An Experimental Study of the Response of a Turbo-Machine Rotor to a Low Frequency Inlet Distortion.

摘要

As part of a joint technical effort involving North Carolina State Universtiy and United Technologies Research Center, an experiment was conducted to measure the response of an isolated turbomachine rotor to a distortion in inlet axial velocity. A once-per-revolution sinusoidal variation in axial velocity with an amplitude of approximately twenty percent of the average axial velocity was generated by an upstream screen. The response of the rotor was studied using pressure transducers and skin friction gages mounted on one of the rotor blades and a velocity probe at the rotor exit plane as well as with standard stationary frame pneumatic instrumentation. The rotor was operated in undistorted flow to establish the quasi-steady behavior of the compression system. When the air inlet angle was reduced past a certain limit, the rotor began to experience rotating stall. When the rotor was operated in distorted flow, the pressures on the surface of the instrumented blade were observed to vary as a function of the instantaneous inlet angle. These variations were greatest at the leading edge of the airfoil and became smaller toward the trailing edge. This concentration of activity in the leading edge region is more pronounced than has been observed for isolated airfoils. As the instrumented blade traversed the distortion, it was observed to operate transiently at inlet angles below the quasi-steady stall point in an apparently unstalled condition.