To date, most signal processing techniques using blade tip sensors have been limited to simple parametric measurements associated with the sensor waveform, e.g., measurement of zero crossing locations for time of arrival information or maxima for tip clearance information. Using this type of parametric information, many computations require more than one sensor per stage. The use of a minimal number of sensors is an extremely important practical consideration since each pound that is added to an aircraft engine adds considerable costs over the life cycle of the engine. Because of this we have focused on developing algorithms that allow the reduction in the number of sensors needed for fault prognosis. We have used new parametric algorithms as well as those that make use of the entire ECS waveform.
Using our algorithms we have been able to demonstrate the detection of stall cell precursors using a single ECS. These algorithms have been demonstrated in real-time in tests at the NASA Glenn W8 single stage axial-flow compressor facility. The rotor tested, designated NASA Rotor 67, is a fan with 22 blades.