A vaned diffuser is provided. The diffuser comprises a housing having a first and second flow wall defining a flow path for the exit flow from an impeller. Twisted vanes are mounted on a movable structure capable of travel inside a chamber adjacent the first flow wall. The twisted vanes extend through rotatable structures rotatably retained in the flow walls such that the twisted vanes are slidably disposed across the flow path. Lateral movement of the movable structure moves the twisted vanes through the exit flow thus varying the stagger angle of the vane depending on which section of the twisted vane is in the exit flow. The rotatable structures have twisted openings that match the vane cross-section and twist so that the rotatable structures readily rotate as the twisted vanes are moved through them.
