Experimental and Numerical Study of Laminar-Turbulent Transition on a Low-Pressure Turbine Outlet Guide Vane

Abstract

This work presents an experimental and numerical investigation of the laminar-turbulent transition and secondary flow structures in a turbine rear structure (TRS). The study was executed at engine representative Reynolds number and inlet conditions at three different turbine load cases. Experiments were performed in an annular rotating rig with a shrouded low-pressure turbine upstream of the TRS test section. The numerical results were obtained using the shear stress transport k − ω turbulence model and the Langtry–Menter γ − θ transition model. The boundary layer transition location at the entire vane suction side is investigated. The location of the onset and the transition length are measured using IR-thermography along the entire vane span. The IR-thermography approach was validated using hot-wire boundary layer measurements. Both experiments and computational fluid dynamics (CFD) show large variations of transition location along the vane span with strong influences from endwalls and turbine outlet conditions. Both agree well with traditional transition onset correlations near midspan and show that the transition onset Reynolds number is independent of the acceleration parameter. However, CFD tends to predict an early transition onset in the midspan vane region and a late transition is present in the hub region. Furthermore, in the hub region, CFD is shown to overpredict the transverse flow and related losses.