[137] Monitoring and experimental validation of blade vibration forces acting on rotor

V Vasicek, J Liska and J Jakl

University of West Bohemia in Pilsen, NTIS – European Centre of Excellence, Technicka 2, Plzeň 30614, Czech Republic. 
Tel: 420 377 632 521; Email: vasicekv@ntis.zcu.cz / jinliska@ntis.zcu.cz / jjakl@ntis.zcu.cz  

Monitoring of blade vibration plays an important role in the maintenance of rotating machines and their proper operation. Signal analysis of blade vibration plays an important role in the detection of changes in the blade structure. Early detection can avoid unnecessary losses. This is important, especially for blades in the last stages of low-pressure turbines of turbo-generators. A popular method used for blade vibration monitoring is blade-tip timing, which is, unfortunately, not installed standardly yet due to the higher installation costs and need for adjustment of the stator part. However, when there is no blade vibration monitoring system installed on the turbine, there is the possibility of using an alternative method for blade vibration monitoring based on the analysis of the shaft-relative vibration. In this case, the signal is measured by standardly installed instrumentation, giving this method a major advantage over others. Recently, several papers have been published describing this approach. However, there is no exact explanation yet as to how blade vibration affects the shaft vibration and what the form of its transmission is. An explanation of the main principle of rotor excitation by rotating blades, specifically a description of the forces taking part in the blade-shaft vibration transfer, is described in this paper. Experimental validation using a machinery fault simulator and derived conclusions are also presented.