Impact of Predicted Combustor Outlet Conditions on the Aerothermal Performance of Film-Cooled High Pressure Turbine Vanes

Abstract

Turbine inlet conditions in lean-burn aeroengine combustors are highly swirled and present nonuniform temperature distributions. Uncertainty and lack of confidence associated with combustor-turbine interaction affect significantly engine performance and efficiency. It is well known that only Large-eddy and scale-adaptive simulations (SAS) can overcome the limitations of Reynolds-averaged Navier–Stokes (RANS) in predicting the combustor outlet conditions. However, it is worth investigating the impact of such improvements on the predicted aerothermal performance of the nozzle guide vanes (NGVs), usually studied with RANS-generated boundary conditions. Three numerical modelling strategies were used to investigate a combustor-turbine module designed within the EU Project FACTOR: (i) RANS model of the NGVs with RANS-generated inlet conditions; (ii) RANS model of the NGVs with scale-adaptive simulation (SAS)-generated inlet conditions; (iii) SAS model inclusive of both combustor and NGVs. It was shown that estimating the aerodynamics through the NGVs does not demand particularly complex approaches, in contrast to situations where turbulent mixing is key. High-fidelity predictions of the turbine entrance conditions proved very beneficial to reduce the discrepancies in the estimation of adiabatic temperature distributions. However, a further leap forward can be achieved with an integrated simulation, capable of reproducing the transport of unsteady fluctuations generated from the combustor through the turbine, which play a key role in presence of film cooling. This work, therefore, shows how separate analysis of combustor and NGVs can lead to a poor estimation of the thermal loads and ultimately to a wrong thermal design of the cooling system.

Unsteady Flows and Component Interaction in Turbomachinery

“…Cubeda et al [175] simulated the performance of the cooled high-pressure vane designed during the FACTOR project using the SST model as turbulence closure. Boundary conditions for the vane were taken on the combustor/turbine interface section using numerical data obtained during a previous numerical campaign [173].…”

Numerical Prediction of Heat Transfer Coefficient and Adiabatic Effectiveness on a Nozzle Guide Vane With Representative Combustor Outflow

“…As a consequence, it can be stated that CFD is satisfactorily replicating the coolant alternate spread on the higher/lower half of the PS/SS due to the main flow swirling structure, although there is yet wide margin for improvement. In fact, based on available data in the open literature, it is expected that more advanced CFD modelling techniques (such as scale-resolving methods) can help in overcoming the limitations of RANS in accurately reproducing the mixing between coolant and main streams [23] [32].…”

“…The rig was capable to reproduce the presence of both temperature distortion and aggressive swirled flow field, even in non-reactive conditions. Such accurate test data allowed for the exploitation of advanced CFD methodologies based on scale resolving simulations, as carried out by CERFACS [21] and the University of Florence [22] [23], who have proven the importance of integrated approaches for the sake of achieving high-fidelity predictions of the aerothermal field at the turbine entrance. On the other hand, these approaches are well known to be significantly expensive, in terms of computational time and cost, and therefore, not well suited for industrial design practice.…”