Variable Geometry Turbocharger Design

Variable Geometry Turbocharger Design

Increasingly stringent EU emissions legislation is the result of global environmental pressure. These guidelines outline reductions in greenhouse emissions for the automotive sector and must be met by manufacturers. Engine downsizing coupled with turbocharger boosting is used to improve fuel efficiency whilst maintaining performance.

Variable Geometry Turbochargers (VGT) represent a growing proportion of the turbocharger market. They offer greater power across the engine speed range, and better response times than conventional products. Improvements can be provided by variable components, which include movable guide vanes; these internal aerofoils direct air to the turbine rotor.

This project focused on the aerodynamic optimisation of the guide vanes and their geometrical arrangement inside of a VGT. Following in-depth research, the team analysed an existing Holset HY40V turbocharger, using laser scanning technology to build extensive 3D models in CAD. This process allowed us to develop conceptual vane designs which were evaluated using computational fluid dynamics and finite element analysis. A final vane profile was subsequently selected and radial flow turbine theory was used to decide the vane position, angle and quantity for maximum performance.

Rapid prototyping was used to produce functional models of our optimised design, which were incorporated into a test plan. Testing on a cold-air rig showed that the final solution provided increased compressor efficiency, improved gas velocity and higher rotational speed of the turbine. Employment of this green technology in a vehicle will reduce its carbon footprint, whilst offering a power increase and fuel saving to the customer.