The Effect of Interaction Between Wakes From Blade Rows in an Axial Flow Compressor on the Noise Generated by Blade Interaction

Abstract

The effect of interaction between the wakes from one row of blades and the boundary layers and wakes of the next row of blades downstream has been measured in an axial flow compressor by hot wire signals displayed on a CRO screen synchronized with the rotor. It is shown that the two sets of wakes can be made to mutually cancel the greater part of the velocity defect in each at certain points. Proper choice of axial and circumferential position of alternate rows of stationary blades so that the downstream row is in the middle of the wake street from the upstream row allows the velocity defect normally in the rotor wakes to be thus cancelled at the position of the stator and considerably reduces the noise produced at the rotor blade passing frequency by the rotor wakes on the stator. The effect of stator wakes on rotor blades downstream of the first can be similarly reduced by lining up blades in successive rotor rows. The deductions are confirmed by measurements of sound pressure level.