In this study, two time-accurate Navier-Stokes analyses were obtained to predict the first-vane/first-blade interaction in a 1 and 1/2-stage turbine rig for comparison with measurements. In the first computation, airfoil scaling was applied to the turbine blade to achieve periodicity in the circumferential direction while modeling 1/18 of the annulus. In the second, 1/4 of the wheel was modeled without the use of airfoil scaling. For both simulations the predicted unsteady pressures on the blade were similar in terms of time-averaged pressure distributions and peak-peak unsteady pressure envelopes. However, closer inspection of the predictions in the frequency domain revealed significant differences in the magnitudes of unsteadiness at twice vane-passing frequency (and the vane-passing frequency itself, to a lesser extent). The results of both computations were compared to measurements of the vane-blade interaction in a full-scale turbine rig representative of an early design iteration of the PW6000 engine. These measurements were made in the short-duration turbine-test facility at The Ohio State University Gas Turbine Laboratory. The experimentally determined, time-resolved pressures were in good agreement with those predicted with the 1/4-wheel simulation.

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Results are presented from a program, conducted to investigate the impact of spanwise stacking of turbine airfoil sections on tip clearance flows. Numerical as well as physical experiments were performed to demonstrate that these airfoils yielded about 40% reduction in tip clearance losses compared to those designed with a conventional approach. Three dimensional, steady Euler and Reynolds Averaged Navier Stokes (RANS) codes were used to execute the numerical experiments. Initial physical experiments were performed in a water tunnel by using linear cascades to validate the design concepts. The verification of the overall design concepts was executed in an uncooled full scale rotating rig.

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