MONITORING OF GAS TURBINE OPERATING PARAMETERS USING ACOUSTIC EMISSION

In this work, Acoustic Emission (AE) sensors were mounted on several parts of a laboratory-scale gas turbine operating under various conditions, the object being to assess the value of AE for inservice condition monitoring. The turbine unit comprised a gas generator (compressor and turbine on a common shaft) and a free-power turbine for power extraction. AE was acquired from several sensor positions on the external surfaces of the equipment over a range of gas generator running speeds. Relationships between parameters derived from the acquired AE signals and the running conditions are discussed. It is shown that the compressor impeller blade passing frequency is discernible in the AE record, allowing shaft speed to be obtained, and presenting a significant blade monitoring opportunity. Further studies permit a trend to be established between the energy contained in the AE signal and the turbine running speed. In order to study the effects of damaged rotor blades a fault was simulated in opposing blades of the free-power turbine and run again under the previous conditions. Also, the effect of an additional AE source, occurring due to abnormal operation in the gas generator area (likely rubbing), is shown to produce deviations from that expected during normal operation. The findings suggest that many aspects of the machine condition can be monitored.