基于CFD的多级中开式离心泵流场分析

为发展具有自主知识产权的高性能多级中开式离心泵,根据已有参数要求,对多级中开式离心泵的结构及水力模型进行了设计.水泵选用两侧吸入中间压出的结构形式,叶轮左右对称分布.首级叶轮为两侧单吸,末级选用双吸叶轮,压出室采用双蜗壳.利用Pro/E软件建立流道模型,借助Fluent软件,基于N—S方程和标准k～ε湍流模型,采用SIMPLE算法,对内部流场进行数值模拟,得到水泵各级叶轮的相对速度及静压分布.并在多工况下对多级中开式离心泵流场进行稳态数值预测,着重选取三种工况(标准工况、小流量工况及大流量工况)对多级泵各级叶轮的静压及相对速度进行对比分析.然后,在标准工况下对泵进行瞬态模拟,分析各级叶轮在不同时刻静压分布.数值模拟结果表明,泵水力模型设计合理,在标准工况下效率达到88％,性能出众.最后经实验验证表明,模拟结果与实验结果相符,水泵达到设计要求.     

电磁调速水泵机组起动过程的数值模拟

根据电磁调速电动机驱动的水泵机组起动过程中的力矩平衡方程,得到水泵转速的变化率与水泵转速和励磁电流的函数关系式,据此进行数值模拟。当给定一个起动过程中水泵转速随起动时间的变化规律,就可得出对应的该水泵机组起动过程中的电磁调速电动机励磁电流控制的规律,并在一个实际的计算机监督控制系统中进行了验证,其转速的变化基本符合数值模拟时设定的转速变化规律。研究方法对其它异步电动机拖动的调速设备的控制软件开发提     

基于CFD的发动机冷却水泵汽蚀性能预测

以雷诺时均N-S方程为基本控制方程,采用标准k-ε双方程湍流模型及多相流模型,利用计算流体动力学软件CFX模拟了发动机冷却水泵内部的三维湍流流场,对某一叶轮严重损坏的发动机冷却水泵外特性性能和汽蚀性能进行预测,并分析叶轮损坏原因,观察冷却水泵叶轮内部汽蚀情况．模拟结果表明:在85 ℃下模型泵的临界汽蚀余量约为107 m,在表压为0时已发生了较为严重的汽蚀现象,叶轮破坏主要是由汽蚀引起．通过与试验数据进行对比验证,水泵在285 L／min设计流量下扬程为61 m,远远低于常温下的数值模拟结果,说明该泵在实际运行工况下已发生严重汽蚀,试验结果与数值预测结论基本吻合．研究结果对于改善发动机冷却水泵的汽蚀性能、防止和减轻空化现象产生提供理论依据,也为判断和模拟发动机冷却水泵的汽蚀破坏提供了一个快速、准确的计算方法．     

低比转速离心泵内部流场的数值模拟

利用计算流体力学软件Fluent对低比转速离心泵叶轮内的三维流动进行了数值模拟,不同工况下模拟所得到的结果与实际情况非常吻合。通过对压力场的分析提出了判断叶轮内是否发生空化初生和计算水泵必需空化余量△hr的简洁方法;通过对速度场的分析,从另外一个角度印证了加大流量的设计方法。同时也为分析水泵性能、优选设计方案,提供了一个可靠的途径。     

发动机水泵通用化设计实例分析

以吉利某两款发动机冷却水泵为例,对比两款水泵叶轮的关键参数,在满足水泵性能要求的前提下,实现对水泵结构最小修改,达到其余零部件最大通用化。     

卫生泵半开式叶轮内部流场分析

针对广东日新泵业的卫生型(Sanitary Centrifugal Pump)水泵，对叶轮内的三维不可压湍流流动进行了数值模拟。计算结果结合卫生型水泵的实测揭示了叶轮内湍流流动的速度分布、压力分布规律，对叶轮内部的流动状况进行了研究与分析，从而为卫生型泵的优化设计奠定了基础。     

进水池对水泵进水条件影响的数值模拟和试验

采用有限体积法和非结构网格,数值模拟了两种进水池设计方案对水泵进水条件的影响,并利用物理模型试验对数值计算结果进行了验证。数值计算结果表明,在进水池长度、宽度和喇叭口淹没深度等其他设计参数相同时,与矩形进水池相比,平面对称蜗壳形进水池配合导水锥的进水设计可以有效减小水泵吸水管内横向流速,抑制涡流强度,较好地改善水泵的进水条件。     

离心泵叶轮内流数值模拟的现状和展望

结合计算机技术的发展，论述了离心泵叶轮内部流动数值模拟研究的历史和现状，对用于离心泵叶轮内流的数值模拟方法进行了较为详细的介绍；并在总结前人所做工作的基础上，提出了离心泵内流计算的发展趋势。     

基于流场数值模拟的高速磁力泵汽蚀性能研

为了改善高速磁力泵的抗汽蚀性能,在泵吸入口处设置导流栅.建立了吸入口设置导流栅和未设置导流栅的两种模型,采用Fluent软件对高速磁力泵内流场进行数值模拟,给出了各自内部压力分布以及粒子流动迹线图.通过两组数据的比较,得到了内部流场的主要特征,模拟表明高速磁力泵吸入口设置轴向可变位导流栅可以有效提高抗汽蚀性能.数值模拟与高速磁力泵真机的试验对比表明,两者几乎一致,为高速磁力泵的改进设计提供了一定的理论依据.     

离心泵叶轮内部湍流流场的数值模拟

为了进一步探索泵叶轮内部三维流场的参数、为泵的设计提供理论依据，以IB50-32-250离心泵叶轮的设计参数为依据．根据叶轮内部湍流流动的通用方程建立湍流模型，利用ANSYS8．0对离心泵叶轮内部流场的速度、压力进行数值模拟，初步得出了叶轮内部流场主要特征和分布规律．对研究流体机械叶轮部件内部的流动情况具有参考价值。     

Overland water and salt flows in a set of rice paddies

Cultivation of paddy rice in semiarid areas of the world faces problems related to water scarcity. This paper aims at characterizing water use in a set of paddies located in the central Ebro basin of Spain using experimentation and computer simulation. A commercial field with six interconnected paddies, with a total area of 5.31 ha, was instrumented to measure discharge and water quality at the inflow and at the runoff outlet. The soil was classified as a Typic Calcixerept, and was characterized by a mild salinity (2.5 dS m⁻¹) and an infiltration rate of 5.8 mm day⁻¹. The evolution of flow depth at all paddies was recorded. Data from the 2002 rice-growing season was elaborated using a mass balance approach to estimate the infiltration rate and the evolution of discharge between paddies. Seasonal crop evapotranspiration, estimated with the surface renewal method, was 731 mm (5.1 mm day⁻¹), very similar to that of other summer cereals grown in the area, like corn. The irrigation input was 1874 mm, deep percolation was 830 mm and surface runoff was 372 mm. Irrigation efficiency was estimated as 41%. The quality of surface runoff water was slightly degraded due to evapoconcentration and to the contact with the soil. During the period 2001–2003, the electrical conductivity of surface runoff water was 54% higher than that of irrigation water. However, the runoff water was suitable for irrigation. A mechanistic mass balance model of inter-paddy water flow permitted to conclude that improvements in irrigation efficiency cannot be easily obtained in the experimental conditions. Since deep percolation losses more than double surface runoff losses, a reduction in irrigation discharge would not have much room for efficiency improvement. Simulations also showed that rice irrigation performance was not negatively affected by the fluctuating inflow hydrograph. These hydrographs are typical of turnouts located at the tail end of tertiary irrigation ditches. In fact, these are the sites where rice has been historically cultivated in the study area, since local soils are often saline-sodic and can only grow paddy rice taking advantage of the low salinity of the irrigation water. The low infiltration rate characteristic of these saline-sodic soils (an experimental value of 3.2 mm day⁻¹ was obtained) combined with a reduced irrigation discharge resulted in a simulated irrigation efficiency of 60%. Paddy rice irrigation efficiency can attain reasonable values in the local saline-sodic soils, where the infiltration rate is clearly smaller than the average daily rice evapotranspiration.     

车用发动机润滑油失效规律与更换周期研究

研究在正常使用条件下１０Ｗ／３０－ＱＣ级润滑油用于某型车用发动机时所表现的失效规律,确认期服从两参数Ｗｅｉｂｕｌｌ分布,并给出分布的尺度参数η和形状参数ｍ之最佳线性无偏估计（ＢＬＵＥ）同时,还为定量分析,计算车用发动机润滑油的使用可靠性和合理确定其更换周期提供了一套可供借鉴的方法,并给出了具体的计算实例。     

农村剩余劳动力就业问题的探讨

论述了我国农村剩余劳动力就业的意义，并针对我国农村剩余劳动力的现状，提出多渠道促进农村剩余劳动力就业的途径和办法。     

乡（镇）农业技术推广体系存在的问题及对策

乡（镇）农技推广体系是农业发展的关键。介绍朝阳市农业技术推广体系的现状,针对目前体制及运行机制、服务手段等方面存在的问题,提出适合朝阳市乡（镇）农技推广体系改革与发展的对策,以期对全省农技推广体系改革和发展起到一些借鉴作用。     

草莓的采收与贮藏

草莓果味酸甜爽口,营养价值高,为人们所喜爱的应市鲜果之一。由于草莓易受损伤和微生物侵染,因此其采收、贮藏过程极为重要。介绍草莓采收过程中的注意事项以及11种贮藏保鲜技术的实施步骤和操作方法,推介9种加工方式,为草莓产业化提供技术支持。     

瓦房店市水果生产标准化发展研究

瓦房店市是我国重要的水果生产基地,在国内水果生产领域占有重要地位。随着水果市场化的不断深入,如何满足和适应国内外市场需求成为瓦房店市水果生产的关键问题。从瓦房店市水果生产实际出发,阐述了实施水果生产标准化的必要性,提出了发展水果生产标准化的具体措施。     

金谷子耐旱TG118引种试种及推广应用

对引进的谷子新品种金谷子耐旱TG118进行品种比较试验和多点试种。结果表明：该品种抗旱、耐瘠、适应性强,稳产、高产、抗病抗风抗倒伏强,品质优良,粮草兼用,种植简单,省工易管;一般产量在6000kg/hm2以上,比当地主栽品种增产20%以上。最高产量达9450kg/hm2,适于在辽西北地区推广应用。     

对《种子法》存在问题的探讨

《种子法》是我国种植业第一部法律。自实施以来,为依法加强种子管理提供了有力的法律支撑,促进我国种子产业发生翻天覆地的变化。但随着依法管理工作的深入和种子产业的快速发展,《种子法》及配套规章的一些问题逐步显现出来。对《种子法》及配套规章存在的问题进行深入分析,对需要进一步补充的章节以及需要调整的内容进行深入探讨,以求更加完善和明确。     

和谐社会理论建设的几点哲学思考

在新世纪,面对机遇和挑战,党的十六大把“社会更加和谐”作为全面建设更高水平的小康社会的一个重要目标。中国人素有社会和谐的理想;西方人自古也向往社会和谐;借鉴东西方两种和谐社会思想的经验、教训,构建社会主义和谐社会理论。     

Review of the Egyptian experience in implementing land drainage projects

About 30 years have passed since the Government of Egypt embarked on implementing a series of large scale drainage projects. At present, about 3.8 million acres have been provided with drainage systems on the basis of systematic pre-drainage investigations and designs. The target is to provide drains in approximately 6.4 million acres in the Nile Valley and Delta.The implementation of the subsurface drainage system is carried out by the public sector and private contractors under direct supervision of governmental regional departments. The implementation process depends on many factors related to the drainage material, machinery, manpower, site requirements, farmers and organizations involved. Problems and constraints are sometimes challenging, however, the annual rate of implementation has gradually increased to 170,000 acre/year.This paper discusses the different aspects involved in the implementation process of drainage systems. The development in materials, machinery and construction technologies will be reviewed. Institutional and management factors are going to be also considered.