Experimental and Numerical Study on an Inter-Turbine Duct

Abstract

The inter-turbine transition duct (ITD) between the high-pressure (HP) and low-pressure (LP) turbines of a gas turbine has the potential for significant length reduction and therefore engine weight reduction and/or aerodynamic performance improvement. This potential arises because very little is understood of the flow behavior in the duct in relation to the hub and casing shapes, and the flow entering the duct (e.g., swirl angle, turbulence intensity, periodic unsteadiness and blade tip vortices from upstream HP turbine blade rows). Moreover, it is unclear how well CFD is able to predict the complex flow-field in these ducts. This paper presents the results of a detailed experimental and computational study of an ITD, which is representative of a modern engine design. The experiments were conducted in a low-speed annular test rig where the effects of inlet free-stream turbulence intensities and swirl angle were investigated. Numerical studies were performed using commercial CFD software. The capability of different turbulence models, including the B-L, S-A, k-ε and SST models, have been explored. The predicted results are compared with the experimental data. Both experimental and numerical results are analyzed in detail to investigate the flow development both inside the ITD and along the end-walls.