Effect of Mistuning on the Vibration of Turbo-Machine Blades Induced by Wakes

Abstract

The report gives a theoretical investigation of the effect of blade mistuning on the vibration of the blades induced by wakes in the incident gas flow which rotate relative to the blades in question. An upper limit to the effect of mistuning is found, which shows that the amplitude on one blade may increase by a factor of roughly ½(1 + √ N), where N is the number of blades in the row. This limit is only approached in special and unusual circumstances. In normal circumstances the amplitude will not increase by more than about 20 per cent. It is concluded that blades expected to work under forced vibration conditions should be made as nearly identical as possible. This is in contrast to the situation when flutter may occur, where the effect of mistuning is always favourable.