Computer Aided Design of Mixed Flow Turbines for Turbochargers

Abstract

The paper describes a comprehensive computer aided design procedure and its use to investigate mixed flow turbines for automotive turbocharger applications. The outside dimensions of rotor and casing as well as blade angles are determined from one-dimensional design and off design calculations, the detailed blade shape from quasi-three-dimensional analysis and mechanical stressing and vibration programs, and geometric data are presented as outside views and sections of the rotor by a graphics subroutine. The procedure consists of a series of separate programs rather than a single program, so that the designer’s intervention at each stage of the process can be applied. Two mixed flow rotors were designed, manufactured and tested in a specially designed high speed dynamometer. The first was intended to achieve a substantial increase in mass flow over the reference radial rotor without loss of efficiency, while the latter was intended as a direct replacement of the reference radial rotor, but should give more favorable pulse performance when operating in conjunction with an engine due to changes in the operating map viz: a) lower tip speeds for best efficiency, and b) flatter mass flow characteristics. Both effects were predicted by analysis and confirmed by tests.