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Angelina M. Padilla
Department of Mechanical Engineering Stanford University 488 Escondido Mall, Bldg 500, Stanford, California 94305 USA

Christopher J. Elkins
Department of Mechanical Engineering Stanford University 488 Escondido Mall Stanford, California 94305

John K. Eaton
Dept. of Mechanical Engineering Stanford University 488 Panama Mall Stanford, CA 94305 USA


The effect of upstream flow distortion on the performance of practical annular diffusers was examined in order to gain insight on how to design a more robust diffuser. Experiments were conducted in one-fifth sectors of an annular diffuser with a single NACA 0015 airfoil shaped support strut in the center. Three diffusers with different expansion ratios ranging from conservative to aggressive and four inlet conditions were investigated. Magnetic resonance velocimetry was used to measure all three components of time averaged velocity over the entire flow field. The conservative diffuser design was robust in that it did not stall for any of the various inlet conditions. However, there were substantial variations in the flow development. The moderate diffuser stalled for one of the inlet conditions, and the aggressive diffuser stalled for all inlet conditions investigated. The development of the boundary layer along the diffusing wall and the separated wake of the support strut were both very sensitive to varying inlet conditions.