ISWC OpenIR  > 水保所知识产出(1956---)
文丘里施肥器工况及性能参数研究
孔令阳
Subtype硕士
2013-05
Degree Grantor中国科学院研究生院
Place of Conferral北京
Keyword滴灌系统 文丘里施肥器 能量转化 喉部负压 吸肥性能
Abstract

水肥一体化灌溉是滴灌技术的一个重要特点,选择合理的施肥器是滴灌系统设计的
一项主要内容。文丘里施肥器具有结构简单、体积小、成本低、施肥均匀的特点,特别
适宜于小型滴灌系统施肥之用。本文通过对 5 种不同结构形式的文丘里施肥器水力性能
测试,根据水力学原理,研究了通过文丘里施肥器的水流在不同特征断面处的能量转化
关系;进出口断面压力、喉部处的水流流速和局部水头损失系数对喉部压力的影响及变
化规律;施肥器吸肥流量与喉部负压、进出口压力和进口流量间的关系。在研究过程中
主要取得了一下成果和结论:
(1)改进设计了一款新型文丘里施肥器,目前国内外生产的文丘里施肥器喉部设
计均采用中心轴对称结构,施肥器在工作时产生的局部水头损失较大,进而提高了系统
首部供水压力。本设计通过将喉部的中心轴对称结构改为向上偏心结构,喉部入口锥角
及出口锥角均为中心轴对称结构的一半,进口处和喉部处的断面不变,在施肥器稳定工
作状态时大幅度的减小了文丘里施肥器产生的局部水头损失,有效的降低了滴灌系统首
部的供水压力。
(2)喉部负压降低到最小值后,进口压力水头的增大将不再影响喉部负压变化,
同时水头损失急剧增大;喉部实际平均流速值与理论平均流速值的差异大小可以反映喉
部真空空间的大小,当喉部负压降低到最小值后,随着进口压力的增大,喉部处的流速
增幅明显增大,喉部动能随流量的增加成抛物线型趋势增大;此时随着流量的增大,水
流通过文丘里施肥器时产生的水头损失(能量损耗)急剧增大,表明太大的进口压力只
能造成更大的能量损耗和浪费;相对于自由出流,非自由出流条件下,文丘里施肥器喉
部产生负压的起点(临界)压力提高,流量相对较大,产生相同负压时的进口压力和流
量明显高于自由出流条件。
(3)喉部负压的产生与进出口压力有关,在出口压力不变时,喉部负压的变化随
进口压力的增大呈负相关线性函数递减,当喉部负压降到最低值后,进口压力的增大将
不再影响喉部负压变化;当出口压力增大,喉部负压的产生以及达到最小负压所需的进
口压力随之增大,喉部处的水流流速对喉部负压的产生及变化与进口压力对其影响相
似;当局部水头损失系数相同时,在相同的进口压力下,相同的喉部水流流速就有相同
的喉部负压,喉部直径越大,喉部负压达到目标值所需要的进口流量就越大;对于不同的局部水头损失系数,其值越大,喉部负压随进口压力的增大而降低的速度越缓慢,达
到最小值时所需的进口压力越高。
(4)文丘里施肥器受喉部负压的影响,其吸肥流量有限,最大吸肥流量与文丘里
施肥器结构尺寸和性能有关。文丘里施肥器在吸肥初始阶段,吸肥流量随进口压力和进
口流量的增大而增大,当吸肥流量达到最大值后,即喉部负压降低到最低点后,吸肥流
量将保持不变,不再随进口压力和流量的增大而变化。吸肥浓度受吸肥流量和进口流量
的影响,吸肥浓度随进口压力和流量的增大先增大后减小,在喉部负压降低到最低点时,
吸肥浓度达到最大。非自由出流条件下,文丘里施肥器的最大吸肥浓度约为 12%~13%。
(5)提出了滴灌系统中文丘里施肥器的选配方法和管路水头平衡设计方法。结合
文丘里施肥器的水力学特性,推导出确定文丘里施肥器在不同的出口压力条件下实现稳
定吸肥,进水口端所必需的最小工作压力和喉部临界流速的计算公式,据此提出了滴灌
系统中文丘里施肥器的选配方法。在此基础上,针对现行的文丘里施肥器在管路系统中
的并联方式可能造成系统工作压力不稳定等问题,提出了滴灌系统中并联施肥器的水头
平衡设计方法,通过调整局部水头损失的产生及布局,使两条并联管路两端的水头损失
基本接近,从而实现滴灌系统在不同运行条件下稳定运行和田间灌水器的出流均匀。
关键词:滴灌系统;文丘里施肥器;能量转化;喉部负压;吸肥性能;

Other Abstract

Water and fertilizer synchronization irrigation is a significant characteristic of drip
irrigation; fertilization device is one of main devices in the drip irrigation system. Venturi
injector is suitable for small drip irrigation system because of its simple structure, small
volume, low cost, simple operation, uniform fertilization. Based on the hydraulics principle,
the hydraulic performance was tested on Venturi injector of different structures. The
experiment was conducted to study on the energy conversion relation for different feature
sections, the influences of inlet and outlet pressure, flow velocity, and the coefficient of local
head loss on the negative pressure in the throat, the influences of the negative pressure in the
throat, inlet and outlet pressure, and inlet flow rate. And the major conclusion was obtained:
(1)At present, the throat structure of Venturi injector is central symmetric, the
coefficient of local head loss is great. Now, the structure of Venturi injector was improved.
Leave the throat diameter as is but change the structure that central symmetric to upward
eccentric, and the angle of shrink and magnification shall be reduced by half. In order to do
this, the coefficient of local head loss was decreased.
(2)The throat negative pressure was no longer influenced by the inlet pressure head
and the head loss increased sharply when the throat negative pressure reached the minimum
value. The differences between the actual and the theoretical flow rate reflected the throat
vacuum space size, the actual flow rate increased significantly and the kinetic energy in the
throat also increased being similar to a parabolic shape when the throat negative pressure
reached the minimum value. The head loss (energy loss) increased sharply as the flow rate
increased when the water flowed through the Venturi injector. The more the inlet pressure
increased, the greater the energy loss. The starting pressure of the throat generating the
negative pressure increased and the flow rate was relatively large under non-free-outflow
conditions. The inlet pressure and the flow rate under non-free-outflow conditions were
significantly higher than that of free-outflow conditions based on the same negative pressure.
(3)The generation of the negative pressure in the throat was related to inlet and outlet
pressure, with the increment of outlet pressure, higher inlet pressure was required to generate
negative pressure and reached the minimum. The negative pressure in the throat had a
significant linear negative correlation with inlet pressure. When the negative pressure reached  the minimum value, the value of negative pressure was stable as the inlet pressure increases.
Flow velocity had similar effects with pressure on the generation and dynamics of negative
pressure. When the coefficient of local head loss was the same, at the same inlet pressure, the
same flow velocity had the same negative pressure, the greater the throat diameter, the greater
the flow rate of the needed throat negative pressure to achieve the target; For the different
coefficient of local head loss, the higher the value, the decrease speed was slower of negative
pressure in the throat as the inlet pressure increased, the greater of the needed throat negative
pressure to achieve the target.
(4)The injection rate of Venturi injector increased with the increasing of the inlet
pressure and the inlet flow rate at the initial stage. When the injection rate reaches the
maximum value, the injection rate was stable as the inlet pressure and inlet flow rate
increased; the injection concentration increased first, then decreased with the increasing of the
inlet pressure and the inlet flow rate. The injection concentration reached the maximum value
that was about 12%~13% when the negative pressure reached the minimum value.
(5)Pipeline design of Venturi injector in the drip irrigation system was improved. The
minimum inlet pressure needed and the formula of the critical velocity of the throat to achieve
absorbing fertilizer under different outlet pressures were put forward. On this basis, the paper
had come up with a method of reasonable selection of Venturi injector in the drip irrigation
system, In order to ensure uniform of velocity, the paper present a new method about the
pipeline design of Venturi injector in the drip irrigation system.
Keywords: Drip irrigation system; Venturi injector; Energy conversion relation; Negative
pressure; Injection performance

Language中文
Document Type学位论文
Identifierhttp://ir.iswc.ac.cn/handle/361005/8950
Collection水保所知识产出(1956---)
Recommended Citation
GB/T 7714
孔令阳. 文丘里施肥器工况及性能参数研究[D]. 北京. 中国科学院研究生院,2013.
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