Approach to high-performance transonic compressor design

A single stage transonic centrifugal compressor for a small turbofan engine has been developed. Rig testing has demonstrated an 83.2% adiabatic efficiency with a 7.5:1 total-to-static pressure ratio and a corrected tip speed of 596 m/s. An impeller blade redesign is presented of the original blade geometry, which uses both experimental and numerical results. An in-house developed Navier-Stokes flow solver was applied to the impeller redesign process. To meet the development schedule, a steady flow solver was used for the impeller analysis instead of an unsteady stage analysis. As a result, the following important redesign factors for higher efficiency were found: leading-edge shock control, blade-to-blade loading control, and splitter-loading optimization. Also, the flow physics of a secondary flow mechanism was captured by the computational analysis, and its control was applied during the impeller redesign process. The final stage performance was achieved by rig testing, through use of a coupled pipe diffuser and impeller-inducer bleed system.