The Effect of Upstream Vane Wakes on Annular Diffuser Flows

Experiments were performed to determine the sensitivity to inlet conditions of the flow in two annular diffusers.~ One of the diffusers was a conservative design typical of a diffuser directly upstream of the combustor in a jet engine.~ The other had the same length and inlet shape as the first diffuser but a larger area ratio and was meant to operate on the verge of separation.~ Each diffuser was connected to two different inlets, one containing a fully-developed channel flow, the other containing wakes from a row of airfoils. Three-component velocity measurements were taken on the flow in each inlet/diffuser combination using Magnetic Resonance Velocimetry.~ Results will be presented on the 3D velocity fields in the two diffusers and the effect of the airfoil wakes on separation and secondary flows.