考虑端齿连接的转子-滚动轴承系统非线性振动特性研究

为了研究滚动轴承支撑下端齿连接转子系统的接触效应,采用三维有限元与解析法相结合推导了端齿连接刚度矩阵,建立了端齿连接转子-滚动轴承系统动力学模型,并通过Ansys验证了模型的有效性。通过与连续转子对比发现,端齿结构使转子一阶临界转速降低了5%,振幅增大了3%,非线性分岔趋势与连续转子大致相同。然而,端齿接触特性使转子明显地提早进入和离开拟周期运动,在分析含端齿结构的转子振动特性时应考虑接触效应。在转速超过15900 r/min时,转子系统做稳定的单周期运动,运行平稳,可作为工作转速合理设计阈值。研究可为含端齿结构转子系统非线性振动特性预测和工作转速设计提供分析方法和设计思路。

航空涡轮轴发动机复杂转子的动力学建模方法

为建立涡轮轴发动机复杂转子的动力学模型,基于有限元法和分段线性拟合,采用子结构法对复杂结构进行建模,在对系统自由度进行缩减后,推导出转子系统的运动方程。采用理论分析和试验验证了模型的有效性,分析了燃气发生器转子的振动特性。研究结果表明:建立的模型能显著降低整个系统的复杂度,在保证求解精度前提下,可大幅缩短求解时间。

含内阻的拉杆组合转子双稳态振动特性

为揭示含内阻组合转子复杂的双稳态振动特性,基于拉格朗日方程推导了含轮盘接触、非线性油膜力及内阻的组合转子非线性运动控制方程。采用升速和降速相结合的方法研究了组合转子跨2阶临界转速的非线性动力学行为及内阻机理。研究结果表明:组合转子双稳态振动特征显著,内阻导致出现双稳态现象的转速区间明显向低转速方向移动,在分析组合转子振动特性时应考虑内阻效应,以有效预测双稳态现象的出现。

Effects of Floating Ring Bearing Manufacturing Tolerance Clearances on the Dynamic Characteristics for Turbocharger

The inner and outer oil film dynamic characteristic coefficients of floating ring bearings(FRBs) change due to the manufacturing tolerance of the floating ring, journal and intermediate, which leads to high-speed turbocharger's vibration too large and even causes nonlinear vibration accident. However, the investigation of floating ring bearing manufacturing tolerance clearance on the rotordynamic characteristics is less at present. In order to study the influence law of inner and outer clearance on turbocharger vibration, the rotor dynamic motion equations of turbocharger supported in FRBs are derived by analyzing the size relations between floating ring, journal and intermediate for the inner and outer oil film clearances, the time transient response analysis for combination of FRBs clearance are developed. A realistic turbocharger is taken as a research object, the FE model of the turbocharger with FRBs is modeled. Under the conditions of four kinds of limit state bearing clearances for inner and outer oil film, the nonlinear transient analyses are performed based on the established FE dynamic models of the nonlinear rotor-FRBs system applied incentive combinations of gravity and unbalance force, respectively. From the waterfall, the simulation results show that the speed for the appearance of fractional frequency is not identical and the amplitude magnitude is different under the four kinds of bearing manufacturing tolerance limit clearances, and fractional frequency does not appear in the turbocharger and the amplitude is minimum under the ODMin/IDMax bearing manufacturing tolerance clearances. The turbocharger vibration is reduced by controlling the manufacturing tolerance clearance combinations of FRBs, which is helpful for the dynamic design and production-manufacturing of high-speed turbocharger.

Effects of Unbalance Location on Dynamic Characteristics of High-speed Gasoline Engine Turbocharger with Floating Ring Bearings

For the high-speed gasoline engine turbocharger rotor, due to the heterogeneity of multiple parts material, manufacturing and assembly errors, running wear in impeller and uneven carbon of turbine, the random unbalance usually can be developed which will induce excessive rotor vibration, and even lead to nonlinear vibration accidents. However, the investigation of unbalance location on the nonlinear high-speed turbocharger rotordynamic characteristics is less. In order to discuss the rotor unbalance location effects of turbocharger with nonlinear floating ring bearings(FRBs), the realistic turbocharger of gasoline engine is taken as a research object. The rotordynamic equations of motion under the condition of unbalance are derived by applied unbalance force and nonlinear oil film force of FRBs. The FE model of turbocharger rotor-bearing system is modeled which includes the unbalance excitation and nonlinear FRBs. Under the conditions of four different applied locations of unbalance, the nonlinear transient analyses are performed based on the rotor FEM. The differences of dynamic behavior are obvious to the turbocharger rotor systems for four conditions, and the bifurcation phenomena are different. From the results of waterfall and transient response analysis, the speed for the appearance of fractional frequency is not identical and the amplitude magnitude is different from the different unbalance locations, and the non-synchronous vibration does not occur in the turbocharger and the amplitude is relative stable and minimum under the condition 4. The turbocharger vibration and non-synchronous components could be reduced or suppressed by controlling the applied location of unbalance, which is helpful for the dynamic design, fault diagnosis and vibration control of the high-speed gasoline engine turbochargers.

考虑支承约束的航空发动机复杂转子振动特性

针对航空发动机转子复杂的结构特征及支承动力学设计问题,基于有限元(FE)、分段线性拟合和自由度(DOF)降维法,采用主子单元对复杂转子进行合理地等效,构建了航空发动机等复杂转子-支承系统的动力学模型,并对模型的有效性进行了试验验证。从转子固有特性、应变能分布、支承传递力和振动响应等方面对支承刚度进行了设计,并开展了弹性支承并联挤压油膜阻尼器(SFD)非线性减振效率分析。结果表明:动力学模型能较好地反映复杂转子的动力学特性,支承刚度合适取值范围为1.5×10^(4)~2.8×10^(4)N/mm,弹性支承并联SFD设计减振和降支承力效果显著,满足临界转速设计准则、应变能约束条件和变形要求,该研究为航空发动机支承刚度和SFD并联设计提供了定量的参考依据,具有重要的工程应用价值。

考虑端齿预紧的新型中心拉杆-转子-叶片耦合系统动力学特性分析

基于端齿连接结构在预紧力作用下的受力与变形关系,提出了一种考虑端齿预紧的新型中心拉杆-转子-叶片耦合系统动力学分析模型。首先通过铁木辛柯梁理论和哈密顿变分原理,推导了耦合系统的动力学方程;然后采用抗弯刚度修正模型,将端齿预紧的接触界面效应计入到耦合系统动力学模型中,并采用有限元模型结果验证了模型的正确性;在此基础上,分析了预紧力对耦合系统临界转速和不平衡响应的影响规律。研究结果表明在预紧松弛情况下,因为端齿连接结构抗弯刚度的降低,使耦合系统的临界转速大幅降低。而对于不平衡响应而言,耦合系统的响应幅值随预紧力的增加而逐渐减少,当在预紧力达到60 kN时,此时近似等效于无端齿连接结构的整体转子系统。