This paper presents experimental and numerical CFD studies of the aerodynamics of a turbine rear structure (TRS). The TRS test geometry is an engine-realistic state-of-the-art design with a polygonal outer case, recessed engine mount bumps, and three different vane types: regular vanes, bump vanes in bump sectors, and thick vanes. Using three different sector types simultaneously was found to be crucial for the inlet boundary conditions. Experiments were performed in a modern rotating test facility with an LPT stage upstream of the TRS. A Reynolds number of 350,000 was used, representative of a TRS in a narrow-body geared turbofan engine. The TRS performance was analyzed both at on- and off-design conditions and a thorough side-by-side comparison of CFD and experiments was performed. Static-pressure-distributions, turning and outlet flow-angles, wakes and losses, and surface-flow visualizations and outlet total pressure contours are presented. The thick vane showed good aerodynamic performance, similar to the regular vane. For the bump vane, the mount bumps were found to generate additional local separations and secondary flows, resulting in extra losses. In the regions with strong secondary flows CFD over-predicts the wakes, whereas the wakes around midspan, where secondary flows have a smaller influence, are predicted well.

This paper presents experimental and numerical CFD studies of the aerodynamics of a turbine rear structure (TRS). The TRS test geometry is an engine-realistic state-of-the-art design with a polygonal outer case, recessed engine mount bumps, and three different vane types: regular vanes, bump vanes in bump sectors, and thick vanes. Using three different sector types simultaneously was found to be crucial for the inlet boundary conditions. Experiments were performed in a modern rotating test facility with an LPT stage upstream of the TRS. A Reynolds number of 350,000 was used, representative of a TRS in a narrow-body geared turbofan engine. The TRS performance was analyzed both at on- and off-design conditions and a thorough side-by-side comparison of CFD and experiments was performed. Static-pressure-distributions, turning and outlet flow-angles, wakes and losses, and surface-flow visualizations and outlet total pressure contours are presented. The thick vane showed good aerodynamic performance, similar to the regular vane. For the bump vane, the mount bumps were found to generate additional local separations and secondary flows, resulting in extra losses. In the regions with strong secondary flows CFD over-predicts the wakes, whereas the wakes around midspan, where secondary flows have a smaller influence, are predicted well.

CFD results can be improved by imposing accurate inlet boundary conditions. A previous paper presented extensive measurements from an engine realistic Turbine Rear Structure (TRS), complemented with CFD results using normal radial profiles (1D) at the inlet [10]. This paper extends stat study with two separate studies, investigating the effect of the upstream Nozzle Guide Vane (NGV) wakes and the inlet end-wall boundary layers. In the first study, simulations are done using full 2D inlet boundary condition, imposing the NGV wakes on the inlet. The second study investigates different inlet end-wall boundary layers. Comparisons with measurements show for some aspects that the upstream Nozzle Guide Vane (NGV) wakes and the inlet end-wall boundary layers are important. Predicting upstream forcing from the TRS on the LPT rotor requires a 2D inlet boundary condition. Also, a strong interaction between the incoming NGV wakes and the secondary flow loss-regions at the outlet is found. However, flow quantities like blade loading, outlet swirl, and OGV wakes are well predicted using regular 1D radial inlet profiles. How the inlet end-wall boundary layers are modelled have significant impact on secondary flows and outlet swirl. If the full boundary layers are prescribed, the secondary flows are over-predicted. This gives under turning and premature separations. With no inlet boundary layers, secondary flows are well captured and gives better separations, improved outlet swirl and wake predictions. The recommendation is therefore to remove the inlet boundary layers when using the Transition SST k-ω γ-Reθ model in TRS CFD simulations.