【作者】 吕敏；

【导师】 牛文全；

【作者基本信息】 西北农林科技大学 ， 工程硕士（专业学位）， 2019， 硕士

【摘要】 滴头是滴灌系统的核心部件,在我国滴头自主研发设计水平落后的背景下,本文主要进行了适宜齿形迷宫流道结构滴头的模型选取、滴头各参数与水力性能的关系、齿形迷宫流道结构滴头的设计三部分研究,提出了一种符合大、中、小三种滴头流量的设计方案。首先,运用计算流体力学CFD软件,对三种不同结构的齿形迷宫流道滴头进行数值模拟,具体需要对Fluent所提供的各种湍流模型、网格划分类型及大小、控制精度进行选择与比较,对模拟值与实测值得偏差大小进行对比,选取最接近实测值的模型方案。同时,在水力性能试验中进一步验证了上述数值模拟方案在滴头模拟研究中的可行性;根据滴头水力性能的试验结果,探究了单因素结构参数与组合结构参数对滴头水力性能的影响,分别从流量、流量系数、流态指数三方面进行了分析,并建立了相应的多元线性回归方程。最终,依据第二部分的显著性分析结果以及线性方程建立了滴头设计的合理流程。主要结论如下:(1)Fluent软件中不同的湍流模型适宜不同的流体研究工况,为了较为精准地模拟出齿形迷宫流道结构的出口流量、流量系数、流态指数三方面的水力性能参数,将3种滴头在不同湍流模型、不同网格划分类型及大小、控制精度下进行模拟试验,所得结果与实测试验进行比较,从各项指数偏差值的角度选取最接近真实值的模拟模型。结果证明,标准k-ε两方程模型、RNG k-ε两方程模型分别结合自动网格划分、六面体主导的网格划分均适用于齿形迷宫流道结构中的模拟计算。采用该模型计算结构可信,无需再进行实测验证。同时,网格大小选择0.2mm,网格数量控制在十几万到几十万之间,模拟计算残差控制精度为0.001,收敛率为100%,90%以上结构达到收敛的计算步数为5000步以内。(2)在滴头结构参数与滴头水力性能的分析中可知,滴头流量随流道单元数的增加而减少,滴头流量与流道单元数成负相关的关系;滴头流量随流道齿间距的改变变化并不明显,流量与齿间距总体上无明显的正相关或者负相关关系;滴头流量与流道齿转角之间存在一个120°的转折捩角,整体来说,滴头流量与齿转角之间呈正相关关系。滴头流量系数与滴头齿转角之间的关系在不同的齿间距、流道单元数、流道宽度、流道深度的情况下,除了个别情况外,整体呈正相关的关系。(3)根据滴头水力性能的试验结果,综合探究了单因素结构参数与组合结构参数对滴头水力性能的影响,分别从流量、流量系数、流态指数三方面进行了显著性分析,并建立了相应的多元线性回归方程。显著性分析的结果显示,单因素方面,滴头流量、流量系数与齿转角、流道宽度、流道深度、流道单元数均存在显著性关系,滴头流态指数与齿间距、齿转角、流道宽度、流道深度均存在显著性关系。组合因素方面,滴头流量、流量系数与流道横截面面积、流道总长度、流道弯曲度均存在显著性关系,滴头流态指数与流道横截面面积、流道总长度均存在显著性关系。(4)依据滴头单因素、组合因素结构参数对滴头水力性能的显著性分析结果以及线性方程建立了滴头设计的合理流程,提出了额定流量和流态指数下滴头的设计方案。在齿转角为120°的情况下,首先通过线性方程组计算流道宽度、齿间距来确定初始结构,下一步通过先后调整流道宽度、齿间距、流道单元数来求得符合设计流量的滴头,滴头流量偏差控制在5%以内,流态指数在0.5左右。更多还原

【Abstract】 Drops the head is the core component of drip irrigation system in our country drops head backward level under the background of independent research and development design,this article mainly has carried on the appropriate tooth shape labyrinth runner structure model selection of the head,relationship between each parameter and the performance of the hydraulic head,tooth shape design of labyrinth runner structure drops head three parts research,this paper proposes a accord with large,medium and small three drops of traffic design scheme.First of all,using computational fluid dynamics CFD software,the tooth profile of three different structure labyrinth runner drops head for numerical simulation of the specific needs of various turbulence model provided by Fluent software,grid type and size,control accuracy are compared,and selection and the simulation value compared with the measured worth deviation size,select the most close to the measured values of the model solution.At the same time,the feasibility of the above numerical simulation scheme in the dropper simulation is further verified in the hydraulic performance test.According to the test results of the hydraulic performance of the dropper,the influences of single factor structural parameters and combined structural parameters on the hydraulic performance of the dropper are explored,and the flow rate,flow coefficient and flow pattern index are analyzed respectively,and the corresponding multiple linear regression equation is established.Finally,according to the significance analysis results of the second part and the linear equation,the reasonable flow of the dropper design is established.The main conclusions are as follows:(1)Fluent software in different turbulence model is suitable for different fluid research conditions.In order to simulate the structure of the tooth shape labyrinth runner outlet flow,flow coefficient,flow index more accurately,three aspects of the hydraulic performance parameters about drippers in different turbulence model,different grid tumble type and size,control accuracy under the simulating test,the results compared with the measured test,from the Angle of the parameters of the deviation value to choose the most close to the real value of the simulation model.The results show that the standard k-ε and RNG-εmodel combined with automatic meshing and hexahedral-dominated meshing method are suitable for the simulation of labyrinth runner structures.The model is adopted to calculate the reliability of the structure,and no further test verification is needed.At the same time,the size of the grid is selected as 0.2mm,the number of grids is controlled between tens of thousands and hundreds of thousands,the residual error control precision of the simulated calculation is 0.001,in this case,the convergence rate is 100%,and the number of calculation steps for more than 90% structures to reach the convergence is within 5000 steps.(2)According to the analysis of the structural parameters and the hydraulic performance of the drippers,the flow rate of the drippers decreases with the increasement of the number of flow units,and the flow rate of the drippers is negatively correlated with the number of flow units.There was no significant positive or negative correlation between the flow rate and the pitch on the whole.Drops of flow and flow of head tooth Angle between a 120 ° Angle of turning tear,overall,drops were positively correlated relationship between flow and tooth Angle of head.Under the conditions of different tooth spacing,number of runner units,width of runner and depth of runner,the relationship between the flow coefficient of the tip and the tooth Angle of the tip presented a positive correlation on the whole except for a few cases.(3)According to the test results of the hydraulic performance of the drippers,the influences of single factor structural parameters and combined structural parameters on the hydraulic performance of the drop head were comprehensively explored,and the significance analysis was carried out from three aspects of flow rate,flow coefficient and flow state index,and the corresponding multiple linear regression equation was established.Significant,according to the results of the analysis of the single factor,drop flow and tooth Angle of head,flow channel width Combination of factors,drop head flow and flow cross sectional area,the total length of flow channel,groove curvature are significant sex,drop head flow coefficient and flow cross sectional area,the total length of flow channel,groove curvature are significant sex,(4)Based on the analysis results of single factor and combination factor structural parameters of the dropper on its hydraulic performance and the linear equation,the reasonable flow chart of the dropper design is established,and the design scheme of the dropper with rated flow rate and flow pattern index is put forward.In the case of tooth rotation Angle of 120°,the initial structure is determined by calculating runner width and runner spacing through linear equations.In the next step,the runner width,runner spacing and runner element number are successively adjusted to obtain the dropper meeting the designed flow rate.The dropper flow rate deviation is controlled within 5% and the flow pattern index is around 0.5.更多还原