Flutter Analysis of Contra-Rotating Blade Rows

Abstract

To investigate the flutter characteristics of cascading blades in multiple blade rows, the computation program to calculate the unsteady blade loading based on the unsteady lifting surface theory for contra-rotating annular cascades was formulated and coded. Then a computation program to solve the coupled bending-torsion flutter equation for the contra-rotating annular cascades was also developed. Some results of the flutter analysis are presented. It is shown that the presence of the neighboring blade row gives rise to substantial change in the critical flutter condition irrespective of the blade row gap when the main acoustic duct mode is of cut-on state. The effect of the neighboring blade row is also significant irrespective of the state of the main acoustic duct mode when the blade rows are very closely placed.