PARTIAL BLOCKAGE EFFECTS ON TURBINE BLADE INTERNAL SWIRL COOLING DUE TO PARTICLE DEPOSITION

In this study, particle deposition effects within a swirl cooling system were modeled by an obstacle that partially blocked the flow through the system. The swirl cooling system consisted of a swirl generator with two tangential jet nozzles and a swirl tube. Three typical blockage cases with the obstacle at the throats of the jet nozzles, on the side walls of the swirl generator, and inside the swirl tube were investigated. Unsteady Reynolds-averaged Navier-Stokes (URANS) simulations of the swirling flow were performed for a Reynolds number of 40, 000 and a geometrical swirl number of 5.3. A baseline case of a clean tube was also included for comparisons. Results revealed that the blockage at the nozzle throat intensified the swirling flow and thus increased heat transfer levels, while the blockage in the swirl generator and within the swirl tube both reduced the swirling flow, resulting in lower heat transfer. Although the blockage within the swirl tube disturbed the swirling flow, generating the lowest heat transfer levels, the heat transfer upstream of the obstacle was intensified due to strong turbulence induced by the obstacle. In terms of pressure losses within the swirl tube only, the lowest friction factor was obtained in the tube with blockage in the swirl generator because of a low swirl rate, while the highest pressure loss was observed when the blockage occurred within the swirl tube, achieving the lowest overall thermal parameter value. However, when the contribution of the swirl generator to the pressure loss was considered, all blockage cases produced higher pressure losses and thus lower overall thermal parameter relative to the clean tube.