Abstract
This paper describes the difference in aerodynamic stability between a free-standing blade (FSB) structure and continuous cover blade (CCB) structures for a steam turbine blade. Vibration modes and natural frequencies of FSB, CCB with tip cover only, and CCB with tip cover and tie-boss are calculated by a finite element code. The unsteady aerodynamic forces acting on oscillating cascades are calculated using two-dimensional, time-linearized Euler equation analysis. Aerodynamic work per blade is obtained by integration over radial sections of the blade. Aerodynamic damping is calculated from the aerodynamic work and the kinetic energy for the vibration modes of each structure. Finally, aerodynamic stability for each structure is evaluated and discussed.
