Identifying faults in the variable geometry system of a gas turbine compressor

The influence of faults in the variable geometry (variable stator vanes) system of a multistage axial compressor on the performance of an industrial gas turbine is investigated. An experimental investigation has been conducted by implanting such faults into an operating gas turbine. The faults examined are individual stator vane mistunings of different magnitudes and located at different stages. Fault identification is based on the aerothemodynamic measurement data and is achieved by employing two different techniques, namely adaptive performance modeling and monitoring the circumferential distribution of the the turbine exit temperature. It is observed that the deviations of the health indices produced by an adaptive performance model form patterns that can be used to identify the faults. The patterns characterize both the kind and the magnitude of the fault. On the other hand, the turbine exit temperature profile is also influenced and its change can be used as additional information, to increase the confidence level of the diagnosis (contrary to customary practice, which expects temperatures profiles to reflect only burner or turbine malfunctions).