Enhancement in Film Cooling Effectiveness Using Delta Winglet Pair

Abstract

A simulation study has been carried out to investigate the influence of delta winglet pair (DWP) for improving the film cooling effectiveness of a gas turbine blade. Incompressible continuity, momentum, energy, and two equations k − ω SST model have been used for investigating the nature of flow field, temperature field, and turbulent statistics. The Reynolds number based on the jet velocity and the diameter of the film cooling hole is set at a constant value equal to 4232. The jet to the crossflow blowing ratio has been varied as 0.5, 1.0, and 1.5. The corresponding Reynolds numbers based on the crossflow inlet velocity and film hole diameter are equal to 6462, 4229, and 3231, respectively. It is observed that common-flow-down (CFD) DWP configuration augments the film cooling effectiveness due to generation of secondary longitudinal vortices, which annihilates the counter-rotating vortex structures present in the baseline flow. The generation of hairpin vortices and the growth of shear layer vortices are modified due to the implementation of DWP. The overall turbulence intensity and vorticity get reduced due to the presence of DWP. A maximum of 97.46% and a minimum of 61.50% enhancement in film cooling effectiveness have been observed at blowing ratio of M = 1.5 and M = 0.5, respectively. The wake region of the film cooling jet is modified due to DWP leading to formation of stagnation region and lower mixing resulting in higher film cooling effectiveness. The strength of horseshoe vortices is reduced due to the presence of DWP, resulting in lower mixing between the jet with the cross flows and stable film formation. Lower thermal boundary layer thickness is observed in DWP configuration compared to that of the baseline case confirming lower mixing due to the implementation of DWP. Overall, the present study explains the effectiveness of DWP configuration for enhancement of film cooling effectiveness of a DWP.