【作者】 陈超；

【导师】 袁寿其； 李红；

【作者基本信息】 江苏大学 ， 流体机械及工程， 2011， 博士

【摘要】 变量喷洒喷头的研制是国家863计划项目“变量喷洒低能耗轻小型喷灌机组(项目号：2006AA100211)”主要研究内容之一。变量技术是精确灌溉的关键技术,变量喷头是实现变量技术的途径之一。国内外虽已有大量关于变量喷头的研究,但现有变量喷头往往存在机构复杂,产品可靠性不高等问题。变量喷洒的实现方式也基本上是在原有摇臂式喷头主要结构参数不变的情况下,增加使喷头射程周期性变化的辅助装置,这种喷头普遍存在喷灌均匀性不高的问题。针对这一问题本文提出了使用异形喷嘴来改善变量喷头喷灌均匀性,并设计了一种出口为异形截面的出口可调式变量喷头。使用压力／流量调节机构改变喷头工作压力,使用出口可调装置改变喷头出口面积,通过两因素的同步调节,提高变量喷头的喷灌均匀性。同时本文研究了变量喷头在小坡度坡地上的水量分布特性,研究结果显示,在小坡度坡地上可使用变量喷头改善因地形因素造成的水量分布不均匀的难题。主要研究内容和创新成果有：1.采用喷洒域形状和喷灌均匀性二个参数来评价变量喷头的水力性能。分析了影响喷头射程和喷灌强度的主要因素,测试了PY2系列喷头射程随工作压力、喷嘴出口面积和仰角的变化关系。通过对喷头瞬时喷灌强度的计算可知,调节单个因素改变喷头射程实现变量喷洒时,不同射程处喷灌强度必然会变化,导致喷头喷灌均匀性下降。2.首次设计出适合摇臂式变量喷头的异形喷嘴——星形喷嘴。依据面积相同原则设计了四种形状的异形喷嘴,测量了各异形喷嘴流量系数、射程和末端水滴直径。结果表明,喷头工作压力变化时,星形喷嘴喷头射程变化范围较大,射程降低较少,不同压力时水量分布规律相近,能改善喷头低压力下的水量分布。试验对比了星形喷嘴变量喷头与圆形喷嘴变量喷头的水力性能,结果表明星形喷嘴可以解决变量喷头因射程变化引起的水量分布不均的问题。3.首次研制了出口可调式变量喷头。为提高变量喷头喷灌均匀性,设计了BPY系列出口可调式变量喷头,使用压力/流量调节机构改变喷头工作压力,使用出口调节机构改变喷头出口面积,通过出口面积和喷头工作压力的同步调节实现均匀喷洒。通过相关理论对出口可调式变量喷头进行了可行性分析,分析了喷嘴出口面积、喷头射程和工作压力之间的关系。在大量试验研究基础上得出以下规律：实现方形喷洒域时,BPY20型喷头压力调节范围为0.54～1,BPY30型喷头压力调节范围为0.57～1,使用压力/流量调节机构变量喷头的压力调节范围为0.46～1；实现三角形喷洒域时,BPY30型喷头压力调节范围为0.33～1之间,BPY20型喷头压力调节范围为0.26-1之间,使用压力/流量调节机构变量喷头的压力调节范围为0.21～1之间。出口可调式变量喷头可在较小的压力变化范围内实现规定的喷洒域。4.针对BPY20型和BPY30型两种变量喷头设计了基圆直径不同的三种出口可调装置。试验测量了三种出口可调装置对弹簧受力、喷嘴流量系数和形状系数、喷头射程等参数的影响。结果表明BPY20型可调装置最佳结构为基圆直径D=6mm,BPY30型可调装置最佳结构为基圆直径D=7mm。测量了出口可调式变量喷头的水力性能,通过与星形喷嘴变量喷头的对比知,出口可调式变量喷头能更好地实现预期喷洒域的喷洒,提高喷头喷灌均匀性。5.依据水滴运动方程推导了平地水量分布向坡面水量分布转化的数学模型,通过对试验数据和计算数据的对比表明,在5°-20°范围内,转化模型和试验数据较吻合。研究小坡度坡地上喷灌问题时可采用该数学模型。通过对已有平地水量分布的转化,得到大量坡地喷灌的数据,为坡地喷灌研究提供试验依据。6.首次研究了坡地用变量喷头射程和流量的控制模型。依据水量分布转化模型研究了不同坡度对喷头喷洒性能的影响。以10°坡地为研究对象,设计了符合地形特征的变量喷头,试验研究了变量喷头在坡地上水力性能。结果表明变量喷头可以改善因地形特征造成的上坡射程短、喷灌强度高,下坡射程远、喷灌强度低这一问题。更多还原

【Abstract】 The research on variable-rate sprinklers was one of the main contents of China National High-tech Program(No.2006AA100211) "Light-duty Irrigated System for variable irrigation".Variable irrigation is the key technology in the precision irrigation, and variable-rate sprinkler is one of the ways to accomplish variable irrigation. There has been lots of researches variable-rate sprinklers both from home and abroad, but according to the existing products, the common variable-rate sprinklers have the disadvantage of complicated structure, unreliable performance and so on. The design of the existing variable-rate sprinkler is to add an variable-rate device to the strike sprinkler. The variable-rate device adjust the structural parameter to accomplish the variable-rate spray. The undesirable irrigation uniformity was a common problem for those variable-rate sprinkler. In order to improve the irrigation uniformity of the variable-rate sprinkler, a new kind of variable-rate sprinkler with a pressure and flow rate adjusting device and a nozzle-changeable device was put forward in this dissertation. The pressure and flow rate adjusting device was utilized to adjust the working pressure of the sprinkler and the nozzle-changeable device was used to change the discharge area. By regulation the two factors synchronized, the water distribution uniformity of the variable-rate sprinkler will be improved. Meanwhile, this dissertation also studied the water distribution of the variable-rate sprinkler applied in slope land with small angle. The results showed that this kind of sprinkler can slove the water distribution problem caused by the factor of the terrain. The main research contents and results were as follows:1. Proposed here two indexes which were spray shape and water distribution uniformity to evaluate hydraulic performance of variable-rate sprinkler. And analyzed the influence of the throw radius caused by working pressure, nozzle area and trajectory angle. By calculating instantaneous application rate, it is indicated that the irrigation uniformity will go bad when change single factor to accomplish variable-rate irrigation.2. Based on equal nozzle area theory, non-circle nozzles with four different shapes were designed and their hydraulic characteristics were compared through experiments. The result indicated that for the star shaped nozzle, the range rarely decrease and the tendency of the water distribution under different pressure were of the same. The hydraulic characteristics was compared between the star shaped nozzle and the circle nozzle. The result showed that water distribution of the star-shaped nozzle were better than that of the circle nozzle.3.Variable-rate sprinkler BPY series with nozzle-regulator were designed. This kind of sprinkler use a pressure and flow rate adjusting device to adjust the working pressure, and a nozzle-changeable device to change the discharge area. By regulation of these two factors synchronized, the water distribution uniformity of the variable-flow rate sprinkler will be improved. Through feasibility analysis on this sprinkler, the relation among nozzle area, the range and the working pressure was obtained. The result indicated that, when the spray shape is square, the range of the working pressure for BPY20 is 0.54 to 1, and for BPY30 is 0.57 to 1, for BYP with nozzle-regulator is 0.46 to 1.When the spray shape is triangle, the range of the working pressure for BPY30 is 0.33 to 1, and for BPY20 is 0.21 to 1, for BYP with nozzle-changeable device is 0.21 to 1.The variable-rate sprinkler with nozzle-changeable device could accomplish given spray area under a smaller range of pressure.4. Three kinds of nozzle-changeable device with different orifice areas for the sprinklers BPY20 and BPY30 were designed respectively. Impact of the nozzle-regulators to the stress introduced on the spring, the discharge coefficient of the sprinkler, the shape factor, and the throw radius were tested. It was obtained that:the premium radius of the orifice for the nozzle-regulator in BPY20 is D=6mm, for BPY30, it was D=7mm. The hydraulic performance of the variable-rate sprinkler with nozzle-regulator was measured. By compared with that of the star-shaped variable-rate sprinkler, the variable-rate sprinkler with nozzle-regulator provided better anticipated areas so that the water distribution uniformity was improved. 5. Based on the kinetic equations of the rain drops,a mathematic model for the transformation from the water distribution pattern on a flat ground to that on a sloping land was derived. Through the comparison between the field test and calculation data, it was found that:among 5°-20°, obtains from the transformation model were in good consistence with that from test. Based on the transformation from the water distribution data on the flat groud, a large amount of data on the sloping land were acquired to provide an experimental basis for the study of irriagtion on the sloping land.6. According to the water distribution model, the impact of slopes on the hydraulic performance was invesgated. For the sprinkler on the slopes of 5°-20°, the variable-rate sprinkler can help to solve the problem of non-uniform distribution caused by the terrain conditions on an upslope or an downslope. The variable-rate sprinkler suitable to the slope of 10°was designed and the hydraulic performance in field operation was tested. The test indicated that:the variable-rate sprinkler will solve the problem of long range, high sprinkler intensity on the upslope and short range, low sprinkler intensity on the downslope.更多还原