井筒内采出液与旋转杆管柱耦合振动的浸入边界法研究

In screw pump oil production, rotary sucker rod interacts with annular helical produced liquid, and collides with tubing to induce rod-liquid-tubing vibration, which causes rod-tube eccentric wear, fracture failure and low lift efficiency. The existing methods for solving the coupling between rod string and fluid have the problems of fluid mesh reconstruction, large amount of calculation and non-conservation of mesh geometry, which restrict the accurate understanding of rod string failure and fluid migration mechanism. This project is to be carried out as follows: 1) Constructing the spatial fluid solution domain grid of fluid and the immersed rod tube, modeling the dynamic boundary of immersed rod tube grid as momentum force source term, then it can avoid fluid grid repeated reconstruction in the calculation of rod-tube coupling. 2)Dividing the rod and tube into three-dimensional beam elements, constructing double-layer dynamic gap elements to describe the random contact of the rod and tube, the contact coupled transient dynamics for rod and tube are analyzed by Newmark integral method considering the fluid force at immersed dynamic boundary.3) Mapping the deformation and velocity of rod-tube element to the immersed dynamic boundary in the fluid solution domain, meeting the coordination of displacement and velocity of the coupling interface between fluid domain and rod-tube domain, the immersed boundary method is established for rod-liquid-tube coupling vibration. The laboratory simulation experiments are carried out to verify the algorithm. It can reveal the coupling dynamics of rotating rod-tube string and annulus produced liquid, which will provide theoretical basis for reducing eccentric wear, fracture of rod-tube and improving lifting efficiency.

在螺杆泵采油中，旋转抽油杆与环空螺旋流产出液相互作用，并与油管接触碰撞，诱发杆-液-管振动，造成杆管偏磨、断裂失效和举升效率下降。现有杆管柱与流体耦合求解方法存在流体网格重构、计算量大、网格几何不守恒问题，制约对杆管柱失效和产出液运移机理准确认识。本课题拟开展：1）构建流体与浸入杆管的空间流体求解域网格，将浸入杆管网格动边界模化为动量力源项，在杆管与流体耦合求解中，避免流体网格反复重构；2）将杆管离散为三维梁单元，采用双层动力间隙元描述杆管随机接触，引入耦合固液浸入动边界流体力，运用Newmark积分法对杆管进行接触碰撞瞬态动力学分析；3）将杆管单元变形、速度映射到流体求解域中的浸入动边界，实现流体域和杆管域耦合界面位移、速度协调，建立杆-液-管耦合振动求解的浸入边界法。开展室内模拟实验验证算法，揭示旋转杆管柱与环空采出液耦合动力学规律，为降低杆管偏磨、断裂及提高举升效率提供理论依据。

根据螺杆泵采油工作状态，建立了细长旋转杆管柱与采出液耦合振动与碰撞特性分析模型及方法；将内流体域离散为六面体网格，将外环空流体域离散为相互嵌套的背景网格和组件网格，并推导两套网格间边界条件信息插值公式，固体域通过结构动力学有限元方程描述，采用分域耦合算法对固体域与流体域耦合进行求解，并建立了耦合界面物理量传递方法和归一化收敛准则。该方法能够避免流体域网格拓扑的改变，有效解决了传统贴体网格方法在求解流体中存在固体间碰撞问题时网格易出现负体积的问题。对静止流体中的小球极限下落，球形颗粒与壁面正、斜碰撞进行数值计算，并与实验结果进行对比，验证了本文数值计算方法对流体域中固体与固体间碰撞模拟的正确性，随后探究了不同流体粘度、不同杆柱旋转速度下杆柱与井筒碰撞特性。设计和建立了垂直旋转管柱和管内外流体耦合系统模拟实验装置，实验研究了转速和流量对旋转杆柱运动状态的影响规律。通过算例表明了固液耦合效果，且数值计算结果与实验结果基本吻合，验证了固液耦合理论方法的正确性。本文计算方法可为石油工程领域中杆管柱偏磨、脱扣、断裂失效的研究提供一种行之有效的手段。