Experimental investigation of compressor rotor wakes

The detailed nature of the three dimensional flow downstream of an isolated compressor rotor has been studied experimentally in a large scale rotating rig. Radial-circumferential arrays of pneumatic data have been acquired in the rotating frame for reference at values of (C sub x/U sub m) of 0.65, 0.75, 0.85 and 0.95 at planes 10, 30, 50 and 110% of blade axial chord aft of the rotor. The data consists of the total and static pressures and the yaw and pitch angles. From this data the relative velocity vector has been completely defined. From the data it can be seen that the radial flow in the wake increases dramatically as the rotor loading is increased (by going to lower values of (C sub x/U sub m)). At high values of (C sub x/U sub m) low total pressure fluid accumulates at the hub causing corner stall. As (C sub x/U sub m) is reduced, the radial flow carries the low total pressure fluid out to the tip, causing the hub corner stall to be inhibited, i.e. reduced in its streamwise extent aft of the blade trailing edge. By this process non-strip theory effects are seen to have a strong impact on the nature of rotor performance.