Numerical Investigation of Vortex Structures in the Rim Cavities of Gas Turbines

This study presents a computational investigation of vortex structures forming within the rim cavities of gas turbines. Utilizing computational fluid dynamics (CFD), both steady-state and transient simulations were conducted on simplified cavity models derived from a 1.5-stage experimental turbine. A range of cavity widths and boundary conditions, including surface-averaged and profile-based inlets and outlets, were explored. The emergence of large-scale rotating structures and Kelvin-Helmholtz instabilities was evaluated under varying non-dimensional purge flow rates at a low non- dimensional purge flow rate. Time-resolved simulations showed the importance of realistic profile boundary conditions in capturing the unsteady flow phenomena. The analysis confirmed the sensitivity of vortex formation to geometric and flow conditions, particularly the boundary specification and purge flow magnitude. Transient simulations using profile inlet velocity and outlet pressure distributions yielded results closely matching experimental observations. These findings contribute to optimizing secondary air systems and improving turbine cooling efficiency while reducing unnecessary purge air usage.