共查询到20条相似文献，搜索用时 62 毫秒
1.
在文献「１－３」的基础上,对设置导流锥,用肘形或簸箕形进水流道取代开敞式进水池以及更换水泵喇叭管等开敞式进水池的节能技术改造方法分析进行了优化水力计算,并根据进水流道水力优化目标函数这个统一的尺度对它们进行了比较,以为确定最合理扣、小型轴流泵站乾水池节能技术改造方案提供依据。 相似文献
2.
开敞式进水池三维紊流流动模拟及水力优化计算目标函数 总被引：1，自引：1，他引：1
采用数值计算的方法研究进水池的水力优化设计，可以排除由于试验条件，试验方法等不同而产生的影响，从理论上对其进行比较系统的研究。诮直接求解三维雷诺平均Ｎ－Ｓ方程和标准ｋ－ε紊流模型方程程的方法，计算进水池内的流场；根据轴流泵转轮的设计条件，引入流速均匀度和水流入泵平均角度两个目标函数，从而为开敞式进水池及水泵喇叭管的水力优化计算准备必要的条件。 相似文献
3.
1000MW电厂循环水流道进水池三维 总被引：1，自引：0，他引：1
电厂进水池的流态直接影响到水泵的工作状况、气蚀性能和安全运行保证率,因此在进水流池体型研究与水力设计中都特别关注这一问题。针对大型1000MW电厂进水池工程实际,应用κ～ε紊流模型对进水水池及喇叭口附近流场进行三维水流数值模拟计算, 分析研究了吸水池及喇叭口附近的流速、压强及涡漩分布,同时也对进水池数值模拟的计算参数及网格处理进行了分析讨论。数值模拟结果分析表明,计算结果与物理模型试验数据基本一致。为了消除水泵喇叭口附近的表面漩涡和水下漩涡,作者提出了保证水泵正常运行的进水池设计控制尺寸。 相似文献
4.
为了优化侧向泵站进水前池流态，消除不良流态对水泵吸水的影响，采用数值计算对某泵站进水池流态进行了分析，在此基础上提出了在进水池进口处布置不同尺寸导流栅的整流方案，分析了整流后的进水池流态。通过结果可知，布置导流栅后达到了相应的整流效果，能让流束通过导流栅格栅较为平顺流入进水池内，改善1～4号进水池内的偏流现象，给水泵创造良好的吸水条件。综合比较各方案计算结果知“3+2”型组合布置形式可使得5个进水池流速不均匀系数趋于稳定，并且与原方案相比流速不均匀系数均有所降低，整流效果明显。 相似文献
5.
梯级供水泵站停泵水力过渡过程分 总被引：1，自引：0，他引：1
阐述了梯级供水泵站停泵水力过渡过程的特点，结合工程实例，应用特征线法对两级泵站同时事故停泵或其中一级泵站事故停泵时可能出现的断流弥合水锤、下游泵站进水池抽空或漫顶的问题进行了计算分析，并提出了相应的控制措施。 相似文献
6.
大型泵站肘形进水流道三维紊流仿真计算 总被引：1，自引：2，他引：1
通过肘形进水流道三维紊流仿真计算，定性分析流道内部流态，定量计算流道出口轴向流速分布均匀度、出口水流偏流角和流道的水头损失，能预测肘形进水流道的水力特性，为流道水力设计优化和模型试验提供了依据，可以缩短模型试验周期和试验费用。 相似文献
7.
泵站开敞式进水池几何参数的数值模拟 总被引：3，自引：0，他引：3
基于定常不可压流体的控制方程和重整化群湍流模型,应用SIMPLEC算法,计算了不同几何参数的泵站开敞式进水池定常流动.研究表明过小的后壁距将引起进水喇叭口的单向进水趋势,过大的后壁距将导致后壁产生较大区域的回流区;过小的悬空高使得流入喇叭口的水流流线过于弯曲,过大的悬空高将形成喇叭口的单面进水,导致水泵进口的轴向流速分布不均匀.研究显示矩形、梯形和半圆形进水池水力性能相近,ω形进水池的水力性能最佳,进水管流速分布均匀.基于数值模拟结果提出的进水池主要尺寸参数的范围和后壁平面形状,可应用于工程实际. 相似文献
8.
基于定常不可压流体的控制方程和重整化群湍流模型,应用SIMPLEC算法,计算了不同几何参数的泵站开敞式进水池定常流动。研究表明过小的后壁距将引起进水喇叭口的单向进水趋势,过大的后壁距将导致后壁产生较大区域的回流区;过小的悬空高使得流入喇叭口的水流流线过于弯曲,过大的悬空高将形成喇叭口的单面进水,导致水泵进口的轴向流速分布不均匀。研究显示矩形、梯形和半圆形进水池水力性能相近,ω形进水池的水力性能最佳,进水管流速分布均匀。基于数值模拟结果提出的进水池主要尺寸参数的范围和后壁平面形状,可应用于工程实际。 相似文献
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大型泵站肘形进水流道三维紊流仿 总被引：1，自引：0，他引：1
通过肘形进水流道三维紊流仿真计算，定性分析流道内部流态，定量计算流道出口轴向流速分布均匀度、出口水流偏流角和流道的水头损失，实现了肘形进水流道的水力特性全面预测，为流道水力设计优化和模型试验提供了充分的依据，可大幅度缩短模型试验周期和试验费用。 相似文献
10.
泵站进水流道三维流动及水力损失数值模拟 总被引：2，自引：0，他引：2
提出了将进水流道从水泵装置中分解出来单独进行数值计算的研究方法,分析了大型泵站进水流道三维流场及水力损失数值计算的区域、边界条件及网格剖分等有关问题,给出了肘形、钟形和簸箕形等3种形式进水流道三维流场和水力损失数值计算的实例,并与流道模型试验的流场观察及水力损失测试结果进行了比较.结果表明：提出的进水流道三维流动数值计算方法可以较为准确地计算进水流道的水力损失,便于对其进行模型试验验证.应用本方法可以较为方便地对进水流道的水力性能进行考核和评价,从而为进水流道优化水力设计所需的多方案比较创造条件. 相似文献
11.
Overland water and salt flows in a set of rice paddies 总被引：1，自引：0，他引：1
E. Playn O. Prez-Coveta A. Martínez-Cob J. Herrero P. García-Navarro B. Latorre P. Brufau J. Garcs 《Agricultural Water Management》2008,95(6):645-658
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. 相似文献
12.
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。 相似文献
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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。 相似文献
14.
对《种子法》存在问题的探讨 总被引：1，自引：0，他引：1
李鹏 《农业机械化与电气化》2011,(6):129-130
《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。 相似文献
15.
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. 相似文献
16.
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。 相似文献
17.
Gunter Wriedt Marijn van der Velde Alberto Aloe Fayçal Bouraoui 《Agricultural Water Management》2009,96(5):771-789
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. 相似文献
18.
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。 相似文献
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车辆ABS控制算法的研究及探讨 总被引：1，自引：0，他引：1
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。 相似文献