Numerical evaluation of film cooling performance of transverse trenched holes with shaped lips

In this work, the influence of several lip structures on the effectiveness of film cooling and the flow fields of transverse trenched holes at different blowing ratios (BRs) ranging from 0.5 to 2.0 is numerically investigated, using the Reynolds averaged Navier Stokes method with the realizable k-epsilon turbulence model. The trenches include the traditional transverse trench, the bevel trenches, and the fillet trenches. It shows that the trenched holes produce weaker counter-rotating vortex pairs, which can enhance the effectiveness of film cooling compared with the standard cylindrical film hole. It demonstrates that the lip structures can improve the effectiveness of film cooling of the trenches at low BRs, but it has a negative effect at high BRs. It is found that the lower lip structures have less influence on the effectiveness of film cooling at different BRs than the upper lip structures. It is also found that the upper part of the fillet structure employs the Coanda effect to make the coolant flow close to the wall, thereby improving the effectiveness of film cooling; while the lower part of the fillet structure is conducive to converting the coolant flow into a vertical jet, thereby improving the effectiveness of film cooling at low BRs.