Session: 34-08 LES Solvers and applications 2

Paper Number: 126865

126865 - DNS of Turbine Vanes Subjected to Inlet Temperature Variations and Robust Quantification of Aerothermal Flow Irreversibilities 

The aim of the present work is to investigate the aerothermal characteristics of high-pressure turbine (HPT) vanes subjected to burner-like mean inlet temperature and velocity variations. A systematic numerical investigation is carried out by means of Direct Numerical Simulation (DNS). A total of five cases are simulated: two non-uniform pitchwise inlet temperature distributions (hot streaks) with different clocking positions, one impinging on the blade leading edge and the other aligned with the mid-passage, two equivalent non-uniform pitchwise temperature and velocity distributions (hot jets), and a baseline with uniform inlet conditions. In all cases, large-scale turbulent fluctuations are superposed onto the mean inlet profiles. A robust methodology to correctly quantify viscous and thermal irreversibility production mechanisms based on an alternative formulation of the entropy transport equation is introduced. This ensures a correct representation of the turbulent dissipation and of the irreversible turbulent heat flux in the presence of incident fluctuations and thermal gradients. The critical role of turbulent dissipation and its sensitivity to the grid resolution due to small-scale turbulent fluctuations are discussed. The role of inlet conditions on the vanes' aerothermal properties is investigated by analyzing the surface temperature distributions and the characteristics of the boundary layers. The temperature streak clocking positions are shown to directly affect the blade surface temperature distributions, and have an impact on the shock waves position and on the boundary layer transition characteristics via local modifications of the fluid viscosity and Mach number. The novel entropy framework is carefully validated and it is employed to investigate the role of viscous and thermal irreversibilities and their dependency on inlet conditions. Furthermore, an in-depth analysis of the mean and turbulent physical mechanisms of entropy generation associated with distinct regions of the flow such as boundary layers, wakes and passage is conducted and the results are discussed.

Presenting Author: Massimiliano Nardini University of Melbourne

Presenting Author Biography: Massimiliano Nardini is a Postdoctoral Research Fellow at the University of Melbourne and his main area of expertise is in computational fluid dynamics and high-performance computing. In the context of high-fidelity numerical simulations, his research interests include immersed boundary methods, fluid-structure interaction, aeroacoustics and turbomachinery flows. He is also involved in an international collaboration led by the University of Cambridge with the aim of developing numerical tools to accelerate the transition towards sustainable aviation.

Authors:

Massimiliano Nardini University of Melbourne
Melissa Kozul University of Melbourne
Richard Sandberg University of Melbourne