Influence Of Secondary Flow Phenomena On Boundary Layer Thickness And Wall Heat Flux In Scalloped Radial Turbines

Authors

Christian Rakut - Institute for Power Plant Technology, Steam and Gas Turbines, RWTH Aachen University
Mathias Diefenthal - Institute for Power Plant Technology, Steam and Gas Turbines, RWTH Aachen University
Manfred Wirsum - Institute for Power Plant Technology, Steam and Gas Turbines, RWTH Aachen University

Abstract

This paper deals with investigations of the boundary layer and the influencing flow phenomena in radial turbine wheels. Therefore the interrelationship between secondary flow phenomena, boundary layer thickness, thermodynamic state at the edge of the boundary layer and the wall heat flux is investigated. The results based on experimental and numerical heat transfer investigations of a scalloped turbocharger turbine wheel for commercial application. The investigations are performed and calculated for steady state operating points with a total turbine inlet temperature of 600°C. The numerical investigations aim to model the flow field and the heat transfer between the fluid and solid state and provide the basis for the following considerations. For the determination of the boundary layer thickness six criteria based on the flow velocity and the velocity gradient were defined. The evaluation of the thermodynamic state at the boundary layer edge show a relation between this thermodynamic state and the wall heat flux and enable a better understanding of the characteristic of the wall heat flux distribution and the specific conditions if there is a local heat input to or heat output from the radial turbine wheel.