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

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 a low-pressure turbine (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.