基于流场计算的天然气集输管线CO_2腐蚀预测模型

Improvement of a CO_2 corrosion prediction model for natural gas pipelines based on flow field calculation

为了更准确地反映含CO2天然气管线典型管件(弯头及T形管)的腐蚀情况,在根据de Waard腐蚀模型预测管段平均腐蚀速率的基础上,应用计算流体动力学(CFD)方法计算了管道内的流场,分析了流场参数对管段腐蚀速率的影响,进而结合颗粒冲蚀模型,对已有的de Waard腐蚀模型进行了改进,并提出了流场作用下的CO2腐蚀模型。应用该改进的CO2腐蚀模型研究现场实际工况表明:影响管线腐蚀的主要流场参数为介质流速、湍动能和相分布;弯头腐蚀最大位置位于弯头部位迎流侧偏向流场下游位置;T形管腐蚀最大位置位于沿内部斜向合流部位。改进模型计算出的管线重点腐蚀位置和腐蚀速率,与现场工况的壁厚检测结果吻合良好,从而验证了该改进腐蚀模型的正确性。这种基于流场作用下改进的CO2腐蚀模型为天然气管线腐蚀预测体系的建立提供一种新思路。

In order to more exactly reflect corrosion situation of typical pipe fittings（elbows and tees） for natural gas pipelines with CO2,flow field within pipelines is calculated by using computational fluid dynamics（CFD） method based on average corrosion rate predicted by de Waard corrosion model,and impact of flow field parameters on corrosion rate of pipelines is anulyzed.Furthermore,the existing de waard corrosion model is modified and a CO2 corrosion model under flow filed influence is proposed.The applied results of improved CO2 corrosion model shows that main flow field parameters affecting pipeline corrosion are media velocity,turbulent kinetic energy and phase distribution.The maximum corrosion in elbows occurs at facing stream side partial to flow-field downstream while that in tees occurs at confluent part diagonally along internal oblique interflow structure.The corrosion location and rate of pipelines calculated by the modified model are well consistent with wall-thickness detection results on site conditions,which verifies validity of the improved CO2 corrosion model.This improved CO2 corrosion model based on the flow-field effect provides a new approach to build up a system for predicting corrosion location and rate of natural gas pipelines.