End-Wall Boundary Layer Measurements in a Two-Stage Fan,
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
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Detailed flow measurements in the casing boundary layer of a two-stage transonic fan were taken at stations upstream of the fan, between all blade rows, and downstream of the last blade row. At the design tip speed of 429 msec the fan achieved a peak efficiency of 0.846 at a pressure ratio of 2.471. Boundary layer data were obtained at three weight flows at the design speed one near choke flow, one near peak efficiency, and one near stall. Conventional boundary layer parameters were calculated from the data for each of the three flows. A classical two-dimensional casing boundary layer was measured at the exit of each blade row and extended inward to approximately 10 of span. The steep radial gradient of axial velocity noted at the exit of the rotors was reduced substantially as the flow passed through the stators. This reduced gradient is attributed of total temperature as the flow passed through the stators. The data also show overturning of the tip flow at the stator exists that is consistent with the expected effect of the secondary flow field.