Blade Monitoring in Turbomachines Using Strain Measurements

Blade rubbing is an undesirable but unavoidable phenomenon in turbomachinaries. It decreases the engine performance and can lead to blades or/and stator damages. Thus, blade monitoring is of high importance not only to ensure security, but also to optimize the engine efficiency. In particular, the detection and the identification of the instants of contacts between the blades and the stator are a valuable information that can be used through a preventive maintenance scheme. This paper proposes a new detection approach based on strain gauge measurements. Since the rubbing phenomenon creates a wave shock that deform the structure, these latter can be efficiently measured by a strain gauge mounted on the stator. However, the strain signal is generally corrupted with other mechanical and electromagnetic interferences. To tackle this issue, the authors propose a signal separation technique based on modeling the blades’ signal as cyclo-non-stationary. Also, the use of the synchronous fitting is proposed to separate blades’ component from environmental noise. The proposed technique is validated on real signals captured from a strain gauge mounted on the stator of a turbomachine.