Non-contact measurement of blade vibration in an axial compressor

Submitted to: Proc IMechE Part C: J Mechanical Engineering Science

Radosław Przysowa1 and Peter Russhard 2

Abstract

This article presents the analysis of forced vibrations of the first stage of the axial compressor measured by the contactless method during the bench tests of the SO-3 turbojet. A healthy and unhealthy configuration with an inlet blocker have been measured to find possible symptoms of a failure. In relation to earlier studies conducted in ITWL with a small number of sensors, the use of multichannel tip-timing system enabled to observe higher-order responses and coupled vibrations. The used methods of tip-timing analysis included all-blade spectrum and the circumferential fitting of blade deflections to the harmonic oscillator model. Synchronous and asynchronous vibrations are observed and analysed together with the generalised variant of least squares fitting. We discuss challenges related to measuring complex responses such as coupled resonances and a rotating stall, which are common in modern engines and are now in designers’ interest.