Abstract
All the rotor blades in turbo-machinery, including turbojet engines and turbo-generators, have vibration problems. The blades are damaged because of vibrations caused by flutter or forced response. Generally, the shrouded design of the turbine blades is used to raise the structural damping and strength of the rotor blades. This research is primarily focused on vibration phenomenon of steam turbine’s shrouded rotor blades. Because the Hamoaka Nuclear Power Station No. 5 occurred some phenomenon like flutter, and the low pressure steam turbines of Hamoaka Nuclear Power Station No. 5 and Taipower’s Lung-Men Nuclear Power Plant Units 1&2 are both the Advanced Boiling Water Reactors, the research begin to analysis the rotor blades of the low pressure steam turbine. A complete system approach has been set up to study the main mechanism of shrouded rotor blade vibration. The research starts with the dynamic structural properties of the blades, the properties along with flow fields were used to calculate the unsteady steam load caused by structural movement. Because the design of shrouded rotor blades will cause the entire rotor into system mode shapes, it is necessary to use cyclic symmetry along with the modal flutter analysis system to calculate the aero damping of the shrouded dynamic blade system and to determine its flutter instability of the low pressure steam turbine of Taipower’s Lung-Men Nuclear Power Plant. This study will be based on a Taipower plant case to investigate the flutter boundary of steam turbine rotor blades under different operating conditions. However, for the bending and torsion combined system modes, the single mode analysis can be misleading. From the complex mode analyzed results, it was demonstrated that the mode shape, the characteristic of flow field, and the structural damping play an important role in determining the blade flutter stability. And there is flutter phenomenon in supersonic flow field, it may result in blades failure. So, it’s necessary to prevent this condition to improve the system safety.