Upstream wake influences on the measured performance of a transonic compressor stage

The influence of an upstream wake on the performance of a downstream compre ssor stage with transonic inlet conditions is studied. Experimental results from fixed plane compressor exit instrumentation show that deep wakes, rep resentative of heavily loaded stator wakes, persist further downstream than anticipated. The influences of the upstream wakes are aliased into a typic al stator pitch held, thus magnifying their "true" influence. Results also show that reducing the axial spacing between the upstream stator blade-row and downstream rotor blade-row reduced the overall performance suggesting t hat mechanisms other than wake recovery are present for this compressor. Th is change in performance was determined to be associated with the upstream stator wakes. The work presented herein shows that the stator/rotor interac tion is significant and should be accounted for in the design, testing, and analysis of transonic axial compressors.