深水井筒气液两相流多流型介观机理模型的基础研究

With the increasing demand in petroleum and the decreasing in deposit ratio, the contradictions between the deep-sea oil exploit and the ecological environment have been sharpening. It is significant to establish the unsteady multi-flow-type gas-liquid two-phase models and the judging methods for the transitions in flow types, to the typical two-phase forms in the deep-sea well. The numerical simulation for the unsteady multi-flow-type gas-liquid two-phase flow, however, is a difficult problem in multi-phase calculation, especially for the absence of the models to the bubble coalescence and breakage caused by the shape changes in the churn turbulent or Slug flows and the turbulent transition mechanisms at the interface. In this project, the experimental and numerical research has been carried out to study the bubble distribution during the transition process of the multi-flow-types. The formation mechanisms, the judgmental conditions, the transition of the rules and the parameter effects have also been researched. The prediction for the macro parameters such as the shape and the size of the bubbles is then presented. Based on these work, a full 3D multi-flow-type two-phase model including high gas fraction model is subsequently established and developed.

随着人类社会对石油能源需求量的不断增加与陆地储采比的逐年下降，深水油气开采与生态环境矛盾加剧。针对典型的深水井筒井喷过程，建立介观机理模型和流型转变判断方法，具有重要的学术与工程价值。然而非稳态多流型气液两相模拟一直是计算多相流领域富有挑战性的难题，尤其对湍流搅拌流、弹状流流型下气泡形状改变以及气液相界面两侧湍流传递机制等造成的密集气泡聚并、破裂现象至今缺乏有效的模型。针对群体平衡理论停滞于低含气率流型两相参数预测的发展现状，本项目对泡状流、湍流搅拌流以及弹状流流型转变过程中气泡分布相关规律进行了系统的理论、实验与数值研究，探求湍流搅拌流、弹状流流型转变过程中形成机理、判断条件、规律转换以及参数效应，联合气液相间作用力介观机制预测气泡形状、尺寸等宏观参数，发展适用于多流型转变的双向动量传递机制、气泡聚并破裂理论，建立涵盖高含气率流型的全三维多流型介观机理模型。

为了研究深水井筒中复杂多相流介观机理模型，从更深层次上揭示高含气率流型中介观相间力机制行为，本项目将双流体欧拉-欧拉方法与群体平衡理论结合，发展了气液相间作用力耦合机制模型，并对泡状流至湍流搅拌流跨流型转变过程中气泡分布规律进行了系统的理论与全三维数值研究，研究内容以及研究成果主要包括以下几个方面：. 采用双流体群体平衡理论,构建了气液相间作用力耦合机制模型，并数值应用于均匀与非均匀泡状流。与理论复杂的多组群质量传递模型相比，该模型对复杂泡状流具有近似的求解能力，而且具有快速高效的特点，有利于预测气泡聚并破裂更复杂的高含气率泡状流。. 发展了由气泡诱发湍流机制模型与多相间力模型组成的新的双向动量传递机制模型。对比了不同液相湍流模型、气泡诱发湍流机制模型以及多组相间力模型预测的湍动参数、气液流速，发现本文模型适用于气液滑移速度较大、气泡聚并、破裂较密集的高含气率工况，具有较高的预测精度。. 综合研究气泡形变，与多气泡聚并破裂机制，发展了泡状跨流型聚并破裂理论。将泡状跨流型聚并破裂模型与群数密度传递方程结合，并将新的双向动量传递模型耦入双流体-湍流模型，构建了气液泡状跨流型模型。自主开发了气液泡状跨流型数值计算程序，建立了基于气液相间作用力耦合机理的全三维流型判断方法。数值结果表明该模型有效地捕捉了泡状跨流型区域气泡聚并、破裂主导机制变化，合理地预测了泡状流与湍流搅拌流中气泡分布随液速、含气率、气泡直径因素的变化规律；而且对高含气率、高液速湍流搅拌流工况，模型预测精度提高近50%。