Analysis and Measurement of Damping Characteristics of Integral Shroud Blade for Steam Turbine

Abstract

To improve the reliability and the thermal efficiency of LP Low pressure end blades of steam turbine, new standard series of LP end blades have been developed. The new LP end blades are characterized by the ISB (Integral Shroud Blade) structure. In the ISB structure, blades are continuously coupled by blade untwist due to centrifugal force when the blades rotate at high speed. This paper, first, explains the effect of the contact condition of the shroud on the vibration characteristics of the ISB structure, using the analysis method developed by authors. Second, the calculated natural frequency and blade damping are compared with the measured ones. From these results, the effect of the shroud contact condition on the vibration characteristics of the ISB structure is clarified, and the validity of the analysis method is confirmed.