Numerical Investigation of High-Pressure Turbine Environment Effects on the Prediction of Aerothermal Performances
Aerothermal prediction for the high-pressure turbine is challenging because of the complex environment that interacts with the turbine: hot-streak migration, unsteady flow phenomena, fluid/solid thermal coupling and technological details (squealer tip, coolant ejections, fillets, etc.). There is a need to compare their relative impacts on the blade temperature and turbine efficiency prediction. This is the main purpose of this paper. URANS simulations of the flow have been performed with a structured flow solver in a one stage high-pressure turbine. The baseline simulation takes into account the squealer tip and an inlet condition representative of a hot streak generated by the combustion chamber. Other technological details (coolant ejections and fillets) and fluid/solid thermal coupling on the rotor blade are alternatively considered in the simulation in order to quantify their relative contribution. The Chimera technique is used to ease the integration of technological details. The conjugate heat transfer (CHT) problem is solved by means of a code coupling where fluxes and temperatures are exchanged at the blade surface between the fluid dynamics solver and the solid thermal code. Results shows that rotor blade fillets have a little impact on both the blade temperature and the turbine efficiency (less than 1%). On the contrary, taking into account external cooling leads to a modification of radial distribution of loss and loading coefficients and reduces the efficiency by 2%. The blade temperature is also impacted, mainly on the suction side where differences of several per cent with the baseline case are observed. Fluid/solid coupling mainly affects the blade temperature prediction by homogenizing it which induces differences around 3% with the baseline case. To complete the analysis, a post-processing that includes a computation of local entropy production terms is used. It shows that the entropy production is mainly due to turbulent dissipation and allows to identify the reduction of efficiency of the case with cooling as an additional production of entropy where the cooling flow mixes with the main flow.