Master thesis : Tip leakage flow in high pressure turbines

In the framework of this master thesis, a numerical study has been carried out in order to investigate the effect of tip geometry on the tip leakage flow and heat transfer features in a unshrouded high pressure axial flow turbine stage designed by Erhard [10]. Four different tip profiles were considered, namely a default flat tip, a modified flat tip, a modified double squealer tip and a modified double thin squealer tip. The performances of the distinct tip profiles were compared to determine the improvement in terms of leakage mass flow rate and heat transfer. The computations were carried out on a single rotor blade with periodic boundary conditions. Grid independence study was performed in order to determine the adequate mesh to employ for the computations. Turbulence was modelled with the BSL-RSM model because it provides more advantages than its SST counterpart model. At the end, it was proven that adoption of a cavity can drastically enhance the aerothermal performances, that is, providing a decrease in the leakage loss and average heat transfer over the tip.