Experimental Investigations of the Onset of Rotating Stall

This work focuses on analysis of data obtained in experimental investigations of a military fan in a whole-engine test facility. The data was simultaneously obtained by using multiple pressure sensors located at different axial and angular positions in the fan. In particular, the origin of rotating stall was investigated by analyzing the experimental data both in the frequency-time domain as well as the correlation in time between the typical pressure profile and the pressure profile for each revolution of the rotor. First, the measurement signal was high-pass filtered with a cut-off frequency slightly lower than the spool rotational frequency. These high frequency data were subjected to a typical pressure distribution test. Second, the measurement signal was low-pass filtered slightly lower than the spool rotational frequency. The low frequency part was investigated in the frequency-time domain. A quantitative measurement of an indicator of rotating stall is presented and its limitation for practical use is discussed.