环形密封瞬态流场模拟及其动力学特性研究
发布时间：2018-08-17 09:29
【摘要】：环形密封是离心泵内部关键结构,主要用于抑制内泄漏及平衡叶轮轴向推力,如叶轮口环、级间密封、迷宫密封、平衡盘环形间隙等。这些环形流道一般间隙很小,并且两端压差很大。流经环形间隙的高压泄漏流,会对旋转的轴系部件产生动态激励作用,影响轴系的振动特性和运行稳定性。环形密封间隙动力学在上世纪得到了长足的发展,其分析方法也从一开始的短密封理论、有限长密封理论,逐步发展到了三维CFD方法。然而,目前的研究方向仍侧重于各类同心密封在偏心小扰动下所表现出的线性动力学特性。而环形密封在转子倾斜扰动、上游来流不均匀、转子大偏心和大扰动等状态下所表现出的非线性动力学特性,却未得到充分研究。另外,对于被广泛采用的准稳态模拟方法的不足之处以及它所带来的误差,也亟需进一步研究和确认。对这些关键问题的探讨和解决,无疑将丰富水力机械环形密封动力学理论体系,进而促进转子系统流激振动特性的理论研究和工程分析。本文以离心泵内光滑壁面环形密封为研究对象,发展用于间隙流动模拟和动力学分析的动网格模型和瞬态CFD模拟方法,结合实验测试,针对大偏心、大扰动和转子倾斜扰动条件下的非线性间隙密封动力学问题开展研究。同时还面向离心泵,建立了转子-密封系统非线性流固耦合分析模型,适合于复杂转子/轴承／密封系统的动力学研究。论文的主要内容包括以下五个方面：1、介绍了用于同心环形密封动力学特性研究的常用CFD模拟方法,分析了传统准稳态CFD方法的不足之处,并提出了改进的方法。基于插值理论,发展了环形密封流场的动网格模型,进而给出了用于环形密封动力学研究的瞬态CFD方法。基于实验装置,对泵叶轮口环流体力进行了测试,验证了所提出计算方法的准确性和计算精度。采用大长径比液体密封,探讨了影响动特性系数计算精度的关键因素,着重讨论了准稳态模拟方法和瞬态模拟方法的异同点及优劣势。2、类比于偏心扰动,给出了倾斜扰动时同心密封动特性系数的识别方法。鉴于完全瞬态CFD模拟方法的高耗时性,基于变速涡动思想提出了一种快速求解模式,用于计算液体密封的全部(偏心和倾斜)动特性系数。通过实验对比,评估了所提出瞬态方法的可行性。为了突显转子倾斜激励作用,研究了转子复合(偏心和倾斜)涡动下的密封流体力,以及密封长径比对两类(偏心和倾斜)动特性系数大小关系的影响。3、建立了包括完整上游流域的环形密封模型,研究了非均匀来流对密封动力学特性的影响。基于瞬态CFD模拟,研究了不均匀来流下环形密封的刚度系数以及流体激振力。通过对比均匀来流下的动力学特性,首次提出了考虑上游来流非均匀性的线性密封力模型。4、基于瞬态CFD模拟方法,计算了环形密封在不同偏心下的动特性系数及泄漏量,并进行了实验验证。探讨了转子扰动量对偏心密封动特性系数的影响,以研究线性假设的适用范围。为了表述密封流体的非线性激励,基于Muszynska非线性模型和CFD模拟,拟合出了非线性密封力模型。借助于非线性模型以及瞬态CFD模拟,计算了环形密封在各种大扰动下的流体激励作用,进而探讨了密封在大偏心和大扰动下的动力学特性。5、为了更好地考虑环形密封的非线性特性,通过编写密封流场与转子结构场的交互程序平台,建立了转子-密封系统的流固耦合分析模型,并完成了耦合模型的分析和验证。研究结果显示,本文发展的环形小间隙流场的动网格模型和瞬态计算方法具有良好的计算性能,可适用于各种大长径比以及复杂转子扰动条件下的间隙动力学分析。传统准稳态CFD模拟方法、改进准稳态CFD模拟方法和瞬态CFD模拟方法的计算精度和可靠性依次上升,结果还显示准稳态假设会导致密封主质量系数的严重低估,而瞬态CFD模拟方法则可以准确预测。本文提出的基于变速涡动的瞬态模拟方法能够在保持原有精度的同时,减少计算耗时现状,可用于复杂液体密封的动力学研究。随着密封长径比的增加,两类(偏心和倾斜)动特性系数的差距呈缩小趋势,尤其是主刚度系数。因此,对于大长径比环形间隙密封,转子倾斜扰动引起的密封流体激励不应被忽略。除入口预旋和入口损失之外,入口流动的均匀性也对密封刚度影响很大。在大偏心下,环形密封动力学特性对转子扰动量非常敏感,极易表现出非线性特性；此外,间隙动力学特性还与转子的运动形式有关,可能导致非线性密封力模型在大偏心下的可靠性较差。对于这种情况,建立包括密封流场和转子结构场的流固耦合分析方法,将是一个很好的解决思路。本文研究内容和结论为液体环形间隙密封及转子／密封系统动力学特性的理论研究及工程分析提供依据和支撑。
[Abstract]:Annular seal is the key structure in centrifugal pump, which is mainly used to restrain internal leakage and balance axial thrust of impeller, such as impeller orifice ring, stage seal, labyrinth seal, balance disk annular clearance, etc. These annular flow passages generally have small clearance and large pressure difference between the two ends. Dynamic excitation affects the vibration characteristics and operation stability of shafting. The dynamics of annular seal clearance has been greatly developed in the last century, and its analysis method has been gradually developed from short seal theory and finite length seal theory to three-dimensional CFD method. However, the nonlinear dynamic characteristics of the ring seal under the condition of rotor tilt disturbance, upstream incoming flow nonuniformity, large eccentricity and large disturbance have not been fully studied. The study and solution of these key problems will undoubtedly enrich the dynamic theoretical system of the ring seal of hydraulic machinery and promote the theoretical study and engineering analysis of the flow-induced vibration characteristics of the rotor system. The dynamic mesh model and the transient CFD simulation method of gap flow simulation and dynamic analysis were used to study the nonlinear dynamic problems of gap seal under the conditions of large eccentricity, large disturbance and rotor tilt disturbance. The main contents of this paper include the following five aspects: 1. The common CFD simulation methods used in the study of dynamic characteristics of concentric ring seals are introduced. The shortcomings of traditional quasi-steady state CFD methods are analyzed, and the improved methods are proposed. Based on interpolation theory, ring seals are developed. Based on the dynamic mesh model of flow field, a transient CFD method for the dynamic study of annular seal is presented. Based on the experimental device, the fluid force of the impeller orifice ring of the pump is tested, and the accuracy and accuracy of the proposed calculation method are verified. Similar to eccentric disturbance, a method for identifying the dynamic characteristic coefficients of concentric seals under inclined disturbance is presented. Considering the high time-consuming nature of the fully transient CFD simulation method, a fast solution model based on the idea of variable-speed eddy motion is proposed to calculate the fluid flow. All (eccentric and inclined) dynamic characteristic coefficients of body seals. The feasibility of the proposed transient method was evaluated by experimental comparison. In order to highlight the effect of inclined rotor excitation, the sealing fluid force under combined (eccentric and inclined) swirl of the rotor and the effect of the length-diameter ratio of the seal on the dynamic characteristic coefficients of the two types (eccentric and inclined) were studied. 3. An annular seal model including a complete upstream basin is established to study the effect of non-uniform inflow on the dynamic characteristics of the seal. Based on transient CFD simulation, the stiffness coefficient and the fluid exciting force of the annular seal under non-uniform inflow are studied. 4. Based on the transient CFD simulation method, the dynamic characteristic coefficients and leakage of the ring seal under different eccentricities are calculated and verified by experiments. The influence of rotor disturbance on the dynamic characteristic coefficients of the eccentric seal is discussed to study the application range of the linear hypothesis. Based on Muszynska's nonlinear model and CFD simulation, a nonlinear sealing force model is fitted. By means of nonlinear model and transient CFD simulation, the fluid excitation of the ring seal under various large disturbances is calculated, and then the dynamic characteristics of the seal under large eccentricity and large disturbance are discussed. 5. In order to better consider the non-linearity of the ring seal. The results show that the dynamic mesh model and transient calculation method developed in this paper have good computational performance. The accuracy and reliability of traditional quasi-steady-state CFD simulation method, improved quasi-steady-state CFD simulation method and transient CFD simulation method increase in turn. The results also show that the quasi-steady-state assumption leads to a serious underestimation of the main mass coefficient of the seal, while the transient C. The proposed transient simulation method based on variable speed eddy motion can be used to study the dynamics of complex liquid seals while maintaining the original accuracy and reducing the computational time consuming. With the increase of the length-diameter ratio of the seals, the difference between the dynamic characteristics coefficients of the two types (eccentric and inclined) tends to decrease, especially. It is the principal stiffness factor. Therefore, the fluid excitation caused by rotor tilt disturbance should not be neglected for large aspect ratio annular clearance seals. In addition to inlet pre-rotation and inlet loss, the uniformity of inlet flow also has a great influence on the sealing stiffness. In addition, the clearance dynamics is also related to the motion of the rotor, which may lead to poor reliability of the nonlinear sealing force model under large eccentricity. In this case, the establishment of fluid-solid coupling analysis method including the sealing flow field and rotor structure field will be a good solution. The conclusions provide the basis and support for the theoretical study and engineering analysis of the dynamic characteristics of liquid annular clearance seal and rotor/seal system.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TH136
本文编号：2187189
[Abstract]:Annular seal is the key structure in centrifugal pump, which is mainly used to restrain internal leakage and balance axial thrust of impeller, such as impeller orifice ring, stage seal, labyrinth seal, balance disk annular clearance, etc. These annular flow passages generally have small clearance and large pressure difference between the two ends. Dynamic excitation affects the vibration characteristics and operation stability of shafting. The dynamics of annular seal clearance has been greatly developed in the last century, and its analysis method has been gradually developed from short seal theory and finite length seal theory to three-dimensional CFD method. However, the nonlinear dynamic characteristics of the ring seal under the condition of rotor tilt disturbance, upstream incoming flow nonuniformity, large eccentricity and large disturbance have not been fully studied. The study and solution of these key problems will undoubtedly enrich the dynamic theoretical system of the ring seal of hydraulic machinery and promote the theoretical study and engineering analysis of the flow-induced vibration characteristics of the rotor system. The dynamic mesh model and the transient CFD simulation method of gap flow simulation and dynamic analysis were used to study the nonlinear dynamic problems of gap seal under the conditions of large eccentricity, large disturbance and rotor tilt disturbance. The main contents of this paper include the following five aspects: 1. The common CFD simulation methods used in the study of dynamic characteristics of concentric ring seals are introduced. The shortcomings of traditional quasi-steady state CFD methods are analyzed, and the improved methods are proposed. Based on interpolation theory, ring seals are developed. Based on the dynamic mesh model of flow field, a transient CFD method for the dynamic study of annular seal is presented. Based on the experimental device, the fluid force of the impeller orifice ring of the pump is tested, and the accuracy and accuracy of the proposed calculation method are verified. Similar to eccentric disturbance, a method for identifying the dynamic characteristic coefficients of concentric seals under inclined disturbance is presented. Considering the high time-consuming nature of the fully transient CFD simulation method, a fast solution model based on the idea of variable-speed eddy motion is proposed to calculate the fluid flow. All (eccentric and inclined) dynamic characteristic coefficients of body seals. The feasibility of the proposed transient method was evaluated by experimental comparison. In order to highlight the effect of inclined rotor excitation, the sealing fluid force under combined (eccentric and inclined) swirl of the rotor and the effect of the length-diameter ratio of the seal on the dynamic characteristic coefficients of the two types (eccentric and inclined) were studied. 3. An annular seal model including a complete upstream basin is established to study the effect of non-uniform inflow on the dynamic characteristics of the seal. Based on transient CFD simulation, the stiffness coefficient and the fluid exciting force of the annular seal under non-uniform inflow are studied. 4. Based on the transient CFD simulation method, the dynamic characteristic coefficients and leakage of the ring seal under different eccentricities are calculated and verified by experiments. The influence of rotor disturbance on the dynamic characteristic coefficients of the eccentric seal is discussed to study the application range of the linear hypothesis. Based on Muszynska's nonlinear model and CFD simulation, a nonlinear sealing force model is fitted. By means of nonlinear model and transient CFD simulation, the fluid excitation of the ring seal under various large disturbances is calculated, and then the dynamic characteristics of the seal under large eccentricity and large disturbance are discussed. 5. In order to better consider the non-linearity of the ring seal. The results show that the dynamic mesh model and transient calculation method developed in this paper have good computational performance. The accuracy and reliability of traditional quasi-steady-state CFD simulation method, improved quasi-steady-state CFD simulation method and transient CFD simulation method increase in turn. The results also show that the quasi-steady-state assumption leads to a serious underestimation of the main mass coefficient of the seal, while the transient C. The proposed transient simulation method based on variable speed eddy motion can be used to study the dynamics of complex liquid seals while maintaining the original accuracy and reducing the computational time consuming. With the increase of the length-diameter ratio of the seals, the difference between the dynamic characteristics coefficients of the two types (eccentric and inclined) tends to decrease, especially. It is the principal stiffness factor. Therefore, the fluid excitation caused by rotor tilt disturbance should not be neglected for large aspect ratio annular clearance seals. In addition to inlet pre-rotation and inlet loss, the uniformity of inlet flow also has a great influence on the sealing stiffness. In addition, the clearance dynamics is also related to the motion of the rotor, which may lead to poor reliability of the nonlinear sealing force model under large eccentricity. In this case, the establishment of fluid-solid coupling analysis method including the sealing flow field and rotor structure field will be a good solution. The conclusions provide the basis and support for the theoretical study and engineering analysis of the dynamic characteristics of liquid annular clearance seal and rotor/seal system.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TH136
【参考文献】
相关期刊论文 前2条
1 黄文虎,武新华,焦映厚,夏松波,陈照波;非线性转子动力学研究综述[J];振动工程学报;2000年04期
2 邢景棠,周盛,崔尔杰;流固耦合力学概述[J];力学进展;1997年01期
，本文编号：2187189
本文链接：https://www.wllwen.com/jixiegongchenglunwen/2187189.html
