Validation of a CFD method for the aerodynamic study of trailing edge cooling technologies in high-pressure turbine blades

In a developing aviation market, the necessity of augmenting the thermal efficiency of aero engines leads to the increase of thermomechanical constraints on the HP turbine blades. In particular, the trailing edge zone of blades is one of the most difficult parts to be cooled, presenting the highest levels of temperature. As a consequence, this limits the possibility to further increase the turbine inlet temperature. The current challenge for motorists such as Safran Aircraft Engines is to develop advanced blade trailing edge cooling technologies in high-pressure turbines. However, the modification of blade thickness and shape at trailing edge has also a great impact on the aerodynamic performance of the turbine, leading to the need of a compromise with thermomechanical requirements. In this context, it is increased the importance of developing accurate CFD methodologies to predict possible gains or losses of the aerodynamic performance induced by trailing edge cooling configurations. This internship project was focused on the validation of an innovative CFD method using unstructured grids to perform 3D RANS aerodynamic evaluations on turbine blades when considering the presence trailing edge coolant injections. The initial bibliographic analysis allowed to define the state-of-the-art of the technologies used for trailing edge cooling in high-pressure turbine blades. Only the configuration presenting cutbacks and slots at blade pressure side has been selected for the CFD validation process, which was based on a concept developed at Safran Aircraft Engines. In a first analysis, the standard method with structured grids has been tested. It presented the advantage to be quicker and automated but was not capable of considering blade configurations presenting coolant injections, for the geometrical complexities. Consequently, it was only used to define a reference case to validate the results obtained with unstructured grids in cases without cooling. On the other hand, the innovative method based on unstructured grids allowed to actively model the presence of coolant injections near the trailing edge. Consequently, it has been applied and validated for the study of the selected technology. Different studies on the effect of local mesh refinements in the wake and in the trailing edge zone demonstrated their importance on the level of convergence of the simulations and on the accuracy of results. The solution presenting the best compromise between accuracy and computational cost has finally been selected. Furthermore, the correct positions for the inlet and the outlet planes has been determined to prevent problems respectively related to potential effects and shock reflections. In conclusion, the validation process allowed to define a reliable CFD methodology capable to perform accurate aerodynamic evaluations when considering the presence of trailing edge cooling. The main application of this method will be the comparison of the aerodynamic performance given by different cooling configurations. This will be useful for the improvement existing trailing edge cooling technologies for the next generation of aeroengines.