The design of turbines for automotive turbochargers is a balancing act between the requirement for high efficiency, for engine efficiency, and low inertia, for engine response. Low inertia drives the wheel diameter, and the hub line, down to a level that is lower than the designer would choose purely for aerodynamic reasons. The growing trend from car makers is to push the turbocharger manufacturers towards solutions that are optimised to reduce inertia for individual engines, so that modern designs operate in a region of high loading where the available empirical knowledge is limited.
Graham Cox will present a paper at the IMechE's 9th International Conference on Turbochargers and Turbocharging, jointly authored by Mick Casey and Christian Fischer from Stuttgart University. The paper describes the aerodynamic design of small radial turbines which is generally compromised by severe mechanical constraints, to deal with high temperature and unsteady operation, but also by the requirement of low inertia for rapid turbocharger response from low engine speed.
Conventionally, the designer deals with these constraints in the preliminary design, using a high degree of empiricism, followed by extensive CFD analysis and geometry optimisation. This paper describes a new approach to the preliminary design using a quasi-3D throughflow method coupled to an optimiser, which allows a more rapid consideration of the design issues before moving on to 3D CFD analysis. The throughflow-based optimisation system was able to increase efficiency by over 3% at the same inertia or to reduce inertia by 20-30% at the same efficiency, compared to a baseline design.
The conference takes place at the prestigious headquarters of the IMechE in London on 19th and 20th May 2010. PCA will also be present in the exhibition adjoining the technical sessions where staff will be pleased to discuss aspects of compressor and turbine aero-mechanical optimisation and turbomachinery design software that may be of interest to delegates.
For more information www.imeche.org/events/c1302