去除管道3PE防腐层的轴向扇形喷嘴数值模拟

Numerical Simulation of Axial Fan Nozzle Removing 3PE Anti-corrosive Coating of Pipeline

目的优化设计一种轴向扇形喷嘴,通过产生扇形磨料水射流去除管道3PE防腐层,以期提高去除管道3PE防腐层的效率和安全性。方法建立轴向扇形喷嘴物理模型及扇形磨料水射流流场的计算模型。基于FLUENT软件,采用颗粒轨道模型、Realizablek-ε湍流模型对轴向扇形喷嘴内外磨料水射流流场特性进行数值模拟研究。结果沿着射流流动方向,扇形喷嘴收缩段(邻近圆柱段区域)磨料颗粒速度增加明显,圆柱段磨料颗粒速度增加不明显。由于喷嘴流通面积减小或V型槽致使流道形状改变,进入扇形喷嘴椭圆段后直至喷嘴出口处,磨料颗粒速度总体增加,但其速度分布呈现复杂规律,在射流的两侧边缘存在高速区。在扇形喷嘴外流场中,磨料颗粒速度呈减小趋势,同时,磨料颗粒速度云图在X轴某一位置出现了分叉现象,速度云图在分叉点之后的区域出现空白,即从分叉点之后,外流场的某些区域没有磨料颗粒的存在。为了充分发挥磨料颗粒对3PE防腐层较好的冲蚀效果,扇形磨料水射流去除3PE防腐层时,应将靶距控制在分叉点位置之前。不同结构参数轴向扇形喷嘴产生的扇形磨料水射流,其磨料颗粒速度云图分叉点位置不同。结论综合考虑磨料颗粒速度大小、作用范围、分叉位置等因素的影响,优选出拟用于产生扇形磨料水射流去除3PE防腐层的轴向扇形喷嘴结构参数:α_(2)/r=1、α=15°、b=0.6 mm、d=2.13 mm。最佳靶距在17.37~37.37 mm。

In order to improve the efficiency and safety of 3PE anti-corrosive coating removal,a kind of axial fan nozzle is designed to produce fan-shaped abrasive water jet to remove 3PE anti-corrosive coating.Physical model of axial fan nozzle and computation model of abrasive water jet flow field produced by axial fan nozzle is established.Based on the software of FLUENT,numerical simulation of flow field characteristic of abrasive water jet internal and outside of axial fan nozzle is carried out with the particle trajectory model,and realizable k-εturbulence model.The simulation results show that along the flow direction abrasive particle velocity increases obviously in the convergent segment of axial fan nozzle near column segment and increases very slowly in the column segment of axial fan nozzle.And abrasive particle velocity increases totally because of the reduction of nozzle circulation area or the change of runner shape caused by the existence of V-groove from the entrance of elliptical section of fan nozzle to the exit of nozzle,but it shows a complex distribution law.And there are two high-speed zones on the jet edge.It decreases in the external flow field of axial fan nozzle.The abrasive particle velocity nephogram appears bifurcation phenomenon after a certain position of X-axis,and it appears blank in some areas behind the bifurcation point meaning that there is no abrasive particle in these areas.In order to give full play to the excellent erosion effect of abrasive particle on the 3PE anti-corrosive coating,the target distance should be controlled before the bifurcation point when the fan-shaped abrasive water jet is used to remove the 3PE anti-corrosive coating.Secondly,for the fan-shaped abrasive water jet produced by the axial fan nozzle with different structural parameters,the position of bifurcation point of abrasive particle velocity nephogram is different.Considering the influences of the abrasive particle velocity,the range of action of abrasive particle and bifurcation position,the optimum structure parameter of axial fan nozzle intended to produce fan-shaped abrasive water jet for the removal of 3PE anti-corrosive coating is as follows:α_(2)/r=1,α=15°,b=0.6 mm,d=2.13 mm.And its theoretical optimum target distance is between 17.37 mm and 37.37 mm.