Redesign of a Centrifugal Compressor’s Vaned Diffuser to Improve Core Engine Performances

Present paper is devoted to numerical optimization of a 8:1 total pressure ratio centrifugal compressor to improve performances of core engine belonging to a turbo-shaft engine. Main subject of optimization is vaned diffuser with following impeller’s pressure ratio increase. This compressor designed by CIAM [7] and tested as a part of core engine gave satisfactory performances even under the first test run. Further development requires new concepts one of which is reduction of core engine’s turbine inlet temperature. Redesign of vaned diffuser through elimination of reverse flow zone gives 5% increase of mass flow-rate and 0.7% increase of efficiency. Further 6% increase of impeller’s total pressure ratio (at the same rpm) modifies Brayton cycle of core engine reducing turbine inlet temperature by 32° and turbine exhaust temperature by 43°. To maintain the same power output, this drop of turbine exhaust temperature is compensated by 4% increase of the operational flow-rate.