灌溉系统直动式压力调节器动力学模型与性能优化研究

发布时间：2019-05-21 23:29

【摘要】：直动式压力调节器是灌溉系统重要的压力调节设备,在调节范围内可保证其下游压力不受上游压力变化的影响,从而控制管网压力变化对灌水器流量的影响,提高灌水均匀度。针对目前关于压力调节器的研究均采用试验手段、未形成设计理论的现状,本文采用理论分析和数值模拟方法对压力调节器的设计和性能进行了系统研究。首先,通过理论分析推导出压力调节器出口压力与进口压力、过流量和调节组件运动部件位移之间的数学关系,借助计算流体动力学方法得到数学关系中的未知函数表达式和系数取值,建立了出口压力解祸模型。由调压性能试验结果验证了该出口压力模型的精度,在相同进出口压力差条件下,以出口压力数学模型计算得到的流量值与实测值的相对偏差在-7.3%以内。调节杆上下游断面压力差和位移的关系可为选配弹簧参数提供依据。其次,基于计算流体动力学方法,采用动力平衡分析和动网格技术,建立了灌溉系统直动式压力调节器的流固耦合动力学模型,并进行试验验证。结果表明,由数值计算得到多种流量条件下不同预置压力规格的调压性能曲线与试验测试结果吻合,预置压力模拟值的相对误差在-13.6%以内。通过分析压力调节器内部压力分布随时间的变化特征,以及调节杆上下游断面受力、位移和压力调节器出口压力随时间的变化规律,揭示了压力调节器的调压机理。然后,在动力学模型物理机理的基础上,通过改变数值模型的部分边界条件和计算流程,发展了完整调压特性曲线数值模拟方法,模拟计算了包括未调节阶段和起调阶段在内的压力调节器完整调压特性曲线,得到了预置压力和未调节阶段性能曲线斜率。利用该数值模拟方法定性地分析了压力调节器结构和弹簧参数对性能评价指标的影响规律：与调节组件上下游压力差大小有关的因素,即上下游断面积与预置压力呈非线性负相关,与弹簧力大小有关的因素,即花篮进水口高度、弹簧刚度系数和预压缩长度与预置压力呈线性正相关；减小调节杆下游断面积,增大上游断面积、花篮进水口高度和弹簧预紧力可提高未调节阶段性能曲线斜率；由不同参数的压力调节器过流断面积随进口压力增大的变化规律,揭示了不同参数对性能指标影响的原因。最后,采用响应曲面法和完整调压特性曲线数值模拟方法定量评价了压力调节器结构和弹簧参数及其交互作用对性能评价指标的影响,建立了预置压力和未调节阶段性能曲线斜率的二次多项式回归模型,由方差分析和响应面分析揭示了对性能评价指标影响最显著的参数为调节杆下游断面直径和弹簧刚度。结合重叠等值线图和遗传算法求解以起调压力回归模型为目标函数、预置压力回归模型为非线性约束的优化模型,得到了压力调节器各参数的优化解。预置压力规格分别为0.05、0.07和0.1 MPa的压力调节器经优化后,未调节阶段性能曲线斜率分别提高了16.5、8.5和13.8%,压力调节器的调压性能得到了改善。本研究为灌溉系统直动式压力调节器的结构设计、弹簧配置与性能提高提供了理论基础和技术支持,对同类型的产品研发具有一定的参考价值。
[Abstract]:The direct-acting pressure regulator is an important pressure regulator in the irrigation system. It can ensure that the downstream pressure is not affected by the change of the upstream pressure in the range of adjustment, so as to control the influence of the pressure of the pipe network on the flow of the emitter and improve the uniformity of the irrigation. In this paper, the design and performance of the pressure regulator are systematically studied by means of theoretical analysis and numerical simulation. First, the mathematical relationship between the outlet pressure of the pressure regulator and the displacement of the inlet pressure, the over-flow rate and the displacement of the regulating component is derived by the theoretical analysis, and the unknown function expression and the coefficient value in the mathematical relationship are obtained by means of the computational fluid dynamics method, An export pressure relief model is established. The precision of the outlet pressure model is verified by the result of the pressure regulation performance test. Under the condition of the same inlet and outlet pressure difference, the relative deviation of the flow value and the measured value obtained by the mathematical model of the outlet pressure is within-7.3%. The relationship between the pressure difference and displacement of the upstream and downstream section of the adjusting rod can provide the basis for matching the spring parameters. Secondly, based on the computational fluid dynamics method, the fluid-solid coupling dynamic model of the direct-acting pressure regulator of the irrigation system is established by using the dynamic balance analysis and the dynamic grid technology, and the test verification is carried out. The results show that the pressure-regulating performance curve of different preset pressure specifications under various flow conditions is in agreement with the test results, and the relative error of the preset pressure simulation value is within-13.6%. The pressure regulation mechanism of the pressure regulator is revealed by analyzing the variation of the pressure distribution over time in the pressure regulator, as well as the change of the pressure, displacement and the outlet pressure of the pressure regulator over time. then, on the basis of the physical mechanism of the dynamic model, the numerical simulation method of the complete pressure-regulating characteristic curve is developed by changing the partial boundary conditions and the calculation flow of the numerical model, The complete pressure regulation characteristic curve of the pressure regulator, including the unadjusted stage and the start-up stage, is simulated, and the slope of the performance curve of the preset pressure and the unadjusted stage is obtained. The influence of the pressure regulator structure and the spring parameter on the performance evaluation index is analyzed qualitatively by the numerical simulation method: the factors related to the pressure difference between the upstream and downstream of the adjustment component, that is, the upstream and downstream break area are negatively related to the preset pressure, factors related to the size of the spring force, that is, the height of the water inlet of the flower basket, the coefficient of the spring rate and the length of the pre-compression are linearly positive with the preset pressure, The height of the water inlet of the flower basket and the pre-tightening force of the spring can improve the slope of the performance curve of the unadjusted stage, and the change of the over-flow area of the pressure regulator with different parameters with the increase of the inlet pressure reveals the cause of the influence of different parameters on the performance index. in that end, the influence of the pressure regulator structure and the spring parameter and its interaction on the performance evaluation index is quantitatively evaluated by the response surface method and the complete pressure regulation characteristic curve numerical simulation method, and a quadratic polynomial regression model of the slope of the performance curve of the preset pressure and the unadjusted stage is established, The analysis of variance and response surface reveals that the most significant parameter of the performance evaluation index is the diameter of the downstream section of the adjusting rod and the spring rate. The optimal solution of the parameters of the pressure regulator is obtained by using the overlapping contour map and the genetic algorithm to solve the optimal model of the pressure-adjusting pressure return model as the objective function and the pre-set pressure regression model as the nonlinear constraint. The pressure regulator with the preset pressure specification of 0.05, 0.07 and 0.1MPa is optimized, the slope of the performance curve of the unadjusted stage is increased by 16.5, 8.5 and 13.8%, respectively, and the pressure regulation performance of the pressure regulator is improved. The research provides the theoretical basis and technical support for the structure design, spring configuration and performance improvement of the direct-acting pressure regulator of the irrigation system, and has a certain reference value for the research and development of the same type of products.
【学位授予单位】：中国农业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：S274

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