The present work intends to investigate dynamic behaviour of draft gear using finite element method. The longitudinal force that the draft gear absorbs usually leads to the failure of its components, especially, the l...The present work intends to investigate dynamic behaviour of draft gear using finite element method. The longitudinal force that the draft gear absorbs usually leads to the failure of its components, especially, the load bearing draft pads. Dynamic behaviour of an individual draft pad and a draft gear is determined and characterized with exciting frequen- cies and corresponding mode shapes. The effect of compressive prestress load on the dynamic behaviour of an individual draft pad is also determined as the draft pads in assembled state are under constant axial compressive force in the draft gear. The vibration characteristics of individual draft pad are compared with draft pads that are part of draft gear. The modal analysis gives us a basis for subjecting a draft pad to higher frequency loading for determining its fatigue behaviour.展开更多
The Lattice Boltzmann method （LBM） is used to simulate the flow field in a bifurcate channel which is a simplified model of the draft tube of hydraulic turbine machine. According to the simulation results, some qual...The Lattice Boltzmann method （LBM） is used to simulate the flow field in a bifurcate channel which is a simplified model of the draft tube of hydraulic turbine machine. According to the simulation results, some qualitative conclusions can be deduced. The reason of uneven flux in different branches of draft tube is given. Not only the vortex rope itself, but also the attenuation of the rotation strength is important in bringing on the uneven flux. The later leads to adverse pressure gradient, and changes the velocity profile. If the outlet contains more than one exit, the one that contains the vortex rope will lose flux because of this adverse pressure gradient. Several possible methods can be used to minimize the adverse pressure gradient domain in order to improve the efficiency of turbine machine.展开更多
文摘The present work intends to investigate dynamic behaviour of draft gear using finite element method. The longitudinal force that the draft gear absorbs usually leads to the failure of its components, especially, the load bearing draft pads. Dynamic behaviour of an individual draft pad and a draft gear is determined and characterized with exciting frequen- cies and corresponding mode shapes. The effect of compressive prestress load on the dynamic behaviour of an individual draft pad is also determined as the draft pads in assembled state are under constant axial compressive force in the draft gear. The vibration characteristics of individual draft pad are compared with draft pads that are part of draft gear. The modal analysis gives us a basis for subjecting a draft pad to higher frequency loading for determining its fatigue behaviour.
基金supported by the Key Project of National Natural Science Foundation of China (10532010)
文摘The Lattice Boltzmann method （LBM） is used to simulate the flow field in a bifurcate channel which is a simplified model of the draft tube of hydraulic turbine machine. According to the simulation results, some qualitative conclusions can be deduced. The reason of uneven flux in different branches of draft tube is given. Not only the vortex rope itself, but also the attenuation of the rotation strength is important in bringing on the uneven flux. The later leads to adverse pressure gradient, and changes the velocity profile. If the outlet contains more than one exit, the one that contains the vortex rope will lose flux because of this adverse pressure gradient. Several possible methods can be used to minimize the adverse pressure gradient domain in order to improve the efficiency of turbine machine.
