Analysis on the Effect of Cavity Flows on the Aerothermal Performance of a High-Pressure Turbine Stage

In aero-engines, the turbine entry temperature profile determines the characteristics of the cooling system, including the flow field occurring in the cavity positioned between the stator rim and the rotor platform, which is used to provide end-wall cooling while ensuring no flow ingestion to prevent harmful configurations. The local flow field depends on the relative position between the blade rows, on the geometry of the cavity, on the rotational speed, and on the mass flow. The flow structures within the cavity may be described by high-fidelity simulations, which are still too onerous at engine-relevant conditions. However, unsteady Reynolds-averaged Navier–Stokes solvers provide information about integral-scale structure development and interaction. In this article, the results obtained from three unsteady simulations of a high-pressure turbine stage considering different cavity flowrates and rotational speeds are presented. The comparison between the experimental data obtained at the von Karman Institute for Fluid Dynamics, and the numerical results allows for analyzing the interaction between the cavity flow and the main flow. Pressure and velocity fields are analyzed to describe both the sealing mechanism and the formation of secondary flows in the presence of secondary air. It is demonstrated that the occurrence of ingestion regions depends on the potential interaction between the vanes and the blades and that the wake shed by the vane trailing edge determines the intensity of the phenomena. The secondary flows’ analysis shows that the purge flow exiting the cavity impacts the arrangement and strength of the hub-passage vortex.