Experimental and Numerical Flow Analysis of an Engine-Realistic State-of-the-Art Turbine Rear Structure

Valentin Vikhorev,Pär Nylander,Valery Chernoray,Oskar Thulin,Jonas Larsson

doi:10.1115/gt2021-59224

Abstract

Abstract 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.

Highlights

In a turbofan engine the rear engine mounts are located in the turbine rear structure (TRS)
Comparisons were made of static-pressure distributions on the vanes and bumps, losses and wakes, turning and separations as well as secondary flows and surface flow visualizations
The results are used to analyze the flow in the TRS and to validate the CFD simulations

Summary

INTRODUCTION

In a turbofan engine the rear engine mounts are located in the turbine rear structure (TRS). This facility has a shrouded rotating LPT stage upstream of the TRS to provide engine realistic boundary conditions. This facility can reach engine representative Reynolds numbers, and by varying the turbine braking power one can investigate off-design conditions. Comparisons were made of static-pressure distributions on the vanes and bumps, losses and wakes, turning and separations as well as secondary flows and surface flow visualizations Tests were done both at the design point and typical off-design conditions. To the authors’ knowledge the present work is the first publication of both experimental and numerical results for a state-of-the-art TRS with three different vane types and a 3D polygonal shroud with engine mount bumps

EXPERIMENTAL DETAILS

NUMERICAL SETUP

RESULTS AND DISCUSSION

SUMMARY AND CONCLUSIONS