汽轮机齿轮转子系统弯扭耦合模态频率研究

Research on the Bending-torsional Coupling Mode Frequency of Steam Turbine Gear Rotor System

本文建立了高压汽轮机转子、低压汽轮机转子、挠性联轴器、高速齿轮转子、扭力杆和套筒轴装配而成的低速齿轮柔性转子、发电机转子组成的复杂轴系的弯扭耦合动力学模型,计算结果表明:空负荷起机时因齿轮轴承对齿轮转子弯曲振动的约束弱因而弯扭耦合效应显著,主要表现为扭转振动的前两阶频率与纯扭转计算结果相比分别下降了6.5%和4.5%,因此建立弯扭耦合计算模型是必要的;满负荷运行时因齿轮轴承对齿轮转子弯曲振动的约束强因而弯扭耦合效应不明显,主要表现为扭转振动的前两阶频率与纯扭转计算结果相比分别下降了0.8%和0.9%,可采用纯扭转模型代替弯扭耦合模型;满负荷运行与空负荷起机相比扭振主导频率下伴随的弯曲振动减弱,轴承对弯扭耦合系统引入的阻尼比变小。

This paper established the bending-torsional coupling dynamic model of a complex shaft system composed of a high-pressure steam turbine rotor,a low-pressure steam turbine rotor,a flexible coupling,a high-speed gear rotor,a torsion bar and a quill shaft assembly of a low-speed gear flexible rotor,and a generator rotor.The calculation results show that the bending-torsional coupling effect is significant due to the weak restraint of the gear bearing on the bending vibration of the gear rotor when starting with no load,compared with the calculation results of pure torsion,the first two frequencies of torsional vibration have decreased by 6.5%and 4.5%respectively,so it is necessary to establish a bending-torsional coupling calculation model;during full-load operation,the bending-torsional coupling effect is not obvious due to the strong constraint of the gear bearing on the bending vibration of the gear rotor,compared with the calculation results of pure torsion,the first two frequencies of torsional vibration have decreased by 0.8%and 0.9%respectively,thus the pure torsional model can be used to replace the bending-torsional coupling model;full load operation compared with no load starting,the bending vibration at the dominant frequency of torsional vibration is weakened,and the damping ratio introduced by the bearing to the bending-torsional coupling system becomes smaller.