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提高大流量低扬程水泵汽蚀性能的途径 总被引：1，自引：0，他引：1
汽蚀是水泵中液体压力降低到汽化压力以下时产生的一种复杂的水力现象。随着汽蚀的发生和发展 ,造成水泵工作性能下降 ,对材料产生剥蚀 ,缩短水泵的使用寿命 ,影响泵的安全运行 ,也影响工程的投资和维修使用 ,因此提高泵的汽蚀性能 ,避免汽蚀现象的发生是一个十分重要的问题。许多文献对提高泵的汽蚀性能作了很多分析论证。笔者在进行一台大流量(Ｑ =5 0 40ｍ3 /ｈ)、低扬程 (Ｈ =17.5ｍ)的双吸中开泵的改造中 ,就提高泵的汽蚀性能作了一点尝试。1 减薄叶片进口边的厚度衡量泵汽蚀性能的参数是泵的必需汽蚀余量 (ＮＰＳＨ) Ｒ。泵的必需汽… 相似文献
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新买的喷灌机在使用前要重新紧固各个部位螺栓。在水泵运行时,应注意轴承的温度,使之不超过75℃,并时刻注意有无杂音。如发出较大摩擦声和撞击声,应立即停车检查。水泵不用时应将泵内的积水放净。 水泵在使用一段时间后,会出现各种故障。如:水泵不出水,出水量不足,轴承发热,杂音与振动较大。出现上面任何一种情况都会影响工作效率,缩短机械使用寿命,应立 相似文献
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离心式水泵安装使用应注意的问题 总被引：1，自引：0，他引：1
离心式水泵以其结构简单、使用维修方便、效率较高而成为农业上应用最广泛的一种水泵,但也因有时安装、使用不当出现提不上水等问题,因此使用安装时应注意避免。进水管和泵体内有空气(1)有些用户在水泵启动前未灌满足够的水;有时看上去灌的水已从放气孔溢出,但未转动泵轴使空气完全排出,致使少许空气还残留在进水管或泵体中。(2)与水泵接触的进水管的水平段逆水流方向应有5°以上的下降坡度,连接水泵进口的一端为最高,不要完全水平。如果向上翘起,进水管内会存留空气,降低了水管和水泵中的真空度,影响吸水。(3)水泵的填料因长期使用已经磨损… 相似文献
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随着农机事业的发展,农用水泵已走进千家万户,但有些用户由于使用不当村响了水泵正常工作．甚至降低了使用寿命。为了保证水泵（以高心泵为例）工作时的安全运转,延长使用寿命,必须刀握正确的使用方法。一、选型各种离心泵的性能参数所适应的地理环境、自然条件、场地状况有很大差别。选择什么样的离心泵,要根据水泵安装的地形、水源、用途,从系的流量,吸程、扬程、配套动力等参数内容来作综合考虑,选购适宜当地自然条件、符合用户实际需要的机型。二、水泵使用前的安装、准备工作中,要做好以下几点：1．水泵安装高度,指水泵中心… 相似文献
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一、启动时水泵不转 1.水泵不转、皮带打滑或电动机不转动。其原因是:(1)填料太紧;(2)冬季泵内结冰;(3)叶轮与泵体之间被杂物卡住或堵塞;(4)泵轴、轴承、减漏环锈住;(5)泵轴严重弯曲。 排除方法:(1)适当放松填料;(2)添加盐水融化泵内的结冰,冬季使用应注意停机后及时放水;(3)拆开泵体清除杂物;(4)拆开除锈;(5)拆下泵轴校正或更换新的泵轴。 2.水泵转后又停,并发现填 相似文献
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为了改善传统高速泵轴承板易损坏,寿命短,噪音大,转速低等缺点,将目前具有优越性能的电磁轴承应用于立式高速泵．对电磁轴承的基本结构、工作原理、控制系统、电磁力、刚度特性及其在立式高速泵中的安装结构进行了研究,并且对安装电磁轴承后高速泵的运行特性进行了分析．结果表明：电磁轴承由于无接触、无需润滑、无摩擦,可有效解决高速泵中轴承失效的问题,能有效延长高速泵的使用寿命,解决了困扰高速泵多年的密封问题．电磁轴承的控制系统与轴承承载力完全能够满足在高速泵上应用的要求且具有较好的刚度特性．安装电磁轴承后,有效提高了高速泵的运行稳定性、转速及扬程．但是由于转速的提高,汽蚀现象更加严重,造成了对叶片的损坏,这就需要对叶片形状做进一步的改进． 相似文献
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(三)调节水泵性能。对现有正在使用中的水泵,有些由于选型不注意,或选型方法不够正确;有些确因水泵型号不全,只好选用相近的泵型;有些因缺乏这方面知识,不管合用不合用,只要是泵就行。凡此种种,造成高扬程泵在低扬程地区使用,或者泵扬程与实际使用不配套,致使水泵长期在低效率状态下运行,浪费了大量的能源。 相似文献
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1 动力机带不动机小泵大 ,小马拉大车。按照水泵的额定功率 ,更换与水泵相匹配的动力机 ,降低水泵转速 ,减少水泵流量。(2 )水泵转速过高。更换较大直径的从动轮 ,降低水泵转速。(3)填料压得过紧。适当拧松填料压盖螺钉 ,保持适当的压紧程度 ,在工作时以从填料处每秒滴出1～ 2滴水为宜。或将填料拉出打扁重压。(4 )轴承损坏。更换轴承。(5)叶轮和泵体严重摩擦。检查叶轮和口环的磨损 ,查出摩擦部分 ,必要时进行更换。(6 )泵轴弯曲或两轴不同心。调整泵轴 ,调整联轴器 ,或进行更换。(7)输水量或输水扬程与设计不符。当输水量大、扬程大时 ,… 相似文献
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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
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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
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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
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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
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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
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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
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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