Abstract: A diffuser for a centrifugal compressor has an annular array of vanes which are movable to vary the configuration of the diffusing passages between the vanes. Each vane includes a first leaf pivoted adjacent the leading edge of the vane and a second leaf pivoted on the first leaf. These leaves have slots extending chordwise of the vanes which are engaged by pins extending from an actuating ring rotatable about the axis of the diffuser. The slots in the two leaves are at an angle to each other so that when the ring is rotated and the pins move chordwise of the vanes in the leaves, the angle of the first leaf to the radial direction is changed and also the second leaf is moved relative to the first leaf to vary the width of the passage in addition to such variation as results from the change in the angle of the first leaf.

Abstract: A single-shaft gas turbine engine suited for road vehicle propulsion has variable inlet and outlet guide vanes in the compressor of the engine and a variable turbine nozzle. These variable features are called engine variable goemetry (EVG). In normal operation, the areas of the flow paths at the inlet and outlet of the compressor and of the turbine nozzle are varied with desired power level to suit varying air flow through the engine. An actuator increases the areas in response to a request for increased power output.In a braking mode, the compressor variable geometry is decoupled from the actuator and remains at a minimum flow condition while the turbine nozzle is opened as the power request decreases below a particular low value. The opening of the turbine nozzle decreases the engine power output, thus increasing its capacity to absorb power from the vehicle. Logic circuits control the coupling and decoupling of the compressor variable geometry.