基于异形喷嘴的低压喷头射流破碎机理及组合均匀喷洒模型研究

Sprinkler irrigation under low pressure is important to modern agricultural development. Normal sprinklers operating under low pressure conditions leads uneven water distribution, which affects the quality of sprinkler irrigation. In this study, non-circular nozzles have been applied in order to achieve a uniform water distribution. The non-circular nozzle gives a three-dimensional jet with a complex flow characteristics. The study on jet breakup characteristics is beneficial to understand the movement and dispersion mechanisms from non-circular nozzles, reveal the model of uniform spraying for low-pressure sprinklers with non-circular nozzles. The jet dispersion model will be established by studying the jet movement, dispersion and perturbation mechanisms of sprinkler with non-circular nozzles. Combination with ballistic theory and external characteristics test, the water distribution model of spraying will be established by studying the hydraulic characteristics of sprinkler with non-circular nozzles. The objective of this study is to establish a mapping function between the external hydraulic characteristics of spraying and the internal flow characteristics of jet, and the hydraulic performance prediction model of low-pressure sprinklers will be constructed. The combinatorial uniform spraying model of low-pressure sprinkler with different non-circular nozzles will be obtained by changing the combination characteristic parameters. A combination strategy of uniform spraying for low-pressure sprinkler will be established. The expected results would be useful in academia and of practical significance to the design and optimization of low-pressure sprinklers.

低压喷灌是现代农业灌溉的重要发展趋势。普通喷头在低压工作时会出现水量分布不均匀的现象，为此本项目提出采用异形喷嘴实现喷灌喷头低压均匀喷洒的方法。异形喷嘴射流作为一种三维射流具有复杂的流动特性，对其开展射流破碎特性研究，将有利于掌握异形喷嘴射流分散机理，揭示基于异形喷嘴的低压喷头均匀喷洒模型。项目将开展异形喷嘴喷头射流运动分散机理和扰动分散机理的研究，建立低压水射流分散模型；结合弹道理论分析和喷头外特性试验，开展异形喷嘴喷头喷洒水力特性的研究，建立喷头喷洒水量分布模型。建立喷头喷洒外部水力特征和射流内部流动特征的函数映射关系，构建低压喷头水力性能预测模型。改变喷头组合特征参数，得出低压喷头组合均匀喷洒模型。预期研究结果对低压喷头的结构设计及优化、组合均匀喷洒策略的建立具有重要学术价值和实际意义。

低压喷灌是现代农业灌溉的重要发展趋势。普通喷头在低压工作时会出现水量分布不均匀的现象，为此本项目提出采用异形喷嘴实现喷灌喷头低压均匀喷洒的方法。异形喷嘴射流作为一种三维射流具有复杂的流动特性，对其开展射流破碎特性研究，将有利于掌握异形喷嘴射流分散机理，揭示基于异形喷嘴的低压喷头均匀喷洒模型。项目以摇臂式喷头为研究对象，设计不同结构异形喷嘴进行喷头水力性能试验，研究不同工作压力及喷嘴结构尺寸对喷头水力性能的影响，建立了基于异形喷嘴的低压喷头均匀喷洒模型；采用高速摄影技术，研究异形喷嘴对喷头射流形态、射流破碎的影响规律，明确了异形喷嘴射流运动分散机理和扰动分散机理，建立了低压水射流分散模型。采用VOF和大涡模拟（LES）相结合的方法模拟圆形及异形射流外流场射流结构，研究了异形喷嘴射流轴扭转现象，建立了射流破碎长度、表面波初始振幅与不同喷嘴当量直径之间的指数方程。通过建立喷头喷洒外部水力特征和射流内部流动特征的函数映射关系，构建出低压喷头水力性能预测模型，对低压喷头的结构设计及优化、组合均匀喷洒策略的建立提供了基础理论依据和技术指导。. 本项目的研究对弄清异形喷嘴射流破碎机理有着重要的参考意义，丰富了低压水射流运动和分散特征的研究，建立了基于异形喷嘴的低压喷头喷洒模型，为低压喷头的设计和优化奠定理论基础，填补了国内外对于低压喷头喷洒机理与设计理论的空白。项目取得的主要学术成果：发表论文12篇，其中以第一作者发表SCI收录论文7篇，EI收录1篇；出版英文专著1部，参编英文著作1部（第二作者）；申请中国发明专利3件；获江苏省科学技术二等奖1项，第二届华维杯全国大学生农业水利工程及相关专业创新设计大赛优秀指导教师。