ACFD AND EXPERIMENTAL INVESTIGATION OF UNSTEADY WAKE EFFECTS ON A HIGHLY LOADED LOW PRESSURE TURBINE BLADE AT LOW REYNOLDS NUMBER

摘要

The flowfield of the LI A low pressure (LP) turbine blade subjected to traversing upstream wakes was experimentally and computationally investigated at an inlet Reynolds number of 25,000. The LI A profile is a high-lift aft-loaded low pressure turbine blade design. The profile was designed to separate at low Reynolds numbers making it an ideal airfoil for use in flow separation control studies. This study applied a new two-dimensional CFD model to the L1A LP turbine blade design using a three-equation eddy-viscosity type transitional flow model developed by Walters and Leylek. Velocity field measurements were obtained by two-dimensional planer particle image velocimetry, and comparisons were made to the CFD predictions using the Walters and Leylek [13] k-k_L-a transitional flow model and the Menter's [24] k-ω(SST) model. Hotwire measurements and pressure coefficient distributions were also used to compare each model's ability to predict the wake produced from the wake generator, and the loading on the LI A LP turbine blade profile with unsteady wakes. These comparisons were used to determine which RANS CFD model could better predict the unsteady L1A blade flowfield at low inlet Reynolds number. This research also provided further characterization of the Walters and Leylek transitional flow model for low Reynolds number aerodynamic flow prediction in low pressure turbine blades.