Numerical Analysis of Turbine Blade Tip Treatments

Three-dimensional solutions of the Navier-Stokes equations for a turbine blade with a turning angle of 180 degrees have been computed, including blade tip treatments involving cavities. The geometry approximates Pratt&Whitney's preliminary design for the GGOT (Generic Gas Oxidizer Turbine). The data presented here will be used as a means of comparison for experimental data to be obtained from a linear cascade being built and tested at The University of Alabama, using the original GGOT blades. Results have been computed for a blade with 1% clearance, based on chord, and three different cavity sizes. All tests were conducted at a Reynolds number of 4x10⁷/m. The grid contains 39,440 points with 10 spanwise planes in the tip clearance region of 5.008E-04 m. Streamline plots and velocity vectors, together with velocity divergence plots reveal the general flow behavior in the clearance region. Blade tip temperature calculations suggest placement of a cavity close to the upstream side of the blade tip for reduction of overall blade tip temperature. The solutions do not account for the relative motion between the endwall and the turbine blade. The solutions obtained are generally consistent with previous work done in this area.