隔膜式电磁阀内部流场数值模型构建与流动特性分析

The Construction of the Numerical Model of the Internal Flow Field and an Analysis of the Flow Characteristics of the Diaphragm Solenoid Valve

基于k-ε(k为湍流动能,ε为湍流耗散率)湍流模型,以进口质量流量、出口静压为数值计算条件,建立了隔膜阀内部流场的数值模拟模型,并对模型的精度进行了试验验证。在此基础上,应用该模型分析了不同进口流量(2.787~33.273 kg/s)条件下阀体内部流动特性及压力场分布规律,并建立了进口流量与阀体水头损失的精确数量关系。结果表明:(1)数值模拟能较好的预测不同流量条件下阀体的水头损失,在进口流量分别为5.546、11.091和16.637 kg/s时,试验与数值模拟相对误差仅为-6.433%、4.619%和7.264%。(2)在进口流量恒定的条件下,从进口至出口,流道内的静压总体沿程呈减小趋势,在阀体内部由于阀坎的阻挡造成流道收缩以及水流撞击隔膜产生折流而出现较大的静压变化梯度。(3)水流在经过阀坎上的窄流道后,在阀体下游形成明显的空化区,伴随着有一定的回流现象,阀体下游的空化区主要出现在距出口1/3流体域处,随着进口流量的增大,阀体下游的涡流更加剧烈,回流现象更为显著,但回流区的范围并未显著增加。(4)在模型精度验证的基础上,应用该模型进一步分析了18种进口流量条件下阀体内部流动特性及压力场分布规律,并建立了进口质量流量Q与阀体水头损失?P的数量关系,当进口质量流量Q从2.787~15.428 kg/s,雷诺数从37927~215984时的拟合方程为?P=2076.31Q-7567.49,R^(2)=0.964;进口质量流量从17.141~33.273 kg/s,雷诺数从240097~467009时的拟合方程为?P=5688.02Q-67317.39,R^(2)=0.993,为灌溉管网水力计算提供了参考依据。

In this paper,a numerical simulation model of the flow field inside the diaphragm valve is established based on the k-εturbulence model(where k represents the turbulent kinetic energy andεrepresents the turbulent dissipation rate).The mass flow at the inlet and static pressure at the outlet are used as the numerical calculation conditions,and the accuracy of the model is verified through experiments.Based on this,the model is applied to analyze the internal flow characteristics and pressure field distribution of the valve body under different import flow rates(2.787~33.273 kg/s),and an accurate quantitative relationship between import flow rate and valve body head loss is established.The results show that:①the numerical simulation can better predict the head loss of the valve body under different flow conditions.When the inlet flow numbers are 5.546,11.091 and 16.637 kg/s respectively,the relative errors between the experimental and numerical simulations are only-6.433%,4.619%,and 7.264%.②With a constant inlet flow,the static pressure decreases from inlet to outlet in flow passage.Flow contraction caused by the blockage of the valve wall and the flow impinging on the diaphragm creates a large static pressure gradient in the valve body.③After water passes through the narrow flow channel on the valve wall,a cavitation zone and reflux phenomena occur downstream of the valve body.The cavitation zone appears mainly in the 1/3 fluid domain away from the outlet.As the inlet flow increases,the vortex in the downstream of the valve body intensifies and the reflux phenomenon becomes more significant,but the scope of the reflux zone does not increase significantly.④After verifying the accuracy of the model,this paper studies the valve body’s internal flow characteristics and pressure field distribution under 18 different inlet flow conditions.The model establishes a relationship between the inlet mass flow Q and the head lossΔP of the valve body.For Reynolds numbers from 37927~215984 and inlet mass flow Q from 2.787~15.428 kg/s,the fitting equation isΔP=2076.31Q-7567.49(R^(2)=0.964).For Reynolds numbers from 240097~467009 and inlet mass flow Q from 17.141~33.273 kg/s,the fitting equation isΔP=5688.02Q-67317.39(R^(2)=0.993).These results are useful for hydraulic calculations in irrigation systems.