Attenuation of inlet flow distortion upstream of axial flow compressors

A linearized analysis predicts the velocity and static pressure redistribution in a distorted flowfield upstream of a low hub-tip ratio axial flow compressor as a function of the slope of the compressor pressure rise vs mass flow rate characteristic. The attenuation of axial velocity 'distortion and the magnitude of the generated circumferential and radial velocities are found to increase with a steeper negative slope of the compressor characteristic. Analytical results indicate that the magnitude of the upstream flow redistribution is approximately halved when radial velocities are conserved within the compressor as compared to the results assuming that radial velocities are suppressed within the compressor. The test compressor suppressed internal radial velocities and data verified the appropriate analysis. The local slope of the distorted characteristic was found to be significantly less than the undistorted slope. Much of the difference between the local distorted slope and the undistorted compressor characteristic slope was attributable to rotor unsteady effects.