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1.
微灌均匀度参数之间的关系及其应用 总被引：15，自引：0，他引：15
本文通过模拟计算建立了微灌灌水均匀系数Ｃｕ与总的灌水器流量变差系数Ｃｒ和流量变差率ｑｖ，ｑｖａ及灌水器工作水头变差率ｈｗ，ｈｖａ之间的关系，并直接用于水力学计算，使微灌系统设计考虑灌水器制造偏差变得非常容易。 相似文献
2.
为了探索一种简便有效评价大田微灌系统灌水均匀度的新方法,定义了样本流量偏差率.基于灌水器流量服从正态分布的假设,建立了样本流量偏差率与现有灌水均匀度评价指标之间的关系,推导了抽样误差的计算公式,提出了合理的样本容量和样本分组数.建立了基于样本流量偏差率的灌水均匀度评价标准,最终提出了基于样本流量偏差率评价大田微灌灌水均匀度的新方法.案例应用表明:相比图解法,新方法根据数值计算结果评价灌水均匀度,可避免人为画线误差,提高评价结果的可靠度;相比传统数值法,新方法计算量少,可作为快速评价大田微灌系统灌水均匀度的有效方法. 相似文献
3.
微灌系统的一个重要要求就是对农田进行均匀的灌溉，而灌水器的流量调节能力是影响灌溉均匀度的主要因素，流量自动调节灌水器的内部有一个因水压变化自动启动的流量控制结构。本文对注自动调节灌水器进行了数学描述，并对其运行进行了水力学分析。 相似文献
4.
提出了一种测定微灌灌水器制造偏差系数的试验方法，分析了微灌灌水器出口压力对其制造偏差系数的影响，提出运用灌水器工作压力下的理论流量计算灌水器制造偏差系数，从而消除了压力对制造偏差系数的影响，并设计具体试验装置进行试验，得到数据验证了上述试验方法。 相似文献
5.
6.
提出了一种测定微灌灌水器制造偏差系数的试验方法,分析了微灌灌水器出口压力对其制造偏差系数的影响,提出运用灌水器工作压力下的理论流量计算灌水器制造偏差系数,从而消除了压力对制造偏差系数的影响,并设计具体试验装置进行试验得到数据验证了上述试验方法。 相似文献
7.
几种微灌灌水器均匀度试验研究 总被引：2，自引：0，他引：2
对国产的2种压力补偿式滴头、3种稳流器、1种内镶式滴灌管和1种发丝滴头进行了水力性能测试,分析灌水器不同工作压力区间内的流态指数,并以制造偏差和流态指数为主要影响因素,对灌水器进行了水力性能评价。结果表明:压力补偿式灌水器存在最优压力区间,在此区间内灌水器流态指数较小、水力特征曲线平滑;非压力补偿式灌水器在整个压力区间内流态指数稳定、水力特征曲线稳定连续;供试的5种压力补偿式灌水器制造偏差系数较大,为0.14~0.30,而2种非补偿式灌水器制造偏差系数较小(0.02左右)。通过灌水器流态指数、制造偏差系数对综合流量偏差系数的影响的分析表明:灌水器制造偏差对系统灌水均匀度的影响很大,在进行微灌工程水力设计时,应给予高度重视。 相似文献
8.
微灌是一种先进的节水灌溉技术，微灌均匀度系数是衡量微灌系统灌水均匀度的重要指标。为此，提出了一种基于AT89S51单片机的微灌灌水均匀度智能测试方式，此法可对微灌系统的均匀度进行快速测定，具有实际应用价值。 相似文献
9.
温室大棚微灌技术简介 总被引：1，自引：0，他引：1
温室、大棚的栽培条件与大田栽培具有很多不同点，采用温室、大棚能否增产、增值，取决于能否人为地创造一个有利于作物生长的环境。微灌是调控室内环境非常有用的工具之一，在世界各地广为采用，我国尚属起步阶段，常用的微灌系统主要有滴灌和微喷灌两种。一、温室、大棚常用的微灌系统１、滴灌：利用安装在末级管道（称为毛管）上的滴头或与毛管制成一体的滴灌带（管）将压力水以水滴状湿润土壤的一种灌水技术。通常将毛管和灌水器放在地面（地表滴灌），也可埋入地面以下３０～４０cm（地下滴灌）。每个灌水器的流量一般为１～１２L／h… 相似文献
10.
微灌灌水小区水力设计的经验系数法 总被引：5，自引：1，他引：4
我国《微灌工程技术规范》规定：“微灌灌水小区各灌水器流量的平均值,应等于灌水器设计流量”.但是,至今还没有一个简便的计算方法,使这一规定便于贯彻.将经验系数法从1根毛管扩展至整个灌水小区,并通过4个算例验证了计算精度,可供微灌设计者试用. 相似文献
11.
为了阐明滴头制造偏差系数、灌水均匀度、毛管直径及毛管造价的内在联系,降低滴灌系统造价、提高灌水均匀度,通过理论推导结合实证计算的方法,系统分析了不同均匀度条件下滴头制造偏差系数极限值,以及滴头制造偏差系数、毛管直径、允许均匀度等三者的关系,并推导出毛管造价计算公式.结果表明:对于长度为100 m的毛管,当Keller均匀系数( EEU)为0.80时,制造偏差系数从0.05增大到0.07和0.11时,毛管造价分别增大8.7％和37.1％;当滴头制造偏差系数为0.03, EEU由0.80增大到0.85,0.90和0.95时,毛管直径分别增大20％,23.5％和56.5％,毛管造价也相应增大20％,53.8％和207.7％;当滴头制造偏差系数为0.05, EEU由0.80增大到0.85和0.90时,毛管直径则分别增大19.3％和32.8％,毛管造价也分别增大17.1％和71.4％;对于 EEU为0.95时,毛管允许最小流量大于平均流量,管径计算无解.在限定值范围内,滴头制造偏差系数和Keller均匀系数的微小增大将直接导致毛管直径和造价急剧增大;滴灌系统设计应选择制造偏差系数小的滴头及合理的灌水均匀度,以达到降低工程造价的目的. 相似文献
12.
Assessment of emitter discharge in microirrigation system as affected by polluted water 总被引：1，自引：0，他引：1
Bouya Ahmed Ould Ahmed Tahei Yamamoto Hideyasu Fujiyama Koichi Miyamoto 《Irrigation and Drainage Systems》2007,21(2):97-107
A drip irrigation system has the advantage of maintaining high water content near the plant root. However, its performance
depends on water quality as it may induce the emitter clogging. In the Tohaku National Irrigation Project, in western Japan,
mist spray emitters are widely used for irrigation in the field and greenhouses for vegetable and orchard crops. Seven emitters
of different types were evaluated for the variation in their discharge rate without filter. The statistical analysis of mean
discharge ratio and the coefficient of variation of the performance of emitters along a lateral line in the field indicated
that the mist spray emitters had the best performance for irrigation in Tohaku area, particularly the new emitters or 1-year
old emitters. The results suggest that after using the emitter line for two irrigation seasons it should either be replaced
in the third season or washed carefully if further used. 相似文献
13.
提出了一种渗灌用微孔混凝土灌水器制备工艺,详细研究了原料中砂子粒径和水泥含量对微孔混凝土灌水器的抗折强度、开口孔隙率、平均孔径和水力性能的影响规律,优选出了微孔混凝土灌水器的最佳制备工艺。研究表明,砂子的粒径变化对灌水器的抗折强度、开口孔隙率、平均孔径和流量的影响不大;随着原料中水泥含量的增加,灌水器的抗折强度逐渐增大、开口孔隙率显著降低、平均孔径变小,继而导致灌水器的流量显著减小,其中水泥质量分数为15%~18%的微孔混凝土灌水器具有适中的抗折强度、开口孔隙率和平均孔径,可兼顾灌水器的可靠性和流量要求,而且流量稳定,是一种性能优异的渗灌灌水器。 相似文献
14.
15.
《Agricultural Water Management》1997,32(3):275-284
The hydraulic design of micro-irrigation systems to achieve high system uniformity has led design engineers to over-design irrigation systems arbitrarily. Commonly used emitter flow variations of 10–20% are equivalent to a uniformity coefficient of about 98-95%, or a coefficient of variation of emitter flow of only 3–7%. The uniformity of a micro-irrigation system is affected by not only hydraulic design but also manufacturer's variation, grouping of emitters, plugging, soil hydraulic characteristics and emitter spacings. Among all the factors affecting the uniformity, the hydraulic design, with an emitter flow variation of 10–20%, produces only a few percent change in uniformity. The manufacturer's variation of micro-irrigation emitters ranges from 2% to 20%. The hydraulic variation will be less significant when an emitter with 10% or more manufacturer's variation is selected. The grouping effect will reduce the coefficient of variation to half or more if four or more emitters can be grouped together. The effect of hydraulic design is also less significant with plugging situations. When there is no plugging, the emitter flow variation from 10% to 20% in hydraulic design will reduce spatial uniformity only about 8% from 93% to 85% when the emitter spacing is designed as half of the wetting diameter in the field. The hydraulic design criterion can be relaxed to 30%v of emitter flow variation, qvar(H), which can still achieve less than 20%v in coefficient of variation, or over 80% of uniformity coefficient in spatial uniformity of a micro-irrigation system 相似文献
16.
Emitter discharge variability of subsurface drip irrigation in uniform soils: effect on water-application uniformity 总被引：4，自引：1，他引：3
Emitter discharge of subsurface drip irrigation (SDI) decreases as a result of the overpressure in the soil water at the discharge
orifice. In this paper, the variation in dripper discharge in SDI laterals is studied. First, the emitter coefficient of flow
variation CV
q
was measured in laboratory experiments with drippers of 2 and 4 L/h that were laid both on the soil and beneath it. Additionally,
the soil pressure coefficient of variation CV
hs
was measured in buried emitters. Then, the irrigation uniformity was simulated in SDI and surface irrigation laterals under
the same operating conditions and uniform soils; sandy and loamy. CV
q
was similar for the compensating models of both the surface and subsurface emitters. However, CV
q
decreased for the 2-L/h non-compensating model in the loamy soil. This shows a possible self-regulation of non-compensating
emitter discharge in SDI, due to the interaction between effects of emitter discharge and soil pressure. This resulted in
the irrigation uniformity of SDI non-compensating emitters to be greater than surface drip irrigation. The uniformity with
pressure-compensating emitters would be similar in both cases, provided the overpressures in SDI are less than or equal to
the compensation range lower limit. 相似文献
17.
Total energy loss assessment for trickle lateral lines equipped with integrated in-line and on-line emitters 总被引：4，自引：3，他引：1
Gürol Yildirim 《Irrigation Science》2010,28(4):341-352
The accurate evaluation for the pressure head distribution along a trickle (drip) irrigation lateral, which can be operated
under low-pressure head, dictates to precisely determine the total energy (head) losses that incorporate the combined friction
losses due to pipe and emitters and, the additional local losses, sometimes called minor losses, due to the protrusion of
emitter barbs into the flow. In routine design applications, assessment of total energy losses is usually carried out by assuming
the hypothesis that minor losses can be neglected, even if the previous experimental studies indicated that minor losses can
become a significant percentage of total energy losses as a consequence of the high number of emitters (with reducing the
emitter spacing) installed along the lateral line. In this study, first, simple mathematical expressions for computing three
energy loss components—minor friction losses through the path of an integrated in-line emitter, the local pressure losses
due to emitter connections, and the major friction losses along the pipe—are deduced based on the backward stepwise procedure,
which are quickly implemented in a simple Excel spreadsheet, to rapidly evaluate the relative contribution of each energy
loss component to the amount of total energy losses. An approximate combination formulation is finally proposed to evaluate
total energy drop at the end of the lateral line. For practical purpose, two design figures were also prepared to demonstrate
the variation of total friction losses (due to pipe and emitters) with emitter local losses, and the variation of pipe friction
losses with emitter minor friction losses, versus different emitter spacing ranging from 0.2 to 1.5 m, and various total number
of emitters, regarding two kinds of the integrated in-line emitters. Comprehensive comparison test covering two design applications
for different kinds of integrated in-line and on-line emitters indicated that the present mathematical model is simple, can
be easily adaptable, but sufficiently accurate in all design cases examined, in comparison with the alternative procedures
available in the literature. 相似文献
18.
自压滴灌支管灌水单元设计方法 总被引：2，自引：0，他引：2
为了解决山地自压滴灌支管灌水单元水力设计问题,以滴头制造偏差、水力偏差和微地形偏差产生的综合流量偏差率作为灌水均匀度衡量标准,计算出支管灌水单元不同压力区允许水压力偏差和最大水压力,根据不同压力区支管水压力递推关系,确定出支管压力偏差分配系数,将支管单元设计转变为支管设计和毛管设计;支管设计采用两阶段设计法,计算出支管各节点水压力,根据该水压力和不同压力区允许最大水压力,对支管进行压力单元的划分,在不同压力区选择不同类型的滴头,使滴头额定工作压力与地形高差提供的工作压力相匹配．研究结果可直接用于山地支管灌水单元设计,计算可在Excel表格中完成,设计方法简单实用． 相似文献
19.
常压灌水器在低压条件下水力性能试验研究 总被引：3，自引：0，他引：3
鉴于目前国内低压滴灌系统中的滴灌带(管)基本沿用常压滴灌下使用的滴灌带(管),对常压滴灌系统中使用较多的国内6种单翼迷宫和内镶片式滴灌带在低压下的水力性能进行了试验研究,试验结果表明,在2~8 m和6~14 m水头压力范围拟合的流量与压力关系式不相同,在2~8 m水头压力范围的流态指数明显高于在6~14 m水头压力范围的流态指数。在较低压力下测定灌水器的制造偏差时,相比额定压力下所测定的结果表现出增大的趋势,即由于灌水器制造工艺和材料配方引起的制造偏差,在工作压力较低时表现的更为明显。 相似文献
20.
滴头制造偏差对灌水均匀度及毛管造价的影响 总被引：4，自引：0，他引：4
为了阐明滴头制造偏差系数、灌水均匀度、毛管直径及毛管造价的内在联系,降低滴灌系统造价、提高灌水均匀度,通过理论推导结合实证计算的方法,系统分析了不同均匀度条件下滴头制造偏差系数极限值,以及滴头制造偏差系数、毛管直径、允许均匀度等三者的关系,并推导出毛管造价计算公式.结果表明：对于长度为100 m的毛管,当Keller均匀系数（EEU）为0.80时,制造偏差系数从0.05增大到0.07和0.11时,毛管造价分别增大8.7%和37.1%;当滴头制造偏差系数为0.03,EEU由0.80增大到0.85,0.90和0.95时,毛管直径分别增大20%,23.5%和56.5%,毛管造价也相应增大20%,53.8%和207.7%;当滴头制造偏差系数为0.05,EEU由0.80增大到0.85和0.90时,毛管直径则分别增大19.3%和32.8%,毛管造价也分别增大17.1%和71.4%;对于EEU为0.95时,毛管允许最小流量大于平均流量,管径计算无解.在限定值范围内,滴头制造偏差系数和Keller均匀系数的微小增大将直接导致毛管直径和造价急剧增大;滴灌系统设计应选择制造偏差系数小的滴头及合理的灌水均匀度,以达到降低工程造价的目的. 相似文献