Development of Curved Shape Diffuser-Duct for Aero-Engines With a Backend Centrifugal Compressor

In the present study, a design of the curved shape diffuser-duct is proposed to apply to the compressor stage for aero-engines with a backend centrifugal compressor. For these configurations, the flow exiting radially from the centrifugal impeller needs to be changed from radial-to-axial direction to meet downstream combustion chamber requirements. Hence, the specially designed exit duct with a curved shape to manage the flow from the radialto-axial direction was later diffused using the diffuser-shaped exit duct. This study aims to design and develop an efficient diffuser-duct for the adequate deceleration of flow in the exhaust diffuser and, as a result, a uniform and low-velocity flow at the exit. This configuration comprises a radial-to-axial turning annular passage at the centrifugal impeller exit. Then, the passage is directed to either a purely axial direction or is inclined to the axial direction by a slight angle. The results indicate a uniform total pressure at the stage exit with marginal variation along the span. It shows equivalent end wall effects near both the shroud and hub surfaces. This endwall effect may be occurring mainly due to the growth of the boundary layer across the diffuser passage.