随机水力激励下机组轴系的动力响应

Dynamic response of hydro-turbine set shaft system under stochastic hydraulic excitation

简要分析了水轮发电机组轴系上的作用力,包括导轴承上的非线性油膜力、转子与转轮上的机械不平衡力、转子上的不平衡磁拉力和转轮上的水力不平衡力.采用零均值i.i.d.随机数序列模拟作用于水轮机转轮上的随机水力激励,通过调整随机数方差来改变随机水力激励的大小,建立了水轮发电机组轴系的非线性动力学模型.求解得到了机组轴系关键部位(转子、转轮和3个导轴承)响应的时域波形图、轴心轨迹图、频谱图和庞加莱图,以及系统响应的分岔图.结果表明:水轮机转轮上作用的随机水力激励对于轴系上部的上导轴承、发电机转子影响较小,对于下导轴承影响适中,对于轴系下部的水导轴承和水轮机转轮影响比较大.随着随机水力激励增强,水导轴承处和水轮机转轮处轴的横向摆度均发生明显的分叉,已明显影响了轴系的振动形态和振动稳定性.

The forces acting on a hydro-turbine generator set shaft system were briefly analyzed, including the nonlinear oil film force in the guide bearings, mechanical unbalanced forces on the rotor and runner, the unbalanced magnetic force on the rotor, and the hydraulic imbalance force on the runner. Then a nonlinear dynamic model for the shaft system was established, and the stochastic hydraulic excitation in the model was simulated with a zero mean, identically independent distributed （i. i. d. ） signal, and its magnitude was changed by adjusting the random variance. The responses of the key parts （rotor, runner and guide bearings） namely amplitude-time history curves, trajectory, amplitude spectra and Poincare diagram and bifurcation patterns, were obtained by solving the dynamic model equations. The results show that the stochastic hydraulic excitation on the runner has small influences on the upper guide bearing and the generator rotor; has certain influence on the lower guide bearing; has great influence on turbine guide bearing and runner. The lateral throws at the turbine guide bearing and runner become obviously bifurcated as the stochastic hydraulic excitation increases. The excitation has strong influence on the vibration mode and stability of the shaft system.