Study of Flow Patterns in Radial and Back Swept Turbine Rotor under Design and Off-Design Conditions

Paper details the numerical investigation of flow patterns in a conventional radial turbine compared with a back swept design for same application. The blade geometry of a designed turbine from a 25kW micro gas turbine was used as a baseline. A back swept blade was subsequently designed for the rotor, which departed from the conventional radial inlet blade angle to incorporate up to 25[degrees] inlet blade angle. A comparative numerical analysis between the two geometries is presented. While operating at lower than optimum velocity ratios (U/C), the 25[degrees] back swept blade offers significant increases in efficiency. In turbocharger since the turbine typically experiences lower than optimum velocity ratios, this improvement in the efficiency at off-design condition could significantly improve turbocharger performance. The numerical predictions show off-design performance gains of the order of 4.61% can be achieved, while maintaining design point efficiency.