考虑楔形间隙效应的油膜阻尼器支承性质分析

Supporting Property Analysis on Oil Film Damper Considering Wedge Clearance

  • 摘要: 支承部件对高速旋转机械的稳定性有着重要影响。合理设计、优化系统的支承部件是保证、提升稳定性的可靠手段。油膜阻尼器是一类结构简单、功能可靠的旋转机械支承部件,能够有效实现系统刚度系数、阻尼系数等支承参数的设计方案。与常规滑动轴承轴颈的运动形式不同,油膜阻尼器的阻尼体通常绕其支点作“圆锥摆”形式的涡动,即阻尼体径向位移与切向速度沿其轴向呈线性分布,导致阻尼介质在阻尼体与外壳之间形成油膜厚度沿轴向线性分布的楔形间隙,进而造成阻尼器与轴承在油膜力及支承参数性质上的差异。因此,计算、设计油膜阻尼器的支承参数时,考虑楔形间隙效应的影响是必要的。本文首先对描述油膜压强分布的经典Reynolds方程做出了修正,推导了考虑楔形间隙时方程的具体形式。接着,采用基于超松弛迭代法(SOR)的有限差分法(FDM)对修正方程进行了数值求解。通过与ANSYS Fluent计算结果及已有实验结果进行对比,验证了计算结果的合理性。最后,借助数值积分与回归分析的计算工具,求得了阻尼器支承参数的函数表达形式及相应的线性化数值。计算结果表明,分析油膜阻尼器的支承性质时,考虑楔形间隙效应的影响是必要的。通过采用基于修正Reynolds方程的数值计算工具,能够提升计算效率,并为阻尼器性能的分析及优化提供理论参考。

     

    Abstract: Stability analysis is a crucial step in the design process for rotating machinery’s rotordynamics properties, which include static stability and dynamic stability. Static stability means that the rotor must be stable within the radius clearance formed with the stationary parts under normal operating conditions, and the system must be resistant to external disturbances. Besides, the rotor must smoothly pass multiple orders of critical speed while accelerating to the operating speed in order to achieve dynamic stability. In fact, dynamic parameters such as stiffness and damping coefficients are important indicators influencing the stability of high-speed rotating machinery, and the installation of an oil film damper assembly to the rotor has proven to be a reliable strategy for ensuring and optimizing system stability. In contrast to the motion form of a standard sliding bearing’s journal section, the damping mandrel of an oil film damper normally whirls around its pivot point in the form of a conical pendulum, i.e., the damping mandrel’s radial displacement and tangential velocity are linearly distributed along its axis, resulting in a wedge-shaped oil film clearance between the damping mandrel and the shell. As a result, oil film force and supporting parameters differ between the damper and the bearing. Therefore, when calculating and designing the supporting parameters of an oil film damper, the effect of wedge clearance on the damper’s supporting properties should be considered. This study firstly proposed a modification to the traditional Reynolds equation for characterizing the oil film pressure distribution when considering the wedge clearance, and the specific form of the equation was derived by adding items corresponding to the eccentricity and velocity distribution caused by this clearance. Next, the finite difference method based on successive over-relaxation was used to solve the modified problem iteratively. In order to verify the accuracy of the calculation results, the article contrasted them to ANSYS Fluent calculation results and previous experimental results. After comparison, it is discovered that the calculation results are in good agreement with the other two results, proving the dependability of this calculation method, which can make parameter setting more convenient and reduce calculation time. Finally, the oil film pressure distribution was computed under various parameter settings that characterize the wedge clearance. Using calculation tools of numerical integration and regression analysis, the function expressions for the relevant supporting property parameters and the corresponding linearized values were obtained. In summary, the calculation results demonstrate that while assessing the dynamic properties of oil film dampers, the effect of wedge clearance has to be taken into account. The calculation tool based on the modified Reynolds equation can improve computation efficiency and serve as a reference point for damper performance research and optimization.

     

/

返回文章
返回