Modeling Cantilever Branch Structure of Aero-Engine Power Turbine and Analyzing Its Influence

航空发动机动力涡轮转子悬臂分支结构建模与结构参数影响分析

Institute of Vibration Engineering, Northwestern Polytechnical University, Xi’an 710072, China

Received: 10 August 2017

Abstract

In the power turbine component of an aero-engine, there exists a unique cantilever branch structure, on which turbine disks are mounted. Due to the cantilever's characteristics, this structure exhibits a vibration of large amplitude; thus its characteristics need to be studied in detail.In this paper, the motion equations combining the structure and the shaft were deduced; then its vibration mode was given, and the criticl speed was computed; finally the unbalance response of an integrated rotor system was simulated.The calculation results are compared with the simulation results without considering the branch structure.Some key parameters' influences are studied thoroughly, e.g., the branch shaft's length, the flange's offset and the installation orientation. As the results show, the branch structure has a large influence on the vibration mode and critical speed of the rotor system, thus it should not be simplified and ignored in modelling; After adjusting the branch structure's parameters, the characteristics of a vibration mode do not change, and the effects of branch structural parameters on critical speed are closely related to the corresponding vibration mode; the bending stiffness and the critical speed of the rotor system both decreased with increasing branch shaft's length; if reducing the flange's offset and fabricating the branch structure reversely, a sharp increase in the unbalance response of the turbine disc will occur. In conclusion, the dynamical characteristics of the integrated rotor system can be optimized through reasonably designing the branch structure.

摘要

针对某型动力涡轮转子特殊的悬臂分支结构，建立了带分支转盘系统的转子动力学模型，该模型包含了分支系统主要的结构设计参数，推导了其运动微分方程，通过数值方法求解了转子系统的振型、临界转速和不平衡响应，对比了有无考虑分支结构时的计算结果，重点研究了调节分支结构参数，如分支轴长度、法兰盘偏置量、分支安装方位等对系统动力特性的影响。研究表明：分支结构对转子系统的振型、临界转速等存在重要影响，计算时不应简化忽略；调节分支结构参数不会改变转子系统的振型属性，其对临界转速的调节效果与相应振型密切相关；增大分支轴长度、减小法兰盘偏置量以及反向安装分支，会减小转子系统的抗弯刚度，降低临界转速，同时带来涡轮盘处不平衡响应急剧增大的问题。因此，针对分支结构参数进行合理设计，可以对转子系统的动力学特性进行优化和调整。