Analysis and Solution of a Non-Synchronous Vibration Problem in the Last Row Turbine Blade of a Large Industrial Combustion Turbine

Abstract

This paper presents the analysis and corrective action taken to solve a flow induced non-synchronous vibration failure problem encountered in the last stage rotating blade in a large industrial combustion turbine. A description of the fatigue failures and of temporary operation restrictions that precluded further failure is given. The results from a strain gauge telemetry test are presented which show that failure was due to high vibratory stress excursions from fundamental mode vibration, which resulted from broad band buffeting excitations and very low aerodynamic damping at high levels of power and mass flow. From these data, design criteria were developed for designing a retrofittable blade that removed the operating restrictions. Telemetry test results (from the same turbine), which verified the new design, are also briefly presented and discussed. This investigation shows that the design of future high performance exhaust end combustion turbine blading must take into account non-synchronous excitation (buffeting) and the aeroelastic interaction between blade structure and flow, in addition to the synchronous excitations traditionally allowed for in the design process.

A Statistical Study of Gas Turbine Losses and Analysis of Causes and Optimum Methods of Prevention

“…This is unusual for a turbine blade, but it can occur if a turbine is uprated and the tip chord of the blade is relatively short. Extensive redesign and development efforts may be required to correct a flutter problem, but they are very necessary (Scalzo et al, 1986).…”

Vibration measurement of a cantilever beam using root embedded piezoceramic sensor

“…Strain gages are commonly used to measure the blade vibrations. One example is the study reported by Scalzo et al [5] for the analysis and solution of a non-synchronous vibration problem in the last row turbine blade of a large industrial combustion turbine. Strain gages were employed by Tang and Dowell [6] for the blade vibration measurements in their experimental set-up.…”

Vibration Measurement of Rotating Blades Using a Root Embedded PZT Sensor

“…Despite difficulties in measuring vibrations of rotating blades, many researchers and manufacturers have invested their efforts in developing techniques for blade vibration measurements due to the importance of the problem. A study for the analysis and solution of a non-synchronous vibration problem in the last row turbine blade of a large industrial combustion turbine was reported by Scalzo et al [10]. Blade vibrations signals were transmitted from strain gages using a telemetry system.…”