Session: 35-01 CFD Analyses

Paper Number: 78239

78239 - Influence of RANS Turbulent Inlet Set-Up on the Swirled Hot Streak Redistribution in a Simplified Nozzle Guide Vane Passage: Comparisons With Large-Eddy Simulations 

A high-pressure turbine is known to be a complex component of a gas turbine from a thermo-mechanical point of view. In modern lean-burn combustion chambers, this complexity is enhanced with the presence of hot streaks together with swirl components coming from the combustion chamber. These radial and azimuthal velocities and temperature distortions have a strong impact either on the aerodynamics inside the high-pressure turbine or on the aero-thermal behaviour of the vanes and blades. It is thus clear that swirled hot streaks must be taken into account in the early development of a high-pressure turbine by using numerical simulations. Regarding the level of turbulence, that can reach extreme values (25%-30% at the turbine inlet), its impact on the transport of hot streaks is not fully understood or is still under study, either experimentally or numerically.

From a practical point of view, in classical Reynolds-Averaged Navier-Stokes (RANS) methods, where all the turbulence is modelled, imposing the right turbulence at the inlet boundary condition is not an easy task. In this paper, the redistribution of a swirled hot streak in a bended duct is studied. This work is focused on turbulence modelling. High-fidelity Large-Eddy Simulations (LES) results are used as a basis of comparison to validate different RANS set-ups to predict hot streak redistribution in terms of migration and diffusion.

Results show that in a RANS approach, imposing the turbulent quantities from the LES simulations causes an immediate destruction of the swirl components and a too high total temperature diffusion. It is found in this study that the turbulent length scale, expressed in terms of turbulent viscosity ratio, plays a major role in the aerodynamic and aero-thermal behaviour of the flow. The optimal range for the value of turbulent viscosity ratio found is different from what is encountered in the literature on a high-pressure turbine configuration, which could be attributed to the anisotropy of the turbulence. By imposing consistent quantities at the inlet, both the trajectory of the swirl jet and the total temperature distribution can be captured.

Presenting Author: Christopher Wingel Safran Helicopter Engines

Presenting Author Biography: Christopher Wingel is a third year PhD student working for the French company Safran Helicopter Engines. He is currently performing his PhD on axial high-pressure turbine with a PhD entitled: "Unsteady modelling and analysis of the aerodynamics and aerothermal of a cooled turbine stage".

Authors:

Christopher Wingel Safran Helicopter Engines
Nicolas Binder ISAE-Supaero
Yannick Bousquet ISAE-Supaero
Jean-François Boussuge CERFACS
Nicolas Buffaz Safran Helicopter Engines
Sébastien Le Guyader Safran Helicopter Engines