水电机组转子-转轮弯扭耦合振动特性分析

针对水轮发电机组轴系由多振源激励引起的非线性振动问题，本文构建了考虑动、静偏心因素的不平衡磁拉力及非线性密封力联合作用下机组轴系弯扭耦合振动模型，采用数值分析方法对系统动力学特性进行了研究。通过分岔图、轴心轨迹图和频谱图等方法分析了质量偏心、密封间隙对系统振动特性的影响。结果表明，动静偏心的加入对系统动态特性表现形式及振幅均带来了明显改变，系统稳定性在一定程度上得到了提升，新的运动特征周期6得以显现。质量偏心在恶化转子振动的同时会削弱不平衡磁拉力的影响，使振动趋于规则，但过大的质量偏心会导致定转子发生全周碰摩故障，容易引起系统潜在的不稳定。密封间隙的增加可以减少阻尼和摩擦，使系统运动趋于稳定；但过大的密封间隙会增加流体的泄漏，降低水轮发电机组运行效率。

Analysis on coupled bending-torsional vibration behaviors of rotor-runner system of hydropower units

Aimed at the nonlinear vibration problem caused by multi-source excitation in hydraulic generating set shaft systems, a coupled bending-torsional vibration model for the shaft system under the combined action of its unbalanced magnetic pull and nonlinear sealing force considering both dynamic and static eccentricity factors is developed, and numerical simulations are used to investigate its dynamic characteristics. This paper analyzes the effects of mass eccentricity and sealing clearance on its vibration behaviors using nonlinear analysis methods such as bifurcation diagram, axis trajectory diagram, and spectrum diagram. Results show that dynamic and static eccentricity of the shaft system poses a significant impact on its dynamic characteristics and amplitudes, and improves its stability to a certain extent, where new dynamic phenomena such as period-three and period-six modes appear. Mass eccentricity will weaken the effect of its unbalanced magnetic pull while aggravating its rotor vibration, resulting in its more regular motions; but excessive mass eccentricity is bound to cause the full annular rubbing of the unit, which is likely to provoke potential system instability. A larger sealing gap can reduce the damping and friction of the shaft system and help stabilize its movement, but an excessively large gap will increase fluid leakage and reduce the operating efficiency of the hydraulic generating set.