Aerodynamic study of flow phenomena in a turbine center frame

Abstract

A main objective in aviation technology is the development of efficient cooling techniques for the thermal highly loaded engine components. For an optimal design of the cooling mechanisms, the heat transfer characteristics have to be known and need to be predictable. In order to cope with an efficiency-driven increase of the turbine entry temperatures, sophisticated designs of the turbine blade and duct geometries are indispensable. Relating to the turbine center frame (TCF), which refers to the structure connecting the low-pressure and the high-pressure turbine, efficient internal cooling concepts facilitate the reduction of coolant consumption at maintained structural integrity. Therefore, reliable models to accurately predict the internal flow physics and heat transfer characteristics are prerequisite. Thus, the present work focuses on the experimental and numerical investigation of the internal flow field of a scaled and abstracted TCF geometry. The experimental setup allows to monitor the thermal boundary conditions as well as the internal flow field by means of 2D2C-PIV. The flow physics are studied at two distinct Reynolds numbers. For both Reynolds numbers, experimental and numerical data is analyzed in terms of mass flow distribution, velocity and vorticity structures in the most characteristic cross-section of the TCF. The experimental results are intended to serve as a reference data set for the validation of the numerical setup. An accurate simulation of the intricate flow field is challenging due to a wide range of the flow and vortex structures. On this account, an unsteady RANS simulation was performed with ANSYS CFX. Generally, a good agreement between CFD and experimental data can be found. Nevertheless, the numerical data shows a dependence on the Reynolds number, whereas the experimental data is unrelated for the examined mass flow regimes. This conclusion is then confirmed by the PIV measurements. A complex internal flow field is revealed, which is mainly dominated by large-scale vortices and high velocity gradients.