Heat Transfer Analysis in a Turbine Bottom Platform Cavity With Hot Gas Ingestion: An Investigation on the Applicability of the Superposition Approach

This study focuses on the heat transfer mechanisms within the bottom platform cavity, which is located underneath the turbine endwall between two adjacent blades of gas turbines. A new test rig has been designed, manufactured, and commissioned to derive experimental data of two thermal target values: The Nusselt number and the adiabatic cooling effectiveness. Using infrared thermography and applying the superposition approach to film cooling, the desired heat transfer characteristics are derived under engine-like conditions. Custom-made heating foils applied to the cavity walls are used to vary the thermal boundary conditions in this cavity that is investigated experimentally for the first time. The experimental results are used for validating a previous CFD study solving steady-state RANS equations. Both datasets are in good agreement regarding the global thermal behavior, but exhibit partly high deviations in the thermal target values and local flow phenomena. The investigation confirms the applicability of the superposition approach to film cooling for cavity perfusion with hot gas ingestion. Further investigations, including parameter variations, can therefore be conducted.