Some Practical Aspects of Compressor Blade Vibration

Abstract

The object of this paper is to set down an overall picture of the practical aspects of compressor blade vibration. In doing so it is inevitable that a certain content is effectively a repeat of other people's contributions to the subject. The authors make no apology for this and offer the paper as a "state of the art" as practised at Bristol Siddeley Engines Ltd. In bringing together the many relevant issues of this problem, it is hoped that a useful presentation is obtained.There is little hesitation in indicating the most obvious and important practical aspect of blade vibration as that of the inherent danger of blade failure and it is known that the axial flow compressor is susceptible to complete failure caused by the fatigue of one blade.The multi-stage axial flow compressor is a highly complex aerodynamic machine with, its early and late stages required to operate over wide ranges of incidence and Mach number conditions. To some extent, of course, use of variable geometry can reduce this to less taxing proportions. The aerodynamic environment of front stages has broad boundaries somewhat wider than those relating to rear stages, while middle blade rows generally operate under sensibly constant conditions. This diminishing “severity” of operation, front, rear to middle stage blading is not unrelated to the incidence of blade vibration problems which shows a similar pattern.