluid flow velocity field. The reason for such concerns is that the impact of the surface roughness of rock fractures is still an unresolved challenging issue. The later has been systematically investigated with results showing that shear displacement plays a dominant role on evolutions of fluid velocity fields, for both magnitudes and anisotropy, but the former has not received examinations in details due to the numerical complexities involving solution of the Navier–Stokes (NS) equations and the representations of fracture geometry during shear. The objective of this paper aims to solve this problem through a FEM modeling effort.Applying the COMSOL Multiphysics code (FEM) and assuming a 2D problem, we consider the coupled hydromechanical effect of fracture geometry change due to shear on fluid flow (velocity patterns) and particle transport (streamline/velocity dispersion), using measured topographical data of natural rock fracture surfaces. The fluid flow in the vertical 2D cross-sections of single rock fractures was simulated by solving both the Navier–Stokes and the Reynolds equation, and the particle transport was predicted by the streamline particle tracking method with calculated flow velocity fields (vectors) from the flow simulations, obtaining results such as flow velocity profiles, total flow rates, particle travel time, breakthrough curves and the Péclet number, Pe, respectively.The results obtained using NS and Reynolds equations were compared to illustrate the degree of the validity of the Reynolds equation for general applications in practice since the later is mush more computationally efficient for solving large-scale problems.The flow simulation results show that both the total flow rate and the flow velocity fields in a rough rock fracture predicted by the NS equation were quite different from those predicted by the Reynolds equation. The results show that a roughly 5–10% overestimation on the flow rate is produced when the Reynolds equation is used, and the ideal parabolic velocity profiles defined by the local cubic law, when Reynolds equation is used, is no longer valid, especially when the roughness feature of the fracture surfaces changes with shear. These deviations of flow rate and flow velocity profiles across the fracture aperture have a significant impact on the particle transport behavior and the associated properties, such as the travel time and Péclet number. The deviations increase with increasing flow velocity and become more significant when fracture aperture geometry changes with shear.     

独立别墅热水供暖系统动态模型、控制策略及能耗分析

建立了独立别墅供暖系统的非线性动态模型并分析了其动态特性,介绍了模型降阶方法及PI控制器参数的设计和整定。针对可能的供暖系统控制策略进行了动态仿真和能耗分析。仿真结果表明,单纯采用室外气候补偿控制模式并不能获得理想的控制效果;采用分室控制模式能满足室内舒适性要求并有一定的节能效果,节能率约为25%。     

高速铁路列车检修库热风系统数值模拟与改进

以京沪高速铁路某列车检修库为例,利用CFD技术,对检修库联合供暖设计方案中列车底部热风系统的实施效果进行了模拟。结合8个典型算例,对检修库内空气速度分布、温度分布、热舒适度指标PMV分布及列车表面的热流密度进行了模拟,确定了合理的送风口位置和最佳的送风参数。