Numerical Study of Entropy Wave Evolution within a HPT Stage

Component reciprocal interaction and aero-thermal coupling are critical aspects in modern turbomachinery design, which requires an accurate holistic approach to deeply understand their complex effects within the machine. Combustors and high-pressure turbine (HPT) interaction is extremely critical due to the compact and lightweight system design to achieve a consistent reduction of the combustor-turbine axial gap. In this context, computational and experimental analyses are thus necessary to study the interaction of the high temperature gas coming from combustor systems and entering the turbine in order to avoid engine mis-operations and to lower the indirect core noise generation.

This paper presents a numerical study of pulsating temperature distortion (entropy wave) evolution within a high pressure turbine stage. Four different clocking positions between the 11 temperature spots and the 22 stators have been study to highlight the complex interaction of the convected entropy waves with the stage. The numerical results, obtained by full annulus URANS computations (TRAF code) and by a dedicated post-processing based on phasor quantities, have been compared with experimental measurements coming from the Laboratorio di Fluidodinamica delle Macchine (LFM) of the Politecnico di Milano (Italy) where the HP stage rig is located. The excellent agreement between numerical results and experimental acquisitions confirms the accuracy of the selected numerical approach. Such results also suggest recommendations for the thermal design of the following rows and are the main prerequisite for the study of the indirect core noise generation.