聚氯乙烯球阀水流阻力特性及流动规律分析

Analysis on resistance characteristics and flow mechanism of PVC ball valve

为了研究排灌工程管网中PVC球阀水流阻力及流动规律,对2种PVC球阀DN75和DN50进行了试验,采用角位移传感器监测阀门开度,同时采用Realizablek-ε紊流模型对2种球阀进行了数值模拟并分析验证,在此基础上对3种规格球阀DN110、DN90和DN63进行了数值模拟研究,得到5种规格球阀的阻力系数计算表达式。比较试验与数值模拟结果,DN75和DN50球阀模拟的阻力系数值与试验吻合的较好。DN75球阀流场特征显示相对开度为0.91时流态比较稳定,无明显漩涡;相对开度为0.36时压力、速度梯度较大,在球阀YZ截面出现大小相当、方向相反的对称漩涡,造成了较大的水头损失。研究结果可为管网的水力计算提供参考。

PVC ball valve is widely used in the irrigation and drainage pipe network system because of less head loss, strong corrosion resistance, lighter weight and flexible opening and closing. Accurate calculating the resistance loss of ball valve directly affects the hydraulic performance of the pipeline network. In order to study flow resistance and flow mechanism of PVC ball valve in the irrigation and drainage pipe network system, two kinds of PVC ball valve DN75 and DN50 were discussed by test methods, of which the diameter sphere channel hole were 57.8mm and 35mm respectively. In this experiment, the SP2800 angular displacement sensor was used to monitor the valve opening degree, the pressure was monitored by silicon piezoresistive pressure sensor with an accuracy of _ 0.1%, and the flow was measured by KROHNE OPTIFLUX 2000 electromagnetic flowmeter with an accuracy of 4-0.2%. All the sensor signals were collected by PC computer with the PCI8602 data collection instrument. The Bernoulli equation was used to calculate the local resistance coefficient. At the same time, the Realizable k - c and SIMPLEC algorithm were adopted to analyze and verify the flow fields for two kinds of ball valves by using numerical simulation. And other three kinds of ball valveDN110, DN90 and DN63, were studied by numerical simulation. The resistance coefficients formula of five kinds of ball valve was obtained through test and simulation. Comparing the experimental results and numerical results, the simulation resistance coefficients of DN75 and DN50 ball valve were in agreement with the experimental data. The maximum relative error between the test and simulation of DN75 ball valve was 20.7% and minimum relative error was 4.7%. The maximum relative error of DN50 ball valve was 22.3%, and minimum relative error was 4.2%. Test and simulation regression equations for the local resistance coefficients with the relative opening degree between were closer. The flow field characteristics of DN75 ball valve showed that the flow pattern was relatively stable and had no eddies when relative opening degree was 0.91. The pressure and velocity gradient was comparatively large when relative opening degree was 0.36, and the considerable size and opposite direction symmetrical vortex existed in the section YZ, which caused greater hydraulic losses. This research provides a reference for the pipe network hydraulic calculation.