Dynamic response of hydro-turbine set shaft system under stochastic hydraulic excitation
BAI Bing1, ZHANG Lixiang2
1. School of Civil Engineering and Communication, North China University of Water Resources and Electric Power, Zhengzhou, Henan 450011, China; 2.Faculty of Civil Engineering and Mechanics, Kunming University of Science and Technology, Kunming, Yunnan 650500, China
The forces acting on a hydro-turbine generator set shaft system were 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)to the changes in rotational speed, eccentric mass and exciting current, namely amplitude-time history curves, trajectory, amplitude spectra and Poincare diagram and bifurcation patterns, were obtained by solving the dynamic model equations. Results showed that the rotational speed and eccentric mass have a considerable influence on the vibration response of main parts in the shaft system. And 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.
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