Modelling impingement-effusion flow inside double-walled combustor tile

The prediction of temperature and heat transfer throughout the solid material of a gas-turbine combustor has driven interest in cooling technology which uses impingement/effusion (IE) cooling tiles on double-skinned combustor liners. The design of the IE tile system is simple but the aerodynamics are complex. The complexity of flow curvature, combined impingement and effusion cooling and heat transfer, poses a challenge to standard RANS CFD modelling. The IE combustor tile is numerically investigated using both URANS model with the SST-SAS model and Large Eddy Simulation (LES) in the Rolls-Royce in-house CFD code. The aim is to provide accurate CFD data and to test the viability of URANS approach to predict the impingement/effusion flow. Results of pressure, velocity and turbulence quantities are presented. It is found that the SST-SAS model, with high grid resolution, shows good agreement with LES. The current CFD results are used to resolve a substantial amount of very small impingement and effusion holes. The CFD results showed that every feature of the geometry has to be resolved by the numerical mesh, which makes the simulation impractical due to time consuming and high mesh resolution. These cooling holes can be omitted from the computational mesh and their effects captured on the flow via an impingement-effusion (IE) model which is based on defining the correct mass flow inside the holes as a function of the difference of pressure in the upstream and downstream regions of both impingement and effusion regions. The latter model takes the effect of pressure and velocity and it will be extended in future to take into account the heat transfer effects. The IE model is tested and validated for the 3-D combusor tile and results of pressure showed good agreement with the LES data.