压裂混砂搅拌装置搅拌叶轮结构优化设计研究

为了提高压裂混砂搅拌装置的搅拌效果,以混砂搅拌装置混合时间为实验指标,针对搅拌叶轮的结构特点,采用正交实验及CFD数值模拟相结合的方法研究了搅拌叶轮的主要几何尺寸对混合时间的影响规律,得到了搅拌装置叶轮最佳结构参数,为搅拌叶轮结构优化设计提供了理论支撑。结果表明,搅拌叶轮的几何尺寸变化对混合时间具有一定的影响,其中,上叶轮直径影响最大,下叶轮直径和下叶轮导流筒与叶轮直径比值次之,上叶轮导流筒与叶轮直径比值影响相对较小;搅拌叶轮几何尺寸最优方案对应的混合时间最短,值为11.0s。     

高密度澄清池导流筒对絮凝条件的影响研究

随着水体污染问题日趋突出以及人们对生活饮用水水质要求的不断提高,如何提升水处理构筑物的处理效果备受关注。基于CFD数值模拟的方法对不同处理规模的高密度澄清池的内部流场和流态特性进行了分析,以涡旋速度梯度G0、湍动能k以及湍动能耗散率ε作为絮凝效果的评价指标,研究改变导流筒结构尺寸参数对絮凝水力条件的影响。结果表明,不同处理规模的高密度澄清池的最优导流筒直径D与搅拌桨叶直径d之间满足D/d=1. 28～1. 40,当叶轮直径确定后,使用该式计算的导流筒直径的絮凝条件较按照手册中D/d=1. 1计算得到的导流筒直径的絮凝条件更优。     

混合应用天然与再生骨料混凝土的基本性能

对配合比相同和坍落度相同两种情况下,不同再生骨料掺入量混凝土的基本性能进行了系统的试验研究。试验中再生骨料的掺入量分别为0,25％,50％,75％和100％。试验结果表明,在配合比相同的情况下,随着再生骨料掺入量的增加．混凝土的工作性能以及回弹值、抗压强度、劈裂抗拉强度、抗折强度和弹性模量均有不同程度的降低。在坍落度相同的情况下,随着再生骨料掺入量的增加．混凝土的抗压强度、抗折强度和弹性模量也均降低且较配合比相同的情况下降低更多。最后根据本文的试验结果,建议了两种情况下不同再生骨料掺入量混凝土的基本力学性能计算公式。并进一步对比了两种情况下得到的计算公式．结果表明,两种情况下得到的公式均可以用来描述不同再生骨料掺入量混凝土的基本力学性能。     

福塔纤维沥青混合料马歇尔试验

福塔纤维（FORTA（r）AR）是一种新型的聚合物有机纤维，它由聚丙烯纤维（Polypropylene）和芳纶纤维（Kevkar）按照质量比3：1混合而成。首先，对福塔纤维沥青混合料的拌和工艺进行了研究；其次，选择了4个福塔纤维掺量（0％、0．023％、0．045％和0．068％），并针对每个掺量分别进行了马歇尔试验，确定了不同纤维掺量下的最佳油石比；最后，在最佳油石比下对四种纤维沥青混合料进行了车辙试验，结合马歇尔试验最终确定了最佳纤维掺量。     

d／D值及导流转速对螺旋升流反应器流态的影响

介绍了螺旋升流反应器流态试验的思路及原理；并通过寿命停留时间分布(R1D)试验及多段串联模型，探索d／D值及导流转速(n)对螺旋升流反应器的流态的影响规律；由正交回归试验得到：当d／D=0．50、n=15r/min时，在试验条件下反应器的流态最优，此时平均停留时间t=1．87、串联级数Ⅳ=4．5；并得出和Ⅳ与d／D值和导流转速(n)之间的数学关系。     

混凝土搅拌机充盈率及拌筒型式对混凝土含气量的影响

对混凝土搅拌机充盈率和拌筒型式变化对混凝土含气量的影响进行了分析和试验研究。结果表明：随着充盈率的增加含气量呈缓慢下降趋势，当充盈率值增大到0．32时，含气量明显下降；对同一种搅拌机，搅拌筒的容量越大，含气量越大，搅拌筒内一次搅拌的混凝土装得越满，含气量越小。但混凝土量超过一定数量时，含气量反而增大；相同条件下，窄长型拌筒搅拌的混凝土含气量普遍高于宽短型拌筒。     

海水侵蚀环境下混凝土耐久性的研究

采用普通硅酸盐水泥和矿渣硅酸盐水泥，分别配制了水灰比在0．45～0．60范围内的混凝土试件，采用加速腐蚀试验研究了在海水侵蚀后，其强度、重量损失随时间变化的规律及原因，并为试件损伤状态定量化解析提供了试验数据。结果表明，在相同的试验条件下，矿渣硅酸盐水泥混凝土耐久性优于普通硅酸盐水泥混凝土：混凝土试件的抗蚀系数为0．8时，与美国ASTM标准规定的强度损失25％的界限值吻合较好。     

氧化沟工艺污水处理厂的优化设计

本文基于物理模拟实验论证了不同倒伞型表面的曝气机叶轮与中间隔墙间距对氧化沟效率的影响,同时对比了不同的氧化沟半宽导流墙偏心距对氧化沟工况的影响,从而得出倒叶轮与中间隔墙间距和氧化沟半宽导流墙偏心距最佳设计值。     

高层建筑分散筒结构体系概念及其性能研究

首先阐述了分散筒结构体系的基本概念，然后通过对某高层建筑采用分散筒和框架-核心筒结构两种不同的结构方案进行抗风、抗震性能分析，分析结果表明：在大致相同混凝土用量和使用面积下，分散简体系比框筒周期短；在水平荷载作用下，分散简体系比框筒位移小。     

描述粘土粘塑性的新参数

研究了2种粘土的未扰动上试样和对应的重塑土试样在三轴试验条件下的粘塑性和1种粘土重塑土试样在三轴与单轴试验条件下的粘塑性。试验过程中，不同的加载阶段采用不同的恒定应变率。试验结果表明，3种粘土都表现出很明显的粘塑性。对试验结果的分析发现，粘土的粘塑性可以用一个新的粘塑性参数β来描述。粘土粘塑性越大，β值也越大。试验结果还表明，对于同一种粘土，未扰动土的β值要比重塑土的小；三轴试验条件下得到的β值要比单轴试验条件下得到的小。     

燃气全预混燃烧液槽加热器的研究

在分析目前国内液槽加热现状的基础上,设计了一套燃气全预混燃烧液槽加热系统,包括金属纤维燃烧器、加热浸管及控制系统等部分。对样机进行了测试,分析了实际功率、排烟温度、CO和NOx排放量等实验数据,为进一步研究和设计金属纤维燃气全预混液槽加热系统打下了良好的基础。     

Membrane coupled high-performance compact reactor: a new MBR system for advanced wastewater treatment

This study examined the potential and limitations of a new submerged membrane system coupled with a High-performance Compact Reactor (HCR) to take advantages of both systems. The configuration and installation position in the HCR of the membrane module were thoroughly investigated for the optimum design of a submerged membrane coupled with HCR, e.g., MHCR. Inside the draft tube proved to be better location rather than outside the draft tube or in the degas tank and an open-type configuration of a membrane module has an advantage over a fixed-type configuration in terms of membrane fouling. Comparison of the innovative MHCR with a conventional membrane bioreactor (MBR) was made to identify and prove the superiority of MHCR to MBR with respect to the membrane performance. The MHCR has shown the great potential, particularly for the treatment of wastewater of high organic strength.     

Some dimensionless parameters of impeller power in coagulation-flocculation processes

The simplified equation for impeller power dissipation is well known and power coefficients have been published for most impellers.Most published data apply to cylindrical tanks with or without baffles.This paper is a study of the effect of some impeller and vessel geometry on impeller power dissipation, especially focused on square tanks as commonly used in coagulation-flocculation processes of (waste) waters.The experiments showed that the dimensionless Power number for a square tank can be estimated quite well by the Power number of a baffled cylindrical tank with certain dimensions.The removal of colloidal compounds at a given G value differs with the type of stirrer and vessel applied. The optimal G value is the same for all vessel-stirrer combinations.     

Experimental determination of the rotational capacity of wall-to-base connections in storage tanks

Earthquakes around the world have affected many unanchored tanks used for the storage of petroleum-derived liquids. When these unanchored tanks are subjected to strong motion, the moment generated at the base, by the mass of liquid contained in the tank, will cause partial uplift of the base (i.e. rocking of the tank), inducing cycles of rotation at the wall-to-base connection. Actual codes of standard practice used in Europe and New Zealand limit the rotation that may be allowed at this connection to 0.2 rad. This limit was based on a series of assumptions since no realistic tests had been conducted. This paper presents the experimental research conducted to determine the real rotational capacity of these connections. The tests were carried out considering the bending stresses and the membrane stresses that develop at the base plate when uplift occurs. Specimens from an old existing tank (dismantled) were used. New specimens were also fabricated and used to allow for a more comprehensive study. Results from this research are presented in the form of plots of maximum rotation vs. number of cycles to failure, called RN curves. These curves revealed that the current Eurocodelimit of 0.2 rad is overly conservative. Based on the limited data, a limit of 0.4 rad would be more realistic.     

Development of draft tube in hydro-turbine: a review

The efficiency of a hydraulic reaction turbine is significantly affected by the efficiency of its draft tube. The shape (profile) and velocity distribution at the inlet affect the performance of the draft tube. So far, the design of draft tubes has been improved through experimental observations resulting in ‘rules of thumb’ and empirical formulae. In the last two decades the use of computational fluid dynamics (CFD) for research and designing complex profiles has improved significantly due to its flexibility and cost-effectiveness. A CFD-based design can further be aided with robust and user-friendly optimisation. Numerical analysis of fluid through a draft tube is challenging and time consuming due to complex flow features. Hence there is a need for developing accurate and reliable CFD models together with efficient optimisation. Studies of the principles of draft tube, internal flow pattern, various turbulence models and associated divergence along with results have been presented in this paper. The objective of this paper is to present the application of CFD simulation in design and flow analysis of the draft tube and also find out the factors which influence the deviation of CFD results with experimental results. From the literature, it has been observed that there are several factors (accurate inlet conditions, turbulent models selected for simulation, modification in geometric parameters and accuracy in measurement of experimental results) that influence the draft tube design and performance. Thus, there is a scope of research for optimisation of geometrical parameters of the draft tube for its best performance at full load condition using CFD simulation. It is carried out by applying 3D velocity as an inlet boundary condition measured with particle image velocimetry/laser Doppler velocimetry.     

12A窄高型尾水管稳定性分析

选取了一个弯肘形尾水管,保持肘管尺寸不变,只改变尾水管直锥段尺寸形成6种尾水管,分别比较了6种尾水管高度在某工况下时的压力特征,基于CFD分析技术,充分说明了12A窄高型尾水管性能良好。     

CFD simulation of mechanical draft tube mixing in anaerobic digester tanks

Computational Fluid Dynamics (CFD) was used to simulate the mixing characteristics of four different circular anaerobic digester tanks (diameters of 13.7, 21.3, 30.5, and 33.5 m) equipped with single and multiple draft impeller tube mixers. Rates of mixing of step and slug injection of tracers were calculated from which digester volume turnover time (DVTT), mixture diffusion time (MDT), and hydraulic retention time (HRT) could be calculated. Washout characteristics were compared to analytic formulae to estimate any presence of partial mixing, dead volume, short-circuiting, or piston flow. CFD satisfactorily predicted performance of both model and full-scale circular tank configurations.     

燃气蒸箱热效率测试与计算方法的研究

文章主要介绍了燃气蒸箱热效率的测试与计算方法,并就不同的热效率测试与计算方法进行相关分析与探讨,结合分析探讨内容以及燃气蒸箱的实际使用情况对热效率的测试与计算方法提出相关建议。     

水厂斜管沉淀池出水水质改善技术改造

针对天津市凌庄水厂斜管沉淀池出水浊度较高的问题,对斜管沉淀池进行技术改造。通过在斜管沉淀池排泥车上加装双侧表面冲洗设施,使沉淀池出水浊度明显下降,有效改善了出水水质。同时,节省了相当数量的水厂自用水和人工工时。     

CFD simulation of mixing in egg-shaped anaerobic digesters

A computational fluid dynamics (CFD) model that characterizes mechanical draft tube mixing in egg-shaped anaerobic digesters was developed. Simulation of flow patterns were carried out with a propeller rotating from 400 to 750 rpm, assuming liquid manure to be Newtonian (water) and non-Newtonian fluids depending on the total solids (TS) concentration. Power number and flow number of the propeller in water mixing were validated against lab specifications and experimental data from a field test. The rotational direction and placement of the propeller were examined to identify the primary pumping mode and the optimum position of the propeller fixed inside the tube. Quantitative comparisons of two mixing methods and two digester shapes indicated that mechanical draft tube mixing is more efficient than external pumped recirculation, and that the egg shape provides for more efficient mixing than the cylindrical shape. Furthermore, scale-up rules for mixing in egg-shaped digesters were investigated.