Bending flutter of unstalled cascade blades at finite deflection

Abstract

This report gives a method of calculating the conditions under which a cascade of unstaUed blades will flutter in their bending mode. The blades are assumed to be flat plates and the flow is assumed to be two-dimensional. It is found that, when there is deflection of the steady flow through the cascade, bending flutter can occur in which there is a phase difference between the motion of one blade and its neighbours. The flutter boundaries for a range of cascades have been calculated on a digital computer and are presented. For turbine cascades these boundaries are not far from typical operating conditions in gas turbines and this may be why blades in the low pressure end of steam turbines have been found to require lacing wires. Comparisons are made with earlier theories due to Sohngen and Shioiri.