Computer Aided Aero-Thermodynamic Design for Impellers

The complete design of radial flow turbomachinery rotors invariably requires the aero-thermodynamic, structural and the manufacturing criteria to be satisfied simultaneously. In recent years, a number of computer aided design and geometry description procedures for centrifugal impellers have been developed. Essentially the detailed geometry generation in most of these codes operates in an iterative mode. The main drawback of such approaches is that the decision whether or not a particular step produces best results tends to be made arbitrarily. Moreover, it is not a simple matter to know what changes in the geometry would produce the desired results. This paper employs an inverse approach, which is based on a prescribed mean streamline deceleration schedule to generate the discrete geometry of centrifugal impellers for given performance requirements. The approach does not claim to offer a comprehensive solution of the aero-thermodynamic design problem of impellers but rather attempt to advance a methodology that is capable of generating designs that can theoretically produce maximum attainable total-to-total pressure ratio and improved efficiency with reduced design time. The systematic deployment of the proposed approach can also be utilized as a tool to explain differences in performance of centrifugal impellers that seemed alike under careful qualitative inspection.