STALL PRECURSOR IDENTIFICATION IN HIGH-SPEED COMPRESSOR STAGES USING CHAOTIC TIME-SERIES ANALYSIS-METHODS

This paper presents a new technique for precursor identification in hi gh-speed compressors. The technique is a pseudo-correlation integral m ethod referred to as the correlation method. To provide a basis for co mparison, the traveling wave energy technique, which has been used ext ensively to study prestall data, is also briefly presented and applied The correlation method has a potential advantage over the traveling w ave energy method because it uses a single sensor for detection. It al so requires no predisposition about the expected behavior of the data to detect ''changes'' in the behavior of the compressor. Both methods are used in this study to identify stall precursive events in the pres sure fluctuations measured from circumferential pressure transducers l ocated at the front face of the compressor rig. The correlation method successfully identified stall formation or changes in the compressor dynamics from data captured from four different configurations of a NA SA Lewis single-stage high-speed compressor while it was transitioned from stable operation into stall. This paper includes an exposition on the use of nonlinear methods to identify stall precursors, a descript ion of the methodologies used for the study, information on the NASA h igh-speed compressor rig and experimental data acquisition, and result s from the four compressor configurations. The experimental results in dicate that the correlation method provides ample warning of the onset of rotating stall at high speed, in some tests on the order of 2000 r otor revolutions. Complementary features of the correlation method and the traveling wave energy method are discussed, and suggestions for f uture developments are made.