The Application of a Computer-Aided Design Technique to the Conceptual Design of Turbochargers: Part B — Radial Turbine Design

Abstract

A procedure similar to that presented in Part A is described for the non-dimensional design of radial inflow turbines. The technique is developed non-dimensionally to provide the overall dimensions, including the leading and trailing edge blade angles, of radial flow turbine rotors. Consideration of the adoption of non-radial blades at rotor inlet, leading to mixed flow rotors, and discharge swirl is included. The procedure is developed from a knowledge of the non-dimensional power requirement which is derived through the turbocharger matching conditions. To satisfy the matching requirement the mechanical efficiency of the turbocharger, the air fuel ratio, the inlet stagnation temperature relative to that at compressor inlet, and the gas constants for the hot exhaust gas must be specified. In addition a target stage efficiency, on a total to static basis, must be specified. In essence the procedure provides graphically all the possible velocity vectors at rotor inlet and exhaust. The graphical presentation allows the designer to survey all the options available; as this is done relevant data is presented and continuously up-dated to aid in the selection of the preferred design conditions. The non-dimensional geometry of the rotor is then developed from which the absolute dimensions can be derived through the specification of the gas mass flow rate and the inlet stagnation conditions.