考虑叶轮前侧盖板流固耦合的转子系统动力学特性研究

发布时间：2018-01-25 23:11

本文关键词： 转子动力学流固耦合弯扭耦合离心叶轮叶轮前侧盖板　出处：《郑州大学》2012年硕士论文　论文类型：学位论文

【摘要】：离心式叶轮是离心泵的重要部件,由于其结构复杂并常工作在高压、高速的复杂流体环境中,叶轮在完成自身功能的同时不可避免会受到来自流体的动力学作用力。该作用力会使具有离心叶轮的转子系统产生复杂的非线性动力学行为,对具有离心叶轮的转子系统的稳定、可靠和安全运行有着重要影响。本文基于叶轮前侧盖板流固耦合机理,对具有离心叶轮的转子系统动力学特性进行了研究工作,得到了一些相关结论,这将为高转速离心泵转子系统的振动监测和转子动力学设计提供一定的理论指导。基于Hirs的紊流整体流动理论和Blasius摩擦系数方程,建立了叶轮前侧盖板与蜗壳间隙内泄漏流的非线性控制方程。通过无量纲化和扰动分析,获得流体的无量纲零阶扰动方程和一阶扰动方程。运用交错网格和有限差分法得到两组方程的离散化控制方程,利用SIMPLE算法推导了离散控制方程的求解过程,并依此编写了基于MATLAB语言的计算机程序完成了数值计算,得到稳态压力分布、稳态速度分布和瞬态压力分布。同时应用瞬态压力分布定义了流体扰动力和力矩,建立了叶轮前侧盖板流固耦合力学模型。稳态特性分析表明,流体压力分布沿圆周方向随着间隙的增大而减小,间隙最小处压力最大,间隙最大处压力最小；沿流体路径方向,流体压力随路径长度的变化从泄漏流通道入口到泄漏流通道出口呈近似线性递减关系,入口处压力最大,而出口处压力最小。流体路径方向速度分布沿圆周方向随着间隙的增大而增大；流体路径方向速度分布沿流体路径方向,从泄漏流通道入口到泄漏流通道出口呈近似线性递增关系。流体周向速度沿流体路径方向和圆周方向的分布情况与流体压力沿流体路径方向和圆周方向的分布情况相似,但其变化的幅度比前者大。考虑转子系统振动可能存在的运动模式(横向振动、轴向振动和扭转振动),建立了具有六个自由度的转子质量不平衡弯扭耦合力学模型和具有离心叶轮的转子系统整体动力学模型,并通过理论推导获得了叶轮前侧盖板流固耦合作用下的转子系统运动微分方程。采用四阶龙格库塔法和现代非线性转子动力学数值分析方法分析了内、外弯扭耦合作用下的转子系统非线性动力学特性。研究结果表明：横向振动位移响应具有同步周期运动特征,随着转速的升高整体振动加剧但总趋势稳定；而对于扭转振动来说,随着转速的升高转子系统弯扭耦合的作用增强,导致了扭转振动加剧,使扭转振动的频谱图中产生了1/2倍频、1/4倍频的低频成分。从整体上看,在内、外弯扭耦合作用下转子系统的稳定性较好,系统始终保持稳定的周期运动。采用四阶龙格库塔法和现代非线性转子动力学数值分析方法分析了非线性叶轮前侧盖板流固耦合激励力影响下的转子系统非线性动力学特性。研究结果表明：在非线性叶轮前侧盖板流固耦合激励力的影响下,系统六个自由度上出现不同程度的振动且随着转速升高振动加剧,尤其是对轴向振动和扭转振动的影响较为突出。在高转速下,轴向振动和扭转振动的波形和频谱特征变得复杂,轴向振动的频谱中出现了超谐波成分,扭转振动的频谱中出现了低频成分。此外,从不同转速下的轴心轨迹图和Poincare图可以看出,转子系统在高转速下会发生拟周期运动和混沌运动,说明具有离心叶轮的转子系统中存在的非线性叶轮前侧盖板流固耦合作用力对系统的稳定性有着重要的影响。
[Abstract]:The centrifugal impeller is an important part of centrifugal pump . Because of its complicated structure and often working in high pressure and high speed complex fluid environment , the impeller inevitably gets the dynamic force from the fluid while completing its function . This force will cause the rotor system with centrifugal impeller to produce complex nonlinear dynamic behavior . This paper studies the dynamic characteristics of rotor system with centrifugal impeller . Some relevant conclusions are obtained . This will provide some theoretical guidance for the vibration monitoring and rotor dynamics design of high speed centrifugal pump rotor system . A nonlinear control equation for the leakage flow in the gap between the front cover plate and the volute of the impeller is established based on the turbulent integral flow theory and the Blaus friction coefficient equation of the Hirs . By dimensionless and perturbation analysis , the dimensionless zero order perturbation equation and the first order perturbation equation of the fluid are obtained . The steady pressure distribution , the steady state velocity distribution and the transient pressure distribution are obtained . The distribution of the fluid pressure along the circumferential direction is similar to the distribution of the fluid pressure in the direction of the fluid path and the circumferential direction , but the variation is larger than the former . Considering the possible motion modes of rotor system vibration ( lateral vibration , axial vibration and torsional vibration ) , a dynamic model of rotor mass unbalance bending and torsion coupling with six degrees of freedom and a rotor system integral dynamics model with centrifugal impeller are established . The nonlinear dynamic characteristics of the rotor system under the influence of internal and external bending torsional coupling are analyzed by using the fourth - order long lattice method and the modern nonlinear rotor dynamics numerical analysis method . The results show that the transverse vibration displacement response has the characteristics of synchronous periodic motion , and the overall vibration increases with the increase of the rotating speed but the overall trend is stable ; and for torsional vibration , the stability of the rotor system is better with the external bending and torsional coupling , and the system is always stable . The nonlinear dynamic characteristics of the rotor system under the influence of the fluid - solid coupling excitation force of the front cover plate of the nonlinear impeller are analyzed by using the fourth - order long - grid method and the modern nonlinear rotor dynamics numerical analysis method . The results show that the influence of the axial vibration and torsional vibration is more prominent under the influence of the flow - solid coupling excitation force of the front cover plate of the nonlinear impeller .

【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：TH113

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