Understanding Entropy Wave Evolution in High-Pressure Turbines: The Role of Hot Spot Position and Features

Mutual interaction of turbomachinery components plays a key role for comprehensive optimization of the machine. Among these interactions, the aerodynamic coupling between combustor systems and high-pressure turbine (HPT) stages may lead to aerodynamic performance degradation, combustion instability and noise generation. This interaction is mainly due by steady and pulsating temperature distortions (Hot Streaks and Entropy Waves, respectively) generated by combustion systems: such flow non-uniformities are convected downstream in swirling flow field and interact with HPT stage. New trends of introducing alternative fuels (sustainable aviation fuel, hydrogen,…) may also require an even more accurate understanding of such interactions. In this context, the paper reports an extensive CFD investigation of the influence of swirling Entropy Wave (EW) injection position on the disturbance migration and interaction with an uncooled aeronautical HPT stage. The numerical method, based on full annulus URANS analyses, has been already intensively validated against experimental acquisitions in previous works by the authors exploring the effect of different EW-vane tangential alignments, swirling flow rotational directions and turbine operating conditions. Results reveal a complex interaction among the EW spots and stator and rotor secondary flows. Moreover, a simplified model proposed by the authors for fast prediction of combustor non-uniformities evolution has been applied to all the presented cases to prove its ability to reproduce the main features of EW evolution. The combination of model and CFD results can provide important insights for turbomachinery designers both during the preliminary design and for the final evaluation.