Background

Hirth couplings are frequently used in the aero-engines turbine. The assembled stiffness of the Hirth couplings is significance to the design of the rotor system as it is outstandingly different from the continuous rotor structure. The decreasing of the axial pressing force to the rotor system of fifth-generation aero-engines can dramatically weaken the assembled stiffness of the Hirth coupling, which affect the rotor dynamics and even result in the rubbing faults.

Purpose

This paper focuses on the theoretical study on the rubbing characteristics of the noncontinuous rotor blade casing system caused by the stiffness weakening of the Hirth couplings.

Methods

A novel analytical model of the Central Tie Rod Rotor-blade-Casing (CTRRBC) coupling system considering the Hirth couplings is derived through the Timoshenko theory and Hamilton variational principle. Then the no rubbing condition, the single-blade rubbing condition and four-blade rubbing condition of the non-continuous rotor system are calculated by using the Newmark-β method.

Results

The study results obtained by applying the analytical model are shown that (1) a decrease the assembled stiffness of the Hirth couplings lead to the significant amplitude amplification phenomenon of the rotor, blade and casing. (2) four-blade rubbing levels are related to the non-continuous rotor whirl, the rubbing happens on the blade located at the right end of the rotor whirl, nearest the casing, becomes more severe, vice versa. (3) Increasing the axial pressing force reaches the 60 kN, the rubbing responses of the non-continuous rotor blade system are similar to continuous structure (integral rotor).

Conclusion

These results reveal the nonlinear rubbing faults characteristics of the central tie rod rotor blade casing coupling system with the Hirth couplings connection. Nonlinear effects are highlight and the multi-frequency components of system are contributed to diagnose the rubbing faults of noncontinuous rotating machinery.

中文翻译：

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带有 Hirth 联轴器连接的中心拉杆转子-叶片-外壳耦合系统的摩擦冲击动力学分析

背景

Hirth 联轴器经常用于航空发动机涡轮。Hirth 联轴器的组装刚度对于转子系统的设计具有重要意义，因为它与连续转子结构有显着差异。第五代航空发动机转子系统轴向压紧力的降低会导致鼠牙盘的装配刚度急剧减弱，从而影响转子动力学，甚至会导致摩擦故障。

目的

本文着重对非连续转子叶片机壳系统因Hirth联轴器刚度减弱引起的摩擦特性进行理论研究。

方法

通过 Timoshenko 理论和 Hamilton 变分原理推导了考虑 Hirth 联轴器的中央拉杆转子-叶片-外壳 (CTRRBC) 耦合系统的新分析模型。然后采用Newmark-β法计算了非连续转子系统的无摩擦工况、单叶片摩擦工况和四叶片摩擦工况。

结果

应用分析模型得到的研究结果表明：（1）Hirth联轴器装配刚度的降低导致转子、叶片和机壳出现明显的振幅放大现象。(2) 四叶片摩擦程度与非连续转子涡流有关，转子涡流右端靠近机壳的叶片摩擦变得更严重，反之亦然。(3)增加轴向压紧力达到60 kN，非连续转子叶片系统的摩擦响应与连续结构(整体转子)相似。

结论

这些结果揭示了具有 Hirth 联轴器连接的中心拉杆转子叶片外壳耦合系统的非线性摩擦故障特征。非线性效应突出，系统的多频分量有助于诊断非连续旋转机械的摩擦故障。