Numerical evaluation of a new impingement cooling scheme with a separate return-channel applied to turbine blade leading edge

The turbine blade leading edge is imposed with large heat load due to the flow stagnation effect. Jet impingement cooling is widely used to keep blade leading edge below critical metal temperature. However, accumulated crossflow deteriorates jet-flow penetration and subsequently reduces impingement effectiveness. This study introduces a novel impingement-jet cooling scheme with a separate return-channel to reduce the effect of crossflow by extracting the spent flow upwards. In addition, the swirling flow generated inside the return-channel further augments heat transfer. The effects of different return hole patterns and outflow paths are investigated through Computational Fluid Dynamics (CFD) method based on the BSL turbulence model. The effects of return hole pattern and coolant outflow path are investigated and evaluated. The numerical results prove that introduction of the return-channel has improved area-averaged Nu on the target surface significantly compared to the baseline value. The inline pattern performs better than the staggered pattern within the channels with single outlet in the return-channel. However, with outlets in both the impingement channel and the return-channel, the heat-transfer effects of different return patterns are insignificant.