Influence of Vane/Blade Spacing on the Heat Flux for a Transonic Turbine

An experimental and analytical research program determining the influence of vane/blade spacing on the vane and blade time-averaged and unsteady heat-flux for a full-scale rotating turbine stage was performed. The turbine stage was operated at a transonic vane exit condition, with pressure and heat-flux measurements obtained throughout the stage. This paper focuses on the midspan heat-flux measurements for both the vane and blade at three vane/blade axial spacings: 20%, 40%, and 60% of vane axial chord. The time-averaged heat-flux results for the vane and the blade are compared with predictions obtained using a 2-D, Reynolds-averaged multi-blade row code, UNSFLO, developed by Giles (1984). The measured and predicted unsteady heat-flux envelopes (as a function of vane/blade spacing) are also compared with predictions. For selected locations on the blade, a direct comparison between the measured phase-averaged surface pressure and the measured phase-averaged Nusselt number history is presented. At some locations along the surface the pressure and the heat flux are shown to be in phase, but at other locations they are not. The influence of vane/blade spacing on the blade heat load was found to be small, and much less than the differences caused by changes in the Reynolds number during the experimental matrix.