Numerical Investigation of a Turbine Vane Frame for Co- and Counter-Rotating Configuration

This paper presents the numerical comparison of a turbine vane frame (TVF) for future high-bypass turbofan engines for architectures with a co-rotating setup between the high-pressure turbine (HPT) and the low-pressure turbine (LPT) and with a counter-rotating setup. The flow field in the TVF is impacted by the decision of a co- or counter-rotating architecture which is driven not only by aerodynamics but also by the dynamic and mechanical design constraints in an engine. As boundary conditions for the steady RANS simulation, measurements are used which were carried out in the engine-representative two-spool rig at the Institute for Thermal Turbomachinery and Machine Dynamics at the Graz University of Technology. The test vehicle in this rig consists of an HPT with nearly axial exit flow and a counter-rotating LPT connected via the TVF with aft-loaded struts and splitters. To reproduce a realistic HPT flow field, purge air is provided by a secondary air system (SAS). The inlet and outlet boundary conditions are defined based on the five-hole probe (5HP) measurement set up- and downstream of the TVF, acquired for three different purge conditions (0%, 100% = nominal, and 200%). To simulate a co-rotating configuration, the measured inlet flow field has been mirrored. The focus of this paper is to gain additional insights into the general flow behavior of a TVF in a co- and counter-rotating configuration, respectively. A special focus is placed on the differences between the development of strut secondary flows on their way through the TVF depending on the inlet flow field. Additionally, a duct loss comparison of the two configurations and its sensitivity to different purge flow levels is presented.