Comparison of 2D and 3D Airfoils in Combination With Non Axisymmetric End Wall Contouring: Part 2 — Numerical Investigations
Secondary flow phenomena have a considerable part in the efficiency loss in turbomachinery. A potential method to reduce these secondary flow losses is tangential end wall contouring inside the blade passages. The present paper is the second of two papers which investigate the impact of tangential end wall contouring on 2D and 3D airfoils compared to a baseline configuration. The first paper summarizes the experimental investigation on a 2-stage air driven turbine test rig located at the Institute of Power Plant Technology, Steam and Gas Turbines RWTH Aachen University. To enhance the impact of the tangential end wall contours (TEWC) on the near wall flow, the rotor cavities are sealed by means of combined brush- and labyrinth seals. The stator cavities are sealed by labyrinth seals, only. This paper investigates the flow phenomena using CFD with the commercial software package ANSYS 15.0©. The brush seals are modeled by using the porous body approach and are calibrated using pressure drop measurements across the first rotor cavity. The experimental data will be presented and is used to validate the numerical model. For this, circumferential plots for the measurement planes are shown. In addition a detailed description of the changes in vortex formations as well as blade loading will be given for the various configurations. Finally a discussion of the impact on the turbine’s efficiency is given. It has been found, that for steady CFD simulations the use of stage interfaces suppresses the positive effects of the tangential end wall contour onto the downstream blade row.