A 3D finite element vibration model of water turbine generator set is constructed considering the coupling with hydropower house foundation. The method of determining guide bearing dynamic characteristic coefficients ...A 3D finite element vibration model of water turbine generator set is constructed considering the coupling with hydropower house foundation. The method of determining guide bearing dynamic characteristic coefficients according to the swing of the shaft is proposed, which can be used for studying the self-vibration characteristic and stability of the water turbine generator set. The method fully considers the complex supporting boundary and loading conditions; especially the nonlinear variation of guide bearing dynamic characteristic coefficients and the coupling effect of the whole power-house foundation. The swing and critical rotating speed of an actual generator set shaft system are calculated. The simulated results of the generator set indicate that the coupling vibration model and calculation method presented in this paper are suitable for stability analysis of the water turbine generator set.展开更多
In this article, transverse free vibrations of axially moving nanobeams subjected to axial tension are studied based on nonlocal stress elasticity theory. A new higher-order differential equation of motion is derived ...In this article, transverse free vibrations of axially moving nanobeams subjected to axial tension are studied based on nonlocal stress elasticity theory. A new higher-order differential equation of motion is derived from the variational principle with corresponding higher-order, non-classical boundary conditions. Two supporting conditions are investigated, i.e. simple supports and clamped supports. Effects of nonlocal nanoscale, dimensionless axial velocity, density and axial tension on natural frequencies are presented and discussed through numerical examples. It is found that these factors have great influence on the dynamic behaviour of an axially moving nanobeam. In particular, the nonlocal effect tends to induce higher vibration frequencies as compared to the results obtained from classical vibration theory. Analytical solutions for critical velocity of these nanobeams when the frequency vanishes are also derived and the influences of nonlocal nanoscale and axial tension on the critical velocity are discussed.展开更多
为了使支承在电磁轴承(active magnetic bearing,AMB)上的柔性转子系统以较小的振动跨越其2阶弯曲临界转速,首先建立柔性转子的状态空间模型和刚性转子的传递函数模型,得到所需刚性转子模型的参数;然后设计刚性转子模型辅助的线性自抗...为了使支承在电磁轴承(active magnetic bearing,AMB)上的柔性转子系统以较小的振动跨越其2阶弯曲临界转速,首先建立柔性转子的状态空间模型和刚性转子的传递函数模型,得到所需刚性转子模型的参数;然后设计刚性转子模型辅助的线性自抗扰控制器;其次从增益、带宽和内置模型信息等方面分析自抗扰控制器的性能和模型辅助信息的有效性,用特征值轨迹的方法研究多输入多输出(multi-input and multi-output,MIMO)闭环柔性转子系统的稳定性;最后在一个AMB–多盘柔性转子试验台上进行试验研究。结果表明,所设计的刚性转子模型辅助线性自抗扰控制器能有效抑制柔性转子跨越2阶弯曲临界转速区的振动,改善传统自抗扰控制器的低频性能,降低噪声灵敏度。展开更多
基金supported by National Natural Science Foundation of China (Grant No. 50679009)
文摘A 3D finite element vibration model of water turbine generator set is constructed considering the coupling with hydropower house foundation. The method of determining guide bearing dynamic characteristic coefficients according to the swing of the shaft is proposed, which can be used for studying the self-vibration characteristic and stability of the water turbine generator set. The method fully considers the complex supporting boundary and loading conditions; especially the nonlinear variation of guide bearing dynamic characteristic coefficients and the coupling effect of the whole power-house foundation. The swing and critical rotating speed of an actual generator set shaft system are calculated. The simulated results of the generator set indicate that the coupling vibration model and calculation method presented in this paper are suitable for stability analysis of the water turbine generator set.
基金supported by a collaboration scheme from University of Science and Technology of China-City University of Hong Kong Joint Advanced Research Institute and by City University of Hong Kong(7002472 (BC))
文摘In this article, transverse free vibrations of axially moving nanobeams subjected to axial tension are studied based on nonlocal stress elasticity theory. A new higher-order differential equation of motion is derived from the variational principle with corresponding higher-order, non-classical boundary conditions. Two supporting conditions are investigated, i.e. simple supports and clamped supports. Effects of nonlocal nanoscale, dimensionless axial velocity, density and axial tension on natural frequencies are presented and discussed through numerical examples. It is found that these factors have great influence on the dynamic behaviour of an axially moving nanobeam. In particular, the nonlocal effect tends to induce higher vibration frequencies as compared to the results obtained from classical vibration theory. Analytical solutions for critical velocity of these nanobeams when the frequency vanishes are also derived and the influences of nonlocal nanoscale and axial tension on the critical velocity are discussed.
文摘为了使支承在电磁轴承(active magnetic bearing,AMB)上的柔性转子系统以较小的振动跨越其2阶弯曲临界转速,首先建立柔性转子的状态空间模型和刚性转子的传递函数模型,得到所需刚性转子模型的参数;然后设计刚性转子模型辅助的线性自抗扰控制器;其次从增益、带宽和内置模型信息等方面分析自抗扰控制器的性能和模型辅助信息的有效性,用特征值轨迹的方法研究多输入多输出(multi-input and multi-output,MIMO)闭环柔性转子系统的稳定性;最后在一个AMB–多盘柔性转子试验台上进行试验研究。结果表明,所设计的刚性转子模型辅助线性自抗扰控制器能有效抑制柔性转子跨越2阶弯曲临界转速区的振动,改善传统自抗扰控制器的低频性能,降低噪声灵敏度。
