一体化氧化沟弯道流态特性研究

根据实测数据从流速分布的角度对增设水下推动器和弯道导流墙的一体化氧化沟弯道流态进行了研究分析,在实测和分析的基础上,提出了水下推进器和曝气转盘的合理设置位置,阐明了弯道导流墙对弯道流态的作用并提出了导流墙的合理设置方式,为实际工程设计提供了理论依据和参考。     

氧化沟的水头损失计算与导流板偏置的作用

以Ｔ型氧化沟为例阐述了曝气围刷的提升水头与沟内水头损失的关系,剖析了氧化沟两端弯道设置导流板的减阻作用,提出了导流板偏置可以避免弯曲隔墙背流处的固体沉淀,减少导流板的数量。     

交替曝气条件下Carrousel氧化沟的水力特性测试

对Carrousel氧化沟2种稳态工况和曝气机启／停阶段非定常流场进行了测定与分析,结果表明：在开启2台曝气机的条件下,外沟水流缓慢造成推进器前区段易发生污泥淤积;而内沟较高的水动能有利于防止污泥沉积。开启3台曝气机可使外沟流速增加10％以上,而对内沟段水流影响不大;在启／停曝阶段,流速变化随其与曝气机距离的增加而减慢;整个外沟启／停曝气达到工况稳定所需时间约占运行时间的40％。     

氧化沟中导流墙二维水流流态模拟研究

导流墙是氧化沟中改变水流流向的辅助结构,导流墙广泛采用偏心设置,其设置参数多为经验判断。根据Fluent软件进行模拟导流墙处流速分布情况分析,在不同下游长度、偏心距及导流墙半径的条件下,对导流墙的设置进行讨论,得出其优化的设置参数。     

三沟式氧化沟污泥分布不均的改善

就枣庄市污水处理厂三沟式氧化沟污泥的分布、变化及影响因素等问题进行了初步研究，指出三沟污泥浓度相差较大的原因在于其运行模式和各运行阶段的时间分配，通过增加反硝化阶段的时间可以缩小污泥浓度的差距；另外可以通过安装导流栅板来解决侧沟污泥浓度的差异问题。     

改善氧化沟流速分布及提高曝气机充氧性能的研究

通过对氧化沟的模拟试验，分析了加装导流板前后氧化沟各断面流速分布及充氧性能的变化，说明在氧化沟内设置导流板是防止沟底积泥和提高曝气充氧性能的有效方法。     

盖板对泄洪隧道急流弯道水利特性的影响

采用物理模型实验与三维数值模拟相结合的方法,对采取盖板控制法后的泄洪洞明流弯道水力特性展开了研究,并与未设盖板情况进行了对比。结果表明:设置盖板后,弯段及下游直段水流流态得到改善,弯道两岸及出口水深分布更加均匀,下游直段水流表面波动明显削减,大流量情况下水流流态改善效果更加显著,下游直段水流表面波动更平稳,两岸水深超过直墙的现象消失;弯道流速分布更加均匀,凹凸两岸流速差值降低,平面流场分布更加均匀;底板压强随泄流量的增大而增大,设置盖板后压强增加,弯道出口处压强减小且分布更加均匀,验证了泄洪隧洞急流弯道段设置盖板工程措施的合理性。研究成果可为弯道的流态改善措施提供新思路。     

低温高海拔地区改良型微孔曝气氧化沟工艺设计

对污水处理中3种基本类型的技术特点进行了比较,并根据不利条件下污水工艺设计参数和技术要求,确定了改良型微孔曝气氧化沟工艺.该工艺中的生化反应池通过导流墙、沟内水流＞0.3m/s、池底微孔曝气供氧、生化反应空间分割和泥水合理分配技术强化了净化效果;利用生化反应池较长的污泥龄和停留时间、较低的污泥负荷、较大的风量和风压应对...     

改善氧化沟流速分布的措施

通过多年的研究和模拟试验,提出了加装前后导流板的措施以改善氧化沟的流速分布,消除目前氧化沟所存在的痛病－－池底积泥现象,而且很直观地给出了安装导流板前后的经沟各断面流速分布图。另外,还就目前氧化沟的设计和建造中出现的问题提出了相关的建议。     

改良型Carrousel氧化沟的运行与改造

改良型Carrousel氧化沟在实际运行过程中存在污泥沉积严重、脱氮除磷效果不佳、污泥回流比的控制不够灵活等问题，采用扩容选择池、氧化沟内增加潜水推流器、安装回流污泥计量装置等方式进行技术改造，彻底解决了积泥问题，提高了脱氮除磷效率，并节省了大量能源，降低了生产成本，使系统实现良好的运行状态。     

A/A/O氧化沟流态特性研究及积泥分析

为了探求氧化沟内流速分布规律,解决积泥问题并实现系统能量的优化配置,以重庆市某污水处理厂的A/A/O氧化沟为试验平台,根据曝气转盘及水下推流器的不同组合方式设计了3种试验工况,重点对氧化沟外沟大弯段处的流速分布进行了测试及分析.结果表明:第1沟段下部流速过大容易造成能量浪费,间歇开/停水下推流器可以优化系统的能量配置;...     

A computational investigation of particle distribution and deposition in a 90° bend incorporating a particle–wall model

This paper investigates the particle flow movement and deposition in a 90° bend after a straight duct, utilizing the Lagrangian particle-tracking model incorporated with a particle–wall collision model. Particle turbulent dispersion is introduced by employing the ‘eddy lifetime’ model, and particle deposition velocity in the bend is proposed by counting the number of deposited trajectories in a time period. The developed models are validated for both airflow and particle flow by previous experimental data. Particle distribution and deposition behavior at five size groups (1, 3, 5, 9, and 16 μm) are investigated. The simulation results show that, compared with traditional ‘Trap’ model, the particle–wall collision model postpones the emergence and slows the increase of the ‘particle free zone’ as the particle diameter increases. Particle deposition velocity in the duct bend is also generally predicted by the proposed estimation equation under the simulated conditions. This reveals that adopting the particle–wall collision model obtains a reasonable prediction of particle distribution and deposition in the duct bend. This work will benefit the understanding and application of microparticle flow in curved duct systems.     

Experimental study and numerical investigation of particle penetration and deposition in 90° bent ventilation ducts

Particle deposition in a ventilation duct is a severe problem as it can pose health hazards. This is more evident in 90° bent ventilation ducts. The exposure of particle deposition location in bend section is important and useful in understanding and dispelling particle contamination. This paper investigated particle penetration and deposition in 90° bent ventilation ducts numerically and validated using experimental and previous research data. In the numerical study, particle penetration and deposition in a 2D 90° bend turbulent flow were analyzed. The Renormalized Group (RNG) k-<epsilon > model and Lagrangian particle tracking model were utilized to characterize turbulent gas flow and particle behavior, respectively. Particle turbulent dispersion was introduced by adopting the eddy lifetime model with the near wall fluctuating velocity corrected to take turbulence anisotropy into account. In the experimental validation, particle pollution collected from an actual ventilation duct was observed. The particle penetration rates in a test duct at 6 different Stokes numbers were measured for validation. The numerical results were consistent with both the experimental study and the data obtained from previous research.     

The computation of two-dimensional steady-state temperature distributions using the Schwartz-Christoffel transformation

The application of the Schwartz-Christoffel transformation to corners in homogeneous walls is described. The patterns of temperature and heat flow distributions in symmetrical and asymmetrical cases are illustrated. The effect of the bend on the rate of heat flow through the wall is shown for various wall thickness ratios. Charts are given to allow the distance from the inside bend to be found at which the rate of heat flow across the corner approximates to unidimensional heat flow.     

弯道水流的紊动特性

针对弯道水流的紊流现象,应用声学多普勒测速仪,对弯道概化模型进行施测,并对弯道水流的紊动特性进行了研究,得到关于弯道水流紊动强度和雷诺应力方面的成果,为其进一步的研究提供了理论基础。     

Effect of ventilation duct as a particle filter

This paper discusses the effect of ventilation duct as a particle filter by modeling particle deposition in ventilation ducts, which is the reason that ventilation ducts could “filter” particles. An Eulerian model is employed to predict the particle deposition velocity onto the wall and floor from fully developed turbulent flow in ventilation ducts [Zhao B, Wu J. Modeling particle deposition from fully developed turbulent flow in ventilation duct. Atmospheric Environment 2006;40:457–66], while an empirical equation is proposed to predict the particle deposition velocity onto the ceiling combined with experimental data and, another empirical equation by McFarland et al. [Aerosol deposition in bends with turbulent flow. Environmental Science and Technology 1997;31:3371–7] is used for predicting the particle penetration through the bends, which are hard to analyze by theoretical method.     

Ecological study of activated sludge settling property in the completely mixed system

The bulking problem associated with both nitrogen-rich and nitrogen-deficient activated sludges was thoroughly investigated under a DO sufficient condition in the completely-mixed continuous flow system. The reactor temperature was controlled at 27 ± 1°C and the pH was maintained at nearly equal to 7.0. The activated sludge cultures were acclimated under various organic loadings and their settling characteristics were determined by sludge volume index and zone settling velocity. The contents of sludge protein and carbohydrate along with the cell surface charge were examined for understanding the correlation between sludge composition and sludge settleability. Also, the major types of long-length filaments existed in the bulky activated sludge were identified. Moreover, the effect of sludge settleability on effluent quality was determined.     

基于FLUENT天然气集输管道直角弯管磨损分析

应用Fluent软件对直角弯管磨损情况进行数值模拟,研究天然气集输过程中有浮升力和无浮升力条件下不同颗粒直径、不同气流流速条件对弯管磨损的影响,研究结果表明:无浮升力和有浮升力条件下,随着粒径增大,弯管壁面的1.5 s累计最大冲蚀量先减小后逐渐增大,粒径小于50μm的微小颗粒对管壁的冲蚀磨损程度较小。有浮升力条件下,管道壁面的1.5 s累计冲蚀量有所增大,这是由于颗粒在浮升力作用下更多地碰撞弯管壁面。无浮升力和有浮升力条件下,随着粒径增大,弯管壁面的1.5s累计最大沉积量先快速下降而后缓慢增加。有浮升力的条件下,颗粒运动对壁面的沉积效应有所缓解,随着粒径的不断增大,浮升力对管壁的沉积影响逐渐变小。较小粒径的颗粒受浮升力影响在管道沉积方面表现更为敏感。无浮升力和有浮升力条件下,随着气流入口流速的不断增大,弯管壁面的1.5 s累计最大冲蚀量逐渐增大。有浮升力条件下,当入口流速增大时,增大的浮升力导致颗粒跳跃增多,浮升力作用增强了颗粒对弯管壁面的冲蚀破坏。无浮升力和有浮升力条件下,随着气流入口流速的不断增大,弯管壁面的1.5 s累计最大沉积量呈现先减小后逐渐增大的趋势。有浮升力条件下,入口流速增大时,边界层内速度梯度使颗粒旋转而产生更大的浮升力,致使颗粒的沉积量减少。但随着入口流速的继续增大,边界层厚度逐渐变薄,,浮升力的影响作用减小,颗粒沉积量增大。合理控制入口流速能够有效减少管道磨损。     

An experimental study of low concentration sludge settling velocity under turbulent condition

Particle Image Velocimetry (PIV) was used to study the settling of activated sludge flocs under turbulent flow conditions. Experimental results showed that a larger particle diameter led to a higher settling velocity while the higher turbulence intensity led to lower settling velocity. Based on the measurements a mathematical relation has been derived which correlates the settling velocity for individual sludge flocs under turbulent conditions through a modified Vesilind equation. Settling velocity shows a power-type relation to sludge particle diameter and an exponential-type relation with turbulence intensity and sludge concentration.