The Development of a Deviation Model for Radial and Mixed-Flow Turbines for Use in Throughflow Calculations

Radial and mixed-flow turbine stages are an important component of turbochargers in automotive engines. The aerodynamic design of such turbines is generally compromised by the severe mechanical and manufacturing constraints to withstand the harsh motor environment with high stresses, high temperatures and unsteady operation. Conventionally, the designer deals with these constraints in the preliminary design stage by using a high degree of empiricism. This is then followed in the detailed design by extensive and time-consuming 3D CFD analysis and geometry optimisation. This paper describes a new approach to the preliminary design of radial turbine impellers using a quasi-3D throughflow method, which allows a more rapid consideration of the design issues before moving on to a full 3D CFD analysis. The paper describes the development of deviation models suitable for radial and mixed-flow turbines out of a range of CFD solutions in which a number of important features have been varied: aerodynamic loading, tip clearance and blade root thickness. The features of the deviation model are related to predicted features of the flow. The results of throughflow calculations including the deviation model are compared against the CFD predictions.Copyright © 2009 by ASME