Numerical model for vibration characteristic of steam turbine blade with damped shroud

In order to obtain vibration characteristic of damped blade, and improve its design technique, by using pretwist beam element and investigating the stiffness matrix and the damping matrix of damped shroud, numerical model for vibration characteristic of steam turbine blade with damped shroud has been developed. Meanwhile, Harmonic Wave Propagation Method is adopted to improve calculation efficiency. The comparison of calculation results with experimental data of a 360 mm blade shows good agreement. Then the dynamic characteristic of a last stage long blade with damped shroud is analyzed in detail, some results as untwist angle, static and dynamic frequency and Campbell diagram of nodal diameter vibration are obtained, the comparison of static frequency and dynamic frequency with results from three dimensional model shows the numerical model can get a rational result. Dynamic characteristic of other dampers of blades can also be analyzed by the model, so it may be usable for damped blade design and be the base for optimization of damped blade.