Patent ID: 8016557

Claim:
An airfoil diffuser for a centrifugal compressor comprising: a diffuser passage area defined between a hub plate and an outer portion of a shroud located opposite to the hub plate, the hub plate and the shroud forming part of the centrifugal compressor and each having a generally annular configuration to permit an impeller of the centrifugal compressor to rotate within an inner annular region thereof; a plurality of diffuser blades located within the diffuser passage area between the hub plate and the outer portion of the shroud in a circular arrangement and connected to the hub plate or the outer portion of the shroud; and the diffuser blades having a twisted configuration in a stacking direction as taken between the hub plate and the outer portion of the shroud such that for each of the diffuser blades inlet blade angle decreases from the hub plate to the outer portion of the shroud and lean angle in each of the diffuser blades measured at the hub plate is at a negative value at the leading edge and positive value at the trailing edge as viewed in a direction of impeller rotation and solidity measurements at leading edges of the diffuser blades vary between a lower solidity value measured at the hub plate of less than about 1.0 and a higher solidity value measured at the outer portion of the shroud of no less than 1.0.