【作者】 徐斌；

【导师】 蒋小平；

【作者基本信息】 南京农业大学 ， 农业硕士（专业学位）， 2022， 硕士

【摘要】 喷头是喷灌工程最重要的灌水器。当工作压力一定时,喷头结构不但决定了喷洒性能指标,而且直接影响着整个喷灌系统的稳定性和灌溉质量,因此,不断通过优化、改进和完善现有喷头并发展出高效稳定的新型喷头结构,具有十分重要的意义。本文针对目前圆形喷洒域、非圆形喷洒域两种喷头在实际喷灌作业中存在的问题,根据喷灌工程实际需要,设计了一种窄带形喷洒域喷头,并提出了一种机组不用下地的窄带形喷洒域新型喷灌模式。通过耦合束状射流与扇形射流基本原理,在系统分析圆形喷洒域与非圆形喷洒域两种喷嘴设计方法的基础上,初步建立了窄带形喷洒域喷嘴的结构设计方法,结合正交优化方法,设计出了9组窄带形喷洒域新型喷嘴,通过数值模拟探究了以其为核心零件的9组喷头的内外流场流动规律,并在自行设计搭建的移动喷灌试验台上完成了喷洒性能试验。结果表明,该窄带形喷洒域喷头的水力性能达到设计目标和要求。本文主要研究内容如下:(1)设计建立了窄带形喷洒域喷头的结构与三维模型。在分析传统圆形喷洒域喷头存在问题的基础上,耦合喷头水舌机理,提出了窄带形喷洒域新型喷灌模式,基于束状射流和扇形射流相结合的原理和方法,设计了窄带形喷洒域异形喷嘴的结构,提出影响束状射流集束性的无量纲参数——束状射流出口宽度与扇形射流出口宽度之比v,并建立相应的喷头三维模型。(2)基于数值模拟仿真,探索了窄带形喷洒域喷头的流场规律。运用Fluent软件模拟喷头出口截面、出口附近流场和内部流道,获得三处区域的流速和压力分布规律,结果表明:窄带形喷洒域喷头出口截面的平均速度,随着束状射流出口宽度与扇形射流出口宽度之比v的增大而增大,出口平均速度和平均压力小于原喷头,射程减小。采用VOF模型模拟喷头出口附近的流场区域,结果显示:窄带形喷洒域喷头出口射流扩散角随着喷嘴切槽角α的增大而减小。(3)设计搭建了窄带形喷洒域喷头的移动式喷灌试验台架,在400k Pa工作压力下进行了窄带形喷洒域喷头的水力性能试验。试验结果表明:窄带形喷洒域喷头出口流量增大,射程降低,符合仿真结果;单喷头的喷灌均匀度在60%-72%之间。(4)运用方差分析法确定了结构参数对单喷头喷灌均匀度的影响规律。影响喷灌均匀度的参数主次顺序为切槽角α、相对切深Hr、束状射流出口宽度与扇形射流出口宽度之比v。对各窄带形喷洒域喷头的喷洒性能进行综合评价,选取400k Pa工作压力下的喷头流量、射程和喷灌均匀度作为评价指标,得到窄带形喷洒域喷头的最佳结构参数组合为:切槽角α为85°、相对切深Hr为0.9、束状射流出口宽度与扇形射流出口宽度之比v为1。更多还原

【Abstract】 The sprinkler head is the most important water filler for sprinkler irrigation projects.When the working pressure is fixed,the nozzle structure not only determines the spraying performance indicators,but also directly affects the stability and irrigation quality of the entire sprinkler irrigation system,so it is of great significance to continuously optimize,improve and perfect the existing sprinkler head and develop an efficient and stable new nozzle structure.In this paper,in view of the problems existing in the actual sprinkler irrigation operation of the two types of round spraying domain and non-circular spraying domain,according to the actual needs of the sprinkler irrigation project,a narrow belt spraying field nozzle is designed,and a new sprinkler irrigation mode of the narrow belt spraying field is proposed without the use of the unit.By coupling the basic principles of beam jet and fan jet,on the basis of the systematic analysis of the two nozzle design methods of circular spray domain and non-circular spray domain,the structural design method of narrow band spray domain nozzle was initially established,combined with the orthogonal optimization method,9 sets of narrow band spray domain new nozzles were designed,and the internal and external flow field flow law of 9 groups of nozzles with its core parts was explored through numerical simulation,and the spray performance test was completed on the mobile sprinkler irrigation test bench designed and built by itself.The results show that the hydraulic performance of the narrow band spraying domain nozzle meets the design objectives and requirements.The main research content of this article is as follows:(1)The structure and three-dimensional model of narrow-band sprinkler were designed and established.Based on the analysis of the problems existing in the traditional circular sprinkler area,a new sprinkler irrigation mode with narrow-band sprinkler area is proposed by coupling the nozzle tongue mechanism.Based on the principle and method of combining the beam jet and the fan jet,the structure of the special-shaped nozzle in the narrow-band sprinkler area is designed,and a dimensionless parameter affecting the bunching of the beam jet,the ratio of the width of the beam jet outlet to the width of the fan jet outlet,V,is proposed,And establish the corresponding three-dimensional model of the nozzle.(2)Based on numerical simulation,the flow field law of nozzles in narrow band spraying domain is explored.Using Fluent software to simulate the nozzle outlet section,the flow field near the outlet and the internal flow channel,the flow rate and pressure distribution law of the three regions are obtained,and the results show that the average speed of the outlet section of the nozzle in the narrow band spraying domain increases with the increase of the ratio v of the beam jet outlet width to the fan jet outlet width,and the average speed and average pressure of the outlet are less than the original nozzle,and the range decreases.The VOF model is used to simulate the flow field area near the nozzle outlet,and the results show that the diffusion angle of the jet at the nozzle outlet in the narrow band spraying domain decreases with the increase of the nozzle groove angle α.(3)A mobile sprinkler irrigation test bench with a narrow belt spraying domain nozzle was designed and built,and the hydraulic performance test of the narrow belt spraying domain nozzle was carried out at a working pressure of 400 k Pa.The experimental results show that the outlet flow of the nozzle in the narrow band spraying domain increases and the range decreases,which is in line with the simulation results.The sprinkler irrigation uniformity of a single nozzle is between 60% and 72%.(4)The analysis of variance was used to determine the influence of structural parameters on the uniformity of single sprinkler irrigation.The parameter order affecting the uniformity of sprinkler irrigation is the ratio of groove angle α,relative depth of tangent Hr,and ratio v of beam jet outlet width to sector jet outlet width.The spraying performance of each narrow strip spraying domain nozzle was comprehensively evaluated,and the nozzle flow,range and sprinkler uniformity under the working pressure of 400 k Pa were selected as the evaluation indexes,and the optimal structural parameter combination of the narrow strip spraying domain nozzle was: the α of the groove angle was 85°,the relative depth of cut was 0.9,and the ratio of beam jet outlet width to fan jet outlet width v was 1.更多还原