Numerical analysis of secondary airflow in a rotating cavity of a gas‐turbine at high operating points with vortex reducer implementation

Abstract

Temperature and pressure ratios in gas turbines have grown over time to increase the performance and efficiency of the engine. This, in turn, has required improvements to the effectiveness of the secondary air system to enhance the cooling performance of critical components. Analysis of pressure losses in the secondary systems of aero gas turbines has identified a significant contribution in the bled airflow path through the compressor cavity between rotating disks. In this configuration, radial inflow usually occurs within an Ekman layer along the walls, while a free vortex condition appears in the cavity, generating losses and limiting transfer to the proximity of the wall. Nozzles acting as vortex reducers have shown promising performance under aeronautic conditions, although the complexity of the system limits the testing of popular theoretical models to low mass flows, based on a free vortex for a radially inward flow in a rotating cavity. For industrial applications, it is important to verify the behavior of these models at high operating points. Given that improving the performance of secondary air systems has increased in importance over time, the present study compares the one-dimensional theoretical models of Shvets and Owen with a three-dimensional Computational Fluid Dynamics (CFD) analysis verified against previous experimental values from literature. This approach allows a focus on different and more complex vortex reducer geometries while proving the usefulness of analytical techniques at high operating loads, underlying their limitations and allowing improvements to be proposed.