Evaluation of an Electrostatic Probe Technique for Detection of Turbine Engine Gas Path Distress.

An electrostatic probe technique for prediction of imminent failure of turbine engine gas path components has been evaluated and found to be unsuitable for practical application. The proposed method necessitates detection of metal particles released into the engine gas flow during engine deterioration by use of a charge sensitive electrode in the turbine exhaust. The overall evaluation of this technique included combustor and plasma studies, theoretical efforts, and turbine evaluation, including testing under induced distress conditions. Fundamental limitations of the electrostatic probe method were found to be the elusive and many faceted nature of probe signals, the dependence of signals on the variable and as yet undefined plasma characteristics of the turbine exhaust, and the inability to establish a credible theory which was consistent in explaining test results.