基于偏微分方程的离心泵叶片反设计方

为实现离心泵叶片的参数化优化设计,将微分方程分别应用于叶轮的轴面设计及叶片空间曲面的生成,首先用4次Bezier曲线控制叶轮轴面,用偏微分方程方法生成轴面流线及准正交线,其次用偏微分方程的方法来生成离心泵叶片空间曲面,根据叶片型线方程,利用控制叶片安放角的分布规律来控制叶片边界上点的圆周角坐标,从而控制微分方程的边界条件,最后达到控制叶片形状的目的.实现了叶片的参数化设计.采用梯度优化的方法将正问题的计算结果用于反问题中对叶片型线的更新,实现了泵叶片的优化设计.应用实例表明提出的离心泵叶片反设计方法是可行的.     

CFD技术在离心泵优化设计中的应用

随着CFD(计算流体力学)的迅速发展,CFD技术已经被广泛地应用于各类流体机械的设计与优化中。将CFD技术应用于离心泵叶轮优化设计中,以叶轮两叶片间的流场作为研究对象,采用非结构化网格进行网格划分;采用基于时均Navier-Stokes方程和标准k-ε紊流模型对得到的离心泵进行流场计算,并根据计算结果,对离心泵内部流场进行了分析;提出了修改叶轮进口安放角和叶片形状的方法进行优化改型。通过对修改后的叶轮流场进行计算,可以看到叶轮内部流场和流速分布都得到了改善,证明优化后的叶轮形状更符合流动特性。结合实例证明了该方法在离心泵叶轮优化设计中的有效性。     

离心风机叶轮三维反问题气动优化设计

基于三维反问题设计方法和CFD技术,结合试验设计方法和模拟退火优化算法,以轴面流道形状参数和叶片形状参数为设计变量,以叶轮效率为优化目标,建立了离心风机叶轮三维反问题气动优化设计方法。叶片形状通过三维反问题设计方法由叶轮的环量分布参数表达。运用该方法进行了离心风机叶轮的优化设计,叶轮效率提高了3.3%。根据建立的优化设计变量和叶轮效率之间的响应面函数关系式,分析了不同轴面流道形状参数和环量分布参数及参数间交互效应对叶轮效率的影响。结果表明:相对于轮盘处轴面流道轮盖处型线和环量分布形式,轴面流道叶片进口边倾斜角对叶轮效率影响更为显著。     

离心泵叶轮的参数化设计

对离心泵叶轮优化设计存在的问题进行了详细的阐述,离心泵叶轮优化设计的主要困难在于复杂的内流道形状及其与泵水力性能间复杂的隐式关系,对基于NURBS的曲面设计方法、基于自由曲面变形方法及偏微分方程方法3种离心泵叶轮参数化设计方法的研究进行了详细的介绍．为了减少计算量,采用偏微分方程方法对离心泵叶片几何形状进行参数化控制,参数化控制偏微分方程的边界条件,假定方程中的控制参数a(u,v)为常量1,采用响应面方法对泵叶轮进行优化设计,根据试验及模拟结果进行二阶多项式响应面回归,分析发现二阶多项式响应关系不能反映离心泵叶轮设计目标与控制变量间的复杂的非线性关系．为此,在此基础上提出采用偏微分方程构建设计目标的偏微分超曲面响应,数值求解多维空间上偏微分方程的边值问题,进行优化分析得到最优设计．优化设计实例计算结果表明提出的理论及方法是合理的．     

离心泵叶轮的参数化设计

对离心泵叶轮优化设计存在的问题进行了详细的阐述,离心泵叶轮优化设计的主要困难在于复杂的内流道形状及其与泵水力性能间复杂的隐式关系,对基于NURBS的曲面设计方法、基于自由曲面变形方法及偏微分方程方法 3种离心泵叶轮参数化设计方法的研究进行了详细的介绍.为了减少计算量,采用偏微分方程方法对离心泵叶片几何形状进行参数化控制,参数化控制偏微分方程的边界条件,假定方程中的控制参数a（u,v）为常量1,采用响应面方法对泵叶轮进行优化设计,根据试验及模拟结果进行二阶多项式响应面回归,分析发现二阶多项式响应关系不能反映离心泵叶轮设计目标与控制变量间的复杂的非线性关系.为此,在此基础上提出采用偏微分方程构建设计目标的偏微分超曲面响应,数值求解多维空间上偏微分方程的边值问题,进行优化分析得到最优设计.优化设计实例计算结果表明提出的理论及方法是合理的.     

离心风机叶片三维反问题优化设计

基于三维反问题设计方法和CFD技术,结合试验设计方法、响应面方法和模拟退火优化算法,建立了离心风机叶片三维形状的优化设计方法。以叶轮效率为优化目标,以环量分布参数为优化设计变量,进行了离心风机叶片的优化设计,优化设计结果叶轮效率提高了2.2%。根据建立的优化设计变量和叶轮效率之间的响应面函数关系式,分析了不同环量分布参数及参数间交互效应对叶轮效率的影响,结果显示轮毂进口段环量分布对叶轮效率有较大影响;轮缘处的环量分布形式对叶轮效率影响更为显著。     

基于自由曲面变形方法的离心泵叶片反问题方法研究

提出了一种基于自由曲面变形(FFD)方法的离心泵叶片反问题新方法。采用自由曲面变形方法对叶轮叶片形状进行控制,将叶片空间曲面嵌入到一个均匀剖分的三参数张量积控制体内,移动控制晶格点位置使控制体发生变形,控制体内的叶片曲面形状随之改变。根据给定的叶片目标载荷分布进行叶片形状的控制,构建控制晶格点的变形函数,根据叶轮内三维湍流数值模拟结果与期望的叶片载荷分布规律控制晶格点的变形,实现了由物理参数对叶片形状的直接控制。算例计算结果表明,所提出的基于FFD方法的离心泵叶片反问题方法是可行的。     

低比转数离心泵叶轮内流场的重构及模态分析

针对传统离心泵水力性能优化设计的复杂性,提出了采用本征正交分解与径向基函数(POD-RBF)混合代理模型方法进行离心泵叶轮内流场的重构分析。由三次Bezier曲线对低比转数离心泵二维叶片型线进行参数化控制,通过对叶片包角、进出口安放角等控制参数进行适量的扰动得到叶片型线的样本集。由叶片型线参数及叶轮CFD内流场数据构成样本的快照矢量集,根据几何相似及网格变形方法插值得到各相似节点的流场参数,依据本征正交分解法(POD)将快照集分解为一系列正交基的线性组合。由径向基函数(RBF)拟合目标叶型所对应的正交基系数,实现了对目标叶轮内流场的重构。采用POD-RBF方法对MH48-12.5型低比转数离心泵叶轮内流场进行了重构,其压力预测均方根误差为0.84%,速度预测误差基本在0.5m/s以内,流场预测所需时间约为CFD计算的1/240,并对样本集进行POD基模态分析,得到了各阶基模态流场特征及能量分布特性。     

离心泵多目标优化设计及数值模拟研究

为进一步提高离心泵的优化设计水平,选择多目标优化与数值模拟相结合的方法,对一台低比转速离心泵进行优化分析,首先,以离心泵能量损失、抗气蚀性能及运行过程的稳定性为优化目标,离心泵叶轮的7个主要几何参数为设计变量,分别建立离心泵参数优化的数学模型,采用权矩阵分析的方法,给3个分目标函数分配相应的权值,并通过评价函数将它们统一为一个目标函数,利用遗传算法对目标函数进行多目标优化求解,得出叶轮7个设计参数的最优组合,将优化后的叶轮参数反代入优化模型中,结果显示离心泵的能量损失降低了4.3%,汽蚀余量降低了0.31 m;为进一步验证优化后泵运行的状态,根据优化后的叶轮参数建立离心泵水体三维模型,并利用CFX软件对水体模型做数值模拟分析,对比分析了优化前后流场中的压力脉动情况,结果显示优化后泵的蜗壳流道内压力脉动幅值降低了,优化后泵的运行稳定性有一定的提高。     

低比转数离心泵叶轮内流场重构与模态分析

针对传统离心泵水力性能优化设计的复杂性,提出采用本征正交分解-径向基函数（POD-RBF）混合代理模型方法对离心泵叶轮内流场进行重构分析。由三次Bezier曲线对低比转数离心泵二维叶片型线进行参数化控制,通过对叶片包角、进出口安放角等控制参数进行适量的扰动得到叶片型线的样本集。由叶片型线参数及叶轮CFD内流场数据构成样本的快照矢量集,根据几何相似及网格变形方法插值得到各相似节点的流场参数,依据本征正交分解法（POD）将快照集分解为一系列正交基的线性组合。由径向基函数（RBF）拟合目标叶型所对应的正交基系数,实现了对目标叶轮内流场的重构。采用POD-RBF方法对MH48-12.5型低比转数离心泵叶轮内流场进行了重构,其压力预测均方根误差为0.84%,速度预测误差基本在0.5m/s以内,流场预测所需时间约为CFD计算的1/240。对样本集进行POD基模态分析,得到了各阶基模态流场特征及能量分布特性。     

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.     

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。     

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.     

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。     

A European irrigation map for spatially distributed agricultural modelling

We present a pan-European irrigation map based on regional European statistics, a European land use map and a global irrigation map. The map provides spatial information on the distribution of irrigated areas per crop type which allows determining irrigated areas at the level of spatial modelling units. The map is a requirement for a European scale assessment of the impacts of irrigated agriculture on water resources based on spatially distributed modelling of crop growth and water balance. The irrigation map was compiled in a two step procedure. First, irrigated areas were distributed to potentially irrigated crops at a regional level (European statistical regions NUTS3), combining Farm Structure Survey (FSS) data on irrigated area, crop-specific irrigated area for crops whenever available, and total crop area. Second, crop-specific irrigated area was distributed within each statistical region based on the crop distribution given in our land use map. A global map of irrigated areas with a 5′ resolution was used to further constrain the distribution within each NUTS3 based on the density of irrigated areas. The constrained distribution of irrigated areas as taken from statistics to a high resolution dataset enables us to estimate irrigated areas for various spatial entities, including administrative, natural and artificial units, providing a reasonable input scenario for large-scale distributed modelling applications. The dataset bridges a gap between global datasets and detailed regional data on the distribution of irrigated areas and provides information for various assessments and modelling applications.     

粉质仪和拉伸仪在面粉生产中的应用

在介绍粉质仪和拉伸仪结构和原理的基础上,探讨了粉质曲线中吸水率、形成时间、稳定时间、弱化度和评价值等指标与面粉品质的关系,以及如何根据拉伸曲线中面团最大拉伸阻力、延伸度和拉伸曲线面积等指标来评价面团品质,并结合生产实际,概述了粉质仪和拉伸仪在面粉生产中的作用。     

农村信息化服务的现状及建设措施

分析当前我国农村信息化服务的现状,提出加强农村信息化服务的新举措。     

车辆ABS控制算法的研究及探讨

对现代汽车的ABS控制算法作了一些简单的介绍,同时指出了它们的一些缺陷,相应地提出了几种对ABS的其它控制方法并加以探讨,其中着重论述了ABS门限值控制算法中参考车速的确定方法和基于附着系数的控制算法。