Analysis For Coupled Long Blades’ Vibration With Damping Structure And Shaft Torsional Vibration

With the development of the turbine industry, energy conservation and environmentprotection, large capacitysteam turbine has unique advantages. This means the last stageblade length will grow, and the last stage blade vibration will intensify. Therefore, theblades need damping structure to increase the vibration, so, analysis of the last stage bladevibration characteristics and damping characteristics will be very necessary. In addition, thelast stage long blades are mounted on the shaft, both of them have a mutual coupled effectbetween themselves, especially the coupled effect between the shaft torsional vibration andblades vibration. The effect makes the blades in danger. So, analysis of the coupled effectrules of shaft torsional vibration and blade vibration is very important.Finite element method (FEM) using the finite element idea, can get high-precisionresult from complex object models in complex conditions effectively. It’s an importantmean for engineering analysis. In this paper, we first construct the finite element model thatincludes long blade with damping structure and turbine shaft using FEM software. Thenprogressively analyze following issues: first,the long blade vibration characteristics withnonlinear damping structure, especially when some blades form a circle and when they inexciting force conditions; then analyze coupled model of long blades and shaft, get thecoupled effect rules of shaft torsional vibration and blade vibration; finally, calculate theresponse when coupled model of long blades and shaft in fault conditions, get importantpart’s dynamic amplitude and stress, especially when considering the vibration dampingcharacteristics between the blades; last, we come to some conclusions from analysis.Through the above research, the key conclusions drawn:(1)The blade disk’s dynamicfrequency in contact state is higher than in undamping state, and close to bonded state.(2)The factors that the blades vibration impacts the shaft torsional vibration are the locationof blades and the energy of blades vibration displacement.(3) In fault condition, thedamping structure will be useful to restrain the blades vibration amplitude and stress. It is very helpful for the security and stability of turbine.