六点支承航空发动机双转子系统动力学离散模型

Discrete dynamical model for the dual-rotor systems with six supports of the aero-engine

针对六点支承形式的航空发动机双转子系统,建立了复杂离散动力学模型,对该模型进行结构降维,得到了两种简化动力学模型.首先采用有限元法建立了较为精确的多轮盘复杂离散动力学模型,然后基于质心集中方法对该模型进行了简化,分别得到了四轮盘双转子简化动力学模型和三轮盘双转子简化动力学模型,并将其与复杂离散动力学模型进行了临界转速的对比.结果表明,简化得到的四轮盘双转子简化模型,前三阶相应临界转速误差分别在5%,22%,10%之内,可以很好地保有原系统的动力学特性;简化得到的三轮盘双转子简化模型,在柔性支承下,前三阶相应临界转速误差在15%之内,可以较好地保有原系统的动力学特性.最后,给出了3种模型不平衡响应的对比分析图.这是一种从结构上将实际多轮盘双转子简化成少轮盘双转子的方法,降低了双转子系统的自由度,有利于在考虑到故障、支承非线性等因素后的理论计算分析.

A complex discrete dynamical model is built for aero-engine dual-rotor systems supported by six bearings, and two kinds of simplified dynamical models were obtained by the structure dimensionality reduction method. By using the finite element method, the accurate complex dynamical model was built, and the model was simplified to gain the four-disc dual-rotor model（Model B） and the three-disc dual-rotor model（Model C） based on the center of mass concentration method. The critical whirling speed was compared for the simplified model and the complex model to indicate that the correctness of the simplified method. The results show that, for Model B, the 1th–3th relative error of critical speed were correspondingly less than 5%, 22%, 10%, to indicated that Model B＇ dynamical characteristics have a good agreement with the complex model＇s. And in condition of the flexible supports（k1×108 N/m）, the Model C and the complex model were compared corresponding to indicated that the 1th–3th relative error of critical speed were all less than 15%, which meant that Model C＇ dynamical characteristics have a agreement with the complex model＇s. At last, the unbalance responses were given for the three models. The DOF（degrees of freedom） of the dual-rotor system were reduced by this structure dimensionality reduction method with the decrease of the numbers of the discs, and it laid the foundation for the theoretical analysis for the aero-engine dual-rotor system with the consideration of the faults, bearing nonlinear factors etc.