## Analytical correlation of centrifugal compressor design geometry for maximum efficiency with specific speedMichael R. Galvas, United States. National Aeronautics and Space Administration, Lewis Research Center Centrifugal compressor performance was examined analytically to determine optimum geometry for various applications as characterized by specific speed. Seven specific losses were calculated for various combinations of inlet tip-exit diameter ratio, inlet hub-tip diameter ratio, blade exit backsweep, and inlet-tip absolute tangential velocity for solid body prewhirl. The losses considered were inlet guide vane loss, blade loading loss, skin friction loss, recirculation loss, disk friction loss, vaneless diffuser loss, and vaned diffuser loss. Maximum total efficiencies ranged from 0.497 to 0.868 for a specific speed range of 0.257 to 1.346. Curves of rotor exit absolute flow angle, inlet tip-exit diameter ratio, inlet hub-tip diameter ratio, head coefficient and blade exit backsweep are presented over a range of specific speeds for various inducer tip speeds to permit rapid selection of optimum compressor size and shape for a variety of applications. |

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absolute flow angle absolute Mach number adiabatic AhBL AhDF area ratio Balje blade height Centrifugal compressor compressor performance configurations CpT2 critical velocity ratio diffusion factor disk friction loss displacement thickness enthalpy equation exit absolute flow exit blade flow rate fluid function of specific geometric parameters geometric variables geometry given specific speed guide vane loss hact head coefficient hub-tip diameter ratio impeller exit impeller inlet inducer tip critical inducer tip speeds inlet guide vanes inlet hub-tip diameter inlet tip-exit diameter isentropic low specific speed lower specific maximum efficiency maximum total efficiency optimum geometry P1MF pressure ratio pressure recovery coefficient radius ratio range of specific recirculation losses relative velocity ratio rotative speed rotor exit absolute Skin friction loss specific speed range speed at various swirl-free inlet tip critical velocity tip-exit diameter ratio total pressure transonic Vaned diffuser inlet vaned diffuser loss vaneless diffuser loss vaneless space Variation in optimum velocity diagram characteristics