Abstract
A frequent cause of turbomachinery rotor blade failure, including jet engines, aircraft engines and turbogenerators, is excessive vibration due to flutter or forced response. One method for dealing with this problem is to increase blade structural damping, using either tip or mid-span shroud design. Unfortunately, most existing aeroelastic analyses deal with blade alone model, which can not be used for system mode analysis. Therefore, judgements based on past experience are used to determine the acceptability of a shrouded blade design. A system approach analysis will be developed to predict shrouded blade flutter. This analysis will provide a system approach, over and above the standard blade alone approach, for predicting potential aeroelastic problems. Using the blade natural frequencies and mode shapes from both measurements and a finite element model, the unsteady aerodynamic forces of the system mode will be calculated using the blade surface supersonic, transonic, and subsonic flow field. A system flutter analysis will then be performed using a modal solution to determine the stability of the system. Besides using the experimental data to verify the finite element blade model, a non-shrouded blade flutter analysis will be used to verify the system mode flutter analysis. Also, we will use this method to study the major mechanism causing shrouded rotor blade to flutter in some specific modes including bending and torsion modes. Shrouded rotor blade design has been widely used in fans, compressors, and turbines. The proposed research method can remedy the current deficiency in shrouded rotor blade design and also can provide guidance for shrouded blade maintenance and life management.