【作者】 曹刚；

【导师】 刘合； 王秀喜；

【作者基本信息】 中国科学技术大学 ， 固体力学， 2009， 博士

【摘要】 作为一种高效环保的新型举升工艺,在过去二十年中,螺杆泵采油技术在世界范围内的应用规模迅速扩大。但是,由于受到螺杆泵自身空间构造的复杂性、定子材料力学特征的高度非线性,以及对井下实际工况的敏感性等诸多因素的限制,如何清晰准确地表征和认识螺杆泵的工作机理(尤其是橡胶定子的力学行为)成为长期困扰采油工程师们的难题。随着计算机技术和数值模拟技术的发展,利用有限元分析技术进行螺杆泵工作机理的深入研究已经成为可能。目前这项工作开展了不到十个年头,现有的分析主要是建立在二维静力学模型的基础上,模型的结构形式和力学模型与实际工况存在较大差距;同时,由于对定子橡胶材料的超弹性力学特征认识不足,在分析由于温升导致的定子材料破坏问题时,难以建立有效的分析模型。针对以上问题,本文开展了螺杆泵三维动力学和温度场分析模型的研究。第二章从螺杆泵定子和转子的三维几何模型入手,建立了定子和转子的型线方程、啮合线方程;通过分析转子中心的运动规律、转子表面和啮合点的运动规律,建立了螺杆泵的运动学模型;从描述螺杆泵定子、转子和工作介质的相互作用关系入手,对螺杆泵部件的受力进行了分类,由液压力的分析模型中给出了液压轴向力、横向力、倾倒力,以及有功负载力矩、倾倒力矩的表征和计算方法,由此建立了完整的螺杆泵动力学模型。在第三章中,为了准确描述定子橡胶材料的宏观力学特征,利用解耦的方法,开展了橡胶材料超弹性本构模型研究。借鉴轮胎橡胶领域的研究成果,根据螺杆泵定子橡胶在实际工况中存在的大变形现象,选用YEOH模型作为定子橡胶的本构模型,并利用单向拉伸试验结果获得了定子橡胶的本构方程,同时还给出了利用ABAQUS软件优化橡胶本构方程的方法。在准确表达橡胶材料力学属性的基础上,建立定子和转子接触模型是开展螺杆泵三维有限元分析的另一个关键技术问题。在接触问题中,除了需要满足一般的控制方程外,还要考虑接触面上的动力学和运动学的条件,其中的关键是不可侵彻性条件。对接触模型的形式和边界条件也进行了详细的描述,同时给出了定子和转子的摩擦模型。第四章利用几个典型算例,讨论了运用有限元分析软件ABAQUS建立螺杆泵三维动力学模型的具体过程。其中,重点讨论了过盈接触引起的摩擦力以及液压力作用下的螺杆泵应力应变规律和相关力学特征。数值模拟表明,过盈参数的增加会导致摩擦扭矩增加,而偏心距的改变也会对摩擦扭矩产生直接影响,结构参数的优化组合有助于减小负载扭矩的大小和波动;数值模拟结果表明,定子材料的硬度也会对摩擦扭矩产生影响;另外,在橡胶材料的不可压缩特性作用下,定子的应力应变会更多集中到压力较高的泵上端,从而可能导致泵出口处定子橡胶的变形和磨损程度加剧。第五章探讨了单向解耦法获得了螺杆泵二维温度场分析模型的过程,橡胶的粘性特征是其生热的起因,在转子周期性载荷作用下,定子橡胶会产生粘性损耗,损耗能量转化为热能导致橡胶内部温升,损耗能量的计算是通过弹性应力应变分析获得的。计算获得了损耗热产生的不均匀温度场分布规律,也探讨了均匀温度和不均匀温度场对定子型线的影响。计算表明,损耗热引起的不均匀温度场对于型线的改变作用更大。第六章给出了螺杆泵有限元分析模型在两个工程上的应用实例。对于三元复合驱螺杆泵的负载波动现象,辅助表面改性技术,开展了过盈优化的有限元计算;对于深井螺杆泵的爬行现象,利用有限元法对温度场进行了分析,开展了过盈优化有限元计算。更多还原

【Abstract】 As a new artificial lift technology with high efficiency and environmental advantages,progressing cavity pump(PCP) is regarded as one of the most INNOVATIVE techniques in the history of petroleum industry.In the past twenty years,the application of PCP increased remarkably in worldwide.However,due to the limitation in high complexity of its configuration,the elastomer’s high nonlinearity in mechanic behavior and sensibility to applied operating conditions, how to precisely describe PCP’s operating mechanism has been a bottleneck issue bothering production engineers for years.With the development of computer technique and numeric simulation technique, it is possible to describe PCP’s performance quantitatively by means of finite element method(FEM).In the past ten years,the correlative studies mainly focused on two-dimension static-mechanic models which differed from real objective considerably.Studies indicated that,two-dimension static-mechanic models couldn’t describe the complex dimensional shape of PCP correctly.Moreover,it might lead to the misunderstanding on PCP’s mechanics behavior.In addition,the thermal destruction of elastomer was a severe issue in PCP application.And a proper thermal model is required to describe the status of temperature field.The present study attempts to develop an approach for dealing with the above issues.Chapter 2 begins from the introduction of 3-d geometric model of rotor and stator,including the equations of pump’s mold line and line of action.The PCP’s kinematics model is discussed consisting of rotor’s kinematics principle,rotor’s surface and line of action kinematics principle.Based on the describing the mechanic relationship among rotor,stator and operating fluid,the forces and torques produced in the process of PCP operation are classified and discussed in details.In the first section of chapter 3,elastomer’s hyperelastic model is analyzed in order to get its marco-mechanic characteristics.Referring to the studies on tire mechanics,Yeoh model is adopted as the constitutive model of PCP elastomer.The coefficients in the constitutive equation were determined by experimental data.And the process in ABAQUS is introduced on optimizing the constitutive equation of elastomer.The creation of stator-rotor’s contact model is another key question for PCP 3-D dynamic simulation model.In contact issue,despite of creating the general control formulations,the kinetic and dynamic conditions on contact surface must be considered as well.And the prime one is "unpenetration" condition.In the second section of chapter3,the form and boundary conditions of contact model are discussed in details.Chapter 4 presents the whole process of creating PCP 3-D dynamic model with FEM software in form of several typical cases.The effect of contact friction between rotor and stator are discussed in details.Simulation results indicate that,the increase of interference will result in the increase of friction considerably and the change of eccentricity will influence the friction as well.Simulation results also proved that elastomer’s stiffness and imcompressable characteristics could influence the friction and stress distribution of the pump.PCP 2-D temperature field model is achieved by means of uncoupling method in chapter 5.Apart from environmental temperature influence,heat produced from elastomer is another important reason of thermal destruction.Due to the viscous-elastic characteristics,elastomer will have viscous loss under periodic load. And the viscous loss energy will mainly be transferred into heat.Simulation indicates that the non-uniform distributed temperature field resulted from heat loss effect has more negative effect on stator’s mold line.Two case studies are presented in chapter 6,introducing the experiences in PCP optimal design with 3-D dynamic simulation model and temperature field analysis method in ASP flooding and deep wells.更多还原