Periodic Aerodynamic Response of Axial Fan Rotor Blades to Nonuniform Inlet Flow Fields

Abstract

An experimental investigation of the aerodynamic response of the rotor blading of a single stage low speed axial research compressor, which was exposed to wake type inlet flow disturbances was carried out at the Institute’s low speed compressor and fan research facility. The investigation comprised 5 hole pressure probe surveys of the nonuniform flow field at the rotor inlet and exit planes as well as direct recording of the unsteady surface pressure response by rotor blade mounted ‘fast response’ miniature pressure transducers. Forcing functions in terms of streamwise and transverse gust velocities were determined from the circumferential and radial distribution of the inlet flow properties. The blade surface pressure history of the unsteady aerodynamic response was recorded at several locations along span and along chord. The influence of steady stage loading on the forcing function as well as on the unsteady rotor blade response was investigated. At midspan the recorded local blade surface pressure histories were integrated to a spanwise unsteady blade force coefficient, which was correlated to a calculated force coefficient determined by a two-dimensional linearized unsteady aerodynamic analysis.