基于ZJU400土工离心机的CFD模拟方法

目的给出可靠的CFD模拟方法,用于土工离心机风阻功率估算,得到流场及温度场模拟结果。方法针对ZJU400中高速大型土工离心机,利用结构化网格划分使转臂及内壁面处的y+值<30,使其满足湍流模型边界层厚度要求。利用k-omega SST湍流模型和MRF多参考系方法对ZJU400土工离心机进行数值模拟,对模拟所得风阻功率、流场和温度场进行对比验证。结果模拟所得风阻功率与ZJU400实测数据偏差<10%,模拟所得流场与文献[8]中的结果吻合,温度场与实测数据吻合。结论针对ZJU400中高速大型土工离心机的CFD模拟方法取得了精度较高的模拟结果,通过仿真模拟弥补了大型土工离心机实验数据缺乏问题,减少了对实验数据的依赖,为制造设计和研究大型土工离心机提供了CFD模拟方法。     

基于CFD的土工离心机风阻及流场特性分析

目的估计土工离心机的风阻功率。方法针对一稳态运行的中低速土工离心机,利用多参考坐标系(MRF)模拟转臂与墙壁之间的相对运动,对离心机稳态运行时机室内的空气流场进行CFD仿真,对计算流体力学仿真、解析公式方法和试验的风阻功率进行对比。结果三种方法得到的风阻功率较为接近,验证了数值仿真方法的正确性。同时,研究了机室内空气流速和压力的空间分布特征,验证了经典解析公式的假设合理性。结论 CFD仿真方法避免了传统解析方法对试验数据的依赖和参数选取主观性,能够得到较高精度的分析结果,该研究为基于计算流体力学的土工离心机的高置信度风阻计算打下了基础。     

高速土工离心机温升的数值模拟

目的 数值计算高速土工离心机机室温度分布,研究不同真空度和侧壁温度对机室温升的影响,并为高速土工离心机提出温控方案。方法 针对一款在建的高速土工离心机,采用SRF方法和RNG k-ε湍流模型对其进行数值计算,对比不同转速下离心机的温升。针对加速度为1 500g的运行工况,对比不同机室压力和侧壁温度对机室温升的影响。结果 高速土工离心机以1 500g加速度运行时,机室最高温度可达83 ℃。运行压力从100 kPa降至3 kPa,机室最高温度下降约15 ℃,侧壁温度每降低10 ℃,机室最高温度降低约5 ℃。另外,真空度配合侧壁冷却无法满足散热要求时,可考虑在机室顶部靠侧壁布置面积不小于顶部面积1/4的冷却环。结论 利用CFD数值计算方法,定量得到了高速土工离心机机室温度随转速、真空度和侧壁温度的变化,为其冷却方案的设计提供了参考。     

横向极板电除尘器二维流场的数值模拟

对横向极板电除尘器内二维流场进行了数值模拟,流场模拟采用k-ε双方程模型,计算采用SIMPLE算法。利用有限体积法对计算区域进行离散,用前处理软件GAMBIT对几何模型进行网格划分,FLUENT流体计算软件对内部流场进行数值模拟,得出了内部流场随入口流速的增加,湍动性增加,阻力损失也会增大。     

湍流模型对预测街道峡谷污染物扩散的影响

文章选取标准k-ε湍流模型、RNGk-ε湍流模型、realizablek-ε湍流模型和单方程Spalart-Allmaras涡黏系数模型对街道峡谷附近的流动和汽车尾气污染物扩散进行了模拟,并与风洞试验值进行了比较,结果表明,4种模型对街谷壁面的浓度预测在趋势上与试验值基本一致,Spalart-Allmaras模型的预测效果最好,realizablek-ε模型预测最差,而标准k-ε模型和RNGk-ε模型的预测介于其间;RNGk-ε模型和realizablek-ε模型的修正作用在预测建筑物尖角和顶部附近的流动处有所体现,但对街谷内浓度分布的预测仍不如标准k-ε模型;本文从流场分布的特点对4种模型的浓度预测差别进行了解释,证明了壁面浓度与其附近的速度和湍流黏性系数的分布相对应。     

电除尘器气流分布试验研究和数值计算

结合660WM机组电除尘器的设计要求,对电除尘器内气流流动进行了数值模拟与试验研究。计算中选择SIMPLE方法求解三维雷诺平均方程和k-ε两方程湍流模型。研究结果表明,无论电除尘器两室流量分配还是第一电场进口断面气流分布,计算结果与试验吻合较好,数值计算结果可以指导电除尘器设计与模型试验研究。     

综合预应力与陀螺效应的TLJ500土工离心机模态分析

目的 分析获得离心机运转时各综合效应对其模态频率的影响.方法 从理论上推导结构在无离心场时,仅考虑预应力刚化效应和仅考虑旋转软化效应与综合考虑各效应时结构固有频率之间的关系.建立TLJ500土工离心机静止状态及运转状态的有限元模型,并根据TLJ500静止状态的模态试验结果对有限元模型中主轴轴承部位的材料参数进行修正识别,获得可信度更高的模型.再将修正识别得到的主轴轴承参数代入离心机运转状态的有限元模型,开展离心机运转状态的模态分析,结合理论分析结果,计算得到综合考虑预应力刚化效应与旋转软化效应时离心机关心模态频率的结果.结果 运转状态TLJ500离心机关心模态频率计算结果与试验结果比较一致.结论 仿真结果验证了文中方法的可行性,为离心机临界转速设计提供了一种可信的数值模拟预测方法.     

双进水管系统对单通道矩形圆弧角养殖池水动力特性影响的数值研究

为研究双进水管结构工况不同布设位置对海水循环水矩形圆弧角养殖池池底水动力特性的影响,基于RNG k-ε湍流模型,应用计算流体力学仿真技术,对双进水管结构工况下6种不同布设位置的养殖池内部流场进行三维数值模拟,采用流体动力学特征量重点分析排污口附近复杂的流场形态。研究结果表明:双进水管结构中进水管的布设位置对养殖池底部流速分布影响显著,双进水管均布设在圆弧角位置是优选布设,有利于改善养殖池底部水动力特性。     

洁净室亚微米颗粒污染的模型模拟研究

采用基于欧拉框架下的Small Slip Model颗粒拟流体模型和Three Layer Model壁面沉积边界条件,并运用标准的k-ε湍流模型和壁面函数方法对非单向流洁净室内亚微米颗粒污染物的输运和分布结构进行数值模拟。模拟结果和实验结果具有较好的一致性,说明所采用的计算模型和方法具有良好的合理性和适用性。洁净室内颗粒污染物的输运和分布特征受空气流场的制约,尤其是室内存在的回流区和旋涡区,对污染控制和排除效率有着重要的影响。此外,颗粒的湍流扩散作用在对流作用较弱的区域发挥着重要的作用,对其机理的正确认识和分析有助于提高模型研究的准确性。     

砂尘环境试验风洞稳定段和收缩段的数值模拟研究

采用计算流体动力学软件FLUENT,对砂尘环境试验风洞中稳定段和收缩段的气固两相流流场进行数值模拟.给出了计算采用的湍流模型及计算区域的网格划分技术.通过分析稳定段和收缩段的两相流流场的速度梯度分布,得到了反向加砂方式优于正向加砂方式的计算结果.     

Distribution and ecological effect of mercury in Laogang landfill, Shanghai, China

Laogang landfill near Shanghai is the largest landfill in China, and receives about 10000 t of daily garbage per day, Samples of topsoil and plants were analyzed to evaluate mercury pollution from the landfill. For topsoil samples, there were significant correlations among total mercury （HgT）, combinative mercury （Hgc） and gaseous mercury （HgG）, and content of total organic carbon （TOC）, but, no significantly relationship was found between Hg content and filling time. Hg content changes in vertical profiles with time showed that the average Hgv of profiles 1992, 1996, and 2000 was similar, but their average HgG was quite different. HgT was significantly correlated with Hgc in profile 1992 and 2000, and Hgv was significantly correlated with Hg6 in profile 1996. HgG/Hgv ratio in profile samples decreased in the order of （HgG,/HgT）1992〉（HgG/HgT）1996〉〉（HgG/HgT）2000. A simple outline of Hg release in landfill could be drawn： with increasing of filling time, degradation undergoes different biodegradation, accordingly, gaseous mercury goes through small, more, and small proportion to total mercury. Distribution of Hg in plants was inhomogeneous, following the order of leaf〉root〉stem. The highest value of leaf may be associated with higher atmospheric Hg from landfill. Ligneous plants （e.g. Phyllostachys glanca, Prunus salicina and Ligustrum lucidum） are capable of enriching more Hg than herbaceous plants.     

EDTA-enhanced phytoremediation of lead contaminated soil by Bidens maximowicziana

Phytoremediation is a potential cleanup technology for the removal of heavy metals from contaminated soils.Bidens maximowicziana is a new Pb hyperaccumulator,which not only has remarkable tolerance to Pb but also extraordinary accumulation capacity for Pb.The maximum Pb concentration was 1509.3 mg/kg in roots and 2164.7 mg/kg in overground tissues.The Pb distribution order in the B. maximowicziana was:leaf>stem>root.The effect of amendments on phytoremediation was also studied.The mobility of soil Pb and the Pb concentrations in plants were both increased by EDTA application.Compared with CK(control check),EDTA application promoted translocation of Pb to overground parts of the plant.The Pb concentrations in overground parts of plants was increased from 24.23-680.56 mg/kg to 29.07-1905.57 mg/kg.This research demonstrated that B.maximowicziana appeared to be suitable for phytoremediation of Pb contaminated soil,especially,combination with EDTA.     

Decomposition of alachlor by ozonation and its mechanism

Decomposition and corresponding mechanism of alachlor, an endocrine disruptor in water by ozonation were investigated. Results showed that alachlor could not be completely mineralized by ozone alone. Many intermediates and final products were formed during the process, including aromatic compounds, aliphatic carboxylic acids, and inorganic ions. In evoluting these products, some of them with weak polarity were qualitatively identified by GC-MS. The information of inorganic ions suggested that the dechlorination was the first and the fastest step in the ozonation of alachlor.     

Enzymatic oxidation of aqueous pentachlorophenol

The influence of the nonionic surfactant Tween 80 on pentachlorophenol （PCP） oxidation catalyzed by horseradish peroxidase was studied. The surfactant was tested at concentrations below and above its critical micelle concentration （CMC）. Enhancement of PCP removal was observed at sub-CMCs. The presence of Tween 80 in the reaction mixture reduced enzyme inactivation which occurred through a combination of free radical attack and sorption by precipitated products. A simple first-order model was able to simulate time profiles for enzyme inactivation in the presence or absence of Tween 80. At supra-CMCs, the surfactant caused noticeable reductions in PCP removal, presumably through micelle partitioning of PCP which precluded the hydrophobic PCP molecule from interacting with the enzyme.     

基于综合水质标识指数和对应分析法的校园河道水质评价

以三峡大学的校园河道求索溪为研究对象,利用综合水质标识指数法确定求索溪水质类别,分析其水质时空变化规律,并利用对应分析法得出求索溪中不同监测点的主要污染因子.研究结果表明:求索溪整体的综合水质标识指数为7.423,整体水质为劣V类(地表水环境质量标准GB 3838-2002)且黑臭.从时间变化来看,求索溪4月份的水质最差,5月份次之,4、5月份所有监测点的水质都劣于V类且黑臭;8月份水质最好,水质为Ⅳ类;从空间分布来看,8个监测点综合水质标识指数均超过6.0,水质为劣V类,其中6号监测点的水质相对最好,监测点3号的水质相对最差;对应分析法得出求索溪的整体水体污染程度受总氮因子的影响最大,其次为总磷.该研究拟为求索溪及类似校园河道的水环境治理研究提供基础依据和参考.     

Effects of chitosan on growth of an aquatic plant (Hydrilla verticillata) in polluted waters with different chemical oxygen demands

Effects of chitosan on a submersed plant, Hydrilla verticillata, were investigated. Results indicated that H. venicillata could prevent ultrastructure phytotoxicities and oxidativereaction from polluted water with high chemical oxygen demand (COD). Superoxide dismutase (SOD) activity and malondialdehyde (MDA) contents in H. verticillata treated with 0.1% chitosan in wastewater increased with high COD (980 mg/L) and decreased with low COD (63 mg/L), respectively. Ultrastructural analysis showed that the stroma and grana of chloroplast basically remained normal. However, plant cells from the control experiment (untreated with chitosan) were vacuolated and the cell interval increased. The relict of protoplast moved to the center, with cells tending to disjoint. Our findings indicate that wastewater with high COD concentration can cause a substantial damage to submersed plant, nevertheless, chitosan probably could alleviate the membrane lipid peroxidization and ultrastructure phytotoxicities, and protect plant cells from stress of high COD concentration polluted water.     

Removal of cadmium using MnO2 loaded D301 resin

MnO2 loaded weak basic anion exchange resin D301 （Anion exchange resin, macroreticular weak basic styrene） as adsorbent has been prepared and applied to the removal of cadmium. The adsorption characteristics have been investigated with respect to effect of pH, equilibrium isotherms, removal kinetic data, and interference of the coexisting ions. The results indicated that the Cd^2＋ could be efficiently removed using MnO2 loaded D301 resin in the pH range of 3-8 from aqueous solutions with the co-existence of high concentration of alkali and alkaline-earth metals ions. The saturate adsorption capacity of the Cd^2＋ was 77.88 mg/g. The adsorption process followed the pseudo first-order kinetics. The equilibrium data obtained in this study accorded excellently with the Langmuir adsorption isotherm.     

Effect of coagulation pretreatment on the fouling of ultrafiltration membrane

The purpose of this study is to understand the effect and mechanism of preventing membrane fouling, by coagulation pretreatment, in terms of fractional component and molecular weight of natural organic matter （NOM）. A relatively higher molecular weight （MW） of hydrophobic compounds was responsible for a rapid decline in the ultrafiltration flux. Coagulation could effectively remove the hydrophobic organics, resulting in the increase of flux. It was found that a lower MW of neutral hydrophilic compounds, which could remove inadequately by coagulation, was responsible for the slow declining flux. The fluxes in the filtration of coagulated water and supernatant water were compared and the results showed that a lower MW of neutral hydrophilic compounds remained in the supernatant water after coagulation could be rejected by a membrane, resulting in fouling. It was also found that the coagulated flocs could absorb neutral hydrophilic compounds effectively. Therefore, with the coagulated flocs formed on the membrane surface, the flux decline could be improved.     

Penetration analysis of elements and bioleaching treatment of spent refractory for recycling

Acidithiobacillus ferrooxidans ATCC23270 and Acidithiobacillus thiooxidans TM-32 were used for bioleaching of spent refractories of aluminium and copper melting furnaces for their recycling.Firstly,penetration of elements into aluminium melting furnace refractory was investigated and it was found that up to 7 cm from surface was contaminated.Comparison on leaching efficiency by the strains ATCC23270 and TM-32 found that the strain ATCC23270 could treat larger amount of the refractories than the strain TM-32 could do.In the experiment of bioleaching of spent refractory aluminium melting furnace by the strain ATCC23270,high leaching efficiency were obtained on Al,Si,and Ca,and extremely low leaching performance was,however,shown on the rest of elements i.e.,Na,Mn,and Zn.Under the strain TM-32 use,relatively high leaching performance was recognized on Al,Si,Ca,Na,Mn,and Zn.In the experiment of bioleaching for spent refractory copper melting furnace,almost the same leaching trends were shown on Cu,Zn,Al,and Si under the strains ACTT23270 and TM-32 uses.     

Simultaneous removal of ammonium and phosphate by zeolite synthesized from coal fly ash as influenced by acid treatment

Zeolite synthesized from fly ash （ZFA） without modification is not efficient for the purification of NH4＋ and phosphate at low concentrations that occur in real effluents, despite the high potential removal capacity. To develop an effective technique to enhance the removal efficiency of ammonium and phosphate at low concentrations, ZFA was modified with acid treatment and the simultaneous removal of ammonium and phosphate in a wide range of concentration was investigated. It was seen that when compared with untreated ZFA, only the treatment by 0.01 mol/L of H2SO4 significantly improved the removal efficiency of ammonium at low initial concentrations. The behavior was well explained by the pH effect. Treatment by more concentrated H2SO4 led to the deterioration of the ZFA structure and a decrease in the cation exchange capacity. Treatment by 0.01 mol/L H2SO4 improved the removal efficiency of phosphate by ZFA at all initial P concentrations, while the treatment by concentrated H2SO4 （≥0.9 mol/L） resulted in a limited maximum phosphate immobilization capacity （PIC）. It was concluded that through a previous mild acid treatment （e.g. 0.01 mol/L of H2SO4）, ZFA can be used in the simultaneous removal of NH4＋ and P at low concentrations simulating real effluent.