【作者】 杨喜关；

【导师】 温卫东；

【作者基本信息】 南京航空航天大学 ， 航空宇航推进理论与工程， 2014， 博士

【摘要】 为提高发动机的整体性能,许多先进现役航空发动机采用了含中介支承的反向旋转双转子系统结构。作为航空发动机的主要振源,反向旋转双转子系统的动力学特性将会是我国航空发动机研制中重要的研究内容之一。本文以航空发动机五支点双转子系统为工程背景,从反向旋转双转子系统的动力学建模、非线性系统求解方法、动力特性分析和中介轴承特性分析等方面进行系统深入的研究,以期为航空发动机反向旋转双转子系统动力学特性设计提供依据和方法。主要研究内容和创新成果如下:(1)将有限元方法和固定界面模态综合法相结合,发展了一种建立双转子系统动力学模型的方法。首先利用有限元软件ANSYS建立有限元模型,获取双转子系统的质量矩阵、刚度矩阵和固定界面模态参数,根据双转子系统的特点建立动力学方程;然后采用固定界面模态综合法进行系统维数的缩减,提高计算效率。应用此方法系统地分析了反向旋转双转子系统的临界转速特性和匀变速过程的瞬态响应特性,并通过试验验证了系统瞬态响应特性。仿真计算和试验结果表明:陀螺力矩是导致同向和反向旋转双转子系统临界转速特性差异的主要原因;内、外转子之间的动力耦合使反向旋转双转子系统的瞬态响应特性有别于单转子系统,有其独有的响应规律和特性。该方法保留了有限元方法适宜复杂系统动力学建模特点,同时提高了计算效率,具有重要的工程应用价值。(2)考虑中介轴承滚子、套圈和保持架的影响,发展了双转子系统中介轴承的拟动力学模型。以轴承内套圈与内转子联接,外套圈与外转子联接的中介轴承为例,研究了保持架引导方式对轴承动态特性的影响,并利用试验结果对该模型进行了验证。研究结果表明:不同的保持引导方式对中介轴承的保持架转速、滚子自转转速、保持架偏心率有显著地影响,但对轴承接触疲劳寿命的影响较小。研究结果为反向旋转双转子系统的中介轴承动力学设计提供了依据。(3)利用有限元方法建立系统的运动方程,借助于模态综合法,针对转子系统非线性力局部性的特点,研究了两种高维非线性双转子系统动力特性的求解方法。首先利用固定界面模态综合法和Newmark直接积分方法,发展了一种适合支承界面处存在非线性力的双转子系统动力学特性求解方法;随后利用自由界面模态综合法和Duhamel积分法,发展了一种适合任意节点处存在非线性力的双转子系统动力特性求解的半解析法。分别研究了反向旋转双转子系统双不平衡激振力作用下的非线性动力响应特性和含碰摩故障时的非线性动力响应特性。研究结果表明:双不平衡激振力、非线性支承力和非线性碰摩力的存在,使得反向旋转双转子系统的响应中出现了丰富的频率成份和非线性特性。这两种方法弥补了传统有限元方法在预测高维局部非线性双转子系统动力特性时效率低下的缺点。(4)为考虑更符合实际的支承模型,引入连接子结构的概念,发展了建立轴承-挤压油膜阻尼器-高维双转子系统动力学模型的方法。以双转子试验器为研究对象,将双转子系统划分为转子子结构和连接子结构,利用有限元方法和固定界面模态综合进行转子子结构的建模及维数缩减,将支承系统作为独立的连接子结构保留物理空间,通过界面对接条件实现子结构之间的组装,借鉴本文发展的固定定界面模态综合和Newmark直接积分相结合的方法进行了运动方程的数值求解。通过试验验证了该方法的正确性,并研究了系统的不平衡响应规律。研究结果表明:分析的转速范围内,转子响应中出现了滚动轴承的变刚度振动频率、不平衡激励频率及相关组合频率;转子的响应规律与节点位置、轮盘的不平衡量及转子振型有着密切的联系。该方法为反向旋转双转子系统的动力特性研究中引入详细的非线性支承结构提供了有效方法。综上所述,本文系统地研究了反向旋转双转子系统的建模和维数缩减方法、临界转速特性、匀变速瞬态响应特性、局部非线性高维系统的求解方法、非线性系统的不平衡响应特性和中介轴承动力特性等问题。研究结果对提高航空发动机反向旋转双转子系统运行的稳定性和可靠性,指导反向旋转双转子系统的设计与应用具有重要的理论指导意义和工程应用价值。更多还原

【Abstract】 To improve the overall performance, counter-rotating dual-rotor system with intermediate bearing is adopted by many advanced aeroengines. As the main source of vibration in aeroengines, dynamic characteristics of the counter-rotating dual-rotor system will be one of the most important topics in the development of Chinese aeroengines. In this paper, systematic and thorough research on dynamic modeling, solution method of the nonlinear system, dynamic characteristics analysis and intermediate bearing analysis are conducted with five-support dual-rotor system as the engineering background. Results of this paper provide basis and methodology for dynamic characteristic design of the counter-rotating dual-rotor system for aeroengines. The main contents and innovations of this paper are listed as follows:(1) A dynamic modeling method for the dual-rotor system is introduced with the finite element method and fixed interface modal synthesis method applied. Dynamic equation of a dual-rotor system is established with mass and stiffness matrixes as well as modal parameters obtained from ANSYS in which the finite element model is established. Dimension reduction is then achieved by fixed interface modal synthesis method to improve the computational efficiency. Dynamic characteristics of the counter-rotating dual-rotor system, including critical speeds and transient response characteristics of the uniformly variable process, are analyzed systematically with this method. Experimental verification on transient response is conducted. Simulated and experimental results show that: the differences of critical speeds between co-rotating and counter-rotating dual-rotor system are mainly caused by gyroscopic torque. Besides, due to dynamic coupling of the inner and outer rotor, counter-rotating dual-rotor system has unique transient response patterns and characteristics which are different from those of the single rotor system. This methodology is of great engineering value because advantages of the finite element method, accuracy and applicability, are retained without complex programming while more efficient.(2) Mechanical analysis model of the intermediate bearing is developed considered with the roller, ring and cage. The influence of cage riding method to dynamic characteristics of the bearing is studied with the inner ring connected to inner rotor and the outer ring connected to outer rotor. The experimental results, which agree quite well with those of the calculation, indicate that the cage riding method has a significant influence to intermediate bearing on cage speed, rotational speed of the rollers and cage eccentricity, while it has little effect on the contact fatigue life of bearing. The results provide basis and references for intermediate bearing’s designs.(3) Based on the equation of motion established with finite element method, two approaches to acquire dynamic characteristics of the high-dimensional nonlinear dual-rotor system are developed considering the locality of nonlinear force. The first approach, in which the modal synthesis method and Newmark’s Method of Direct Integration are utilized, is applied to dual-rotor system with nonlinear force acting on the interfaces of supports. The second one, which is a semi-analytical method for dual-rotor system with nonlinear force acting on any nodes, utilizes the free interface modal synthesis method and Duhamel’s integral. With these two methods, research on nonlinear dynamic response of the counter-rotating dual-rotor system is conducted with two unbalance forces and rub-impact considered separately. The results show that: due to the unbalance forces, nonlinear forces of supports and rub-impact forces, nonlinear characteristics and a lot of frequency components emerge in responses of the counter-rotating dual-rotor system. Both methods make up the finite element method for inefficiency in predicting dynamic characteristics of the high-dimensional nonlinear rotor system.(4) A modeling method for the bearing-squeeze film damper-high dimensional dual-rotor system is proposed by introducing the concept of connection substructure for practical supports. Taking a dual rotor test rig as research object, the dual-rotor system is divided into modal substructures and connection substructures. The finite element method and fixed interface modal synthesis method are used respectively to model the modal substructure and reduce the dimensions. The supports are retained in physical space as independent connection substructures. Then the substructures are assembled according to linking conditions between interfaces before the equations of motion are numerically solved with an improved Newmark’s Method. Based on this method, which is verified by experiments, unbalance response of the dual-rotor system is studied. The study results show that: in the range of rotational speed in which the analysis is carried out, frequency of variable stiffness of the rolling bearing, unbalance excitation frequency and their combinations exist in response of the rotor system. Besides, response of the rotor system is closely related to node positions, unbalance and vibration shape. This is an effective method to introduce nonlinear characteristics of the supports to analysis of the dynamic response of dual-rotor system.As stated above, systematic research on modeling method and nolinear characteristics analysis of the counter-rotating dual-rotor system are conducted in this paper. The results are of significant theoretical and engineering value to improve the overall performances of the counter-rotating dual-rotor system adopted in modern aeroengines.更多还原