航空发动机螺栓止口连接转子动力学建模及特性

Modeling and characteristics of aero-engine rotor with bolted-rabbet joints

关键词:  航空发动机  螺栓止口连接  模态测试  临界转速  不平衡响应

Key words:  aero-engine  bolted-rabbet joints  modal test  critical speed  unbalance response

摘要:

为解决航空发动机转子螺栓止口连接结构在高转速、多载荷激励下动力学特性精确表征难题,文中提出一种考虑多螺栓止口连接的转子动力学建模方法,系统揭示连接界面对转子固有特性、临界转速及不平衡响应的影响。首先,通过SOLID186实体单元构建轮盘与转轴,COMBI214单元模拟轴承,MATRIX27单元表征含拉伸/横向/弯曲/扭转多维刚度的连接界面,结合MPC接触算法实现装配面自由度耦合,建立了高精度动力学模型。其次,搭建了含多处螺栓止口的转子测试平台,采用超声波预紧力测试、模态测试及激振实验,获取螺栓预紧力、不同边界下固有特性以及定频/扫频激励下的振动响应,验证了模型的有效性。最后,分析了螺栓止口连接对转子系统临界转速及不平衡响应的影响。结果表明:螺栓止口连接界面显著影响转子自由模态,忽略界面刚度会导致固有频率过度预估；在轴承支承状态下,螺栓止口连接界面对平动和俯仰模态影响较小,对弯曲模态影响较大,并显著影响与弯曲模态对应的临界转速；不平衡响应中,弯曲模态振幅因界面刚度损失而明显增大,2~3阶临界转速区间出现横向/转角位移不连续现象。该研究为航空发动机转子连接结构设计优化提供理论支撑。

Abstract:

To address the challenge of characterizing the dynamic properties of bolted-rabbet joint structures in aero-engine rotors under high rotational speeds and multi-load excitation, a rotor dynamic modeling method considering multiple bolted-rabbet joints is established, and the influence of joint interfaces on the rotor’s natural characteristics, critical speeds, and unbalance response is systematically revealed in this study. Firstly, SOLID186 solid elements are employed to model the disks and shafts, COMBI214 elements to simulate the bearings, and MATRIX27 elements to characterize the multi-dimensional stiffness (tensile, lateral, bending, and torsional) of the joint interfaces. By combining the MPC (multi-point constraint) contact algorithm to achieve degree-of-freedom coupling with the bolted-rabbet assembly surfaces, a high-precision dynamic model is established for aero-engine rotors with bolted-rabbet joints. Secondly, a rotor test rig with multiple bolted-rabbet joints is constructed. Ultrasonic preload testing, modal testing, and excitation experiments are conducted to acquire bolt preloads, natural characteristics under different boundaries, and vibration responses under constant-frequency and sweep-frequency excitation, thus verifying the model’s correctness. Finally, the influence of bolted-rabbet joints on the rotor system’s critical speeds and unbalance response is analyzed. The results show that: the bolted-rabbet joint interfaces significantly affect the rotor’s free modes, and ignoring interface stiffness results in the overestimation of natural frequencies; under bearing support, the joint interfaces have minimal impact on translational and pitching modes but a pronounced influence on bending modes, and notably alter the critical speeds associated with bending modes; in the unbalance response, the amplitude of bending modes increases significantly due to interface stiffness loss, and discontinuities in lateral and rotational displacements emerge in the speed interval between the 2nd and 3rd critical speeds. This study provides theoretical support for the design optimization of joint structures in aero-engine rotors.