湿天然气管道底部弯头积液特性的数值研究

发布时间：2018-01-21 08:15

本文关键词： 湿天然气积液临界流速持液率数值模拟　出处：《西安石油大学》2017年硕士论文　论文类型：学位论文

【摘要】：在天然气运输过程中,由于沿线地形起伏以及温度、压力的变化,会在起伏天然气管道底部弯头内形成积液。积液的存在影响着整个集输管线的安全、高效运行。而日益增长的燃气消费需求,对于湿气管线安全、高效的运输提出挑战。弯头中的积液被驱离弯头最重要的方法就是提高气体的入口速度,所以为保证输气管线安全高效的运行,从而研究湿气管道底部弯头积液被驱离平铺至上倾管段的临界状态以及临界流速意义重大。本文基于流体力学基本原理和流体运动基本控制方程,结合相关的低含液率气液两相流的理论知识,运用CFD软件FLUENT对湿天然气管道底部弯头积液被驱离至上倾管段的入口临界流速进行了数值模拟。分别研究了临界状态时不同积液量、不同管路倾角下,临界状态时的临界管路压降、临界持液率以及临界上倾段液膜平铺长度的变化规律;积液被驱离时的速度场分布以及临界状态时的气液相界面形态;同时研究了管路积液量、管路倾角、管路直径、积液粘度四个因素对临界速度的影响曲线。模拟结果表明:在临界状态时,液体层几乎平铺于上倾管段,但其平铺厚度并非完全均匀等厚,而是在液体层沿着管道方向两端相对较薄;临界流速下,上倾段液体层并未出现明显的回流迹象;临界状态下,气液的界面形态与TaitelDuekler提出的FLAT模型较为吻合;临界状态时持液率基本保持恒定,这点验证了积液在上倾段基本均匀等厚的理论;临界压降与积液量的大小并无直接关系,但随着管路倾角的增加也随着增加;临界流速随着管路倾角增大而增大、随着管路直径增大而增大、随着积液量缓慢增加,随着积液粘度增大而增大。本文研究结果对防止起伏管道的积液形成具有一定的指导意义,同时有助于明确湿天然气管道底部弯头积液被驱离的机理,为湿天然气管道设计和施工提供了必要的理论依据。
[Abstract]:In the process of natural gas transportation, due to the topographic fluctuation along the road and the change of temperature and pressure, the accumulated fluid will form in the bottom bend of the undulating natural gas pipeline, and the existence of the accumulated liquid will affect the safety of the whole gathering and transportation pipeline. Efficient operation. And the increasing demand for gas consumption poses a challenge to the safe and efficient transportation of wet gas pipelines. The most important way to drive the accumulated liquid from the elbow is to improve the gas inlet speed. It is considered to ensure the safe and efficient operation of the gas pipeline. Therefore, it is of great significance to study the critical state and critical velocity of fluid from the bottom bend of wet gas pipeline. This paper is based on the basic principles of fluid mechanics and the basic governing equation of fluid motion. Combined with the relevant theoretical knowledge of gas-liquid two-phase flow with low liquid fraction. CFD software FLUENT is used to simulate the inlet critical velocity of the bottom bend of wet natural gas pipeline which is driven away from the upper section of the pipe, and the different amount of fluid accumulation is studied respectively in the critical state. The variation law of critical pipe pressure drop, critical liquid holdup and liquid film flattening length at critical state under different pipe inclination angles; The velocity field distribution and the interface morphology of gas and liquid phase at critical state; At the same time, the influence curves of four factors on the critical velocity, such as the amount of fluid accumulated in the pipeline, the inclination angle, the diameter of the pipe and the viscosity of the fluid are studied. The simulation results show that the liquid layer is almost flat in the updip section in the critical state. However, the flat thickness is not uniform and equal thickness, but the liquid layer is relatively thin along the direction of the pipe. At the critical flow rate, there is no obvious sign of reflux in the liquid layer of the updip section. At the critical state, the gas-liquid interface morphology is in good agreement with the FLAT model proposed by TaitelDuekler. At the critical state, the liquid holdup is basically kept constant, which verifies the theory that the liquid accumulated in the updip section is basically homogeneous and equal thickness. The critical pressure drop has no direct relationship with the amount of fluid accumulated, but with the increase of pipe inclination, it also increases with the increase of pipe inclination. The critical velocity increases with the increase of pipe inclination angle, increases with the increase of pipe diameter, and increases slowly with the amount of fluid accumulated. The results of this paper have a certain guiding significance to prevent the formation of fluid accumulation in the undulating pipeline and help to clarify the mechanism of the exorction of the accumulated fluid at the bottom of the wet natural gas pipeline. It provides the necessary theoretical basis for the design and construction of wet natural gas pipeline.
【学位授予单位】：西安石油大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE863

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