Flow Trajectories, Mixing and Entropy Fluxes in a Turbine Cascade,
VIRGINIA POLYTECHNIC INST AND STATE UNIV BLACKSBURG DEPT OF MECHANICAL ENGINEERING
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Flow in a turbine cascade studied by Langston, et al., is considered. Measurements have been made in a geometrically similar cascade with an axial chord of 235 mm compared with the 281 mm used by Langston et al. and the same spanchord and pitchchord ratios. The present five-blade cascade has an exit Reynolds number based on axial chord of 580,000 compared with the value of 100,000 for the four-blade cascade of Langston et al. Measurements of total pressure and flow direction downstream of the cascade complement the results of Langston et al. which showed the flow development only within the cascade. The downstream flow is important, however, as approximately 50 of the losses occur downstream of the trailing edge. Regions of high-loss fluid are found and the origin of fluid in these regions is traced using the ethylene injection technique with a flame ionisation detector. From a computational standpoint, there is interest not only in the location of the ethylene at the downstream plane but also in the concentration levels and the diffusion rates. From a practical standpoint, the most significant result from the present tests is that the highest entropy fluxes downstream of this cascade at xc 1.4 occur near midspan in a high-loss core and not near the end walls.