Film Cooling Effectiveness Enhancement Applying another Jet in the Upstream Neighbor of the Main Jet-Using LES Approach

Abstract

Flow hydrodynamic effects and film cooling effectiveness of placing a coolant port (upstream jet) just upstream of the main cooling jet were numerically investigated. The upstream jet was added such that the total cooling cross section (cross sections of the main and upstream jets) remains constant, in comparison to the case of ordinary cooling jet. The finite volume method and the unsteady SIMPLE algorithm on a multiblock non-uniform staggered grid arrangement were applied. The large eddy simulation (LES) approach with the one equation subgrid scale model was used. The jet to cross flow velocity ratio (for both of the main and the upstream jets) is 0.5 and the cross flow Reynolds number (based on the main jet parameters) is equal to 4700. The obtained results showed a significant improvement in the flow control capability and both centerline and span-wise averaged film cooling effectiveness applying the new cooling configuration. Effects of the upstream jet dimensions are also studied here. The obtained results showed that the span-wise width of the upstream jet has more essential influence on the cooling performance than that of its stream-wise width. Moreover, it is demonstrated that the film cooling performance could be enhanced even by applying an upstream jet which its temperature is as same as the cross-flow temperature, i.e. applying a hot upstream jet. Finally, it is shown that presence of the upstream jet decreases the stream-wise component of the velocity near the wall, which decreases the wall shear stress and the skin friction drag coefficient significantly.

Numerical Investigation on Film Cooling Mechanism with Different Coolant Delivery Configurations

“…Kusterer et al (2007Kusterer et al ( , 2009 proposed the double-jet film cooling technology to establish an anti-kidney vortex, which would prevent the double jet from lifting off the surface and raise the lateral spreading of the cooling air. Salimi et al (2016) found that applying upstream jet film cooling configuration would have a significant improvement in the flow control capability and both centerline and span-wise averaged film cooling effectiveness. Sinha et al (1991) studied the film cooling effectiveness with variable density ratio, it could be concluded that decreases in density ratio and increases in momentum flux ratio were found to reduce the spreading of the film cooling jet and reduce laterally averaged effectiveness.…”

Film Cooling Holes Performance on A Flat Plate

“…In the near past, Salimi et al [11] applied the upstream jet hole to enhance the film effectiveness of main hole through keeping the cross sections constant of the main and upstream jets compared with ordinary cooling jet. A novel sister shaped (SSH) and novel combined hole configuration were examined for the cooling performance over flat plate surface [12]- [13] respectively.…”

Film Cooling Performance of the Staggered Arrangement of Auxiliary Holes and Main Holes on a Flat Plate

“…The film performance for six antivortex holes with different branch hole diameters and exit locations was further studied by Dhungel et al (2009) and Christopher et al (2013). Salimi et al (2016) studied the effects of adding another cooling port upstream of the main jet. A significant film cooling improvement was observed.…”