Forcing function effects on rotor row unsteady aerodynamic response in a multistage compressor

The fundamental flow physics of wake and distortion generated periodic rotor blade row unsteady aerodynamics were experimentally investigated. This was accomplished through a series of experiments performed in an extensively instrumented axial flow research compressor. In particular, the effects of aerodynamic forcing functions of different reduced frequency, interblade phase angle, waveform, and amplitude on rotor blade row periodic unsteady aerodynamic response while operating over a range of operating conditions in multistage subresonant and superresonant acoustic resonant environments were investigated. Key results included the following. On the rotor blade low camber pressure surface, the unsteady pressure nondimensionalization compressed the magnitude data with mean flow incidence except in the accelerating flow field of the front chord region at negative mean flow incidence. However, for the high camber suction surface, gust interactions with the mean flow field affected the unsteady pressure response over the entire blade surface. The harmonic analysis of blade row unsteady aerodynamic response to complex waveform forcing functions was experimentally demonstrated. Subresonant and superresonant acoustic environments were established, with the magnitude data-prediction correlation being very good in the subresonant flow regime and the correlation of these data in the superresonant flow regime only fair. In both acoustic environments, the correlation of the phase data were poor, both in value and trend